Technical Field

The invention relates to a system for feeding an electrical load. Especially to a voltage system for feeding an electrical load.

Background

Different types of voltage or power systems are known in the art. A voltage system may be configured to feed an electrical load or drive an electrical motor by electrical power. The latter e.g. being part of an electrical vehicle or a hybrid vehicle.

The voltage system may also be configured to receive power, i.e. to be loaded by an external power source, such as a wind power plant or a solar power plant.

Therefore, examples of voltage systems are systems for driving an electrical motor of electrical vehicles or hybrid vehicles. Other non-limiting examples are systems coupled to wind power plants and solar power plants.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a system for feeding a load, the system comprises a first set of voltage modules and at least one second set of voltage modules connected to a load, wherein each set of voltage modules of the system is active when at least one of its voltage modules is in active mode so that an output voltage of the active set of voltage modules is larger than zero, and non-active when all of its voltage modules are in non-active mode so that an output voltage of the non-active set of voltage modules is equal to zero; and wherein i) during a first time period T1 , the first set of voltage modules is active and configured to feed the load when the second set of voltage modules is non-active and configured to not feed the load; ii) during a second time period T2 following the first time period T1 , the first set of voltage modules is active and the second set of voltage modules is active so that both the first set of voltage modules and the second set of voltage modules are configured to feed the load during an overlap time period; and iii) during a third time period T3 following the second time period T2, the first set of voltage modules is non-active and configured to not feed the load when the second set of voltage modules is active and configured to feed the load.

The system may also be denoted as a power system or a voltage system. The load may be an electrical load or in other words a device or an arrangement that needs or consumes electrical power for its functioning.

It is understood that the states i) to iii) can be repeated. For example, repeated with a periodicity. In such case the system goes from state iii) to i) e.g. due to one or more conditions that are fulfilled.

An advantage of the system according to the first aspect is that due to the feeding overlap time period when both the first and second sets of voltage modules feed the load the efficiency of the system is improved due to reduced switching losses. This is e.g. due to improved voltage matching. Further, with the present solution no energy buffering circuits, such as LC networks, is needed as in conventional solutions.

Also since the set of voltage modules are modular service on the set of voltage modules can be simplified. Further, the safety aspect is much improved since the voltage levels to be handled during service is only that of each module instead of a dangerously high voltage level of multiple connected batteries as in conventional solutions.

In an implementation form of a system according to the first aspect, the system is configured to switch from i) to ii) when an output voltage of the first set of voltage modules is smaller than a first threshold voltage V™.

Thereby, a condition is provided when the system should switch from state i) to ii).

In an implementation form of a system according to the first aspect, the first threshold voltage V _Thi is dependent a nominal voltage V _n of the load. An advantage of this implementation form is that the output voltage and hence the power provided to the load is adapted to the nominal voltage of the load.

In an implementation form of a system according to the first aspect, the first threshold voltage V _Thi is lower than the nominal voltage V _n of the load.

In an implementation form of a system according to the first aspect, the first threshold voltage V _Thi is larger than 90 % of the nominal voltage V _n of the load.

An advantage of this implementation form is that the output voltage and hence the power provided to the load is upheld to a reasonable level so that the load can operate or function properly.

In an implementation form of a system according to the first aspect, the system is configured to switch from i) to ii) when the output voltage of the second set of voltage modules is larger than a second threshold voltage V _Th 2.

Thereby, a further condition is provided when the system should switch from state i) to ii).

In an implementation form of a system according to the first aspect, the second threshold voltage V _Th 2 is higher or equal to a nominal voltage V _n of the load.

Thereby, a possible low output voltage of the first set of voltage modules may be compensated for.

In an implementation form of a system according to the first aspect, the second threshold voltage V _Th 2 is dependent on at least one of the first threshold voltage V™ and the nominal voltage V _n of the load.

An advantage of this implementation form is that the output voltage of the second set of voltage modules may be determined more accurate for better performance or functioning of the load.

In an implementation form of a system according to the first aspect, the second threshold voltage V _Th 2 is dependent on a difference voltage between the first threshold voltage V™ and the nominal voltage V _n of the load. An advantage of this implementation form is that a possible low output voltage of the first set of voltage modules may be compensated for.

In an implementation form of a system according to the first aspect, the system further comprises an overlap transfer circuit comprising at least one first controllable switch coupled between the first set of voltage modules and the load and configured to couple or uncouple the first set of voltage modules to the load; and at least one second controllable switch coupled between the second set of voltage modules and the load and configured to couple or uncouple the second set of voltage modules to the load.

In an implementation form of a system according to the first aspect, the first controllable switch is configured to receive first control signals and the second controllable switch is configured to receive second control signals, so that both the first controllable switch and the second controllable switch both are conductive during the overlap time period, wherein the first control signals and the second control signals are simultaneous or non-simultaneous clocked.

In an implementation form of a system according to the first aspect, wherein the first control signals and the second control signals are non-simultaneous clocked with a time offset dependent on at least one of: a current provided to the load, and a difference in output voltage between the first and second sets of voltage modules.

In an implementation form of a system according to the first aspect, comprising at least one equalizing switch coupled between a positive line of the first set of voltage modules and a positive line of the second set of voltage modules, and wherein a difference in output voltage between the first set of voltage modules and the second set of voltage modules is equalized when the equalizing switch is set in conductive mode.

An advantage of this implementation form is that all non-active set of voltage modules can share their voltages, current and power so as to equalize the non-active set of voltage modules of the system.

In an implementation form of a system according to the first aspect, the duration of the second time period T2 is dependent on a switching time of the first controllable switch and/or a switching time of the second controllable switch. An advantage of this implementation form is that the switching losses can be held as low as possible.

In an implementation form of a system according to the first aspect, the duration of the second time period T2 is less than 10 % of the duration of the first time period T 1 and/or the duration of the third time period T3.

In an implementation form of a system according to the first aspect, an output voltage of a set of voltage modules is dependent on the number of active voltage modules in the set of voltage modules.

In an implementation form of a system according to the first aspect, each set of voltage modules comprises at least one voltage module having a nominal voltage and at least one voltage module having a variable voltage.

An advantage of this implementation form is that the output voltage may be adapted with higher granularity for more precis and improved voltage matching.

In an implementation form of a system according to the first aspect, the system is further configured to connect non-active sets of voltage modules to an external voltage source so as to load the voltage modules of the non-active sets of voltage modules.

An advantage of this implementation form is that the non-active sets of voltage modules can be reloaded or re-powered by the external voltage or power source.

In an implementation form of a system according to the first aspect, the system further comprises a control arrangement configured to control each set of voltage modules, each voltage module and each switch of the system.

In an implementation form of a system according to the first aspect, the switching frequency of the control arrangement is higher than or equal to 10 kHz.

An advantage of this implementation form is that good AC wave forms can be generated. In an implementation form of a system according to the first aspect, the switching frequency of the control arrangement is lower than or equal to 300 kHz.

An advantage of this implementation form is that the switching losses can be held low.

Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

- Fig. 1 shows a system according to embodiments of the invention;

- Fig. 2 shows a one switch implementation and a two switch according to embodiments of the invention;

- Fig. 3a and 3b show state diagram for a one switch implementation according to embodiments of the invention;

- Fig. 4 shows a state diagram for a two switch implementation according to embodiments of the invention;

- Fig. 5 shows a system according to an embodiment of the invention;

- Fig. 6 illustrates a set of voltage modules of a system according to an embodiment of the invention;

- Fig. 7 illustrates a voltage module having a switching arrangement according to an embodiment of the invention;

- Fig. 8 illustrates two different voltage modules each having a three switch switching arrangement according to an embodiment of the invention;

- Fig. 9 shows a first set of voltage modules according to an embodiment of the invention;

- Fig. 10 shows a first set of voltage modules coupled to a second set of voltage modules according to an embodiment of the invention;

- Fig. 11 shows a plurality of sets of voltage modules coupled to each other according to an embodiment of the invention;

- Fig. 12 shows a plurality of sets of voltage modules coupled to each other according to an embodiment of the invention;

- Fig. 13 illustrates a system comprising two ports which may be coupled to a power consumer or a power source;

- Fig. 14 shows overlap circuit according to embodiments of the invention;

- Figs. 15 - 17 illustrate an overlap circuit according to embodiments of the invention;

- Fig. 18 shows an embodiment of the invention including a control device; and Figs. 19 - 21 illustrate different aspects of controlling the controllable switches.

Detailed Description

Fig. 1 shows a system for feeding a load according to an embodiment of the invention. The system 100 comprises a first set of voltage modules 112 and at least one second set of voltage modules 122 connected to a load 200. Each set of voltage modules of the system 100 is active when at least one of its voltage modules is in active mode so that an output voltage of the active set of voltage modules is larger than zero. Further, each set of voltage modules of the system 100 is non-active when all of its voltage modules are in non-active mode so that an output voltage of the non-active set of voltage modules is equal to zero.

According to embodiments of the invention, the following states are executed/performed: i) during a first time period T1 , the first set of voltage modules 112 is active and configured to feed the load 200 when the second set of voltage modules 122 is non-active and configured to not feed the load 200; ii) during a second time period T2 following the first time period T1 , the first set of voltage modules 112 is active and the second set of voltage modules 122 is active so that both the first set of voltage modules 112 and the second set of voltage modules 122 are configured to feed the load 200 during an overlap time period; and iii) during a third time period T3 following the second time period T2, the first set of voltage modules 112 is non-active and configured to not feed the load 200 when the second set of voltage modules 122 is active and configured to feed the load 200.

Therefore, during the second time period T2 there will be a feeding overlap time period when both the first set of voltage modules 112 and the second set of voltage modules 122 feed the load 200.

It is realised that states or steps i) to iii) can be repeated an arbitrary number of times, e.g. with a periodicity. Flence, when being in state iii) the system 100 is further configured to return back to state i), continue to state ii) and thereafter to state iii), and so on. Such cyclic repetitions may be controlled by a control arrangement 102 of the system 100 which is configured to control each set of voltage modules, each voltage module and each switch of the system 100. The control arrangement 102 will be explained more in detail in the following disclosure.

In embodiments of the invention, different conditions may be set or used for switching from state i) to ii). The conditions may relate to the output voltage of the first set of voltage modules 112 and its associated threshold parameters and/or the output voltage of the second set of voltage modules 122 and its associated threshold parameters. The switching between the states may in embodiments be controlled by the control arrangement and be performed by means of an overlap circuit which is described further in the following disclosure.

Therefore, the system 100 may be configured to switch from state i) to ii) when an output voltage of the first set of voltage modules 112 (also denoted a first output voltage herein) is smaller than a first threshold voltage V™ which implies that the first output voltage may be continuously checked against the first threshold and if it is found that this condition is fulfilled the system 100 switches from state i) to ii), i.e. to the second time period T2 when the first and second sets of voltage modules feed the load 200 at the same time. The first threshold voltage V _Thi may be dependent a nominal voltage V _n of the load 200. A nominal voltage of the load 200 can be understood as an expected voltage of the load 200, an operating voltage of the load, a working voltage of the load 200, etc. Different types of nominal voltages may be considered. One type is static or more or less constant, meaning a constant nominal voltage value, e.g. for a load demanding a constant power. Another type is when the nominal voltage value takes discrete values which e.g. may be predefined, e.g. different power levels of a microwave oven. Yet another type is when the nominal voltage value can take continuous values, e.g. an electrical motor of a vehicle such as a car or a truck.

In embodiments of the invention, the first threshold voltage V™ is lower than the nominal voltage V _n of the load 200 which means that the load 200 has drained the power of the first set of voltage modules to some extent. However, for proper functioning of the load 200 the first output voltage should not drop to much and therefore in further embodiments of the invention the first threshold voltage V™ is larger than 90 % of the nominal voltage V _n of the load 200. It is however noted that the percentage of the nominal voltage is dependent on the application or type of the load 200 and hence in embodiments of the invention, the first threshold voltage V _Thi is larger than X % of the nominal voltage V _n of the load 200, where X % is dependent on or based on the proper functioning of the load 200. In other words, the lower limit for the load 200 to work or operate properly.

Another type of conditions primarily relates to the output voltage of the second set of voltage modules (also denoted a second output voltage herein) but it will be envisaged that such conditions may also in turn depend on the conditions related to the first output voltage previously described. Therefore, in embodiments of the invention, the system 100 is configured to switch from state i) to ii) when the second output voltage is larger than a second threshold voltage V _Th 2. This also implies that the system 100 may continuously check the value of the second output voltage and compare it to a second threshold voltage. The second threshold voltage V _Th 2 may be higher or equal to a nominal voltage V _n of the load 200. It has further been realised that the second threshold voltage V _Th 2 may be dependent on at least one of the first threshold voltage V™ and the nominal voltage V _n of the load 200. For example, the second threshold voltage V _Th 2 may be higher than the first threshold voltage V™ and the nominal voltage V _n .

In embodiments of the invention, it is determined a difference voltage between the first threshold voltage V™ and the nominal voltage V _n of the load 200, and then the second threshold voltage V _Th 2 is determined based on such a difference voltage. For example, the second threshold voltage V _Th 2 may be set as the nominal voltage plus the difference voltage. A non-limiting example would be: nominal voltage V _n = 200 V, first threshold voltage V™ = 190 V, which means that 200 - 190 = 10 V is the difference voltage and hence the second threshold voltage V _Th 2 is set to 10 + 200 = 210 V.

The skilled person understands that when the system 100 returns back from state iii) to state i) the aforementioned conditions can be applied, mutatis mutandis.

The voltage modules of the system 100 are in embodiments of the invention coupled to the load 200 via an overlap transfer circuit 300 comprising controllable switches 130a, 130b,..., 130n. Therefore, at least one first controllable switch 130a is coupled between the first set of voltage modules 112 and the load 200 and configured to couple or uncouple the first set of voltage modules 112 to the load 200. Further, at least one second controllable switch 130b is coupled between the second set of voltage modules 122 and the load 200 and configured to couple or uncouple the second set of voltage modules 122 to the load 200.

Fig. 2a and 2b show two different cases. In Fig. 2a each set of voltage modules are coupled to the load 200 via one controllable switch 130a and 130b while in Fig. 2b each set of voltage modules are coupled to the load via two separate controllable switches, i.e. 130a, 130a ^' and 130b, 130b ^' . In the latter case it is noted that the two switches are opposite coupled to each other in a current direction as shown in Fig. 2b. The switches are in this case field effect transistors (FETs) but can be any suitable type of switches. It is to be noted that when a transistor is in ON mode it is fully conductive in both directions and when in OFF mode the transistor is only conductive in the direction of the body diode which is also shown.

For illustrative purpose, exemplary output voltages of the first 112 and second 122 sets of voltage modules are also shown. In Fig. 2a the first set 112 is active, and has an output voltage of 199 V and is feeding the load 200 (switch 130a = ON); while the second set 122 is inactive, and has 0 output voltage and is not coupled (switch 130b = OFF) to the load 200. In Fig. 2b the same case as in Fig. 2a is illustrated but with the difference that each set of voltage modules are coupled to the load 200 via two separate switches as aforementioned.

Fig. 3a and 3b illustrates a switching diagram for the one switch case. In Fig. 3a the first 112 and second 122 sets of voltage modules and its switches 130a, 130b are illustrated. Also, the load 200 and the how the current flows (bold lines and arrows) is shown in Fig. 3a.

At I in Fig. 3b, the first set of voltage modules 112 is active (first output voltage = 200 V) and is feeding the load 200 since its switch 130a is in ON mode. The second set of voltage modules 122 is non-active (second output voltage = 0 V) and its switch 130b is in OFF mode.

At II in Fig. 3b, the first set of voltage modules 112 is still feeding the load 200 but the first output voltage has dropped to 198 V due to the previous feeding of the load 200.

At III in Fig. 3b, the first set of voltage modules 112 is still feeding the load but its switch 130a has been set in OFF mode which means that the switch is not fully conductive but is still conductive through its body diode. When the current flows a body diode of a transistor there will be losses over the body diode.

At IV in Fig. 3b, the first set of voltage modules 112 is still feeding the load 200 but also the second set of voltage modules 122 has been activated and feeds the load 200 with 200 V but its switch 130b is in OFF mode which means that the current flows through the body diode. This is a feeding overlap time period or state of the system 100.

At V in Fig. 3b, the second set of voltage modules 122 feeds the load 200 via its switch 130b which is in ON mode. The first set of voltage modules 112 does however not the feed the load 200 anymore but is still active (first output voltage = 198 V).

At VI in Fig. 3b, the first set of voltage modules 112 is non-active (first output voltage = 0 V) and only the second set of voltage modules 122 is feeding the load 200 with a second output voltage of 200 V.

Fig. 4 illustrates a switching diagram for the two-switch case when they are opposite coupled with each other in the current direction. The opposite coupling is used for preventing a current rush between the sets of voltage modules of the system 100 during time periods when they are active and coupled to each other. For simplicity, a switch in ON mode is illustrated as a conductor while a switch in OFF mode is illustrated with its body diode which is always conducting when its threshold voltage has been reached.

At I in Fig. 4, the first set of voltage modules 112 is active (first output voltage = 199 V) and feeds the load 200 as its switches 130a, 130a ^' are in ON mode which also means that the first set of voltage modules 112 can both feed and receive current. The second set of voltage modules 122 is non-active (second output voltage = 0 V) and its switches 130b, 130b ^' are in OFF mode.

At II in Fig. 4, the first set of voltage modules 112 is still active (first output voltage = 199 V) and feeds the load 200 and the second set of voltage modules 122 has been activated (second output voltage = 200 V) but does not feed the load 200 as both its switches are in OFF mode.

At III in Fig. 4, the first set of voltage modules 112 is still active (first output voltage = 199 V) but switch 130a ^' has been set in OFF mode so that the first set of voltage modules 112 only can feed current but not receive any current so as to prevent current rush from the second set of voltage modules 122. The second set of voltage modules 122 is active but does not feed the load 200 since both its switches 130b, 130b ^' are still in OFF mode.

At IV in Fig. 4, both the first set of voltage modules 112 and second set of voltage modules 122 feed the load 200 at the same time as both sets are active and switch 130b has been set in ON mode. This is the feeding overlapping timer period and is also denoted T2 in the present disclosure. Since the second output voltage (second output voltage = 200 V) is higher than the first output voltage (first output voltage = 199 V) the second set of voltage modules 122 will successively take over the feeding of the load 200 from the first set of voltage modules 112. Also, as previously mentioned there will be no current rush from second set of voltage modules 122 to the first set of voltage modules 112 since it is also noted that both the first set of voltage modules 112 and the second set of voltage modules 122 only can feed current but not receive current due to their respective switching configuration.

At V in Fig. 4, the first set of voltage modules 112 is still active (first output voltage = 199 V) but is uncoupled from the load 200 as both its switches 130a, 130a ^' have been set in OFF mode. The second set of voltage modules 122 is active and is feeding the load 200 alone via the body diode of its switch 130b ^' is in OFF mode so there will be a small power loss over the body diode. At VI in Fig. 4, the second set of voltage modules 122 is active and is feeding the load 200 but with both its switches 130b, 130b ^' set in ON mode and hence no losses in any body diode will occur. The first set of voltage modules 112 is still active (first output voltage = 199 V) but uncoupled to the load 200.

At VII in Fig. 4, the first set of voltage modules 112 is in non-active mode and hence the first output voltage is 0 V. The second set of voltage modules 122 is however active and continues to feed the load 200.

When the second set of voltage modules 122 has lost some of its power the first set of voltage modules 112 may take over and feed the load 200 as described herein so that states I to VII are repeated.

It is also to be realised that more than two different sets of voltage modules can feed the load 200 by using a feeding pattern. It is important to stress that the feeding overlapping time periods herein disclosed should be employed in which at least two different sets of voltage modules feed the load 200 at the same time. For example, consider three sets of voltage modules (or blocks or chains of voltage modules) for simplicity denoted B1 , B2, and B3. The following feeding pattern may be employed:

1 . B1 feeds the load; B2 is non-active; B3 is non-active.

2. B1 is non-active; B2 feeds the load; B3 is non-active.

3. B1 is non-active; B2 is non-active; B3 feeds the load.

This pattern from step 1 to 3 is repeated e.g. according to a control pattern of the control arrangement 102.

Furthermore, for providing voltage or power shareability among the voltage modules of the system, non-active sets of voltage modules may be electrically coupled with each other so as to equalize the voltages of the non-active sets of voltage modules. In respect dedicated switches for such purpose may be employed. In other words, the system may comprise at least one equalizing switch 410 coupled between a positive line L1 of the first set of voltage modules 112 and a positive line L1 ^' of the second set of voltage modules 122, and wherein a difference in output voltage between the first set of voltage modules 112 and the second set of voltage modules 122 is equalized when the equalizing switch 410 is set in conductive mode. From the above example it is realised that: at step 1 - B2 and B3 can be coupled to each other and share power; at step 2 - B1 and B3 can be coupled to each other and share power; and at step 3 - B1 and B2 can be coupled to each other and share power. To reload the system 100 with power the non-active sets of voltage modules of the system 100 may be connected to an external voltage source so as to power the voltage modules of the non-active sets of voltage modules.

Furthermore, it was also noted from Fig. 2b that the system 100 may have measuring resistances R coupled in parallel to the two controllable switches 130. This is naturally also possible in the one switch case as shown in Fig. 2a however with only one measuring resistance R. The measurements made over the resistances R can be used by the control arrangement 102 for controlling the output voltage of the system 100. The output voltage can therefore be adapted or matched to the nominal voltage of the load 200. The output voltage can also be adapted to a nominal voltage of a power source if the system 100 is coupled to such a source for power loading.

Furthermore, the characteristics of the switches may have an influence on the second time period T2. Therefore, in embodiments, the duration of the second time period T2 is dependent on a switching time of the first controllable switch 130a and/or a switching time of the second controllable switch 130b due to the fact that the second time period T2 should be held as short as possible due to losses in the body diode but at the same time minimizing the risk of having the switches in ON mode and be fully conductive since that could lead to current rush between the different sets of voltage modules.

Due to such characteristics the second time period is often much shorter than the first time period T1 and the third time period T3. Accordingly, the duration of the second time period T2 may be less than 10 % of the duration of the first time period T 1 and/or the duration of the third time period T3. In embodiments of the invention, the second time period T2 may be less than 1 % of the duration of the first time period T 1 and/or the duration of the third time period T3.

Moreover, further adaptiveness of the system 100 relates to scalability of the output voltage of the sets of voltage modules. Generally, in the present solution an output voltage of a set of voltage modules is dependent on the number of active voltage modules in the set of voltage modules and the type of voltage modules. This is also explained more in detail in the following disclosure.

Fig. 5 shows a system 100 according to an embodiment of the invention. The system 100 comprises a first set of voltage modules 112a, 112b,..., 112n and a control arrangement 102 configured to control each voltage module 112n. The control arrangement 102 can e.g. control each voltage module 112n via switches or any other suitable components. The control arrangement 102 can control the voltage modules via control signalling illustrated with the dashed arrows from the control arrangement 102 to the voltage modules 112a, 112b,..., 112n. Suitable control protocols may be used in this respect and be performed over known wired communication means, such as CAN busses or other communication busses. Also, wireless communication means can be used by the control arrangement 102 for controlling the components of the system 100.

The control arrangement 102 may e.g. comprise one or more processors and one or more memory units and may be connected to one or more sensors and devices from which the control arrangement may receive input that may be used for controlling the voltage modules and other components of the system 100. More details of such aspects are described in the following disclosure.

The control arrangement 102 may operate using a switching or a clock frequency when controlling the different components of the system 100. For example, the switching frequency of the control arrangement may be higher than or equal to 10 kHz and lower than or equal to 300 kHz. If the frequency is lower than 10 kHz it will be difficult to provide good alternating current (AC) waveforms such as a sinusoid curve. On the other hand, if the frequency is higher than 300 kHz the efficiency of the system will be reduced due to switching losses in the system.

The system 100 may further comprise a first port P1 including a first side S1 pi configured to be connected to an external power consumer 210, such as a load or electrical motor, or an external power source 220 and a second side S2 _Pi configured to be connected to the first set of voltage modules 112a, 112b,..., 112n. The first port P1 thus allows voltage and hence power to be supplied to and from the system 100. For example, voltage or power may be supplied from one or more of the first set of voltage modules 112a, 112b,..., 112n to the external power consumer 210 or voltage may be supplied from the external power source 220 to one or more of the first set of voltage modules 112a, 112b,..., 112n.

With reference to Fig. 6, each voltage module 112n in the first set of voltage modules 112a, 112b,..., 112n comprises an voltage depot 114n including a first connection 116n coupled to a first common line L1 of the first set of voltage modules 112a, 112b,..., 112n and a second connection 118n coupled to a second common line L2 of the first set of voltage modules 112a, 112b,..., 112n. 11. The second common line L2 may be coupled to the second side S2P _I of the first port P1 , as shown in Fig. 6. According to embodiments of the invention, each voltage depot 114n includes at least one of a battery B and a capacitor C, see Fig. 7. In embodiments where the voltage depot 114n includes both a battery B and a capacitor C, the battery B and the capacitor C may be coupled in parallel to each other between the first common line L1 and the second common line L2.

The batteries herein may be any suitable batteries known in the art and with any voltage rating. Non-limiting examples are Lithium battery rated is 3.6V and 3 - 4 Ah. With 6 such batteries in series, the rated voltage of a voltage module would become 21 .6 V. The voltage range per module goes from discharged to fully charged 18V-25V. Other non-limiting examples are LiFe, Lilon and LiFe batteries. SuperCap batteries can also be interesting.

The capacitors herein may be any suitable capacitors known in the art. For example, in C modules, ceramic capacitors are selected for the modules' maximum voltage. These have relatively low Ri, which means low heating and heat loss during loading and unloading. A suitable minimum capacitor value is with a BLOCK-time of 2.5ps (200kFlz) and a voltage drop <1% and 10A current to the load = 100pF. This is conveniently achieved by connecting a number of ceramic capacitors in parallel. Capacitors with different value, voltage resistance and chemistry may be included in a parallel circuit to minimize resistance.

In embodiments, each voltage depot may include a transformer T, see Fig. 7. The transformer may have 1 :1 relation between its primary and secondary windings. Therefore, each voltage depot may include any combinations of batteries B, capacitors C and transformers T. The transformers herein may be any suitable transformer known in the art. For example, with < 10A current and 25V rated voltage per module, the power requirement may be at least 250VA. A non-limiting example is CoilCrafts PL300-100 with 1 :1 coupling which is designed for 300W at 200kFlz. The 1 :1 ratio, implying unregulated voltage transmission, means that rings, etc. undesirably can be reduced to a minimum.

In embodiments of the invention, each voltage depot has a nominal (fixed) voltage or a variable or tuneable voltage. In a non-limiting example, each voltage depot can have 25 V so that for each activate voltage module the set of voltage module will have a common/output voltage that is equal to the number of activated modules times 25 V. Flowever, for fine tuning the output voltage each set of voltage modules may have one or more voltage modules that can provide voltages with higher granularity, e.g. from 1.2 V up to 21.6 V in steps of 1.2 V, i.e. 18 units. The voltage depots can e.g. be built with one or more batteries coupled in the voltage depot. It is noted that the actual voltage of a battery depends on if the battery is charged or discharged. Therefore, in embodiments, each set of voltage modules comprises at least one voltage depot having a nominal voltage and at least one voltage depot having a variable voltage. Thereby, the common voltage of each set of voltage modules can be adjusted or fine tuned, e.g. to the nominal voltage of the external power consumer or the external power source. Furthermore, by activating and de-activating voltage modules, e.g. with a rate set by a clock frequency used by the control arrangement 102, different waveforms can be generated. Therefore, e.g. sinusoidal AC waveforms can be generated at the output of the system 100.

In a low complex implementation example, each set of voltage modules has at least one voltage depot having a nominal voltage and a single voltage depot having a variable voltage. By having only one voltage depot having a variable voltage also the cost can be held low but still provide adaptability of the value of the common voltage for each set of voltage modules.

Each voltage module 112n further comprises an internal switching arrangement 120n coupled to the voltage depot 114n. The control arrangement 102 is configured to control each voltage module 112n to operate in a first mode M1 in which an voltage of its voltage depot 114n is added to a common voltage of the first set of voltage modules 112a, 112b,..., 112n, or a second mode M2 in which an voltage of its voltage depot 114n is shared to one or more other voltage modules in the first set of voltage modules 112a, 112b,..., 112n. The control arrangement 102 may control each voltage module 112n between the first mode M1 and the second mode M2 by controlling the switching arrangement 120n of the voltage module 112n. Thus, the control arrangement 102 may in embodiments be configured to control a voltage module 112n by controlling its switching arrangement 120n. The control arrangement 102 may be configured to control each switching arrangement 120n to operate in a first switching mode SM1 in which the voltage depot 114n is coupled in series with one or more other voltage depots of the first set of voltage modules 112a, 112b,..., 112n so that its voltage is added to the common voltage of the first set of voltage modules 112a, 112b,..., 112n; or a second switching mode SM2 in which the voltage depot 114n is coupled in parallel with one or more other voltage depots of the first set of voltage modules 112a, 112b,..., 112n so that its voltage is shared with to one or more other voltage modules in the first set of voltage modules 112a, 112b,..., 112n.

Fig. 7 illustrates such embodiments. The switching arrangement of the voltage module can switch the voltage module between the first mode M1 (also denoted active mode) and the second mode M2 (also denoted non-active mode), respectively. In Fig. 7 the switching arrangement is in the first switching mode SM1 and therefore the voltage depot 114 will be serially coupled to a voltage depot of an adjacent voltage module (not shown) which means the voltage of this particular voltage module will be added to the common/output voltage of the set of voltage modules it belongs to. Therefore, the common voltage of a set of voltage modules will be the sum of all its voltage modules that are in its first mode M1 . However, if the switching arrangement is in its second switching mode SW2 the voltage depot will be coupled in parallel with an voltage depot of an adjacent voltage module which means that the voltage of the voltage depot will be equalized with other voltage depots in the set of voltage modules that are in the second mode M2. Therefore, the voltage will be equalized among the voltage modules that are in the second mode M2. If all voltage modules of a set of voltage modules are coupled in parallel with each other the common or output voltage of the set will be zero.

In embodiments of the invention, each switching arrangement 120n includes three switches. Fig. 8 shows such switching arrangement 120a of a first voltage module 112a according to an embodiment of the invention. The switching arrangement 120a includes a first switch SW1 , a second switch SW2, and a third switch SW3 and is coupled between the first voltage module 112a and an adjacent second voltage module 112b. Therefore, the switching arrangement includes a first switch SW1 coupled between the first connection 116n of the voltage depot 114n and a first connection 116n of an adjacent voltage depot 114n, a second switch SW2 coupled between the second connection 118n of the voltage depot 114n and a second connection 118n of the adjacent the voltage depot 114n, and a third switch SW3 coupled between the first connection 116n of the voltage depot 114n and the second connection 118n of the adjacent the voltage depot 114n. Fig. 8 only shows first 112a and second 112b voltage modules for illustration but it is realised that a set of voltage modules can comprise any number of voltage modules.

In this case, the control arrangement 102 may be configured to control each switching arrangement 120n to operate in the first SM1 and second SM2 switching modes by controlling the first switch SW1 , the second switch SW2, and the third switch SW3, respectively. For example, in the first switching mode SM1 , the first switch SW1 and the second switch SW2 are switched OFF when the third switch SW3 is switched ON; and in the second switching mode SM2, the first switch SW1 and the second switch SW2 are switched ON when the third switch SW3 is switched OFF. A switch that is switched ON can be understood to fed/led current/voltage, i.e. allow current to pass through the switch, while a switch that is switched OFF can be understood to not fed/led any current/voltage, i.e. prevent current to pass through the switch.

With further reference to Fig. 8, the first switch SW1 is coupled between the first connection 116a of the first voltage depot 114a and the first connection 116b of the second voltage depot 114b, the second switch SW2 is coupled between the second connection 118a of the first voltage depot 114a and the second connection 118b of the second the voltage depot 114b, and the third switch SW3 is coupled between the first connection 116n of the first voltage depot 114a and the second connection 118b of the second voltage depot 114b. It is further noted that the first switch SW1 and the second switch SW2 are not switched at the same time instance as the third switch SW3, or vice versa, since this would result in a short circuit.

The control arrangement 102 may control the first switching arrangement 120a to operate in the first SM1 and second SM2 switching modes. As previously described, in the first switching mode SM1 , the first switch SW1 and the second switch SW2 are switched OFF when the third switch SW3 is switched ON. This means that the first voltage depot 114a is coupled in series with the second voltage depot 114b and hence that voltage can be added to the common voltage of the first set of voltage modules 112a, 112b,..., 112n. In the second switching mode SM2, the first switch SW1 and the second switch SW2 are switched ON when the third switch SW3 is switched OFF. Thus, the first voltage depot 114a is coupled in parallel with the second voltage depot 116b and hence that its voltage can be shared to one or more other voltage modules in the first set of voltage modules 112a, 112b,..., 112n. The common voltage of a set of voltage modules may be denoted as a common voltage or an output voltage of the set of voltage modules when the voltage depots are voltage depots, such as batteries, capacitors, and transformers.

The control arrangement 102 may further be configured to control each voltage module 112n to operate in a third mode M3 in which a voltage of the voltage depot 114n is measured. In this case, each voltage module 112n may comprise a measuring resistance R coupled in parallel to the second switch SW2 and between the second connection 118n of the voltage depot 114n and a second connection 118n of an adjacent voltage depot 114n. This is illustrated in Fig. 9.

The measuring resistance R may have the same value for all voltage modules and may be used for voltage sharing between different voltage modules. The measuring resistance R can e.g. be of SMD type which allows the transistors in each voltage module to be of LV type. If measuring resistance R is selected too large, the voltage distribution may be dependent on the leakage currents of the voltage module's other components. If measuring resistance R on the other hand is selected too little, the power consumption may be unnecessarily high. For example, the value may be higher than 1 kQ/V so that each 25V voltage module could have a value higher than 25kQ. This means a "leakage" of max 1 mA, which means loss of max 0.25W at 250V. By having the first SW1 , the second SW2 and the third switch SW3 in their OFF mode, the voltage can be measured over the second switch SW2. Such measurements can be used by the control arrangement 102 for determining relevant control parameters such as if the current is DC or AC, frequency of AC, amplitude, etc. Based on such control parameters the control arrangement 102 can decide when and what to couple to the external power consumer or power source. If the system 100 should be coupled to an external power consumer the output voltage of the system 100 at the port should be higher than the nominal voltage of the external power consumer so that the external power consumer will be fed with power by the system 100. On the other hand, if the system 100 should be coupled to an external power source the output voltage of the system at the port should be lower than the nominal voltage of the external power source so that the system 100 is fed by the external power source.

In other words, the control arrangement and hence the system 100 can be configured to:

• Obtain a nominal voltage of a power consumer or a power source,

• Obtain one or more measurements at one or more voltage modules,

• Determine control parameters, such as DC, AC, AC frequency and amplitude, based on the one or more measurements, and

• Control or adapt an output voltage or a common voltage of the system 100 to the nominal voltage of the power consumer or the power source based on the control parameters.

In embodiments of the invention, the system 100 comprises a controllable switch 130n coupled between the first set of voltage modules 112a, 112b,..., 112n and the second side S2 _Pi of the first port P1 as shown in Fig. 9. Also, the controllable switch 130n may be configured to be controlled by the control arrangement 102. In this respect, the control parameters may also be used for controlling the overlap circuit and its switches. When the controllable switch 130n is in ON mode the set of voltage modules are conductively coupled to the first port P1 .

It is further noted that voltage module 112a and 112c are in the second mode M2 while voltage module 112c is in the first mode in the example in Fig. 9. Thereby, the common voltage or the output voltage will be the voltage of voltage module 112b in this particular example.

With reference to Fig. 10, in embodiments of the invention, the system 100 further comprises at least one second set of voltage modules 122a, 122b, ... , 122n connected to the second side S2pi of the first port P1 . Each voltage module 122n in the second set of voltage modules 122a, 122b,..., 122n comprises an voltage depot 124n including a first connection 126n coupled to a first common line LT of the second set of voltage modules 122a, 122b,..., 122n and a second connection 128n coupled to a second common line L2 ^' of the second set of voltage modules 122a, 122b,..., 122n and a switching arrangement 126n coupled to the voltage depot 124n.

As shown in Fig. 10 the first common line L1 ^' of the second set of voltage modules 122a, 122b, ... , 122n is coupled to the first common line L1 of the first set of voltage modules 112a, 112b,..., 112n via an equalizing switch 410; and the second common line L2 ^' of the second set of voltage modules 122a, 122b,..., 122n is coupled to the second common line L2 of the first set of voltage modules 112a, 112b,..., 112n via an equalizing switch 410. The control arrangement 102 is configured to control each voltage module 122n in the second set of voltage modules 122a, 122b,..., 122n to operate in the first mode M1 or in the second mode M2. As previously mentioned for the first set of voltage modules the second set of voltage modules can comprise at least one voltage module with a nominal voltage value and at least one voltage module with variable voltage value so that the output voltage of the second set of voltage modules can be varied and adapted.

With reference to Fig. 11 and 12, according to embodiments of the invention, the system 100 may comprise a plurality of sets of voltage modules coupled to each other according to the above described principals. For simplicity, only the first L1 and the second L2 common line of the first set of voltage modules are shown but it is noted the first common line of each set of voltage modules are coupled to each other and correspondingly the second common line of each set of voltage modules are coupled to each other via switches of the type shown in Fig. 10.

In embodiments of the invention, the system 100 also comprises at least one second port P2 as shown in Fig. 11 , 12 and 13. The second port P2 includes a first side S1 p ₂ configured to be connected to an external voltage consumer 210 or to an external voltage depot 220 and a second side S2 _P2 coupled to at least one of the second common line L2 of the first set of voltage modules 112a, 112b,..., 112n and the second common line L2 ^' of the second set of voltage modules 122a, 122b,..., 122n.

Hence, the present system 100 may be coupled to a multiple ports P1 , P2,..., Pn which in turn are coupled to one or more external power consumers 210 or external power sources 220. An external power consumer may e.g. be an electrical load or an electrical motor. An external power source 220 may be configured to charge the system 100 with electrical power/energy, e.g. a wind power plant, a solar power plant, grid power system or any other suitable plant or power system. It is noted from Fig. 13 that a load 210 is coupled between P1 and P2. Further a positive voltage can be generated from port P1 to port P2 and a negative voltage from port P2 to port P1 . Hence, both positive and negative voltage can be generated.

With reference to Fig. 14 according to embodiments of the invention, the overlap transfer circuit 300 comprises a first controllable switch 130a configured to be coupled between the first set of voltage modules 112 and the load; and a second controllable switch 130b configured to be coupled between the second set of voltage modules 122 and the load.

With reference to Fig. 14 and Figs. 15-17 in embodiments of the invention: i) during a first time period T1 , the first controllable switch 130a is configured to feed a first current from the first set of voltage modules 112 to the load 200 when the second controllable switch 130b is configured to block a second current i ₂ from the second set of voltage modules 122 to the load 200; ii) during a second time period T2 following the first time period T1 , the first controllable switch 130a is configured to feed a first current i _t from the first set of voltage modules 112 to the load 200 when the second controllable switch 130b is configured to feed a second current i ₂ from the second set of voltage modules 122 to the load 200; and iii) during a third time period T3 following the second time period T2, the first controllable switch 130a is configured to block a first current i _t from the first set of voltage modules 112 to the load 200 when the second controllable switch 130b is configured to feed a second current i ₂ from the second set of voltage modules 122 to the load 200. The second time period T2 therefore defines a time period when both the first and second power sources delivers current to the load 200 at the same time. This time period may therefore be denoted an overlap power transfer time period or overlap time period. It is known that in conventional solutions the power transfer is not overlapping but instead separated using so called deadtimes. More about this will be explained in the following disclosure.

Further, in embodiments of the invention, iv) during a fourth time period T4 following the third time period T3, the first controllable switch 130a is configured to feed a first current i _t from the first set of voltage modules 112 to the load 200 when the second controllable switch 130b is configured to feed a second current i ₂ from the second set of voltage modules 122 to the load 200. This case is not shown in the Figs but it is understood that the fourth time period T4 is also an overlap time period when both the first and second sets of voltage modules feed/supply current to the load 200 at the same time. Moreover, steps i) to iv) described previously may be repeated any number of times.

It is also herein disclosed different methods for switching between the steps i) to iv) by using the overlap circuit and its switches. As previously described mentioned parameters, thresholds and relations therebetween can be employed, i.e. the first threshold voltage V™, the second threshold voltage V _Th 2, nominal voltages V _n , difference between voltages, etc.

In embodiments of the invention, the first controllable switch 130a is configured to receive first control signals CTRL1 and the second controllable switch 130b is configured to receive second control signals CTRL2, so that both the first controllable switch 130a and the second controllable switch 130b both are conductive during an overlap time period, wherein the first control signals CTRL1 and the second control signals CTRL2 are simultaneous or non- simultaneous clocked. The control signals may be provided by the previously describe control arrangement 102. In case the first control signals CTRL1 and the second control signals CTRL2 are non-simultaneous clocked, a time offset between the first and second control signals may depend on at least one of: a current provided to a power consumer, currents provide by a power source to the first and second sets of voltage modules, and a difference in output voltage between the first and second sets of voltage modules. In yet further embodiments of the invention, the offset may also be dependent on the mentioned control parameters obtained by using the measurement modes of the voltage modules.

More specifically, the first control signals CTRL1 and the second control signals CTRL2 may comprise ON signals and OFF signals, e.g. ones and zeros (1/0). An ON signal sets a controllable switch, such as the first controllable switch 130a and second controllable switch 130b, in a conductive mode and an OFF signal sets a controllable switch in a non-conductive mode. Flence, in the conductive mode a current can pass through the controllable switch while in the non-conductive more the current is blocked and cannot pass through the controllable resistor device. With this reasoning the first control signals CTRL1 and the second control signals CTRL2 may be simultaneous or non-simultaneous clocked in relation to each other which may mean that the first and second control signals are sent or received at the same time instance or in different time instances. Both simultaneous or non-simultaneous clocked control signalling works well. In the latter case when the first control signals CTRL1 and the second control signals CTRL2 are non-simultaneous clocked there is a time offset between CTRL1 and CTRL2. The frequency, clocking and time offset may be determined based on the mentioned control parameters.

Fig. 19 shows control signalling according to prior art while Fig. 20 shows examples of control signalling according to embodiments of the invention. In Fig. 19 and 20, the x-axis shows time and the y-axis OFF state and ON state of respective controllable switches. It may be noted that when a control signal is received by a controllable switch there is always a delay from non conductivity to fully conductivity mode or state, or vice versa, which may be denoted raise time and fall time before the component is in fully conductive mode (ON) or in blocking mode (OFF). Further, a switch may also be represented as variable resistance having a varying resistivity with mentioned raise and fall times.

In Fig. 19, it is shown exemplary deadtimes DTs, i.e. DT1 - DT4, according to prior art. During such deadtimes no current is provided to a load since both resistors are in non-conductive or blocking mode, i.e. OFF. Between the deadtimes, each switch passes or feeds a current to the common load but never at the same time. Flence, during time period ON1 only a first switch is in ON state is passing current to the load. After deadtime DT2 during time period ON2 only a second switch is in ON state is passing current to the load as shown in Fig. 19.

Fig. 20 on the other hand shows when the first and second controllable switches are controlled according to embodiments of the invention with overlapping power transfer conductivity. It is firstly noted that no deadtimes exists at all in Fig. 20. This may be formulated such that there is no time period when both the first and second controllable switches are in non-conductive mode, i.e. in OFF state. Further, overlap or overlapping time periods are shown in Fig. 20, and during such an overlap power transfer time period both the first (ON state) and second (ON state) controllable switches are conductive and hence pass current to the load at the same time period. For example, during a first time period T 1 the first controllable switch is conductive when the second controllable switch is non-conductive, and during the second time period T2 both the first and second controllable switches are conductive. It is however to be noted that during the second time period T2, the resistance R1 of the first controllable switch is raising from fully conductive to fully non-conductive state while the resistance R2 of the second controllable switch is decreasing from fully non-conductive to fully conductive state. This also means that the current via the first controllable switch will decrease accordingly and the current via the second controllable switch will increase accordingly during the second time period T2. During the third time period T3 the second controllable switch is conductive when the first controllable switch is blocking.

It may further be noted that there is a certain time instance when the first and second controllable switches will have the same resistance values marked Tl in Fig. 20, and Fig. 21 shows more in detail such time instances disclosing two different examples TI1 and TI2. The vertical lines in Fig. 21 illustrates control signal CTRL1 , CTRL2 instances or clocking instances. In a first example the control signals for the first and second controllable switches are simultaneously clocked, denoted “Sim.” in Fig. 21 , compared to a second example in which the control signals are non-simultaneously clocked, denoted “non-sim.” in Fig. 21 . In the first example in Fig. 21 during a first time period T1 only the first controllable switch is conductive. During second timer period T2 when Sim. 1 is clocked R1 starts to increase and at the same time R2 starts to decrease and both first and second controllable switches are hence conductive during T2. At time instance TI1 , the resistivity of R1 equals R2, R1 =R2. During the third time period T3 only the second controllable switch is conductive and the first controllable switch is therefore blocking. Hence, this is an example when there is no time offset in the clocking of control signals CTRL1 and CTRL2.

In the second example in Fig. 21 , the situation during the first timer period T1 is the same as in the first example. However, during time period T2 ^' a clocking time offset is introduced between CTRL1 and CTRL2 signals which may mean that time period T2 ^' is extended in time compared to time period T2. During time period T2 ^' the value of RT is increasing while the value of R2 is decreasing. The clocking offset means that a time instance TI2 when the resistivity of RT equals R2, R1 ^' =R2, is offset in time leading to a lower resistivity and hence higher current compared to the first example. Thereby, the current delivered to the load can be controlled by controlling the time offset. It has therefore been realised that the time offset may be dependent on at least one of: a current provided to the load 210, a voltage difference between the first and second sets of voltage modules, a resistance value when a resistance R1 of the first controllable switch 130a equals a resistance R2 of the second controllable switch 130b.

The switches herein may be any suitable switches known in the art. For example, solid state transistors, such as MOSFET or any other transistor types. The selected switch may depend on the application e.g. being high voltage or low voltage switches. For example, the switches in each module may be of a first type, the equalizing switches may be of a second type, and the controllable switches in an overlap transfer circuit may be of a third type, but they may also be of the same type. The high voltage switches may be any suitable high voltage switches known in the art. They should be able to handle much higher voltages than the switches in the voltage modules. For example, they could be able to handle voltages from 25 V up to 600 V if each voltage module provides 25 V.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.