Technical Field

The present invention relates to power control systems, and in particular, but not exclusively, to controlling the rate and direction of power flow between an electrical network and a power storage module.

Background

Power distribution systems, such as a mains electricity grid, are used to deliver power to electrical loads, such as those associated with particular commercial or residential properties. The power demanded by the various electrical loads connected to a power distribution system typically contains a number of peaks and troughs over a given period of time. For example, on a weekday, the power demand attributable to residential properties may peak in the morning and in the evening, but be relatively low during the middle of the day and throughout the night.

Accommodating such demand fluctuation places a significant burden on power generation and distribution systems, and creates undesirable inefficiencies in the system. For example, a power generation system requires capacity to deliver the peak power demand from connected electrical loads, on demand, despite only being required to supply this power for a relatively small percentage of the time. Furthermore, the volatility of the power demanded by the various electrical loads makes it impractical to predict the exact power demand at any given point in time. This demand level volatility has been exacerbated in recent years by the introduction of an increased volume of renewable energy sources, which add unreliable levels of power generation into the power distribution system.

The increasing peak demand levels and volatility experienced by power distribution systems requires significant development in terms of increasing the capacity overhead of power generation and distribution systems. Therefore, it would be desirable to provide measures which could alleviate this pressure on power distribution systems. Summary

According to a first aspect of the present invention, there is provided a power control circuit for controlling power flow between a power storage module and an electrical network, the power control circuit comprising:

an electrical network interface for connecting the power control circuit to the electrical network, the electrical network interface comprising a live terminal and a neutral terminal;

a power storage interface for connecting the power control circuit to the power storage module, the power storage interface comprising a positive voltage terminal, a negative voltage terminal and a zero voltage terminal;

an internal connection, electrically connecting the neutral terminal of the electrical network interface to the zero voltage terminal of the power storage interface; an inductive component, electrically connecting the live terminal of the electrical network interface to a signal generation node; and

a controllable switching arrangement, controllable to selectively connect the positive voltage terminal or the negative voltage terminal of the power storage interface to the signal generation node,

wherein the switching arrangement is controllable to generate an alternating current signal at the signal generation node, wherein the generated alternating current signal is synchronised with an alternating current signal provided in the electrical network, and

wherein the switching arrangement is controllable in relation to the alternating current signal provided in the electrical network whereby to control the direction and rate of power flow between the electrical network and the power storage module via the inductive component.

According to a second aspect of the present invention, there is provided a method of operating a power control circuit to control power flow between a power storage module and an electrical network, the power control circuit comprising an electrical network interface for connecting the power control circuit to the electrical network and a power storage interface for connecting the power control circuit to the power storage module, the electrical network interface comprising: a live terminal, electrically connected to a signal generation node via an inductive component; and

a neutral terminal, electrically connected to a zero voltage terminal of the power storage interface,

the method comprising:

controlling a controllable switching arrangement to selectively connect a positive voltage terminal or a negative voltage terminal of the power storage interface to the signal generation node;

controlling the controllable switching arrangement to generate an alternating current signal at the signal generation node,

controlling the controllable switching arrangement to synchronise the generated alternating current signal with an alternating current signal provided in the electrical network; and

controlling the controllable switching arrangement to adjust the generated alternating current signal in relation to alternating current signal provided in the electrical network whereby to control the direction and rate of power flow between the electrical network and the power storage module via the inductive component.

According to a third aspect of the present invention, there is provided a computer program product (for example computer software) adapted to perform the method of the second aspect of the present invention.

Embodiments comprise a computer program product comprising a non- transitory computer-readable storage medium having computer readable instructions stored thereon, the computer readable instructions being executable by a computerised device to cause the computerised device to perform the method of the first aspect of the present invention.

According to a fourth aspect of the present invention, there is provided a power control system for controlling power flow in an electrical network, the power control system comprising:

a plurality of power control circuits;

a plurality of power storage modules, each said power storage module corresponding to a said power control circuit; and a central remote control entity, responsible for configuring each said power control circuit,

wherein each said power control circuit comprises:

an electrical network interface for connecting the power control circuit to the electrical network, the electrical network interface comprising a live terminal and a neutral terminal;

a power storage interface for connecting the power control circuit to the respective corresponding power storage module, the power storage interface comprising a positive voltage terminal, a negative voltage terminal and a zero voltage terminal;

an internal connection, electrically connecting the neutral terminal of the electrical network interface to the zero voltage terminal of the power storage interface; an inductive component, electrically connecting the live terminal of the electrical network interface to a signal generation node; and

a controllable switching arrangement, controllable to selectively connect the positive voltage terminal or the negative voltage terminal of the power storage interface to the signal generation node,

wherein each switching arrangement is controllable to generate an alternating current signal at the respective signal generation node, the generated alternating current signal being synchronised with an alternating current signal provided in the electrical network,

wherein each switching arrangement is controllable in relation to the alternating current signal provided in the electrical network whereby to control the direction and rate of power flow between the electrical network and the respective corresponding power storage module via the respective inductive component.

According to a fifth aspect of the present invention, there is provided a power control circuit for controlling power flow between a power storage module and an electrical network, the power control circuit comprising:

an electrical network interface for connecting the power control circuit to the electrical network, the electrical network interface comprising a live terminal and a neutral terminal; a power storage interface for connecting the power control circuit to the power storage module, the power storage interface comprising a positive voltage terminal, a negative voltage terminal and a zero voltage terminal;

an internal connection, electrically connecting the neutral terminal of the electrical network interface to the zero voltage terminal of the power storage interface; an inductive component, electrically connecting the live terminal of the electrical network interface to a signal generation node; and

a controllable switching arrangement, controllable to selectively connect the positive voltage terminal or the negative voltage terminal of the power storage interface to the signal generation node,

wherein the switching arrangement is controllable to generate an alternating current signal at the signal generation node, wherein the generated alternating current signal is synchronised with an alternating current signal provided in the electrical network, and

wherein the switching arrangement is controllable in relation to the alternating current signal provided in the electrical network whereby to control the direction and rate of power flow between the electrical network and the power storage module via the inductive component

wherein the controllable switching arrangement comprises:

a first controllable switching element for selectively connecting the positive voltage terminal of the power storage interface to the signal generation node,

a second controllable switching element for selectively connecting the negative voltage terminal of the power storage interface to the signal generation node, and

a third controllable switching element for selectively connecting the zero voltage terminal of the power storage interface to the signal generating node. According to a sixth aspect of the present invention, there is provided apparatus substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings. According to a seventh aspect of the present invention, there is provided methods substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a block diagram of an electrical network in which embodiments of the invention may be practiced,

Figure 2 illustrates a schematic diagram of power control circuit 110 according to embodiments,

Figure 3 illustrates the operation of a controllable switching arrangement for generating an alternating current signal according to embodiments,

Figure 4 shows a block diagram of an electrical network in which embodiments of the invention may be practiced,

Figure 5 illustrates a schematic diagram of a portion of a power control circuit according to embodiments,

Figure 6 illustrates a schematic diagram of a portion of a power control circuit according to embodiments,

Figure 7 illustrates a schematic diagram of a portion of a power control circuit according to embodiments, and

Figure 8 illustrates a schematic diagram of a portion of a power control circuit according to embodiments.

Detailed Description

Figure 1 is a block diagram of an electrical network 100 in which embodiments of the invention may be practiced. Electrical network 100 includes a power distribution system 102 and an electrical load 104. In some embodiments, power distribution system 102 comprises a connection to a mains electricity grid. In some embodiments, electrical load 104 comprises, or is attributable to, one or more electrical appliances associated with a consumer premises, such as a residential building. Electrical network 100 provides interconnection between power distribution system 102 and electrical load 104, which comprises a live connection 108 and a neutral connection 106. In some such embodiments, the electrical network is a single-phase network.

Power control circuit 110 is connected to the live and neutral connections of electrical network 100. In some embodiments, power control circuit 110 is connected to electrical network 100 between power distribution system 102 and electrical load 104. Power control circuit 110 interfaces between electrical network 100 and power storage module 112, in order to control the direction and rate of power flow between power storage module 112 and electrical network 100. In some embodiments, both real and reactive power are controlled together. In some embodiments, real and reactive power are controlled separately.

In some embodiments, power control circuit 110 interfaces between electrical network 100 and power storage module 112, in order to control the direction and rate of current flow between power storage module 112 and electrical network 100.

In embodiments, power storage module 112 comprises one or more power storage cells, such as batteries. In further embodiments, power storage module 110 may comprise further power storage means, such as high capacity capacitors, or so called 'super-capacitors' .

Figure 2 illustrates a schematic diagram of power control circuit 110 according to embodiments. Power control circuit 110 includes electrical network interface 200 for connecting power control circuit 110 to electrical network 100. Electrical network interface 200 includes live terminal 204 for connecting power control circuit 110 to the live connection 108 of electrical network 100, and neutral terminal 202 for connecting power control circuit 110 to the neutral connection 106 of electrical network 100.

Power control circuit 110 also includes power storage interface 206 for connecting power control circuit 110 to power storage module 112. Power storage interface 206 includes positive voltage terminal 208, zero voltage terminal 210, and negative voltage terminal 212. Zero voltage terminal 210 is so-called because it is used as a reference or notional 'zero' voltage for power control circuit 110. Positive voltage terminal 208 and negative voltage terminal 212 are so-called because they are configured to operate with positive and negative voltages respectively with reference to zero voltage terminal 210. In embodiments, zero voltage terminal 210 is electrically connected to neutral terminal 202 of electrical network interface 200 via internal connection 236. In this manner, the notional 'zero' voltage reference of power control circuit 110 may be considered to be 'tied' to the neutral voltage of electrical network 100.

In embodiments, power control circuit 110 comprises a common mode filter. In embodiments, power control circuit 110 comprises a common mode choke between the power control circuit terminals and the electrical network terminals. In embodiments, power control circuit comprises an inductor connected between neutral terminal 202 and zero voltage terminal 210 coupled to an inductor connected between live terminal 204 and inductor 234.

Power storage module 112 may comprise one or more cells. According to the embodiments depicted in Figure 2, power storage module 112 comprises battery arrangements 214, 216, in this case battery arrangements, connected in series. In embodiments, each battery arrangement 214, 216 may comprise one or more cells. Battery arrangement 214 is connected between positive voltage terminal 208 and zero voltage terminal 210 of power storage interface 206, such that the positive voltage terminal 208 has a positive voltage with reference to zero voltage terminal 210. Battery arrangement 216 is connected between zero voltage terminal 210 and negative voltage terminal 212 of power storage interface 206, such that the negative voltage terminal 212 has a negative voltage with reference to zero voltage terminal 210. In some embodiments (not shown) power storage module 112 may comprise a single battery arrangement, with a 'centre-tap' connection. In such embodiments, the positive terminal of the battery arrangement may be connected to positive voltage terminal 208, the negative terminal of the battery arrangement may be connected to negative voltage terminal 212, and the centre-tap terminal of the battery arrangement may be connected to zero voltage terminal 210. In further embodiments (not shown) one of battery arrangement 214 and battery arrangement 216 may be replaced with a buck-boost converter arrangement, configured to generate the respective positive or negative voltage terminal 208, 212, without the need for a second battery arrangement.

In some embodiments (not shown), a boost converter may be used in conjunction with one or more of battery arrangement 214 and battery arrangement 216 to increase the magnitude of the voltage at positive voltage terminal 208 and/or negative voltage terminal 212. Such embodiments are described in more detail below in relation to Figures 5 to 8.

In some embodiments, one or more of battery arrangement 214 and battery arrangement 216 may comprise one or more super-capacitors in addition to, or instead of, conventional cell batteries.

Power control circuit 110 includes controllable switching arrangement 218, which is controllable to selectively connect the positive voltage terminal 208 or the negative voltage terminal 212 of power storage interface 206 to signal generation node 220. In embodiments, controllable switching arrangement 218 comprises controllable switching element 222, for selectively connecting positive voltage terminal 208 of power storage interface 206 to signal generation node 220, and controllable switching element 224 for selectively connecting negative voltage terminal 212 of power storage interface 206 to signal generation node 220. In embodiments, controllable switching arrangement 218 comprises a 'half bridge' switching arrangement. Controllable switching elements 222 and 224 may be controlled through the use of control signals applied via switch control terminals 226 and 228 respectively. In some embodiments, controllable switching elements 222 and 224 comprise Insulated Gate Bipolar Transistor (IGBT) switches. In some embodiments, alternative controllable switching elements may be used, such as Field Effect Transistor (FET) based switches. In embodiments, antiparallel diodes 230, 232 may be provided in parallel with controllable switching elements 222 and 224, in order to allow for 'free-wheeling' currents to flow while the controllable switching elements are off (i.e. 'open').

Through control of switching arrangement 218, an alternating current signal may be generated at signal generation node 220, as described in further detail below in relation to Figure 3. Signal generation node 220 is electrically connected to live terminal 204 of electrical network interface 200 via inductive component 234, through which power may flow between electrical network 100 and power storage module 112. In embodiments, inductive component 234 comprises a line inductor. In embodiments, inductive component 234 may comprise electrically resistive as well as inductive properties.

Figure 3 illustrates the operation of controllable switching arrangement 218 for the generation of alternating current signal 300 at signal generation node 220 according to embodiments. Graph 3 A shows the operation of switching element 222, graph 3B shows the operation of switching element 224, and graph 3C shows the resulting alternating current signal 300 generated at switching node 220, according to embodiments. Graphs 3A and 3B show example control signals suitable for controlling switching elements 222 and 224, for example via switch control terminals 226 and 228 respectively. In the embodiments depicted in Figure 3, a relatively high signal level on graph 3A or 3B indicates that the respective switching element 222, 224 is controlled to be on (i.e. 'closed'), whereas a relatively low signal level indicates that the respective switching element is controlled to be off (i.e. open'). In the embodiments depicted in Figure 3, switching elements 222 and 224 are switched in anti-phase, in order to prevent both switching elements from being on (i.e. 'closed') at the same time, which may cause a short circuit in power control circuit 110.

Switching arrangement 218, including switching elements 222 and 224, is controlled to generate alternating current signal 300 at signal generation node 220 which tracks a target current waveform. In the embodiments depicted in Figure 3, the target current waveform is approximately a sine wave. In embodiments, switching elements 222 and 224 are switched at a frequency greater than the frequency of the target current waveform and/or generated signal 300. The duty cycle, i.e. the amount of time that each switching element is on (i.e. 'closed') during each period of the switching frequency is varied over the course of one period of the target current waveform in order to control the shape of generated signal 300. The relative amounts of time for which each of positive voltage terminal 208 and negative voltage terminal 212 are connected to signal generation node 220 within a period of the switching frequency is adjusted to shape the generated alternating current signal 300 to follow the target current waveform.

With reference to Figure 3, the timespan between to and t ₂ shows one period of generated signal 300. The timespan between to and ti shows a positive half-cycle of generated signal 300, whereas the timespan between ti and t ₂ shows a negative half- cycle of generated signal 300. During the depicted positive half cycle, the duty cycle of switching element 222 increases in the region of the peak of the generated signal 300, whereas the duty cycle of switching element 224 decreases in the same region. In this region, positive voltage terminal 208 is connected to signal generation node 116 for more of the switching period than negative voltage terminal 212, therefore generating a higher positive current in generated signal 300. Conversely, during the depicted negative half cycle, the duty cycle of switching element 222 decreases in the region of the trough of the generated signal 300, whereas the duty cycle of switching element 224 increases in the same region. In this region, negative voltage terminal 212 is connected to signal generation node 116 for more of the switching period than positive voltage terminal 208, therefore generating a higher negative current in generated signal 300. In some embodiments, the duty cycles of switching elements 222, 224 are changed continuously between the peaks and troughs in the target current waveform / generated signal 300, to enable the target current waveform to be tracked more smoothly by generated signal 300.

In the embodiments described above, switching elements 222 and 224 are both on (i.e. "closed") for a portion of both the positive and negative half cycles of the target current waveform / generated signal 300. Such operation may be referred to as a bipolar switching scheme. In alternative embodiments (not shown), switching element 224 may remain off (i.e. "open") for the duration of the positive half cycle of the target current waveform / generated signal 300, and switching element 222 may remain off (i.e. "open") for the duration of the negative half cycle of the target current waveform / generated signal 300. In such embodiments, switching element 222 is on (i.e. "closed") for varying portions of the positive half cycle, and switching element 224 is on (i.e. "closed") for varying portions of the positive half cycle, as previously described in relation to Figure 3. Such operation may be referred to as a unipolar switching scheme.

Controllable switching arrangement 218 is controllable to adjust generated alternating current signal 300 in relation to the alternating current signal provided in electrical network 100. In embodiments, control of controllable switching arrangement 218 comprises controlling the duty cycles of the switching elements 222, 224. In some embodiments, the duty cycles of switching elements 222, 224 are dynamically changed over time in order to cause generated alternating current signal 300 to more closely track the target current waveform. For example, if generated signal 300 is below the target current at a given point during a positive half cycle of the target current waveform, then switching element 222 may be kept on (i.e. closed) for a longer portion of the switching period in order to increase the current of generated signal 300. In embodiments, switching elements 222 and 224 are switched such that a guard period is included between a switching element being switched off and the next switching element being switched on, as depicted in Figure 3. Such guard periods accommodate for transition periods between the on state (i.e. closed) and off state (i.e. open) of switching elements 222, 224, during which some current may flow through the respective switching element.

Switching arrangement 218 is controlled such that generated signal 300 is synchronised with a signal provided in electrical network 100. In some such embodiments, the signal provided in electrical network 100 is a mains electricity signal associated with power distribution system 102. Therefore, in embodiments, the target current waveform is configured to be synchronised with the signal provided in electrical network 100. In embodiments, synchronisation of the target current waveform and/or generated signal 300 with the signal provided in electrical network 100 comprises the signals having substantially the same frequency. In some embodiments, synchronisation of the target current waveform and/or generated signal 300 with the signal provided in electrical network 100 comprises the signals having a defined phase relationship.

As described above, in embodiments, the switching frequency of switching arrangement 218 is higher than the frequency of one or more of the target current waveform and generated signal 300. Therefore, in some embodiments, the switching frequency of switching arrangement 218 is higher than the frequency of the signal provided in electrical network 100. In the embodiments depicted in Figure 3, the switching frequency of controllable switching arrangement 218 is eight times higher than the frequency of generated signal 300. However, in some embodiments the switching frequency of controllable switching arrangement 218 is significantly higher than this. In some embodiments, the switching frequency of switching arrangement 218 is more than 100 times greater than the frequency of one or more of the target current waveform, generated signal 300 and the signal provided in electrical network 100. In some embodiments, the switching frequency of switching arrangement 218 may be in the region of 18 kHz. The relatively low switching frequency depicted in Figure 3 is shown in order to aid intelligibility of the figures and assist in the reader's understanding of the disclosure. In embodiments, switching arrangement 218 is further controlled to adjust generated alternating current signal 300 in relation to the alternating current signal provided in electrical network 100, in order to control the direction and rate of power flow between electrical network 100 and the power storage module 112 via inductive component 234. The alternating current signal generated at signal generation node 220 controls the rate and direction of current flow via inductive component 234, and therefore the power flow between electrical network 100 and the power storage module 112.

The characteristics of generated alternating current signal 300 relative to the alternating current signal provided in electrical network 100, control the direction and rate of power flow between electrical network 100 and the power storage module 112. For example, where alternating current signal 300 is generated in phase with the alternating current signal provided in electrical network 100, then power will flow from power storage module 112 into electrical network 100 via inductive component 234. Where alternating current signal 300 is generated 180° out of phase (or in-phase, but with a negative amplitude) with respect to the alternating current signal provided in electrical network 100, then power will flow from electrical network 100 into power storage module 112 via inductive component 234. In such embodiments, the magnitude of generated current signal 300 determines the rate of power flow between electrical network 100 and power storage module 112 via inductive component 234.

Hence, according to embodiments, power control circuit 110 provides measures for controlling the power flow between electrical network 100 and power storage module 112. During operation of power control circuit 110, the current flowing through inductive component 234 sums with the current flowing in electrical network 100, i.e. the current drawn by electrical load 104. In this manner, the power demand placed on power distribution system 102 may be modified through the use of power control circuit 110. Hence, embodiments of the present disclosure enable the demand placed on power distribution system 102 to be decoupled from the actual power consumed by electrical load 104. For example, in order to reduce the demand on power distribution system 102, power control circuit 110 may cause power to flow from power storage module 112 into electrical network 100. Conversely, the demand on power distribution system 102 may be increased by power control circuit 110 through causing power to flow from electrical network 100 into power storage module 112. It will be seen that in this manner, power control circuit 110 may be used to smooth the demand profile of electrical load 104 on power distribution system 102, by charging power storage module 112 when the power consumed by electrical load 104 is relatively low, and discharging power storage module 112 when the power consumed by electrical load 104 is relatively high. Such a system does not require modification of the power consumption behaviour of the electrical load. In some arrangements, the power that can be transferred from power storage module 112 into electrical network 100 may exceed the simultaneous power consumption of electrical load 104. In such embodiments, power control circuit 110 may be used to supply power back into power distribution system 102.

In addition, the architecture of power control circuit 110 in some embodiments enables a power control circuit to be deployed which is relatively small and low cost, in comparison to conventional circuits used in solar power storage for example. Such known circuits may typically use so-called 'H-bridge' inverter arrangements, and relatively low voltage batteries for power storage. In contrast to these systems, embodiments require relatively fewer switching elements 222, 224. Further, utilising a power storage module 112 which operates at the voltage level of the alternating current signal provided in electrical network 100 enables efficient and compact power storage and conversion, and allows the use of a transformer to be avoided.

In some embodiments, power control circuit 110 may include one or more power storage interface filters (not shown) arranged between controllable switching arrangement 218 and power storage interface 206. Such power storage filters act to isolate power storage module 112 from one or more high frequency components of generated signal 300. Such high frequency components of generated signal 300 may result from the high switching frequency of controllable switching arrangement 218, for example. In some embodiments, power control circuit 110 may additionally, or alternatively, include one or more electrical network interface filters (not shown) arranged between controllable switching arrangement 218 and electrical network interface 200. Such electrical network interface filters act to isolate electrical network 100 from one or more high frequency components of generated signal 300. In some embodiments, power control circuit 110 may be provided as part of a power control apparatus which also includes power storage module 112.

As described above, in embodiments, controllable switching arrangement 218 is controllable to synchronise generated alternating current signal 300 with the alternating current signal provided in electrical network 100. In embodiments, control of controllable switching arrangement 218 comprises controlling the switching frequency of the controllable switching arrangement. In some embodiments, the switching frequency of switching elements 222 and 224 may be dynamically adjusted over time in order to maintain synchronisation with the alternating current signal provided in electrical network 100. For example, if the frequency of generated alternating current signal 300 is greater than the frequency of the alternating current signal provided in electrical network 100, then the switching frequency of controllable switching arrangement may be decreased to compensate. Conversely, if the frequency of the alternating current signal provided in electrical network 100 is greater than the frequency of generated alternating current signal 300, then the switching frequency of controllable switching arrangement may be increased to compensate. By adjusting the switching frequency of controllable switching element 218 in this manner, fine adjustments can be made to the frequency of generated signal 300 in order to maintain synchronisation with the alternating current signal provided in electrical network 100.

In embodiments, synchronisation of generated alternating current signal 300 with the alternating current signal provided in electrical network 100 is achieved through the detection of one or more zero-crossing points of the alternating current signal provided in electrical network 100. The difference between the zero crossing points of the alternating current signal provided in electrical network 100 and generated alternating current signal 300 may be compared with the intended phase difference of the target current waveform, and appropriate adjustments made to the frequency of generated signal 300 to correct for discrepancies.

As described above, where alternating current signal 300 is generated in-phase, or 180° out of phase with respect to the alternating current signal provided in electrical network 100, the power flow between electrical network 100 and power storage module 112 may be considered 'real' power, as the power flow has a negligible reactive component. However, in some embodiments, the target current waveform, and therefore generated alternating current signal 300, may be configured with a defined phase shift with relation to the alternating current signal provided in electrical network 100; in such embodiments, the power flow between electrical network 100 and power storage module 112 may be considered 'reactive' power, as the power flow has a not insignificant reactive component. Such a reactive power flow may be configured to offset a reactive demand presented by electrical load 104, for example.

Figure 4, shows a block diagram of an electrical network 100 in which further embodiments of the invention may be practiced. Elements of Figure 4 with the same reference numerals numbers are as previously described in relation to Figures 1 to 3, unless described otherwise hereafter. In the embodiments depicted in Figure 4, power control circuit 110 further comprises control module 400. In embodiments, control module 400 is responsible for controlling controllable switching arrangement 218. In some such embodiments, power control module is configured to supply control signals to switch control terminals 226 and 228. In some such embodiments, the control signals are pulse width modulated (PWM) signals. The control signals may be configured by control module 400 to control the switching frequency and/or duty cycles of switching elements 222 and 224.

In some embodiments, power control circuit 110 comprises one or more signal sensors. In the embodiments depicted in Figure 4, power control circuit 110 comprises power distribution signal sensor 402, load signal sensor 404, and power storage signal sensor 406. Power distribution signal sensor 402 is configured to measure one or more of the current and the power drawn from power distribution system 102, load signal sensor 404 is configured to measure one or more of the current and the power drawn by the electrical load, and power storage signal sensor 406 is configured to measure one or more of the current and the power drawn by the power storage module. In embodiments, through the use of one or more of signal sensors 402, 404 and 406, control module 400 is capable of monitoring the flow of power in electrical network 100. In some embodiments, power control circuit 110 comprises two of signal sensors 402, 404 and 406. In such embodiments the third measurement may be derived by summing the current/power values measured by the two existing sensors.

In some embodiments, power control circuit 110 comprises at least one sensor 402, 404, 406 configured to measure the alternating current signal provided in electrical network 100. In such embodiments, power control module 400 may be configured to utilise the at least one sensor to detect zero-crossings of the alternating current signal provided in electrical network 100. The detected zero-crossings may then be used for synchronisation of generated alternating current signal 300 with the alternating current signal provided in electrical network 100, as described previously above. In some embodiments, control module 400 comprises a phase-locked loop (PLL) arrangement for performing the synchronisation.

In embodiments, control module 400 is responsible for configuring the target current waveform. In further embodiments, control module 400 is configured to adjust the target current waveform in order to control power flow between electrical network 100 and power storage module 112, and thereby modify the power demand from power distribution system 102 by electrical load 104. In this manner, control module 400 is capable of generating a modified demand profile for electrical load 104. In such embodiments, control module 400 may be configured to monitor the power consumed by electrical load 104, for example through the use of load signal sensor 404, or by summing the measurements made by power distribution signal sensor 402 and power storage signal sensor 406, and modify the power flow between electrical network 100 and power storage module 112 in order to maintain a target demand profile for electrical load 104.

According to embodiments, the target demand profile may comprise an averaged demand profile for electrical load 104, which aims to smooth the demand drawn from power distribution system 102 to a flat line (or an approximation thereof). In some embodiments, the target demand profile may comprise a peak capped demand profile, which aims to prevent the power drawn from power distribution system 102 from exceeding a pre-determined maximum value. For example, a peak capped demand profile may be achieved by supplying power from power storage module 112 into electrical network 100 when electrical load 104 is consuming peak power. In some embodiments, the target demand profile may comprise a banded demand profile, which aims to prevent the power drawn from power distribution system 102 from both exceeding a pre-determined maximum value and falling below a predetermined minimum value. In further arrangements, the target demand profile may comprise a time-shifted demand profile, which aims to move the peak power consumption to a time when demand is relatively low. In some embodiments, the target demand profile may comprise a reactive demand profile, which is configured to counteract a reactive power demand in electrical network 100. In yet further embodiments, further predetermined demand profiles may be configured.

In some embodiments, power control circuit 110, may be configured to detect changes in the alternating current signal provided in electrical network 100, for example via power distribution signal sensor 402, and adjust demand profile of electrical load 104 to help compensate for such changes. Such changes may include variances in the frequency or shape of the alternating current signal provided in electrical network 100. In this manner, power control circuit 110 can be considered to provide virtual inertia to power distribution system 102.

In embodiments, power control circuit 110 may be configured to receive override messages from a remote control entity (not shown), for example via a telecommunications network such as the internet. In some embodiments, control module 400 is configured to receive such override messages. In response to receipt of an override message, control module 400, or more generally power control circuit 110, is configured to override the target demand profile. In this manner, if the power distribution network is experiencing an unusual aggregate demand from the various electrical loads in the system, then power control circuit 110 can be remotely triggered to modify the power flow between electrical network 100 and power storage module 112 to help mitigate the unusual demand. For example, if the power distribution network is experiencing an unusually high aggregate demand from the various electrical loads that it supplies power to, an override message may be transmitted from the remote control entity to power control circuit 110. This override message may instruct power control circuit 110 to transfer power from power storage module 112 into electrical network 100 in order to help alleviate the demand on the power distribution network. In embodiments, the remote control entity is associated with an operator of power distribution system 102.

In some embodiments, a plurality of power control circuits may be provided, each arranged with a corresponding electrical load, in order to provide a combined effect on the overall demand on a power distribution network. In this manner, multiple relatively low capacity power storage modules can be aggregated to create a large power storage and demand modification resource for the power distribution network. In embodiments, the plurality of power control circuits may be configured in combination to achieve a desired demand modification for the power distribution network. In some embodiments, each of the power control circuits in the plurality may be remotely configurable by a central remote control entity.

In some embodiments, electrical network 100 comprises local power generator 408. In some such embodiments, local power generator 408 is attributable to the same commercial or consumer premises as electrical load 104. In embodiments, local power generator 408 comprises a solar power generator, a hydro-electric power generator or a wind power generator. In some embodiments, local power generator 408 comprises a so-called 'local micro-generator' . In such embodiments, power may flow into electrical network 100 from local power generator 408, as well as power distribution system 102. Provisioning of power control circuit 110 in such scenarios enables the power generated by local power generator 408 to be diverted into power storage module 112, if it exceeds the simultaneous energy consumption of electrical load 104. In this manner, the generated power may be time-shifted until it is required by electrical load 104. In some embodiments, local power generator 408 may comprise an alternative power source, such as a fuel powered generator, or an alternative energy storage resource, such as the battery of an electric car connected to electrical network 100.

In some arrangements, power control circuit 110 may interface with one or more so-called 'smart appliances' comprised within electrical load 104, for example via control module 400. Such smart appliances are able to adjust their power consumption in response to receipt of suitable instructions, for example by delaying certain power consuming functions, or entering an 'energy-saving' standby mode. By co-ordinating control of such smart appliances power control circuit 110 is capable of increasing its capacity for managing the demand profile of electrical load 104. Further, in some embodiments, power control circuit 110 may act as an intermediary between the smart appliances comprised within electrical load 104 and a remote control entity. Such an arrangement serves to obfuscate the nature of the smart devices associated with electrical load 104, and thereby acts to alleviate privacy concerns associated with direct control of smart appliances by the remote control entity. In some embodiments, power control circuit 104 is configured to broker its demand management capacity, which may include one or more smart appliances comprised within electrical load 104, to power distribution system 102 and/or the remote control entity.

Figure 5 illustrates a schematic diagram of a portion 580 of a power control circuit (for example power control circuit 110) according to embodiments. The schematic of Figure 5 includes some overlap with that of Figure 2 and like numerals in Figure 5 indicate corresponding components in Figure 2.

In embodiments, power control circuit portion 580 comprises two battery arrangements 214, 216, where battery arrangement 214 is connected to positive voltage terminal 208 and zero voltage terminal 210 of power storage interface 206, and battery arrangement 216 is connected to negative voltage terminal 212 and zero voltage terminal 210 of power storage interface 206.

In embodiments, power control circuit portion 580 comprises sensors 510 and 520 for sensing battery arrangement currents. In embodiments, power control circuit portion 580 comprises means (not shown) for sensing battery arrangement voltages.

Power control circuit portion 580 comprises a charge equalising converter 502 connected between positive voltage terminal 208 and negative voltage terminal 212 of the power storage interface. In embodiments, charge equalising converter 502 is connected to zero voltage terminal 210 of the power storage interface. Charge equalising converter 502 is configured to transfer charge between battery arrangements 214 and 216 in response to detecting (for example via one or more of sensors 510, 520) a voltage and/or current imbalance between battery arrangements 214 and 216.

In embodiments, charge equalizing converter 502 comprises a buck-boost converter; in some such embodiments, the buck-boost converter does not require isolation. In embodiments, charge equalizing converter 502 comprises a bi-directional flyback converter.

Figure 6 illustrates a schematic diagram of a portion 680 of a power control circuit (for example power control circuit 110) according to embodiments. The schematic of Figure 6 includes some overlap with that of Figure 2 and like numerals in Figure 6 indicate corresponding components in Figure 2.

In embodiments, power control circuit portion 680 comprises two battery arrangements 214, 216 which feed a direct current to direct current converter 660 which acts as a charging regulator for one or more output devices 670. In embodiments, direct current to direct current converter 660 is connected between positive voltage terminal 208 and negative voltage terminal 212 of power storage interface 206; in such embodiments, direct current to direct current converter 660 is configured to regulate charge from one or more battery arrangements 214 and 216 to one or more output devices 670.

One or more of battery arrangements 214, 216 can be of large capacity if rapid charging is desired. In some embodiments, charging regulator 660 provides adequate galvanic isolation. In other embodiments, battery arrangements 214 and 216 are isolated from the mains supply with a contactor and any point tied to earth (assuming adequate insulation throughout the system).

In the embodiments of Figure 6, one or more input devices 670 (for example one or more electric vehicles) are capable of working with the full voltage provided by both battery arrangements 214 and 216.

Figure 7 illustrates a schematic diagram of a portion 780 of a power control circuit (for example power control circuit 110) according to embodiments. The schematic of Figure 7 includes some overlap with that of Figures 2, 5 and 6, and like numerals in Figure 7 indicate corresponding components in Figures 2, 5 and 6.

Power control circuit portion 780 comprises a direct current to direct current converter 660 connected between positive voltage terminal 208 of power storage interface 206 and zero voltage terminal 210 of power storage interface 206.

Power control circuit portion 780 also comprises a charge equalising converter 502 connected between positive voltage terminal 208 and negative voltage terminal 212 of power storage interface 206.

In the embodiments of Figure 7, direct current to direct current converter 660 is configured to regulate charge from battery arrangement 214 to one or more output devices 670.

In the embodiments of Figure 7, charge equalising converter 502 is configured to transfer charge between the battery arrangements 214 and 216 in response to detection of a voltage and/or current imbalance between battery arrangements 214 and 216 due to charge regulated by direct current to direct current converter 660 to one or more output devices 670. The embodiments of Figure 7 can for example be employed in a system where a battery arrangement 214 which is larger than battery arrangement 216 is retro-fitted in place of an existing (smaller) battery arrangement. Such embodiments can provide rapid charging if required. Any imbalance created by operation of the retro-fitted (larger than previously) battery arrangement 214 can then be compensated for using charge equalising converter 502.

In the embodiments depicted in Figure 7, one or more output devices 670 are capable of working with just the voltage provided by battery arrangements 214 and not the voltage provided by both battery arrangements 214 and 216.

In alternative embodiments, power control circuit portion 780 comprises a direct current to direct current converter 660 connected between negative voltage terminal 212 and zero voltage terminal 210 of power storage interface 206 (instead of between positive voltage terminal 208 and zero voltage terminal 210). In such embodiments, direct current to direct current converter 660 is configured to regulate charge from battery arrangement 216 to one or more output devices 670.

In further alternative embodiments, power control circuit portion 780 comprises a direct current to direct current converter 660 connected between negative voltage terminal 212 and positive voltage terminal 208 of power storage interface 206. In such embodiments, direct current to direct current converter 660 is configured to regulate charge from both battery arrangement 216 and battery arrangement 214 to one or more output devices 670.

In the embodiments of Figure 6 and/or Figure 7, one or more output devices 670 may comprise one or more batteries of one or more electric vehicles.

Figure 8 illustrates a schematic diagram of a portion 880 of a power control circuit (for example power control circuit 110) according to embodiments. The schematic of Figure 8 includes some overlap with that of Figure 2, and like numerals in Figure 8 indicate corresponding components in Figure 2.

The embodiments of Figure 8 comprise a bi-directional AC to DC converter.

In embodiments, controllable switching arrangement 818 comprises a third controllable switching element 828 for selectively connecting the zero voltage terminal 210 of power storage interface 206 to signal generating node 220. In embodiments, third controllable switching element 828 comprises a bidirectional switch.

In the embodiments of Figure 8, controllable switching arrangement 818 comprises a bi-directional switch 828. Bi-directional switch 828 is configurable such that during positive half cycles of the alternating current signal (generated at signal generation node 220), controllable switching element 224 is inactive and controllable switching element 222 is active (bi-directionally) via bi-directional switch 828. Bidirectional switch 828 is configurable such that during negative half cycles of the alternating current signal (generated at signal generation node 220), controllable switching element 222 is inactive and controllable switching element 224 is active (bi- directionally) via the bi-directional switch 828.

In some embodiments, the phrase "during positive half cycles of the alternating current signal" comprises the half cycle when the voltage is positive. In other embodiments, the phrase "during positive half cycles of the alternating current signal" comprises the half cycle when the current is positive.

In embodiments, bi-directional switch 828 is connected between signal generation node 220 and the neutral terminal 202 of the electrical network interface.

In embodiments, bi-directional switch 828 comprises third 812 and fourth 813 controllable switching elements connected in series. In embodiments, third 812 and fourth 813 controllable switching elements form a half-bridge.

By use of the embodiments of Figure 8, the switching frequency voltage appearing across inductor 814 can be halved. Therefore, for a given level of current ripple, the inductor value can be halved, thus saving weight and space (and associated cost). The embodiments of Figure 8 can be combined with any of the other embodiments described herein, including those depicted in any of Figures 1 to 7.

Embodiments comprise a power control circuit for controlling power flow between a power storage module and an electrical network, the power control circuit comprising:

an electrical network interface for connecting the power control circuit to the electrical network, the electrical network interface comprising a live terminal and a neutral terminal; a power storage interface for connecting the power control circuit to the power storage module, the power storage interface comprising a positive voltage terminal, a negative voltage terminal and a zero voltage terminal;

an internal connection, electrically connecting the neutral terminal of the electrical network interface to the zero voltage terminal of the power storage interface; an inductive component, electrically connecting the live terminal of the electrical network interface to a signal generation node; and

a controllable switching arrangement, controllable to selectively connect the positive voltage terminal or the negative voltage terminal of the power storage interface to the signal generation node,

wherein the switching arrangement is controllable to generate an alternating current signal at the signal generation node, wherein the generated alternating current signal is synchronised with an alternating current signal provided in the electrical network, and

wherein the switching arrangement is controllable in relation to the alternating current signal provided in the electrical network whereby to control the direction and/or rate of current flow between the electrical network and the power storage module via the inductive component.

In embodiments, power control circuit 110 comprises a processor or processing system, as depicted by processor 410 in Figure 4. In embodiments, the processing system is comprised within control module 400, as depicted Figure 4. In embodiments, the processing system comprises one or more processors and/or memory. In embodiments, the one or more processors include one or more of a digital signal processor (DSP), microprocessor, microcontroller, or central processing unit (CPU). One or more of the aspects of the embodiments described herein with reference to the drawings comprise methods or processes performed by control module 400, or more generally by power control circuit 110. In embodiments, power control circuit 110 and/or control node 400 comprises one or more processing systems or processors configured to carry out these processes. In this regard, embodiments may be implemented at least in part by computer software stored in (non-transitory) memory and executable by the processor, or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Embodiments also extend to computer programs, particularly computer programs on or in a carrier, adapted for putting the above described embodiments into practice. The program may be in the form of non-transitory source code, object code, or in any other non-transitory form suitable for use in the implementation of processes according to embodiments. The carrier may be any entity or device capable of carrying the program, such as a RAM, a ROM, or an optical memory device; etc.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. For example, where embodiments above have been described in relation to generating a particular target current waveform at signal generation node, in alternative embodiments, those skilled in the art will understand that a target voltage waveform may be similarly generated. Additionally, where the embodiments described above have been directed to operation of the power control circuit in conjunction with a single-phase electrical network, alternative embodiments may operate in conjunction with a three-phase electrical network through use of three power control circuits, each power control circuit corresponding to one phase of the three-phase electrical network. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.