Description

The invention is related to an electrical energy buffering, storing and management system and is, in particular, applicable in the fields of renewable energy electric drives for vehicles, boats and submarines.

According to the heavily growing importance of renewable energy in global energy production on the one hand and of electric and hybrid drives for cars on the other, the development of sophisticated energy buffering and storing systems has become a crucial aspect. Whereas wind farms and solar energy plants produce a rapidly increasing share of electrical energy in a couple of developed countries, the buffering of the energy produced by such power plants and the smart management of future electrical power supply systems ("smart grids") is, to a large extent, still unresolved. Likewise, the smart buffering and management of electrical energy is crucial for a significant market share and for an ecologically beneficial operation of electric cars on a broad scale. Such systems have to be tailored both to the typically discontinuous production or consumption of electrical energy and to the physico-chemical peculiarities and restraints of available battery systems.

In electronics and low-voltage systems, capacitors, and among them electrolytical capacitors, have long been known as useful and efficient energy storing means.

However, their low capacitance and, resulting therefrom, low energy storage capacity do not allow them to be used as storing means in electrical energy supply systems. Recently, electrochemical double layer capacitors (EDLC), meanwhile also known as supercapacitors, have been used in "energy smoothing" applications and momentary- load devices. They have been used as energy-storing means in vehicles and in smaller power-plant application, like home solar energy systems.

It is an object of the invention to provide a sophisticated electrical energy buffering system on the basis of supercapacitors which, more specifically, is usable for power generation control applications, as well as for power consumption control

applications, on an industrial scale.

It is a further object of the invention to provide an electrical storing system, making use of supercapacitors, which allows to store electrical energy generated from renewable energy sources in an efficient manner on an industrial scale.

It is a further object of the invention to provide an electrical energy storing system, making use of supercapacitors as essential part of an improved electric or hybrid drive in vehicles etc. which are equipped with rechargeable batteries.

Still further, it is an object of the invention to provide an electrical energy

management system, making use of supercapacitors, which allows for a smart management of electrical energy in electric and hybrid drives and with respect to other loads which are typically connected to up-to-date energy supply systems.

With the invention, an electrical energy buffering system of claim 1 is provided, as well as an electrical energy storing system of claim 9, and an electrical energy management system of claim 12. Embodiments of the invention are subject of the respective dependent claims.

According to an aspect of the invention, an energy buffering means of the proposed system comprises a plurality of supercapacitors and control means for controlling the operation of the energy buffering means by selectively switching the supercapacitors according to a specific scheme. According to a further aspect of the invention, the plurality of supercapacitors are switchably connected in parallel to each other in a circuit comprising the energy source means and an electrical power output, and the control means comprise buffer monitoring means for monitoring a parameter representing the charge or discharge state, respectively, of each of the

supercapacitors and are adapted to sequentially switch single supercapacitors or groups of supercapacitors on or off, respectively.

According to a further aspect of the invention, the switching on is responsive to the detection of a first predetermined charge or discharge state of the respective supercapacitor or group, and the switching off is responsive to the detection of a second predetermined charge or discharge state, respectively.

In an important field of application of the invention, the energy source means comprise a photovoltaic converter arrangement. A further beneficial application is in a fuel cell arrangement. However, these fields of use of the invention are not exhaustive, and further useful applications related to renewable energies and beyond are possible. In other arrangements, the energy source means comprises a rechargeable battery, preferably of the Li-ion type or NiM H type or NiCd type or metal/air type.

In an embodiment of the invention, the control means comprise threshold discriminator means provided at the respective outputs of the monitoring means, for providing a switch-on or switch-off signal, respectively, responsive to the detection of a parameter value above a predetermined upper threshold value or below a predetermined lower threshold value. More specifically, herein the threshold discriminator means comprise programming means for adjustably setting a respective threshold value.

In a further embodiment, the buffer monitoring means are adapted for monitoring the output voltage of each of the supercapacitors.

In a still further embodiment, the control means are adapted to immediately combine a switching-off of a first supercapacitor or group of supercapacitors with a switching-on of a second supercapacitor or group of supercapacitors, essentially without delay time. Insofar, a "chain" of off-on switching operations is being implemented, ensuring an uninterrupted delivery of sufficient electrical power for buffering an electrical energy generating, storing or consuming process.

According to a further embodiment, the control means comprise source monitoring means for monitoring a performance parameter of the energy source means, preferably an output voltage and/or output current thereof, and for providing an auxiliary control signal for influencing the switching-on of supercapacitors or groups of supercapacitors responsive to a detected value of the performance parameter.

The proposed electrical energy storing system, in principle, comprises energy storing means connected to the power output of the above-explained electrical energy buffering system. Herein, output side switches are provided for each of the supercapacitor or group of supercapacitors, and the control means are adapted to sequentially actuate the output-side switches for connecting the supercapacitors or groups of supercapacitors to the energy storing means responsive to the detection of a third predetermined charge or discharge state, respectively, and for

disconnecting them from the energy storing means responsive to the detection of a fourth predetermined charge or discharge state, respectively.

In important embodiments of such a system, the energy storing means comprise a rechargeable battery, preferably of the Li-ion type or NiM H type or NiCd type or metal/air type (referenced further above as energy source means, related to the basic energy buffering system). In further embodiments, the energy storing means comprise an electrical motor for converting electrical energy into mechanical energy and mechanical energy storing means coupled to the motor. Flywheels are well-known as energy storing means of this type.

The proposed electrical energy management system, in principle, in addition to the above-specified electrical energy buffering system, comprises load means consuming electrical energy, connected to the power output of the buffering system. Herein, output side switches are provided for each of the supercapacitor or group of supercapacitors, and the control means are adapted to sequentially actuate the output-side switches for connecting the supercapacitors or groups of supercapacitors to the load means responsive to the detection of a third

predetermined charge or discharge state, respectively, and for disconnecting them from the load means responsive to the detection of a fourth predetermined charge or discharge state.

In an embodiment of such system, a switchable direct connection is provided between the energy source means and the load means, and the control means is adapted to selectively switch-on and switch-off either the direct connection between the energy source means and the load means or a connection via a supercapacitor or group of supercapacitors.

According to another aspect of the electrical energy management system, the load means is connected to an additional power output of the buffering system, provided in addition to its output for connecting the energy storing means. Herein, output side switches are provided for each of the supercapacitor or group of supercapacitors, and the control means are adapted to sequentially actuate the output-side switches. On the one hand, this actuation is for connecting the supercapacitors or groups of supercapacitors to the load means responsive to the detection of a third predetermined charge or discharge state, respectively, and for disconnecting them from the load means responsive to the detection of a fourth predetermined charge or discharge state. Furthermore, the energy management system comprises a switchable direct connection between the energy storing means and the load means, wherein the control means is adapted to selectively switch on or off either the direct connection between the energy storing means and the load means or the connection between the energy source means and the load means via a supercapacitor or a group of supercapacitors.

Preferred applications of such a management system are with the load means which comprise an electrical motor, preferably of a vehicle drive, boat drive or submarine drive.

The invention provides, at least in embodiments thereof, for a simpler and more efficient energy buffering in electrical energy supply and drive systems and, more specifically, in renewable energy applications, due to the sophisticated embedding of supercapacitors, making use of their specific advantages over electrochemical sells. The insensitivity of capacitors to charging conditions and the simplicity of defining and monitoring the basic parameters for controlling such system provide for a simplified construction of charger and converter components and ensure a robust system operation over a broad range of environmental and operating conditions, with a considerably increased overall efficiency and utilization of the electrical energy provided by several types of energy sources.

Further embodiments and advantages, as well as important aspects of the invention, become apparent from the following description of embodiments of the invention according to the figures.

Fig. 1 shows a diagram of a prior art electrical energy management system,

Fig . 2 shows a diagram of an electrical energy management system of the present invention,

Fig. 3 shows a diagram of an electrical energy buffering circuit arrangement of an embodiment of the invention, and

Fig . 4 shows the structure of a controller of such buffering circuit in more detail.

Fig. 1 schematically shows the structure of a conventional electrical energy utilization or management system 1, which e.g. can be used in an electric or hybrid car or a home renewable energy system. The energy management system 1 comprises a system input (energy source input) 3, to which a system battery block (energy storing means) 5 is connected via a system battery charger block 7. A wind generator or solar panel can be connected to the system input 3 in energy supply applications, whereas a combustion engine is connected to the input in a hybrid car (and even in a conventional car). Furthermore, the system battery block 5 is connected to an output 9 via a DC-AC converter block 11, for supplying stored electrical energy to a load, which can be an electric motor or any other electrically driven equipment. For controlling the battery charging and discharging operations, as well as the DC-AC conversion and further functions of the system, a control unit 13 is provided .

Fig . 2 is a block diagram illustrating the general structure of an energy

management system according to the present invention. Identical or similar components to those in Fig. 1 are designated with the same or corresponding reference numerals. In Fig . 2, an energy source 15 and a load 17 are shown as components of the overall system, whereas in Fig . 1 these components have not been shown. On the other hand, in Fig. 2 any DC-DC or DC-AC converter components are omitted, please refer to Fig. 3 and details provided further below.

In the electrical energy management system of Fig. 2, a supercapacitor block 19 comprising a number of supercapacitors 19i connected in parallel, is a core component. A supercap charging unit 8 and a supercap discharging unit 10 are associated to the supercapacitor 19, both the charging and discharging units 8, 10 comprising a "channel" structure corresponding to the structure of block 19 and providing individual charging and discharging operations for each of the

supercapacitors 19i.

In the figure, it is shown that an output of the supercap charging unit 8 is connected to the load 17, via the discharging unit 10 and the (first) output 9, and likewise an output of the supercap discharging unit 10 is connected to the battery block 5 via the charging unit 8 and the (second) output 12. This second output 12 is also connected to the supercap charging unit 8, which can have an input function, as explained below. The arrangement and mutual connections of the supercap charging unit 8, the supercap discharging unit 10, the system battery block 5 and the load 17 are adapted to provide for multiple energy supply paths from the energy source 15 to the system battery block 5 and/or to the load 17, via the supercapacitor block 19, or from the system battery block 5 to the

supercapacitor 19 and/or to the load 17, as explained further above in the general part of the description.

A modified control and monitoring unit 13' is provided for controlling the

respective energy flows and, more specifically, the consecutive charging/discharging operations of the supercapacitors 19i, to provide the outstanding system performance. The control and monitoring unit 13' can be embodied as an industrial standard PLC and can be equipped with remote control means, both for programming its operation and for implementing at least part of its monitoring functions. Such remote control can be implemented both as short- distance remote control, via WLAN or Bluetooth or similar standards, e.g. in home renewable energy applications, and as long-distance remote control, via mobile telecommunications networks, i.e. for implementing distributed renewable energy applications and smart grids. In Fig . 2 it is also illustrated that within the overall energy management system and energy buffering system 1A' - including the energy source 15 but not including the supercap discharge unit 10, the system battery block 5 and the load 17 - and an energy storing system I B' - including all components except the load 17 - can be defined as sub-systems.

Fig . 3 shows an electrical energy storing system 101 basically comprising a 12V battery 103, an energy source input 105, a load output 107, a power source step- up/step-down DC-DC converter 109, a 12V/24V DC-DC converter 111, and an energy buffering sub-system 113.

The energy buffering sub-system 113 comprises n supercapacitors CI ... Cn connected between the power input 105 and the load output 107 in parallel, via charging switches SCI ...SCn at the input side and discharging switches SDl ...SDn at the output side. Additionally, at the output side of each supercapacitor branch, a Schottky diode 115 is provided, for blocking any reverse current flow. A toggle switch TG is provided at the circuit's output, for switching the output voltage between the two predetermined levels 12V or 24V.

For controlling the operation of the energy buffering sub-system 113, a buffering controller 117 is provided, which delivers control signals for actuating the supercapacitor charging switches SCI to SCn and discharging switches SDl to SDn to a capacitors commutator (switch actuator) 119. Charging feedback signals A and discharging feedback signals B are provided to respective inputs of the buffering controller 117 from the charging switches block 121 or discharging switches block 123, respectively. Besides those feedback signals, the buffering controller 117 monitors input (power source) voltages on the one hand and output (load) voltages on the other and controls the charging or discharging switches responsive to the result of a predetermined internal processing of the signals gained through its monitoring function.

The buffering controller 117 controls the charging switches SCI to SCn such that, upon application of a sufficient source voltage, charging of the supercapacitors CI to CQn starts with the first supercapacitor CI, up to a predetermined upper threshold voltage. Once this upper threshold voltage is achieved, the respective charging switch SCI is opened, immediately followed by closing the second charging switch SC2, associated to the second supercapacitor C2, until the second supercapacitor reaches its upper threshold voltage, and so forth.

Vice versa, if a load disconnected to the output 107 and the buffering controller 117 is instructed to provide electrical energy to the load, discharging of the supercapacitors starts with actuating the discharging switch SD1 associated to the first supercapacitor CI, until a predetermined lower threshold voltage is reached. At this point of time, the first discharging switch SD1 is opened, immediately followed by closing the second discharging switch SD2 to discharge the second supercapacitor C2 to the load, and so forth.

In a preferred operation scheme of the energy buffering sub-system 113, supposed that an energy source and a load are connected to the second arrangement 101 at the same time, charging and discharging operations of the supercapacitors are carried out consecutively, i.e. the discharging of one of the supercapacitors down to a predetermined output voltage is immediately followed by starting its recharging up to a predetermined voltage, when at the same time the next one of the supercapacitors is being discharged, and so forth. This process will, supposed that no failure appears, continue until the system will powered off or a connected energy source is no longer able to provide a minimum amount of energy (input voltage). In such situation, the buffering sub-system will be waiting until a lower input voltage level is reached, to automatically re-start its operation.

If no load is connected to the output on the circuit arrangement, a corresponding operation scheme can be applied for charging the internal battery 103. The battery under 3 can even be charged in parallel to the consecutive charging of the supercapacitors, depending on the implemented specific control scheme, and optionally on a monitor charge/discharge state of the supercapacitors. Furthermore, the buffering controller 117 can actuate the charging switches and discharging switches such that the battery 103 is discharged through the output 107, in this way serving as (secondary) energy source for supplying electrical energy to a load connected to the output 107.

The power source step-up/step-down DC-DC converter 109 provides for a broad range of usable input voltages (6V DC... 32V DC), in a preferred embodiment with an efficiency > 92% and an output current up to 10A. The converter 109

comprises a pulse charge controller 25 bid irectionally connected to a conversion monitor 127, which latter is connected to the input 105, in parallel to a switch device 129. The switch device 129 provides, at an output SW thereof, a signal to the conversion monitor 127, whereas it receives, besides the voltage applied to the input 105, a control signal from a step-up/step-down DC-DC converter 131. Furthermore, the converter 109, comprises a system monitor 133, inputs of which are connected to respective outputs of the controller 131, a current sensor 135 and the power line 137 connecting the input 105 to the supercapacitors CI to Cn.

The converter 109 acts on power switches 139 provided in the power line 137. Given that supercapacitors are being used, the maximum voltage of which is 16.2V, the converter output voltage is set to 15.5V, so that the supercapacitors CI to Cn will charge up to about 15.2V. As far as the detailed operation scheme of the converter 109 is concerned, such type of converters is, as such, none to one of ordinary skill in the art, so that we can refrain from explaining it in more detail.

The configuration of the 12V/24V DC-DC converter 111 is basically identical to that of the converter 109, i.e. it comprises likewise a pulse charge controller 141, a conversion monitor 143, a switch device 145, a step-up/step-down DC-DC controller 147, and a system monitor 149, and it receives signals from a (second) current sensor 151 and (second) power line 153 and acts on power switches 155. At its input side, the converter 111 is connected to the battery 103, instead of an external energy source, and at its output side it is connected to the system output 107, through the toggle switch TG. In a preferred embodiment equipped with standard ICs, it can be operated with an efficiency up to 95% and an output current up to 6A.

Fig. 4 shows a controller structure of the arrangement illustrated in Fig. 3 in more detail. The buffering controller 117 comprises a charging controller part 117A and discharging controller part 117B, each part comprising an integrated logic as its core, the signal inputs and outputs IN I to IN4 and OUT1 to OUT4 of both parts being connected in a feedback manner, to provide for the step-up/step-down operation of the (exemplified four) supercapacitors of the system in the above- explained consecutive operating scheme. In each of the respective parallel output lines, connected to a single control signal output 117C, a charging relay RC1 to RC4 or discharging relay RD1 to RD4, each followed by a relays current limiting device CL1 to CL8, are arranged .

The embodiments and aspects of the invention explained above are not

determined to limit the scope of the invention, which is exclusively to be determined by the attached claims. Many modifications of the inventive concept are possible within the scope of the claims and, more specifically, arbitrary combinations of the several claim features are considered to be within the scope of the invention.