DE102011056135A1 - Power generation system e.g. photovoltaic system for supplying electric power to e.g. public supply network, has control device that is provided to control switch device based on direct voltage power supplied by power generator - Google Patents

Abstract

The power generation system (1) has an energy-storage unit (7) for storage of energy which is fed to an inverter (8). The energy-storage unit is provided with battery units (17,18) which are attached at an output unit (6) of a power generator (4). A switch device (31) is provided to interconnect the battery units either in parallel or in series with each other and parallel to the generator. A control device (16) is provided to control the switch device based on the direct voltage power supplied by the generator. An independent claim is included for a method for operating power generation system.

Description

The present invention relates to a power plant having an energy storage system and a method of operating such a power plant.

Generating electrical energy from renewable energy, eg. Of solar generators, wind power generators, fuel cells and the like. To feed them into a network, eg. A public utility network, or to supply connected consumers are well known. The energy supplied by the respective generator can vary greatly depending on the ambient and operating conditions. For example, The power delivered by a photovoltaic generator depends strongly on the solar radiation, temperature etc. On warm, sunny summer days at lunchtime, the generator delivers the maximum power, while under cloudy or shaded conditions or in the evening when the sun is low generator power drops. At night, a photovoltaic generator delivers no power.

The power delivered by a generator can be greater than the power consumed by connected loads or fed into a grid. However, there is a desire to operate the power generation plant always optimized performance such that the generator always delivers the maximum power according to the current ratio. This operating point with the currently largest power output is referred to as the MPP point (maximum power point), in particular for photovoltaic generators. A regulator device, the so-called MPP tracker, always adjusts the operating point of the photovoltaic generator to the MPP point during operation. If the power generation plant is to be optimized in terms of performance and yield, any excess generator energy must be stored in the meantime. The stored energy can then be used in times of lower energy supply.

This is, for example, from the EP 1 965 483 A1 an additional device for switching between a public power grid and a self-generating system, eg photovoltaic system, known, wherein the auxiliary device several consumers are connected, which are optionally supplied by the own generating plant or from the supply network with energy. Furthermore, a memory in the form of a battery is connected to the auxiliary device via a connected to the AC side of the system inverter. The battery is charged at times of high energy delivery and used by the in-house generation facility during periods of low energy delivery to provide energy to consumers. Furthermore, an additional generator, for example an electric generator, can be connected to the auxiliary device as an alternative power supply. For larger energy requirements, several parallel connected batteries can be provided with associated converters.

The coupled to the power generation plant battery as an energy storage makes it possible, if necessary, the difference energy between the generated by the generating plant and the energy consumed easily exchange. Due to the coupling to the AC side of the power generation plant, however, relatively high conversion losses occur with predominant energy generation by the power generation plant. To charge the batteries, e.g. the DC power provided by the photovoltaic generator is converted by an inverter into an AC power having a voltage conforming to the supply network, e.g. with the amplitude of 230 V and the frequency of 50 Hz, and a suitable alternating current to be converted. Subsequently, this voltage is converted back by the rectifier associated with the battery to a DC voltage of, for example, only 12 or 24 V, generally a maximum of 48 V, which is suitable for the battery. This leads to high conversion losses.

In addition, a three-phase system with AC-side coupling of storage batteries provides a complex system that has many individual components and is relatively expensive. For each phase, at least one battery or a group of batteries connected in parallel must be stored, which are charged and discharged by associated inverters.

From the DE 100 18 943 A1 a photovoltaic system is known in which all required for a photovoltaic island system energy sources and energy sinks are coupled via converters exclusively to a DC bus with freely selectable voltage level. A photovoltaic generator is connected via a matching converter to the DC bus, to which a battery via a bidirectional charge controller and an island inverter with a consumer are connected. A control and regulating device is connected to the energy management via the evaluation of the voltage level of the DC bus.

In this arrangement, the battery is connected on the DC side of the stand-alone inverter to the DC bus. However, to create the DC bus additionally a boost converter is needed as a matching converter, which increases the conversion losses.

In addition, as with other known from practice solutions for buffering the energy supplied by a generator, it is disadvantageous that to work with a low battery voltage. Typically, this is a maximum of 48 V and thus only a fraction of the generator voltage. This increases conversion losses during both charging and discharging of the batteries. In addition, relatively large cable cross sections are required for larger power.

Based on this, it is an object of the invention to overcome the above-mentioned disadvantages and deficiencies of conventional systems and to provide a power generation plant with the possibility of efficient energy storage and use of excess generator energy. In particular, it is an object of the present invention to provide a power generation plant, in particular for use of regenerative energy, which makes it possible to provide excess energy provided by a generator which supplies a variable DC power depending on the respective ambient and / or operating conditions Optionally store and use avoidance or reduction of conversion losses. This in particular with the least possible effort and with high efficiency and flexibility.

Another object of the present invention is to provide a method of operating such a power plant with the possibility of efficient and flexible storage of electrical energy.

These objects are achieved according to the present invention by the power generation plant having the features of claim 1 and the operating method according to claim 12.

In one aspect of the present invention, there is provided a power generation plant, in particular for regenerative energy, comprising a generator, an inverter, an energy storage system, and a controller. The generator provides at its output a variable DC power, which is dependent on the current operating and / or environmental conditions. The inverter is connected with its input at the output of the generator, parallel to this and set up for converting an input-side DC power into an output-side AC power. The AC power can then be fed into a grid, e.g. public power grid, or for connected consumers. The energy storage system is configured to store energy as needed and recover the stored energy to power the inverter. The energy storage system has a first storage device which is connected to the output of the generator, a second storage device, which is also connected to the output of the generator, and a switching device. The switching means is arranged and arranged to electrically connect the first and second storage means electrically either in parallel or in series with each other and in parallel with the generator. The control device is set up to control the switching device as a function of the DC power supplied by the generator.

According to the invention, therefore, the energy storage system for on-demand storage, for example, of an excess part of the generator energy and to use the same at least a first and a second memory device. These are arranged and coupled via the switching device that they can be switched depending on the operating conditions parallel to each other and to the generator to give a state of low voltage across the memory devices, so that the memory devices are charged, if necessary, even at low generator voltage can. Depending on the operating condition, the memory devices can then also be discharged symmetrically with low voltage from both parallel branches of the memory devices. Alternatively, the memory devices can also be connected in series with one another and the series connection can then be connected in parallel to the generator. This makes it possible to achieve a high voltage across the series-connected memory devices, which are close to the optimal operating points of an inverter, for example, also over 50 V, generally between 200 V and 700 V can be. As a result, conversion losses can be minimized or at least greatly reduced. In addition, depending on the operating condition, the series connection of the energy storage devices can be charged with high voltage, which also largely avoids conversion losses. All this is with the switching device according to the invention, whose interconnection options cover the different functionalities for the different operating cases, in Achieved combination with the control device according to the invention, which evaluates the operating conditions and controls the switching device depending on the operating case and switches.

The energy generating plant according to the invention is preferably a photovoltaic system with a photovoltaic generator which converts the absorbed solar energy into direct-current electrical energy, and a photovoltaic inverter which supplies an alternating voltage and an alternating current at its output. However, the invention can also be used for a wind turbine with a wind power generator, a fuel cell with an associated inverter and other generating facilities for supplying consumers and / or for feeding energy into a network.

The inverter may be a one- to three-phase inverter, which preferably has high-frequency switchable switching elements, such as MOS field-effect transistors, IGBTs or the like, which can be driven with a predetermined pattern, for example. Pulsweitenmoduliert, to perform the direction of change. Suitable inverter circuits, e.g. in half or full bridge design are well known in the art. The inverter preferably operates transformerless to allow high efficiencies. In principle, however, any well-known inverter circuits can be used.

The first and the second storage device are each preferably formed by rechargeable battery units, which are also referred to as accumulators. Electrochemical cells, such as lithium-ion batteries, nickel-cadmium batteries or nickel-metal hydride batteries, conventional lead-acid batteries and the like can be used. Suitable accumulators have a high energy absorption capacity with low self-discharge. In principle, storage capacitors, such as so-called. Ultra-caps, usable.

Each battery unit is preferably composed of a plurality of electric batteries, which are connected in series with each other. Such a battery stack may provide the high battery voltage required for the applications provided herein. For example. For example, such a battery stack can provide a voltage of at least 100 V or even up to or above 500 V, so that the optimum operating points, for example, of a photovoltaic inverter can be covered with the series connection of the memory devices according to the invention. All provided battery stacks are preferably substantially the same, in particular designed for the same nominal sizes of the output voltage, charging voltage, charging current, etc.

It can also be provided more than two memory devices that can be connected in parallel or in series with each other. For example, At least one third or further storage device may be provided which corresponds to the first and second storage device.

Each memory device is preferably arranged in an associated branch which is connected in parallel with the generator and has a DC voltage converter arrangement (also referred to as DC / DC controller) assigned to the respective memory device. The DC-DC converter arrangement adapts the generator or DC link voltage to the battery voltage or the battery voltage to the DC voltage in the DC link at the input of the inverter.

Advantageously, the DC-DC converter arrangement for this purpose a combined up-converter, which is also referred to as boost converter, and down converter, which is also referred to as buck converter, with switch units belonging to the switching device. The switch units can then be driven to fulfill the boost converter function, depending on the operating condition. The voltage of the generator can be reduced, for example, to charge the battery unit. Conversely, the voltage of the battery unit when unloading, if necessary, be increased to the required intermediate circuit level.

As this suitable DC-DC converter various circuit arrangements are known. Inductive transducers may preferably be used which use an inductance consisting of a coil or a transformer transformer for buffering the energy. Capacitive transducers or other suitable transducers could also be used.

In an advantageous embodiment of the invention, the DC-DC converter arrangement has a first electronic Switch unit with a switch and an antiparallel freewheeling diode for the down conversion, a connected to the first electronic switch unit in series second electronic switch unit with a switch and a reverse antiparallel freewheeling diode for the up-conversion and an inductance on. The switch units are connected in series and connected in parallel to the generator output. The inductor is connected on the one hand to the connection point between the first and the second switch unit and on the other hand to a first pole of a respective memory device, for example the positive pole of a battery stack.

The branches with the DC-DC converter arrangement and the associated storage device or battery unit can use substantially identical components, so that a clear, low-complexity circuit arrangement is provided. In each memory device, a first pole, e.g. the positive terminal of a battery stack, to be connected to the DC-DC converter arrangement, in particular its inductance, while the second pole, e.g. the negative terminal of a battery pack, with a DC voltage terminal of the generator, e.g. the negative DC voltage branch is connected or connectable. In this case, the negative pole of the first memory device can be hardwired to the negative DC voltage branch, while in the second and possibly each further memory device, a switch between the negative pole and the negative DC voltage branch is inserted.

In an alternative embodiment, the positive poles of the first and second memory device can also be firmly connected to the positive DC voltage branch or can be connected via a switch, while the negative poles are connected to the respective DC voltage converter arrangements, in particular their inductances.

In a simple embodiment of the invention, the switching device has a first and a second switch. The first switch is arranged and arranged to connect between a pole of a first polarity of the first memory device, e.g. the positive pole (alternatively negative pole) of the first battery stack, with an opposite second pole of the second switching device, e.g. the negative pole (alternatively positive pole) of the second battery stack to establish or cancel. The second switch is arranged and arranged to provide a connection between the opposite second pole of the second switching means, e.g. the negative pole (alternatively positive pole) of the second battery stack, and a DC voltage branch, in particular the negative (alternatively positive) DC voltage branch to establish or cancel. By selectively closing the first switch and opening the second switch of the switching device or opening the first switch and closing the second switch, the two memory devices can be connected in series or parallel to each other and parallel to the generator or the intermediate circuit of the inverter.

In a modified embodiment, the first memory device is connected with its one pole of a first polarity with one of the DC voltage branches and with its other pole of opposite polarity with the DC-DC converter arrangement, while the second memory device with its one pole of the first polarity with the DC-DC converter arrangement and with its other pole opposite polarity is connected to the other of the DC voltage branches. The switching device then preferably has only a single switch for connecting the other pole of opposite polarity of the first memory device to the one pole of the first polarity of the second memory device. The second switch for connection to one of the DC voltage branches is then advantageously not needed. While the memory devices in this embodiment can not be serially connected or discharged by boosting the series connection voltage unless an additional boost converter is provided, the memory devices may otherwise be charged or discharged in parallel by being connected in series or in parallel ,

The switching of the switching device can be done solely under the control of the control device according to the invention, which has a suitable control logic for this purpose. Furthermore, a sensor device is preferably provided which is set up to detect operating parameters, which include, in particular, the DC output voltage and the DC output current of the generator and the voltages at the memory devices. The control device then evaluates the parameters of the operating parameters supplied by the sensor device and controls the switches of the switching device as a function of these operating parameters. Communication with the inverter may be possible so that the controller need not form an integral part of the inverter or its controller.

The control device is designed to always take the maximum possible power from the generator and not negatively affect the control of the inverter.

The system according to the invention makes it possible to provide different operating modes with an optional series or parallel connection of the memory devices while keeping the conversion losses low. For example. can be selected in times of low power delivery by the generator, eg shading or in the evening or night hours, by a series connection of the memory devices, a high battery voltage, which may be close to the optimum operating point of a photovoltaic inverter. Depending on the operating condition, the battery units may be discharged either symmetrically with low voltage from both branches or by series connection into a single high voltage stack. The charging of the battery units can also be done either in series or in parallel. Then it is possible even at low generator or DC link voltage to recharge them by connecting the battery units in parallel. With these functionalities, a variety of operating cases can be realized with a small number of components and with high efficiency. The system is flexible and of low complexity.

In a further aspect of the invention, a method for operating a power generation plant, in particular for the use of regenerative energy, is provided, wherein the power generation plant has a generator which supplies at its output a variable DC power depending on operating and / or environmental conditions, and an inverter which is connected in parallel to the output of the generator to convert an input side DC power into an output side AC power. The method includes providing at least a first and a second electrical storage device for storing part of the energy supplied by the generator and / or the intermediate circuit on demand. The method further comprises that a switching device is provided, which allows coupling of the first and the second memory device to the generator optionally in series or in parallel connection of the memory devices. The method further includes sensing operating parameters that include at least the DC voltage provided by the generator, the DC current provided by the generator, and voltages at the first and second memory devices. The method further includes implementing different modes of operation at the power plant and operating the power plant according to the sensed operating conditions according to at least one of the following implemented modes of operation: the inverter is powered by the power supplied by the generator and / or the memory devices are connected in series coupled to each other or parallel to each other and the inverter is supplied with energy from the series connection or parallel connection of the memory devices or the memory devices are charged with energy from the generator.

In a preferred application of the photovoltaic plant method according to the invention, the step of operating the power plant further comprises operating the photovoltaic generator at its individual maximum power point, the MPP point, to derive the maximum power from the generator under current ambient and operating conditions and provide the maximum DC input line to the DC link of the inverter.

Advantageously, the step of charging the memory devices, depending on the size of the available generator voltage or DC link voltage and the voltages on the memory devices, may include selectively switching the memory devices in parallel or in series and charging the memory devices in parallel or series connection. In parallel, the memory devices can be charged even at low available generator voltage or DC link voltage.

In an advantageous embodiment, the memory devices are provided with a frequency-affected current, e.g. pulsed, charged or discharged. In this case, for the reduction of current ripples, the individual current pulses for charging or discharging of the respective storage devices can be output offset in time from one another, preferably without overlap.

The invention makes it possible to store electrical energy very efficiently and flexibly. There are a variety of applications, which include, for example, self-consumption optimization, island / backup solutions, network services for energy companies, such as. Provision of control energy or capping peak loads, etc. With the invention, these applications can be realized easily and with little technical effort. It is possible to use standard components, even two or more identical DC / DC controllers for DC voltage conversion. Individual components can be reduced by integration to a few assemblies. Due to the flexibility of the measure according to the invention allows a reduction of the effort for the application in different device classes of inverters. The invention can be easily retrofitted in existing systems. By a suitable choice of operating modes depending on the given operating conditions longer Use periods of the power generation plant, for example, a power generation with energy from the batteries in the night, with high efficiencies are possible.

Incidentally, the advantages of the power generation plant according to the invention to the operating method of the invention to the same extent good and vice versa.

Further details of advantageous embodiments of the invention are the subject of the drawing, the description and the claims. Embodiments of the invention are illustrated in the drawings, wherein the drawing is merely illustrative of and does not limit the principles of the invention, and wherein like reference numerals are used in the drawings to designate the same or similar parts. In the drawing show:

1 a highly simplified block diagram of a power plant with an energy storage system according to the invention;

2 a circuit arrangement according to the energy generation system with an energy storage system 1 illustrated in greater detail;

3 a flow diagram illustrating an operating method for a power generation plant according to an embodiment of the invention;

4 a simplified circuit arrangement of a power plant with a modified embodiment of an energy storage system according to the invention; and

5 a simplified circuit arrangement of a power generation plant with a further modified embodiment of an energy storage system according to the invention.

In 1 is a power generation plant for the use of renewable energy to produce electrical energy, illustrated. The total with 1 In particular, the designated power generation plant may be a photovoltaic plant that converts solar energy into AC electrical energy, which then either enters a grid 2 , in particular a public supply network, fed or to supply local consumers 3 is used as in 1 shown greatly simplified. The power generation plant 1 may also be a wind turbine, a hydropower plant, a fuel cell based plant or other suitable facility that generates electricity preferably from renewable energy sources.

The power generation plant 1 has a generator 4 on, depending on ambient and / or operating conditions, a variable DC power at its output 6 supplies. For example. can the generator 4 be a photovoltaic generator that converts solar energy into electrical energy, whose size is influenced by solar radiation, depending on the cloudiness, shading, season, time of day, temperature and other environmental factors and the respective operating state.

Furthermore, the power generation plant points 1 an energy storage system 7 and an inverter 8th on, parallel to the output 6 of the generator 4 are connected. The energy storage system 7 serves to that of the generator 4 optionally buffer stored energy to make it usable at a later date. Furthermore, the energy storage system is used 7 to the generator 4 in providing input power to the inverter 8th to support or replace, if the energy of the generator 4 for the sole supply of the inverter 8th not enough. The energy storage system 7 is explained in greater detail below.

The inverter 8th is preferably formed by an electronic inverter switch assembly, which may comprise a basically conventional structure with components or assemblies and operations that allow him to those at its input or DC link 9 provided DC input voltage U _ZK and the injected DC into AC and AC at its output 11 to convert, with respect to the amplitude, frequency and phase, for example, to the AC voltage of the connected network 2 or the corresponding sizes of consumers 3 are adjusted. The DC link 9 is here through an energy cache 10 , in particular a buffer capacitor, formed in parallel with the generator 4 between the DC output branches 6a . 6b of the generator are connected. The DC link 9 could also be formed by a series arrangement of two or more buffer capacitors or other suitable energy storage.

Although different forms of implementation of an inverter 8th with or without transformer in single or three phase design, depending on the application, for use with the present invention are possible, it should be noted that the inverter 8th generally a regulator device 12 for regulating the generator 4 taken power, an inverter arrangement 13 , a sensor device 14 , the environmental and operating parameters of the power plant 1 detected, and a control device 16 that is from the sensor device 8th receives captured parameter values and, based thereon, monitors and controls the operation of the components.

Referring to a photovoltaic generator as an example, the regulator means 12 the photovoltaic generator 4 downstream and has a DC-DC converter or the like., Which takes over the MPP tracking. MPP (Maximizing Power Point) tracking is the operation of the photovoltaic modules at their individual maximum power point in order to achieve optimum power generation of the individual photovoltaic modules. The maximum power point (MPP point) depends on the irradiance, the temperature and the type of photovoltaic cells. So that the photovoltaic generator always works at the MPP point, the MPP tracker regulates the voltage to the required value, usually varies the DC voltage by a small amount, then determines the product of current and voltage and sets the operating voltage in the direction of higher power to. Thus, even with changing irradiation conditions always operate the photovoltaic generator 4 in the MPP point. The photovoltaic generator 4 The power drawn is at the DC link or inverter input 9 provided.

The inverter arrangement 13 is a one- to three-phase inverter circuit, which is the function of the sinusoidal transformation of the DC link power at the DC link 9 for the network 2 or the consumer 3 takes over. The inverter circuit 13 may have any configurations as are well known in the art. Preferably, it has an array of high-frequency switchable switching elements, such as. MOSFET, IGBT switches or the like., Which are modulated with a predetermined pattern, preferably pulse widths, driven to the output 11 of the inverter to produce the required AC voltages and currents. A specific embodiment of an exemplary inverter circuit 13 for use with the present invention is hereinafter related to 2 described in more detail.

The sensor device 16 has (not shown here) sensor means, such as current and voltage sensors, which allow signals at different points of the power plant 1 , in particular of the inverter 8th , capture. In particular, the input DC voltage U _G supplied by the generator, the injected generator current I _G , voltages and currents in the energy storage system explained below 7 , the intermediate circuit voltage U _ZK , the injected alternating currents and output-side alternating voltages, but also parameters, for example, the current environmental conditions, eg the setting strength and temperature at the photovoltaic generator 4 , affect, be recorded. The sensor device 14 is with the control device 16 communicatively connected and provides the measured values recorded to this.

The control device 16 controls the operation of both the inverter in the preferred embodiment illustrated herein 8th as well as the energy storage system 7 depending on the sensor device 14 supplied signals. For this purpose, the control device processes 16 the received signals in accordance with predetermined logical rules to output signals, for example. For driving the switch elements of the inverter 8th as well as control signals for the energy storage system 7 and for the regulator device 12 issue. The regulator device 12 is here as part of the controller 16 but may also be implemented separately from it. Furthermore, for the inverter 8th a separate (not illustrated here) control provided and the control device 12 then, for example, be connected with this communication.

As already mentioned, the energy storage system is 7 provided in times of high energy supply of the generator 4 to temporarily store the DC power provided by this to make it available later in times of low energy supply. However, such energy storage and recovery should be done as efficiently as possible, with little conversion losses. Conversion losses occur in particular when high input voltages are converted into low charging voltages for energy stores, for example batteries, or when low battery voltages have to be transformed into relatively high DC link voltages.

To avoid such conversion losses as possible, has the energy storage system 7 according to the present invention at least a first storage device 17 and a second storage device 18 , Each storage device 17 . 18 is formed by a rechargeable battery unit, which is generally referred to as an accumulator and has a series of series-connected electric batteries, which together form a battery stack or stack. Each battery stack is preferably designed for a nominal voltage of at least 230 V, preferably up to 300 V or even more. In contrast to known energy storage systems, such as those used in existing photovoltaic systems, which operate with a low battery voltage of typically a maximum of 48 V, in the invention the maximum battery voltages are significantly higher due to the interconnection of many individual batteries.

Each storage device 17 . 18 is in a separate memory branch 19 . 21 arranged, both substantially parallel to the output 6 of the generator 4 are connected. In particular, a first branch 19 with the DC output branches 6a . 6b of the generator 4 hardwired and has one of the memory device 17 assigned, in 1 as arranged in series with this arranged DC-DC converter arrangement (DC / DC controller) 22 on, which serves the voltage U _{ZK of} the DC intermediate circuit 9 to the battery voltage U _{B1 of} the first memory device 17 and vice versa. The first DC-DC converter arrangement 22 is here with the positive pole 23 the first battery unit 17 connected while the negative pole 24 the battery unit 17 with the negative DC branch 6b connected is.

Similarly, the second branch 21 a second DC-DC converter arrangement 27 on the one hand with the positive DC branch 6a 4 and on the other hand with the positive pole 27 the second battery unit 18 connected is. Unlike the first battery unit 17 is the negative pole 28 the second battery unit 18 with the negative DC branch 6b not directly, but via a switch 29 connected to a switching device 31 of the energy storage system 7 belongs.

The switching device 31 is configured to the first and the second storage device 17 . 18 optionally electrically connected either in parallel or in series with each other and in parallel to the generator 4 to switch. For this purpose, the switching device 31 a first switch 32 and a second switch passing through the switch 29 is formed. The first switch 32 the switching device 31 is set up and connected to a connection between a first pole and the positive pole of the first battery unit 17 and an opposite second pole or the negative pole 24 the second battery unit 18 produce or cancel. This is the first switch 32 in a branch 33 arranged, which is the connection point between the first DC-DC converter arrangement 22 and the positive pole 23 the first battery unit 17 with a connection point between the negative pole 24 the second battery unit 18 and the second switch 29 the switching device 31 combines. When the first switch 32 is closed, the two battery units 17 . 18 connected in series.

The second switch 29 is on the one hand with the negative pole 24 the second battery unit 18 and a terminal of the first switch 32 and on the other hand with the negative DC branch 6b of the generator 4 connected.

As further out 1 is apparent, is at the positive DC voltage branch 6a between the generator 4 and the rest of the system, the energy storage system 7 and the inverter 8th a protection diode 34 present, which is a discharge of the battery units 17 . 18 over the generator 4 prevented. For bridging the protective diode as required 34 is a switching element parallel to this 36 intended.

A specific embodiment of the power generation plant according to the invention is shown in greater detail in FIG 2 illustrated. The representation after 2 differs from the one after 1 merely in that here concrete embodiments for the first and second DC-DC converter arrangement 22 . 26 as well as the inverter 8th are indicated. It should be noted, however, that these are only exemplary embodiments and also other implementation options exist. With regard to the other components shown, reference is made to the above statements with reference to the same reference numerals 1 Referenced.

As in 2 is illustrated each DC-DC converter device 22 . 26 an inductive converter formed by a combined up-converter and down-converter. In particular, the first DC voltage converter device has a first electronic switch unit 37 with a switch 38 and a freewheeling diode connected in antiparallel thereto 39 , a second switch unit 41 with a switch 42 and an antiparallel freewheeling diode 43 and an inductor which also passes through a transformer coil can be formed. The first and the second switch unit 37 . 41 are connected in series with each other between the DC voltage branches 6a . 6b connected. The first switch unit 37 is used for down conversion and is between the positive DC branch 6a and a terminal of the second switch unit 41 arranged. The other terminal of the second switch unit 41 is with the negative DC branch 6b connected. The inductance 44 on the one hand with the connection point between the two switch units 37 . 41 and on the other hand with the positive pole 23 the first battery unit and the first switch 32 containing branch 33 connected. The second switch unit 41 serves the upward conversion of the battery voltage U _{B1 of} the first battery unit to the intermediate circuit _voltage U _ZK .

Similarly, the second DC-DC converter arrangement 26 one between the DC voltage branches 6a . 6b connected series circuit of a first switch unit 46 and a second switch unit 47 , each one a switch 48 . 49 and an antiparallel freewheeling diode for this purpose 51 . 52 have, as well as an inductance or transformer coil 53 on. The first switch unit 46 serves the down conversion of the intermediate circuit voltage U _ZK and is between the positive DC voltage branch 6a and a terminal of the second switch unit 47 arranged, whose other terminal to the negative DC branch 6b connected is. The inductance 53 is with the connection point between the switch units 46 . 47 and the positive pole of the second battery unit 18 connected.

The inverter 8th is here in the form of a so-called multilevel inverter, which has an extended input voltage range. Unlike the in 1 schematically illustrated embodiment, the intermediate circuit 9 in 2 two energy stores in the form of

capacitors 54 . 56 on that between the DC voltage branches 6a . 6b in series with each other and parallel to the generator 4 are arranged. The connection point of the capacitors 54 . 56 is with the through the circuit arrangement of the inverter 13 passed neutral conductor (N) 57 connected.

Parallel to the series connection of the capacitors 54 . 56 is a half-bridge circuit of the inverter 8th arranged, the two switch elements connected in series 58 . 59 has, in each case in parallel and in the opposite forward direction, a freewheeling diode may be connected in order to protect against reverse currents. In series with the respective switches 58 . 59 are rectifier diodes 61 . 62 provided in the same passage direction as the switch elements 58 respectively. 59 are arranged.

The half-bridge has two further switch elements 64 . 66 each with antiparallel freewheeling diodes 67 . 68 on. The switch elements 64 respectively. 66 are at outputs of a respective DC-DC boost converter 61 respectively. 71 arranged, which serves to increase the potential at the positive or negative DC voltage _branch , which is to be designated here by U _ZK1 , to a magnitude higher voltage potential U _ZK2 . A first DC-DC boost converter 69 has an inductance 72 that with the positive DC voltage connection 6a is connected, a switching means 73 , on the one hand with the other terminal of the inductor 72 and on the other hand with the neutral conductor 57 connected, and a diode 74 on, whose anode is connected to the junction between the inductor 72 and the switching means 73 is connected and the cathode with the switch element 64 connected is. The other terminal of the switch element 64 is again with the center tap 63 connected to the half bridge. Further, at the output of the boost converter 69 a buffer capacitor 76 arranged between a connection point of the diode 74 with the switch element 64 and the neutral conductor 57 is arranged.

Similarly, the second DC-DC boost converter 71 an inductance 77 connected to the negative DC branch 6b is connected, one with the inductor 77 connected switching means 78 on the other hand, on the neutral conductor 75 connected, and a diode 79 on, whose cathode with the connection point between the switching means 78 and the inductance 77 is connected and the anode to the switch element 66 is connected in the same passage direction. The switch element 66 is in turn with its other connection to the center tap 63 connected to the half bridge. A buffer capacitor 81 is between the connection point of the switch element 66 with the diode 79 and the neutral conductor 63 the half-bridge connected to buffer the high _{DC link voltage} U _ZK2 .

The circuit arrangement 13 of the inverter 8th also has two freewheel paths 82 . 83 on, parallel to each other between the center tap 63 the half-bridge and the neutral conductor 57 run. Every freewheel path 82 . 83 has a switch element 84 respectively. 86 with a freewheeling diode optionally connected in antiparallel with this and a rectifier diode arranged in series therewith 87 respectively. 88 on, the same passage direction as the associated switch element 84 respectively. 86 having. Incidentally, the Rectifier diodes 87 . 88 in the individual freewheel paths 82 . 83 switched in the opposite passage direction to each other.

The center tap 63 the half bridge is over a connecting line 89 in which a storage choke 91 is provided to temporarily store energy supplied by the half-bridge and, for example, to an AC voltage network 2 or a consumer 3 with an AC voltage connection 92 connected to an AC voltage circuit. Between the AC voltage connection 92 and the neutral conductor 57 can be a smoothing capacitor 93 be inserted to filter out high-frequency voltage components.

Although the in 2 illustrated circuit arrangement of an inverter 13 is only exemplary in nature, it is particularly advantageous in that it allows, even with insufficient generator voltages with high efficiency AC or AC voltage at the output of the inverter 13 to create. The operating range of the inverter can be significantly extended. Regarding details will be on the DE 10 2006 010 694 B4 expressly referred to the structure and operation of the here in 2 shown inverter circuit 13 describes in detail.

For the purposes of the present invention, the following brief description of the operation suffices:
In normal operation, in the case of a positive half wave, according to a normal operating mode, the one to the positive DC branch 6a connected upper switch 58 the inverter half-bridge clocked high-frequency, while the switch element 84 in the first freewheel path 82 remains closed during the entire positive half cycle of the output voltage. The other switch elements are all open. Every time the switch is closed 58 a magnetizing current flows through the storage choke 91 that magnetically charges them. When opening the switch element 64 A freewheeling current now flows over the freewheeling path 82 with the rectifier diode 87 and the closed switch element 84 , The one through the storage throttle 91 flowing current follows on average the course of the output AC voltage.

Once the generator voltage, in particular the intermediate _{circuit voltage} U _ZK1 for a sufficient charging of the choke coil 91 is insufficient, is switched to an extended operating mode, in which, still considering the positive half cycle of the output side AC voltage, now the first DC-DC boost converter 69 is used to convert the intermediate _{circuit voltage} U _ZK1 to an increased intermediate _{circuit voltage} U _ZK2 , while that with the _boost converter 69 connected switch element 64 is clocked high frequency to the increased DC link potential to the center tap 63 to apply the half-bridge so as to the choke coil 91 aufzumagnetisieren. To the high setting is the switching means 73 of the boost converter 69 switched with a suitable duty cycle. Further, the upper switch 58 the half-bridge permanently closed to the freewheeling current of the storage choke in the freewheeling phases 91 respectively. The remaining switches are permanently open.

Similarly, during the negative half-cycle of the output AC voltage in the normal operating mode, the lower switch becomes 59 the half bridge clocked high frequency to the storage choke 91 during the freewheeling current through the second freewheeling path 83 with the now closed switch element 85 and the rectifier diode 88 flows. In the extended operating mode and with negative half-wave of the output AC voltage, the second DC-DC boost converter 71 activated, its switching means 78 is switched with appropriate duty cycle, and the switch element 66 at the output of the boost converter 71 is clocked high-frequency to the storage choke 91 aufzumagnetisieren. The free-wheeling current now commutes over the permanently closed lower switch 59 the half bridge.

The mode of operation of the power generation plant according to the invention described so far 1 Now, with additional reference to Table 1 below, it will now be described, in the form of a simplified form, various exemplary operating modes of the power plant 1 with the energy storage system 7 according to the invention together with the respective switch positions or circuits lists. As mentioned, the operation of the power plant is under the control of the controller 16 according to the of the sensor device 14 recorded current operating parameters. As a concrete example, a photovoltaic system is to be adopted below. 1. switch ( 32 ) 2. Switch ( 29 ) DC / DC converter ( 22 ) DC / DC converter ( 26 ) explanation 1a on to Step-down converter (switch 37 clocked) Step-down converter (switch 46 clocked) s of the batteries Lad in parallel connection 1b to on inactive Low setter (switch 46 clocked) Charging the batteries in series 2 on to inactive inactive Generating electricity from generator 3a to on inactive energized Generating energy from batteries in series 3b to on inactive Boost converter (switch 47 clocked) Energy generation from batteries in series and generator 4 on to Boost converter (switch 41 clocked) Boost converter (switch 47 clocked) t Electricity generation from batteries in parallel and generator 5 on to Step-down converter (switch 37 clocked) Step-down converter (switch 46 clocked) Generating electricity from generator and charging batteries in parallel Table 1: Exemplary Operating Modes of the Energy Storage System 7

In a first operating mode, with sufficient voltage of the photovoltaic generator 4 the first and second battery units 17 . 18 to be charged. The battery is charged by the generator 4 and the DC-DC converter arrangements 22 . 26 who work in this operating case as a buck converter. For this purpose, the first switch units 37 . 46 the DC-DC converter arrangements 22 . 26 controlled with a suitable duty cycle to a suitable battery charging voltage for charging the battery units 17 . 18 provide. The battery units 17 . 18 are preferably connected parallel to each other during charging and to the generator (mode 1a ), by opening the first switch 32 ("On") the switching device 31 and closing the second switch 29 ("To") is effected.

In a modified first mode of operation 1b can the batteries 17 . 18 be charged in series connection with sufficient generator voltage. This is the first switch 32 the switching device 31 closed, and the second switch 29 will be opened. The second DC-DC converter arrangement 26 is by appropriate timing of the first switch unit 46 used as a buck converter.

In a second mode of operation, when the generator voltage is sufficient, the alternating current is generated in a conventional manner from the generator voltage. That is, the generator 4 feeds the inverter 13 that is related to 2 as explained above, can be operated either in the normal operating mode or in the extended operating mode. At least one of the switches 29 . 32 the switching device 31 is open to discharge the battery units 17 . 18 to avoid. The DC-DC converter devices 22 and 26 are inactive. In particular, all of their switch units 37 . 41 . 46 . 47 preferably opened.

In another operating mode 3a can in the event that no energy from the generator 4 is available, the inverter 13 solely from the battery units 17 . 18 be fed. For example, the batteries are connected in series with each other by the first switch 32 the switching device 31 closed and the second switch 29 the switching device 31 is opened. The current for magnetizing the storage choke 91 flows through the second DC-DC converter arrangement in this case 26 , in particular their inductance 53 and the freewheeling diode 51 the first switch unit 46 , In order to avoid forward losses, it is also possible to use the second DC-DC converter arrangement 26 to bridge for this case by a switch not shown here.

Should be at the same time energy from the generator 4 and the battery units 17 . 18 , which are connected in series, be removed (mode 3b ), it is through the second DC-DC converter arrangement 26 possible, the voltage of the series connection of the battery units 17 . 18 on the potential of the generator 4 or DC link 9 variable up. This continues to be an MPP tracking on the generator 4 possible. To Hochsetzstellung the second switch unit 47 the second DC-DC converter arrangement 26 switched with the required clock ratio, the current from the batteries via the freewheeling diode 51 the first switch unit 46 flows.

Is the generator voltage lower than the voltage of the series connection of the battery units 17 . 18 Thus, in a fourth mode of operation, the batteries are connected in parallel symmetrically through the first and second DC-DC converter arrangements 22 . 26 to discharge and to the intermediate circuit voltage level of the DC link 9 pull up. This is the first switch 32 the switching device 31 opened and the second switch 29 closed. The second switch units 41 . 47 the voltage converter 22 . 26 are switched with the appropriate for the boosting of the intermediate circuit voltage duty cycle.

It is also possible to use the operating mode 1a and the operating mode 2 to combine with each other, so the inverter 13 with energy from the generator 4 to feed and at the same time the battery units 17 . 18 to unload in parallel. The first switch 32 the switching device 31 is then open when the second switch 29 closed is. The DC-DC converter arrangements 22 . 26 Both operate as a buck converter with the appropriate duty cycle to provide from the DC link voltage the appropriate voltage for charging the batteries.

Of course, in all the above operating modes, it is also possible to use the inverter 8th in both the normal operating mode and the extended operating mode, as discussed above 2 explained, in order to exploit the possible operating range as far as possible.

As already mentioned, the protection diode prevents 34 between the generator 4 and the energy storage system 7 that the battery units 17 . 18 over the generator 4 can discharge. Is enough energy in the generator 4 present, the protective diode 34 preferably with the switching element 36 bridged to reduce losses.

Thus, with the power generation plant according to the invention 1 Many operating cases are covered with relatively little effort for the production and operation of the plant. There may be standard components, in particular also two or more identical DC / DC converters for the DC-DC converter arrangements 22 . 26 and possibly also for any boost converter of the inverter 8th be used. As a result, the number of individual components can be significantly reduced. The energy storage system according to the invention is flexible in terms of use and can be easily integrated into existing inverters and / or power generation plants. By better utilization of the generator power higher efficiencies can be achieved. This also due to the larger sized battery voltage of the energy storage system according to the invention 7 and the possibility of this by series or parallel connection of the battery units 17 . 18 for the respective operating case with low conversion losses.

3 shows a flowchart of an embodiment of a method according to the invention for operating a power generation plant, in particular a photovoltaic system, for the use of renewable energy. In particular, the method is for use in the power generation plant according to the invention 1 determined as described above.

The method begins with the step S1, according to which at least one first and one second electrical storage device for on-demand storage of energy, in particular the above-mentioned battery units or stacks 17 . 18 , to be provided. The battery units 17 . 18 are suitably selected for the respective application so that they generate the required intermediate circuit voltages for the inverter for power generation 13 can provide during operation.

In a step S2, a switching device, for example, the switching device is further 31 , which is arranged and arranged such that it connects the first and the second memory device to the generator 4 optionally in series or in parallel circuit of the memory devices allows. For this purpose, the branch 33 with the first and the second switch 32 . 29 in the in the 1 and 2 illustrated manner can be coupled.

The method further comprises sensing (S3) operating parameters including at least the DC input voltage provided by the generator, the DC current provided by the generator, and the instantaneous voltages at the first and second memory means. Other operating parameters, such as the intermediate circuit voltage, the output AC voltage generated by the inverter and the alternating current and others, are also detected.

In a step S4, furthermore, the respective operating mode is selected as a function of the detected operating conditions in order to operate the power generation plant according to the selected operating mode in step S5. The plant may be operated according to one or a sensible combination of the following implemented operating modes:

In a normal operating mode, the inverter is supplied with the power supplied by the generator (S6). The generator voltage is sufficient to provide the required intermediate circuit voltage for the inverter, which generates at its output the desired AC voltage and the AC power for feeding in a network or to supply consumers.

If the generator voltage is sufficient, the storage devices can be charged with energy from the generator (S7). The switching device is generally controlled in such a way that a parallel connection of the batteries is achieved. With sufficient generator voltage, the batteries can also be switched and charged in series.

In addition, it is also possible to charge the batteries simultaneously during normal operation when the generator is powering the inverter.

In addition, it is possible to provide a bidirectional inverter and to charge the batteries with power from a network connected to the output of the inverter.

In another operating mode, the energy stored in the batteries can be used to generate electricity. For this purpose, the batteries can, for example, be coupled in series with one another and the inverter can be supplied with energy from the series connection of the batteries (S8). This can be done in parallel with the supply by the generator, in which case the voltage of the series connection of the batteries is set to the predetermined by the generator potential or DC link potential.

If the generator voltage is lower than the voltage of the series connection of the batteries, then it is possible in a further operating mode S9 to couple them in parallel to each other and to feed the inverter with energy from the parallel connection of the batteries. In particular, the batteries are discharged symmetrically in parallel connection by respective boost converter, wherein the boost converters increase the voltages of the batteries to the intermediate circuit voltage.

When the batteries are used in parallel with the generator for power generation, it is possible to always operate the generator at its individual maximum power point, the MPP point, to extract the maximum power from the generator and deliver it to the inverter.

In addition, it is possible to use in the charging mode S7 a pulsed or otherwise frequency-sensitive current for charging the batteries and offset in time to spend each other, so that, for example, the charging current pulses do not overlap or only slightly overlap. As a result, can be attributed to the charging current ripple in the circuit arrangement, which also affect the generated alternating current, to a minimum.

In the 4 and 5 modified embodiments of the invention are illustrated. As far as matches in construction and / or function to the embodiments according to 1 to 3 Reference is made to the above description with reference to the same reference numerals

The in the 4 and 5 Illustrated embodiments of the invention are different from the 1 - 3 essentially in the embodiment of the storage system 7 More specifically, the arrangement of the storage devices or battery units 17 . 18 and the associated training and arrangement of the switching device 31 ,

In the embodiment according to 4 are the first and the second memory device 17 . 18 not against the negative DC branch 6b as in the 1 and 2 but against the positive DC branch 6a connected. In particular, the first storage device 17 with her plus pole 23 directly on the positive DC voltage branch 6a of the generator 4 connected while the negative pole 24 the first storage device 17 with the associated DC-DC converter arrangement 22 , in particular the inductance 44 connected is. The positive pole 27 the second storage device 18 is over the second switch 29 the switching device 31 also with the positive DC voltage branch 6a of the generator 4 connectable while the negative pole 28 the second storage device 18 with the associated DC-DC converter arrangement 26 , in particular the inductance 53 connected is. The switching device 31 here has a first switch 32 who is in a branch 33 is arranged, which is the negative pole 24 the first storage device 17 with the positive pole 27 the second storage device 18 connects, and the second switch 29 on that between the positive DC branch 6b and the connection point of the branch 33 with the battery unit 18 is inserted.

Again, as in the embodiment according to the 1 and 2 when closing the first switch 32 and opening the second switch 29 the switching device 31 optionally a series connection between the battery units 17 . 18 formed, while in the opposite case, when the first switch 32 is open and the second switch 29 is closed, a parallel connection of the battery units 17 . 18 is formed.

In contrast to the embodiment according to the 1 and 2 but here are for charging the battery units 17 . 18 the second switch units 41 . 47 the DC / DC converter 22 . 26 clocked to lower the generator voltage, while the freewheeling current through the freewheeling diode 39 . 51 the respective first switch unit 37 . 46 commutated. In the series connection of the battery units 17 . 18 is only the second switch unit 47 active. For discharging the battery units 17 . 18 become the first switch units 37 . 46 the DC / DC converter 22 . 26 clocked to boost the battery voltages as needed, while the diodes 43 . 52 the second switch units 41 . 47 take over the Freilafstrom. In the series connection of the battery units 17 . 18 is only the first switch unit 46 active. Incidentally, the operating modes and the associated operation of the embodiment according to 4 those after 1 - 3 ,

In the embodiment according to 5 are the first and the second memory device 17 . 18 switched against different DC voltage branches. The first storage device 17 is with her plus pole 23 directly with the positive DC branch 6a and with her negative pole 24 with the inductance 44 connected. The second storage device 18 is with her plus pole 27 with the inductance 53 and with her negative pole 28 directly with the negative DC branch 6b connected. The branch 33 with the switch 32 the switching device 31 is here between the negative pole 24 the first battery unit 17 and the positive pole 27 the second battery unit 18 arranged.

The main advantage of the embodiment according to 5 lies in the fact that here is the second switch 29 the switching device 31 can be saved. The battery units 17 . 18 can then be alone with the first switch 31 be switched between parallel and series connection. This is bought with the slight disadvantage that no lowering of the generator voltage when charging the series connection of the battery units 17 . 18 and no boosting the battery voltage in series on discharge is possible, but otherwise the other operating modes and advantages of the embodiments described above but can also be realized, and this with reduced Schaltungs- and Ansteuerungsaufwand.

It should be noted that the terms "first" and "second" in this specification are used for convenience only to distinguish one element from another and are not intended to be limiting of the disclosure. For example, the battery unit could 17 also as the second and the battery unit 18 are referred to as the first storage device. Furthermore, those skilled in the art will appreciate numerous modifications, adaptations or extensions in the light of the present disclosure which, while capable of requiring structural or functional remodeling, are encompassed by the scope of the invention as defined in the following claims.

It is a power generation plant 1 and a method for operating the same, wherein the power generation plant 1 a generator 4 , which supplies at its output a variable DC power depending on operating and / or environmental conditions, and an inverter connected in parallel to the generator 8th for converting an input-side DC power into an output AC power. According to the invention, an energy storage system 7 to store as needed at least a portion of the energy supplied by the generator and recover the stored energy to power the inverter 8th intended. The energy storage system 7 has a first battery unit 17 connected to the output of the generator is a second battery unit 18 , which is connected to the output of the generator and a switching device 31 which is arranged and arranged to the first and second battery unit 17 . 18 optionally electrically either in parallel or in series with each other and in parallel with the generator 4 connect to. A control device 16 controls the switching device 31 depending on the generator 4 available DC power suitable to the battery units 17 . 18 either in series or parallel to either charge or discharge to the inverter 8th if necessary to feed with battery energy.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1965483 A1 [0004]
• DE 10018943 A1 [0007]
• DE 102006010694 B4 [0069]

Claims (16)

Power generation plant, in particular for regenerative energy, with a generator ( 4 ), which at its output ( 6 ) provides a variable DC power depending on operating and / or environmental conditions; with an inverter ( 8th ) whose input ( 9 ) with the output ( 6 ) of the generator ( 4 ), for converting an input-side DC power into an output-side AC power; and with an energy storage system ( 7 ) to store energy as needed and recover the stored energy to the inverter ( 8th ), the energy storage system ( 7 ) comprises: a first memory device ( 17 ) located at the exit ( 6 ) of the generator ( 4 ) connected; a second storage device ( 18 ) located at the exit ( 6 ) of the generator ( 4 ) connected; and a switching device ( 31 ) arranged and arranged to store the first and second storage means ( 17 . 18 ) optionally electrically either in parallel or in series with each other and in parallel with the generator ( 4 ) connect to; and with a control device ( 16 ) for controlling the switching device ( 31 ) as a function of the generator ( 4 ) supplied DC power. Power generation plant according to claim 1, characterized in that the power generation plant ( 1 ) is a photovoltaic system having a photovoltaic generator ( 4 ), and that the inverter ( 8th ) preferably a one- to three-phase inverter circuit ( 13 ) with high-frequency switchable switching elements ( 58 . 59 . 64 . 66 ) having. Power generation plant according to claim 1 or 2, characterized in that the first and second storage means ( 17 . 18 ) are each formed by a rechargeable battery unit. Power generating plant according to claim 3, characterized in that each battery unit ( 17 . 18 ) consists of a plurality of electric batteries connected in series to allow a maximum battery voltage of at least about 100 V to about 500 V or even more. Power generating plant according to one of the preceding claims, characterized in that at least one further memory device is provided, which via the switching device ( 31 ) either in parallel or in series with the first and second memory devices ( 17 . 18 ) is connectable. Power generation plant according to one of the preceding claims, characterized in that each storage device ( 17 . 18 ) in a branch ( 19 . 21 ) arranged parallel to the generator ( 4 ) is connected and one of the respective storage device ( 17 . 18 ) associated DC-DC converter arrangement ( 22 . 26 ) having. Power generating plant according to one of the preceding claims, characterized in that the DC-DC converter arrangement ( 22 . 26 ) a combined boost converter ( 41 . 44 ; 47 . 53 ) and down-converters ( 37 . 44 ; 46 . 53 ) with switch units ( 37 . 41 . 46 . 47 ) connected to the switching device ( 31 ) belong. Power generation plant according to claim 7, characterized in that the DC-DC converter arrangement ( 22 . 26 ) a first switch unit ( 37 ; 46 ) with a switch ( 38 ; 48 ) and an antiparallel freewheeling diode ( 39 ; 51 ) for down conversion, a second switch unit connected in series to the first switch unit (US Pat. 41 ; 47 ) with a switch ( 42 ; 49 ) and an antiparallel freewheeling diode ( 43 ; 52 ) for the up-conversion and an inductance ( 44 ; 53 ), which on the one hand with the connection point between the first and the second switch unit and on the other hand with a first pole ( 23 . 27 ) of the respective storage device ( 17 . 18 ) connected is. Power generating plant according to one of claims 6-8, characterized in that the first and the second memory device ( 17 . 18 ) with a pole ( 23 . 27 ; 24 . 28 ) of a first polarity with the respective DC-DC converter arrangement ( 22 . 26 ), the first memory device ( 17 ) with her other pole ( 24 ; 23 ) of opposite polarity with one of the DC voltage branches ( 6a . 6b ) of the generator ( 4 ) and the second memory device ( 17 ) with her other pole ( 28 ; 27 ) of opposite polarity via a switch ( 29 ) of the switching device ( 31 ) with the same DC branch ( 6a . 6b ) of the generator ( 4 ) is connectable. Power generating plant according to one of the preceding claims, characterized in that the switching device ( 31 ) a first switch ( 32 ), which is set up and connected to establish a connection between a pole ( 23 . 27 ) of a first polarity of one of the memory devices ( 17 . 18 ) and a pole ( 28 . 24 ) of opposite polarity of the other memory device ( 18 . 17 ), and a second switch ( 29 ) which is set up and connected to establish a connection between the pole ( 28 . 24 ) of opposite polarity of the other memory device ( 18 . 17 ) and a DC branch ( 6a . 6b ) of the generator ( 4 ) or cancel. Power generating plant according to one of claims 6-8, characterized in that the first storage device ( 17 ) with its one pole ( 23 ) of a first polarity with one of the DC voltage branches ( 6a . 6b ) and with her other pole ( 24 ) of opposite polarity with the DC-DC converter arrangement ( 22 ), the second memory device ( 18 ) with its one pole ( 27 ) of the first polarity with the DC-DC converter arrangement ( 26 ) and with her other pole ( 28 ) of opposite polarity with the other of the DC voltage branches ( 6a . 6b ) and the switching device ( 31 ) a switch ( 32 ), which is set up and connected to connect between the other pole ( 24 ) of opposite polarity of the first memory device ( 17 ) and the one pole ( 27 ) of the first polarity of the second memory device ( 18 ) or cancel. Power generation plant according to one of the preceding claims, characterized in that the control device ( 16 ) with a sensor device ( 14 ) is connected to the detection of operating parameters, to which the DC output voltage and the DC output current of the generator ( 4 ) and the voltages at the memory devices ( 17 . 18 ), and the control device ( 16 ) the switching device ( 31 ) in dependence on these operating parameters in the sense of a maximum power extraction from the generator ( 4 ). Method for operating a power generation plant, in particular for regenerative energy, comprising a generator ( 4 ), which at its output ( 6 ) provides a variable DC power depending on operating and / or environmental conditions, and an inverter ( 8th ) parallel to the output ( 6 ) of the generator ( 4 ) is connected to convert an input side DC power into an output side AC power, the method comprising: providing at least first and second electrical storage devices ( 17 . 18 ) for on-demand storage of energy; Provision of a switching device ( 31 ), which is a coupling of the first and second memory device ( 17 . 18 ) to the generator ( 4 ) optionally in series or parallel connection of the memory devices allows; Detecting operating parameters, at least those of the generator ( 4 ) supplied DC voltage, the DC supplied by the generator and voltages at the first and the second memory device ( 17 . 18 ); and operating the power generation plant according to at least one of the following implemented operating modes depending on the detected operating conditions: - Inverter power ( 8th ) with the generator ( 4 ) supplied energy; Loading the memory devices ( 17 . 18 ) with energy from the generator; - coupling the memory devices ( 17 . 18 ) in series with one another and powering the inverter with energy from the series connection of the memory devices; - coupling the memory devices ( 17 . 18 ) parallel to each other and feeding the inverter with energy from the parallel connection of the memory devices. A method according to claim 13, characterized in that it further comprises operating the generator ( 4 ) at its individual maximum power point to extract the maximum DC input power to the generator under current ambient and operating conditions. Method according to one of claims 13 or 14, characterized in that the step of loading the memory devices ( 17 . 18 ) depending on the size of the available generator voltage and the voltages of the memory devices, an optional switching of the memory devices ( 17 . 18 ) in parallel or in series with one another and charging the memory devices in parallel or series connection. Method according to one of claims 13 to 15, characterized in that the memory devices ( 17 . 18 ) are loaded or unloaded in time offset with frequency-dependent current.

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