WO2011098471A2

WO2011098471A2 - Energy supply system with regenerative current source and method for operating an energy supply system

Info

Publication number: WO2011098471A2
Application number: PCT/EP2011/051870
Authority: WO
Inventors: Siegfried Limmer; Markus GÖTZ; Thomas Fischer
Original assignee: Futuree Fuel Cell Solutions Gmbh
Priority date: 2010-02-10
Filing date: 2011-02-09
Publication date: 2011-08-18
Also published as: WO2011098471A3; CN102884698B; CN102884698A; DE102010000350A1; DE102010000350B4

Abstract

The invention relates to an energy supply system. Said energy supply system is a multi-component system comprising different types of energy sources, including electrical energy sources. The electrical energy sources differ from each other within their type. The energy supply system is based on a plurality of components of which at least one energy source is provided as a primary electrical energy source in the system.

Description

Power supply system with regenerative power source and method for operating a power supply system

The present invention relates to a power supply system having at least one power source capable of supplying DC power to a DC bus, wherein the operating point, referred to as power point of the power supply system, varies depending on external parameters. Furthermore, the present invention relates to a method for operating a power supply system with a DC bus, in which at least one energy source has a maximum power point, which varies in particular depending on external parameters.

Based on the classic subdivision of a power engineer who subdivides types of energy sources into primary energy sources and secondary energy sources, the present invention speaks of primary energy sources when the energy source can convert electrical energy from energy derived from an energy source such as hydro, wind or solar. Among other things, the secondary energy source is referred to as a secondary energy source in one way because it can deliver the energy initially present as electrical energy, possibly temporarily stored in the form of stored hydrogen, again to a DC voltage bus. The primary energy source is thus the source from which primarily the electrical energy of the energy supply system comes. The secondary energy source serves to supplement the electrical energy from the primary energy source. In parallel with the secondary energy source, part of the electrical energy of the primary energy source can be fed into another energy source or into another energy interconnection system, such as a power supply network. Electric energy of the primary energy source is thus passed on to either a load or a consumer network. The secondary energy source supplements a part of the electrical energy of the primary energy source (directly or indirectly) and influences the electrical energy on the DC bus in addition to, further or by specifying energetic components.

Particularly advantageous are primary energy sources based on renewable energy sources. Regenerative energy sources are those sources of energy that, in human judgment, are not consumable in a short-term period, such as several years or several decades. Particularly popular primary energy sources are photovoltaic modules (PV modules), fuel cells and fuel cell modules based on hydrogen or fuel cell modules based on a liquid or gaseous energy source such as methanol, ethanol or biogas, wind turbines and hydropower plants or hydropower generators when used as regenerative energy sources. The primary energy source is a device that can convert a first energy source, such as sunlight, into electrical voltage and current. The primary energy source thus converts energy from an energy source that is considered sustainable, thus can be referred to as regenerative energy source. she can not be completely consumed within a few decades, the energy source is therefore regenerative during the period under consideration. The primary energy source may also be referred to as a regenerative primary energy source.

The primary source of electrical energy is the power source to which the entire power system is optimized. The energy source, which is referred to as the primary source of electrical energy, represents the central source of energy, so a performance optimization is to be performed. In contrast, secondary electrical energy sources represent auxiliary energy sources.

On a DC bus, which must comprise at least two lines, so that two potentials, hence a voltage between the lines can be formed, is the primary energy source. The electrical energy from the primary energy source is provided on the DC bus. However, the voltage level of the primary energy source can deviate from a customary, further to be used voltage. For this reason, it is common to connect voltage converting members, such as a DC to AC converter, also commonly referred to as a DC / AC inverter, to the primary power source.

Printed prior art

For example, in DE 20 2006 001 063 U1 (Applicant: Institute for Solar Energy Supply Technology, filing date: 23.01.2006), it is proposed to use a PV module which can provide an output voltage of 800 V at approximately 200W. The voltage is considered too high for other devices and modules to be connected. For this reason, a step-down converter is connected downstream, which is to supply a current intermediate circuit. The power link serves as an energy source for an inverter. The voltages at the three phases of the inverter are fed back into the power supply system. In general, it can be stated that the voltage can be adjusted to the downstream voltage levels via step-down converter, step-up converter or other voltage-converting elements. Similarly, DE 199 19 766 A1 (Applicant: SMA Regelsysteme GmbH, filing date: 29.04.1999) proposes to increase the performance of the PV modules by connecting individual strings in parallel. Strings are understood to mean series connections of several PV modules. The document proposes to avoid a complicated DC distribution between the individual PV modules in that many inverters are installed in the overall system through the use of modular inverter arrangements. The document thus two approaches for the control of PV modules can be removed. One approach is to switch active DC distribution links behind the PV modules. Alternatively, a large number of inverters can be used. The inverters are necessary because each PV module has its own performance. The individual PV modules should be operated as close as possible to their maximum power point, so that the highest possible energy yield is possible. The maximum power point of a single module is referred to as MPP in the jargon (short for the English term "maximum power point") because it is not clear in advance exactly where the maximum power point lies, also the maximum power point varies depending on many environmental parameters The so-called tracking methods of MPP, also referred to as MPPT methods, are intended to guide the operating point of the primary energy source in a near range around the maximum power point Absolute power maximum is usually never fully achievable and sustainable in the long run Although the MPPT techniques are referred to as finding and maintaining or maintaining the maximum power point, they typically keep the primary power source in a range of about 10% 5% below the maximum most of the time. There is only an approximation to the maximum power point.

Alternatively or additionally, the voltage converting element can also be specially adapted. A specially developed step-down converter can be found in DE 10 2005 046 379 B4 (assignee: Siemens AG Austria, filing date: 28.09.2005), to which two PV modules can be connected. Specially adapted buck converters or special, adapted voltage converting members often have the difficulty to be suitable only for a very specific circuit constellation, in the case described can be so only two photovoltaic modules (PV modules) connect to each other.

If the individual PV modules are each followed by DC-DC voltage converters, then each individual PV module can be operated as described in DE 101 36 147 A1 (Applicant: Kolm, date of application: Jul 25, 2001). Between the individual PV modules and the DC bus, a separate device must be installed as a DC-DC converter. Only at the end of the DC bus can be followed by a DC voltage AC converter. How the MPPT method can be realized can be found both in DE 32 12 022 A1 (Applicant: Siemens AG, filing date: 31.03.1982) and in EP 1 750 193 A1 (Applicant: SMA Technologie AG, priority date: 15.07.2005 ) with numerous further proofs to further MPPT procedures. The MPPT methods disclosed therein are no longer fully discussed in all details for readability purposes of the present description, but the disclosure scope of the cited references and their references to suitable MPPT methods are fully incorporated into the disclosure of the present specification by these references , Another interesting aspect for the design of inverters can be found in DE 10 2004 059 100 A1 (Applicant: Kolm, date of filing: 08.12.2004), which states that a further monitoring method should be installed in the decentralized energy supply system. The DC-AC converter should thus include a monitoring method that checks whether the power generation system is connected to the mains voltage. Furthermore, the entire energy supply system should have MPPT processes at appropriate locations in order to increase the electric current or energy yield.

How various electrical energy sources, which include a wind generator and a solar panel, can be combined via an auxiliary electrical circuit, shows the DE 41 28 962 A1 (Applicant: Kuffer, Filing: 28.08.1991). An increase in efficiency in the energy yield of different energy sources, which can provide very fluctuating energy available, should be achieved by the fact that the diode circuits that connect the energy sources, are also equipped with a deep discharge protection. The operating point of a synchronous generator can be selected by setting an exciter current.

US 2009/076 661 A1 (inventor: Pearson et al., Priority date: 25.07.2007) describes a multiple source power supply system as a hybridized electric power system. The control system of the power supply system comprises several modules, i. a. a prioritization module for electrical energy sources. The energy sources that use non-fuel converting energy conversion techniques should receive preferential prioritization.

US 2006/192 435 A1 (inventor: Parmley, priority date: 26.02.2005) describes a central DC bus in a device with many voltage regulation inputs and outputs to which such devices as an electrolyzer or photovoltaic array are to be connected. With the help of the DC intermediate bus, it is possible to obtain energy from many sources and to provide a stable load.

Unlike the more complex control circuits comprising many components or electrical components and electronic components, US 4 341 607 A (patentee: EF Technology Inc., filing date: 08.12.1980) proposes at selected points in the connecting lines between a photovoltaic array, an electrolyzer , a fuel cell and a DC-AC converter to install a diode for determining the flow of current. A photovoltaic array gem. US 4,341,607 A operates in a range between 5.5 percent and 99.5 percent of its maximum power. Thus, it is difficult to speak of an increase in efficiency with respect to the photovoltaic array. invention description

Contrary to the trend observed in the patent literature to make energy supply systems for regenerative energy sources such as PV modules ever more complicated, there is a desire to design a power supply system that is as simple as possible and reliably ensures the highest possible energy yield of the primary energy source. It is advantageous if the number of parts and assemblies can be reduced.

The object of the invention is achieved by a power supply system according to claim 1. A suitable operating method can be found in claim 16. Advantageous developments can be found in the respective dependent claims.

In the following, an energy source is also used if, due to the design of energy, it can be stored at least temporarily in the device or component. Thus, an accumulator is referred to as an energy source, although it is rechargeable. Likewise, a fuel cell system is referred to as an energy source, although with the aid of an electrolyzer belonging to the fuel cell system, electric energy in the form of hydrogen is temporarily stored. Unlike the other components, the AC-to-DC converter is referred to from the primary side from the supply network perspective, while the remaining components are considered to be the DC bus as the primary side.

As the invention divides the energy sources, the loads can be classified. The primary electrical load is composed of one or more loads for which the power supply system is intended as a supply system. In addition to the primary electrical load, there may be secondary electrical loads that may consume excess power or caching excess power of the power system.

The design of an energy source also makes it possible to harness the energy stored in the energy source. An energy source is thus a device that can release energy stored in it back into convertible, in particular electrical, form for use.

The energy supply system is a multi-component system. The energy supply system has different types of energy sources. There are electrical energy sources. The electrical energy sources differ in type. The power supply system is based on multiple components, of which at least one power source is present as the primary source of electrical energy in the system. It is said to be a primary source of electrical energy when it is the first electrical energy source from which power is to be drawn. The primary electrical Energy is the source of origin in electrical form. The electrical energy source can be operated at different power points. A possible credit is the maximum credit. The maximum credit is usually not always fully complied with. The operating point fluctuates around the maximum power point. For example, the maximum power point may represent a local or absolute maximum. The power supply system is operated to supply an electrical voltage and a short-range electric current around the maximum power point. The near range extends on a characteristic plotted on the ordinate in a range of up to 10%, ideally only up to 5%, around the maximum. In the power supply system, a DC bus is present. The electrical energy source is connected to the DC bus. The DC bus has at least two lines with two different potentials. The DC bus is intended to connect several energy sources together and to be available as a coupling bus. In addition to the primary energy source, at least one additional energy source connected to the DC voltage bus is present. The power source connected to the DC bus serves as a secondary electrical power source. In particular, one or more of the following energy sources can be selected as energy sources in a non-exhaustive list: a fuel cell system, an AC / DC converter, a wind turbine, a wind turbine with an unregulated or weakly regulated DC voltage output, ie with a correspondingly large voltage strokes covering several two-digit voltage ranges DC output, or a wind turbine with stabilized DC output. The further energy source impresses a DC voltage on the DC bus. The voltage directly determines the voltage value of the power operating point of the primary electric power source. By the voltage of the secondary electric power source, the power operating point of the primary power source and thus the entire power supply system is specified. Only a few parts make it possible to set a supply-safe power supply system with at least one voltage value to be preset. Via the voltage originating from the secondary energy source, an operating point which is as optimal as possible, ie characterized by a high energy yield, is set. The MPPT method is operated so that the voltage is adjusted by the primary power source operating close to the MPP.

To the power supply system can also be counted an electrical load. An electrical load can be connected directly to the DC bus. There are different types of electrical loads. For example, there are primary and secondary electrical loads. The primary electrical loads are connected in one embodiment directly to the DC bus.

Depending on the configuration of the energy supply system, photovoltaic modules, in particular photovoltaic modules, are not included in the list of primary electrical energy sources in a non-exhaustive list. Fuel cell or wind turbine calculated. Depending on the configuration of the energy supply system, AC-DC converters, supply network connections, fuel cell systems with and without electrolyzers and accumulator systems are counted among the group of electrical secondary energy sources. The fuel cell systems can be equipped with and without hydrogen storage tanks.

Furthermore, it is advantageous if the energy supply system also includes a primary electrical energy source, the at least one electric regenerative energy module such. B. an electrical photovoltaic element is. The credit point, d. H. the operating point with the maximum possible power of the primary power source, the power supply system, in particular the regenerative energy module, depends on external operating parameters to which the power supply system has no direct influence. The power supply system must be able to perform an adaptive operating point shift depending on the external operating parameters. The adaptive operating point shift takes place successively. A permanently performed MPPT procedure is operated. Outer operating parameters that have a significant effect on the power output and thus on the power operating point of the primary power source are the sunlight irradiation intensity and the operating temperature. To reduce the operating temperature, the photovoltaic elements can be equipped with an active, in particular back, cooling. The possible electrical power is also determined by the current drawn from the photovoltaic module. With increasing current the voltage decreases. A distribution of power to the different sources can contribute to an overall performance increase. In each case a part of the total current is drawn from different sources. The heat development in an electrical module is limited by this mode of operation and kept under control. For the MPPT process to be performed reliably, the power output should be measured. There is a power meter in the power supply system. Ideally, all modules of the same type, for example all photovoltaic modules, can be combined via a power meter. In this context, the DC bus is divided into individual sections. At each section of the DC bus only modules of the same type, z. B. fuel cell systems and fuel cell stack connected. In an alternative embodiment, a power meter is connected to each module. There is a power meter between the module and the DC bus. The more power meters that are available, the more accurate the power flow in the power supply system can be in a central controller.

The central controller processes weather data. The weather data are data that either reflect the current weather or represent a weather forecast. The weather data determine the expected exploitation of the photovoltaic modules or the wind turbine. The weather data can be set in relation to the desired amounts of energy. In a further development of the energy supply system, this is further distinguished by the fact that it has at least two secondary electrical energy sources. The secondary electrical energy sources are operated with different priorities. This means that one of the energy sources has a higher priority than the other electrical energy source. Energy sources of the same kind, eg. As secondary electrical energy sources, differ from each other by their assigned priority. The priorities are formed as a function of different edge parameters of the energy supply system. In the case of predicted high levels of solar radiation, the energy module "accumulator" would be associated with a higher priority than the energy source "fuel cell module" in the run-up to solar radiation. The electric current is composed of the different energy sources with different priority. The electric current is used to supply the electrical load. The regenerative energy module contributes to the energy supply, as long as it can provide sufficient energy. The primary electrical energy sources are connected directly, ie without active voltage conversion, to the DC bus. There is a direct coupling of each of the primary energy sources to the DC bus. A voltage drop of a primary electrical energy source can not take place independently of the other similar energy sources. All energy sources are mutually immediate at the same voltage. No component shears out of the voltage band or from the voltage level of the DC bus. The power supply system stabilizes at an operating point by the impressed voltage.

In the power supply system, the at least one primary electric power source is advantageously coupled without a voltage converting member. The voltage levels are not converted. The voltage of the primary electric power source is switched directly to the DC bus. There is no DC / DC converter between power source and DC bus. No energy is consumed for voltage level adjustments. The overall efficiency can be increased. Due to the absence, no losses occur in the DC / DC converter.

The voltage in the power system is dictated at a single central location. At a single voltage terminal, the voltage of a secondary power source is impressed on the DC bus. The voltage connection can be z. B. advantageously form by two copper bars. The secondary power source provides voltage on the DC bus. From a central location, the overall power point can be adjusted. A more complicated networking between the individual MPPT modules is eliminated because there is only a single MPPT module. For the sake of simplicity, a fast, successive iteration method to the MPPT is used in the central controller. The MPPT method uses different step sizes, which are varied during operation. The energy supply system thus oscillates around its maximum power point. The Power system is approaching its maximum power point. With the aid of the M PPT method, the energy supply system does not stay in the MPP, but it fluctuates around its maximum. The exact modes of operation can be found in the MPP method described above.

The energy supply system used in an advantageous embodiment, at least one of the secondary electrical energy sources as a buffer. The buffer takes at least a portion of the electrical energy from the DC bus. The secondary electric power source temporarily draws a portion of the energy from the DC bus, operating temporarily as a secondary electrical load. With the help of the secondary electric power source electrical energy is provided for a connected electrical load on the voltage converting member as needed. Excess electrical energy can be converted or stored in the secondary electrical load.

The voltage converting member can be made as simple as possible, when the voltage level of the DC bus is adapted to the voltage range of the electrical load or the electrical loads. In a 12V load system, for example, the voltage level can be settled between 10V and 15V. In a 24 V load system, for example, the voltage level can be set between 20 V and 30 V. For example, in telecommunications networks operating at voltages of 48V, the voltage range in one embodiment should be in a range between 40V and 60V. If the DC bus is designed so that the voltage converting member is an inverter for a high-voltage system, the voltage range may cover a range of 230V to 600V. The respective voltage strokes can be covered by stacks of polymer electrolyte membrane fuel cells operating on hydrogen and air. If the wind energy plant, because they are only weakly regulated, for example, tuned to this voltage range, fuel cell stack and wind turbine can be connected directly and directly to the same DC bus. The number of fuel cells is tuned to the voltage range. The number of photovoltaic elements is matched to the voltage range. The usual operating range and the voltage deliverable per module are within the voltage range.

Due to the parallel connection of the different energy sources in the energy supply system, the set maximum power point is a total power point of all primary electric power sources connected to the DC bus. Only one summed power point that applies to all primary electrical energy sources is determined and formed. The power point will often or almost usually deviate from the respective individual maximum power point of a single primary electrical energy source. The Simplification in control and in the number of components justifies the deviation from the maximum power points of each individual module.

The energy supply system comprises in an advantageous embodiment, at least one photovoltaic module. One of the primary sources of electrical energy is a photovoltaic module with multiple photocells. The photocells are interconnected in parallel or in series for greater current or voltage. One of the secondary electrical energy sources is another electrical device that provides regenerative electrical energy. When considering the power point of the power system, the power point of each photocell or each PV module is no longer considered. This leads to a simplification of the overall system.

In this case, all primary electrical energy sources work in a voltage window around a nominal voltage of the load to be connected. The voltages are matched to the electrical load to be connected. The matching of the electrical energy sources to the expected load promotes the simplification of the overall system.

The voltage window can, if a wind power plant is connected, determined by the voltage width of the output voltage of the regulated voltage at the wind turbine. The voltage can be decoupled weakly regulated. Within a large speed range of the wind energy plant, it is no longer necessary to precisely adjust the voltage from the energy source. A weak control provides simple means, such as a stabilized half-wave rectification, for voltage stabilization in a limited voltage swing range.

A secondary electric power source of the power supply system is an AC-to-DC converter connected to the electrical supply network. The electrical energy is thus additionally obtained from the supply network. In the opposite case can serve as electrical load, and in the discharge case as an energy source, the supply network as a buffer. The supply network assumes the function of an almost infinitely large accumulator. The battery is in the state of charge as a load to consider in the discharge state as an energy source.

The energy supply system can provide power to secondary electrical loads. For this purpose, excess energy from the primary electrical energy source in the secondary electrical load is converted or stored as part of the energy supply system. In accordance with the hierarchical terms of the electrical energy sources, the electrical loads can also be prioritized. They are turned on and off in accordance with their priority. Preferably, the primary electrical devices, such as primary electrical energy source or primary electrical load, are operated with higher priority than downstream electrical devices. Subordinate electrical appliances are secondary or tertiary electrical energy sources. If the energy from the primary sources of electrical energy is insufficient, then the secondary electrical loads disconnected from the DC bus. The electrical energy is concentrated on the primary electrical loads.

The secondary electrical load comprises - in another embodiment - an electrolyzer in a fuel cell system. Thus, the electrical energy can be stored in the form of hydrogen. Especially with energetic isolated solutions, a system designed in this way is advantageous. In an advantageous embodiment, the energy supply system has a component which is a secondary electrical voltage source, such as a fuel cell system and an electrolyzer, as a secondary electrical load. The secondary electrical load and the secondary electrical voltage source are combined to form a hydrogen energy system as a subunit, in particular in its own housing.

The multi-component power supply system can be operated by the following method. For operating a power supply system having at least one primary electric power source, such as a photovoltaic element, and at least one secondary electric power source having a DC output, a maximum power point for all the primary electric power sources connected to a common DC bus is set by a single MPPT method. Thus, a maximum power point is set for all primary electric power sources connected to the DC bus. Not every single device is operated in its MPP. The maximum power point results as summarily formed maximum power point of all devices that can be operated as primary electrical energy sources. The secondary electrical energy sources specify the voltage of the power point. The method can be applied if there is one or if there are multiple secondary electrical energy sources.

The method performs switch on and off of loads in accordance with their characterization as a primary, secondary, and tertiary electrical load according to a priority list. The central controller follows at least two independent priority lists, one for the energy sources, one for the loads.

The method processes information about future events in an advantageous embodiment. Future events are weather forecasts. At the same time or in addition, the current weather data can be collected. The expected performance of the regenerative energy sources, in particular the photovoltaic modules, is included in the priority calculation. In accordance with the measured power, either total power or partial power, the priority list is followed and the electrical loads are added or removed. There is a switching of the electrical loads on the DC bus in accordance with the energy measurements. There is a switching of the electrical loads on the DC bus in accordance with the data, in particular the weather forecast data. There is a switch of electrical loads on and off the DC bus in accordance with the energy measurements and in accordance with the prediction data.

The present system and the present method are characterized by the fact that among other things it has been recognized that the optimization of each individual device and module with respect to its maximum power point can only be produced by a disproportionate effort. Significantly easier, and yet at least almost equally efficient, it is when the devices are connected directly to a DC bus. From a source comes the specified voltage value, which is determined according to criteria of a maximum power point. By specifying the voltage value on the DC bus, such operating points are set directly in the respective devices and components, resulting in a total of a maximum power point. The maximum power point can represent a local or absolute maximum, depending on the selected criterion.

The power supply system is centrally located around a DC bus with a central controller. All components are located directly on the DC bus. All modules can be switched on and off on the DC bus. Individual power meters are installed in the power supply system. The controller works with priority tables. The controller works with calculation over current energy distributions in the energy supply system and possibly with future (expected) energy distributions. Power on the DC bus can be cached in stores. As memory serve in alternative embodiments accumulators, fuel cell systems with electrolyzer and hydrogen storage and more global supply networks. The main source of energy supply, provided that it is sufficiently available, is the photovoltaic modules. Energy can be taken down from the DC bus and switched back to below desired outputs.

Brief Description

The invention can be better understood by reference to the accompanying figures, in which:

Fig. 1 Typical current-voltage characteristics and performance characteristics of a photovoltaic module as a function of the radiation intensity; on the abscissa the tension is removed; the ordinate measures the current for the current-voltage characteristics and the power for the power characteristics;

Fig. 2 Typical performance characteristics of a photovoltaic module as a function of the temperature of the PV module; on the abscissa the tension is removed; the ordinate measures the power; Fig. 3 equivalent circuit diagram of a first embodiment of the invention

Energy supply system with a primary energy source;

Fig. 4 equivalent circuit diagram of a second embodiment of the invention

Energy supply system with two primary energy sources;

Fig. 5 equivalent circuit diagram of a third embodiment of the invention

Energy supply system with two primary energy sources and other secondary energy sources;

figure description

FIG. 1 shows a comparison of different PV characteristic curves 2, ie of typical current-voltage characteristics 3 and performance characteristics 5 of a conventional PV module. The different curves of the current-voltage characteristics 3 and the power characteristics 5 result from a respective changed, the PV module offered, radiation intensity. Depending on the radiation intensity, the current increases or decreases. At lower radiation intensity, the current decreases. As the radiation intensity increases, the current increases. Four different radiation intensities, between 1000 and 400 W / m ² inclusive, are shown on the basis of the current efficiency. The power characteristics which result from the respective current and a voltage that can be applied externally to the PV module have a variable maximum power point MPP as a function of the radiation intensity of the solar radiation. The voltage range covers those voltage values to which the DC voltage bus 8 (see, for example, FIG. 3) is tuned. The voltage range in which the PV module is operated extends from a lower MPP to an upper MPP. The voltage range is matched in one embodiment to the number of fuel cells of a fuel cell stack and the consumers to be supplied (primary / secondary / tertiary load). The operating voltage range of the fuel cell stack is consistent with the voltage range of the PV module.

Fig. 1 shows on the abscissa the voltage of the PV module in volts. The voltage range covers the operating range of the largest PV module for the 1000 W / m ² -PV characteristics. For smaller radiation intensities, such as 400 W / m ² , the voltage operating range decreases. On the ordinate, the current I is plotted for the current-voltage characteristics 3 and the power P for the power characteristics. The current range sweeps the greatest current range for the 1000 W / m ² stream-voltage characteristic. For smaller radiation intensities, such as 400 W / m ² , in contrast, decreases the current-moderate operating range. The power range covers the largest power range for the 1000 W / m ² power curve. For smaller radiation intensities, such as 400 W / m ² , the power operating range decreases in contrast. The illustrated current or power curves 3, 5 as a function of the voltage are indicated in FIG. 1 for an ambient temperature of 25 ° Celsius. Fig. 2 shows performance curves 6, which are plotted against the voltage U. The performance characteristics of a PV module depend not only on the radiation intensity of the incident light (see FIG. 1), but also on the temperature of the PV module. If the PV module has a lower temperature, a larger power can be obtained. In the diagram of Fig. 2 performance curves 6 are plotted as a function of different temperatures. The highest power output is obtained at a low temperature, such as 263 K, ie, about minus 10 degrees Celsius. The temperature of the PV module must be as low as possible. For this purpose, in one embodiment, the PV module is actively cooled. The lowest power output is obtained at a high temperature, such as 333 K, ie plus 60 ° C. The lowest power output could also be obtained at a high temperature, such as 373K, ie plus 100 ° Celsius.

Fig. 2 shows on the ordinate the power P of the PV module in watts and on the abscissa the voltages U at 1000 W / m ² radiation intensity. At 263 K, ie at minus 10 ° Celsius, the voltage range, ie the voltage operating range, of the PV module and the power range is greatest. At 333 K, ie at plus 60 ° C, and thus at the highest of the in Fig. 2Fig. 2, the power range and the voltage range are the smallest.

As one skilled in the art will see, the MPP will vary depending on many external parameters, such as radiation intensity (Figure 1) and, for example, PV module temperature (Figure 2). In order to avoid having to distribute vast amounts of different sensors across the power supply system, the maximum power point search is accomplished by an MPPT method. As a slightly variable size can be used for this purpose according to an aspect of the invention, the voltage. The voltage can be impressed on the PV module (s) via a DC bus. For this purpose, a method for determining the maximum power point (MPP) is performed.

3 shows a first embodiment of the energy supply system 1 according to the invention. The power supply system 1 has, in the first embodiment, a power source 4 provided as a primary electric power source 4. The power source 4 is here a photovoltaic module 60, short PV module. The photovoltaic module 60 includes a plurality of photocells 64, which are interconnected for a larger current or a larger voltage. In the first embodiment, the photocells 64 are connected in series for a larger voltage. They could also be connected in parallel for a larger current. A combination of series and parallel circuits for greater voltage and current efficiency are conceivable and possible.

The power source 4 supplies an electric voltage U _p and an electric current I _p in the vicinity of its maximum power point MPP. The primary power source 4, 60, 64 is connected to a DC bus 8. The DC voltage bus 8 as a separate system component of the power supply system 1 is shown delimited in FIG. 3 by the separating line 9 (bus characteristic) from the rest of the power supply system 1. The power source 4, 60, 64 is directly coupled to the DC bus 8. The DC voltage bus 8 comprises two lines 12, 16. The DC voltage bus 8 is intended for the connection of several energy sources. In the first embodiment, three additional power sources 20, 24, 28 are connected to the DC bus 8. One or more energy sinks, ie one or more consumers, can also be connected to the DC voltage bus 8. To the DC bus 8, an electrical device, such as an electromagnetic energy converter, be connected, which can change their operating state so that they can act on the one hand as energy source on the other hand as Energiesenke.

The power source 20 is a secondary electric power source. The energy source 20 is here a constructed with an electrolyzer 72, based on a fuel cell stack 56, realized DC generator. The DC voltage generator 20 supplies a DC voltage IL with negligible ripple. The energy source 24 is a secondary electrical energy source, namely a fuel cell system 24. The fuel cell system 24 as a secondary electrical energy source comprises an electrolyzer 72. The energy source 28 is also a secondary electrical energy source, namely a voltage converting member 48 in the form of an AC-DC voltage Converter 28.

Each of the further energy sources 20, 24, 28, when connected to the DC voltage bus 8, impress a DC voltage LL on the DC voltage bus 8. In the illustrated operating state of the power supply system 1, the DC voltage generator 20 impresses its DC voltage LL on the lines 12, 16 of the DC bus 8. In addition to the DC voltage generator, depending on the priority setting, the rectifier of the AC to DC converter 28 can also apply a voltage.

The DC voltage LL directly gives the voltage value of the power operating point POP, namely POP = LL ^* _1p , to the primary electric power source 4. Because of the direct coupling of all primary and secondary energy sources 4, 60, 20, 24, 28 to the DC voltage bus 8, the voltage value of the DC voltage LL is identical to the voltage value U _{P of} the PV module.

The AC-DC converter 28 serves to couple the power supply system 1 to an electric power grid. The electrical energy network is coupled to an electrical supply network 76. In the electric power network of the first embodiment, a single-phase AC voltage is the operating voltage. It is conceivable and possible to design the electrical energy network for a three-phase alternating voltage with or without neutral. In this case, there would have to be at least three AC voltage / DC converters 28 operating in phase-shifted manner, each of which can take a phase voltage from the power grid or the supply network 76.

The electrical energy network, which can supply the energy supply system 1 with electrical energy from the supply network 76 via the AC-to-DC converter 28, is symbolically delimited from the energy supply system 1 in FIG. 3 by the dividing line 17.

The primary electric power source 4 is a regenerative electric power module 32 in the form of a PV module 60. The PV regenerative power module 32 includes at least one photovoltaic electric element 36. The regenerative electric power module 32 is dependent on external operating parameters, in the first embodiment, these are substantially Sunlight intensity and operating temperature, an adjustable maximum power point MPP.

In the first embodiment, there are three secondary electric power sources 20, 24, 28. The secondary electrical energy sources 20, 24, 28 contribute to the supply of an electrical load 80 with different priorities, which are determined from different edge parameters. The electrical load 80 may be a primary electrical load.

The primary electrical energy sources 4 are switched to the DC bus 8 without active voltage conversion.

In the described operating state, a single voltage connection 52 of a secondary energy source 20, namely the voltage connection of the DC voltage generator 20, provides the impressed voltage LL on the DC voltage bus 8.

The secondary electric energy source 20, in the form of the fuel cell system 24, supplies at least part of the electrical energy from the DC voltage bus 8 to supply the electrolyzer 72. The fuel cell system 24 provides electrical energy for the electrical load 80 to be connected as required.

The primary electric power source 4 operates in a voltage window around a nominal voltage U _{N of} the electrical load 80 to be connected.

The power supply system 1 of the first embodiment is controlled by a central controller 40. The controller 40 controls the power supply system 1 via a control bus 41. The control bus 41 may be a control network. The Control network can be a wireless network. The controller 40 may be incorporated into a higher level power control system. In particular, with increased security requirements, the control bus 41 is preferably a wired transmission device for transmitting control signals from the controller 40. The controller 40 controls the primary and secondary power sources 4, 20, 24, 28. The controller 40 controls the primary power sources 4 indirectly. The controller 40 controls the secondary energy sources directly. The controller 40 indirectly controls the primary energy sources by directly controlling the secondary energy sources. In an alternative, not shown variant, the direct control of the primary energy source by the controller 40 is possible. The controller 40 may selectively couple the primary and secondary power sources to the DC bus 8 via control signals of the control bus 41. In the control of the primary and secondary energy sources, weather data 10, in particular data for weather forecasts, such as air temperature, cloud density, radiation intensity, etc., flow. In the control of the primary and secondary energy sources and environmental data, such as air pollution data, etc., can be incorporated. The control of the primary and secondary energy sources can also include market data, such as raw material prices or prices or price forecasts for resources such as purchased electricity.

In the first embodiment, in the power supply system 1, only the primary electric power source 4 is coupled without a voltage converting member 48. The power source 4 is without a voltage converting member 48, d. H. directly, can be coupled to the DC bus 8.

There is a power meter 7 in the power supply system 1 of the first embodiment. The power meter 7 measures the power output from the primary power source 4. The power meter 7 detects to determine the power of the primary power source 4 substantially the electric voltage U _p and the electric current l _{p of} the PV module 60. The controller 40 can read the measured power from the power meter 7 via the control bus 41. The controller 40 executes an M PPT method, whereby the primary power source 4 is kept close to its maximum power point MPP. The controller 40 knows from the power measurement the prevailing on the DC bus 8 voltage LL. If the deviation is too great, such as 10% or 5%, etc., the actual voltage from the desired voltage that can be determined with the aid of the power measurement causes the controller 40 via the control bus 41 a corresponding change in the terminal voltage of the secondary energy source 20 or 28 That is, the controller 40 causes the increase or decrease in the voltage level by impressing the output from the secondary energy source 20 and 28 target voltage on the DC bus 8. In this way, the primary power source 4 can be kept in the vicinity of their maximum power point MPP , 4 shows a second embodiment of the energy supply system 1 according to the invention, which has two primary energy sources 4. For the second embodiment, what has been said above for the first embodiment applies analogously. The two primary energy sources 4 are PV modules 60 of the same type, ie the PV characteristics, in particular the power characteristics of the two PV modules 60 match as possible. Each of the two primary energy sources 4 of the second embodiment can be coupled to the DC voltage bus 8 independently of the respective other energy source 4 via a switch 42. In the illustrated operating state, both switches 42 are closed, ie both primary energy sources 4 are coupled to the DC voltage bus 8. The two switches 42 can be opened or closed independently of each other. The opening or closing of the switch 42 can be done automatically via the controller 40.

The set maximum power point of the power supply system 1 according to the second embodiment is a total power point gMPP of all connected to the DC bus 8 primary electric power sources 4, of which in particular the respective individual maximum power point MPP of a primary electric power source 4 deviates.

In the second embodiment, all PV modules 60 of the same type can be combined via a power meter 7. In an alternative embodiment, a separate power meter 7 can be connected to each PV module 60. The more power meters 7 are present, the more accurate can be in the central controller 40, the power flow in the power supply system 1 follow.

The power supply system 1 according to the second embodiment provides energy as an energy supply system 1 to the secondary electric load 44. The secondary electrical load 44 is provided only when there is an excess of energy in the supply of the primary electrical load 80 to the secondary electrical load 44.

FIG. 5 shows a third embodiment of the energy supply system 1 according to the invention, which has two primary energy sources 4, 73 and three secondary energy sources 20, 24, 68. For the first primary power source 4 and the two secondary power sources 20 and 24, what is said in the first or second embodiment applies analogously, but the DC voltage generator 20 in the third embodiment has no battery pack 68. The second primary power source 73 is a wind turbine. The wind turbine 73 is connected to the DC bus 8 via a voltage converting member 48, a DC-DC converter. The third secondary energy source 68 is a separate accumulator system 68. The third secondary energy source is thus another electrical device 68 that provides regenerative electrical energy. The accumulator system 68 is also connected via a voltage converting member 48, also a DC-DC converter, to the DC bus 8. The voltage window in which the primary electric energy sources 4 operate in a voltage window around a nominal voltage U _{N of} the electrical load 44 to be connected is determined by the voltage width of the output voltage of the regulated voltage at the wind turbine 73.

The primary electrical load 80 and the secondary electrical load 44 can be connected to the DC bus 8.

The power supply system 1 of all three embodiments is operated by a method according to the invention, wherein the voltage LL of the at least one secondary electrical energy source 20 occurs at a DC voltage output 84 of the secondary electrical energy source 20.

A maximum power point MPP is set for all primary electric power sources 4 connected to a common DC bus 8 by a single M PPT method, so that a common maximum power point gMPP is set for all primary electric power sources 4 connected to the DC bus 8.

An activation and deactivation of the energy sources 4, 20, 24, 28, 32, 36, 56, 60, 68, 76 takes place in accordance with their characterization as a primary, secondary and tertiary energy source according to a priority list. The tertiary electrical load 88 is present only in FIG. 5 in the third embodiment.

LIST OF REFERENCE NUMBERS

Energy supply system 72 Electrolyzer

PV characteristic 73 Wind energy plant

Current-voltage characteristic 76 electrical supply network primary (electrical) power source 80 primary electrical load

Power characteristic 84 DC output of the power characteristic secondary power source

Power meter 88 tertiary electrical load

DC bus

Bus line abbreviations and size signs

Weather data U _p electrical voltage of the primary line power source

Line l _p electric current of primary power line power source

secondary (electric) energy source MPP maximum power point

Fuel cell system LL DC voltage of the secondary AC-DC power source

Converter POP power operating point of the primary regenerative power module energy source

electric photovoltaic element U _N nominal voltage

central controller gMPP common maximum

Control bus power point

Switch U voltage

(secondary) electrical load I current

P performance

tension-converting member

voltage connection

cache

photovoltaic module

photocell

electric device

Claims

claims

1 . Energy supply system (1) with at least one energy source (4),

- Which is present as the primary electrical energy source (4) and

5 - which provides an electrical voltage (U _p ) and an electric current (l _p ) in the vicinity of their maximum power point (MPP) around and

- which is connected to a DC bus (8),

- Which comprises at least two lines (12, 16) and

- which is intended for the connection of several energy sources (20, 24, 28), i o characterized in that

there is at least one further energy source (20) connected to the DC voltage bus (8),

- Which serves as a secondary electric power source (20), such as a

Fuel cell system (24) or an AC-DC converter

15 (28), and

the further energy source (20) impresses a DC voltage (LL) on the DC voltage bus (8),

which directly specifies the voltage value of the power operating point (POP) of the primary electric power source (4).

20

2. Energy supply system (1) according to claim 1,

characterized in that

the primary electrical energy source (4) at least one electrical

Regenerative energy module (32), such as a photovoltaic electric element (36),

25

in particular depending on externa ßeren operating parameters, such as

Sunlight intensity or operating temperature, has an adjustable maximum power point (MPP).

30 3. Energy supply system (1) according to one of the preceding claims,

characterized in that

the power supply system (1) is controlled by a central controller (40) on the basis of weather data, in particular data for weather forecasts.

35 4. Energy supply system (1) according to one of the preceding claims,

characterized in that

at least two secondary electrical energy sources (20) are present, which with different priorities, which are determined from different boundary parameters, contribute to the supply of an electrical load (80), and

preferably the primary electrical energy sources (4) without active

Voltage conversion to the DC bus (8) are switched.

Energy supply system (1) according to one of the preceding claims,

characterized in that

in the power supply system (1) only the primary electric power source (4) without a voltage converting member (48) is coupled.

Energy supply system (1) according to one of the preceding claims,

characterized in that

a single voltage terminal (52) provides a secondary energy source (20) with the impressed voltage (IL) on the DC bus (8).

Power supply system (1) according to one of claims 5 or 6,

characterized in that

the secondary electrical energy source (20) as intermediate storage (56) receives at least a portion of the electrical energy from the DC bus (8) to provide electrical energy for the electrical load (80) to be connected via the voltage converting member (48) as needed.

Energy recovery system (1) according to one of the preceding claims,

characterized in that

the set maximum power point is a total power point (gMPP) of all primary electric power sources (4) connected to the DC bus (8), of which in particular the respective individual maximum power point (MPP) of a primary electric power source (4) deviates.

Energy supply system (1) according to one of the preceding claims,

characterized in that

at least one of the primary electrical energy sources (4) is a photovoltaic module (60) with a plurality of photocells (64) interconnected with each other for a greater current or voltage, and preferably one of the secondary electrical energy sources (20) is another electrical device ( 68) which provides regenerative electrical energy.

10. Energy supply system (1) according to one of the preceding claims, characterized in that

all primary electrical energy sources (4) operate in a voltage window around a nominal voltage (U _N ) of the load (80) to be connected.

1 1. Power supply system (1) according to claim 10,

characterized in that

the voltage window is determined by the voltage width of the output voltage of the regulated voltage at a wind turbine (73).

12. Energy supply system (1) according to one of the preceding claims 1 to 9, characterized in that

a secondary electrical energy source (20) of the power supply system (1) is an AC to DC converter (28) connected to the electrical supply network (76).

13. Energy supply system (1) according to one of the preceding claims,

characterized in that

the energy supply system (1) provides energy to secondary electrical loads (44) that is provided only when there is excess energy in supplying the primary electrical load (44) to the secondary electrical load (44).

14. Energy supply system (1) according to one of the preceding claims,

characterized in that

the power supply system (1) comprises the secondary electrical power source (20) such as a fuel cell system (24) and an electrolyzer (72) as a secondary electrical load (44), preferably the secondary electrical load (44) and the secondary electrical power source (20). are combined to form a hydrogen energy system.

15. Energy supply system (1) according to one of the preceding claims,

characterized in that

the at least one primary electrical load (80) and the at least one secondary electrical load (44) are connectable to the DC bus (8) without an active voltage regulation to supply the load (44, 80).

16. A method for operating a power supply system (1), in particular according to one of the preceding claims,

with at least one primary electrical energy source (4) such as a

Photovoltaic element (36) and

with at least one secondary electrical energy source (20) having a

DC output (84),

characterized in that

a maximum power point (MPP) for all at one common

DC bus (8) connected primary electrical energy sources (4) by a single M PPT method is set so that a common maximum power point (gMPP) for all on the DC bus (8) connected primary electric energy sources (4) is set.

17. The method according to claim 16,

characterized in that

connecting and disconnecting the loads (44, 80, 88) in accordance with their characterization as a primary, secondary and tertiary electrical load (44, 80, 88) according to a priority list.