DE102012023426A1 - Electrical arrangement and electrical system with an electrical arrangement - Google Patents

Abstract

An electrical arrangement is described, to which a generator and an energy store can be connected, each of which can feed a DC voltage into the arrangement, and which has an inverter which generates as an output voltage a single-phase or multi-phase AC voltage which the arrangement has at least one output line outputs, the output voltage having a voltage level and frequency such that it is suitable for supplying a local installation and for feeding into a voltage supply network, the arrangement controlling a plurality of electromechanical switches, so that the output voltage in a first operating mode (mains operation) on the voltage supply network is present, and in a second operating mode (island operation) is applied to the local installation and is separated from the power supply network, the arrangement producing an output signal in the second operating mode and using a loca in the second operating mode len installation outputs connected output line, the output signal generally signals the presence of the second operating mode or the presence of a reduced energy delivery capacity of the generator and / or the energy store. The invention also relates to an electrical system which has such an electrical arrangement.

Description

The invention relates to an electrical arrangement to which a generator and an energy storage can be connected, each of which can supply a DC voltage in the arrangement, and which has an inverter which generates a single or multi-phase AC voltage as output voltage, which the arrangement via at least one Output line outputs, wherein the output voltage has such a voltage level and frequency that it is suitable for supplying a local installation and for feeding into a power supply network, the arrangement controls a plurality of electromechanical switches, so that the output voltage in a first mode is applied to the power supply network, and in a second mode is applied to the local installation and disconnected from the power supply network. The invention also relates to an electrical system having such an electrical arrangement.

Electrical systems for the conversion of renewable energy, such as wind power or photovoltaic systems usually have an arrangement with an inverter, which outputs a voltage in the height and frequency of the usual mains AC voltage. It is usually provided that the electrical output power of the inverter can be fed in addition to a local consumer network and all or part of a public power grid.

The problem leading to the invention will be explained below by way of example and without restricting the general public on the basis of a photovoltaic system. Photovoltaic systems for the at least supportive energy supply of buildings are becoming increasingly widespread. The electrical power output of a photovoltaic generator is subject to fluctuations over the course of the day and therefore practically never corresponds exactly to the instantaneous energy demand of the consumers installed in the building, which in the following are collectively referred to as local installation as a local installation.

Thus, a photovoltaic system can generate an electric power during the light hours of the day, which goes far beyond the electrical power requirements of the local installation, so that excess electrical energy can be fed into a public power grid. In the rest of the time it may be necessary to remove electrical energy from the public power supply network to compensate for energy shortages.

Photovoltaic systems with a so-called self-consumption optimization have accumulators as energy storage, which can store several kilowatt hours of electrical energy. The supply or removal of electrical energy from the public power grid takes place here only when the buffering capacity of the energy storage is exceeded or if this is due to daytime electricity tariffs profitable.

For the operation of such systems, therefore, different modes are provided, namely, first, the operation with coupling to the power supply network, referred to in the present text as network operation, and secondly the decoupled from the power supply operation, which is named here as island operation. The island operation allows in a power failure operation of consumers of a local installation over a period of time from the energy of a generator and / or an energy storage.

In mains operation, the mains voltage and the mains frequency are specified by the power supply network. A change of these two parameters by the inverter is not possible. The inverter operates as a power source and feeds depending on the amount of energy from the photovoltaic generator or from an energy storage electrical energy into the power grid.

In isolated mode, the inverter is completely disconnected from the power supply network. It is the function of the inverter to provide a preferably three-phase power supply, as provided by the power supply network in network operation. Load fluctuations, for example due to the switching on and off of connected loads, must be completely compensated by the inverter. The goal is to ensure a voltage supply independent of the output current. In this respect, the inverter is to be regarded here as a voltage source.

With regard to the availability of electrical energy and power, however, there are restrictions compared to grid-connected operation. First, the output current of the inverter is limited by the dimensioning of its power electronics to a certain value. In addition, no more electrical energy can be made available than the sum of the energy currently supplied by the photovoltaic generator and the energy present in the energy store. This results in the necessity of energy or performance management.

It set itself the task of creating an electrical arrangement that allows a particularly simple and cost-effective way an energy management in island operation of an electrical system.

This object is achieved according to the invention in that the arrangement (in the second mode of operation produces an output signal and outputs via an output line connected in the second mode to the local installation, the output signal being generally the presence of the second mode or the presence of reduced power delivery capability of the generator and / or the energy storage signaled.

It is advantageous that the transmission of the output signal requires no additional lines and installations.

The signaling of the presence of the second mode of operation, ie island operation, or a reduced energy delivery capability of the generator and / or the energy storage can be done in various advantageous ways by at least one electrical variable of the output voltage is varied in a characteristic manner, without the function of the power supply This is significantly impaired. In particular, a voltage reduction, a frequency change or a repeated or in particular periodic or cyclic variation of the magnitude of the output voltage can be provided. All of these types of signaling can advantageously be detected automatically by detection means within the local installation and trigger appropriate measures regarding energy-saving operation of the consumers belonging to the local installation.

These measures can be advantageous in that certain consumers are operated with a reduced electrical power or even switched off completely. A shutdown can be done either immediately or after a predetermined time. It can also be provided to first convert consumers to a safe state before switching off, for example, to shut down computers before switching them off.

For most consumers can advantageously be provided a lowering of the supply voltage. Many consumers with a high power consumption exhibit the electrical behavior of an ohmic resistance. In such consumers, the power consumption can be effectively limited by a voltage reduction, since the power consumption drops quadratically with voltage reduction (P ~ U ² ). In the interconnected network, a voltage tolerance of ± 10% is permissible. With this voltage change results in a power variation of about ± 20%. In this respect, a voltage reduction is an effective measure for power reduction. It can even be provided an even greater voltage reduction, because with respect to the island network not necessarily applicable for a power supply network tolerance limits must be adopted.

A voltage reduction reaches important consumers such as emergency lighting, telecommunications equipment, refrigerators, as long as possible to keep in operation. Such consumers are usually equipped with electronic switching power supplies that allow a much larger voltage variance without having functional limitations.

It is particularly advantageous that a voltage reduction is directly energy-saving effect, without relying on detection means.

Instead of or in addition to a voltage reduction, the island operating mode of the electrical arrangement, and in particular also an outgoing energy supply of the energy store can be signaled by a cyclic voltage variation. It can be provided, for example, that the output voltage of the electrical arrangement is lowered periodically by 10% every second and then raised again. This signaling, which of course does not have to be permanent, but can also be repeated cyclically at intervals, can be detected by an automatic detection means.

In addition, it can lead to conspicuous effects (such as brightness fluctuations of electrical lamps or speed fluctuations of electric drives), so that this signaling is easily recognizable as an indication to human users. This allows either the detection means automatically or the user to initiate a suitable response to the signaled mode by manual means.

As a further possibility of the signaling, a frequency change of the output voltage can be provided. Frequency changes in the per thousand range generally do not have a direct effect on the operation of electrical consumers and are therefore not directly perceptible by a user. By an electronic detection means such frequency changes are easily recognizable and evaluated.

In the following, the invention will be explained in more detail with reference to an embodiment shown in the drawing. The 1 and 2 each show in the form of a block diagram of the structure of an electrical system, the electrical energy to supply a local installation, which may be given by the entirety of the electrical systems and consumers of a building, provides and can also feed electrical energy into a public power grid , The 3 represents details of the local installation. The 4 to 6 show in each case a diagram of possible output signals.

Central element of the 1 and 2 shown electrical system is highlighted by a dashed border, an electrical arrangement 5 to which a photovoltaic generator 10 and an energy store 11 can be connected. The photovoltaic generator 10 consists of a plurality of, not shown here, photovoltaic modules, which in turn each have a plurality of solar cells. The photovoltaic generator 10 converts radiant energy of the sun into electrical energy, whereby the emitted electrical power can vary in the course of the day depending on the momentary incidence of light.

To the power output of the electrical arrangement 5 better to the needs of the local installation 3 adapt, is the energy storage 11 is provided, which preferably consists of an interconnection of accumulators with a total capacity in the order of several kilowatt hours. The energy storage 11 can by the photovoltaic generator 10 discharged electrical energy to be charged. In addition, he can at times when the power requirements of the local installation 3 The output power of the solar generator 10 exceeds, compensate for the lack of performance.

Both the photovoltaic generator 10 as well as the energy storage 11 is within the electrical arrangement 5 one DC / DC converter each 8th . 9 associated with those of the photovoltaic generator 10 or the energy storage 11 delivered voltages to that for feeding into the public power grid 1 bring required voltage level. The output voltages of the DC / DC converters 8th . 9 be from a DC / AC converter 7 , the following as an inverter 7 is designated in one to supply the local installation 3 or for feeding into the power supply network 1 converted suitable multi-phase AC voltage. The DC / DC converter 9 is bidirectional to charge the energy storage 11 from the output voltage of the DC / DC converter 8th to enable.

The output voltage U of the inverter 7 is via a circuit breaker 30 on a first output line 13 led, which has a solar energy meter 4 with a connection node 6 the main line 12 is interconnected. The solar energy meter 4 serves to determine the of the photovoltaic generator 10 and the energy storage 11 in the local installation 3 or the power supply network 1 supplied amount of energy.

Into the main 12 connecting the public power grid 1 and the local installation 3 is a bidirectional measuring electronic energy meter 2 looped in, both from the public power grid 1 as well as those in the public power supply network 1 entered amount of energy detected.

The output of the inverter 7 is also with a second output line 14 connected to the switching contacts of an electromechanical switch 22 a switching device 20 is guided.

The in the 1 and 2 simplified illustrated alternating current and voltage leading lines 12 . 13 . 14 comprise in addition to a neutral all belonging to the electrical system phase conductors and are therefore made four-wire for the usual three-phase voltage networks.

The electrical arrangement 5 has a microcontroller, not shown here, the inner and outer processes of the electrical arrangement 5 controlled. The electrical arrangement 5 thus controls in particular a switching device 20 on which two controllable electromechanical switches 21 . 22 , designed as contactors or relays, as well as one in the output line 13 switched disconnector 30 , which consists of at least two electromechanical switches 31 . 32 consists of series-connected switch contacts. The number of poles of the electromechanical switches 21 . 22 . 31 . 32 corresponds at least to the number of conductors of the cables connected to it 12 . 13 . 14 so the switches 21 . 22 . 31 . 32 the wires 12 . 13 . 14 disconnect or connect to each other.

The 1 illustrates as the standard mode of operation of the network operation of the electrical system. The circuit breaker 30 is closed here, so that the output of the inverter 7 now over the counter 4 at the connection node 6 the main line 12 connected. About the closed switch 21 the switching device 20 is the main also with the local installation 3 connected, so the local installation 3 both from the power supply network 1 as well as by the arrangement 5 can be supplied with electrical energy.

In mains operation, the inverter behaves 7 like a power source; Mains voltage and mains frequency are supplied by the power supply network 1 imprinted. In this respect, a control or regulation of the mains voltage and mains frequency is not required and not at all possible. The task of the inverter 7 is it, its output current in phase to the line voltage profile in the power grid 1 feed. Depending on the requirements of the grid operator, the inverter 7 also reactive power in the power supply network 1 feed in, so that a phase shift can occur between the mains voltage and the output current.

The 2 should clarify the island operation of the electrical system in which the consumers of the local installation 3 completely independent of the power supply network 1 operate. For island operation is the local installation 3 completely from the power supply network 1 disconnected because in case of failure of the generating units in the power grid 1 the at the power supply network 1 remaining loads (outside the local installation 3 ) the output voltage of the inverter 7 otherwise short circuit.

This complete separation is firstly through the open circuit breaker 30 causes the main 12 from the output of the inverter 7 separates and secondly by the switching of the two coupled switches 21 . 22 the switching device 20 , About the closed switch 22 the switching device 20 and the second output line 14 is the local installation 3 in island mode directly to the output of the inverter 7 turned on.

In island operation, the inverter is 7 operated as a voltage source, which means that grid voltage and grid frequency is now from the inverter 7 be managed. Only the same amount of power is needed in the local installation 3 fed, that sets the desired voltage curve in the respective load situation.

Basically, problematic in island operation is that this mode is usually usually maintained only for a limited period of time, depending on the dimensions of the photovoltaic generator 10 and the energy storage 11 , from the momentary energy input in the photovoltaic generator 10 and the state of charge of the energy storage 11 , as well as the current power consumption of the consumers in the local installation 3 ,

To extend this period for the island operation as far as possible, which is particularly in the event of a failure of the power supply network 1 is advantageous, in a given electrical system is the simplest parameter of the instantaneous power consumption of the consumers of the local installation 3 influenced.

For this it is essential to the local installation 3 to signal that the electrical system is in island operation mode. This could in principle be via one of the electrical arrangement 5 outgoing special signal line, which is the current operating mode of the electrical arrangement 5 coding signal to the local installation 3 transmitted. However, it may be very expensive to install such a signal line along a larger local installation. Another problem is that the usual connection means of the electrical consumers of the local installation 3 , So plug and sockets, provide no contact for such a signaling line.

Therefore, it is provided, an island mode informing output signal AS together with the output voltage U of the inverter 7 over in island operation with the local installation 3 connected output line 14 issue. Preferably, the output signal AS results simply by a targeted influencing of an electrical variable of the output voltage U. This results in particular the advantage that no additional lines must be installed, since the information implicitly over the output line 14 is transmitted with.

The 3 illustrates some possible execution details of a local installation 3 , Illustrated are three consumers V1, V2, V3 connected to the local installation 3 can be operated. Solid lines represent fixed cable connections, dashed lines represent separable electrical connections, which are preferably made on unillustrated plugs and sockets. The consumers V1 and V2 are each associated with a detection means D1 or D2, which signaling by an output signal AS of the electrical arrangement 5 can recognize. The detection means D1, D2 react to at least one and ideally to each of the provided signaling modes, which can in particular use a frequency variation, or a reduction or variation of the voltage level of the output voltage U. It can also be provided that different types of signaling lead to different reactions of the detection means D1, D2 with different influencing of the associated consumers V1, V2.

The detection means D1 is here as permanently installed part of the local installation 3 shown, the one about connectable via a plug connection Can influence consumer V1 in the presence of a drive signal AS and in particular can turn off.

On the other hand, the detection means D2 is an integral part of an "intelligent" consumer V2, so that the detection means D2 can, in the presence of a control signal AS, influence the consumer V2 in a specific manner internally determined in the consumer V2.

In contrast, consumer V3 is not connected to any internal or external detection means. By lowering the output voltage U by the electrical arrangement 5 but also this consumer V3 can be operated with a reduced electrical power.

The types of signaling proposed here are in the 4 to 6 each further illustrated by a diagram.

In the 4 is the output voltage U against the percentage discharge value of the energy storage 11 applied. By way of example, two possible courses of a lowering of the output voltage U are shown. According to the solid line, when the energy store discharges 80%, it discharges 11 lowered the output voltage by about 20%.

The additional dashed line indicates that as an alternative to the previous strategy, from a given discharge state, in this case 50%, a continuous voltage reduction can also be initiated, in which the output voltage U increases as the energy store discharges 11 from 100% initially, gradually reaching a voltage value of 80% of the rated voltage. Of course, other courses of a discharge-dependent voltage reduction can be provided. In addition, a phase-selective voltage reduction can be realized.

In the case of imminent energy shortage there is alternatively the possibility of a change in the frequency f of the output voltage U as a function of the discharge state of the energy store 11 , Two exemplary courses are in the 5 sketched by a solid and a dashed line.

The adjustment of the output frequency takes place in only a small range of, for example ± 0.5 Hz, so that the energy transfer itself is not affected. This form of regulation is based on the so-called primary control in the interconnected grid. Here, too, the energy state of the network is signaled by means of frequency variation.

It is intended to signal the shortage of energy to future "intelligent" consumers, so that such consumers reduce their energy requirements. As an example, the reduction of temperature in a washing machine or the extension of a washing program should be mentioned here, so that the current power requirement can be lowered and thus the power consumption of the device can be reduced or delayed. A time delay of the energy consumption of a device has the advantage that under certain circumstances by the natural course of the photovoltaic power generation energy can be recovered from a solar generator and thus a collapse of the entire energy supply can be avoided. If neither of the above measures is successful, the user should be made aware of the approaching end of the power supply.

This can be signaled by a targeted voltage variation, z. B. by a cyclical voltage drop in the second cycle, as shown in the 6 outlined. Plotted is the output voltage U against the time t. The value of the output voltage U here shows a cyclic variation of about 10% with a period of, for example, one second. The cyclic change makes it clear that a critical energy state has been reached.

The goal here is for the user to bring important systems to a safe state before the power supply collapses completely. Particularly important systems may include information technology equipment (computers, routers or the like) or medical monitoring and therapy facilities.

LIST OF REFERENCE NUMBERS

1

Power supply network

2

Energy meter (bidirectional)

3

local installation

4

Solar energy meters

5

electrical arrangement

6

Connection node

7

Inverter (DC / AC converter)

8th

DC / DC converter

9

DC / DC converter (bidirectional)

7, 8, 9

DC converter

10

Photovoltaic generator (generator)

11

energy storage

12

main

13, 14

Output line (s)

12, 13, 14

cables

20

switching

21, 22

(electromechanical) switches

30

disconnectors

31, 32

(electromechanical) switches

AS

output

D1, D2

detection means

f

frequency

U

output voltage

V1, V2, V3

consumer

Claims (12)

Electrical arrangement ( 5 ) to which a generator ( 10 ) and an energy store ( 11 ), each having a DC voltage in the arrangement ( 5 ), and an inverter ( 7 ), which as output voltage (U) generates a single-phase or multi-phase AC voltage, which the arrangement ( 5 ) via at least one output line ( 13 . 14 ), wherein the output voltage (U) has such a voltage level and frequency that it can be used to supply a local installation ( 3 ) and for feeding into a power supply network ( 1 ), the arrangement comprising a plurality of electromechanical switches ( 21 . 22 . 31 . 32 ), so that the output voltage (U) in a first operating mode on the power supply network ( 1 ) and in a second mode at the local installation ( 3 ) and from the power supply network ( 1 ), characterized in that the arrangement ( 5 ) generates an output signal (AS) in the second operating mode and via a local installation in the second operating mode (FIG. 3 ) connected output line ( 14 ), wherein the output signal (AS) is generally the presence of the second operating mode or the presence of a reduced energy delivery capacity of the generator (FIG. 10 ) and / or the energy store ( 10 ) signals. Electrical arrangement according to claim 1, characterized in that the output signal (AS) information about the state of charge of the energy store ( 11 ) contains. Electrical arrangement according to claim 1, characterized in that the output signal (AS) from a reduction of the inverter ( 7 ) output voltage (U). Electrical arrangement according to claim 1, characterized in that the output signal (AS) from a changed frequency (f) of the inverter ( 7 ) output voltage (U). Electrical arrangement according to claim 1, characterized in that the output signal (AS) from a cyclic variation of the voltage level of the inverter ( 7 ) output voltage (U). Electrical arrangement according to claim 1, characterized in that the arrangement ( 5 ) Is part of a photovoltaic system. Electrical arrangement according to claim 6, characterized in that the generator ( 10 ) is a photovoltaic generator. Electrical system with an electrical arrangement ( 5 ) according to claim 1, characterized in that the installation is a local installation ( 3 ) has at least one electrical load (V1, V2, V3), and that the presence of the output signal (AS) on one with the local installation ( 3 ) connected output line ( 14 ) causes a reduction in the electrical power consumption of at least one electrical load (V1, V2, V3). Electrical installation according to claim 8, characterized in that the local installation ( 3 ) has at least one detection means (D1, D2), which the output signal (AS) on one with the local installation ( 3 ) connected output line ( 14 ) and, when the output signal (AS) is detected, controls at least one electrical load (V1, V2) in a state with a reduced electrical power consumption. Electrical system according to claim 9, characterized in that the detection means (D1, D2) controls an electrical load (V1, V2) in stand-by mode when the output signal (AS) is detected. Electrical system according to claim 9, characterized in that the detection means (D1, D2) completely disconnects an electrical load (V1, V2) when the output signal (AS) is detected. Electrical system according to claim 9, characterized in that at least one electrical consumer (V2) internally comprises a detection means (D2).

Images