AT520835B1 - network simulator - Google Patents

Abstract

The invention relates to a network simulator (10) for testing devices that can be connected to an AC voltage network having a predetermined rated network voltage and nominal network frequency, in particular inverters, consumers or generators, comprising: - a large-signal generator (11) for generating a large-voltage signal at its output, the amplitude of which is substantially the rated network voltage corresponds, and - a small signal generator (12) for generating a low voltage signal at its output whose amplitude is less than 50%, in particular less than 25%, the nominal network voltage, - wherein the output of the large signal generator (11) and the output of the small signal generator (12) are galvanically decoupled from each other, - one pole of the output of the large signal generator (11) is connected to one pole of the output of the small signal generator (12) and the respective other two poles form the output of the network simulator (10), - wherein the small signal generator (11), cont if necessary also the large signal generator (12) has at least one control input for specifying at least one control signal, and wherein the small signal generator (12), possibly also the large signal generator (11), is adapted to apply a voltage signal in dependence on a parameter contained in the control signal , in particular the amplitude and / or the frequency to create. According to the invention, a control unit (126) is provided, which is designed to measure a current reading for the current at the output of the network simulator (10) or the small signal generator (12), in particular at predetermined, preferably periodically fixed, times, and - the small signal generator (12) with according to predetermined criteria of dependence on the determined current measured value, possibly also of further determined measured values, in particular continuously and / or to, preferably periodically, predetermined timing control signals to control.

Description

Description: The invention relates to a network simulator for testing devices that can be connected to an AC voltage network, such as inverters, consumers or generators. Preferably, a network with a predetermined impedance can also be simulated with a network simulator according to the invention. Furthermore, the invention relates to a method for testing such a device.

Different network simulators are known from the prior art, with which it is particularly possible to simulate certain, incorrect or error-free, network constellations for individual devices to be connected to the network in question. Such network simulators are known for example from CN 104852616 A and CN 106487240 A. The background of such a test is to test the occurrence of certain problematic situations or to test the effects of such situations on the devices, although such situations generally do not occur due to the high quality of public networks.

Just as an example, the situation is cited that the internal resistance of the public network has a non-negligible value, which ultimately leads to the fact that with the removal of electricity from the public network, a significant reduction of the mains voltage is accompanied.

In addition, other network situations such as changes in network frequency or the like can be simulated with a network simulator or a method according to the invention.

In known from the prior art network simulators, there is usually the problem that the used for the simulation or emulation of the mains voltage components, these are in particular power transistors, for large voltage swings, as they are required in the context of network simulation , have only a low actuating speed, so that the specification of a certain voltage curve regularly means that in the large signal range for the desired emulation, the switching frequency of the individual switching transistors would have to be exceeded and, accordingly, the desired or required for the simulation voltage waveform can not be specified.

However, in the context of the invention typical application of a non-negligible large network impedance requires that the grid voltage reacts very quickly to the detection of the removal of a mains current. Preferably, it should be achieved that a network simulation already reacts in very short time periods, which are in particular shorter than 500 ~ ps (2 kHz).

The invention also makes use in this context of the fact that voltage drops and voltage increases, which are required in the context of adjusting the mains voltage to a pure sine wave voltage, are usually low, i. E. Have voltage differences, which are typically less than 50%, in particular less than 20%, the rated network voltage depending on the connection and short-circuit performance.

The invention solves the problem set with the characterizing features of claim 1 in a network simulator of the type mentioned.

The invention solves the problem set with the characterizing features of claim 9 in a method of the type mentioned.

According to the invention is provided in a network simulator that - a control unit which is designed to - a current reading for the current at the output of the network simulator or the small signal generator; in particular at predetermined, preferably periodically fixed, times, to measure, and - to control the small signal generator with according to predetermined criteria of dependence on the ascertained current measurement value, possibly also of further determined measured values, in particular continuously and / or, preferably periodically, predetermined times control signals ,

In order to achieve a particularly simple and efficient control of the small signal generator, it can be provided that the control unit is further designed to: a voltage measurement for the voltage at the output of the mains simulator or the small signal generator, in particular at predetermined, preferably periodically fixed, times, to measure, and - the small signal generator with according to predetermined criteria depending on the determined current reading and the determined voltage reading, in particular continuously and / or, preferably periodically, predetermined timing control signals to control.

In order to achieve a particularly simple and efficient control of the large signal generator, it can be provided that a further control unit is provided for the large signal generator, which is further designed to - a voltage reading for the voltage at the output of the mains simulator or the large signal generator, in particular at predetermined, preferably periodically fixed, times to measure, and - to control the large signal generator with according to predetermined criteria of dependence on the determined current reading and the determined voltage reading, in particular running and / or, preferably periodically, predetermined timing control signals.

In order to achieve a particularly stable coupling of the control units of the small signal generator and the large signal generator, it can be provided that the control unit and the further control unit are synchronized and are adapted to measure voltage and current readings each simultaneously and to specify control signals simultaneously.

A modular construction of the small signal generator can be achieved by that the control unit is designed exclusively for determining currents that occur at terminals of the small signal generator or that occur on individual components of the small signal generator, and / or that the control unit exclusively for the determination of voltages is formed, which occur between terminal nodes or nodes within the small signal generator.

In order to make additional modifications in the large signal range, for example, to change the mains frequency or to simulate large dips in the mains voltage, it can be provided that the control unit is adapted to drive the small signal generator such that the voltage applied to the connection of the mains simulator in predetermined manner depends on the current flowing at the connection of the network simulator current, in particular such that the network simulator acts as a voltage source with the predetermined nominal network voltage and an impedance connected in series thereto.

It can be provided in particular that the further control unit designed to specify the large-voltage signal generated by the large signal generator with respect to individual large-signal parameters, in particular to specify the amplitude and / or the frequency of the large voltage signal.

An advantageous and easy to carry out feasible measure for creating a large signal provides that the large signal generator by a predetermined, in particular public power system is formed, wherein the large signal generator, if necessary, an additional, the public power grid downstream DC voltage link for stabilizing the AC voltage in the voltage range of the rated network voltage and in the frequency range of the nominal network frequency.

For simple and advantageous specification of small signals can be provided that - to power the network simulator a DC voltage source is provided, - the large signal generator and the small signal generator each comprise an inverter, and - the galvanic decoupling of large signal generator and small signal generator takes place, - that one of the signal generators, in particular of the large signal generator, has at its output a transformer whose primary terminal is connected to the inverter of this signal generator and whose secondary terminal forms the output of the respective signal generator, and / or - that at the input of one of the signal generators, in particular the small signal generator, a galvanically isolated, at least two quadrant capable DC / DC converter is provided which electrically isolates the output of the DC voltage source from the inverter of the respective signal generator.

A particularly advantageous specific embodiment of a network simulator, which requires only a single external power supply, provides that a DC voltage source is provided for the power supply of the network simulator, - that the large signal generator and the small signal generator each comprise an inverter, wherein a galvanic decoupling of Large signal generator and small signal generator is provided.

For galvanic isolation of the large signal generator and the small signal generator, the two following measures can be provided: - that one of the signal generators, in particular the large signal generator, has at its output a transformer whose primary terminal is connected to the inverter of this signal generator and whose secondary terminal the output forms the respective signal generator, and / or - that at the input of one of the signal generators (11, 12), in particular of the small signal generator (12), a galvanically isolated, at least two quadrant capable DC / DC converter is provided, the output of the DC voltage source from the inverter of the each signal generator electrically isolated.

A particularly simple implementation of the inverter provides that the inverter of the large signal generator and / or the small signal generator is realized by a half-bridge or H-bridge controlled by the control unit power transistors.

In addition to the single-phase implementation, the invention also allows the creation of a multi-phase network simulator, which manages with a single DC voltage source. If one wants to implement such a multi-phase network simulator with only a single DC voltage source, it can be provided in order to avoid overloads that occur in the network simulator, wherein - a large-signal generator for generating a large-voltage signal at its output, the amplitude of which essentially corresponds to the nominal network voltage, is provided for each phase connection corresponds, and - a small signal generator for generating a low voltage signal at its output, whose amplitude is smaller than 50%, in particular less than 25% of the nominal network voltage, - wherein the outputs of the associated large signal generators and small signal generators are galvanically decoupled from each other, - wherein each one Pol of the output of the large signal generator is connected to a pole of the output of the respective small signal generator, wherein the other pole of the small signal generator is connected to the neutral conductor (N) and the other pole of the large signal generator forms the phase output (L ^ L2, L3), - wherein each small signal generator, optionally also each large signal generator, has at least one control input for specifying at least one control signal, and wherein the small signal generator, possibly also the large signal generator, is adapted to a voltage signal depending on a parameter contained in the control signal, in particular the amplitude and / or the frequency to create, - is provided for the individual small signal generators one or each control unit, which is adapted to - a current reading for the current at the output of the network simulator or a small signal generator, in particular at predetermined, preferably periodically fixed, times to measure, and - the small signal generator with according to predetermined criteria of dependence on the determined current reading, possibly also of further determined measured values, in particular running and / or at, preferably periodically, predetermined times control signals to control.

An inventive method provides that - a voltage reading for the voltage at the output of the network simulator, in particular at predetermined, preferably periodically fixed, times, is measured, - a current reading for the current at the output of the network simulator, in particular to predetermined, preferably periodically determined, times, is measured, and - the large-signal parameters and the small-signal parameters are determined according to predetermined criteria of dependence on the determined voltage measurement and current measurement, in particular current and / or, preferably periodically, predetermined times.

To simulate a non-vanishing or relevant network impedance can be provided that the parameters of the small signal generator are controlled such that the voltage applied to the connection of the mains simulator depends in a predetermined manner on the current flowing at the connection of the mains simulator power, in particular such that The network simulator acts like a voltage source with the predetermined rated network voltage and an impedance connected in series. For controlling the small signal network simulator, it can be provided in particular that the small signal parameters are given in the form of discrete voltage values for a number of times, preferably during a signal period of the nominal network frequency over 10000 voltage values are predetermined, and / or that the large signal parameters are given in the form of discrete voltage values for a number of times, preferably during a signal period of Netznennfre above 100 voltage values.

Several embodiments of the invention are described in more detail below with reference to the following drawing figures: FIG. 1 shows a first embodiment of the invention in a single-phase system.

Fig. 2 shows a first possible embodiment of a DC intermediate circuit of the large voltage generator.

Fig. 3 shows an embodiment of the inverter of a large signal generator with bridge circuit.

Fig. 4 shows an embodiment of a control unit for a large signal generator.

Fig. 5 shows an embodiment of a DC / DC converter.

Fig. 6 shows a first possible embodiment of a DC intermediate circuit of the low voltage generator.

Fig. 7 shows an embodiment of the inverter of a small signal generator with bridge circuit.

Fig. 8 shows an embodiment of a control unit for a small signal generator.

9 shows a preferred circuit for the concrete realization of such a polyphase network simulator at a glance.

Fig. 10 shows a preferred embodiment of the large signal portion of the polyphase network simulator shown in Fig. 9.

Fig. 11 shows a preferred embodiment of the large signal portion of the polyphase network simulator shown in Fig. 9.

In Fig. 1, a first embodiment of a network simulator 10 according to the invention is shown. The network simulator 10 has the task, basically to provide a network with a predetermined nominal network voltage and a predetermined nominal network frequency.

This has a large signal generator 11 and a small signal generator 12. Both the large signal generator 11 and the small signal generator 12 are connected to a DC voltage source 13. The two outputs of the large signal generator 11 and the small signal generator 12 are connected in series with each other and form the output of the network simulator 10th

In the present embodiment, the DC voltage source 13 is a balanced DC voltage source whose output has a center port m, a positive pole + and a negative pole - has. Depending on the respective network to be simulated, an intermediate circuit voltage in the form of DC voltage is selected between the positive pole + and the center terminal m and between the center terminal m and the negative pole - which lies approximately in the range of the peak line voltage.

The connected to the DC voltage source 13 large signal generator 11 comprises in the present embodiment, a DC voltage intermediate circuit 112 is provided, whose structure is shown in more detail in Fig. 2. The DC intermediate circuit 112 used here has one input and one output with three terminals each, namely a positive pole, a negative pole and a center terminal. The positive pole, the negative pole and the center terminal of the input side are connected to the corresponding terminals of the DC power source 13. In the present embodiment, the individual terminals of the input are each guided directly to the output of the DC voltage intermediate circuit 112.

In the present exemplary embodiment, the following elements are connected in parallel to each other between the positive pole + and the center terminal m: a resistor - a capacitor - a measuring unit Vm1 whose measurement result is the actual value for the regulation described below by the control unit 116 (Fig. 1) can be used.

Between the center terminal m and the negative pole - in the present embodiment, the following elements are connected in parallel to each other: - a resistor R2 - a capacitor C2 - a measuring unit Vm2, the measurement result as the actual value for the control described below of the Control unit 116 (Fig. 1) can be used.

The capacitances or resistances shown in FIG. 2 are dimensioned as follows in the present exemplary embodiment: Rt = 220 kOhms R2 = 220 kOhms

Ct = 64pF

C2 = 64pF

Purpose of the DC intermediate circuit 112 is to keep as constant as possible at the output of the DC voltage source or the DC voltage intermediate circuit 112 or at the input of the DC intermediate circuit 112 inverter 113 so that the output of the inverter 113 as precise as possible specification of voltage values can.

The DC voltage intermediate circuit 112, an inverter 113 is connected downstream, which is shown in Fig. 3 in more detail. The inverter 113 essentially has two controllable power transistors 113a, 113b, which are connected to one another in series.

In this case, the inverter 113 of the large-signal generator 11 comprises two power transistors 113a, 113b. The first switching input of the first power transistor 113a is connected to the positive pole or input of the inverter 112. The second switching input of the second power transistor 113b is connected to the negative pole or input of the inverter 112. The other two terminals of the two power transistors 113a, 113b are connected to one another and via an inductance L ^ which in the present case has 0.340 mH, led to the output Out + of the inverter 113. The two power transistors 113a, 113b are, for example, silicon, silicon carbide or gallium nitride MOSFETs or IGBTs (insulated gate bipolar transistors).

The two control inputs of the power transistors 113a, 113b are controlled by a control unit 116, as described in more detail later (FIG. 4). Moreover, in this present embodiment, the inverter 113 has a series circuit connected between the positive pole + of the input and the output Out +, which comprises two capacitors C3, C4.

In addition, the inverter 113 has a series circuit connected between the negative pole of the input and the output Out +, which comprises two capacitors C5, C6.

The capacitors or resistors shown in FIG. 3 are dimensioned in the present exemplary embodiment as follows:

C3 = 520nF

C4 = 520nF

C5 = 520nF

C6 = 520nF

Lt = 0.340 mH

The two capacitors C4 and C6 are used in the present case to reduce the voltages occurring at the individual capacitors and may optionally be omitted, if in each case a capacitor with suitable dielectric strength is used.

Furthermore, the inverter 113 has a number of voltage and current measuring devices which are designed to measure the following voltages and currents: The voltage measuring unit Vm1 measures the voltage between the center connection m and the output Out +. - The voltage measuring unit Vm, 2 measures the voltage V2 between the positive pole + and the output Out +. The voltage measuring unit Vm3 measures the voltage VG between negative pole and the output Out +. The current measuring unit Am1 measures the current h through the series connection of the capacitors C4, C2 lying between the positive pole + of the input and the output Out +. The current measuring unit Am, 2 measures the current I2 through the series connection of the capacitors C3, C4 lying between the negative pole of the input and the output Out +. - The current measuring unit Am, 3 measures the current through the inductance L3. or the current supplied by the inverter 113 lG.

The output side of the inverter 113 form the already mentioned output Out + and the center connection m. By driving the two control inputs of the power transistors 113a, 113b, the voltage at the output of the inverter, ie between the output Out + and the center port m can be specified.

As already mentioned above, the control unit 116 then controls the individual control inputs of the signal generators 11, 12 or their inverters 113, 123 to certain

To simulate network situations closer. Typically, the individual measuring devices used in this context periodically generate measured values which are then fed to the control unit 16 at predetermined times, in particular also synchronously and if necessary clocked. The control unit 16 is designed, for example, to further process these periodically incoming measurement signals at recurring times and to set the individual control parameters specified for the inverters such that the network situation to be simulated is generated.

In particular, the voltage and current measurement values of the large signal generator 11 required for the regulation are measured at predetermined, preferably periodically fixed, times. The control unit 126 then controls the large signal generator 11 with control signals according to one of the abovementioned criteria as a function of the measured values determined, in particular continuously and / or at, preferably periodically, predetermined times.

The measurement of the individual voltage and current values is carried out by the control unit 116 at regular time intervals. For a given bandwidth, which is about 40 times the nominal network frequency, for example, about 2 kHz, about 200,000 values per second, ie 100 values per period of a determined by the maximum bandwidth oscillation are determined. After determining the relevant measured values, the controller also generates control signals with the same frequency, ie approximately 200,000 control signals per second.

In the embodiment shown in FIG. 4, the control unit 116 of the large-signal generator 11 has connections for the two determined currents h, l2, for the voltage at the output of the inverter 113 and for a predetermined setpoint voltage VG *, which the nominal voltage curve at the output of the large signal generator pretends. This setpoint voltage curve VG * is essentially determined by the nominal network voltage and the rated network frequency and can be preset differently based on predetermined test criteria.

Starting from the DC voltage intermediate circuit 122 of the small signal generator (FIG. 2) determined voltages VZi, VZ2 a normalization factor nf is determined, which serves as a reference for the voltage at the output of the small signal generator VK and for the target voltage VK *.

In the two multiplication elements 501, 502, the voltage value VG at the output of the inverter 113 of the large signal generator 11 and the setpoint voltage VG * are each weighted with the normalization factor nf. The two results thus obtained are subtracted from each other in the difference unit 503. The difference value thus obtained is then fed to a PI member 504, which is dimensioned as follows. KP = 0.25, KI = 16000 Ts = 5ps1. The output of the PI is supplied to the difference unit 508.

The two detected currents h, l2 at the capacitors C3, C4 and C5, C6 are fed to the adder 505, whose output is fed to a damping unit 506. The damping unit emulates a series resistance to the filter coil and behaves so dampening at the resonant frequency of the filter. The output of the attenuation unit 506 is weighted by the multiplication element 507 with the normalization factor nf. The value thus obtained, which is applied to the output of the multiplication element 507, is supplied to the difference unit 508.

The result determined by the difference unit 508 is supplied to an addition unit 509 as well as the output of the multiplication element 502. The value thus obtained by addition by means of addition unit 509 is added in a further addition unit 510 to a predetermined constant value c (c = 0.5) so that only positive values in the range of 0 -1 are supplied to the PWM modulation.

The output of the addition unit 510 is supplied to a circuit 511 with saturation effect, the task of which is to limit the value applied to the output of the addition unit 510 manipulated variable in size, since only the value range 0-1 is allowed for the PWM modulation. ,

The manipulated variable thus calculated is then fed to a pulse width modulation 512 in order to drive the power transistors 113a, 113b of the large signal generator 11 with the control signals sa, sb. The control signals sa, sb provided by the pulse width modulation 512 are in each case driven in the opposite direction.

The large signal generator 11 further includes a transformer 114 (FIG. 1) whose primary side is connected to the output of the inverter 113 of the large signal generator 11 and whose secondary side forms the output of the large signal generator 11.

In a separate switching arrangement of the DC voltage source 13 is a small signal generator 12 connected downstream, which has a two- or vierquadrantenfähigen DC / DC converter 121, a Gleichspannungsziwschenkreis122 and an inverter 123.

In the present embodiment, a two-quadrant DC / DC converter 121 is used, which is shown in more detail in FIG. In the present embodiment, the input has two terminals which are connected to the two poles + and - of the DC generator 13. The output of the DC / DC converter 121 has three terminals, namely a positive pole DC + a negative pole DC "and a center terminal m In the present example, the voltage between the two poles DC + and DC" has a value of about 100V, between the poles DC + and DCm about 50V.

In this embodiment of the invention is a bridge circuit comprising a total of four power transistors, each of which two are connected in series, wherein these two series circuits of the power transistors are connected between the positive and negative input of the inverter. The two middle points of the series circuits of the power transistors are each guided via an inductance to one of the outputs of the inverter, wherein one of these outputs forms a central terminal and the other forms a positive pole. The negative output terminal corresponds in this embodiment, the negative input terminal of the inverter.

The DC / DC converter 121 has a number of switching transistors 31a, 31b; 32a, 32b. These are connected in series, the two series circuits of the power transistors 31a, 31b; 32a, 32b are at the positive pole + or negative pole - on. The control inputs of the power transistors 31a, 31b; 32a, 32b are controlled by a control unit 129, which generates a pulse-width-modulated signal by the emission of control pulses or by setting a pulse duty factor between the switching transistors 31a, 31b; 32a, 32b is applied. The pulse width modulated signal is in each case conducted via a coil L2, L3 to the voltage outputs DC + and DCm of the DC / DC converter 121. The outputs are each connected via a capacitor C to the negative pole - which is also guided to the output of the DC / DC converter 121.

To control the switching transistors, a control unit 129 is used, which is also supplied with the measurement results of a number of current and voltage measuring units. In this case, individual currents and voltages are measured with individual measuring units V "m1, V" m2, V "m3, A" m1, A "m2 and the measured values thus obtained are fed to the control unit 129. On the basis of the currents and voltages determined, the control unit can be used for the Switching transistors determine a control with which the voltages at the outputs DC +, DCm have a constant as possible, predetermined value.

The DC / DC converter 121 is followed by a DC intermediate circuit 122, which substantially corresponds to the DC intermediate circuit 112 of the large signal generator 11 and shown in Fig. 6.

The DC voltage intermediate circuit 122 is followed by an inverter 123 (FIG. 7) whose structure substantially corresponds to the structure of the inverter 113 of the large signal generator 11 (FIG. 3). Again, the two capacitors C4 and C6 are used in the present case to reduce the voltages occurring at the individual capacitors and may be omitted, if a capacitor with a suitable dielectric strength is used in each case.

Due to the fast-switching (high voltage gradient) power transistors used, the inverter 123 is able to make faster switching and provide higher-frequency signals at its output available as the inverter 113 of the large signal generator 11. The output of the inverter 123 forms the output the small signal generator 12th

In the simplest case, the control unit 126 of the small signal generator 12 has a single current measuring unit 15, which determines the current I K flowing through the output of the small signal generator 12 and, based on this determined current value, determines a voltage value V K 'which predetermines an output voltage should rest at the output of the small signal generator 12. In the simplest case, a connection between current and voltage at the small signal generator can be produced in this way and such a linear or non-linear impedance can be simulated.

Moreover, it is also possible for the small-signal generator to determine temporal change rates or derivatives on the basis of the previously determined current values and the previously specified voltage values, and to determine a voltage value based on these values according to predetermined criteria. In this case, for example, the behavior of a linear or nonlinear impedance can be simulated.

A further improvement can be achieved by additionally measuring the voltage UK applied to the small signal generator 12 in addition to the current I K flowing through the small signal generator 12. In this case, the small-signal generator 12 can make a regulation such that the control signals given by it actually produce a voltage at the output of the small-signal generator 12 which corresponds to the predetermined voltage. In addition, with a voltage measuring unit at the output of the small signal generator 12 time derivatives of the determined voltage can be calculated more accurately, since these do not correspond to the specifically determined voltages and not the predetermined by the small signal generator 12 voltages.

Finally, it is also possible to provide for more precise control of the output from the small signal generator 12 voltage signal further separate measuring units, as shown for example in Fig. 3. As can be seen here, the currents h, l2 flowing through the two capacitors C3, C4, C5, C6 as well as those at the two series circuits of capacitors C3, C4; C5, C6 applied voltages V ^ V2 and measured at the output of the small signal generator 12 voltage VK measured. The control function performed by the control unit 126 is shown schematically in FIG.

In the present exemplary embodiment, a setpoint output voltage VK *, which is present at the output of the small signal generator 12 in the event that no current flows through the small signal generator 12, can be predetermined for the regulation. If the target output voltage is to be zero, the components shown in FIG. 8 components 604, 605, 611 can be omitted.

In a first step, the current IK measured at the output of the small signal generator 12 is supplied to a PDT element 601, which in the present case is dimensioned as follows KP = Rv = 1 KD = 800e-6, T = 1.59e-5, where in this case, for example, a resistor with R = 1 Ω and an inductance with L = 800 pH is emulated. The value obtained therefrom is then added in adding element 602 to the voltage measured at the output of small signal generator 12.

Starting from the voltages VZ1, VZ2 determined in the DC intermediate circuit 122 of the small signal generator (FIG. 2), a normalization factor nf is determined which serves as reference for the voltage at the output of the small signal generator VK and for the setpoint voltage VK *. In the two multiplication elements 603, 604, the voltage value at the output of the addition element 602 and the setpoint voltage are respectively weighted with the normalization factor. The two results thus obtained are subtracted from each other in the difference unit 605. The difference value thus obtained is then fed to a PI member 606, which is dimensioned as follows. <Please specify> The output of the PI is supplied to the difference unit 610.

The two detected currents 1½, l'2 at the capacitors C'3, C'4 or C'5, C'6 are fed to the adder 607, whose output is fed to a damping unit 608. The damping unit emulates a series resistance to the filter coil and thus behaves damping at the resonance frequency of the filter. The output of the damping unit 608 is weighted with the multiplication element 609 with the normalization factor nf. The value thus obtained, which is applied to the output of the multiplication element 609, is fed to the difference-forming unit 610.

The result obtained by the difference unit 610 is supplied to an addition unit 611 as well as the output of the multiplication element 604. A predetermined constant value (c = 0.5) is added to the value thus obtained in a further addition unit 612, so that only positive values in the range from 0 to 1 are supplied to the PWM modulation.

The output of the addition unit 612 is supplied to a circuit with saturation effect, the task of which is to limit the voltage applied to the output of the addition unit manipulated variable in size, since only the value range 0-1 is allowed for the PWM modulation [0092] The manipulated variable thus calculated is subsequently fed to a pulse width modulation 614 in order to drive the power transistors 123a, 123b of the small signal generator 12 with the control signals s'a, s'b. The control signals s'a, s'b provided by the pulse width modulation 614 are each driven in the opposite direction.

The measurement of the individual voltage and current values is carried out by the control unit 126 - as in the control unit 116 of the large signal generator 11 - at regular time intervals, but it should be noted that the small signal generator can typically achieve much faster response times.

In particular, the voltage and current measurement values of the small signal generator 12 required for the regulation are measured, in particular at given, preferably periodically fixed, times. The control unit 126 subsequently controls the small signal generator 12 with control signals according to one of the abovementioned criteria as a function of the determined measured values, in particular continuously and / or at, preferably periodically, predetermined times.

For a given bandwidth, which is about 40 times the nominal network frequency, for example, about 2 kHz, about 200,000 values per second, ie 100 values per period of a determined by the maximum bandwidth oscillation are determined. After determining the relevant measured values, the controller also generates control signals with the same frequency, ie approximately 200,000 control signals per second.

The control becomes more stable when the control units 116, 126 of the small and large signal generator are synchronized with each other. The two control units 116, 126 are preferably designed to measure voltage and current measurement values in each case at the same time and to specify control signals simultaneously.

It is particularly advantageous in the invention, in particular for achieving a modular design, also possible to form a control unit 126 of the small signal generator 12, which taps exclusively voltage and current measurements within the circuit of the small signal generator. The control unit 126 is designed exclusively for the determination of currents that occur at terminals of the small signal generator 12 or occur on individual components of the small signal generator. Likewise, the control unit 126 may be designed exclusively for determining voltages that occur between terminal nodes or nodes within the small signal generator 12.

A network situation which is particularly preferred in connection with the invention can consist in that the control unit also controls the small signal generator 12, if necessary, the large signal generator 11 in such a way that the voltage applied to the connection of the network simulator 10 is in a predetermined manner from that at the connection of the network simulator 10 flowing electricity depends. This dependency can be described particularly preferably by specifying a network impedance. This means that the network generated by the network simulator 10 should have an effect that comes as close as possible to the effect of an ideal AC voltage source to which a predetermined impedance is connected.

In principle, the impedance can be any impedance required in the simulation, it being advantageously possible to ensure that all control measures required in connection with the control are achieved exclusively by driving the inverter 123 of the small-signal network generator 12.

For example, if a real, faulty two-phase network to be simulated, which has a relatively high impedance, so for example the large signal generator 11 can be set to the rated line voltage and all caused by the current flow changes in voltage by changing the voltage of the small signal generator 12 are generated , For this purpose, the current determined by the current measuring device 15 is measured and, depending on this, in each case a voltage drop value is determined which corresponds to the determined current value multiplied by a predetermined resistance. Due to the control of the small signal generator 12 in the predetermined manner, a voltage reading is determined at the output of the network simulator 10, which corresponds to the ideal rated network voltage of the large signal generator 11 minus the current-dependent voltage at the small signal generator 12.

In addition, other network models can be simulated, such as cases of additional or alone present capacitive or inductive loads. The network models can either be defined directly in the internal control or simulated using external control units.

In principle, different devices can be connected to the two outputs of the network simulator 10, which are to be subjected to a specific test for which the network simulation is required. These may be, for example, inverters, as are customary in the field of photovoltaic systems, or consumers or generators with associated power electronic circuitry whose behavior is to be checked in unusual grid situations.

Both the large signal generator 11 and the small signal generator 12 in the present embodiment each have different control units 116, 126.

All measured values produced by the individual voltage or current measuring devices can be forwarded to the control unit 16. In the present case, the control parameters are the two voltage values, also referred to as large-signal parameters, at the input of the power transistor transistors 113a, 113b of the inverter 113 of the large-signal generator 11 and the two corresponding voltage values, also referred to as small-signal parameters, at the input of the control transistors of the inverter 123 of the small-signal generator 12.

A further embodiment of a network simulator 20 according to the invention for simulating a three-phase network is shown in greater detail in FIGS. 9 to 11. As in the first embodiment of the invention, a DC voltage source 23 is used, the structure of which also corresponds to the structure of the DC voltage source 13.

The construction of the large-signal generator 22 (FIG. 10) also largely corresponds to the construction of the large-signal generator 12 of the first embodiment of the invention shown in FIG.

Instead of a single inverter arrangement with the two power transistor transistors 213a, 213b, the inverter in this embodiment of the invention comprises three pairs of inverters 2131a, 2131b; 2132a, 2132b; 2133a, 2133b, which are connected in pairs in series, wherein the respective ends of the series connection are respectively connected to the positive or negative pole +, -. The other two terminals of each of the pairs of power transistors 2131a, 2131b; 2132a, 2132b; 2133a, 2133b are connected in pairs with each other and each via an inductance L ^ L2, L3, led to a respective phase output OutL1, OutL2, OutL3 of the inverter 213. The center connection is also routed to the output of inverter 213 and forms the neutral output OutN.

The large signal generator 21 comprises for each phase in each case a separate transformer 2141, 2142, 2143. To the primary side of each of the transformers 2141, 2142, 2143 respectively the neutral output OutL and one of the phase outputs OutL1, OutL2, OutL3 are connected. The individual connections of the secondary side of the transformers together form the output of the large signal generator 21.

Also, the small-signal generator 22 of the polyphase network simulator 20 is constructed similarly to the first embodiment of the invention shown in Figs. 1 to 4. Both the DC / DC converter 221 and the DC voltage intermediate circuit 222 correspond to the DC / DC converter 121 or DC intermediate circuit 122 used in the first exemplary embodiment of the invention.

In its basic structure, the inverter 223 of the large-signal generator 21 connected downstream of the DC intermediate circuit 222 corresponds in particular to a neutral conductor output N or neutral point and a number of phase outputs Lt, L2, L3 corresponding to the number of phases used.

The neutral output N of the small signal generator 21 form the neutral output N of the network simulator 20. The individual phase outputs L ^ L2, L3 are connected to the secondary side of each one of the transformers at the output of the large signal generator. The sum of the voltage VGi at the output of a transformer 2141 of the large signal generator 21 and the voltage Vk1 between a phase output L1 of the small signal generator 22 and the neutral output N of the small signal generator 22 together form one of the phase voltages of the mains simulator 20.

Likewise, the sum of the voltage VG2 at the output of the second transformer 2142 of the large signal generator 21 and the voltage Vk2 between the second phase output L2 of the small signal generator 22 and the neutral output N of the small signal generator 22 together form the second phase voltage V2 of the network simulator 20.

Similarly, the sum of the voltage VG3 at the output of the third transformer 2143 of the large signal generator 21 and the voltage Vk3 between the third phase output L3 of the small signal generator 22 and the neutral output N of the small signal generator 22 together form the third phase voltage V3 of the network simulator 20th

In all the aforementioned embodiments of the invention, a galvanic isolation has been effected by means of a transformer.

This separation causes the generated large and small signals are generated with the same voltage generator 13, 23, but can be added by series connection, without due to the same reference potential shorts occur.

Instead of a transformer, alternatively, a galvanically separated two-quadrant DC / DC converter can be used. In this case, it is alternatively also possible for decoupling to separate only the small signal generator 12, 22 from the DC voltage source 13, 23 by an isolated DC / DC converter 121, 221. The transformers at the output of the large signal generator 11, 21 can be omitted in this case.

It is also sufficient if the outputs of the small signal generator 12, 22 and the large signal generator 11, 21 from each other, as here by transformers 114, 2141, 2142, 2143 separated, without that an isolated DC / DC converter 121, 221 be provided.

Another way of mutual galvanic decoupling of large signal and small signal generators may be to use as a large signal generator directly available public network and to feed the small signal generator by a separate power source, such as battery powered, or the small signal generator via a galvanic decoupled AC / DC converter to operate.

Furthermore, it is possible in all the illustrated embodiments of the invention that the large signal generator instead of an inverter only in the voltage terminals of a public power network, which optionally a DC voltage intermediate circuit 112 is connected downstream. In this case, the task of the DC intermediate circuit 112 is to stabilize the AC voltage supplied by the public grid and to provide a possibly trouble-free or ideal large-voltage signal which corresponds to an ideal sine voltage with a predetermined nominal network voltage and nominal network frequency.

Claims (17)

claims A network simulator (10) for testing devices that can be connected to an AC voltage network having a predetermined rated network voltage and rated network frequency, in particular inverters, consumers or generators, comprising: - a large signal generator (11) for generating a high voltage signal at its output, the amplitude of which is substantially the nominal network voltage corresponds, and - a small signal generator (12) for generating a low voltage signal at its output, whose amplitude is less than 50%, in particular less than 25%, the rated network voltage, - wherein the output of the large signal generator (11) and the output of the small signal generator (12 a pole of the output of the large signal generator (11) is connected to one pole of the output of the small signal generator (12) and the respective other two poles form the output of the network simulator (10), - ), possibly also the big one Signal generator (12), at least one control input for specifying at least one control signal has, and wherein the small signal generator (12), optionally also the large signal generator (11) is adapted to a voltage signal in response to a parameter contained in the control signal, in particular the Amplitude and / or frequency to create, characterized by - a control unit (126) which is adapted to - a current reading for the current at the output of the network simulator (10) or the small signal generator (12), in particular at predetermined, preferably periodically fixed, Time points to measure, and - the small signal generator (12) with according to predetermined criteria of dependence on the determined current reading, possibly also of other measured values, in particular continuously and / or, preferably periodically, predetermined timing control signals to control. 2. network simulator (10) according to claim 1, characterized in that the control unit (126) is further adapted to - a voltage reading for the voltage at the output of the network simulator (10) or the small signal generator (12), in particular at predetermined, preferably periodically - to determine the small signal generator (12) with control signals according to predefined criteria as a function of the determined measured current value and of the determined voltage measured value, in particular continuously and / or, preferably periodically, predetermined times. 3. network simulator (10) according to claim 1 or 2, characterized in that a further control unit (116) for the large signal generator (11) is provided, which is further adapted to - a voltage reading for the voltage at the output of the network simulator (10) or the large signal generator (12), in particular at predetermined, preferably periodically fixed, times, to measure, and - the large signal generator (12) according to predetermined criteria depending on the determined current reading and the voltage measurement value, in particular running and / or, preferably periodically to control signals to predetermined times. 4. Network simulator (10) according to any one of the preceding claims, characterized in that the control unit (126) and the further control unit (116) are synchronized and there to be formed to measure voltage and current readings each simultaneously and to specify control signals simultaneously. 5. mains simulator (10) according to any one of the preceding claims, characterized in that the control unit (126) is designed exclusively for the determination of currents that occur at terminals of the small signal generator (12) or occur on individual components of the small signal generator, and / or in that the control unit (126) is designed exclusively for determining voltages which occur between connection nodes or nodes within the small-signal generator (12). 6. Network simulator (10) according to any one of the preceding claims, characterized in that the further control unit (116) is designed exclusively for the determination of currents that occur at terminals of the large signal generator (11) or occur on individual components of the large signal generator (11) , and / or that the further control unit (116) is designed exclusively for determining voltages which occur between connection nodes or nodes within the large-signal generator (11). 7. Network simulator (10) according to any one of the preceding claims, characterized in that the control unit (126) is adapted to the small signal generator (12) to control such that the voltage applied to the connection of the mains simulator (11) in a predetermined manner by the on Connection of the network simulator flowing current depends, in particular such that the network simulator (10) acts as a voltage source with the predetermined nominal network voltage and an impedance connected in series. 8. Network simulator (10) according to any one of the preceding claims, characterized in that the further control unit (116) designed to specify the large-voltage signal generated by the large signal generator with respect to individual large-signal parameters, in particular to specify the amplitude and / or the frequency of the large voltage signal. 9. network simulator (10) according to any one of the preceding claims, characterized in that the large signal generator (11) by a predetermined, in particular public power grid, is formed, wherein the large signal generator (11) optionally an additional, the public power grid downstream DC voltage intermediate circuit (112 ) for stabilizing the AC voltage in the voltage range of the rated network voltage and in the frequency range of the network nominal frequency. 10. Network simulator (10) according to one of the preceding claims, characterized in that the control unit (126) of the small signal generator (12) is adapted to specify the small signal parameters in the form of discrete voltage values for a number of times, and preferably during a Signal period above 10000 discrete voltage values, and / or that the further control unit (116) of the large signal generator (11) is adapted to specify the large signal parameters in the form of discrete voltage values for a number of times, and preferably during a signal period over 100 discrete Specify voltage values. 11. Network simulator (10) according to one of the preceding claims, characterized in that - a large DC generator is provided for powering the network simulator, - that the large signal generator and the small signal generator each comprise an inverter, and - that the galvanic decoupling of large signal generator and small signal generator thereby takes place in that one of the signal generators, in particular of the large signal generator, has at its output a transformer whose primary terminal is connected to the inverter of this signal generator and whose secondary terminal forms the output of the respective signal generator, and / or - that at the input of one of the signal generators (11, 12), in particular of the small signal generator (12), a galvanically isolated, at least two quadrant capable DC / DC converter is provided which electrically isolates the output of the DC voltage source from the inverter of the respective signal generator. 12. Network simulator (10; 20) according to any one of the preceding claims, characterized in that the inverter (113, 123) of the large signal generator (11) and / or the small signal generator (12) by a half-bridge or H-bridge controlled by the control unit power transistors is realized. A multiphase network simulator (20) according to any one of the preceding claims, comprising one of the following terminals: - a neutral conductor (N), - a number of phase terminals (L ^ L2, L3), - each phase connection being provided in each case: - A large signal generator (21) for generating a large voltage signal at its output, the amplitude of which substantially corresponds to the nominal network voltage, and - A small signal generator (22) for generating a low voltage signal at its output, whose amplitude is less than 50%, in particular less than 25% , the net nominal voltage, - wherein the outputs of the associated large signal generators (21) and small signal generators (22) are galvanically decoupled from each other, - wherein one pole of the output of the large signal generator (21) is connected to a pole of the output of the respective small signal generator (22) , wherein the other pole of the small signal generator (22) is connected to the neutral conductor (N) and d he respective other pole of the large signal generator (21) forms the phase output (Li, L2, L3), - wherein each small signal generator (21), optionally also each large signal generator (22), has at least one control input for specifying at least one control signal, and wherein the Small signal generator (22), optionally also the large signal generator (21), is adapted to create a voltage signal in dependence on a parameter contained in the control signal, in particular the amplitude and / or the frequency, - wherein for the individual small signal generators one or each one Regulating unit (126) is provided, which is designed to: - measure a current reading for the current at the output of the network simulator (10) or a small signal generator (12), in particular at predetermined, preferably periodically fixed, times, and - the small signal generator ( 12) with according to predetermined criteria of dependence on the determined current measured value, calc if appropriate, also to control signals from further measured values, in particular continuously and / or at, preferably periodically, predetermined times. 14. A method for testing a connectable to an AC voltage network with a predetermined nominal network voltage and nominal network frequency device, in particular an inverter, load or generator, - a large signal generator provides at its output a large voltage signal whose amplitude substantially corresponds to the nominal network voltage, and - a small signal generator its output provides a low voltage signal whose amplitude is smaller than 50%, in particular less than 20%, the rated network voltage, - wherein the output of the large signal generator and the output of the small signal generator are galvanically decoupled from each other, - one pole of the output of the large signal generator to a pole the output of the small signal generator is connected and the respective other two poles form the output of the network simulator, characterized in that - a voltage reading for the voltage at the output of the mains simulator, in particular to pre given, preferably periodically determined, times, is measured, - a current reading for the current at the output of the network simulator, in particular at predetermined, preferably periodically fixed, times, is measured, and - the large-signal parameters and the small-signal parameters according to predetermined criteria Depending on the determined voltage reading and current reading, in particular running and / or to, preferably periodically, predetermined times are set. 15. The method according to claim 14, characterized in that the parameters of the small signal generator are controlled such that the voltage applied to the connection of the mains simulator depends in a predetermined manner on the current flowing at the connection of the mains simulator power, in particular such that the mains simulator as a voltage source with the predetermined nominal network voltage and an impedance connected in series acts. 16. The method according to any one of claims 14 or 15, characterized in that is used as a large signal generator by a predetermined, in particular public power grid, wherein the large signal generator is optionally additionally stabilized to a stable AC voltage in the voltage range of the nominal network voltage and frequency range of the nominal network frequency leave. 17. Method according to claim 1, characterized in that the small-signal parameters are specified in the form of discrete voltage values for a number of times, wherein preferably over 10000 voltage values are preset during a signal period of the nominal network frequency, and / or that the large-signal Parameters are given in the form of discrete voltage values for a number of times, preferably over 100 voltage values are predetermined during a signal period of the network nominal frequency.