Determination of filter parameters in inverters

Abstract

The invention is for improved regulation of a switching device (2) of an inverter (1) with a filter circuit (3) and a mains relay (4), wherein the filter circuit (3) is composed of at least one filter inductance (LF) arranged in a conductor (P1, P2, P3, P4) and at least one filter capacitance (CF) connecting two conductors (P1, P2, P3, P4) to one another and for the filter circuit (3) an equivalent circuit (15) composed of an effective filter inductance (LF m ) and an effective filter capacitance (CF m ) is used, which effective filter inductance results from at least one filter inductance (LF) of the filter circuit (3) and the topology of the filter circuit (3), and which effective filter capacitance results from at least one filter capacitance (CF) of the filter circuit (3) and the topology of the filter circuit (3), wherein the effective filter inductance (LF m ) and the effective filter capacitance (CF m ) are used as object parameters. In order to determine the object parameters, a voltage pulse is applied between a first conductor output (W1, W2, W3, W4) and a second conductor output (W1, W2, W3, W4) when the mains relay (4) is open; the first conductor output (W1, W2, W3, W4) and the second conductor output (W1, W2, W3, W4) are connected by the switching device (2) to form a closed oscillation circuit (8, 8', 8"), which oscillation circuit extends from the first conductor output (W1, W2, W3, W4) and the first conductor (P1, P2, P3, P4) connected to the first conductor output (W1, W2, W3, W4) via the filter circuit (3) and the second conductor (P1, P2, P3, P4) to the second conductor output (W1, W2, W3, W4) connected to the second conductor (P1, P2, P3, P4); the current and / or voltage change curve (11, 12) in the oscillation circuit (8, 8', 8") is used to determine the current values of the effective filter inductance (LF m ) and the effective filter capacitance (CF m ) as object parameters, with which current values the switching device is regulated.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for regulating a switching device of an inverter with a regulator, and to an inverter with a corresponding system controller with a regulator. BACKGROUND

[0002] The switching device of an inverter usually comprises a bridge circuit, for example in the form of a four-quadrant regulator or a similar topology, which generates an alternating current in the corresponding line conducting the alternating current by pulsing the semiconductor switches contained therein on the alternating current side. The regulator of the switching device can be performed, for example, in the sense of pulse width modulation in order to achieve a good approximation of the desired alternating current shape, usually a sinusoidal shape.

[0003] Since only rectangular pulses can be generated by the switching device alone, a filter stage is provided downstream of the switching device in each phase, which smoothes the alternating current signal by means of an arrangement of capacitors and chokes (inductances) to approximate the desired sinusoidal shape.

[0004] The theoretical basis of such filter stages is sufficiently known and does not pose a hindrance in optimizing the rated values of the components. However, problems always arise in practice again. In particular, the actual characteristic values of the components often differ from the known rated values, and the characteristic values can change over time due to aging or due to changing environmental conditions.

[0005] For example, the filter stage in a single-phase or two-phase inverter can consist of at least one inductance and at least one capacitor. In a three-phase inverter, there are usually at least three capacitors and three inductances, respectively. The characteristic values of these components have a large influence on the regulation behavior and the tendency to oscillate of the inverter, since they are object parameters (or system parameters) of the regulation and thus influence the regulation behavior. The capacitors also have an influence on the regulation of the reactive power of the inverter. In the regulation of the inverter, the characteristic values of these components are stored and influence the regulator parameters executed. If the regulation is now based on incorrect or inaccurate characteristic values, this can lead to undesirable oscillations, stability problems and deviations in the reactive power. For example, the harmonic oscillations and distortions of the alternating current cannot be adjusted when the characteristic values are incorrect.

[0006] In order to be able to comply with the tight limit values of the reactive power output of different national standards and in order to be able to optimally regulate the inverter, it is therefore necessary to know the component values of the filter stage and thus the object parameters accurately.

[0007] The component values are usually measured when manufacturing the inverter and stored as parameters in the regulator. These working steps are relatively complex and also do not reflect ageing effects or other operating influences which change the component values, for example temperature influences. In order to achieve a predefined reactive power output, additional current measurements can be carried out at the output on the grid side of the inverter, however this represents a significant outlay.

[0008] Precise component values of capacitances and inductances can be determined by methods which are currently known in the prior art. These methods are usually only suitable for specific topologies. Furthermore, these methods are also limited in the case of an increasing number of components.

[0009] EP3232217A1 discloses a method for determining a current value of a filter capacitor, wherein an oscillation circuit is established by means of a semiconductor switch in the case of a charged filter capacitor, which oscillation circuit comprises one or more filter capacitors. An oscillation in the oscillation circuit driven by the initially charged filter capacitor is evaluated in order to determine the current value of the filter capacitor. The value of the filter inductance required for the determination is assumed to be unchangeable and known. The determination of the filter capacitor serves for monitoring the state of the filter capacitor. In particular, it is checked by comparison with a stored nominal value whether the filter capacitor is still in an operating state. The regulation of the switching device cannot therefore be improved.

[0010] EP3069158B1 discloses a method for determining a capacitance value of a capacitor of an energy supply device, wherein a three-phase inverter is operated with separate grid relays in order to build an island network. Here, at least two outputs of the inverter bridge are applied with an equal-phase alternating voltage. The current flowing at the outputs of the inverter bridge and at least one voltage present on an intermediate circuit capacitor and / or a filter capacitor are used to determine the current capacitance value of the filter capacitor and / or the intermediate circuit capacitor. Here, the determination of the capacitance value also serves for checking the functionality of the filter capacitor. The regulation of the switching device cannot therefore be improved. SUMMARY

[0011] In addition, it is the task of the present application to provide a method with which the regulation of a switching device of an inverter having a filter circuit can be improved.

[0012] According to a first aspect, the tasks and other tasks are solved by a method according to the application and by an inverter according to the application having a corresponding regulator.

[0013] The method according to the application for regulating a switching device of an inverter with a regulator, wherein the inverter has a switching device, a filter circuit and a grid relay, and the regulator takes into account object parameters of the filter circuit of the inverter, wherein the switching device has at least two conductor outputs and each conductor output is connected to the filter circuit by a conductor and the conductor of the inverter which is provided for connection to the grid is connected to the grid relay, wherein the filter circuit is composed of at least one filter inductance arranged in a conductor and at least one filter capacitance which connects two conductors to one another and for the filter circuit an equivalent circuit composed of an effective filter inductance and an effective filter capacitance is used, the effective filter inductance being derived from the at least one filter inductance of the filter circuit and the topology of the filter circuit, the effective filter capacitance being derived from the at least one filter capacitance of the filter circuit and the topology of the filter circuit, wherein the effective filter inductance and the effective filter capacitance are used as object parameters, and the method has the following steps, which are carried out when the grid relay is open:

[0014] applying a voltage pulse between the first conductor output and the second conductor output,

[0015] connecting the first conductor output and the second conductor output via the switching device to establish a closed oscillation circuit which extends from the first conductor output and the first conductor connected to it via the filter circuit and the second conductor to the second conductor output connected to the second conductor,

[0016] determining a current and / or voltage progression in the oscillation circuit,

[0017] evaluating the current and / or voltage progression for determining at least one current value of the effective filter inductance and the effective filter capacitance of the filter circuit as object parameters of the filter circuit, and

[0018] regulating the switching device of the inverter when the grid relay is closed taking into account the determined current value of the effective filter inductance and the effective filter capacitance of the filter circuit.

[0019] The inverter according to the application comprises a switching device with semiconductor switches and a system controller in which a regulation with a regulator with regulator parameters is carried out for regulating the switching of the semiconductor switches, wherein the inverter additionally comprises a filter circuit and a grid relay and the regulation is designed to take into account object parameters of the filter circuit of the inverter, wherein at least two conductor outputs are provided on the switching device and each conductor output is connected via a conductor with the filter circuit and the conductor of the inverter which is provided for the connection with the grid is connected with the grid relay, wherein in the filter circuit at least one filter inductance which is arranged in a conductor and at least one filter capacitance which connects two conductors with one another are provided. As object parameters, the effective filter inductance and the effective filter capacitance of the equivalent circuit of the filter circuit are provided, which effective filter inductance results from the at least one filter inductance of the filter circuit and the topology of the filter circuit, which effective filter capacitance results from the at least one filter capacitance of the filter circuit and the topology of the filter circuit, the switching device is designed to apply a voltage pulse between a first conductor output and a second conductor output when the grid relay is open, the switching device is designed to connect the first conductor output and the second conductor output after the voltage pulse has been applied in order to establish a closed oscillation circuit which extends from the first conductor output, via the filter circuit, the second conductor to the second conductor output which is connected with the second conductor, the system controller is designed to determine the current in the oscillation circuit and / or the voltage in the oscillation circuit, and the system controller is designed to determine the current values of the effective filter inductance and the effective filter capacitance of the filter circuit from the current and / or the voltage determined in the oscillation circuit, and the system controller is designed to regulate the inverter with the determined current values of the effective filter inductance and the effective filter capacitance of the filter circuit when the grid relay is closed.

[0020] The method allows the determination of the object parameters of the filter circuit in the case of a large number of different inverter and filter circuit topologies. For this purpose, without having to know the specific component values or individual component values, the overall effect of one or more combinations of the components which are connected with one another is determined. Here, the current change curve can be measured, for example, on one of the inductances. The determination of the voltage change curve can preferably be measured between the two conductors which participate in the oscillation circuit or between one of the conductors with respect to another reference potential, for example, the star point or the intermediate circuit point. For the regulation, it is sufficient to know the effective filter inductance and the filter capacitance. Thus, changing component values in the filter circuit can be tracked and, as a result, changing regulation characteristics of the inverter can be compensated.

[0021] In an advantageous manner, the method steps of applying a voltage pulse, establishing an oscillation circuit and determining and evaluating a current change curve and / or a voltage change curve can be repeated on a plurality of different conductor pairs. Thereby, in particular the effective filter inductance and the effective filter capacitance of each phase can be determined in the case of a multiphase inverter. In such embodiments, the detailed component values of the electrical components of the filter circuit can also be determined as required. For the voltage pulse, the energy stored in the intermediate circuit capacitor can be used.

[0022] In an advantageous manner, at least one current value of the effective filter capacitance of the filter circuit and at least one current value of the effective filter inductance of the filter circuit are determined as object parameters. In connection with the present disclosure, the values determined at present corresponding to the individual components of the filter circuit or the values determined at present corresponding to the calculated components of the equivalent circuit of the filter circuit are referred to as "effective" filter capacitance or "effective" filter inductance, depending on whether the values of the actual components or only the values of the equivalent circuit can be determined as a result of the respective filter circuit. The "effective" filter capacitance or "effective" filter inductance can also be further related to one another by mathematical relationships in order to convert them into effective values available for the regulation.

[0023] Depending on the topology of the inverter, different conductors can be used to determine the effective filter inductance and the effective filter capacitance. In inverters having a conductor provided for feedback from the filter circuit to the switching device, one of the other conductors of the inverter is advantageously used as the first conductor, and the conductor provided for feedback from the filter circuit to the switching device is used as the second conductor. The effective values of the individual phases can thus be determined directly. Here, too, undesired clamping can be prevented when determining the effective filter inductance and the effective filter capacitance.

[0024] In inverters having no conductor provided for feedback from the filter circuit to the switching device, one of the available conductors of the inverter is advantageously used as the first conductor, and another one of the available conductors of the inverter is used as the second conductor. This is in principle also possible in inverters having a neutral conductor connection. In order to prevent undesired clamping here, it can be provided that the conductor of the inverter not used for determining the effective filter inductance and the effective filter capacitance is brought to the intermediate circuit potential by means of a switching device. Thereby, a free-floating potential of such a non-used conductor, which can lead to clamping, can be prevented. This enables a more precise determination of the effective filter inductance and the effective filter capacitance.

[0025] The conductor provided for feedback from the filter circuit to the switching device is a conductor which is not connected to the grid relay or to the neutral conductor of the grid via the grid relay at all.

[0026] In an advantageous manner, the resonance frequency of the oscillation circuit can be determined from the current and / or voltage change curve, wherein the value of the effective filter inductance can be determined according to the formula

[0027] In an advantageous manner, the resonance frequency of the oscillation circuit can be determined from the current and / or voltage change curve, wherein the value of the effective filter inductance can be determined according to the formula

[0028] In an advantageous embodiment of the method, the decay behavior can be determined and taken into account in the regulation. Thereby, for example, the mass or the damping of the oscillation circuit can be calculated. The ohmic resistance of the oscillation circuit relevant thereto can also be determined thereby and can be used for the regulation. The decay behavior can be taken into account, for example, when designing the regulator of the regulation, for example, when determining the regulator parameters.

[0029] In another advantageous embodiment, the closed oscillation circuit can be established directly after the voltage pulse. Thereby, an oscillation can be generated in the oscillation circuit even when the capacitor is completely discharged. In connection with the present disclosure, "directly after the voltage pulse" means a time duration in which the voltage and current states in the involved components do not undergo a relevant change. This is in particular the case when the respective values change less than 10% about their entire fluctuation amplitude between the end of the voltage pulse and the establishment of the oscillation circuit.

[0030] In another aspect, the present disclosure relates to an inverter for connection to a power grid via a power grid relay, which is implemented accordingly.

[0031] The present disclosure also relates to a computer program having a program code for carrying out the above-mentioned method steps when the computer program is executed on a system controller of an inverter. Here, the computer program can advantageously determine the topology of the inverter before the execution of the method steps. The topology of the switching means of the inverter can be selected, for example, from the group consisting of H5, HERIC, REFU, FB-DCBP, FB-ZVR, NPC, Conergy-NPC and related topologies thereof. The topologies described in this way are known in the art and therefore do not have to be explained in detail here.

[0032] The person skilled in the art is able to apply the teachings disclosed here to all mentioned topologies. This also allows the use of the same computer program in a plurality of different inverters and also makes remote maintenance of the inverters easy. BRIEF DESCRIPTION OF DRAWINGS

[0033] Reference is made in the following to the drawings Figures 1 to 11 ​​The application is explained in detail, the figures exemplary, schematically and non-limitingly show advantageous design variants of the application. Herein:

[0034] Figure 1 The inverter is shown in a schematic, general diagram,

[0035] Figure 2 A schematic diagram of the circuit of the inverter is shown,

[0036] Figure 3 A part of the circuit of the inverter is shown, which has an alternative embodiment of the filter circuit,

[0037] Figure 4 A schematic diagram of another circuit of the inverter is shown,

[0038] Figure 5 A schematic diagram of the circuit of the inverter is shown, which has four conductors, which can be connected to the outer conductor and the neutral conductor of the power grid,

[0039] Figure 6 A schematic diagram of the circuit of the inverter is shown, which has three conductors;

[0040] Figure 7 Another schematic diagram of the circuit of the inverter is shown, which has four conductors;

[0041] Figure 8 A schematic diagram of the equivalent circuit is shown, which has an equivalent total capacitance,

[0042] Figure 9 A schematic diagram of the voltage pulse, the current curve and the voltage curve is shown, as it can be derived for example for the specific method,

[0043] Figure 10 The regulation of the inverter is shown, and

[0044] Figure 11 The equivalent circuit of the filter circuit is shown. DETAILED DESCRIPTION

[0045] Figure 1 The inverter 1 is shown, which converts a direct voltage generated by a direct voltage source 5 into an alternating voltage, which can be fed into a power grid 7 (also as island network). Figure 1 The inverter 1 is implemented three-phased with three phases L1, L2, L3 and a neutral conductor N.

[0046] The direct voltage source 5 generates a potential difference U DC, said potential difference being applied to the switching device 2 of the inverter 1 via two direct current side inputs DC1 and DC2. Depending on the system, the direct current side inputs DC1, DC2 can either directly come from a direct voltage source 5 or from an upstream direct voltage converter or MPP tracker. The switching device 2 comprises in a known manner an intermediate circuit consisting of at least one intermediate circuit capacitor C ZK (not shown) and a plurality of semiconductor switches T which are pulsed switched by a system controller 6 depending on a modulation scheme. Usually, a freewheeling diode D is arranged in parallel to the semiconductor switches T. The semiconductor switches T are often arranged in the form of a half-bridge circuit, wherein each phase is provided with at least one half-bridge consisting of at least two semiconductor switches T in series. The resulting alternating voltage can be applied to the respective conductor P via one or more conductor outputs W of the switching device 2. Each phase of the inverter is provided with at least one conductor P, wherein a plurality of conductor outputs W can also be combined into one phase (so-called interleaved inverter topology).

[0047] The conductor P is guided via a filter circuit 3 to a grid relay 4, wherein in the case of a closed grid relay 4 the conductor P of the inverter 1 is connected to the respective conductor of the grid 7, i.e. for example a phase conductor (phase L1) or an outer conductor (phases L2, L3) and a neutral conductor N, if necessary also a protective conductor can be considered.

[0048] The conductor P, to which an alternating voltage can be applied via the switching device 2, is also referred to as "phase conductor" in connection with the specific description. In connection with the present disclosure, not only phase conductors or outer conductors but also neutral conductors are generally referred to as "conductors". If it is meaningful or necessary to distinguish between a phase conductor and a neutral conductor, it is explicitly stated in the text that it is not logical and is derived by the described relationship.

[0049] The filter circuit 3 usually comprises at least one filter inductance LF (choke) which is arranged in the conductor P directly adjacent to the respective conductor output W and at least one filter capacitance CF which connects the two conductors P to each other, preferably "behind" the filter inductance LF, that is to say between the filter inductance LF and the grid relay 4. If necessary, in a multiphase topology a star point and a further filter capacitance CF can be connected.

[0050] In connection with the disclosure, components and elements that occur multiple times in the figures in similar or identical form are denoted by a capital letter combination (e.g. input end DC on the DC side, semiconductor switch T, conductor output W, conductor P, filter inductance LF, filter capacitance CF, etc.) identifying the element and are each assigned a subindex number. This differentiation is only for better distinguishability and is not to be interpreted restrictively.

[0051] According to embodiments of the inverter 1, the inverter can be equipped with two, three or four conductors P. An inverter with two conductors P1, P2 can for example be connected to two phases L1, L2 of the power grid 7 or to one phase L and the neutral conductor N. An inverter 1 with three conductors P1, P2, P3 can for example be connected to three phases L1, L2, L3 of a three-phase power grid 7. An inverter 1 with four conductors P1, P2, P3, P4 can for example be connected to three phases L1, L2, L3 of a three-phase power grid 7 and to the neutral conductor N thereof.

[0052] The disclosure is not limited to a specific topology of the inverter 1, in particular of the switching device 2 and the filter circuit 3. Rather, the teachings disclosed herein can be applied to a variety of different topologies, provided certain conditions are met, which will be exemplified below with reference to some more specifically elaborated circuitry.

[0053] The inverter 1, in particular the switching device 2 of the inverter 1, is regulated by a regulation 16, as is schematically shown in Figure 10 The regulation 16 is preferably implemented in the system controller 6 based on microprocessor-based hardware, preferably as software. The system controller 6 with the regulation 16 can also be implemented as an integrated switching circuit, for example as an application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA), or also as an analog circuit.

[0054] For the regulation 16, there are provided regulators R(RP) with regulation parameters RP, wherein these regulation parameters RP match the object parameters SP of the regulation object to be regulated in order to achieve the desired regulation behavior. The filter circuit 3 influences the regulation 16 of the inverter 1 such that the object parameters SP derived therefrom are taken into account in the regulation 16, in particular in the regulator R, for example in the form of the regulation parameters RP, or influence the values of the regulation parameters RP in the regulator. In addition to the object parameters SP derived by the filter circuit 3, of course further object parameters can also be taken into account in the regulation 16. The design of the regulator R with a predefined regulation law (for example PI regulator, PID regulator, etc.) by means of which the regulation parameters RP and their relationship to the object parameters SP are determined is sufficiently known to the person skilled in the art, so that it does not have to be explained further. In order to regulate the inverter 1, in particular the switching device 2 or the semiconductor switches T of the switching device 2, the regulator R determines, depending on predefined setpoint parameters SG, for example a desired current per phase or a desired voltage per phase, adjustment variables ST for the switching device 2, for example switching commands or a duty cycle for a pulse width modulation (PWM) regulation for the semiconductor switches T, which is subsequently converted into switching commands.

[0055] For the regulation of the inverter 1, for the filter circuit 3, for each phase of the inverter 1, an equivalent circuit consisting of an effective filter inductance L m and an effective filter capacitance C m is used, Figure 11 the filter inductance L m is derived from at least one filter inductance LF of a phase of the filter circuit 3 and the topology of the filter circuit 3, the effective filter capacitance C m is derived from at least one filter capacitance CF of a phase of the filter circuit 3 and the topology of the filter circuit 3. The effective filter capacitance C m and the effective filter inductance L m are object parameters SP of the regulation 16 for the switching device 2 and are derived from the measured values of the current i(t) and the voltage u(t), for example in the system controller 6 as described below.

[0056] Figure 2 and Figure 4 An exemplary embodiment of an inverter 1 for connection with an outer conductor (phase L1) and a neutral conductor N is shown, in which object parameters, such as the effective filter capacitance C m and the effective filter inductance L m are determined.

[0057] Figure 2 An embodiment of an inverter 1 with a conventional H-bridge circuit is shown, in which at the high potential (positive DC+ ) between the low potential (negative DC - ) and the high potential (positive DC DC The voltage difference U between the low potential (negative DC

[0058] Positive current: T1 and T4 closed, T3 and T2 open

[0059] Negative current: T2 and T3 closed, T1 and T4 open

[0060] Zero volts via DC + : T1 and T3 closed, T2 and T4 open

[0061] Zero volts via DC - : T2 and T4 closed, T1 and T3 open

[0062] The respective modulation schemes are sufficiently known in the art and therefore do not need to be described in detail here.

[0063] Irrespective of the topology, the circuit of the semiconductor switches T generates on the conductor outputs W respectively a rectangularly extending alternating current according to the modulation scheme, which must be converted into a sinusoidally as uniformly as possible extending wave before being fed into the power grid 7. This is ensured by the filter circuit 3 and the filter inductances LF1, LF2 and the filter capacitance CF provided therein. Through the specific filter topology of the filter circuit 3 and the characteristic values of the filter capacitance CF and the filter inductances LF present in the filter, the filter circuit 3 is endowed with a defined filter characteristic, which can be described by component values. These values depend on the respective frequency, wherein for the adjustment of the switching device 2 not only the characteristic in the case of the frequency of the alternating current (typically for example 16.7 Hz, 50 Hz, 60 Hz) can be taken into account, but if necessary also the characteristic in the case of interference frequencies and / or frequencies of fluctuation control signals for the power grid operator. In the operation of the inverter 1, a reactive current flows through the filter capacitance CF, which is adjusted by the regulation in the system controller 6. The filter capacitance CF and the filter inductances LF1, LF2 thus influence the regulation of the inverter 1.

[0064] In order to improve the accuracy of the value of the reactive power to be regulated and / or to optimize the regulation 16 of the system controller 6, it is important to identify the characteristic values of the object parameters SP for regulating the switching device 2 as precisely as possible. However, these object parameters SP or components of the filter circuit 3 which are integrated in the object parameters SP for regulation are subject to changes caused by aging or changes in environmental influences.

[0065] Depending on the topology of the filter circuit 3, the individual component values of the filter capacitances CF and the filter inductances LF can only be determined with great effort. Therefore, for the regulation 16 according to the application, for each phase an equivalent circuit 15 of the filter circuit 3 with an effective filter capacitance C m and an effective filter inductance L m is used, as is shown exemplarily in Figure 11 . In the equivalent circuit 15 for one phase of the inverter 1, all filter inductances LF of this phase are integrated in the effective filter inductance L m or neglected (L emv） . Likewise, all filter capacitances CF of this phase are integrated in the effective filter capacitance C m . It is clear that the manner in which this integration is carried out depends on the topology of the filter circuit 3. However, the person skilled in the art is in any case able to determine the effective filter capacitance C m and the effective filter inductance L m of the equivalent circuit 15 from the specific filter circuit 3. The regulator parameters RP of the regulation 16, in particular of the regulator R of the regulation 16, are designed by means of the equivalent circuit 15.

[0066] In the following, a method is described with which the current object parameters SP of the filter circuit 3 of the inverter 1 can be determined quickly, simply and precisely, with reference to the circuit shown in Figure 2 . In the best case, this method can be carried out before the inverter 1 is connected to the power grid 7 by closing the grid relay 4. Therefore, the object parameters SP can be carried out, for example, regularly or on demand, before the grid relay 4 is closed or also after the grid relay 4 is opened, so that the current object parameters SP can always be determined and taken into account in the regulation. Therefore, changes in the object parameters SP can be taken into account continuously in the regulation.

[0067] The method is carried out when the grid relay 4 is open, that is to say, the inverter 1 is disconnected from the grid 7 or its outer conductors (phases L1, L2, L3) and the neutral conductor N and all semiconductor switches T are open. By briefly closing the first and fourth semiconductor switches T1 and T4, for example for a period of a few microseconds (for example 5 microseconds), a voltage pulse is applied across the conductor outputs W1 and W2 in such a way that the intermediate circuit voltage is applied for the period in question. Alternatively, the voltage pulse can also be generated with the opposite polarity by closing the second and third semiconductor switches T2, T3. Immediately after the connection of the conductor outputs W1 and W2 is established in the switching device 2, so that an oscillation circuit 8 is established which, starting from the first conductor output W1, extends via the first conductor P1, the first filter inductance LF1, the filter capacitor CF, the second conductor P2, the second filter inductance LF2 to the second conductor output W2 and is closed by the connection between W1 and W2. The oscillation circuit 8 is shown in Figure 2 Fig. 3 by the dotted line. In the topology shown, the connection between W1 and W2 can be achieved by closing the "upper" semiconductor switches T1 and T3 or by closing the "lower" semiconductor switches T2 and T4. However, in many topologies it is also possible to connect the conductor outputs W to one another without a potential difference existing between them. If necessary, further semiconductor switches can be provided for this purpose, for example the semiconductor switch T5 shown in dashed lines, with which the bridge circuit can be separated from the positive DC voltage supply. +

[0068] If the filter capacitor CF is charged before the voltage pulse is applied, the problem of overcurrent, for example when the capacitor is charged too high, can be avoided with an advantageous embodiment of the method. Overcurrent can in principle be avoided with a sufficiently short voltage pulse and additionally with a correspondingly selected polarity. In a further embodiment of the method, the filter capacitor CF is discharged before the voltage pulse is applied, in order to rule out overcurrent and to enable a repeated determination of the object parameter under similar conditions.

[0069] At the beginning of the complete discharge of the filter capacitor CF, a free oscillation is also established in the oscillation circuit 8 directly after the voltage pulse, which can be determined as a current profile i(t) (for example a current measurement 9 on the first or second filter inductance LF1, LF2) and a voltage profile u(t) (a voltage measurement 13 across the filter capacitor CF). The frequency of the current profile (and of the voltage profile) corresponds to the resonance frequency f reso of the oscillation circuit 8. From the current profile I(t) and the voltage profile U(t) it is thus possible to determine the resonance frequency f reso , the voltage amplitude U and the current amplitude I. From these values it is possible to determine the effective filter inductance L m ​and the effective filter capacitance C m .

[0070] By means of the law of conservation of energy used on the oscillation circuit of the equivalent circuit 15 with the filter circuit 3

[0071] (Equation 1)

[0072] and the cardiac oscillation equation

[0073] (Equation 2)

[0074] results in the effective filter inductance

[0075] (Equation 3)

[0076] and the filter capacitance

[0077] (Equation 4).

[0078] the effective filter inductance L m and the effective filter capacitance C m can be derived from the single or multiple physical components of the filter circuit 3.

[0079] In the simple filter circuit 3 shown in Figure 2 , the determined effective filter capacitance C m corresponds to the current value of the filter capacitance CF. The effective filter inductance L m corresponds to the sum of the two filter inductances LF1 and LF2.

[0080] By determining the decay characteristic of the free oscillation, the mass or the damping of the oscillation circuit 8 can be calculated. From this, the ohmic resistance associated therewith can also be determined. The mass or the damping and the ohmic resistance of the oscillation circuit 8 can then be taken into account as further parameters for regulating the inverter 1 for generating the alternating current and the alternating voltage or for regulating optimization.

[0081] It is apparent that for determining the effective filter capacitance C m and the effective filter inductance L m in the inverter 1 as in Figure 2 , it is not important whether the inverter is connected to a phase conductor (phase L1) and a neutral conductor N (as in Figure 2 ) or to phase conductors (phases L1, L2). At the disconnection of the network relay 4, only the conductor P of the inverter 1 is present, which is used to construct the oscillation circuit 8. Likewise, the specific embodiment of the switching device 2 is not decisive for this.

[0082] As already mentioned with reference to Figure 3As explained above, the method can also be applied to more complex filter circuits 3. Filter circuit 3 includes a filter inductor LF1 in the first conductor P1 and an EMV choke L serving as a second inductor for attenuating high-frequency interference. EMV1 In addition to the second filter inductor LF2, the second conductor P2 also includes an EMV choke L. EMV2 Instead of the single filter capacitor CF, two filter capacitors CF1 and CF2 are arranged in parallel in filter circuit 3, wherein the two EMV chokes L EMV It is arranged between the first filter capacitor CF1 and the second filter capacitor CF2. The rest of inverter 1 is... Figure 3 The circuit not shown in the diagram may correspond to, for example, the circuits shown in the diagram. Figure 2 .

[0083] therefore, Figure 3 The oscillation circuit 8 is divided into two parallel branches between the two filter inductors LF1 and LF2. The first branch includes the first filter capacitor CF1, and the second branch includes the first EMV choke L connected in series. EMV1 Second filter capacitor CF2 and second EMV choke L EMV2 .

[0084] Regarding the method described above for determining object parameters SP, EMV choke L EMV The effect can be ignored in calculations. Because EMV chokes are typically designed for frequencies significantly higher than the filter inductance LF and are relatively very small, they do not introduce any disadvantages. The EMV choke has a negligible effect on the oscillation characteristics of the oscillator circuit 8. Therefore, the effective filter inductance L used in the equivalent circuit 15... m It is determined in a similar manner to that described above, and it corresponds to the sum of the two filter inductors LF1 and LF2. Effective filter capacitance C m It can also be determined by analogy, and in this case it corresponds to the sum of the two parallel filter capacitors CF1 and CF2.

[0085] Regarding the adjustment 16 of the switching device 2, the effective filter capacitor C... m and effective filter inductor L m The understanding is sufficient, so that the additional costs of determining the individual values ​​of the parallel filter capacitors CF1 and CF2 and the two filter inductors LF1 and LF2 are unnecessary and can be eliminated.

[0086] Figure 4Another example is shown in the form of a multi-level inverter 1, in which the switching device 2 in this case corresponds to a so-called "NPC topology". "NPC" in this case stands for "Neutral Point Clamped", that is to say the conductor output W of the switching device 2, in the case shown the second conductor P2, is connected to the intermediate circuit midpoint MP between the two intermediate circuit capacitors C ZK1 , C ZK2 . The second conductor P2 is connected to the filter circuit 3 and in this embodiment to the neutral conductor N of the power supply network 7 when the power supply network relay 4 is closed. On the conductor output W1 of the switching device to which the first conductor P1 is connected, more than two voltage levels (DC + , DC - ) can now be set due to the topology of the switching device 2. In the design according to Figure 4 , the voltage level 0 can now also be adjusted by the internal semiconductor switches T2, T3 and the clamping diodes D 11 , D 12 . The four semiconductor switches T1 to T4 of the NPC semiconductor bridge can be switched in particular to the following states:

[0087] Positive current: T1 and T2 closed, T3 and T4 open

[0088] Negative current: T3 and T4 closed, T1 and T2 open

[0089] Zero voltage via two zero voltage diodes: T2 and T3 closed, T1 and T4 open

[0090] In order to determine the object parameter SP, a voltage pulse is also applied to the conductor outputs W1, W2 when the power supply network relay 4 is open (for example by closing the two "upper" semiconductor switches T1 and T2 or the two lower semiconductor switches T3 and T4), in such a way that the intermediate circuit voltage is applied and immediately after by opening the two outer semiconductor switches T1, T4 and closing the two middle semiconductor switches T2 and T3, the first conductor output W1 is connected to the second conductor output W2 by one of the two clamping diodes D 11 , D 12 and an oscillating circuit 8 is established.

[0091] The determination of the object parameter SP is again carried out according to the above-described method, in which case only the filter inductance LF and the filter capacitance CF are taken into account. The values of the individual filter components can thus be determined directly. The effective filter capacitance C m corresponding to the current value of the filter capacitance CF and the effective filter inductance L mCorresponds to the current value of the filter inductance LF. However, more complex topologies of the filter circuit 3 are usually set, so that this simple correlation is not always present and is only used for illustration.

[0092] By means of the teaching of the exemplary disclosure of the single-phase or two-phase inverter described in connection with Figures 2 to 4 The present disclosure can also be applied to many other single-phase, two-phase or three-phase inverters with different topologies by means of the teaching of the exemplary disclosure of the single-phase or two-phase inverter described in connection with

[0093] The present teaching can advantageously be applied to three-phase inverters 1 with a filter circuit 3 which is fed back into the switching device 2 by means of a conductor P4, as is illustrated in the following with reference to Figure 5 and Figure 7 The conductor P4 for the feedback can also be connected to the neutral conductor N of the power grid 7 when the power grid relay 4 is closed. The main advantage is that the determination method of the object parameter SP can be used independently of the number of capacitors.

[0094] The three-phase inverter 1 can be manufactured, for example, by combining three single-phase inverters. On the other hand, special circuits for three-phase (with feedback or without feedback) inverters can also be used. The structure and topology of single-phase, two-phase and three-phase inverters are known per se to the person skilled in the art. The topologies listed and described in connection with the above-mentioned inverter 1 can also be used for three-phase systems by extending the circuit accordingly. Basically, the present disclosure is not limited to a particular topology, unless specific technical reasons (e.g. incompatible topologies) contradict the implementation of the teaching disclosed herein.

[0095] Figure 5An inverter 1 is shown with a switching device 2 with four conductor outputs W1 to W4, wherein the first three conductors P1 to P3 are connected via network relays 4 to the outer conductors (phases L1 to L3) of a network 7, and the fourth conductor P4 is connected to the neutral conductor N (however this is not mandatorily necessary). In the first three conductors P1 to P3, directly next to the respective conductor output W, a filter inductance LF1 to LF3 is provided and behind it a filter capacitance CF1 to CF3 is arranged between the respective conductor P1 to P3 (phase conductor) and the fourth conductor P4 (which serves to feed back the filter circuit 3 to the switching device 2 and is connected to the neutral conductor N when the network relays 4 are closed), which are thus arranged in a star arrangement. The phase conductors P1 to P3 can be loaded by the switching device 2 with an (in particular pulse width modulated) alternating voltage each. The fourth conductor P4 for feedback can be located in the switching device 2 on the intermediate circuit midpoint MP between the two intermediate circuit capacitances C ZK1 , C ZK2 . Figure 4 .

[0096] The method for determining the object parameter disclosed above in connection with the single-phase or two-phase inverter 1 is in principle suitable for an inverter 1 which can establish an oscillation circuit 8 between every two outputs of the switching bridge via the filter circuit 3 and which can be applied, for example, to the filter topology of Figure 5 .

[0097] For determining the object parameter SP, first a voltage pulse is applied to one of the first three conductor outputs W1 to W3. After the voltage pulse, from the conductor output, via the associated conductor P, via the filter circuit 3 and the conductor P4 provided for feedback and connected on the conductor output W4, an oscillation circuit 8' is built. The oscillation circuit 8' can be guided by the respective filter inductance LF, the respective filter capacitance CF and the fourth conductor P4 provided for feedback in such a way that the respective conductor output W1 to W3 is connected via the switching device 2 with the fourth conductor output W4. Such an oscillation circuit 8' is shown in Figure 5 by the dotted line between the conductor output W1 and the conductor output W4. In this sense, the method is also applied to the remaining conductor outputs W1 to W3. In this way, the effective filter capacitance C m and the effective filter inductance L m of each phase of the inverter 1 as described above are obtained.

[0098] Figure 7Another embodiment of the three-phase inverter 1 is shown, which has a conductor P4 configured for feedback from the filter circuit 3 to the switching device 2, wherein the switching device 2 corresponds to a 3L-NPC (Three Level Neutral Point Clamped) topology. Of the four conductors P1 to P4, when the grid relay 4 is closed, the three first conductors P1 to P3 are respectively assigned to one phase L1 to L3 (phase conductor) of the grid 7, and the fourth conductor P4 is assigned to the neutral conductor N and connected to the intermediate circuit midpoint MP. However, this connection between conductor P4 and the neutral conductor N is not mandatory when the grid relay 4 is closed.

[0099] Filter circuit 3 includes a filter inductor LF1 to LF3 for each conductor P1, P2, and P3. Additionally, an EMV choke L is provided in each conductor P1, P2, and P3. EMV Among them, the EMV choke L EMV For the determined object parameter SP, it can be ignored as already explained. In the filter inductors LF1 to LF3 and the EMV choke L... EMV A first star circuit with three filter capacitors CF1 to CF3 is arranged between them, and an EMV choke L is also present. EMV A second star circuit with three additional filter capacitors CF4 to CF6 is then arranged. The midpoints of the two star circuits are respectively connected to a fourth conductor P4 for feedback to the switching device 2.

[0100] With the aid of the switching device 2 shown, a positive potential (positive DC) can be applied in the form of a voltage pulse to each of the three conductors L (i.e., the three first conductors P1 to P3), that is, to each phase of the inverter 1. + ), negative potential (negative DC) - ) or the neutral potential of the intermediate circuit midpoint MP between them (the corresponding circuit of semiconductor switch T corresponds to the combination Figure 4 (Described operating method). Therefore, an oscillation circuit 8 can be established for each phase of inverter 1, which starts from the midpoint MP and passes through the two clamping diodes D of the corresponding phase. x1 D x2 and two intermediate semiconductor switches T x2 T x3 The corresponding phase conductor output terminal W, the filter inductor LF, the two parallel filter capacitors CF of the corresponding phase, and the fourth conductor P4 are extended to the midpoint MP of the intermediate circuit for feedback.

[0101] As a voltage pulse, a positive voltage pulse (semiconductor switch T) can be applied. x1 and T x2a positive voltage pulse (semiconductor switch T x3 and T x4 closed). The oscillation circuit 8 is then established again as described above and the current and / or voltage change curve is measured and evaluated. The procedure is carried out for each of the three phases. Thereby, as object parameters SP the values of the effective filter inductance L m and the effective filter capacitance C m for each phase can be determined, inter alia.

[0102] In Figure 7 , the oscillation circuit 8 for the first phase, i.e. via the conductor P1, is shown by a dotted line. The evaluation of the characteristics of the oscillation circuit 8 allows to determine the values of the effective filter inductance L m and the effective filter capacitance C m in the form of the first filter inductance LF1, which in the case corresponds to the sum of the two parallel filter capacitances CF1 and CF4 of the oscillation circuit 8 and is determined as the total capacitance. The effective filter inductance L m and the effective filter capacitance C m for the other two phases are determined in an analog manner. Due to the connection of the star point of the filter capacitors CF to the intermediate circuit midpoint MP, the effective filter inductance L m and the effective filter capacitance C m for the respective phase can be formed in a simple manner with the oscillation circuit 8 between one of the conductor outputs W1, W2, W3 of the conductors P1, P2, P3 and the conductor output W4 of the conductor P4 provided for feedback.

[0103] On the other hand, two "phase outputs" (i.e. two of the first three conductor outputs W1 to W3) can also be connected to each other by the switching device 2, respectively. This is possible for Figure 5 and Figure 7 , but this is particularly suitable for Figure 6 and Figure 8 , since there is no feedback of the filter circuit 3 to the switching device 2 here. The corresponding oscillation circuit 8" is slightly more complex and is exemplarily shown in Figure 5 and Figure 6 by a dotted line between the conductor outputs W2 and W3. In Figure 5 , this exemplary oscillation circuit 8" comprises a second filter inductance LF2, a second filter capacitance CF2, a third filter capacitance CF3 and a third filter inductance LF3 in a series circuit.

[0104] Thus, in embodiments according to Figure 5 or Figure 7 six different oscillation circuits 8', 8" are available for use (whereas, for example, in Figure 6Three different oscillating circuits (8”) are available in the circuit shown below (as described below). Figure 5 In the simple case shown (oscillator circuit 8'), it is also possible to accurately determine the parameters of all filter capacitors CF and filter inductors LF by means of the evaluation of the three oscillator circuit 8' guided by the three conductors L4 (i.e., the output terminal W4 of the fourth conductor) set for feedback. For example, Figure 6 In the circuit described herein, the parameters related to a single filter capacitor cannot be determined using the method disclosed herein, but the effective filter inductance L can be determined. m and effective filter capacitor C m This is sufficient for the regulation 16 of inverter 1. Therefore, the preferred variations of this method depend on the specific topology of the switching device 2 or the filter circuit 3 connected thereto.

[0105] If there is another filter capacitor CF in filter circuit 3 (such as in...), Figure 5 As shown by the filter capacitors CF4 to CF6 (drawn by dashed lines), they can also be considered as effective filter capacitors C. m Determine the total value of the filter capacitors connected in parallel in the oscillating circuit.

[0106] Figure 6 A three-phase inverter 1 is shown, however, it has a filter circuit 3 that does not feed back to the switching device 2. The three conductor output terminals W1 to W3 are respectively connected to conductors P1 to P3, wherein the conductors can be connected to phases L1 to L3 of the power grid 7, respectively.

[0107] Filter circuit 3 includes (in the direction from conductor output terminal W to mains relay 4) three filter inductors LF1 to LF3 (one for each conductor), a star circuit with three filter capacitors CF1 to CF3 and a free star contact, and three EMV chokes L. EMV1 To L EMV3 (One for each conductor) and three filter capacitors CF4 to CF6 in the delta circuit. When the mains relay 4 is closed, the free star contact can also be connected to the neutral conductor N of the mains 7.

[0108] Each combination of star and / or delta circuits for capacitors can be represented as an equivalent circuit in either a pure star or pure delta circuit form. In this sense, for Figure 6 In the case of a star-delta circuit, one can imagine replacing the delta circuit composed of CF4, CF5, and CF6 with an equivalent star circuit. Thus, using the star circuit composed of CF1, CF2, and CF3, two star circuits are obtained, which can then be integrated into a unique equivalent star circuit. Therefore, for Figure 6 According toFigure 8 The equivalent circuit 15 has an effective filter capacitor C that serves as the equivalent total capacitance. m1 C m2 C m3 .

[0109] In order to determine Figure 6 The object parameter SP is first applied to one of the three conductor output terminals W1 to W3. Immediately after the voltage pulse, an oscillation circuit 8 is constructed from the conductor output terminal via filter circuit 3”, wherein the conductor output terminal is short-circuited via a switching device 2 having one of the two remaining conductor output terminals W1 to W3. Here, the corresponding oscillation circuit 8” extends in parallel through the star and delta circuits of filter circuit 3, as with the previous voltage pulse, wherein the EMV choke L… EMV It was ignored again. Calculated, by... Figure 8 The equivalent total capacitance is determined in the middle to obtain Figure 6 The effective filter capacitor C in the equivalent circuit 15 is... m1 C m2 C m3 .

[0110] If we consider a star circuit as such for Figure 6 exist Figure 8 The equivalent circuit 15 in the diagram allows us to determine the three total capacitances C using the method described above. m12 C m23 C m31 In the case of a star-equivalent circuit, these capacitances correspond to the capacitances of every two equivalent total capacitances (C). m1 C m2 C m3 The total capacitance of the series circuit consisting of ( ) is calculated using the determined total capacitance C. m12 C m23 C m31 The following system of equations can be listed:

[0111]

[0112]

[0113]

[0114] The effective filter capacitance C for each phase can be determined from this set of equations. m1 C m2 C m3 The method is based on the effective filter capacitance C. m1 C m2 C m3 Decomposing the above system of equations yields the following equations:

[0115]

[0116]

[0117]

[0118] To illustrate, Figure 9 The voltage pulse 10 is shown in the first graph and the reaction of the oscillation circuit 8" to the voltage pulse 10 is shown in two further graphs, for example according to Figure 8 In the shown example, the oscillation circuit 8" consists of the effective filter capacitances C m2 , C m3 and the filter inductances LF2, LF3, which in this example correspond to the effective filter inductances L m . By the determined current curve 11 or voltage curve 12, in addition, the resonance frequency (f reso = 1593.8 Hz), the current amplitude (I = 32.9 A) and the voltage amplitude (U = 32.9 V) can be determined. Using equation 4, for the effective total capacitance C m23 , a value of C m23 = 100 μF is obtained. In the same way, C m12 and C m31 can be determined with the method C. Thus, the effective filter capacitances C m1 , C m2 , C m3 can be determined with the above equation system.

[0119] The effective filter capacitances C m1 , C m2 , C m 3 correspond to the effective filter capacitances for the current values required for the regulation and can be transformed into the triangle equivalent circuit for the capacitors again by means of star-triangle transformation if required, if the regulation 16 requires the effective filter capacitances C m1 , C m2 , C m3 in this form.

[0120] By the above method, the three total inductances L m12 , L m23 , L m31 can also be determined according to Figure 8 With the total inductances, the following equation system can be established:

[0121]

[0122]

[0123]

[0124] With total capacitance C m23 Similarly, the total inductance L is determined. m23 We can use Equation 3 and according to Figure 9 The determined value is used for calculation, where L m23 =100μH. In the same way, the total inductance L m12 and L m31 This method can be used to determine it. Therefore, the above equations can be derived from the effective filter inductance L. m1 =LF1、L m2 =LF2 and L m3 =LF3 is used to solve and calculate the current value:

[0125]

[0126]

[0127]

[0128] Figure 9 The exemplary voltage pulse 10 is generated by the switching device 2 of inverter 1 at time t = 1 ms, where u1 = 600 V. In this example, in the preceding quiescent state (e.g., before normal operation), one or more filter capacitors involved in voltage pulse 10 discharge (u2 = 0 V) ​​and no current (i = 0 A) flows through the involved filter inductor. Current variation curve 11 shows the current through the effective filter inductor L. m The current flows. Under maximum current conditions, according to voltage change curve 12, the effective filter capacitor C... m The measured voltage is minimum or zero, and all the energy of the oscillating circuit 8 is stored in the effective filter inductor C. m In the magnetic field. The oscillating circuit 8 is formed directly after the pulse. Approaching t=1.2ms, it passes through the effective filter inductor L. m The current flow is minimal or zero, and the entire energy of the oscillating circuit 8 is stored in the effective filter capacitor C. m In this context, voltage variation curve 12 represents the maximum voltage. Equation 1 is based on this relationship.

[0129] Therefore, the effective filter capacitance C can be determined based on the aforementioned set of equations. m The current value and effective filter inductance L m The current value.

[0130] However, in an inverter 1 having three or more phase conductors P1, P2, P3 and without a defined zero state, such as in... Figure 6In a topology like that, the effective filter capacitance C of each phase is determined. m and effective filter inductor L m This will sometimes present certain difficulties. Figure 6 In the test scenario shown, the oscillation voltage is distributed across filter capacitors CF2 and CF3. Ideally, the two filter capacitors CF2 and CF3 are of equal size, resulting in a potential at the common star junction of the capacitors. This potential is applied by the switching device 2 for voltage pulses (e.g., DC). + or DC - However, if the two filter capacitors CF2 and CF3 are not of equal value, which is entirely possible in practice, then this no longer applies. In this case, the potential of the capacitor star contact will oscillate. This oscillation of the potential of the capacitor star contact also allows for potential oscillation at the conductor output terminal W1 via the filter inductor LF1, since W1 can be considered open for this test condition. This undesirable oscillation at the conductor output terminal W1 may cause the voltage to exceed the positive intermediate circuit voltage DC. + The potential is either below the negative intermediate circuit voltage DC-. In both cases, one of the unloaded diodes D of the semiconductor switch T becomes conductive in the switching branch at the conductor output terminal W1, thereby allowing current to flow into the intermediate circuit and distorting the current and voltage measurements, which leads to an increase in the effective filter capacitance C. m and effective filter inductor L m The inaccurate determination of this effect is called "clamping." This clamping effect is independent of whether the filter capacitors CF1, CF2, and CF3 are arranged in a star or delta configuration and can occur even with different sizes of the filter inductors LF1, LF2, and LF3. Clearly, this clamping can also occur in different... Figure 6 The same situation occurs in the case of the oscillating circuit 8” formed as shown in the test case. This clamping can be identified by measuring the current via the filter inductor LF (which is to be performed in accordance with the method according to the invention) and considered for adjustment when necessary.

[0131] To prevent this clamping, a topology with a conductor P4 serving as feedback from the filter circuit 3 to the switching device 2, connected to a defined zero state, can be used. Such a topology could be, for example, as shown in... Figure 7 The topology shown here, where conductor P4 is located at the midpoint MP of the intermediate circuit, or as in Figure 5 The topology shown has conductor P4 also located at the midpoint MP of the intermediate circuit. This prevents oscillating potentials at the star junction of the capacitor.

[0132] Another possibility for preventing clamping is to make the phase unused for the corresponding test case (in Figure 6the potential of the conductor P1 ) is not floating, but is placed by the switching means on the potential (i.e. DC + or DC - ) used for the voltage pulse, thus preventing oscillations of the potential on the associated conductor output W. However, with this circuit arrangement, the filter inductance LF1 and the filter capacitance CF1 of the phase or conductor P1 not used for the test case participate in the oscillation circuit 8" of the test case and thus have to be taken into account in determining the effective filter capacitance C m and the effective filter inductance L m . The above equations thus become slightly more complex, but this does not change the basic mode of operation for determining the effective filter capacitance C m and the effective filter inductance L m .

[0133] The decay characteristic of the oscillation circuit is not shown in Figure 9 , however, the parameters for this can likewise be determined and taken into account in the regulation. Due to the decay characteristic, it is important for the accuracy of the sought object parameters SP to take the voltage and current amplitudes U, I of the voltage and current curves 12, 11 as close in time as possible, so that an energy balance can be assumed according to equation 1. The time period depends on the resonance frequency and the decay characteristic and is, for example, one or several cycle durations of the resonance frequency. The method shown in Figure 9 can also be applied to all the remaining previously disclosed and further topologies.

[0134] For the purpose of regulating 16 the switching means 2 of the energy conversion or inverter 1, the object parameters SP in the form of the effective filter capacitance C m and / or the effective filter inductance L m of the filter circuit 3 are sufficient. The determination of the individual component values is not necessary, however, can be derived in the case of determination. The value of the effective filter capacitance C m may also define an allowed value range, wherein for values outside the allowed value range a fault report or fault state of the inverter 1 can be defined.

Claims

1. Method for regulating a switching device (2) of an inverter (1) with a regulator, wherein, The inverter (1) has a switching device (2), a filter circuit (3) and a grid relay (4) and the regulator takes into account the object parameters of the filter circuit (3) of the inverter (1), wherein the switching device (2) has at least two conductor outputs and each conductor output is connected to the filter circuit (3) by a conductor and the conductor of the inverter (1) which is provided for the connection to the grid (7) is connected to the grid relay (4), wherein the filter circuit (3) is composed of at least one filter inductance (LF) arranged in a conductor and at least one filter capacitance (CF) which connects two conductors to one another and for the filter circuit (3) an equivalent circuit (15) composed of an effective filter inductance (L m ) and an effective filter capacitance (C m ) is used, the effective filter inductance being derived from the at least one filter inductance (LF) of the filter circuit (3) and the topology of the filter circuit (3), the effective filter capacitance being derived from the at least one filter capacitance (CF) of the filter circuit (3) and the topology of the filter circuit (3), wherein the effective filter inductance (L m ) and the effective filter capacitance (C m ) are used as object parameters and the method has the following steps, which are carried out when the grid relay (4) is open: applying a voltage pulse between the first conductor output and the second conductor output, connecting the first conductor output and the second conductor output via a switching device (2) to establish a closed oscillation circuit (8, 8', 8") which extends from the first conductor output and a first conductor connected thereto via a filter circuit (3) and a second conductor to a second conductor output connected to the second conductor, determining a current and / or voltage change curve (11, 12) in the oscillation circuit (8, 8', 8"), —Evaluate the current and / or voltage variation curves (11, 12) to determine the effective filter inductance (L) of the filter circuit (3) as an object parameter of the filter circuit (3). m ) and effective filter capacitor (C m At least one current value of ), - and adjusting the switching means (2) of the inverter (1) in consideration of the determined current values of the effective filter inductance (L m ) and the effective filter capacitance (C m ) of the filter circuit (3) when the network relay (4) is closed.

2. The method of claim 1, wherein, repeating the method steps of applying a voltage pulse, establishing an oscillation circuit (8, 8', 8") and determining and evaluating a current and / or voltage change curve (11, 12) on a plurality of different conductor pairs.

3. The method of claim 1, wherein, In an inverter (1) having a conductor provided for feedback from the filter circuit (3) to the switching device (2), one of the other conductors of the inverter (1) is used as the first conductor and the conductor provided for feedback from the filter circuit (3) to the switching device (2) is used as the second conductor.

4. The method of claim 1, wherein, In an inverter (1) having no conductor provided for feedback from the filter circuit (3) to the switching device (2), one of the available conductors of the inverter (1) is used as the first conductor and another of the available conductors of the inverter (1) is used as the second conductor.

5. The method of claim 4, wherein, The conductors of the inverter (1) not used for determining the effective filter inductance (L m ) and filter capacitance (C m ) are placed on the intermediate circuit potential (DC+, DC-) by means of the switching device (2).

6. The method according to any one of claims 1 to 5, characterized in that, The resonant frequency (f reso ) of the oscillation circuit (8, 8', 8") is determined from the current and voltage change curves (11, 12), wherein the value of the effective filter inductance (L m ) is determined in accordance with the formula .

7. The method according to any one of claims 1 to 5, characterized in that, The resonant frequency (f reso ) of the oscillation circuit (8, 8', 8") is determined from the current and voltage change curves (11, 12), wherein the value of the effective filter capacitance (C m ) is determined in accordance with the formula .

8. The method according to any one of claims 1 to 5, characterized in that, The decay behavior of the current and / or voltage change curve (11, 12) in the oscillation circuit (8, 8', 8") is determined and taken into account in the regulation.

9. The method according to any one of claims 1 to 5, characterized in that, The closed oscillation circuit (8, 8', 8") is established directly after the voltage pulse.

10. Inverter, comprising a switching device (2) with semiconductor switches (T) and a system controller (6) in which a regulation (16) is carried out with a regulator (R) with regulator parameters (RP) for regulating the switching of the semiconductor switches (T), wherein, The inverter (1) additionally comprises a filter circuit (3) and a grid relay (4) and the regulation (16) is designed to take into account an object parameter of the filter circuit (3) of the inverter (1), wherein at least two conductor outputs are provided on the switching device (2) and each conductor output is connected via a conductor with the filter circuit (3) and the conductor of the inverter (1) provided for connection with the grid (7) is connected with the grid relay (4), wherein in the filter circuit (3) at least one filter inductance (LF) arranged in a conductor and at least one filter capacitance (CF) connecting two conductors with one another are provided, characterized in that as object parameter an effective filter inductance (L m ) and an effective filter capacitance (C m ) of an equivalent circuit (15) of the filter circuit (3) are provided, which effective filter inductance is derived from the at least one filter inductance (LF) of the filter circuit (3) and the topology of the filter circuit (3), and which effective filter capacitance is derived from the at least one filter capacitance (CF) of the filter circuit (3) and the topology of the filter circuit (3), the switching device (2) is designed to apply a voltage pulse between a first conductor output and a second conductor output when the grid relay (4) is open, the switching device (2) is designed to connect the first conductor output and the second conductor output after the voltage pulse has been applied in order to establish a closed oscillation circuit (8, 8', 8"), which oscillation circuit extends from the first conductor output, via the filter circuit (3), the second conductor to the second conductor output connected with the second conductor, the system controller (6) is designed to determine the current in the oscillation circuit (8, 8', 8") and / or the voltage in the oscillation circuit (8, 8', 8") and to determine the current value of the effective filter inductance (L m ) and the effective filter capacitance (C m ) of the filter circuit (3) from the determined current and / or voltage, and the system controller (6) is designed to regulate the inverter (1) with the determined current value of the effective filter inductance (L m ) and the effective filter capacitance (C m ) of the filter circuit (3) when the grid relay (4) is closed. m m m m m m 11. A system controller (6) of an inverter (1) for carrying out a computer program having program code for carrying out all the method steps according to any one of claims 1 to 9 when the computer program is executed on the system controller (6) of the inverter (1).

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