A generator output impedance measurement circuit

Abstract

This application provides a generator output impedance measurement circuit, relating to the field of power system design technology, for improving the measurement accuracy of generator output impedance. The circuit includes a host computer, a main circuit, and a measurement circuit. The main circuit includes a generator equivalent circuit and a circuit load equivalent circuit. The measurement circuit includes a harmonic injection circuit and a sampling circuit. The harmonic injection circuit is connected to both the generator equivalent circuit and the circuit load equivalent circuit. The impedance of the generator equivalent circuit is lower than that of the circuit load equivalent circuit. The host computer is connected to the harmonic injection circuit and the sampling circuit. The host computer is used to set harmonic injection parameters and, according to these parameters, inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit. The sampling circuit is used to collect the voltage and current between the generator equivalent circuit and the harmonic injection circuit within a predetermined time period of the injected voltage disturbance signal, and transmit the collected voltage and current to the host computer.

Description

Technical Field

[0001] This utility model relates to the field of power system design technology, and in particular to a generator output impedance measurement circuit. Background Technology

[0002] With the development and application of more-electric and all-electric aircraft, more and more power electronic devices are being used in aircraft power systems. Due to the highly nonlinear and time-varying characteristics of power electronic devices, they are prone to causing stability problems in the power system. The commonly used method for power system stability analysis is impedance-based stability analysis, which determines the system stability by measuring the output impedance on the power supply side and the input impedance on the load side.

[0003] Currently, the commonly used method for measuring device impedance is series injection. This involves directly connecting the disturbance signal to the circuit under test (DUT), sampling the port voltage and current of the DUT, and then calculating its impedance values ​​at different frequencies. Because it's series injection, most of the emitted disturbance signal flows to the load section with higher impedance. Therefore, for generators, which have very low inherent impedance, the generated disturbance voltage signal is very small when connected in series with a load with high impedance. Directly measuring the series disturbance signal often results in difficulty in acquiring the corresponding response signal and leads to significant measurement errors. Utility Model Content

[0004] This application provides a generator output impedance measurement circuit to improve the measurement accuracy of generator output impedance.

[0005] This utility model embodiment provides a generator output impedance measurement circuit, the circuit including: a host computer, a main circuit and a measurement circuit, the main circuit including a generator equivalent circuit and a circuit load equivalent circuit, and the measurement circuit including a harmonic injection circuit and a sampling circuit;

[0006] The harmonic injection circuit is disposed between the generator equivalent circuit and the circuit load equivalent circuit, and is connected to the generator equivalent circuit and the circuit load equivalent circuit; the impedance of the generator equivalent circuit is lower than the impedance of the circuit load equivalent circuit.

[0007] The host computer is connected to the harmonic injection circuit and the sampling circuit. The host computer is used to set the harmonic injection parameters and inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit according to the harmonic injection parameters.

[0008] The sampling circuit is used to collect the voltage and current between the generator equivalent circuit and the harmonic injection circuit within a predetermined time period after the voltage disturbance signal is injected, and to transmit the collected voltage and current to the host computer.

[0009] In an optional embodiment, the harmonic injection circuit includes a fundamental frequency blocking circuit and a harmonic receiving source, the fundamental frequency blocking circuit and the harmonic receiving source being connected in series; the host computer includes a harmonic generating source, and the harmonic injection circuit is connected to the harmonic generating source of the host computer through the harmonic receiving source.

[0010] In an optional embodiment, the baseband blocking circuit consists of inductors and capacitors connected in parallel.

[0011] In an optional embodiment, the generator equivalent circuit is a three-phase motor circuit, and the circuit load equivalent circuit consists of three resistors connected in parallel.

[0012] In an optional embodiment, each phase of the three-phase motor circuit is connected in series with a resistor in the equivalent circuit of the circuit load.

[0013] In an optional embodiment, the measuring circuit is used to acquire the current I of phase a in the three-phase motor circuit. a Current I in term b b ; and to collect the voltage Δu between phases ab in the three-phase motor circuit. ab The voltage Δu between phases b and c bc .

[0014] This invention provides a generator output impedance measurement circuit, comprising: a host computer, a main circuit, and a measurement circuit. The main circuit includes a generator equivalent circuit and a circuit load equivalent circuit. The measurement circuit includes a harmonic injection circuit and a sampling circuit. The harmonic injection circuit is located between and connected to the generator equivalent circuit and the circuit load equivalent circuit. The impedance of the generator equivalent circuit is lower than the impedance of the circuit load equivalent circuit. The host computer is connected to the harmonic injection circuit and the sampling circuit. The host computer is used to set harmonic injection parameters and, according to these parameters, inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit. The sampling circuit is used to collect the voltage and current between the generator equivalent circuit and the harmonic injection circuit within a predetermined time period after the voltage disturbance signal is injected, and transmit the collected voltage and current to the host computer. In this embodiment, the host computer controls and outputs harmonic injection parameters of different frequencies. Then, the disturbance signal corresponding to the harmonic injection parameter is injected into the main circuit. The injected disturbance signal will generate a disturbance response in the main circuit with the same frequency as the injected disturbance signal. The generator output impedance can be calculated by the voltage and circuit collected in the sampling circuit. Attached Figure Description

[0015] Figure 1 A circuit diagram for measuring the output impedance of a generator is provided in this application;

[0016] Figure 2 Wiring diagram for generator output impedance measurement circuit provided in this application;

[0017] Figure 3 This application provides a flowchart for measuring the output impedance of a generator;

[0018] Figure 4 Another flowchart for measuring generator output impedance provided in this application;

[0019] Figure 5 Parallel injection circuit diagram for the output impedance of the three-stage generator provided in this application;

[0020] Figure 6 The LC module circuit diagram provided in this application;

[0021] Figure 7 A schematic diagram of the LC module impedance simulation results provided in this application;

[0022] Figure 8 A schematic diagram of the current simulation results provided in this application;

[0023] Figure 9 A schematic diagram of the theoretical and simulation frequency sweep verification results provided for this application. Detailed Implementation

[0024] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0025] Please see Figure 1 This invention provides a generator output impedance measurement circuit, comprising: a host computer 1, a main circuit 2, and a measurement circuit 3. The main circuit 2 includes a generator equivalent circuit 21 and a circuit load equivalent circuit 22. The measurement circuit 3 includes a harmonic injection circuit 31 and a sampling circuit 32.

[0026] like Figure 1 As shown, the harmonic injection circuit 31 is disposed between the generator equivalent circuit 21 and the circuit load equivalent circuit 22, and is connected to the generator equivalent circuit 21 and the circuit load equivalent circuit 22; the impedance of the generator equivalent circuit 21 is lower than the impedance of the circuit load equivalent circuit 22.

[0027] In an optional embodiment, the generator equivalent circuit 21 is a three-phase motor circuit, and the circuit load equivalent circuit 22 consists of three resistors connected in parallel. Each phase of the three-phase motor circuit is connected in series with a resistor in the circuit load equivalent circuit 22.

[0028] In an optional embodiment, the harmonic injection circuit 31 includes a fundamental frequency blocking circuit and a harmonic receiving source, the fundamental frequency blocking circuit and the harmonic receiving source being connected in series; the host computer 1 includes a frequency response analyzer, an excitation small signal generation module, and a linear amplifier unit, the linear amplifier generating a harmonic source, and the harmonic injection circuit 31 being connected to the harmonic generating source of the host computer 1 through the harmonic receiving source. The fundamental frequency blocking circuit is composed of inductors and capacitors connected in parallel.

[0029] In this embodiment, the parameters of the baseband blocking circuit are determined based on the rated operating state of the generator under test. Then, the voltage and current sampling ports are determined. Sampling is achieved through voltage and current probes. Since it is a three-phase circuit, at least two phase voltages and currents need to be sampled. Taking a four-channel frequency response analyzer sampling line voltages ab and bc, and phase currents a and b as an example, the measurement wiring is shown below. Figure 2 As shown.

[0030] Fundamental frequency blocking circuit (Z in the figure) b It is only necessary to exhibit a large impedance at the rated operating frequency (fundamental frequency) of the main circuit, which can be directly obtained. The fundamental frequency blocking circuit in this embodiment is... Figure 1 and Figure 2 The LC parallel module in the circuit contains parameters including the inductance value of inductor L and the capacitance value of capacitor C. The impedance expression for the fundamental frequency blocking circuit is:

[0031]

[0032] Where f is the operating frequency of the generator in the main circuit, and Z(s) is the impedance value that the circuit wants to achieve at this operating frequency (in order to block the fundamental frequency, this value can usually be set to 10^2 or higher). Based on f and the desired Z(s), the required inductance and capacitance values ​​can be calculated according to the impedance expression (the calculated inductance and capacitance values ​​are not unique).

[0033] The host computer 1 is connected to the harmonic injection circuit 31 and the sampling circuit 32. The host computer 1 is used to set the harmonic injection parameters and inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit 31 according to the harmonic injection parameters.

[0034] In an optional embodiment, such as Figure 2The wiring diagram for the generator output impedance measurement circuit shown is illustrated. The disturbance signal is injected into phases b and c of the main circuit through the fundamental frequency impedance circuit. The measurement circuit is used to acquire the current I in phase a of the three-phase motor circuit. a Current I in term b b ; and to collect the voltage Δu between phases ab in the three-phase motor circuit. ab The voltage Δu between phases b and c bc .

[0035] The sampling circuit 32 is used to collect the voltage and current between the generator equivalent circuit 21 and the harmonic injection circuit 31 within a predetermined time period after the voltage disturbance signal is injected, and to transmit the collected voltage and current to the host computer 1.

[0036] In this embodiment, the frequency range, step size, and harmonic amplitude of harmonic injection are set according to measurement requirements. These settings are configured in the frequency response analyzer via a host computer, based on the generator's power, rated frequency, and the desired accuracy of the generator impedance. After configuration, the generator is activated and put into test mode. Harmonic injection at the corresponding frequency is then performed via commands from the host computer. The voltage and current values ​​at the corresponding sampling port are collected for each set frequency harmonic injection. Figure 3 The voltage measured in the sampling is the voltage Δu between phases ab at the generator output terminals. ab The voltage Δu between phases b and c bc The sampled and measured current is the current I of term a in the three-phase motor circuit. a Current I in term b b The collected voltage and current values ​​are input into four channels (CH.1, CH.2, CH.3, and CH.4) of the frequency response analyzer. The generator output stops once the harmonic injection within the set frequency range is complete.

[0037] Finally, the sampled data was analyzed using a host computer. The sequence voltage and sequence current components were obtained through coordinate transformation, and the output impedance of the generator under test was calculated. The positive sequence impedance of the three-phase generator is expressed as Z. p The negative sequence impedance is expressed as Z. n The impedance is related to the measured value Δu. ab , Δu bc I a I b The relational expression is:

[0038] The ordinal components can be obtained:

[0039]

[0040] According to the impedance calculation formula:

[0041]

[0042] The generator sequence impedance expression is:

[0043]

[0044] Among them, Z p Z is the positive sequence impedance of the generator. n This is the negative sequence impedance of the generator.

[0045] This embodiment provides a motor output impedance measurement circuit, which includes a host computer, a main circuit, and a measurement circuit. The main circuit includes a generator equivalent circuit and a circuit load equivalent circuit. The measurement circuit includes a harmonic injection circuit and a sampling circuit. The harmonic injection circuit is located between and connected to the generator equivalent circuit and the circuit load equivalent circuit. The impedance of the generator equivalent circuit is lower than the impedance of the circuit load equivalent circuit. The host computer is connected to the harmonic injection circuit and the sampling circuit. The host computer is used to set harmonic injection parameters and inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit according to the harmonic injection parameters. The sampling circuit is used to collect the voltage and current between the generator equivalent circuit and the harmonic injection circuit within a predetermined time period after injecting the voltage disturbance signal, and transmit the collected voltage and current to the host computer. In this embodiment, the host computer controls and outputs harmonic injection parameters of different frequencies. Then, the disturbance signal corresponding to the harmonic injection parameter is injected into the main circuit. The injected disturbance signal will generate a disturbance response in the main circuit with the same frequency as the injected disturbance signal. The generator output impedance can be calculated by the voltage and circuit collected in the sampling circuit.

[0046] This utility model embodiment provides a method for measuring generator output impedance. The method is applied to the host computer 1 in the aforementioned generator output impedance measurement circuit. The method includes:

[0047] S101, in response to the operation of the generator output impedance measurement circuit, injects voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit according to the harmonic injection parameters.

[0048] The main circuit includes a generator equivalent circuit 21 and a circuit load equivalent circuit 22. In an optional embodiment, before injecting voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit according to the harmonic injection parameters, the method further includes: determining the harmonic injection parameters according to the rated operating state of the generator equivalent circuit 21, wherein the harmonic injection parameters include: the frequency range, step size and harmonic amplitude of the harmonic injection.

[0049] S102, within a predetermined time period for injecting the voltage disturbance signal, the voltage and current between the generator equivalent circuit 21 and the harmonic injection circuit are collected.

[0050] In an optional embodiment, the generator equivalent circuit 21 is a three-phase motor circuit, and the acquisition of voltage and current between the generator equivalent circuit 21 and the harmonic injection circuit includes:

[0051] Collect the current I of phase a in the three-phase motor circuit. a Current I in term b b ; and to collect the voltage Δu between phases ab in the three-phase motor circuit. ab The voltage Δu between phases b and c bc .

[0052] S103 calculates the generator output impedance based on the collected current and voltage.

[0053] In this embodiment, the frequency range, step size, and harmonic amplitude of harmonic injection are set according to measurement requirements. These settings are configured in the frequency response analyzer via a host computer, based on the generator's power, rated frequency, and the desired accuracy of the generator impedance. After configuration, the generator is activated and put into test mode. Harmonic injection at the corresponding frequency is then performed via commands from the host computer. The voltage and current values ​​at the corresponding sampling port are collected for each set frequency harmonic injection. Figure 3 The voltage measured in the sampling is the voltage Δu between phases ab at the generator output terminals. ab The voltage Δu between phases b and c bc The sampled and measured current is the current I of term a in the three-phase motor circuit. a Current I in term b b The collected voltage and current values ​​are input into four channels (CH.1, CH.2, CH.3, and CH.4) of the frequency response analyzer. The generator output stops once the harmonic injection within the set frequency range is complete.

[0054] Finally, the sampled data was analyzed using a host computer. The sequence voltage and sequence current components were obtained through coordinate transformation, and the output impedance of the generator under test was calculated. The positive sequence impedance of the three-phase generator is expressed as Z. p The negative sequence impedance is expressed as Z. n The impedance is related to the measured value Δu. ab , Δu bc I a I b The relational expression is:

[0055] The ordinal components can be obtained:

[0056]

[0057] According to the impedance calculation formula:

[0058]

[0059] The generator sequence impedance expression is:

[0060]

[0061] Among them, Z p Z is the positive sequence impedance of the generator. n This is the negative sequence impedance of the generator.

[0062] This embodiment provides a method for measuring motor output impedance. It utilizes a parallel injection method to direct most disturbance signals to the generator on the source side, where impedance is lower, thus avoiding the problem of insufficient disturbance response due to low impedance. By adding a blocking circuit to limit the current signal generated by the circuit's fundamental frequency voltage, it prevents excessive fundamental frequency current from being generated in the parallel branch when the impedance measurement module is connected in parallel, which could affect the normal operation of the circuit. This ensures that the main current in the parallel branch is generated by the small signal generator.

[0063] This embodiment takes a three-stage generator, a common type of aviation power supply, as an example. Figure 5 An implementation example of a parallel injection circuit for the output impedance of a three-stage generator is shown. For example... Figure 5 As shown, the parallel injection measurement circuit for the output impedance of the three-stage generator in this embodiment includes: a main circuit consisting of a three-stage generator and a load, and a parallel injection circuit consisting of a disturbance source and an LC module. During the small-signal parallel injection process, the disturbance signal is injected into two phases of the main circuit in parallel through the disturbance source. By measuring the port response voltage and current of the device under test, the impedance of the device under test is calculated. To avoid the connection of the parallel injection branch from affecting the normal operation of the original circuit, a series LC module is introduced to limit the fundamental current of the parallel branch, while not weakening the injected disturbance signals in other frequency bands.

[0064] Optionally, the three-stage generator employs proportional-integral closed-loop control, controlling the generator's output voltage to 230V / 400Hz. The load uses a purely resistive circuit; in Example 1, the output power is 100kW, and in Example 2, it is 50kW. The measurement circuit in this embodiment is based on a MATLAB simulation platform. It calculates the impedance by injecting a disturbance signal in parallel and sampling the response signal of the object under test. The sampling circuit is implemented by a voltage and current measurement module. FFT analysis is performed on the sampled data to obtain the impedance at various frequencies, thus obtaining the impedance model for the desired frequency band.

[0065] Figure 6This illustration shows an embodiment of an LC module circuit with fundamental frequency signal blocking function. For example... Figure 5 As shown, the LC parallel module consists of an inductor L and a capacitor C connected in parallel, and its impedance expression is: It can be seen that when the values ​​of L and C are appropriate, the impedance value can be made to have a maximum value only in a certain frequency range, while having a smaller value in other frequency ranges. The value is selected as the fundamental frequency of 400HZ, thereby blocking the fundamental frequency signal and making the signal flowing through the parallel path basically a harmonic injection signal.

[0066] Figure 7 The impedance amplitude-frequency characteristic curve of the LC module in the simulation model of this utility model is when a set of parameters is selected. Its impedance value only shows a large value near the fundamental frequency, which meets the expected requirements.

[0067] Figure 8 The waveform of the parallel injection branch is a specific example. It can be seen that the fundamental frequency current is very small, which can avoid affecting the normal operating mode of the circuit due to the introduction of the parallel branch. At the same time, it can be observed that it does not significantly limit the disturbance signals of other frequency bands emitted by the disturbance source, so that the disturbance signals can be injected into the circuit.

[0068] Figure 9 The results are impedance sweep frequency measurement results in the simulation model of this embodiment. The LC module selected different values ​​to conduct sweep frequency tests. It can be seen that the sweep frequency results are basically consistent with those when using an ideal current source in theory.

[0069] Depend on Figures 7 to 9 As can be seen, the parallel injection measurement circuit for the power supply side output impedance in this embodiment can effectively improve the measurement accuracy of the output impedance of the three-stage generator on the power supply side, and realize the measurement of the output impedance of the generator with low impedance on the source side.

[0070] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0071] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0072] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A generator output impedance measurement circuit, characterized in that, The circuit includes: a host computer, a main circuit, and a measurement circuit. The main circuit includes a generator equivalent circuit and a circuit load equivalent circuit. The measurement circuit includes a harmonic injection circuit and a sampling circuit. The harmonic injection circuit is disposed between the generator equivalent circuit and the circuit load equivalent circuit, and is connected to the generator equivalent circuit and the circuit load equivalent circuit; the impedance of the generator equivalent circuit is lower than the impedance of the circuit load equivalent circuit. The host computer is connected to the harmonic injection circuit and the sampling circuit. The host computer is used to set the harmonic injection parameters and inject voltage disturbance signals of different frequencies into the main circuit through the harmonic injection circuit according to the harmonic injection parameters. The sampling circuit is used to collect the voltage and current between the generator equivalent circuit and the harmonic injection circuit within a predetermined time period after the voltage disturbance signal is injected, and to transmit the collected voltage and current to the host computer.

2. The circuit according to claim 1, characterized in that, The harmonic injection circuit includes a fundamental frequency blocking circuit and a harmonic receiving source, the fundamental frequency blocking circuit and the harmonic receiving source being connected in series; the host computer includes a harmonic generating source, and the harmonic injection circuit is connected to the harmonic generating source of the host computer through the harmonic receiving source.

3. The circuit according to claim 2, characterized in that, The fundamental frequency blocking circuit consists of inductors and capacitors connected in parallel.

4. The circuit according to claim 1, characterized in that, The generator equivalent circuit is a three-phase motor circuit, and the circuit load equivalent circuit consists of three resistors connected in parallel.

5. The circuit according to claim 4, characterized in that, Each circuit in the three-phase motor circuit is connected in series with a resistor in the equivalent circuit of the circuit load.

6. The circuit according to claim 4, characterized in that, The measuring circuit is used to collect the current of phase a in the three-phase motor circuit. Current in item b ; and to collect the voltage between phases ab in the three-phase motor circuit. Voltage between phases b and c .

7. The circuit according to claim 6, characterized in that, The host computer includes: a frequency response analyzer, an excitation small signal generation module, and a linear amplification unit.

8. The circuit according to claim 7, characterized in that, The frequency response analyzer has four channels CH.1, CH.2, CH.3, and CH.4, which are used to receive the voltage between phases a and b, respectively. Voltage between phases b and c Item a: Current Current in item b .

9. The circuit according to claim 7, characterized in that, The host computer is connected to the harmonic injection circuit through the linear amplification unit.

10. The circuit according to any one of claims 1-9, characterized in that, The host computer is used to calculate the generator output impedance based on the collected voltage and current.

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