A bridge arm input voltage stabilizing method and device for an inverter

Abstract

The application discloses a bridge arm input voltage stabilizing method and device for an inverter, and relates to the field of power system stabilizing control. The d-axis of the voltage control loop of the inverter is provided with a voltage feedforward link, and the voltage feedforward link comprises a filter and a regulator. The voltage feedforward link takes the oscillation frequency component in the input voltage of the bridge arm of the inverter as an introduced signal, filters the input voltage of the bridge arm by using the filter to obtain a disturbance component, adjusts the disturbance component by using the regulator to obtain a corresponding voltage feedforward signal, and superimposes the voltage feedforward signal on the voltage reference value of the d-axis to reshape the input impedance of the inverter. The application introduces the voltage feedforward signal with the filter and the PI controller to the d-axis voltage reference value of the voltage control loop, and solves the oscillation of the input voltage of the bridge arm on the direct current side of the inverter which may exist in the high-power scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system stability control, in particular to a bridge arm input voltage stabilization method and device for an inverter. BACKGROUND

[0002] In recent years, with the increase of power demand, the types of loads are more and more, which makes the circuit of the power supply system appear oscillation phenomenon, and further affects the stable operation of the power supply system. At present, the solution to this problem is to improve the low-frequency positive damping characteristics of the whole system, which includes two parts. One is to use passive component devices, that is, to use passive resistance. The other is to use active devices or control algorithms. The former has large loss and is not conducive to economy, so it is rarely used in engineering. The latter is generally realized by using existing power electronic devices combined with related control algorithms, which is also the current mainstream form.

[0003] Patent CN107332259A discloses a DC sending-out power grid ultra-low frequency oscillation suppression method and system, which includes low-pass filtering of the collected frequency signal. After the oscillation of the power grid meets the preset ultra-low frequency oscillation criterion, a control signal is generated according to the frequency deviation signal. The DC valve control system adjusts the DC output power according to the signal to increase the positive damping of the system to achieve the purpose of suppressing ultra-low frequency oscillation.

[0004] Patent CN114389287A discloses a battery energy storage device control method for DC distribution network low-frequency oscillation suppression, which includes obtaining the DC voltage value at the access point of the battery energy storage device to the DC distribution network and the actual current value of the battery energy storage device. The duty cycle compensation signal temporary value for suppressing low-frequency oscillation is calculated and limited to obtain the final value of the duty cycle compensation control signal for suppressing low-frequency oscillation. The final value of the duty cycle control signal is calculated. The control driving signal is obtained. The battery energy storage device is controlled to complete the low-frequency oscillation suppression of the DC distribution network. This method realizes the low-frequency oscillation suppression of the DC distribution network without the need for a start signal and additional hardware circuit support, reduces the risk of oscillation instability of the DC distribution network, and can be applied to other DC distribution networks with self-opening and closing capability that provide low-frequency positive damping characteristics.

[0005] However, suppressing low-frequency oscillation only reduces the risk of oscillation instability of the DC distribution network, and cannot solve the problem of inverter DC side bridge arm input voltage oscillation that may exist in high-power scenarios. SUMMARY

[0006] The present application provides a bridge arm input voltage stabilization method for an inverter, which aims to solve the problem of inverter DC side input voltage oscillation in high-power scenarios in the prior art.

[0007] To achieve the above object, the application adopts the following technical scheme:

[0008] A bridge arm input voltage stabilizing method for an inverter, the inverter voltage control loop having a voltage feedforward link on a d-axis, the voltage feedforward link comprising a filter and a regulator; the voltage feedforward link taking an oscillation frequency component in the inverter bridge arm input voltage as an introduction signal, filtering the bridge arm input voltage by the filter to obtain a disturbance component, adjusting the disturbance component by the regulator to obtain a corresponding voltage feedforward signal, and superimposing the voltage feedforward signal to a voltage reference value at the d-axis to reshape the input impedance of the inverter.

[0009] Preferably, the filter is a high-pass filter, and the center frequency of the high-pass filter is 1 / 10-1 / 5 of the oscillation frequency component.

[0010] Preferably, the high-pass filter is a second-order filter, and the expression is as follows:

[0011]

[0012] wherein G f (s) represents the expression of the high-pass filter, ω n represents the center frequency of the high-pass filter, ζ represents the damping coefficient, and s represents the complex frequency.

[0013] Preferably, the regulator is a proportional-integral regulator, and the expression is as follows:

[0014]

[0015] wherein GPI(s) represents the expression of the proportional-integral regulator, K P represents the proportional coefficient, and K I represents the integral coefficient.

[0016] Preferably, the proportional-integral regulator expression coefficient is determined by impedance stability and feedforward control loop.

[0017] Preferably, the bridge arm input voltage stabilizing method comprises the following steps:

[0018] Collecting the bridge arm input voltage of the inverter, and analyzing the bridge arm input voltage by fast Fourier transform to determine whether the bridge arm input voltage has oscillation;

[0019] When the bridge arm input voltage has oscillation, extracting the oscillation frequency component in the bridge arm input voltage, and separating the bridge arm input voltage by the filter to obtain a disturbance component;

[0020] The disturbance component is adjusted by an adjuster to obtain a corresponding voltage feedforward signal;

[0021] The voltage feedforward signal is superimposed on the voltage reference value of the d-axis to reshape the input impedance of the inverter.

[0022] As preferred, the method further comprises: ending the process when the bridge arm input voltage has no oscillation.

[0023] A bridge arm input voltage stabilizing device, comprising a computer memory, a computer processor, and a computer program stored in the computer memory and executable on the computer processor, wherein the computer program enables the computer to implement the bridge arm input voltage stabilizing method for an inverter as described above.

[0024] The present application has the following beneficial effects:

[0025] (1) The voltage feedforward signal with a filter and a PI controller is introduced into the d-axis voltage reference value of the voltage control loop, solving the oscillation of the bridge arm input voltage of the DC side of the inverter in the high-power scenario.

[0026] (2) The impedance stability is increased by the adjustment of the PI controller, increasing the stability speed of the input voltage of the DC side of the inverter and the stability speed of the output voltage of the AC side of the inverter, solving the inverter reference voltage fluctuation that may exist in the early stage before the voltage feedforward signal is introduced. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 is a structural schematic diagram of a DC power supply system provided by the present application;

[0029] Figure 2 is a flowchart of a bridge arm input voltage stabilizing method for an inverter provided by the present application;

[0030] Figure 3 is a feedforward signal introduction schematic diagram of a bridge arm input voltage stabilizing device provided by the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The terms “first,” “second,” etc., used in the claims and description of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate. This is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The DC power supply system provided in this application is as follows: Figure 1 As shown, the system includes a DC bus for providing power supply voltage, with multiple inverters and converters with EMI filters connected in parallel on both sides of the bus, as well as a DC load at the terminal. The d-axis of the inverter voltage control loop has a voltage feedforward element, which includes a high-pass filter set in the voltage control loop and a proportional-integral controller (PI controller) for regulation control.

[0034] Furthermore, this voltage feedforward circuit uses the oscillation frequency component in the inverter bridge arm input voltage as the input signal, and uses a filter to filter the DC component in the bridge arm input voltage to obtain the disturbance component. Then, a PI regulator is used to control and adjust the disturbance component to obtain the corresponding voltage feedforward signal. Finally, the voltage feedforward signal is superimposed on the voltage reference value on the d-axis to reshape the input impedance of the inverter.

[0035] Furthermore, the filter set in the voltage feedforward stage is a high-pass filter, and its center frequency is 1 / 10 to 1 / 5 of the oscillation frequency component in the inverter bridge arm input voltage.

[0036] Furthermore, this high-pass filter is a second-order filter, expressed as follows:

[0037]

[0038] Among them, G f (s) represents the expression for the high-pass filter, ω n Let ζ represent the center frequency of the high-pass filter, ζ represent the damping coefficient, and s represent the complex frequency. In this embodiment, ζ is preferably 0.707.

[0039] Further, the regulator provided in the voltage feedforward link is a proportional-integral regulator, namely a PI regulator, and the expression is as follows:

[0040]

[0041] Wherein, GPI(s) represents the expression of the proportional-integral regulator, K P represents the proportional coefficient, K I represents the integral coefficient.

[0042] Further, the expression coefficient of the proportional-integral regulator is determined by the impedance stability and the feedforward control loop.

[0043] For the proportional coefficient K P , increasing the proportional coefficient is beneficial to improve the impedance stability, but after increasing to a certain extent, it will reduce the stability speed of the bridge arm input voltage, therefore, factors such as impedance stability and bridge arm input voltage stability speed need to be considered to make reasonable selection, so as to realize the stability of the bridge arm input voltage without affecting the impedance stability; for the integral coefficient K I , increasing the integral coefficient can improve the impedance stability and make the d-axis voltage reference value restore the initial value, but after increasing to a certain extent, it will exacerbate the oscillation and reduce the stability speed of the bridge arm input voltage, therefore, factors such as impedance stability and bridge arm input voltage stability speed need to be considered to make reasonable selection, so as to realize the stability of the bridge arm input voltage without affecting the impedance stability, in this embodiment, K P is selected as 1, and K I is selected as 30.

[0044] In this embodiment, the PI controller is used to adjust the disturbance component, which not only can increase the impedance stability, but also can increase the stability speed of the input voltage of the inverter DC side and the stability speed of the inverter AC output voltage, and then effectively cope with the inverter reference voltage fluctuation that may occur before the voltage feedforward signal is introduced.

[0045] Based on the above voltage feedforward link, the application further provides a bridge arm input voltage stabilization method for an inverter, as shown in Figure 2 , comprising the following steps:

[0046] S110, collecting the bridge arm input voltage of the inverter, and analyzing the bridge arm input voltage by using fast Fourier transform to determine whether the bridge arm input voltage exists oscillation;

[0047] S120, when the bridge arm input voltage exists oscillation, extracting the oscillation frequency component in the bridge arm input voltage, and separating the bridge arm input voltage by using a filter to obtain a disturbance component;

[0048] S130, adjusting the disturbance component through the regulator to obtain a corresponding voltage feedforward signal;

[0049] S140, superimposing the voltage feedforward signal on the voltage reference value of the d-axis to reshape the input impedance of the inverter.

[0050] Specifically, when the bridge arm input voltage does not oscillate, the process ends.

[0051] As Figure 3 shown, the introduction process of the feedforward signal in the bridge arm input voltage stabilizing device provided by the present application is specifically: on the d-axis, the bridge arm input voltage v in is first passed through a second-order high-pass filter to obtain a corresponding disturbance component, then a PI controller is used to control and adjust the disturbance component, and then the obtained voltage feedforward signal is superimposed on the d-axis voltage reference value u dref .

[0052] A bridge arm input voltage stabilizing device, comprising a computer memory, a computer processor, and a computer program stored in the computer memory and executable on the computer processor, characterized in that the computer program causes the computer to implement the bridge arm input voltage stabilizing method for the inverter as described above when executed.

[0053] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the device described above can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0054] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for bridge arm input voltage stabilization for an inverter, characterized in that, The d-axis of the inverter voltage control loop is provided with a voltage feedforward link, the voltage feedforward link comprising a filter and a regulator; the voltage feedforward link takes the oscillation frequency component in the inverter bridge arm input voltage as an introduced signal, filters the bridge arm input voltage to obtain a disturbance component by using the filter, adjusts the disturbance component by using the regulator to obtain a corresponding voltage feedforward signal, and superimposes the voltage feedforward signal on the voltage reference value of the d-axis to reshape the input impedance of the inverter. The regulator is a proportional integral regulator, and the expression is as follows: where G PI (s) represents a proportional-integral regulator expression, K P represents a proportional coefficient, K I represents an integral coefficient, the proportional-integral regulator expression coefficient being determined jointly by impedance stability and feedforward control loop.

2. The method for bridge arm input voltage stabilization for an inverter according to claim 1, characterized in that, The filter is a high-pass filter, and the center frequency of the high-pass filter is 1 / 10-1 / 5 of the oscillation frequency component.

3. The method for bridge arm input voltage stabilization for an inverter according to claim 2, characterized in that, The high-pass filter is a second-order filter, and the expression is as follows: where G f (s) represents a high-pass filter expression, ω n represents a center frequency of the high-pass filter, ζ represents a damping coefficient, and s represents a complex frequency.

4. The method for bridge arm input voltage stabilization for an inverter according to claim 1, characterized in that, The bridge arm input voltage stabilization method comprises the following steps: Collecting the bridge arm input voltage of the inverter and analyzing the bridge arm input voltage by using fast Fourier transform to determine whether the bridge arm input voltage has oscillation; When the bridge arm input voltage has oscillation, extracting the oscillation frequency component in the bridge arm input voltage and separating the bridge arm input voltage by using a filter to obtain a disturbance component; Adjusting the disturbance component by using a regulator to obtain a corresponding voltage feedforward signal; Superimposing the voltage feedforward signal on the voltage reference value of the d-axis to reshape the input impedance of the inverter.

5. The method for bridge arm input voltage stabilization for an inverter according to claim 1, wherein, The method further comprises: when the bridge arm input voltage does not have oscillation, ending the process.

6. A bridge arm input voltage stabilizing device comprising a computer memory, a computer processor, and a computer program stored in the computer memory and executable on the computer processor, characterized in that, The computer program enables the computer to implement the bridge arm input voltage stabilization method for the inverter according to any one of claims 1-5 when executed.

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