Alternating current power grid broadband oscillation simulation device control method based on element physical model

Abstract

The invention relates to the field of power grid simulation, and particularly discloses a control method of an alternating-current power grid broadband oscillation simulation device based on a component physical model, which realizes broadband domain oscillation simulation of an alternating-current power grid based on the component physical model and a notch filter. Specifically, according to the control method of the alternating-current power grid broadband oscillation simulation device based on the element physical model, an adjustable element physical model type and a corresponding impedance parameter serve as input conditions, and a dynamic voltage compensation component excited by power grid impedance is calculated in combination with an adjustable notch filter; and a power grid simulation reference signal is constructed in real time through superposition of an original input reference voltage value and a dynamic voltage compensation component excited by power grid impedance, so that oscillation simulation in a wide frequency domain of the alternating-current power grid is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power grid simulation, and more specifically, to an alternating current power grid wide frequency oscillation simulation device control method based on a physical model of an element. BACKGROUND

[0002] In recent years, with the increasing penetration of new energy, large-scale grid-connected wind power and photovoltaic power exhibit the characteristics of "double high", i.e., high proportion of power electronic devices and high proportion of new energy. The interaction between grid-connected devices and the power grid causes increasingly serious power system stability problems. Specifically, new energy power generation systems mainly based on photovoltaic and wind power are often distributed in remote places such as deserts and islands, and are usually connected to the grid through long-distance transmission and distribution lines. At this time, the system line impedance often changes the impedance characteristics of the power grid, making the power grid exhibit wide frequency domain weak grid characteristics, affecting the working performance of grid-connected devices, and further leading to frequent wide frequency oscillation (frequency range from several hertz to several thousand hertz) problems. Traditional power systems mainly focus on small disturbance stability analysis, mainly focusing on low frequency oscillation (0.1-2 Hz), while after the grid connection of new energy, subsynchronous oscillation (10-50 Hz), supersynchronous oscillation (50-100 Hz) and high frequency resonance (>100 Hz) problems are increasingly prominent. Therefore, the power grid adaptability test before the operation of new energy grid-connected devices urgently needs high-precision simulation devices.

[0003] Existing power grid simulation techniques often oversimplify the power grid, treating it as an infinitely strong grid, and ignoring the influence of the power grid impedance. Although some researchers have considered the power grid line impedance, they usually only model it as an inductance or a resistance-inductance. For example, Chinese patent CN116819210A describes a control method, a control device and a power grid simulator, which uses an improved double voltage-current closed-loop control strategy for the converter in the power grid simulator. The method aims to reduce the difference between the simulated power grid environment and the actual power grid by simulating the blocking inductive impedance equivalence and frequency fluctuation characteristics of the synchronous power source. However, this technology only considers the influence of the blocking inductive impedance at the fundamental frequency, ignoring the capacitive effect and high frequency characteristics. This creates a gap between the simulated power grid and the current actual power grid conditions, which cannot meet the testing needs of new power systems for grid-connected devices.

[0004] The limitations of existing power grid simulation methods also include: Incomplete transmission line modeling: In actual power systems, new energy power generation systems usually need long transmission lines for grid connection. Not only the inductive or resistive-inductive characteristics of the line need to be considered, but also the capacitive effects between the cable and the ground and between the cables themselves. Therefore, the transmission line is not only inductive or resistive-inductive. Current power grid simulators cannot consider different types of power grid lines, let alone study the impact of the equivalent circuit type of the power grid transmission line on the grid simulation control as an input condition. Long-distance lines need to consider resistive, inductive, and capacitive distributed parameters, but existing technologies cannot support dynamic configuration of such complex models.

[0005] Limited frequency range simulation: With the increasing penetration of new energy, a large number of power electronic converters are integrated into the grid. This introduces rich switching harmonics, leading to inaccurate interaction in the high-frequency band and the need to consider a wider frequency domain. Traditional methods only simulate the fundamental frequency impedance (50 / 60Hz), while the switching harmonics of new energy devices can reach kilohertz (e.g., 1kHz), so new energy grid-connected stability testing needs to cover the 10Hz ~ 5kHz frequency range, and only simulating the inductive or resistive-inductive low-frequency range of the transmission line cannot reflect the actual interaction between the grid and the grid-connected device.

[0006] Therefore, due to model simplification, narrow frequency domain, and rigid configuration, current power grid simulation technology cannot accurately reflect the wide frequency domain characteristics of weak power grids under high penetration of new energy, and there is an urgent need for a high-precision simulation scheme that supports dynamic configuration, covers a wide frequency domain, and integrates capacitive effects. SUMMARY

[0007] To solve the above technical problems, the present application is proposed. The present application provides an alternating current power grid wide frequency oscillation simulation device control method based on an element physical model. Through an adjustable element physical model and a notch filter cooperative mechanism, the alternating current power grid wide frequency oscillation simulation is realized. Specifically, the alternating current power grid wide frequency oscillation simulation device control method based on the element physical model takes the element physical model type and the corresponding impedance parameter as the input condition, calculates the dynamic voltage compensation component excited by the grid impedance based on the notch filter, and then constructs the grid simulation reference signal in real time through the superposition of the original input reference voltage value and the dynamic voltage compensation component excited by the grid impedance, thereby realizing high-precision simulation of alternating current power grid wide frequency oscillation.

[0008] The application provides an alternating current power grid wide frequency oscillation simulation device control method based on an element physical model. The alternating current power grid simulation device comprises: an alternating current power supply, an inverter circuit unit, an inverter control unit and a filter circuit unit. The alternating current power supply is connected with the input end of the inverter circuit unit, the output end of the inverter unit is connected with a grid-connected device to be measured, and the inverter control unit is connected with the inverter circuit unit. The inverter control unit is characterized in that the inverter control unit realizes wide frequency oscillation simulation based on an adjustable element physical model and a notch filter, and comprises the following steps: According to the power grid simulation requirement, the type of the element physical model and the corresponding impedance parameters and the parameters of the notch filter are set. The current value of the PCC point is collected I pcc ( s ); Based on the PCC point current value, the element physical model transfer function and the notch filter transfer function, the dynamic voltage compensation component is calculated ΔU pcc (s) ; Based on the original reference voltage value U s ( s ) and the dynamic voltage compensation component ΔU pcc (s) , the PCC point reference voltage is generated ; Based on the PCC point reference voltage , the PCC point measured voltage U pcc (s) and the capacitance current of the filter circuit unit I c , the final modulation signal of the inverter circuit unit is generated; Based on the comparison between the final modulation signal of the inverter circuit unit and the carrier signal, the PWM modulation signal is generated.

[0009] In the alternating current power grid wide frequency oscillation simulation device control method based on the element physical model according to the application, the type of the element physical model comprises type I and type II; the impedance parameters comprise equivalent inductance L , equivalent capacitance C and equivalent resistance R .

[0010] Further, when the type of the element physical model is type I, the element physical model transfer function is ; when the type of the element physical model is type II, the element physical model transfer function is .

[0011] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the dynamic voltage compensation component ΔU pcc (s) The calculation formula is as follows: in, s is the complex frequency variable in the Laplace transform, Z ( s ) is the transfer function of the component physical model, H ( s ) is the transfer function of the notch filter.

[0012] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the PCC point reference voltage calculation formula is as follows: in U s ( s ) is the original reference voltage.

[0013] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the parameters of the notch filter include the band-stop center angular frequency and the quality factor; the transfer function of the notch filter is: in ω r The center frequency of the band stop set by the user, Q Quality factor set by the user.

[0014] Furthermore, the transfer function of the notch filter can be set to: .

[0015] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the PCC point reference voltage , PCC point measured voltage U pcc (s)、 Capacitor current of filter circuit unit I c , generating the final modulation signal of the inverter unit includes: Calculate PCC point reference voltage and the measured voltage U pcc (s) The difference between The difference is input into a voltage controller to generate a preliminary modulation signal; Introduce capacitor current feedforward compensation in the filter circuit: the initial modulation signal is combined with the capacitor current I c After multiplying by the proportional coefficient and taking the difference, the final modulated signal is generated.

[0016] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the device further includes a host computer, which is communicatively connected to the inverter control unit; The host computer is configured as follows: Dynamically set the type and impedance parameter value of the component physical model; Real-time display of impedance simulation frequency domain response characteristics.

[0017] In the control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to the present application, the PCC point is located at any of the following positions: Between the AC power grid wide-frequency oscillation simulation device control method based on the component physical model and the grid-connected equipment under test; The control method of the AC power grid wide-frequency oscillation simulation device based on the component physical model is connected to the transformer, and the transformer is connected to the grid-connected equipment to be tested.

[0018] Compared with the prior art, the control method of the AC power grid wide-band oscillation simulation device proposed in the present invention has the following beneficial effects: 1. Wide-frequency domain dynamic simulation capability: By introducing component physical models (Type I and Type II) and collaborating with notch filters, it achieves AC grid oscillation simulation from fundamental frequency to high frequency bands (kHz level), effectively covering the frequency domain requirements for grid-connected stability analysis of new energy equipment.

[0019] 2. Dynamically configurable parameters: The type of component physical model, impedance parameters, etc. are dynamically set by the host computer, which greatly improves the flexibility and adaptability of the device and can meet the simulation of different power grid environments and test requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other purposes, features, and advantages of the present application will become more apparent through a more detailed description of the embodiments of the present application in conjunction with the accompanying drawings. The accompanying drawings are intended to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the drawings, the same reference numerals generally represent the same components or steps.

[0021] Figure 1 The figure shows a circuit diagram of an AC power grid wide-band oscillation simulation device based on a component physical model according to an embodiment of the present application.

[0022] Figure 2Fig. 3 shows a control block diagram of the inverter control unit of the AC power grid broadband oscillation simulation device according to an embodiment of the present application.

[0023] Figure 3 Fig. 4 shows a workflow diagram of the inverter control unit of the AC power grid broadband oscillation simulation device according to an embodiment of the present application.

[0024] Figure 4 Fig. 5 shows a schematic diagram of the Type I and Type II physical models of the elements according to an embodiment of the present application.

[0025] Figure 5 Fig. 6 shows the PCC point voltage waveform in an ideal state and its FFT analysis result according to an embodiment of the present application.

[0026] Figure 6 Fig. 7 shows the PCC point voltage waveform in a simulation implementation and its FFT analysis result according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] Hereinafter, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part but not all of the embodiments of the present application. It should be understood that the present application is not limited to the described example embodiments.

[0028] Embodiment 1 Figure 1 Fig. 1 shows a circuit diagram of the AC power grid broadband oscillation simulation device based on the physical model of the elements according to an embodiment of the present application. Figure 2 Fig. 3 shows a control block diagram of the inverter control unit of the AC power grid broadband oscillation simulation device according to an embodiment of the present application. The present embodiment provides an AC power grid broadband oscillation simulation device (hereinafter referred to as “simulation device”) based on the physical model of the elements, which is mainly used for grid adaptability test of the measured grid-connected equipment, especially simulating different strength and weakness of the AC power grid and its broadband oscillation characteristics.

[0029] As Figure 1As shown, the simulation device according to the embodiments of the present application comprises a converter module and a master control module for controlling the converter module. Specifically, the converter module comprises a rectifier circuit unit, an inverter circuit unit and a filter circuit unit. The master control module comprises a rectifier control unit and an inverter control unit, wherein the inverter control unit is electrically connected to the inverter circuit unit and is used to control the working state of the inverter circuit unit; the rectifier control unit is electrically connected to the rectifier circuit unit and is used to control the working state of the rectifier circuit unit. In some embodiments of the present application, the wideband oscillation simulation device of the alternating current power grid based on the physical model of the element further comprises a host computer, which is communicatively connected to the inverter control unit.

[0030] More specifically, as shown in Figure 1 In some embodiments of the present application, the input end of the rectifier circuit unit is connected to the alternating current power grid, for converting the input alternating current into direct current. In some specific embodiments, the rectifier circuit unit can be of different types, such as a two-level PWM rectifier, a three-level or multi-level PWM rectifier, etc., and supports bidirectional energy flow. Accordingly, the rectifier control unit is connected to the rectifier circuit unit for controlling the rectification process. Its main function is to control the conduction and turn-off of power devices through PWM pulse width modulation and the like, to adjust and maintain the stability and set value of the output direct current voltage of the rectifier circuit unit, and to provide a constant direct current input power source for the inverter circuit unit. The output voltage is adjusted according to the test requirements to simulate different power grid conditions.

[0031] More specifically, as shown in Figure 1 and Figure 2 In some embodiments of the present application, the inverter circuit unit is connected to the output end of the rectifier circuit unit and can generate an alternating current voltage waveform with a specific frequency and amplitude, for converting direct current into adjustable alternating current output, simulating various characteristics of the target power grid, including the steady-state and transient response of the voltage, the frequency change of the power grid, etc. Accordingly, the inverter control unit is connected to the inverter circuit unit and is the core control unit. It receives the PWM modulation signal sent by the inverter control unit, adjusts its output according to the signal, and realizes accurate control of the simulated power grid voltage. The core function of this unit is to realize dynamic simulation of different degrees of alternating current weak power grid and its wideband oscillation based on the physical model of the element. In the embodiments of the present application, the physical model of the element is modeled by defining the type and impedance parameters, calculating the transfer function of the physical model of the element according to the type and impedance parameter values set by the user, and then further used to calculate the reference voltage of the PCC point.

[0032] More specifically, as shown in Figure 1As shown in some embodiments of the present application, the input end of the filter circuit unit is connected to the output end of the inverter circuit unit, for filtering out high-frequency harmonic components in the inverter output waveform, reducing voltage fluctuation and electromagnetic interference (EMI), and providing a smooth and stable voltage waveform close to the actual power grid. The output end forms the AC output end of the device.

[0033] It is worth mentioning that in some embodiments of the present application, the rectifier control unit and the inverter control unit can work together as needed: the rectifier control unit ensures that the rectifier circuit unit outputs stable DC voltage, providing reliable DC power for the inverter circuit unit. The inverter control unit controls the inverter circuit unit to output a specific AC waveform according to the simulation requirements. Both of them ensure that the entire simulation device is coordinated and stable in energy flow when simulating different grid conditions.

[0034] More specifically, as Figure 1 shown in some embodiments of the present application, the host computer is used to set, modify or burn the related parameters of the element physical model, and to display the impedance simulation frequency domain response characteristics in real time; the parameters include but are not limited to the type of the element physical model and the corresponding impedance parameter values.

[0035] As Figure 1 and Figure 2 shown, in the simulation device according to embodiments of the present application, the PCC point is the connection point between the AC output end of the simulation device (i.e. the output end of the filter circuit unit) and the measured grid-connected device or intermediate device, also known as the public coupling point, and the PCC point is located at any of the following positions: between the AC grid wideband oscillation simulation device based on the element physical model and the measured grid-connected device; between the AC grid wideband oscillation simulation device based on the element physical model and the transformer, and the transformer is connected to the measured grid-connected device.

[0036] Figure 3 Fig. 1 shows the working flowchart of the inverter control unit of the simulation device according to embodiments of the present application, which uses the element physical model to realize the wideband oscillation simulation of the power grid, and the realized functions include: Calculation of dynamic voltage compensation component: The inverter control unit calculates the dynamic voltage compensation component excited by the grid impedance based on the input component physical model type and impedance value. The calculation of this component takes into account the influence of the model type and the notch filter. The notch filter is a special filter that produces deep attenuation at a specific frequency point (or narrow band), while other frequency signals are basically unaffected. Its frequency response resembles a "V" depression, hence the name "notch". In the power system, notch filters are mainly used to eliminate interference or resonance at a specific frequency. In particular, when the notch filter transfer function value is 1, it means that the filter does not attenuate or change the phase of the signal at the current frequency point or frequency range. Users can set it according to the grid simulation requirements.

[0037] Real-time construction of grid reference signal: The inverter control unit superimposes the calculated dynamic voltage compensation component with the original input reference voltage value to generate the final grid simulation reference signal in real time.

[0038] PWM modulation signal generation and output: Based on the above-mentioned real-time constructed grid simulation reference signal, the inverter control unit generates a corresponding PWM modulation signal and outputs it to the inverter circuit unit, driving it to generate an AC voltage waveform that meets the target grid impedance characteristics.

[0039] like Figure 3 As shown, the working process of the inverter control unit mainly includes: According to the power grid simulation requirements, set the type of component physical model and the corresponding impedance parameters and notch filter parameters; The current value of the PCC point collected I pcc ( s ); Calculate the dynamic voltage compensation component based on the PCC point current value, component physical model transfer function, and notch filter transfer function ΔU pcc (s) ; Based on the original reference voltage value U s ( s ) and dynamic voltage compensation components ΔU pcc (s) , generate PCC point reference voltage ; Based on PCC point reference voltage , PCC point measured voltage U pcc (s) and the capacitor current of the filter circuit unit I cgenerating the inverter circuit unit final modulation signal; generating the PWM modulation signal based on comparison between the inverter circuit unit final modulation signal and the carrier signal.

[0040] More specifically, as shown in Figure 4 , the element physical model contains two key parameters: Element physical model type: defines the basic structure of the grid impedance; in some embodiments of the present application, the element physical model type contains Type I and Type II.

[0041] Impedance parameters of the element physical model: define the specific parameter values of each element in the model; in some embodiments of the present application, the impedance parameters of the element physical model include equivalent inductance value L , equivalent capacitance value C , and equivalent resistance value R .

[0042] The above parameters can be directly burned or stored in the inverter control unit, or set by the upper computer and transmitted to the inverter control unit.

[0043] The element physical model transfer function is calculated according to the type and impedance value set by the user, and the formula is as follows: Type I: ; Type II: ; Where L , C, R are the equivalent inductance value, equivalent capacitance value, and equivalent resistance value set by the user, respectively.

[0044] The notch filter transfer function is calculated according to the parameters set by the user, and the formula is as follows: Where ω r is the center angular frequency of the band-stop set by the user, Q is the quality factor set by the user.

[0045] More specifically, based on the PCC point reference voltage , the PCC point measured voltage U pcc (s) , and the capacitance current of the filter circuit unit I c , the inverter unit final modulation signal includes: calculating the difference between the PCC point reference voltage and the measured voltage U pcc (s) ; The difference value is input into the voltage controller to generate a preliminary modulation signal; Capacitance current feedforward compensation is introduced to the filter circuit: the preliminary modulation signal is subtracted from the capacitance current I c After being multiplied by a proportional coefficient, a final modulation signal is generated.

[0046] To verify the technical solutions of the present application, the equivalent parameters of a 30km power transmission line in a certain regional power grid are taken as an example for simulation. By comparing the PCC point voltage waveform achieved by simulation with the actual situation, the effectiveness of the proposed strategy is verified. Figure 5 and Figure 6 The PCC point voltage waveform in the ideal state and the FFT analysis result thereof achieved by simulation according to an embodiment of the present application are shown respectively. It can be seen that, compared with the ideal state, after considering the influence of the physical model parameters of the elements and the notch filter, harmonics appear in the grid voltage, and the frequency range is expanded to 10Hz~3000Hz, among which the amplitude in the 1200Hz~1800Hz frequency band is relatively high, indicating that the AC power grid wide-frequency oscillation simulation device based on the physical model of elements can simulate the high-frequency harmonics induced by the grid impedance, that is, it can simulate the wide-frequency domain oscillation characteristics (f>1kHz).

[0047] The simulation device provided in the present embodiment accurately simulates the voltage characteristics and wide-frequency domain impedance characteristics of the target power grid by using the inverter control unit based on the physical model of elements. The upper computer provides a convenient parameter setting interface. The flexible configuration of the PCC point adapts to different test scenarios. The device is particularly suitable for high-precision and high-dynamic testing and verification of the performance of grid-connected equipment in complex power grid environments (especially containing high-frequency impedance characteristics).

[0048] The above embodiments have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, supplement and equivalent replacement made within the principle range of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for an AC power grid wide-band oscillation simulation device based on a component physical model, the AC power grid simulation device comprising: An AC power supply, an inverter circuit unit, an inverter control unit, and a filter circuit unit; the AC power supply is connected to an input end of the inverter circuit unit, an output end of the inverter unit is connected to a grid-connected device under test, and the inverter control unit is connected to the inverter circuit unit; the inverter control unit is characterized in that it realizes broadband oscillation simulation based on an adjustable component physical model and a notch filter, specifically comprising the following steps: According to the power grid simulation requirements, set the type of component physical model and the corresponding impedance parameters and notch filter parameters; The current value of the PCC point collected I pcc ( s ); Calculate the dynamic voltage compensation component based on the PCC point current value, component physical model transfer function, and notch filter transfer function ΔU pcc (s) ; Based on the original reference voltage value U s ( s ) and dynamic voltage compensation components ΔU pcc (s) , generate PCC point reference voltage ; Based on PCC point reference voltage , PCC point measured voltage U pcc (s) and the capacitor current of the filter circuit unit I c , generating the final modulation signal of the inverter circuit unit; Based on the comparison between the final modulation signal of the inverter circuit unit and the carrier signal, a PWM modulation signal is generated.

2. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1 is characterized in that: The types of the component physical model include type I and type II; the impedance parameters include equivalent inductance L , equivalent capacitance C , equivalent resistance R .

3. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: When the type of the element physical model is type I, the element physical model transfer function is ; When the type of the element physical model is type II, the element physical model transfer function is .

4. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The dynamic voltage compensation component ΔU pcc (s) The calculation formula is as follows: in, s is the complex frequency variable in the Laplace transform, Z ( s ) is the transfer function of the component physical model, H ( s ) is the transfer function of the notch filter.

5. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The PCC point reference voltage calculation formula is as follows: in U s ( s ) is the original reference voltage.

6. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The parameters of the notch filter include the band-stop center angular frequency and the quality factor; the transfer function of the notch filter is: in ω r The center frequency of the band stop set by the user, Q Quality factor set by the user.

7. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The PCC point reference voltage , PCC point measured voltage U pcc (s) and the capacitor current of the filter circuit unit I c , generating the final modulation signal of the inverter circuit unit includes: Calculate PCC point reference voltage and the measured voltage U pcc (s) The difference between The difference is input into a voltage controller to generate a preliminary modulation signal; Introduce capacitor current feedforward compensation in the filter circuit: the initial modulation signal is combined with the capacitor current I c After multiplying by the proportional coefficient and taking the difference, the final modulated signal is generated.

8. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The device further includes a host computer, which is communicatively connected to the inverter control unit; The host computer is configured as follows: Dynamically set the type and impedance parameter value of the component physical model; Real-time display of impedance simulation frequency domain response characteristics.

9. The control method of the AC power grid wide-band oscillation simulation device based on the component physical model according to claim 1, characterized in that: The PCC point is located at any of the following locations: Between the AC grid wide-frequency oscillation simulation device based on the component physical model and the grid-connected device under test; Between the AC power grid wide-frequency oscillation simulation device based on the component physical model and the transformer, the transformer is connected to the grid-connected equipment to be tested.

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