Method for suppressing low-frequency oscillation of VSG-type energy storage inverter based on phase compensator

Abstract

This application proposes a method for suppressing low-frequency oscillations of a VSG-type energy storage inverter based on a phase compensator. The method includes: constructing a phase compensator and designing the transfer function of the phase compensator, where the transfer function includes a gain to be determined and multiple time constants; selecting a compensation phase angle, aiming to balance the steady-state accuracy, phase margin, and response speed of the power system, and using the compensation phase angle to determine multiple time constants that meet the objective; using the multiple time constants to determine the gain; integrating the phase compensator with determined parameters into the reactive power loop of the VSG-type energy storage inverter to compensate for the phase lag of the pure integral link in the reactive power loop, where the phase angles provided by the phase compensator with determined parameters are all positive values. This method suppresses low-frequency oscillations in the VSG-type energy storage inverter by adding a phase compensator to the reactive power loop, enhancing the low-frequency oscillation suppression effect and avoiding negative impacts on the performance of other frequency ranges of the system.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic equipment control, and particularly to a method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator. Background Art

[0002] With the transformation of the energy structure and the increasing demand for clean energy, energy storage inverters have received increasing attention due to their key role in the power system. As an important part of the power system, the stability and reliability of energy storage inverters are crucial for the safe operation of the power grid. Among them, the virtual synchronous generator (VSG)-type energy storage inverter, as a new type of power electronic equipment, has received extensive attention because it can simulate the dynamic characteristics of traditional synchronous generators. The VSG-type energy storage inverter enhances the stability of the system by providing virtual inertia and damping.

[0003] In practical applications, the VSG-type energy storage inverter may generate low-frequency oscillation phenomena when connected to the power grid, which is mainly caused by improper system parameter settings or changes in power grid operating conditions. Low-frequency oscillation will reduce the dynamic performance of the system, affect the power quality, and may even lead to system instability. Therefore, it is necessary to suppress the generated low-frequency oscillation.

[0004] However, the low-frequency oscillation suppression methods in related technologies have poor oscillation suppression effects when the power grid parameters change greatly, and may introduce new unstable factors, reducing the performance of the system in other frequency ranges. Summary of the Invention

[0005] The present application aims to solve at least one of the technical problems in related technologies to some extent.

[0006] To this end, the first object of the present application is to propose a method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator. This method suppresses the low-frequency oscillation in the VSG-type energy storage inverter by adding a phase compensator in the reactive power loop, enhances the low-frequency oscillation suppression effect, avoids negative impacts on the performance of the system in other frequency ranges, and solves the low-frequency oscillation problem that occurs when the VSG-type energy storage inverter is connected to the power grid.

[0007] The second object of the present application is to propose a system for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator.

[0008] The third object of the present application is to propose a non-transitory computer-readable storage medium.

[0009] To achieve the above object, a first aspect of the present application is to propose a method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator, the method comprising the following steps:

[0010] Construct a phase compensator and design the transfer function of the phase compensator, wherein the transfer function includes the gain of the phase compensator to be determined and a plurality of time constants;

[0011] Select a compensation phase angle within the angle range corresponding to the phase compensator, and with the goal of balancing the steady-state accuracy, phase margin, and response speed of the power system, use the compensation phase angle to determine the plurality of time constants that meet the goal;

[0012] Use the plurality of time constants to determine the gain of the phase compensator;

[0013] Integrate the phase compensator with determined parameters into the reactive power loop of the virtual synchronous generator (VSG)-type energy storage inverter, and compensate for the phase lag of the pure integration link in the reactive power loop through the phase compensator with determined parameters to suppress low-frequency oscillation, wherein the phase angles provided by the phase compensator with determined parameters are all positive values.

[0014] Optionally, in an embodiment of the present application, the determining the plurality of time constants that meet the goal includes: setting the maximum phase compensation point of the phase compensator at the oscillation frequency of the VSG-type energy storage inverter to construct a phase compensation equation; combining the phase compensation equation, the compensation phase angle equation, and the selected compensation phase angle to determine the plurality of time constants.

[0015] Optionally, in an embodiment of the present application, the using the plurality of time constants to determine the gain of the phase compensator includes: based on the magnitude of the phase compensator at the maximum phase compensation point being 1, construct a magnitude equation, wherein the magnitude equation includes the gain to be solved; substitute the plurality of determined time constants into the magnitude equation to determine the gain of the phase compensator.

[0016] Optionally, in an embodiment of the present application, the compensating for the phase lag of the pure integration link in the reactive power loop through the phase compensator with determined parameters includes: providing a leading phase at the oscillation frequency through the phase compensator with determined parameters to cancel the phase lag of the pure integration link.

[0017] Optionally, in an embodiment of the present application, when the phase compensator is a first-order phase compensator, the transfer function is represented by the following formula:

[0018]

[0019] Wherein,G ( s ) represents the transfer function, A represents the gain of the phase compensator, T 1 represents the zero time constant of the phase compensator, T 2 represents the pole time constant of the phase compensator, s represents a complex variable.

[0020] Optionally, in an embodiment of the present application, the control equation of the reactive power loop after integrating the phase compensator is represented by the following formula:

[0021]

[0022] Wherein, E represents the voltage amplitude output by the reactive power loop, E ref represents the voltage reference value, K represents the voltage regulation coefficient, Q ref represents the reference value of reactive power, D q represents the reactive power damping coefficient, v pd represents the d-axis component of the voltage at the point of common coupling, q f represents the reactive power output by the virtual synchronous generator VSG on average.

[0023] To achieve the above object, the second aspect of the present application also proposes a suppression system for low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator, including the following modules:

[0024] A design module, configured to construct a phase compensator and design the transfer function of the phase compensator, wherein the transfer function includes the gain of the phase compensator to be determined and multiple time constants;

[0025] A first determination module, configured to select a compensation phase angle within the angle range corresponding to the phase compensator, and use the compensation phase angle to determine the multiple time constants that meet the target with the goal of balancing the steady-state accuracy, phase margin, and response speed of the power system;

[0026] A second determination module, configured to determine the gain of the phase compensator by using the multiple time constants;

[0027] A compensation module is used to integrate the phase compensator after parameter determination into the reactive power loop of a virtual synchronous generator (VSG) type energy storage inverter, and compensate for the phase lag of the pure integral link in the reactive power loop through the phase compensator after parameter determination to suppress low-frequency oscillation. Among them, the phase angles provided by the phase compensator after parameter determination are all positive values.

[0028] To implement the above embodiments, a third aspect embodiment of the present application also proposes a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator in the first aspect above.

[0029] The technical solutions provided by the embodiments of the present application at least bring the following beneficial effects: The present application suppresses low-frequency oscillation in a VSG type energy storage inverter by adding a phase compensator to the reactive power loop. Among them, the phase compensator can provide a leading phase at the oscillation frequency to offset the phase lag brought by the pure integral link in the reactive power loop, and then effectively suppress low-frequency oscillation by accurately compensating for this phase lag. The phase compensator designed in the present application can provide sufficient phase compensation within a wide frequency band, thereby ensuring the oscillation suppression effect, and the phase angles provided by this phase compensator are all positive values, ensuring that while compensating for the phase lag, it will not have a negative impact on the phase margin and the like of the system in other frequency ranges. And the phase compensator provided in the present application sets the maximum phase compensation point at the oscillation frequency. At the same time, the design of the compensation phase angle and each parameter in the transfer function comprehensively considers the steady-state accuracy, stability, phase margin, and response speed of the system. The present application can achieve the suppression of low-frequency oscillation by designing a phase compensator and optimizing the control strategy, reducing the complexity of realizing oscillation suppression and improving the practicability of the oscillation suppression strategy. Thus, the present application enhances the low-frequency oscillation suppression effect, improves the stability margin of the VSG type inverter under a strong power grid, reduces the system oscillation risk, ensures the stable operation of the VSG type energy storage inverter in the power system, and is beneficial to improving the dynamic stability and operation reliability of the power system.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0032] Figure 1 is a flowchart of a method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator proposed by an embodiment of the present application;

[0033] Figure 2 Schematic diagram of the main circuit of a VSG-type energy storage inverter proposed in an embodiment of this application;

[0034] Figure 3 Schematic diagram of the control principle of the active loop and the reactive loop of a VSG-type energy storage inverter proposed in an embodiment of this application;

[0035] Figure 4 Schematic diagram of the control principle of a virtual impedance and a vector double closed-loop proposed in an embodiment of this application;

[0036] Figure 5 Schematic diagram of the control principle of the reactive loop after integrating a phase compensator proposed in an embodiment of this application;

[0037] Figure 6 Schematic diagram of the time-domain simulation of low-frequency oscillation of active power and reactive power proposed in an embodiment of this application;

[0038] Figure 7 Bode plot of a phase compensator proposed in an embodiment of this application;

[0039] Figure 8 Schematic diagram of the time-domain simulation of active power and reactive power under stable operating conditions proposed in an embodiment of this application;

[0040] Figure 9 Schematic diagram of the structure of a system for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator proposed in an embodiment of this application. Detailed implementation manners

[0041] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as a limitation to the present invention.

[0042] It should be noted that there may be stability problems when a grid-forming inverter operates in a high-strength power grid. When a grid-forming inverter is connected to a strong AC power grid with low impedance, the low impedance may cause the inverter to become unstable and pose a risk of low-frequency oscillation. Low-frequency oscillation will reduce the dynamic performance of the system, affect the power quality, and may even cause the system to become unstable. At present, in the related art regarding the low-frequency oscillation problem of VSG-type energy storage inverters, existing research mainly focuses on the analysis of oscillation mechanisms and the discussion of influencing factors, but effective suppression strategies are still relatively lacking.

[0043] For example, in the first related embodiment, oscillations are suppressed by detecting the output electrical angular velocity of the virtual synchronous generator. However, when the grid parameters fluctuate significantly, the effect of this solution is still not ideal. In the second related embodiment, an energy storage VSG control method considering frequency stability and low-frequency oscillation suppression is adopted. Although this solution improves the stability of the system to a certain extent, it may cause the performance of the system to deteriorate in other frequency ranges. In the third related embodiment, a primary frequency modulation control method for suppressing low-frequency oscillations is adopted. Although this solution is effective under specific conditions, its adaptability still needs to be further improved in a changing grid environment.

[0044] In summary, for the problem of low-frequency oscillations in VSG-type inverters, the methods in the related embodiments can suppress low-frequency oscillations to a certain extent. However, when the grid parameters change greatly, the oscillation suppression effect is limited, and new unstable factors may be introduced, resulting in the deterioration of the system performance in other frequency ranges, and the applicability is poor.

[0045] Therefore, this application proposes a method for suppressing low-frequency oscillations of a VSG-type energy storage inverter based on a phase compensator to solve the problem of low-frequency oscillations that occur when the VSG-type energy storage inverter is connected to the grid, thereby improving the dynamic stability and operation reliability of the system, which has important practical significance for the grid connection of a high proportion of renewable energy. This application can be achieved through the optimization of the control strategy, which not only simplifies the complexity of system implementation but also improves the reliability and practicability of the system.

[0046] Next, a method and system for suppressing low-frequency oscillations of a VSG-type energy storage inverter based on a phase compensator proposed in the embodiments of this application will be described with reference to the accompanying drawings.

[0047] Figure 1 FIG. is a flowchart of a method for suppressing low-frequency oscillations of a VSG-type energy storage inverter based on a phase compensator proposed in the embodiments of this application. As Figure 1 shown, the method includes the following steps:

[0048] Step S101, construct a phase compensator and design the transfer function of the phase compensator, where the transfer function includes the gain of the phase compensator to be determined and multiple time constants.

[0049] It should be noted that in this application, a phase compensator is additionally added to the reactive power loop of the VSG-type energy storage inverter to address the phase lag problem caused by the pure integral link in the reactive power loop. By accurately compensating this phase lag, low-frequency oscillations with a frequency less than 50 Hz can be effectively suppressed.

[0050] In specific implementation, a phase compensator and its transfer function are designed first. Among them, the transfer function includes parameters such as the gain and time constant of the phase compensator that can affect the phase lag compensation effect of the phase compensator and will have an impact on the power system in which the VSG-type energy storage inverter is located.

[0051] To more clearly illustrate the implementation principle of suppressing the low-frequency oscillation of the VSG-type energy storage inverter by the phase compensator constructed in this application, the VSG-type energy storage inverter involved in this application will be described in detail below.

[0052] In the embodiment of this application, the main circuit structure of the VSG-type energy storage inverter is as Figure 2 shown. The inverter is connected to the power grid after passing through an LC filter. The DC side of the inverter is provided with a stable DC voltage by a battery pack U dc , e o is the output voltage of the inverter, L f and C f are the filter inductor and capacitor of the LC filter respectively. i o is the output current of the inverter, v p is the voltage at the Point of Common Coupling (PCC for short), i g is the current flowing into the power grid. In this embodiment, the resistance of the power grid impedance is ignored, and only the power grid inductor L g is considered, e g is the power grid voltage.

[0053] Continue to refer to Figure 2 shown, the modulation wave S abc is generated by the d-axis reference voltage E dref and the q-axis reference voltage E qref output by the controller. The generated modulation wave S abc is then generated into a drive signal through Sinusoidal Pulse Width Modulation (SPWM for short). This drive signal is used to control the on and off of the switching devices in the inverter. In this embodiment, v p is used as the output voltage of the inverter and the LC filter as a whole. After converting between the three-phase coordinate system (abc) and the dq coordinate system through the rotation angle θ ,v p Convert to the d-axis component of the output voltage v pd and the q-axis component of the output voltage v pq , and i o Convert to the d-axis component of the output current i od and the q-axis component of the output current i oq .

[0054] Furthermore, through v pd , v pq and i od , i oq the instantaneous output active power of the VSG-type inverter can be calculated p e and the instantaneous output reactive power q e . Subsequently, after passing through a low-pass filter, the two instantaneous output powers obtain the average output active power p f and the average output reactive power q f . Among them, Figure 2 in ω c is the cut-off frequency of the low-pass filter. The calculation formulas for these two average output powers are as follows:

[0055]

[0056] In the control loop of the VSG-type energy storage inverter, the VSG algorithm realizes power supply to the load and the power grid by simulating the operating characteristics of a synchronous generator. The specific control process is as Figure 3 shown. Figure 3 In the upper part of the figure above, the active power-frequency control part (i.e., the active loop) outputs the frequency through the rotor equation, simulating the inertia and primary frequency regulation characteristics of a synchronous generator; the lower part of the reactive power-voltage control part (i.e., the reactive loop) simulates the primary voltage regulation characteristics of a synchronous generator. Based on Figure 3 the control equations of the active loop and the reactive loop are as follows:

[0057]

[0058] Among them, J is the moment of inertia, ω o and ωn respectively represent the output angular frequency of the VSG and the grid angular frequency, P ref is the reference value of the active power, D p represents the active damping coefficient, E is the voltage amplitude output by the reactive power loop, E ref is the voltage reference value, K is the voltage regulation coefficient, Q ref is the reference value of the reactive power, D q represents the reactive damping coefficient.

[0059] It should be noted that for the parameters with defined meanings in this application, they will not be repeatedly explained in the subsequent embodiments. Their meanings are the same, and this application will not elaborate further.

[0060] Furthermore, through the power loop control, the system can obtain the voltage amplitude set by the VSG algorithm, and then through the virtual impedance control and the vector double closed-loop control, finally obtain the d-axis voltage reference value output by the controller E dref and the q-axis voltage reference value output by the controller E qref , and this control process is as Figure 4 shown. The virtual impedance link subtracts the product of the output current and the virtual impedance from the reference voltage to simulate the series impedance of the actual line, thereby adjusting the equivalent impedance between the inverter output terminal and the PCC point. In Figure 4 , R v and L v are the virtual resistance and the virtual inductor respectively. In the vector double closed-loop, E vdref and E vqref are the d-axis voltage reference value and the q-axis voltage reference value of the voltage loop respectively, I dref and I qref are the d-axis current reference value and the q-axis current reference value of the current loop respectively. Both the voltage loop and the current loop are composed of typical PI controllers, and the specific expressions are respectively k vp + k vi / s and k ip + k ii / s . Among them,k vp and k vi are k ip and k ii the different PI control parameters of the voltage loop and the current loop respectively.

[0061] Based on the above content, analyzing the participation factors of the eigenvalues of the small-signal model, it can be known that the voltage amplitude output by the reactive power loop E plays a leading role in low-frequency oscillations. At the same time, from Figure 3 in the reactive power loop control process, it can be observed that there is a pure integral link in this part, and this integral link will bring a phase lag of -90°, resulting in an increase in the risk of low-frequency oscillations of the system. Therefore, this application uses a phase compensator to compensate for the extreme phase lag of the pure integral link. After adding the phase compensator, the control principle of the improved reactive power loop is as Figure 5 shown.

[0062] In an embodiment of this application, when the phase compensator used is a first-order phase compensator, the transfer function of the designed phase compensator is represented by the following formula:

[0063]

[0064] Among them, G ( s ) represents the transfer function, A represents the gain of the phase compensator, T 1 represents the zero time constant of the phase compensator, T 2 represents the pole time constant of the phase compensator, s represents the complex variable.

[0065] Among them, T 1 and T 2 respectively determine the zero frequency and pole frequency of the compensator. This compensator is a first-order phase compensator, which can provide the required phase compensation within a specific frequency range to meet the requirements of system stability. The specific values of the gain and time constant need to be solved later.

[0066] Step S102, select a compensation phase angle within the angle range corresponding to the phase compensator, and use the compensation phase angle to determine multiple time constants that meet the target with the goal of balancing the steady-state accuracy, phase margin, and response speed of the power system.

[0067] Specifically, this step determines the time constant of the designed phase compensator. Among them, the angle range corresponding to the phase compensator is the range of the optimal compensation phase angle that the phase compensator can provide.

[0068] It should be noted that the gain in the above embodiments A determines the influence degree of the phase compensator on the system gain, and affects the steady-state accuracy and dynamic response speed of the system. During the design, it is necessary to observe performance indicators such as phase margin, response speed, and steady-state error of the power system under different gains until the gain value that makes the comprehensive performance of the system optimal is found.

[0069] Time constant T 1 determines the zero point of the phase compensator, and thus affects the starting frequency of phase compensation. When selecting T 1 it is necessary to adjust according to the oscillation frequency characteristics of the system. The time constant T 2 determines the pole of the phase compensator, and thus affects the cut-off frequency of phase compensation. When selecting T 2 it is necessary to take into account both system stability and compensation effect. Through reasonable design of these two time constants, this application can form a phase-advance compensation region near the oscillation frequency, thereby effectively suppressing low-frequency oscillations.

[0070] Based on this, when designing the relevant parameters of the phase compensator in this application, comprehensive and detailed considerations have been made, aiming to balance the steady-state accuracy, stability, phase margin, and response speed of the system, so that the parameters in the designed transfer function can achieve this goal.

[0071] In an embodiment of this application, determining the multiple time constants that meet the target includes: setting the maximum phase compensation point of the phase compensator at the oscillation frequency of the VSG-type energy storage inverter to construct a phase compensation equation; combining the phase compensation equation, the compensation phase angle equation, and the selected compensation phase angle to determine multiple time constants.

[0072] Continuing to refer to the first-order phase compensator in the above embodiments for illustration, since the value of the gain A will directly affect the steady-state accuracy of the system, and the values of the time constants T 1 and T 2 will directly affect the stability and phase margin of the system. In addition, the gain A and the time constants T 1 、 T 2The value of also needs to be balanced in terms of the response speed of the system. Therefore, considering the steady-state accuracy, phase margin, and response speed of the system comprehensively, the present invention sets the maximum phase compensation point of the phase compensator at the oscillation frequency ω low to meet the above objectives. Among them, ω low is a low frequency less than 50 Hz. At the same time, select the compensation phase angle. For example, for a first-order phase compensator, the best compensation phase angle range it can provide is between 45° and 60°. Then, combined with the actual application situation, set the specific value of the compensation phase angle of this system. Furthermore, the time constants T 1 and T 2 can be calculated based on the following method:

[0073] .

[0074] Step S103, determine the gain of the phase compensator by using multiple time constants.

[0075] Specifically, this step determines the gain of the designed phase compensator. When determining the gain, it can be calculated based on the solving process and the solved time constants in the previous step.

[0076] In an embodiment of the present application, determining the gain of the phase compensator by using multiple time constants includes: constructing an amplitude equation based on the amplitude of the phase compensator at the maximum phase compensation point being 1, where the amplitude equation includes the gain to be solved; substituting the determined multiple time constants into the amplitude equation to determine the gain of the phase compensator.

[0077] Specifically, since the compensation point has been designed at the oscillation frequency in the embodiment of the present application, the phase compensator only provides phase compensation at the oscillation frequency and does not affect the amplitude at this point. Therefore, the amplitude of the phase compensator at the maximum phase compensation is 1. Based on this, the value of the parameter A can be determined, and the specific calculation formula is as follows:

[0078]

[0079] Furthermore, substituting the determined time constants T 1 and T 2 into the above formula, the value of the gain A can be determined.

[0080] Thus, based on setting the maximum phase compensation of the phase compensator at the low-frequency oscillation frequency, and by using the calculation method for selecting the angle of the compensation phase angle, the gain and multiple time constants in the transfer function can be determined by simultaneously solving the various formulas in steps S102 and S103 and substituting the known relevant parameters.

[0081] Step S104: Integrate the phase compensator with the reactive power loop of the virtual synchronous generator type energy storage inverter, and compensate for the phase lag of the pure integral link in the reactive power loop through the phase compensator with determined parameters to suppress low-frequency oscillation. Among them, the phase angles provided by the phase compensator with determined parameters are all positive values.

[0082] Specifically, integrate the designed phase compensator into the reactive power loop of the VSG type energy storage inverter to complete the improvement of the reactive power loop. Since the phase compensator takes into account the phase lag brought by the pure integral link in the reactive power loop, by compensating this phase lag, low-frequency oscillation can be effectively suppressed. Moreover, the phase angles provided by the phase compensator designed according to the above parameter determination method of this application are all positive values, so it will not have a negative impact on the phase margin of the system in other frequency ranges.

[0083] Continuing to refer to the above example, the control equation of the reactive power loop after integrating the above first-order phase compensator is expressed by the following formula:

[0084]

[0085] Among them, E represents the voltage amplitude output by the reactive power loop, E ref represents the voltage reference value, K represents the voltage regulation coefficient, Q ref represents the reference value of reactive power, D q represents the reactive power damping coefficient, v pd represents the d-axis component of the voltage at the point of common coupling, q f represents the average reactive power output by the virtual synchronous generator VSG.

[0086] In this embodiment, compensating for the phase lag of the pure integral link in the reactive power loop through the phase compensator with determined parameters includes: providing an advanced phase at the oscillation frequency through the phase compensator with determined parameters to offset the phase lag of the pure integral link.

[0087] Specifically, the phase compensator designed according to the above parameter determination method of the present application can provide a leading phase within a relatively wide frequency band to make up for the phase lag brought by the pure integral link, so as to achieve the suppression of low-frequency oscillation. If other types of compensators are selected, it may not be possible to provide sufficient phase compensation within a wide frequency band, thus affecting the oscillation suppression effect.

[0088] Therefore, the phase compensator proposed in the present application can provide precise phase compensation at the oscillation frequency point, effectively suppress the low-frequency oscillation of the VSG-type energy storage inverter, and significantly improve the stability and reliability of the system.

[0089] In summary, the method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator in the embodiment of the present application suppresses the low-frequency oscillation in the VSG-type energy storage inverter by adding a phase compensator in the reactive power loop. Among them, the phase compensator can provide a leading phase at the oscillation frequency to offset the phase lag brought by the pure integral link in the reactive power loop, and then effectively suppress the low-frequency oscillation by precisely compensating this phase lag. The phase compensator designed by this method can provide sufficient phase compensation within a wide frequency band, thus ensuring the oscillation suppression effect, and the phase angles provided by this phase compensator are all positive values, ensuring that while compensating for the phase lag, it will not have a negative impact on the phase margin and the like of the system in other frequency ranges. And the phase compensator provided by this method sets the maximum phase compensation point at the oscillation frequency. At the same time, the design of the compensation phase angle and each parameter in the transfer function comprehensively considers the steady-state accuracy, stability, phase margin and response speed of the system. This method can achieve the suppression of low-frequency oscillation by designing a phase compensator and optimizing the control strategy, reducing the complexity of realizing oscillation suppression and improving the practicability of the oscillation suppression strategy. Therefore, this method enhances the low-frequency oscillation suppression effect, improves the stability margin of the VSG-type inverter under a strong power grid, reduces the system oscillation risk, ensures the stable operation of the VSG-type energy storage inverter in the power system, and is beneficial to improving the dynamic stability and operation reliability of the power system.

[0090] Based on the above embodiments, in order to more clearly illustrate the suppression effect of the method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator of the present application, the following will illustrate with the specific results of suppressing low-frequency oscillation of an inverter in a specific embodiment.

[0091] In this embodiment, taking the suppression of low-frequency oscillation of a typical 186kW VSG-type energy storage inverter as an example, when the short-circuit ratio is 5, the system can operate stably. When the simulation runs to 10.0s, the short-circuit ratio (SCR) is switched from 5.0 to 6.5. At this time, the time-domain simulation results of the active power and reactive power are as Figure 6 shown. From Figure 6It can be observed that when the short - circuit ratio increases to more than 6.5, both the active power and the reactive power start to exhibit low - frequency oscillations, and the oscillation frequency is around 7.1 Hz.

[0092] In this embodiment, the maximum phase of the phase compensator is set at the oscillation frequency of 7.1 Hz, and the compensation phase angle is taken as 45°. Therefore, through the calculation formula, the parameters of the phase compensator are respectively T 1 = 0.0548, T 2 = 0.0094 and A = 0.414. At this time, the Bode diagram of the phase compensator is as shown in Figure 7 shown. From Figure 7 the amplitude - frequency characteristic curve and the phase - frequency characteristic curve in it, it can be observed that the phase compensator can provide an advanced phase within a relatively wide frequency band to compensate for the phase lag brought by the integral link, and moreover, the phase angles provided by this phase compensator are all positive values.

[0093] Next, further analyze the effect of the additional phase compensator of the reactive power loop proposed in the application to suppress low - frequency oscillations. After adding the additional phase compensator, when the simulation runs to 10.0 s, the short - circuit ratio is switched from 5.0 to 6.5, and the corresponding time - domain simulation results of the system are as shown in Figure 8 shown. From Figure 8 it can be seen that neither the active power nor the reactive power exhibits low - frequency oscillations, and the system can still maintain stable operation. Therefore, the oscillation suppression measure of the additional phase compensator of the reactive power loop proposed in this application is effective. Through further simulation verification, it can be obtained that by using the oscillation suppression measure of this application, the system can still maintain stability when the short - circuit ratio increases to 12.0.

[0094] Thus, this application can effectively suppress the low - frequency oscillations of the VSG - type energy storage inverter, improve the stability margin of the VSG - type inverter under a strong power grid, and reduce the oscillation risk. The oscillation suppression strategy of this application can provide a theoretical reference for the stable operation of the VSG - type energy storage inverter in the power system to achieve a wider range of industrial applications.

[0095] To implement the above - mentioned embodiment, this application also proposes a suppression system for low - frequency oscillations of a VSG - type energy storage inverter based on a phase compensator. Figure 9 For the structural schematic diagram of a suppression system for low - frequency oscillations of a VSG - type energy storage inverter based on a phase compensator proposed in an embodiment of this application, as shown in Figure 9 shown, this system includes: a design module 100, a first determination module 200, a second determination module 300, and a compensation module 400.

[0096] Among them, the design module 100 is used to construct a phase compensator and design the transfer function of the phase compensator, where the transfer function includes the gain of the phase compensator to be determined and multiple time constants.

[0097] The first determination module 200 is used to select a compensation phase angle within the angle range corresponding to the phase compensator, and with the goal of balancing the steady-state accuracy, phase margin, and response speed of the power system, determine multiple time constants that meet the goal using the compensation phase angle.

[0098] The second determination module 300 is used to determine the gain of the phase compensator using multiple time constants.

[0099] The compensation module 400 is used to integrate the phase compensator with determined parameters into the reactive power loop of the virtual synchronous generator (VSG) type energy storage inverter, and compensate for the phase lag of the pure integration link in the reactive power loop through the phase compensator with determined parameters to suppress low-frequency oscillations, where the phase angles provided by the phase compensator with determined parameters are all positive values.

[0100] Optionally, in an embodiment of the present application, the first determination module 200 is specifically configured to: set the maximum phase compensation point of the phase compensator at the oscillation frequency of the VSG type energy storage inverter, and construct a phase compensation equation; combine the phase compensation equation, the compensation phase angle equation, and the selected compensation phase angle to determine multiple time constants.

[0101] Optionally, in an embodiment of the present application, the second determination module 300 is specifically configured to: based on the amplitude of the phase compensator at the maximum phase compensation point being 1, construct an amplitude equation, where the amplitude equation includes the gain to be solved; substitute the multiple determined time constants into the amplitude equation to determine the gain of the phase compensator.

[0102] Optionally, in an embodiment of the present application, the compensation module 400 is specifically configured to: provide a leading phase at the oscillation frequency through the phase compensator with determined parameters to offset the phase lag of the pure integration link.

[0103] It should be noted that the foregoing explanation of the embodiments of the method for suppressing low-frequency oscillations of the VSG type energy storage inverter based on a phase compensator also applies to the system of this embodiment, and will not be elaborated here.

[0104] In summary, the system for suppressing low-frequency oscillations of the VSG type energy storage inverter based on a phase compensator in the embodiments of the present application enhances the low-frequency oscillation suppression effect, improves the stability margin of the VSG type inverter under a strong power grid, reduces the system oscillation risk, ensures the stable operation of the VSG type energy storage inverter in the power system, and is beneficial to improving the dynamic stability and operation reliability of the power system.

[0105] To implement the above embodiments, the present application further provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the method for suppressing low-frequency oscillation of a VSG-type energy storage inverter based on a phase compensator as described in any one of the embodiments of the first aspect above.

[0106] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0107] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0108] Any process or method description shown in a flowchart or described in other ways herein can be understood as representing a module, segment, or part of code including one or more executable instructions for implementing a customized logic function or process. The scope of the preferred embodiments of the present application includes additional implementations, where the functions may be executed in a manner that is not shown or discussed in the order, including in a substantially simultaneous manner according to the functions involved or in the reverse order, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in conjunction with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection portion having one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or otherwise processing as appropriate, and then stored in a computer memory.

[0110] It should be understood that various parts of the present application can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0111] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the methods of the above embodiments can be completed by a program instructing relevant hardware, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0112] In addition, each functional unit in various embodiments of the present application may be integrated into one processing module, may exist separately as individual physical units, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0113] The above-mentioned storage medium may be a read-only memory, a magnetic disk, an optical disc, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator, characterized in that: The following steps are involved: Constructing a phase compensator and designing a transfer function of the phase compensator, wherein the transfer function includes a gain of the phase compensator and a plurality of time constants to be determined; Selecting a compensation phase angle within the angle range corresponding to the phase compensator, and taking the steady-state accuracy, phase margin and response speed of the balanced power system as the goal, using the compensation phase angle to determine the multiple time constants that meet the goal; determining a gain of the phase compensator using the plurality of time constants; The phase compensator with determined parameters is integrated into the reactive loop of the virtual synchronous generator VSG type energy storage inverter, and the phase lag of the pure integral link in the reactive loop is compensated by the phase compensator with determined parameters to suppress low-frequency oscillation, wherein the phase angles provided by the phase compensator with determined parameters are all positive values.

2. The method according to claim 1, characterized in that The determining the plurality of time constants that meet the target comprises: The maximum phase compensation point of the phase compensator is set at the oscillation frequency of the VSG type energy storage inverter to construct a phase compensation equation; The multiple time constants are determined by combining the phase compensation equation, the compensation phase angle equation and the selected compensation phase angle.

3. The method according to claim 2, characterized in that The determining the gain of the phase compensator by using the multiple time constants comprises: Based on the amplitude of the phase compensator being 1 at the maximum phase compensation point, constructing an amplitude equation, wherein the amplitude equation includes a gain to be solved; Substituting the determined multiple time constants into the amplitude equation, the gain of the phase compensator is determined.

4. The method according to claim 2, characterized in that: The phase compensator after the parameters are determined compensates the phase lag of the pure integral link in the reactive loop, including: The phase compensator determined by the parameters provides an advanced phase at the oscillation frequency to offset the phase lag of the pure integral link.

5. The method according to claim 1, characterized in that When the phase compensator is a first-order phase compensator, the transfer function is expressed by the following formula: in, G ( s ) represents the transfer function, A represents the gain of the phase compensator, T 1 represents the zero time constant of the phase compensator, T 2 represents the pole time constant of the phase compensator, s Represents a complex variable.

6. The method according to claim 5, characterized in that The control equation of the reactive loop after the integrated phase compensator is expressed by the following formula: in, E Indicates the voltage amplitude of the reactive loop output, E ref Indicates the voltage reference value, K Indicates the voltage regulation coefficient, Q ref Indicates the reference value of reactive power, D q represents the reactive damping coefficient, v pd represents the d-axis component of the common coupling point voltage, q f It represents the average reactive power output by the virtual synchronous generator VSG.

7. A system for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator, characterized in that: include: A design module, used for constructing a phase compensator and designing a transfer function of the phase compensator, wherein the transfer function includes a gain and a plurality of time constants of the phase compensator to be determined; A first determination module is used to select a compensation phase angle within the angle range corresponding to the phase compensator, and use the compensation phase angle to determine the multiple time constants that meet the target with the steady-state accuracy, phase margin and response speed of the balanced power system as the target; A second determination module, configured to determine a gain of the phase compensator using the multiple time constants; A compensation module is used to integrate a phase compensator with determined parameters into the reactive loop of a virtual synchronous generator (VSG) type energy storage inverter, and to compensate for the phase lag of a pure integral link in the reactive loop through the phase compensator with determined parameters to suppress low-frequency oscillations, wherein the phase angles provided by the phase compensator with determined parameters are all positive values.

8. The system according to claim 7, characterized in that The first determining module is specifically configured to: The maximum phase compensation point of the phase compensator is set at the oscillation frequency of the VSG type energy storage inverter, and a phase compensation equation is constructed; The multiple time constants are determined by combining the phase compensation equation, the compensation phase angle equation and the selected compensation phase angle.

9. The system according to claim 8, characterized in that The second determining module is specifically used to: Based on the amplitude of the phase compensator being 1 at the maximum phase compensation point, constructing an amplitude equation, wherein the amplitude equation includes a gain to be solved; Substituting the determined multiple time constants into the amplitude equation, the gain of the phase compensator is determined.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator as described in any one of claims 1 to 6 is implemented.

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