Phase compensator-based VSG type energy storage inverter low-frequency oscillation suppression method

Abstract

The invention provides a phase compensator-based VSG type energy storage inverter low frequency oscillation suppression method, which comprises the steps of constructing a phase compensator, and designing a transfer function of the phase compensator, the transfer function comprising a gain to be determined and a plurality of time constants; selecting a compensation phase angle, aiming at balancing the steady-state precision, the phase margin and the response speed of the power system, and determining a plurality of time constants meeting the target by utilizing the compensation phase angle; determining a gain using the plurality of time constants; the phase compensator with the determined parameters is integrated into a reactive ring of the VSG type energy storage inverter, phase lag of a pure integration element in the reactive ring is compensated, and phase angles provided by the phase compensator with the determined parameters are all positive values. According to the method, the low-frequency oscillation in the VSG type energy storage inverter is suppressed by adding the phase compensator in the reactive loop, so that the low-frequency oscillation suppression effect is enhanced, and the negative influence on the performance of the system in other frequency ranges is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic equipment control, and in particular 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 energy structure and the growing demand for clean energy, energy storage inverters are gaining more and more attention due to their key role in power systems. As an important part of the power system, the stability and reliability of energy storage inverters are crucial to 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 attracted widespread attention because of its ability to simulate the dynamic characteristics of traditional synchronous generators. VSG type energy storage inverters enhance the stability of the system by providing virtual inertia and damping.

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

[0004] However, the low-frequency oscillation suppression method in the related art has a poor oscillation suppression effect when the 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 one of the technical problems in the related art at least to some extent.

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

[0007] The second objective 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] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0009] To achieve the above-mentioned purpose, the 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: 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.

[0010] Optionally, in one embodiment of the present 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 energy storage inverter to construct a phase compensation equation; and determining the multiple time constants by combining the phase compensation equation, the compensation phase angle equation and the selected compensation phase angle.

[0011] Optionally, in one embodiment of the present application, the use of the multiple time constants to determine the gain of the phase compensator includes: constructing an amplitude equation based on the amplitude of the phase compensator at the maximum phase compensation point being 1, wherein 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.

[0012] Optionally, in one embodiment of the present application, the phase compensator determined by the parameters compensates for 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.

[0013] Optionally, in one embodiment of the present application, when the phase compensator is a first-order phase compensator, the transfer function is expressed by the following formula:

[0014] 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.

[0015] Optionally, in one embodiment of the present application, the control equation of the reactive loop after the integrated phase compensator is expressed by the following formula:

[0016] 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.

[0017] To achieve the above-mentioned purpose, the second aspect of the present application further proposes a low-frequency oscillation suppression system of a VSG type energy storage inverter based on a phase compensator, comprising the following modules: 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.

[0018] In order to implement the above-mentioned embodiments, the third aspect embodiment of the present application also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. 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 in the above-mentioned first aspect is implemented.

[0019] The technical solution provided by the embodiment of the present application brings at least the following beneficial effects: the present application suppresses the low-frequency oscillation in the VSG type energy storage inverter by adding a phase compensator in the reactive loop, wherein the phase compensator can provide an advanced phase at the oscillation frequency to offset the phase lag caused by the pure integral link in the reactive loop, and then effectively suppress the low-frequency oscillation by accurately compensating the phase lag. The phase compensator designed in the present application can provide sufficient phase compensation in a wide band to ensure the oscillation suppression effect, and the phase angle provided by the phase compensator is a positive value, ensuring that while compensating for the phase lag, it will not have a negative impact on the phase margin 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, and 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 and phase margin and response speed of the system. The present application can suppress low-frequency oscillation by designing a phase compensator and optimizing the control strategy, reducing the complexity of realizing oscillation suppression and improving the practicality of the oscillation suppression strategy. Therefore, the present application enhances the low-frequency oscillation suppression effect, improves the stability margin of the VSG inverter under a strong power grid, reduces the risk of system oscillation, ensures the stable operation of the VSG energy storage inverter in the power system, and is beneficial to improving the dynamic stability and operational reliability of the power system.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which: Figure 1 A flow chart of a method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator proposed in an embodiment of the present application; Figure 2 A schematic diagram of a main circuit of a VSG type energy storage inverter proposed in an embodiment of the present application; Figure 3 A schematic diagram of the control principle of the active loop and reactive loop of a VSG type energy storage inverter proposed in an embodiment of the present application; Figure 4 A schematic diagram of the control principle of a virtual impedance and vector double closed loop proposed in an embodiment of the present application; Figure 5 A schematic diagram of the control principle of a reactive loop after an integrated phase compensator proposed in an embodiment of the present application; Figure 6 A schematic diagram of a time domain simulation of low-frequency oscillation of active power and reactive power proposed in an embodiment of the present application; Figure 7 A Bode diagram of a phase compensator proposed in an embodiment of the present application; Figure 8 A schematic diagram of time domain simulation of active power and reactive power in a stable operating state proposed in an embodiment of the present application; Fig. 9 A schematic diagram of the structure of a low-frequency oscillation suppression system for a VSG type energy storage inverter based on a phase compensator proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0022] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0023] It should be noted that there may be stability problems when the grid-type inverter is running in a high-intensity power grid. When the grid-type inverter is connected to a low-impedance strong AC power grid, the low impedance may cause the inverter to become unstable and the risk of low-frequency oscillation. Low-frequency oscillations will reduce the dynamic performance of the system, affect the power quality, and may even cause system instability. At present, in the relevant technology, the research on the low-frequency oscillation problem of VSG type energy storage inverter has mainly focused on the analysis of oscillation mechanism and the discussion of influencing factors, but effective suppression strategies are still relatively lacking.

[0024] For example, in the first related embodiment, the oscillation is suppressed by detecting the output electrical angular velocity of the virtual synchronous generator, but the effect of this solution is still not ideal when the grid parameters fluctuate greatly. In the second related embodiment, a storage VSG control method that considers 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 that suppresses 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.

[0025] In summary, with respect to the problem of low-frequency oscillation of VSG inverters, the methods in the relevant 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 deterioration of the system's performance in other frequency ranges, and the applicability is poor.

[0026] To this end, this application proposes a low-frequency oscillation suppression method for a VSG type energy storage inverter based on a phase compensator to solve the low-frequency oscillation problem that occurs when the VSG type energy storage inverter is connected to the power grid, thereby improving the dynamic stability and operational reliability of the system, which has important practical significance for the high proportion of renewable energy grid connection. This application can be achieved through the optimization of the control strategy, which not only simplifies the complexity of the system implementation, but also improves the reliability and practicality of the system.

[0027] A method and system for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator proposed in an embodiment of the present application will be described below with reference to the accompanying drawings.

[0028] Figure 1 Flow chart of a method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator proposed in an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps: Step S101 : constructing a phase compensator and designing a transfer function of the phase compensator, wherein the transfer function includes a gain of the phase compensator to be determined and a plurality of time constants.

[0029] It should be noted that the present application adds an additional phase compensator in the reactive loop of the VSG type energy storage inverter to deal with the phase lag problem caused by the pure integral link in the reactive loop. By accurately compensating for the phase lag, low-frequency oscillations with a frequency less than 50 Hz can be effectively suppressed.

[0030] In the specific implementation, the phase compensator and its transfer function are designed first. The transfer function includes the gain and time constant of the phase compensator, which can affect the phase lag compensation effect of the phase compensator and the parameters that will affect the power system where the VSG type energy storage inverter is located.

[0031] In order to more clearly illustrate the implementation principle of the phase compensator constructed in the present application to suppress the low-frequency oscillation of the VSG type energy storage inverter, the VSG type energy storage inverter involved in the present application is first described in detail below.

[0032] In the embodiment of the present application, the main circuit structure of the VSG type energy storage inverter is as follows: Figure 2 The inverter is connected to the grid after passing through the LC filter. The DC side of the inverter is provided with a stable DC voltage by the battery pack. U dc, e o is the inverter output voltage, L f and C f They are the filter inductance and capacitance of the LC filter respectively. i o is the inverter output current, v p is the voltage at the point of common coupling (PCC), i g is the current flowing into the grid. In this embodiment, the grid impedance ignores the resistance and only considers the grid inductance. L g , e g is the grid voltage.

[0033] Continue to refer to Figure 2 As shown, the modulation wave S abc The d-axis reference voltage output by the controller E dref and q-axis reference voltage E qref Generate, generate the modulated wave S abc After sinusoidal pulse width modulation (SPWM), a driving signal is generated, which is used to control the on and off of the switching device in the inverter. v p The output voltage of the inverter and LC filter as a whole is determined by the rotation angle θ After the conversion between the three-phase coordinate system (abc) and the dq coordinate system, v p Converted to the d-axis component of the output voltage v pd and the q-axis component of the output voltage v pq ,Will i o Converted to the d-axis component of the output current i od and the q-axis component of the output current i oq .

[0034] Furthermore, through v pd , v pq and i od ,i oq The instantaneous output active power of the VSG inverter can be calculated p e and instantaneous output reactive power q e Then, the two instantaneous output powers are filtered through a low-pass filter to obtain the average output active power of the VSG inverter. p f and average output reactive power q f .in, Figure 2 In ω c is the cut-off frequency of the low-pass filter, and the calculation formulas for these two average output powers are as follows:

[0035] In the control loop of the VSG energy storage inverter, the VSG algorithm simulates the operating characteristics of the synchronous generator to supply power to the load and the grid. The specific control process is as follows: Figure 3 shown. Figure 3 The active power-frequency control part (i.e., active loop) in the upper middle part outputs the frequency through the rotor equation, simulating the inertia and primary frequency regulation characteristics of the synchronous generator; the reactive power-voltage control part (i.e., reactive loop) in the lower middle part simulates the primary voltage regulation characteristics of the synchronous generator. Figure 3 The control equations of the active loop and the reactive loop are as follows:

[0036] in, J is the moment of inertia, ω o and ω n Respectively represent the output angular frequency of VSG and the angular frequency of the grid, P ref is the reference value of active power, D p represents the active damping coefficient, E is the voltage amplitude of the reactive loop output, E ref is the voltage reference value, K is the voltage regulation coefficient, Q ref is the reference value of reactive power, D q Represents the reactive damping coefficient.

[0037] It should be noted that the parameters with defined meanings in this application will not be explained again in the subsequent embodiments, and their meanings are the same, so this application will not elaborate on them.

[0038] Furthermore, through power loop control, the system can obtain the voltage amplitude set by the VSG algorithm, and then through virtual impedance control and 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 , the control process is as follows Figure 4 As shown in the figure. The virtual impedance link simulates the series impedance of the actual line by subtracting the product of the output current and the virtual impedance from the reference voltage, thereby adjusting the equivalent impedance between the inverter output and the PCC point. Figure 4 middle, R v and L v are virtual resistance and virtual inductance respectively. In the vector double closed loop, E vdref and E vqref are the d-axis voltage reference value of the voltage loop and the q-axis voltage reference value of the voltage loop, respectively. I dref and I qref are the d-axis current reference value of the current loop 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 k vp + k vi / s and k ip + k ii / s .in, k vp , k vi and k ip , k ii They are different PI control parameters for the voltage loop and the current loop respectively.

[0039] Based on the above content, the analysis of the participation factor of the small signal model eigenvalue shows that the voltage amplitude of the reactive loop output is E plays a leading role in low-frequency oscillation. Figure 3 It can be observed that there is a pure integral link in the reactive loop control process, which will bring a phase lag of -90°, resulting in an increased risk of low-frequency oscillation in the system. Therefore, the present 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 loop is as follows: Figure 5 shown.

[0040] In one embodiment of the present application, when the adopted phase compensator is a first-order phase compensator, the transfer function of the designed phase compensator is expressed by the following formula:

[0041] 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.

[0042] in, T 1 and T 2 The zero frequency and pole frequency of the compensator are determined respectively. The 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 gain and time constant need to be solved later.

[0043] Step S102, 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 multiple time constants that meet the goal.

[0044] Specifically, this step determines the time constant of the designed phase compensator. The angle range corresponding to the phase compensator is the range of the best compensation phase angle that the phase compensator can provide.

[0045] It should be noted that the gain in the above embodiment A It determines the influence of the phase compensator on the system gain, affecting the steady-state accuracy and dynamic response speed of the system. When designing, it is necessary to observe the performance indicators such as phase margin, response speed and steady-state error of the power system under different gains until the gain value that optimizes the overall performance of the system is found.

[0046] Time constant T 1 Determines the zero point of the phase compensator, which in turn affects the starting frequency of the phase compensation. T 1 It is necessary to adjust according to the system oscillation frequency characteristics. T 2 Determines the pole of the phase compensator, which in turn affects the cutoff frequency of the phase compensation.T 2 By rationally designing these two time constants, the present application can form a phase-advanced compensation region near the oscillation frequency, thereby effectively suppressing low-frequency oscillation.

[0047] Based on this, the present application has undergone comprehensive and careful consideration when designing the relevant parameters of the phase compensator, 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.

[0048] In one embodiment of the present 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 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.

[0049] Continuing to refer to the first-order phase compensator in the above embodiment, due to the gain A The value of will directly affect the steady-state accuracy of the system, and the time constant T 1 and T 2 The value of will directly affect the stability and phase margin of the system. In addition, the gain A and time constant T 1 , T 2 The value of also needs to be compromised in terms of the response speed of the system. Therefore, considering the steady-state accuracy, phase margin and response speed of the system, the present invention sets the maximum phase compensation point of the phase compensator to Set the oscillation frequency ω low to meet the above objectives. ω low At the same time, the compensation phase angle is selected. 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, the compensation phase angle of this system is set. The specific value of. Furthermore, the time constant T 1 and T 2 The calculation can be done based on: .

[0050] Step S103, determining the gain of the phase compensator using a plurality of time constants.

[0051] Specifically, this step determines the gain of the designed phase compensator. When determining the gain, calculation can be performed based on the solution process of the time constant in the previous step and the solved time constant.

[0052] In one embodiment of the present application, the gain of the phase compensator is determined using multiple time constants, including: constructing an amplitude equation based on the amplitude of the phase compensator at the maximum phase compensation point being 1, wherein 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.

[0053] 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 parameter can be determined A The specific calculation formula is as follows:

[0054] Furthermore, the determined time constant T 1 and T 2 Substituting into the above formula, the gain can be determined A The value of .

[0055] Therefore, the present application is based on setting the maximum phase compensation of the phase compensator at the low-frequency oscillation frequency, and at the same time utilizing the calculation method of selecting the angle of the compensation phase angle, by combining the various formulas in step S102 and step S103, and substituting the known related parameters, the gain and multiple time constants in the transfer function can be determined.

[0056] Step S104, integrating the phase compensator with determined parameters into the reactive loop of the virtual synchronous generator type energy storage inverter, and compensating the phase lag of the pure integral link in the reactive loop 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.

[0057] Specifically, the designed phase compensator is integrated into the reactive loop of the VSG type energy storage inverter to improve the reactive loop. Since the phase compensator takes into account the phase lag caused by the pure integral link in the reactive loop, low-frequency oscillation can be effectively suppressed by compensating for this phase lag. Moreover, the phase angles provided by the phase compensator designed according to the above parameter determination method of the present application are all positive values, so it will not have a negative impact on the phase margin of the system in other frequency ranges.

[0058] Continuing with the above example, the control equation of the reactive loop after integrating the above first-order phase compensator is expressed by the following formula:

[0059] 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.

[0060] In this embodiment, the phase lag of the pure integral link in the reactive loop is compensated by the phase compensator with determined parameters, including: providing an advanced phase at the oscillation frequency by the phase compensator with determined parameters to offset the phase lag of the pure integral link.

[0061] Specifically, the phase compensator designed according to the above parameter determination method of the present application can provide an advanced phase in a wider frequency band to compensate for the phase lag caused by the pure integral link, so as to suppress low-frequency oscillations. If other types of compensators are selected, they may not be able to provide sufficient phase compensation in a wide frequency band, thereby affecting the oscillation suppression effect.

[0062] Therefore, the phase compensator proposed in the present application can provide accurate 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.

[0063] In summary, the method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator in an embodiment of the present application suppresses low-frequency oscillations in a VSG type energy storage inverter by adding a phase compensator in a reactive loop, wherein the phase compensator can provide an advanced phase at the oscillation frequency to offset the phase lag caused by the pure integral link in the reactive loop, and then effectively suppress low-frequency oscillations by accurately compensating for the phase lag. The phase compensator designed by the method can provide sufficient phase compensation in a wide band to ensure the oscillation suppression effect, and the phase angle provided by the phase compensator is a positive value, ensuring that while compensating for the phase lag, it will not have a negative impact on the phase margin of the system in other frequency ranges. And the phase compensator provided by the method sets the maximum phase compensation point at the oscillation frequency, and 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 and phase margin of the system and the response speed. The method can suppress low-frequency oscillations by designing a phase compensator and optimizing the control strategy, reducing the complexity of achieving oscillation suppression and improving the practicality of the oscillation suppression strategy. Therefore, this method enhances the low-frequency oscillation suppression effect, improves the stability margin of the VSG inverter under a strong power grid, reduces the system oscillation risk, ensures the stable operation of the VSG energy storage inverter in the power system, and is beneficial to improving the dynamic stability and operation reliability of the power system.

[0064] 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 specific result of suppressing low-frequency oscillation of the inverter in a specific embodiment is described below.

[0065] In this embodiment, taking the suppression of low-frequency oscillation of a typical 186kW VSG 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 active power and reactive power are as follows: Figure 6 As shown. Figure 6 It can be observed that when the short-circuit ratio increases to 6.5, both active power and reactive power begin to oscillate at a low frequency, with the oscillation frequency being around 7.1 Hz.

[0066] In this embodiment, the maximum phase of the phase compensator is set at an oscillation frequency of 7.1 Hz, and the compensation phase angle is 45°. Therefore, through the calculation formula, the parameters of the phase compensator are T 1 =0.0548, T 2 =0.0094 and A =0.414. At this time, the Bode diagram of the phase compensator is as follows Figure 7 As shown. Figure 7 It can be observed from the amplitude-frequency characteristic curve and the phase-frequency characteristic curve that the phase compensator can provide an advanced phase in a wider frequency band to compensate for the phase lag caused by the integral link, and the phase angles provided by the phase compensator are all positive values.

[0067] The following is a further analysis of the effect of the reactive loop additional phase compensator proposed in the application on suppressing low-frequency oscillation. After the phase compensator is added, when the simulation runs to 10.0s, the short-circuit ratio is switched from 5.0 to 6.5. The corresponding time domain simulation results of the system are as follows: Figure 8 As shown. Figure 8 It can be seen that there is no low-frequency oscillation in both active power and reactive power, and the system can still maintain stable operation. Therefore, the oscillation suppression measures of the reactive loop additional phase compensator proposed in this application are effective. Through further simulation verification, it can be obtained that the oscillation suppression measures of this application can ensure that when the short-circuit ratio increases to 12.0, the system remains stable.

[0068] Therefore, the present application can effectively suppress the low-frequency oscillation 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 the present application can provide a theoretical reference for the stable operation of the VSG type energy storage inverter in the power system, so as to achieve a wider range of industrial applications.

[0069] In order to implement the above embodiment, the present application also proposes a low-frequency oscillation suppression system of a VSG type energy storage inverter based on a phase compensator. Fig. 9 A schematic diagram of a structure of a low-frequency oscillation suppression system of a VSG type energy storage inverter based on a phase compensator proposed in an embodiment of the present application is shown in FIG. Fig. 9 As shown, the system includes: a design module 100 , a first determination module 200 , a second determination module 300 and a compensation module 400 .

[0070] The design module 100 is used to construct a phase compensator and design a transfer function of the phase compensator, wherein the transfer function includes a gain of the phase compensator to be determined and a plurality of time constants.

[0071] The first determination module 200 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 multiple time constants that meet the goals with the goal of balancing the steady-state accuracy, phase margin and response speed of the power system.

[0072] The second determination module 300 is used to determine the gain of the phase compensator using multiple time constants.

[0073] The compensation module 400 is used to integrate the phase compensator with determined parameters into the reactive loop of the virtual synchronous generator VSG type energy storage inverter, and compensate the phase lag of the pure integral link in the reactive loop 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.

[0074] Optionally, in one embodiment of the present application, the first determination module 200 is specifically used to: set the maximum phase compensation point of the phase compensator at the oscillation frequency of the VSG energy storage inverter to construct a phase compensation equation; and determine multiple time constants by combining the phase compensation equation, the compensation phase angle equation and the selected compensation phase angle.

[0075] Optionally, in one embodiment of the present application, the second determination module 300 is specifically used to: construct an amplitude equation based on the amplitude of the phase compensator at the maximum phase compensation point being 1, wherein the amplitude equation includes the gain to be solved; substitute the determined multiple time constants into the amplitude equation to determine the gain of the phase compensator.

[0076] Optionally, in one embodiment of the present application, the compensation module 400 is specifically used to: provide an advanced phase at the oscillation frequency through a phase compensator after parameter determination to offset the phase lag of the pure integration link.

[0077] It should be noted that the above explanation of the embodiment of the method for suppressing low-frequency oscillation of a VSG type energy storage inverter based on a phase compensator is also applicable to the system of this embodiment and will not be repeated here.

[0078] To sum up, the low-frequency oscillation suppression system of the VSG type energy storage inverter based on the phase compensator in the embodiment 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.

[0079] In order to implement the above-mentioned embodiments, the present application also proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, a 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 above-mentioned first aspect embodiments is implemented.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0081] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0082] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0083] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0084] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned 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 by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0085] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0086] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, 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. If 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.

[0087] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, 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 cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify 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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