Method and system for power oscillation damping applicable to multi-vsg converter interconnected systems

Abstract

The application discloses a power oscillation suppression method and system suitable for a multi-VSG converter parallel system, which comprises two parts of error power low-pass filter feedforward compensation and error power differential feedforward compensation, the error power low-pass filter feedforward compensation utilizes a low-pass filter link containing virtual inertia and damping coefficient to construct an active feedforward item, and the suppression of low-frequency power oscillation is realized by adjusting the feedforward parameter; the error power differential feedforward compensation utilizes a generalized second-order integrator (SOGI) to construct an active feedforward item, and the suppression of synchronous oscillation is realized by adjusting the differential coefficient. The application realizes the coordinated suppression of low-frequency oscillation and synchronous oscillation of the multi-VSG converter parallel system, and guarantees the safe and stable operation of the multi-VSG converter parallel system.

Description

Technical Field

[0001] The present invention relates to the technical field of power oscillation suppression in a multi-VSG parallel system, and in particular to a power oscillation suppression method and system applicable to a multi-VSG converter parallel system. Background Art

[0002] Distributed power sources, such as electric vehicles, are a crucial component of the development of a new energy system and can effectively alleviate environmental pollution and the shortage of traditional energy. However, the high proportion of large-scale distributed resources connected to the grid will reduce the inertia of the entire grid, accelerate frequency changes, and increase the difficulty of regulation, impacting the safe and stable operation of the grid. If distributed resources such as electric vehicles can be converted into voltage sources that support the stable operation of the grid through cutting-edge power conversion technologies, enabling rapid frequency and voltage regulation, increasing inertia, and providing active support for the grid, the need for additional energy storage power stations can be effectively reduced, saving costs. Virtual synchronous generator technology has emerged to address this issue.

[0003] Virtual synchronous generator technology simulates the characteristics of synchronous machines by introducing virtual inertia and damping, providing the necessary frequency and voltage support for the power grid. However, similar to traditional synchronous machines, VSGs are subject to power oscillations. When the VSG power command experiences a step or the grid frequency experiences a disturbance, the VSG's output active power and output frequency experience significant oscillations. Power oscillations caused by grid frequency disturbances are particularly severe in systems with multiple VSGs connected in parallel. Furthermore, the overcurrent capacity of VSGs is far lower than that of traditional synchronous generators, making them susceptible to equipment damage and grid disconnection due to power oscillations.

[0004] Existing research on output power oscillation suppression has largely focused on a single VSG. While most methods can effectively suppress single-unit power oscillations, their effectiveness is limited when multiple VSGs are connected in parallel. Furthermore, existing research has mostly focused on either low-frequency power oscillations or synchronous power oscillations, without addressing the simultaneous suppression of both low-frequency and synchronous power oscillations, resulting in certain limitations. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology and provide a power oscillation suppression method and system suitable for a multi-VSG converter parallel system, so as to achieve coordinated suppression of low-frequency oscillation and synchronous oscillation of the multi-VSG parallel supercharging system, and ensure the safe and stable operation of the multi-VSG parallel supercharging system.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a power oscillation suppression method applicable to a multi-VSG converter parallel system, comprising the following steps:

[0007] S1, sample the VSG grid-connected side voltage and VSG grid-connected side current, and calculate the VSG output active power P e and reactive power Q e ;

[0008] S2, the VSG active power command value P ref The VSG output active and reactive power value P e Subtract the active power error ΔP and get the VSG reactive power command value Q ref and reactive power value Q e Subtract the active power error ΔP and the reactive power error ΔQ to obtain the effective value E0 and phase angle θ0 of the potential inside the VSG;

[0009] S3, introduce the error power low-pass filter feedforward compensation branch at the active power error ΔP to generate the compensation phase angle θ1; introduce the error power differential feedforward compensation branch at the active power error ΔP, and convert the output ΔP of SOGI into β Multiply by the coefficient k d3 Then generate the compensation phase angle θ2;

[0010] S4, adding the phase angle θ0 to the compensation phase angle θ1 and the compensation phase angle θ2 to obtain the final phase angle θ of the VSG;

[0011] S5, the effective value of the potential E0 and the phase angle θ in the VSG are modulated by PWM, and the VSG switch tube drive signal K is output. PWM .

[0012] The present invention is aimed at a multi-VSG parallel supercharging system. The power oscillation suppression method suitable for the multi-VSG parallel supercharging system is designed based on the error power feedforward compensation design, which can effectively suppress the power oscillation between the parallel VSGs. This solution has no additional communication means and is based on a feedforward compensation scheme without differential operations. Therefore, it is suitable for a homogeneous multi-VSG parallel supercharging system. It does not require additional communication means and differential operations, and does not affect the steady-state averaging effect of the fast charging system. Due to the error power low-pass filter feedforward compensation, it uses the virtual inertia J and the primary frequency modulation parameter D p The low-pass filtering link constructs an active feedforward term, and the ability of the fast charging system to suppress low-frequency power oscillations is improved by adjusting the feedforward parameters, which is equivalent to increasing the damping coefficient in the transient process and reducing the inertia coefficient in the transient process. Therefore, the present invention suppresses low-frequency power oscillations and synchronous power oscillations at the same time, and can achieve coordinated suppression of low-frequency oscillations and synchronous oscillations in the multi-VSG parallel supercharging system, thereby ensuring the safe and stable operation of the multi-VSG parallel supercharging system.

[0013] Effective value of potential inside VSG ΔU=U n -U e, U n 、U e They are the VSG output voltage reference command value and the actual value of the output voltage amplitude respectively.

[0014] VSG phase angle ω n is the rated angular velocity of the multi-VSG converter parallel system, D p is the damping coefficient, and J is the inertia coefficient.

[0015] The transfer function G of the feedforward branch f (s) is expressed as:

[0016] G f (s)=(k d1 s+k d2 ) / [(0.1Js 2 +3D p s+D p )(Js+D p )ω n ];

[0017] Among them, k d1 and k d2 is the feedforward parameter, J is the inertia coefficient, D p is the damping coefficient, s is a complex parameter, s=jω, j is the imaginary unit, ω n is the rated angular velocity of the multi-VSG converter parallel system.

[0018] k d1 =J-1,k d2 =-2D p .

[0019] The transfer function G of the feedforward SOGI branch is q (s) is:

[0020]

[0021] Where Q(s) is the output side ΔP of the feedforward SOGI branch β Regarding the transfer function of ΔP on the input side, k s is the feedforward SOGI branch gain coefficient, k d3 is the differential coefficient.

[0022] Error power differential feedforward compensation uses a generalized second-order integrator (SOGI) to construct an active feedforward term to achieve synchronous frequency power oscillation suppression, while filtering out high-frequency harmonics and reducing the interference of high-frequency harmonic components in the control link. In SOGI, when k s =1, for ω=ω n signal, Q(s) is equivalent to -s / ω n, plays a differential role; for ω<ω n The amplitude of the input and output signals remains unchanged; for ω>ω n The signal Q(s) plays a filtering role, which can reduce the interference of high-frequency harmonic components in the control link. In this solution, k can be set s =1, so it plays a differential role on the synchronous frequency component, and the introduction of the differential effect can move the synchronous oscillation pole away from the 0 axis, thereby suppressing the synchronous oscillation.

[0023]

[0024] As an inventive concept, the present invention also provides a power oscillation suppression system suitable for a multi-VSG converter parallel system, comprising a memory, a processor and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention is aimed at a multi-VSG parallel supercharging system. The power oscillation suppression method suitable for the multi-VSG parallel supercharging system based on the error power feedforward compensation design can effectively suppress the power oscillation between the parallel VSGs.

[0027] 2. The present invention is applicable to a homogeneous multi-VSG parallel supercharging system, which does not require additional communication means and differential operations, and does not affect the steady-state balancing effect of the fast charging system.

[0028] 3. The present invention suppresses low-frequency power oscillations and synchronous power oscillations simultaneously, which can achieve coordinated suppression of low-frequency oscillations and synchronous oscillations in a multi-VSG parallel supercharging system, ensuring the safe and stable operation of the multi-VSG parallel supercharging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of a multi-frequency power oscillation suppression method for a multi-VSG parallel supercharging system according to an embodiment of the present invention;

[0030] Figure 2 This is a SOGI control block diagram of an embodiment of the present invention;

[0031] Figure 3 Schematic diagram of power oscillation simulation of a multi-VSG parallel supercharging system using traditional VSG control;

[0032] Figure 4 Schematic diagram of power oscillation simulation of a multi-VSG parallel supercharging system using the oscillation suppression method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a method for suppressing multi-frequency power oscillations in a multi-VSG parallel supercharging system.

[0036] like Figure 1 As shown, the power oscillation suppression method applicable to a multi-VSG converter parallel system in this embodiment includes two parts: error power low-pass filter feedforward compensation and error power differential feedforward compensation. The error power low-pass filter feedforward compensation uses a low-pass filter link to construct an active power feedforward term, which can achieve low-frequency power oscillation suppression; the error power differential feedforward compensation uses a generalized second-order integrator to construct an active power feedforward term, which can achieve synchronous oscillation suppression. The power oscillation suppression method applicable to a multi-VSG converter parallel system includes the following steps:

[0037] 1) VSG grid-connected side voltage u gabc and VSG grid-connected current i gabc Sampling is performed and the instantaneous power is calculated to obtain the VSG output active power P e and reactive power Q e ;

[0038] 2) Set the VSG active and reactive power command value P ref and reactive power command value Q ref Respectively with the VSG output active and reactive power values ​​P e and reactive power value Q e Subtracting them yields the active power error ΔP and reactive power error ΔQ, and then using traditional VSG control to obtain the VSG internal potential effective value E0 and phase angle θ0; ΔU=U n -U e , U n 、U e are the VSG output voltage reference command value and the actual value of the output voltage amplitude respectively;

[0039] 3) Introduce error power low-pass filter feedforward compensation in the VSG control loop, that is, introduce feedforward G at the active power error ΔP f (s) branch generates compensation phase angle θ1, θ1 = G f (s)ΔP;

[0040] 4) Introduce error power differential feedforward compensation in the VSG control loop, that is, introduce a feedforward SOGI branch at the active power error ΔP, and convert the output ΔP of SOGI into β , multiplied by the coefficient k d3 Then generate the compensation phase angle θ2, θ2 = G q (s)ΔP;

[0041] 5) Add the phase angle θ0 obtained by traditional VSG control to the compensation phase angle θ1 output by the error power low-pass filter feedforward compensation and the compensation phase angle θ2 output by the error power differential feedforward compensation to obtain the final phase angle θ of the VSG;

[0042] 6) The VSG internal potential effective value E0 and the phase angle θ are output through the PWM controller to the VSG switch tube drive signal K PWM .

[0043] The error power low-pass filter feedforward compensation uses a virtual inertia J and a damping coefficient D p The low-pass filter link constructs the active feedforward term, and adjusts the feedforward parameter k d1 and k d2 To improve the ability of the fast charging system to suppress low-frequency power oscillations. The error power low-pass filter feedforward compensation does not require additional communication means and differential operations, and does not affect the steady-state averaging effect of the fast charging system. The error power low-pass filter feedforward branch G f (s) The transfer function is:

[0044] G f (s)=(k d1 s+k d2 ) / [(0.1Js 2 +3D p s+D p )(Js+D p )ω n ] (1)

[0045] Where k d1 and k d2 is the feedforward parameter, k d1 =J-1,k d2 =-2D p .

[0046] Error power differential feedforward compensation uses a generalized second-order integrator (SOGI) to construct an active feedforward term, and adjusts the differential coefficient k d3 To achieve the suppression of synchronous oscillation, it can also filter out high-frequency harmonics and reduce the interference of high-frequency harmonic components in the control link. The error power differential feedforward branch transfer function G q (s) is:

[0047]

[0048] Where Q(s) is the ΔP at the output side of SOGI. β Regarding the transfer function of ΔP on the input side, k s is the SOGI gain coefficient, k d3 is the differential coefficient, k d3 =-1e-6. The SOGI gain coefficient, its value k s = 1. When k s =1, for the frequency is the grid frequency ω n signal, Q(s) is equivalent to -s / ω n , plays a differential role; for frequencies <ω n The amplitude of the input and output signals remains unchanged; for frequencies > ω n The signal Q(s) plays a filtering role, which can reduce the interference of high-frequency harmonic components in the control link.

[0049] like Figure 2 As shown in the SOGI control block diagram of the error power differential feedforward compensation of this embodiment, ΔP is the SOGI input, ΔP α and ΔP β is the output, Q(s) is the ΔP at the output side of SOGI β Regarding the transfer function of ΔP on the input side, k s is the SOGI gain coefficient, the SOGI gain coefficient, its value k s = 1. When k s =1, for the frequency is the grid frequency ω n signal, Q(s) is equivalent to -s / ω n , plays a differential role; for frequencies <ω n The amplitude of the input and output signals remains unchanged; for frequencies > ω n The signal Q(s) plays a filtering role, which can reduce the interference of high-frequency harmonic components in the control link. d3 is the differential coefficient, k d3 =-1e-6.

[0050] The phase angle θ includes three parts: phase angle θ0, compensation phase angle θ1, and compensation phase angle θ2. Phase angle θ=θ0+θ1+θ2. The compensation phase angles θ1 and θ2 are the outputs of the error power low-pass filter feedforward compensation and the error power differential feedforward compensation, respectively. Their values ​​are:

[0051]

[0052] The error power low-pass filter feedforward compensation and the error power differential feedforward compensation need to work together to achieve the coordinated suppression of low-frequency oscillation and synchronous oscillation of the multi-VSG parallel supercharging system.

[0053] like Figure 3 As shown, in this embodiment, the multi-VSG parallel supercharging system adopts a power oscillation simulation diagram under traditional VSG control. The simulation system is a 4VSG parallel supercharging system, and the power instruction changes from 200kW to 240kW. It can be seen from the figure that low-frequency oscillation and synchronous oscillation exist simultaneously in the fast charging system. The maximum amplitude of the low-frequency oscillation is 84.5%, and the amplitude value of the synchronous oscillation increases from 9kW to 13.5kW.

[0054] like Figure 4 Figure 2 shows a schematic diagram of a power oscillation simulation of a multi-VSG parallel supercharging system using the oscillation suppression method according to an embodiment of the present invention. The simulation system is a 4VSG parallel supercharging system, and the power command changes from 200kW to 240kW. The figure shows that the maximum amplitude of the low-frequency oscillation in the fast-charging system is 22.7%, and the amplitude of the synchronous oscillation increases from 6kW to 9kW. The results show that the multi-frequency power oscillation suppression method of a multi-VSG parallel supercharging system according to this embodiment can indeed achieve coordinated suppression of the low-frequency oscillation and synchronous oscillation of the multi-VSG parallel supercharging system.

[0055] Example 2

[0056] Embodiment 2 of the present invention provides a system corresponding to the above-mentioned embodiment 1, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in the above-mentioned embodiment 1.

[0057] In some implementations, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk storage.

[0058] In other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors, which are not limited here.

[0059] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0060] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A power oscillation suppression method applicable to a multi-VSG converter parallel system, characterized in that: The following steps are involved: S1, sample the VSG grid-connected side voltage and VSG grid-connected side current, and calculate the VSG output active power P e and reactive power Q e ; S2, the VSG active power command value P ref The VSG output active and reactive power value P e Subtract and get the active power error ΔP; The VSG reactive power command value Q ref and reactive power value Q e Subtract the active power error ΔP and the reactive power error ΔQ to obtain the effective value E0 and phase angle θ0 of the potential inside the VSG; S3, introduce a feedforward branch at the active power error ΔP to generate a compensation phase angle θ1; introduce a feedforward SOGI branch at the active power error ΔP, and convert the output ΔP of SOGI to β Multiply by the coefficient k d3 Then generate the compensation phase angle θ2; S4, adding the phase angle θ0 to the compensation phase angle θ1 and the compensation phase angle θ2 to obtain the final phase angle θ of the VSG; S5, the effective value of the potential E0 and the phase angle θ in the VSG are modulated by PWM, and the VSG switch tube drive signal K is output. PWM ; The transfer function G of the feedforward branch f (s) is expressed as: G f (s)=(k d1 s+k d2 ) / [(0.1Js 2 +3D p s+D p )(Js+D p )ω n ]; Among them, k d1 and k d2 is the feedforward parameter, J is the inertia coefficient, D p is the damping coefficient, s is a complex parameter, s=jω, j is the imaginary unit, ω n is the rated angular velocity of the multi-VSG converter parallel system; k d1 =J-1,k d2 =-2D p ; The transfer function G of the feedforward SOGI branch is q (s) is: Where Q(s) is the output side ΔP of the feedforward SOGI branch β Regarding the transfer function of ΔP on the input side, k s is the feedforward SOGI branch gain coefficient, k d3 is the differential coefficient.

2. The power oscillation suppression method applicable to a multi-VSG converter parallel system according to claim 1, characterized in that: Effective value of potential inside VSG ΔU=U n -U e , U n 、U e are the VSG output voltage reference command value and the actual value of the output voltage amplitude, respectively. q is the reactive loop damping coefficient, k q is the reactive power regulation coefficient.

3. The power oscillation suppression method applicable to a multi-VSG converter parallel system according to claim 1, characterized in that: VSG phase angle ω n is the rated angular velocity of the multi-VSG converter parallel system, D p is the damping coefficient, and J is the inertia coefficient.

4. The power oscillation suppression method applicable to a multi-VSG converter parallel system according to claim 1, characterized in that:

5. A power oscillation suppression system for a multi-VSG converter parallel system, comprising a memory, a processor, and a computer program stored in the memory; characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 4.

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