A VSG control system and method based on an improved equivalent transient damping

Abstract

The present invention provides a VSG control system and method based on an improved equivalent transient damping. First, a small-signal model of the VSG grid-connected active power closed-loop is established and its active power steady-state deviation is analyzed. Then, a transient damping control link is introduced into the active power control loop of the virtual synchronous generator, and a second-order band-pass filter control module based on the equivalent transient damping is obtained. Furthermore, the active power steady-state deviation after the introduction of the equivalent transient damping control is analyzed. To further eliminate the active power steady-state deviation caused by the primary frequency modulation parameters, an improved equivalent transient damping control G M (s) is introduced. Finally, the small-signal model of the active power based on the equivalent transient damping control is analyzed, and a compensation factor β is introduced into the control G M (s), and the parameter β is adjusted to eliminate the active power steady-state deviation caused by the primary frequency modulation parameters. The VSG control system and method based on the improved equivalent transient damping have a simple structure, wide applicability, and are easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of virtual synchronous generators, and particularly to a VSG control system and method based on an improved equivalent transient damping. Background Art

[0002] By simulating the mechanical rotor motion equation of a synchronous generator in a control algorithm, a converter can also have inertia and damping characteristics similar to those of a traditional synchronous generator. However, while enhancing the system equivalent inertia and equivalent damping, problems such as synchronous frequency oscillation, subsynchronous oscillation, and steady-state active power deviation under grid frequency disturbance also arise. Therefore, a control system and method are needed to solve the problem of steady-state active power deviation of VSG output under grid frequency disturbance and improve the stability and reliability of the system.

[0003] Currently, the stability research based on VSG control mostly focuses on suppressing system synchronous frequency oscillation and subsynchronous oscillation problems. There is less research on eliminating the steady-state active power deviation of VSG output under grid frequency disturbance, and most of them only study the active power steady-state error caused by virtual damping and do not involve the active power steady-state error problem introduced by the primary frequency modulation coefficient. In view of the above problems, the present invention proposes a VSG control system and method based on an improved equivalent transient damping, aiming to improve the dynamic performance and the ability to eliminate steady-state active power deviation of VSG under grid frequency disturbance by introducing an equivalent transient damping control link and adjusting the compensation factor β. Summary of the Invention

[0004] The purpose of the present invention is to provide a VSG control system and method based on an improved equivalent transient damping to solve the problem of steady-state active power deviation of the existing VSG control system under grid frequency disturbance.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides a VSG control method based on an improved equivalent transient damping. A transient damping control link is introduced into the active power control loop of the virtual synchronous generator, and the steady-state active power deviation after introducing the equivalent transient damping control G A (s) is analyzed. The first improved equivalent transient damping control G M (s) is introduced, and then the compensation factor β is introduced into the control G M (s). By adjusting the parameter β, the steady-state active power deviation caused by the primary frequency modulation parameter is eliminated.

[0007] In an implementable embodiment of the first aspect, the method includes the following steps:

[0008] Step 1: Establish a closed-loop small-signal model of grid-connected active power based on VSG control and analyze the influencing factors of active power steady-state deviation. The active power control loop and the output active power small-signal model of VSG are as follows:

[0009]

[0010] In the formula, P ref is the given active power; P e is the output active power of VSG; ω is the output angular frequency; ω n is the rated angular frequency; D p is the virtual damping parameter; k ω is the primary frequency regulation parameter; J p is the virtual inertia parameter; s is the differential operator; δ is the phase angle difference; ω g is the grid frequency; E0 is the steady-state value of the output voltage; U g is the grid voltage amplitude; X is the line reactance;

[0011] According to the above expression, the closed-loop small-signal model of VSG active power is obtained as:

[0012]

[0013] In the formula, K is the synchronization coefficient of VSG, and K = E0U g / X.

[0014] According to the above formula, under the condition of grid frequency disturbance, the active power steady-state deviation is:

[0015]

[0016] In the formula, E Pe is the active power steady-state deviation.

[0017] Step 2: Introduce a transient damping control link into the active power control loop of VSG to obtain a second-order band-pass filter control module based on equivalent transient damping. The transient damping control is as follows:

[0018]

[0019] In the formula, T is the time constant;

[0020] Introduce a second-order band-pass filter control module based on equivalent transient damping:

[0021]

[0022] Based on the above equations, the equivalent transient damping control G A (s) is:

[0023]

[0024] Step 3: Based on Step 2, analyze the active power steady-state deviation after introducing the equivalent transient damping control. To further eliminate the steady-state deviation, introduce the improved equivalent transient damping control G M (s). After introducing the equivalent transient damping control G A (s), the transfer function from Δω g to ΔP e is:

[0025]

[0026] wherein,

[0027] It can be seen from the analysis that it is difficult to eliminate the active power steady-state deviation caused by k A by a simple method only with the control G ω (s). Therefore, introduce the improved equivalent transient damping control G M (s) to replace the control G A (s):

[0028]

[0029] After introducing the control G M (s), the transfer function from Δω g to ΔP e is:

[0030]

[0031] wherein,

[0032]

[0033] Step 4: Based on Step 3, analyze the small-signal model of the active power based on the equivalent transient damping control. Introduce a compensation factor β into the control G M (s), and adjust the parameter β to eliminate the active power steady-state deviation caused by the primary frequency regulation parameter. The improved equivalent transient damping control G F (s) after introducing the compensation factor β is:

[0034]

[0035] After introducing the control G F (s), the transfer function from Δω g to ΔP e is:

[0036]

[0037] At this time, the active power steady-state deviation is as follows:

[0038]

[0039] Adjust the compensation factor β so that β = k ω 2 , to eliminate the steady-state deviation caused by the primary frequency modulation coefficient k ω caused.

[0040] In a second aspect, the present invention provides an electronic device, including: one or more processors; one or more memories; the one or more memories store one or more programs, when the one or more programs are executed by the one or more processors, the electronic device is enabled to execute the steps in the above-mentioned VSG control method based on improved equivalent transient damping. When the program runs, the three-phase voltage and grid-connected current data of the virtual synchronous generator are obtained through sensors.

[0041] In a third aspect, the present invention provides a VSG control system based on improved equivalent transient damping, which includes a data processing module, a voltage sensor, a current sensor and a processor running a control program. The voltage sensor and the current sensor transmit the obtained three-phase output voltage and three-phase grid-connected current data of the virtual synchronous generator to the data processing module, and the data processing module transmits the data to the running processor.

[0042] The beneficial effects of the present invention are as follows:

[0043] (1) The present invention proposes a VSG control method based on improved equivalent transient damping. By introducing an equivalent transient damping control link and adjusting the compensation factor β, the problem of active power steady-state deviation caused by the VSG virtual damping parameter and the primary frequency modulation parameter under grid frequency disturbance is eliminated, and the system damping characteristic can be flexibly adjusted by adjusting the transient damping time constant T.

[0044] (2) By adopting the improved equivalent transient damping control, the system damping characteristic is enhanced. While eliminating the active power steady-state deviation, the system frequency characteristic is also improved in terms of frequency offset, frequency change rate and system response time, and the dynamic stability of the system is improved. The present invention has wide applicability and its structure is simple and easy to implement. Description of the Drawings

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained according to the provided drawings.

[0046] Figure 1 This is the VSG grid-connected topological structure diagram in the present invention;

[0047] Figure 2 This is the improved equivalent transient damping control block diagram based on VSG control in the present invention;

[0048] Figure 3 This is the simulation result of the system active power when the grid frequency is disturbed under three different controls in the present invention;

[0049] Figure 4 This is the active power simulation result based on the equivalent transient damping G A (s) control under different T parameters in the present invention;

[0050] Figure 5 This is the active power simulation result based on the improved equivalent transient damping G F (s) control under different T parameters in the present invention;

[0051] Figure 6 This is the active power simulation result based on the equivalent transient damping G A (s) control under different grid frequency disturbances in the present invention;

[0052] Figure 7 This is the active power simulation result based on the improved equivalent transient damping G F (s) control under different grid frequency disturbances in the present invention. Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] The embodiments of the present invention aim to propose a control method for eliminating the active power steady-state deviation caused by traditional VSG under grid frequency disturbances. By introducing a VSG control method based on improved equivalent transient damping, the purpose of eliminating the grid-connected active power steady-state deviation under grid frequency disturbances is achieved. The present invention studies the topological structure of the VSG grid-connected system, and the topological structure is as Figure 1 shown.

[0055] Based on Figure 1For the VSG grid-connected system topology shown in the figure, establish the active closed-loop small-signal model of the VSG grid-connected system and analyze its active steady-state deviation; then introduce a transient damping control link into the active power control loop of the virtual synchronous generator, and obtain a second-order band-pass filter control module based on equivalent transient damping; further analyze the active steady-state deviation after introducing the equivalent transient damping control, and in order to further eliminate the active steady-state deviation caused by the primary frequency modulation parameters, introduce the first improved equivalent transient damping control G M (s); finally, analyze the active power small-signal model based on the equivalent transient damping control, introduce a compensation factor β into the control G M (s), and obtain the second improved equivalent transient damping control G F (s), and eliminate the active steady-state deviation caused by the primary frequency modulation parameters by adjusting the parameter β.

[0056] This control method specifically includes the following steps:

[0057] Step 1: Establish an active power closed-loop small-signal model based on VSG control, and analyze the influencing factors of the active steady-state deviation. The active power control loop and the output active power small-signal model of the VSG are as follows:

[0058]

[0059] In the formula, P ref is the given active power; P e is the active power output by the VSG; ω is the output angular frequency; ω n is the rated angular frequency; D p is the virtual damping parameter; k ω is the primary frequency modulation parameter; J p is the virtual inertia parameter; s is the differential operator; δ is the phase angle difference; ω g is the grid frequency; E0 is the steady-state value of the output voltage; U g is the grid voltage amplitude; X is the line reactance;

[0060] According to the above expression, the active power closed-loop small-signal model of the VSG is obtained as:

[0061]

[0062] In the formula, K is the synchronization coefficient of the VSG, and K = E0U g / X;

[0063] According to the above formula, it can be seen that under the condition of grid frequency disturbance, the active steady-state deviation is:

[0064]

[0065]

[0066] Wherein, E Pe is the active steady-state deviation.

[0067] Step 2: As Figure 2 shown, introduce a transient damping control link into the active power control loop of the VSG to obtain a second-order band-pass filter control module based on equivalent transient damping. The transient damping control is:

[0068]

[0069] Wherein, T is the time constant;

[0070] Introduce a second-order band-pass filter control module based on equivalent transient damping:

[0071]

[0072] Based on the above equations, obtain the equivalent transient damping control G A (s) as:

[0073]

[0074] Step 3: Based on Step 2, analyze the active steady-state deviation after introducing the equivalent transient damping control. To further eliminate the steady-state deviation, introduce an improved equivalent transient damping control G M (s). According to Figure 2 it can be known that after introducing the equivalent transient damping control G A (s), the transfer function from Δω g to ΔP e is:

[0075]

[0076] Wherein,

[0077] From the expression of the control G A (s), it can be seen that the active steady-state deviation caused by k ω is related to the parameters on the denominator of the control G A (s). After introducing a compensation factor α on the denominator of the control G A (s):

[0078]

[0079] After introducing the equivalent transient damping control G Aα (s) containing the compensation factor α, the transfer function from Δω g to ΔP e is:

[0080]

[0081] To eliminate the active power steady-state deviation caused by k ω the compensation factor α = -k is adjusted ω ; however, when α = -k ω the order of the control G A (s) drops to the first order, resulting in the introduction of a new active power steady-state deviation:

[0082]

[0083] It can be seen through analysis that it is difficult to eliminate the active power steady-state deviation caused by k A by a simple method only with the control G ω Therefore, an improved equivalent transient damping control G M (s) is introduced to replace the control G A (s):

[0084]

[0085] After introducing the control G M (s), the transfer function from Δω g to ΔP e is:

[0086]

[0087] In the formula,

[0088]

[0089] Step 4: Based on Step 3, analyze the active power small-signal model based on the equivalent transient damping control. A compensation factor β is introduced into the control G M (s), and the parameter β is adjusted to eliminate the active power steady-state deviation caused by the primary frequency regulation parameter. The improved equivalent transient damping control G F (s) after introducing the compensation factor β is:

[0090]

[0091] After introducing the control G F (s), the transfer function from Δω g to ΔP e is:

[0092]

[0093] At this time, the active power steady-state deviation is:

[0094]

[0095] Adjust the compensation factor β to make β = k ω 2 , so as to eliminate the steady-state deviation caused by the primary frequency modulation coefficient k ω induced steady-state deviation.

[0096] In order to verify the effect of the proposed control method on eliminating the steady-state deviation of grid-connected active power and its wide applicability, Figures 3 - 7 the active power simulation results under different control methods, different control parameters and different grid frequency disturbances are given respectively.

[0097] Figure 3 The active power simulation results under traditional VSG control, equivalent transient damping control and improved transient damping control are given. It can be seen from Figure 3 that under the -0.05Hz grid frequency disturbance, the active power output deviation under traditional VSG control is the largest, and the steady-state deviation of active power under transient damping control is smaller. This is because the transient damping control can only eliminate the steady-state deviation brought by the virtual damping parameter and cannot suppress the active steady-state deviation caused by the primary frequency modulation of active power; while the improved transient damping control in the embodiment of the present invention can completely eliminate the active power output deviation.

[0098] Figure 4 and Figure 5 give the active power simulation results based on equivalent transient damping control and improved equivalent damping control under different T parameters. At t = 6s, the grid frequency steps -0.05Hz. It can be seen from the simulation results that there are dynamic oscillations and overshoots in the active power. As the parameter T increases, both the active power overshoot and the recovery time decrease, and the oscillation frequency increases accordingly. Therefore, the change of the parameter T is equivalent to adjusting the damping and inertia parameters of the system at the same time. Compared with the equivalent transient damping control, the improved equivalent transient damping control proposed in the embodiment of the present invention can not only completely eliminate the active steady-state deviation, but also has good dynamic characteristics.

[0099] Figure 6 and Figure 7 give the active power simulation results based on equivalent transient damping control and improved equivalent damping control under different grid frequency disturbances. Different grid frequency steps are added as disturbances at t = 6s respectively. It can be seen from the simulation results that the greater the grid frequency step disturbance, the greater the active steady-state error under equivalent transient damping control. However, when the improved equivalent transient damping control is applied, as the grid frequency step disturbance increases, its overshoot also increases, but the active steady-state deviation is zero under different grid frequency steps, with good dynamic performance and active steady-state deviation elimination effect, verifying the wide applicability of the control proposed in the present invention under different working conditions.

[0100] In a second aspect, the present invention provides an electronic device, comprising: one or more processors; one or more memories; the one or more memories store one or more programs, when the one or more programs are executed by the one or more processors, the electronic device is caused to execute the steps in the above-mentioned VSG control method based on improved equivalent transient damping. When the program runs, the three-phase output voltage of the virtual synchronous generator and the grid-connected current data are acquired through sensors.

[0101] In a third aspect, the present invention provides a VSG control system based on improved equivalent transient damping, which includes a data processing module, a voltage sensor, a current sensor and a processor running the above control program. The voltage sensor and the current sensor transmit the acquired three-phase output voltage of the virtual synchronous generator and the three-phase grid-connected current data to the data processing module, and the data processing module transmits the data to the running processor.

[0102] The reference to "an embodiment" or "embodiments" in the specification means that the specific features, structures or characteristics described in connection with the embodiments are included in at least one exemplary implementation or technology disclosed according to the present application. The appearance of the phrase "in an embodiment" in various places in the specification does not necessarily all refer to the same embodiment.

[0103] The present application disclosure also relates to an operating device for executing the control program. The device can be specifically constructed for the required purpose or it can include a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program can be stored in a computer-readable medium, such as, but not limited to, any type of disk, including floppy disks, optical disks, CD-ROMs, magneto-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, application specific integrated circuits (ASICs) or any type of medium suitable for storing electronic instructions, and each can be coupled to a computer system bus. In addition, the computers mentioned in the specification can include a single processor or can be an architecture involving multiple processors for increased computing power.

[0104] The processes and displays presented herein inherently do not involve any particular computer or other apparatus. A variety of general-purpose systems may also be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform one or more method steps. The structure for various such systems is discussed in the following description. Additionally, any specific programming language sufficient to implement the techniques and embodiments disclosed in this application may be used. A variety of programming languages may be used to implement the present disclosure, as discussed herein. Further, the language used in this specification has been principally selected for readability and instructional purposes and may not have been selected to delineate or circumscribe the scope of the disclosed subject matter. Accordingly, the present application disclosure is intended to illustrate rather than limit the scope of the concepts discussed herein.

Claims

1. A VSG control method based on an improved equivalent transient damping, characterized in that Introduce a transient damping control link into the active power control loop of the virtual synchronous generator, and analyze the active power steady-state deviation after introducing the equivalent transient damping control The formula for the equivalent transient damping control is as follows: （6）； wherein, is the rated angular frequency, is the virtual damping parameter, is the primary frequency regulation parameter, is the virtual inertia parameter, s is the differential operator, and T is the time constant; Introduce the first improved equivalent transient damping control , the first improved equivalent transient damping control The formula is as follows: （12）； Then, a compensation factor β is introduced into the first improved equivalent transient damping control to obtain the second improved equivalent transient damping control , to The transfer function is , eliminating the active power steady-state deviation caused by the primary frequency regulation parameters, where the formula for the second improved equivalent transient damping control is: （19）； The active power steady-state deviation is: （21）； Adjust the compensation factor β to make β = k ω 2 to eliminate the steady-state deviation caused by the primary frequency regulation coefficient where is the grid frequency and is the active power output of the VSG.

2. The VSG control method based on an improved equivalent transient damping according to claim 1, characterized in that It includes the following steps: Step 1: Establish a closed-loop small-signal model of grid-connected active power based on VSG control, and analyze the influencing factors of active power steady-state deviation; Step 2: Introduce a transient damping control link into the active power control loop of VSG to obtain a second-order band-pass filter control module based on equivalent transient damping; Step 3: Analyze the active power steady-state deviation after introducing the equivalent transient damping control. To further eliminate the steady-state deviation, introduce the first improved equivalent transient damping control ; Step 4: Establish a small-signal model of active power based on equivalent transient damping control, and introduce a compensation factor β in the control to eliminate the active power steady-state deviation caused by primary frequency regulation parameters by adjusting the compensation factor β.

3. A VSG control method based on an improved equivalent transient damping according to claim 2, characterized in that The small-signal model in Step 1 is a closed-loop small-signal model of grid-connected active power corresponding to the grid frequency of the output active power and under the disturbance of the active power reference. Considering the primary frequency modulation of active power, establish the active power control loop of VSG and the small-signal model of the output active power: （1）； Wherein, is the given active power, is the active power output by the VSG, ω is the output angular frequency, is the rated angular frequency, is the virtual damping parameter, is the primary frequency regulation parameter, is the virtual inertia parameter, s is the differential operator, is the phase angle difference, is the grid frequency, is the steady-state value of the output voltage, is the amplitude of the grid voltage, is the line reactance; According to Equation (1), the closed-loop small-signal model of VSG active power is obtained as: （2）； In the formula, is the synchronization coefficient of the VSG, and .

4. A VSG control method based on an improved equivalent transient damping according to claim 3, characterized in that Under the condition of grid frequency disturbance, the active power steady-state deviation is: （3）； In the formula, is the active power steady-state deviation.

5. A VSG control method based on an improved equivalent transient damping according to claim 4, characterized in that Introduce a transient damping control link into the active power control loop of VSG, and the transient damping control is: （4）； In the formula, T is the time constant.

6. A VSG control method based on an improved equivalent transient damping according to claim 5, characterized in that Introduce a second-order band-pass filter control module based on equivalent transient damping: (5); obtaining equivalent transient damping control based on formula (5) formula 7. The VSG control method based on an improved equivalent transient damping according to claim 6, characterized in that Introduce equivalent transient damping control After that, to The transfer function is as follows: （7）； In the formula, (8); （9）； （10）； （11）； Introduce the first improved equivalent transient damping control to replace the control , and obtain the formula of the first improved equivalent transient damping control ; Introduce the first improved equivalent transient damping control After that, to The transfer function is: （13）； where q1 = (14); b1 = （15）； m1= （16）； n1 = （17）； p1= K (18).

8. The VSG control method based on an improved equivalent transient damping according to claim 7, characterized in that The secondary improved equivalent transient damping control after introducing the compensation factor β Based on the formula, the above-mentioned secondary improved equivalent transient damping control After that, To The transfer function is: （20）。 9. A VSG control system based on an improved equivalent transient damping, characterized in that, It includes: One or more processors; One or more memories; the one or more memories store one or more programs. When the one or more programs are executed by the one or more processors, each step in the VSG control method based on an improved equivalent transient damping according to any one of claims 1-8 is executed. When the program runs, the three-phase voltage and grid-connected current data of the virtual synchronous generator are obtained through sensors.

10. The VSG control system based on an improved equivalent transient damping according to claim 9, characterized in that, It includes a data processing module, a voltage sensor, a current sensor and a processor with an operation control program. The voltage sensor and the current sensor transmit the obtained three-phase output voltage and three-phase grid-connected current data of the virtual synchronous generator to the data processing module, and the data processing module transmits the data to the running processor.

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