VSG control method based on adaptive parameters, computer device and grid-connected converter

Abstract

The invention belongs to the technical field of power control, and particularly relates to a VSG control method based on adaptive parameters, a computer device and a grid-connected converter. The grid-connected converter is controlled through the VSG control method, and the VSG control method comprises the following steps: S1, obtaining the frequency deviation and the frequency change rate of the grid side of the grid-connected converter in real time; s2, the rotational inertia in VSG control is adjusted according to the frequency deviation and the frequency change rate, and if the absolute value of the frequency deviation does not exceed an inertia adjustment deviation threshold value or the absolute value of the frequency change rate does not exceed an inertia adjustment change rate threshold value, the rotational inertia is set to be fixed rotational inertia; if the absolute value of the frequency deviation exceeds an inertia adjustment deviation threshold value and the absolute value of the frequency change rate exceeds an inertia adjustment change rate threshold value, the rotational inertia is set as self-adaptive rotational inertia; the self-adaptive rotational inertia is larger than the fixed rotational inertia. The technical problem that an existing VSG system is poor in robustness is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power control, and particularly relates to a VSG control method based on adaptive parameters, a computer device, and a grid-connected converter. Background Art

[0002] When a grid-connected converter is controlled by a virtual synchronous generator (VSG), it can provide necessary voltage and frequency support for an active distribution network with distributed power sources and provide necessary damping for a microgrid with relatively poor stability. However, traditional VSG grid-connected converters use constant inertia and constant damping control, and their robustness is poor when the system is disturbed.

[0003] The published text of a Chinese patent application with the application publication number CN119171547A and the application publication date of December 20, 2024 discloses a VSG power-frequency control method for a parameter-adaptive energy storage and grid-connected system. This method adaptively adjusts the inertia and damping through the output frequency deviation and frequency change rate of the inverter, realizing stable output of the energy storage and grid-connected system under changes in dispatching instructions or various disturbances. Summary of the Invention

[0004] The object of the present invention is to provide a VSG control method based on adaptive parameters, a computer device, and a grid-connected converter. This method can adaptively adjust system parameters when the power supply system is disturbed to reduce overshoot and maintain system stability.

[0005] To solve the above technical problems, a technical solution of a VSG control method based on adaptive parameters provided by the present invention is as follows: A VSG control method based on adaptive parameters controls a grid-connected converter through the VSG control method. The VSG control method includes:

[0006] S1. Real-time obtain the frequency deviation and frequency change rate on the grid side of the grid-connected converter;

[0007] S2. Adjust the moment of inertia in the VSG control according to the frequency deviation and frequency change rate:

[0008] If the absolute value of the frequency deviation does not exceed the inertia adjustment deviation threshold or the absolute value of the frequency change rate does not exceed the inertia adjustment change rate threshold, set the moment of inertia to a fixed moment of inertia;

[0009] If the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold and the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, set the moment of inertia to an adaptive moment of inertia;

[0010] The adaptive moment of inertia is greater than the fixed moment of inertia.

[0011] The beneficial effect of the above technical solution is that the technical solution of the adaptive parameter-based VSG control method of the present invention is an improved invention. This invention improves the control strategy of existing new energy grid-connected converters. When the system is disturbed, the fluctuation of output power will cause frequency oscillation. By drawing on the static stability regulation principle of synchronous generators, the inertia is adaptively controlled, thereby reducing the oscillation amplitude of power and frequency, accelerating the speed at which power and frequency return to stable values, and improving the power supply stability of the new energy power generation system. This invention solves the technical problem of poor robustness of existing VSG systems.

[0012] Furthermore, if the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold, the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, and the frequency deviation and the frequency change rate have opposite signs, the adaptive moment of inertia is set to the first moment of inertia; the first moment of inertia J1 is obtained according to the following formula:

[0013]

[0014] Wherein, J0 is the fixed moment of inertia; c is the inertia adjustment factor greater than 0; T2 is the inertia time constant; s is the Laplace operator; is the frequency change rate.

[0015] Furthermore, if the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold, the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, and the frequency deviation and the frequency change rate have the same sign, the adaptive moment of inertia is set to the second moment of inertia; the second moment of inertia J2 is obtained according to the following formula:

[0016]

[0017] Wherein, J0 is the fixed moment of inertia; a and b are both inertia adjustment factors greater than 0; T1 is the inertia time constant; s is the Laplace operator; is the frequency change rate; Δf is the frequency deviation.

[0018] Furthermore, the method further comprises:

[0019] S3. Adjust the damping coefficient in VSG control according to the frequency deviation and frequency change rate:

[0020] If the absolute value of the frequency deviation exceeds the damping adjustment deviation threshold and the frequency change rate is not greater than 0, the damping coefficient is set to the first damping coefficient;

[0021] If the absolute value of the frequency deviation exceeds the damping adjustment deviation threshold and the frequency change rate is greater than 0, the damping coefficient is set to the second damping coefficient;

[0022] If the absolute value of the frequency deviation does not exceed the damping adjustment deviation threshold, the damping coefficient is set to the third damping coefficient;

[0023] The first damping coefficient is greater than the third damping coefficient, and the second damping coefficient is greater than the third damping coefficient.

[0024] Further, the second damping coefficient D2 is obtained according to the following formula:

[0025] D2 = D0 + d|Δf|

[0026] where D0 is the third damping coefficient; d is a damping adjustment factor greater than 0; and Δf is the frequency deviation.

[0027] Further, the first damping coefficient D1 is obtained according to the following formula:

[0028]

[0029] where D0 is the third damping coefficient; both e and g are damping adjustment factors greater than 0; is the rate of change of frequency; and Δf is the frequency deviation.

[0030] The present invention also provides a technical solution for a computer device: a computer device includes a processor, and the processor is configured to execute a computer program to implement the steps of the VSG control method based on adaptive parameters as described above.

[0031] The present invention also provides a technical solution for a grid-connected inverter: including an inverter controller, the inverter controller includes a processor, and the processor is configured to execute a computer program to implement the steps of the VSG control method based on adaptive parameters as described above. Description of the Drawings

[0032] Figure 1 is the topology diagram of the basic principle of VSG in the implementation manner of the VSG control method based on adaptive parameters of the present invention;

[0033] Figure 2 is the flowchart of the adaptive control of the moment of inertia J in the implementation manner of the VSG control method based on adaptive parameters of the present invention;

[0034] Figure 3 is the flowchart of the adaptive control of the damping coefficient D in the implementation manner of the VSG control method based on adaptive parameters of the present invention. Detailed Embodiments

[0035] The present invention improves the control strategy of existing new - energy grid - connected converters. When the system is disturbed, the fluctuation of the output power will cause the frequency to oscillate. By referring to the static - stability regulation principle of synchronous generators, the inertia is adaptively controlled, thereby reducing the oscillation amplitude of power and frequency, accelerating the speed of power and frequency recovery to the stable value, and improving the power - supply stability of the new - energy power - generation system. The present invention solves the technical problem of poor robustness of the existing VSG system.

[0036] Implementation manner of the VSG control method based on adaptive parameters:

[0037] The present invention provides a VSG control method based on adaptive parameters. When the new - energy power - generation system is disturbed by the outside world, according to the type of the disturbance suffered by the system, the rotational inertia J and the damping coefficient D are adaptively adjusted to reduce the oscillation and overshoot of the output power of the grid - connected converter, avoid large power shocks leading to over - current protection; at the same time, reduce the adjustment time for the system to return to the steady state after being disturbed, enable the grid - connected converter to have good dynamic and steady - state characteristics, and enable the VSG to balance the stability and response speed under different working conditions.

[0038] As Figure 1 shown, the DC bus is connected to the grid - connected converter through a DC capacitor. The electric energy at the outlet of the grid - connected converter is supplied to the load after passing through an LC filter, and then there is an AC large - scale power grid behind the load. The whole system can work in the off - grid or grid - connected mode. The DC bus, capacitor, grid - connected converter, and LC filter as a whole can be equivalently regarded as a virtual synchronous generator (i.e., Figure 1 described within the dashed box in

[0039] According to the functional expression of the VSG, the functional relationship between the rotational inertia and the VSG frequency change rate is obtained. At the same time, according to the relationship between the rotational inertia and the damping coefficient, the functional relationship between the damping coefficient and the absolute value of the frequency change rate is further obtained. According to the functional relationship, an adaptive rotational - inertia and damping - coefficient control structure diagram is designed, as Figures 2 - 3 shown.

[0040] The adaptive - regulation process of the rotational inertia J is as Figure 2 shown. The system frequency deviation Δf and the frequency change rate df / dt are monitored in real - time. If the absolute value of the frequency deviation Δf does not exceed the inertia - regulation deviation threshold K J0 or the absolute value of the frequency change rate df / dt does not exceed the inertia - regulation change - rate threshold K J1 , then the rotational inertia J is not adjusted (i.e., let J = J0, that is, the rotational inertia is fixed).

[0041] If the absolute value of the frequency deviation Δf exceeds the inertia regulation deviation threshold K J0 , and the absolute value of the frequency change rate df / dt exceeds the inertia regulation change rate threshold K J1 and Δf and df / dt have the same sign (i.e., (df / dt)Δf > 0), set the moment of inertia J (i.e., the second moment of inertia) according to the following formula to make Δf and df / dt return to the allowable range as quickly as possible:

[0042]

[0043] where a and b are both inertia regulation factors, a > 0, b > 0; is a first-order inertia link, T1 is the inertia time constant, and s is the Laplace operator.

[0044] If the absolute value of the frequency deviation Δf exceeds the inertia regulation deviation threshold K J0 , and the absolute value of the frequency change rate df / dt exceeds the inertia regulation change rate threshold K J1 and Δf and df / dt have opposite signs (i.e., (df / dt)Δf ≤ 0), then the moment of inertia J needs to be appropriately increased to make Δf and df / dt quickly return to the allowable range and avoid large oscillations, that is, set the moment of inertia J (i.e., the first moment of inertia) according to the following formula:

[0045]

[0046] where c is the inertia regulation factor, c > 0; is a first-order inertia link, T2 is the inertia time constant, and s is the Laplace operator.

[0047] The adaptive adjustment process of the damping coefficient D is as Figure 3 shown. Real-time monitor the system frequency deviation Δf and the frequency change rate df / dt. If the absolute value of the frequency deviation Δf does not exceed the damping regulation deviation threshold K d , then do not adjust the damping coefficient D (i.e., let D = D0, i.e., the third damping coefficient).

[0048] If the absolute value of the frequency deviation Δf exceeds the damping regulation deviation threshold K d and the frequency change rate df / dt is positive (i.e., df / dt > 0), then the damping coefficient D (i.e., the second damping coefficient) needs to be set according to the following formula to accelerate the recovery of f (the current frequency) to f ref (the frequency reference value), Δf = f - f ref :

[0049] D = D0 + d|Δf|

[0050] where d is the damping regulation factor, d > 0.

[0051] If the absolute value of the frequency deviation Δf exceeds the damping adjustment deviation threshold K d and the rate of change of frequency df / dt is not positive (i.e., df / dt ≤ 0), then the damping coefficient D (i.e., the first damping coefficient) needs to be set according to the following formula to reduce the speed at which f deviates backward from f ref :

[0052]

[0053] where e and g are both damping adjustment factors, e > 0, g > 0.

[0054] Figure 2 、 Figure 3 The control idea of adaptively adjusting the moment of inertia J and the damping coefficient D in ,

[0052] , , ,

[0053] is that when the system is disturbed, by detecting the amount of frequency fluctuation, after setting the corresponding thresholds and constraint conditions, the values of J and D are adaptively adjusted according to the degree of frequency fluctuation.

[0055] During the operation of the system, the active power deviation ΔP, the amplitude of power oscillation, the frequency deviation Δf, and the rate of change of frequency df / dt are monitored in real time; at the same time, the upper and lower limits of the moment of inertia J, the damping D, and their adjustment rates are set to avoid affecting the stability of the system operation due to large mutations of J and D.

[0056] According to the monitored data, when the system is disturbed, in accordance with the control structure diagram of the adaptive adjustment method, the values of the moment of inertia and the damping coefficient are dynamically and adaptively adjusted to make the moment of inertia, the damping coefficient, the frequency, and the power adapt to each other, ensuring the effectiveness and flexibility of the control.

[0057] This adjustment method combines the power angle characteristic curve of the synchronous generator and the frequency oscillation curve to design an adaptive control strategy for the moment of inertia and the damping coefficient. In the specific execution process package, it includes the following steps:

[0058] (1) Obtain the amount of frequency change Δf and the rate of change of frequency df / dt of the system when the system is disturbed.

[0059] (2) Set the change threshold K of Δf J0 、K d and the change threshold K of df / dt J1 to avoid unnecessary actions of the control system caused by small frequency fluctuations.

[0060] (3) Set the corresponding constraint conditions. When the amount of frequency change Δf and the rate of change of frequency df / dt meet the corresponding constraint conditions, the adaptive adjustment of J and D is carried out according to the corresponding mathematical model, and the specific calculation formulas are as shown in Figure 2 、 3 .

[0061] Embodiment of computer device:

[0062] A computer device includes a processor, which is used to execute a computer program to implement the steps of the VSG control method based on adaptive parameters as described above. The specific VSG control method based on adaptive parameters has been introduced in sufficient detail in the above embodiment of the VSG control method based on adaptive parameters, and will not be repeated here.

[0063] Specifically, the processor can be a CPU, or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc. The processor can also be a processor that supports the advanced reduced instruction set machine (ARM) architecture.

[0064] Embodiment of grid-connected inverter:

[0065] A grid-connected inverter includes an inverter controller, and the inverter controller includes a processor, which is used to execute a computer program to implement the steps of the VSG control method based on adaptive parameters as described above. The specific VSG control method based on adaptive parameters has been introduced in sufficient detail in the above embodiment of the VSG control method based on adaptive parameters, and will not be repeated here.

[0066] Specifically, the processor can be a CPU, or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc. The processor can also be a processor that supports the advanced reduced instruction set machine (ARM) architecture.

[0067] The present invention has the following characteristics:

[0068] The adaptive adjustment method of the present invention only changes the control strategy of the new energy grid-connected converter, adaptively adjusts the values of inertia and damping when the power supply system is disturbed, reduces the overshoot and oscillation of power and frequency during the adjustment process, and improves the power supply stability of the system without adding additional hardware devices.

[0069] The present invention sets a smaller threshold. When the system frequency changes, the rate of change of the frequency is reduced by increasing the inertia to improve the stability during the operation of the system; when there is no exponential factor m in the rate-of-change-of-frequency term, without basically changing the inertia adjustment accuracy, the complexity of the inertia adjustment formula is reduced, the configuration requirements of the controller hardware are reduced, and the speed of inertia adjustment is improved.

[0070] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still make modifications to the technical solutions described in the foregoing embodiments without creative efforts, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A VSG control method based on adaptive parameters, characterized in that Controlling a grid-connected converter through a VSG control method, the VSG control method comprising: S1. Obtaining in real time the frequency deviation and the frequency change rate on the grid side of the grid-connected converter; S2. Adjusting the moment of inertia in the VSG control according to the frequency deviation and the frequency change rate: If the absolute value of the frequency deviation does not exceed the inertia adjustment deviation threshold or the absolute value of the frequency change rate does not exceed the inertia adjustment change rate threshold, set the moment of inertia to a fixed moment of inertia; If the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold and the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, set the moment of inertia to an adaptive moment of inertia; The adaptive moment of inertia is greater than the fixed moment of inertia.

2. The VSG control method based on adaptive parameters according to claim 1, characterized in that, If the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold, the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, and the signs of the frequency deviation and the frequency change rate are opposite, set the adaptive moment of inertia to a first moment of inertia; the first moment of inertia J1 is obtained according to the following formula: Among them, J0 is the fixed moment of inertia; c is the inertia adjustment factor greater than 0; T2 is the inertia time constant; s is the Laplace operator; is the frequency change rate.

3. The VSG control method based on adaptive parameters according to claim 1, characterized in that If the absolute value of the frequency deviation exceeds the inertia adjustment deviation threshold, the absolute value of the frequency change rate exceeds the inertia adjustment change rate threshold, and the signs of the frequency deviation and the frequency change rate are the same, set the adaptive moment of inertia to a second moment of inertia; the second moment of inertia J2 is obtained according to the following formula: Among them, J0 is the fixed moment of inertia; both a and b are inertia adjustment factors greater than 0; T1 is the inertia time constant; s is the Laplace operator; is the frequency change rate; Δf is the frequency deviation.

4. The VSG control method based on adaptive parameters according to claim 1, wherein The method further comprises: S3. Adjusting the damping coefficient in the VSG control according to the frequency deviation and the frequency change rate: If the absolute value of the frequency deviation exceeds the damping adjustment deviation threshold and the frequency change rate is not greater than 0, set the damping coefficient to a first damping coefficient; If the absolute value of the frequency deviation exceeds the damping adjustment deviation threshold and the frequency change rate is greater than 0, set the damping coefficient to a second damping coefficient; If the absolute value of the frequency deviation does not exceed the damping adjustment deviation threshold, set the damping coefficient to a third damping coefficient; The first damping coefficient is greater than the third damping coefficient, and the second damping coefficient is greater than the third damping coefficient.

5. The VSG control method based on adaptive parameters according to claim 4, characterized in that The second damping coefficient D2 is obtained according to the following formula: D2 = D0 + d|Δf| where D0 is the third damping coefficient; d is a damping adjustment factor greater than 0; and Δf is the frequency deviation.

6. The VSG control method based on adaptive parameters according to claim 4, wherein The first damping coefficient D1 is obtained according to the following formula: where D0 is the third damping coefficient; both e and g are damping adjustment factors greater than 0; is the frequency change rate; Δf is the frequency deviation.

7. A computer device, comprising a processor, characterized in that, The processor is configured to execute a computer program to implement the steps of the VSG control method based on adaptive parameters according to any one of claims 1 to 6.

8. A grid-connected converter, comprising a converter controller, and the converter controller includes a processor, characterized in that, The processor is configured to execute a computer program to implement the steps of the VSG control method based on adaptive parameters according to any one of claims 1 to 6.

Images