Wind energy conversion system frequency response method controlled by adaptive virtual synchronous generator

Abstract

The invention provides a wind energy conversion system frequency response method controlled by a self-adaptive virtual synchronous generator. The method comprises the step of adaptively adjusting the virtual inertia of the virtual synchronous generator according to the frequency change rate of a power grid. By calculating the rate of power grid frequency change and dynamically adjusting the virtual inertia, the virtual synchronous generator can provide more inertia support when the power grid frequency is disturbed, so that the power grid frequency response is optimized, and particularly, the recovery effect of the power grid frequency can be remarkably improved when small-scale power disturbance occurs. According to the method, the virtual inertia is adjusted through the proportional-integral controller, so that stable operation of the system is ensured, frequency fluctuation is effectively coped, and the problem of unstable frequency or too slow recovery is avoided. The method can flexibly adjust the virtual inertia according to the actual operation condition of the power grid, and improves the frequency adjustment capability of the wind power generation system.

Description

Technical Field

[0001] The present invention generally relates to the technical field of converter control, and in particular to a frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator. Background Art

[0002] With the rapid development of renewable energy, especially the large-scale access of wind power and photovoltaic power generation, traditional power systems are facing unprecedented challenges. Traditional power systems mainly rely on a large number of synchronous generators to maintain the stability of the power grid. These generators have strong rotational inertia and can effectively provide inertial support to help the power grid cope with frequency disturbances. However, renewable energy systems such as wind power and photovoltaic power generation usually use inverters to access the power grid. These systems lack rotational inertia and synchronization capabilities, resulting in a decrease in the inertial support capacity of the power grid and limited frequency regulation capabilities.

[0003] Currently, one way to solve this problem is to simulate the inertia characteristics of synchronous generators through virtual synchronous generator (VSG) technology. VSG controls the inverter output so that renewable energy systems such as wind turbines can provide an inertial response similar to that of synchronous generators when the grid frequency changes, thereby enhancing the stability of the grid. Although VSG technology has improved the frequency regulation capability of the grid to a certain extent, the traditional VSG method usually uses fixed virtual inertia parameters, and such fixed inertia settings cannot be flexibly adjusted according to the actual frequency changes of the grid.

[0004] Traditional VSG control methods have certain limitations, especially when the grid frequency changes greatly. Since the virtual inertia is a pre-set fixed value, when the grid frequency fluctuates greatly or the frequency changes rapidly, the fixed virtual inertia may not be able to provide sufficient inertial support, resulting in slower frequency recovery and even system frequency instability. In addition, the fixed virtual inertia method is also unable to adapt to the needs of different grid load changes and cannot achieve optimal frequency regulation and stability assurance. Therefore, the existing technology urgently needs to be improved to better adapt to the actual needs of grid frequency changes. Summary of the invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a frequency response method for a wind energy conversion system controlled by an adaptive virtual synchronous generator.

[0006] The present invention provides a frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator, comprising:

[0007] S1, based on the minimum rotor speed ω wtmin The lowest value of the grid frequency ω min , calculate the maximum virtual moment of inertia J of the virtual synchronous machineVSG0 ;

[0008] S2, combined with fan to release maximum energy ΔE VSGmax , calculate the maximum rate of change of the grid frequency when a frequency disturbance occurs ω' gridmax ;

[0009] S3, calculate the adaptive virtual inertia multiplication factor K AVSG , set the reference value of adaptive virtual inertia J ref For J VSG0 +K AVSG J VSG0 .

[0010] According to the technical solution provided by the embodiment of the present invention, the maximum virtual moment of inertia J VSG0 The calculation method is:

[0011]

[0012] In the formula, ω wt0 is the optimal rotor speed; ω wtmin is the minimum value of the rotor speed; ω n is the rated frequency of the power grid; ω min is the minimum value of the power grid frequency, J wt is the fan moment of inertia.

[0013] According to the technical solution provided by the embodiment of the present invention, the fan can release the maximum energy ΔE VSGmax The calculation method is:

[0014]

[0015] In the formula, J VSG is the initial virtual inertia of the virtual synchronous machine.

[0016] According to the technical solution provided by the embodiment of the present invention, the maximum change rate ω' of the power grid frequency when a frequency disturbance occurs gridmax The calculation method is:

[0017]

[0018] Where, T g is the time constant of the synchronous generator speed regulator.

[0019] According to the technical solution provided by the embodiment of the present invention, the adaptive virtual inertia multiplication coefficient K AVSG The calculation method is:

[0020]

[0021] In the formula, J SGis the moment of inertia of the synchronous generator, ω' grid It is the rate of change of the grid frequency when a frequency disturbance occurs.

[0022] According to the technical solution provided by the embodiment of the present invention, the reference value J of the adaptive virtual inertia ref The calculation method is:

[0023] J ref =J VSG0 +K AVSG J VSG0 Formula five.

[0024] The beneficial effects of the present invention are:

[0025] The adaptive virtual inertia adjustment method proposed in the present invention adjusts the virtual inertia of the virtual synchronous generator in real time, so that it can flexibly respond to changes in the power grid frequency and enhance the frequency adjustment capability and stability of the power grid. Compared with the traditional fixed virtual inertia control method, this adaptive adjustment method greatly improves the ability of renewable energy systems such as wind power generation to participate in power grid frequency regulation, which helps to improve the overall stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0027] Figure 1 A wind energy conversion system model for virtual synchronous generator control;

[0028] Figure 2 The active power control framework of the proposed adaptive virtual synchronous machine is presented;

[0029] Figure 3 This is the proposed adaptive virtual synchronous machine virtual inertia controller. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] The wind energy conversion system model of virtual synchronous generator control is as follows Figure 1As shown, PMSG is a permanent magnet synchronous generator; MSC is a machine-side converter; GSC is a grid-side converter; PCC is a common connection point; PI is a proportional integral controller; Grid is a power grid; SPWM is an SPWM wave generator; Vector controller is a vector controller; VSG controller is a virtual synchronous machine controller; MPPT is a wind turbine maximum power tracking control curve; P ref is the reference power of the virtual synchronous machine; ω wt is the rotor speed; V dc is the DC bus voltage; V dcref is the DC bus voltage reference value; the function of the VSG controller is to enable the system to support the frequency regulation of the power grid and enhance the stability of the power grid by simulating the inertia of the synchronous generator, while the MPPT control ensures that the system can optimize the extraction of wind energy under different wind speed conditions.

[0033] The proposed active power control framework for adaptive virtual synchronous machines is as follows: Figure 2 As shown, P e is the output power of the VSG controller; P ref is the reference power of VSG controller; D vsg is the damping coefficient of the virtual synchronous machine; ω vsg is the virtual angular frequency; ω pcc is the angular frequency of the common connection point; θ vsg is the virtual attack angle; s is the Laplace operator; J AVSG is the current virtual inertia; the system effectively improves the frequency regulation capability of the power grid, avoids frequency fluctuations, and enhances the stability of the power grid after frequency disturbances by accurately adjusting the virtual inertia and frequency of the virtual synchronous generator. By simulating the inertial response of the synchronous generator, the virtual synchronous generator can provide inertial support when the power grid frequency fluctuates, helping the power grid to quickly restore stability and avoiding the impact of frequency imbalance on the power system.

[0034] The present invention provides a frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator, comprising:

[0035] S1, based on the minimum rotor speed ω wtmin The lowest value of the grid frequency ω min , calculate the maximum virtual moment of inertia J of the virtual synchronous machine VSG0 ;

[0036] S2, combined with fan to release maximum energy ΔE VSGmax , calculate the maximum rate of change of the grid frequency when a frequency disturbance occurs ω' gridmax ;

[0037] S3, calculate the adaptive virtual inertia multiplication factor K AVSG, set the reference value of adaptive virtual inertia J ref For J VSG0 +K AVSG J VSG0 .

[0038] Specifically, the maximum virtual moment of inertia J VSG0 The calculation method is:

[0039]

[0040] In the formula, ω wt0 is the optimal rotor speed; ω wtmin is the minimum value of the rotor speed; ω n is the rated frequency of the power grid; ω min is the minimum value of the power grid frequency, J wt is the fan moment of inertia.

[0041] The fan can release the maximum energy ΔE VSGmax The calculation method is:

[0042]

[0043] In the formula, J VSG is the initial virtual inertia of the virtual synchronous machine.

[0044] The maximum change rate of the power grid frequency when a frequency disturbance occurs ω' gridmax The calculation method is:

[0045]

[0046] Where, T g is the time constant of the synchronous generator speed regulator.

[0047] Adaptive virtual inertia multiplication factor K AVSG The calculation method is:

[0048]

[0049] In the formula, J SG is the moment of inertia of the synchronous generator, ω' grid It is the rate of change of the grid frequency when a frequency disturbance occurs.

[0050] Reference value of adaptive virtual inertia J ref The calculation method is:

[0051] J ref =J VSG0 +K AVSG J VSG0 Formula five.

[0052] The proposed adaptive virtual synchronous machine virtual inertia controller is as follows Figure 3 As shown, J AVSG is the current virtual inertia; PI is the proportional integral controller. First, the system compares the input reference virtual inertia J ref and the current virtual inertia J AVSG , calculate the error signal. This error signal reflects the gap between the current frequency of the power grid and the expected frequency, and serves as the basis for adjusting the virtual inertia. Next, the error signal is input to the PI controller, which adjusts the virtual inertia value in real time according to the proportional P and integral I operations. The proportional term helps the system respond quickly to frequency changes, while the integral term eliminates long-term accumulated errors to ensure stable operation of the system.

[0053] When the grid frequency changes, the virtual inertia J AVSG It will be dynamically adjusted according to the output signal of the PI controller. Specifically, when the grid frequency fluctuates greatly, the virtual inertia of the virtual synchronous generator increases, thereby providing more inertial support and effectively mitigating frequency fluctuations; and when the grid frequency tends to be stable, the virtual inertia decreases to avoid excessive inertial support affecting grid frequency regulation. Through this dynamic adjustment, the system can simulate the inertial characteristics of traditional synchronous generators and enhance the stability of the grid under frequency disturbances.

[0054] The adaptive virtual inertia adjustment method proposed in the present invention adjusts the virtual inertia of the virtual synchronous generator in real time, so that it can flexibly respond to changes in the power grid frequency and enhance the frequency adjustment capability and stability of the power grid. Compared with the traditional fixed virtual inertia control method, this adaptive adjustment method greatly improves the ability of renewable energy systems such as wind power generation to participate in power grid frequency regulation, which helps to improve the overall stability of the power grid.

[0055] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. A frequency response method for a wind energy conversion system controlled by an adaptive virtual synchronous generator, characterized in that: The following steps are involved: S1, based on the minimum rotor speed ω wtmin The lowest value of the grid frequency ω min , calculate the maximum virtual moment of inertia J of the virtual synchronous machine VSG0 ; S2, combined with fan to release maximum energy ΔE VSGmax , calculate the maximum rate of change of the grid frequency when a frequency disturbance occurs ω' gridmax ; S3, calculate the adaptive virtual inertia multiplication factor K AVSG , set the reference value of adaptive virtual inertia J ref For J VSG0 +K AVSG J VSG0 .

2. The frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator according to claim 1, characterized in that: In step S1, the maximum virtual moment of inertia J VSG0 The calculation method is: In the formula, ω wt0 is the optimal rotor speed; ω wtmin is the minimum value of the rotor speed; ω n is the rated frequency of the power grid; ω min is the minimum value of the power grid frequency, J wt is the fan moment of inertia.

3. The frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator according to claim 1, characterized in that: In step S2, the fan can release a maximum energy ΔE VSGmax The calculation method is: In the formula, J VSG is the initial virtual inertia of the virtual synchronous machine.

4. The frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator according to claim 1, characterized in that: In step S2, the maximum change rate ω' of the grid frequency when a frequency disturbance occurs gridmax The calculation method is: Where, T g is the time constant of the synchronous generator speed regulator.

5. The frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator according to claim 1, characterized in that: In step S3, the adaptive virtual inertia multiplication factor K AVSG The calculation method is: In the formula, J SG is the moment of inertia of the synchronous generator, ω' grid It is the rate of change of the grid frequency when a frequency disturbance occurs.

6. The frequency response method of a wind energy conversion system controlled by an adaptive virtual synchronous generator according to claim 1, characterized in that: In step S3, the reference value J of the adaptive virtual inertia ref The calculation method is: J ref =J VSG0 +K AVSG J VSG0 Formula five.

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