A method and device for active power control of a grid-forming converter virtual synchronous generator based on angular frequency correction

Abstract

The application discloses a kind of active power control method and device of network type converter virtual synchronous generator based on angular frequency correction, by utilizing active power error correction virtual synchronous generator output angular frequency, it has solved the contradiction problem that active power control dynamic exists oscillation and steady-state exists power deviation in conventional network type converter virtual synchronous generator control.The application introduces proportional controller on the basis of conventional network type converter virtual synchronous generator control strategy, after active power error is adjusted by proportional controller, it is used to correct the angular frequency of virtual synchronous generator output, and then reaches the goal of active power adjustment, so that the active power control of improved network type converter virtual synchronous generator has inertia and damping characteristics, and there is no power steady-state error.

Description

Technical Field

[0001] The present invention relates to the technical field of grid connection, and in particular to a method and device for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction. Background Art

[0002] In recent years, grid-connected converters have been increasingly studied and applied because they can improve the operational stability of renewable energy power systems. Conventional grid-connected converter virtual synchronous generator technology often uses active power control to adjust the output voltage frequency and reactive power control to adjust the output voltage amplitude. However, conventional virtual synchronous generator active power control strategies often have the contradictory problem of being difficult to simultaneously suppress dynamic power oscillations, overshoot, and steady-state power deviations. Although existing literature has studied improved grid-connected converter virtual synchronous generator active power control strategies, such methods often only consider the problem of power oscillation suppression, or require the use of differential operations, resulting in low stability.

[0003] The document "Wang Yajun, Yang Libo, Ma Bin, et al. Coordinated optimization method of inertia and damping coefficient of virtual synchronous generator [J]. Power System Protection and Control, 2022, 50(19): 88-98." discusses the coordinated optimization method of inertia and damping coefficient to improve the dynamic performance of active power of virtual synchronous generator. The proposed method can reduce the dynamic oscillation and overshoot of active power, but does not study the active power deviation problem that occurs when the grid frequency offsets.

[0004] The paper "Xu Haizhen, Yu Changzhou, Mao Fubin, et al. Virtual inertia optimization control strategy based on frequency stability improvement [J]. Power System Protection and Control, 2022, 50(12): 126-133" proposes a method of adding active power and frequency first-order differential feedforward compensation links to the forward channel of the traditional virtual synchronous generator active power frequency control loop to increase the system's transient damping and reduce active power oscillations and steady-state errors. However, the introduction of the differential algorithm will amplify the impact of noise and, in severe cases, reduce system stability.

[0005] The paper "Ji Xiaotong, Li Zhe, Liu Dan, et al. Active Power Control Method and Device for Virtual Synchronous Generators in Grid-Type Converters [P]. Hubei Province: CN202410032817.0, March 26, 2024" proposes a virtual synchronous generator active power control method based on damping power proportional-integral adjustment. This method uses a proportional-integral controller to dynamically adjust the damping power, achieving active power oscillation and overshoot suppression, while also eliminating steady-state power deviation. However, the introduction of a proportional-integral controller increases the complexity of conventional virtual synchronous generator control strategies. There is still a lack of rigorous theoretical basis for the reasonable design of proportional and integral coefficients, and the parameter debugging process is time-consuming.

[0006] From the above analysis, it can be seen that although existing literature has studied the problems of active power oscillation, overshoot and steady-state deviation suppression in the control of virtual synchronous generators in grid-connected converters, some literature only considers the problems of active power oscillation and overshoot. Although some literature has studied the problem of simultaneously achieving active power oscillation, overshoot suppression and steady-state power deviation elimination, these methods either require the addition of differential operations or proportional-integral controllers, which increases the system debugging complexity and reduces the system stability. Summary of the Invention

[0007] In order to overcome the contradictory problem of dynamic oscillation and steady-state power deviation in the active power control of virtual synchronous generators of conventional grid-type converters, the present invention discloses a method and device for active power control of virtual synchronous generators of grid-type converters based on angular frequency correction.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction is characterized by comprising the following steps:

[0010] Step 1: Difference the set grid rated angular frequency ω0 and the angular frequency ω output by the virtual synchronous generator control strategy of the grid-type converter, and multiply it by the droop coefficient k ω The first power deviation ΔP1 is obtained, which satisfies:

[0011] ΔP1=(ω0-ω)*k ω

[0012] Among them, the rated angular frequency ω0 of the power grid is 100πrad / s;

[0013] Step 2: Set the virtual synchronous generator active power reference value P ref Add the first power deviation ΔP1 obtained in step 1 and subtract the active power P output by the virtual synchronous generator e , and obtain the second power deviation ΔP2, which satisfies:

[0014] ΔP2=P ref +ΔP1-P e

[0015] Among them, active power P e It is calculated based on the power angle output by the virtual synchronous generator at the previous moment;

[0016] Step 3: Integrate the second power deviation ΔP2 obtained in step 2 according to the following formula to obtain the first frequency deviation Δω1, which satisfies:

[0017]

[0018] Where s represents the Laplace operator, J represents the virtual inertia of the virtual synchronous generator;

[0019] Step 4: After passing the second power deviation ΔP2 obtained in step 2 through a proportional controller, a second frequency deviation Δω2 is obtained, which satisfies:

[0020] Δω2=k p ΔP2

[0021] Among them, k p is the proportional coefficient of the proportional controller.

[0022] Step 5: Add the first frequency deviation Δω1 obtained in step 3 to the set grid rated angular frequency ω0, and add the second frequency deviation Δω2 obtained in step 4 to obtain the angular frequency ω output by the virtual synchronous generator, satisfying:

[0023] ω=ω0+Δω1+Δω2

[0024] Step 6: Subtract the actual angular frequency ω of the power grid from the angular frequency ω of the virtual synchronous generator output obtained in step 5 g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies:

[0025]

[0026] Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next moment e .

[0027] Furthermore, the active power P output by the virtual synchronous generator in step 2 is e The calculation formula satisfies:

[0028] P e =Kδ'

[0029] in, U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, and δ' is the power angle output by the virtual synchronous generator at the previous moment.

[0030] A grid-type converter virtual synchronous generator active power control device based on angular frequency correction, comprising:

[0031] The first power deviation calculation module is used to make a difference between the set grid rated angular frequency ω0 and the angular frequency ω output by the grid-type converter virtual synchronous generator control strategy, and multiply it by the droop coefficient k ω The first power deviation ΔP1 is obtained, which satisfies:

[0032] ΔP1=(ω0-ω)*kω

[0033] Among them, the rated angular frequency ω0 of the power grid is 100πrad / s;

[0034] The first power deviation calculation module is used to set the virtual synchronous generator active power reference value P ref Add the first power deviation ΔP1 and subtract the active power P output by the virtual synchronous generator e , and obtain the second power deviation ΔP2, which satisfies:

[0035] ΔP2=P ref +ΔP1-P e

[0036] Among them, active power P e It is calculated based on the power angle output by the virtual synchronous generator at the previous moment;

[0037] The first frequency deviation calculation module is used to integrate the second power deviation ΔP2 according to the following formula to obtain a first frequency deviation Δω1, which satisfies:

[0038]

[0039] Where s represents the Laplace operator and J represents the virtual inertia of the virtual synchronous generator.

[0040] The angular frequency calculation module is used to add the first frequency deviation Δω1 to the set grid rated angular frequency ω0, and add the second frequency deviation Δω2 to obtain the angular frequency ω output by the virtual synchronous generator, satisfying:

[0041] ω=ω0+Δω1+Δω2

[0042] The second frequency deviation Δω2 is obtained by adjusting the second power deviation ΔP2 through the proportional controller, satisfying:

[0043] Δω2=k p ΔP2

[0044] Among them, k p is the proportional coefficient of the proportional controller.

[0045] The power angle calculation module is used to subtract the actual angular frequency ω of the power grid from the angular frequency ω output by the virtual synchronous generator. g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies:

[0046]

[0047] Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next momente .

[0048] Furthermore, the active power P output by the virtual synchronous generator e The calculation formula satisfies:

[0049] P e =Kδ'

[0050] in, U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, and δ' is the power angle output by the virtual synchronous generator at the previous moment.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] Compared with conventional methods, the method of the present invention simultaneously considers the problems of dynamic oscillation and steady-state deviation suppression of power, and the method of the present invention does not require the introduction of differential operations. It only requires the reasonable adjustment of the proportional coefficient parameter in the proportional controller to make the active power output by the virtual synchronous generator of the grid-type converter have both good dynamic characteristics, no overshoot and oscillation, and good steady-state characteristics, no steady-state error. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is the block diagram of active power control of virtual synchronous generator for conventional grid-connected converter;

[0054] Figure 2 This is a control block diagram of a method for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction proposed in the present invention;

[0055] Figure 3 The figure shows the comparative simulation results of the conventional method and the method of the present invention. DETAILED DESCRIPTION

[0056] 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 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.

[0057] like Figure 2 As shown, an embodiment of the present invention provides a method for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction, comprising the following steps:

[0058] Step 1: Difference the set grid rated angular frequency ω0 and the angular frequency ω output by the virtual synchronous generator control strategy of the grid-type converter, and multiply it by the droop coefficient k ω The first power deviation ΔP1 is obtained, which satisfies:

[0059] ΔP1=(ω0-ω)*k ω

[0060] Among them, the rated angular frequency ω0 of the power grid is 100πrad / s;

[0061] Step 2: Set the virtual synchronous generator active power reference value P ref Add the first power deviation ΔP1 obtained in step 1 and subtract the active power P output by the virtual synchronous generator e , and obtain the second power deviation ΔP2, which satisfies:

[0062] ΔP2=P ref +ΔP1-P e

[0063] Among them, active power P e It is calculated based on the power angle δ' output by the virtual synchronous generator at the previous moment, satisfying:

[0064] P e =Kδ'

[0065] in, U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, and δ' is the power angle output by the virtual synchronous generator at the previous moment.

[0066] Step 3: Integrate the second power deviation ΔP2 obtained in step 2 according to the following formula to obtain the first frequency deviation Δω1, which satisfies:

[0067]

[0068] Where s represents the Laplace operator, J represents the virtual inertia of the virtual synchronous generator;

[0069] Step 4: After passing the second power deviation ΔP2 obtained in step 2 through a proportional controller, a second frequency deviation Δω2 is obtained, which satisfies:

[0070] Δω2=k p ΔP2

[0071] Among them, k p is the proportional coefficient of the proportional controller.

[0072] Step 5: Add the first frequency deviation Δω1 obtained in step 3 to the set grid rated angular frequency ω0, and add the second frequency deviation Δω2 obtained in step 4 to obtain the angular frequency ω output by the virtual synchronous generator, satisfying:

[0073] ω=ω0+Δω1+Δω2

[0074] Step 6: Subtract the actual angular frequency ω of the power grid from the angular frequency ω of the virtual synchronous generator output obtained in step 5 g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies:

[0075]

[0076] Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next moment e .

[0077] An embodiment of the present invention further provides an active power control device for a virtual synchronous generator of a grid-connected converter based on angular frequency correction, comprising:

[0078] The first power deviation calculation module is used to make a difference between the set grid rated angular frequency ω0 and the angular frequency ω output by the grid-type converter virtual synchronous generator control strategy, and multiply it by the droop coefficient k ω The first power deviation ΔP1 is obtained, which satisfies:

[0079] ΔP1=(ω0-ω)*k ω

[0080] Among them, the rated angular frequency ω0 of the power grid is 100πrad / s;

[0081] The first power deviation calculation module is used to set the virtual synchronous generator active power reference value P ref Add the first power deviation ΔP1 and subtract the active power P output by the virtual synchronous generator e , and obtain the second power deviation ΔP2, which satisfies:

[0082] ΔP2=P ref +ΔP1-P e

[0083] Among them, active power P e It is calculated based on the power angle δ' output by the virtual synchronous generator at the previous moment, satisfying:

[0084] P e =Kδ'

[0085] in, U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, and δ' is the power angle output by the virtual synchronous generator at the previous moment.

[0086] The first frequency deviation calculation module is used to integrate the second power deviation ΔP2 according to the following formula to obtain a first frequency deviation Δω1, which satisfies:

[0087]

[0088] Where s represents the Laplace operator and J represents the virtual inertia of the virtual synchronous generator.

[0089] The angular frequency calculation module is used to add the first frequency deviation Δω1 to the set grid rated angular frequency ω0, and add the second frequency deviation Δω2 to obtain the angular frequency ω output by the virtual synchronous generator, satisfying:

[0090] ω=ω0+Δω1+Δω2

[0091] The second frequency deviation Δω2 is obtained by adjusting the second power deviation ΔP2 through the proportional controller, satisfying:

[0092] Δω2=k p ΔP2

[0093] Among them, k p is the proportional coefficient of the proportional controller.

[0094] The power angle calculation module is used to subtract the actual angular frequency ω of the power grid from the angular frequency ω output by the virtual synchronous generator. g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies:

[0095]

[0096] Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next moment e .

[0097] In order to verify the effectiveness of the proposed method, the active power control strategy of the virtual synchronous generator of the conventional grid-connected converter ( Figure 1 During the simulation, the active power reference value P ref 5kW before 4s, P at 4s ref The actual angular frequency of the power grid increases from 5kW to 10kW at 7s. g It suddenly decreases from 100πrad / s (50Hz) to 99.8πrad / s (49.9Hz). The virtual inertia J is 1kg / m 2, the grid rated angular frequency ω0 is 100πrad / s, the droop coefficient k ω The grid phase voltage peak is 311 V, and the virtual synchronous generator output voltage peak is 311. The grid line resistance is 2 Ω and the line inductance is 3 mH.

[0098] Figure 3 The simulation results of the active power control of the virtual synchronous generator of the conventional grid-type converter and the proposed invention are given. During the simulation, the virtual damping coefficient D of the conventional method is 0 and 10Ws / rad respectively, and the proportional coefficient k of the proposed method is p It is 0.00033.

[0099] Depend on Figure 3 It can be seen that when the virtual damping coefficient D is zero, the active power and frequency output by the conventional virtual synchronous generator show obvious oscillation and overshoot. When the virtual damping coefficient D increases to 10, the oscillation is significantly suppressed. Figure 3 It can be seen that an increase in the virtual damping coefficient leads to a significant increase in the steady-state deviation of active power (approximately 1973 W) when the grid frequency deviates (after 7 seconds). Therefore, conventional virtual synchronous generator active power control strategies cannot simultaneously suppress active power dynamic oscillations and eliminate steady-state static errors by adjusting the virtual damping coefficient.

[0100] At the same time, by Figure 3 As can be seen, when the proposed method is used, the active power output of the virtual synchronous generator has neither dynamic oscillation nor overshoot, nor steady-state active power deviation. This shows that the proposed method can simultaneously suppress dynamic active power oscillations and eliminate steady-state static errors. This demonstrates the effectiveness of the proposed method.

[0101] The present invention is different from conventional methods in that it introduces a proportional controller to adjust the power deviation, and uses the adjusted power deviation to correct the angular frequency output by the virtual synchronous generator, so that the active power control strategy of the virtual synchronous generator of the grid-type converter has both inertia and damping characteristics and no power steady-state error.

[0102] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction, characterized in that: The steps include: Step 1: Difference the set grid rated angular frequency ω0 and the angular frequency ω output by the virtual synchronous generator control strategy of the grid-type converter, and multiply it by the droop coefficient k ω Get the first power deviation ,satisfy: ； Among them, the rated angular frequency ω0 of the power grid is 100π rad / s; Step 2: Set the virtual synchronous generator active power reference value P ref The first power deviation obtained in step 1 Add and subtract the active power P output by the virtual synchronous generator e , get the second power deviation ,satisfy: ； Among them, active power P e It is calculated based on the power angle output by the virtual synchronous generator at the previous moment; Step 3: The second power deviation obtained in step 2 Perform integration according to the following formula to obtain the first frequency deviation ,satisfy: ； Where s represents the Laplace operator, J represents the virtual inertia of the virtual synchronous generator; Step 4: The second power deviation obtained in step 2 After passing through a proportional controller, the second frequency deviation is obtained ,satisfy: ； in, is the proportional coefficient of the proportional controller; Step 5: The first frequency deviation obtained in step 3 Add the set grid rated angular frequency ω0 and the second frequency deviation obtained in step 4 , we get the angular frequency ω of the virtual synchronous generator output, which satisfies: ； Step 6: Subtract the actual angular frequency ω of the power grid from the angular frequency ω of the virtual synchronous generator output obtained in step 5 g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies: ； Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next moment e .

2. The method for controlling active power of a virtual synchronous generator of a grid-connected converter based on angular frequency correction according to claim 1, characterized in that: The active power P output by the virtual synchronous generator in step 2 e The calculation formula satisfies: ； in, , U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, It is the power angle output by the virtual synchronous generator at the previous moment.

3. A grid-type converter virtual synchronous generator active power control device based on angular frequency correction, characterized in that: include: The first power deviation calculation module is used to make a difference between the set grid rated angular frequency ω0 and the angular frequency ω output by the grid-type converter virtual synchronous generator control strategy, and multiply it by the droop coefficient k ω Get the first power deviation ,satisfy: ； Among them, the rated angular frequency ω0 of the power grid is 100π rad / s; The first power deviation calculation module is used to set the virtual synchronous generator active power reference value P ref Deviation from the first power Add and subtract the active power P output by the virtual synchronous generator e , get the second power deviation ,satisfy: ； Among them, active power P e It is calculated based on the power angle output by the virtual synchronous generator at the previous moment; The first frequency deviation calculation module is used to calculate the second power deviation Perform integration according to the following formula to obtain the first frequency deviation ,satisfy: ； Where s represents the Laplace operator, J represents the virtual inertia of the virtual synchronous generator; Angular frequency calculation module, used to calculate the first frequency deviation Added to the set grid rated angular frequency ω0 and the second frequency deviation , we get the angular frequency ω of the virtual synchronous generator output, which satisfies: ； The second frequency deviation By the second power deviation After adjustment by the proportional controller, it satisfies: ； in, is the proportional coefficient of the proportional controller; The power angle calculation module is used to subtract the actual angular frequency ω of the power grid from the angular frequency ω output by the virtual synchronous generator. g After that, the integral operation is performed to obtain the power angle δ output by the virtual synchronous generator, which satisfies: ； Among them, the power angle δ is used to calculate the active power P output by the virtual synchronous generator at the next moment e .

4. The active power control device of a virtual synchronous generator of a grid-connected converter based on angular frequency correction according to claim 3, characterized in that: Active power P output by virtual synchronous generator e The calculation formula satisfies: ； in, , U is the grid voltage amplitude, E is the amplitude of the virtual synchronous generator output voltage, X is the grid equivalent line impedance, It is the power angle output by the virtual synchronous generator at the previous moment.

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