Method and device for controlling active power of virtual synchronous generator of network construction type converter based on angular frequency correction

Abstract

The invention discloses an angular frequency correction-based active power control method and device for a virtual synchronous generator of a network-forming converter, and the method comprises the steps: correcting the angular frequency outputted by the virtual synchronous generator through an active power error; the contradictory problem that the active power control dynamic state has oscillation and the steady state has power deviation under the control of the virtual synchronous generator of the conventional grid-forming converter is solved. According to the method, a proportional controller is introduced on the basis of a control strategy of a virtual synchronous generator of a conventional grid-forming converter, and an active power error is adjusted by the proportional controller and then is used for correcting an angular frequency output by the virtual synchronous generator, so that the target of adjusting the active power is achieved; therefore, the improved active power control of the virtual synchronous generator of the grid-forming converter not only has inertia and damping characteristics, but also has 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 a 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 operating 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 that dynamic power oscillations, overshoots, and steady-state power deviations are difficult to suppress at the same time. Although existing literature has studied improved active power control strategies for virtual synchronous generators in grid-connected converters, such methods often only consider the problem of power oscillation suppression, or require the use of differential operations, and have 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 deviates.

[0004] The literature "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." proposed 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 frequency control loop to increase the transient damping of the system and reduce active power oscillation and steady-state error. However, the introduction of the differential algorithm will amplify the impact of noise, and in severe cases, it will reduce the stability of the system.

[0005] The document "Ji Xiaotong, Li Zhe, Liu Dan, et al. Active power control method and device for virtual synchronous generator of grid-connected converter [P]. Hubei Province: CN202410032817.0, 2024-03-26." proposes a virtual synchronous generator active power control method based on damping power proportional integral adjustment. The proportional integral controller is used to dynamically adjust the damping power, realize active power oscillation and overshoot suppression, and eliminate steady-state power deviation. However, the introduction of the proportional integral controller increases the complexity of the conventional virtual synchronous generator control strategy. How to reasonably design the proportional coefficient and integral coefficient still lacks a strict theoretical basis, and the parameter debugging process is time-consuming.

[0006] From the above analysis, it can be seen that although the existing literature has studied the problems of active power oscillation, overshoot and steady-state deviation suppression in the virtual synchronous generator control of the grid-connected converter, some literature only considers the problems of active power oscillation and overshoot. Although some literature has studied the problem of simultaneously realizing active power oscillation, overshoot suppression and steady-state power deviation elimination, these methods either need to increase differential operations or increase proportional-integral controllers, which increases the debugging complexity of the system 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 active power control of virtual synchronous generator of conventional grid-connected converter, the present invention discloses an active power control method and device of virtual synchronous generator of grid-connected converter 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, characterized in that it comprises 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-connected 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, the 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 the second power deviation ΔP2 obtained in step 2 passes 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 of the virtual synchronous generator output 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 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:

[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, the 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] Wherein, 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 a 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 moment.e .

[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 of the virtual synchronous generator output 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 takes into account the dynamic oscillation of power and the suppression of steady-state deviation at the same time, and the method of the present invention does not need to introduce differential operations. It only needs to reasonably adjust the parameter of the proportional coefficient in the proportional controller to make the active power output by the virtual synchronous generator of the grid-connected 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 a block diagram of active power control of a virtual synchronous generator for a conventional grid-connected converter;

[0054] Figure 2 A control block diagram of an active power control method of a virtual synchronous generator of a grid-connected converter based on angular frequency correction proposed by 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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the 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 creative work are 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-connected 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, the 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 of the virtual synchronous generator output 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 the second power deviation ΔP2 obtained in step 2 passes 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] The embodiment of the present invention further provides an active power control device of 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 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:

[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, the 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 of the virtual synchronous generator output 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] Wherein, 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 a 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 is compared with that 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 voltage peak of the grid phase is 311V, and the peak voltage of the virtual synchronous generator output is 311. The grid line resistance is 2Ω, and the line inductance is 3mH.

[0098] Figure 3 The simulation results of the virtual synchronous generator active power control 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 invention 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 the increase of the virtual damping coefficient will cause the grid frequency to deviate (after 7s), and the active power steady-state deviation will also increase significantly (the active power deviation is about 1973W). It can be seen that the conventional virtual synchronous generator active power control strategy cannot achieve active power dynamic oscillation suppression and steady-state static error elimination by adjusting the virtual damping coefficient at the same time.

[0100] At the same time, by Figure 3 It can be seen that when the method proposed in the present invention is used, the active power output by the virtual synchronous generator has neither dynamic oscillation and overshoot nor steady-state active power deviation, which shows that the method proposed in the present invention can simultaneously achieve active power dynamic oscillation suppression and steady-state static error elimination. This proves the effectiveness of the method proposed in the present invention.

[0101] The present invention is different from the conventional method in that a proportional controller is introduced to adjust the power deviation, and the adjusted power deviation is used 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 is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope 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-connected converter, and multiply it by the droop coefficient k ω The first power deviation ΔP1 is obtained, which satisfies: ΔP1=(ω0-ω)*k ω Among them, the rated angular frequency ω0 of the power grid is 100πrad / s; 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: ΔP2=P ref +ΔP1-P e Among them, the active power P e It is calculated based on the power angle output by the virtual synchronous generator at the previous moment; 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: Where, s represents the Laplace operator, J represents the virtual inertia of the virtual synchronous generator; Step 4: After the second power deviation ΔP2 obtained in step 2 passes through a proportional controller, a second frequency deviation Δω2 is obtained, which satisfies: Dω2=k p ΔP2 Among them, k p is the proportional coefficient of the proportional controller; 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: ω=ω0+Δω1+Δω2 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: P e =Kδ' 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 of the virtual synchronous generator output at the previous moment.

3. A grid-connected 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 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: ΔP1=(ω0-ω)*k ω Among them, the rated angular frequency ω0 of the power grid is 100πrad / s; 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: ΔP2=P ref +ΔP1-P e Among them, the 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 integrate the second power deviation ΔP2 according to the following formula to obtain a first frequency deviation Δω1, which satisfies: Wherein, s represents the Laplace operator, and J represents the virtual inertia of the virtual synchronous generator. 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: ω=ω0+Δω1+Δω2 The second frequency deviation Δω2 is obtained by adjusting the second power deviation ΔP2 through a proportional controller, satisfying: Dω2=k p ΔP2 Among them, k p 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 is characterized in that: The active power P output by the virtual synchronous generator e The calculation formula satisfies: P e =Kδ' 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 of the virtual synchronous generator output at the previous moment.

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