A virtual synchronous machine control method for grid-connected inverter with networking function

Abstract

The invention discloses a control method for a virtual synchronous machine of a grid-connected inverter with a networking function, comprising: a front-end networking strategy module, and a virtual synchronous machine strategy module connected in series behind the networking strategy module, wherein the networking strategy module comprises: a first proportional link, a second proportional link and a first low-pass filter; the virtual synchronous machine strategy module comprises: a first integrator, a second integrator, a second low-pass filter, a third proportional link, and a proportional plus integral link; the control method for a virtual synchronous machine of a grid-connected inverter with a networking function clearly divides the virtual synchronous machine strategy and the networking strategy, and can ensure the integrity and independence of the virtual synchronous machine strategy and the networking strategy during virtual synchronous machine control, thereby ensuring that the grid-connected inverter can realize seamless switching between grid connection and off-grid connection and multi-machine networking, and realize accurate tracking of active and reactive instructions within the dead zone range of grid frequency and grid voltage amplitude.

Description

Technical Field

[0001] The present invention relates to the field of grid-connected technology, and in particular to a grid-connected inverter virtual synchronous machine control method with networking function. Background Art

[0002] With the rapid development of new energy, its penetration rate continues to grow, and the power grid is calling for new energy units to participate in power grid control and auxiliary services. In this form, there are two technical routes to choose from: one is to create a new networking theory for the new power system dominated by new energy; the other is for new energy units to simulate the synchronous machine mode. The former involves a comprehensive technological innovation of the power system, which is difficult and costly; the latter can be based on the existing power system. The transition to a power system dominated by new energy is relatively small. Considering the difficulty and cost, taking the latter route has become an inevitable choice at the current stage, so how new energy units simulate the operation of synchronous machines has also become a research hotspot.

[0003] There are two characteristics of the existing research on virtual synchronous machine technology: first, the control architecture is diverse; second, almost all of them are based on the horizontal division of active loop and reactive loop. There is no clear division between the virtual synchronous machine strategy and the networking strategy, which leads to some control architectures either missing the networking strategy in the active control loop or missing the networking strategy in the reactive control loop. It is necessary to switch the control strategy to adapt to the grid-connected and off-grid switching operation. It is impossible to accurately track the active and reactive commands within the dead zone of the grid frequency and grid voltage amplitude; it is impossible to ensure that the active power setting and reactive power setting of the input virtual synchronous machine are within the unit capacity. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a virtual synchronous machine control method for a grid-connected inverter with a networking function. The virtual synchronous machine control method for a grid-connected inverter with a networking function clearly divides the virtual synchronous machine strategy and the networking strategy, and can ensure the integrity and independence of the virtual synchronous machine strategy and the networking strategy during virtual synchronous machine control, thereby ensuring that the grid-connected inverter can achieve seamless switching between on-grid and off-grid and multi-machine networking, and achieve accurate tracking of active and reactive commands within the dead zone of grid frequency and grid voltage amplitude.

[0005] To solve the above technical problems, the present invention provides a virtual synchronous machine control method for a grid-connected inverter with networking function, comprising: a front networking strategy module, and a virtual synchronous machine strategy module connected in series behind the networking strategy module.

[0006] The networking strategy module includes: a first ratio link k f , the second proportional link k v and a first low pass filter LPF1;

[0007] The virtual synchronous machine strategy module includes: a first integrator Second integrator A second low-pass filter LPF2, a third proportional link D, and a proportional plus integral link PI;

[0008] The networking strategy module adopts a networking strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at rated frequency is n The difference between the rotor angular velocity ω of the virtual synchronous machine and the first proportional link k f Get the active power given ΔP ref , the active power is given by ΔP ref With external active power given P ref Add together to get the input active power P of the virtual synchronous machine m ; The rated modulus V of the three-phase AC grid voltage vector nm and the filtered value V of the grid voltage modulus after passing through the first low-pass filter LPF1 gm_filt Make the difference, and then go through the second proportional link k v Get the reactive power given ΔQ ref , the reactive power is given by ΔQ ref Then with the external reactive power given Q ref Add together to get the input reactive power Q of the virtual synchronous machine total_ref ;

[0009] The virtual synchronous machine strategy module adopts the virtual synchronous machine strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at the rated frequency is n Defined as the rated angular velocity ω of the virtual synchronous machine rotor n , the input active power P of the virtual synchronous machine obtained by the networking strategy m The measured value of active power P e The difference is then passed through the first integrator The third proportional link D is used as the closed-loop link of the negative feedback channel to obtain the rotor angular velocity adjustment value Δω of the virtual synchronous machine. The angular velocity adjustment value Δω is then compared with the rated angular velocity ω of the rotor of the virtual synchronous machine. n The virtual synchronous machine rotor angular velocity ω is obtained by adding the virtual synchronous machine rotor angular velocity ω, and the virtual synchronous machine rotor angular velocity ω is further integrator The vector position θ of the stator induced voltage of the virtual synchronous machine is obtained; the virtual synchronous machine input reactive power Q obtained by the networking strategy is total_ref The measured value of reactive power Q e The filtered value Q after the second low-pass filter LPF2 e_filtThe vector modulus adjustment value ΔE of the stator induced voltage of the virtual synchronous machine is obtained by the proportional plus integral link PI, and the vector modulus adjustment value ΔE is then compared with the rated voltage vector modulus value E of the virtual synchronous machine. n The induced voltage vector modulus E of the virtual synchronous machine is obtained by adding them together.

[0010] Preferably, the first ratio link k f is a proportional link with a dead zone, the second proportional link k v It is a proportional link with a dead zone.

[0011] Preferably, the active power given ΔP ref The output is then passed through the first limiting link Sat1, and the limiting setting of the first limiting link Sat1 is dynamically set according to the current regulation capability of the new energy unit.

[0012] Preferably, the reactive power given ΔQ ref The output is then passed through the second limiting link Sat2, and the limiting setting of the second limiting link Sat2 is dynamically set according to the current regulation capability of the new energy unit.

[0013] Preferably, the input reactive power Q total_ref and instantaneous reactive power filter value Q e_filt After the difference, the "proportional plus integral link PI" is changed to a "pure integral link".

[0014] Preferably, the closed-loop link with D as the negative feedback channel removes the negative feedback channel and becomes a pure integral link, so that the virtual synchronous machine strategy tracks the active power without difference.

[0015] Preferably, the closed-loop link with the third proportional link D as the negative feedback channel adds a high-pass filter in the negative feedback channel, so that the virtual synchronous machine has a damping effect in dynamic state and the damping effect is 0 in steady state, thereby realizing steady-state error-free tracking of active power.

[0016] Preferably, the high-pass filter is implemented by subtracting the input signal from the signal after the input signal passes through the third low-pass filter LPF3.

[0017] Preferably, the first ratio link k f The maximum steady-state deviation of the grid voltage angular frequency allowed by the grid connection guidelines is obtained by dividing the rated active power of the new energy unit by the absolute value; the second proportional link k v The absolute value of the maximum steady-state deviation allowed by the grid voltage modulus specified in the grid connection guidelines is obtained by dividing the rated reactive power of the new energy unit by the grid voltage modulus specified in the grid connection guidelines.

[0018] After adopting the above method, the virtual synchronous machine control method of the grid-connected inverter with networking function includes: a front networking strategy module, and a virtual synchronous machine strategy module connected in series behind the networking strategy module; the networking strategy module includes: a first proportional link k f , the second proportional link k v and a first low-pass filter LPF1; the virtual synchronous machine strategy module includes: a first integrator Second integrator The second low-pass filter LPF2, the third proportional link D, the proportional plus integral link PI; the networking strategy module adopts the networking strategy: the angular velocity ω of the three-phase symmetrical grid voltage vector at the rated frequency n The difference between the rotor angular velocity ω of the virtual synchronous machine and the first proportional link k f Get the active power given ΔP ref , the active power is given by ΔP ref With external active power given P ref Add together to get the input active power P of the virtual synchronous machine m ; The rated modulus V of the three-phase AC grid voltage vector nm and the filtered value V of the grid voltage modulus after passing through the first low-pass filter LPF1 gm_filt Make the difference, and then go through the second proportional link k v Get the reactive power given ΔQ ref , the reactive power is given by ΔQ ref Then with the external reactive power given Q ref Add together to get the input reactive power Q of the virtual synchronous machine total_ref ; The virtual synchronous machine strategy module adopts the virtual synchronous machine strategy: the angular velocity ω of the three-phase symmetrical grid voltage vector at the rated frequency n Defined as the rated angular velocity ω of the virtual synchronous machine rotor n , the input active power P of the virtual synchronous machine obtained by the networking strategy m The measured value of active power P e The difference is then passed through the first integrator The third proportional link D is used as the closed-loop link of the negative feedback channel to obtain the rotor angular velocity adjustment value Δω of the virtual synchronous machine. The angular velocity adjustment value Δω is then compared with the rated angular velocity ω of the rotor of the virtual synchronous machine. n The virtual synchronous machine rotor angular velocity ω is obtained by adding the virtual synchronous machine rotor angular velocity ω, and the virtual synchronous machine rotor angular velocity ω is further integrator The vector position θ of the stator induced voltage of the virtual synchronous machine is obtained; the virtual synchronous machine input reactive power Q obtained by the networking strategy is total_ref The measured value of reactive power Q eThe filtered value Q after the second low-pass filter LPF2 e_filt The vector modulus adjustment value ΔE of the stator induced voltage of the virtual synchronous machine is obtained by the proportional plus integral link PI, and the vector modulus adjustment value ΔE is then compared with the rated voltage vector modulus value E of the virtual synchronous machine. n The induced voltage vector modulus E of the virtual synchronous machine is obtained by adding them together; the virtual synchronous machine control method of the grid-connected inverter with networking function clearly divides the virtual synchronous machine strategy and the networking strategy, which can ensure the integrity and independence of the virtual synchronous machine strategy and the networking strategy during virtual synchronous machine control, thereby ensuring that the grid-connected inverter can achieve seamless switching between on-grid and off-grid and multi-machine networking, and achieve accurate tracking of active and reactive commands within the dead zone of grid frequency and grid voltage amplitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a virtual synchronous machine control diagram of the prior art;

[0020] Figure 2 This is a control diagram of Embodiment 1 of a method for controlling a virtual synchronous machine of a grid-connected inverter with a networking function according to the present invention;

[0021] Figure 3 This is a control diagram of Embodiment 4 of a method for controlling a virtual synchronous machine of a grid-connected inverter with a networking function according to the present invention;

[0022] Figure 4 The control method of the fifth embodiment of the grid-connected inverter virtual synchronous machine control method with networking function of the present invention is Figure 1 ;

[0023] Figure 5 The control method of the fifth embodiment of the grid-connected inverter virtual synchronous machine control method with networking function of the present invention is Figure 2 . DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Embodiment 1

[0026] See also Figure 2 , Figure 2 It is a control diagram of Embodiment 1 of a method for controlling a virtual synchronous machine of a grid-connected inverter with networking function of the present invention; this embodiment discloses a method for controlling a virtual synchronous machine of a grid-connected inverter with networking function, comprising: a front-end networking strategy module, and a virtual synchronous machine strategy module connected in series behind the networking strategy module.

[0027] The networking strategy module includes: a first ratio link k f , the second proportional link k v and a first low pass filter LPF1;

[0028] The virtual synchronous machine strategy module includes: a first integrator Second integrator A second low-pass filter LPF2, a third proportional link D, and a proportional plus integral link PI;

[0029] The networking strategy module adopts a networking strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at rated frequency is n The difference between the rotor angular velocity ω of the virtual synchronous machine and the first proportional link k f Get the active power given ΔP ref , the active power is given by ΔP ref With external active power given P ref Add together to get the input active power P of the virtual synchronous machine m ; The rated modulus V of the three-phase AC grid voltage vector nm and the filtered value V of the grid voltage modulus after passing through the first low-pass filter LPF1 gm_filt Make the difference, and then go through the second proportional link k v Get the reactive power given ΔQ ref , the reactive power is given by ΔQ ref Then with the external reactive power given Q ref Add together to get the input reactive power Q of the virtual synchronous machine total_ref ;

[0030] The virtual synchronous machine strategy module adopts the virtual synchronous machine strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at the rated frequency is n Defined as the rated angular velocity ω of the virtual synchronous machine rotor n , the input active power P of the virtual synchronous machine obtained by the networking strategy m The measured value of active power P e The difference is then passed through the first integrator The third proportional link D is used as the closed-loop link of the negative feedback channel to obtain the rotor angular velocity adjustment value Δω of the virtual synchronous machine. The angular velocity adjustment value Δω is then compared with the rated angular velocity ω of the rotor of the virtual synchronous machine. n The virtual synchronous machine rotor angular velocity ω is obtained by adding the virtual synchronous machine rotor angular velocity ω, and the virtual synchronous machine rotor angular velocity ω is further integrator The vector position θ of the stator induced voltage of the virtual synchronous machine is obtained; the virtual synchronous machine input reactive power Q obtained by the networking strategy is total_ref The measured value of reactive power Qe The filtered value Q after the second low-pass filter LPF2 e_filt The vector modulus adjustment value ΔE of the stator induced voltage of the virtual synchronous machine is obtained by the proportional plus integral link PI, and the vector modulus adjustment value ΔE is then compared with the rated voltage vector modulus value E of the virtual synchronous machine. n The induced voltage vector modulus E of the virtual synchronous machine is obtained by adding them together.

[0031] This embodiment can ensure the integrity of the design of the networking strategy and the virtual synchronous machine strategy by dividing the virtual synchronous machine control architecture vertically into the networking strategy and the virtual synchronous machine strategy.

[0032] Embodiment 2

[0033] This embodiment 1 is based on the embodiment 1. In this embodiment, the first ratio link k f is a proportional link with a dead zone, the second proportional link k v It is a proportional link with a dead zone;

[0034] By introducing dead zone in the networking strategy, accurate tracking of active and reactive power instructions can be achieved within the dead zone range of grid frequency and grid voltage amplitude;

[0035] The first proportional link k f The maximum steady-state deviation of the grid voltage angular frequency allowed by the grid connection guidelines is obtained by dividing the rated active power of the new energy unit by the absolute value; the second proportional link k v The absolute value of the maximum steady-state deviation allowed by the grid voltage modulus specified in the grid connection guidelines is obtained by dividing the rated reactive power of the new energy unit by the grid voltage modulus specified in the grid connection guidelines.

[0036] Embodiment 3

[0037] This embodiment is based on the first embodiment. In this embodiment, the input reactive power Q total_ref and instantaneous reactive power filter value Q e_filt After the difference is made, the "proportional plus integral link PI" is changed to a "pure integral link";

[0038] The closed-loop link with D as the negative feedback channel removes the negative feedback channel and becomes a pure integral link, so that the virtual synchronous machine strategy can track the active power without error;

[0039] Embodiment 4

[0040] See also Figure 3 ; Figure 3 It is a control diagram of Embodiment 4 of a grid-connected inverter virtual synchronous machine control method with networking function according to the present invention.

[0041] This embodiment is based on the first embodiment. In this embodiment, the networking strategy module further includes a first limiting link Sat1. The active power given ΔP ref After passing through the first limiting link Sat1, the limiting setting of the first limiting link Sat1 is dynamically set according to the current regulation capability of the new energy unit; the networking strategy module also includes a second limiting link Sat2, the reactive power given ΔQ ref The output is then passed through the second limiting link Sat2, and the limiting setting of the second limiting link Sat2 is dynamically set according to the current regulation capability of the new energy unit.

[0042] In the networking strategy, a limiting link that can be dynamically adjusted according to the current unit capacity is introduced to ensure that the active power setting and reactive power setting of the input virtual synchronous machine are within the unit capacity range.

[0043] According to the first embodiment, no matter how large the frequency deviation is, as long as there is a deviation, an active power setting ΔP will be generated. ref ; No matter how large the voltage amplitude deviation is, as long as there is a deviation, there will be no power given ΔQ ref The existence of these two adjustment variables will result in the grid active power P e Unable to track the external active power given P ref , grid-connected reactive power Q e_filt Unable to track the external reactive power given Q ref When the frequency deviation and voltage amplitude deviation are within a certain range, the superior dispatcher still hopes that the new energy unit can track the command without error, so as to ensure that the output command of the superior dispatcher can be accurately executed. In addition, considering the current regulation capability of the new energy unit, such as the current power reserve value, current limit capability and other constraints, the output active power given by ΔP after the limiting link ref and reactive power given ΔQ ref Since the current regulating capacity is variable, the limiting value of the limiting link is also designed to be variable.

[0044] Embodiment 5

[0045] See also Figure 4 and Figure 5 ; Figure 4 The control method of the fifth embodiment of the grid-connected inverter virtual synchronous machine control method with networking function of the present invention is Figure 1 , Figure 5 The control method of the fifth embodiment of the grid-connected inverter virtual synchronous machine control method with networking function of the present invention is Figure 2 .

[0046] This embodiment is based on embodiment one or embodiment four. In this embodiment, the virtual synchronous machine strategy module includes a third low-pass filter LPF3, and the closed-loop link with the third proportional link D as the negative feedback channel adds a high-pass filter in the negative feedback channel, so that the virtual synchronous machine has a damping effect in the dynamic state and the damping effect is 0 in the steady state, thereby realizing steady-state error-free tracking of the active power.

[0047] The high-pass filter is realized by subtracting the input signal from the signal after the input signal passes through the third low-pass filter LPF3.

[0048] According to the above-mentioned embodiment 1 or embodiment 2, due to the existence of the damping third proportional link D, the measured value of the active power P in the steady state is e The input active power P of the virtual synchronous machine m There is a steady-state error between . To eliminate the steady-state error, Figure 4 The third low-pass filter LPF3 is connected in series to the damping branch to ensure that the damping branch has no output in a steady state and still has a damping effect in a dynamic state; Figure 5 The damping branch is removed. Since the previous networking strategy has the equivalent effect to the damping branch, the system still has the damping characteristics.

Claims

1. A method for controlling a virtual synchronous machine of a grid-connected inverter with networking function, characterized in that: include: A front-end networking strategy module, and a virtual synchronization machine strategy module connected in series behind the networking strategy module; The networking strategy module includes: a first ratio link k f , the second proportional link k v and a first low pass filter LPF1; The virtual synchronous machine strategy module includes: a first integrator Second integrator A second low-pass filter LPF2, a third proportional link D, and a proportional plus integral link PI; The networking strategy module adopts a networking strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at rated frequency is n The difference between the rotor angular velocity ω of the virtual synchronous machine and the first proportional link k f Get the active power given ΔP ref , the active power is given by ΔP ref With external active power given P ref Add together to get the input active power P of the virtual synchronous machine m ; The rated modulus V of the three-phase AC grid voltage vector nm and the filtered value V of the grid voltage modulus after passing through the first low-pass filter LPF1 gm_filt Make the difference, and then go through the second proportional link k v Get the reactive power given ΔQ ref , the reactive power is given by ΔQ ref Then with the external reactive power given Q ref Add together to get the input reactive power Q of the virtual synchronous machine total_ref ; The virtual synchronous machine strategy module adopts the virtual synchronous machine strategy: the angular velocity ω of the voltage vector of the three-phase symmetrical power grid at the rated frequency is n Defined as the rated angular velocity ω of the virtual synchronous machine rotor n , the input active power P of the virtual synchronous machine obtained by the networking strategy m The measured value of active power P e The difference is then passed through the first integrator The third proportional link D is used as the closed-loop link of the negative feedback channel to obtain the rotor angular velocity adjustment value Δω of the virtual synchronous machine. The angular velocity adjustment value Δω is then compared with the rated angular velocity ω of the rotor of the virtual synchronous machine. n The virtual synchronous machine rotor angular velocity ω is obtained by adding the virtual synchronous machine rotor angular velocity ω, and the virtual synchronous machine rotor angular velocity ω is further integrator The vector position θ of the stator induced voltage of the virtual synchronous machine is obtained; the virtual synchronous machine input reactive power Q obtained by the networking strategy is total_ref The measured value of reactive power Q e The filtered value Q after the second low-pass filter LPF2 e_filt The vector modulus adjustment value ΔE of the stator induced voltage of the virtual synchronous machine is obtained by the proportional plus integral link PI, and the vector modulus adjustment value ΔE is then compared with the rated voltage vector modulus value E of the virtual synchronous machine. n The induced voltage vector modulus E of the virtual synchronous machine is obtained by adding them together.

2. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The first ratio link k f is a proportional link with a dead zone, the second proportional link k v It is a proportional link with a dead zone.

3. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The networking strategy module also includes a first limiting link Sat1, the active power given ΔP ref The output is then passed through the first limiting link Sat1, and the limiting setting of the first limiting link Sat1 is dynamically set according to the current regulation capability of the new energy unit.

4. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The networking strategy module also includes a second limiting link Sat2, the reactive power given ΔQ ref The output is then passed through the second limiting link Sat2, and the limiting setting of the second limiting link Sat2 is dynamically set according to the current regulation capability of the new energy unit.

5. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The input reactive power Q total_ref and instantaneous reactive power filter value Q e_filt After the difference, the "proportional plus integral link PI" is changed to a "pure integral link".

6. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The closed-loop link with the third proportional link D as the negative feedback channel removes the negative feedback channel and becomes a pure integral link, so that the virtual synchronous machine strategy tracks the active power without difference.

7. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The closed-loop link with the third proportional link D as the negative feedback channel adds a high-pass filter in the negative feedback channel, so that the virtual synchronous machine has a damping effect in dynamic state and the damping effect is 0 in steady state, thereby realizing steady-state error-free tracking of active power.

8. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 7, characterized in that: The virtual synchronous machine strategy module further includes a third low-pass filter LPF3, and the high-pass filter is implemented by subtracting the input signal from the signal after the input signal passes through the third low-pass filter LPF3.

9. The method for controlling a virtual synchronous machine of a grid-connected inverter with networking function according to claim 1, characterized in that: The first ratio link k f The maximum steady-state deviation of the grid voltage angular frequency allowed by the grid connection guidelines is obtained by dividing the rated active power of the new energy unit by the absolute value; the second proportional link k v The absolute value of the maximum steady-state deviation allowed by the grid voltage modulus specified in the grid connection guidelines is obtained by dividing the rated reactive power of the new energy unit by the grid voltage modulus specified in the grid connection guidelines.

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