Governor regultaion E xcitation regulation Q V P Fig. 3 ... · under symmetrical and asymmetrical...
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1. The VSG’s structure and control algorithm Wed-Mo-Po3.09-11 Abstract—To solve the low-voltage ride-through (LVRT) issue of a virtual synchronous generator (VSG) under severe grid fault, this paper proposes the solution of a modified flux-coupling-type superconducting fault current limiter (SFCL). According to the equivalent analysis circuit of the VSG under the fault, the functions of the SFCL are discussed from the aspects of current limitation, voltage compensation, and energy dissipation. Using MATLAB, symmetrical and asymmetrical faults are both simulated to assess the transient behaviors of the VSG, and the SFCL parameters are changed to clarify the quantitative effects. From the simulation results, the SFCL parameters are properly determined to provide favorable performance. The SFCL can visibly decrease the fault current of each phase lower than the safety margin, and make the VSG own a preferable voltage profile. Additionally, the SFCL is able to positively stabilize the VSG by enhancing the active power, mitigating the frequency fluctuation and consuming the excess energy. A satisfactory LVRT operation is gained, and the efficacy of the SFCL on reinforcing the VSG robustness is validated. Lei Chen a,* , Guocheng Li a , Hongkun Chen a , Meng Ding a , Xuyang Zhang a , Ying Xu b , Li Ren b , Yuejin Tang b a School of Electrical Engineering and Automation, Wuhan University, Wuhan 430072, China b Huazhong University of Science and Technology, Wuhan 430074, China 3. Performance evaluation of the SFCL for LVRT enhancement of the VSG Fig. 6. Short-circuit current of the VSG under the symmetrical fault. (a) Phase-A, (b) Phase-B and (c) Phase-C. Fig. 7. Transient behaviors of the VSG under the symmetrical fault. (a) Active power and (b) generator frequency. Fig. 8. Three-phase voltage of the VSG under the symmetrical fault. (a) No SFCL and (b) with the SFCL of Rsc = 2 Ω. 4. Conclusion This paper explores the feasibility of applying a modified flux- coupling-type SFCL in fulfilling the LVRT enhancement of a VSG under symmetrical and asymmetrical faults. From the theoretical analysis and simulation validation, a proper design of the SFCL parameters is obtained to offer great contributions. i) The SFCL is able to powerfully reduce the fault current of each phase within the safety margin, and to make the VSG have a preferable voltage profile. ii) The SFCL can visibly improve the active power and decrease the frequency fluctuation for the VSG. Thereupon, a satisfactory LVRT operation is realized. Fig. 5. Fault analysis circuit of the VSG with the SFCL. Fig. 1. Schematic diagram of a VSG integrating the SFCL in the PCC. Fig. 2. Block diagram of the VSG control algorithm. 2. Description of the SFCL and Its effects Fig. 3. (a) Modified flux-coupling-type SFCL. (b) Schematic inner connection diagram of the SC. Application Study of a Flux-Coupling-Type SFCL for Low-Voltage Ride-Through Operation of a Virtual Synchronous Generator * Corresponding author: Asso. Prof. Lei Chen. E-mail address: [email protected] Local load AC Grid SFCL Energy supply unit PCC Power calculation VSG control algorithm P* Q* V* ω* Drive signals Ri Li Inverter P, Q PWM 1 s K Q +_ _ 1 Js D + _ + _ + _ + V * V Q * Q E θ E,θ abc e a e b e c ω + _ ω * ω pcc P e + Governor regultaion Excitation regulation P m + P * + 1 ω * +_ + + ω pcc T d T m -T e ΔP Rotor mechanical regulation ΔV * K ω PI S load I s M S cs I 2 U s R L 1 L 2 Z s I 1 I r I cs moa SC (a) In Out (b) SF CL E U res L eq i f R eq L i R i VSG + _ + _ 2 1 lim 2 lim lim 2 2 2 2 1 lim 2 lim 0 2 2 2 2 sin( ) sin( ) ( ) ( ) sin sin ( ) ( ) f f SC res f f SC f L L t R R res f f SC f E t U t i R R L L E U I e R R L L t 0 t 1 t 2 t 3 t / s R SC R(t)/ Ω (a) (b) Fig. 4. SC modeling method. (a) Electrical model for MATLAB simulation. (b) Quench and recovery behaviors. Concerning that the SC resistance is increased to RSC = 2 Ω, the SFCL may suppress the fault current of each phase within 1.3 times of the rated level, and an adequate safety margin is produced. Furthermore, the VSG frequency dynamic is visibly inhibited by the SFCL, and the maximum frequency deviation is reduced from 0.5 Hz to 0.1 Hz. Fig. 9. Short-circuit current of the VSG under the asymmetrical fault. (a) Phase-A and (b) Phase-B. Fig. 10. Transient characteristics of the VSG under the asymmetrical fault. (a) Active power and (b) generator frequency. Fig. 11. Energy dissipating feature of the SFCL under fault conditions.
Transcript of Governor regultaion E xcitation regulation Q V P Fig. 3 ... · under symmetrical and asymmetrical...
1. The VSG’s structure and control algorithm
Wed-Mo-Po3.09-11
Abstract—To solve the low-voltage ride-through(LVRT) issue of a virtual synchronous generator (VSG)under severe grid fault, this paper proposes thesolution of a modified flux-coupling-typesuperconducting fault current limiter (SFCL).According to the equivalent analysis circuit of theVSG under the fault, the functions of the SFCL arediscussed from the aspects of current limitation,voltage compensation, and energy dissipation. UsingMATLAB, symmetrical and asymmetrical faults areboth simulated to assess the transient behaviors ofthe VSG, and the SFCL parameters are changed toclarify the quantitative effects. From the simulationresults, the SFCL parameters are properly determinedto provide favorable performance. The SFCL canvisibly decrease the fault current of each phase lowerthan the safety margin, and make the VSG own apreferable voltage profile. Additionally, the SFCL isable to positively stabilize the VSG by enhancing theactive power, mitigating the frequency fluctuationand consuming the excess energy. A satisfactory LVRToperation is gained, and the efficacy of the SFCL onreinforcing the VSG robustness is validated.
Lei Chen a,*, Guocheng Li a, Hongkun Chen a, Meng Ding a, Xuyang Zhang a, Ying Xu b, Li Ren b, Yuejin Tang ba School of Electrical Engineering and Automation, Wuhan University, Wuhan 430072, China
b Huazhong University of Science and Technology, Wuhan 430074, China
3. Performance evaluation of the SFCL for LVRT enhancement of the VSG
Fig. 6. Short-circuit current of the VSG under the symmetrical fault. (a) Phase-A, (b) Phase-B and (c) Phase-C.
Fig. 7. Transient behaviors of the VSG under the symmetrical fault. (a) Active power and (b) generator frequency.
Fig. 8. Three-phase voltage of the VSG under the symmetrical fault. (a) No SFCL and (b) with the SFCL of Rsc = 2 Ω.
4. Conclusion
This paper explores the feasibility of applying a modified flux-coupling-type SFCL in fulfilling the LVRT enhancement of a VSGunder symmetrical and asymmetrical faults. From thetheoretical analysis and simulation validation, a proper designof the SFCL parameters is obtained to offer great contributions.i) The SFCL is able to powerfully reduce the fault current of eachphase within the safety margin, and to make the VSG have apreferable voltage profile.ii) The SFCL can visibly improve the active power and decreasethe frequency fluctuation for the VSG. Thereupon, a satisfactoryLVRT operation is realized.
Fig. 5. Fault analysis circuit of the VSG with the SFCL.
Fig. 1. Schematic diagram of a VSG integrating the SFCL in the PCC.
Fig. 2. Block diagram of the VSG control algorithm.
2. Description of the SFCL and Its effects
Fig. 3. (a) Modified flux-coupling-type SFCL. (b) Schematic inner connection diagram of the SC.
Application Study of a Flux-Coupling-Type SFCL for Low-Voltage Ride-Through Operation of a Virtual Synchronous Generator
* Corresponding author: Asso. Prof. Lei Chen. E-mail address: [email protected]
Local
load
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SFCL
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control
algorithm
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Governor regultaion Excitation regulation
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Fig. 4. SC modeling method. (a) Electrical model for MATLAB simulation. (b) Quench and recovery behaviors.
Concerning that the SC resistance is increased to RSC = 2 Ω, theSFCL may suppress the fault current of each phase within 1.3times of the rated level, and an adequate safety margin isproduced. Furthermore, the VSG frequency dynamic is visiblyinhibited by the SFCL, and the maximum frequency deviation isreduced from 0.5 Hz to 0.1 Hz.
Fig. 9. Short-circuit current of the VSG under the asymmetrical fault. (a) Phase-A and (b) Phase-B.
Fig. 10. Transient characteristics of the VSG under the asymmetrical fault. (a) Active power and (b) generator frequency.
Fig. 11. Energy dissipating feature of the SFCL under fault conditions.
