Application Research Of FACTS In Stability Control Of Power System Integrated With Large-scale Wind Farm

Potential threats for security and stability of the power system will be caused bylarge-capacity wind farm integration (LWFI). So the security and stability of thepower system containing large-capacity wind farm (PSCLWF) has been paid greatattention. The successful application of flexible ac transmission system (FACTS) inpower system shows that FACTS is effective measures to improve the security andstability of PSCLWF. This paper makes researches on available transfer capability(ATC) improvement of the PSCLWF transmission line, inhibition ability of lowfrequency oscillation of PSCLWF, transient voltage stability improvement of LWFIand reactive power compensation of LWFI. The main achievements are as follows:(1) It is a contradiction in the rapid increase of wind power generation capacityand the relatively weak transmission network. Therefore, it is proposed that the TCSCvariable impedance controller added a Bang-Bang transient stability control canimprove obviously ATC of LWFI transmission line. The controller’s advantage is thatcan real-time track the active output change with wind speed of wind farms, andreal-time flexibly adjust the impedance of the transmission lines in order to real-timeadjust the active power of transmission line. The controller can improve effectivelythe transient stability limit of ATC, enhance the low-voltage though ability of LWFI,and increase the efficiency of wind energy.(2) The excess energy accumulated by high short circuit current in protectiondevice can cause TCSC protection misoperation. This will weaken the dampingeffectiveness of TCSC damping controller. The corresponding relation between thecorrection energy function of PSCLWF tie-line and the model transformation momentof TCSC is analyzed in detail. A segmented TCSC damping controller based ontie-line correction energy function and its control strategy are proposed. The TCSCcontroller uses the voltage and current double closed-loop control during stablecondition to guarantee the active power flow being in expectation. But it uses thetransient stability control based on tie-line correction energy function to improve theability to endure large disturbance and improve the transient stability of the grid.(3) When a large disturbance or a failure occurs, the large-capacity wind farmneeds to absorb a lot of reactive power. This will cause easily voltage collapse of thepower system. Furthermore, large-scale wind farm tripping is easy to cause the systemoscillation. Combining with the advantages of STATCOM in adjusting instantaneously reactive power and restoring rapidly voltage after fault, a adaptiveSTATCOM controller and its control strategy are proposed to realize transient voltagestability control of LWFI. By comparing with other control method simulation, theeffectiveness of the controller is proved to improve the transient voltage stability andstrengthen low voltage though ability of wind farm integration.(4) STATCOM can compensate reactive power rapidly and flexibly, but its costis too high. The cost of the parallel capacitor groups is low, but it can’t compensatereactive power smoothly and real-time. A coordination optimization reactive powercompensation scheme using STATCOM and auto-switching parallel capacitorgroups(APFC) is proposed. Its control strategy is proposed also. APFC compensatethe static reactive power under different working wind speed during stable condition.STATCOM compensates the dynamic reactive power during the switching gap ofAPFC and the transient reactive power during fault condition. The control scheme isbased on economy of reactive power compensation equipments, static stability andtransient stability. It is a coordination optimization reactive power compensationscheme because of considering economy, security and stability at the same time.