Improving The Transient Voltage Stability Of The Wind Farm With SVC And SSSC

The development of present society is rapid, and the progress of science and technology brings the economic benefits but also brings the environment pollution problems that to be solved immediately, so the development and utilization of renewable energy becomes important topic. Among them, the wind as main clean energy, more and more gets people’s attention, the proportion of wind power in grid is also more and more high. However, due to the asynchronous motor can not control the reactive voltage effectively, and the asynchronous wind power generati- on system will absorb a large number of reactive power from the grid in the starting stage, it can cause serious unbalanced distribution of reactive power in the grid and transient voltage losses the stability. When large disturbance appears in the system, such as short circuit fault, the system also needs to absorb reactive power from grid to re-establish the voltage of the machine, it also will cause the transient voltage of grid to loss stability. Aiming at the existing problem of asynchronous wind power generation system, this paper puts forward that makes the FACTS devices SVC and SSSC to be installed in the system, to achieve the purpose to solve the problem.First of all, this paper analyzes the working characteristic of the asynchronous generator, and establishes the mathematical model of wind farms based on asynchronous generator. The corresponding simulation model of wind farms is setted up in the Matlab/Simulink, to simulate the power fluctuation of wind farm with wind speed changing continually, and in the absence of any compensation measures, simulates the various operation parameters of wind farms when a fault occurs in wind farm, highlights the research significance of this topic..Secondly, this paper respectively gives the structure and working principle of SVC and SSSC, establishes the corresponding mathematical model, specifically analyzes both working characteristic combined with the mathematical model, and the consequence is verified by simulation. In this paper, SVC is used to provide reactive power support for system when fault appears, raises the voltage of the machine, provides reactive power for system after the fault is eliminated, restores the voltage of the machine, maintains the stability of system; SSSC is used to reduce the short circuit current when fault occurs, reduces the degree of bus-bar voltage dropping, maintains the system’s voltage stability.Finally, this paper uses SVC and SSSC in asynchronous wind power generation system, focus on each control strategy design of the SVC and SSSC and the establishment of the joint action of both SVC and SSSC. In this paper, the classical PI control manner is used for SVC to regulate reactive power from SVC, achieve to the rapid reactive compensation and continuous reactive power adjustment for system, improves the voltage stability of system. The control manner of SSSC is double closed loop reactance control method in this paper, this way has higher precision, and the effect of fault current limiting is better. After accomplishing the respectively control of SVC and SSSC, unifies SVC and SSSC by setting the corresponding signal, accomplishes the combination of both SVC and SSSC, designs the corresponding control strategy. This paper establishes the simulation model of wind farms with SVC and SSSC in Matlab/Simulink, verifies the effectiveness of the proposed strategy. The results shows that SVC can continuously provide reactive power compensation for system, maintains the transient stability of system; when a serious fault appears, this strategy can efficiently reduce the fault current by jointing SVC and SSSC, recovers the voltage of machine; SVC and SSSC can work together to solve the problem of the transient voltage stability of the wind farm.