Research On Industrial Prototype Of220kV Novel Solid-State Fault Current Limiter

With the continuous development and the growing size of the power system, the short-current capacity of the power system is increasing rapidly, which has a significant negative impact on its safe and stable operation. Therefore, research on effective short-current limiting technology including designing and manufacturing feasible short-current limiting device has become a hotspot in the field of power electric automation, bringing great benefit on the enhancement of power system stability and cost reduce of power electrical installations. In order to develop a short-current limiting device feasible for high-voltage high-capacity power system, research group where I’m in has put forward to a novel bridge-type Solid-State Fault Current Limiter(SSFCL) coupled by auto-transformer through continuous researches. Moreover, the proposed SSFCL is designated as the suggestion for industrial prototype of developing short-current limiting device installed in220kV power system.The comparison between the proposed SSFCL and resonant-type SSFCL, magnetic saturation-type SSFCL indicates that the proposed SSFCL has significant advantages, such as lower cost and volume, better operating charasteriscs, and thereby is suitable for industrial realization in220kV power system. Detailed study is conducted on the topology and principle of novel SSFCL. Three operating modes referring to normal stage, transit current-limiting stage and fully current-limiting stage are carried out and resolved by equivalent circuit modeling, and further verificated by simulation results. Analysis of novel SSFCL bringing benefits to power system’s stability is also studied, inllustrating that the novel SSFCL can reduce the generator’s imbalance between input mechanical power and output electromagnetic power after a fault occurs, accordingly avoid generator’s losing synchronous operation and enhance stability of the generator’s power angle. Besides, it alleviates voltage drop after circuit faults and maintains voltage stability of power system simutaneously. Further study also discusses the feasibility of220kV novel SSFCL’s industrial realization.According to the short-current liminting requirement of220kV power system, the design of220kV novel SSFCL industrial prototype is given. It can be devided into three parts:design of electric apparatus in main circuit, design of water cooling system, design of control and protection system. Thereinto, the design of electric apparatus in main circuit mainly includes saturated auto-transformer, thyristor valves in rectify bridge, DC current limiting reactance, metal-oxide-varistor in parallel with the secondary side of auto-transformer, voltage and current transformer, circuit breakers, and so on. The design of water cooling system should take into account power losses of different modes during SSFCL’s operation, and choose the largest one among them as the cooling capacity of the cooling system. Modular design is used in hardware of control and protection system, in order to make individual function model work independently. The software design of control and protection system considers all cases of SSFCL’s operation except for the current limiting strategy. At last, the design is verified by simulation results.Owing to the thyristors’unable to shutdown, the rectify bridge quit operating just after the inrush current which emerges in the rectify bridge after crosses zero. Considering the time delay that a thyristor needs to be fully blocked, the bridge thyristors shut off nearly a frequency cycle after faults in the worst case. The long-lasting and high-amplitude inrush current during transit current-limiting stage not only brings strong demand of bridge’s safety, but also amplifies the current ratings of thyristors and the volume cost of the DC reactance. Several improved topologies of bridge based on full-controlled power electronic devices are introduced, and to make further efforts, a topology-improved novel SSFCL containing a composite full-controlled switch is also proposed. By closing the switch immediately after faults, run duration of the bridge is shortened, along with the duration of inrush current compressed by thyristors and reactance. Thus, the parameters of thyristors and reactance can be designed smaller, and so are the cost and volume of the rectify bridge. Simulation and experiment results prove the feasibility and efficiency of the proposed SSFCL.