The Design Of10kV New Type Solid State Transfer Switch

With the development of science and technology, the number of impact equipment and non-linear load which can affect power quality of power system is increasing, on the other hand sensitive load which are strict at power quality such as medical apparatus and precision laboratory equipment are becoming more and more, thus improving power quality is very imperative. According to relevant statistics, voltage sag and short supply belonging to transient power quality problems take up90%of the power quality problems occurring in power system, and that the number of accident caused by voltage sag is about10times of voltage short supply. Power electronic equipments with faster and more controllable property become an important means to solve power quality problems. There are many power electronic equipments to manage voltage sag such as DVR, UPS, CVTS, SSTS etc, moreover energy storage device is required in equipments as UPS, DVR and CVTS, which are expensive and can’t solve voltage long supply problem. SSTS which works without other energy storage device is a cost effective method to solve power quality problems.The design of Solid State Transfer Switch which is applied to10kV power distribution system in this paper is scientific research project of Guangdong Electric Power Institute. Nowadays, mainstream electronic type SSTS are divided into hybrid transfer switch composed of solid state switch and high speed mechanical switch in parallel and pure electronic solid state switch. But the operating speed of hybrid transfer switch is limit by mechanical switch part, so it can’t be applied to some occasion requiring high switching speed. A solid state transfer switch with series thyristor topological structure is designed in this paper which has high switching speed and simple switching control strategy. The traditional solid state transfer switch with series thyristor topological structure adopts RC branch to realize dynamic and static state voltage-sharing. However some improvement on traditional solid state transfer switch with series thyristor topological structure have been proposed in this paper, which will increase the overvoltage absorption region of SSTS.After analysed and contrasted with typical voltage detection, this paper have chose dq transformation algorithm as voltage detection of lOkV SSTS, further more a new dq transformation algorithm which adds unsymmetrical fault component in the process of calculating is proposed, then simulated the voltage detection result of the new dq transformation algorithm under all kinds of voltage sag faults, the experiments show that the new dq transformation algorithm has a short detection time and a wide range of fault detection. At the same time the MBB Switching strategy of SSTS is designed according to design objective. Finally the SSTS-380V low tension model device is introduced, which have provided the circuit topology and hardware circuit diagram. And that some experiment of low tension model device have been done, the result have proved that the new dq transformation algorithm and MBB Switching strategy of SSTS are feasible.