Research On Solid State Transfer Switch (SSTS)

With the development of China's economy, power loads appear to increase rapidly. Meanwhile non-linear and impact loads grow continually. These loads bring serious pollution to power quality of power system. However, sensitive loads and high-tech products have higher requirements on power quality. For instance, high performance household appliances, office facilities, micro test apparatus and automatic control equipments which have the continuous, precise production process.The research and analysis are made on the basis of the project of Solid State Transfer Switch (SSTS), which is charged by China Electric Power Research Institute. Solid State Transfer Switch (SSTS) is a measurement and control technology which utilizes power electronics. It is based micro-processor, fiber-optical communication and digital signal processing. SSTS is used to supply uninterrupted power for loads. It is one of the most economic and effective approaches to deal with the power quality problems for sensitive loads and critical loads. Therefore, studying SSTS control and protection system has great significance.Solid State Transfer Switch (SSTS) control and protection system is the nervous system of SSTS project, the dynamic performance of the control and protection system affects the operation characteristics of SSTS.This paper analyzes the operating principle of SSTS which is used to restrain voltage sag. Based on this principle, the control system design of SSTS is put forward. This design achieves the functions, for instance, the data acquisition and control protection unit, and human-computer interface.The design of data acquisition unit includes the choice of voltage transformer and current transformer, the design of signal conditioning circuit, the choice of A/D chip and the circuit design. The design of data processing includes the design of power switching circuit, clock circuit, expanded circuit of external memory and interface circuit of JTAG simulation. The control protecting unit includes the hardware interface circuit of CAN controller besides the clock circuit. In the design of the human-computer interface, the hardware circuits of the development board are presented. The circuits includes the LCD interface circuit, the interface circuit of CAN controller and the interface circuit of serial port. Meanwhile, the picture displaying program, the CAN communication driver and the GSM modem program are presented in the paper.Finally, the experimental results are presented to show the feasibility of the control system, so SSTS can improve power quality.