Research On The Synchronous Switching Device Of Reactive Power Compensation Based On DSP

Electric power is the pillar energy and economic lifeline of modern society.Reactive power imbalance will cause voltage fluctuations or even collapse of the system,destroying the stability of the system,therefore,the reactive power needs to be compensated.Synchronous condenser can realize the smooth adjustment of the reactive power,however it is difficult to implement fast dynamic control and operation and maintenance is very complex.While SVC can realize continuous and rapid control of the reactive power,but thyristor zero switching device may lead to investment increases,complex control,and it is difficult to solve the over-heat problem caused by frequent switching of the SCR.STATCOM can dynamically compensate the instantaneous reactive power of wide range and rapidly changing,but some throretical issues,key technologies,as well as the cost problem still has not been resolved,so STATCOM is still in the stage of theoretical and experimental research,and rarely implemented in the practice.Shunt capacitor compensation is flexible and convenient,but random switching will generate serious electromagnetic transient effect.Therefore the concept of synchronous switching is proposed,according to this concept,the capacitor is input at the voltage zero crossing and output at the current zero crossing.Sope of the voltage over-zero is very great,minimal closing time deviation corresponds to the great change in voltage,therefore,synchronous closing demands higher controlling accuracy.In this paper,a closing strategy when capacitor and system voltage both come to the peak point at the same time is proposed,which can suppress the inrush current and over-voltage in the capacitors' closing process.The capacitor banks synchronous switching control strategy of star neutral point grounded and ungrounded connection mode is analysized,and the shortest delay time of switch closing in optimal phase for a different reference voltage signal of UA,UB and UC is given.In order to improve the breaker synchronous closing precision,the main factors of the switch action time is analysized and the method of multi-element liner regression is handled to dynamically predict the breaker operating timing and trend.In this paper,an Synchronous Switching Controller with DSP and microcontroller as the core was designed,which can acquire real-time grid signal,drive the switch according to technical indicators,achieve capacitors into or out of operation in the expectation phase to reduce the transient impact.Hardware and software structure of controller uses a modular design concept to enhance the versatility and portability of the device.The hardware includes main control module,data processing and data acquisition module,drive protection module,capacitor charging and discharging control module and power module,and the software part includes the main program module and the interrupt program processing module.In order to further improve reliability,the anti-jamming measures from both hardware and software were proposed.The theoretical calculation and simulation analysis indicated that the synchronous switching device can achieve synchronous closing and removal,significantly weakening the over-voltage and inrush current,which initially achieved the desired effects come true.