Research On The Protection Strategy For D-STATCOM On Non-normal State

In recent years, with economy developing rapidly and national modernizationimproving continuously, the whole community’s requirements to the quality of electricalenergy also has risen. Distribution Static Synchronous Compensator (D-STATCOM), asan important member of the Flexible AC Transmission Systems (FACTS), can effectivelycompensate reactive power, eliminate harmonic and suppress imbalance in the powergrid, so it is of great research significance and practical value. In the grid, how to ensurethe safe running of D-STATCOM and maximize the compensation performance ofD-STATCOM under abnormal running states, is one of the key research aspects ofD-STATCOM engineering applications.This paper introduces the fundamentals of D-STATCOM devices and analyzes theabnormal running states in practical applications, including overload of non-linear loads,all kinds of short circuit, and common faults of the D-STATCOM device itself. Moreover,this paper indicates the importance of research on the operation strategy of D-STATCOMunder abnormal states, and introduces the methods to deal with the failures of theD-STATCOM device itself.Later, the paper analyzes the advantages and disadvantages and the ranges ofapplications of two traditional over-current protection methods of D-STATCOM, andproposes a new method for limiting protection, Real-time limiting equidistantly. Thismethod can effectively prevent the D-STATCOM from outputting over-current underabnormal states, and ensure the devices continues running in the grid with betterharmonic compensation. Then according to the actual operation of D-STATCOM devices,we proposed a grading protection strategy, to take appropriate protection strategies fordifferent operational issues to ensure device security and efficiency improvement ofD-STATCOM. In addition, we build a three-phase four-wire D-STATCOM model onMatlab/Simulink platform, and compare the performances of the traditional method oflimiting and the method proposed in this paper by simulation. It proves that with themethod proposed, not only the over-current of the devices is limited more effectively, butalso better harmonic compensation is achieved.Finally, we develop a380V10kVA D-STATCOM prototype based on DSPTMS320F2812. We conduct experiments about the method proposed on the prototype, to verify the correctness and validity of the proposed limiting strategy.