Real-time digital modelling, test and fault simulation of ±200MVA STATCOM

摘要

This paper involves real-time digital modelling, testing and fault simulation on the large-capacity static var compensator (STATCOM). STATCOM is one of the most advanced reactive power compensation devices for smart grid. The main features of the China Southern Grid (CSG) STATCOM project involving in the paper are the largest capacity (±200MVA) in the world, two sets of parallel operation, high-voltage access to power grid (35kV), basing on the IEGT switching device and the pulse width modulation (PWM) control technology. Technology difficulty of STATCOM project in this paper lies in the first application of the chain valve group basing on voltage source converter (VSC) and its complicated control systems. The Real-time Digital Simulator (RTDS) is used in this paper to assess the function and dynamic performances of actual C&P devices of STATCOM when the disturbance or fault is simulated in power systems. Real-time and closed-loop test systems composed of RTDS digital modelling and actual C&P devices of STATCOM are first set up. STATCOM primary models and power grid are simulated in RTDS and STATCOM C&P devices adopt practical cabinets. Necessary signals such as voltage and current are sent from RTDS to STATCOM C&P cabinets through digital simulation signal amplifier. STATCOM C&P cubicles send triggering pulse signals to RTDS to fire IEGT model, thus a real-time and closedloop test system is composed. STATCOM valve group of units and their interface are simulated in RTDS using small time-step technology (2μs simulation time-step). Power grid modelling, in which STATCOM is accessed, is simulated using large time-step (80μs simulation time-step). The world's most large-scale AC/DC power grid modelling in RTDS is established in this paper. The power grid simulated in RTDS include 5 HVDC systems, 40 units (equivalent) generators and transformers, 132 three-phase nodes and 223 transmission lines. Typical experiments items are designed from the purpose of inspecting STATCOM C&P functions dynamic characteristics. More than 50 items are tested, which include routine inspection of STATCOM C&P cubicles, control function test, control mode switch function test, preventing errors and protection function test and dynamic performance test. The single phase ground fault on April 28 and two phases' ground fault on May 5 in 2012 occurred during operation of the ±200MVA CSG STATCOM project. Both "4.28" fault and "5.5" fault are simulated in the paper using RTDS and actual C&P cabinets of STATCOM. Several manufacturer design defects about C&P are found and solved in this paper to improve control and protection function of STATCOM significantly, which is of great significance for production debugging, operation and maintenance of STATCOM project. Research results show that the proposed RTDS simulation model and the closed-loop test systems of STATCOM in this paper are reasonable and suitable for actual fault simulation and anti-fault measures test. Dynamic performance of STATCOM may be improved significantly by control and protection anti-fault measures proposed in the paper.