Research Of The Measurement And Control System For ±50MVA Cascaded STATCOM

The 220kv Xijiao substation is located at the central area of northwest distinct in Shanghai, which is the core substation in Huangdu subzone of Shanghai electric power grid. The load in this area is concentrated large and the volume of power exchange is numerous. The change rate of bus voltage along with the load is also quick. The current reactive power compensation equipment cannot provide the dynamic voltage supporting when there is the system failure. Eventually it cannot guarantee the operational stability of the power network in the area. It is deserved to pay a close attention to the project that how to control the bus voltage in west suburb in a safe, reliable, effective way, especially in the case of system failure. The Static Synchronous Compensator (STATCOM) belongs to the power flow control equipment of Flexible AC Transmission Systems (FACTS). The reactive current output can be stable when the voltage fluctuates in a large range. It can still provide a powerful reactive power supporting when the voltage is low, and can be continuous from capacitive status to inductive status. STATCOM can also restraint voltage flicker and increase system transient stability. Considering our country's basic condition and current technology, developing STATCOM is an effective method to solve problem of the voltage stability in our country. This paper concludes the author's research works on STATCOM, the main contents are stated below:1. It proposes a general design of 50MVA STATCOM project. After comparison and analysis of several versions and the experience of 20MVA STATCOM, the main circuit of 50MVA STATCOM use chain pattern inverter, and the power device use IGCT. STATCOM mainly consist of single phase inverter with three phases chain pattern, 6 connected reactors, high voltage switchboard, boosting transformer, control/supervisor units, protection unit, water cooling system, central control board, and remote control console. The connecting reactors, boosting transformer and heat abstractor for water cooling system are equipped outsides, while the high voltage room, controlling room, inverter room, water cooling system and spares room is inside.2. The measurement and control system is the main part of STATCOM. It provides the different functions by controlling and drivering the turn on or turn off devices. This paper introduces the control system, the construction of the monitoring and fault diagnostic system and the design of the communication system. The realization of the measurement and control system is also highlighted. Tests results confirmed that all performance requirements are met.3. The emerging problem is how to put the STATCOM into practical operation in Shanghai electric network. The paper makes the cascade unit in the STATCOM as the experimental subject. Using the back-to-back cascade pattern to test all double cascade link. Experiment shows that the main circuit unit, control and protection unit, test and fault diagnosis unit, and cooling system is working well.At the end of this dissertation, a systematical summary is given. Further work to be studied is pointed out.