تجزیه و تحلیل عملکرد از SSSC بر اساس معکوس کننده PWM چند پل سه سطحی

This paper describes a static synchronous series compensator (SSSC) based on three-level multi-bridge pulse width modulation inverter. The dynamic characteristic of proposed SSSC was analyzed by simulation with EMTP and experiment with a scaled hardware model, assuming that the SSSC is inserted in the transmission line of one-machine-infinite-bus power system. The proposed SSSC can be directly inserted in the transmission line without coupling transformers, and has flexibility in expanding the operation voltage to increase the number of bridges in series connection.

Flexible AC transmission system (FACTS) devices using voltage source inverter with gate turn-off thyristor (GTO) have been studied since the beginning of 1990s. Static synchronous compensator (STATCOM) is the first FACTS device to compensate the reactive power connected in parallel with the power system bus. Although static synchronous series compensator (SSSC) has the same configuration of power circuit as STATCOM, it is connected in series with the transmission line and operated with different control scheme. The function of SSSC is to control the voltage across the transmission line by injecting voltage in series with the transmission line [1] and [2]. The maximum sustain voltage of currently available GTO for FACTS application is about 5 kV, which is much lower than the operation voltage of power system. In order to solve this problem step-down transformers are used for properly interfacing the FACTS device with the power system, and power converters with series-connected GTO's are used. Although series connection of GTO's is proven technology, there still is restriction in maximum allowable number of units. Multi-level inverter was proposed to increase the system operation voltage avoiding series connection of switching devices. However, multi-level inverter has complexity in the formation of output voltage and requires many back-connection diodes. In order to complement this weak point, a multi-bridge inverter with pulse amplitude modulation composed of 5 H-bridge modules per phase was proposed by Peng and Lai for STATCOM application [3] and [4]. In this paper an SSSC composed of six three-level half-bridge modules per phase is proposed. The operation of proposed system is verified through simulations with EMTP and experiments with scaled hardware module [5]. The advantages of proposed system over the existing one are direct insertion in the transmission line without transformers and easy expansion of the output voltage by increasing the number of modules.

This paper proposes an SSSC composed of multi-bridge inverter, which has six three-level half-bridge modules per phase. The dynamic operation of proposed SSSC was analyzed through computer simulations with EMTP. And the feasibility of hardware implementation was verified by means of experimental works with a scaled prototype. The proposed system has flexibility to optimize the operation voltage required in the power system by adding or subtracting number of bridges. Another advantage of this system is that it can be directly inserted into the transmission line without coupling transformer. The developed simulation model and scaled prototype could be used to obtain design and manufacturing data for the actual system.