Novel controllers based on instantaneous p-q power theory for transformerless SSSC and STATCOM

This paper investigates the operational performances of transformerless static synchronous series compensator (SSSC) and transformerless static synchronous shunt compensator (STATCOM), based on novel control schemes which are founded on instantaneous p-q power theory. In this paper, as reactive power compensators, the transformerless SSSC is used for controlling power flow of a 132 kV transmission line and the transformerless STATCOM is designed to regulate a bus voltage in a 6.6 kV distribution system. The proposed control systems use instantaneous p-q power theory in innovative ways that devote themselves not only to meet the reactive power demand but also to balance the DC link voltages. As a result, it is shown that the DC link voltage balancing control is simpler for the transformerless SSSC compared with the transformerless STATCOM. In addition, the control systems are based on phase shifted carrier modulation strategy, which has no restriction on the cascade number of H-bridge voltage source inverters. Comprehensive simulations are performed based on MATLAB/ Simulink to validate the analysis.