Distribution static compensator (DSTATCOM) is very popular in compensating the linear, nonlinear, balanced and unbalanced loads. Any change in the load affects the DC-link voltage (DCLV) directly. The proper operation of DSTATCOM requires variation of the DCLV within the prescribed limits. This paper presents modified synchronous reference frame (SRF) method for real time generation of compensating current for harmonic mitigation and instantaneously active and reactive power compensation. Conventionally, a PI controller is used to maintain the DCLV to the reference value it uses deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI DCLV is slow. In this paper, a fast-acting DCLV controller based on the energy of a dc-link capacitor is proposed. Mathematical equations are given to compute gains of proposed controller and the detailed simulations of the four cases such as balanced linear, balanced non linear, unbalanced linear, unbalanced nonlinear are carried out on MATLAB/SIMULINK R2009b environment employing a three phase three wire DSTATCOM test system.
Key words: DC-link voltage (DCLV), distribution static compensator (DSTATCOM), point of common coupling (PCC), linear, nonlinear, power factor, power quality (PQ), voltage source converter (VSC), proportional-Integral (PI) control, CHB multilevel inverter, P-Q reference frame theory
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