Performance Enhancement of a Battery and Grid-Tied Robust Dual-Stage Modular Power Converter

This paper describes a Proportional-Integral (PI) control of a Dual-Stage Modular (DSM) converter. The DSM converter includes a battery-connected interleaved DC-DC bidirectional converter, a two-level full-bridge single-phase grid-tied inverter with a common DC link. The control technique regulates a DC link voltage and average inductor currents of the interleaved converter using a Unipolar Pulse Width Modulation (UPWM) principle and dynamic time-averaged modelling of the interleaved converter. The control further includes decoupled regulation of active and reactive power exchange with the grid by inverter current control in a synchronously rotating dq reference frame of the grid using a robust Phase Locked-Loop (PLL) and a Bipolar Pulse Width Modulation (BPWM) method. The singlephase PLL utilises the principle of a Second Order Generalised Integrator (SOGI) filter to synchronize the inverter with the single-phase grid to achieve the decoupled power control. The robust PLL design works for worst case grid conditions including presence of harmonics and a DC offset in the grid voltage. The proposed control scheme is validated and presented by MATLAB simulation results.