A Plug and Play Three Terminal Active Power Decoupling Circuit

Inhalt:
The widespread adoption of electric vehicles (EVs) and solar photovoltaic (PV) systems has increased the demand for efficient and reliable single-phase inverters. However, these inverters introduce doubleline frequency ripple current, which disrupts maximum power point tracking (MPPT) in PV systems and accelerates battery pack degradation in EVs. Conventional two terminal active power decoupling (APD) circuits create a low-impedance alternate path to divert this ripple current; however, their effectiveness diminishes when the DC source exhibits low-impedance at double-line frequency. To address this, an alternate three terminal APD circuit (TT-APDC) has been proposed in the literature that increases the source impedance by emulating a small impedance in series with the source. However, this approach requires sensing source current, unlike conventional two terminal solutions. This leads to higher cost due to additional sensing circuitry. This work presents a modified control strategy for the TT-APDC that enhances source impedance while maintaining sensing requirements similar to the two terminal APD circuit. This reduces control complexity and cost compared to the conventional control approach used for TT-APDC.The proposed controller incorporates parallel LC resonance emulation strategy to enhance the source impedance at double-line frequency. At the same time, it creates a low-impedance alternate path for the ripple current by emulating series LC resonance behaviour. When compared to the conventional control strategy, the proposed technique reduces the double-line frequency ripple in the source current from 7% to 4%. The steady-state performance of the proposed controller is supported by simulation studies using MATLAB/Simulink. Its effectiveness is further validated through experimental studies on a 1.2 kW laboratory prototype of single-phase inverter incorporating the TT-APDC.