Coordinated Control Strategy for Unbalanced Power and Bipolar Voltage in Electrolytic Capacitorless Vienna Rectifier

In bipolar DC-bus systems, the extreme-value constraint on the neutral point (NP) current limits the unbalanced power operating range and degrades grid-side power quality in electrolytic capacitorless Vienna rectifiers. To address these challenges, this article proposes a coordinated control strategy for unbalanced power and bipolar voltage. A prediction-based clamping selection mechanism is proposed by computing a one-step-ahead NP voltage estimate at each sampling instant, effectively suppressing bipolar voltage fluctuations. Furthermore, the mapping between the power imbalance degree and the bipolar voltage is exploited to derive the optimal voltage imbalance degree, through which the unbalanced power operating range under NP current constraints is expanded. Additionally, a voltage vector trajectory optimization based on vertical projection minimizes the voltage vector synthesis errors within infeasible regions. Experimental results demonstrate that the proposed strategy extends the unbalanced power operating range, improves grid-side power quality, and enhances the stability of the bipolar DC-bus voltage in an electrolytic capacitorless Vienna rectifier.