Modified one-cycle-controlled three-phase pulse-width modulation rectifiers under low-output DC voltage conditions

The saddle pulse-width modulation (PWM) that can be obtained by injecting third harmonic current into sampled three-phase input currents is proposed to introduce in the conventional one-cycle control (OCC) strategy-based three-phase PWMrectifier on this study. In addition, for the three-level boost-type neutral-point-clamped structure rectifiers such as three-phase Vienna rectifier, the fluctuation in the neutral-point-potential (NPP) is analysed under modified OCC strategy. The proposed control scheme can not only improve the utilisation of DC bus voltage and the efficiency of converter without sacrificing the advantages of the conventional OCC scheme, such as no phase-locked loop and constant switching frequency, but also is beneficial to suppress the ripple in the DC-link voltage. Moreover, the neutral-point voltage loop is added in the proposed OCC scheme, and the neutral-point voltage controller is employed for controlling the unbalance DC voltage in the NPP which caused by the non-uniformity of parameters of components. The validity of the theoretical analysis and feasibility of the modified OCC strategy are verified by system simulation and experimental results based on a 5-kW prototype.