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The two-level voltage source inverter fed dual three-phase motor (DTPM) induces the high-frequency common-mode voltage (CMV) and generates the unwanted adverse effects. As one of the effective common-mode suppression methods, the conventional CMV elimination (CMVE) pulsewidth modulation (PWM) schemes are generally based on the voltage-balance mode for DTPM systems which suffer from the parameter asymmetry induced phase current imbalance. This article proposes two current-balance mode unified CMVE PWM schemes which has no restriction on the reference voltages and angle displacement between the two sets of three-phase windings. Thus, the proposed methods can be utilized in different types of DTPMs with different angle displacements between the two winding sets, and the CMVE effect can be retained both in the conditions of symmetrical and asymmetrical system parameters which is more practical than conventional CMVE schemes in real application. The function and performance of the proposal is proved by simulations and experiments. [ABSTRACT FROM AUTHOR]

Leakage current issues are worthy of attention for nonisolated grid-connected systems. This article introduces the method of eliminating common-mode (CM) voltage and reducing the leakage current based on modulation, and analyzes the correlation between actual effects of the method and the flying capacitor (FC) voltage balance in three-phase three-level FC grid-connected inverter. The proposed carrier-based modulation can balance the FC voltage by changing the transmission sequences of pulses and theoretically achieve zero CM voltage. In order to deal with the low frequency fluctuation and bias voltage of FC caused by asymmetry of actual hardware, the control method is introduced, which controls FC voltage by changing the action times’ distribution of switches, while still eliminating the CM voltage. Simulation and experimental results are provided to validate that the proposed method can control FC voltage and achieve good performance in suppressions of CM voltage, leakage, current and CM electromagnetic interference noise. [ABSTRACT FROM AUTHOR]

The increased phase number of multiphase systems enables us to exploit more degrees of freedom, such as the shape of phase carriers in pulsewidth modulation (PWM). The sawtooth carrier-based PWM (SCPWM) techniques are proposed in this article to reduce common-mode voltage (CMV) in both the peak-to-peak amplitude and the changing frequency, and it can be easily extended to symmetrical multiphase two-level inverters with any odd phase number. Theoretical analysis reveals that the switching between mirror-symmetrical carriers within one phase narrows the range of the sum of switching states in all phases, which leads to the reduction of CMV amplitude. Meanwhile, the overlapping of sawtooth carriers’ straight edges among different phases slows down the change of the sum of switching states, which results in the decrease of CMV changing frequency. Moreover, the effects of voltage harmonics injection and switches’ dead-time settings on the CMV reduction performance under the proposed SCPWM techniques are investigated. Finally, the experiment results in a five-phase induction machine and multiphase RL loads verify the improved CMV performance and the extensibility of the proposed SCPWM methods. [ABSTRACT FROM AUTHOR]

The voltage-source inverter with pulsewidth modulation (PWM) is widely used in motor drive applications owing to the technical maturity and simplicity. However, the inverter operating in the discrete and impulse state generates the high-frequency common-mode voltage (CMV) in the neutral point terminal of stator winding, which induces the negative effects. This article proposes a CMV elimination modulation scheme for the dual two-level inverter-fed asymmetrical six-phase permanent magnet synchronous motor, which has two sets of three-phase windings spatially shifted by 30° electrical degrees. The modulation algorithm shifts the PWM signals with the designed end-to-end cyclic sequence, which can retain the zero-voltage vectors for each sub-CMV of dual three-phase windings and theoretically eliminate the total CMV for the motor drive system. The validation of the proposal is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper introduces a novel pulsewidth modulation (PWM) scheme for an open-winding permanent magnet synchronous machine (OW-PMSM) driven by dual two-level three-phase inverter with common dc bus, which can effectively deal with the inherent zero-sequence current (ZSC) problem. Based on the conventional symmetrical unipolar double-frequency sinusoidal PWM scheme with an appropriate phase shift, the common mode voltage (CMV) of two inverters remains same and cancel out each other to eliminate the modulated zero-sequence voltage (ZSV) disturbance source. In this case, the double-frequency effect can be retained to reduce the ac side current ripple and suppress both corresponding motor vibration and acoustic noise, which is advantageous to improve the synthetic performance of motor. The dc-bus voltage utilization of the novel PWM scheme is proved to reach the same maximum value comparing to the conventional modulated ZSV elimination scheme. Meanwhile, a zero-sequence controller is designed to suppress ZSC by further adjusting the two CMVs to counteract other zero-sequence disturbance sources. To verify the analysis, the proposed PWM technique associated with the control method is implemented in an OW-PMSM experimental setup to validate the superiority of the proposed method. [ABSTRACT FROM AUTHOR]