Multi-functional Converter System Research Articles

Cost-Efficient Fault-Tolerant Scheme for Three-Phase Surface-Mounted Permanent Magnet Synchronous Machines Fed by Multifunctional Converter System Under Open-Phase Faults

Considering the innately connected neutral point in a multifunctional converter system (MFCS) fed three-phase surface-mounted permanent magnet synchronous machine (SPMSM) drive, this article develops its fault self-tolerance toward open-phase faults (OPFs) without assisted hardware. First, the operating principle of the MFCS fed SPMSM drive is explained by building a zero-sequence model. Second, to achieve fault-tolerant operations, an unconventional current vector trajectory is proposed, aiming at maintaining the torque and average input power invariable. The shape of the proposed trajectory tends to be like a heart rather than a circle with the rise of motor speed. Moreover, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{d}$</tex-math></inline-formula> -axis and zero-sequence currents vary with the position of rotor. By considering the limits of inverter voltage and current, the postfault output capability of the drive is explicitly analyzed. Third, a new fault-tolerant control strategy is thus proposed, in which the OPF is detected by comparing the deviation between predictive and actual currents. To track the time-varying current references, a differential flatness-based current controller is further developed. Finally, experimental results are given to verify the effectiveness.

Modeling, Control, and Experimental Evaluation of Multifunctional Converter System

The multifunctional converter system (MFCS) is a special topology of three-phase ac motor drives, which inherently integrates a dc-voltage regulation function. First, in order to explain the mechanism of the MFCS, an average model is derived in this article. An equivalent circuit is developed, which explicitly reveals that the MFCS is equivalent to a cascaded dc/dc converter-dc motor drive system. Second, the inverter's mean duty cycle is identified as an independent control degree of freedom for the dc-bus voltage. Then, the influence of pulsewidth modulation (PWM) on the dc-bus voltage is studied. It concludes that space vector PWM is invalid for the MFCS. To address this problem, the zero-sequence voltage injection PWM (ZSVIPWM) is proposed and actually sinusoidal PWM is a special case of the ZSVIPWM. Third, an overall control strategy is proposed for the MFCS, which includes not only the vector control for the motor but also a closed-loop control for the dc-bus voltage. Finally, comparative experiments with the standard topology are carried out on a permanent magnet synchronous machine prototype to verify these theoretical analyses and the control strategy.

Reduction of Device Currents for One Motor Type Multi-Functional-Converter-System

There is no doubt that Hybrid Electrical Vehicle can preserve the environment. These vehicles have several electrical power sources. The power flows among these sources are controlled generally using DC/DC converters. Therefore the DC/DC converter is the important device in HV. This paper shows the method how to reduce the inverter device current of the Multi-Functional Converter System (MFCS) in our laboratory. The MFCS consists of a motor, inverters and additional wires except of DC/DC converters. The MFCS can realize controlling the power among several AC or DC electrical power sources besides controlling motor torque. The characteristic of this MFCS in this paper is that the MFCS has two three-phase star connected coils in one motor. The proposed method is realized using the characteristic. This paper shows the validity of the proposed method using the experiment examinations.