In this paper a rectifier-inverter system including a three phase diode rectifier and a dual output inverter is proposed for independently supplying two three-phase loads. This system employs less number of semiconductor devices compared to former dual output inverters More
In this paper a rectifier-inverter system including a three phase diode rectifier and a dual output inverter is proposed for independently supplying two three-phase loads. This system employs less number of semiconductor devices compared to former dual output inverters proposed in the literature and uses only six active switches for controlling two three-phase loads. Reducing the number of switches and hence drive and control circuits and also cooling system may result in a reduction in overall cost of the system, may reduce its semiconductor power loss and as a result increases efficiency and reliability especially in applications with low and medium voltage and power ratings. The new configuration is introduced and its carrier-based PWM schemes are developed. Analysis of sizing of the DC link capacitors is also performed so as to minimize the DC link voltage ripple, to reduce the value of DC link capacitors and to improve the grid current THD and the grid current balance. Furthermore, loss profile of the system is studied and the results are compared with counterpart topologies. Simulation and experimental results are presented to verify the authenticity of the theoretical model.
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The flying-capacitor modular multilevel converter (FC-MMC) has been introduced as a hardware development of the conventional MMC with the aim of reducing the cell capacitor ripple voltage in the application of electrical drive at low speeds. The capacitor ripple voltage More
The flying-capacitor modular multilevel converter (FC-MMC) has been introduced as a hardware development of the conventional MMC with the aim of reducing the cell capacitor ripple voltage in the application of electrical drive at low speeds. The capacitor ripple voltage of the cells in this converter is reduced only by injecting high frequency circulating current between the arms. In the conventional control method of this converter, the circulating current component is injected with the aim of complete elimination of the voltage ripple at low frequencies, which leads to an unnecessary increase of the current amplitude in the converter arms. In this paper, the converter control system is modified by finding the relationship between the cell capacitor voltage ripple and the high frequency circulating current amplitude. Then, by injecting the appropriate amplitude of the circulating current, the voltage ripple is controlled in an acceptable range. It is shown that by partial compensation (instead of full elimination of the voltage ripple), in addition to reducing the amplitude of the arm currents, the losses of the electrical system are significantly reduced. The results of simulations and experiments confirm the successful performance of the proposed method.
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