This paper presents the carrier based discontinuous space vector pulse width modulation (DSVPWM) for two-phase four-leg voltage source inverters (VSI) fed resistive and inductive loads. This proposed technique is focused on the switching losses and output current ripple reduction in each phase-leg of inverter which does not depends on the lagging and leading power factor load. In addition, the carrier based DSVPWM is modified from conventional two-phase four-leg VSI by replacing the zero space vector in each switching sequence. This proposed discontinuous modulation strategy has 180 degrees for unmodulated region. Experimental results provide the performance comparison between the discontinuous SVPWM (DSVPWM) and the traditional continuous SVPWM (CSVPWM) techniques to confirm the reduction of switching losses and output current ripple at high modulation index. The experimental results show that total average values of normalized switching losses of the DSVPWM and the CSVPWM are 7.908 and 11.174, respectively in which the proposed DSVPWM can reduce the switching losses from the conventional CSVPWM up to 29 percent.
Słowa kluczowe: Two-phase four-leg inverter, Switching losses, Ripple current, Discontinuous space vector pulse width modulation.
W artykkule opisano nieciągła technikę modulacji szerokości impulsu DSVPWM zastosowaną w dwufazowych czterogałęźnym przekształtniku VSI obciążonym indukcyjnością i rezystancją. Projekt zakładał ograniczeniu strat przełączania i zafalowania prądu. Eksperymentalnie porównano zaprojektowany układ z tradycyjnym układem ciągłym.
Keywords: przekształtnik dwufazowy, nieciągła modulacja szerokości impulsu DSVPWM.
An increase of performance of the three-leg voltage source inverter can be enhanced by reducing the switching losses and output ripple current when the discontinuous space vector pulse width modulation (DSVPWM) technique for high modulation index has been performed [1-3]. Many types of DSVPWM techniques such as DPWMMIN, DPWMMAX, DPWM 0, DPWM 1 and DPWM 2 of threephase voltage source inverters (VSIs) depend on types of power factor load. For example, DPWM 0 is suitable for a leading power factor load and DPWM 2 is fit for a lagging power factor load . In addition, three-leg voltage source inverters can be applied to two-phase induction motor of both of the asymmetrical and symmetrical parameter types for industrial application . Especially, the two-phase fourleg voltage source inverter fed two-phase motors drive has an advantage of a lower DC bus voltage requirement compared to the DC bus voltage of two-leg and three-leg VSI at the same output voltage of inverter . On the other hand, a disadvantage of four-leg VSI is more number of switching devices than two and three-leg VSI. Therefore, to reduce the switching losses in switching devices in each leg, the modulating function of DSVPWM technique for twophase four-leg inverter fed balanced R-L load is proposed in this study. The experimental results of a decrease of switching losses and output current ripples for the proposed DSVPWM modulation are compared with the conventional CSVPWM. Fig. 1. A proposed two-phase four-leg voltage source inverter Table 1. Switching state and corresponding active space vector SV1 SV2 SV3 SV4 SV5 SV6 SV7 SV8 SV0 SV9 2Vdc 2Vdc [...]
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