INTRODUCTION
Pulse width modulation at constant switching frequency is widely used in inverter applications.To reduce the size of filter components and improve the harmonic characteristics of inverters, higher switching frequency is preferred. However, a drawback of higher switching frequency is the increase of switching losses. Switching losses are due to diode reverse recovery and hard turn off and turn on of active switches. As a result, the system efficiency is reduced. In higher power applications, where relatively slow switches are used, the switching loss is one of the major concerns. Various soil switching techniques (zero voltage switching (ZVS) and zero current switching (ZCS)) have been proposed to reduce the switching losses and improve the efkiency in inverters. DC link switches are commonly used to achieve ZVS in different power electronic applications. The switch voltage stress limitation is one of the major issues in using DC link or clamp switches .The inverter with a clamp switch proposed can achieve zero voltage switching while limiting the voltage stress of the DC link to the input voltage.
In this project, to improve the system efficiency further, the singlephase inverter with the previously proposed DC-link switch is extended to operate with the hybrid pulse width modulation (HPWM) control scheme. With HPWM control, only two of the four switches in the full bridge inverter are pulse width modulated at high frequency.Compared to the case when all four switches are pulse width modulated, the switching loss of the inverter is reduced to one half.
Pulse width modulation at constant switching frequency is widely used in inverter applications.To reduce the size of filter components and improve the harmonic characteristics of inverters, higher switching frequency is preferred. However, a drawback of higher switching frequency is the increase of switching losses. Switching losses are due to diode reverse recovery and hard turn off and turn on of active switches. As a result, the system efficiency is reduced. In higher power applications, where relatively slow switches are used, the switching loss is one of the major concerns. Various soil switching techniques (zero voltage switching (ZVS) and zero current switching (ZCS)) have been proposed to reduce the switching losses and improve the efkiency in inverters. DC link switches are commonly used to achieve ZVS in different power electronic applications. The switch voltage stress limitation is one of the major issues in using DC link or clamp switches .The inverter with a clamp switch proposed can achieve zero voltage switching while limiting the voltage stress of the DC link to the input voltage.
In this project, to improve the system efficiency further, the singlephase inverter with the previously proposed DC-link switch is extended to operate with the hybrid pulse width modulation (HPWM) control scheme. With HPWM control, only two of the four switches in the full bridge inverter are pulse width modulated at high frequency.Compared to the case when all four switches are pulse width modulated, the switching loss of the inverter is reduced to one half.
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