Pwm Research Paper

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4.3.2.6. Hysteresis-Band Current Control PWM:- Hysteresis-band PWM is basically an instantaneous feedback control method of PWM where the actual current continually tracks the command current within a hysteresis band. Fig explain the operation principle of hysteresis band PWM for a half-bridge inverter. The control circuit generates the sine reference current wave of desired magnitude and frequency, and it is compared with the actual phase current wave. As the current exceeds a prescribed hysteresis band, the upper switch in the half-bridge is turned off and the lower switch is turned off and the upper switch is turned on. A lock out time (td) is provided at each transition to prevent a shoot through fault. The actual current wave is thus forced to track the sine reference wave within the hysteresis band by back and front (or bang bang) switching of the upper and lower switches. The inverter then essentially becomes a current…show more content…
The resonant-arm filter is shown in fig. 4.3 (2-a) is more appropriate for situations where low order harmonics are present. The parallel-arm, LP, CP and series-arm, LS, CS both are turned to the inverter output frequency. Fig. 4.3 (2-a) The Parallel-arm presents infinite impedance at the fundamental frequency and also reducing impedance to higher frequencies. The series-arm presents zero impedance to the fundamental frequency and also finite increasing impedance to higher frequencies. 4.7.3 Over The Top (OTT) Filters: The OTT filter is shown in fig. 4.3(3-a) is an extremely useful circuit when used in conjunction with parallel inverters. It performs three important functions and also it provides a sine-wave output, thus essential elimination of the harmonic content to the load. It gives good load regulation while at the same time maintaining a capacitive load to the inverter over a large load range of load power

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