Design and simulation analysis of Different PWM schemes for open loopZ-Source converter
Inverter is one of the most important parts of renewable energy system. To overcome disadvantage of voltage source and current source inverter, Impedance source inverter (ZSI) ,which is buck boost inverter without the need of a dc-dc converter has been presented in recent year. To be an economic alternative to conventional inverters, Z source inverter should have higher efficiency and lower cost and sustain a high quality output voltage. For meeting these requirements we used various control
... various control method. An alternative power conversion concept recently proposed by Z-source converter because it has both voltage buck and voltage boost capabilities .In ZSI hasan unique X-shaped impedance network which couples converter main circuit to the power source. In this paper we deal with comparative analysis of different modified PWM control methods of Z source inverter (ZSI), which is also known as impedance source inverter. For obtain boosted outturn voltage, a shoot through state should be created followed by an active state. Therefore, small changes have been made by us in the classical three phase sinusoidal Pulse Width Modulation (PWM) technique to provide different control techniques for the ZSI. Simple boost control with triangular carrier wave, simple boost control with sinusoidal carrier waveform, maximum boost control, maximum boost control with third harmonic injection, constant boost control and constant boost control. In this paper, simulations of various shoot through Control techniques are performed for the same modulation index and outline parameters of the ZSI. The output voltage and output current of the inverter for the same input and load conditions are analyzed using MATLAB/SIMULINK. Index Terms-Sinusoidal and PWM, maximum boost control, simple boost control, constant boost control, impedance source inverter (ZSI),MATLAB/SIMULINK-R2013a. I. INTRODUCTION In switching waveform distribution the shoot through of the traditional pulse width modulation is the key factor to control the z-source inverter. Diagonal capacitor voltage, control range of AC output voltage, voltage stress across switching devices and harmonic profile of the output profile are purely based on the method control algorithm adapted to insert the shoot through .There are many number of control method which have been presented so for to control the Z-source inverter .This paper deal with three type of PWM control algorithm: Simple boost control (SBC), Maximum boost control (MBC), Constant boost control (CBC). The buck boost operation of z source converter is based on the boost factor, which is based on the placement of the shoot-through time period in between the active state. Shoot through period is carefully inserted before or after the active states by keeping the time period of the active states constant. With the help of z-source inverter dc input voltage can be boosted with no requirement of dc-dc boost converter or step up transformer, by this we overcome output voltage limitation as well as lower its limitation as well as lower its cost. If we take comparison among conventional PWM inverter, dc to dc boosted PWM inverter, and Z-source inverter.ZSI shows that Z source inverter employs the lowest semiconductors and control circuit cost which are the main costs of a powerelectronics system. It is a new approach to compare all of them with the same circuit parameters to get a certain comparison. These advantages result in increasing attention on Z-source inverter, especially for the application where the input DC source has a wide voltage variation range, such as the photovoltaic (PV) grid tied generation and fuel cell motor drive system Moreover, for Z source inverter, EMI influence is free from concern since shoot through is welcome and even exploited, which in turn enhances the inverter reliability.