Research On Pulse Width Amplitude Modulation Of Single Phase Inverter

With the progress and development of society,renewable energy will gradually replace fossil fuels and take a leading position.Microgrid and distributed generation are playing an increasingly important role,The efficiency and life of the inverter are the key factors,and it is of great significance to improve the efficiency and life of the inverter.The conventional switching method for single-phase inverters has a large switching loss,and the inverter has a short lifetime due to electrolytic capacitors,for theses problems,the new modulation method—Pulse Width Amplitude Modulation(PWAM)is studied detailly in this dissertation.A novel PWAM technique for single phase inverter is proposed in this dissertation.Unlike conventional modulation method,the proposed PWAM is capable of reducing more than 50% of the switching losses of the single-phase inverter and allows electrolytic capacitor-less dc-link design.With the benefits of considerably reduced switching losses and electrolytic capacitor-less design,a higher efficient,more compact and long lifetime single-phase inverter can be designed in practical application.The principle of the PWAM technique is described.Detailed operating modes and working states of each mode of the inverter has been analyzed.The switching losses of the PWAM method and the conventional modulation method are compared through theoretical calculations.PSIM software is employed to simulate the four modulation methods.The harmonic characteristics of the output voltage,and the harmonic contents of the bridge arm voltage of the four modulation methods are compared.The correctness and advantage of PWAM are verified.A photovoltaic system based on PWAM is proposed.The photovoltaic system is modular structure,including a number of p arallel photovoltaic modules,and take the form of plug and play.It is composed of front-end MPPT controller,back-end full bridge inverter and Buck/Boost decoupling converter with energy storage.The working principle and control method of each circuit o f the photovoltaic system are analyzed.The feasibility and good anti-interference of the PWAM of the photovoltaic system are verified by the simulation of the system level.On the basis of theoretical analysis and experimental simulation verification,the hardware and software of the circuit are designed,the main parameters of the hardware system in the circuit and the block diagram of the software system are given.The 200 W experimental prototype is built,the data of two modulation methods of SPWM and PWAM are tested,the switching loss and efficiency of the two modulation methods are compared,and the consistency between experimental results and the theory is analyzed.