Research On The Control Strategy Of Independent/grid-connected Dual-mode Inverter Power Supply

Environmental and energy problem has become a global problem,the construction of a safe,clean energy interconnection network is to address today's social development and the environment,the way of energy relationship,now all countries put forward the energy conservation and emissions reduction of energy policy,actively develop new energy sources such as wind power and solar energy into hair distribution power grid,made of the new energy power generation micro power grid has become the main way of national new energy power supply.In this paper,the key equipment in new energy generation--independent/grid-connected dual mode inverter power supply is studied.According to its system structure,the control strategy is designed to realize flexible operation control.Firstly,the research background and significance of this paper are summarized,the research status of independent/grid-connected dual-mode inverter power supply at home and abroad is investigated,and the existing problems and key technologies of new energy power generation and inverter power control strategy are analyzed.This paper focuses on the study of the dual-mode inverter,designs its overall structure and modulation strategy,selects the LCL-type filter T-type three-level as the main circuit topology,and analyzes in detail the converter path of T-type three-level inverter.The three-level SVPWM modulation strategy is adopted to specifically study the saddle-type SVPWM modulation strategy and carrier implementation method,and finally obtain the structure of dual-mode inverter with high performance.Secondly,a dual mode inverter control strategy based on virtual synchronous generator is proposed.The mathematical model of virtual synchronous generator is established,including stator electrical equation,rotor motion equation,excitation regulator,prime mover regulator and voltage and current double closed-loop control strategy.The mathematical model of active power control loop in grid-connected mode is established,and the influence of inertia,damping and other parameters on the dynamic characteristics of the system is analyzed in detail.A presynchronization control method based on double phase locked loop is designed,which can realize seamless switching between off-grid and grid-connected modes and theoretically eliminate the risk of switching failure.Finally,the MATLAB/Simulink simulation model was built to verify the effectiveness of the T-type three-level dual-mode inverter control strategy based on virtual synchronous generator control in four modes: off-grid,off-grid to grid-connected,grid-connected,and grid-connected to grid-connected to grid-connected to grid-connected to grid-connected.The hardware experiment platform of T-type three-level dual-mode inverter is designed.