The Inverse Optimal Control Of Grid Connected Inverter And Design Of Fault Current Limiter

With the rapid development of China's national economy,the demand for electricity energy is also growing rapidly.Traditional centralized power generation and long distance transmission of power grid construction mode have showed more and more limitations.In this paper,the distributed energy is connected to the grid as the research object,and the control of the inverter and the fault processing of the system are studied.Current inverter control has optimal control and PID.When the inductance and capacitance of the inverter are irrational,the optimal control of the Riccati equation is difficult to solve.At the same time,the time constant of PID control can not be determined.For the short circuit fault system,the surge current caused great impact on the short line,the most direct way is to access the bridge limiting controller.There are two kinds of bridge current limiter IGBT control,logic circuit and fuzzy control.But the sensitivity of logic circuit and the fuzzy control is low,the switch action delay is serious,and sometimes it may not be in time to deal with the short circuit condition.In addition to the single fault treatment,when there is a lightning and voltage collapse,it may be unnecessary and wrong operation.The object of optimal control of inverter required is solving Jacobian partial differential equation.But it is very difficult to solve Jacobi partial differential equation.In order to solving the HJB partial differential equations is the main obstacle to the optimal control of nonlinear systems.In order to avoid solving the HJB partial differential equation,this paper introduces the inverse optimal control scheme into the inverter control system.The inverse optimal reduces the complexity of solving Riccati equation in a large extent,it solve this problem which is the control of the inverter,when the inverter component is a non ideal state which leads to the error term of the system equation.In order to solve the problem that the IGBT control loop can not respond in time,the research of the new current limiting scheme or the current limiting technology is imminent.In this thesis,a new type of fault current limiter based on BP neural network is proposed in this thesis,which is based on the traditional fault current limiter.It can only be used in some extreme situations.When the short circuit point is far away from the power supply,the control circuit of the judgment will have a greater error,and sometimes even the IGBT gate circuit does not act.BP neural network is introduced into fault classification.The stability and applicability of the fault current limiter are obviously raised.The test results show that the intelligent classification model of neural network can improve the sensitivity and accuracy of the bridge fault current limiter.