Research On Photovoltaic Maximum Power Point Tracking And Static Modeling Of Photovoltaic Grid-connected Generation System

With the increasing importance of photovoltaic power generation in China's energy structure,photovoltaic power generation technology has become one of the hot spots recently.The maximum power point tracking(MPPT)is a commonly used method to improve the efficiency of photovoltaic power generation and reduce the cost of per unit generation.There are two problems in the research of MPPT: on one hand,there is still room for improvement in the existing single-peak and multi-peak MPPT methods;on the other hand,in the existing research on static modeling of photovoltaic grid-connected power generation systems,the impact of MPPT control is neglected,which may lead to inaccuracy in some cases.To solve the above problems,taking photovoltaic power generation system as the research object,this thesis launches the research on photovoltaic maximum power point tracking and static modeling of photovoltaic grid-connected generation system.In the research on photovoltaic single-peak MPPT method,the output characteristics of PV module is studied;based on the trust region algorithm which doesn't include complex mathematical operations,a photovoltaic single-peak MPPT method is proposed.In order to reduce the cost of detection segment,the method is low-cost improved.The simulation test shows that the MPPT method based on the trust region algorithm can realize single-peak MPPT,has better ability in dynamic response,and improve the efficiency of photovoltaic generation.In the research on photovoltaic multi-peak MPPT method,an improved photovoltaic multi-peak MPPT method based on Quantum-behaved particle swarm optimization(QPSO)algorithm is proposed.The method applies the QPSO algorithm to the global search for the maximum power point.The total number and the voltages of the particles are initialized according to the distribution character of the extreme points on the P-U curves of the partially shaded photovoltaic arrays.A convergence criterion which is more suitable for photovoltaic multi-peak MPPT is proposed according to the characteristics of the particles' personal best voltages when the QPSO algorithm converges.The simulation test shows that the improved method can realize multi-peak MPPT quickly and effectively.It also has the ability to respond to the change of the light condition and improves the efficiency of the photovoltaic power generation when partially shaded.In the research on static modeling of photovoltaic grid-connected generation system,the structures and operation control strategies of the system are studied,and the current expressions are deduced according to the unbalanced operation control strategies including the average positive sequence control and the average power factor control.Considering the impact of MPPT control,a static model of photovoltaic grid-connected generation system is proposed,and the suggestion on how to use it in the fault calculation is given.