Research On Stability Of Photovoltaic Battery Hybrid Power System

There is still a large amount of population in the world suffers from lacking of electrical power,most of them locate in remote rural area and have a great demand of rural electrification.One of the ways to meet the energy demands in this regions is grid extinction,which has the disadvantage of high constructing costs,poor power quality at the end of grid and low efficiency due to long transmission lines.These drawbacks can be overcome by some kinds of distributed generation system.As a kind of flexible and renewable energy distributed power system,Photovoltaic-battery hybrid power system(PBHPS)is widely concerned and applied.Due to the application of power electronic converters,Photovoltaic-battery hybrid power system has a very strong nonlinearity.With the variation of light intensity,state of charge of the battery,and the load condition,the system needs to switch among different operating modes.Under some specific operating modes,this system will exhibit nonlinear dynamic behavior that affects stability.Firstly,this paper discusses the internal energy flow relationship under different working conditions of the system,analyzes the operation status of each module,and presents various possible operating modes of an independent PBHPS and the energy management methods suitable for the system.Under the different operating modes of PBHPS,Hopf bifurcation and catastrophic bifurcation phenomena are reflected in the simulation,and then they are mathematically analyzed to obtain the physical essence of bifurcation behavior.Furthermore,the stability of PBHPS under a single source supply power to the load is investigated.The stability of the whole system is analyzed by solving the eigenvalues of the Jacobean matrix,and the small signal stability criterion is derived.Then,the stability theorem of the mixed potential function is used to obtain the large signal stability criterion based on the simplified model.The obtained stability criterions give the stable boundary of the key parameters of the system.And the influence of the key parameters on the stability has been discussed.Finally,the validity of stability boundaries have been verified by the simulations and experiments.Finally,the stability analysis of the system is based on the large-signal model of multi-source system.The source converters in multi-source systems are divided into bus voltage control converter(BVCC)and bus current control converter(BCCC),and a large-signal model for multi-source systems with multiple converters is obtained after reasonable simplification.Based on the large-signal model,the sufficient conditions for stable operation of multi-source systems under large signal disturbances are deduced according to the stability theorem of the mixed potential function.The stability boundary of key parameters is drawn by the stability criterion,and how to select the key parameters to ensure the stable operation of the system is analyzed.Finally,the correctness of large signal stability criterion of system is verified by simulations and experiments.The work in this paper mainly complements the research on the stability of multi-source power systems with multiple converters,such as a PBHPS,and provides guidance for the overall design of these multi-source systems and the selection of key parameters.