Research On Coordinated Control Of Multi-Distributed Generations

With the advancement of industrial civilization,the demand for energy is increasing gradually.The supply of traditional energy gradually reduces and exposed shortcomings are increasingly apparent.Environmental pollution has become a important problem urgently to be solved in the present world.In order to solve this problem,the distributed power generation technology develops rapidly in recent years.its non-pollution,flexibility and reliability make up for the deficiency of the traditional power grid.The proposed microgrid concept integrates the advantages of distributed generation technology and alleviates the conflict with the grid.It is an important technology to realize high efficiency,environmental protection and high quality power supply of future smart grid.With the increase in the permeability of the distributed generation supply,energy bi-directional flow is not balanced,which will greatly affect the stability of power grid.Under the condition that different multiple distributed generation supply is added to the power grid,as a result of their different characteristics,it is an important task for to take appropriate control strategy to make them stable.In this paper,the coordinated control of multi distributed generation is used as the center based on the analysis of typical distributed generation supply model characteristics,control strategy of distributed generation microgrid,control strategy of the distributed generation inverter and the conversion of two operating states of the microgrid are studied deeply.The main content of the study are as follows:First,overview of the distributed generation supply and microgrid research status at home and abroad are given,through the analysis of working principle of several kinds of typical distributed generation,the corresponding dynamic simulation model is set up.Second,the current distributed generation inverter control strategy is studied.Topology structure and the mathematical model of three-phase inverter are established and the inverter LC filter is designed.The principle of the existing constant power control,the constant voltage constant frequency control and droop control are analyzed and their advantages and disadvantages are compared.For the droop control,a power decoupling control improvements is given.With the introduction of inertia and damping characteristics of virtual synchronous machine control,the control can make the power electronic device fit the excellent characteristics of the synchronous motor,which is helpful to enhance the stability of the system.The control algorithm of the virtual synchronous machine,power frequency controller and the excitation controller are designed.Third,microgrid control strategy is studied and the selection of different control strategies has great influence on the operation of microgrid.In order to solve the problems of microgrid in parallel operation and off-grid running switching state,a control method of microgrid switching in combination with virtual synchronous machine is put forward.The energy storage device is added to the microgrid to maintain the power balance of the system.From connected grid to island,the SOC of the storage battery is combined with the control of the virtual synchronous machine to obtain droop control method of dynamic adjustment.The pre-synchronization controller was designed.when the grid power is supplied,it can also participate in frequency and voltage regulation,to a certain extent,to enhance the running reliability and stability of the microgrid system.Fourth,article has used Matlab/Simulink system to build microgrid model with multi distributed generation.Under the equivalent structure control,multi distributed generation control strategy is adopted,microgrid contains three types of four distributed generation supply.The photovoltaic system adopts PQ,micro gas turbine uses droop control and VSG control is adopted to battery energy storage and integrated simulation model is established,and simulation results validate the effectiveness of this coordination control strategy.