Research On Optimal Operation Of Microgrid Based On Grid-connection Technology Of Permanent Magnet Wind Power Generators

Energy is an important factor in the development of human society.In the case of reducing greenhouse gas carbon dioxide emissions has become a global con sensus,wind energy,as a clean energy,is one of the key areas of national development.Converting wind energy into usable electric energy involves wind power generation technology.Wind power generation technology includes wind turbine design,frequency conversion technology,motor electronic technology and chip control technology.At present,due to the high intermittency and instability of wind power generation,in order to maximize the use of wind energy resources and reduce the adverse impact of wind power on the power grid,the power electronic wind power integration and the optimal operation control of related systems are becoming a research hotspot,Among them,multi terminal DC microgrid system based on flexible DC transmission technology and AC microgrid system based on large capacity energy storage technology are two effective ways of wind power integration and wind energy utilization.This paper focuses on the topology and mathematical model of permanent magnet direct drive fan,AC grid connected control strategy of permanent magnet fan,AC microgrid optimal operation of permanent magnet fan,DC grid connected control strategy of permanent magnet fan,multi terminal DC microgrid optimal operation of permanent magnet fan.The main innovations are as follows:(1)AC grid connected control strategy of permanent magnet fan.In this paper,based on the topology of "uncontrollable rectifier+boost chopper circuit+three-phase voltage source PWM inverter",the principle of maximum power tracking control(MPPT)on the generator side and double closed-loop control on the grid side are described in detail;A double closed-loop control strategy of "speed outer loop and current inner loop" is proposed for the maximum power tracking control of the generator side;Aiming at the grid side mainstream "voltage outer loop and current inner loop" double closed-loop grid control strategy,through the improvement of control algorithm,the AC grid control performance of permanent magnet fan is improved,and the following three AC grid connected goals are achieved:1)reducing current harmonics and improving dynamic response speed;2)The decoupling of active power and reactive power is realized to achieve unit power factor grid connection and stable output of DC bus voltage;3)Improve the control accuracy,anti-interference ability and robustness of the system.(2)Optimal operation of AC microgrid based on AC grid connected permanent magnet fan.Based on the AC microgrid with wind power,schedulable distributed generation(diesel generator),energy storage system and partial load,this paper proposes a new efficient power management method according to the current mainstream intelligent algorithm,and adopts appropriate prediction technology to deal with the uncertainty of wind energy and power consumption in the microgrid.The proposed energy management optimization objective aims to minimize the expenditure of microgrid on fuel,operation and maintenance,as well as power import from the main grid,and maximize the energy output of microgrid to the upstream grid.Based on the economic operation of AC microgrid,this paper proposes an optimal operation strategy of AC microgrid based on Petri net and hybrid heuristic group optimization algorithm.Firstly,according to the operation characteristics of each distributed new energy,the corresponding Petri net model is established,which effectively describes the mode switching and control process of microgrid operation.On this basis,the mathematical model of AC microgrid economic operation is established,and the hybrid heuristic group optimization algorithm is used to solve the mathematical model,and the switching state and specific output of each distributed generation in AC microgrid are obtained.Finally,the strategy proposed in this paper is applied to a specific case for simulation analysis.(3)DC grid connected control strategy of permanent magnet fan based on flexible DC transmission technology.Based on the control strategy analysis of VSC converter station,this paper proposes a control strategy of permanent magnet fan DC grid connected based on mrnc-hvdc;Firstly,a three terminal DC grid connected system of permanent magnet fan is established,including permanent magnet fan side and two AC grid sides;Then,based on the thrce terminal DC grid connected system,a three-layer control strategy is proposed,including system level,converter station level and converter valve level.For the converter station control on the fan side,the traditional single loop control with constant AC voltage is transformed into a double closed-loop control with"voltage outer loop PR current inner loop decoupling" by using the characteristic of improved PR con trol without static error tracking,which solves the problem of symmetrical fault ride through of VSC converter station when the AC voltage on the fan side is distorted.(4)Optimal operation control of multi terminal DC microgrid based on DC grid connected permanent magnet fan.Based on the "DC microgrid test platform" of National Smart Grid Research Institute,this paper studies the optimal control strategy of multi terminal DC microgrid based on VSC-MTDC under the condition of wind turbine grid connected.This "DC microgrid test platform" is mainly composed of wind turbine,AC/DC converter,DC/DC converter,programmable load,line and fault simulator and supporting related equipment.After the completion of the system,it will be able to simulate the real large-scale DC power grid system.Based on the operation strategy of DC microgrid test platform when wind turbines participate in power regulation,a new optimal control strategy for grid connected operation is designed based on smart multi-agent technology of microgrid and isolated bi-directional full bridge DC-DC energy storage technology.Firstly,the six terminal DC microgrid system is established,and the mathematical model and control strategy of each port are studied.Then,taking the optimal operation and fault ride through of DC microgrid as the control objective,a new grid connected operation control strategy and fault ride through control strategy are designed based on the smart multi-agent technology of microgrid and isolated two-way full bridge DC-DC energy storage technology,and the multi terminal DC-DC system is realized The stable operation of DC microgrid and the effective control of wind turbine output fluctuation ensure the stable power supply and cost optimization of the load in DC microgrid.Finally,simulation verification and fault operation research are carried out on the "DC microgrid test platform" to verify whether the new DC microgrid grid connected optimization control strategy and fault ride through control strategy can effectively coordinate and control,at the same time,the maximum use of wind energy resources.