Font Size: a A A

Research On The Energy Management And Coordinated Control Strategy Of Microgrid In The Autonomous Mode

Posted on:2018-05-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:H Y WangFull Text:PDF
GTID:1362330566467347Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
The Distributed Energy Resources are mainly connected to the medium-and low-voltage level utility grid by the microgrid,which is composed by distributed generations,loads,energy storages,monitoring and protection devices.If the utility grid is scheduled to be blackout,microgrid must be changed from the grid-connected mode to the autonomous mode.Therefore,how to ensure reliable and stable operation of microgrid is a key problem especially when the capacity of distributed generations and energy storage devices is limited.In this dissertation,the grid-connected microgrid has been studied,including topological structure and control strategy.Besides,the energy management and optimal scheduling of microgrid in the autonomous mode are also analyzed to improve the energy management strategy of microgrid,offering the theoretical basis and technical support for the optimized operation and reliability of microgrid.In order to satisfy the grid-tied requirements of distributed generation with respect to voltage levels and capacity in the simulation,a power conversion method is proposed.The topologies,operation modes and control strategies of microgrid are firstly studied to establish the simulation models of photovoltaic power generation and energy storage system.Afterwards,micro source simulation model with arbitrary voltage and power is obtained with an extra power conversion in the grid-tied side according to the nominal grid-tied voltage and power.Based on the above component model,the off line and real-time simulation models of microgrid with photovoltaic and energy storages in the peer control mode have been built.The results further verify the correctness of the established microgrid and its operation control strategies.A load shedding strategy is proposed for microgrid based on surplus energy evaluation.When operating under the autonomous mode,it predicts the surplus energy continuously.According to the critical-level of the loads,the non-critical loads are scheduled to disconnect with the microgrid duly to ensure the power supply of the critical loads.Additionally,load switching moments are optimized to extend the load power supply time as long as possible.Therefore,an optimal load shedding strategy is formed for power supply reliability of loads.A load shifting strategy is proposed for microgrid by the consideration of demand-side response,aiming at improving the reliability of microgrid and enhancing the utilization of photovoltaic power generation.For the grid-tied microgrid in the autonomous mode,the storage energy is estimated by considering both power generation/consumption and the real-time power balance.Combining the demand-side response technique,operation time zones of the shiftable loads in microgrid are optimized to achieve that the shiftable loads in the period with insufficient power generation are shifted to the period with sufficient power generation.A hierarchical coordination scheduling strategy is proposed for microgrid based on rolling evaluation and feedback compensation due to that the accuracy of scheduling strategy is influenced by the prediction error of renewable energy power,and the prediction accuracy is increasing with the reducing time scale.The rolling optimal power dispatch consists of"day-ahead rough scheduling,intra-dayexact scheduling and real-time subtle scheduling".It is implemented in microgrid based on the rolling energy and power evaluation of energy storages.Furthermore,the real energy and power values of energy storages are regarded as feedback information to correct the scheduling strategy repeatedly to make the scheduling results approach the actual operation.A forementioned autonomous energy management and its optimal scheduling strategy of microgrid have been analyzed with the typical structure involving photovoltaic and energy storages in multi-scenario simulations.The results show that the strategies proposed in this dissertation are correct and effective.The power supply reliability of microgrid in the autonomous mode is also enhanced.Beside,the utilization of photovoltaic power generation are improved significantly by applying the proposed strategies.
Keywords/Search Tags:Island microgrid, simulation modeling, energy management, surplus energy, demand side response, coordination scheduling
PDF Full Text Request
Related items