Distributed Fault Recovery Method For Distribution Network With DG

Fault recovery is an important part of the fault handling process of distribution network,and it plays a vital role in improving the power supply reliability of the distribution network.Recently,with the continuous improvement of distributed generation technology,distributed generation(DG)have been connected to the distribution network in large quantities,which has changed the distribution network from a single power supply network to a multi-source network,and the direction of the power flow has changed from one-way flow to two-way.Due to the randomness of DG's output,the fluctuations of voltage and power flow in distribution network have also increased.Traditional fault recovery methods of distribution network cannot be directly applied to the distribution network with DG.It is urgent to find new fault recovery methods for distribution network with DG.At present,the fault recovery of the distribution network mostly adopts the centralized control mode,and the central processor of the main station is set up.Each terminal unit in the distribution network uploads the collected information of local switch status and electrical quantities to the main station.Then the main station carries out the optimization calculation of fault recovery,formulates specific fault recovery scheme,and sends the'switch action instructions to each terminal unit.The centralized mode relies on the main station and has high requirements on the communication system.With the increasingly complexity of distribution network structure,the exiting problems are large computational complexity and long fault recovery time.As aforementioned,the miain contents of this thesis are as follows:(1)A new distributed fault recovery scheme for "hand in hand" distribution network with DG is proposed.The scheme pre-divides one or more different planned islanding regions for each DG in the distribution network,analyses the voltage variation at the point of common coupling(PCC)of DG during the fault reclosing process after distribution network faults,and fully considers the influence of reclosing on low voltage ride through(LVRT)of DG.Different fault recovery methods are implemented according to the different fault conditions of the fault location and the voltage variation at the connecting point of DG.Finally,based on PSCAD software,"hand in hand"distribution network with DG examples are simulated,and the effectiveness and feasibility of the proposed scheme are verified.(2)A distributed fault recovery scheme based on dynamic islanding algorithm for complex distribution network with DG is proposed.The proposed fault recovery objectives are the maximum recovery load and the highest priority of important load recovery.When the fault occurs in the distribution network,the network mathematical model is simplified by the equivalent of the main power supply,DG and load of the distribution network.Furthermore,the self-adaptability of the formed island and the network operation constraints are analyzed.The fault recovery operation range of multiple island with DG and main power supply as the power supply nodes is finally obtained by optimizing calculation,thereby achieving the purpose of fault recovery.Finally,the simulation calculation of the example is simulated based on MATLAB software,and the effectiveness of the proposed scheme is verified.(3)A fully distributed fault recovery coordination control method based on multi-agent system is proposed.The multi-agent system is composed of the bus agent(BA)installed at each bus.Each agent can directly obtain local power and load information,but cannot access the global information of the system directly.The neighboring agents can exchange information through the peer-to-peer communication network,and realize the function of acquiring global information of the system by local information by means of the average consensus algorithm.Taking the two target systems of Chapter 2 and Chapter 3 as examples,the practical application of distributed control system in fault recovery process is introduced in detail.(4)A fault recovery software module is loaded on the existing BA device,and the RTDS platform is used to test whether the device can achieve the proposed fault recovery scheme.A hand-in-hand distribution network model with DG is built on RTDS platform.Several closed-loop simulation tests are carried out according to different fault locations relative to DG.The test results show that the proposed fault recovery scheme is feasible and effective.