Research On Preventive Control For Distribution Network Based On Maximum Power Supply Capability

With the rapid development of social economy,the issues of fossil energy crisis and high-level load growth rate become increasingly prominent and the problem of shortage of network power supply capability(PSC)occurs in many areas.As a part of the smart grid,the smart distribution network's operation model is more flexible and changeable and the distributed generations in network can be used more efficient.Thus,when the network PSC become inadequate,changing the output of various types of distributed generations and the state of operable switch to improve the PSC and ensure the network operate on a certain safety margin become the new requirements for smart distribution network operation and control.Therefore,this paper conducts a research on the preventive control strategy in the non-fault state of distribution network.Firstly,the basic concept of distribution network maximum power supply capability(MPSC)is introduced and the influence factors of MPSC are analyzed,included the load level,the network topology and the load growth model in the evaluation times.The MPSC can reflect the maximum load level that the network can support and the variable-step repetitive power flow method is used to calculate the capability.Subsequently,the typical distributed generations' output models are introduced and studying their effectives to the MPSC.The simulation results show that the distribution network weak parts can be found quickly and accurately by the proper evaluation of the MPSC and the distributed generations inserted into the network weak parts can effectively improve the MPSC.Secondly,the distribution network preventive reconfiguration model is constructed,which regard the maximum value of the MPSC as the object.In this model,when changing the operation topology of distribution system,the electrical constrains and network topology constrains are considered to ensure the correctness of the results.On the basis of summarizing the existing types of network reconfiguration algorithms,the hybrid particle swarm algorithm is adopted to solve the target problem.For increasing the efficient of calculation,the concept of branch group is introduced to simplify the network and decrease the coding dimensions.The simulation results show the correctness and validity of this algorithm and demonstrate that changing the network operation topology can increase the MPSC.Finally,on the basis of the above concepts and analysis,a preventive control model combining the energy storage and network reconfiguration is established,which regards the MPSC as the safety index of distribution network operation.Considering the frequent changes of network topology will decrease the stability of system and increase operating costs,the minimum reconfiguration times during a day is taken as the first-level object and the maximum charge state of energy storage system and the MPSC index are considered as the second-level objects.Then,a multi-level objective model of preventive control is established.A strategy involving energy storage output and network reconfiguration is developed and a combining regulation method is proposed.When the MPSC is below the pre-defined warning value,it is prior to regulate with energy storage and the combining regulation will be conducted when the former can't meet the requirement.The simulation results show that the frequent changes of network topology can be avoided by the preventive control strategy combining the energy storage and reconfiguration and this strategy can ensure the distribution network operation reliability on a large scale.The model and the strategy are finally validated...