Research On The Locating And Sizing Of Multi-Type Distributed Generations And The Optimal Operation

In recent years, in the background of a new round of energy revolution with the center of elctricity, shape and functions of the traditional power grid is undergoing profound changes. Distributed generation with its unique technical advantages are more widely applied. Generally believed, Distributed generation (DG) is a small, environment compatible independent power systems which is placed on the user side of tens of kilowatts to tens of megawatts to meet the specific needs of the user or support the existing distribution network’s economic operation and sometimes meet the both requirements.The access of DG to traditional distribution grid will bring some impects on line flows, network loss, note voltage and reliability. Different types of distributed gererations have different power output characteristics when running with the grid. Therefor, how to reasonably allocate the sitting and sizing of DGs and wisely control their output to coordinate the running of the distribution network and make it economic and reliable become an urgent problem.The paper introduces two kinds of DG contained power flow calculation method based on forward and backward substitution algorithm and Newton Raphson algorithm. The distributed generations are divided into two different categories on the locating and sizing issues. One is the DGs whose output power is stochastic, the other is the DGs whose output power is controllable. Taking the wind turbine as an example, the paper discribe the application in the locating and type selection of stochastic DGs. According to the different output characteristics, the concept of controllable DGs’capacity is redefined and divided. To minimize the network loss, voltage deviation and static voltage stability index, Particle swarm optimization (PSO) is applied to the locating and sizing of controllable DGs. In view of the two groups of variables (location and capacity), a cross feedback PSO (CFPSO) based on improved PSO is proposed. Take IEEE-33 node distribution system as an example, the proposed model and algorithms are validated.According to the different output characteristics of controllable DGs, a comprehensive optimization model is established which contains the control variables of PQ-type DG’s power factor, PI-type DG’s current amplitude value and PV-type DG’s voltage amplitude value and the objective function of network loss minimization. Take the IEEE-33 node distribution system as an example, optimal calculation is conducted on a certain time section to determine the conrtol vairables of DGs. After optimization, network loss of distribution network is significantly improved so as to provide a good reference for multi-type DGs’output.