Research On The External Characteristics Of Distributed Generations And Loads

Nowadays, while central power generation, long-distance transmission system and large interconnectecl power system is greatly expanded, tapping new resources of energy and increasing use of renewable energy, a new power supply method is built up, which combines large power grids with distributed generation. Distributed generation is highly penetrative in the power system and applied widely. Distributed generation system is changing from scattered, small-scale development, local consumer satisfaction to large-scale, concentrated development and transmission high-voltage gradually. There would be some impacts on power system operation because of DGs integrating into power grid. To analysis of the influence of DGs incorporating into power network, on one hand, we need research on the external characteristics of DGs and its networking mechanism; on the other hand, we should focus on induction motor loads dispersed over distribution network mixed with all kinds of DGs, because the load model directly affects the accuracy and reliability of calculation results of the micro-grid voltage stability, transient stability.Based on the analysis aboved, this paper classifies distributed generations and loads into AC supplys and DC ones, sets up the detail mathematical model of several popularly used DGs, builds its' simulation models on PSCAD/EMTDC Platform, researches on the grid-connection control of two types of ports of DGs and its'impacts on power system after they incorporating into power network. The main work is as follows:(1) Modeling and simulation research on AC-type DGs and load. Setting up the mathematical model of wind power generation system in three aspects: wind turbine, DFIG and its control system, and design the controller of DFIG. Set up the mathematical model of microturbine and PMSG, which output high or variable frequency alternating current. Set up composite load model in distribution network containing DGs. Finally, the above models were simulated.(2) Modeling and simulation research on DC type DGs. Researching on the mathematical model of PV system and designing maximum power point tracking method. Researching on the mathematical model of battery, and finally the DC-type models aboved were simulated.(3) Research and simulat on grid-connection strategy mixed with all kinds of DGs. Design grid inverter of AC-type and DC-type DGs respectively, and grid-connection strategy is relevantly given. Control strategy based on DC distribution network is proposed in order to simple design method of DGs with different types, different capacities and different positions in micro grid composed of some DGs. (4) The permeability of distributed generations is higher and higher while the capacities of DGs increasingly larger and larger. Research on impacts of static stability and transient stability of grid consider of load modeling when DGs connection with grid in large scale.