Study On Load Flow Calculation Method And Dynamic Simulation For Shipboard Power System

The shipboard power system (SPS) is an isolated power system. The loads and power generation equipment are strong coupled. To ensure that all types of load, especially the vital loads can be operated normally, the electric power quality of SPS must strictly satisfy the correlation standard, which include such as steady state and transient criteria of voltage, frequency, voltage waveform, as well as harmonic content of the system. The electric power quality of SPS can be tested after the ship was built, however, once the system is built, it is difficult to amend. Then there is an urgent necessary to pursuit assistance analysis method for SPS design and operation, especially with the increasing scale of SPS and the complex network configuration. The traditional design methods are difficulty satisfy the design requests.The steady state criteria of electric power quality can be analysed through three-phrase load flow calculation of SPS, including voltage distribution, asymmetry and so on. Transient voltage and frequency may be verified through the dynamic simulation method. Therefore, the load flow calculation algorithm and dynamic simulation of SPS are studied in this thesis. As a result, these two kind of platform for SPS analysis have been set up. A modified forward/backward sweep algorithm for shipboard power system load flow calculation is proposed in this thesis, which is derived from the traditional three-phase backward/forward power flow method for distribution network. Firstly, three-phase models for shipboard power system elements are established according to the features of SPS.Based on this, the backward/forward power flow method for radial distribution network is extended in order to deal with PV node and transformer model. For weakly meshed distribution network, a new three-phase power flow method based on the superposition principle is presented. The weakly meshed network is firstly divided into two networks using the superposition principle: one is the pure radial network and another is the pure meshed network. Three-phase power flow is solved separately on both the networks. The solutions are superposed together, and the final power flow solution is obtained by repeating to solve the power flow of the two networks. The presented method is tested by a typical shipboard power system, and the power flow solution is given. The results indicate that the proposed method is effective.The dynamic simulation models of shipboard power system are established based on the PSCAD/EMTDC, which provides analysable platform for examining the dynamic electrical energy quality of SPS. The main SPS elements are modelled and verified, including synchronous machine, the exciter and governor, variety of loads, the transducer and etc. Consequently the dynamic simulation platform for SPS is set up. Dynamic simulation analysis of typical operation condition are carried out.