A New Method for Dynamic Analysis of Multi-Machine Power Systems Including HVDC-links due to Symmetrical and Asymmetrical Faults

In this paper, a new method is proposed for dynamic modeling of multi-machine power systems including HVDC-links facing symmetrical and asymmetrical faults. In the proposed method, the space phasors based sequence networks are used to power systems modeling during the fault time. In the sequence networks, synchronous generators and HVDC-links are modelled by injected current space phasors and loads are modelled by constant impedances. In each step time of simulation, after solving Y-matrix equations of the sequence networks, fault current and generators terminal sequence voltages are obtained in the synchronous reference frame. Then, for each generator, these voltages are transferred to the rotor reference frame and the machine dynamic equations are solved. By solving the synchronous machines and HVDC-links dynamic equations the state variables are updated and the current space phasors are calculated and the procedure is repeated for the next time steps. In a single-machine-infinite-bus (SMIB) network and a two-open-conductor faults. Moreover, the simulation results of the method have been compared to EMTP for the standard 33-bus-bar IEEE power system including a HVDC-link, the simulation results of the proposed method and EMTP software have been compared for a single-phase-to-ground and a two-open-conductor faults. The simulations results show the proposed method is reliable.