A TSP/PSCAD Hybrid Simulation Program For AC-DC Power Systems

With the rapid development of modern power systems, many high-power electronic devices have been widely applied in them, such as HVDC links and FACTS devices. This has made system operation and control become more complex than ever before, at the same time setting down higher requirements for power system simulation and analysis techniques.HVDC links and FACTS devices, which respond rapidly to system failures, are mainly simulated with electro-magnetic transient program (EMTP) nowadays to study the detailed transients of instantaneous voltages and currents caused by system disturbances. Due to the limitation of computer storage and computation capability, however, it is barely possible to simulate a large power system with EMTP, even with parallel algorithms. On the other hand, transient simulation program (TSP), based on single-phase quasi-steady state models, can provide a large power system simulation with efficiency, but not instantaneous detailed simulation of these electronic devices. In order to overcome the disadvantages of both methods mentioned above, hybrid simulation algorithms have been developed, which implement EMTP simulation for electronic devices to get accurate dynamic characteristics, and TSP simulation for the external AC power system to raise the efficiency.The hybrid simulation algorithm presented in this paper embeds a transient stability program into the main program of commercial electro-magnetic simulation software PSCAD through the user interface. HVDC links and FACTS devices, along with their control systems, are constructed with the component library of PSCAD, and simulated in detail, meanwhile the external AC power system is simulated with TSP; data exchange are implemented through the interface buses at which these two parts interact. The effect of frequency deviation on electro-magnetic simulation caused by system disturbances is considered in this algorithm, the frequencies of the voltages at interface buses are updated dynamically. Thevenin equivalent circuit is used to replace the effect of the external AC power system on HVDC simulation, and the HVDC system is replaced with time-variant constant-power loads in transient stability simulation. Simulative tests for the proposed algorithm are performed on a AC-DC system based on Kundur's two-area system, and the obtained simulation results are compared with those by PSCAD software, comparison results show that the proposed method can reflect accurately the dynamics of power systems with HVDC links caused by system disturbances.