A comparison of HVDC transient simulation algorithms

By setting up an identical test system, the authors have shown that the two main algorithms used for the simulation of AC/DC disturbances, namely TCS (transient converter simulation) and EMTDC, can be made to agree in their prediction of the dynamic responses. The TCS algorithm, though reputed to be less efficient, uses fewer approximations and provides automatic selection of optimal integration steps. As a result the TCS responses are very consistent. With careful selection of the integration step the EMTDC program can produce practically the same responses as the state variable technique for reasonably symmetrical conditions. However some deterioration occurs with highly asymmetrical disturbances. This has been traced to the phase advance prediction, required by the subsystem concept, thus the EMTDC algorithm provides a very efficient solution at the expense of some accuracy. It can be concluded that both the EMTDC and TCS algorithms can be used with confidence to simulate the transient response of AC/DC convertors