Analytical modelling of HVDC-HVAC systems

A new HVDC-HVAC analytical model is presented in this paper. The model comprises of three subsystems: AC system, PLL and DC system. The model is structured in such a manner to enable small signal analysis of HVDC-HVAC interactions and possible problems arising from these interactions. CIGRE HVDC Benchmark model is used as a test system. Model verification, performed using PSCADKMTDC simulations, showed good response matching for all DC and AC system variables. As an example of application of this model the influence PLL dynamics on the system stability is studied offering the important rules for tuning of PLL gains.