Constant-Parameter Average-Value Model of Power-Electronic Voltage-Source Converters With Direct Interface in Electromagnetic Transient Simulators

Average-value models (AVMs) of voltage-source converters (VSCs) are widely used as numerically efficient alternatives to their discrete switching models in electromagnetic transient (EMT) simulations. Recently, a so-called directly-interfaced AVM (DI-AVM) has been developed for VSCs, permitting large simulation time steps favorable for system-level offline and/or real-time studies. Although enabling large step sizes, the conductance/resistance matrix of the DI-AVM is time-varying and needs to be calculated at every simulation time step, which requires additional computational resources. This paper proposes a constant-parameter DI-AVM (CP-DI-AVM) for more efficient simulations of VSC-based power-electronic systems that does not require re-calculation of the network conductance matrix in EMT simulators. This is achieved by using a numerical approximation that only slightly reduces the solution accuracy. The performance of the proposed CP-DI-AVM is demonstrated on a large-scale VSC-based energy conversion system implemented in PSCAD/EMTDC. The proposed CP-DI-AVM is shown to have numerical advantages over the prior DI-AVM and the conventional AVMs of VSCs.