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This paper presents a time domain model of a HVDC-VSC system suitable for real-time simulations and its application to a wind energy conversion system (WECS). The HVDC-VSC model comprises two voltage source converters (VSC) linked together by a DC-link cable, their control systems and interfacing transformers. The operations of the VSC are based on pulse width modulation (PWM). The WECS is represented by a scaled-down system comprising a three-phase induction machine driven by a controllable DC servomotor running at a speed that corresponds to a full-size asynchronous wind generator. The mathematical model of the HVDC-VSC system is implemented in the real-time simulation environment using a commercially available real-time station (RTS). The power output profile of the scaled-down WECS is entered into the HVDC-VSC model residing in the RTS and fed to an external load using the digital-to-analogue converters (DAC) of the RTS. The effect of fluctuating wind speed is simulated in the scaled-down WECS and the response of the HVDC-VSC system to maintain voltage regulation to the load is assessed. The detailed implementation and configuration of the test environment is described in the paper.