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This work addresses discrete time modeling, implementation and design options for the current control of three phase grid tied PWM converters. Based on an accurate discrete time model of the PWM converter, closed loop current control is reviewed from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed leading to the formulation of a general controller framework based on space vector resonators: the Resonant Space Vector (RSV) regulator. It can embody multiple SFPI regulators on different frequencies and allows a consistent design of state feedback controllers as well as an efficient implementation. For this control framework an insightful design procedure based on the root locus method for complex system models is introduced. Finally, the performance of the presented control design and implementation concepts is demonstrated experimentally.

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This paper describes the design of a digital control for a 3.3 kV, 1 MVA three-level PWM converter operating as test generator for disturbances in medium-voltage grids according to standards like IEC 61000, EN 50160, and IEEE 1547.The proposed control combines state-feedback with additional dynamic output feedback. It is designed fully in the stationary reference frame to avoid processing of complex transformations into different rotating reference frames. Resonant controllers provide zero steady-state error for up to ten harmonics.A DSP platform is used for implementing the control. It replaces the control unit of a commercial converter. Experimental results of a downscaled breadboard construction verify the functionality of the control.

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