Spatial Repetitive Controller based Harmonic Mitigation Methodology For Wide Varying Base Frequency Range

Repetitive control is one of the main methods to regulate and mitigate higher-order current-harmonics in PWM converter systems. However, one of the main drawbacks of conventional repetitive control is that it cannot operate under varying base frequency, e.g. in electrical drives. This paper proposes a spatial repetitive controller (SRC) that applies fictive spatial samplers for extending the operating range of repetitive controllers to a wide range of base frequencies. The concept of SRC is illustrated in detail with focus on digital resampling process. This process is essential to achieve a strong harmonic mitigation as it decouples the ratio between sampling frequency and base frequency from the number of delay elements in the controller. First, a discretized quasi-linear fictive sampler model is developed. Consequently, a control framework for the digital implementation of SRC is developed and key design parameters are identified. An insightful design procedure based on dynamic stiffness and root location is introduced. Finally, the effectiveness of the proposed SRC is evaluated in experiments that are conducted on an electric load emulator test bench.