Journal
IEEE TRANSACTIONS ON POWER ELECTRONICS
Volume 34, Issue 7, Pages 6183-6199Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TPEL.2018.2865813
Keywords
Active power filter (APF); delay-compensation control link; dual-loop current control; robustness
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Funding
- National Natural Science Foundation of China [51777191]
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This paper is focused on a dual-loop current control method (grid current loop and fundamental current loop) for digitally controlled LCL-type shunt active power filters (APFs). Normally, a proportional-resonant (PR) unit is used as the fundamental current controller, where the proportional part of PR unit actually serves as the proportional feedback of inverter-side current and provides a certain degree of damping for LCL resonance. However, its valid damping region is only up to one-sixth of the sampling frequency (f(s)/6), which leads to less robustness to the grid impedance. To address this issue, a delay-compensation control link is proposed in this paper to replace the proportional part of the PR fundamental current controller and widen the effective damping region. As a result, the system robustness is improved without adding extra sensors or introducing an extra active clamping loop. Theoretical analysis proves that it can obtain a wider damping region of (0,f(s)/4). Moreover, a systematic controller parameter design criterion is studied. In particular, a numerical optimization algorithm is developed to optimize damping property, and a design method based on root locus plot and Bode diagram is presented to enhance harmonic compensation accuracy. Finally, experimental results implemented on a 30 kVA APF prototype have validated the feasibility of the proposed current controller and parameter design criterion.
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