Design of a cooperative voltage harmonic compensation strategy for islanded microgrids combining virtual admittance and repetitive controller

Abstract

A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. Abstract-Non-linear loads (NLLs) in three-phase systems are known to produce current harmonics at -5, 7, -11, 13… times the fundamental frequency; harmonics of the same frequencies are induced in microgrid voltage, reducing therefore the power quality. Dedicated equipment like active power filters can be used to compensate the microgrid harmonics; alternatively, each distributed generation (DG) unit present in the microgrid can be potentially used to compensate for those harmonics. The use of the virtual admittance concept combined with a PI-RES control structure has been recently proposed as a harmonic compensation sharing strategy when multiple DGs operate in parallel. The drawback of this methodology is that a large number of RES controllers might be required to compensate for all harmonic components induced by NLLs. This paper proposes the combined use of virtual admittance control loop and repetitive controller (RC) for harmonic compensation. The main advantage of the proposed method is that only one RC is required to compensate for all the harmonic components, significantly reducing the computational burden and the design complexity.

The optimal design of repetitive controllers based on inverse frequency response

“…where the notation ℜ[z] represents the real part of the complex number z. Considering the two terms inside (7), the first term can be rewritten as…”

“…Based on the previous tracking error and the control input signal, the RC scheme repeatedly changes the control input signal to achieve tracking error convergence. Most recent applications of RC involve power electronics, such as active power filters, 1,2 uninterruptible power supply (UPS), 3 magnetically suspended rotors, 4 and microgrids 5‐7 . Other RC applications include rehabilitation robots 8,9 and manufacturing 10,11 …”

“…Most recent applications of RC involve power electronics, such as active power filters, 1,2 uninterruptible power supply (UPS), 3 magnetically suspended rotors, 4 and microgrids. [5][6][7] Other RC applications include rehabilitation robots 8,9 and manufacturing. 10,11 Performance tracking of the RC system relies directly on the effectiveness of the repetitive controller.…”