Negative Imaginary Theory-Based Proportional Resonant Controller for Voltage Control of Three-Phase Islanded Microgrid

Abstract

This paper demonstrates the design of robust proportional resonant (PR) controller using negative imaginary (NI) theorem for voltage control of three-phase islanded microgrid (MG) application. While operating MG as the islanded mode, different types of random and unknown load dynamics affect the MG. These loads eventually deteriorate the proper execution of MG-inducing disturbances in voltage and current. Therefore, to improve the performance of the three-phase MG, a simple, second-order controller is designed with the combination of NI theory and PR (NI-PR) controller. This controller is capable of providing higher level of damping as well as excellent stability properties. The stability and effectiveness of this controller are examined through imposing uncertainties, in terms of several load dynamics as well as different fault conditions. The comparison with respect to linear quadratic regulator and model predictive controller also ascertains the robustness of the designed controller. The NI-PR controller and the system are simulated in MATLAB/SIMULINK platform. Keywords Islanded microgrid • Negative imaginary theory • Second-order controller • Voltage control • Robust performance 1 Introduction Keeping the pace with progressive advanced facilities, demand for energy is rising lavishly. But due to the environmental protection, depletion of fossil fuel and sustainable development resulted in critical need for a cleaner energy technology (Bouchebbat and Gherbi 2017; Islam et al. 2020c). Hence, renewable energy sources are playing a vital role in today's power system applications. Some popular renewable energy sources are wind energy, photovoltaic (PV) system, biomass, wave energy, hydro-power, etc. (Coelho et al. 2018). Renewable energy sources-based distributed generators (DGs) are mainly small-scale power generation

A two‐level hybrid control strategy to augment transient stability and tracking accuracy of hybrid microgrid coupled with industrial loads

“…In (7), I cn and I N describe the capacitor current and load current, respectively. Now the state-space representation of the single phase SN with disturbance can be written as:…”

“…The term $$\triangle (s) = \def\eqcellsep{&}\begin{bmatrix} 0\\ -\frac{1}{C_1} \end{bmatrix}I_N(s)$$ indicates the uncertainty added with the system output from the input. The parameters for single phase SN are chosen from [7] so that it can act like a real‐time load corresponding to the controlled DC bus and consume power to enable the SN load premises via the LC filter with a value of 2 $$mH$$ and 15 $$\mu F$$. The controller is designed for the voltage control of the SN associated with the PV, battery and utility grid through the elimination of the non‐linear disturbance current $$I_{N}$$ in the state space representation.…”

“…In spite of providing a number of benefits, the efficiency of the HMG falls when operates with several industrial loads. The addition of a sub/secondary network (SN) with the HMGs is an alternative to drive different industrial loads at high efficiencies given that the relevant challenges like stability and control issues are addressed properly [6,7]. Several approaches have already been proposed to maintain the stable performance of the DC bus voltage through the controlling of DC-DC converter [13,14].…”

Improved voltage tracking of autonomous microgrid technology using a combined resonant controller with lead-lag compensator adopting negative imaginary theorem

“…However, they are extremely sensitive to frequency variation and require accurate tuning. Negative imaginary (NI) based-resonant (NI-R) [33], proportional resonant [34] and proportional plus lead compensator controllers [35] also promote voltage tracking performance along with damping resonant peak in islanded MG system, and exhibit robust performance against different load dynamics. However, they show poor performance in minimizing transient oscillation in some cases, and also the magnitude and phase errors in voltage tracking degrade their performance.…”