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Integration of rooftop solar-PV (RTSPV) systems and extensive use of nonlinear loads in the low-voltage distribution system (LVDS) leads to poor power quality (PQ). Therefore, it is necessary to address the issues leading to poor PQ at the point of common coupling of the LVDS. In this article, a multi-band hysteresis current control (MB-HCC) for the multi-functional inverter (MFI) is proposed which improves the efficiency of the MFI and also enhances the PQ of the LVDS. The MB-HCC uses simple switching logic and outperforms in its multi-functional tasks such as active power injection and power conditioning. MB-HCC offers better efficiency over variable double-band HCC (VDB-HCC) as it operates at a lower switching frequency. The performance of the proposed system is simulated by using MATLAB/Simulink and validated by OPAL-RT based real-time simulation studies. During the variation of solar irradiation, the proposed MFI has an average efficiency of 98.5% under the ideal grid and 97.34% under the distorted grid. Moreover, the percentage of Total Harmonic Distortion under ideal and distorted grid conditions is brought down to below 5%, and also, reactive power compensation maintains unity power factor operation complying with the IEEE-519-2014 and 1547 standards. These results substantiate the hypothesis of scalability of the single-phase MB-HCC-based MFI for an LVDS contributing to economy and ecology.

Industrial power system consists of several linear and non-linear loads. The proliferation of non-linear loads in power system causes the power system harmonics. Passive filters (PFs) are one of the ancient solutions to mitigate the harmonics. Some of the industrial power systems use PFs for harmonic compensation. Owing to dynamic load variation, the PFs are not the appropriate solution for harmonic compensation. To improve the system performance with existing PFs, this study presents the conservative power theory (CPT)-based hybrid active power filter (HAPF) with Type-II current controller for compensation of harmonics, reactive power and also the unbalance caused by different linear and non-linear loads of an industrial power system. In this system, the CPT is used as a harmonic reference generator and Type-II controller is designed for current control operation. The proposed HAPF overcomes the drawbacks of PFs and performs the compensation tasks effectively. The industrial power system with the proposed HAPF is modelled in MATLAB/Simulink environment and implemented in the real-time (RT) using OPAL-RT-based RT simulator. The RT results are in compliance with IEEE 519-2014 standard.

Objective A conservative power theory (CPT) based two‐stage three‐phase multi‐functional grid‐connected photovoltaic (PV) inverter (MGCPI) with auxiliary battery storage system (BSS) is proposed in this article. This proposed configuration offers selective power injection and power conditioning to the consumers. A power management (PM) algorithm is developed to decide the best mode of operation of the MGCPI, taking into account the state‐of‐charge (SOC) of the BSS and the available power at the solar‐PV source for effective coordination between BSS and PV source. Methods CPT is used for computing the MGCPI current reference signals for multi‐functional operations. The feed‐forward linear control systems are designed using classical frequency response analysis for a synergetic operation of BSS and MGCPI. The whole system configuration is modeled using MATLAB/Simulink and validated in real‐time with PM algorithm for unbalanced linear and nonlinear loads using OPAL‐RT based OP4500 grid emulator. Result The injected power, percentage THD of individual phase currents, true power factor, and unbalanced current are measured for various modes of operation. The proposed MGCPI with BSS improves the power quality (PQ) and also injects seamless power at the point of common coupling (PCC) to reduce the grid consumption. Conclusion The real‐time results demonstrate the effectiveness of the proposed approach for unbalanced nonlinear loads in smart electric grid, provisioning harmonic‐free electrical power as per the requirements of IEEE 519‐2014, IEEE 1547a‐2018 standards.

The proliferation of nonlinear loads and integration of renewable energy sources require attention for accurate harmonic estimation along with estimation of fundamental amplitude, phase, and frequency for protection, improving power quality, and managing power effectively in a smart distribution grid. There are currently different Windowed Interpolated Fast Fourier Transform (WIFFT) algorithms for harmonic voltage estimation, but estimation of current harmonics using WIFFT is not explored sufficiently. The existing WIFFT algorithms, when used for current harmonic estimation result in low accuracy due to spectral leakage and picket fence effect. On the other hand, Interpolated Discrete Fourier Transform (DFT) is used for synchrophasor quality metrics, but it is effective only when there are no harmonics and the fundamental frequency is constant. This paper proposes a unified solution, comprising of peak location index search (PLIS)-based Dual-Spectrum Line Interpolated Fast Fourier Transform (DSLIFFT) algorithm with 4-Term Minimal Sidelobe Cosine Window (4MSCW) for estimating both low-amplitude voltage or current harmonics and synchrophasor under variable frequency conditions for high-penetration renewable energy utility grids. The effectiveness of the proposed algorithm is validated by simulation studies and real-time experimentation using the National Instruments reconfigurable embedded system under nonlinear loading conditions.