Neha Beniwal

Abstract: In this work, a simple phase-locked loop - less control is presented for a single-stage solar photovoltaic (PV) - battery-grid-tied system. As compared to traditional solar PV systems, the system has reduced losses due to the absence of boost converter and a flexible power flow due to the inclusion of a storage source (battery). The synchronous reference frame theory is used to generate the pulses for switching the voltage-source converter (VSC), while maximum power is extracted from the solar PV array by using perturb and observe-based maximum power point tracking technique. The inherent feature of shunt active filtering by the VSC has also been incorporated in this system. Test results for the system operation under fixed power and variable power mode are studied on a prototype developed in the laboratory. During fixed power mode, a fixed amount of power is fed to the grid, whereas in variable power mode the power fed to the grid varies. Test results obtained are in accordance with the IEEE-519 standard. This work is a basis for the upcoming power market, where solar PV consumers can manage the generated electricity and maximise their profit by selling the power to the grid judiciously.

Abstract: This study presents a solar photovoltaic distribution static compensator (SPV-DSTATCOM) system feeding a non-linear load connected at point of common coupling. A hybrid variable step size-least mean square-least mean fourth (VSS-LMS-LMF) algorithm is proposed for the control of voltage source converter, which acts as DSTATCOM. A weighing factor is used so that LMS and LMF work simultaneously, and a varying step-size helps in obtaining an adaptable system. The proposed control shows high convergence rate and low value of mean square error. The SPV array uses perturb and observe technique for maximum power extraction. The transition of SPV-DSTATCOM to DSTATCOM and vice-versa is also studied. In SPV-DSTATCOM mode, the SPV feeds power to the load and the grid, resolving the power quality issues of the system, whereas in DSTATCOM mode, the grid feeds power to the load at unity power factor. The system is first simulated in MATLAB environment and then these results are experimentally verified on the developed prototype in the laboratory. The system is studied for both power factor correction and zero voltage regulation modes and under distorted grid conditions. The obtained results adhere to an IEEE-519 standard.

Abstract: This paper deals with the use of a distribution static compensator (DSTATCOM) to the system constituted by a nonlinear load fed from a distorted grid. Moreover, an improved proportionate normalized least mean square (i-PNLMS) control algorithm is proposed for the DSTATCOM. The system is first modeled on a MATLAB/Simulink platform and its performance is analyzed under steady state and load increment cases. The frequency response of the compensated system is also obtained. Tests are conducted on a laboratory prototype to analyze the system's performance under steady state and load unbalancing. This algorithm helps in achieving the desired grid currents easily and efficiently, and it shows an inherent tendency to adapt to the system's requirements. The obtained total harmonic distortion of grid currents and point of common coupling voltages are within the limits defined in the IEEE-519 standard.

Abstract: In this paper, a Volterra-filter-based control algorithm is developed to generate reference currents for a solar photovoltaic-distribution static compensator (PV-DSTATCOM) system in the distribution network The developed control is analyzed for being stable under Lyapunov stability criterion; consequently, the error function of the system converges to zero asymptotically The PV-DSTATCOM system is integrated to the grid to compensate the nonlinear load, while supplying solar PV array active power to the grid The system is modeled in MATLAB and is executed on a developed prototype in the laboratory, under balanced, unbalanced loading conditions, and variable insolation conditions Moreover, the harmonic distortion of the grid currents is observed under the IEEE-519 standard

Abstract: This paper proposes an adaptive modified least mean fourth (MLMF) control scheme with perturb and observe (P&O) technique for a voltage source converter (VSC) connected to solar photovoltaic array (SPV), three single-phase non-linear loads in a three-phase, 4-wire system with DSTATCOM (Distributed Static Compensator) capabilities. The adaptive control scheme based on MLMF shows low mean square error and converges faster. The system is modelled and simulated for power factor correction and zero voltage regulation modes. Due to single stage topology, the system shows high efficacy at high voltages. The neutral load current is well compensated by the VSC's fourth leg current. The harmonics in grid currents are well under the IEEE-519 standard.

Abstract: The paper discusses load compensation using a distribution static compensator (DSTATCOM). It is assumed that the DSTATCOM is associated with a load that is remote from the supply. It is shown that the operation of a DSTATCOM assuming that it is connected to a stiff source in such situations will result in distortions in source current and voltage at the point of common coupling. To avoid this, the DSTATCOM is connected in parallel with a filter capacitor that allows the high frequency component of the current to pass. However, this generates control issues in tracking, as standard controls such as a hysteresis control are not suitable in these circumstances. This paper proposes a new switching control scheme and demonstrates its suitability for this problem. It also proposes a scheme in which the fundamental sequence components of a three-phase signal can be computed from its samples. The overall performance of the proposed scheme is verified using digital computer simulation studies.

Abstract: Rapid industrialization and its automation on the globe demands increased generation of electrical energy with more reliability and quality. Renewable energy (RE) sources are considered as a green form of energy and extensively used as an alternative source of energy for conventional energy sources to meet the increased demand for electrical power. However, these sources, when integrated to the utility grid, pose challenges in maintaining the power quality (PQ) and stability of the power system network. This is due to the unpredictable and variable nature of generation by these sources. The distributed flexible AC transmission system (DFACTS) devices such as distributed static compensator (DSTATCOM) and dynamic voltage restorer (DVR) play an active role in mitigating PQ issues associated with RE penetration. The performance of DFACTS devices is mostly dependent on the type of control algorithms employed for switching of these devices. This paper presents a comprehensive review of various conventional and adaptive algorithms used to control DFACTS devices for improvement of power quality in utility grids with RE penetration. This review intends to provide a summary of the design, experimental hardware, performance and feasibility aspects of these algorithms reported in the literature. More than 170 research publications are critically reviewed, classified, and listed for quick reference for the advantage of engineers and academician working in this area.

Abstract: Modern utility grid is experiencing a transition from conservative centralized generation structure to a more distributed and decentralized structure. To achieve this transition, decentralized energy sources and loads must be seamlessly integrated and isolated from main grid structure. Realization of one such approach is termed as “Microgrid”. Microgrids (MGs) are a source of clean, efficient, and an economical way to integrating renewable energy sources and loads to the main grid. Higher penetration levels of MG would lead to significant perturbations with time periods being lower than conventional dynamic responses. This may pose problems of stable operation for the entire utility grid. For addressing this problem, this paper gives an in-depth literature review on the different control structure of MGs. As control dynamics required vary significantly, depending upon the integrated source, connected loads and ratings of the MG, it is important to understand the different structures of MG. Thus, categorization of MG based on different criteria such as distributed energy resources (DERs), type of distribution systems, modes of operation, and types of communication links used are first studied. As modern control structures are layered to achieve dynamic responses at different time constants, hierarchical controls are implemented. To address this concern, different levels of hierarchical controls are also discussed along with the control strategies of integrating various renewable energy resources in MGs. Different methods of controls are analyzed and assessed in each category and the major issues faced in the current infrastructure are noted. As the grid is moving towards optimal design of microgrid structures this manuscript reviews a number of optimization techniques along with their benefits and drawbacks.

Abstract: In this work, a simple phase-locked loop - less control is presented for a single-stage solar photovoltaic (PV) - battery-grid-tied system. As compared to traditional solar PV systems, the system has reduced losses due to the absence of boost converter and a flexible power flow due to the inclusion of a storage source (battery). The synchronous reference frame theory is used to generate the pulses for switching the voltage-source converter (VSC), while maximum power is extracted from the solar PV array by using perturb and observe-based maximum power point tracking technique. The inherent feature of shunt active filtering by the VSC has also been incorporated in this system. Test results for the system operation under fixed power and variable power mode are studied on a prototype developed in the laboratory. During fixed power mode, a fixed amount of power is fed to the grid, whereas in variable power mode the power fed to the grid varies. Test results obtained are in accordance with the IEEE-519 standard. This work is a basis for the upcoming power market, where solar PV consumers can manage the generated electricity and maximise their profit by selling the power to the grid judiciously.

Abstract: The power system is experiencing an ever-increasing integration of photovoltaic power plants (PVPPs), which leads to the demand on the power system operators to force new requirements in order to sustain quality and reliability of the grid. Subsequently, a significant quantity of flexible power point tracking (FPPT) algorithms have been proposed in the literature to enhance functionalities of PVPPs. The intention of FPPT algorithms is to regulate the PV power to a specific value imposed by the grid codes and operational conditions. This will inevitably interfere the maximum power point tracking (MPPT) operation of PV systems. Nevertheless, the FPPT control makes PVPPs much more grid-friendly. The main contribution of this article is to comprehensively compare available FPPT algorithms in the literature from different aspects and provide a benchmark for researchers and engineers to select suitable FPPT algorithms for specific applications. A classification and short description of them are provided in this article. The dynamic performances of the investigated algorithms are compared with experimental tests on a scaled-down prototype. Directions for future studies in this area are also presented.