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This article proposes an enhanced integrated control strategy to mitigate grid current harmonics and power ripples for a three-phase grid-tied photovoltaic (GTPV) system without a phase-locked loop (PLL) unit. The proposed control strategy consists of an enhanced proportional resonant (EPR) current controller, which suppresses the harmonics of grid injected current under distorted grid voltage conditions. A phase compensated reference current generator (PCRCG) is integrated with the proposed EPR controller and used to eliminate active and reactive power oscillations under grid voltage sags and swells. The proposed integrated control strategy is implemented in the αβ stationary reference frame. The synchronization task is included in the PCRCG and making the system PLL-less. Thus, the associated computational burden and implementation complexity are reduced. Further, the frequency adaptability of the GTPV system is enhanced as compared to the PLL-based control strategy in the presence of grid frequency variations using the proposed control strategy. To ensure the fast maximum power point tracking, a modified incremental conductance maximum power point tracking algorithm is implemented in integration with the proposed control strategy. The effectiveness of the proposed control strategy is validated using OPAL-RT, real-time digital simulator and compared with the conventional PLL-based control strategy.

This article proposes an advanced integrated control strategy for enhanced grid current harmonic compensation with power ripple mitigation in a grid–integrated photovoltaic systems (GIPVS) under distorted grid voltage conditions. The proposed control strategy consists of an advanced proportional multiresonant (APMR) current controller and a compensator for grid voltage sag (CGVS), which is implemented with a phase-locked loop block. The APMR is designed in the α–β reference frame and minimizes the harmonics of the grid injected current. The CGVS, along with the APMR, eliminates the active and reactive power ripples under unbalanced voltage sags conditions. Further, an adaptive step size incremental conductance (ASINC) maximum power point tracking controller in integration with the proposed control strategy is implemented. Along with current harmonic reduction by APMR, the ASINC method ensures effective and faster tracking of maximum power point and negligible oscillations in the steady-state under different environmental conditions. By utilizing the proposed APMR control strategy, the frequency adaptability of the GIPVS is improved compared to the conventional proportional multiresonant (PMR) control strategy under grid frequency deviations. It successfully keeps the grid current total harmonics distortion below the acceptable limits for the grid voltage polluted by several odd harmonics, up to the nineteenth harmonics. The proposed control strategy of APMR with CGVS almost completely eliminates the power ripples in even severe unbalanced voltage sag conditions. Experimental studies are carried out using a real-time digital simulator to verify the effectiveness of the proposed control strategy in comparison with the conventional PMR controller.

The grid-integrated solar photovoltaic (PV) inverter is generally used to provide active power (P) support to the distribution grid operated at maximum power point (MPP) condition. Moreover, it should also be capable of providing reactive power support (Q) to the distribution grid. Therefore, an appropriate range of reactive power should be known at MPP condition to ensure satisfactory operation of the grid-integrated PV system (GIPV). In this work, an improved mathematical methodology is proposed to derive the P-Q capability curve of GIPV for managing the reactive power injection into the grid at MPP condition for various environmental conditions. By evaluating all the possible set of working point within the stable region of operation, this methodology is used to obtain reactive power limits of a utility-scale single-stage three-phase PV system connected to the IEEE 33 bus distribution grid. The considered PV system is simulated using software-in-the-loop (SIL) environment based on OPAL-RT OP4510 real-time digital simulator with coordinated closed-loop control of dc-link voltage controller, maximum power point tracking (MPPT) controller, and active and reactive power controller. To validate the effectiveness of the improved mathematical methodology, the reactive power injection to the grid is changed, and the corresponding active power injection to the grid are measured, which are compared with the P-Q values obtained from the improved mathematical methodology.

This paper presents a phase-locked loop less (PLL-less) control scheme (PLCS) with an improved proportional resonant (IPR) controller for a grid-tied solar photovoltaic system (GTPVS). The proposed control scheme operates in a self-synchronized mode without the need of a PLL block. This reduces the computational burden on the controller and eliminates the delay due to the PLL block. In addition, it also improves the dynamic performance of the GTPVS under grid frequency deviations. The improved proportional resonant (IPR) controller reduces grid current harmonics under distorted grid voltages. Further, this control scheme is utilized to eliminate the active and reactive power ripples during grid fault or sag conditions. In order to extract the maximum power from photovoltaic (PV) array, a variable step-size incremental conductance (VSS-INC) maximum power point tracking (MPPT) algorithm is implemented. Real-time experiments are carried out using OPAL-RT real-time simulator to verify the effectiveness of the proposed PLCS compare to the conventional PLL-based control scheme (PBCS).

Integration of renewable energy with conventional energy sources is very challenging due to the uncertain nature of renewable energy, which creates imbalance and congestion in the system. Moreover, every market participant/player in deregulated power market wants to achieve the economic benefits within critical system constraints like congestion. Therefore, this paper presents a simple, efficient and reliable two-step optimization strategy to solve the congestion problem along with maximization of system profit, minimization of system generation cost, congestion cost and emission by optimal placement & numbers of Thyristor Controlled Series Compensator (TCSC) along with wind generators in a deregulated power market. Two new indices i.e. ‘Congestion Detection Index (CDI)’ and ‘Index of Total Congestion Cost (ITCC)’ have been proposed towards faster identification and reduction of system congestion effectively. The pool & bilateral deregulated market model has been considered for this study. The maximum system profit has been considerably achieved after optimal placement of wind generator and TCSC(s) in the system. The effectiveness of the proposed approach has been analyzed and tested in modified IEEE 14 bus and modified IEEE 118 bus test system. The proposed approach has been compared with the existing related approach for congestion mitigation, and better results have been achieved from the proposed approach.

This paper proposes an enhanced proportional resonant (EPR) current controller for a grid-connected photovoltaic system (GCPVS) without phase-locked loop (PLL). The EPR current controller suppresses the grid current harmonics in the presence of distorted grid voltages. The overall control strategy of the proposed system is implemented in the α-β reference frame without PLL and the park’s transformation. Consequently, the computational requirement of the GCPVS is reduced. Further, the dynamic performance of the system is enhanced under the grid frequency deviation. Moreover, a modified incremental conductance maximum power point tracking (MINC MPPT) algorithm is implemented, which is characterized by faster tracking ability under rapidly changing environmental conditions and maintaining low power oscillations in the steady-state. The effectiveness of the proposed PLL-less EPR control strategy is validated through a real-time digital simulator OPAL-RT under distorted grid voltage conditions and compares it with the conventional PR PLL based control strategy.

Power is the most paramount ingredient of infrastructure for growth in economics and welfare of a nation. Development for sustaining the growth of the Indian economy in the existing infrastructure is crucial. The power sector of India is one of the largest expanded power sectors in the world. Due to the continuous increment in electricity demand day-by-day, Indian power sector is interfacing some challenges to maintain the balance between the power generation and demand with suffering from supply constraints and shortages in power. For maintaining the ratio of generation and demand of power, moving from conventional sources to non-conventional sources is not only an option, it is a necessity. The importance of using solar as an energy source in India׳s perspectives in not only to increase power generation, but also to expand energy reliability with considering the environmental, social, independent and financial beneficial properties. This paper analyzes the recent scenario, strategies, availability, future potential, policies and development of solar energy in emerging Indian power sector.

A grid connected inverter with an unbalanced voltage at the point of common coupling creates oscillation in DC link voltage at twice the grid frequency and inject highly distorted current into the grid. In this paper analytical expression for oscillation of DC link voltage and distortion in current injected to the grid are derived. Two control strategies for grid connected inverter are implemented and the analytical result obtained for dc link voltage oscillation and distortion in grid current are verified through simulation and experimental results.