Jeyraj Selvaraj

Multilevel Inverter For Grid-Connected PV System Employing Digital PI Controller

This paper presents a single-phase five-level photovoltaic (PV) inverter topology for grid-connected PV systems with a novel pulsewidth-modulated (PWM) control scheme. Two reference signals identical to each other with an offset equivalent to the amplitude of the triangular carrier signal were used to generate PWM signals for the switches. A digital proportional-integral current control algorithm is implemented in DSP TMS320F2812 to keep the current injected into the grid sinusoidal and to have high dynamic performance with rapidly changing atmospheric conditions. The inverter offers much less total harmonic distortion and can operate at near-unity power factor. The proposed system is verified through simulation and is implemented in a prototype, and the experimental results are compared with that with the conventional single-phase three-level grid-connected PWM inverter.

Single-Phase Seven-Level Grid-Connected Inverter for Photovoltaic System

This paper proposes a single-phase seven-level inverter for grid-connected photovoltaic systems, with a novel pulsewidth-modulated (PWM) control scheme. Three reference signals that are identical to each other with an offset that is equivalent to the amplitude of the triangular carrier signal were used to generate the PWM signals. The inverter is capable of producing seven levels of output-voltage levels (Vdc, 2Vdc/3, Vdc/3, 0, -Vdc, -2Vdc/3, -Vdc/3) from the dc supply voltage. A digital proportional-integral current-control algorithm was implemented in a TMS320F2812 DSP to keep the current injected into the grid sinusoidal. The proposed system was verified through simulation and implemented in a prototype.

Multistring Five-Level Inverter With Novel PWM Control Scheme for PV Application

This paper presents a single-phase multistring five-level photovoltaic (PV) inverter topology for grid-connected PV systems with a novel pulsewidth-modulated (PWM) control scheme. Three PV strings are cascaded together in parallel configuration and connected to a five-level inverter to produce output voltage in five levels: zero, +1/2V dc, V dc, -1/2V dc, and -V dc. Two reference signals that were identical to each other with an offset that was equivalent to the amplitude of the triangular carrier signal were used to generate PWM signals for the switches. DSP TMS320F2812 is used to implement this PWM switching scheme together with a digital proportional-integral current control algorithm. The inverter offers much less total harmonic distortion and can operate at near-unity power factor. The validity of the proposed inverter is verified through simulation and implemented in a prototype. The experimental results are compared with a conventional single-phase multistring three-level grid-connected PWM inverter.

Fuzzy-Logic-Controller-Based SEPIC Converter for Maximum Power Point Tracking

This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The FLC proposed presents that the convergent distribution of the membership function offers faster response than the symmetrically distributed membership functions. The fuzzy controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the voltage without any changes, in the variable-load case, represented in small steady-state error and small overshoot. The proposed scheme ensures optimal use of PV array and proves its efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load) side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both simulation and experiment at different operating conditions. The performance of the proposed FLC-based MPPT operation of SEPIC converter is compared to that of the conventional proportional-integral (PI)-based SEPIC converter. The results show that the proposed FLC-based MPPT scheme for SEPIC can accurately track the reference signal and transfer power around 4.8% more than the conventional PI-based system.

Implementation of Hysteresis Current Control for Single-Phase Grid Connected Inverter

This paper describes a control method for single- phase grid-connected inverter system for distributed generation application. Single-band Hysteresis Current Controller is applied as the control method. The control algorithm is implemented in digital signal processor (DSP) TMS320F2812. The control method provides robust current regulation and achieve unity power factor. Simulation and experimental results are provided to demonstrate the effectiveness of the design.

Fuzzy logic controller based SEPIC converter of maximum power point tracking

This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The FLC proposed presents that the convergent distribution of the membership function offers faster response than the symmetrically distributed membership functions. The fuzzy controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the voltage without any changes, in the variable-load case, represented in small steady-state error and small overshoot. The proposed scheme ensures optimal use of PV array and proves its efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load) side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both simulation and experiment at different operating conditions. The performance of the proposed FLC-based MPPT operation of SEPIC converter is compared to that of the conventional proportional-integral (PI)-based SEPIC converter. The results show that the proposed FLC-based MPPT scheme for SEPIC can accurately track the reference signal and transfer power around 4.8% more than the conventional PI-based system.

Control Methods and Objectives for Electronically Coupled Distributed Energy Resources in Microgrids: A Review

Increased penetration of distributed energy resources into conventional power systems increases control challenges. These can be suitably met by microgrids. This paper examines the architecture of microgrids and reviews their classifications and the literatures discussing their control objectives during islanded mode. It finds the use of microgrids enhancing the conventional power systems grid smartness. It also summarizes microgrid control objectives and their most common problems and solutions.

Hysteresis Current Control and Sensorless MPPT for Grid-Connected Photovoltaic Systems

This paper describes a control method for single-phase transformerless grid-connected inverter system for photovoltaic (PV) application. The system consists of a DC-DC Boost Converter and a full-bridge inverter. The DC-DC Boost Converter implements a Sensorless Maximum Power Point Tracker (MPPT) algorithm with regulated DC bus voltage while the full-bridge inverter implements a Hysteresis Current Control as the control method. These control method provides robust current regulation, achieve unity power factor, low THD and optimize the PV energy extraction suitable for grid connected PV systems. Simulation and experimental results are provided to demonstrate the effectiveness of the design.

DC-to-DC Converter With Low Input Current Ripple for Maximum Photovoltaic Power Extraction

This paper presents a dc-to-dc converter, which offers continuous input and output energy flow and low input current ripple, applicable and mandatory for photovoltaic (PV) arrays and maximum power tracking applications. The PV array yields exponential curves for current and voltage where maximum power occurs at the curves mutual knee. Conventional dc-to-dc converters have a relatively high input current ripple which causes high power losses when connected to nonlinear sources like PV arrays. The proposed converter maximizes the power that can be sourced from the PV array, without the need of any electrolytic filtering capacitance. The effect of current ripple can be significant and decreases PV system efficiency. Converter simulations and experimental results support and extol the system concept.

Rain-fall optimization algorithm: A population based algorithm for solving constrained optimization problems

Abstract This paper proposes rain-fall optimization algorithm (RFO), a new nature-inspired algorithm based on behavior of raindrops, for solving of real-valued numerical optimization problems. RFO has been developed from a motivation to find a simpler and more effective search algorithm to optimize multi-dimensional numerical test functions. It is effective in searching and finding an optimum solution from a large search domain within an acceptable CPU time. Statistical analysis compared the solution quality with well-known heuristic search methods. In addition, an economic dispatch (ED) optimization problem is run on an IEEE 30-bus test system, and the results, compared with those of recent optimization methods, show RFO performing relatively well, sufficiently effective to solve engineering problems. The constraint-handling strategy of the proposed method for solving ED problem is to generate and work with feasible solutions along all the optimization iterations without any mismatch between electricity demand and the total amount of power generation. Unlike the penalty methods, this strategy is unaffected by parameter setting of applied optimization method and its applicability for solving constrained optimization problems is not hampered. Eventually, its robustness is validated by the results of a sensitivity analysis of the parameters.