Grid-connected solar photovoltaic (PV) systems are increasingly attracting the attention of industry and academia mainly motivated by potential to provide an alternative to the conventional fossil fuel generation. This helps to meet out the increasing energy demands and to limit the pollution of environment caused by fossil emissions. This paper presents a comprehensive overview of the grid-connected solar PV systems. The intention of this review is to provide a wide spectrum on architecture of grid-connected solar PV system and its constituent components such as solar cell, PV array, maximum power point tracking, filters, DC-DC converters, single-phase inverters, and three-phase inverters to the researchers, designers, and engineers working on solar energy and its integration into the utility grid. Brief overview of control techniques for the single and three-phase inverters has also been presented. More than 100 research publications on the topologies, configurations, and control techniques of grid-connected solar PV systems and their major constituent components have been thoroughly reviewed and classified for quick reference.

Comprehensive overview of grid interfaced solar photovoltaic systems

DC–DC boost converters have been widely employed at the dc input of grid-tied photovoltaic (PV) inverters. In order to comply with grid standards, their control systems must usually work in two operation modes: Maximum power point tracking (MPPT) mode and limited power tracking (LPT) mode. MPPT algorithms reach high dynamic and static efficiencies when they operate with high-speed PV voltage control, because PV voltage is not significantly dependent on solar irradiance variations. On another hand, high-speed LPT mode can be obtained by controlling inductor current, which is proportional to the power injected into the dc bus. Both modes can be integrated in a cascade control scheme with an inner and fast current loop and an outer voltage loop. The main challenge is that both voltage and current small-signal models are highly dependent on the operation point of the PV array, temperature, and solar irradiance. This may cause control interactions between both loops and instability, especially when small film capacitors are used in parallel with the PV array. A common approach is to increase the input capacitance and design a low-speed PV voltage controller, which is not the best solution when high MPPT dynamic efficiency is necessary. To overcome these challenges, this paper proposes a cascade control structure based on an inner non-linear current controller and an outer adaptive voltage controller with fast detection of the PV array's model without requiring extra current sensor. A control design methodology and a MATLAB stability analysis tool are presented to support application engineers. The proposed control system has been experimentally validated using a PV array and a boost converter switched at 40 kHz. PV voltage settling time lower than 8 ms has been achieved for low and high solar irradiance, demonstrating the efficacy of the proposed technique.

Cascade Control With Adaptive Voltage Controller Applied to Photovoltaic Boost Converters

Optimised hydrogen production by a photovoltaic-electrolysis system DC/DC converter and water flow controller

In recent years, it is getting attention for renewable energy sources such as solar energy, fuel cells, batteries or ultracapacitors for distributed power generation systems. This paper proposes a general mathematical model of solar cells and Matlab/Simulink software based simulation of this model has been visually programmed. Proposed model can be used with other hybrid systems to develop solar cell simulations. Also, all equations are performed by using Matlab/Simulink programming.

Simulation of a photovoltaic panels by using Matlab/Simulink

In this paper a new method (Algorithm) of controller design for boost type dc-dc converter is proposed. A feedback-feedforward controller for DC-DC boost converter is designed to obtain and keep output voltage constant. To do so, a digital unit is used as the heart of the control system which it tracks and provides pulse-width-modulation signal to control power electronic device in boost converter. The boost converter will be able to direct couple with inverter for solar photovoltaic system. Simulations using Matlab-Simulink are carried out and the obtained results show that the analyzed system exhibits good steady state performances and fast dynamical response. Moreover, this application significantly improves the line and load regulations of the output voltage of a boost converter rating an output power up to 1.44kW. Indeed, these parameters are less than 1% over a wide range of changes in the input voltage as well as in the load.

Application of feedback-feedforward loop digital control to a PWM dc-dc boost converter used for solar photovoltaic systems

A modern maximum power point tracking (MPPT) method based on the incremental conductance (IncCond) control algorithm is discussed. This method features a variable step iteration of duty ratio to get over the trade-off between dynamic performance and steady state oscillation around maximum power point (MPP). Moreover, in the aim to get an excellent precision and a swift response independently of the climatic conditions, an α-MPP pass through detection and β-acceleration mechanism are introduced.

A modern MPPT control algorithm based on α-MPP pass-through detection and β-acceleration mechanism

A 360 W photovoltaic (PV) module power with a maximum power point tracking (MPPT) algorithm is analysed and presented. In this study, the control algorithm is improved and then applied to the PV system. The results obtained show the ability of this algorithm to control high powers when weather conditions are changing. Under the same conditions, this improved technique offers, in steady state regime, a high dynamic tracking, but also a very satisfactory stability and precision of the MPP which has an improvement of the overall conversion system.

Efficiency improvement of a photovoltaic system by acting on the characteristics of MPPT control

In PV (photovoltaic) power systems, a MPPT (maximum power point tracking) algorithm is vital in increasing their efficiency But it is also vital to take into account the non ideal conditions resulting from complex physical environments in such PV power systems To minimize the degradation of performances caused by these conditions, and therefore adding reliability and robustness, this paper presents an implementation of a digitally controlled system using a topology based on series connected DC-DC buck converters for a stand-alone PV power system applications, operating with local and autonomous controls, to track the maximum power points of PV modules in non ideal conditions Simulations are carried out by using C-MEX S-functions under MATLAB-SIMULINK environment A PV system of 144 kWc is described and simulation results are presented

Design and Implementation of a Digitally Controlled Photovoltaic System Using Series Connected Buck Converters

A modern Maximum Power Point Tracking (MPPT) method based on the incremental conductance (IncCond) control algorithm is discussed. This method features a variable step iteration of duty ratio in order to get over the trade-off between dynamic performance and steady state oscillation around maximum power point (MPP). This is done through an MPP pass-through detection α and an acceleration mechanism β. Besides, a full stability test of the DC-DC power converter transfer functions is carried out using the Z-transform and has shown satisfactory results. Moreover, and since partially shaded series-connected PV modules exhibit multiple power maxima due to their integrated bypass diodes, all the centralized MPP trackers with all the available optimizations cannot harvest the max power delivered by the total PV sources and hence, are considered as non cost-effective. From that point on, the authors propose a distributed architecture driven by an intelligent α − β MPPT-based algorithm.

El Mamoun Aziz

Papers

Application of feedback-feedforward loop digital control to a PWM dc-dc boost converter used for solar photovoltaic systems

A modern MPPT control algorithm based on α-MPP pass-through detection and β-acceleration mechanism

Efficiency improvement of a photovoltaic system by acting on the characteristics of MPPT control

Design and Implementation of a Digitally Controlled Photovoltaic System Using Series Connected Buck Converters

Highly efficient distributed MPPT architecture driven by α − β algorithm for partially shaded PV modules