Abstract In a gridconnectedphotovoltaic (PV) system, dynamic control strategy is essential to use the solar energy efficiently as well as for an energy optimization. This paper presents a decoupledcontrol of gridconnectedphotovoltaicsystemusingFractionalOrder Proportional–Integral (FO- PI) controller. In the proposed system, closed loop high gain multilevel DC/DC converter is also implemented to meet the regulated DC link voltage at the inverter input. The decoupledcontrol strategy allows independent control of real power (P) and reactive power (Q) according to the power generated by photovoltaic systems and the power consumed by the utility grid. A complete study of the dynamic behavior of the gridconnected PV system is presented using Matlab/Simulink. Simulation results are presented to validate the system response during disturbance with FO-PI con- troller, power factor control at the grid and the Total Harmonic Distortion (THD) of grid current for any solar irradiation.
Robust control, with high stability and robustness, has been successfully applied in a variety of high-performance applications, such as inverter control –, rectifier con- trol ,  and motor control – etc. In –, the model inaccuracy, the perturbation, and parameters tolerance are considered. By selecting the proper weight functions, the H∞ controller is designed to solve Riccati equation -, , . However, solving the Riccati equation is restricted by the system model, making it com- plicated to implement in real applications. Due to that the perturbation is distributed in the system, the LMI method , ,  is usually conservative. The struc- tured singular value ( µ) based controller is proposed to improve the system performance, and the robust level and perturbations are expressed by the uncertainties in µ frame- work , , –. However, conventional solutions to solve µ synthesis problem, such as D–K iteration method, usually lead to a high ordersystem, and the complexity of the system is also increased . Even though the better control performance can be obtained by these methods, but the weight functions are selected through the repeated trial and experience. Due to the nonlinear grid-connected inverter, the approximated linear mathematical model cannot preserve the real quality of the nonlinear system .
V. Khadkikar in  presents a comprehensive review of the UPQC to enhance the electric power quality at distribution levels. It provides an overview of the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. Paper  proposed a synchronous reference frame control method for current unbalance compensation in the microgrid. This method is based on the proper control of Distributed Generations (DGs) interface converters. It also proposed the direct change of the current reference to compensate for current unbalance. The fault analysis with hybrid compensation for unbalanced distribution systems is discussed in Reference . The method employs the unbalanced three-phase model to analyse faults. Two matrices containing information on the topological characteristics of distribution networks were built along with the proposed hybrid-compensation method for analysis. Ting-Chia Ou et al.  have shown dynamic operation and control strategies for a microgrid hybrid wind-Photovoltaic (PV)-Fuel Cell (FC) based power supply system. The system consists of the PV power, wind power, FC power, Static VAr Compensator (SVC), and an intelligent power controller. Paper  proposed a novel intelligent damping controller for the Static Synchronous Compensator (STATCOM) to reduce the power fluctuations, voltage support, and damping in a hybrid power multi-system. This paper also discussed the integration of an offshore wind farm and a seashore wave power farm via a high-voltage, alternating current electric power transmission line that connects the STATCOM and the 12-bus hybrid power multi-system.
The utilization of grid-connected solar systems is increasingly being pursued as a supplement and an alternative to the conventional fossil fuel generation in order to meet increasing energy demands and to limit the pollution of the environment. The major concerns of integrating PV into the grid are stochastic behaviours of solar irradiations and interfacing of inverters with the grid. Because of high initial investment, changes in solar irradiation, and reduced life-time of PV systems, as compared with the traditional energy sources, it is beneficial to extract maximum power from PV systems. Maximum power point tracking (MPPT) techniques are widely used to extract maximum power from the PV system that is delivered to the grid through the inverter. Interconnections among PV modules within a shaded PV field can affect the extraction of maximum power. A study of all possible shading scenarios and interconnection schemes for a given PV field, to maximize the output power of PV array, is proposed in previous methodology. Inverters interfacing PV modules with the grid perform two major tasks—one is to ensure that PV modules are operated at maximum power point (MPP), and the other is to inject a sinusoidal current into the grid. In order to evaluate these tasks effectively, we need one efficient control schemes are essential .In a grid-connected PV system, control objectives are met by a strategy using a pulse width modulation (PWM) scheme.
V/f control strategy is to regulate AC voltage through the feedback voltage after inverter, so as to ensure the output voltage stable. The double loop control scheme of voltage outer ring and current inner ring is taken. The outer ring uses the PI controller, whose inputs are the load voltage, d and q axis components of reference volt- age, with the purpose of making the steady state accuracy of load voltage 0 and stabilizing the load voltage; Output of voltage ring serves as the reference value of inner ring. The current servo system formed by the inner ring can speed up dynamic process of disturbance resistance. The inner ring uses the proportional controller P, which can improve the dynamic response speed of system.(Figure 5)
The increasing of the world energy demand, due to the modern industrial society and population growth, is motivating a lot of investments in alternative energy solutions, in order to improve energy efficiency and power quality issues. The use of photovoltaic energy is considered to be a primary resource, because there are several countries located in tropical and temperate regions, where the direct solar density may reach up to 1000 W/m2. At present, photovoltaic (PV) generation is assuming increased importance as a renewable energy sources application because of distinctive advantages such as simplicity of allocation, high dependability, absence of fuel cost, low maintenance and lack of noise and wear due to the absence of moving parts .
increasing use of the fossil fuels has led to the problem of air pollution, global warming concerns. Also, high usage of fossil fuels may create a crisis for power in near future as they are in a stage of depletion. As an impact of this, renewable energy resources (RES) are being considered as an alternative source of energy all over the world. In this paper, the topology and the control scheme of the photovoltaic three-phase gridconnected SVPWM inverter based on voltage-oriented control (VOC) connected distribution system is analyzed. In VOC, a current control loop is used. The currents are controlled in a synchronous rotating dq-frame using a decoupled feedback control. The simulations of the system based on Matlab/Simulink environment are presented too.
controllers; the DC-side controller for the boost DC/DC converter, and AC-side controller for the inverter. The DC/DC converter is controlled to maintain the fixed DC link voltage enough high to make the inverter operate, to achieve the maximum power from the PV array. Many algorithms have been developed for the MPPT of a PV array [1,5,15]. A perturbation and observation (P&O) method is applied for the maximum power point tracking (MPPT) controller, the MPPT techniques is most popular because of the simplicity of its control structure. ACMC is a current control technique that has an almost constant frequency and produces a user-deﬁned current waveform. It has a fast response time and is capable of supporting a wide range of power circuit topologies. ACMC is based on a compensator circuit which compensate the poles of an integrating ﬁlter transfer function. It uses this integrating ﬁlter to produce an average current error signal that is compared to a triangular waveform to produce the required pulse width modulation signal .
Recently , the photovoltaic power era system has been engaged as a standout amongst the most noteworthy energy sources because of the rising worry about an Earth-wide temperature boost, and the expansion of electrical power utilization. What's more, the PV module has no moving parts, which have made it extremely powerful, long lifetime and low upkeep gadget. Despite the fact that the PV module is as yet costly, however because of the huge scale manufacturing it has turned out to be progressively less expensive over the most recent couple of years. It has been accounted for in that the point of reference of 100GW introduced PV power everywhere throughout the world was achieved toward the finish of 2012 and expanded to 140GW toward the finish of 2013, and the larger part were grid associated. Consequently, an expectation has been made in that the future grid tied PV system will assume an imperative part in the direction of the conventional power system.
The electrical energy supplied by a photovoltaic power generation systems depends on the solar irradiation and temperature. The PV system can supply the maximu m power to the load at a particular operating point which is generally called as maximu m power point, at which the entire photo voltaic system can be operated with ma ximu m efficiency and can be used to produces ma ximu m power through it. Genera lly, MPPT is included to track the ma ximu m power point in the PV system. The effic iency of MPPT depends on both the MPPT control algorithm and the MPPT hardware[1-4]. The MPPT control algorithm is usually applied in the DC-DC Buck boost converter, which is normally used as the MPPT circuit. Hence, MPPT methods are used to maximize the PV panel output power by tracking continuously the ma ximu m power point. One of the most applied and studied MPPT method is the well-
The internal protections and various control systems required for performing efficient PV system operation. The scope of the MPPT is to optimise the performance of the PV modules by tracking the maximum power point of the current/voltage characteristic with the highest possible accuracy, in function of the conditions affecting the DC power supplied (solar irradiance and temperature). In addition, the electrolytic capacitor C acts as buffering storage device to balance the fluctuations of the single-phase instantaneous power demand at the AC side, that occur at double frequency with respect to the grid frequency, in order to limit the DC voltage ripple at the input section of the PCU. The other controls are aimed at providing AC power supply with acceptable features in terms of high power factor and reduced waveform distortion . In the presence of multiple PV systems operating in a close portion of the distribution system, the PV system interactions have to be specifically analysed [4, 5], since they could lead to malfunctioning of the controls, being each control typically designed on the basis of the individual PV system characteristics.
The block diagram of the current system is depicted in Fig 1. A six switch inverter is used for RES output which has a GRID and RES to supply set of linear and non linear loads. The proposal system uses renewable energy like Solar and Wind energy where in the turbine can be connected with DC link of Inverter (Grid Interfacing). In the proposed model, three phase four switch inverter replaces the existing three phase inverter. The PI Controller is replaced by FOPID controller. The transfer function of FOPID controller is as follows:
T.Kranthi kumar et al. (2011) This paper presents a method to operate a gridconnected hybrid system. The hybrid system composed of a Photovoltaic (PV) array and a Proton exchange membrane fuel cell (PEMFC) is considered. Two operation modes, the unit-power control (UPC) mode and the feeder-flow control (FFC) mode, can be applied to the hybrid system. In the UPC mode, variations of load demand are compensated by the main grid because the hybrid source output is regulated to reference power. Renewable energy is currently widely used. One of these resources is solar energy. The photovoltaic (PV) array normally uses a maximum power point tracking (MPPT) technique to continuously deliver the highest power to the load when there are variations in irradiation and temperature. The disadvantage of PV energy is that the PV output power depends on weather conditions and cell temperature, making it an uncontrollable source. Furthermore, it is not available during the night. In order to overcome these inherent drawbacks, alternative sources, such as PEMFC, should be installed in the hybrid system. By changing the FC output power, the hybrid source output becomes controllable. Therefore, the reference value of the hybrid source output must be determined. In the FFC mode, the feeder flow is regulated to a constant, the extra load demand is picked up by the hybrid source, and, hence, the feeder reference power m ust be known. He system can maximize the generated power when load is heavy and minimizes the load shedding area. When load is light, the UPC mode is selected and, thus, the hybrid source works more stably. The changes in operating mode only occur when the load demand is at the boundary of
Abstract: A new method of present control strategy for the photovoltaic (PV) systemconnected to the grid is presented in this paper. The connection of the photovoltaicsystem with the grid is a difficult task because the solar radiation is a nonlinear quantity. The purpose of this work is to create a photovoltaicsystem is to develop a model in which maximum power point tracking (MPPT) system is implemented by implementing new control technology. The considered system includes a PV system, MPPT (incremental conductance) controller, boost converter, voltage source inverter (VSI), three phase filter, a controlsystem, a distribution network, load and grid. Initially, the model of photovoltaic array was developed and then designed from an MPPT controller and a DC-DC boost converter. To connect the PV system to the grid, a power electronics converter is required which can convert the DC voltage to AC voltage in three steps. After that there is a simulation of the last model using MATLAB / SIMULINK and different output waves are analysed for different conditions. Finally, the fault analysis system is found to inspect the behaviour.
We have taken into account the complete ranges of operating conditions (minimum and maximum input voltages, i.e., v dc min and v dc max , and minimum and maximum load resistances, i.e., r l min and r l max . This assures the compliance of the existence condition for the full operating ranges of the converters. In the case of designing an SM controller with a static sliding surface, a practical approach is to design the sliding coefficients to meet the existence conditions for steady-state operations. Under such consideration, the state variables i C and v dc can be substituted with their expected steady-state parameters, i.e., i C SS and v dc SS , which can be derived from the design specification.
A grid-connected inverter controlling method to analyze dynamic process of large-scale and grid-connected photo- voltaic power station is proposed. The reference values of control variables are composed of maximum power which is the output of the photovoltaic array of the photovoltaic power plant, and power factor specified by dispatching, the con- trol strategy of dynamic feedback linearization is adopted. Nonlinear decoupling controller is designed for realizing decoupling control of active and reactive power. The cascade PI regulation is proposed to avoid inaccurate parameter estimation which generates the system static error. Simulation is carried out based on the simplified power system with large-scale photovoltaic plant modelling, and the power factor, solar radiation strength, and bus fault are considered for the further research. It’s demonstrated that the parameter adjustment of PI controller is simple and convenient, dynamic response of system is transient, and the stability of the inverter control is verified.
Due to the global awareness on the importance of energy savings and of energy efficiency, the use of renewable energy in the production of electricity has become popular all over the world. Out of the different sources of renewable energy, the photovoltaicsystem seems to be most promising energy source. PV installations are increasing now due to their relatively small size and noiseless operation . Due to the feed-in-tariff and the reduction of battery cost, gridconnected PV systems has gained popularity now-a-days. Major concerns of integrating PV into the grid are stochastic behaviours of solar irradiations and the interfacing of inverters with the grid. Efficient control schemes are essential to deliver maximum power with changes in atmospheric conditions.
An important electrical characteristic that had to be considered while incorporating a transistor controlled optocoupler in the current controllersystem was the propagation rise and fall times. This was due to the high speed switching generated by the pulse width modulation control technique and the requirement to have reactions times in the low microseconds when the error reached the tolerance band. Figure 5.3 displays a plot sourced from the HCPL-2503 data sheets of the typical propagation delay times with respect to temperature. It demonstrates a maximum delay time at 25° of approximately 530 and 420 ns for low-high and high-low transitions respectively. This time was less than the acceptable time of approximately 1µs and therefore guarantied successful implementation into the photovoltaicsystem
PV array is an unregulated dc power source which has to be properly conditioned in order to connect it with the grid or any other power source. For extracting the maximum power available for a particular insolation level, a dc-dc converter is placed in between the PV panel and load. By maximum power transfer theorem maximum power may be transferred to the load when load impedance equals source impedance. This is done by varying the duty cycle of dc-dc converter. The performance of PV array system will depend on operating conditions. The output voltage, current and power of PV array vary as functions of solar irradiation level, temperature and load current.
A photovoltaicsystem, also PV system or solar power system is a power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and convert sunlight into electricity, a solar inverter to change the electric current from DC to AC, as well as mounting, cabling and other electrical accessories to set up a working system. It may also use a solar tracking system to improve the system's overall performance and include an integrated battery solution, as prices for storage devices are expected to decline. Strictly speaking, a solar array only encompasses the ensemble of solar panels, the visible part of the PV system, and does not include all the other hardware, often summarized as balance of system (BOS). Moreover, PV systems convert light directly into electricity and shouldn't be confused with other technologies, such as concentrated solar power or solar thermal, used for heating and cooling.