Single-phase Photovoltaic System Research Articles

A New LCL Filter Design Method for Single-Phase Photovoltaic Systems Connected to the Grid via Micro-Inverters

A New LCL Filter Design Method for Single-Phase Photovoltaic Systems Connected to the Grid via Micro-Inverters

LADRC-based grid-connected control strategy for single-phase LCL-type inverters.

To ensure that grid-connected currents are of high quality, it is crucial to optimize the dynamic performance of grid-connected inverters and their control. This study suggests using a combination of reduced-order linear active disturbance rejection control (LADRC) and a Proportional-Integral (PI) controller. By applying this control strategy to a single-phase photovoltaic grid-connected system, the system's ability to suppress grid harmonics is significantly improved. The validity and effectiveness of this control approach have been confirmed through simulations and experiments. The results show that the LADRC-based control system is robust and capable of rejecting disturbances, resulting in a significant reduction in the Total Harmonic Distortion (THD) of grid-connected currents. Comparative analysis with traditional control methods demonstrates the superior performance of the proposed approach.

Single Phase Transformer Less Inverter for Grid Connected Photo Voltaic System

Sustainable power generation systems have been developed as a result of increased consumption of energy, the rapid depletion of fossil fuels, and environmental degradation worldwide. Thus, the demand for photovoltaic systems is increasing, owing to the increased need for renewable resources worldwide. Transformers are often used in photovoltaic systems to offer voltage ratio conversions between input and output along with galvanic isolation. The inverter, that may be a transformer-less or with a transformer, is the enabling technology in PV systems. But, the efficiency and power density of these traditional iron and copper-based transformers are decreased while the inverter's weight, size, and cost are increased. Thus, it is recommended to refrain from utilizing transformers within the inverter. For this reason, transformer-less inverters for grid-tied, low-voltage, single-phase photovoltaic (PV) systems have gained more attention thesedays. To comply with the safety requirements imposed by grid regulations, there are a few distinctive challenges, particularly with respect to leakage current problems, which need to be sufficiently handled. Owing to this In recent years, distributed solar grid-tied systems have made widespread use of single phase transformerless Voltage Source Inverters.
 This paper explores a novel transformer-less solar inverter for grid connected PV system and Results are investigated in MATLAB Simulink provided a significant reduction in distortion in voltage and current at load side.

Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter

Transformerless inverters have an important role in the electrical energy market. The high-efficiency and reliable inverter concept is one of the most widely used inverters in single-phase photovoltaic systems because of its high efficiency, low cost, and reduced leakage ground current. However, the leakage ground current behavior depends on the power and weather conditions, which can increase the parasitic capacitance value, thus producing an increase in the leakage ground current magnitude. In this paper, it is proposed to add a passive inductive–capacitive output filter to the inverter structure in order to reduce the dependency of the leakage ground current on the system power and weather conditions. The inductive–capacitive output filter is designed in such a way that it can provide a low impedance path for the leakage ground current, different from the ground path. The proposed system was evaluated both through simulations and experimentally in a 1 kW laboratory prototype.

Research on the overvoltage suppression strategy of single-phase photovoltaic grid-connected systems based on FCS-MPDPC

For the overvoltage problem brought by the access of high-penetration photovoltaic power plants to the low-voltage distribution network, this paper chooses to deal with it by using the reactive power regulation capability of photovoltaic power plant inverters, which reduces the equipment investment in distribution line voltage regulation. Based on the reactive power regulation theory of the inverter, a finite set model predictive direct power control method is proposed by constructing a virtual voltage vector, taking a single-phase cascaded 2H bridge grid-connected inverter as an example, to realize independent control of active and reactive power. By setting different power reference values, the inverter can be made to have two functions: grid-connected per-unit power factor and reactive power control during overvoltage. Finally, the two modes of inverter operation are verified by Simulink simulation, and the verification by example shows that the method can limit the grid-connected voltage deviation to within 7% and meet the requirements of grid-connected regulations.

Assessment of Energy Conversion in Passive Components of Single-Phase Photovoltaic Systems Interconnected to the Grid

This paper presents a mathematical analysis of how energy return in grid-connected single-phase photovoltaic systems affects the sizing of passive components. Energy return affects the size of the link capacitor, making it larger than reported in the literature. One of the main points of this article is that an inverter connected to the grid using a DC–DC converter with an appropriate link capacitor is analyzed. The energy return is caused by the value (in Henry units) of the L-filter, which is also analyzed in this paper. The analysis shows that there is a link between the value of the L-filter and the voltage of the DC bus. The analysis assumes two conditions: (1) the DC bus voltage is always higher than the peak value of the grid sinusoidal voltage, and (2) there is a unity power factor at the connection point between the grid and the L-filter. To operate in an open loop, a compensation phase angle is calculated and introduced in the single-phase inverter modulation; this phase angle compensates the phase shift caused by the L-filter, avoiding the use of a phase-locked-loop (PLL) control system. The L-filter ripple current is evaluated by Fourier analysis, and the DC bus ripple voltage is evaluated by considering the energy returned to the link capacitor. The results of the analyses are compared with existing methods reported in the literature. The results also show that, to minimize the value of the L-filter, the DC voltage must be almost equal to the maximum voltage of the grid. Equations to assess the value of the DC-link capacitor and the L-filter in function of their ripples are developed. The results were verified with simulations in Simulink and experimentally.

The Impact of Single-Phase Photovoltaic Systems on Fault Current in Asymmetric Low-Voltage Distribution Networks

This paper presents the impact of adding single-phase photovoltaic systems on the fault current of short-circuit faults in asymmetric 400 V low-voltage feeders. This study also attempts to investigate the impact of various parameters on the fault current, such as the penetration coefficient of photovoltaic systems, the impact of downstream or upstream fault on the system installation location, and distance of photovoltaic systems and fault location. Simulations were carried out in the DIgSILENT software. The results show that the fault current will be more different when using photovoltaic systems and that difference is sometimes incremental and sometimes decremental. Therefore, if the penetration coefficient of the system is high, it will sometimes have a significant impact on the protection system.

Enhanced Power Quality in Single-Phase Grid-Connected Photovoltaic Systems: An Experimental Study

The main aim of the research work presented in this paper consists of proposing an effective control scheme for a grid-connected single-phase photovoltaic (PV) system to enhance not only the power quality at the point of common coupling (PCC) but also to operate with a maximum power point tracking (MPPT) controller. Moreover, an orthogonal signal generator (OSG) module for effective grid synchronization, a current reference generation controller, and a PWM generating block have also been designed and included in this paper. The proposed control strategy allows the MPPT controller to switch to faulty mode and maintains the voltage according to network requirements using an adaptive neuro-fuzzy inference system (ANFIS)-based control whenever a fault occurs at the PCC. The performance of the analyzed control strategy, which is based on the static compensation of the DC-link voltage fluctuations in a grid-connected inverter powered by PV, is further explored through simulations in MATLAB, and the results are included in this paper. Moreover, the control scheme is implemented experimentally using a dSPACE DS 1104 control board and then assessed on a small laboratory-scale single-phase PV system that is subjected to some fault scenarios. The simulation and experimental results have shown improved power quality and robustness against grid fluctuations, resulting in better dynamic performance.

RL 부하 연동 단상 태양광 발전 시스템의 부하 전류 센서리스 무효 전류 보상기법

The PV (photovoltaic) system can be used with RL loads on the grid side. However, when RL Load is connected, the phase of the grid current and voltage will not match due to the reactive current component. The reactive current generated at this time can be compensated by the inverter. In the case of such a single-phase PV system, a total of two current sensors are used to detect the inverter output current and the RL load current. This paper proposes a compensation technique using one current sensor without using two current sensors in a single-phase photovoltaic power generation system connected with an RL load.

Back Propagation Neural Network PO-based Grid Connected Dual PV Management and Reliability Improvement

A single-phase Photovoltaic (PV) system that is based on an Maximum Power Point Tracking (MPPT) and use the perturb and observe algorithm to track the extreme power point. As a consequence of interactions between a variety of semiconductors and changing loads, the input source suffers from power quality concerns such as harmonic distortion, voltage sags, and voltage spikes. These issues are caused by fluctuating loads. As a method for enhancing the excellence of the electricity, the Grid-connected PV and Neural Network System was suggested as a solution. The Perturb and observe algorithm (P&O)-based MPPT technology offers a solution to the issue of partial shadowing, in addition to other unbalanced components that are problematic for PV arrays. Due to the fact that each PV cell in the system’s two panels is identical, it

A Study on the Reduction of 120 Hz Ripple Voltage Effect and Current Distortion Rate by the Compensation of Reactive Power on Single-phase Photovoltaic Systems

A Study on the Reduction of 120 Hz Ripple Voltage Effect and Current Distortion Rate by the Compensation of Reactive Power on Single-phase Photovoltaic Systems

Control of line voltage unbalance factor in three-phase distribution grids caused by single-phase photovoltaic systems

This study investigates the use of photovoltaic systems to regulate the voltage amplitude of electric power networks and to analyze their impact on the stability of Line Voltage Unbalance Factor (LVUF). It will be shown that instability of the LVUF can occur when single-phase domestic photovoltaic systems equipped with a voltage controller are connected to the three-phase low voltage network. The degradation of the LVUF is one of the problems to be avoided in three-phase electrical networks. To address this problem, this paper presents a complementary algorithm to be applied on the existing controller of the photovoltaics system. This algorithm calculates the optimum reference voltage for the controller, to keep the voltage amplitude within the permitted range, and at the same time prevent the degradation of the LVUF.

Multimode Features of CIPNLMS-MFX Controlled Single-Phase PV System With Finite State Machine Based Islanding/Synchronization Under Grid Outage

This article presents multimode features of a single-phase photovoltaic (PV) system controlled through a combined improved proportionate-normalized least mean square with modified filtered-X (CIPNLMS-MFX) technique. This system waves off from using the battery storage and successfully operated in standalone mode to achieve the load demand even under the grid outage. The CIPNLMS-MFX based current control technique includes asymmetry parameters and the optimized selection of these parameters provides fast convergence speed, good steady-state response, and improved power quality at nonlinear loads. This PV system is also supported with the synchronization and mode transfer control so that the PV system has autonomous operation under outage and recovery of the grid without disturbing the supply across the domestic loads. A fast detection of a dual cascaded generalized integrator synchronization/islanding structure is presented to evaluate fundamental grid voltage, phase angles, and change in frequency. This structure is robust against the abnormal conditions at the utility grid. The experimental results show that presented CIPNLMS-MFX, DCGI, and finite state machine based logic for islanding/synchronization techniques achieve considerably good performance under various operating scenarios, e.g., outage/ restoration of grid power, varying nonlinear loads, and outage of solar power.

Linear Quadratic Regulator and Fuzzy Control for Grid-Connected Photovoltaic Systems

This work presents a control scheme to control a grid-connected single-phase photovoltaic (PV) system. The considered system has four 250 W solar panels, a non-inverting buck-boost DC-DC converter, and a DC-AC inverter with an inductor-capacitor-inductor (LCL) filter. The control system aims to track and operate at the maximum power point (MPP) of the PV panels, regulate the voltage of the DC link, and supply the grid with a unity power factor. To achieve these goals, the proposed control system consists of three parts: an MPP tracking controller module with a fuzzy-based modified incremental conductance (INC) algorithm, a DC-link voltage regulator with a hybrid fuzzy proportional-integral (PI) controller, and a current controller module using a linear quadratic regulator (LQR) for grid-connected power. Based on fuzzy control and an LQR, this work introduces a full control solution for grid-connected single-phase PV systems. The key novelty of this research is to analyze and prove that the newly proposed method is more successful in numerous aspects by comparing and evaluating previous and present control methods. The designed control system settles quickly, which is critical for output stability. In addition, as compared to the backstepping approach used in our past study, the LQR technique is more resistant to sudden changes and disturbances. Furthermore, the backstepping method produces a larger overshoot, which has a detrimental impact on efficiency. Simulation findings under various weather conditions were compared to theoretical ones to indicate that the system can deal with variations in weather parameters.

Grid voltage sensor-less protection scheme for one cycle-controlled single-phase photovoltaic inverter systems

Grid voltage sensor-less protection scheme for one cycle-controlled single-phase photovoltaic inverter systems

Distributed Control Strategy of Single-Phase Battery Systems for Compensation of Unbalanced Active Powers in a Three-Phase Four-Wire Microgrid

Unbalanced active powers can affect power quality and system reliability due to high penetration and uneven allocation of single-phase photovoltaic (PV) rooftop systems and load demands in a three-phase four-wire microgrid. This paper proposes a distributed control strategy to alleviate the unbalanced active powers using distributed single-phase battery storage systems. In order to balance the unbalanced active powers at the point of common coupling (PCC) in a distributed manner, the agents (households’ single-phase battery storage systems) must have information on the active powers and phases. Inspired by supervised learning, a clustering approach was developed to use labels in order to match the three-phase active powers at the PCC with the agents’ phases. This enables the agent to select the correct active power data from the three-phase active powers. Then, a distributed power balancing control strategy is applied by all agents to compensate the unbalanced active powers. Each agent calculates the average grid power based on information received from its neighbours so that all agents can then cooperatively operate in either charging or discharging modes to achieve the compensation. As an advantage, the proposed distributed control strategy offers the battery owners flexibility to participate in the strategy. Case studies comparing performance of local, centralized, and the proposed distributed strategy on a modified IEEE-13-bus test system with real household PV powers and load demands are provided.

Short-circuit modeling of three-phase 4-wire unbalanced networks in presence of single-phase photovoltaic systems

Due to the growing diffusion of single-phase Photovoltaic Systems (PVSs), the analysis of active unbalanced three-phase 4-wire distribution networks in short-circuit operating conditions is nowadays of great interest. However, this analysis is not trivial due to various factors (e.g., environmental conditions, inverter control system, limits of the inverter current, location and type of the fault, PVS self-protection systems) influencing the contribution of PVSs to the short-circuit conditions. Among these factors, the greatest challenge is to model the complex behavior of the inverter control system that must comply with actual and future grid requirements, or with national and international standards, in both normal and abnormal operating conditions.An analytical model based on the phase-coordinates approach is proposed in this paper to evaluate the short-circuit contributions of single-phase PVSs connected to unbalanced three-phase 4-wire LV distribution networks. The model of the PVSs takes into account the main factors that influence the PVS contributions, with particular attention to the model of the control system which injects reactive power to support grid voltage in normal operating conditions and to perform low-voltage ride-through (LVRT) dynamic grid support during the fault.In this paper, control systems for next-generation single-phase PVSs able to satisfy grid code requirements are explored; they include constant average active power control, constant active current control and constant peak current control. Extensive numerical experiments are presented with reference to the Cigrè European LV Distribution Network Benchmark, considering different fault types, effects of various control strategies and the evaluation of the impact of the PVSs in LVRT conditions w.r.t. the passive network, i.e., the network under fault with no installed PVSs.

Harmonic Distortion Assessment in the Single-Phase Photovoltaic (PV) System Based on SPWM Technique

The solar electric (photovoltaic or PV) system generates the electrical power at the day time. The current and voltage distortions are caused by the nonlinearities present in PV system which lead to the power issues. In the proposed PV system, the Insulated Gate Bipolar Junction Transistor switches the boost converter and multilevel inverter to regulate the output power of the system. In case of PV system, boost converter output is fed to an inverter to transform power from direct current to alternating current thereby inducing harmonic. The harmonic causes unnecessary overheating of the equipment, nuisance tripping of breakers and power factor reduction. The proportional integral derivative controller along with sinusoidal pulse width modulation is implemented in the proposed single-phase PV system to reduce the harmonic distortion and to improve the system performance. In the scope of this paper, the performance analysis of the PV system is done as far as accuracy, robustness and stability.

Dynamic Modeling and Control of a Single-Phase Grid-Connected photovoltaic System

Designing control strategies to connect a photovoltaic (PV) system to the grid has been significantly challenging. This paper focuses on developing a controller for a single-phase PV system connected to the grid and its implementation to modify the power factor in the distribution power system. To design a grid-connected PV system, its components are modeled, such as PV panels, Maximum Power Point tracking (MPPT) algorithm, the grid interface inverter with the appropriate filter, and the DC link capacitor. SIMULINK / MATLAB is used for simulation in this study. The proposed control strategy is designed to track the maximum power point of The PV panels and control the PV active and reactive output power. In this paper, the presented reactive power control provides the PV system with power factor correction (PFC) capability. The proposed technique for checking controller validity is tested, and the results prove that the proposed controller is good and provides the required performance.

A modified carrier-based PWM technique for minimization of leakage current in transformer less single-phase grid-tied PV system

This paper discusses the impact of leakage current and its dependency on common mode voltage in transformer less single-phase grid connected photovoltaic (PV) system. Further a new carrier-based PWM method is derived for H bridge single-phase grid-tied PV inverter to minimize leakage current. The proposed modulation strategy is compared with conventional techniques through simulation in MATLAB R2018a. The superiority of the proposed technique is validated in laboratory prototype of a 500 W single-phase grid-tied PV system. The hardware results validate the theoretical findings in appropriate.