Grid-connected Photovoltaic Power Generation Research Articles

Online Control of Smart Inverter for Photovoltaic Power Generation Systems in a Smart Grid

The main purpose of this study is to engage in research on a grid-connected photovoltaic (PV) power generation system smart inverter. The research content includes a smart maximum power point tracking (MPPT) controller and an inverter with power regulation. First, use the PSIM software package to establish the simulation environment of the grid-connected photovoltaic power generation system and use the Sanyo HIP-186BA19 photovoltaic module to form a 744 W system for simulation. In order to enable the photovoltaic module array (PVMA) to output the maximum power under different solar insolation and ambient temperature, the architecture is based on the extension theory-based smart MPPT method to improve the dynamic response and steady-state performance of photovoltaic power generation systems compared to perturb and observed (P&O) MPPT. When the sunshine is 1,000 W/m2, the photovoltaic power generation system adopts the extension theory-based maximum power tracking method. The time required to track the maximum power point is only 0.32 s, and the steady-state ripple is only 4.127 W. However, using the traditional P&O method requires 0.741 s to track the maximum power point, and the steady-state ripple reaches 18.131 W. Thus, the dynamic response speed of the maximum power tracking method proposed is 50% faster than that of the P&O method. The steady-state performance is also better compared to the P&O method. At the same time, a simple proportional-integral (PI) controller is used to regulate the DC-link voltage, output voltage, and current of the inverter to make the voltage of the grid-connected point stable at an effective value of 220 V. Then, the voltage-power control technology is added to the photovoltaic grid-connected inverter, and a simple proportional-integral controller is used to regulate the output of the smart inverter reactive power to improve the power quality of grid voltage. Finally, simulation and experimental results are used to verify the effectiveness of the regulation performance of the developed smart inverter.

Design of a Three Phase Z-Source Inverter for Photovoltaic Systems

Due to the danger of extinction of fossil energy resources and their harmful effects on the environment, interest in renewable energy sources has increased today. Furthermore, the photovoltaic energy, which is among renewable energy sources, has started to gain importance day by day. Especially, grid-connected Photovoltaic (PV) power generation systems have begun to be installed and used widely. In the grid-connected power generation systems, variable environmental conditions cause the DC voltage obtained from the PV systems to vary continuously. In the applications where traditional inverters are used, additional DC/DC converters are required to obtain an output at the desired frequency and amplitude. On the other hand, Z-source inverters which are a new concept can perform this raising and lowering process without the need for any intermediate circuit elements, thanks to the impedance network in their structures. For this reason, in this paper, Z-source inverter is designed for the PV systems. Z-source inverter modeling with impedance network is realized by using a simple boost switching method, and the modulation index and duty cycle parameters are adjusted to increase the DC voltage applied to its input. It is observed from the simulation results that using of the Z-source inverter is proper and efficient in the PV power generation systems.

Optimization of Grid-Connected Photovoltaic Power Generation Technology Based on Nonlinear Back-Stepping Controller

To address the issue of energy scarcity and to use solar photovoltaic energy as a renewable source, a three-phase grid-connected photovoltaic inverter system with uncertain system model parameters is investigated, which converts DC power into AC power, feeds it into the grid, and maintains the grid-connected part’s quality. An enhanced back-stepping approach is proposed to explore the control strategy of three-phase solar grid-connected inverter, which includes adaptive control, dissipative theory, sliding mode control, and rapid terminal sliding mode control, respectively. It is verified that the system is subjected to external interference F = 5 during 0.5 s–0.8 s. As per the simulation results, the improved adaptive terminal sliding mode control method can suppress the interference to a certain extent and has strong robustness to the external interference. When compared with the adaptive sliding mode control approach, the anti-interference ability is better, and the system stability is improved. Then, to improve the above approach, a high speed terminal sliding mode control method is proposed, which can swiftly converge in finite time and the estimated value of uncertain parameters is closer to the actual value, thereby boosting the system’s robustness.

A modified power decoupling control strategy for a grid-connected inverter with a low switching frequency under unbalanced grid voltages

In the photovoltaic grid-connected power generation system, when proportional resonant (PR) control is adopted for the grid-side inverter in the two-phase stationary coordinate (αβ), there is a coupling problem between active power (P) and reactive power (Q). Under unbalanced grid conditions, especially in high-power applications where the switching frequency of the grid inverter needs to be reduced, the power coupling problem will be exacerbated. Based on the instantaneous power response characteristics of the grid inverter, expressions of the power coupling coefficient under unbalanced power grids are derived in this paper, and the influence of the unbalanced grid voltage on the power coupling is revealed. Moreover, a decoupled grid-side model of the grid inverter is established, and a modified controller based on positive and negative sequence (P–N sequence) decoupling is proposed to solve the power coupling problem. The closed-loop transfer function of the system with the modified current controller is studied, and the stability of the modified controller is analyzed according to the bilateral frequency response diagram. Based on analysis of the coupling coefficient, the degree of coupling between P and Q can be reduced significantly by applying the proposed control method. Furthermore, in order to solve the influence of the delay on the power coupling caused by the low switching frequency, the decoupling compensation link for the delay is introduced, which can eliminate the influence of delay on power coupling. Finally, experiments are performed on a grid-connected inverter prototype. The experimental results show that when the grid voltage is unbalanced, the proposed control method can reduce the coupling degree of the P and Q, which also improves the dynamic performance of the grid-connected inverter with a low switching frequency.

Power output control method of small power photovoltaic grid connected power generation under complex illumination

Due to the irregular change of lighting conditions, there is a large error in the control of photovoltaic grid connected power output. Therefore, this paper proposes proposes a power output control method for low-power photovoltaic grid-connected power generation considering complex illumination. Based on the analysis of the basic characteristics of photovoltaic grid connected power generation, the output characteristics of photovoltaic array under complex lighting conditions are studied. Combined with its variation characteristics, based on fuzzy control strategy, the output of photovoltaic grid connected energy storage system is adjusted by filter control with variable time constant, and economic operation and stable operation are taken as constraints. The test results show that the design method has a high degree of fit between the control of photovoltaic grid connected power output and the actual results, and the error is within a reasonable range, which is obviously due to the two groups of comparison methods.

Analysis of the Economic Viability of the Installation of a Photovoltaic System at Jorge de Abreu Regional Hospital in Sinop-MT

Brazilian consumers have the possibility to produce their own energy using renewable sources or qualified cogeneration and even provide the surplus for the distribution network of their locality, as determined by the publication of Normative Resolution 482/2012 by the National Electric Energy Agency (ANEEL). In view of this, the use of photovoltaic systems for electricity generation has grown surprisingly, reaching the mark of 8 gigawatts of installed power on Brazilian soil in the year 2021 [1]. In Brazil, public agencies represent 0.1% with 4.7MW installed [1], and in the state of Mato Grosso 0.38% [14]. Thus, aiming at the rise of electricity generation in public buildings, due to the possibility of reducing costs with the electric bill, the present work deals with the dimensioning, budget quotation and economic feasibility analysis regarding the installation of a grid-connected photovoltaic power generation system to meet the energy demands of the Jorge de Abreu Regional Hospital in the city of Sinop, Mato Grosso state, Brazil. Whose, after carrying out the necessary research based on the techniques present in the economic sciences, as Minimum Attractiveness Rate (MRA), Net Present Value (VLP), Internal Rate of Return (IRR) and calculation of Payback. The present work considered a grid-connected solar energy generation system of 585 kW to supply the hospital's average monthly consumption of 93.829 kWh/month. The investment analysis showed that the project for the implementation of the photovoltaic system will have its NPV viable from the 4th year of installation and the Payback (return on investment), observing the monetary corrections, of approximately 4,29 years, thus configuring the system as economic financially.

Analysis of the Economic Viability of the Installation of a Photovoltaic System at Jorge de Abreu Regional Hospital in Sinop-MT

Brazilian consumers have the possibility to produce their own energy using renewable sources or qualified cogeneration and even provide the surplus for the distribution network of their locality, as determined by the publication of Normative Resolution 482/2012 by the National Electric Energy Agency (ANEEL). In view of this, the use of photovoltaic systems for electricity generation has grown surprisingly, reaching the mark of 8 gigawatts of installed power on Brazilian soil in the year 2021 [1]. In Brazil, public agencies represent 0.1% with 4.7MW installed [1], and in the state of Mato Grosso 0.38% [14]. Thus, aiming at the rise of electricity generation in public buildings, due to the possibility of reducing costs with the electric bill, the present work deals with the dimensioning, budget quotation and economic feasibility analysis regarding the installation of a grid-connected photovoltaic power generation system to meet the energy demands of the Jorge de Abreu Regional Hospital in the city of Sinop, Mato Grosso state, Brazil. Whose, after carrying out the necessary research based on the techniques present in the economic sciences, as Minimum Attractiveness Rate (MRA), Net Present Value (VLP), Internal Rate of Return (IRR) and calculation of Payback. The present work considered a grid-connected solar energy generation system of 585 kW to supply the hospital's average monthly consumption of 93.829 kWh/month. The investment analysis showed that the project for the implementation of the photovoltaic system will have its NPV viable from the 4th year of installation and the Payback (return on investment), observing the monetary corrections, of approximately 4,29 years, thus configuring the system as economic financially.

Visualized calculation of regional power grid power data based on multiple linear regression equation

Abstract The power generation of distributed power generation systems in regional power grids is mainly affected by external environmental factors, and there are volatility and intermittent power generation issues. This paper establishes a relatively simple multiple linear regression prediction model to predict grid-connected photovoltaic power generation systems. The article uses a hybrid modelling method to filter more important weather forecast input variables through a step-by-step linear regression method to realize the visual calculation of power data. The research results show that the multiple linear regression equation methods proposed in the article have pervasive application value in the actual application of solar photovoltaic power consumption data.

Research on New Energy Power Generation Technology under Smart Grid

The paper introduces the new energy solar photovoltaic grid-connected power generation technology and system composition in the smart grid, and describes the basic working principles and functions of photoelectric conversion components and inverters. The article introduces the single-phase photovoltaic grid-connected inverter system and its control system design, tests and analyzes the harmonics generated by the inverter system after grid-connected, and proposes some further improvements and research and development work for the system in the future view.

Risk Assessment of Power Systems Dispatching Decision Considering Photovoltaic Systems Penetration

Grid-connected photovoltaic power generation is an important form of new energy utilization, which can effectively reduce the dependence of power system on traditional energy sources. However, the randomness and uncertainty of the output of photovoltaic power generation system will also pose some risks to power grid dispatching decision-making. The source of dispatching decision risk is analyzed, and a risk index system including line overload risk, reserve shortage risk, load shedding risk and light abandonment risk is established. Then a risk assessment model for optimal dispatch of grid-connected photovoltaic power generation is established. The time of power flow calculation is greatly simplified by using power flow distribution factor. Finally, through the risk assessment of IEEE RTS-79 system scheduling decision-making, the risk of scheduling decision-making under different photovoltaic acceptance is analyzed, and the feasibility of the model is verified.

Research on the Influence of Photovoltaic Module Power Generation Efficiency and Manufacturing Technology on Power Grid Connection

The power generation efficiency of a photovoltaic power generation system is closely related to factors such as the material of the photovoltaic module, the tilt angle of the module installation, and the power of the module. At present, the output power of large-scale grid-connected photovoltaic power generation systems has large fluctuations and strong randomness. In order to accurately predict the output power of photovoltaic power stations to solve the problems of peaking and dispatching caused by large-scale photovoltaic grid-connected power generation to the grid. The article introduces the design of single-phase photovoltaic grid-connected inverter system and its control system based on big data technology. The research found that the photovoltaic manufacturing and grid-connected algorithms proposed in this paper can achieve the best power generation benefits of photovoltaic power plants, while improving the operation and maintenance efficiency of photovoltaic power plants.

Forecasting and uncertainty analysis of day-ahead photovoltaic power using a novel forecasting method

The primary means to promote grid-connected photovoltaic power generation is through accurately forecasting the power output from photovoltaic power stations. This paper proposes a method for day-ahead photovoltaic power forecasting (PPF) and uncertainty analysis using fuzzy c-means (FCM), whale optimization algorithm (WOA), least squares support vector machine (LSSVM), and non-parametric kernel density estimation (NPKDE). The FCM clustering algorithm was used to cluster historical data on numerical weather prediction and photovoltaic power stations, whereby daily data sharing similar meteorological information were clustered into one class. The rapid convergence speed and high convergence accuracy of the WOA were used to optimize the penalty factor and kernel function width of the LSSVM model; this was done to improve the calculation speed and forecasting accuracy of the LSSVM model. The WOA-LSSVM forecasting model was trained using the clustered numerical weather prediction and historical data of a photovoltaic power station. This was subsequently utilized to forecast day-ahead photovoltaic power. The NPKDE method was used to accurately calculate the probability density distribution of forecasting error and the confidence interval of the day-ahead PPF. The root mean square error (RMSE) values of the forecasting power of the WOA-LSSVM, PSO-LSSVM, LSSVM, LSTM and PSO-BP models are 2.55%, 3.00%, 5.60%, 6.03% and 3.18%, respectively, and the calculation results show that the forecasting accuracy of the WOA-LSSVM was higher relative to other models including PSO-LSSVM, LSSVM, LSTM and PSO-BP. Moreover, the NPKDE method was able to accurately describe the probability density distribution of the forecasting error.

Evaluation of the viability potential of four grid-connected solar photovoltaic power stations in Jiangsu Province, China

Grid-connected solar photovoltaic (GCSPV) power generation is conducive to the large-scale promotion of PV power generation. The aim of this study was to analyze the feasibility of the construction of 1-MW GCSPV power stations at four locations in Jiangsu Province, China. The economic, environmental, sensitivity, and risk analyses of the proposed systems were performed using the RETScreen clean energy management software. The GCSPV systems in Xuzhou are more economically viable than those in the other regions under consideration, whereas the systems in Nanjing are relatively less economically feasible. The GCSPV power stations in Xuzhou have the largest reduction in annual greenhouse gases emissions, because of producing the most electricity from the proposed system. Sensitivity analysis results on the net present value (NPV) show significant variations owing to the variations of the electricity export rate (EER) and initial costs (ICs) parameters. The NPV of the proposed system increases from $707,589 to $2,046,766 with an increasing EER, while the NPV of the system decreases with increasing ICs at the same EER. The risk analysis shows the largest influence on the NPV of the project is the change of the EER with positive correlation, while the least impact on the NPV is the debt term with positive correlation.

Neutral Point Clamped Transformer-Less Multilevel Converter for Grid-Connected Photovoltaic System

Transformer-less (TL) inverter topologies have elicited further special treatment in photo-voltaic (PV) power system as they provide high efficiency and low cost. Neutral point clamped (NPC) multilevel-inverter (MLI) topologies-based transformer-less are being immensely used in grid-connected medium-voltage high-power claims. Unfortunately, these topologies such as NPC-MLI, full-bridge inverter with DC bypass (FB-DCBP) suffer from the shoot-through problem on the bridge legs, which affect the reliability of the implementation. Based on the previous above credits, a T type neutral point clamped (TNP)—MLI (TNP-MLI) with transformer-less topology called TL-TNP-MLI is presented to be an alternate which can be suitable in the grid-connected PV power generation systems. The suggested TL-TNP-MLI topologies free from inverter bridge legs shoot-through burden, switching frequency common-mode current (CMC), and leakage current. The control system of the grid interface with hysteresis current control (HCC) strategy is proposed. The effectiveness of the proposed PV connected transformer-less TNP-MLI topology with different grid and PV scenario has been verified through the MATLAB/Simulink simulation model and field-programmable gate area (FPGA)-based experimental results for a 1.5 kW system.

Design and performance analysis of PV grid-tied system with energy storage system

With the increasing demand for solar energy as a renewable source has brought up new challenges in the field of energy. However, one of the main advantages of photovoltaic (PV) power generation technology is that it can be directly connected to the grid power generation system and meet the demand of increasing energy consumption. Large-scale PV grid-connected power generation system put forward new challenges on the stability and control of the power grid and the grid-tied photovoltaic system with an energy storage system. To overcome these problems, the PV grid-tied system consisted of 8 kW PV array with energy storage system is designed, and in this system, the battery components can be coupled with the power grid by AC or DC mode. In addition, the feasibility and flexibility of the maximum power point tracking (MPPT) charge controller are verified through the dynamic model built in the residential solar PV system. Through the feasibility verification of the model control mode and the strategy control, the grid-connected PV system combined with reserve battery storage can effectively improve the stability of the system and reduce the cost of power generation. To analyze the performance of the grid-tied system, some real-time simulations are performed with the help of the system advisor model (SAM) that ensures the satisfactory working of the designed PV grid-tied System.

A rapid harmonic detection method for grid-connected photovoltaic when three-phase voltage is unbalanced

Abstract By using power electronic devices, photovoltaic grid-connected power generation may inject harmonics into the power system. As the photovoltaic grid-connected inverter has the same basic structure as the active power filter, so the unified control of the photovoltaic grid and active filtering can be achieved. When the current unified control system compensates harmonics of the grid side, it mainly uses ip-iq harmonic detection method, which is based on instantaneous reactive power theory. When the three-phase voltage is unbalanced, the method has a large voltage phase angle detection error and the signal of the low-pass filter tracking system is long, detection time delay and even failure occur. This paper proposes an improved fast harmonic detection method. When phase deviation or amplitude change occurs to the three-phase voltage, the positive and negative-sequence voltages are simultaneously park transformed. The negative-sequence component is filtered by the current average module to obtain the fundamental amount of the voltage, then the phase angle of the positive-sequence voltage is accurately calculated to improve the harmonic current detection accuracy. Through the study of the integral method, it is found that the least common multiple of each harmonic period can be used as the integral interval, and the integral value is also zero, so the detection delay time is reduced by replacing the low-pass filter with an integration module. The simulation results show that the proposed harmonic detection algorithm can accurately detect harmonics when the three-phase voltage is unbalanced, and about 0.057 s improve the harmonic detection speed compared with the commonly used ip-iq method.

Reactive PowerControl of Grid-Connected Photovoltaic Power Generation

In order to solve the problem of grid-connected point voltage exceeding the limit caused by large-scale photovoltaic power stations connected to the grid, and to increase the penetration rate of photovoltaics in the grid, photovoltaic power stations should have more flexible reactive voltage regulation capabilities to provide reactive power support to the grid. To this end, this paper establishes an equivalent aggregation model for large-scale photovoltaic power plants. Under the premise that the photovoltaic power station is not equipped with reactive power compensation devices and the inverter reactive power output is zero, it is analyzed that due to the existence of line and transformer impedance, photovoltaic access reduces the grid the problem of voltage stability. Based on the above reasons, this paper proposes a three-layer reactive power control strategy for photovoltaic power plants from the perspective of the cooperation between the reactive power compensation device and the grid-connected inverter. This strategy coordinates the reactive power output between the reactive power compensation device and the photovoltaic power generation unit and between the inverters of a single photovoltaic power generation unit. Under this control strategy, the photovoltaic power plant can regulate the grid voltage more effectively, and the active and reactive power losses of the grid are minimized on the premise that the grid voltage is maintained within the required range. Combined with the photovoltaic array power reduction operation strategy, the stable operation of the power grid is ensured under the premise of a certain reactive power output capacity of the photovoltaic power station. Finally, an example is used to verify the correctness and effectiveness of the strategy.

Application of distributed photovoltaic power generation technology in electric vehicles

In this paper, a photovoltaic grid connected electric vehicle charging station suitable for plateau application is developed by using two-way energy storage photovoltaic grid connected power generation technology; Introduce a medium-sized electric bus to carry out long-term operation test in Tibet; The detection experimental device and evaluation method suitable for electric vehicle power battery in plateau area are constructed; Carry out strategic research on the impact evaluation of the development of electric vehicles on the power grid side in the plateau weak current network area.

Application of Improved Droop Control Based on Grid Impedance in Photovoltaic Grid-Connected Power Generation system

When the power grid impedance mutates, the output power of the grid-connected photovoltaic power generation system controlled by drooping will become very unstable. To solve this problem, an improved droop control algorithm based on network impedance detection is proposed. Taking photovoltaic grid-connected power generation system as the research object, the influence of power grid impedance on traditional droop control is firstly expounded by introducing power grid impedance value into traditional droop control. Then the method of real-time network impedance extraction is introduced. Furthermore, according to the bandwidth and phase angle constraints of the equivalent output impedance phase frequency characteristics of the photovoltaic grid-connected inverter, the controller parameters are updated in real time to achieve the purpose of adaptive network impedance mutation. Finally, the proposed method is tested and verified by real-time simulation in the loop respectively. The results show that the proposed method is correct.

Research on Three-phase Grid-connected Photovoltaic Power Generation System

With the development of world economic and shortage of energy, Research on solar photovoltaic power generation system is of great theoretical and practical significance in alleviating energy and environmental problems, improving the energy consumption structure and the performance of distributed generation systems. Under this background, this paper focus on the three-phase grid-connected photovoltaic power generation system, in the terms of hardware system design, control algorithm and system simulation. In this paper, module of three-phase grid-connected photovoltaic power generation system is established. A variable step-size maximum power point tracking control strategy is proposed. And a control algorithm named double d-q axis phase-locked loop is proposed. Simulation is verified in the form of hardware.