Grid-connected Power Generation Research Articles

Performance Comparison of MIMO Gain/Phase Analysis Methods for Sub-Synchronous Instability

Recently, there has been great interest in the development of stability criteria for grid-connected power converters and generators using frequency-domain impedance models. We consider two recently introduced stability analysis methods and compare their small-signal stability performance for a DFIG wind farm connected to a series-compensated grid. The first method, known as the Low-Complexity Global Nyquist Condition, uses Gershgorin disks derived from the loop gain matrix to provide a stability criterion. The second method, introduced by the authors, uses a combined matrix gain and phase stability analysis. The two methods are compared by using them to predict the onset of instability in a series-compensated wind farm under a tripped line. The results reveal that the gain/phase based approach achieves less conservatism than the Nyquist-based method.

Research on Grid-Connected Control Strategy of Photovoltaic (PV) Energy Storage Based on Constant Power Operation

In order to effectively mitigate the issue of frequent fluctuations in the output power of a PV system, this paper proposes a working mode for PV and energy storage battery integration. To address maximum power point tracking of PV cells, a fuzzy control-based tracking strategy is adopted. The principles and corresponding mathematical models are analyzed for the three-phase voltage PWM converter and bidirectional DC/DC converter, while feedforward decoupling double closed loop, constant power (PQ), and constant voltage charge/discharge control strategies are proposed. Space vector pulse width modulation (SVPWM) technology is utilized to generate power switching tube driver signals. Finally, a simulation model is developed in MATLAB/Simulink for system analysis. The results demonstrate that the proposed method enables constant grid-connected power generation and constant voltage charging of the energy storage battery when the PV cell’s power generation exceeds that of the grid. When insufficient solar power generation occurs, both the PV system and energy storage battery work together to achieve constant grid-connected power.

Photovoltaic capacity dynamic tracking model predictive control strategy of air-conditioning systems with consideration of flexible loads

Building photovoltaic (PV) power generation is intermittent, volatile, random, and uncontrollable; thus, the use of solar grid-connected power generation can lead to a series of problems, such as grid voltage fluctuations and power imbalance. As a typical flexible load, the scheduling and regulation of the heating, ventilation, and air conditioning (HVAC) system load can help a grid-connected solar grid achieve balanced and flexible operation. This study proposes a PV capacity dynamic tracking model predictive control strategy for air-conditioning systems with flexible loads. This strategy aims to effectively address the issue of unstable grid-connected output of solar PV systems. In particular, a solar radiation prediction model based on a long short-term memory neural network optimized by the grey wolf optimization algorithm was established, which effectively improved the model prediction accuracy. The cost function of HVAC flexible load control considers the law of solar PV output and the human thermal comfort model. A genetic algorithm (GA) is used to obtain the optimal control parameters for dynamic regulation. The GA was employed to efficiently and effectively optimize the control of flexible HVAC loads, considering the variability of the solar PV output and ensuring human thermal comfort. A dynamic regulation model was developed for a typical office building with a grid-connected solar PV power generation system. TRNSYS was utilized for verification based on the actual measured data and relevant meteorological parameters of the case building. A new evaluation metric, volatility, was proposed to evaluate net load fluctuation. The simulation platform based on the physical building yield results indicated a strong resemblance between the energy consumption curve under the predicted control conditions using the flexible model and the PV generation curve. Additionally, the net load volatility was measured to be 2.63. Compared with the predicted control condition without the flexible model, the net load volatility of the grid was reduced by 47.08%, and the energy-saving rate reached 10.89% in the summer.

Research Progress of Flexible Peak Shaving Technology for Coal-Fired Boilers

In the face of the pressing challenges of climate change and carbon emissions, China's energy and power sectors are actively working towards the strategic goal of establishing a new power system, where wind and solar energy will constitute a rapidly expanding portion of grid-connected power generation. Nevertheless, the inherent characteristics of these renewable energy sources, such as their randomness, intermittency, and volatility, pose significant challenges to ensuring the secure and stable operation of the power grid. Presently, China heavily relies on pulverized coal power plants, which lack the flexibility required to accommodate the fluctuating demands posed by renewable energy generation. Overcoming this technical obstacle and enabling efficient grid integration of renewable energy necessitates a thorough exploration of the potential of existing pulverized coal furnaces for flexible peaking operations, especially under extreme peak shaving conditions. To address this challenge, coal self-preheating combustion technology has emerged as a pioneering solution developed by the Institute of Engineering Thermophysics, Chinese Academy of Sciences. By implementing preheating modification activation, this innovative approach alters the traditional combustion reaction path of pulverized coal, significantly enhancing its reaction activity. This advancement holds immense promise for achieving efficient and stable combustion, as well as facilitating rapid load changes in pulverized coal boilers operating at low loads. This study primarily focuses on discussing prevalent means of peaking technology, including low-load stable combustion technology, rapid load regulation technology, coupled peaking technology, and the development status of peaking technology for coal power units. Through in-depth research and innovation, it is anticipated that the effectiveness and viability of peaking technology will be further enhanced, promoting the sustainable development of pulverized coal boiler generating units and optimizing the operation of energy systems. Furthermore, the self-preheating combustion technology will increasingly play a pivotal role in multiple sectors and directions, such as flexible and deep peaking of coal power, driving the advancement and adoption of clean and effective coal utilization technology.

Topology of Wind Power DC Collection Converter Based on Double Bus Structure and Its Power Balancing Control Strategy

Wind power collection technology is the key to grid-connected wind power generation. Compared with AC wind integration, DC wind power collection is more advantageous. Using a triple active bridge (TAB) converter as a submodule, this paper proposes a wind power DC converter topology and its control strategy for medium-voltage dc (MVDC) grid connection. The converter adopts a double bus structure, with the MVDC bus connected to the grid and the low-voltage dc (LVDC) bus handling the mismatched power. It has independent maximum power point tracking (MPPT) control, power balancing, and autonomous voltage balancing on the output side. The converter system is simulated and verified on the MATLAB/SIMULINK software platform. The simulation results show the effectiveness of the control strategy and the ability of the converter to operate stably under multiple conditions.

A decentralized control strategy for single‐phase cascaded photovoltaic inverters with MPPT ability

AbstractCascaded inverters can improve efficiency and reduce cost, so it is widely used in photovoltaic (PV) grid connected power generation system. However, aging or partial shielding of PV panels will lead to their different maximum power points (MPP). This paper proposes a decentralized control strategy for grid‐connected cascaded PV inverters without any communication, which is capable of integrating PV inverters of different capacities connected in series into the grid, and enable them to achieve maximum power point tracking (MPPT) independently. Compared with the traditional centralized control method relying on real‐time communication, the proposed scheme has advantages of improved reliability and decreased costs. The overall system stability is analysed, and the stability condition is derived as well. The Hardware‐In‐the‐Loop test results show that all the inverters in the cascaded system have their output frequency and voltage phase synchronized autonomously, and achieve MPPT independently even in the presence of variation of light condition. Thus, the feasibility of the proposed method is verified.

Grid Integration of Livestock Biogas Using Self-Excited Induction Generator and Spark-Ignition Engine

This study developed a grid-connected biogas power generation system for a rural community using a 3-phase 2.2 kW squirrel-cage induction machine as the self-excited induction generator. The generator was driven by a 196 cc single-cylinder spark-ignition engine fueled by biogas. We developed a back-to-back converter that consists of a 3-phase PWM rectifier as the generator-side converter and a single-phase LCL-filtered grid-connected inverter. The generator-side converter transferred the active power to the grid-side converter and supplied the reactive power control back to the generator. The notch filter-based bus voltage control on the generator side mitigated the inter-harmonics in the generator current. The injected grid current complied with the IEEE 1547 standard because of the multi-frequency unbalanced synchronous reference frame control. The proposed system was validated with biogas produced from pig manure at a pig farm in central Thailand, which found a maximum output of 1.2 kW with a thermal system efficiency of 10.7%. The proposed system was scheduled to operate at 1.2 kW for 8 h per day with a levelized cost of 0.07 US$/kWh, 42% cheaper than the retail electricity price, and a payback period of 2.76 years. The proposed system is suitable for a farm with a minimum of 34 pigs.

Design and Performance Analysis of a Novel Integrated Solar Combined Cycle (ISCC) with a Supercritical CO2 Bottom Cycle

The integrated solar combined cycle (ISCC) system is a proven solution for grid-connected power generation from solar energy. How to further improve the ISCC system efficiency and propose a more efficient system solution has become a research focus. A novel gas turbine combined cycle (GTCC) benchmark system is proposed by replacing the conventional steam Rankine bottom cycle with a supercritical CO2 Brayton cycle, whose output power and efficiency are increased by 9.07 MW and 1.3%, respectively, compared to those of the conventional GTCC system. Furthermore, the novel ISCC systems are established with the parabolic trough solar collector (PTC) and the solar tower (ST) collector coupled to the novel GTCC system. Thermal performance analysis, exergy performance analysis, and the sensitivity analysis of the ISCC systems have been performed, and the results show that the system efficiencies of both ISCC systems are lower than that of the GTCC system, at 57.1% and 57.5%, respectively, but the power generation of the ISCC system with PTC is greater than that of the benchmark system, while that of the ISCC system with ST is less than that of the benchmark system. The photoelectric efficiency of the ISCC system with PTC is 27.6%, which is 2.1% greater than that of ISCC system with ST. In the ISCC system with PTC, the components with the highest exergy destruction and the lowest exergy efficiency are the combustion chamber, and PTC, respectively. ST is the component with the highest exergy destruction and the lowest exergy efficiency in the ISCC system with ST. With the increase in direct normal irradiance (DNI), the total output power, solar energy output power, and photoelectric efficiency of the ISCC system with PTC increase, while the system efficiency decreases; the solar energy output power and photoelectric efficiency of the ISCC system with ST increase, while the total output power and system efficiency decrease. The photoelectric efficiency of the ISCC system with PTC is greater when the DNI is greater than 600 W/m2; conversely, the photoelectric efficiency of the ISCC system with ST is greater. After sensitivity analysis, the optimal intercooler pressure for the ISCC system is 11.3 MPa.

Different DC-Link Control Methods with Multilevel Inverter for Low Harmonic and Efficient Power Transfer in Grid-Tied Hydrogen Fuel Cell Systems

In grid-connected power generation systems, dc-link voltage control is needed to prevent energy losses, reduce voltage fluctuations and provide a stable energy flow. In addition, control of the power factor via the voltage source inverter is a process that supports the efficient use of the energy produced. Moreover, keeping the total harmonic distortion (THD) of the current injected into the grid in accordance with IEEE-519 harmonic standards (

Research on Dynamic Modeling and Parameter Identification of the Grid-Connected PV Power Generation System

With the increasing proportion of renewable energy in the new power system, the grid-connected capacity of photovoltaic (PV) units shows an obvious upward trend, but its dynamic behavior under different penetration rates significantly affects the transient stability of the power system, so it is crucial to establish a dynamic model that meets the actual working conditions and select a suitable parameter identification method. Therefore, in this paper, based on the electromechanical transient characteristics of the grid-connected PV power generation system, the corresponding dynamic discrete equivalent model is established, and the simulation platform of the grid-connected PV power generation system is built in MATLAB/Simulink to study the adaptability of the dynamic discrete equivalent model of the grid-connected PV power generation system from the single and multiple scenarios using the ordinary least squares (OLS) and bat algorithm (BA) while comparing the generalization ability of the parameters identified by the two methods to the model. The simulation results show that the generalization ability of the parameters identified by the OLS and BA for the model in the single scenario is better, indicating that the model has good adaptability; the generalization ability of a set of general parameters identified by the BA for the model in the multiple scenarios is better than that of the OLS, indicating that the parameters identified by the BA have better adaptability. In conclusion, the dynamic discrete equivalent model of the grid-connected PV power generation system proposed in this paper can accurately reflect the dynamic characteristics of the grid-connected PV power generation system, and the parameters identified by the BA are more generalized than the OLS.

Parameter identification of photovoltaic discrete-time equivalent model using the bat algorithm

As the development of photovoltaic (PV) power generation continuously accelerated the total installed capacity of PV, the traditional static load model is difficult to meet the needs of the power grid with the increasing penetration of PV. And the dynamic model of grid-connected PV power generation is complicated and there are plenty parameters need to be identified, so the dynamic model of grid-connected PV power generation are extremely challenging to apply in wide-area power system. In this paper, a discrete-time equivalent model of PV (PDEM) is established based on the third-order dynamic differential equation of the PV power generation system and the parameters of the PDEM are identified using the least squares (LS) and the bat algorithm (BA). Besides, the dynamic characteristics of the PV power generation grid connected system with different permeability and the fitting residuals of the two methods is analyzed in the IEEE14-bus system incorporated into the PV system. The applicability of the PDEM is verified by setting short circuit grounding fault and changing the PV permeability and voltage dip. The simulation results demonstrate that the PDEM has a strong adaptability and good applicability in the case of high PV permeability with a wide application. And the applicability of the BA in identification of PDEM are given in this paper.

A New Intrinsic Power Balancing Control Method for Boosting Grid-Connected PV System Power Stability

Photovoltaic sources have recently become economical electrical generation resources with high potential power generation systems. The increasing rate of PV system penetration and grid integration has raised serious concerns about the stability and reliability of energy networks. The grid-connected inverter and its operations are taken into consideration in the architecture to provide grid failure robustness. As a result, the capacity of the Low Voltage Ride-Through photovoltaic grid-connected power production system to inject more reactive power into the grid when the voltage disturbance is large has become the most critical issue correlated to the grid. The proposed IPBC controller circuit automatically adjusts the duty cycle value, a desired constant output voltage value, and the load output. To achieve this objective, a suitable feedback controller is necessary to regulate the output voltage to a reference value by automatically controlling the system’s duty cycle, quick response and output load, minimum overshoot zero steady-state error. The effectiveness and reliability of the proposed IPBC controller-based grid-connected solar power generation are developed and verified MATLAB 2017 b software environment. Several simulation programs are based on the operation and performance under different operating conditions evaluated for each of different parameters like steady-state error, THD, and system efficiency.

Agricultural Grid Connected Photovoltaic System Design and Simulation in Egypt by using PVSYST Software

Agricultural Photovoltaic Systems are a key technology to achieve sustainable development goals by reducing competition between land for food and electricity. In addition, Agricultural Photovoltaic Systems are at the heart of the link between power generation, crop production and irrigation water conservation. The main ecophysiological constraint on crop production under photovoltaics is the reduction of light. It is difficult to recommend shade tolerance for some plant varieties due to insufficient information on shading conditions for most plants. The use of shading panels (photovoltaic panels) requires more crop-specific research to determine the optimal percentage of panels and their placement that will not reduce agricultural yields. Crop yield variation versus field shading and availability to maximize the system require extensive research. This study aims to develop a standard procedure for designing an agricultural grid-connected photovoltaic power generation system for solar power generation in an agricultural area in Bahteem, Egypt. The technical and annual performance of the grid-connected PV system was simulated using PV Syst software. The paper started with a pre-feasibility study of a grid-connected photovoltaic system using PV Syst. Software with an extensive database of meteorological data, including global daily horizontal solar irradiance, and a database of various renewable energy system components from different manufacturers. In this work, a comprehensive literature review of agricultural solar photovoltaic systems is conducted, with a particular focus on grid-connected systems, followed by a design procedure for grid-connected solar photovoltaic systems. The planned photovoltaic system will generate a total of 400 KWp of electricity. This generated electricity can drive down electricity prices by exporting excess electricity to the national grid. In addition, solar power systems are fuel-efficient and have a low environmental impact.

LVRT and Reactive Power/Voltage Support of Utility-Scale PV Power Plants during Disturbance Conditions

This paper proposes a control technique for a large-scale grid-connected photovoltaic (PV) plant that maintains the connection of an inverter to the grid voltage under different types of faults, while injecting a reactive power to accommodate the required grid connection. This control strategy is suggested to improve the low-voltage ride-through (LVRT) capability of grid-connected PV power generation plants. A 20 MW solar PV power plant is modeled and simulated using Matlab/Simulink. The power plant is composed of 10 parallel groups of arrays with a power rating of 2 MWp. The solar PV arrays are connected to a medium-voltage side-rated 22 KV to the utility grid. A dynamic analysis of the grid-connected large-scale solar PV power plant is introduced. This analysis is accomplished in order to determine the impact of three-phase short-circuits at the point of common-coupling (PCC), where the solar PV power station is connected to ensure a practical voltage level by injecting active and reactive power. The reactive power support allows for faster restoration of voltage values at the PCC. When subjected to transient disturbances, the stability of the studied system relies on both the type of the disturbance and the initial operating situation. The disturbance may be either small, resulting from electrical load changes, or large, such as from a transmission line short-circuit (fault) and significant generator loss.

Dynamic phasor-based hybrid simulation for multi-inverter grid-connected system

To realize the efficient transient simulation of a grid-connected power generation system based on multiple inverters, this paper proposes a hybrid simulation method integrating the models of electromagnetic transient and dynamic phasors. Based on a demonstration of the concepts and properties of dynamic phasors, the models of single-phase and three-phase inverters described by dynamic phasors are established first. Considering the numerical compatibility problem between dynamic phasors and instantaneous values, an interface scheme between dynamic phasors and instantaneous values is designed, and the efficiency and precision differences of various transformation methods are compared in detail. Finally, by utilizing MATLAB/Simulink, a hybrid simulation platform of a multi-inverter grid-connected system is built, and the efficiency and accuracy of the hybrid simulation are validated via comparison with the full electromagnetic transient simulation.

Solar-driven Dish Stirling System for sustainable power generation in Bangladesh: A case study in Cox’s Bazar

In recent years, the power sector of Bangladesh has seen a major development in terms of generation capacity. But as before, it is heavily dependent on fossil fuels overlooking the potential of renewable energy resources. The scope for grid-connected renewable energy systems has not been explored too far and in terms of solar thermal energy and concentrating solar power (CSP), it is even less. This study focuses on assessing the techno-economic feasibility of solar-driven Dish Stirling system for large-scale grid-connected power generation in Bangladesh. Detailed modeling and optimization of a 100 MW Dish Stirling power plant have been carried out in Cox’s Bazar, Bangladesh, a location suitable for solar energy harnessing due to favorable climatic conditions. The modeling parameters and weather data have been collected from relevant literature, various solar data providers, and specific plant parameters have been optimized for the Bangladeshi climatic condition. Simulation of the modeled plant carried out by the System Advisor Model (SAM) shows that, it can supply 129.856 GWh electricity annually operating at an overall efficiency of 24.91% which is much higher than the values reported in similar literature for the South-Asian regions. The levelized cost of electricity (LCOE) has been determined to be 10.18 cents/kWh, which is highly competitive and promising. The insights obtained from this study can be a perfect starting point for the policymakers and concerned authorities of Bangladesh to further explore the viability of this technology for renewable and sustainable power.

Architecture design of grid-connected exploratory photovoltaic power generation based on Internet of Things and construction of power marketing system

Abstract Solar energy, as a prominent clean energy source, is increasingly favored by nations worldwide. However, managing numerous photovoltaic (PV) power generation units via wired connections presents a considerable challenge. The advent of the Internet of Things (IoT) and cloud service technologies has facilitated the creation of an efficient and convenient PV grid-connected management system. This paper investigates IoT technology and PV grid-connected systems, integrating wireless sensor network technology, cloud computing service platforms and distributed PV grid-connected systems. We propose a Zigbee wireless network featuring ad hoc network functionality and Narrow Band Internet of Things (NB-IoT) smart gateway with multi-protocol and multi-device support. This system enables the collection and uploading of PV grid-connected system data to cloud service platforms, addressing daily operation and maintenance as well as intelligent management of distributed PV power stations. Furthermore, it expedites the aggregation and analysis of PV power generation data, streamlining power marketing across various regions.

Research on the joint optimal allocation of hydropower, wind energy and photovoltaic power generation in the basin

To improve the constancy of hydropower, wind energy and photovoltaic hybrid power generation systems for power furnish to the grid, the joint optimal allocation of hydropower, wind, and photovoltaic is studied. Firstly, the goal of the highest load-matching degree of hydropower, wind energy, and photovoltaic power is put forward. Considering the constraints such as the maximum total power generation ability of hydropower, wind energy, and photovoltaic power generation and the water balance of the reservoir, a joint optimal allocation model of hydropower, wind energy, and photovoltaic power generation in the basin is created, and solved by a progressive optimization algorithm. An example is given to illustrate the influence of source load matching degree on optimal allocation, and the validity of this approach is verified. The simulation results indicate that during grid-connected operation, hydropower, wind energy and photovoltaic complementary power generation can ensure high electricity furnish reliability and deliver more stable power to the grid.

Research on reactive power and voltage coordinated control of intelligent distributed network

with the continuous expansion of the scale of distributed new energy grid-connected power generation in the distribution network and the continuous improvement of penetration rate, the problem of distribution network voltage out of limit caused by distributed new energy grid connected can not be ignored. This paper analyzes the basic principle of voltage out of limit caused by the connection of distributed new energy sources to the distribution network,and analyzes the factors affecting the reactive power and voltage of the active distribution network with distributed new energy sources through BPA simulation, The compensation effects of the distributed series reactor and distributed shunt reactor are compared.

Effects on Frequency Stability of Power System for Photovoltaic High-Penetration Ratio Grid-Connected Power Generation

In this paper, the effects of three typical operation modes, namely short-circuit fault, load change, and chemical energy storage on the frequency of a regional power grid after photovoltaic asynchronous interconnection were studied with different penetration ratios, taking the power grid in Northern Henan Province as the research object. It was found that with an increase in the photovoltaic penetration ratio, the maximum value of the system frequency and the fluctuation amplitude gradually increased, and the power grid system in Northern Henan became less and less stable. With an increase in the penetration ratio, the peak value of the system frequency at the corresponding node gradually increased, and the valley value gradually decreased. With an increase in load, the peak value of the frequency curve gradually increased, and the valley value gradually decreased. When photoelectricity was connected to the grid through chemical energy storage, the system stability during a short-circuit fault and load change operation was significantly improved. Compared with that before energy storage, the frequency amplitude of the system after energy storage was reduced to approximately one tenth of the original. Compared with the case before energy storage, when the load changed, the frequency amplitude of the system decreased to approximately a quarter of the original.