Stand-alone Power Generation System Research Articles

A study of automatic output power control methods for stand-alone photovoltaic power generation systems

Abstract The conventional power generation system’s output power automatic control structure is generally unidirectional, and the control coverage is small, leading to the increase in the random error obtained in the final test. Therefore, the design and research of this article are proposed. According to the current control demand, the generation system shall be stabilized first, and the power compensation shall be calculated. The multi-step mode shall be adopted to improve the control coverage and design the multi-step automatic control structure. According to this, it is constructed, and the automatic control processing is realized using jump balance. The test results show that compared with the traditional DFIG-DRWT system power output automatic control method and the traditional three-phase asynchronous generation system power output automatic control method, the random error finally obtained by the designed independent photovoltaic power station output power automatic control method is relatively effective. This indicates that the application effect and coverage of the designed power automatic control method are high, that controllability has been significantly improved, and that control flexibility has also been strengthened.

Modeling of hydropower plant in islanded mode for different operating conditions

Most countries have access to abundant water resources through rivers and canals. Utilizing this renewable resource, electricity can be generated in an environmentally friendly manner without causing pollution. In rapidly developing countries like India with the abundance of natural resources and diversities, the development of Hydropower is gaining in importance to meet the country’s demand. This work discusses the different operating conditions that may occur in real time of the standalone hydro power generation system. In this work, various operating conditions are considered in terms of faults and disturbances that occur on the load side. These effects of faults and disturbances may be caused in the generating side. It takes into consideration some major events from the load side i.e. small disturbance, load addition, load rejection, large disturbance. In this work, the above-mentioned objectives are achieved by creating a model of a hydro power plant in MATLAB Simulink and keeping its operating environment same, simulate different scenarios related to load side, and study its effect on the generator and generating system. This is achieved by changing the load side for different conditions like introducing a small fault into the system, changing the load on a larger scale, etc The conditions that are introduced are simulated in a period of 10 s time frame. The reaction of the generating side from these conditions is recorded and plotted on parameters that can show the effect directly on the generator.

Photovoltaic Stand-Alone Power Generation System with Multilevel Inverter

This paper proposes a decentralized stand-alone photovoltaic (PV) system, which presents a set of advantages when compared to conventional stand-alone PV system. In the proposed system, the generated energy by the PV arrays is processed by multi-string MPPT step-up converters, which assure a maximum utilization of this energy. The storage system is designed in a decentralized configuration, enabling to achieve a reduction of maintenance cost of back-up system. Moreover, the output stage is composed by a multilevel dc-ac inverter, which enables higher efficiency, low distortion ac waveforms, low leakage currents and the use of low voltage rating semiconductor devices.

Sizing of a Hybrid Energy System for Al Mazyouna Area

Natural gas and diesel currently are the main fuel for electrical power generation in Oman. Decreasing the dependence on national gas and diesel is one of the main goals for Oman’s vision of 2040. This paper discusses the optimum design of a hybrid stand-alone power generation system for the power station of Al-Mazyouna located west of Dhofar governorate using HOMER Pro Software. Real load data and solar radiation of Al-Mazyouna were utilized in the modelling approach. Different scenarios of power systems were investigated, using mainly, diesel generators, PV solar panels, and storage batteries to reach an optimal solution. The main factors that were considered to decide the wining setup of a power system are the net present cost, cost of energy and the amount of emissions. The optimum scenario resulted in a net present cost of $84.8 M and a cost of energy of $0.161/kWh compared to a net present cost of $99.4M and a cost of energy of $0.188/kWh for the current system. Additionally, the optimum scenario system limits toxic emissions significantly compared to the base system. The results of the winning scenario showed that the emitted quantities of harmful gases are all reduced by about 28% compared to the base system.

Modelling and performance analysis of hybrid electrical power generation system for condensate fractionation plant

Refinery industries are mostly installed at the rural area or distant islands considering the hazardous conditions and transportation facilities. However, more often than not these islands or rural areas have no grid connections to facilitate electrification for these kinds of plants. Even if a grid extension is possible, the availability of power cannot be guaranteed in such rural areas. In any case, disruption in power continuity is not allowed for keeping every subsystem (e.g., heating, reaction subsystem) of the refinery industries under running condition. So, having a standalone, failure free and robust power generation system is a prerequisite criterion before starting up such plants in those areas. Diesel generator is the inevitable choice to meet the demand of electricity in such situation, although the cost of running a diesel generator dependent power system to support these sophisticated plants has been quite a challenge. However, with the available modern technologies, it is possible to think of a stable renewable power generation system that can ensure power availability at any time with the lowest possible operating cost. In this paper, a hybrid power generation system is modelled for a Condensate Fractionation Plant (CFP). Optimization, performance analysis and validation of the proposed model are assessed by using HOMER simulation tool

Power Quality Improvement of a Hybrid Renewable Energy Sources Based Standalone System Using Neuro-Fuzzy Controllers

Wind and Photovoltaic (PV) based hybrid standalone systems for supplying electricity to remote consumers are becoming increasingly popular around the world. In general, power generation from both PV and wind is always variable due to irradiance and speed fluctuations. Furthermore, the load is unpredictably variable and changes at random. As a result, one of the main challenges in such standalone micro grids is maintaining power quality. To maintain power quality in such standalone systems, a novel controller should be developed. Furthermore, due to the unpredictable random changes in wind speed, solar irradiance, and load, a battery bank must be integrated into the standalone system via a bidirectional converter. Furthermore, the interconnection of multiple wind turbines and PV panels can create a powerful hybrid system. This paper examines a 1 MW stand-alone power generation system using numerous PV and wind systems. Maximum power points tracking devices with perturbed and observe algorithms are used to optimize the utilization of individual PV modules and wind turbines. Because of its superior priority over conventional PI controllers, a Neuro-Fuzzy integrated controller-based novel control scheme for both inverter and bidirectional converter is proposed to achieve precise response while maintaining power quality. This paper discusses extensive results obtained by establishing hardware-in-the-loop on the OPAL-RT platform to evaluate the responses of proposed controllers. The experimental results also included to provide strength to the paper.

A techno-economic assessment for fuel cells hybrid systems in stationary applications

ABSTRACT This study evaluates the techno-economic feasibility of integrating fuel cells into stand-alone power generation systems, combined with different technologies such as diesel generators, wind turbines, and batteries. An optimisation analysis was performed using the Hybrid Optimization Model for Multiple Energy Resources (HOMER) software to minimise energy costs and several system architectures were obtained for different operating scenarios. The performance and cash flow of the selected system were included. The results suggest that the combination of traditional technologies for fuel cell power generation could be feasible for a country like Colombia, depending on economic factors such as the Consumer Price Index (CPI), the discount rate, and the availability of renewable resources. The proposed system achieves a Levelized Cost of Electricity (LCOE) of $0.112/kWh, comparable to state-of-the-art systems in the literature. This research contributes to the global effort of transitioning to alternative energy sources and reducing carbon emissions.

Evaluation of wind-solar hybrid power generation system based on Monte Carlo method

<span lang="EN-US">The application of wind-photovoltaic complementary power generation systems is becoming more and more widespread, but its intermittent and fluctuating characteristics may have a certain impact on the system's reliability. To better evaluate the reliability of stand-alone power generation systems with wind and photovoltaic generators, a reliability assessment model for stand-alone power generation systems with wind and photovoltaic generators was developed based on the analysis of the impact of wind and photovoltaic generator outages and derating on reliability. A sequential Monte Carlo method was used to evaluate the impact of the wind turbine, photovoltaic (PV) turbine, wind/photovoltaic complementary system, the randomness of wind turbine/photovoltaic outage status and penetration rate on the reliability of Independent photovoltaic power generation system (IPPS) under the reliability test system (RBTS). The results show that this reliability assessment method can provide some reference for planning the actual IPP system with wind and complementary solar systems.</span>

An intelligent converter and controller for electric vehicle drives utilizing grid and stand-alone solar photovoltaic power generation systems

In this study, a battery energy management system for electric vehicle (EV) applications is proposed with a standalone photovoltaic (PV) source and controlled based on the availability of grid, PV source, load consumption, and energy stored in the battery. This paper proposes a single-ended primary-inductance converter (SEPIC) DC-DC converter for charging the battery through the utility and PV source that provides good load regulation. The bidirectional nature of the proposed DC-DC converter provides the charging and discharging of the EV battery in the succeeding modes of operation, i) grid-tied charging, ii) PV-tied charging, iii) discharging to the load in the absence of utility and PV source, and iv) regenerative braking. An improved perturb and observe-based maximum power point tracking (MPPT) algorithm is proposed to track the maximum power from the PV source. In addition, to handle the four modes of operation, a dedicated controller is also proposed. Firstly, the proposed system is validated using MATLAB/Simulink software by considering different operating conditions, and the performance is compared with the traditional MPPT algorithms. Finally, the effectiveness of the suggested system is validated through an experimental prototype. The result proved the superiority of the converter and controller over the traditional systems.<div align="center"> </div>

Optimized Torque Ripple Suppression Method for Standalone Brushless Doubly Fed Induction Generator With Special Loads

In the standalone power generation system based on brushle doubly fed induction generator (BDFIG), the special loads such as unbalanced loads and nonlinear loads will cause negative sequence, fifth and seventh harmonic components in power winding (PW) and the corresponding harmonic components in control winding, which will cause some torque ripple so as to make the machine unable to output stable active power, increase the vibration and noise, and so on. This article will first analyze the harmonic components of the torque in details, and then propose an optimized torque ripple suppression method. Through the low frequency harmonic control method of the line side converter without additional sensors, the negative sequence, and fifth harmonic components of PW voltage are controlled to achieve the suppression of the second and sixth harmonic components of the torque. Compared with traditional active filtration method, the proposed method in this article needs to satisfy fewer constraints and tune fewer parameters, and can be utilized more flexibly. Comprehensive experimental results based on a 5-kVA BDFIG demonstrate the effectiveness of the proposed method.

Optimization of stand-alone and grid-connected hybrid solar/wind/fuel cell power generation for green islands: Application to Koh Samui, southern Thailand

This paper presents the optimization of stand-alone and grid-connected hybrid power generation systems for green islands, with application to Koh Samui in southern Thailand. A techno-economic optimization analysis is applied using the Hybrid Optimization Model for Electric Renewable (HOMER) Pro simulation tool. Four scenarios are identified to select the most suitable solution for a hybrid renewable energy system (HRES) integrating solar photovoltaic (PV), wind turbine generator (WTG), fuel cell (FC), and battery energy storage (Li-Ion), with backup diesel generation or grid connection with the mainland as options. The NASA-SSE and MERRA databases are used as inputs to analyze the solar and wind energy potentials, respectively. The results show that the levelized cost of energy (LCOE) of the HRES with a grid connection to the mainland (Scenario 3) has the lowest LCOE (0.132 US$/kWh), but at large greenhouse gas (GHG) emission costs (20.5 ktonnes/year) due to the high carbon intensity of Thailand’s power portfolio. A stand-alone, 100% renewable energy system (Scenario 4) includes a PV capacity of 182 MW, a wind power capacity of 8 MW, a fuel cell system of 10 MW, a 17.9 MW power converter, and 211 MWh of battery storage. The net present cost (NPC) of this system is 542 MUS$ and the LCOE is 0.309 US$/kWh, with 89% of the energy generated by the solar PV system. Therefore, a 100% renewable energy-based microgrid system is possible on Koh Samui as it can provide a more suitable and reliable solution when considering a HRES system for the total load demand (104 MW of peak load) of the island. Finally, the economic analysis also reveals that the investment in a HRES system is feasible as the payback period is 9 years under an internal rate of return (IRR) of 10% and an appropriate Feed-in-Tariff (FiT) of 0.385 US$/kWh.

An optimized off-grid hybrid system for power generation in rural areas

Stand-alone hybrid power generation system for a cow farm in Jordan is economically and technically optimized to meet the daily electrical load of the farm. A combination of photovoltaics, biogas generators, diesel generators, wind turbines, and batteries are used to determine the best scenario for the farm's power generation. In accordance with the price and technical data of the components, the systems were first studied technically and economically, and then simulated using hybrid optimization model for multiple energy resources (HOMER) software to identify the best configuration. Several options were analyzed to determine the best configuration. The optimized hybrid system includes photovoltaics, a biogas generator, batteries, and a diesel generator. The optimum configuration had a levelized cost of energy of $0.06 per kWh and a net present cost of $2,100,000. The renewable fraction of the total system electrical yearly production was 94%. Furthermore, the results showed that the optimized hybrid system could reduce the emitted gasses by about 92%.

Review of Latest Advances and Prospects of Energy Storage Systems: Considering Economic, Reliability, Sizing, and Environmental Impacts Approach

Studies have shown that the role of energy storage systems in human life is increasing day by day. Therefore, this research aims to study the latest progress and technologies used to produce energy storage systems. It also discusses and compares the most recent methods used by researchers to model and optimize the size of these tools and evaluates the strengths and weaknesses of each. Investigations have shown that using energy storage systems in hybrid stand-alone power generation systems based on renewable energy increases the reliability of the power generation systems and increases their efficiency. It has also reduced the cost of transmitting the power grid to remote areas. Furthermore, this study showed that advances in energy storage technology in recent years have led to the development and promotion of clean microgrids. In addition, this review paper also addresses energy storage technology issues and proposes practical and applied solutions.

Feasibility Analysis and Development of Stand-Alone Hybrid Power Generation System for Remote Areas: A Case Study of Ethiopian Rural Area

This paper proposed a standalone solar/wind/micro-hydro hybrid power generation system to electrify Ethiopian remote areas that are far from the national utility grid. The aim is that it will lead to the development of renewable energy sources, using a hybrid optimization model for energy renewables (HOMER) as an optimization and sensitivity tool and MATLAB as a design tool. The system uses 100% renewable energy. This system incorporated solar photo-voltaic (PV), wind turbines, micro-hydro systems, and battery systems. The net present cost of the system is $4,377,731, incorporating capital depreciation and levelized operation and maintenance costs. During the hybrid energy system’s lifetime, the cost of a grid extension power supply is $22.185 million, which is nearly $17,808,000 more than the cost of the proposed standalone system. So, developing solar/wind/micro-hydro hybrid power generation will save $17,808,000 versus extending the national utility grid. As a result of a thorough examination of renewable energy resources, standalone solar, wind, and micro-hydro hybrid power generation is a technically and economically viable option for the case study area of Maji town.

Thermodynamic analyses of a standalone diesel-fueled distributed power generation system based on solid oxide fuel cells

Solid oxide fuel cell (SOFC) recently emerges as a promising technology for distributed power generation with high energy efficiency. While H2 production and delivery are still the hurdles, diesel can be accessed easily. Thus, it would be of great advantage to generate electricity through an SOFC-based power generation system fueled with diesel. In this work, a standalone diesel-fueled SOFC distributed power generation system combining a steam reformer, a water condenser, a desulfurizer, an SOFC, and a burner is proposed and analyzed thermodynamically. C16H34 is used as a diesel surrogate fuel in the analysis. To realize independent operation of the system, all the heat required by the reformer is supplied by the combustion of the unreacted flue gas from SOFC. With a steam to carbon ratio of 3.5, a reformer temperature of 800 ℃, and an SOFC temperature of 800 ℃, the fuel utilization is determined to be 0.72, and the system presents an energy efficiency of 52.4%. The water condenser is of great importance to improve the system efficiency by eliminating fuel-dilution effect attributing to the existence of H2O, without which the energy efficiency decreases to 50.6%. Further, to add a desulfurization unit or to use pre-desulfurized fuel is of great importance as the existence of H2S will cause an immediate drop of the system efficiency of ∼ 5% and may lead to irreversible damage. A parametric study is performed and presented and the implications for future research focus are discussed.

Variable DC-Link Voltage Control of Dual Active Bridge Converter in a Standalone Wind Power Generation System for High-Efficiency Battery-Discharging Operation

In this study, we deal with a dual active bridge (DAB) converter-based battery charger in a standalone wind power generation system (WPGS) with a small-scale wind turbine. However, the power conversion efficiency under the low power output in the discharging mode is low. In this paper, we propose variable DC-link voltage control in a standalone WPGS with a DAB converter under a light load. The proposed control can compensate for the shortage of generated power and suppress the peak value of the transformer current. Simulation results demonstrate that the proposed control can decrease the peak value of the transformer current and improve the power conversion efficiency of the DAB converter. An experimental setup was constructed to confirm the basic operation of the variable DC-link voltage control. In addition, a reference DC-link voltage switchover control is proposed to enable a high-efficiency drive under all load ranges. From simulation results, the power loss can be reduced by the switchover control of the reference DC-link voltage.

Artificial Intelligence and Bio-Inspired Soft Computing-Based Maximum Power Plant Tracking for a Solar Photovoltaic System under Non-Uniform Solar Irradiance Shading Conditions—A Review

Substantial progress in solar photovoltaic (SPV) dissemination in grid-connected and standalone power generation systems has been witnessed during the last two decades. However, weather intermittency has a non-linear characteristic impact on solar photovoltaic output, which can cause considerable loss in the system’s overall output. To overcome these inevitable losses and optimize the SPV output, maximum power point tracking (MPPT) is mounted in the middle of the power electronics converters and SPV to achieve the maximum output with better precision from the SPV system under intermittent weather conditions. As MPPT is considered an essential part of the SPV system, up to now, many researchers have developed numerous MPPT techniques, each with unique features. A Google Scholar survey from 2015–2021 was performed to scrutinize the number of published review papers in this area. An online search established that on different MPPT techniques, overall, 100 review articles were published; out of these 100, seven reviews on conventional MPPT techniques under shading or partial shading and only four under non-uniform solar irradiance are published. Unfortunately, no dedicated review article has explicitly focused on soft computing MPPT (SC-MPPT) techniques. Therefore, a comprehensive review of articles on SC-MPPT techniques is desirable, in which almost all the familiar SC-MPPT techniques have to be summarized in one piece. This review article concentrates explicitly on soft computing-based MPPT techniques under non-uniform irradiance conditions along with their operating principles, block/flow diagram. It will not only be helpful for academics and researchers to provide a future direction in SC-MPPT optimization research, but also help the field engineers to select the appropriate SC-MPPT for SPV according to system design and environmental conditions.

An Integrated Design of Lng Cold Energy Recovery for Supply Demand Balance Using Energy Storage Devices

Conventionally, massive cold energy from the re-gasified process of liquefied natural gas (LNG) in the receiving station is harvested by power cycles. In addition, geothermal energy is widely used in LNG receiving station for its clean, sustainable and fast advantages, which is regarded as an effective way to improve the power cycle efficiency. However, the issue of mismatch between power generation and power demand has not been effectively solved yet. Therefore, a standalone power generation system (SAP) integrated with a liquid air energy storage system (LAES) is carried out. Firstly, the mathematical models are established based on thermodynamic equations, and the authority of simulation results are preliminarily verified. After introducing geothermal energy, the thermodynamic analysis results demonstrate that the net power output and round trip efficiency of the LAES subsystem reach 143 kW and 166%, respectively, showing outstanding competitiveness compared with previous literature. Significantly, the balance of power generation and demand has been achieved, owing to the LAES subsystem with 180 MWh/day efficient power storage and release. The economic analysis results indicate that the SAP-LAES subsystem and desalination subsystem have considerable economic benefits, with 3.8 and 2.8 dynamic payback years, respectively.

Slot-PM-Assisted Hybrid Reluctance Generator With Self-Excited DC Source for Stand-Alone Wind Power Generation

This article proposed a new slot-permanent-magnet (PM)-assisted hybrid reluctance generator (SPMa-HRG) with self-excited dc source for stand-alone wind power generation system. By introducing PM excitation in stator slot openings, enhanced torque density due to flux modulation effect can be achieved compared with the original reluctance topology. Moreover, the introduced PMs make it feasible to build a self-excited dc source to fed dc field winding without using extra power supply. In particular, a simple design of ac supply winding is proposed, by splitting a small portion of ac armature winding to provide electrical power to dc field winding through a diode rectifier and small-capacity H-bridge converter. Compared with using separate dc source, the device cost is reduced, and the system reliability is improved. In this article, the generator structure and operation principle are introduced. PM usage is optimized to obtain the optimal torque. The feasibility of the optimal design with self-excited dc source is verified by field-circuit coupled finite element analysis.

The use of waste heat recovery (WHR) options to produce electricity, heating, cooling, and freshwater for residential buildings

In recent years, there is a growing attention drawn to the area of building-integrated CCHP systems, due to its high capability in cost and energy saving. In this study, a residential scale multigenerational system is proposed to generate power by using solid oxide fuel cell and gas turbine (hybrid SOFC/GT), heating (by using HRSG), cooling (by using a double-effect absorption chiller) and freshwater (by using a Revers osmose plant). The system is modeled in engineering equation solver and studied from energy, exergy, economic and environmental standpoints. A parametric study is conducted in order to define the crucial decision variables in the system, and their effect on the overall exergy efficiency and unit product cost, along with the rate of freshwater production is observed. Results of the parametric study demonstrated that fuel utilization factor, stack temperature difference, current density, and the pressure ratio of air compressor have the most substantial influence on the behavior of the proposed system. Moreover, obtained results revealed that the energy and exergy efficiency of the system reaches 86.32% and 69.06%, respectively. In addition, the rate of freshwater production and unit product cost of the entire system becomes 256 L/day and 37.78 $/GJ.hr. Furthermore, the emission of the proposed system becomes 0.225 ton/MW.hr, which faces a 31% reduction compared to the standalone power generation system.