Dump Load Research Articles

Control of ILC in an Autonomous AC–DC Hybrid Microgrid With Unbalanced Nonlinear AC Loads

This article presents a multiobjective control scheme for a bidirectional interlinking converter (ILC) of renewable energy based ac–dc hybrid microgrid. The prime focus of the power management algorithm is to feed the ac loads, and dc loads from ac source, and photovoltaic battery energy storage (BES), respectively. The second objective is to utilize the solar power to maximum capacity, by feeding it to dc load, BES, and ac load, in the given order of priority. The ac and dc subgrids operate independently, while supporting each other in case of overloading/underloading, thus reducing the amount of power reserve required in each, and eliminating the need of dump loads. The ANFIS-MN-based power quality control is integrated in order to ensure the total harmonics distortion of ac source current remains below 5% as per IEEE 519 standard, irrespective of the nature of load connected. In addition, the ILC control prevents any negative sequence currents from entering the ac source, even if there is any open circuit fault leading to unbalanced loading on the three phases. The performance of ANFIS-MN-based ILC control is demonstrated to be superior when compared with the conventional and contemporary techniques under different scenarios.

An Advanced Artificial Neural Network Energy Management in Standalone PV Systems

With the ever-increasing prevalent power crisis and pollution of the environment, solar power, has attracted greater attention as a new and clean energy source. It provides an alternative solution for isolated sites with an unavailable grid connection. However, it is not without any drawbacks, mainly its intermittent nature, related primarily owing to its reliance on meteorological variables such as the temperature outside and the amount of sunlight. In effect, the PV systems that produced electrical energy could well display an electricity excess or deficit at the loads level, likely to result in system service discontinuity. In this respect, the present paper is designed to provide an intelligent management strategy to PV station owners with a dump load. It can involve serving two customers simultaneously according to the following scenarios: the PV production installation of the customer1 is greater than their required load; however, the customer2's neighboring station does not have enough power to cover its electrical load. This case brings electrical energy from the initial station to make up for the shortfall, and vice versa. Lithium-ion batteries step in the case when the essential electrical power cannot be delivered either by the local station or the neighboring one or to keep the accumulated power excess. If one of the stations (1 or 2) detects a power surplus and the batteries are completely charged, the generated power excess must be redirected to a secondary load, commonly known as the dump load. Relying on the artificial neural network controller, the suggested exchange control is used for two independent PV-battery stations with dump load. The MATLAB/Simulink attained simulation turns out to demonstrate the advanced controller’s noticeable performance and effectiveness in managing the standalone PV system’s operability in terms of continuous electrical energy delivery flow to the resistive load while reducing power waste and increasing the lithium-ion battery lifespan.

Mixed-Integer Distributed Ant Colony Optimization of Dump Load Allocation with Improved Islanded Microgrid Load Flow

Dump load (DL) utilization at low demand hours in highly penetrated islanded microgrid is of great importance to offer voltage and frequency regulation. Additionally, load flow (LF) convergence is vital to optimize the working states of the DL allocation problem. Hence, more analysis is necessary to highlight the significance of DL in power regulation while observing the influence of LF on solution accuracy. This article proposes two LF techniques derived from backward/forward sweep (BFS), viz., general BFS (GBFS) and improved special BFS (SBFS-II). The latter is based on global voltage shared between generating units, while the former has a more general approach by considering generating bus’s local voltage. The optimal sizing and sitting of DL with optimum droop sets are determined using the mixed-integer distributed ant colony optimization (MIDACO) with the two new LF methods. The optimization problem was formulated to minimize voltage and frequency deviations as well as power losses. The problem was validated on IEEE 69- and 118-bus systems and compared with established metaheuristics. Results show that DL allocation using MIDACO with SBFS-II and GBFS has improved the solution speed and accuracy, respectively. Furthermore, the enhanced voltage and frequency results highlight DL as an efficient power management solution.

Impact of Different Solar Trackers on Hydrogen Production: A Case Study in Iran

Currently, solar energy is considered one of the most suitable options for overcoming the problems of fossil fuel depletion, and global warming. Also, the high costs associated to photovoltaic systems, renders the maximum utilization of solar cells, a fundamental and undeniable necessity. Technical-economic-environmental analysis, using HOMER software, was performed under four different scenarios: without the tracker, with the horizontal axis tracker, with the vertical axis tracker, and with the dual-axis tracker. Consequently, the best configuration was chosen for each scenario. The optimal system for all four scenarios, in the circumstance of disconnection from the grid, only involves the solar cells, while in the circumstance of connection to the grid; both the solar cells and the wind turbine are included. The results demonstrate that in the off grid situation, the scenario involving the use of a vertical axis tracker would be the most cost-effective, with the price of 0.812 $/kWh for energy produced, while the lowest price for producing one kg of hydrogen is $77.97 is attributable to the scenario without the use of a solar tracker. In the circumstance of being connected to the power grid, the scenario involving the use of a vertical axis tracker would be most cost-effective, with the price of each kWh of energy produced equal to $ 0.223. At the price of $29.33 per kilogram, the scenario involving the use of a vertical axis tracker would also be most suitable for the production of hydrogen. Another important fact revealed through the results, is the crucial role of dump load, in the provision of the heat required in an off-grid situation. However, dump load is not associated to heat provision in a grid-connected situation.

Complete Transitions of Hybrid Wind-Diesel Systems with Clutch and Flywheel-Based Energy Storage

A Wind Diesel Hybrid System (WDHS) is an isolated power system that combines Diesel Generators (DGs) and Wind Turbines (WTGs). The WDHS has three operation modes: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The latter mode is the only one resulting in substantial savings, as the DG consumes fuel even with no load. Moreover, adding an energy storage system (ESS) can significantly reduce the start/stop cycles in the DG. The FESS is robust, immune to deep discharges and its state of charge (SOC) is simple to monitor. The WDHS considered in this article uses a friction clutch to disengage the diesel engine (DE) from the synchronous generator (SG) in WO mode. The AVR regulates the voltage amplitude and the frequency regulation results from balancing the power produced by the DG and WT with the power consumed by the load and dump load along with the FESS utilisation. The control algorithms of the different elements present in the WHDS are explained, as well as the general control. The FESS always has priority over the DL for the maximum harnessing of the wind power. Simulations assess the proposed solutions for the different operation modes in the WDHS.

Allocation of Dump Load in Islanded Microgrid Using the Mixed-Integer Distributed Ant Colony Optimization

In highly penetrated microgrids (MGs), the problem of voltage and frequency deviations exceeding their permissible limits, becomes significant with higher share of renewable based distributed generation (DG). The existing real-time control systems of highly penetrated MGs cannot cope on its own with such deviations, owing to the large generation and demand mismatch mainly during off-peak hours. A dump load (DL) can help with voltage and frequency regulation by consuming excess generation. However, further investigation is required to highlight the importance of optimal DL allocation on the operation of MGs. The mixed-integer distributed ant colony optimization is introduced as a novel application in droop controlled islanded MGs to minimize voltage and frequency deviations and system losses. The optimization problem was formulated as a single- and multiobjective problem to allocate a DL and the optimal droop settings for DG in islanded microgrid (MG) during off-peak hours. The proposed optimization method was teamed up with a special backward/forward sweep load flow method to account for DG droop characteristics and enhance the solution convergence. The method was applied to the IEEE 69- and 118-test systems and validated against competitive swarm and evolutionary metaheuristics. Results have shown that an optimally sized and allocated DL with optimized droop setting could minimize voltage and frequency deviations to an acceptable level, while reducing power losses incurred by the installation of such load into the MG.

Hardware Implementation of Cooperative Multitasking Control and Stability Analysis for DC Off-Grid System

In this article, the design and implementation of a cooperative multitasking control strategy for standalone photovoltaic (SPV) system is presented. A double-loop control strategy based on the fuzzy logic controller is developed to achieve high performance from the SPV without using the maximum power point technique, balance the power in the system, regulate the common dc-link voltage, and maintain system operation stability under disturbance. To ensure uninterruptible power supply to the critical loads during diminution of generated power from the SPV, turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> the diesel generator and the dc dump load, power management technique based on load scheduling technique is developed and implemented using the state-flow approach. Furthermore, the stability analysis in open and closed-loop using the average model of the dc–dc buck-boost converter is investigated. The performance of the dc off-grid configuration based on a single dc–dc converter and their control strategies are performed under load and solar irradiation change using MATLAB/Simulink and in real-time through hardware prototyping with DSP controller TMDS28379D.

Performance Investigation of Synchronized Three-Phase AC Chopper-Based Controller for Small Hydrogeneration Systems

This article presents the design, development, and performance analysis of a three-phase synchronized ac chopper (SynACC)-based controller for small hydrogeneration systems. The three-phase SynACC-based controller is used to control the voltage and frequency of a three-phase self-excited induction generator (SEIG)-based small hydropower generation system. The SynACC-controlled dump load is connected at the point of common coupling across the consumer load that controls the system frequency and voltage using instantaneous power balancing method. The SynACC-based controller has synchronized the system frequency feedback-based pulsewidth modulated current delivered to the dump load with the SEIG output voltage in order to make the equal instantaneous currents and similar frequency spectrum of current in all the three phases of the dump load circuit. The equal instantaneous currents and similar frequency spectrum of currents in all the three phases of the dump load circuit significantly improve the system stability. That also improves the system efficiency by removing the multiple and fast fluctuating torque generation problem in three-phase SEIG-based small hydrogeneration systems. The SynACC controller improves the system power factor, since it reduces the reactive power demanded by the dump load circuit. The laboratory prototype of the scheme has been developed and detailed mathematical modeling along with the simulation and experimental results are presented in the article to validate the claims. The technique presented in this article may also be used to develop an improved power quality heating furnace system for chemical and process industry applications.

Coordinate Control of Grid Power, Battery SoC and LVRT Protection in Single VSC Tied DFIG

This paper proposes a coordinate control scheme for the single VSC tieddoubly-fed induction generator (DFIG). In this control scheme, both the gridpower and battery SoC (State of Charge) are maintained to provide an un-interrupted power supply. During the continuous operation of DFIG in thesub synchronous region, there is scope for complete battery discharge. Henceto overcome this drawback, the coordinated control scheme maintains thebattery SoC level within the limits. If the SoC falls below the specified lowerlimit, then the proposed scheme curtails the grid power. Instead of dischargingthe battery, the control shifts the battery to charging mode until the safelimit of SoC is attained. During the continuous operation of DFIG in thesuper synchronous region, if the SoC reaches its upper limit, the proposedscheme discharges the extra power to the dump load. Further, this controlscheme also introduces the low voltage ride through (LVRT) aspect accordingto IEGC (Indian electricity grid code) of 15% of nominal voltage and also an enhanced rotor position computation is implemented for the effectiveestimation of rotor position for single VSC tied DFIG. This control makesthe topology more robust and improves the reliability of the system. Theproposed scheme is validated for a test system of 3.7 kW Wound RotorInduction Machine based DG unit and investigations are done in MATLABsimulation.

Evaluation of the Symmetrically Switched Converter Structures on the Frequency Regulation of Standalone Micro Hydro Power Plants

Micro hydro power plants (µHPP) are typically used to supply electric energy to microgrids outside the national power grids taking care of the frequency control of the isolated system. A conventional way to maintain the load balance in the system is to use thyristor switched AC-AC converters controlled dump loads. A disadvantage of the AC-AC converters is their reactive power consumption decreasing the power factor at the generator output. To avoid this problem the authors have earlier proposed two converter topologies utilizing symmetrical switching scheme resulting to zero reactive power consumption. The objective of this paper is to evaluate the frequency regulation loop performance of the dump load controlled single generator system by using the symmetrically switched converter structures. Evaluation is carried out by analyzing the performances of different converter structures in a simulator representing the operation of a Cuban µHPP “Los Gallegos”. The results showed that the frequency regulation loop performance using each proposed converter structure satisfied the Cuban standard of frequency regulation, but with the symmetrically switched structures reactive power consumption was reduced resulting to reduced losses and improved effective current delivery capacity of the generator.

Combined Method of Flow-Reduced Dump Load for Frequency Control of an Autonomous Micro-Hydropower in AC Microgrids

Nowadays, microgrids (MGs) play a crucial role in modern power systems due to possibility of integrating renewable energies into grid-connected or islanded power systems. The Load Frequency Control (LFC) is an issue of paramount importance to ensure MGs reliable and safe operation. Specifically, in AC MGs, primary frequency control of each energy source can be guaranteed in order to integrate other energy sources. This paper proposes a micro-hydro frequency control scheme, combining the control of a reduced dump load and the nozzle flow control of Pelton turbines operating in autonomous regime. Some works have reported the integration of dump load and flow control methods, but they did not reduce the dump load value and adjust the nozzle flow linearly to the power value demanded by users, causing the inefficient use of water. Simulation results were obtained in Matlab®/Simulink® using models obtained from previous research and proven by means of experimental studies. The simulation of the proposed scheme shows that the frequency control in this plant is done in correspondence with the Cuban NC62-04 norm of power energy quality. In addition, it is possible to increase energy efficiency by reducing the value of the resistive dump load by up to 7.5% in a case study. The validation result shows a 60% reduction of overshoot and settling time of frequency temporal behavior of the autonomous micro-hydro.

Transient thermographic studies of resistive system protection load for wind turbines

The present paper reports findings of the transient thermography studies of three-phase resistive system protection load (RSPL) or diversion dump load used for safeguarding the wind turbines during extreme wind conditions. RSPLs with coil-type and plate-type resistive elements made of Nichrome 80 and SS 304, respectively, were studied. The first set of studies was conducted on the permanent magnet synchronous generator (PMSG) test bench with 24 and 48 V PMSGs as power sources. The second set of studies was conducted on the auto-transformer-based test setup. For both the studies, surface temperature distributions over the resistive elements of the RSPLs were captured under the different test conditions using transient thermography and compared. Quantitative comparison of the variation in maximum temperature of RSPL heating elements and PMSG's rotational speed for a given power rating for both the RSPLs was carried out. Thermographs revealed the presence of localized hotspots in RSPLs with Nichrome 80 based coil-type heating elements. Similar localized hotspots were absent in RSPLs with SS 304 based plate-type heating elements. Maximum surface temperatures of RSPLs with coil-type resistive elements were found to be about 8.25% higher than the other RSPL. Based on these observations, it was inferred that as against the conventional approach of using RSPLs with a coil-type heating element made of Nichrome 80, RSPLs with a plate-type heating element made of SS 304 offered better safety for the wind turbines.

Renewable Energy-Based Systems on a Residential Scale in Southern Coastal Areas of Iran: Trigeneration of Heat, Power, and Hydrogen

The use of small-scale Combined Heat and Power (CHP) to meet the electrical and thermal needs of buildings has grown exponentially and plans have been made in Iran to expand these systems. In view of the above, in the present work, for the first time, sensitivity analysis has been performed on the parameters of natural gas price, annual interest rate, and the price of pollutant penalties. The CHP system studied included fuel cell, biomass generator, solar cell, wind turbine, and gas boiler. The techno-econo-enviro simulations were performed by HOMER software and the study area was Abadan. The use of a dump load to convert excess electricity into heat and heat recovery in a biomass generator and fuel cell are other advantages presented by the present work. The minimum Cost of Energy (COE) is 1.16 $/kWh. The results also showed that the use of biomass generators was economical when the annual interest rate was 30 %. The significant effect of using dump load on the required heat supply and the lowest price per kg of hydrogen produced equal to $ 35.440 are other results of the present work. In general, the results point to the superiority of solar radiation potential over wind energy potential of the study area and the prominent role of dump load in providing heat on a residential scale is clearly seen. Also, for the current situation, using biomass is not cost-effective.

High Performance MPPT Approach for Off-Line PV System Equipped With Storage Batteries and Electrolyzer

The current publication is directed to achieve a high-performance stand-alone PV system having the capability of tracking maximum output power, providing fixed output DC voltage, and attaining efficient system utilization, under different irradiation levels. A new maximum power point tracking (MPPT) approach integrating the incremental conductance algorithm and fuzzy logic control, and enhanced with PI-controller, was proposed to track maximum power. To provide fixed output DC voltage and approaching full system utilization, the PV system is equipped with a battery bank, electrolyzer; as a dump load, and buck-boost converter, with two controllers. The results of the proposed MPPT technique; modified incremental conductance (MINC), are compared with the corresponding results of three prevalently implemented MPPT algorithms: perturbed and observed (P&amp;O), modified variable step-size P&amp;O (VSZ-PO) and the ordinarily incremental conductance (INC). The highest output power, best tracking efficiency and best output power response are achieved by utilizing the proposed MPPT method. The results of the output voltage response and electrolizer on/off states confirm the ability of the PV scheme to provide fixed DC voltage and attain efficient system utilization, under varying irradiances.

Study of the Intelligent Control and Modes of the Arctic-Adopted Wind–Diesel Hybrid System

For energy supply in the Arctic regions, hybrid systems should be designed and equipped to ensure a high level of renewable energy penetration. Energy systems located in remote Arctic areas may experience many peculiar challenges, for example, due to the limited transport options throughout the year and the lack of qualified on-site maintenance specialists. Reliable operation of such systems in harsh climatic conditions requires not only a standard control system but also an advanced system based on predictions concerning weather, wind, and ice accretion on the blades. To satisfy these requirements, the current work presents an advanced intelligent automatic control system. In the developed control system, the transformation, control, and distribution of energy are based on dynamic power redistribution, dynamic control of dump loads, and a bi-directional current transducer. The article shows the architecture of the advanced control system, presents the results of field studies under the standard control approach, and models the performance of the system under different operating modes. Additionally, the effect of using turbine control to reduce the effects of icing is examined. It is shown that the advanced control approach can reduce fuel consumption in field tests by 22%. Moreover, the proposed turbine control scheme has the potential to reduce icing effects by 2% to 5%.

Modelling Large Heaped Fill Stockpiles Using FMS Data

The frequent best practice for managing large low-grade run-of-mine (ROM) stockpiles is to average the entire stockpile to only one grade. Modern ore control and mineral processing procedures need better precision. Low-precision models hinder the ability to create a digital mine-to-mill model and optimize the holistic mining process. Prior to processing, poorly characterized stockpiles are often drilled and sampled, despite there being no geological reason for relationships between samples to exist. Stockpile management is also influenced by reserve accounting and lacks a common operational workflow. This paper provides a review of base and precious metal run-of-mine (ROM) pre-crusher stockpiles in the mining industry, and demonstrates how to build a spatial model of a large long-term stockpile using fleet management system (FMS) data and geostatistical code in Python and R Studio. We demonstrate a framework for modelling a stockpile believed to be readily workable for most modern mines through use of established geostatistical modelling techniques applied to the type of data generated in a FMS. In the method presented, each bench of the stockpile is modeled as its own geological domain. Size of dump loads is assumed to contain the same volume of material and grade values that match those of the grade data tracked in the FMS. Despite the limitations of these inputs, existing interpolation techniques can lead to increased understanding of the grade distribution within stockpiles. Using the framework demonstrated in this paper, engineers and stockpile managers will be able to leverage operational data into valuable insight for empowered decision making and smoother operations.

Supply side management in microhydro using battery bank: A case study of Pinthali microhydro plant, Kavre

Geographical difficulties and slow development of power generation, transmission and distribution, related activities have made many remote areas not assessable to national grids in Nepal. Electricity demand is increasing day by day in urban as well as rural areas but instant extension of national grid seems difficult in many remote places of Nepal. Thousands of Micro hydropower are being installed throughout the country where extension of grid is difficult. This paper presents the introduction of battery bank for the supply side management in the micro hydropower plants. Surplus power during off load time is stored in a battery instead of wasting in dump load. The system is designed in Matlab Simulink where system containing Electronic Load Controller(ELC), Battery Management System(BMS), three phase ac/dc converter were used. Synchronous Generator which generates constant power feeds the load, battery and dump load according to requirement. Battery uses the power for charging during off load hour and supplies deficit power during peak hour. Case study of Pinthali microhydro power of capacity 8.1 KW was carried out for load survey to calculate excess power. Simulated system was able to distribute the power to load when load demand was higher than generation through the battery.

Experimental and simulation testing of an EGLC controller for an IAG-EGLC system for electrifying off-grid rural sites

The voltage support at consumer terminals is required in remote areas. This voltage support should be provided economically. In the manuscript, the study carried out emphasis on the designing methodology and hardware implementation of an electronic generator load controller (EGLC) for an isolated asynchronous generator (IAG) feeding single-phase loads. The EGLC is build using the uncontrolled rectifier bridge, an IGBT based chopper switch with series connected dump load. The driving signals for the IGBT based chopper switch is generated using Pule Width Modulation PWM IC. The generator is providing power to the two loads connected in shunt across each other. The objective of the controller is to maintain constant load on the generator during the entire operation of the generator. The expected simulated outcomes are verified using a hardware model of the EGLC prototype developed for an IAG in the laboratory. The closeness of both the simulated and experimental results justified its application for the electrification of various off grid remote sites available in hilly areas.Article HighlightsAn EGLC Controller is designed, fabricated and tested in the laboratory for an IAG for voltage and frequency support.The proposed controller maintains constant load on the generator irrespective of nature of varying load.The prototype developed for an IAG-EGLC proves to be cost effective and can be proposed for electrification of off grid sites.

Energy management of a renewable-based isolated micro-grid by optimal utilization of dump loads and plug-in electric vehicles

This paper proposes a new day-ahead energy management system (EMS) for an off-grid fishing island micro-grid (MG). The MG considered in this work is well equipped with smart grid infrastructure and embedded with plug-in electric vehicles (PEVs). Moreover, it is a green and fossil fuel free MG without any conventional power plant. The MG provides its load demand by solely renewable generations, including wind farms (WF) and photovoltaic (PV) power plants. Therefore, keeping balance between generation and demand is a difficult task in day-ahead operation planning of this MG. In order to overcome this obstacle, the MG uses a mega-scale battery energy storage system (BESS). However, the capacity of the BESS is limited and it is not economically feasible to increase the BESS capacity. Therefore, the MG considers PEVs G2V/V2G operation modes planning and dump loads optimal utilization as supplementary balance options. The main dump loads in this MG are industrial fish refrigerators (IFRs) and reverse osmosis desalination system (RODS). These dump loads in addition to PEVs’ G2V/V2G modes of operation are scheduled in the EMS proposed in this paper. Numerical studies show that the proposed EMS reduces total daily wasted energy and energy not served by 96% and 30% respectively.

Effect of Emission Penalty and Annual Interest Rate on Cogeneration of Electricity, Heat, and Hydrogen in Karachi: 3E Assessment and Sensitivity Analysis

Pakistan is the world’s sixth-most populous country with a semi-industrialized economy. It has been always an energy importer and dependent on fossil fuels. Great pressure is imposed on Pakistan’s national grid from the rise in fossil fuel costs, variations in the annual interest rate, and increased costs of greenhouse emissions. To meet the ever-increasing energy demand, the Government of Pakistan has decided to further harness wind and solar energies currently having a negligible share in Pakistan’s energy portfolio. Despite the importance of this issue, no study has been conducted so far on the cogeneration of power, heat, and hydrogen in Pakistan. Accordingly, this study is aimed at technical–economic–environmental sensitivity analysis of supplying electric and thermal loads of a residential building in Karachi by an off-grid wind-solar-fuel cell system. To this end, 4500000 possible cases were analyzed, simulated, and optimized with the HOMER software using 20-year average meteorological data from the NASA website. A sensitivity analysis was performed on this system for the first time in Pakistan. The other novelties are the use of dump loads for converting the surplus electricity into heat and also heat recovering in the fuel cells. The results showed the great potential of the station understudy for supplying the required power and heat by renewable energies. Hydrogen production was also affordable at every emission penalty price with an interest rate of less than 9%. Moreover, dump loads play a key role in supplying the thermal demand. Comparison of the wind turbine–solar cell–fuel cell–battery system with the wind turbine–solar cell–battery and solar cell–battery systems indicated that the internal rate of return and the payback period were, respectively, 9.39% and 11.4 years and 11.7% and 11 years. According to these results, it is recommend that Pakistani authorities promote the use of renewable energies through incentives and investment subsidies.