Quality Of Power Supply Research Articles

Review of Key Technologies of mobile energy storage vehicle participating in distribution network dispatching under the high proportion of renewable energy access

With modern society’s increasing reliance on electric energy, rapid growth in demand for electricity, and the increasingly high requirements for power supply quality, sudden power outages are bound to cause damage to people’s regular order of life and the normal functioning of society. Currently, the commonly used emergency power protection equipment is mainly based on diesel generator sets, while there is also flywheel energy storage equipment in the application of emergency power protection. In today’s society, we strongly advocate green, energy-saving, and emission reduction background, and the demand for new mobile power supply systems becomes very urgent. Mobile energy storage vehicles can not only charge and discharge, but they can also facilitate more proactive distribution network planning and dispatching by moving around. The basic model and typical application scenarios of a mobile power supply system with battery energy storage as the platform are introduced, and the input process and key technologies of mobile energy storage devices under different operation modes are elaborated to provide strong support for further input and reasonable dispatch of mobile energy storage vehicles.

Power Quality Control System of High-Power-Density Switching Power Supply for Green Environment

There is higher harmonics and electromagnetic interference caused by high-power-density switching power supply during high-frequency and normal operations which affects power quality of switching power supply and also impacts the environment. To solve this problem, this paper proposes a dual digital signal processor (DSP) controller suitable for unified power quality regulators and designs high-power-density switching power supply control system for promoting green environment. The overall structure of the system is divided into two parts, the power main circuit and the control circuit. In the main power circuit, the electromagnetic interference (EMI) filter is used to filter the input AC voltage and convert it into a stable DC voltage. A high-frequency inverter is used to invert the DC voltage into a high-frequency AC voltage to achieve harmonic control and reactive power compensation. In the control circuit, dual DSP controller is used to improve real-time detection, control of the output voltage, and current and driver temperature of the high-power-density switching power supply, while high-precision analysis and processing system collect different information and then achieve the power quality control of the switching power supply based on system software to keep this environment green. The experimental results suggest that the harmonic content of the experimental objects controlled by the system is reduced by 16.7% compared with the existing power quality control and the absolute error of the system is less than 0.02 V which improves the de-noising performance. The power generation systems require that the consumption of natural resources and renewable energy solutions can assist in saving the natural resources.

Rapid Harmonic Detection Scheme Based on Expanded Input Observer

The existence of harmonics will cause the quality of power supply in a power system to decline and will affect the normal use of the power system. Therefore, it is important to suppress harmonics in the power system, and the first step of harmonic suppression is harmonic detection. To address this phenomenon, a fast harmonic detection method is proposed in this paper. It is based on the input observer theory to construct a state space model based on the original signal and harmonic components and estimate the state variables so as to achieve harmonic extraction. The characteristic roots are used to prove the convergence of the observer. In addition, the Second-Order Generalized Integration (SOGI) frequency estimation method is chosen to cascade with it so that harmonic detection can be accomplished with unknown frequencies. The simulation results prove that the proposed method can quickly converge and accurately extract each harmonic in the case of fluctuations in the fundamental amplitude, fundamental frequency and phase of the input signal, and the whole process can be completed in 0.02 s. The possible effects of white noise on harmonic extraction are also simulated, and the results prove that the accuracy of harmonic extraction can still be guaranteed in the presence of white noise. By using the Speedgoat real-time target machine built Rapid Control Prototype (RCP) as a testbed, experiments with similar simulation conditions were performed. The results show that the method has fast and accurate harmonic detection performance.

An auxiliary-power-compensation droop control strategy for multi-terminal flexible interconnected distribution network

The emergence of multi-terminal flexible interconnected distribution network can effectively improve the consumption level of new energy and enhance the power supply quality of distribution network. At present, the droop control strategy is widely used in the modular multilevel converter (MMC) in multi-terminal flexible interconnected distribution network, which can adjust and distribute DC voltage and power autonomously according to the droop characteristic curve. However, this type of strategy is challenging to cope with the sudden working conditions. These conditions include the power reversal, the outage of station and large fluctuation of new energy sources, which can cause abnormal fluctuation of DC voltage. Therefore, this paper proposes a control strategy based on the auxiliary power compensation in the flexible interconnected distribution network to solve the problem. This compensation strategy introduces an auxiliary power reference and simplifies the control loop, effectively suppressing the power fluctuation and optimizing the dynamic performance of the system. Compared with the traditional improved droop control strategy, this strategy does not need to change the parameters of the control system, has a stronger ability to suppress the voltage fluctuation, and the response speed of the control system is faster. The reliability and effectiveness of the proposed control strategy are verified by simulation.

Construction of Grid Reliability Assessment Model Based on Sensitivity Analysis

The traditional reliability of power supply only focuses on the continuity of power supply and does not include the impact of power quality on customers in the assessment. In this paper, we use “the ability of the grid to provide continuously available power to customers” as the criterion to reflect more realistically the level of reliability perceived by customers. This reliability assessment, which is closer to the customer’s perspective, can also be used as a basis for quality-based pricing in the electricity market that is acceptable to both the supplier and the consumer, and the difference between the reliability of electricity consumption and the reliability of electricity supply statistics can also be used by power supply companies to evaluate their own power supply quality and service level. This paper uses the AC algorithm to calculate the reliability indexes of the power system in combination and proposes to use the component sensitivity analysis to rank the system components to obtain the key component information for the combination of the power system reliability indexes.

Design and Implementation of Hybrid Harmonic Filter for Converter System

Quality of power is essential for all electrical systems towards their reliable operation. In specific voltage/current magnitude, frequency and waveforms are the key parameters that decide the quality of electric power supply. Recently enormous nonlinear loads such as converters, inverters, variable frequency drives, and uninterrupted power supply are used in all modern industrial sectors which leads to power quality disturbance in power systems In particular, harmonic distortion is one of the main power quality causes produced by nonlinear loads which will affect the reliable operation of industrial electrical equipment. Harmonic filters help to maintain the harmonic limits as per the IEEE 519-2014 standard. This research article overviews the various types of harmonic filters and the design procedure for the passive harmonic filter. Also, this research paper briefly converses the design and control technique procedure for the proposed hybrid harmonic filter, used to control the harmonic distortion produced by the three-phase converter system. The results of the experimental setup with the implementation of a hybrid harmonic filter clearly show that the harmonic distortion is greatly reduced. The high accuracy power quality analyzer used in this research work measures the real-time voltage/current waveforms, power/energy, and harmonic profiles.

Modelling electric vehicles uptake on the Greek islands

For decades, the Greek islands have been facing challenges in terms of quality of power supply, increased carbon dioxide equivalent (CO2eq) emissions, and costs due to their reliance on oil-fired generation subsidised by the Greek state. In light of the recent reforms to decarbonise the islands' region while enhancing their local grids, this study investigates the impact of electromobility considering an autonomous electricity system supported by storage versus an interconnected one. Two Electric Vehicles (EVs) deployment scenarios coupled with several charging strategies have been modelled using the PLEXOS energy systems model. The results highlight that the Vehicle-to-Grid (V2G) scenarios demonstrate the most evident benefits for the islands' electricity systems, performing adequately under both the Autonomous and Interconnection scenarios concerning the economic and environmental impact. Such scenarios have the potential to reduce emissions by 8.5% while dropping costs up to 20% by 2040, when combined with the required renewables expansion plan. From the security of supply perspective, the results demonstrate improvements under the interconnected context accompanied by thermal generation restrictions without however eliminating power shortages recorded already in a non-EV case. The analysis also showcases an escalated impact on power shortages and curtailments during the maximum week, particularly when combined with an ambitious EV deployment. Yet, V2G may increase renewables share up to 7% in 2040. In this context, EVs could mobilise the additional deployment of 600 MW renewables by 2040 if interconnections with the mainland are realised. Assuming islands continue operating as autonomous electricity systems, the additional capacity to accommodate may reach 720 MW.

AUTOMATED SYSTEM FOR PROVIDING POWERFUL COMPUTING SYSTEMS WITH A COMPLEX OF EQUIPMENT

With the development of the cryptocurrency market, the need for automated support for mining hardware is growing. At present, there are practically no flexible systems for selecting equipment to fully meet the complex needs of providing complex features of mining processes, and software has not been developed that could take into account all the features of cryptocurrency developers. The purpose of this work is to develop the principles and algorithm for solving the problem of organizing the provision and selection of the necessary equipment for complex and powerful computing systems in the form of an automated system for the procurement and supply of the main computing and additional related equipment, organizing its installation, monitoring the conditions and characteristics of operation and subsequent output out of operation after the resource has been depleted or in order to increase the computational characteristics of mining farms and their cooling systems. Modern powerful computing systems are a huge amount of interconnected diverse equipment, located at different sites and interacting with each other by high-speed neural connections. The success of creating such complexes depends on the level of training of a team of specialists, which must have comprehensive and deep knowledge on the issues of building the engineering infrastructure of a computing complex, reasonable equipment with the necessary equipment, calculating the maximum energy load and providing such objects with a cooling system for computing elements and the system as a whole. Computing power is realized with the help of Data-centers, mining farms with more than 5000 computing modules. The problem of ensuring the quality of power supply of mining farms, a high level of efficiency in the use of power sources, protecting expensive equipment from overheating while ensuring high computing performance is very relevant, it requires constant attention and the use of special equipment and technologies. The developed system described in this paper relates to the management and optimization of resources of large computing centers, namely, to the organization of mass purchases of equipment, its installation and effective maintenance during operation, ensuring the efficient operation of cooling systems and the decommissioning of mining farms after completion. their work. This system allows users to create their own equipment catalogs in the form of models and then effectively organize the planning and management of devices in the form of an abstract model that consolidates all devices. Such a model is easy to control, find and perform actions on related objects, scale and make changes as needed. On the practical side, this developed product is simple in terms of the graphical interface and does not require much time for staff training and use in practice.

A micro off-grid power solution for solid oxide fuel cell waste heat reusing enabled peak load shifting by integrating compressed-air energy storage

Nowadays, the proportion of thermal power generation is still large, the waste of electricity will lead to more environmental pollution. With the continuous increase in electricity demand, how to improve the quality of power supply, reduce transmission loss and ease the burden of power grid are urgent problems to be solved. The combination of fuel cell and energy storage technology could be a good solution. In this article, a new off-grid system with peak load shifting function is proposed to solve problems of power supply in remote regions. This combined system consists of a solid oxide fuel cell, a regenerative Brayton cycle, an organic Rankine cycle and a compressed-air energy storage system. By rational utilization of waste heat in exhaust gas, the cascade utilization of energy can be realized. The results indicate that the fuel cell-waste heat recovery system can achieve higher thermal efficiency and exergy efficiency, with an improvement of 6.69% and 6.46%, respectively. The application of compressed-air energy storage system not only makes the system have the functions of energy storage and peak regulation, but also improves the economic performance. The system reaches a minimum payback time of 4 years in the case presented. In conclusion, this new combined system is clean, efficient and economical, which can provide a good solution for power supply in coteaux, suburbs and islands.

The use of frequency converter and active rectifier of voltage for the power quality improvement in coal longwalls

Improvement of productivity and performance in coal longwall mining is achievable via transition to longwalls to 250–400 m long and by increasing installed capacity of longwall equipment systems up to 4200–5600 kW. The up-to-date longwall mining uses energy- and resource-saving machines equipped with variable frequency motors. In this case, inclusion of the frequency converters in the machinery electrics results in essential distortion of voltage from the nominal sine waveform and leads to the power quality degradation in longwalls. With a view to enhancing power quality in longwall networks, the authors propose to use variable frequency motors with frequency converters with active rectifiers of voltage. When selecting a frequency converter with the active rectifier for voltage in underground power network, it is recommended to take into account the longwall power supply specifics, the cross-effect of the frequency converters operating in neighbor lines, the variable nature of power system loads and the change in the number of the frequency converters in simultaneous operation. To that end, the power supply model is developed to study consumed power quality with regard to the power network topology, parallel-operating frequency converters and actual loads of electric motors. The modeling has determined the mechanisms of effect exerted by the frequency converters on the power quality in operation with active rectifiers of voltage. The carrier frequency and inductance of the buffer reactor of the threelevel active rectifier, which ensure the standard quality power supply in longwall, are substantiated.

The configuration optimized design method based on real-time efficiency for the application of vanadium redox flow battery in microgrid

To realize the efficient, economical and stable operation of vanadium redox flow battery (VRB) in a microgrid containing a high proportion of renewable energy, a coupling calculation model is constructed and a configuration optimized design method is proposed in this paper. First, the coupling calculation model involving the fluid mechanics model and electrochemistry model is established to obtain the real-time efficiency of VRB. Second, an economic model of VRB is constructed considering the investment costs, operation costs, economic benefits and renewable energy utilization. Finally, a configuration optimized design method based on typical load and real-time efficiency is further proposed to cope with practical application scenarios. Two different objectives, including the lowest average daily cost and the lowest renewable energy curtailment, are selected in the method. The results are presented as follows. First, the energy efficiency of the battery is increased from 76.90% to 80.45% with the increase of electrolyte flow rate. With the optimal selection of porous electrode porosity, the merit energy efficiency and system efficiency are presented. Better VRB performance can be obtained at the electrolyte flow rate of 120 ml/min and the porous electrode porosity of 0.93. Second, the novel proposed configuration design method can be implied to improve the renewable energy consumption capacity while ensuring system economics. Finally, with the lowest average daily cost as the objective, the optimal configuration of VRB is 891 kW and 7344 kWh, respectively, while the time average efficiency is 79.26%. The total amounts of renewable energy curtailment in one day decreases from 12,380 kWh to 6,281 kWh. At the same time, the power supply quality is significantly improved after accessing various distributed energy sources to the microgrid.

An energy cooperative system concept of DC grid distribution and PV system for supplying multiple regional AC smart grid connected houses

This paper proposed a suitable control strategy for power sharing management for hybrid AC/DC residential PV systems. This control method is used as an Energy Cooperative Approach (ECA) to manage the power flow between a PV and battery-fed smart grid within a DC micro-grid, supplying some connected houses. In fact, using an ECA which is based on photovoltaic (PV) power transfer between three houses, connected to the AC network; through a DC micro-grid, the photovoltaic energy can be effectively used to satisfy the load demand. Such a process ensures a continuous demand satisfaction, lengthens the storage system life time by minimizing the resort of the battery, and alleviates the stress of the main grid minimizing the consumption of electricity fed by the AC grid. In fact, this strategy increases the system efficiency and the power supply quality. To achieve such purposes, a control algorithm for distributed flexible network residential PV systems was properly developed. The decision criterion for the developed supervisor is based on the instantaneous PV power, the required power, and the battery state of charge in order to manage the power flow under six operating modes. The control strategy was proposed also to regulate DC bus voltage and maintain the power balance within the micro-grid. The simulation results validated the effectiveness and feasibility of the proposed control strategy under various conditions. To highlight this strategy benefits, a comparative study between strategies without and with ECA was performed. The results of this study showed that using the ECA on a typical day, the energy PV contribution to satisfy the loads (Fpv) grows by a rate that varies from 15.5% to 23.45%, the battery contribution part (Fbat) recorded a decrease that varied between 8.77% and 18.42%, while the main grid contribution (Fgrid) was reduced by a rate that varied between 2.41% and 13.1%.

Improved Hybrid Reactive Power Compensation System Based on FC and STATCOM and Its Control Method

The purpose of this study is to solve the main problems in distribution networks, including increased line loss and reduced power supply quality caused by insufficient capacitive reactive power. To reduce the capacity, voltage, and current stress of an active module of a compensation device and improve the cost performance of the device, an improved hybrid reactive power compensation system based on a fixed capacitor (FC) and a static synchronous compensator (STATCOM) is proposed. The topological structure and basic operating principle of the proposed reactive power compensation system are introduced. In addition, from the perspectives of output voltage, current, power, loss of the active part, and system compensation cost, the performances of the proposed reactive compensator and the inductively coupled STATCOM (L-STATCOM) are compared and analyzed. Furthermore, the key parameters of the proposed system are designed, and the joint optimization control strategy of the FC and STATCOM is studied. The correctness and effectiveness of the proposed topology structure and control method are verified by simulations.

A Novel Virtual Voltage Comparison Compensation for Dynamic Voltage Restorer

In view of the high-quality requirements of the power supply quality of the user-side sensitive equipment, the system for voltage sag in the grid operation is stable and efficient. This paper proposes a new virtual voltage comparison compensation dynamic voltage recovery method. The algorithm that uses the invariant constant signal as the input quantity, and the real-side input load side signal reduces the influence of the input quantity uncertainty change on the generated compensation signal and improves the simplicity of the system operation control and the system stability. The flexibility of the proposed control strategy, as well as the effectiveness of the optimal design method, is verified by both simulation and experimental results.

The Contribution of Small Modular Reactors to the Resilience of Power Supply

In recent years, there has been a growing interest in the design, development and commercialization of nuclear power Small Modular Reactors (SMRs). Actual SMR designs cover the full spectrum of nuclear reactor technologies, including water-, gas-, liquid-metal-, and molten-salt-cooled. Despite physical and technological differences, SMRs share some relevant design features, such as small size, modularity, inherent and passive safety systems. These features are expected to enhance availability, recoverability, promptness and robustness, thereby contributing to the resilience of power supply. Thanks to the peculiar design features of SMRs, they are likely to satisfy a number of Functional Requirements (FRs) for this objective, namely: (i) low vulnerability to external hazards; (ii) natural circulation of primary coolant; (iii) prompt, unlimited and independent core cooling under shutdown conditions; (iv) shutdown avoidance in response to variations of the offsite power supply quality and electrical load; (v) island mode operation; (vi) robust load-following; (vii) independent, self-cranking start. These make advanced Nuclear Power Plants (aNPPs) comprised of SMRs perfect candidates to withstand a broader range of natural disruptions and to recover faster from them, compared to conventional Nuclear Power Plants (cNPPs), thus rendering them a major potential asset for guaranteeing resilience and security of power supply. The review focuses on Natural Technological (NaTech) events that impact a typical Integrated Energy System (IESs) within which SMRs are embedded: IESs are, indeed, being developed to integrate different power generation plants with gas facilities, through gas and electricity infrastructures, because they are expected to bring increased security and resilience of power supply, as shown in the qualitative case study presented.

Optimal Transmission Switching Based on Analytical Target Cascading Algorithm

The penetration of a high proportion of renewable energy sources (RES) into the power grid intensifies the source–load imbalance, which greatly weakens the network transmission performance and power supply quality, and the effect of relying only on individual regulation within the region is negligible. To enhance the capacity of interconnection and coordination among different areas of power systems and improve the accommodation level of RES and low-carbon efficiency, an optimal transmission switching model based on the bus tearing method is proposed in this article. Firstly, the complex power system is decomposed based on the bus tearing method, and thus, the interconnected power grid structure of the multiarea system is constructed. Secondly, the optimal model of interconnected power grid decomposition and coordination structure considering renewable energy generation is constructed, based on exquisite modeling, to reduce the difficulty of unified analysis and decision-making of the multiarea interconnected power system, and the expression of the model is simplified in the form of the matrix. Then, the analytical target cascading (ATC) method is used to decouple the complex model from the main problem and subproblem and solve the distributed parallel problem, to understand the optimization of the decomposition and coordination structure of the interconnected power grid with source–load coordination. Finally, based on the case studies of the IEEE 14-bus system and IEEE 118-bus system, the effectiveness of the proposed model and method is verified, the coordinated operation of the interconnected power grid and the optimal allocation of network resources are achieved, and the economy of power system operation is improved.

Seven level aligned multilevel inverter with new SPWM technique for PV, wind, battery-based hybrid standalone system

Abstract Power generation using renewable energy sources is becoming popular in current scenario due to their capability of reduction in carbon emission as well as reliable power supply to consumers. However, power generation from a single renewable energy source cannot able to provide stable power. Hence, integration of renewable energy sources-based power generations needs to be established for providing continuous power supply to consumers. Solar energy and wind power are two major available sources on earth, hence, photovoltaic (PV) and permanent magnet synchronous generator (PMSG) based wind power generation system is considered in this paper. On the other hand, many loads are AC loads that required conversion from DC to AC such as inverters. Generally, multilevel inverters can able to provide quality supply to loads than normal inverters. However, the number of switches used in the multilevel inverter is more and also increasing size and complexity by increasing the level of the inverter. Therefore, an aligned multilevel inverter is implemented for a PV-Wind-based stand-alone system that has a smaller number of switches. Both solar irradiance and wind speed are depending on weather conditions and are unstable, hence a battery bank is incorporated with the help of a bidirectional DC to DC converter to provide an uninterrupted power supply to loads. A novel controller for 7 levels aligned inverter is implemented in this paper to supply quality power to loads under various scenarios. The proposed Aligned Multilevel Inverter needs half of the switches when compared to existing multilevel inverters as diode-clamped, flying-capacitor, and cascaded H-Bridge topologies. The hardware-in-loop is developed with OPAL-RT to present results under various case studies.

Single-Phase Transformerless Five-Leg AC–DC–AC Multilevel Converter for Voltage Step-Up Applications

This article proposes a single-phase transformerless ac–dc–ac multilevel converter composed of a three-leg module series-connected to an H-bridge at the load side to achieve a higher and multilevel voltage at this side. The proposed structure is appropriated for applications with the same input and output frequencies, such as uninterrupted power supply and unified power quality conditioner, and for electric power conversion systems in which the output voltage required is higher than the input voltage (voltage step-up applications). System model, converter power analysis, dc-link voltage specifications, and a space vector PWM strategy are developed. The proposed system control ensures fixed load voltage with constant amplitude and frequency, maximizes the grid power factor, and regulates the dc-link voltages. Compared with conventional solutions, the proposed configuration has presented lower dc-link voltage ratings and lower mean switching frequency on the semiconductor devices, lower harmonic contents, and lower switching losses. The comparative analysis shows that the mean weighted total harmonic distortion (WTHD) of the generated voltages of the proposed topology are reduced about 27% and 16%, respectively, compared to the topologies 4L and 3L, and 4L-LLC; and the total semiconductor losses are reduced about 26%, 10%, and 49%, respectively, compared to 4L, 3L, and 4L-LLC, when all topologies operate with the same mean WTHD. Operating with the same switching frequency, the proposed converter presented total semiconductor losses similar to conventional 3L, and about 17% and 45% lower than 4L and 4L-LLC. Experimental results demonstrate the operation of the proposed converter under load transients and grid voltage variations.

How Valuable is the Reliability of Residential Electricity Supply in Low-Income Countries? Evidence from Nepal

We use contingent valuation to estimate the willingness to pay (WTP) for improved electricity service in Nepal following the end of the country’s load-shedding crisis of 2007-2016. Using a nationally representative survey of grid-connected Nepali households, we calculate the WTP per outage-day avoided and the value of lost load (VoLL) for residential customers and analyze their key drivers, including income, education, and investments in own generation or electricity storage equipment. Households are willing to pay, on average, 123 NR ($1.11) per month for improved quality of power supply. In other words, they would be prepared to see a 65% increase in their monthly bill to avoid outages. Our preferred estimates of the VoLL range from 5 to 15 NR/kWh (04.7-014/kWh). These estimates are below the marginal cost of avoided load shedding, and are virtually the same as valuations at the beginning of the load-shedding crisis.

Modelling and Simulation of Dynamic Voltage Restorer in Power System

Abstract: Recently, Power quality is one of major concerns in the present era. It has become important, especially, with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. To improve the power quality, custom power devices are used. The device considered in this work is Dynamic Voltage Restorer. Thispresents modelling, analysis and simulation of a Dynamic Voltage Restorer (DVR) constructed in Simulink environment. Here, different supply voltage conditions are considered for linear loads. The major problems dealt here are voltage sag, voltage swell, and voltages unbalances. The role of DVR to compensate load voltage is investigated during the different supply conditions like voltage sag, voltage swell, and supply voltage unbalance. Therefore, it is a highly prospective branch of energy, which would play a significant role in the future.