Low-voltage Systems Research Articles

Hosting capacity improvement for solar systems based on model predictive controller of volt-watt-var smart inverter functions

ABSTRACT Photovoltaic (PV) system adoption is accelerating quickly, raising worries among electricity network service providers about how to accommodate more PV while keeping system operating indices within acceptable bounds. This idea, which is typically about Hosting Capacity (HC), has recently gotten more interest. Modern smart inverters provide control possibilities in Volt-Var and Volt-Watt based on system voltage level management. In this paper, the impact of various connection standards that encompass these tactics on the capacity of solar PV systems to store energy and their usability in the delivery of low-voltage systems is thoroughly examined. Modeling of smart inverters has been validated using MATLAB SIMULINK with various Volt-Var and Volt-Watt control functions. Volt-Watt-Var control has been designed based on Model Predictive Control (MPC) and comparing the results with a PID controller. The proposed MPC control has been applied on the IEEE-9 bus with combined controls. The impact of various connection requirements on photovoltaic Hosting Capacity (PVHC) is investigated to determine the best connection strategy(s) to handle the problem of voltage encroachment. In addition, the paper gives a deeper knowledge of HC enhancement using sophisticated inverter control features within a low-voltage distribution network of converters, besides it shows the effects of over-voltage and under-voltage on the system parameters.

Circulating Current Control for a Three-Phase Modified Modular Multilevel Converter With a Reduced Number of Current Sensors

The high capacitance requirement becomes a significant problem when modular multilevel converters (MMCs) are applied to medium or low-voltage systems. This paper proposes a capacitor voltage control scheme for a three-phase modular multilevel converter (MMC) with optimized capacitor sizing. Unlike the existing circulating current control, the proposed controller uses the middle capacitor voltage to control the second-order harmonic component of the circulating current. Therefore, it is unnecessary to measure the two arm currents; only one voltage sensor is required, which reduces the number of current sensors. The proposed controller can effectively control the circulating current to be constant or inject second-order harmonics to reduce the capacitor sizing. The detailed analysis, controller design, and performance of the proposed scheme are presented in this paper. The effectiveness of this study is confirmed by simulation and experimental results.

Academic Investigation of Low Voltage Systems in Electrical Transmission Lines

Academic Investigation of Low Voltage Systems in Electrical Transmission Lines

LEAK CURRENT DETECTOR IN LOW VOLTAGE NETWORK (JTR) SYSTEM USING ZMPT101B SENSOR BASED ON THE INTERNET OF THINGS (IoT)

Phase-to-ground leakage in low-voltage network systems can cause transformer damage due to overload. Overloading on transformers is not caused by customer usage but rather by wasted electrical energy to the ground which causes losses. If there is a current leakage, the potential difference between neutral and ground is measured to produce a voltage value. Considering that there is little written about transformer damage caused by current leakage to ground in low voltage network systems, in this research a tool is made that can detect current leakage to ground in low voltage network systems using the ZMPT101B voltage sensor based on IoT.
 This research is in the form of design and manufacture of a leakage current detector to ground. The method used is the Research and Development method (research and development), namely in the form of observation, literature study. The research stage starts from a literature study in the form of finding references related to research, designing tools, making tools and programs, and testing the tools that are made.
 Based on the results of Based on the results of the research, this tool can detect leakage current to the ground from the lowest voltage of 24.3 Volts to the highest voltage of 184 Volts so that it can be displayed on the LCD and the blynk application and the system automatically sounds a buzzer as a warning of current leakage to ground. .

Joint Planning Method of Virtual Power Plant for Distributed Generation and Grid in AC-DC Medium and Low Voltage Distribution Network

The high proportion of virtual power plants (VPPs) used for distributed generation may cause problems such as power fluctuations and voltage distribution. In contrast, AC/DC hybrid power grid has strong transmission capacity due to its power information transmission. However, Its power grid structure and the location and capacity of VPP have an impact on the consumption capacity of the system, and the relationship between them are closely coupled. In addition, Under different operation modes, power grids of different voltage levels also have great differences. Therefore, the cooperative planning of medium and low voltage AC and DC distribution networks can improve the transmission capacity of the power grid Further improve the ability of distribution network to consume distributed power, A method is proposed in this paper about siting and capacity determination and AC-DC distribution grid frame transformation planning for medium and low voltage systems. The upper-layer model mainly focuses on AC-DC transformation scheduling in the power grid, distributed node location in the access grid and transmission line transmission capacity, while the lower-layer model effectively communicates with the low-voltage system through information flow and changes the operation of the power grid to a certain extent.The results show that the distributed generation system can reduce the operation cost and improve the overall operation efficiency of the power grid.

Modeling of Single-Phase Photovoltaic Generators for System-Wide Harmonic Power Flow Studies

An important power quality concern of integrating single-phase photovoltaic (PV) generators to low-voltage (LV) residential systems, is their impact on harmonic distortions due to their power electronic-based interface through a voltage source converter (VSC). Unfortunately, most existing single-phase PV models are focused on the analysis of an individual device, and do not provide a modular circuit model that can be directly integrated into a commercial harmonic power flow simulation tool for large-scale power system studies. In response, this paper derives a single-input single-output harmonic model for single-phase PVs that is independent of grid parameters, thus enabling multiple of these devices to be considered simultaneously in system-wide harmonic power flow analyses. The model is validated with electromagnetic transient simulations and then, characterization studies are conducted to determine the expected harmonic impact of these PV generators on a real LV system. Results demonstrate these devices can increase system damping at typical low order harmonics and are unlikely to introduce new resonances at this frequency range. In addition, it is essential to model the VSC controller effect for a more accurate assessment of its harmonic impact. Sensitivity studies reveal how different VSC parameters affect this behavior.

Optimization and fault diagnosis of 132 kV substation low-voltage system using electrical transient analyzer program

<p><span lang="EN-US">In this paper, a simulation and analysis of 132 kV Substation in feeds western Iraq have been presented including a short circuit (S.C) analysis. This work helps to properly control and coordinate the protection equipment used in this grid interconnection spot. This work includes power flow analysis carried out using electrical transient analyzer program (ETAP) simulator. Also, the most common types of faults are investigated for the substation buses using International Electrotechnical Commission (IEC) and the American National Standards Institute (ANSI) standards to discover the behavioral characteristics under different scenarios for the substation transformers connection to assess the range of S.C current this substitution can ride through. Finally, the results of ANSI and IEC are theoretically investigated for validity to ensure reliability and quality assurance in the case study substation.</span></p>

On load voltage regulating device of long-distance mine low-voltage power supply system based on solid-state voltage regulator

In order to solve the problem of voltage loss caused by long-distance power supply system, considering the solid state power boost (SSPB) of solid-state voltage regulator, this paper proposes an on load voltage regulating device for long-distance mine low-voltage power supply system based on solid-state voltage regulator, which aims to solve the problem of voltage loss and fluctuation caused by line voltage drop and coal mining equipment startup and shutdown. Firstly, the terminal voltage of the line is deduced through the mathematical model of the motor under different working conditions, and a terminal voltage prediction algorithm is proposed, which calculates the terminal voltage state according to the electrical parameters at the head side of the substation; Then, an on load voltage regulation technology based on solid-state voltage regulator is designed and implemented, which compensates by controlling the output voltage of the inverter in series into the first end of the line. When the motor is in rated operation and start-up and stop stages, the motor voltage operates within a reasonable range; Finally, the simulation model of on load voltage regulation technology is built by using MATLAB/SIMULINK software, and the feasibility of this technology is verified by different experimental settings.

99%, 15W/cm<sup>3</sup> Capacitively Coupled Modular DCPET for Low-Voltage DC Power Supply Systems

99%, 15W/cm<sup>3</sup> Capacitively Coupled Modular DCPET for Low-Voltage DC Power Supply Systems

저압직류계통에서 용량성 부하의 차단아크 특성

This study investigates the characteristics of series arcs during the breaking operation of DC switch on capacitive loads. Critical capacitance of capacitive loads at which series arc does not occur is analyzed through experiments of DC series arc on capacitive loads. This study presents the estimated critical capacitance of capacitive loads in relation to load power levels and supply voltages in low-voltage dc systems.

A leakage protection method for low-voltage power supply systems based on flexible regulation of the neutral point voltage

Low-voltage power supply systems, which are very prone to leakage faults, are deep in the customer terminal, and the operation environment is complex. The traditional leakage protection devices applied in TN-S systems cannot isolate single-phase leakage faults while maintaining power supply. Thus, a leakage protection method based on flexible regulation of the neutral point voltage for a low-voltage power supply system is proposed. By extracting the potential of the fault phase, using a single-phase regulating transformer to reverse the voltage applied between the zero line and the protection ground line, and adjusting the ratio of the single-phase regulating transformer to regulate the fault phase to ground voltage, the fault phase to ground voltage is suppressed to 0 V and the leakage fault residual current is eliminated. In the PSCAD/EMTDC simulation environment and in a 10 kV real-type distribution network laboratory, a TN-S system model was built to simulate various fault conditions. The simulation and experimental test results show that the method can actively isolate single-phase leakage faults and eliminate potential leakage problems without affecting the power supply of users.

Bi-directional non-isolated impedance converter for extra low-voltage battery system safety

Bi-directional non-isolated impedance converter for extra low-voltage battery system safety

Comprehensive Solution Method Considering Load Distribution for Determining Low‐Voltage Network Configurations

AbstractSignificant photovoltaic (PV) penetration accelerates voltage problems in distribution networks. We have so far studied what kind of low voltage system configurations are desired in the planning stage. In our previous studies, possible equipment measures were classified into several categories, formulating the ‘low‐voltage system configuration determination problem’; in addition, a solution algorithm based on the practical priorities of classified measures was proposed. In this study, we propose a more efficient and comprehensive solution method while considering load distribution. Several numerical simulations were conducted to verify the performance of the proposed method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Design and Modelling of Heat-Coupled Storage System with High- and Low-Pressure Bypass: Electrothermal Characteristics and Peak Regulating Performance

To achieve a balance between supply and demand during cogeneration system operation, it is necessary to improve the peak regulation capacity and regulatory flexibility of the unit. Considering the excellent performance of energy storage systems, a heat-coupled storage system with high- and low-pressure bypass is proposed to increase peak regulation capacity. Employing a 300 MW heating unit as the research object, thermal system models of a traditional-pumping steam-heating system, a high- and low-pressure bypass heating system, and a coupled system were built using Aspen Plus software. The electric heating characteristics of the three systems, as well as the peak regulation capacity and peak regulation depth of the coupled system, were analysed under different storage and heat release loads. Results indicate that the high- and low-voltage bypass system and the coupled system both improve the peak capacity and control flexibility of the unit. Moreover, the coupled system has a greater influence on the maximum thermoelectric ratio and minimum charge rate than the high- and low-voltage bypass heating system, thereby extending the range of safe operation. The peak capacity and depth of heat storage are 65.55 MW and 21.85%, respectively, while the peak capacity and the depth of the heat-release process are 39.32 MW and 13.10%.

A Novel Air Core Current Limiter Reactor for Medium and Low Voltage Systems

A Novel Air Core Current Limiter Reactor for Medium and Low Voltage Systems

Time Synchronization Method of Low-Voltage Distribution Network Based on Wi-Fi and Voltage Detection

Under the background of frequent electric fires caused by leakage and arc faults, the low-voltage distribution network uses the Internet of Things technology to solve the problem of low-voltage monitoring, so as to ensure the safe use of electricity. In order to tag the collected data with time tags, a large number of low-voltage terminal units need to have time synchronization function, while the cost and accuracy of existing time synchronization methods cannot adapt to the demand of low-voltage distribution network monitoring system. Based on analyzing the demand of low-voltage distribution network monitoring function for time synchronization, this paper puts forward a time synchronization method combining WiFi communication with voltage detection by taking advantage of the characteristics of short low-voltage line and small voltage phase angle change at both ends of the line. Time synchronization of low-voltage terminal unit at the time when the power frequency voltage crosses the zero point, using WiFi communication to transmit time synchronization commands. This method is economical and does not require additional equipment. Finally, the feasibility of the method is verified by building a test system, and the time synchronization accuracy can be within 1 ms.

Leakage Protection of Low Voltage TN-C System Based on Characteristic Currents Amplitude Ratio

With the repeated grounding of the PEN line, load fluctuation, and other factors, there is no available leakage protection for the low-voltage TN-C system, which is very dangerous when a leakage fault occurs. And TN-C grounding mode is still widely used, and the reformation is slow. The single-phase leakage fault and load fluctuation characteristics of the TN-C system are analyzed, and a leakage protection method for the TN-C system based on the amplitude ratio of characteristic currents is proposed. This method takes the amplitude of the residual current sudden change as the starting criterion, and constructs the action criterion according to the amplitude ratio of load current sudden change and residual current’s sudden change, so as to realize the discrimination of leakage fault and load fluctuation. The proposed method can overcome the influence of load fluctuation and other factors, suitable for TN-C systems with high sensitivity and reliability. The effectiveness of the protection is verified by simulation.

Design and Implementation of a Low-Voltage Photovoltaic System Integrated with Battery Energy Storage

In this paper, the simulation and design of a power converter suitable for a low-voltage photovoltaic (PV) battery energy storage converter was investigated. The converter was suitable for sources and loads with near voltage levels and were aimed at efficiency improvement. The converter was called a series partial power converter (SPPC). A continuous current and a boost SPPC topology based on an isolated Cûk converter was constructed. The operation modes of the converter were analyzed. The efficiency verification test of the SPPC in a laboratory environment was completed using an outdoor start-up test, a photovoltaic full cover test and a steady-state operation test under different power levels. The results show that the SPPC can achieve 95–98% converter efficiency within the 87 W–242 W power range. The incremental conductance method based on the SPPC can realize the dynamic MPPT under constant illumination and changing meteorological conditions.

Low-Voltage dc System Building Blocks: Integrated Power Flow Control and Short Circuit Protection

Low-voltage direct current (LVdc) systems are a promising technology for systems with a high penetration of renewable sources and storage that operate with bidirectional power flow. In this article, a fundamental building block for LVdc is presented for different applications, such as charge controllers, voltage regulation in street-lighting systems, and current limiters in meshed dc grids. The developed building block integrates a solid-state circuit breaker (SSCB) and partially rated power flow control converter (PFCC) capable of achieving the given control objectives with extremely high system efficiency and full short circuit protection.

Performance Comparison Analysis of a High Voltage DC LLC Resonant Converter for Telecom and Datacenter Applications

Intermediate Bus Architecture (IBA) is used for power distribution in information communication technology (ICT) equipment due to the flexibility of its power distribution and cost-effectiveness compared to centralized or DC-mediated power. The reason for IBA's good performance in this context is its greater reliability and efficient Intermediate Bus Converter (IBC). Existing IBAs comprise low-voltage systems with multiple power, resulting in power loss. This study outlines the need for a high-voltage DC-to-DC converter to solve the problems associated with conventional 48 VDC converters. A 300 W LLC series resonant converter is utilized for the design and analysis of converter efficiency and losses across various input voltages. The results indicate that the maximum converter efficiency is >92% at full load. MATHCAD is used to analyze the performance of the LLC converter and understand the suitable operating zones for zero-voltage-switching. The LLC converter's efficiency is investigated for multiple input voltage ranges. The LLC converter is designed and developed in MATLAB and the results of the simulation are presented. Trade-offs in the LLC converter's design are also discussed, with the goal of operating the converter in an optimal manner and achieving the maximum possible efficiency.