Overcurrent Protection Function Research Articles

Automation of Methodology for Analysis of Overcurrent Protection Functions in Electrical Power Systems

Automation of Methodology for Analysis of Overcurrent Protection Functions in Electrical Power Systems

Research and Design of Microgrid Simulation System Based on Single Chip Microcomputer

With the continuous development of modern power electronics and chip technology, numerical control inverter power supply is more and more widely used in industrial control and civil fields. High performance numerical control inverter has become one of the research focuses in the power supply field. In this paper, a micro grid simulation system based on single-chip microcomputer is designed. The effective value of the load line current of the inverter part is within 2A, the effective value of the line voltage changes within 24V ± 0.07V, the frequency fluctuation is 50Hz ± 0.2Hz, the total harmonic distortion (THD) of the AC bus voltage is not more than 1.6%, and the power output efficiency reaches 91.6%, achieving good performance. In addition, the system can manually set the power supply output voltage frequency by pressing the key, and display the output voltage and current in real time. At the same time, the system has over-current protection function, which greatly improves the safety and stability when the current is too large.

IEC 61850-Based Protection Scheme for Multiple Feeder Faults and Hardware-in-the-Loop Platform for Interoperability Testing

The existing Overcurrent Protection Function (OCPF) of distribution systems is vulnerable to Multiple Feeder Faults (MFF), which involve at least two feeders simultaneously, leading to the incoming feeder relay trip faster than the faulted feeder relays, although the OCPF of the relays can be coordinated for all fault current values. In this case, all feeders connected to the power transformer are de-energized, even the healthy ones, directly impacting the network reliability, service quality and availability of the electricity utilities and ultimately leading to outage costs for the customers. In light of this, an IEC 61850-based OCPF scheme with the directional element is proposed to support existing OCPF to deal with MFF and encompass the integration of distributed generation, and can be directly implemented in the digital substations without requiring further equipment installation. Moreover, an hardware-in-the-loop platform is developed for testing the interoperability of the proposed scheme with multi-vendor protection relays, which can assist electricity utilities also in the validation of their protection and control schemes based on their requirements before the field implementation. Test cases are specifically elaborated to study the interoperability of the proposed scheme with three real devices—whose configuration details are also provided to aid protection engineers—in a real distribution system, under different conditions such as switching operations, MFF types, resistance and location, integration of distributed generation. The results show that the proposed scheme manages to enhance the selectivity and reliability of the digital substation protection system, hence representing a valuable complement to existing OCPF schemes.

Research on Latching Current Limiter Circuit of Aerospace Power System

The input terminal of the aerospace power system is connected with surge suppression and overcurrent protection circuits. However, prior art methods have many demerits such as complex circuits, high surge currents, and slow response of overcurrent protection. Hence, this paper proposes a novel latching current limiter (LCL) circuit with both surge suppression and over-current protection functions. When over-current occurs, the circuit snap into the current limiting state within the adjustable time-delay period. When the over-current fault despairs during the time-delay period, the LCL circuit turns into the output lock state and rapidly lock down the output bus wire. Theoretical analysis of LCL circuit including the three operation states (i.e., the normal operation state, current limiting state and output lock state) and basic circuit equation derivation have been carried out. And the experimental platform is set up to validate the superior performance of the proposed LCL circuit. Results show that the proposed LCL circuit can effectively suppress the inrush current and sensitively respond the over-current fault of dc-link bus wire.

A high-efficiency micro-grid simulation system based on STM32

A high-efficiency micro-grid simulation system based on STM32 is designed. The hardware circuit includes two three-phase half-bridge inverter circuits, AC voltage and current sampling circuits, and LC filter circuits. STM32F407 is used as the main controller, and outputs SVPWM waves. The main inverter has low THD when running on its own, so that can stably convert DC power into three-phase AC power. When working in parallel, the system realizes that the output power ratio of the two inverter circuits is adjustable. Through theoretical analysis and testing, the micro-grid has high efficiency, and the circuit also performs well when testing the load regulation rate. In addition, the system uses OLED screens and matrix keyboards to achieve human-computer interaction, and has overcurrent and overvoltage protection functions.

Hardware-In-the-Loop Simulation to Test Advanced Automation Devices in Power Distribution Networks

The sustainable development of power distribution systems must evolve into smart grids, where advanced automation with fast communication channels is essential. The analysis of their behavior uses the Hardware-In-the-Loop simulation for studying normal and critical operating conditions. In this work, we propose a hybrid technique for transient simulation in distribution systems by combining the high sample rate of the time domain models for voltage profile and electrical current monitoring with the processing speed of algorithms that operate the quasi-stationary, or permanent, phasor models. The proposed simulation platform is also based on the state of the art of standardized communication protocols of the power system. Its evaluation is performed using the comparison with specialized commercial software to assess the transient simulation. The time overcurrent protection function and the verification of messages exchanged between the simulator and the tested device highlights the applicability of the proposed methodology.

Novel approach for optimum coordination of overcurrent relays to enhance microgrid earth fault protection scheme

Ground faults are the most common type of faults in the microgrid. In addition, the configuration of the grounding strategy significantly affects the characteristics of the ground faults response and intensity. Consequently, affecting insulation specifications, equipment safety, and protection requirements. Therefore, extensive knowledge of the grounding strategies used is a significant and prominent factor in the protection of the microgrid. In this study, a new different objective function (OF) has been suggested for overcurrent relay (OCR) coordination based on combining the phase and earth overcurrent protection functions in the formulation of OCR coordination problem. Converse to the traditional coordination strategies in the literature review which depends on the phase OCR function in solving the OCR coordination problem, this approach merges the phase and earth OCR functions to ensures selectivity and speed in isolating all ground and phase faults currents and avoid sympathetic tripping situations. Also, this paper proposes an optimal and single protection scheme suitable for all type of faults based on a single line to ground fault calculations. A new optimization algorithm based on an evaporation rate water cycle algorithm (ER-WCA) is used. A modified IEC microgrid benchmark network implemented in ETAP to investigate the effectiveness of the proposed new approach to enhance the constrained optimization technique.

A Novel Multiresonant DC–DC Converter With Wide Output-Voltage Range

A novel multiresonant dc–dc converter with notch filter function is proposed in this article. The converter can regulate the output voltage over a wide range and has significant advantages in terms of gain. Due to its gain characteristics, the multiresonant converter has better inherent soft startup capability and over-current protection function. In addition, the switches of the converter can realize zero-voltage switching over the entire output-voltage range, and the output rectifier diode can realize zero-current switching. Compared with the traditional LLC converter, the multiresonant converter can use third harmonic to transmit the active power, and the loss caused by the reactive power cycle of the converter is reduced, which improve the efficiency. The converter parameters are optimized from the perspective of gain and efficiency in this article. Finally, a 2.5-kW experimental prototype is designed and the peak efficiency is 97.27%. The correctness of the theoretical analysis and the rationality of the parameter design are proved by the experimental results.

大功率半导体激光器驱动电源及温控系统设计

In order to solve the output wavelength and power stability of high power semiconductor laser, high power semiconductor laser constant current driver and temperature control system were designed. Deep negative feedback circuit was used to control the laser drive current, the analog Proportional-Integral (PI) circuit and constant current driver were adopted to control the working current of Thermoelectric Cooler (TEC), the laser working temperature can be kept accurately. The design can realize the linear adjustment of output current from 0-12.5 A, and has the function of current detection, over-current protection and Transistor-Transistor Logic (TTL) modulation. The control precision of the temperature control system can achieve 0.05℃. Temperature can be adjusted continuously and can be monitored in real time. Experiment results show that the design can guarantee the output current and temperature control stably, which satisfies the requirement of high power semiconductor laser.

Design of High Power CO2 Laser Controller Based on DSP Technology

The paper use CPLD chip EPM7812 to output 100 ~ 500Hz pulse signal and the trigger signal source with the single pulse signal, and design IGBT driving circuit with overcurrent and overvoltage protection function and electromagnetic compatibility (EMC) design of using optocoupler HCPL-3120. And for high power CO2 laser is developed, this paper designs a control system of digital signal processor based on DSP technology, and introduce respectively circuit from two aspects: hardware and software core unit control system in detail; in order to overcome the strong electromagnetic interference generated in the working process of laser, we design power filtering, grounding, safety the key data storage of digital filtering, self-recovery, anti-interference design reset. After a long run test, the control system is stable and reliable, and the control response is fast. It is of great practical and popularization value.

Flux Linkage Detection Based Ground Fault Identification and System Diagnosis in High-Resistance Grounding Systems

High-resistance grounding (HRG) is preferred in many industrial applications where the operation continuity is critical under ground fault conditions, such as pulp, paper, oil refining, chemical, glass, and metal industries. This is due to: 1) continuity of service; 2) minimized productivity impact with the scheduled system downtime; and 3) improved safety concerns—elimination of phase to ground arc flash hazards, suppression of transient line to ground overvoltages, and minimization of the equipment damage at the point of ground fault. However, there are also some drawbacks in accurately detecting and locating a ground fault in adjustable speed drive (ASD) systems: 1) the HRG fault current (1–10 A) cannot reliably trip the overcurrent protection function in drives; 2) the existing methods are based on the line voltage/frequency (50/60 Hz), making it hard to detect and locate low-voltage/low-frequency ground faults; and 3) with the existing methods, the possible fault locations will be manually checked one by one using an Ammeter by a trained technician. This paper will present a flux linkage detection based HRG fault identification method for ASD systems. The proposed method can solve: 1) reliable HRG fault detection with wide motor speed range; 2) the HRG fault can be easily identified in multiple systems; and 3) the identification process is performed by the proposed system diagnosis method, no trained technician is required during the identification process.

Study of Emergency Power Based on Solar Battery Charging

To study an emergency power based on solar battery charging. Based on the electric-generation principle of solar panel, solar energy is changed into electrical energy. Through voltage conversion circuit and filter circuit, electrical energy is stored in the energy storage battery. The emergency power realizes the conversion from solar energy to electrical energy. The battery control unit has the function of PWM (Pulse-Width Modulation) charging, overcharging protection, over-discharging protection and over-current protection. It also realizes the fast and safe charging of energy storage battery. The emergency power could provide both 12V AC power for emergency equipment such as miniature PSA oxygen concentrator and 5V USB for electronic equipment (mobile phone, GPS device, rechargeable light, etc.).

Design of Programmable DC Power Supply Based on ARM

This paper designed a DC programmable power-supply system based on ARM Cortex-M3 as the main controller. The main power module is supplied with PAF600 from TDK-lambda. This system uses 12 bit serial high speed chip analog-to-digital conversion from TI (Texas Instruments) and 12 bit parallel high resolution analog-to-digital conversion chip from AD (Analog Devices) for the signal of the power supply system of acquisition and adjustment. The system not only can use the encoder and the keyboard to adjust and control, but also can through the RS-232 interface apply the PC software to send command to do that. The signal of power supply system can realize software over-voltage protection and over-current protection function by high speed DAQ (Data Acquisition) ,the rapid data processing of ARM and the least squares curve fitting. This system runs steadily and reliably and also has high adjusting precision and simple operation. The best is to read these instructions and follow the outline of this text.

A High Effcient Brushless DC Motor Drive Technology for Solar Array

This paper analyzes the working principle of solar array and drive requirements and presents an efficient drive technology of brushless DC motor for solar array. The technology solves the phenomenon of step-out in stepping motor control system. Brushless DC motor mathematical model is inferred and the possibility of driving solar array by brushless DC motor are analyzed in this paper. To achieve speed feedback loop control, reversing, over-current protection function, high-efficiency motor control chip are used in the system for brushless DC motor closed-loop control. Experimental results show that the system has simple structure and it can works in the harsh environments.

The Research and Desige of the CNC Constant Voltage Power

CNC constant voltage power is composed by the analog power circuit, MCU control circuit , pulse width modulation circuit, a power driver amplifier , analog to digital conversion circuit , the input voltage setting circuit and the output voltage display circuit. The power possesses the functions of digital regulator, high precision output, short-circuit & over-current protection and alarm functions, especially for a higher accuracy requirements for various occasions. DOI: http://dx.doi.org/10.11591/telkomnika.v12i6.5443 Full Text: PDF

The Research of CNC Constant Voltage Power

CNC constant voltage power is composed by the analog power circuit, MCU control circuit , pulse width modulation circuit, a power driver amplifier , analog to digital conversion circuit , the input voltage setting circuit and the output voltage display circuit. The power possesses the functions of digital regulator, high precision output, short-circuit & over-current protection and alarm functions, especially for a higher accuracy requirements for various occasions.

The Design of the Parallel Switching Power Supply System

This study introduces a parallel switching power supply system which is controlled by C8051F020 MCU. The system consists of DC/DC converter, voltage-controlled constant current source circuit, over-current protection circuit and auxiliary power supply. TPS54331 is used to constitute a highly efficient DC/DC converter, reducing the input DC voltage to supply the voltage-controlled constant current source circuit. The parallel current-sharing of the system is realized by the voltage-controlled constant current source circuit. The output current of the two parallel power supply can be adjusted by changing the control voltage. When the output current exceeds the set value, the system starts over-current protection circuit to cut off the power and delays to restore power automatically after a certain period of time. The test results show that the system is stable and reliable, easy to control and has a function of over-current protection and automatic recovery.

Proposal of a New Sensitive Ground Overcurrent Protection for High-Impedance Faults

This paper presents the development of a sensitive ground overcurrent protection algorithm. The proposed algorithm is able to detect high-impedance faults produced by downed conductors in solidly grounded primary distribution networks. It presents a higher level of accuracy when compared to conventional overcurrent protection functions. The algorithm is based only on current measurements and uses additional conditions to generate the trip signal, in order to prevent false tripping due to its high level of sensitivity. This paper presents a detailed description of the proposed algorithm, the hardware prototype developed during the research and its performance in laboratory tests.

Design of a Step-down DC-DC Converter ASIC Applied to Portable Electronic Products

Using CSMC 0.5μm process model, a Step-Down DC-DC converter ASIC applied to portable electronic products was designed. The peak current-mode control PWM with slope compensation was adopted in the power management chip to improve the dynamic response speed of the system; the error amplifier and PWM comparator was redesigned to improve the response speed and stability of the chip; the over-current protection function was included in the peak current sampling circuit; in addition, the circuit with the pulse-skipping mode reduce the battery energy loss. Capable of delivering 600mA Output Current over a wide input voltage range from 3.1 to 5.5V, the ASIC, that has a fixed operation frequency of 800kHz and 95% conversion efficiency, is ideally suited for portable electronic products. No external Schottky diode is required in practical application.

Design of Controller in Electric Bicycle

Base on PIC16F72, a design of brushless DC motor controller strategy applied to the electric bicycle control system was presented in the paper. Through analyzed some possible problems when electric bicycle running daily. Function of over-current protection, under-voltage protection and helping were accomplished. Schematic diagrams of each function and drive circuit were given in the paper, the controller was debugged in rated voltage 36V and power rating 250W brushless DC motor, experiment turned out controller has better dynamic characteristics and ran steadily.