Characteristics and high frequency switching power supply applications in power system

      In power systems, DC power supply as a relay, automatic device, control circuit operation, lighting and emergency lighting and other audio signal power, is on the more important power plant and substation equipment. DC power failure caused by accidents have occurred, so the reliability of the DC power supply, high stability requirements. Most of the traditional DC power supply using thyristor rectifier. In recent years, many intelligent DC power supply manufacturers have introduced high-frequency switching power supply, this power system has many advantages: safe, reliable, high degree of automation, with smaller size and weight, high comprehensive efficiency and low noise to meet the network development, be widely used.
      At present, the DC power system is also used by traditional power gradually phased-frequency switching power supply to the modular transformation. High-frequency switching power supply rectifier works: AC power access rectifier module, by filtering and three-phase full-wave rectifier into DC after, then access to high-frequency inverter circuit, the DC is converted to high frequency AC, and finally by the high frequency transformer, rectifier bridge, filter the output steady DC. This high-frequency switching power supply mainly from the high-frequency switch charging module, focus monitor and batteries etc., which charge module and centralized monitor with built-in microprocessors, high intelligence. High-frequency switching power supply systems up and running, the charger output and battery run parallel to regular load power, while charging the battery to float to supplement the battery self-discharge. When the AC power input after the interruption, the battery power to the load, to ensure uninterrupted power supply to load when the AC power is restored, the system automatically for all battery charging the battery discharged for a large number of additional power in the fast .
      Intelligent High Frequency Switching Power Supply with traditional power compared with control, the Department of the main technical indicators are better than standard grades 1 and 2 above, with the following features.
      (1) power silicon rectifier phased master-slave with 1 +1 backup mode, and high-frequency switching power supply module with N +1 redundant parallel combinations of power, that is, if N-modules of the output current to meet the charge current needs, then N +1 module using the average distribution, therefore, can improve the system reliability. Failure of individual modules can be charged to replace, does not affect the normal operation of the system, expansion and maintenance.
      (2) SCR rectifier operating on the floating charge mode, the DC output ripple are larger, have occurred in the central signal and high frequency relay protection device malfunction signal errors such as accidents, the ripple factor is not required by the ministerial than 2%. In addition, parallel operation of thyristor rectifier and battery, ripple coefficient is bigger, if the float voltage fluctuations or low pulse charging the battery will discharge phenomenon occurs, the battery negative. High-frequency switching power supply using multiple intelligent charging device parallel combination of power supply modules, making power supply quality and technical parameters improved significantly. Module technology using quasi-resonant (or pulse width modulation), and current and voltage loop control technology to increase the switching frequency, opening loss, the output voltage ripple factor is very small, generally ≤ ± 0.1% rated voltage, and thus prevent the battery pulse charge and discharge, extended battery life, higher reliability.
      (3) high-frequency switching power supply rectifier module has built-in microprocessor, is the foundation to improve equipment management level, to meet the DC system fault signal should be the premise of perfect, so that wiring is simple, quick installation. In addition to the panel directly on the display module output current and voltage, and a variety of operating conditions, but also of the power system through the control module and the substation automation network or communicate direct current class monitoring system, remote surveillance and the operation of the module to achieve four remote functions. The traditional DC power supply cabinet is usually in the installation screen current, voltage meters and other special devices to monitor the equipment, and these measurements can not be achieved through communication port remote monitoring (except for computer-based). Even if remote, is also the DC sampling method, sampling points are few, reflecting the variety of operating conditions on the signal contacts also means access to the optical plates or remote communication screen, therefore, cumbersome wiring, the low degree of automation to achieve remote control and remote transfer function difficult.
      (4) according to the ministerial requirements of the precision error of charging the steady flow ≤ ± 5%, float charging voltage regulator precision of ≤ ± 2%. The high frequency switching power supply regulation, steady flow more precise, the error is ≤ ± 0.5%, to avoid battery over charge, less filling, to ensure the battery is running in the best condition. Valve-regulated battery capacity, discharge rate to maintain a low volume of filial piety, for large-capacity DC power supply. View from the principles of performance, high-frequency switch module for use with the valve-regulated battery package.
      (5) high-frequency switching power supply rectifier with parallel operation mode automatic current sharing. At the same time, with over-current, overvoltage and transient short-circuit protection, safe and reliable lightning protection measures, can effectively withstand the impact of output short circuit. Also, take multiple effective measures to prevent high-frequency power supply and AC power grid side harmonic interference.
      (6) integrated high-frequency switching power conversion efficiency, most manufacturers of conversion efficiency above 90%, while the phase-controlled power conversion efficiency is usually only 60% to 80%.
      Because of this power system equipped with computer-based centralized monitoring device that can support multiple communication protocols, and the dispatch center or the DC ban substation monitoring system communication, and four remote monitoring of DC system, the main features are:
      (1) through the MODEM and the telephone network and the monitoring center, from the communication port to read high-frequency switching power supply of information;
      (2) measurement module output current and voltage, DC bus current and voltage, power supply output current and voltage, battery charge and discharge current and voltage;
      (3) control the power supply output current and the steady flow, the control power switch machine;
      (4) The high-frequency switching power supply to achieve the battery float, are fully automatic mode conversion;
      (5) control of silicon chains automatically or manually switching to ensure the accuracy of control bus of the regulator, thereby ensuring the protection of computer and transistor reliability of electricity to prevent Misoperation;
      (6) regulating charge current limit value and the total output current steady flow value;
      (7) with local and remote control mode, using passwords to allow or prohibit the operation mode to enhance system reliability.
      At the same time, the system microcomputer equipped with special insulation monitoring device, real-time display bus voltage and positive and negative bus-to-ground insulation resistance of unusual size and send alarm, on the back for inspection of insulation to the situation, instructed the specific failure loop, this route selection function is a great convenience DC Ground.
      At present, China is vigorously implementing the unattended substation management, therefore, the choice of equipment will be toward the small, oil-based, low-maintenance or maintenance-free and high degree of automation direction. High-frequency switching DC power supply is able to adapt to such a request, after several years of running the test, the performance of this product have been gradually mature and stable. With superior technical performance and good price performance ratio, high frequency switching DC power supply will be the first choice replacement.

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