How to apply the new switching power supply module to the power system
Time:2020-05-08 10:51:39 Click:1221
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At present, the DC power supply used in my country's power system is also gradually changing from a traditional phase-controlled power supply to a modular high-frequency switching power supply. The working principle of the high-frequency switching power supply rectifier: AC power is connected to the rectifier module, after filtering and three-phase full-wave rectifier, it becomes DC, and then connected to the high-frequency inverter circuit, which converts DC to high-frequency AC. Frequency transformer, rectifier bridge, filter output smooth DC. This high-frequency switching power supply is mainly composed of a high-frequency switching charging module, a centralized monitor and a battery pack, etc., wherein the charging module and the centralized monitor have a built-in microprocessor, and the degree of intelligence is high. When the high-frequency switching power supply system is running normally, the output of the charger runs in parallel with the battery pack to supply power to the regular load, and at the same time, the battery is float-charged to supplement the self-discharge of the battery. When the AC power input is interrupted, the battery pack supplies power to the load to ensure continuous and uninterrupted power supply to the load. When the AC power supply returns to normal, the system automatically charges the battery evenly, and quickly replenishes the battery after a large amount of discharge.
Compared with the traditional phase-controlled power supply, the intelligent high-frequency switching power supply module has main technical indicators that are better than 1 to 2 levels of the ministry standard, and have the following characteristics.
(1) The phase-controlled power supply silicon rectifier adopts 1+1 master-slave backup mode, and the high-frequency switching power supply module uses N+1 module redundant parallel combination to supply power, that is, if the output current of N modules can meet the charging current requirement, then N+1 modules are evenly distributed, therefore, the system operation reliability can be improved. When individual modules are faulty, they can be replaced with power on, without affecting the normal operation of the system, and easy for expansion and maintenance.
(2) When the thyristor is operated in floating charging mode, the DC output ripple coefficient is relatively large. There have been accidents such as malfunction of the central signal device and false signal transmission of the high-frequency relay protection. Greater than 2%. In addition, the silicon controlled rectifier operates in parallel with the battery. When the ripple coefficient is large, if the float charging voltage fluctuates or is too low, the battery pulsating charge and discharge phenomenon will occur, which is harmful to the battery. The charging device of the high-frequency switching power supply adopts multiple intelligent modules in parallel to supply power, which significantly improves the power supply quality and technical parameters. The module adopts quasi-resonant technology (or pulse width modulation technology) and current and voltage double-loop control technology to increase the switching operating frequency, low turn-on loss, and low output voltage ripple coefficient, generally ≤±0.1% of rated voltage, which can prevent battery ripple Charge and discharge, prolong the service life of the battery, and higher reliability.
(3) The high-frequency switching power supply rectifier module has a built-in microprocessor, which is the basis for improving the level of equipment management. On the premise of meeting the DC system fault signal, it should be as simple as possible to make the wiring simple and quick to install and debug. In addition to directly displaying the output current and voltage and various operating conditions of the module on the panel, it can also communicate with the automation network of the power system or the DC shift monitoring system of the substation area through the monitoring module to perform remote monitoring and various operations on the module , To achieve four remote functions. The traditional DC power supply generally installs current, voltmeter and other special devices on the screen cabinet to monitor the equipment, and these measured values cannot be remotely monitored through the communication port (except for microcomputers). Even if there is telemetry, the DC sampling method is used, and there are not many sampling points. The signals reflecting various operating conditions are also connected to the optical plate or the remote signal screen in a contact mode. Therefore, the wiring is cumbersome, the degree of automation is low, and remote control and remote control are realized. It is more difficult to adjust the function.
(4) According to the requirements issued by the Ministry, the accuracy error of steady current during charging is ≤±5%, and the accuracy error of voltage regulation during floating charging is ≤±2%. The high-frequency switching power supply has higher voltage stabilization and steady current accuracy, and its error is generally ≤±0.5%, which can avoid overcharging and undercharging the battery and ensure that the battery operates in the best state. The valve-regulated battery has large capacity, small maintenance, and low discharge rate. It is suitable for large-capacity DC power supplies. From the principle performance, the high-frequency switch module is suitable for use with valve-regulated batteries.
(5) The high-frequency switching power supply module rectifier module has an automatic current sharing function in parallel operation mode. At the same time, it is equipped with over-current, over-voltage and instantaneous short-circuit protection, safe and reliable lightning protection measures, which can effectively withstand the output short-circuit impact. In addition, take multiple effective measures to prevent the interference of high-frequency power and harmonics on the AC grid side.
(6) The comprehensive conversion efficiency of high-frequency switching power supplies is high. The conversion efficiency of most manufacturers reaches more than 90%, while the conversion efficiency of phase-controlled power supplies is generally only 60% to 80%.
Because this power system is equipped with a microcomputer-based centralized monitor, it can support multiple communication protocols, communicate with the DC monitoring system of the dispatch center or substation area, and perform four-remote monitoring of the DC system. The main functions are:
(1) Communicate with the monitoring center through MODEM and telephone network, and read the information of high-frequency switching power supply from the communication port;
(2) Measuring module output current and voltage, DC bus current and voltage, power supply output current and voltage, battery charging and discharging current and voltage, etc.;
(3) Control the output current and steady current of the power supply, control the power supply switch, etc.;
(4) Control high-frequency switching power supply to realize automatic conversion of battery floating and equalization modes;
(5) Control the automatic or manual switching of the silicon chain to ensure the voltage regulation accuracy of the control bus, thereby ensuring the reliability of the power supply for the protection of the microcomputer and the transistor to prevent the protection from malfunctioning;
(6) Adjust the charging current limit value and the total output current steady current value;
(7) It has local and remote control modes, and uses password to allow or prohibit operation to enhance the reliability of system operation.
At the same time, this system is equipped with a special microcomputer insulation monitoring device, which can display the bus voltage and the size of the positive and negative bus insulation resistance to ground in real time and send out abnormal alarms. It can inspect the insulation of each feedback line to indicate the specific failure. Loop, this line selection function brings great convenience to find DC grounding. At present, my country is vigorously implementing the unattended management of substations. Therefore, the selection of equipment will be developed in the direction of miniaturization, no oil, less maintenance or maintenance-free, and a high degree of automation. The high-frequency switching DC power supply is able to meet this requirement. After years of operation tests, the performance of this product has gradually matured and stabilized. With superior technical performance and good price-performance ratio, high-frequency switching power supply will become the preferred product for the replacement of DC power supply.
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