Description of the composition of the DC power supply of the power communication inverter
The power communication inverter DC power supply occupies a very important position in the power communication system. The rapid development of power communication inverters puts forward higher requirements for the power communication DC power supply. Next, the editor of Baowei special introduces the composition of the power communication inverter DC power supply in detail.
The communication DC power supply is a complex system. At present, the power communication DC power supply adopts -48V high-frequency switching DC power supply. The typical power communication DC power supply structure in the power system is shown in the following figure. From the figure, it can be seen that the power communication DC power supply is composed of The AC part, rectifier, DC distribution part, battery pack and monitoring module are combined as required.
①Communication part. The mains input of the AC part is generally two 380V three-phase four-wire AC inputs. Sometimes, two 220V single-phase AC inputs are sometimes used when the power supply capacity is small to ensure reliable power supply. In order to prevent lightning strikes and overvoltage damage, a lightning arrester should be installed at the input end of the mains. Commonly used are ordinary zinc oxide arresters and OBO lightning protection modules; because the lightning protection here is mainly for the surge voltage of non-direct lightning strikes. Therefore, the flow rate of the arrester is generally selected at 15-20KA, and the residual voltage is about 1.5KV, which can effectively protect the power supply equipment. In order to realize the on-off interlock and automatic switching of the two input AC power, an AC switching device must be installed, using mechanical interlocking or electrical interlocking, but it should be noted that the two AC power sources are not allowed to be connected at the same time at any time Or the phenomenon of simultaneous disconnection. After the switching device, the AC input is divided into the rectifier module input and the AC branch output. The AC branch output provides power for other AC electrical equipment in the computer room, such as computers, UPS, etc.
②The rectifier part. The rectifier is the most important part of the communication DC power supply. The power supply quality of the communication DC power supply mainly depends on the electrical indicators of the rectifier. It completes the AC-DC conversion and supplies power to the communication equipment in parallel current sharing mode, and at the same time, the battery pack is constant current Voltage-limiting charging and monitoring the power supply of the module. Now all communication DC power supplies use modular high-frequency switching rectifiers, which have the advantages of small size, high efficiency, modularity, high power factor, wide input voltage range, low noise, high reliability, and hot pluggability. ; The high-frequency switch rectifier module used in the power communication DC power supply is generally single-phase 220V AC input, the power factor can reach 0.99 or more, and the module capacity is generally 20A/－48V～50A/－48V per block; in actual use, if The input is a 380V three-phase four-wire AC power supply, so all rectifier modules should be equally distributed to each phase; at the same time, in order to improve the reliability of the rectifier, excess spare capacity should be considered in the design, and the module configuration adopts N+1 redundancy. More. The high-frequency switch rectifier module has two types: internal control and external control. The internal control rectifier is equipped with an independent monitoring unit, which can set, detect and display the parameters of the rectifier module. It is connected to the monitoring module of the system by RS-485 bus. ; The externally controlled rectifier does not have an independent monitoring unit inside, and is completely controlled by the system monitoring module. If the monitoring module fails, the rectifier module turns to an autonomous working state, and its output voltage and current obey the initial set value.
③DC distribution part. The DC distribution part distributes the DC voltage output by the rectifier, charging the battery pack all the way, and distributing the others to the communication equipment and other DC users for power supply. The DC distribution part determines the final distribution capacity of the equipment, so it is required that the number of users and capacity of the DC branch output should be fully considered in the design to meet the needs of future communication equipment access. An under-voltage protection relay should be installed before the shunt switch for charging the battery pack. When the battery pack is discharged to the under-voltage alarm value, an alarm will be issued. When the battery pack is discharged to the under-voltage cut-off value, the battery pack will be automatically disconnected to protect the battery pack. It will be damaged due to over-discharge. Nowadays, air switches are mostly used in DC branch output switches, and attention should be paid to the use of DC air switches, because DC air switches have strong arc extinguishing capabilities, and ordinary AC air switches should not be used.
④Battery pack. The battery pack is an indispensable part of the communication DC power supply. Once the battery pack fails, when the mains input power fails, all communication equipment using the battery pack as a backup power supply will stop working, causing communication interruption. The battery packs currently in use are all valve-regulated sealed lead-acid batteries (VRLA for short), which completely replace the ordinary open-ended lead-acid batteries used in the past. It adopts a sealed structure and basically has no acid gas leakage. It can be installed in the same room with the equipment without adding Electrolyte maintenance; vertical, horizontal, single-layer, multi-layer, and other combined installation methods can be used, and the installation is flexible; the floating charging system is applied to make the voltage of the power supply system more stable; the life, capacity, etc. are greatly affected by temperature. The capacity of the battery pack determines the operating time of the communication equipment after the mains power failure. Generally, the capacity of the battery pack can be selected according to the size of the load and the discharge time. The calculation method is: load capacity (A) × discharge time (h) ÷ discharge time hours Rate discharge capacity coefficient.
⑤Monitoring module. The monitoring module has the function of an intelligent control center for the communication DC power supply. It mainly has monitoring functions, including monitoring the AC input voltage and current, the parallel output voltage value of the rectifier modules and the output current of each rectifier module, load current, and battery charging and discharging. Current and voltage, etc.; control functions, including the power system switch on and off, the switch on and off of each rectifier module, the setting of DC output voltage and output current limit value, and the limit value setting of battery pack floating charge, equalizing charging voltage and charging current , Battery temperature coefficient compensation and battery pack under-voltage protection settings, etc.; alarm function, when certain parameters reach or exceed the alarm set value during the operation of the power supply, the monitoring mode will send out an audible and visual alarm, and display the fault location and cause . In addition, the monitoring module should also be able to communicate with the superior monitoring center through the RS232/RS485 interface to achieve centralized monitoring.