Components of DC power supply system

The DC power system mainly consists of two parts. One part is the battery screen, and the other part is the DC charging screen (DC charging screen). A battery screen is a cabinet (800 × 600 × 2260) that can hold multiple batteries. The batteries in the battery screen are generally composed of 2V-12V batteries connected in series with 9 to 108 cells, corresponding to a voltage output of 110V or 220V. The batteries currently in use are mainly valve regulated sealed maintenance free lead-acid batteries. The DC screen mainly consists of a cabinet, rectifier module system, monitoring system, insulation monitoring unit, battery inspection unit, switch detection unit, voltage reduction unit, and a series of AC input, DC output, voltage display, current display and other distribution units.
Rectification module system
The power rectification module is a standalone module that rectifies AC power into DC power. It is usually rated based on the current passing through it (such as 2A module, 5A module, 10A module, 20A module, etc.), and can also be divided into air-cooled module, independent air duct module, self cooling module, self energy air-cooled module, and self energy self cooling module according to different design concepts. It can be used in parallel with multiple units, achieving N1 redundancy. The module output is a stable and adjustable DC voltage of 110V and 220V. The module itself has various comprehensive protection functions such as input overvoltage protection, output overvoltage protection, output current limiting protection, and output short circuit protection.
monitoring system
The monitoring system is the control and management core of the entire DC system. Its main task is to conduct long-term automatic monitoring of various functional units and batteries in the system, obtain various operating parameters and status in the system, process them in a timely manner based on measurement data and operating status, and control the system based on this to achieve fully automatic management of the power system, ensuring its continuity, reliability, and safety. There are currently two types of monitoring systems: one is button type and the other is touch screen type. The monitoring system provides a human-machine interface to display system operating parameters, control operations, and set system parameters.
Insulation monitoring unit
The insulation monitoring unit of the DC system is a device that monitors the insulation condition of the DC system, and can monitor the resistance of the line to the ground drain in real time. This value can be set according to the specific situation. When the insulation of the line to ground decreases to the set value, an alarm signal will be issued. The insulation monitoring unit of the DC system currently includes busbar insulation monitoring and branch insulation monitoring.
Battery inspection unit
The battery inspection unit is a device that performs loop inspection on the online voltage status of the battery. It can detect the voltage of each battery in real time. When the voltage of a battery exceeds or falls below the set value, an alarm signal will be issued, and the monitoring system can display which battery has malfunctioned. The battery inspection unit can generally detect 2V-12V batteries and patrol 1-108 batteries.
Switching quantity detection unit
The switch quantity detection unit is a device for online detection of switch quantities and output of alarm dry nodes. For example, in the entire system, if a circuit breaker trips due to a fault or if a fuse is blown, the switch detection unit will issue an alarm signal and display which circuit breaker trips due to a fault or which fuse is blown through the monitoring system. At present, the switch quantity detection unit can collect 1-108 switch quantities and multiple passive dry node alarm outputs.
Voltage reducing unit
The voltage reduction unit is a voltage reduction and stabilization device, which is used to input the combined bus voltage into the voltage reduction unit, and then output it to the control bus to adjust the control bus voltage within the set range (110V or 220V). When the combined voltage changes, the voltage reduction unit automatically adjusts to ensure stable output voltage. The voltage reduction unit is also nominal based on the magnitude of the output current. There are currently two types of voltage reducing units, one is a stepped voltage reducing silicon chain, and the other is a stepless voltage reducing chopper. The stepped down silicon chain has 5 levels of voltage reduction and 7 levels of voltage reduction, with a voltage regulation point of 3.5V. This means that when the bus voltage increases or decreases by 3.5V, the stepped down silicon chain automatically adjusts the stable control bus voltage. Stepless step-down chopper is a step-down module that is smaller in size than a step-down silicon chain. It does not have a voltage regulation point, so the output voltage is more stable than a step-down silicon chain. It also has functions such as overvoltage, overcurrent, and battery over discharge. However, the current technology of stepless voltage reduction and chopping is not yet mature and often malfunctions, so the use of voltage reduction silicon chains is still widely effective.
Distribution unit
The distribution unit is mainly composed of devices used in the DC screen to achieve functions such as AC input, DC output, voltage display, and current display, such as power lines, terminal blocks, AC circuit breakers, DC circuit breakers, contactors, lightning arresters, splitters, fuses, transfer switches, button switches, indicator lights, and current and voltage meters.