The seven components of DC power supply system

The DC system is mainly composed of two parts. One part is the battery panel and the other part is the DC charging panel (DC panel). The battery panel is a cabinet (800×600×2260) that can hold multiple batteries. The batteries in the battery panel are generally composed of 2V-12V batteries in series with 9 to 108 sections, and the corresponding voltage output is 110V or 220V. The batteries currently used are mainly valve-controlled sealed maintenance-free lead-acid batteries. The DC panel is mainly composed of a cabinet, a rectifier module system, a monitoring system, an insulation monitoring unit, a battery inspection unit, a switch detection unit, a step-down unit, and a series of AC input, DC output, voltage display, current display and other distribution units.

1. Rectifier module system

The power rectifier module is a stand-alone module that rectifies AC power into DC power. It is usually rated by the current (such as 2A module, 5A module, 10A module, 20A module, etc.). According to different design concepts, it 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. It can be used in parallel with multiple units to achieve N1 redundancy. The module output is a stable and adjustable DC voltage of 110V or 220V. The module itself has various relatively complete protection functions such as input overvoltage protection, output overvoltage protection, output current limiting protection and output short circuit protection.

2. Monitoring system

The monitoring system is the control and management core of the entire DC system. Its main tasks are: to conduct long-term automatic monitoring of each functional unit and battery in the system, obtain various operating parameters and status in the system, process them in time according to the measurement data and operating status, and control the system based on this, so as to realize the full automatic management of the power supply system and ensure the continuity, reliability and safety of its operation. There are currently two types of monitoring systems: one is a button type and the other is a touch screen type. The monitoring system provides a human-machine interface to realize the display of system operating parameters, system control operations and system parameter settings.

3. Insulation monitoring unit

The DC system insulation monitoring unit is a device that monitors the insulation of the DC system. It can monitor the line-to-ground leakage resistance in real time. This value can be set according to the specific situation. When the line-to-ground insulation drops to the set value, an alarm signal will be issued. The DC system insulation monitoring unit currently has busbar insulation monitoring and branch insulation monitoring.

4. Battery inspection unit

The battery inspection unit is a device that inspects the online voltage of batteries. It can detect the voltage of each battery in real time. When the voltage of a battery is higher or lower than the setting, an alarm signal will be issued, and the monitoring system can display which battery is faulty. The battery inspection unit can generally detect 2V-12V batteries and inspect 1-108 batteries.

5. Switching quantity detection unit

The switch quantity detection unit is a device for online detection of switch quantities and alarm dry node output. For example, if a circuit breaker fails and trips or a fuse blows in the entire system, the switch quantity detection unit will send out an alarm signal, and can display which circuit breaker fails and trips or which fuse blows through the monitoring system. Currently, the switch quantity detection unit can collect 1-108 switch quantities and multi-channel passive dry node alarm output.

6. Step-down unit

The buck unit is a step-down voltage stabilization device. It is a step-down unit that receives the combined mother voltage as input. The step-down unit then outputs to the control mother and adjusts the control mother voltage within the set range (110V or 220V). When the combined mother voltage changes, the buck unit automatically adjusts to ensure that the output voltage is stable. The buck unit is also rated by the output current. There are currently two types of buck units, one is a step-down silicon chain and the other is a stepless buck chopper. The step-down silicon chain has 5-level buck and 7-level buck, and the voltage adjustment point is 3.5V. That is to say, when the combined mother voltage increases or decreases by 3.5V, the buck silicon chain automatically adjusts and stabilizes the control mother voltage. The stepless buck chopper is a buck module. It is smaller than the buck silicon chain. It has no voltage adjustment point, so the output voltage is more stable than the buck silicon chain. It also has functions such as overvoltage, overcurrent, and battery over-discharge. However, the stepless buck chopper technology is not yet very mature and often fails, so the buck silicon chain is still widely used.

7. Power distribution unit

The power distribution unit mainly refers to the devices used in the DC panel to realize functions such as AC input, DC output, voltage display, current display, etc., such as: power cord, terminal blocks, AC circuit breakers, DC circuit breakers, contactors, lightning arresters, shunts, fuses, transfer switches, push button switches, indicator lights, current and voltage meters, etc.