Composition, Principle and Analysis of DC Power Supply

DC power has positive and negative electrodes. The potential of the positive electrode is high and the potential of the negative electrode is low. When the two electrodes are connected with the circuit, they can maintain a constant potential difference between the two ends of the circuit, so as to form a current from the positive electrode to the negative electrode in the external circuit.   The difference of water level alone can not maintain a stable water flow, but by continuously sending water from low to high with the help of water pump, a certain water level difference can be maintained to form a stable water flow. Similarly, the electrostatic field generated by the charge alone can not maintain a stable current. With the help of the DC power supply, the positive charge can be returned from the negative electrode with lower potential to the positive electrode with higher potential through the interior of the power supply through the non electrostatic effect (hereinafter referred to as "non electrostatic force") to maintain the potential difference between the two electrodes, so as to form a stable current. Therefore, DC power supply is an energy conversion device, which converts other forms of energy into electric energy supply circuit to maintain the stable flow of current.

The DC system is mainly composed of two parts. One part is the battery screen, and the other part is the DC charging screen (direct current screen). The battery screen is a cabinet (800 & tips; 600 & tips; 2260) that can place multiple batteries. The battery in the battery panel is generally composed of 2v-12v batteries in series from 9 to 108, and the corresponding electrical voltage output is 110V or 220V. At present, the batteries used are mainly valve regulated sealed maintenance free lead-acid batteries. DC panel is mainly composed of cabinet, rectifier module system, monitoring system, insulation monitoring unit, battery inspection unit, switching value detection unit, step-down unit and a series of AC input, DC output, voltage display, current display and other distribution units.

1. Rectifier module system: power rectifier module is a stand-alone module that rectifies AC into DC. It is usually nominal according to 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 cooling module, independent air duct module, self cooling module, self energy air cooling module and self energy self cooling module. It can be used in parallel to realize N1 redundancy. The module output is 110V, 220V stable and adjustable DC voltage. The module itself has various perfect 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 whole DC system. Its main task is to automatically monitor each functional unit and battery in the system for a long time, obtain various operating parameters and states in the system, process them in time according to the measured data and operating states, and control the system on this basis to realize the full-automatic management of the power supply system, Ensure the continuity, reliability and safety of its work. At present, the monitoring system is divided into two types: one is button type and the other is touch screen type The monitoring system provides man-machine interface * to realize system operation parameter display, system control operation and system parameter setting.

3. Insulation monitoring unit: DC system insulation monitoring unit is a device to monitor the insulation of DC system, which can monitor the line to ground leakage resistance in real time, and this value can be set according to specific conditions. When the line insulation to ground decreases to the set value, an alarm signal will be sent out. The insulation monitoring unit of DC system currently includes bus insulation monitoring and branch insulation monitoring.

4. Battery inspection unit: battery inspection unit is a kind of equipment for ring inspection of battery online voltage. The voltage of each battery can be detected in real time. When the voltage of which battery is too high or too low, an alarm signal will be sent, and the fault of which battery can be displayed through the monitoring system. The battery inspection unit can generally detect 2v-12v batteries and 1-108 batteries.

5. Switching value detection unit: switching value detection unit is a kind of equipment for on-line detection of switching value and output of alarm dry node. For example, in the whole system, after which circuit breaker trips or which fuse blows, the switching value detection unit will send an alarm signal, and can display which circuit breaker trips or which fuse blows through the monitoring system. At present, the switching value detection unit can collect 1-108 channels of switching values and multiple passive dry node alarm outputs.

6. Step down unit: the step-down unit is the step-down and voltage stabilizing equipment, which is the bus voltage input step-down unit, and then the step-down unit outputs it to the control bus to adjust the control bus voltage within the set range (110V or 220V). When the bus voltage changes, the step-down unit automatically adjusts to ensure the stability of the output voltage. The buck unit is also nominal according to the size of the output current. At present, there are two kinds of step-down units, one is the step-down silicon chain, and the other is the stepless step-down chopper. The step-down silicon chain has 5-step step-down and 7-step-down, and the voltage regulation point is 3.5V, that is, when the closing bus voltage increases or decreases by 3.5V, the step-down silicon chain will automatically adjust and stabilize the bus voltage. Stepless step-down chopper is a step-down module. It is smaller than the step-down silicon chain. It has no voltage regulation point, so the output voltage is more stable than the step-down silicon chain. It also has the functions of overvoltage, overcurrent and battery overdischarge. However, at present, the stepless step-down chopper technology is not very mature and often fails, so the step-down silicon chain is widely used.

7. Distribution unit: the distribution unit is mainly the devices used in the DC panel to realize the functions of AC input, DC output, voltage display, current display, etc., such as power line, wiring terminal, AC circuit breaker, DC circuit breaker, contactor, lightning arrester, shunt, fuse, transfer switch, button switch, indicator light, current and voltmeter, etc.

Basic working principle and analysis of DC power supply

When the mains power is connected to the transformer through the input switch to convert the mains power voltage into the designed voltage, it enters the pre voltage stabilizing circuit. The pre voltage stabilizing circuit is to preliminarily stabilize the required output voltage. Its purpose is to reduce the tube voltage drop between the input and output of the high-power regulator, reduce the power consumption of the high-power regulator and improve the working efficiency of the DC power supply, The pre regulated power supply is generally regulated by thyristor stepless phase-shifting adjustment, and the tap output of transformer is switched by relay. The voltage obtained after pre regulated power supply and filter â‘  is basically stable, and the DC with relatively small ripple will obtain the DC voltage with regulated accuracy and performance meeting the standard after accurate and rapid top voltage through the high-power regulating tube controlled by the control circuit, and then pass through filter â‘¡ to obtain the output DC I need. In order to obtain the power transmission I need We also need to sample and detect the output voltage value and current value and transmit them to the control / protection circuit, The control / protection circuit compares and analyzes the detected output voltage value and current value with the value set by the voltage / current setting circuit, and then drives the pre voltage stabilizing circuit and high-power regulator so that the DC regulated power supply can output the voltage and current value set by us, At the same time, when the control / protection circuit detects abnormal voltage or current value, it will start the protection circuit to make the DC power supply enter the protection state.