Centralized DC power distribution protection device

Abstract

The invention discloses a centralized direct-current power distribution protection device, which comprises a current acquisition circuit and a circuit breaker which are connected in series on each branch, the current acquisition circuit carries out signal conditioning on the acquired current signal on the branch through a signal conditioning circuit, and then inputs the current signal to an MCU through an AD converter, and the MCU compares the received signal with a set threshold value, and outputs the current signal to the circuit breaker. Therefore, the on-off states of the branch circuit breakers where the signals are located are controlled. According to the device, current signals of twelve branches can be accurately detected at the same time, the sampling precision is controlled within 0.2%, the misoperation rate of system protection is remarkably reduced, and the fault processing capacity of a multi-branch direct current power distribution system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current distribution branch protection, and in particular to a centralized direct current distribution protection device. Background Art

[0002] As the power system develops towards diversification and intelligence, low-voltage DC distribution systems are widely used in data centers, new energy access, microgrids, etc. due to their high efficiency and flexibility. However, the increasingly complex structure of multi-branch low-voltage DC distribution networks poses new challenges to system protection, including rapid and accurate fault location, protection strategy coordination, and system stability maintenance.

[0003] The common branch protection method is to equip one branch with a protection device. Therefore, multiple protection devices are required in a multi-branch DC power distribution system. This protection method has a complex structure, which increases the equipment cost and installation space. In addition, most of the detection and control circuits use imported chips, and the device cost is relatively high. In order to solve the problem that the protection device in the multi-branch power grid of the DC power distribution system has a complex structure, is difficult to quickly and accurately locate the fault, and has a high cost, the patent with application number 202320229874.9 proposes a centralized protection device for DC multi-branch power grids. Although the device realizes the detection and protection of multiple DC branches, the accuracy of the device is low, and it cannot accurately identify the fault current and the maximum current during normal operation, which is easy to cause protection misoperation. In addition, the chip cost of the device is relatively high, and the CPU used in the device contains 24 analog signal acquisition ports. The 12-bit SAR analog-to-digital converter ADC integrated in the CPU can only detect eight branch signals. Summary of the invention

[0004] Purpose of the invention: The purpose of the invention is to provide a centralized DC distribution protection device with small sampling error and fast on-off response.

[0005] Technical solution: To achieve the above-mentioned purpose, a centralized DC power distribution protection device described in the present invention includes a current acquisition circuit and a circuit breaker connected in series on each branch. The current acquisition circuit will collect the current signals on the twelve branches through a signal conditioning circuit for signal conditioning, and then input them to the MCU through an AD converter. The MCU compares the received signal with the set threshold value, thereby controlling the switching state of the branch circuit breaker where each signal is located.

[0006] Wherein, the AD converter is a 16-bit ADCS1862 analog-to-digital converter.

[0007] The AD converter includes two groups, each group is connected to six current acquisition circuits.

[0008] Wherein, the MCU is a microcontroller unit of GD32F407RET6.

[0009] Wherein, the current acquisition circuit includes a direct current Hall sensor connected in series to the branch.

[0010] Among them, the signal conditioning circuit includes an isolation operational amplifier connected to the output end of the current acquisition circuit, the output end of the isolation operational amplifier is respectively connected to the in-phase input of the operational amplifier and resistor R1, the other end of resistor R1 is grounded, the output end of the operational amplifier is respectively connected to the input end of the AD converter and capacitor C1, and the other end of capacitor C1 is grounded.

[0011] Among them, the MCU controls the switching state of the branch circuit breaker where each signal is located through a switch output circuit, and the switch output circuit includes a photoelectric coupler OP1 connected to the MCU signal output end, the other input end of the photoelectric coupler OP1 is grounded, one output end of the photoelectric coupler OP1 is connected to a +24V power supply, and the other output end is connected to the coil of a relay, the other end of the coil is grounded, one end of the relay switch is grounded, and the other end is connected to the circuit breaker release, and the other end of the release is connected to a 220V power supply.

[0012] It also includes a switch quantity input circuit for transmitting the switch state of the circuit breaker to the MCU in real time, and the switch quantity input circuit includes a photocoupler OP2, one input end of the photocoupler OP2 is connected to the switch K1, and the other end is grounded, and the other end of the switch K1 is connected to a +24V power supply; one output end of the photocoupler OP2 is simultaneously connected to a resistor R3 and a switch quantity signal input end of the MCU, the other end of the resistor R3 is connected to a 3.3V power supply, and the other output end of the photocoupler OP2 is grounded.

[0013] Among them, the MCU compares the received signal with the set threshold value to control the working state of the switch output circuit of the branch where the signal is located. Specifically, the MCU compares the digital quantity of each branch converted by the AD converter with the set current setting value. When the digital quantity of the branch is greater than the current setting value and lasts for a set time, it is determined that a fault has occurred in the branch, and the switch output circuit on the branch where the MCU signal is located issues a trip command.

[0014] It also includes communication circuit, monitoring center and display. The communication circuit realizes communication between MCU and monitoring center through Ethernet transceiver YT8522H, and the display uses TFT screen.

[0015] Beneficial effects: The present invention has the following advantages: 1. The device of the present invention can accurately detect the current signals of twelve branches at the same time, and its sampling accuracy is controlled within 0.2%, which significantly reduces the false operation rate of the system protection and effectively improves the fault handling capability of the multi-branch DC distribution system; 2. The device of the present invention can accurately collect and compare current signals, accurately identify fault currents through MCU, issue tripping commands in time, and shorten fault response time; 3. The ADCS1862 analog-to-digital converter and GD32F407RET6 microcontroller unit used in the device of the present invention have superior performance and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a principle block diagram of the protection device of the present invention;

[0017] Figure 2 This is a branch circuit protection flow chart of the protection device of the present invention;

[0018] Figure 3 This is a circuit structure diagram of the protection device described in the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described in detail below in conjunction with the embodiments and drawings.

[0020] like Figure 1 As shown, the centralized DC power distribution protection device of the present invention includes a current acquisition circuit, a signal conditioning circuit, an AD converter, a microcontroller unit (MCU), a switch output circuit, a circuit breaker, a switch input circuit, a communication circuit, a monitoring center and a display.

[0021] The current acquisition circuit collects current signals from each branch and transmits them to the signal conditioning circuit. The processed current signal is transmitted to the AD converter, which converts the signal from analog to digital, and then transmits the digital quantity to the signal input port of the MCU. The MCU compares the digital quantity with the current setting value to determine whether the branch has a fault. If the judgment result is that a fault has occurred, a disconnection instruction is issued to the switch output circuit, and the switch output circuit controls the circuit breaker to disconnect and remove the branch fault; if the judgment result is that no fault has occurred, no instruction is issued. The switch input circuit transmits the circuit breaker opening or closing status to the MCU in real time. The MCU forms a protection monitoring network with the background monitoring center through the communication circuit. The MCU transmits the information to the display through RS-485 communication to display the collected branch current value, operating status, fault record and other information.

[0022] The current acquisition circuit includes a DC current Hall sensor connected in series in each branch; the signal conditioning circuit corresponds to the current acquisition circuit one by one, including an isolation operational amplifier, a resistor R1, an operational amplifier, a resistor R2 and a capacitor C1, wherein the resistor R2 and the capacitor C1 constitute a filter circuit; the MCU integrates a signal input port, a signal output port, a communication port and a DA output port; the switch output circuit includes an optocoupler OP1 and a relay; the circuit breaker is connected in series in each branch and is used to disconnect when the branch fails; the switch input circuit corresponds to each switch output circuit one by one, including a switch K1, an optocoupler OP2 and a resistor R3; the communication circuit realizes communication between the MCU and the monitoring center through the Ethernet transceiver YT8522H; the display uses a TFT screen, and the specific work flow is as follows Figure 2 shown.

[0023] The circuit structure of the protection device is as follows Figure 3 As shown, each branch AL is connected in series with a DC current Hall sensor to obtain the current of each branch. The output end of the DC current Hall sensor on each branch is connected to an isolation operational amplifier to suppress interference, isolate each signal, and ensure the correct transmission of the signal to meet the high-precision requirements. Taking branch A as an example, the output end of the isolation operational amplifier A is connected to the in-phase input end of the operational amplifier A, and a resistor R1A is connected in parallel to the connected line, the other end of the resistor R1A is grounded, and the inverting input end of the operational amplifier A is connected to its output end. The output end of the operational amplifier A is also connected to the resistor R2A, and the other end of the resistor R2A is respectively connected to the AD converter input end and the capacitor C1A, and the other end of the capacitor C1A is grounded.

[0024] The AD converter converts the analog current signal processed by the signal conditioning circuit into a digital current signal. The signal output port of the AD converter is connected to the digital signal input port of the MCU, and the digital signal is transmitted to the MCU for analysis and judgment.

[0025] The MCU compares the digital quantity of each branch after AD conversion with the set current setting value. When the digital quantity of the branch is greater than the current setting value and lasts for a certain period of time, it is determined that the branch has a fault and jumps to the fault protection program. The fault protection program issues a trip command, which is output from the MCU signal output terminal to the switch output circuit corresponding to the branch.

[0026] Taking branch A as an example, the MCU signal output terminal is connected to the switch output circuit, specifically, the MCU signal output terminal is connected to the input terminal of the photocoupler OP1A, the other input terminal of the photocoupler OP1A is grounded, one output terminal of the photocoupler OP1A is connected to the +24V power supply, and the other output terminal is connected to the coil of the relay, and the other end of the coil is grounded. One end of the relay switch is grounded, and the other end is connected to the release of the circuit breaker, and the other end of the release is connected to the 220V power supply.

[0027] When a branch circuit in the system is judged to meet the conditions for a fault to occur, the MCU sends a conduction signal to the input end of the optocoupler OP1A, controlling the output end of the optocoupler OP1A to conduct, thereby energizing the coil of the relay, controlling the switch of the relay to close, and then energizing the release of the circuit breaker, controlling the circuit breaker to disconnect, and cutting off the faulty branch circuit to prevent the fault scope from expanding.

[0028] The switch signal input end of the MCU is connected to a switch input circuit. Taking branch A as an example, specifically: one end of the input end of the photocoupler OP2A is connected to the switch K1A, and the other end is grounded. The other end of the switch K1A is connected to the +24V power supply. One of the output ends of the photocoupler OP2A is connected to the resistor R3A and the switch signal input end of the MCU at the same time. The other end of the resistor R3A is connected to the 3.3V power supply, and the other output end of the photocoupler OP2A is grounded. When the circuit breaker on branch A is closed, the switch K1A is disconnected, and the signal received by the MCU is a high level; when the circuit breaker on branch A is disconnected, the switch K1A is closed, the input end of the photocoupler OP2A is energized, the output end is turned on, and the signal received by the MCU is a low level. The photocoupler OP2A, switch K1A and resistor R3A together constitute a switch input circuit, which transmits the status of the circuit breaker on branch A to the MCU in real time.

[0029] The present invention uses an isolation operational amplifier in the signal conditioning circuit, which can suppress interference, isolate various signals, ensure correct signal transmission, and then amplify the signal through the operational amplifier, and filter the clutter by the filter circuit. The signal conditioning circuit as a whole cooperates with the 16-bit AD converter of ADCS1862 to realize 16-bit 8-channel synchronous sampling input, and the sampling error is controlled at 0.2%, ensuring high-precision sampling, avoiding the MCU from receiving signals with errors, failing to accurately identify the fault current and the maximum current during normal operation, and issuing wrong instructions, reducing the system protection malfunction rate, improving the fault handling capability of the multi-branch DC power distribution system, shortening the fault response time, avoiding the expansion of the fault range, and enhancing the system power supply reliability. At the same time, the MCU adopts GD32F407RET6, the main frequency of the chip is as high as 168MHz, and it can effectively suppress temperature drift.

Claims

1. A centralized DC power distribution protection device, comprising a current collection circuit and a circuit breaker connected in series on each branch, characterized in that: The current acquisition circuit will collect the current signals on the twelve branches through the signal conditioning circuit for signal conditioning, and then input them to the MCU through the AD converter. The MCU compares the received signal with the set threshold value to control the switch state of the branch circuit breaker where each signal is located.

2. The centralized DC power distribution protection device according to claim 1, characterized in that: The AD converter is a 16-bit ADCS1862 analog-to-digital converter.

3. The centralized DC power distribution protection device according to claim 1, characterized in that: The AD converter includes two groups, each group is connected to six current collection circuits.

4. The centralized DC power distribution protection device according to claim 1, characterized in that: The MCU is a microcontroller unit of GD32F407RET6.

5. The centralized DC power distribution protection device according to claim 1, characterized in that: The current acquisition circuit includes a direct current Hall sensor connected in series to the branch.

6. The centralized DC power distribution protection device according to claim 1, characterized in that: The signal conditioning circuit includes an isolation operational amplifier connected to the output end of the current acquisition circuit, the output end of the isolation operational amplifier is respectively connected to the in-phase input of the operational amplifier and resistor R1, the other end of the resistor R1 is grounded, the output end of the operational amplifier is respectively connected to the input end of the AD converter and capacitor C1, the other end of the capacitor C1 is grounded.

7. The centralized DC power distribution protection device according to claim 1, characterized in that: The MCU controls the switch state of the branch circuit breaker where each signal is located through a switch output circuit. The switch output circuit includes a photoelectric coupler OP1 connected to the MCU signal output end, the other input end of the photoelectric coupler OP1 is grounded, one output end of the photoelectric coupler OP1 is connected to a +24V power supply, the other output end is connected to the coil of a relay, the other end of the coil is grounded, one end of the relay switch is grounded, and the other end is connected to the circuit breaker release, and the other end of the release is connected to a 220V power supply.

8. The centralized DC power distribution protection device according to claim 7, characterized in that: It also includes a switch quantity input circuit for transmitting the switch state of the circuit breaker to the MCU in real time, the switch quantity input circuit includes a photocoupler OP2, one end of the input end of the photocoupler OP2 is connected to the switch K1, the other end is grounded, and the other end of the switch K1 is connected to the +24V power supply; One output end of the photocoupler OP2 is connected to the resistor R3 and the switch signal input end of the MCU at the same time, the other end of the resistor R3 is connected to the 3.3V power supply, and the other output end of the photocoupler OP2 is grounded.

9. The centralized DC power distribution protection device according to claim 1, characterized in that: The MCU compares the received signal with the set threshold value to control the working state of the switch output circuit of the branch where the signal is located. Specifically, the MCU compares the digital quantity of each branch converted by the AD converter with the set current setting value. When the digital quantity of the branch is greater than the current setting value and lasts for a set time, it is determined that a fault has occurred in the branch, and the switch output circuit on the branch where the MCU signal is located issues a trip command.

10. The centralized DC power distribution protection device according to claim 1, characterized in that: It also includes a communication circuit, a monitoring center and a display. The communication circuit realizes communication between the MCU and the monitoring center through the Ethernet transceiver YT8522H, and the display uses a TFT screen.

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