Automatic bus connection monitoring and control method for direct current system

Abstract

The invention relates to the technical field of substation direct current system detection and control, and discloses a direct current system automatic bus connection monitoring and control method, which comprises the steps of detecting the voltage of two sections of direct current buses in real time, judging the parallel connection condition and controlling the closing operation of a contactor. Voltage change can be monitored when an input part has a fault, and whether two sections of direct current buses are connected in parallel or not is determined. If the condition is met, the contactor is closed and sends an alarm to the background management system; otherwise, the system also gives an alarm. In addition, current sampling can be carried out, the current direction is judged through an internal sensor, and therefore the power supply direction and the load transfer condition are recognized. Meanwhile, the resistance value after parallel connection is calculated, whether the loop resistance is too large or not is detected, and abnormal conditions are fed back to a background management system in time. The method has the technical effects that the closing condition of the interconnection switch can be accurately judged, the load transfer is monitored in real time, the bus coupler loop resistance is detected, and an effective guarantee is provided for stable operation of a direct current system.

Description

Technical Field

[0001] The invention relates to the technical field of detection and control of a DC system in a transformer substation, and in particular to a method for monitoring and controlling an automatic bus connection of a DC system. Background Art

[0002] In today's power system, most substations have achieved unattended operation, which has brought great convenience in improving efficiency and reducing labor costs. However, this model also exposes many potential problems, especially in the reliability and safety of DC power supply systems.

[0003] 1. Challenges of DC power supply failure

[0004] When a DC system in a substation fails, on-site operators and professional technicians are unable to arrive on site in time to deal with the problem due to unattended operation. This delay may result in an inability to quickly switch to the backup DC power supply line, thus affecting the stability and reliability of the entire power system. The key to solving this problem is to implement an automated monitoring and control system that can automatically respond to failures, switch power supply lines in a timely manner, and reduce human intervention.

[0005] 2. Risks of charging devices

[0006] The lack of maintenance and monitoring of unattended charging devices may result in the battery pack not being able to be charged properly in a timely manner. For example, if the charging device fails or is set incorrectly, the alarm system fails to respond in time, which will cause the battery to be in a state of low capacity for a long time. In the long run, the capacity of the battery may suffer irreversible loss, which will eventually affect the safety and stable operation of the power grid. For this reason, it is crucial to introduce a more intelligent charging management system into the system, which can ensure that the battery is always in the best condition by monitoring the battery status in real time and adjusting the charging parameters in time.

[0007] 3. DC bus voltage difference problem

[0008] In a DC system, if the bus voltage difference does not meet the requirements, it may involve an impact current when operating the bus tie switch. In the case of no one on duty, if the operator misjudges the bus operating conditions, a huge impact current may be generated, which will not only damage the battery and other equipment, but also threaten the safety of the operator. Therefore, it is necessary to consider designing an automatic detection and control system. When the system detects that the bus voltage difference does not meet the standard, it can automatically lock the operation to prevent safety accidents caused by misoperation.

[0009] 4. Solution for automatic busbar connection device

[0010] Based on the above problems, it is necessary to develop a DC system automatic busbar connection device. The device will have the following core functions:

[0011] Automatic fault detection and switching: Real-time monitoring of DC power supply status. Once a fault is detected, it can automatically switch to another DC power supply line to minimize the impact of the fault on power supply.

[0012] Intelligent charging management: The integrated intelligent charging device can automatically adjust the charging parameters according to the real-time status of the battery. It also has fault alarm and remote monitoring functions to avoid battery depletion and damage.

[0013] Voltage difference monitoring and protection mechanism: Real-time monitoring of the voltage difference of the DC busbar is carried out, and a safety threshold is set. Once an abnormality is detected, the operation of the busbar switch is automatically locked to avoid equipment damage and personal safety accidents caused by impact current.

[0014] Therefore, it is urgent to develop a DC system automatic bus connection monitoring and control method to solve the existing problems. Summary of the invention

[0015] The present invention provides a method for monitoring and controlling an automatic bus connection of a DC system. The method is based on a DC system bus connection loop state monitoring device and aims to solve key problems existing in the DC power supply system in the current unmanned substation, such as untimely fault response, delayed abnormal processing of charging devices, and failure of the DC bus voltage difference to meet operating conditions, so as to ensure the safe and stable operation of the power grid, while protecting the personal safety of operators and the healthy maintenance of battery packs.

[0016] The technical solution adopted by the present invention is:

[0017] A method for monitoring and controlling an automatic bus connection of a DC system, the method for monitoring and controlling an automatic bus connection of a DC system is based on a DC system bus connection circuit state monitoring device, and comprises the following steps:

[0018] Step 1: Install the DC system bus-coupled circuit state monitoring device in the substation, and connect two sections of DC busbars to the DC system bus-coupled circuit state monitoring device;

[0019] Step 2: Real-time detection of the voltages of the two DC buses by a DC system bus-coupling circuit status monitoring device;

[0020] Step 3: When the input part fails, only the battery is supplying power. When the battery continues to supply the load, the terminal voltage will drop. When it is detected that the terminal voltage of a certain DC bus is lower than the set value, the DC system bus coupling circuit state monitoring device starts to determine whether the conditions for parallel connection of two sections of DC buses are met;

[0021] Step 4, the DC system bus-coupled circuit status monitoring device determines whether the conditions for connecting the two DC busbars in parallel are met; if so, the DC system bus-coupled circuit status monitoring device controls the contactor to close, so that the two DC busbars are connected in parallel, and an alarm is sent to the background management system; if not, an alarm is directly sent to the background management system.

[0022] Furthermore, the DC system bus-connection circuit status monitoring device determines whether the parallel connection conditions of the two DC bus sections are met, and the judgment is made based on whether the voltage difference between the two DC bus sections is within a specified range; when the voltage difference between the two DC bus sections is within 5V, the parallel connection conditions are met; otherwise, the parallel connection conditions are not met.

[0023] Further, the DC system bus-coupled circuit state monitoring device includes a device housing, a group of positive and negative input terminals of a segment I DC bus installed on one side of the device housing, a group of positive and negative input terminals of a segment II DC bus installed on the other side of the device housing, a display screen installed above the device housing, and a control circuit board, an air switch and a DC contactor located inside the device housing and connected to a group of positive and negative input terminals of a segment I DC bus and positive and negative input terminals of a segment II DC bus respectively;

[0024] The control circuit board is electrically connected to the display screen and the DC contactor; the positive and negative input terminals of the I-section DC bus and the positive and negative input terminals of the II-section DC bus are respectively connected to the two DC buses.

[0025] Furthermore, the control circuit board is equipped with an MCU, a power supply electrically connected to the MCU, a voltage detection circuit electrically connected to the positive and negative input terminals of the I-section DC bus and the positive and negative input terminals of the II-section DC bus, a contactor control circuit electrically connected to the DC contactor, and a wireless module electrically connected to the MCU.

[0026] Furthermore, the voltage detection circuit is divided into two groups, each group of voltage detection circuits includes two groups of voltage divider networks composed of a number of resistors, and an isolated operational amplifier connected to the voltage divider network; the voltage divider network of each group of voltage detection circuits is connected to an external voltage monitoring interface, and the isolated operational amplifier is connected to the MCU through a current limiting resistor.

[0027] Furthermore, the power supply includes an AC / DC conversion module, the input end of the AC / DC conversion module is connected to the external power supply, and the output end is connected to the input end of the buck regulator LMR14050; the output end of the buck regulator LMR14050 is connected to the input end of the second-stage buck regulator U9, and the output end of U9 is connected to the MCU.

[0028] Furthermore, the contactor control circuit includes a contactor, a relay and a phototransistor; the output end of the MCU is connected to the base of the phototransistor, and when the MCU outputs a low level, the phototransistor is turned on and the relay contacts are closed; conversely, when the MCU outputs a high level, the phototransistor is disconnected and the relay contacts are opened; the relay controls the coil of the contactor, and when the normally open contact of the relay is closed, the contactor coil is energized, the main contacts are closed, and the DC bus is connected.

[0029] Furthermore, the MCU includes an STM32F103C8T6 main controller, a wireless module connected to the main controller, a high-speed crystal oscillator circuit, a power-on reset circuit, a startup mode selection circuit, a power decoupling circuit and a program download circuit; the main controller is connected to the power supply through the power decoupling circuit.

[0030] Furthermore, the DC system automatic bus connection monitoring and control method also includes:

[0031] Step 5, when the DC system bus-coupled circuit state monitoring device controls the contactor to close and connects the two sections of DC bus in parallel, the current sensor inside the device samples the current of the DC bus; if the voltage of the #1 DC bus is higher than the voltage of the #2 DC bus, the current sensor monitors a positive current, the MCU displays a positive current value on the display screen, and transmits it to the background management system through the wireless module; conversely, if the voltage of the #2 DC bus is higher than the voltage of the #1 DC bus, the current sensor monitors a reverse current, the MCU displays a negative current value on the display screen, and transmits it to the background management system through the wireless module; in this way, it is determined which DC bus supplies the load;

[0032] Step 6: Based on the voltage detection of the two DC buses in step 4 and the current sampling of the DC bus by the current sensor in step 5, the DC system bus-connected loop status monitoring device calculates the resistance value of the two DC buses in parallel according to Ohm's law; based on the calculated resistance value, it is determined whether the loop resistance is too large, and if so, an alarm is sent to the background management system.

[0033] Furthermore, after the DC system bus-coupled circuit status monitoring device is installed, the background management system can remotely send electrical signals to the contactor opening and closing control contacts of the device through the communication module to control the closing and closing of the internal contactors of the device; at the same time, at the installation location of the DC system bus-coupled circuit status monitoring device, the closing and closing of the contactor can be manually controlled by buttons.

[0034] The beneficial effects of the present invention are:

[0035] 1. Judgment of closing conditions of intelligent tie switch

[0036] Real-time monitoring and analysis: The DC system bus-coupler circuit status monitoring device can monitor the voltage status of the two DC bus sections in real time, and automatically determine whether the closing conditions are met through data analysis.

[0037] Accurate early warning mechanism: When an input failure or other abnormal situation is detected, the device can quickly and accurately issue an early warning to prevent misoperation or equipment damage.

[0038] Improve operational safety: Reduce safety hazards caused by human misjudgment through real-time monitoring and judgment of the closing conditions of the tie switch.

[0039] 2. Automatic load transfer detection function

[0040] Intelligent load switching: When the load is transferred from one section of the DC bus to another, the system can intelligently identify and display the current load power supply status through voltage monitoring and current sampling.

[0041] Fault management and response speed: During the load transfer process, once an abnormality occurs, the system can quickly feedback to the management platform, reducing fault response time and improving system reliability.

[0042] Visual operation: The load transfer status is displayed in real time on the display screen, so that managers can intuitively understand the current flow and load distribution, enhancing the convenience of operation and maintenance.

[0043] 3. Loop resistance detection function

[0044] Real-time resistance detection: By calculating and monitoring the resistance value after parallel connection, it is possible to promptly determine the poor contact or line fault between the busbars to ensure safe and stable operation of the system.

[0045] Intelligent fault warning: If the loop resistance is detected to be too large, the system will immediately send an alarm to the background management system to ensure that potential electrical faults can be handled in advance.

[0046] Reduce maintenance costs: Through active monitoring and fault warning, frequent manual inspections can be reduced, the operation and maintenance efficiency of equipment can be improved, and the overall maintenance costs can be reduced.

[0047] 4. Remote control and manual intervention

[0048] Remote monitoring and convenient operation: The background management system can remotely control the closing and opening operations of the contactor through the communication module, enhance operational flexibility and response speed, and adapt to changes in different needs.

[0049] Convenient manual intervention: When necessary, managers can quickly control the contactor through key operations, which is convenient for on-site maintenance and emergency handling.

[0050] 5. Overall system integration and optimization

[0051] Comprehensive information processing platform: Integrate monitoring, control, alarm and other functions to form an efficient information processing platform to improve the intelligent management level of the power system.

[0052] Scalability and compatibility: The system design allows for future expansion through software or hardware modules to adapt to changing requirements of different DC systems.

[0053] In summary, based on the DC system automatic bus connection monitoring and control method, intelligent monitoring and control of the DC bus is realized, which not only improves the safety and stability of the system itself, but also reduces the operation and maintenance costs, significantly enhances the reliability and economy of the power system, and provides important support for the intelligent and automated development of modern power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0055] Figure 1 and Figure 2 It is a structural diagram of a DC system bus-coupling circuit state monitoring device of the present invention;

[0056] Figure 3 A schematic diagram of the connection relationship of a DC system bus-coupling circuit state monitoring device according to the present invention;

[0057] Figure 4 is a circuit diagram of a voltage detection circuit of the present invention;

[0058] Figure 5 is a circuit diagram of the AC / DC conversion module of the present invention;

[0059] Figure 6 The circuit diagram of the buck regulator LMR14050 of the present invention;

[0060] Figure 7 is a circuit diagram of the second-stage buck regulator U9 of the present invention;

[0061] Figure 8 A circuit diagram of a contactor control circuit of the present invention;

[0062] Fig. 9 A circuit diagram of the MCU of the present invention;

[0063] Fig.10 It is a flow chart of the DC system automatic bus connection monitoring and control method of the present invention;

[0064] In the figure: 1. Device casing; 2. Positive input terminal of section I DC bus; 3. Negative input terminal of section I DC bus; 4. Positive input terminal of section II DC bus; 5. Negative input terminal of section II DC bus; 6. Control circuit board; 7. Circuit breaker; 8. DC contactor; 9. Display screen. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0066] Example 1

[0067] In view of the problems of long operation time and unclear judgment of operation and maintenance personnel in the monitoring and maintenance process of the power station DC system, this embodiment provides a DC system bus-connected circuit state monitoring device.

[0068] like Figure 1 and Figure 2 As shown, the DC system bus-coupled circuit state monitoring device includes a device housing 1, a positive input terminal 2 of a DC bus section I and a negative input terminal 3 of a DC bus section I installed on one side of the device housing 1, a positive input terminal 4 of a DC bus section II and a negative input terminal 5 of a DC bus section II installed on the other side of the device housing 1, a display screen 9 installed above the device housing 1, and a control circuit board 6, a circuit breaker 7 and a DC contactor 8 located inside the device housing 1 and connected to a group of positive and negative input terminals of the DC bus section I and the positive and negative input terminals of the DC bus section II, respectively.

[0069] The control circuit board 6 is electrically connected to the display screen 9 and the DC contactor 8. The positive input terminal 2 of the I-stage DC bus and the negative input terminal 3 of the I-stage DC bus are connected to the #1 DC bus, and the positive input terminal 4 of the II-stage DC bus and the negative input terminal 5 of the II-stage DC bus are connected to the #2 DC bus.

[0070] After the two ends of the DC bus are connected, if the circuit breaker 7 is closed and the contactor is closed, the two sections of the DC bus are connected in parallel. Circuit breaker 7 has two functions: one is that circuit breaker 7 trips in the event of a fault to prevent the two sections of the DC bus from being connected together, and the other is that the device can be manually disconnected from the original circuit.

[0071] Further, such as Figure 3As shown, the control circuit board 6 in this embodiment is equipped with an MCU, a power supply electrically connected to the MCU, a voltage detection circuit electrically connected to the positive input terminal 2 of the I-section DC bus, the negative input terminal 3 of the I-section DC bus, the positive input terminal 4 of the II-section DC bus and the negative input terminal 5 of the II-section DC bus, a contactor control circuit electrically connected to the DC contactor 8, and a wireless module electrically connected to the MCU.

[0072] There are two groups of voltage detection circuits, each of which includes two groups of voltage divider networks composed of several resistors, and an isolated operational amplifier connected to the voltage divider network; the voltage divider network of each group of voltage detection circuits is connected to the external voltage monitoring interface, and the isolated operational amplifier is connected to the MCU through a current limiting resistor.

[0073] like Figure 4 As shown, a series of resistors are used to divide the bus voltage, and then the voltage is input into the isolation amplifier for isolation. The voltage output by the isolation amplifier is detected by the ADC of the MCU, and then the bus voltage is calculated based on the voltage division. In the voltage detection circuit, U2 is the #1 DC bus voltage sampling isolation amplifier. The series resistors R3, R2, R1, R5, R7, R8, and R9 divide the voltage of the I-section DC bus. The interfaces are A_P and A_N. R5 is a sampling resistor. The voltage on R5 is isolated and connected to the ADC1 interface of the MCU. Then the MCU calculates the #1 DC bus voltage based on the amplification factor and the voltage division ratio.

[0074] U4 is the #2 DC bus voltage sampling isolation operational amplifier. The series resistors R15, R14, R13, R18, R20, R21, and R22 divide the voltage of the II DC bus. The interfaces are B_P and B_N. R18 is a sampling resistor. The voltage on R18 is amplified and isolated and connected to the ADC2 interface of the MCU. Then the MCU calculates the #2 DC bus voltage according to the amplification factor and the voltage division ratio.

[0075] The power supply includes an AC / DC conversion module, the input end of the AC / DC conversion module is connected to the external power supply, and the output end is connected to the input end of the buck regulator LMR14050; the output end of the buck regulator LMR14050 is connected to the input end of the second-stage buck regulator U9, and the output end of U9 is connected to the MCU.

[0076] like Figure 5As shown, AC85V~AC275V, DC110V~DC385V input, output DC24V. In the power supply circuit, the AC / DC conversion module U32 is a high-efficiency green module power supply in a small package. The power supply has excellent ripple and noise performance. Under full load, the peak-to-peak value of ripple and noise is between 100-150mv. It also has the advantages of AC / DC dual-use, wide input voltage range, high reliability, low power consumption, and safe isolation. The power supply has an efficiency of up to 90% and an ultra-low no-load power consumption of less than 0.1W. It can provide the most basic dustproof and waterproof functions. The peripheral circuit is an EMC electromagnetic compatibility circuit. It can improve the stability of the power supply module in a complex electromagnetic environment.

[0077] like Figure 6 As shown, DC24V input, DC5V output. The buck regulator LMR14050 device is a 40V, 5A buck regulator with an integrated high-side MOSFET. The device has a wide input voltage range of 4V to 40V, the regulator has a wide adjustable switching frequency range, and the output voltage is adjusted by R31 and R40. Internal loop compensation means that there is no need to bear the tedious work of designing loop compensation components, and it can also minimize the number of external components of the device. The precision enable input simplifies regulator control and system power sequencing. In addition, the device has built-in multiple protection features: cycle-by-cycle current limit protection, thermal sensing and thermal shutdown protection for excessive power dissipation, and output overvoltage protection.

[0078] like Figure 7 As shown in the figure, the MCU operating voltage is 3.3V, and the power supply output voltage is 5V, which needs to be further stepped down; the second-stage buck regulator U9 is a high-performance, 500mA linear regulator with extremely high PSRR power supply rejection ratio and ultra-low output voltage. The +5V input connection of this device is as follows Figure 6 At the +5V output, diode D3 further reduces the voltage, and the output of the second-stage buck regulator U9 is connected in parallel with two capacitors C15 and C16 to act as a filter.

[0079] The contactor control circuit includes a contactor, a relay and a phototransistor; the output end of the MCU is connected to the base of the phototransistor. When the MCU outputs a low level, the phototransistor is turned on and the relay contacts are closed; conversely, when the MCU outputs a high level, the phototransistor is disconnected and the relay contacts are opened; the relay controls the coil of the contactor. When the normally open contact of the relay is closed, the contactor coil is energized, the main contacts are closed, and the DC bus is connected.

[0080] like Figure 8As shown in the figure, the contact system of the contactor usually includes main contacts and auxiliary contacts. The main contacts are used to control the on and off of the main circuit. When the coil is energized, the action of the contact system causes the main contacts to close, thereby connecting the power supply. Conversely, when the coil is de-energized, the action of the contact system causes the main contacts to open, thereby cutting off the power supply. In the contactor control circuit, a relay is used to control whether the coil of the contactor is energized or not. The contactor often has an auxiliary contact that can output the action status of the main contact of the contactor. If the auxiliary contact is a normally open contact, then its on and off state is the same as the main contact. If it is a normally closed contact, then its on and off state is opposite to that of the main contact. After OUT2 is limited by resistor R27, it is connected to the OUT2 interface of the MCU. When OUT2 of MCU outputs low level, phototransistor U5 is turned on, the base of transistor Q2 is pulled down, its source and collector are turned on, the normally open contact of relay RLY2 is closed, COIL+ and COIL- are equivalent to the power switch of the contactor coil, COIL+ and COIL- are turned on, and the contactor is attracted. Connect the DC bus at both ends. R28 is a pull-up resistor and R26 is a current limiting resistor.

[0081] The MCU includes an STM32F103C8T6 main controller, a wireless module connected to the main controller, a high-speed crystal oscillator circuit, a power-on reset circuit, a startup mode selection circuit, a power decoupling circuit and a program download circuit; the main controller is connected to a power supply through the power decoupling circuit.

[0082] like Fig. 9 As shown in the figure, STM32F103C8T6 is used as the main controller. The basic circuit of the SMT32 microcontroller needs to have an external high-speed crystal oscillator circuit, a power-on reset circuit, a startup mode selection circuit, a power decoupling circuit, and a program download circuit. Among them, C10 to C13 are decoupling circuits, SW1 is a reset circuit, X1 is a high-speed crystal oscillator, and H1 is a program download circuit. U1 is the main control chip, its 20th and 44th pins are power-on boot boots, resistors R11 and R10 are connected in series to the negative power supply, and pins 5 and 6 are external clock input pins, which need to be connected to both ends of the crystal oscillator X1, and C8 and C9 are connected to the negative power supply. H1 is the program burning interface, which is connected to the debug pins SWCLK and SWDIO of the main control. The main control has 3 power pins, which need to be connected to a 3.3V power supply, and capacitors C10, C11, and C13 are connected in parallel to act as filters. ADC1 and ADC2 are connected to the DC voltage detection output respectively. U13 is a wireless module, which can be connected to the serial port 2 of the MCU to expand the wireless control function.

[0083] Example 2

[0084] This embodiment provides a DC system automatic bus connection monitoring and control method. The DC system automatic bus connection monitoring and control method is based on a DC system bus connection circuit state monitoring device, such as Fig.10 As shown, the following steps are included:

[0085] Step 1: Install the DC system bus-coupled circuit state monitoring device in the substation, and connect the two sections of DC bus to the DC system bus-coupled circuit state monitoring device. Specifically, the positive input terminal 2 of the I-section DC bus and the negative input terminal 3 of the I-section DC bus of the DC system bus-coupled circuit state monitoring device are connected to the #1 DC bus, and the positive input terminal 4 of the II-section DC bus and the negative input terminal 5 of the II-section DC bus are connected to the #2 DC bus.

[0086] Step 2, real-time detection of the voltages of the two DC buses by the DC system bus-coupling circuit state monitoring device. Specifically, after the #1 DC bus passes through the I-section DC bus positive input terminal 2, the I-section DC bus negative input terminal 3, and a set of voltage detection circuits of the DC system bus-coupling circuit state monitoring device, the MCU calculates the #1 DC bus voltage according to the amplification factor and the voltage division ratio. After the #2 DC bus passes through the I-section DC bus positive input terminal 2, the II-section DC bus negative input terminal 5, and a set of voltage detection circuits of the DC system bus-coupling circuit state monitoring device, the MCU calculates the #2 DC bus voltage according to the amplification factor and the voltage division ratio.

[0087] Step 3, when the input part fails, only the battery is supplying power. When the battery continues to supply the load, the terminal voltage will drop. When it is detected that the terminal voltage of a certain DC bus is lower than the set value, the DC system bus circuit status monitoring device begins to determine whether the conditions for parallel connection of two DC buses are met.

[0088] Step 4, the DC system bus-coupled circuit status monitoring device determines whether the conditions for connecting the two DC busbars in parallel are met; if so, the DC system bus-coupled circuit status monitoring device controls the contactor to close, so that the two DC busbars are connected in parallel, and an alarm is sent to the background management system; if not, an alarm is directly sent to the background management system.

[0089] The DC system bus-tie circuit status monitoring device determines whether the parallel connection conditions of the two DC bus sections are met. Specifically, the MCU of the DC system bus-tie circuit status monitoring device determines whether the voltage difference of the #1 DC bus voltage calculated according to the amplification factor and the voltage division ratio, and the #2 DC bus voltage calculated according to the amplification factor and the voltage division ratio is within the specified range. If the voltage difference between the two DC buses is within 5V, the parallel connection condition is met; otherwise, the parallel connection condition is not met.

[0090] Example 3

[0091] On the basis of Example 2, in this embodiment, a current sensor is installed in the DC system bus tie loop state monitoring device; based on the current sensor, the load automatic transfer detection function and the loop resistance detection function are realized, and the DC system automatic bus tie monitoring and control method provided in Example 2 is optimized. Specifically, the DC system automatic bus tie monitoring and control method also includes:

[0092] Step 5: When the DC system bus-connecting circuit state monitoring device controls the contactor to close and connect the two sections of DC buses in parallel, the current of the DC bus is sampled by the current sensor inside the device.

[0093] If the voltage of DC bus #1 is higher than that of DC bus #2, the current sensor detects a positive current, and the MCU displays the positive current value through display screen 9, and transmits it to the background management system through the wireless module.

[0094] On the contrary, if the voltage of DC bus #2 is higher than that of DC bus #1, the current sensor detects a reverse current, and the MCU displays a negative current value through display screen 9, and transmits it to the background management system through the wireless module.

[0095] Based on this, the load automatic transfer detection function is realized to determine which DC bus supplies the load.

[0096] Step 6, after the #1 DC bus passes through the I-section DC bus positive input terminal 2, the I-section DC bus negative input terminal 3, and a set of voltage detection circuits of the DC system bus-coupling circuit state monitoring device, the MCU calculates the #1 DC bus voltage according to the amplification factor and the voltage division ratio. After the #2 DC bus passes through the I-section DC bus positive input terminal 2, the II-section DC bus negative input terminal 5, and a set of voltage detection circuits of the DC system bus-coupling circuit state monitoring device, the MCU calculates the #2 DC bus voltage according to the amplification factor and the voltage division ratio;

[0097] When the DC system bus-coupling circuit state monitoring device controls the contactor to close, so that the two sections of DC buses are connected in parallel, the current of the DC bus is sampled through the current sensor inside the device;

[0098] The MCU of the DC system bus-connection circuit status monitoring device calculates the resistance value of the two DC bus sections connected in parallel according to Ohm's law: I=U / R; based on the calculated resistance value, it determines whether the circuit resistance is too large. If so, an alarm is sent to the background management system.

[0099] It should be noted that in Example 2 and Example 3, since the DC system bus-coupled circuit status monitoring device is equipped with a wireless module, after the DC system bus-coupled circuit status monitoring device is installed, the background management system can remotely send electrical signals to the contactor separation control contacts of the device through the communication module to control the internal contactor of the device to close and close; at the same time, at the installation location of the DC system bus-coupled circuit status monitoring device, the contactor can be manually controlled to close and close by pressing buttons. The background management system can remotely control the closing and opening operations of the contactor through the communication module, enhance the operational flexibility and response speed, and adapt to changes in different needs. When necessary, the management personnel can achieve rapid control of the contactor through key operations, which is convenient for on-site maintenance and emergency handling.

[0100] In summary, based on the DC system automatic bus connection monitoring and control method, intelligent monitoring and control of the DC bus is realized, which not only improves the safety and stability of the system itself, but also reduces the operation and maintenance costs, significantly enhances the reliability and economy of the power system, and provides important support for the intelligent and automated development of modern power systems.

[0101] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for monitoring and controlling an automatic bus connection of a DC system, the method for monitoring and controlling an automatic bus connection of a DC system is based on a DC system bus connection loop state monitoring device, and is characterized in that: The following steps are involved: Step 1: Install the DC system bus-coupled circuit state monitoring device in the substation, and connect two sections of DC busbars to the DC system bus-coupled circuit state monitoring device; Step 2: Real-time detection of the voltages of the two DC buses by a DC system bus-coupling circuit status monitoring device; Step 3: When the input part fails, only the battery is supplying power. When the battery continues to supply the load, the terminal voltage will drop. When it is detected that the terminal voltage of a certain DC bus is lower than the set value, the DC system bus coupling circuit state monitoring device starts to determine whether the conditions for parallel connection of two sections of DC buses are met; Step 4, the DC system bus-coupled circuit status monitoring device determines whether the conditions for connecting the two DC busbars in parallel are met; if so, the DC system bus-coupled circuit status monitoring device controls the contactor to close, so that the two DC busbars are connected in parallel, and an alarm is sent to the background management system; if not, an alarm is directly sent to the background management system.

2. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 1, characterized in that: The DC system bus-connection circuit status monitoring device determines whether the parallel connection conditions of the two DC bus sections are met. It makes the judgment based on whether the voltage difference between the two DC bus sections is within the specified range. When the voltage difference between the two DC bus sections is within 5V, the parallel connection conditions are met; otherwise, the parallel connection conditions are not met.

3. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 1, characterized in that: The DC system bus-coupled circuit state monitoring device comprises a device housing, a group of positive and negative input terminals of a segment I DC bus installed on one side of the device housing, a group of positive and negative input terminals of a segment II DC bus installed on the other side of the device housing, a display screen installed above the device housing, and a control circuit board, an air switch and a DC contactor located inside the device housing and connected to a group of positive and negative input terminals of a segment I DC bus and a group of positive and negative input terminals of a segment II DC bus respectively; The control circuit board is electrically connected to the display screen and the DC contactor; the positive and negative input terminals of the I-section DC bus and the positive and negative input terminals of the II-section DC bus are respectively connected to the two DC buses.

4. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 1, characterized in that: The control circuit board is equipped with an MCU, a power supply electrically connected to the MCU, a voltage detection circuit electrically connected to the positive and negative input terminals of the I-section DC bus and the II-section DC bus, a contactor control circuit electrically connected to the DC contactor, and a wireless module electrically connected to the MCU.

5. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 4, characterized in that: The voltage detection circuit is divided into two groups, and each group of voltage detection circuits includes two groups of voltage divider networks composed of a number of resistors, and an isolated operational amplifier connected to the voltage divider network; the voltage divider network of each group of voltage detection circuits is connected to the external voltage monitoring interface, and the isolated operational amplifier is connected to the MCU through a current limiting resistor.

6. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 4, characterized in that: The power supply includes an AC / DC conversion module, the input end of the AC / DC conversion module is connected to an external power supply, and the output end is connected to the input end of the buck regulator LMR14050; the output end of the buck regulator LMR14050 is connected to the input end of the second-stage buck regulator U9, and the output end of U9 is connected to the MCU.

7. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 4, characterized in that: The contactor control circuit includes a contactor, a relay and a phototransistor; the output end of the MCU is connected to the base of the phototransistor, when the MCU outputs a low level, the phototransistor is turned on, and the relay contacts are closed; conversely, when the MCU outputs a high level, the phototransistor is disconnected, and the relay contacts are opened; the relay controls the coil of the contactor, when the normally open contact of the relay is closed, the contactor coil is energized, the main contacts are closed, and the DC bus is connected.

8. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 4, characterized in that: The MCU comprises an STM32F103C8T6 main controller, a wireless module connected to the main controller, a high-speed crystal oscillator circuit, a power-on reset circuit, a startup mode selection circuit, a power decoupling circuit and a program download circuit; the main controller is connected to a power supply through the power decoupling circuit.

9. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 1, characterized in that: The DC system automatic bus connection monitoring and control method also includes: Step 5, when the DC system bus-coupled circuit state monitoring device controls the contactor to close and connects the two sections of DC bus in parallel, the current sensor inside the device samples the current of the DC bus; if the voltage of the #1 DC bus is higher than the voltage of the #2 DC bus, the current sensor monitors a positive current, the MCU displays a positive current value on the display screen, and transmits it to the background management system through the wireless module; conversely, if the voltage of the #2 DC bus is higher than the voltage of the #1 DC bus, the current sensor monitors a reverse current, the MCU displays a negative current value on the display screen, and transmits it to the background management system through the wireless module; in this way, it is determined which DC bus supplies the load; Step 6: Based on the voltage detection of the two DC buses in step 4 and the current sampling of the DC bus by the current sensor in step 5, the DC system bus-connected loop status monitoring device calculates the resistance value of the two DC buses in parallel according to Ohm's law; based on the calculated resistance value, it is determined whether the loop resistance is too large, and if so, an alarm is sent to the background management system.

10. The method for monitoring and controlling the automatic bus connection of a DC system according to claim 1, characterized in that: After the DC system bus-coupled circuit status monitoring device is installed, the background management system can remotely send electrical signals to the contactor opening and closing control contacts of the device through the communication module to control the closing and closing of the internal contactors of the device; at the same time, at the installation location of the DC system bus-coupled circuit status monitoring device, the closing and closing of the contactors can be manually controlled by buttons.

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