Universal high voltage direct current intelligent contactor based on isolated current detection and method

Abstract

The application relates to a unified high-voltage direct-current intelligent contactor and method based on isolated current detection, which is suitable for the field of 270V and 540V high-voltage direct-current intelligent power distribution. The current can be isolated and sampled, the safety is relatively high, and the current range of sampling is wide. The sampling scheme is simple, the cost is relatively low, the shunt is integrated on the bus bar, and the weight and volume of the power distribution product can be greatly reduced. Meanwhile, based on the position recognition and load specification recognition method of the machine position code, corresponding I 2 T overcurrent protection curve, the functions of the intelligent control module at the corresponding machine position are executed, unified design of the high-voltage direct-current intelligent contactor control module is facilitated, and the technical state management and quality control of the product are easier. Moreover, the intelligent control modules at different machine positions are interchangeable and can be replaced in the field, so that the maintainability and security of the product are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of aviation high-voltage DC intelligent power distribution, and relates to a unified high-voltage DC intelligent contactor and method based on isolated current detection. Specifically, it relates to a load current isolation detection and intelligent control module specification identification method applicable to 270V and 540V high-voltage DC power supply systems. Background Technology

[0002] Currently, in the field of aviation power systems, with the increasing variety and capacity of loads, the complexity of power distribution centers is growing. Highly reliable and interference-resistant intelligent power distribution control technology plays an increasingly important role in the safe operation, fault monitoring, fault protection, and isolation of power distribution systems. Currently, AC intelligent power distribution technology is maturing, while high-voltage DC intelligent power distribution technology is still in the research stage. A single-line diagram of a certain high-voltage DC intelligent power distribution system is shown below. Figure 1 As shown. Intelligent power distribution is accomplished by intelligent contactors (SMTC), and its principle is as follows. Figure 2 As shown, it mainly consists of three parts: a high-voltage DC contactor, an intelligent control module (SMTCCU), and a current detection module. The high-voltage DC contactor distributes power to high-power loads, while the intelligent control module provides control, overcurrent protection, status monitoring, fault isolation, and communication functions for the contactor. The current detection module detects the load current. Its core technology is the intelligent control module design technology.

[0003] Traditional intelligent control modules are available in series for different loads, with specifications such as 35A, 50A, 75A, 100A, 150A, and 300A. Different specifications of intelligent control modules have different current sampling and conditioning circuits, requiring hardware matching resistors for specification selection. This makes it difficult to control the technical condition and product quality, and the load channels of different power distribution branches are not interchangeable, posing certain difficulties for field maintenance and repair. Summary of the Invention

[0004] Technical problems to be solved

[0005] To overcome the shortcomings of existing technologies, this invention proposes a standardized high-voltage DC intelligent contactor and method based on isolated current detection. The hardware and software design remain completely identical for different machine locations and load specifications. Employing a shunt-based isolated current sampling and conditioning circuit scheme and an external connector pin encoding scheme for machine position signals, it features low cost, online programmable load specifications, and high flexibility, making technical status management and quality control easier. Furthermore, it offers interchangeability; the intelligent control modules at different machine positions can be replaced in the field, greatly improving product maintainability and reliability.

[0006] Technical solution

[0007] A unified high-voltage DC intelligent contactor based on isolated current detection includes a contactor connected between a high-voltage DC busbar and each load; its key feature is that it also includes an intelligent contactor control module connected to the contactor; the intelligent contactor control module includes a CPU minimum system, a power processing circuit, a level conversion circuit, a current sampling and conditioning circuit, a discrete input acquisition circuit, a discrete status output circuit, a contactor output positive and negative control drive circuit, a BIT test circuit, a CAN communication circuit, and a machine position code recognition circuit; the current sampling and conditioning circuit acquires the current signal of the load and sends it to the CPU for real-time monitoring of the load branch current; the discrete signal sampling and conditioning circuit acquires discrete signals, including the normally closed and normally open contact signals of the contactor, and sends them to the CPU for discrete status monitoring through the level conversion circuit; the CPU minimum system, based on the acquired signals... The system uses analog and discrete signals to control the contactor; the positive and negative control drive circuits amplify the contactor control signals output by the CPU and output them to the two ends of the contactor coil to control the contactor's on / off circuit; the discrete signal status output circuit outputs the discrete overcurrent signal in hard-wired form; the CAN communication transceiver circuit communicates with the host computer, uploading relevant electrical parameters, status information, and fault information of the power distribution branch to the host computer; the power supply processing circuit converts the two external 28V power supplies into ±15V and 5V power supplies to power each circuit module; the BIT test circuit generates a current excitation signal and checks the current sampling and conditioning circuit during BIT self-test to determine if it is working properly; the machine position code recognition circuit receives 4-bit machine position codes, recognizes the permutation and combination of the 4-bit machine position codes, and inputs them into the CPU to select different I... 2 The T-overcurrent protection curve enables current protection for the corresponding load specifications.

[0008] The current sampling and conditioning circuit includes an isolation operational amplifier U1, a high-precision operational amplifier U2, a reference voltage chip U4, an isolation voltage conversion chip U3, a differential-mode filter circuit composed of R2, R7, and C4, as well as bias resistors and capacitors for each chip; the differential voltage across the shunt is V shunt_P -V shunt_NThe differential-mode noise is filtered out by a differential-mode filter circuit composed of R2, R7, and C4, and the common-mode noise is filtered out by capacitor C6. After processing by the isolation operational amplifier U1, the voltage is amplified to -2.05 to 2.05V. Then, after level conversion by a differential amplifier circuit composed of R1, R3, R6, R8 and high-precision operational amplifier U2, a 1.5V reference bias voltage is superimposed, and the final output voltage becomes 0 to 3V, which is sent to the AD sampling circuit for AD digital-to-analog conversion. During the operation of the circuit, since the isolation operational amplifier U1 requires an isolated power supply, an isolation voltage conversion chip U3 is set to realize the isolation processing of the 5V to 5V power supply. The isolated 5V power supply is 5V_ISO, which supplies power to the high-voltage side of the isolation operational amplifier. U4 is a reference voltage chip that realizes the conversion of 5V to 1.5V voltage, generating a high-precision 1.5V reference voltage.

[0009] The CPU minimum system is connected to a watchdog circuit to ensure reliable program operation and monitor CPU operating status.

[0010] The CPU minimum system is connected to the storage circuit to record monitoring data and fault information.

[0011] A method for overcurrent protection using the aforementioned unified high-voltage DC intelligent contactor based on isolated current detection, characterized by the following steps:

[0012] Step 1: Acquire the output voltage V of the current sampling and conditioning circuit. o Calculate the actual current value:

[0013]

[0014] Among them, R shunt The shunt resistor value, V o This refers to the output voltage.

[0015]

[0016] Among them, V shunt =V shunt_P -V shunt_N V is the voltage across the shunt. shunt =I*R shunt =I*R5;

[0017] Step 2: Define the position code for each intelligent power distribution channel of the high voltage DC intelligent power distribution system according to the machine position identification code configuration table, that is, define the pin-based encoding of the 4-bit machine position code discrete signal outside each intelligent control module;

[0018] Camera Position Identification Code Configuration Table

[0019]

[0020] Step 3: Based on the load current specifications obtained in Step 2, calculate the corresponding overcurrent protection threshold value for each specification;

[0021] Step 4: Based on the actual current value obtained in Step 1, determine the overcurrent condition: when the actual current exceeds the overcurrent protection threshold value of the corresponding specification, proceed according to I. 2 The T-inverse delay curve is used to calculate the accumulated heat. When the delay time is up, overcurrent protection is activated and the control contactor is disconnected; otherwise, overcurrent protection is not activated.

[0022] The overcurrent protection threshold is 1.265 times the rated current.

[0023] The I 2 The formula for calculating the T-inverse delay curve is: I0 is the rated load current.

[0024] Beneficial effects

[0025] This invention proposes a unified high-voltage DC intelligent contactor and method based on isolated current detection. For different load specifications, the intelligent control module uses an isolated current sampling scheme based on a shunt, applicable to 270V and 540V high-voltage DC intelligent power distribution. It achieves isolated current sampling, offering high safety and a wide sampling current range. The sampling scheme is simple and low-cost; the shunt is integrated into the busbar, significantly reducing the weight and size of the power distribution product. Furthermore, based on the location identification and load specification identification method using the machine position code, it can programmably and automatically select the corresponding It through different permutations and combinations of the machine position code. 2 The T-overcurrent protection curve executes the function of the intelligent control module at the corresponding machine location, facilitating the standardized design of the high-voltage DC intelligent contactor control module and making product technical status management and quality control easier. Furthermore, it is interchangeable; the intelligent control modules at different machine locations can be replaced in the field, greatly improving the product's maintainability and reliability. Attached Figure Description

[0026] Figure 1 Single-line diagram of a high-voltage DC intelligent power distribution system

[0027] Figure 2 High-voltage DC intelligent contactor schematic diagram

[0028] Figure 3 Hardware block diagram of the intelligent control module

[0029] Figure 4 Principle of Load Current Isolation Detection and Specification Identification for Integrated Intelligent Control Module

[0030] Figure 5 Shunt-based isolated current sampling and conditioning circuit Detailed Implementation

[0031] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0032] A unified high-voltage DC intelligent contactor based on isolated current detection includes a contactor connected between a high-voltage DC busbar and each load; its characteristic is that it also includes an intelligent contactor control module connected to the contactor.

[0033] The hardware block diagram of the intelligent control module is as follows: Figure 3 As shown, it mainly consists of the following functional circuits: CPU minimum system, power supply processing circuit, watchdog circuit, storage circuit, level conversion circuit, current sampling and conditioning circuit, discrete input acquisition circuit, discrete status output circuit, contactor output drive circuit (positive / negative control), BIT test circuit, and CAN communication circuit. The functional principles of each circuit are as follows:

[0034] The current sampling and conditioning circuit acquires and conditions the current signal, and sends it to the CPU for real-time monitoring of the load branch current.

[0035] The discrete signal sampling and conditioning circuit acquires and conditions discrete signals, and sends them to the CPU for discrete quantity status monitoring through a level conversion circuit.

[0036] The CPU minimum system implements contactor control, overcurrent protection, self-testing, status monitoring, and communication functions based on the collected analog and discrete quantities.

[0037] The contactor output drive circuit (positive control / negative control) amplifies the contactor control signal output by the CPU after software logic judgment, and finally outputs it to both ends of the contactor coil to control the contactor's on / off state.

[0038] Discrete quantity status output circuits output overcurrent and other status conditions in discrete quantity hard-wired form.

[0039] The CAN communication transceiver circuit is used to communicate with the host computer and upload relevant electrical parameters, status information, and fault information of the power distribution branch to the host computer.

[0040] The storage circuit records monitoring data and fault information.

[0041] An externally designed watchdog circuit is used to ensure the reliable operation of the program and to monitor the CPU's operating status.

[0042] The power processing circuit filters, regulates, and converts the two externally supplied 28V power supplies into ±15V and 5V power supplies to power each circuit module.

[0043] The BIT test circuit is used to generate a current excitation signal. During BIT self-test maintenance, the current sampling and conditioning circuit is checked to determine whether it is working properly.

[0044] The principle of the unified intelligent control module load current isolation detection and specification identification scheme is as follows: Figure 4 As shown. The load current is detected using an electrically isolated method based on positive line sampling. The shunt is connected in series in the busbar at the rear of the contactor's main contacts. The shunt converts the load current into a weak voltage signal in the mV range. After processing by the isolated current sampling and conditioning circuit, it is converted to a 0-3V voltage and sent to the DSP's AD conversion module for current sampling. For different load specifications (35A, 50A, 75A, 100A, 150A, 300A), different isolated current sampling and conditioning circuits and I... 2 The overcurrent protection algorithm is exactly the same, requiring no adjustment of coefficients or parameters. The intelligent control module uses a 4-bit machine position identification code (ID1~ID4) to determine the current specifications and machine position. The high-order bit (ID4) is used for machine position identification, determining whether it is the left or right power distribution center; the low-order bits (ID1~ID3) can identify eight load specifications to distinguish different channel loads. After passing through the machine position code identification circuit, the 4-bit machine position identification code is sent to the DSP's GPIO port; the DSP selects different I / O ports based on the permutation and combination of the 4-bit code. 2 The T-overcurrent protection curve enables current protection for the corresponding load specifications.

[0045] The arrangement and combination of the 4-digit serial number is defined by the pin coding of the external electrical connector, and is controlled by grounding the corresponding lines. During use, the SMTCCU should be configured according to the configuration table shown in Table 1. See... Figure 4 The principle of load current isolation detection and specification identification of the unified intelligent control module.

[0046] Table 1. Configuration Table of Camera Position Identification Code

[0047]

[0048]

[0049] See the isolated current sampling and conditioning circuit. Figure 5As shown, this circuit enables isolated sampling and conditioning of the load current, suitable for 270V and 540V high-voltage DC power distribution systems. Considering the impact of the high-voltage DC voltage across the shunt on the acquisition accuracy, this invention employs a low-power, high-precision isolation amplifier chip for current sampling. Its input voltage range is ±250mV, with a fixed gain of 8.2, and it features low nonlinearity, low input offset voltage, and low gain drift. An internal isolation barrier with high magnetic field immunity isolates the output from the input. The isolation barrier can provide a maximum isolation voltage of 5kVRMS.

[0050] To improve the current sampling range, reduce the power loss of the shunt (R5), and improve sampling accuracy, a shunt of 0.4mΩ is selected for small load (<80A) current sampling; a shunt of 0.25mΩ is selected for large load (≥80A, ≤150A) current sampling; and a shunt of 0.1mΩ is selected for ultra-large load (>150A, ≤300A). Figure 4 Suitable for shunts with a voltage range of -250 to 250mV, its working principle is based on the differential voltage (V) across the shunt. shunt_P -V shunt_N The differential-mode noise is filtered out by a differential-mode filter circuit composed of R2, R7, and C4, and the common-mode noise is filtered out by capacitor C6. Then, after processing by the isolation operational amplifier U1, the voltage is amplified to -2.05V to 2.05V. After level conversion by a differential amplifier circuit composed of R1, R3, R6, R8, and the high-precision operational amplifier U2, a 1.5V reference bias voltage is superimposed, resulting in a final output voltage of 0-3V. This voltage is then fed into the AD sampling circuit for digital-to-analog conversion. During circuit operation, because the isolation operational amplifier U1 requires an isolated power supply, an isolation voltage conversion chip U3 is used to achieve 5V to 5V power supply isolation. The isolated 5V power supply is 5V_ISO, which powers the high-voltage side of the isolation operational amplifier. U4 is a reference voltage chip that can convert 5V to 1.5V, generating a high-precision 1.5V reference voltage.

[0051] The principle calculation of the current sampling and conditioning circuit is as follows:

[0052] Output voltage V o for

[0053]

[0054] Among them, V shunt =V shunt_P -V shunt_N This is the voltage across the shunt.

[0055] V shunt =I*R shunt =I*R5. (2)

[0056] Based on equations (1) and (2), the formula for calculating the load current is as follows:

[0057]

[0058] Among them, R shunt This is the resistance value of the shunt.

[0059] Identification steps:

[0060] Step 1: Follow Figure 4 The circuit shown collects the output voltage of the current sampling conditioning circuit and calculates the actual load current value according to formula (3);

[0061] Step 2: According to Table 1 Figure 1 In the high-voltage DC intelligent power distribution system, each intelligent power distribution channel is defined with a position code. That is, the 4-bit discrete signal of the machine position code is defined by pin insertion outside each intelligent control module. For example, 00 represents the first load specification of 35A in the left power distribution center, and 01 represents the second load specification of 50A in the left power distribution center.

[0062] Step 3: Based on the load current specifications obtained in Step 2, calculate the corresponding overcurrent protection threshold value for each specification, which is 1.265 times the rated current.

[0063] Step 4: Based on the actual current value obtained in Step 1, determine the overcurrent condition. When the actual current exceeds the overcurrent protection threshold value of the corresponding specification, proceed according to I... 2 T-inverse delay curve ( I0 (where I0 is the rated load current) is used for heat accumulation calculation. When the delay time expires, overcurrent protection is activated, and the control contactor disconnects. Otherwise, overcurrent protection is not activated.

Claims

1. A method for overcurrent protection using a standardized high-voltage DC intelligent contactor based on isolated current detection, characterized in that, The standardized high-voltage DC intelligent contactor based on isolated current detection includes: a contactor connected between the high-voltage DC busbar and each load, and an intelligent contactor control module connected to the contactor; the intelligent contactor control module includes a CPU minimum system, a power processing circuit, a level conversion circuit, a current sampling and conditioning circuit, a discrete input acquisition circuit, a discrete status output circuit, a contactor output positive and negative control drive circuit, a BIT test circuit, a CAN communication circuit, and a machine position code recognition circuit; the current sampling and conditioning circuit acquires the current signal of the load and sends it to the CPU for real-time monitoring of the load branch current; the discrete signal sampling and conditioning circuit acquires discrete signals, including the normally closed and normally open contact signals of the contactor, and sends them to the CPU for discrete status monitoring through the level conversion circuit; the CPU minimum system, based on the acquired analog signals... The system includes discrete quantity output circuits to control the contactor; positive and negative control drive circuits amplify the contactor control signals output by the CPU and output them to the two ends of the contactor coil to control the contactor's on / off circuit; discrete quantity status output circuits output overcurrent signals as separate discrete signal lines; CAN communication transceiver circuits are used to communicate with the host computer, uploading relevant electrical parameters, status information, and fault information of the power distribution branch to the host computer; power supply processing circuits convert two external 28V power supplies into ±15V and 5V power supplies to power each circuit module; BIT test circuits generate current excitation signals and check the current sampling and conditioning circuits during BIT self-tests to determine if they are working properly; the machine position code recognition circuit receives 4-bit machine position codes, recognizes the permutations and combinations of the 4-bit machine position codes, and inputs them into the CPU to select different I... 2 The T-overcurrent protection curve enables current protection for the corresponding load specifications; The current sampling and conditioning circuit includes an isolation operational amplifier U1, a high-precision operational amplifier U2, a reference voltage chip U4, an isolation voltage conversion chip U3, a differential-mode filter circuit composed of R2, R7, and C4, as well as bias resistors and capacitors for each chip; the differential voltage across the shunt is... Differential-mode noise is filtered out by a differential-mode filter circuit composed of R2, R7, and C4, and common-mode noise is filtered out by capacitor C6. After processing by the isolation operational amplifier U1, the voltage is amplified to -2.05V to 2.05V. Then, after level conversion by a differential amplifier circuit composed of R1, R3, R6, R8, and the high-precision operational amplifier U2, a 1.5V reference bias voltage is superimposed, resulting in an output voltage of 0-3V, which is then sent to the AD sampling circuit for digital-to-analog conversion. During circuit operation, since the isolation operational amplifier U1 requires an isolated power supply, an isolation voltage conversion chip U3 is used to achieve 5V to 5V power supply isolation. The isolated 5V power supply is 5V_ISO, which powers the high-voltage side of the isolation operational amplifier. U4 is a reference voltage chip that converts 5V to 1.5V, generating a high-precision 1.5V reference voltage. The overcurrent protection method has the following steps: Step 1: Acquire the output voltage of the current sampling and conditioning circuit. Calculate the actual current value: in, This is the shunt resistor value. This refers to the output voltage. in, The voltage across the shunt is ; Step 2: Define the position code for each intelligent power distribution channel of the high voltage DC intelligent power distribution system according to the machine position identification code configuration table, that is, define the pin-based encoding of the 4-bit machine position code discrete signal outside each intelligent control module; The configuration information for the machine location identification code is as follows: where "0" indicates that the signal is open and "1" indicates that the signal is grounded, and the rated current of the load is the load specification. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 0000, it is the first load, and the rated load current is 35A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 0001, it is the second load, and the rated load current is 50A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 0010, it is the third load, and the rated load current is 50A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 0011, it is the 4th load, and the rated load current is 75A. When the addresses ID4, ID3, ID2, and ID1 are in the state of 0100, it is the 5th load, and the rated current of the load is 100A. When the address identification codes ID4, ID3, ID2, and ID1 are in the states of 0101, it is the 6th load, and the rated load current is 150A. When the address identification codes ID4, ID3, ID2, and ID1 are in the states of 0110, it is the 7th load, and the rated load current is 300A. When the address identification codes ID4, ID3, ID2, and ID1 are in the state of 0111, it is the 8th load, and the rated load current is 100A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1000, it is the 9th load, and the rated load current is 100A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1001, it is the 10th load, and the rated load current is 150A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1010, it is the 11th load, and the rated load current is 100A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1011, it is the 12th load, and the rated load current is 75A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1100, it is the 13th load, and the rated load current is 50A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1101, it is the 14th load, and the rated load current is 150A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1110, it is the 15th load, and the rated load current is 75A. When the address identification codes ID4, ID3, ID2, and ID1 are all in the state of 1111, it is the 16th load, and the rated load current is 35A. Step 3: Based on the load current specifications obtained in Step 2, calculate the corresponding overcurrent protection threshold value for each specification; Step 4: Based on the actual current value obtained in Step 1, determine the overcurrent condition: when the actual current exceeds the overcurrent protection threshold value of the corresponding specification, proceed according to I. 2 The T-inverse delay curve is used to calculate the accumulated heat. When the delay time is up, overcurrent protection is activated and the control contactor is disconnected; otherwise, overcurrent protection is not activated.

2. The method for overcurrent protection using a standardized high-voltage DC intelligent contactor based on isolated current detection according to claim 1, characterized in that: The CPU minimum system is connected to a watchdog circuit to ensure reliable program operation and monitor CPU operating status.

3. The method for overcurrent protection using a standardized high-voltage DC intelligent contactor based on isolated current detection according to claim 1, characterized in that: The CPU minimum system is connected to the storage circuit to record monitoring data and fault information.

4. The method for overcurrent protection using a standardized high-voltage DC intelligent contactor based on isolated current detection according to claim 1, characterized in that: The overcurrent protection threshold is 1.265 times the rated current.

5. The method for overcurrent protection using a standardized high-voltage DC intelligent contactor based on isolated current detection according to claim 1, characterized in that: The I 2 The formula for calculating the T-inverse delay curve is: , This is the rated load current.

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