An electric compressor controller overload protection method and system

Abstract

This invention discloses an overload protection method for an electric compressor controller. When the compressor speed is in the low-speed range, a dynamic compressor load protection strategy is executed. During this strategy, compressor parameters are acquired in real time. Based on the compressor load, compressor speed, and a preset phase current RMS protection threshold, the current phase current RMS protection threshold is obtained according to the current compressor load, compressor speed, and compressor speed. The current compressor phase current RMS value is compared with the protection threshold to determine whether an overload protection shutdown strategy should be triggered. This invention prioritizes overload shutdown protection before the IGBT (Integrated Geometric Transformer) begins to accumulate heat under low-speed, high-load conditions, preventing frequent overheating that could lead to IGBT thermal breakdown. This dynamic overload protection strategy offers higher accuracy and faster response, providing pre-emptive overload protection for IGBT temperature under low-speed, high-load conditions.

Description

Technical Field

[0001] This invention relates to the field of automotive air conditioning technology, and in particular to a dynamic overload protection technology for the temperature of an electric compressor controller. Background Technology

[0002] The market penetration rate of new energy vehicles is steadily increasing, and the application scope of electric compressors is expanding significantly accordingly. According to industry surveys, semiconductor devices in converter systems are the most prone to failure, accounting for 34% of all failures, with over-temperature failures accounting for 55% of all semiconductor device failures. The electric compressor controller is a typical converter system; its core function is to convert the high-voltage DC power input from the vehicle battery into three-phase AC power by controlling the switching and conduction of power devices. This AC power is then supplied to the motor to drive mechanical components to compress the gaseous refrigerant, achieving the vehicle's cooling / heating functions. In the thermal management system, the electric compressor's main function is to compress low-temperature, low-pressure gaseous refrigerant (intake port) into high-temperature, high-pressure gaseous refrigerant (exhaust port). During operation, the low-temperature gaseous refrigerant at the intake port washes over the metal wall of the controller housing on the other side of the IGBT mounting location, carrying away the heat generated by the IGBT. When the compressor operates at low speed, the refrigerant flow rate is low, and the IGBT's heat dissipation effect deteriorates. When the system load is high, the IGBT power and heat generation increase simultaneously. Therefore, for electric compressors, low speed and high load conditions are the worst operating conditions. Under these conditions, the heat generated by the IGBT is higher than the heat dissipation, and the rapid accumulation of heat leads to a sharp increase in temperature, making the probability of overheating and breakdown much higher than under other conditions.

[0003] The common temperature protection measure for discrete IGBT devices is to set a thermistor (NTC) to collect the temperature of the IGBT pin in real time. When the collected temperature reaches the set over-temperature protection threshold, the compressor will stop for protection.

[0004] For example, the published document with announcement number CN117028226B, publication date November 10, 2023, and patent title "A Control Method for a Compressor System, a Compressor System and a Vehicle" discloses a control method for a compressor system that includes: acquiring the current temperature of a switching element; controlling an electric compressor to enter a first shutdown state when the current temperature is greater than or equal to a first preset temperature threshold; and controlling the electric compressor to enter a second shutdown state when the number of times the electric compressor enters the first shutdown state reaches a first preset number threshold, wherein the shutdown time of the electric compressor in the second shutdown state is greater than the shutdown time in the first shutdown state.

[0005] The temperature value obtained by monitoring the IGBT pin temperature through NTC will have a certain error with the actual temperature of the IGBT internal wafer, and there will be a time lag. The temperature feedback lag problem is particularly serious during the stage of rapid heat accumulation and heating, which greatly increases the probability of IGBT over-temperature breakdown. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to achieve a method that avoids frequent overheating leading to thermal breakdown of IGBT, so that the overload protection of the electric compressor controller is more accurate and the response is faster, and the temperature of IGBT is protected in advance by overload protection under low speed and high load conditions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: an overload protection method for an electric compressor controller, wherein when the compressor speed is in the low speed range, a dynamic protection strategy for compressor load is executed;

[0008] When implementing the compressor load dynamic protection strategy, the compressor parameters are acquired in real time, including the compressor load, the effective value of the compressor phase current, the compressor speed, and the compressor input bus voltage.

[0009] Based on the compressor load, compressor speed, and a preset phase current effective value protection threshold, the phase current effective value protection threshold is obtained according to the current compressor load, compressor speed, and compressor speed. The current compressor phase current effective value is compared with the phase current effective value protection threshold to determine whether an overload protection shutdown strategy is triggered.

[0010] The method for determining whether the overload protection shutdown strategy is triggered is as follows: if the effective value of the compressor phase current monitored by the compressor reaches the effective value protection threshold of the currently executed phase current and the duration is >2s, the compressor overload shutdown protection strategy is triggered.

[0011] When the compressor load, compressor speed, and compressor speed are preset with a phase current RMS protection threshold, the standard includes:

[0012] The effective value of the compressor phase current is positively correlated with the compressor load;

[0013] Under the same load, the compressor I GBT temperature is negatively correlated with the compressor speed.

[0014] At the same rotational speed and bus voltage, the compressor I GBT temperature is positively correlated with the compressor load.

[0015] At the same speed and load, the compressor I GBT temperature is positively correlated with the high-voltage bus voltage.

[0016] The compressor speed is set in 200 rpm intervals as a current level, and the effective value protection threshold of the phase current is set under different bus voltage values ​​in each speed range.

[0017] The effective value protection threshold of phase current = k × bus voltage + T, where k and T are constants.

[0018] When the compressor speed is in the high speed range, the effective value of the compressor phase current is obtained. When the effective value of the phase current is greater than the protection constant threshold and is maintained for more than the set time, the compressor overload shutdown protection is activated.

[0019] The low speed range is defined as the upper limit of the compression speed being 2800rpm-3200rpm and the lower limit being 600rpm-900rpm. The high speed range is defined as the compressor speed being above the low speed range. The protection constant threshold is 17A.

[0020] When the compressor is working, the temperature of the IGBT pin is acquired in real time. When the detected temperature reaches the set temperature, the over-temperature protection strategy is triggered.

[0021] The set temperature is 105℃. When the over-temperature protection strategy is executed, the compressor is controlled to stop. After the over-temperature protection strategy is triggered, if the temperature of the IGBT pin is lower than 100℃ and the fault disappears after the over-temperature shutdown time is greater than 30 seconds, the compressor is controlled to restart.

[0022] An overload protection system for an electric compressor controller includes an NTC attached to an IGBT. The NTC is connected to and outputs a sensing signal to the controller assembly of the electric compressor. The controller assembly acquires the compressor load, effective value of compressor phase current, compressor speed, and input bus voltage of the electric compressor. The controller assembly executes the overload protection method for the electric compressor controller.

[0023] This invention's electric compressor controller overload protection system and method, while retaining conventional NTC temperature detection and protection schemes, adds a dynamic protection strategy for compressor load in the low-speed range of 800rpm to 3000rpm. Under low-speed, high-load conditions, before the IGBT heat begins to accumulate but the temperature reaches its crystallization temperature of 175°C, the overload shutdown protection strategy is prioritized to prevent frequent overheating leading to IGBT thermal breakdown. This dynamic overload protection strategy offers higher accuracy and faster response, providing pre-emptive overload protection for IGBT temperature under low-speed, high-load conditions. Attached Figure Description

[0024] The following is a brief explanation of the content and markings in each of the accompanying drawings in this specification:

[0025] Figure 1 This is a schematic diagram of the compressor structure;

[0026] The markings in the above figures are: 1-compressor intake port; 2-compressor exhaust port; 3-controller assembly; 4-drive motor assembly; 5-mechanical compression structure. Detailed Implementation

[0027] The following description, with reference to the accompanying drawings, details the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0028] The temperature values ​​obtained by monitoring the IGBT pins via NTC have a certain margin of error compared to the actual temperature of the IGBT's internal wafer, and there is also a time lag, especially during the rapid heat accumulation phase. This temperature feedback lag is particularly severe, significantly increasing the probability of IGBT over-temperature breakdown. To address this issue, this invention, in addition to retaining the conventional NTC temperature detection and protection scheme, adds a dynamic compressor load protection strategy in the low-speed range. During the low-speed, high-load heat accumulation phase, before the IGBT temperature rises to its upper limit, the compressor prioritizes the overload shutdown protection strategy to avoid frequent over-temperature shutdowns that could lead to IGBT over-temperature breakdown.

[0029] This invention attaches a thermistor (NTC) to the IGBT device of an electric compressor. The controller assembly 3 is connected to and acquires the temperature signal of the NTC. The controller assembly 3 is connected to and outputs a control signal to the drive motor assembly 4. The controller assembly 3 outputs a control signal to the drive motor assembly 4 based on the temperature signal of the NTC. At the same time, the controller assembly 4 acquires the compressor load, the effective value of the compressor phase current, the compressor speed, and the input bus voltage of the electric compressor. The controller assembly executes a new overload protection method for the electric compressor controller.

[0030] The overload protection method of the electric compressor controller retains the original IGBT temperature protection strategy, that is, by monitoring the IGBT pin temperature through NTC, when the detected temperature reaches 105℃, the over-temperature protection strategy is triggered, and the compressor stops for self-protection.

[0031] The temperature of the IGBT metal pins is monitored by an NTC (Network Temperature Controller). Through heat conduction in the metal material, the internal wafer temperature is transferred to the pins. When the NTC-monitored temperature reaches 105°C, an over-temperature protection strategy is triggered, and the compressor shuts down as a self-protection mechanism. The fault disappears and the compressor restarts after the NTC-monitored temperature drops below 100°C and the over-temperature shutdown time exceeds 30 seconds.

[0032] While implementing the above control method, a new dynamic protection strategy for compressor load in the low-speed range (800rpm-3000rpm) is added. Based on the correlation between four parameters—compressor load (i.e., suction / discharge pressure), compressor phase current RMS value, compressor speed, and input bus voltage—data calibration under multiple operating conditions in the low-speed range is performed on a test bench. This yields the calculation formulas for the phase current RMS protection threshold and the speed and bus voltage, thus establishing the phase current RMS protection threshold for each speed range and different input bus voltage values. During normal operation, when the phase current RMS value reaches the set protection threshold, it indicates that the heat generated by the controller IGBT under this load exceeds the heat dissipation, and its temperature will accumulate rapidly. Two seconds after the phase current RMS value reaches the protection threshold, an overload protection shutdown strategy is triggered, promptly cutting off the compressor before the IGBT temperature rises to a risk value, thus preventing IGBT failure caused by frequent IGBT overheating under low-speed, high-load conditions.

[0033] Specifically

[0034] When the speed is above 3000 rpm, the compressor phase current protection threshold is constant at 17A. That is, if the effective value of the phase current is greater than 17A for more than 2 seconds, the compressor will be shut down due to overload.

[0035] A dynamic load protection strategy for the compressor in the low-speed range (800rpm-3000rpm) is added. Based on the compressor unit bench calibration data in Table 1 below, the relationship between the following parameters can be basically derived:

[0036] 1. The effective value of the compressor phase current is positively correlated with the compressor load (suction / discharge pressure).

[0037] 2. Under the same load, the compressor I GBT temperature is negatively correlated with the compressor speed;

[0038] 3. Under the same rotational speed and bus voltage, the compressor I GBT temperature is positively correlated with the compressor load (i.e., the effective value of the phase current);

[0039] 4. Under the same speed and load, the compressor I GBT temperature is positively correlated with the high-voltage bus voltage.

[0040]

[0041] Table 1: Basic Data for Compressor Unit Bench Calibration

[0042] Based on the positive correlation between the effective value of the compressor phase current and the compressor load (suction / discharge pressure), we have developed a method to judge whether this overload protection strategy has been achieved using the effective value of the phase current. When the effective value of the phase current monitored by the compressor reaches a set threshold > 2 seconds, the compressor overload shutdown protection strategy is triggered. The phase current protection threshold setting at low speeds is related to two input factors: compressor speed and bus voltage. The relationship among these three factors is as follows:

[0043] Based on the bench calibration data in Table 1, the corresponding relationship between phase current protection thresholds and compressor speeds was established, with each 200 rpm representing a different current level, as detailed in Table 2 below.

[0044]

[0045] Table 2: Relationship between phase current protection threshold and rotational speed

[0046] Based on the protection threshold values ​​of the effective phase current under different bus voltage values ​​in Table 2, it can be concluded that the effective phase current value is negatively correlated with the bus voltage. The linear relationship formula between the two parameters in each speed range is calculated based on existing data:

[0047] Phase current RMS protection threshold = k × bus voltage + T (k, T constant)

[0048] By incorporating this linear formula and the calibration data from Table 2 into the compressor controller, the compressor phase current protection thresholds for different speeds and input bus voltages within the low-speed operating range of 800rpm-3000rpm can be calculated in real time. During normal operation, when the effective value of the phase current reaches the calculated protection threshold, an overload protection shutdown strategy is triggered. This promptly shuts down the compressor before the IGBT temperature rises to a risk value, preventing IGBT failures caused by frequent IGBT overheating under low-speed, high-load conditions. This presents a dynamic overload protection strategy for the electric compressor controller's temperature.

[0049] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An overload protection method for an electric compressor controller, characterized in that: When the compressor speed is in the low speed range, the compressor load dynamic protection strategy is executed. When implementing the compressor load dynamic protection strategy, the compressor parameters are acquired in real time, including the compressor load, the effective value of the compressor phase current, the compressor speed, and the compressor input bus voltage. Based on the compressor load, compressor speed, and compressor input bus voltage, a phase current effective value protection threshold is preset. The effective value of the phase current is obtained according to the current compressor load, compressor speed, and compressor input bus voltage. The current effective value of the compressor phase current is compared with the phase current effective value protection threshold to determine whether to trigger the overload protection shutdown strategy. The method for determining whether the overload protection shutdown strategy is triggered is as follows: if the effective value of the compressor phase current monitored by the compressor reaches the effective value protection threshold of the currently executed phase current and the duration is >2s, the compressor overload shutdown protection strategy is triggered. The low-speed range is defined as an upper limit of compression speed between 2800 rpm and 3200 rpm, and a lower limit of 600 rpm to 900 rpm.

2. The overload protection method for an electric compressor controller according to claim 1, characterized in that: When a protection threshold for the effective value of phase current is preset based on the compressor load, compressor speed, and compressor input bus voltage, the standard includes: The effective value of the compressor phase current is positively correlated with the compressor load; Under the same load, the compressor IGBT temperature is negatively correlated with the compressor speed. At the same rotational speed and bus voltage, the compressor IGBT temperature is positively correlated with the compressor load. Under the same speed and load, the compressor IGBT temperature is positively correlated with the high-voltage bus voltage.

3. The overload protection method for an electric compressor controller according to claim 2, characterized in that: The compressor speed is set in 200 rpm intervals as a current level, and the effective value protection threshold of the phase current is set under different bus voltage values ​​in each speed range. The effective value protection threshold of phase current = k × bus voltage + T, where k and T are constants.

4. The overload protection method for an electric compressor controller according to claim 3, characterized in that: When the compressor speed is in the high speed range, the effective value of the compressor phase current is obtained. When the effective value of the phase current is greater than the protection constant threshold and is maintained for more than the set time, the compressor overload shutdown protection is activated.

5. The overload protection method for an electric compressor controller according to claim 4, characterized in that: The high-speed range refers to the compressor speed being above the low-speed range, and the protection constant threshold is 17A.

6. The overload protection method for an electric compressor controller according to any one of claims 1-5, characterized in that: When the compressor is working, the temperature of the IGBT pins is acquired in real time. When the detected temperature reaches the set temperature, the over-temperature protection strategy is triggered.

7. The overload protection method for an electric compressor controller according to claim 6, characterized in that: The set temperature is 105℃. When the over-temperature protection strategy is executed, the compressor is controlled to stop. After the over-temperature protection strategy is triggered, if the IGBT pin temperature is lower than 100℃ and the fault disappears after the over-temperature shutdown time is greater than 30 seconds, the compressor is controlled to restart.

8. An overload protection system for an electric compressor controller, wherein an NTC is attached to the IGBT of the system, and the NTC is connected to and outputs a sensing signal to the controller assembly of the electric compressor, characterized in that: The controller assembly acquires the compressor load, compressor phase current RMS value, compressor speed, and input bus voltage of the electric compressor, and executes the electric compressor controller overload protection method as described in any one of claims 1-7.

Images