Overload protection method and system for electric compressor controller

Abstract

The invention discloses an overload protection method for an electric compressor controller, which comprises the following steps: when the rotating speed of a compressor is in a low rotating speed interval, executing a compressor load dynamic protection strategy; when the compressor load dynamic protection strategy is executed, compressor parameters are obtained in real time, a phase current effective value protection threshold value is preset based on the compressor load, the compressor rotating speed and the compressor rotating speed, and the phase current effective value protection threshold value is obtained according to the current compressor load, the compressor rotating speed and the compressor rotating speed; and the current compressor phase current effective value is compared with the phase current effective value protection threshold value, and whether an overload protection shutdown strategy is triggered or not is judged. Under the working conditions of low rotating speed and high load, before the heat of the IGBT begins to accumulate but the temperature value does not reach the crystallization temperature 175 DEG C, the overload shutdown protection strategy is preferentially reflected, and the thermal breakdown of the IGBT caused by frequent over-temperature is avoided. The dynamic overload protection strategy is higher in precision and faster in response, and preposed protection of the temperature of the IGBT is achieved in advance in an overload protection mode under the low-rotating-speed and high-load working condition.

Description

Technical Field

[0001] The invention relates to the technical field of automobile air conditioners, and in particular to a dynamic overload protection technology for the temperature of an electric compressor controller. Background Art

[0002] The penetration rate of the new energy vehicle market has steadily increased, and the application scope of electric compressors has increased significantly. According to industry surveys, semiconductor devices in the inverter system are the most likely components to fail, with a failure rate of 34%, and over-temperature failure accounts for 55% of the failure rate of semiconductor devices. The electric compressor controller belongs to a typical inverter system. Its core function is to convert the high-voltage DC input from the vehicle battery into three-phase AC input to the motor by controlling the switching and conduction of the power device, which is used to drive the mechanical components to compress the gaseous refrigerant to achieve the cooling / heating function of the vehicle. The main function of the electric compressor in the thermal management system is to compress the low-temperature and low-pressure gaseous refrigerant (inhaled at the air intake) into a high-temperature and high-pressure gaseous refrigerant (exhausted at the exhaust port). During operation, the low-temperature gaseous refrigerant at the air intake flushes the metal wall of the controller housing on the other side of the IGBT fitting installation position, taking away the heat generated by the IGBT. When the compressor runs at a low speed, the refrigerant flow is low, and the heat dissipation effect of the IGBT becomes worse. 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 their worst operating conditions. At this time, the heat generated by the IGBT is higher than the heat dissipation. The rapid accumulation of heat causes the temperature to rise sharply, and the probability of over-temperature breakdown is much higher than in other conditions.

[0003] The temperature protection measure commonly used for discrete IGBT devices is to set a thermistor (NTC for short) to collect the IGBT pin temperature in real time. When the collected temperature reaches the set over-temperature protection threshold, the compressor is shut down for protection.

[0004] For example, the public document with announcement number CN117028226B, publication date November 10, 2023, and patent name "A control method for a compressor system, a compressor system and a vehicle", discloses a control method for a compressor system including: obtaining the current temperature of a switching element; when the current temperature is greater than or equal to a first preset temperature threshold, controlling the electric compressor to enter a first shutdown state; when the number of first-level protection times the electric compressor enters the first shutdown state reaches a first preset number threshold, controlling the electric compressor to enter a second shutdown state, 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] There will be a certain error between the temperature value obtained by monitoring the IGBT pin temperature through NTC and the actual temperature of the IGBT internal wafer, and there will be a time lag. Especially in the stage of rapid heat accumulation and temperature rise, the temperature feedback hysteresis problem is particularly serious, 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 realize a method to avoid thermal breakdown of IGBT caused by frequent overheating, so that the overload protection accuracy of the electric compressor controller is higher and the response is faster, and the pre-protection of the IGBT temperature is realized in advance by overload protection under low speed and high load conditions.

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

[0008] When executing the compressor load dynamic protection strategy, the compressor parameters are obtained in real time, and the compressor parameters include the compressor load, the effective value of the compressor phase current, the compressor speed, and the input bus voltage of the compressor;

[0009] Based on the compressor load, compressor speed, and compressor speed, a phase current effective value protection threshold is preset. 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 the overload protection shutdown strategy is triggered.

[0010] The method for judging whether to trigger the overload protection shutdown strategy is that the compressor phase current effective value monitored by the current compressor reaches the currently executed phase current effective value protection threshold and the duration is greater than 2s, triggering the compressor overload shutdown protection strategy.

[0011] When there is a phase current RMS protection threshold preset based on compressor load, compressor speed, and compressor speed, the standards include:

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

[0013] The compressor IGBT temperature is negatively correlated with the compressor speed under the same load

[0014] The compressor I GBT temperature is positively correlated with the compressor load at the same speed and bus voltage;

[0015] The compressor IGBT temperature is positively correlated with the high-voltage bus voltage value at the same speed and load.

[0016] The compressor speed is divided into a current gear every 200 rpm, and the phase current effective value protection threshold is set at different bus voltage values ​​in each speed range;

[0017] Phase current effective value protection threshold = 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 is shut down for overload protection.

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

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

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

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

[0023] The electric compressor controller overload protection system and method of the present invention retains the conventional NTC temperature detection and protection scheme, and adds a dynamic protection strategy for the compressor load in the low speed range of 800rpm to 3000rpm. Under low speed and high load conditions, when the IGBT heat begins to accumulate but the temperature value does not reach its crystallization temperature of 175°C, the overload shutdown protection strategy is preferentially implemented to avoid frequent overheating and thermal breakdown of the IGBT. This dynamic overload protection strategy has higher accuracy and faster response, and realizes pre-protection of the IGBT temperature in advance in the form of overload protection under low speed and high load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following is a brief description of the contents expressed in each figure in the specification of the present invention and the marks in the figure:

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

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

[0027] The following is a further detailed description of the specific implementation methods of the present invention, such as the shape, structure, relative position and connection relationship between the various components involved, the function and working principle of each part, the manufacturing process and operation method, etc., through the description of the embodiments with reference to the accompanying drawings, so as 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] There will be a certain error between the temperature value obtained by monitoring the IGBT pin temperature through NTC and the actual temperature of the IGBT internal wafer, and there will be a time lag. Especially in the stage of rapid heat accumulation and temperature rise, the temperature feedback hysteresis problem is particularly serious, which greatly increases the probability of IGBT over-temperature breakdown. In order to solve this problem, the present invention not only retains the conventional NTC temperature detection and protection scheme, but also adds a dynamic protection strategy for the compressor load in the low-speed range. In the low-speed and high-load heat accumulation stage, before the IGBT temperature rises to its upper limit, the compressor will give priority to the overload shutdown protection strategy to avoid frequent over-temperature shutdowns that lead to IGBT over-temperature breakdown.

[0029] The present invention attaches a thermistor (NTC for short) to the IGBT device of the electric compressor, the controller assembly 3 is connected to and obtains 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 the temperature signal of the NTC to the drive motor assembly 4 for execution, and at the same time, the controller assembly 4 obtains the compressor load, the effective value of the compressor phase current, the compressor speed, and the input bus voltage of the electric compressor, and the controller assembly executes a new electric compressor controller overload protection method.

[0030] The overload protection method of the electric compressor controller retains the original IGBT temperature protection strategy, that is, the IGBT pin temperature is monitored by NTC. When the detected temperature reaches 105°C, the over-temperature protection strategy is triggered and the compressor shuts down for self-protection.

[0031] The temperature of the IGBT metal pin is monitored by NTC. The internal wafer temperature is transferred to the pin through the heat conduction of the metal material. When the NTC monitoring temperature value reaches 105℃, the over-temperature protection strategy is triggered and the compressor shuts down for self-protection. When the NTC monitoring temperature value drops to <100℃ and the over-temperature shutdown time is >30 seconds, the fault disappears and the compressor restarts;

[0032] While executing the above control method, a new dynamic protection strategy for compressor load in the low speed range (800rpm-3000rpm) is added. According to the correlation between the four parameters of compressor load (i.e., suction / exhaust pressure), compressor phase current effective value, compressor speed, and input bus voltage, the data calibration of multiple working conditions in the low speed range is carried out through the test bench, and the calculation formula of the phase current effective value protection threshold and the speed and bus voltage is obtained, so as to formulate the phase current effective value protection threshold under each speed range and different input bus voltage value working conditions. During normal operation, when the effective value of the phase current reaches the set protection threshold, it means that the heat generated by the controller IGBT under this load is greater than the heat dissipation, and its temperature will accumulate rapidly. When the effective value of the phase current reaches the protection threshold 2s later, the overload protection shutdown strategy is triggered, and the compressor is cut off in time before the IGBT temperature rises to the risk value, so as to avoid IGBT failure caused by frequent overheating of the IGBT of the compressor under low speed and high load conditions.

[0033] Specifically,

[0034] When the speed is above 3000rpm, 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 shut down for overload protection.

[0035] Add a dynamic protection strategy for the compressor load in the low speed range (800rpm-3000rpm). Based on the basic data of the compressor bench calibration in Table 1 below, the relationship between the following parameters can be basically obtained:

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

[0037] 2. The compressor IGBT temperature is negatively correlated with the compressor speed under the same load;

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

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

[0040]

[0041] Table 1: Basic data of compressor unit bench calibration

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

[0043] According to the bench calibration data in Table 1, the corresponding relationship between the phase current protection threshold and the compressor speed is formulated, with each 200 rpm being a current gear, as shown in Table 2.

[0044]

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

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

[0047] Phase current effective value protection threshold = k × bus voltage + T (k, T constants)

[0048] By applying this linear formula and the calibration raw data in Table 2 to the compressor controller, the compressor phase current protection thresholds at different speeds and different input bus voltages in the low-speed working 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, the overload protection shutdown strategy is triggered, and the compressor is cut off in time before the IGBT temperature rises to the risk value, avoiding IGBT failure caused by frequent overheating of the IGBT under low-speed and high-load conditions, presenting a dynamic overload protection strategy for the temperature of the electric compressor controller.

[0049] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they 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 executing the compressor load dynamic protection strategy, the compressor parameters are obtained in real time, and the compressor parameters include the compressor load, the effective value of the compressor phase current, the compressor speed, and the input bus voltage of the compressor; Based on the compressor load, compressor speed, and compressor speed, a phase current effective value protection threshold is preset. 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 the overload protection shutdown strategy is triggered.

2. The electric compressor controller overload protection system according to claim 1, characterized in that: The method for determining whether to trigger the overload protection shutdown strategy is that the compressor phase current effective value monitored by the current compressor reaches the currently executed phase current effective value protection threshold and the duration is greater than 2s, triggering the compressor overload shutdown protection strategy.

3. The electric compressor controller overload protection system according to claim 2, characterized in that: When there is a phase current RMS protection threshold preset based on compressor load, compressor speed, and compressor speed, the standards include: The effective value of the compressor phase current is positively correlated with the compressor load; The compressor IGBT temperature is negatively correlated with the compressor speed under the same load The compressor IGBT temperature is positively correlated with the compressor load at the same speed and bus voltage; The compressor IGBT temperature is positively correlated with the high-voltage bus voltage value at the same speed and load.

4. The electric compressor controller overload protection system according to claim 3, characterized in that: The compressor speed is divided into a current gear every 200 rpm, and the phase current effective value protection threshold is set at different bus voltage values ​​in each speed range; Phase current effective value protection threshold = k × bus voltage + T, where k and T are constants.

5. The electric compressor controller overload protection system according to claim 4, 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 is shut down for overload protection.

6. The electric compressor controller overload protection system according to claim 5, characterized in that: The low speed range is that the upper limit of the compression speed is 2800rpm-3200rpm, and the lower limit of the speed is 600rpm-900rpm. The high speed range is that the compressor speed is above the low speed range. The protection constant threshold is 17A.

7. The electric compressor controller overload protection system according to any one of claims 1 to 6, characterized in that: When the compressor is working, the IGBT pin temperature is obtained in real time. When the detected temperature reaches the set temperature, the over-temperature protection strategy is triggered.

8. The electric compressor controller overload protection system according to claim 7, characterized in that: The set temperature is 105°C. When the over-temperature protection strategy is executed, the compressor is controlled to shut down. After the over-temperature protection strategy is triggered, if the IGBT pin temperature is lower than 100°C and the fault disappears after the over-temperature shutdown time is greater than 30 seconds, the compressor is controlled to restart.

9. An electric compressor controller overload protection system, 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 obtains the compressor load, compressor phase current effective value, compressor speed, and input bus voltage of the electric compressor, and the controller assembly executes the electric compressor controller overload protection method as described in any one of claims 1-8.

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