Temperature estimation method of switching element

Abstract

To provide a temperature estimation method of a switching element in a motor drive inverter device, after a motor lock occurs.SOLUTION: The temperature estimation method of the switching element constituting the motor drive inverter device includes: referring to operation point information distribution data in which operation point information of the switching element at the time of a motor lock occurrence is accumulated; and estimating an initial estimated temperature of the switching element at the time of the motor lock occurrence from the operation point information of the switching element at the time of the motor lock occurrence.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a method for estimating the temperature of a switching element that constitutes an inverter device for driving a motor. [Background technology]

[0002] An inverter device for driving a motor includes multiple switching elements. The temperature of these switching elements rises due to heat loss during operation. Therefore, it is necessary to monitor the temperature of the switching elements to protect them from overheating. In particular, when a motor lock occurs, a large current may continue to flow through a specific switching element among the multiple switching elements depending on the current phase at the time of the motor lock. Therefore, after a motor lock occurs, there is a large imbalance in the temperature rise among the multiple switching elements that make up the inverter device, making it difficult to estimate the temperature of each of the multiple switching elements. Even in such cases, a technology is needed to accurately estimate the temperature of each of the multiple switching elements.

[0003] In a conventional temperature estimation method, the temperature of each of a plurality of switching elements is estimated by adding the temperature rise estimated from the operating point information of the switching elements to the coolant temperature. An example of this type of temperature estimation method is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 162755 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional temperature estimation methods, the initial estimated temperature of a switching element when a motor lock occurs is set to the coolant temperature when the motor lock occurs. However, the actual temperature of the switching element when the motor lock occurs varies significantly depending on the operating state of the switching element at that time. If there is a large difference between the initial estimated temperature and the actual temperature of the switching element, the estimated temperature of the switching element after the motor lock occurs may significantly deviate from the actual temperature, making it impossible to adequately protect the switching element from overheating. This specification aims to provide a method for estimating the temperature of a switching element after a motor lock occurs in an inverter device for driving a motor. [Means for solving the problem]

[0006] The method for estimating the temperature of a switching element constituting an inverter device for driving a motor disclosed in this specification may comprise referencing operating point information distribution data that accumulates operating point information of the switching elements when motor lock occurs, and estimating an initial estimated temperature of the switching element when motor lock occurs from the operating point information of the switching element when motor lock occurs.

[0007] In the temperature estimation method, if the operating point information of the switching element at the time of motor lock occurrence is, for example, a low-probability event in the operating point information distribution data, the initial estimated temperature of the switching element at the time of motor lock occurrence may be adjusted. In this way, the temperature estimation method can correct the initial estimated temperature of the switching element at the time of motor lock occurrence by using the operating point information distribution data. As a result, the temperature estimation method can accurately estimate the temperature of the switching element after motor lock occurrence. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a motor drive system. [Figure 2] FIG. 10 is a diagram illustrating an outline of a flow of a post-lock temperature estimation process executed by a controller. DETAILED DESCRIPTION OF THE INVENTION

[0009] Fig. 1 shows the configuration of a motor drive system 1 to which the technology disclosed in this specification is applied. The motor drive system 1 is not particularly limited, and may be mounted on a vehicle, for example. The motor drive system 1 is a device that supplies three-phase AC power to a motor M, and includes a battery 2 that serves as a main power source, an inverter device 4, a cooling device 6, a controller 8, and a storage device 10. If necessary, a DC / DC converter device may be provided between the battery 2 and the inverter device 4.

[0010] A positive power supply line L1 is connected to the positive electrode of the battery 2, and a negative power supply line L2 is connected to the negative electrode of the battery 2. The inverter device 4 converts the DC voltage supplied from the battery 2 to the pair of power supply lines L1 and L2 into a three-phase (i.e., U-phase, V-phase, and W-phase) AC voltage and outputs it to the motor M. The DC voltage VH on the input side of the inverter device 4 is measured by a voltage sensor connected between the pair of power supply lines L1 and L2 and input to the controller 8. The inverter device 4 includes three switching circuits (i.e., a U-phase switching circuit, a V-phase switching circuit, and a W-phase switching circuit) connected in parallel between the pair of power supply lines L1 and L2. Each of the three switching circuits has a common circuit configuration and includes a pair of switching elements SW connected in series between the pair of power supply lines L1 and L2.

[0011] The inverter device 4 and the motor M are connected by three AC wirings (i.e., a U-phase wiring 10U, a V-phase wiring 10V, and a W-phase wiring 10W). One end of each of the three AC wirings 10U, 10V, and 10W is connected to the midpoint of the corresponding phase of the inverter device 4, and the other end is connected to the neutral point of the motor M. Of the three AC wirings 10U, 10V, and 10W, the V-phase wiring 10V and the W-phase wiring 10W are each provided with a current sensor, and the currents iv and iw measured by these current sensors are input to the controller 8. In addition, the motor M is provided with a resolver, and the rotation angle θ of the rotor relative to the stator is input to the controller 8. The controller 8 can calculate the current iu flowing through the U-phase based on the currents iv and iw and the rotor rotation angle θ. Note that a current sensor may also be provided in the U-phase wiring 10U.

[0012] The cooling device 6 is a cooling device that cools the switching elements that constitute the inverter device 4. A temperature sensor is provided in a flow path through which a coolant (for example, water) circulates, and detects the temperature T W is input to the controller 8.

[0013] The controller 8 generates a PWM signal from the modulated wave and the carrier wave based on the torque command value. The controller 8 can switch the carrier frequency of the carrier wave based on, for example, the rotation speed and output torque of the motor M. The controller 8 outputs the generated PWM signal to the inverter device 4. Drive circuits (not shown) provided corresponding to each of the multiple switching elements SW control the on / off of the switching elements SW based on the input PWM signal. This allows the inverter device 4 to output three-phase AC power to the motor M.

[0014] The controller 8 is further connected to a storage device 10 so as to be able to communicate with the storage device 10. The storage device 10 stores temperature rise map data that associates operating point information (voltage, current, and carrier frequency) of the switching element SW after a motor lock occurs with a temperature rise of the switching element. Note that the temperature rise map data referred to here may be map data that directly associates the temperature rise with the operating point information, or map data that associates the operating point information with a coefficient of a function describing the temperature rise. The storage device 10 also stores operating point information distribution data that accumulates operating point information of the switching element SW when a motor lock occurs. The operating point information distribution data may be data that accumulates operating point information of the switching element SW when a motor lock occurs in the present vehicle in the past, or may be data that accumulates operating point information of the switching element SW when a motor lock occurs in a different vehicle (for example, a vehicle equipped with the same type of motor drive system 1). The storage device 10 may be provided in the vehicle or in an external server.

[0015] The controller 8 refers to the data stored in the storage device 10 and estimates the temperature of each of the multiple switching elements SW after the motor M is locked. Hereinafter, the post-lock temperature estimation process executed by the controller 8 will be described with reference to FIG.

[0016] When the rotation speed of the motor M becomes equal to or lower than a predetermined rotation speed (for example, 100 rpm), the controller 8 determines that the motor has locked and executes the post-lock temperature estimation process. When the rotation speed of the motor M is higher than the predetermined rotation speed, the post-lock temperature estimation process is not executed.

[0017] The estimated temperature T estimated by the post-lock temperature estimation process E is the cooling water temperature T W The initial estimated temperature T0 when the motor lock occurs, and the temperature rise ΔT of the switching element SW after the motor lock occurs. SW It is expressed as the sum of and.

number

[0018] Here, the temperature rise of the switching element ΔT SW is the sum of the temperature rise due to the on-loss caused by the on-resistance of the switching element SW and the temperature rise due to the switching loss of the switching element SW. The on-loss and switching loss of the switching element SW depend on the voltage, current, and carrier frequency of the switching element SW. Therefore, the temperature rise ΔT of the switching element SW SW is estimated based on the operating point information of the switching element SW. More specifically, the controller 8 first calculates the voltage and current of each of the multiple switching elements based on the DC voltage VH, the currents iv and iw, and the rotor rotation angle θ. The carrier frequency is acquired from the carrier wave generated by the controller 8. Next, the controller 8 refers to the temperature rise map data stored in the storage device 10, and calculates ΔT based on this operating point information (voltage, current, and carrier frequency). SW At the time when the motor lock occurs, ΔT SW is zero.

[0019] The initial estimated temperature T0 when the motor locks is a correction value that reflects the operating state of the switching element SW when the motor locks. When the switching element SW is in a normal state, the initial estimated temperature T0 is zero. On the other hand, when the switching element SW is in a state other than normal, the initial estimated temperature T0 is adjusted to a value other than zero.

[0020] When a motor lock occurs, the controller 8 refers to the operating point information distribution data stored in the storage device 10 and determines whether the operating point information of the switching element SW at the time of the motor lock occurrence is a low-probability event in the operating point information distribution data. When the operating point information of the switching element SW is a low-probability event, it is considered that the switching element SW is in an abnormal state. More specifically, the controller 8 acquires, for example, 3σ (σ is the standard deviation) of the operating point information distribution data and determines whether the operating point information of the switching element SW at the time of the motor lock occurrence is an event that occurs with a probability of 3σ or more. If the operating point information of the switching element SW at the time of the motor lock occurrence is an event that occurs with a probability of 3σ or more, the controller 8 sets a positive temperature to the initial estimated temperature T0. Specific examples include the following cases. For example, if the current of the switching element SW at the time of the motor lock occurrence is extremely large (an event of 3σ or more), it is considered that there is a large difference between the actual temperature of the switching element SW and the temperature of the coolant at that time. By adjusting the initial estimated temperature T0 to a positive temperature, it is possible to correct such a temperature difference. This allows the controller 8 to accurately estimate the temperature of the switching element SW after the motor lock occurrence. The temperature adjustment amount for the initial estimated temperature T0 may be set in advance as a predetermined amount, or may vary depending on the probability of the operating point information of the switching element SW when the motor lock occurs.

[0021] The controller 8 executes the above-described post-lock temperature estimation process to estimate the temperature of each of the multiple switching elements SW that constitute the inverter device 4. The controller 8 compares the estimated temperatures of each of the multiple switching elements SW and identifies the highest estimated temperature among them. For example, the controller 8 may execute an overheat protection operation when the identified highest estimated temperature is equal to or higher than a threshold temperature.

[0022] In the above-described post-lock temperature estimation process, the operating point information distribution data referred to by the controller 8 may be selected based on the driving mode, the place of use, the season, the duration of use, etc. This allows the controller 8 to more accurately estimate the temperature of the switching element SW after the motor lock has occurred. [Explanation of symbols]

[0023] 1: Motor drive system, 2: Battery, 4: Inverter device, 6: Cooling device, 8: Controller, 10: Storage device

Claims

[Claim 1] A method for estimating the temperature of a switching element constituting an inverter device for driving a motor, comprising: a switching element temperature estimation method comprising: referencing operating point information distribution data that accumulates operating point information of the switching elements when the motor lock occurs, and estimating an initial estimated temperature of the switching elements when the motor lock occurs from the operating point information of the switching elements when the motor lock occurs.

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