JP7625946B2 - Electric motor control method and electric motor control system - Google Patents

Description

The present invention relates to an electric motor control method and an electric motor control system.

Patent document 1 proposes an electric motor control system that detects the temperature of a smoothing capacitor provided on the input side of an inverter that drives an electric motor, and adjusts the control gain of the feedback control of the inverter based on the detected temperature.

JP 2005-354763 A

The motor control system of Patent Document 1 aims to achieve stable feedback control by adjusting the control gain according to the temperature of the smoothing capacitor. However, the motor control system of Patent Document 1 does not suppress the temperature change (particularly the temperature rise) of the smoothing capacitor itself. For this reason, depending on the manner in which the temperature rise of the smoothing capacitor occurs, the range of change in the control gain may become large, which may impair the control stability of the operation of the motor.

Therefore, the object of the present invention is to provide a motor control method and a motor control system that can suppress temperature changes in a smoothing capacitor while maintaining the motor in a desired operating state.

According to one aspect of the present invention, there is provided a motor control method that is executed in a motor control system that includes a generator, a capacitive element that temporarily stores the generated power output by the generator, and a motor that is driven by the generated power, and that controls the operation of the generator and the motor.

When the temperature of the capacitance element is equal to or higher than a predetermined threshold, a temperature suppression control is executed to suppress an increase in the temperature of the capacitance element by reducing a current of the generator.
A method for controlling an electric motor.

In this motor control method, when the temperature of the capacitance element is equal to or higher than a predetermined threshold, a temperature suppression control is performed to suppress the rise in temperature of the capacitance element by reducing the current of the generator. The motor control system further includes a first motor functioning as a motor and a second motor different from the first motor. The temperature suppression control includes a first suppression process for reducing the current of the generator while maintaining the generated power, a suppression region determination process for determining whether the state of the motor control system is in a temperature suppression region where a certain degree of effect of suppressing the rise in the temperature of the capacitance element can be obtained, and a second suppression process for increasing the output of the second motor while maintaining the sum of the output of the first motor and the output of the second motor when it is determined that the state of the motor control system is in the temperature suppression region. In particular, in the suppression region determination process, when a combined change in loss, which is a change in loss of the capacitance element caused by a change in the output of the first motor and a change in loss of the capacitance element caused by a change in the combined output of the generator and the first motor, is in a decreasing direction, it is determined that the state of the motor control system is in the temperature suppression region.

The present invention makes it possible to suppress temperature changes in the smoothing capacitor while maintaining the motor in a desired operating state.

FIG. 1 is a diagram illustrating the configuration of an electric motor control system according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating the temperature suppression control. FIG. 3 is a map showing the relationship between the operating points of the engine and the generator and the generated current.

Each embodiment of the present invention will be described in detail below with reference to the drawings.

Figure 1 is a diagram illustrating the configuration of an electric motor control system 100 in which the electric motor control method of this embodiment is executed. It is assumed that the electric motor control system 100 of this embodiment is mounted on an electric vehicle or a hybrid vehicle, particularly a 4WD hybrid vehicle (hereinafter simply referred to as a "vehicle").

The motor control system 100 has a drive motor 10 (particularly a front motor 10fr and a rear motor 10rr), a battery 12, an inverter 14 (particularly a front inverter 14fr and a rear inverter 14rr), a generator 16 as a power generator, an engine 18 as a drive device, and a controller 20.

The drive motor 10 is composed of a front motor 10fr located at the front of the vehicle (on the front wheel side) and driving the front wheels, and a rear motor 10rr located at the rear (on the rear wheel side) and driving the rear wheels.

The front motor 10fr is configured as a three-phase AC motor. The front motor 10fr receives power from the battery 12 and provides driving force to the front wheels. The front motor 10fr also converts regenerative driving force obtained from the front wheels while the vehicle is running into AC power.

On the other hand, the rear motor 10rr is configured as a three-phase AC motor. The rear motor 10rr receives power from the battery 12 and provides driving force to the rear wheels. The rear motor 10rr also converts regenerative driving force obtained from the rear wheels while the vehicle is running into AC power.

The battery 12 is an on-board DC power source composed of a lithium-ion secondary battery or the like. The battery 12 is charged with power generated by the generator 16, and is configured to be able to supply power to the drive motor 10 or receive regenerative power from the drive motor 10.

The inverter 14 adjusts the input and output power of each of the drive motor 10, the battery 12, and the generator 16. In particular, the inverter 14 is composed of a front inverter 14fr and a rear inverter 14rr.

The front inverter 14fr has a smoothing capacitor 30 as a capacitance element that temporarily stores the generated power output by the generator 16, a front motor power converter 32 that adjusts the power supplied from the battery 12 to the front motor 10fr (i.e., the output of the front motor 10fr), and a generator power converter 34 that adjusts the power supplied from the generator 16 to the battery 12 (i.e., the generated power). The front motor power converter 32 and the generator power converter 34 are connected in parallel to the smoothing capacitor 30.

The smoothing capacitor 30 functions as a common capacitance element for the front motor power converter 32 and the generator power converter 34. In addition, the smoothing capacitor 30 is provided with a temperature sensor 36 that detects the temperature of the smoothing capacitor 30 (hereinafter also referred to as "capacitor temperature _Tc ").

The front motor power converter 32 is mainly composed of a switching circuit made up of semiconductor elements such as IGBTs, and a switching control device (not shown) for driving the switching circuit. The switching control device generates a PWM signal for driving (switching) the switching circuit, based on a command value of an output torque for the front motor 10fr (hereinafter also referred to as "front motor torque _{Tfr_m} ") input from the controller 20. In particular, the front motor power converter 32 adjusts the DC power from the battery 12 so as to supply three-phase AC power based on the front motor torque _{Tfr_m} to the front motor 10fr. For ease of explanation, a current equivalent to the DC power from the battery 12 will be referred to as a "front motor DC current _{Idc_fm} " below. A three-phase AC current equivalent to the three-phase AC power supplied to the front motor 10fr will be referred to as a "front motor current _{Iac_fm} ". In particular, the front motor power converter 32 manipulates the front motor current _{Iac_fm} so that the actual output torque of the front motor 10fr approaches the front motor torque _{Tfr_m} .

The generator power converter 34 is mainly composed of a switching circuit made up of a plurality of semiconductor elements such as IGBTs, and a switching control device (not shown) for driving the switching circuit. The switching control device generates a PWM signal for driving (switching) the switching circuit based on a command value for the rotation speed of the generator 16 (hereinafter also referred to as "generator rotation speed _{Nfr_g} ") input from the controller 20. In particular, the generator power converter 34 adjusts the three-phase AC power output by the generator 16 so as to output DC generated power based on the generator rotation speed _{Nfr_g} . For ease of explanation, a current equivalent to this DC generated power is referred to as "generated current _{Idc_fg} " below. A current equivalent to the three-phase AC power output by the generator 16 is referred to as "generator current _{Iac_fg} ".

In particular, the generator power converter 34 calculates an appropriate output torque of the generator 16 (hereinafter also referred to as "generator torque _{Tfr_g} ") from the generator speed _{Nfr_g} based on a predetermined speed control logic that uses as feedback the actual speed N of the generator 16 detected by a sensor (not shown) or the like. More specifically, the generator power converter 34 calculates the generator torque _{Tfr_g} based on the following equation (1).

ただし、式中の「Ｋｐ」、「Ｋｉ」、及び「Ｎ」はそれぞれ、比例ゲイン、積分ゲイン、及びジェネレータ１６の実回転数Ｎのフィードバック値を意味する。なお、本実施形態では、エンジン１８とジェネレータ１６が変速機構を介さずに直結していることを仮定して、定常状態（エンジン１８の回転とジェネレータ１６の回転が相互に同期した状態）において、ジェネレータトルクＴ_{ｆｒ_ｇ}とエンジン１８の出力トルク（以下、「エンジントルクＴ_ｅｎｇ」とも称する）の符号が反対で、且つほぼ同一の大きさとなるようにジェネレータ回転数Ｎ_{ｆｒ_ｇ}を定める。すなわち、定常状態において、Ｔ_{ｆｒ_ｇ}≒－Ｔ_ｅｎｇとなるジェネレータ回転数Ｎ_{ｆｒ_ｇ}を定める。なお、エンジン１８とジェネレータ１６との間に変速機構が存在する場合には、そのギヤ比に応じてジェネレータトルクＴ_{ｆｒ_ｇ}とエンジントルクＴ_ｅｎｇの比が定まることとなる。

In the formula, "Kp", "Ki", and "N" respectively mean a proportional gain, an integral gain, and a feedback value of the actual rotation speed N of the generator 16. In this embodiment, it is assumed that the engine 18 and the generator 16 are directly connected without a speed change mechanism, and the generator rotation speed N fr_g is determined so that the generator torque T _{fr_g} and the output torque of the engine 18 (hereinafter also referred to as "engine torque T _eng ") have opposite signs and are substantially the same magnitude in a steady state (a state in which the rotation of the engine 18 and the rotation of the generator 16 are synchronized with each other). That is, the generator rotation speed N _{fr_g} is determined so that T _{fr_g} ≈ -T _eng in the steady state. In addition, when a speed change mechanism is present between the engine 18 and the generator 16, the ratio between the generator torque T _{fr_g} and the engine torque T _eng is determined according to the gear ratio of the speed change _mechanism .

Then, the generator power converter 34 adjusts the generator current _{Iac_fg} so that the actual output torque of the generator 16 approaches the calculated generator torque _{Tfr_g} .

For ease of explanation, hereinafter, the total power supplied from the battery 12 to the front inverter 14fr, i.e., the power obtained by combining the DC power from the battery 12 to the front motor power converter 32 (front motor DC current _{Idc_fm} ) and the power generated by the generator 16, will be referred to simply as "composite power." The DC current equivalent to this composite power will be referred to as "composite current _{Idc_f} ."

On the other hand, the rear inverter 14rr has a smoothing capacitor 40 as a storage element arranged on the input side of the battery 12, and a rear motor power converter 42 that adjusts the power supplied from the battery 12 to the rear motor 10rr (i.e., the output of the rear motor 10rr).

The rear motor power converter 42 is composed of a switching circuit made up of a plurality of semiconductor elements such as IGBTs, and a switching control device (not shown) for driving the switching circuit. The switching control device generates a PWM signal for driving (switching) the switching circuit, based on a command value for the output torque for the rear motor 10rr (hereinafter also referred to as "rear motor torque _{Trr_m} ") input from the controller 20. In particular, the rear motor power converter 42 adjusts the DC power from the battery 12 so as to supply three-phase AC power based on the rear motor torque _{Trr_m} to the rear motor 10rr. For ease of explanation, a current equivalent to this DC power will be referred to as "rear motor DC current _{Idc_rm} " below. Also, a three-phase AC current equivalent to the three-phase AC power supplied to the rear motor 10rr will be referred to as "rear motor current _{Iac_rm} ". In particular, the rear motor power converter 42 manipulates the rear motor current _{Iac_rm} so that the actual output torque of the rear motor 10rr approaches the rear motor torque _{Trr_m} .

The controller 20 controls the operation of the front motor 10fr, rear motor 10rr, generator 16, and engine 18 via the front inverter 14fr and rear inverter 14rr based on various input information.

The generator 16 is a generator that receives the driving force of the engine 18 to generate electricity to drive the front motor 10fr and the rear motor 10rr, and supplies the electricity to the battery 12. The generator 16 may be configured to receive power from the battery 12 depending on the situation and perform powering operation to drive the engine 18. This allows the generator 16 to be used to perform cranking (motoring), for example, when starting the engine 18.

The engine 18 is connected to the generator 16 via mechanical elements such as gears (not shown), and transmits power for generating electricity to the generator 16. In other words, the engine 18 is used as a drive source for generating electricity by the generator 16. In particular, the engine 18 operates at an operating point according to an engine torque T _eng (described later) input from the controller 20.

The controller 20 is composed of a computer equipped with a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input/output interface (I/O interface), and is programmed to execute each process described below. In particular, when the electric motor control system 100 of this embodiment is mounted on a vehicle, the functions of the controller 20 can be realized by any on-board computer such as a vehicle controller (VCM: Vehicle Control Module) and a motor controller, and/or a computer installed outside the vehicle. The controller 20 may be realized by a single piece of computer hardware, or may be realized by distributing various processes across multiple pieces of computer hardware.

The controller 20 operates the front inverter 14fr, rear inverter 14rr, generator 16, and engine 18 based on various input information.

In particular, the controller 20 distributes the total output required of the electric motor control system 100 (e.g., the total driving force required of the vehicle according to the accelerator pedal operation amount) to the front motor 10fr and the rear motor 10rr according to a predetermined distribution ratio κ. More specifically, the controller 20 determines the above-mentioned front motor torque _{Tfr_m} and rear motor torque _{Trr_m} from the total required output according to the distribution ratio κ. Then, the controller 20 outputs the determined front motor torque _{Tfr_m} and rear motor torque _{Trr_m} to the front inverter 14fr (particularly the front motor power converter 32) and the rear inverter 14rr (rear motor power converter 42), respectively.

Furthermore, the controller 20 determines an operating point (generator speed _{Nfr_g} ) of the generator 16 based on the required generated power (engine torque T _eng ) determined according to the remaining charge capacity of the battery 12, and the capacitor temperature _Tc . In particular, the controller 20 of this embodiment sets the generator speed _{Nfr_g} to either a basic generator speed _{Nfr_g0} determined from the viewpoint of achieving _the required generated power, or a corrected speed command value _{Nfr_g1} determined from the viewpoint of suppressing an increase in the capacitor temperature _Tc , under a predetermined condition related to the capacitor temperature Tc.

Furthermore, the controller 20 determines an operating point (engine torque T _{eng ) of the engine 18 so as to maximize the energy efficiency (optimum fuel consumption point) based on the required power generation and the capacitor temperature Tc. In particular, the controller 20 of this embodiment sets the engine torque T eng to either} a basic engine torque T _eng0 determined from the viewpoint of achieving the required power generation, or a correction engine torque T _eng1 determined from the viewpoint of suppressing an increase in the capacitor temperature _Tc , under a predetermined condition related to the capacitor temperature Tc. Then, the controller 20 controls the operation of the engine 18 by operating peripheral actuators (such as a throttle valve) of the engine 18 according to the determined _engine torque T _eng .

The controller 20 of this embodiment acquires the capacitor temperature _Tc from the temperature sensor 36, and executes temperature suppression control to suppress an increase in the capacitor temperature _Tc . In the motor control system 100 of this embodiment, the capacitor temperature Tc varies depending on the magnitude of the front motor DC current _{Idc_fm} , the generator current _{Iac_fg} , or the combined power (combined current _{Idc_f} ) in the front inverter 14fr. For this reason, in the temperature suppression control, when _{the capacitor temperature Tc rises} above a certain value, the above currents (particularly the generator current _{Iac_fg} ) are reduced to suppress an increase in the capacitor temperature _Tc . Details of the temperature suppression control will be described below.

Fig. 2 is a flowchart illustrating the temperature suppression control. The controller 20 repeatedly executes each process shown in the flowchart in Fig. 2 at a predetermined calculation cycle. Note that, as a prerequisite for executing this process, it is assumed that the generator rotation speed _{Nfr_g} and the engine torque _Teng are set to the normal basic generator rotation speed _{Nfr_g0} and basic engine torque _Teng0 , respectively.

As shown in the figure, in step S101, the controller 20 determines whether the capacitor temperature _Tc is equal to or higher than the reference value α. If the controller 20 determines that the capacitor temperature _Tc is less than the reference value α, the controller 20 ends this routine while maintaining the generator speed _{Nfr_g} and the engine torque _Teng at the basic generator speed _{Nfr_g0} and the basic engine torque _Teng0 , respectively. On the other hand, if the controller 20 determines that the capacitor temperature _Tc is equal to or higher than the reference value α, the controller 20 proceeds to the process of step S102 and subsequent steps.

In step S102, the controller 20 executes a first suppression process. Specifically, the controller 20 changes the generator rotation speed _{Nfr_g} from the basic generator rotation speed _{Nfr_g0} to the corrected rotation speed command value _{Nfr_g1} , and changes the engine torque _Teng from the basic engine torque _Teng0 to the corrected engine torque _Teng1 .

FIG. 3 is a map showing the relationship between the operating points of the engine 18 and the generator 16 and the generator current I _{ac_fg} . In the figure, "g0" represents the operating point before the change (hereinafter also referred to as "basic operating point g0"). Furthermore, "g1" represents the operating point after the change (hereinafter also referred to as "corrected operating point g1"). Furthermore, "C1" represents a set of operating points where the output of the engine 18 (=engine torque T _eng ×engine speed N _eng ) is constant (hereinafter also referred to as "engine output line C1"). Furthermore, "C2" represents a set of operating points where the output of the generator 16 (=generator torque T _{fr_g} ×generator speed N _{fr_g} ) is constant (hereinafter also referred to as "generator output line C2"). Furthermore, "C3" represents a set of generator current I _{ac_fg} when the output of the generator 16 is constant (hereinafter also referred to as "constant output current line C3").

As shown in the figure, in this embodiment, the controller 20 increases the generator rotation speed _{Nfr_g} from the basic generator rotation speed _{Nfr_g0} to the corrected rotation speed command value _{Nfr_g1} while maintaining the output of the generator 16 constant (along the generator equal output line C2). Accordingly, the magnitude (absolute value) of the generator torque _{Tfr_g} decreases, and the generator current _{Iac_fg} decreases (see the section from g0 to g1 on the equal output current line C3). Therefore, in the process in which the operating point of the generator 16 transitions from the basic operating point g0 to the corrected operating point g1, the amount of heat generated by the smoothing capacitor 30 can be reduced and the rise in the capacitor temperature _Tc can be suppressed compared to when the basic operating point g0 is maintained.

Furthermore, in this embodiment, the correction operation point g1 is adjusted to an operation point where the generator current I _{ac_fg} is at a minimum value. More specifically, the controller 20 obtains the generator rotation speed N fr_g when the generator current I ac_fg is at a minimum value from the relationship between the generator rotation speed N _{fr_g} and the generator current I _{ac_fg} obtained by applying the value of the output of the generator _{16 at the basic operation point g0 to a map showing the relationship between the predetermined output of the generator 16, the generator rotation speed N fr_g , and} the generator current I _{ac_fg} , and sets this as the correction operation point g1. This can further enhance the effect of suppressing the rise in the capacitor temperature T _c . More specifically, even in a scene where the generator current I _{ac_fg} is relatively large (for example, a scene affected by a weak field current in a high rotation range) despite the magnitude of the generator torque T _{fr_g} being relatively small, the rise in the capacitor temperature T _c can be suitably suppressed.

As described above, in the process in which the operating point transitions from the basic operating point g0 to the correction operating point g1, the generator current _{Iac_fg} decreases, but the output of the generator 16 is maintained constant. As a result, the generated power (generated current _{Idc_fg} ) output by the generator 16 is maintained, and the combined power in the front inverter 14fr can also be maintained. In other words, the power (front motor DC current _{Idc_fm} , front motor current _{Iac_fm} ) supplied to the front motor 10fr can be maintained to maintain its operation in a desired state, while suppressing an increase in the capacitor temperature _Tc .

Returning to Fig. 2, the controller 20 judges whether or not the transition of the operating point to the correction operating point g1 has been completed. Specifically, the controller 20 judges that the transition to the correction operating point g1 has been completed when the difference between the generator rotation speed N _{fr_g} and the actual rotation speed N is equal to or smaller than a predetermined difference threshold value β. That is, the controller 20 judges that the transition to the correction operating point g1 has been completed when the following formula (2) is satisfied.

Then, when the controller 20 determines that the transition to the correction operation point g1 is complete, it proceeds to step S104.

In step S104, the controller 20 executes a suppression region determination process to determine whether the state of the motor control system 100 is in the temperature suppression region. Specifically, the controller 20 executes this determination using the logic described below.

First, after the transition to the correction operation point g1 is completed, the controller 20 changes the distribution ratio κ while maintaining the total output of the motor control system 100, i.e., the total driving force of the vehicle (the sum of the front motor torque _{Tfr_m} and the rear motor torque _{Trr_m} ), thereby decreasing the front motor torque _{Tfr_m} by ΔT (>0) and increasing the rear motor torque _{Trr_m} by ΔT. Note that ΔT is set to a suitable value from the viewpoint of minimizing the discomfort felt by the vehicle occupants while realizing a desired reduction in the front motor current _{Iac_fm} . Then, the controller 20 determines whether the condition of the following equation (3) is satisfied.

Here, the first equation of equation (3) represents the condition under which the front motor current _{Iac_fm} decreases when the front motor torque _{Tfr_m} is decreased by ΔT (i.e., the condition under which the capacitor temperature _Tc actually decreases). Meanwhile, the second equation of equation (3) specifies the condition under which the decrease in loss in the smoothing capacitor 30 due to a change in the front motor current _{Iac_fm} (front motor DC current _{Idc_fm )} ( ^Δ_loss ( _{Iac_fm} )) exceeds the increase in loss in the smoothing capacitor 30 due to a change in the combined power (combined current _{Idc_f} ) in the front inverter 14fr (Δ ⁺ loss( _{Idc_f} )) when the front motor torque _{Tfr_m} is decreased and the rear motor torque Trr_m is increased as described above. That is, in some cases, it is expected that the effect of suppressing the rise in capacitor temperature _Tc will not be sufficiently achieved even if the front motor current _{Iac_fm} (front motor DC current _{Idc_fm} ) is reduced because the combined current _{Idc_f} will increase. Therefore, the second equation of equation (3) specifies the conditions related to the state of motor control system 100 that provide the effect of suppressing the rise in capacitor temperature _Tc .

The front motor current _{Iac_fm} and its ^loss_loss ( _{Iac_fm} ) can be calculated by using a map determined in advance for the torque and rotation speed of the front motor 10fr. The combined current _{Idc_f} can be calculated by calculating the change in combined power from the rotation speed and torque of the front motor 10fr and the rotation speed and torque of the generator 16, and using the battery voltage. The loss ⁺ loss( _{Idc_f} ) of the combined current _{Idc_f} can be calculated by using a map determined in advance for these parameters.

Then, if the controller 20 determines that the condition of formula (3) is satisfied, it proceeds to step S105, and if the condition is not satisfied, it ends this routine.

In step S105, a second suppression process is executed. Specifically, the controller 20 reduces the front motor torque _{Tfr_m} and increases the rear motor torque _{Trr_m} while maintaining the total driving force of the vehicle, thereby suppressing an increase in the capacitor temperature _Tc . In particular, in this process, similarly to step S104, it is preferable to determine the amount of decrease in the front motor torque _{Tfr_m} (the amount of increase in the rear motor torque _{Trr_m} ) so as to minimize the discomfort felt by the vehicle occupants.

According to the first suppression process (step S102) of the temperature suppression control described above, the generator current _{Iac_fg} is reduced while maintaining the generated power output by the generator 16, so that the rise in the capacitor temperature _Tc can be suppressed without changing the composite power of the front inverter _14fr . Furthermore, according to the suppression region determination process (step S104) and the second suppression process (step S105), in a scene (temperature suppression region) where a certain degree of temperature suppression effect can be obtained depending on the increase or decrease in loss due to the change in the front motor current Iac_fm and the increase or decrease in loss due to the change in the composite power (composite current _{Idc_f} ) of the front inverter 14fr, the distribution ratio κ is changed while maintaining the total output of the motor control system 100 (total driving force of the vehicle) to reduce the front motor current _{Iac_fm} . Therefore, the rise in the capacitor temperature _Tc can be more effectively suppressed while ensuring the output performance of the motor control system 100 (driving performance when mounted on a vehicle).

The motor control method of this embodiment described above provides the following effects:

According to this embodiment, there is provided an electric motor control method that is executed by an electric motor control system 100 including a generator 16 as an electric power generator, a smoothing capacitor 30 as a capacitive element that temporarily stores the generated power (generated current I _{dc_fg} ) output by the generator 16, and a front motor 10fr as an electric motor driven by this generated power, and that controls the operation of the generator 16 and the front motor 10fr.

In this motor control method, when the temperature of the smoothing capacitor 30 (capacitor temperature _Tc ) is equal to or higher than a predetermined threshold value (reference value α), a temperature suppression control (particularly, a first suppression process and/or a second suppression process) is executed to suppress the rise in the capacitor temperature _Tc by reducing the generator current _{Iac_fg} of the generator 16.

As a result, without changing the output of the front motor 10fr (while maintaining the output at a desired state), the generator current _{Iac_fg} can be reduced to suppress heat generation in the smoothing capacitor 30, and the rise in the capacitor temperature _Tc can be suppressed.

In particular, in this embodiment, the temperature suppression control includes a first suppression process (step S102) of reducing the generator current _{Iac_fg} while maintaining the generated power of the generator 16.

This realizes a specific control logic for suppressing an increase in the capacitor temperature _Tc without changing the composite power of the generated power of the generator 16 and the power supplied to the front motor 10fr.

Moreover, the electric motor control system 100 of this embodiment further includes a front motor 10fr as a first electric motor, and a rear motor 10rr as a second electric motor different from the front motor 10fr. The temperature suppression control includes a second suppression process (step S105) that reduces the front motor torque _{Tfr_m} (front motor current _{Iac_fm} ) and increases the rear motor torque _{Trr_m} (particularly the rear motor current Iac_rm) while maintaining the sum of the output of the front motor _10fr (front motor torque _{Tfr_m} ) and the output of the rear motor 10rr (rear motor torque _{Trr_m} ).

This realizes a more specific control logic that can suppress the rise in capacitor temperature _Tc while maintaining the total output (total driving force of the vehicle) of motor control system 100.

In particular, the temperature suppression control of this embodiment includes a suppression region determination process (step _S104 ) that determines whether the state of the motor control system 100 is in the temperature suppression region (equation (3)) where a certain degree of effect is obtained in suppressing the rise in the capacitor temperature Tc, and a second suppression process (step S105) that reduces the front motor torque _{Tfr_m} (particularly the front motor current Iac_fm) and increases the rear motor torque _{Trr_m} (particularly the rear motor current _{Iac_rm} ) while maintaining the sum of the front motor torque _{Tfr_m} and _the rear motor torque _{Trr_m} when it is determined that the state of the motor control system 100 is in the temperature suppression region.

In the suppression region determination process, when the combined change in loss of the smoothing capacitor 30 due to the change in the front motor torque T _{fr_m} (front motor current I _{ac_fm} ) and the change in loss of the smoothing capacitor 30 due to the change in the combined output (combined current I _{dc_f} ) of the generator 16 and the front motor 10fr is decreasing (when the second term of equation (3) is satisfied), the state of the motor control system 100 is determined to be in the temperature suppression region.

This realizes a control logic for executing the second suppression process in more effective scenes, taking into account the balance between the increase and decrease in loss due to changes in the front motor current _{Iac_fm} and the increase and decrease in loss due to changes in the combined power (combined _{current Idc_f} ) of the front inverter 14fr.

The electric motor control system 100 of this embodiment includes a generator power converter 34 that adjusts the generated power of the generator 16, and a front motor power converter 32 that is connected in parallel with the generator power converter 34 to the smoothing capacitor 30 and serves as an electric motor power converter that adjusts the output of the front motor 10fr.

This realizes a system configuration for more reliably suppressing an increase in the capacitor temperature _Tc by reducing the generator current _{Iac_fg} .

Furthermore, in this embodiment, an electric motor control system 100 suitable for executing the above electric motor control method is provided.

This motor control system 100 includes a generator 16 as a power generator, a smoothing capacitor 30 as a capacitive element that temporarily stores the generated power (generated current I _{dc_fg} ) output by the generator 16, a front motor 10fr as a motor driven by the generated power, and a controller 20 as a control device that controls the generator 16 and the drive motor 10.

Then, when the temperature of the smoothing capacitor 30 (capacitor temperature T _c ) is equal to or higher than a predetermined threshold value (reference value α), the controller 20 executes temperature suppression control (particularly, the first suppression process and/or the second suppression process) to suppress the rise in the capacitor temperature T _c by reducing the generator current I _{ac_fg} of the generator 16.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

For example, in the above embodiment, an example was described in which the drive motor 10 is configured with a front motor 10fr that is driven together with the generator 16 by an integrated inverter 14, and a rear motor 10rr. However, this is not limited to this, and the method described in the above embodiment may be applied with some modifications when only one drive motor 10 is provided to provide the total output (total driving force of the vehicle) of the electric motor control system 100 (for example, when the rear motor 10rr is omitted and a configuration is adopted in which the output is provided only by the front motor 10fr).

In addition, in the above embodiment, the description was given on the assumption that the device equipped with the electric motor control system 100 is a vehicle. However, it is also possible to install the electric motor control system 100 in something other than a vehicle and execute the control of the above embodiment.

REFERENCE SIGNS LIST 10 Drive motor, 10fr Front motor, 10rr Rear motor, 12 Battery, 14 Inverter, 14fr Front inverter, 14rr Rear inverter, 16 Generator, 18 Engine, 20 Controller, 30 Smoothing capacitor, 32 Front motor power converter, 34 Generator power converter, 36 Temperature sensor, 40 Smoothing capacitor, 42 Rear motor power converter, 100 Motor control system

Claims (3)

A motor control method that is executed in a motor control system including a generator, a capacitance element that temporarily stores generated power output by the generator, and a motor that is driven by the generated power, and controls operations of the generator and the motor, comprising:
When the temperature of the capacitance element is equal to or higher than a predetermined threshold, a temperature suppression control is executed to suppress an increase in the temperature of the capacitance element by reducing a current of the generator ;
The motor control system further includes a first motor that functions as the motor, and a second motor different from the first motor,
The temperature suppression control includes:
a first suppression process of reducing a current of the generator while maintaining the generated power;
a temperature suppression region determination process for determining whether or not the state of the motor control system is in a temperature suppression region in which a certain degree of effect of suppressing an increase in the temperature of the capacitance element can be obtained;
a second suppression process of reducing the output of the first motor and increasing the output of the second motor while maintaining a sum of the output of the first motor and the output of the second motor when it is determined that the state of the motor control system is in the temperature suppression region,
In the suppression region determination process, when a combined loss change of the loss change of the capacitive element caused by a change in the output of the first motor and a combined loss change of the capacitive element caused by a change in the combined output of the generator and the first motor is decreasing, the state of the motor control system is determined to be in the temperature suppression region.
Electric motor control method. 2. A method for controlling an electric motor according to claim 1 , comprising:
The motor control system includes a generator power converter that adjusts the generated power of the generator, and a motor power converter that is connected in parallel with the generator power converter with respect to the capacitance element and adjusts an output of the motor.
Electric motor control method. A generator,
a capacitance element for temporarily storing the generated power output by the generator;
an electric motor driven by the generated power;
A motor control system including: a control device that controls the operation of the generator and the motor;
The control device includes:
When the temperature of the capacitance element is equal to or higher than a predetermined threshold, a temperature suppression control is executed to suppress an increase in the temperature of the capacitance element by reducing a current of the generator ;
Further comprising a first motor functioning as the electric motor and a second motor different from the first motor,
The temperature suppression control includes:
a first suppression process of reducing a current of the generator while maintaining the generated power;
a temperature suppression region determination process for determining whether or not the state of the motor control system is in a temperature suppression region in which a certain degree of effect of suppressing an increase in the temperature of the capacitance element can be obtained;
a second suppression process for reducing the output of the first motor and increasing the output of the second motor while maintaining a sum of the output of the first motor and the output of the second motor when it is determined that the state of the motor control system is in the temperature suppression region,
In the suppression region determination process, when a combined loss change of the loss change of the capacitance element caused by a change in the output of the first motor and a combined loss change of the loss change of the capacitance element caused by a change in the combined output of the generator and the first motor is decreasing, the state of the motor control system is determined to be in the temperature suppression region.
Motor control system.

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