Motor drive device

Abstract

Motor drive device attached to a vehicle with a power machine (1) and a motor (2050) directly coupled to each other, wherein the vehicle comprises a DC power supply device (2002) configured to supply an electric current to the motor (2050) and charged by an output of the motor (2050), wherein the motor drive device comprises: an inverter (2030) configured to convert an electric DC current supplied by the DC power supply device (2002) into an electric AC current, and to convert an electric AC current received from the motor (2050) into an electric DC current;and a control device (2001) configured to control the inverter (2030), wherein the motor (2050) and the inverter (2030) configured to drive the motor (2050) each comprise a first group with a U-phase, a V-phase and a W-phase and a second group with an X-phase, a Y-phase and a Z-phase; wherein the control device (2001) comprises: a fault detection unit configured to determine whether at least the inverter (2030) and / or the DC power supply device (2002) has a fault, in order to determine whether or not current flow from the motor (2050) to the DC power supply device (2002) is blocked;a DC supply state determination unit configured to determine whether or not the DC supply device (2002) is fully charged, in order to determine whether or not current flow from the motor (2050) to the DC supply device (2002) is blocked;and a switching unit configured to select, when determined by the fault detection unit and the DC supply state determination unit that the current flow from the motor (2050) to the DC supply device (2002) is blocked, a control operation performed in the inverter (2030) from an all-phase shutdown and a three-phase short circuit based on a motor rotation speed of the motor (2050), an induced voltage of the motor (2050) and a DC linkage voltage of the motor (2050), wherein in the all-phase shutdown all switching elements (3) of the inverter (2030) are open;and wherein the control device further comprises a three-phase short-circuit processing unit configured to perform control such that, when a reduction amount of the three-phase short-circuit torque is equal to or greater than a threshold value 4 while the inverter (2030) is performing the three-phase short circuit, one of the first group and the second group performs power operation and another of the first group and the second group performs recovery in order to achieve a rise and a fall of the DC current from zero.

Description

Background of the invention 1. Field of invention The present invention relates to a motor drive device, and in particular a motor drive device configured for selective switching between a three-phase short circuit and an all-phase shutdown based on a motor rotation speed or an induced voltage of a motor. 2. Description of the state of the art In recent years, hybrid and electric vehicles have gained prominence as energy-efficient and environmentally friendly options. Hybrid vehicles utilize both a combustion engine and a conventional engine as power sources, while electric vehicles use a motor as their sole power source. Both hybrid and electric vehicles are configured so that direct current (DC) stored in a battery is converted into alternating current (AC) by an inverter to power a motor and propel the vehicle. The hybrid vehicle also includes a motor-generator with a power generation function. The motor-generator is configured to generate electricity using the rotational energy produced when a power unit is running. The motor-generator is also configured to recover electricity using rotational energy from a tire during coasting. Any electrical current or power generated in this way by the motor-generator is stored in a battery. In a prior art motor drive device attached to a vehicle having the configuration described above, if a problem occurs such that a motor is not driven and a battery fails in a power-generating state, a connecting element connecting the motor drive device and the battery becomes loose, or a disconnect switch or the like inserted between connecting elements is opened, a voltage of a charging path of a control circuit of the motor drive device increases rapidly.As a result of the voltage increase, a large overvoltage occurs, and this overvoltage is applied to circuit elements in the motor drive device, such as smoothing capacitors, or is applied to any device connected to the motor drive device as a load of a DC power supply, causing problems such as deterioration and damage to the circuit elements or any device. To address these problems, Japanese patent JP 4 675 299 B2, for example, proposes a control device that includes an overvoltage detection device for determining an overvoltage in the output circuit of an electric rotary machine, and an instruction value calculation device for transitioning current generation instruction values ​​and field current instruction values ​​to zero when the overvoltage detection device determines an overvoltage. In the configuration described in Japanese patent JP 4 675 299 B2, when the overvoltage detection device determines an overvoltage, an electric current conversion device is controlled to cause the electric rotary machine to enter a phase short-circuit state, allowing a short-circuit current to flow through the electric rotary machine to suppress the maximum value of the overvoltage and rapidly reduce it.Furthermore, circuit elements used in the control device or the loads of the electric rotary machine can be protected from deterioration, damage, and the like caused by overvoltage. However, it is concerning that when the electrical current conversion device is controlled to establish the phase short-circuit state after an overvoltage is detected, as in the Japanese patent JP 4 675 299 B2 discussed above, a period of time elapses during the overvoltage state. Consequently, the circuit elements used in the control device or the loads of the electric rotary machine cannot be protected from deterioration, damage, and the like caused by the overvoltage during this time. Furthermore, the overvoltage detection process can be complex and may lead to an increase in costs. Systems in which a power unit and a motor are directly coupled via a drive shaft are also configured to recover current or power via an induced voltage generated when the motor is rotated by the power unit. However, in some cases, current is prevented from flowing to the power supply side, for example, due to a fault or malfunction in the power supply or because a battery is fully charged. DE 10 2011 081 173 A1 describes an operating state circuit for controlling an inverter which supplies an n-phase electrical machine with an n-phase supply voltage via phase terminals, where n ≥ 1, with an evaluation device which is connected to the phase terminals of the inverter and which is designed to detect output voltages of the inverter at the phase terminals and to determine a speed of the electrical machine on the basis of the detected output voltages, and a control device which is coupled to the evaluation device and which is designed to switch the inverter into a freewheeling state or an active short circuit depending on the determined speed. DE 11 2011 105 776 T5 describes a control device for an electrically powered vehicle, which controls an electrically powered vehicle comprising a motor that transmits driving force to wheels, an inverter that drives the motor, and a battery that supplies power to the inverter. The control device includes a battery storage capacity estimator for estimating the battery's storage capacity and a rotational speed sensing device for sensing the motor's rotational speed. The inverter's output terminals are short-circuited when the motor's rotational speed reaches or exceeds a predetermined speed, while the storage capacity estimated by the battery storage capacity estimator is equal to or greater than a predetermined amount. US 2020 / 0353820A1 describes a propulsion system for an electric vehicle, comprising a high-voltage battery unit with a first high-voltage battery connected in series with a second high-voltage battery, which may also be referred to as the first and second battery banks, and one or more inverters arranged to connect the battery banks to one or more electric machines. The one or more inverters and the one or more electric machines are configured to form a first and second three-phase system, and the system and procedure relate to fault handling when a fault is detected in either the first or second three-phase system.The architecture with two battery banks and two- and / or multi-phase inverters and electrical machines can provide improved redundancy and emergency operation functionality in cases where a fault or malfunction occurs in the inverter and / or electrical machine, so that a faulty three-phase system can be operated in a safe pulse-off mode. DE 10 2012 216 008 A1 describes an operating state circuit for the inverter of an electric drive, which protects the DC link from overvoltages during fault or generator operation. For this purpose, an active three-phase short circuit is established and maintained as long as the detected input voltage remains above an adjustable short-circuit threshold; this prevents an impermissible increase in the DC link voltage. Alternatively, freewheeling can be provided if the induced motor voltage is sufficiently low. EP 2 644 439 A1 describes a two-wheeled electric vehicle with a motor controller that, upon reaching a short-circuit threshold (e.g., high motor speed / no current control reserve), creates a three-phase short circuit to prevent unintended recuperation and battery overvoltage. The short circuit is only released once defined speed or battery voltage limits are undershot and is pulsed in phases to prevent any inrush current from entering the battery. Additionally, the release is linked to field weakening conditions to ensure a reliable control reserve. Summary of the invention The present invention serves to solve the problems mentioned above and aims to provide a motor drive device that is configured to switch to a three-phase short circuit or an all-phase shutdown in advance to prevent an overvoltage, instead of switching the control after an overvoltage is determined, thereby protecting a DC power supply device and an inverter. The above problem is solved by the subject matter of the independent claim. Examples and technical descriptions of devices, products and / or methods in the description and / or drawings that are not covered by the claims are not presented as embodiments of the invention, but rather as background information or examples that are useful for understanding the invention. Brief description of the drawings Fig. 1 is a schematic configuration diagram of a vehicle according to a first embodiment, a second embodiment, and a third embodiment of the present invention. Fig. 2 is a representative schematic configuration diagram of a motor drive device according to the first embodiment, the second embodiment, and the third embodiment of the present invention. Fig. 3 is a flowchart of a process for determining whether PWM of the motor drive device according to the first embodiment of the present invention is allowed or blocked. Fig. 4 is a flowchart of a process for determining a switch between a three-phase short circuit and an all-phase shutdown based on a motor rotation speed of the motor drive device according to the first embodiment of the present invention.Figure 5 is a flowchart of a process for determining a switch between three-phase short circuit and all-phase shutdown based on an induced voltage of the motor drive device according to the second embodiment of the present invention. Figure 6 is a flowchart of a process for determining a switch between three-phase short circuit and all-phase shutdown based on an estimated induced voltage of the motor drive device according to the third embodiment of the present invention. Figure 7 is a flowchart of the three-phase short-circuit processing of the motor drive device according to the first embodiment of the present invention. Figure 8 is an explanatory diagram illustrating a method for setting a threshold 1 for switching between three-phase short circuit and all-phase shutdown in the motor drive device according to the first embodiment of the present invention. Detailed description of preferred embodiments With reference to the accompanying drawings, a motor drive device of a vehicle according to exemplary embodiments of the present invention is described below. Identical or corresponding parts in the drawings are designated by the same reference numerals for the purposes of description. Before describing a motor drive device according to each embodiment of the present invention, the configuration of a motor driven by the motor drive device and the configuration of a vehicle to which the motor is attached are explained. The configuration of the motor and the configuration of the vehicle explained here are common to all embodiments. Fig. 1 is a schematic configuration diagram of a vehicle according to each embodiment of the present invention. In Fig. 1, a current generator (not shown) is driven by a power engine 1. The current generator produces electricity through the drive, and the generated electrical current is used via an inverter 5 to charge a battery 6. The inverter 5 converts the direct current generated by the generator or the direct current stored in the battery 6 into alternating current and then supplies the alternating current to the motor 8 to drive it. In this way, a tire is driven by the motor 8, thus propelling the vehicle. At the time of braking of the vehicle or the like, the motor 8 is rotated by the tires 4, so that the motor 8 performs energy recovery, and the battery 6 is charged with the electrical current generated by the motor 8 via the inverter. Furthermore, the inverter 5 converts the direct current stored in the battery 6 into alternating current to drive the generator in order to start the power machine 1. The vehicle can also be driven by engaging a clutch 2, which is located between the power unit 1 and the motor 8, in order to transmit drive power from the power unit 1 via the motor 8 to the tires 4. In each of the embodiments described later, the example of a series hybrid vehicle is used, as explained above; however, the present invention is not limited to this, and a parallel hybrid vehicle can be used. The series hybrid vehicle is a hybrid vehicle configured, as explained above, to store an electric current generated by a power unit in a battery and to rotate a motor using the battery's electricity to drive the tires 4. The series hybrid vehicle drives, as explained above, without using the power unit and can therefore be considered a type of electric vehicle in a current-based classification. On the other hand, the parallel hybrid vehicle is a hybrid vehicle configured to drive the tires using two types of power: one from a motor and one from a power unit. The generator and the motor 8 can, as explained above, be a motor-generator, both of which have the functions of propulsion and power generation. In each of the following embodiments, a vehicle is described with a single battery and a single inverter; however, the vehicle may have a plurality of batteries of different voltages, and DC-DC converters or the like for voltage conversion between the generator and the inverter or between the battery and the inverter. Fig. 2 is a schematic configuration diagram of the motor drive device according to each embodiment of the present invention. For the motor drive device, Fig. 2 shows, as an example, a motor-inverter system with a control device for an AC rotary machine. A double three-phase motor 2050 according to Fig. 2 comprises a first winding group (first group) 2051 with three phases: a U-phase, a V-phase, and a W-phase, and a second winding group (second group) 2052 with three phases: an X-phase, a Y-phase, and a Z-phase. The first winding group 2051 and the second winding group 2052 can be controlled individually. The double three-phase motor 2050 corresponds to motor 8 according to Fig. 1. The double three-phase motor 2050 is also provided with a U-phase current sensor 2033, a V-phase current sensor 2034, a W-phase current sensor 2035, an X-phase current sensor 2036, a Y-phase current sensor 2037 and a Z-phase current sensor 2038 to measure current values ​​in the respective phases. The twin three-phase motor 2050 is also equipped with a rotation angle sensor 2006, a first coil temperature sensor 2071, and a second coil temperature sensor 2072. The rotation angle sensor 2006 measures the motor rotation angle or rotation speed of the first winding group 2051 and the second winding group 2052. The first coil temperature sensor 2071 also measures the motor temperature of the first winding group 2051. Similarly, the second coil temperature sensor 2072 measures the motor temperature of the second winding group 2052. A twin three-phase inverter 2030 is connected to the twin three-phase motor 2050. The 2030 dual three-phase inverter contains two sets of six arm switching elements: upper arm switching elements 3UH, 3VH, 3WH, 3XH, 3YH, and 3ZH, and lower arm switching elements 3UL, 3VL, 3WL, 3XL, 3YL, and 3ZL. Arm switching elements 3UH, 3UL, 3VL, 3WH, and 3WL are for the first winding group 2051, and arm switching elements 3XH, 3XL, 3YH, 3YL, 3ZH, and 3ZL are for the second winding group 2052. Hereinafter, these switching elements can be referred to collectively simply as switching elements 3. Each of the switching elements 3 comprises a switching element, for example, an IGBT or a FET, and a feedback diode. The dual three-phase inverter 2030 corresponds to inverter 5 in Fig. 1. A battery (DC power supply device) 2002 is connected to the dual three-phase inverter 2030. The dual three-phase inverter 2030 switches each of the switching elements 3 on and off to convert a direct current received from the battery 2002 into an alternating current, and to convert the alternating current received from the dual three-phase motor 2050 into direct current. The battery 2002 corresponds to battery 6 in Fig. 1. The battery 2002 is equipped with a smoothing capacitor 2031, a voltage sensor 2032, and a current sensor 2004. The smoothing capacitor 2031 smooths the DC voltage of the battery 2002. The voltage sensor 2032 measures the DC link voltage of the battery 2002. The current sensor 2004 measures the current flowing into the battery 2002. Repeatedly switching each of the switching elements 3 on and off is referred to here as performing pulse width modulation (PWM) control. In each of the embodiments described below, the double three-phase motor 2050 is described, which contains two groups of three phases each. However, the present invention is not limited thereto, and the motor may have four phases or more, or may contain three groups or more. A microcontroller unit (MCU) 2001 controls a current based on current values ​​in the respective phases, which are detected by the U-phase current sensor 2033, the V-phase current sensor 2034, the W-phase current sensor 2035, the X-phase current sensor 2036, the Y-phase current sensor 2037, and the Z-phase current sensor 2038. The MCU 2001 controls a current so that a desired torque can be generated at the dual three-phase motor 2050. The motor drive device according to each embodiment of the present invention is explained below. In each embodiment described below, an example of a motor drive device configured to drive the motor shown in Figures 1 and 2 is shown. The motor drive device includes the MCU 2001 and the dual three-phase inverter 2030. First embodiment Figure 3 is a flowchart of the processing flow for determining whether PWM control in the motor drive device according to the first embodiment of the present invention is allowed or disabled. That is, the MCU 2001, in accordance with the processing flow shown in Figure 3, determines whether or not the dual three-phase inverter 2030 can perform PWM control. The MCU 2001 includes a memory (not shown) and has a PWM allow / disable flag stored in the memory. The MCU 2001 sets the PWM allow / disable flag stored in the memory to "allow" or "disable" based on the result of a determination performed in the flow shown in Figure 3. The processing flow shown in Figure 3 is carried out by a fault detection unit (not shown) provided in the MCU 2001. The processing is described in detail below. In step S3001, the MCU 2001 first determines whether the dual three-phase inverter 2030 has a fault or malfunction. Possible faults of the dual three-phase inverter 2030 include, for example, a fault in the current sensor 2004, a fault in the voltage sensor 2032, a fault in one of the switching elements 3, and a fault in a temperature sensor (not shown) configured to measure the temperature of each of the switching elements 3. If step S3001 determines that the dual three-phase inverter 2030 has a fault or malfunction, the MCU 2001 goes to step S3101 to set the PWM allow / disable flag to "Disable" and then terminates the processing flow as shown in Fig. 3. On the other hand, if step S3001 determines that the dual three-phase inverter 2030 has no fault or malfunction, the MCU 2001 proceeds to step S3002. In step S3002, the MCU 2001 determines whether battery 2002 has a fault or malfunction. If it is determined that battery 2002 has a fault, the MCU 2001 proceeds to step S3101 to set the PWM allow / disable flag to "disable" and then terminates the processing flow as shown in Fig. 3. If it is determined that battery 2002 does not have a fault, the MCU 2001 proceeds to step S3003. In step S3002, the MCU 2001 also determines whether battery 2002 is fully charged and whether the dual three-phase inverter 2030 is performing PWM control for power generation. If the determination is positive, the MCU 2001 proceeds to step S3101 to set the PWM allow / disable flag to "Disable" and then terminates the processing flow as shown in Fig. 3. If the determination is negative, the MCU 2001 proceeds to step S3003.In step S3002, the MCU 2001 further determines whether a power supply switch or a connector (not shown), provided between the battery 2002 and the dual three-phase inverter 2030, has a fault or malfunction. If it is determined that either the power supply switch or the connector has a fault, the MCU 2001 proceeds to step S3101 to set the PWM allow / disable flag to "disable" and then terminates the processing flow as shown in Fig. 3. If it is determined that neither the power supply switch nor the connector has a fault, the MCU 2001 proceeds to step S3003. In step S3003, the MCU 2001 sets the PWM allow / disable flag to "allow" and then terminates the processing flow as shown in Fig. 3. Fig. 4 is a flowchart of the MCU 2001's processing for switching between all-phase shutdown, three-phase short circuit, and PWM control based on specific conditions, and for performing the switching control in the motor drive device according to the first embodiment of the present invention. The processing flow or sequence according to Fig. 4 is performed after the flow or sequence according to Fig. 3 has been performed. The processing flow according to Fig. 4 is carried out by a switching unit (not shown) provided in the MCU 2001. All-phase shutdown here means that all switching elements 3 of the dual three-phase inverter 2030 are open (switched off). The three-phase short circuit further means that the upper arm switching elements 3 of the dual three-phase inverter 2030 are open (off) and the lower arm switching elements 3 are closed (on) at the same time to establish a phase short circuit condition so that the short-circuit current flows through the dual three-phase motor 2050. The processing is explained in detail below. In step S4001, the MCU 2001 first determines whether the power supply switch (not shown), provided between the battery 2002 and the dual three-phase inverter 2030, is switched on. If the power supply switch is off, the MCU 2001 proceeds to step S4004. In step S4004, the MCU 2001 performs the all-phase shutdown, namely opening (switching off) all of the switching elements 3 of the dual three-phase inverter 2030, and then terminates the processing flow according to Fig. 4. On the other hand, if step S4001 determines that the power supply switch (not shown), provided between battery 2002 and dual three-phase inverter 2030, is turned on, MCU 2001 proceeds to step S4002. In step S4002, the MCU 2001 determines whether the PWM enable / disable flag, stored in memory, is set to "Disable" in the PWM enable / disable determination processing as shown in Fig. 3. If the flag is not set to "Disable," the MCU 2001 proceeds to step S4201 to perform normal PWM processing, which involves current flow or generation through the dual three-phase motor 2050, and then terminates the processing flow as shown in Fig. 4. On the other hand, if step S4002 determines that the flag is set to "Lock", the MCU 2001 goes to step S4003. In step S4003, the MCU 2001 determines whether the motor rotation speed is equal to or less than the preset threshold value of 1. If the motor rotation speed is equal to or less than the threshold value of 1, the MCU 2001 proceeds to step S4004. In step S4004, the MCU 2001 performs the all-phase shutdown, namely opening (switching off) all of the switching elements 3 of the dual three-phase inverter 2030, and then terminates the processing flow according to Fig. 4. On the other hand, if step S4003 determines that the motor rotation speed is not equal to or less than the threshold value 1, the MCU 2001 goes to step S4101. In step S4101, the MCU 2001 performs the three-phase short circuit, namely by opening (switching off) the upper arm switching elements 3 of the dual three-phase inverter 2030, and simultaneously closing (switching on) the lower arm switching elements 3, and then terminating the processing flow according to Fig. 4. The aforementioned threshold 1 is appropriately preset based on the characteristics of the dual three-phase motor 2050 and experimental results. For example, threshold 1 is set equal to or less than a rotational speed in a range where the induced voltage of the dual three-phase motor 2050, generated during rotation, does not exceed the DC linkage voltage of the battery 2002. When threshold 1 is set, as explained above, the induced voltage of the twin three-phase motor 2050 does not exceed the DC linkage voltage of the battery 2002, even in the all-phase shutdown state where all switching elements 3 of the twin three-phase inverter 2030 are open. Therefore, a large current from the twin three-phase motor 2050 flowing through the feedback diode of each switching element 3 into the battery 2002 is prevented, and the battery 2002 and the twin three-phase inverter 2030 are thus not damaged. Furthermore, threshold 1 can be a characteristic value set for each of a multitude of DC linkage voltages. Through an experiment, a rotational speed is obtained for each of the DC linkage voltages within a range where the induced voltage of the dual three-phase motor 2050, generated during rotation of the dual three-phase motor 2050, does not exceed a DC linkage voltage of the battery 2002. This allows the preparation of a characteristic map in which the rotational speed is preset as threshold 1 for each of the DC linkage voltages. Threshold 1 can be obtained from the characteristic map based on a value of the DC linkage voltage. A voltage value measured by the voltage sensor 2032 is used as the DC linkage voltage at this time. If an experiment reveals that such an overvoltage can be generated which damages the battery 2002 and the dual three-phase inverter 2030 when the control is switched between the three-phase short circuit, the all-phase shutdown and the PWM, the threshold value 1 can further be set to a value with which an overvoltage is not generated. Setting the threshold 1 is explained, for example, with reference to Fig. 8. In Fig. 8, the horizontal axis represents the motor rotation speed and the vertical axis represents the DC linkage voltage. If, as shown in Fig. 8, the DC linkage voltage is 36 V, the threshold 1 is set to a value equal to or less than 1000 rpm. If the DC linkage voltage is 45 V, the threshold 1' is set to a value equal to or less than 1100 rpm. If the DC linkage voltage is 52 V, the threshold 1'' is set to a value equal to or less than 1150 rpm. Furthermore, if in this embodiment a motor rotation speed is greater than the threshold value 1, and an induced voltage of the dual three-phase motor 2050 has exceeded or is likely to exceed a DC linkage voltage of the battery 2002, the three-phase short-circuit condition is established to cause a short-circuit current to flow through the dual three-phase motor 2050, thus preventing current from flowing through the battery 2002. The battery 2002 and the dual three-phase inverter 2030 are therefore not damaged. Furthermore, in this embodiment, as described above, the control system is pre-switched to three-phase short circuit or all-phase shutdown to prevent overvoltage, instead of switching to three-phase short circuit or all-phase shutdown after an overvoltage has been detected. This avoids a situation where switching to three-phase short circuit or all-phase shutdown occurs too late, thus preventing damage to battery 2002 and dual three-phase inverter 2030 due to overvoltage. Additionally, processing to detect an overvoltage is not required, resulting in a motor drive device that avoids processing complications and increased costs. Fig. 7 is a flowchart of three-phase short-circuit processing in the motor drive device according to the first embodiment of the present invention. The process flow according to Fig. 7 is carried out by a three-phase short-circuit processing unit (not shown) provided in the MCU 2001. In Fig. 7, the MCU 2001 first determines in step S7001 that the three-phase short circuit is currently being performed in the dual three-phase inverter 2030. If the three-phase short circuit is performed, the MCU 2001 proceeds to step S7002. If the three-phase short circuit is not performed, the MCU 2001 proceeds to step S7201. In step S7201, the MCU 2001 controls the dual three-phase inverter 2030 to perform the three-phase short circuit in both the first winding group 2051 and the second winding group 2052. Furthermore, in step S7202, the MCU 2001 stores a current three-phase short-circuit torque in its memory. This torque is generated as a result of performing the three-phase short circuit and is a value of the last three-phase short-circuit torque. The processing flow is then terminated as shown in Fig. 7. The three-phase short-circuit torque is measured by a torque sensor (not shown) provided for each of the first winding group 2051 and the second winding group 2052. Alternatively, instead of using the torque sensor, an estimated torque calculated from current values ​​measured by current sensors can be used as the three-phase short-circuit torque.As a further alternative to three-phase short-circuit torque, an estimated torque can be used that is calculated from voltage instruction values ​​of the PWM or actual voltages, instead of using the torque sensors. In step S7002, the MCU 2001 determines whether the three-phase short circuit is performed in both the first winding group 20521 and the second winding group 2052 of the dual three-phase inverter 2030. If the three-phase short circuit is performed in both the first winding group 2051 and the second winding group 2052, the MCU 2001 proceeds to step S7003. If the three-phase short circuit is performed in neither the first winding group 2051 nor the second winding group 2052, the MCU 2001 proceeds to step S7004. In step S7003, the MCU 2001 compares a preset threshold 4 with the difference between the absolute value of a previous three-phase short-circuit torque and the absolute value of a current three-phase short-circuit torque. If the difference is equal to or greater than threshold 4 (i.e., if a reduction in the three-phase short-circuit torque is equal to or greater than threshold 4), the MCU 2001 proceeds to step S7004. Conversely, if the difference is less than threshold 4, the MCU 2001 proceeds to step S7201. Threshold 4 is appropriately preset based on the characteristics of the 2050 dual three-phase motor and experimental results. For example, threshold 4 is set equal to or less than a reduction in a braking torque in a range where the DC balance can be zero. In step S7004, the MCU 2001 controls the dual three-phase inverter 2030 so that the first winding group 2051 of the dual three-phase inverter 2030 can perform a current cycle and the second winding group 2052 can perform a recovery cycle. If it is determined that a braking torque is reduced while the three-phase short circuit is performed, the MCU 2001 can perform the control such that the DC balance can be zero. At this point, a comparable effect can also be obtained if, in a manner inverse to the above, the control is performed such that the first winding group 2051 can perform a recovery cycle and the second winding group 2052 can perform a current cycle. In step S7005, the MCU 2001 stores 0 [Nm] for the last three-phase short-circuit torque stored in the memory and then terminates the processing flow as shown in Fig. 7. In this embodiment, as described above, if it is determined that the dual three-phase inverter 2030 has a fault or malfunction, or that the battery 2002 has a fault or is fully (or nearly) charged, and there is a blockage of current flow from the dual three-phase motor 2050 to the battery 2002, the three-phase short circuit or all-phase shutdown is performed in the dual three-phase inverter 2030 while the PWM control is disabled. If the motor rotation speed of the dual three-phase motor 2050 is greater than the threshold value 1 when the control is switched to three-phase short circuit or all-phase shutdown, i.e.,Then, if an induced voltage of the dual three-phase motor 2050 has exceeded, or is likely to exceed, the DC crossover voltage of the battery 2002, it is determined that current can flow to the battery 2002 side, even if all-phase disconnection is performed, and a switching operation is carried out to establish the three-phase short-circuit condition, causing the short-circuit current to flow through the dual three-phase motor 2050. Consequently, without an additional special device, the current can be prevented from flowing from the dual three-phase motor 2050 to the battery 2002 side, even if the dual three-phase motor 2050 recovers current or power with induced voltages, and the battery 2002 and the dual three-phase inverter 2030 are therefore not damaged. The battery 2002 and the dual three-phase inverter 2030 can thus be protected. Furthermore, in this embodiment, threshold 1 is switched depending on the DC linkage voltage when switching occurs, which can suppress the generation of a braking torque due to the three-phase short circuit in a range where the DC linkage voltage is high and the motor rotation speed is low. In this embodiment, the control system is pre-switched to three-phase short circuit or all-phase shutdown to prevent overvoltage, instead of switching to three-phase short circuit or all-phase shutdown only after an overvoltage is detected. This avoids a situation where switching to three-phase short circuit or all-phase shutdown occurs too late, thus preventing damage to battery 2002 and the dual three-phase inverter 2030 due to overvoltage. Furthermore, the processing required to determine an overvoltage is eliminated, resulting in a motor drive device that avoids processing complications and increased costs. Furthermore, if, in this embodiment, a reduction factor of the three-phase short-circuit torque is equal to or greater than threshold 4 while the dual three-phase inverter 2030 is performing the three-phase short circuit, one of the first and second groups will perform a current flow, and the other will perform a recovery. The control can therefore be configured such that the DC balance can be reduced to zero when a braking torque is reduced while the three-phase short circuit is being performed. Second embodiment Fig. 5 is a flowchart of the processing for switching between all-phase shutdown, three-phase short circuit, and PWM based on respective conditions, and for performing the switching in a controller in a motor drive device according to a second embodiment of the present invention. The processing sequence according to Fig. 5 is performed by a switching unit (not shown) provided in the MCU 2001. The remaining configuration and operation are the same as in the first embodiment. In Fig. 5, steps S5001, S5002, S5004, S5101 and S5201 are the same as steps S4001, S4002, S4004, S4101 and S4201 of Fig. 4 and a corresponding description is not repeated here. In this embodiment, the MCU 2001 determines in step S5003 whether an induced voltage of the dual three-phase motor 2050 is equal to or less than a preset threshold 2. If the induced voltage is not equal to or less than threshold 2, the MCU 2001 proceeds to step S5101 to perform processing for the three-phase short circuit and then terminates the processing flow as shown in Fig. 5. If the induced voltage is equal to or less than threshold 2, the MCU 2001 proceeds to step S5004 to perform processing for the all-phase shutdown and then terminates the processing flow as shown in Fig. 5. The aforementioned threshold 2 is appropriately preset based on the characteristics of the dual three-phase motor 2050 and experimental results. For example, threshold 2 is set to a value such that the induced voltage of the dual three-phase motor 2050, generated during its rotation, does not exceed the DC common-mode voltage of the battery 2002. With threshold 2 set as explained above, the induced voltage of the dual three-phase motor 2050 does not exceed the DC common-mode voltage, even in the all-phase shutdown state, where all switching elements 3 of the dual three-phase inverter 2030 are open.A large current flow from the twin three-phase motor 2050 to the battery 2002 can therefore be prevented by the feedback diode of each of the switching elements 3, and the battery 2002 and the twin three-phase inverter 2030 are thus not damaged. Furthermore, the threshold 2 can be a characteristic value that is set for each of a variety of DC linkage voltages via an experiment carried out for each voltage. In the event that an induced voltage of the dual three-phase motor 2050 exceeds threshold 2 when the control system switches to three-phase short-circuit or all-phase shutdown (i.e., when an induced voltage of the dual three-phase motor 2050 has exceeded or is likely to exceed a DC linkage voltage of the battery 2002), this embodiment further incorporates a switching operation to establish the three-phase short-circuit state, causing a short-circuit current to flow through the dual three-phase motor 2050. Current flow through the battery 2002 is thus prevented, and the battery 2002 and the dual three-phase inverter 2030 are therefore not damaged. Similar to the first embodiment, in this embodiment the control system is also pre-switched to three-phase short circuit or all-phase shutdown to prevent overvoltage, instead of switching to three-phase short circuit or all-phase shutdown after an overvoltage has been detected. This avoids a situation where switching to three-phase short circuit or all-phase shutdown occurs too late, potentially damaging battery 2002 and dual three-phase inverter 2030 due to overvoltage. Furthermore, the processing required to detect an overvoltage is eliminated, resulting in a motor drive device that avoids processing complications and increased costs. Third embodiment Fig. 6 is a flowchart of a processing sequence for switching to all-phase shutdown, three-phase short circuit, and PWM based on specific conditions, and for performing the switching control in a motor drive device of a vehicle according to a third embodiment of the present invention. The processing sequence according to Fig. 6 is performed by a switching unit (not shown) provided in the MCU 2001. The remaining configuration and operation are the same as in the first or second embodiment described above. In Fig. 6, steps S6001, S6002, S6004, S6101 and S6201 are the same as steps S4001, S4002, S4004, S4101 and S4201 respectively according to Fig. 4, and a corresponding description is not repeated here. In this embodiment, the MCU 2001 receives an estimated induced voltage from the dual three-phase motor 2050 at step S6003 and determines whether the estimated induced voltage is equal to or less than a preset threshold 3. If the estimated induced voltage is not equal to or less than threshold 3, the MCU 2001 proceeds to step S6101 to perform three-phase short-circuit processing and then terminates the processing flow as shown in Fig. 6. If the estimated induced voltage is equal to or less than threshold 3, the MCU 2001 proceeds to step S6004 to perform all-phase shutdown processing and then terminates the processing flow as shown in Fig. 6. An estimated induced voltage of the dual three-phase motor 2050 is obtained, for example, by the following procedure. First, an induced voltage value of the dual three-phase motor 2050 is obtained for each motor rotation speed and each motor temperature based on the characteristics of the dual three-phase motor 2050 and experimental results. A three-dimensional characteristic map is then generated in which the value of the induced voltage of the dual three-phase motor 2050 is defined for each motor rotation speed and each motor temperature. The characteristic map is pre-stored in the memory of the MCU 2001. The MCU 2001 refers to the characteristic map based on a motor rotation speed and motor temperature when the controller switches to all-phase shutdown, three-phase short circuit, and PWM, and obtains an estimated induced voltage of the dual three-phase motor 2050 from the characteristic map. The characteristic map is not limited to the three-dimensional map described above; a two-dimensional map can be used in which a value for the induced voltage of the two-phase three-phase motor 2050 is defined for each motor rotation speed, or a two-dimensional map in which a value for the induced voltage of the two-phase three-phase motor 2050 is defined for each motor temperature. Furthermore, a characteristic map can be used that indicates the states of the two-phase three-phase motor 2050, other than motor rotation speed and motor temperature. Furthermore, the aforementioned threshold value 3 is appropriately preset based on the characteristics of the dual three-phase motor 2050 and experimental results. For example, threshold value 3 is set to a value such that an estimated induced voltage of the motor, generated during rotation, does not exceed the DC linkage voltage of the battery 2002. With threshold value 3 set as explained above, an induced voltage of the dual three-phase motor 2050 does not exceed the DC linkage voltage of the battery 2002, even in the all-phase shutdown state, where all switching elements 3 of the dual three-phase inverter 2030 are open.This prevents a large current from flowing from the twin three-phase motor 2050 through the feedback diode of each of the switching elements 3 into the battery 2002, and therefore the battery 2002 and the twin three-phase inverter 2030 are not damaged. Furthermore, threshold 3 can be a characteristic value that is set for each of a multitude of DC linkage voltages via an experiment carried out for each voltage. In this embodiment, if the estimated induced voltage of the dual three-phase motor 2050 is greater than threshold 3 when the control system switches to three-phase short-circuit and all-phase shutdown (i.e., when the estimated induced voltage of the dual three-phase motor 2050 exceeds or is likely to exceed the DC linkage voltage of the battery 2002), a switching operation is performed to establish the three-phase short-circuit state, causing a short-circuit current to flow through the dual three-phase motor 2050. Consequently, current flow through the battery 2002 is prevented, and the battery 2002 and the dual three-phase inverter 2030 are therefore not damaged. Similar to the first and second embodiments, in this embodiment the control system is also pre-switched to three-phase short circuit and all-phase disconnection to prevent overvoltage, instead of switching to three-phase short circuit and all-phase disconnection only after an overvoltage has been detected. This avoids a situation where switching between three-phase short circuit and all-phase disconnection occurs too late, thus preventing damage to the DC power supply and inverter due to overvoltage. The processing required to detect an overvoltage is therefore unnecessary, resulting in a motor drive device that avoids processing complications and increased costs.In this embodiment, the induced voltage of the two-phase three-phase motor 2050 is estimated using the characteristic map, and devices configured to measure the induced voltages of the two-phase three-phase motor 2050 are therefore not required. A motor drive device can thus be achieved in which an increase in costs is more effectively prevented.

Claims

Motor drive device attached to a vehicle with a power machine (1) and a motor (2050) directly coupled to each other, wherein the vehicle comprises a DC power supply device (2002) configured to supply an electric current to the motor (2050) and charged by an output of the motor (2050), wherein the motor drive device comprises: an inverter (2030) configured to convert an electric DC current supplied by the DC power supply device (2002) into an electric AC current, and to convert an electric AC current received from the motor (2050) into an electric DC current;and a control device (2001) configured to control the inverter (2030), wherein the motor (2050) and the inverter (2030) configured to drive the motor (2050) each comprise a first group with a U-phase, a V-phase and a W-phase and a second group with an X-phase, a Y-phase and a Z-phase; wherein the control device (2001) comprises: a fault detection unit configured to determine whether at least the inverter (2030) and / or the DC power supply device (2002) has a fault, in order to determine whether or not current flow from the motor (2050) to the DC power supply device (2002) is blocked;a DC supply state determination unit configured to determine whether or not the DC supply device (2002) is fully charged, in order to determine whether or not current flow from the motor (2050) to the DC supply device (2002) is blocked;and a switching unit configured to select, when determined by the fault detection unit and the DC supply state determination unit that the current flow from the motor (2050) to the DC supply device (2002) is blocked, a control operation performed in the inverter (2030) from an all-phase shutdown and a three-phase short circuit based on a motor rotation speed of the motor (2050), an induced voltage of the motor (2050) and a DC linkage voltage of the motor (2050), wherein in the all-phase shutdown all switching elements (3) of the inverter (2030) are open;and wherein the control device further comprises a three-phase short-circuit processing unit configured to perform control such that, when a reduction amount of the three-phase short-circuit torque is equal to or greater than a threshold value 4 while the inverter (2030) is performing the three-phase short circuit, one of the first group and the second group performs power operation and another of the first group and the second group performs recovery in order to achieve an increase and a decrease of the DC current from zero. Motor drive device according to claim 1, wherein the switching unit is configured to: perform all-phase shutdown in the inverter (2030) when the motor rotation speed is equal to or less than a threshold value 1; and perform three-phase short circuit in the inverter (2030) when the motor rotation speed is greater than the threshold value 1. Motor drive device according to claim 2, wherein the threshold value 1 is switched depending on the DC linkage voltage of the motor (2050). Motor drive device according to claim 1, wherein the switching unit is configured to: perform all-phase shutdown in the inverter (2030) when the induced voltage of the motor (2050) is equal to or less than the DC linkage voltage; and perform three-phase short circuit in the inverter (2030) when the induced voltage of the motor (2050) is greater than the DC linkage voltage. Motor drive device according to claim 1, wherein the induced voltage of the motor (2050) comprises an estimated induced voltage obtained based on the motor rotation speed of the motor (2050) and / or a motor temperature of the motor (2050), and wherein the switching unit is configured to: perform all-phase shutdown in the inverter (2030) when the estimated induced voltage of the motor (2050) is equal to or less than the DC linkage voltage; and perform three-phase short-circuiting in the inverter (2030) when the estimated induced voltage of the motor (2050) is greater than the DC linkage voltage.

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