Power converter

Abstract

This power converter provides a dual inverter with a common ground plane that can efficiently drive motors with open-end windings while expanding the operating range. [Solution] The power converter 1 of the GND-common type dual inverter is equipped with a control device 6 that controls the primary inverter INV1 and the secondary inverter INV2. The control device 6 switches between a high-efficiency operation mode in which the secondary inverter INV2 is stopped or outputs only reactive power, and a high-output operation mode in which the secondary inverter INV2 outputs only active power or active power and reactive power. In the high-output operation mode, the active power output by the secondary inverter INV2 is minimized.

Description

[Technical Field]

[0001] The present invention relates to a power conversion device that applies an AC output to a motor having windings with an open-end structure where both ends are open, using two inverters, a primary inverter and a secondary inverter. [Background technology]

[0002] For example, when driving electric compressors used in the air conditioning systems of electric vehicles such as electric cars and hybrid vehicles, three-phase permanent magnet synchronous motors (IPMSMs) are used. In typical three-phase star-connected permanent magnet synchronous motors using inverters, the switching methods and definitions of operating ranges for maximum torque / current control (high-efficiency operation), flux weakening control (high-output operation), and maximum torque / voltage (high-output operation) are well-established, as shown in Figure 13.

[0003] In Figure 13, the vertical axis represents torque and the horizontal axis represents speed. Maximum torque / current control (high-efficiency operation) is performed in the constant torque operation region at low speeds, flux weakening control (high-power operation) is performed in the operation region at higher speeds, and maximum torque / voltage (high-power operation) is performed in the operation region at even higher speeds (see, for example, Patent Document 1).

[0004] On the other hand, motors driven by inverters tend to have a narrower high-speed driveable range when the input voltage drops, as the driveable rotational speed decreases, or the output torque at high rotational speeds decreases. In the above-mentioned automotive electric compressors, which drive the compression mechanism with a motor housed within a housing, the required input voltage range was not conventionally wide, but in recent years, the requirements for the driveable range in response to changes in input voltage have become stricter even for electric compressors.

[0005] However, in electric compressors used in vehicles, the battery of the electric vehicle is used as the DC power source, which can cause the input voltage to drop. When the input voltage drops, the torque that can be output decreases in the high-speed range.

[0006] Therefore, as a method to increase the output voltage to the motor relative to the input voltage, a dual inverter power conversion device has been proposed in which a motor with a so-called open-end winding structure (a motor with the neutral point of the motor exposed outside without being connected) equipped with multiple stator windings that are open at both ends is sandwiched between two inverters, a primary and a secondary inverter, and the differential voltage between the primary and secondary inverters is applied to the motor to drive it (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5925526 [Patent Document 2] Patent No. 7414923 [Overview of the project] [Problems that the invention aims to solve]

[0008] In a dual-inverter power converter that drives a motor with an open-end winding structure, there are two inverters, a primary and a secondary, which provides flexibility in how the voltage command value is distributed to the two inverters.

[0009] Figure 14 shows a typical dual inverter power converter. In Figure 14, M is a motor with the open-ended winding structure described above, INV1 is the primary inverter, and INV2 is the secondary inverter, which sandwich the stator winding of the motor M.

[0010] A dual inverter power converter with a shared power supply is the simplest type, sharing the primary and secondary power supplies. Because there is only one power supply, the voltage ratings of all semiconductor elements and passive elements (capacitors, etc.) on both the primary and secondary sides must be set according to the power supply voltage, but both the primary and secondary sides can output both active and reactive power. In this method, since a common power supply is used for both the primary and secondary sides, half of the voltage command value will be output by each inverter INV1 and INV2.

[0011] However, in the case of a dual inverter power converter with a shared power supply, there is a path through which zero-sequence current flows, and since this zero-sequence current directly leads to losses, it is necessary to take measures to address it. Furthermore, since the use of zero-sequence current is limited in dual inverter power converters with a shared power supply, it is common practice to control it so that the zero-sequence current becomes 0A. By controlling the zero-sequence current to 0A, it was possible to apply the same theory as a three-phase star-connected permanent magnet synchronous motor.

[0012] Other types of dual-inverter power converters include isolated power supply dual-inverter power converters and floating capacitor dual-inverter power converters. However, isolated power supply dual-inverter power converters require two isolated power supplies, which raises concerns about their size.

[0013] On the other hand, floating capacitor type dual inverter power converters have the advantage of being able to control the secondary voltage and not allowing zero-sequence current to flow, but they require an additional power supply to drive the switching elements of the secondary inverter.

[0014] Furthermore, since the power supply for the secondary inverter is a capacitor, it can only supply reactive power. Therefore, the primary inverter outputs active power at the voltage command value, and the secondary inverter outputs reactive power. In addition, any reactive power that cannot be output by the secondary inverter is borne by the primary inverter.

[0015] This floating capacitor type dual inverter has the advantage of being able to drive the motor while boosting the voltage of the capacitor in the secondary inverter, thus allowing the voltage that can be applied to the motor to be even higher than that of a common power supply type.

[0016] However, the conventional dual-inverter power converters described above all have a large number of components, making it difficult to reduce costs and miniaturize them. In particular, in floating capacitor type dual-inverter power converters, the secondary inverter is at a floating potential, so it is necessary to create a separate power supply (isolated power supply) for driving the gates of the switching elements of the secondary inverter, which has a different reference potential, in addition to the power supply for driving the gates of the switching elements of the primary inverter. This makes it difficult to adopt in devices with limited board area, such as electric compressors for automobiles, due to the component mounting area and cost.

[0017] Therefore, the applicant previously proposed a power conversion device as shown in Figure 1. In this method, the positive power line of the power supply common type shown in Figure 14 is separated by the primary inverter INV1 and the secondary inverter INV2, while only the negative power line is made common, and a capacitor is placed on the secondary side, similar to a floating capacitor type. Hereinafter, this type of power conversion device will be referred to as a GND common type dual inverter. In this method, the secondary voltage can be controlled in the same way as the control of a floating capacitor type dual inverter power conversion device.

[0018] Furthermore, in a power converter with a common ground (GND) dual inverter, it is possible to share the power supply for the drive circuit of the secondary inverter INV2, similar to the common power supply type. This allows the primary inverter INV1 on the power supply side to be constructed with high-voltage components, while the controllable secondary inverter INV2 can be constructed with low-voltage components. The common ground type, which allows the power supply for the drive circuit of the secondary inverter INV2 to be shared with the primary inverter INV1, offers significant advantages in applications where the power supply voltage fluctuates greatly.

[0019] In a power converter with a common ground (GND) dual inverter, the zero-sequence current is used to control the DC link voltage of the secondary inverter, i.e., the secondary voltage. Therefore, it is not always appropriate to control the zero-sequence current to 0A, as is the case with a power converter with a common power supply dual inverter.

[0020] In particular, in operating ranges requiring high output, it becomes necessary to continuously supply a zero-sequence current to output active power from the secondary inverter. That is, the power converter of a ground-common dual inverter can output active power from the secondary inverter by supplying a zero-sequence current.

[0021] Outputting active power through the secondary inverter increases the output degrees of freedom of the voltage vector, enabling high-power operation. On the other hand, allowing zero-sequence current to flow leads to increased losses, so it is desirable to avoid or suppress it as much as possible. However, as in the case of the three-phase star-connected permanent magnet synchronous motor mentioned above, methods for switching between high-efficiency operation and high-power operation modes, and methods for determining the operating range, had not been established.

[0022] The present invention was made to solve the aforementioned conventional technical problems, and provides a power conversion device that can efficiently drive a motor having an open-end winding structure while expanding the operating range using the above-mentioned common-ground dual inverter. [Means for solving the problem]

[0023] To efficiently drive motors with open-end windings over a wide operating range using the above-mentioned GND-common dual inverter power converter, the control device is equipped with a high-efficiency operation mode and a high-output operation mode, which are switched between and executed.

[0024] In other words, the power conversion device of the present invention comprises a primary inverter connected to one end of an open-ended winding of a motor, and a secondary inverter connected to the other end of the winding, and applies the differential voltage between the primary and secondary inverters to the motor, wherein the primary inverter is connected to a DC power supply, the secondary inverter is connected to a capacitor, the negative power lines of the primary and secondary inverters are shared, and the device comprises a control device that controls the primary and secondary inverters, and this control device switches between a high-efficiency operating mode in which the secondary inverter is stopped or outputs only reactive power, and a high-output operating mode in which the secondary inverter outputs only active power or active power and reactive power, and in the high-output operating mode, minimizes the active power output by the secondary inverter.

[0025] The power conversion device of the second invention is characterized in that, in the above invention, the control device executes a high-efficiency operation mode in the constant torque operation region of the motor and executes a high-output operation mode in the operation region at a speed higher than the constant torque operation region.

[0026] The power conversion device of the third invention is characterized in that, in the present invention, the primary inverter and the secondary inverter are each composed of a plurality of switching elements, the positive input terminal of the primary inverter is connected to the positive power line of the DC power supply, the negative input terminal of the primary inverter is connected to the negative power line of the DC power supply, the output terminal of the primary inverter is connected to one end of the winding, the output terminal of the secondary inverter is connected to the other end of the winding, a capacitor is connected between the positive and negative input terminals of the secondary inverter, the positive input terminal of the secondary inverter is not connected to the positive power line of the DC power supply, and the negative input terminal of the secondary inverter is connected to the negative power line of the DC power supply, and an AC output is generated from the DC power supply by switching each switching element with a control device.

[0027] The power conversion device of the fourth invention is such that the control device in the present invention has a dq axis voltage command value V dqref From this, a primary-side voltage vector command value V1 for switching the primary-side inverter ref and a secondary-side voltage vector command value V2 for switching the secondary-side inverter ref An output voltage command generation unit that generates the primary-side voltage vector command value V1 so that the effective power output by the secondary-side inverter is minimized in the high-output operation mode ref and the secondary-side voltage vector command value V2 ref It is characterized by generating

[0028] In the power conversion device of the fifth invention, in the high-output operation mode, the output voltage command generation unit controls the motor current I m and the secondary-side voltage vector command value V2 in the direction opposite to the phase of the motor current I ref It is characterized by minimizing the component of

[0029] In the power conversion device of the sixth invention, in the high-output operation mode, the output voltage command generation unit controls the motor current I by operating the phases of the primary-side voltage vector command value V1 ref and the secondary-side voltage vector command value V2 ref within the output limit, and the secondary-side voltage vector command value V2 in the direction opposite to the phase of the motor current I m It is characterized by executing maximum amplitude output control to minimize the component of ref

[0030] In the power conversion device of the seventh invention, in the fifth invention, the output voltage command generation unit sets the primary-side voltage vector command value V1 ref to be in the same phase as the dq-axis voltage command value V dq ref and, within the output limit, sets the secondary-side voltage vector command value V2 ref to be in the opposite phase to the dq-axis voltage command value V dq ref to minimize the component of the secondary-side voltage vector command value V2 in the direction opposite to the phase of the motor current I m It is characterized by executing secondary-side reverse-phase output control ref

[0031] ​​ The power conversion device of the eighth invention, in the fifth invention, the output voltage command generation unit is the primary side voltage vector command value V1 ref and secondary voltage vector command value V2 ref By manipulating their phases while setting the output limit to I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref Maximum amplitude output control that minimizes the component and primary side voltage vector command value V1 ref The dq axis voltage command value V dq ref With the phase being the same and the output limit set, the secondary voltage vector command value V2 ref The dq axis voltage command value V dq ref By making it out of phase, the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref It has secondary-side reverse-phase output control that minimizes the component of the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref This method is characterized by selecting and executing either maximum amplitude output control that reduces the component, or secondary side inverse phase output control. [Effects of the Invention]

[0032] According to the present invention, in a power conversion device comprising a primary inverter connected to one end of an open-ended winding of a motor and a secondary inverter connected to the other end of the winding, the differential voltage between the primary and secondary inverters is applied to the motor. In this dual inverter with a common ground connection, the primary inverter is connected to a DC power supply, the secondary inverter is connected to a capacitor, and the negative power lines of the primary and secondary inverters are shared. This allows the capacitor to be charged by the secondary inverter via the motor from the DC power supply, and the AC output is applied to the motor using the voltage charged in this capacitor, thereby expanding the drivable range in response to changes in input voltage.

[0033] Furthermore, in a power converter with a common ground (GND) dual inverter, as in the third invention, the positive input terminal of the secondary inverter is not connected to the positive power line of the DC power supply, and the negative input terminal of the secondary inverter is connected to the negative power line of the DC power supply. As a result, the secondary inverter does not become floating potential, and the reference voltages of the primary and secondary inverters are aligned.

[0034] This eliminates the need to create a separate gate drive power supply (isolated power supply) for the switching elements of the secondary inverter, in addition to the gate drive power supply (isolated power supply) for the switching elements of the primary inverter. This allows the switching elements of both the primary and secondary inverters to be switched using a common gate drive power supply, thus expanding the drivable range in response to changes in input voltage without the need for a separate boost converter or similar device.

[0035] Furthermore, since it becomes unnecessary to create a separate power supply for each inverter to drive the gate, the increase in component mounting area can be suppressed, enabling miniaturization and cost reduction. This makes it extremely effective for equipment such as automotive electric compressors, where the input voltage changes significantly, there is a strong demand for cost reduction, and the board area is limited, requiring miniaturization of the power conversion device.

[0036] In particular, the present invention provides a control device that controls the primary and secondary inverters. This control device switches between a high-efficiency operating mode in which the secondary inverter is stopped or outputs only reactive power, and a high-output operating mode in which the secondary inverter outputs only active power or both active and reactive power. Furthermore, in the high-output operating mode, the active power output by the secondary inverter is minimized. Therefore, for example, as in the second invention, by switching the operating mode to execute the high-efficiency operating mode in the constant torque operating range of the motor and the high-output operating mode in the operating speed range higher than the constant torque operating range, the motor can be driven stably over a wide range of operating conditions.

[0037] Furthermore, in high-power operation mode, the active power output by the secondary inverter is minimized, thereby minimizing the zero-sequence current and suppressing the increase in losses in high-power operation mode, making it possible to achieve efficient motor drive across the entire operating range.

[0038] In this case, the control device actually receives the dq axis voltage command value V as in the fourth invention. dq ref Therefore, the primary voltage vector command value V1 for switching the primary inverter. ref The secondary voltage vector command value V2 for switching the secondary inverter. ref An output voltage command generation unit is provided to generate the primary voltage vector command value V1 in the high-power operation mode so that the active power output by the secondary inverter is minimized. ref and secondary voltage vector command value V2 ref Make it generate

[0039] Furthermore, as in the fifth invention, the output voltage command generation unit, in the high-power operation mode, the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref Minimize the component.

[0040] In that case, for example, as in the sixth invention, the output voltage command generation unit generates the primary side voltage vector command value V1 ref and secondary voltage vector command value V2 ref By manipulating their phases while setting the output limit to I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref This performs maximum amplitude output control to minimize the component. This reduces the motor current I that outputs active power. m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref By minimizing this component and reducing the zero-sequence current, it becomes possible to suppress the increase in losses.

[0041] Furthermore, as in the seventh invention, the output voltage command generation unit generates the primary side voltage vector command value V1 ref The dq axis voltage command value V dq ref With the phase being the same and the output limit set, the secondary voltage vector command value V2 ref The dq axis voltage command value V dq ref By making it out of phase, the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref The secondary side reverse-phase output control may be implemented to minimize the component of the motor current I that outputs active power. m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref By minimizing this component and reducing the zero-sequence current, it becomes possible to suppress the increase in losses.

[0042] Furthermore, as in the eighth invention, the maximum amplitude output control and the secondary side inverse phase output control are compared, and the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref You can also choose to execute the option that results in a smaller component. [Brief explanation of the drawing]

[0043] [Figure 1] This is an electrical circuit diagram of a power conversion device with a common ground (GND) dual inverter according to one embodiment of the present invention. [Figure 2] Figure 1 is a block diagram of the control device for the power converter. [Figure 3] This figure illustrates the voltage vector of the power converter shown in Figure 1. [Figure 4] Figure 3 shows the state when the phase of the motor current changes. [Figure 5] Figure 1 illustrates the high-efficiency operating mode performed by the control device of the power converter. [Figure 6] Figure 5 shows the state when the phase of the motor current has changed. [Figure 7]Figure 1 illustrates the maximum amplitude output control performed by the control device of the power converter in the high-power operation mode. [Figure 8] Figure 7 shows the state when the phase of the motor current has changed. [Figure 9] Figures 7 and 8 show the primary dq-axis voltage, secondary dq-axis voltage, and zero-sequence current during maximum amplitude output control. [Figure 10] Figure 1 illustrates the secondary-side reverse-phase output control performed by the control device of the power converter in the high-power operation mode. [Figure 11] Figure 10 shows the primary dq-axis voltage, secondary dq-axis voltage, and zero-sequence current in the secondary-side reverse-phase output control. [Figure 12] This figure illustrates the switching method between the high-efficiency operation mode and the high-output operation mode performed by the control device of the power converter shown in Figure 1. [Figure 13] This diagram illustrates how to switch between high-efficiency operation mode and high-output operation mode when driving a typical three-phase star-connected permanent magnet synchronous motor with an inverter. [Figure 14] This is an electrical circuit diagram of a conventional dual inverter power converter. [Modes for carrying out the invention]

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (1) Power converter 1 Figure 1 is an electrical circuit diagram of a power converter 1 of a common-ground dual inverter in one embodiment to which the present invention is applied. The power converter 1 of this embodiment converts the DC voltage V of a DC power source (e.g., a high-voltage battery of an electric vehicle) 2. dcThis converts the DC voltage to a three-phase AC voltage (AC output) and supplies it to the motor M. The motor M in this embodiment consists of a stator with three-phase windings and a rotor with a built-in magnet that rotates inside it, and is a three-phase permanent magnet synchronous motor (Interior Permanent Magnet Synchronous Motor) that drives an electric compressor used in the air conditioning system of electric vehicles such as electric vehicles and hybrid vehicles. Note that the DC voltage V of the DC power supply 2 dc The primary voltage V of the power converter 1 dc1 This is the DC link voltage of the primary inverter INV1, which will be described later.

[0045] In this embodiment, the power converter 1 consists of a three-phase primary inverter INV1 consisting of upper and lower arm switching elements 3A to 3F, a three-phase secondary inverter INV2 consisting of upper and lower arm switching elements 4A to 4F, and a control device 6 (Figure 2), etc. In this embodiment, each switching element 3A to 3F and 4A to 4F is composed of an insulated gate bipolar transistor (IGBT) with a MOS structure incorporated into its gate portion.

[0046] In this invention, the DC voltage V of the DC power supply 2 is controlled by the primary inverter INV1 and the secondary inverter INV2. dc The voltage is converted to a three-phase AC voltage (AC output), and the difference voltage between inverters INV1 and INV2 is applied to the windings (stator windings) of motor M. Here, the windings of motor M have an open-end structure and are not bundled at the neutral point.

[0047] (2) Primary side inverter INV1 The primary inverter INV1 has a U-phase half-bridge circuit 9U, a V-phase half-bridge circuit 9V, and a W-phase half-bridge circuit 9W. Each of the phase half-bridge circuits 9U to 9W has the aforementioned upper arm switching elements 3A to 3C and lower arm switching elements 3D to 3F, respectively. Furthermore, each of the switching elements 3A to 3F incorporates a freewheeling diode 5 connected in antiparallel.

[0048] The collector electrodes of the upper arm switching elements 3A~3C, which are the positive input terminals of the primary inverter INV1, are connected to the positive power supply line 11 (HV+) of the DC power supply 2. On the other hand, the emitter electrodes of the lower arm switching elements 3D~3F, which are the negative input terminals of the primary inverter INV1, are connected to the negative power supply line 12 (HV-) of the DC power supply 2. Note that 13 in the figure is a capacitor connected between the positive power supply line 11 and the negative power supply line 12, and constitutes a noise filter.

[0049] In this case, the emitter electrode of the upper arm switching element 3A of the U-phase half-bridge circuit 9U of the primary inverter INV1 is connected to the collector electrode of the lower arm switching element 3D, and their connection point (arm midpoint: output terminal of the primary inverter INV1) is connected to one end of the U-phase winding of the motor M.

[0050] Furthermore, the emitter electrode of the upper arm switching element 3B of the V-phase half-bridge circuit 9V and the collector electrode of the lower arm switching element 3E are connected, and their connection point (arm midpoint: output terminal of primary side inverter INV1) is connected to one end of the V-phase stator winding of motor M.

[0051] Furthermore, the emitter electrode of the upper arm switching element 3C of the W-phase half-bridge circuit 9W and the collector electrode of the lower arm switching element 3F are connected, and their connection point (arm midpoint: output terminal of primary side inverter INV1) is connected to one end of the W-phase stator winding of motor M.

[0052] (3) Secondary inverter INV2 The secondary inverter INV2 also has three half-bridge circuits 16U, 16V, and 16W corresponding to each of the UVW phases. Furthermore, the neutral points of each phase of the motor M are not bundled together, and the motor M windings are sandwiched between the half-bridge circuits 9U~9W of the primary inverter INV1 and the half-bridge circuits 16U~16W of the secondary inverter INV2.

[0053] The half-bridge circuits 16U to 16W of the secondary inverter INV2 each have upper arm switching elements 4A to 4C and lower arm switching elements 4D to 4F, respectively. In addition, each switching element 4A to 4F also incorporates a freewheeling diode 10 connected in antiparallel.

[0054] Furthermore, a capacitor C is connected between the collector electrodes of the upper arm switching elements 4A~4C, which are the positive input terminals of the secondary inverter INV2, and the emitter electrodes of the lower arm switching elements 4D~4F, which are the negative input terminals of the secondary inverter INV2.

[0055] However, the collector electrodes of the upper arm switching elements 4A to 4C, which are the positive input terminals of the secondary inverter INV2, are not connected to the positive power supply line 11 of the DC power supply 2, but are disconnected. On the other hand, in this invention, the emitter electrodes of the lower arm switching elements 4D to 4F, which are the negative input terminals of the secondary inverter INV2, are connected to the negative power supply line 12 of the DC power supply 2.

[0056] Then, the emitter electrode of the upper arm switching element 4A of the U-phase half-bridge circuit 16U and the collector electrode of the lower arm switching element 4D are connected, and their connection point (arm midpoint: output terminal of secondary inverter INV2) is connected to the other end of the U-phase winding of motor M.

[0057] Furthermore, the emitter electrode of the upper arm switching element 4B of the V-phase half-bridge circuit 16V and the collector electrode of the lower arm switching element 4E are connected, and their connection point (arm midpoint: output terminal of secondary inverter INV2) is connected to the other end of the V-phase stator winding of motor M.

[0058] Furthermore, the emitter electrode of the upper arm switching element 4C of the W-phase half-bridge circuit 16W and the collector electrode of the lower arm switching element 4F are connected, and their connection point (arm midpoint: output terminal of secondary inverter INV2) is connected to the other end of the W-phase stator winding of the motor M. In other words, the power conversion device 1 of the present invention has the configuration of the aforementioned common-ground dual inverter system.

[0059] (4) Control device 6 Next, Figure 2 shows a block diagram of the control device 6. The control device 6 of this embodiment consists of a microcomputer having a processor, and receives the speed command value ω from the ECU of the electric vehicle. rm ref and secondary voltage command value v dc2 ref Input the current and measure the phase current of motor M (motor current I) from the current sensor (not shown). m The system takes inputs from these inputs and controls the ON / OFF state of switching elements 3A~3F and 4A~4F of the primary inverter INV1 and secondary inverter INV2 based on these inputs (switching).

[0060] Specifically, it controls the gate voltage applied to the gates of each switching element 3A-3F and 4A-4F. The control device 6 in this embodiment is configured to include a speed control unit 21, a dq-axis current control unit 22, a secondary voltage control unit 27, a z-axis current control unit 28, an output voltage command generation unit 29, a primary modulation unit 24, and a secondary modulation unit 26.

[0061] (4-1) Speed ​​control unit 21 The speed control unit 21 performs PI calculation and q-axis current I q The relationship between the current and torque gives the q-axis current command value I q ref Calculate and output the result.

[0062] (4-2) dq axis current control section 22 The dq-axis current control unit 22 controls the d-axis voltage command value V through PI calculation and non-interference control. d ref and q-axis voltage command value V q refCalculate and output. In this case, basically in the dq-axis current control unit 22, the d-axis current command value I d ref and the d-axis current I d (estimated value), the q-axis current command value I q ref and the q-axis current I q (estimated value), and the d-axis voltage command value V d ref and the q-axis voltage command value V q ref are calculated in a direction to eliminate the deviation. These d-axis voltage command values V d ref and the q-axis voltage command values V q ref become the dq-axis voltage command values V dq ref (vector) in the present invention.

[0063] (4-3) Secondary-side voltage control unit 27 The secondary-side voltage control unit 27 outputs a zero-phase current command value I z ref . This zero-phase current command value I z ref is the secondary-side DC link current command value necessary for controlling the secondary-side voltage V dc2 (DC link voltage of the secondary-side inverter).

[0064] (4-4) z-axis current control unit 28 The z-axis current control unit 28 outputs a zero-phase voltage command value V z for controlling the zero-phase current I z ref (secondary-side DC link current) to the zero-phase current command value I z ref .

[0065] (4-5) Output voltage command generation unit 29 The output voltage command generation unit 29 uses the d-axis current I d (estimated value), the q-axis current I q (estimated value), and the d-axis voltage command value V d ref output by the dq-axis current control unit 22, and the q-axis voltage command value V q refThe dq axis voltage command value V consists of the following: dq ref (Vector) and the zero-sequence voltage command value V output by the z-axis current control unit 28 z ref Therefore, the primary voltage vector command value V1 for switching each switching element 3A~3F of the primary inverter INV1. ref The secondary voltage vector command value V2 is used to switch each switching element 4A~4F of the secondary inverter INV2. ref It generates and outputs the output voltage. The operation of this output voltage command generation unit 29 will be described in detail later.

[0066] (4-6) Primary Modulation Unit 24 The primary-side modulation unit 24 controls the primary-side voltage vector command value V1 ref The primary inverter switching signal (PWM signal) is generated and output from the primary inverter INV1 to switch (PWM control) each switching element 3A to 3F. The secondary modulation unit 26 also generates and outputs the secondary voltage vector command value V2 ref From there, it generates and outputs a secondary inverter switching signal (PWM signal) for switching (PWM control) each switching element 4A~4F of the secondary inverter INV2.

[0067] (5) Operation of the output voltage command generation unit 29 Next, the operation of the output voltage command generation unit 29 described above will be explained. In the following explanation, the DC link voltage ratio of the primary inverter INV1 and the secondary inverter INV2 is assumed to be 2:1, and in the embodiment, the DC link voltage of the primary inverter INV1 (primary voltage V dc1 ) to 250V, the DC link voltage of the secondary inverter INV2 (secondary voltage V dc2 Set the voltage to 125V.

[0068] First, we will explain the voltage vector of the power converter 1 of the GND common type dual inverter. Figure 3 is a diagram illustrating the voltage vector of the power converter 1 of the embodiment. In the figure, the vertical axis is the q-axis voltage V q The horizontal axis is the d-axis voltage V. dFurthermore, the outermost dashed circle C1 represents the linear output range of the power converter 1 of the GND-common dual inverter, the innermost dashed circle C2 represents the linear output range of the primary inverter INV1, and the innermost dashed circle C3 represents the linear output range of the secondary inverter INV2.

[0069] As mentioned above, since the DC link voltage ratio between the primary inverter INV1 and the secondary inverter INV2 is 2:1, the radius of circle C3 is half that of circle C2, and the radius of circle C1 is the sum of the radii of circle C2 and circle C3.

[0070] Also, I m V is the vector of the current (motor current) of motor M. dq ref This is the vector of the dq axis voltage command values ​​mentioned above, V1 ref V2 is the primary voltage vector command value for switching the primary inverter INV1 mentioned above. ref The secondary voltage vector command value, θ, is used to switch the secondary inverter INV2 mentioned above. m is the motor current I m This is the phase.

[0071] The output voltage command generation unit 29 of the control device 6 generates the dq axis voltage command value V dq ref Therefore, the dq axis voltage command value V dq ref Primary voltage vector command value V1 for generating (vector) ref and secondary voltage vector command value V2 ref This generates the following. In this case, in order to create a potential difference, the voltage of the secondary inverter INV2 is the opposite of that of the primary inverter INV1, so the secondary voltage vector command value V2 ref A vector with the opposite phase and the primary side voltage vector command value V1 ref The combined vector is the dq-axis voltage command value V dq ref This is the result. Note that Figure 4 shows the motor current I. m This shows the case where the phase changes (d-axis current I d When this flows, the motor current I m (The phase rotates).

[0072] In this case, the motor current I m When a voltage with the same phase as or opposite phase to the vector is output, active power is output, and when a voltage in the orthogonal direction is output, reactive power is output. In Figures 3 and 4, the primary side voltage vector command value V1 ref is the motor current I m Since it is in the same phase, the primary inverter INV1 outputs only active power. On the other hand, the secondary voltage vector command value V2 ref is the motor current I m Since the phase is perpendicular to the direction of the polarity, the secondary inverter INV2 is in a state where it outputs only reactive power.

[0073] Here, when the secondary inverter INV2 outputs active power, steady-state powering or regeneration occurs in capacitor C, so in the operating range where high output is required, the secondary voltage V dc2 (DC link voltage of the secondary inverter) is set to the secondary voltage command value v dc2 ref To keep it in line, a constant zero-sequence current I z It is necessary to flush it.

[0074] In other words, the power converter 1 of the GND common type dual inverter has a zero-sequence current I z By flowing this current, it becomes possible to output active power from the secondary inverter INV2. Outputting active power from the secondary inverter INV2 increases the output degrees of freedom of the voltage vector, enabling high-power operation.

[0075] However, zero-sequence current I z Since releasing it leads to increased losses, it is desirable to avoid or minimize it as much as possible.

[0076] Therefore, in this invention, a high-efficiency operation mode and a high-output operation mode (high-efficiency operation and high-output operation shown in Figure 2) are provided in the output voltage command generation unit 29, and these operation modes are switched and executed depending on the operating range. That is, in this embodiment, the operation mode selection unit 30 of the output voltage command generation unit 29 switches between a high-efficiency operation mode in which the secondary inverter INV2 is stopped or outputs only reactive power with the secondary inverter INV2, and a high-output operation mode in which the secondary inverter INV2 outputs only active power or active power and reactive power, thereby achieving a wide operating range and high efficiency. In the following description, the secondary inverter INV2 will be operated in high-efficiency operation mode.

[0077] (5-1) High-efficiency operation mode Figures 5 and 6 show the voltage vectors in the high-efficiency operating mode and the operating range for each operating mode. Note that Figure 6 shows the motor current I m This shows the case where the phase changes (d-axis current I d When this flows, the motor current I m (The phase rotates). In each figure, circle X1 is the output range for the high-power operation mode, and is basically the same as the linear output range C1 of the power converter 1 of the GND common type dual inverter described above. Also, oval X2 is the output range for the high-efficiency operation mode, and is the same as the linear output range of the primary side inverter INV1 described above, with the secondary side voltage vector command value V2 ref For that portion, the d-axis voltage V d It will be a shifted (expanded) shape in that direction.

[0078] In this high-efficiency operation mode, the output voltage command generation unit 29 generates the motor current I m Refer to the secondary voltage vector command value V2 ref motor current I m The phase is set to be in a direction orthogonal to the secondary side inverter INV2, and the secondary side voltage vector command value V2 is the orthogonal component. ref It continues to output only reactive power. That is, the primary voltage vector command value V1 is set so that the secondary inverter INV2 outputs only reactive power. ref and secondary voltage vector command value V2 ref Distribute it.

[0079] In this case, the secondary inverter INV2 outputs only reactive power, so the steady zero-sequence current I z No current flows, zero-sequence current I z This minimizes losses due to [unspecified factor]. However, in this high-efficiency operating mode, the motor current I m Secondary voltage vector command value V2 in a direction perpendicular to the direction. ref Because it can only output a limited range and the output voltage vector is limited, the dq-axis voltage command value V is only available within the range of the ellipse X2. dq ref It is not possible to output the region between the oval X2 and the circle X1. In other words, the region between the oval X2 and the circle X1 cannot be output, and the entire linear output range C1 of the power converter 1 of the GND-common type dual inverter cannot be output.

[0080] (5-2) High-power operation mode Therefore, the output voltage command generation unit 29 switches the operating mode to the high-power operating mode when high power is required in the operating range. In the following explanation, we will describe the high-power operating mode in which the secondary inverter INV2 outputs active power and reactive power.

[0081] The high-power operation mode allows for the output of dq-axis voltage command values ​​V, which cannot be output in the high-efficiency operation mode. dq ref This applies when outputting the following. In high-power operation mode, the dq axis voltage command value V dq ref Prioritizing the output of the secondary voltage vector command value V2, the secondary inverter INV2 also outputs active power. ref Outputs.

[0082] Furthermore, in high-power operation mode, the secondary inverter INV2 outputs active power, so the secondary voltage V dc2 To control the DC link voltage of the secondary inverter, a constant zero-sequence current I z It is necessary to flow this zero-sequence current I zTo minimize this, the primary voltage vector command value V1 is set so that the active power output from the secondary inverter INV2 is minimized. ref and secondary voltage vector command value V2 ref Distribute it.

[0083] Furthermore, in high-power operation mode, the secondary voltage vector command value V2 of the secondary inverter INV2 ref Since no restrictions are imposed, the entire output range X1 of the power converter 1 of the GND-common type dual inverter becomes the operating range.

[0084] This high-power operation mode uses the primary voltage vector command value V1 ref and secondary voltage vector command value V2 ref Due to the high degree of freedom in output, multiple output methods are possible. In this embodiment, we will describe two of these methods: maximum amplitude output control and secondary side inverse phase output control.

[0085] (5-2-1) Maximum Amplitude Output Control Figures 7 and 8 show the case of maximum amplitude output control. Note that Figure 8 shows the motor current I m This shows the case where the phase changes (d-axis current I d When this flows, the motor current I m (The phase rotates). Maximum amplitude output control is performed using the primary voltage vector command value V1 of the primary inverter INV1, as shown in each figure. ref The length is extended to the output limit circle C2, and the secondary voltage vector command value V2 of the secondary inverter INV2 ref With the length extended to the output limit circle C3, each vector command value V1 ref , V2 ref By manipulating the phase, the dq axis voltage command value V dq ref The following are combined and output. As can be seen from each figure, the secondary voltage vector command value V2 ref is the motor current I m The phase is not perpendicular to the direction, but rather at a larger angle than the perpendicular direction.

[0086] At that time, the output voltage command generation unit 29 generates the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref The component (the vector component shown by arrow Y1 in Figures 7 and 8) is minimized. In practice, the dq-axis voltage command value V dq ref Draw a circle with the same radius as circle C3, centering on the tip of the arrow. Of the two points where this circle intersects with circle C2, find the point where the vector component of arrow Y1 is smaller and set the dq axis voltage command value V dq ref Draw an arrow from the tip, and an arrow in the opposite phase to it, and the secondary voltage vector command value V2 ref This will result in the active power output by the secondary inverter INV2 being minimized, and the zero-sequence current I z This minimizes losses.

[0087] Figure 9 shows the d-axis voltage V of the primary inverter INV1 when switching from high-efficiency operation mode to high-power operation mode and performing maximum amplitude output control in this high-power operation mode. d1 and q-axis voltage V q1 And the d-axis voltage V of the secondary inverter INV2 d2 and q-axis voltage V q2 And, zero-sequence current I z (I z res This indicates that...

[0088] In high-efficiency operation mode, as mentioned above, the zero-sequence current I z It is approximately 0A. On the other hand, in high-power operation mode, the zero-sequence current I z While some noise is present, its increase is kept to a minimum.

[0089] (5-2-2) Secondary side reverse-phase output control Next, Figure 10 shows the case of secondary-side reverse-phase output control. In secondary-side reverse-phase output control, the primary-side voltage vector command value V1 of the primary-side inverter INV1 is as shown in this figure. ref The length of the dq axis is the command value V dq ref The output is extended to circle C2, which is the output limit, in the same phase, and the dq axis voltage command value Vdq ref The difference is the dq axis voltage command value V dq ref The secondary voltage vector command value V2 of the secondary inverter INV2, which is in the opposite phase to the secondary inverter INV2. ref In this case as well, the secondary voltage vector command value V2 ref is the motor current I m The phase is not perpendicular to the direction, but rather at an angle greater than the perpendicular direction.

[0090] In this case as well, the secondary voltage vector command value V2 ref Since the amplitude can be minimized, the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref The component (the vector component shown by arrow Y1 in Figure 10) can be minimized. Therefore, the active power output by the secondary inverter INV2 is minimized, and the zero-sequence current I z This minimizes losses.

[0091] Figure 11 shows the d-axis voltage V of the primary inverter INV1 when switching from high-efficiency operation mode to high-power operation mode and performing secondary-side reverse-phase output control in this high-power operation mode. d1 and q-axis voltage V q1 And the d-axis voltage V of the secondary inverter INV2 d2 and q-axis voltage V q2 And, zero-sequence current I z (I z res This indicates that...

[0092] In high-efficiency operation mode, as mentioned above, the zero-sequence current I z It is approximately 0A. On the other hand, in high-power operation mode, the zero-sequence current I z Although some flow occurs, it can be seen that its increase is kept to a minimum in this case as well.

[0093] (5-3) Switching between high-efficiency operation mode and high-output operation mode The operating mode selection unit 30 of the output voltage command generation unit 29 in the embodiment switches between the high-efficiency operating mode and the high-output operating mode described above according to the operating range, as shown in Figure 12. In Figure 12, the vertical axis represents torque and the horizontal axis represents speed. The operating mode selection unit 30 executes the high-efficiency operating mode in the low-speed constant-torque operating range and the high-output operating mode in the operating range at higher speeds.

[0094] As detailed above, in this invention, by making the power conversion device 1 a GND common type dual inverter, the capacitor C is charged by the secondary inverter INV2 via the motor M from the DC power supply 2, and the AC output is applied to the motor M using the voltage charged to the capacitor C by the secondary inverter INV2, thereby expanding the drivable range in response to changes in input voltage.

[0095] Furthermore, in the power converter 1 of the GND-common dual inverter, the positive input terminal of the secondary inverter INV2 is not connected to the positive power line 11 of the DC power supply 2, and the negative input terminal of the secondary inverter INV2 is connected to the negative power line 12 of the DC power supply 2. As a result, the secondary inverter INV2 does not become a floating potential, and the reference voltages of the primary inverter INV1 and the secondary inverter INV2 are aligned.

[0096] This eliminates the need to create a separate gate drive power supply (isolated power supply) for the switching elements 4A to 4F of the secondary inverter INV2, in addition to the gate drive power supply (isolated power supply) for the switching elements 3A to 3F of the primary inverter INV1. This allows the switching elements 3A to 3F of the primary inverter INV1 and the switching elements 4A to 4F of the secondary inverter INV2 to be switched using a common gate drive power supply, thus expanding the drivable range in response to changes in input voltage without the need for a separate boost converter or similar device.

[0097] Furthermore, since it becomes unnecessary to create a separate gate drive power supply for each inverter INV1 and INV2, the increase in component mounting area can be suppressed, enabling miniaturization and cost reduction. This makes it extremely effective for equipment such as automotive electric compressors, where the input voltage changes significantly, there is a strong demand for cost reduction, and the board area is limited, requiring miniaturization of the power conversion device.

[0098] In particular, the present invention provides a control device 6 that controls the primary inverter INV1 and the secondary inverter INV2. This control device 6 switches between a high-efficiency operation mode in which the secondary inverter INV2 outputs only reactive power and a high-output operation mode in which the secondary inverter INV2 outputs both active and reactive power. Furthermore, in the high-output operation mode, the active power output by the secondary inverter INV2 is minimized. As shown in the embodiment, by executing the high-efficiency operation mode in the constant torque operation range of the motor M and the high-output operation mode in the operating speed range higher than the constant torque operation range, the motor can be driven stably over a wide range of operating conditions.

[0099] Furthermore, in high-power operation mode, the active power output by the secondary inverter INV2 is minimized, so the zero-sequence current I z By minimizing this, it is possible to suppress the increase in losses in high-power operation modes and achieve efficient motor drive across the entire operating range.

[0100] In addition, in this embodiment, the control device 6 is given the dq axis voltage command value V dq ref Therefore, the primary voltage vector command value V1 for switching the primary inverter INV1. ref And the secondary voltage vector command value V2 for switching the secondary inverter INV2. ref An output voltage command generation unit 29 is provided to generate the primary voltage vector command value V1 in the high-power operation mode so that the active power output by the secondary inverter INV2 is minimized. refand secondary voltage vector command value V2 ref The output voltage command generation unit 29 generates the motor current I in the high-power operation mode. m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref By minimizing this component, it becomes possible to appropriately suppress the increase in losses.

[0101] In that case, as described above, the output voltage command generation unit 29 generates the primary side voltage vector command value V1 ref and secondary voltage vector command value V2 ref By manipulating their phases while setting the output limit to I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref By implementing maximum amplitude output control that minimizes the component of the motor current I, the motor current that outputs active power will be reduced. m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref Minimize the component of zero-sequence current I z This minimizes the increase in losses, thereby preventing further growth.

[0102] Furthermore, as mentioned above, the output voltage command generation unit 29 generates the primary side voltage vector command value V1 ref The dq axis voltage command value V dq ref With the phase being the same and the output limit set, the secondary voltage vector command value V2 ref The dq axis voltage command value V dq ref By making it out of phase, the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref Even if secondary-side reverse-phase output control is implemented to minimize the component of the motor current I that outputs active power, m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref Minimize the component of zero-sequence current I z This minimizes the increase in losses, thereby preventing further growth.

[0103] In this embodiment, the secondary inverter INV2 is configured to output only reactive power in high-efficiency operation mode. However, the secondary inverter INV2 may be stopped in high-efficiency operation mode. In that case, the motor current I m The current will flow through the freewheeling diode 10.

[0104] Furthermore, although the high-power operation mode was described in the embodiment as an example in which the secondary inverter INV2 outputs both active and reactive power, it is not limited to this, and in the high-power operation mode, the secondary inverter INV2 may output only active power.

[0105] Furthermore, in high-power operation mode, the aforementioned maximum amplitude output control and secondary-side inverse-phase output control may be switched and executed. In that case, the operation mode selection unit 30 of the output voltage command generation unit 29 compares the calculated value by maximum amplitude output control and the calculated value by secondary-side inverse-phase output control, and determines the motor current I m The secondary voltage vector command value V2 is in the opposite phase direction to this. ref The system will select and execute the option that results in a smaller component (Y1).

[0106] Furthermore, although the switching element described in the examples consists of an IGBT, a MOSFET may also be used. Also, the specific configurations and numerical values ​​shown in the examples are not limited to those, and can be modified without departing from the spirit of the present invention. [Explanation of symbols]

[0107] 1. Power converter 2 DC power supply 3A~3F, 4A~4F switching element 6. Control device 11. Positive power line 12 Negative power line 21 Speed ​​control unit 22 dq axis current control section 24 Primary Modulation Section 26 Secondary Modulation Section 27 Secondary voltage control unit 28 z-axis current control unit 29 Output Voltage Command Generation Unit 30 Operating mode selection section C Capacitor INV1 Primary Inverter INV2 Secondary Inverter M Motor

Claims

1. A power conversion device comprising a primary inverter connected to one end of an open-ended winding of a motor, and a secondary inverter connected to the other end of the winding, wherein the differential voltage between the primary and secondary inverters is applied to the motor, The primary inverter is connected to a DC power supply. The secondary inverter is connected to a capacitor, The negative power supply lines of the primary inverter and the secondary inverter are shared. The system includes a control device that controls the primary inverter and the secondary inverter, The control device is The secondary inverter is stopped, or the secondary inverter switches between a high-efficiency operating mode in which it outputs only reactive power and a high-output operating mode in which it outputs only active power, or active power and reactive power. A power conversion device characterized by minimizing the active power output by the secondary inverter in the high-power operation mode.

2. The power conversion device according to claim 1, characterized in that the control device executes the high-efficiency operation mode in the constant torque operation region of the motor and executes the high-output operation mode in the operation region at a speed higher than the constant torque operation region.

3. The primary inverter and the secondary inverter are each composed of multiple switching elements. The positive input terminal of the primary inverter is connected to the positive power line of the DC power supply, the negative input terminal of the primary inverter is connected to the negative power line of the DC power supply, and the output terminal of the primary inverter is connected to one end of the winding. The output terminal of the secondary inverter is connected to the other end of the winding, and the capacitor is connected between the positive input terminal and the negative input terminal of the secondary inverter. The positive input terminal of the secondary inverter is not connected to the positive power line of the DC power supply, and the negative input terminal of the secondary inverter is connected to the negative power line of the DC power supply. The power conversion device according to claim 1, characterized in that it generates an AC output from the DC power supply by switching each of the switching elements using the control device.

4. The control device is It has an output voltage command generation unit that generates a primary voltage vector command value for switching the primary inverter and a secondary voltage vector command value for switching the secondary inverter from the dq axis voltage command value. The power conversion device according to claim 1, characterized in that the output voltage command generation unit generates the primary voltage vector command value and the secondary voltage vector command value in such a way that the active power output by the secondary inverter is minimized in the high-power operation mode.

5. The output voltage command generation unit, The power conversion device according to claim 4, characterized in that, in the high-power operation mode, the component of the secondary voltage vector command value in a direction opposite in phase to the motor current is minimized.

6. The output voltage command generation unit, The power conversion device according to claim 5, characterized in that it performs maximum amplitude output control by manipulating the phases of the primary voltage vector command value and the secondary voltage vector command value while the primary voltage vector command value and the secondary voltage vector command value are set as output limits, thereby minimizing the component of the secondary voltage vector command value that is in the opposite phase to the motor current.

7. The output voltage command generation unit, The power converter according to claim 5, characterized in that the primary voltage vector command value is set to be in phase with the dq-axis voltage command value and at the output limit, and the secondary voltage vector command value is set to be in opposite phase with the dq-axis voltage command value, thereby performing secondary reverse-phase output control to minimize the component of the secondary voltage vector command value that is in opposite phase with the motor current.

8. The output voltage command generation unit, Maximum amplitude output control that minimizes the component of the secondary voltage vector command value in the opposite phase to the motor current by manipulating their phases while the primary voltage vector command value and the secondary voltage vector command value are set as output limits, The system has a secondary reverse-phase output control that minimizes the component of the secondary voltage vector command value that is in the opposite phase to the motor current by setting the primary voltage vector command value to be in the same phase as the dq-axis voltage command value and at the output limit, and then setting the secondary voltage vector command value to be in the opposite phase to the dq-axis voltage command value. The power conversion device according to claim 5, characterized in that it selects and executes either the maximum amplitude output control or the secondary reverse-phase output control that reduces the component of the secondary voltage vector command value in the direction opposite in phase to the motor current.

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