Power conversion apparatus

Abstract

[Problem] To provide a power conversion apparatus with which it is possible to also improve responsiveness while stably controlling the secondary-side voltage of a GND common-type dual inverter, and to drive a motor having a winding with an open-end structure. [Solution] A primary-side inverter is connected to a DC power supply, a secondary-side inverter is connected to a capacitor, a negative-side power supply line of the primary-side inverter and the secondary-side inverter is shared, and a control device 6 that controls a secondary-side voltage which is the charging voltage of the capacitor is provided. The control device 6 has a secondary-side voltage control system 23 that generates a zero-phase voltage command value for applying a zero-phase current that is required for controlling the secondary-side voltage to a secondary-side voltage command value. The secondary-side voltage control system 23 has a feedforward control unit that outputs a feedforward control variable for the zero-phase voltage command value on the basis of the secondary-side voltage command value and the primary-side voltage.

Description

Power Conversion Device

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

[0002] For example, when driving an electric compressor used in an air conditioning system for an electric vehicle such as an electric car or a hybrid car, a three-phase permanent magnet synchronous motor is used. However, the existing motor control method using an inverter uses a d-axis current i d and q-axis current i q Vector control, which controls the above, is common.

[0003] The controller can be designed by modeling the controller and the controlled object (plant model) as shown in Fig. 26. In other words, modeling the controlled object is important for designing the controller.

[0004] On the other hand, when the input voltage drops, the motor driven by the inverter tends to have a narrower range of high-speed operation because the rotational speed at which it can be driven decreases or the torque that can be output at high rotational speeds decreases.In the above-mentioned electric compressor for vehicle use, which drives the compression mechanism with a motor housed in a housing, the required range of input voltage was not wide in the past, but in recent years, the requirements for the range in which electric compressors can be operated in response to changes in input voltage have become stricter.

[0005] However, in-vehicle electric compressors use the battery of the electric vehicle as a DC power source, which can cause a drop in input voltage. If the input voltage drops, the torque that can be output will decrease in the high rotation speed range.

[0006] Therefore, as a method for increasing the output voltage to a motor relative to the input voltage, various dual inverter power conversion devices have been proposed, in which a motor with a so-called open-end winding structure (a motor in which the neutral point of the motor is not connected but extended to the outside) having multiple stator windings with both ends open is sandwiched between two inverters, one on the primary side and one on the secondary side, and the differential voltage between the primary inverter and the secondary inverter is applied to the motor to drive it (see, for example, Patent Document 1 and Patent Document 2).

[0007] JP 2006-149153 A JP 2005-33984 A

[0008] In a dual inverter power conversion device that drives a motor with an open-end winding structure, there are two inverters, one on the primary side and one on the secondary side, so there is a degree of freedom in how the voltage command value is distributed to the two inverters.

[0009] Conventional dual inverter power conversion devices can be broadly divided into three types shown in Figures 27 to 29. Figure 27 shows a typical common power supply type dual inverter power conversion device. In Figure 27, M is a motor equipped with the open-end structure windings described above, INV1 is a primary side inverter, and INV2 is a secondary side inverter, which sandwich the stator windings of motor M.

[0010] The common power supply dual inverter is the simplest method, sharing the power supply for the primary and secondary sides. Because there is only one power supply, the withstand voltage of all semiconductor elements and passive elements (capacitors, etc.) on the primary and secondary sides must be set according to the power supply voltage. Also, because there is a path through which zero-phase current flows, measures must be taken to prevent zero-phase current, but both the primary and secondary sides can output active power and reactive power.

[0011] In this method, since a common power supply is used for the primary and secondary sides, half of the voltage command value is output from each of the inverters INV1 and INV2.

[0012] Next, Figure 28 shows a power conversion device with an isolated power supply type dual inverter. In Figure 28, M is a motor with open-ended windings, INV1 is a primary-side inverter, and INV2 is a secondary-side inverter, which sandwich the stator winding of motor M, but in this system, two isolated power supplies are provided on the primary and secondary sides, respectively. Since two isolated power supplies must be provided, there is a concern that the device may become larger, but it has the advantages of not allowing zero-phase current to flow and that both the primary and secondary sides can output active power and reactive power.

[0013] In this method, the primary and secondary sides are driven by separate power supplies (voltages), so the output is determined according to the voltage ratio. For example, if the voltage V of the primary side power supply is dc1 is the voltage of the secondary power supply V dc2 When the voltage command value is 1 / 2 of the voltage command value, the primary inverter INV1 outputs 1 / 3 of the voltage command value, and the secondary inverter INV2 outputs 2 / 3 of the voltage command value.

[0014] Next, Figure 29 shows a floating capacitor type dual inverter power conversion device. In Figure 29, M is a motor with open-ended windings, INV1 is a primary-side inverter, and INV2 is a secondary-side inverter, which sandwich the stator windings of motor M. In this system, a floating capacitor C is placed in the secondary-side inverter, and the secondary-side voltage is controlled by charging and discharging the capacitor from the motor side.

[0015] The floating capacitor method has the advantage that the secondary side voltage can be controlled and no zero-phase current flows, but on the other hand, it is necessary to prepare an additional drive power supply to drive the switching elements of the secondary side inverter.

[0016] In addition, since the power supply of the secondary inverter is a capacitor, it can only supply reactive power. Therefore, the primary inverter INV1 outputs the active voltage of the voltage command value, and the secondary inverter INV2 outputs the reactive voltage. In addition, the reactive voltage that cannot be output by the secondary inverter INV2 is also borne by the primary inverter INV1.

[0017] Here, the active power is P, the reactive power is Q, and the active voltage is V. real , reactive voltage is V imag Then, the relationship between them is as shown in the vector diagram of Figure 30, and is defined by the following equations (I) to (III). That is, the apparent power S is calculated by the motor current I as shown in equation (I). m and the motor applied voltage V m It is defined as the product (cross product for vectors) of

[0018] Also, the effective power P is calculated by the motor applied voltage V as shown in formula (II). m Motor current I m The effective voltage V real and motor current I m Furthermore, the reactive power Q is defined as the product of the motor applied voltage V as shown in formula (III). m Motor current I m The reactive voltage V is a component in the direction perpendicular to the imag and motor current I m It is defined as the product of

[0019]

[0020] In the floating capacitor type dual inverter power conversion device shown in FIG. 29 , as described above, the primary side inverter INV1 can output active power P and reactive power Q, and the secondary side inverter INV2 can output only reactive power Q, so with control as shown in the block diagram of FIG. 31 , the voltage command values ​​of the primary side inverter INV1 and the secondary side inverter INV2 are distributed according to the following formulas (IV) and (V) to drive the motor M.

[0021]

[0022] In addition, in FIG. 31, equations (IV) and (V), v d ref is the d-axis voltage command value, v q ref is the q-axis voltage command value, i d is the d-axis current, i q is the q-axis current, θ Im is the motor current phase, v d1 ref is the d-axis voltage command value of the primary inverter INV1, v q1ref is the q-axis voltage command value of the primary side inverter INV1, v d2 ref is the d-axis voltage command value of the secondary inverter INV2, v q2 ref is the q-axis voltage command value of the secondary side inverter INV2.

[0023] Furthermore, in a floating capacitor type dual inverter power conversion device, in addition to driving the motor M, it is necessary to control the DC link voltage of the secondary side inverter INV2, i.e., the secondary side voltage Vdc2, and this adds a component of the voltage vector required to charge the capacitor C.

[0024] In this case, in the power conversion device of the floating capacitor type dual inverter, since no zero-phase current flows, the motor current I m and the voltage vector, the secondary voltage V dc2 That is, as shown in FIG. 32, the phase difference of the voltage vector between the primary inverter INV1 and the secondary inverter INV2 is controlled, and the secondary voltage V dc2 Control the charging and discharging modes of the battery.

[0025] Specifically, when the output voltage vector V2 of the secondary inverter INV2 is advanced by 90 degrees relative to the current phase and then brought closer to the current phase (+β), the charging mode is achieved, and when the phase is further advanced (-β), the discharging mode is achieved. In addition to this method, there are many other ways to create a phase difference and distribute vectors. This floating capacitor type dual inverter power conversion device has the advantage that it can drive the motor M while boosting the capacitor C provided in the secondary inverter INV2, thereby enabling the voltage that can be applied to the motor M to be even higher than in a common power supply type.

[0026] However, the conventional dual inverter power conversion devices described above all require a large number of components, making it difficult to reduce costs and size. In particular, in a floating capacitor type dual inverter power conversion device, the secondary side inverter INV2 has a floating potential, so it is necessary to create a gate drive power supply (insulated power supply) for the switching elements of the secondary side inverter INV2, which has a different reference potential, in addition to the gate drive power supply for the switching elements of the primary side inverter INV1. This makes it difficult to adopt this type of power conversion device in devices with limited board area, such as on-board electric compressors, in terms of component mounting area and cost.

[0027] Therefore, the applicant previously proposed a power conversion device as shown in Figure 1. In this system, the positive side power supply line of the common power supply type shown in Figure 27 is separated between the primary side inverter INV1 and the secondary side inverter INV2, and only the negative side power supply line is shared, with a capacitor placed on the secondary side as in the floating capacitor type shown in Figure 29. Hereinafter, this type of power conversion device will be referred to as a common GND type dual inverter. In this system, the secondary side voltage can be controlled in the same way as the floating capacitor type dual inverter power conversion device described in Figures 30 to 32.

[0028] Furthermore, in a common-ground dual-inverter power conversion device, it is possible to share the power supply for the drive circuit of the secondary-side inverter INV2, just like in a common-power-supply type.The primary-side inverter INV1 on the power supply side can be configured with high-voltage components, and the controllable secondary-side inverter INV2 can be configured with low-voltage components.The common-ground type, which can share the power supply for the drive circuit of the secondary-side inverter INV2 with the primary-side inverter INV1, has great advantages in applications where the power supply voltage fluctuates greatly.

[0029] However, such a common-ground dual inverter power conversion device requires zero-phase current control because it experiences zero-phase current. This means that secondary-side voltage control, due to the nature of the zero-phase current, cannot be controlled in the same way as the floating capacitor type. Furthermore, the secondary-side voltage control and motor control must be performed simultaneously, requiring complex control. Furthermore, like the floating capacitor type, the primary-side inverter INV1 can output both the active and reactive voltages of the voltage command value, while the secondary-side inverter INV2 can only output the reactive voltage. However, until now, a common-ground control theory for driving a motor with an open-end winding structure while stably controlling the secondary-side voltage has not been established.

[0030] The present invention has been made to solve the above-mentioned conventional technical problems, and provides a power conversion device that can stably control the secondary side voltage of the above-mentioned common-GND dual inverter while improving responsiveness and can drive a motor having open-end structure windings.

[0031] In order to stably control the power conversion device of the above-mentioned common ground type dual inverter, the existing vector control of dq axis currents as shown in FIG. 26 is applied to the control of the secondary side voltage, and modeling is performed, and feedforward control is also introduced.

[0032] That is, the power conversion device of the present invention includes 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 a differential voltage between the primary inverter and the secondary inverter to the motor, the primary inverter is connected to a DC power source, the secondary inverter is connected to a capacitor, the negative power supply lines of the primary inverter and the secondary inverter are common, and the secondary voltage V, which is the charging voltage of the capacitor, is dc2 The control device controls the secondary voltage V dc2 is the secondary voltage command value V dc2 ref The zero-phase voltage command value v z refThe secondary voltage control system has a secondary voltage command value V dc2 ref and the primary voltage V dc1 Based on this, the zero-phase voltage command value v z ref The feedforward control amount v z refFF , or the control variable v for deriving it m ref The present invention is characterized by having a feedforward control section that outputs:

[0033] A power conversion device of a second invention is characterized in that in the above invention, the primary side inverter and the secondary side inverter are each composed of upper and lower arm switching elements of each phase connected in series, the positive side input terminal of the primary side inverter is connected to a positive side power supply line of the DC power supply, the negative side input terminal of the primary side inverter is connected to a negative side power supply line of the DC power supply, the output terminal of the primary side inverter is connected to one end of the winding, the output terminal of the secondary side inverter is connected to the other end of the winding, a capacitor is connected between the positive side input terminal and the negative side input terminal of the secondary side inverter, the positive side input terminal of the secondary side inverter is not connected to the positive side power supply line of the DC power supply, and the negative side input terminal of the secondary side inverter is connected to the negative side power supply line of the DC power supply, and the control device generates an AC output from the DC power supply by switching on and off the upper and lower arm switching elements of each phase.

[0034] In a power conversion device according to a third aspect of the present invention, the secondary voltage control system further includes a feedback control unit, and the feedback control unit controls the secondary voltage V dc2 a secondary-side voltage control unit that generates a secondary-side DC link current command value required to control the secondary-side DC link current, and a zero-phase-sequence voltage command value v based on the secondary-side DC link current command value and the secondary-side DC link current, to control the secondary-side DC link current to the secondary-side DC link current command value. z ref Feedback control amount v z refFB The secondary DC link current control unit outputs a secondary DC link current.

[0035] In the power conversion device of the fourth invention, in the above invention, the control device employs a capacitor current flowing through the capacitor as the secondary side DC link current, or employs a zero-phase current i as an index indicating the secondary side DC link current. z The present invention is characterized by the adoption of the following.

[0036] The power conversion device of the fifth invention is a power conversion device according to the above inventions, wherein the secondary voltage control system is a feedforward control variable v z refFF The zero-phase voltage command value v z ref , or the feedforward control amount v z refFF The feedback control amount v z refFB The zero-phase voltage command value v obtained by adding z ref Based on this, the primary side output voltage command value v for switching the primary side inverter is uvw1 ref and a secondary-side output voltage command value v for switching the secondary-side inverter. uvw2 ref The present invention is characterized in that it further comprises an output voltage command generating unit that generates an output voltage command.

[0037] In the power conversion device of the sixth aspect of the present invention, in the above aspect, the output voltage command generating unit generates a dq-axis voltage command value v dq ref The primary side output voltage vector command value and the secondary side output voltage vector command value are generated from the primary side output voltage vector command value, and the primary side output voltage command value v uvw1 ref is generated, and the secondary side output voltage command value v uvw2 ref and the zero-phase voltage command value v is added to the primary side output voltage vector command value and / or the secondary side output voltage vector command value. z ref By adding uvw1 ref and the secondary output voltage command value v uvw2 ref The present invention is characterized by generating

[0038] In the power conversion device of the seventh aspect of the present invention, in the above aspect, the control device is uvw1 ref a primary side modulator that generates a primary side inverter switching signal for switching the primary side inverter from a secondary side output voltage command value v uvw2 ref The inverter further comprises a secondary side modulation section for generating a secondary side inverter switching signal for switching the secondary side inverter from the inverter.

[0039] The power conversion device of the eighth invention is characterized in that in the second invention, the control device has a primary side modulation unit that generates a primary side inverter switching signal for switching the primary side inverter, and a secondary side modulation unit that generates a secondary side inverter switching signal for switching the secondary side inverter, and the primary side modulation unit or the secondary side modulation unit performs two-phase modulation in which an upper arm switching element of one phase is turned on to stop switching, or a lower arm switching element of one phase is turned on to stop switching.

[0040] In a power conversion device according to a ninth aspect of the present invention, in the above-mentioned invention, the primary side modulation unit or the secondary side modulation unit is configured to provide a primary side output voltage command value v for each phase for switching the primary side inverter in two-phase modulation. uvw1 ref , or the secondary-side output voltage command value v of each phase for switching the secondary-side inverter uvw2 ref The same primary side zero-phase voltage command value v z1 ref , or the secondary side zero-phase voltage command value v z2 ref is the modulation value V com By adding as above, the primary side output voltage command value v uvw1 ref , or the secondary output voltage command value v uvw2 ref The upper arm switching element of the phase where the value of the primary side output voltage command value v is maximum is turned on to stop switching, or uvw1 ref , or the secondary output voltage command value v uvw2 refThe lower arm switching element of the phase in which the minimum value is obtained is turned on to stop switching.

[0041] In the power conversion device of the tenth aspect of the present invention, in the above-mentioned invention, the primary side modulation unit is z1 ref is the modulation value V com The primary output voltage command value v uvw1 ref , and the zero-phase voltage command value v z ref The feedforward control amount v z refFF The control variable for deriving the primary side output voltage command value v uvw1 ref The primary output voltage swing V m ref It is characterized in that:

[0042] In the power conversion device of the eleventh aspect of the present invention, in the above-mentioned invention, the secondary side voltage control system is z1 ref The secondary side zero-phase voltage command value v z2 ref and a ripple component canceling control unit that generates a dq-axis voltage command value v dq ref The secondary side zero-phase voltage command value v z2 ref Adding this, the secondary side output voltage command value v uvw2 ref The present invention is characterized by generating

[0043] In the power conversion apparatus of the twelfth aspect of the present invention, in the above-mentioned invention, the ripple component cancellation control unit is z1 ref and the primary side output voltage amplitude V m ref Based on this, the secondary side zero-phase voltage command value v z2 ref The method is characterized by calculating and outputting the following.

[0044] In a power conversion apparatus according to a thirteenth aspect of the present invention, in the eleventh aspect, the ripple component cancellation control unit is configured to generate a primary side zero-phase sequence voltage command value v z1 ref and the primary side zero-phase voltage command value v z1 ref The difference between this and the secondary side zero-phase voltage command value v z2 ref The present invention is characterized in that it outputs the signal as

[0045] A power conversion device according to a fourteenth aspect of the present invention is any one of the eleventh to thirteenth aspects, wherein the secondary voltage control system further includes a feedback control unit, and the feedback control unit controls the secondary voltage V dc2 a secondary-side voltage control unit that generates a secondary-side DC link current command value required to control the secondary-side DC link current, and a zero-phase-sequence voltage command value v based on the secondary-side DC link current command value and the secondary-side DC link current, to control the secondary-side DC link current to the secondary-side DC link current command value. z ref Feedback control amount v z refFB a secondary DC link current control unit that outputs a feedback control amount v z refFB , the secondary side zero-phase voltage command value v z2 ref The present invention is characterized in that it adds to

[0046] In the power conversion device of the fifteenth aspect of the present invention, the control device controls a secondary side voltage command value V dc2 ref The feature is that it has a function of limiting the rate of change of

[0047] According to the present invention, in a power conversion device that includes a primary side inverter connected to one end of an open-ended winding of a motor and a secondary side inverter connected to the other end of the winding, and that applies the differential voltage between the primary side inverter and the secondary side inverter to the motor, the primary side inverter is connected to a DC power supply, the secondary side inverter is connected to a capacitor, and the negative side power supply lines of the primary side inverter and the secondary side inverter are shared, thereby using the above-mentioned common-GND dual inverter, the capacitor is charged by the secondary side inverter from the DC power supply via the motor, and AC output is applied to the motor using the voltage charged in the capacitor by the secondary side inverter, making it possible to expand the drivable range in response to changes in input voltage.

[0048] Furthermore, in a power conversion device with a common GND type dual inverter, as in the second 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, so the secondary inverter does not have a floating potential, and the reference voltages of the primary inverter and the secondary inverter are the same.

[0049] This eliminates the need to create a gate drive power supply (insulated power supply) for the switching elements of the secondary inverter separately from the gate drive power supply (insulated power supply) for the switching elements of the primary inverter, and the switching elements of the primary inverter and the switching elements of the secondary inverter can be switched using a common gate drive power supply, making it possible to expand the drivable range in response to changes in input voltage without using a separate boost converter, etc.

[0050] Furthermore, since there is no longer a need to create a gate drive power supply for each inverter, the increase in component mounting area can be suppressed, and miniaturization and cost reduction can be achieved. This is extremely effective for devices such as automotive electric compressors, where the input voltage varies greatly, there is a strong demand for cost reduction, and the board area is limited, requiring the power conversion device to be miniaturized.

[0051] Furthermore, in the present invention, the secondary voltage Vdc2 A control device is provided to control the secondary voltage V dc2 is the secondary voltage command value V dc2 ref The zero-phase voltage command value v z ref Since the secondary voltage control system is configured to generate the secondary voltage V dc2 It is now possible to model and design a control system for the secondary voltage V dc2 This makes it possible to design the response of the secondary voltage and motor drive control in a stable manner.

[0052] In particular, the secondary voltage V dc2 In the present invention, the secondary voltage control system can be modeled and the control system can be designed, and the secondary voltage command value V dc2 ref and the primary voltage V dc1 Based on this, the zero-phase voltage command value v z ref The feedforward control amount v z refFF , or the control variable v for deriving it m ref Since a feedforward control section that outputs the above is provided, it is possible to realize even faster response by feedforward control.

[0053] In addition, as in the third aspect of the present invention, a feedback control section is further provided in the secondary voltage control system, and the feedback control section is configured to control the secondary voltage V dc2 a secondary-side voltage control unit that generates a secondary-side DC link current command value required to control the secondary-side DC link current, and a zero-phase-sequence voltage command value v based on the secondary-side DC link current command value and the secondary-side DC link current, to control the secondary-side DC link current to the secondary-side DC link current command value. z ref Feedback control amount v z refFB By providing a secondary DC link current control unit that outputs the above, it becomes possible to prevent runaway of the secondary DC link current by feedback control.

[0054] This makes it possible to perform feedforward control by the feedforward control unit and feedback control by the feedback control unit in parallel, thereby realizing a power conversion device that combines the high-speed response performance of feedforward control with the disturbance suppression performance of feedback control, and is therefore both responsive and accurate.

[0055] In the above case, the control device uses the capacitor current flowing through the capacitor as the secondary side DC link current as in the fourth aspect of the invention, or uses the zero-phase current i as an index indicating the secondary side DC link current. z The capacitor current is the secondary side DC link current itself, and the zero-phase current i z However, when the capacitor current is used, a separate sensor is required to detect the current flowing through the capacitor. z If so, each phase current i uvw The control device can detect this.

[0056] Furthermore, as in the fifth aspect of the present invention, the secondary voltage control system is z refFF The zero-phase voltage command value v z ref , or the feedforward control amount v z refFF The feedback control amount v z refFB The zero-phase voltage command value v obtained by adding z ref Based on this, the primary side output voltage command value v for switching the primary side inverter is uvw1 ref and a secondary-side output voltage command value v for switching the secondary-side inverter. uvw2 ref The output voltage command generating unit generates the dq-axis voltage command value v as in the sixth aspect of the present invention. dq ref The primary side output voltage vector command value and the secondary side output voltage vector command value are generated from the primary side output voltage vector command value, and the primary side output voltage command value v uvw1 refis generated, and the secondary side output voltage command value v uvw2 ref and the zero-phase voltage command value v is added to the primary side output voltage vector command value and / or the secondary side output voltage vector command value. z ref By adding uvw1 ref and the secondary output voltage command value v uvw2 ref By using a configuration that generates the above, it is possible to realize more stable secondary side voltage control and motor drive control.

[0057] In this case, as in the seventh aspect of the present invention, the control device controls the primary side output voltage command value v uvw1 ref a primary side modulator that generates a primary side inverter switching signal for switching the primary side inverter from a secondary side output voltage command value v uvw2 ref The secondary side inverter may further include a secondary side modulation section that generates a secondary side inverter switching signal for switching the secondary side inverter from the secondary side inverter.

[0058] Furthermore, as in the eighth aspect of the present invention, if the primary side modulation unit or secondary side modulation unit of the control device performs two-phase modulation in which the upper arm switching element of one phase is turned on to stop switching, or the lower arm switching element of one phase is turned on to stop switching, the number of times the upper and lower arm switching elements of the primary side inverter or secondary side inverter are switched can be reduced compared to the case of three-phase modulation, thereby significantly reducing switching losses and suppressing heat generation.

[0059] In this case, as in the ninth aspect of the present invention, the primary side modulation unit or the secondary side modulation unit is used for two-phase modulation, and the primary side output voltage command value v uvw1 ref , or the secondary-side output voltage command value v of each phase for switching the secondary-side inverter uvw2 ref The same primary side zero-phase voltage command value v z1 ref , or the secondary side zero-phase voltage command value vz2 ref is the modulation value V com By adding as above, the primary side output voltage command value v uvw1 ref , or the secondary output voltage command value v uvw2 ref The upper arm switching element of the phase where the value of the primary side output voltage command value v is maximum is turned on to stop switching, or uvw1 ref , or the secondary output voltage command value v uvw2 ref The lower arm switching element of the phase where the value of the current is smallest is turned on to stop switching.

[0060] Further, as in the tenth aspect of the present invention, the primary side modulation unit z1 ref is the modulation value V com The primary output voltage command value v uvw1 ref When two-phase modulation is performed by adding to the zero-phase voltage command value v z ref The feedforward control amount v z refFF The control variable for deriving the primary side output voltage command value v uvw1 ref The primary output voltage swing V m ref This becomes:

[0061] On the other hand, when the primary side modulation unit performs two-phase modulation as described above, the primary side zero-phase voltage command value v z1 ref Therefore, as in the eleventh aspect of the present invention, a primary side zero-phase sequence voltage command value v z1 ref The secondary side zero-phase voltage command value v z2 ref A ripple component cancellation control unit is provided to generate a dq-axis voltage command value v dq ref The secondary side zero-phase voltage command value vz2 ref Adding this, the secondary side output voltage command value v uvw2 ref By generating the primary side zero-phase voltage command value v z1 ref This compensates for the ripple component of the rectifier, making it possible to suppress the generation of electromagnetic noise and noise due to the ripple current.

[0062] In this case, as in the twelfth aspect of the present invention, the ripple component cancellation control section z1 ref and the primary side output voltage amplitude V m ref Based on this, the secondary side zero-phase voltage command value v z2 ref This allows instantaneous compensation for the ripple component.

[0063] Further, as in the thirteenth aspect of the present invention, the ripple component cancellation control section outputs the primary side zero-phase voltage command value v z1 ref and the primary side zero-phase voltage command value v z1 ref The difference between this and the secondary side zero-phase voltage command value v z2 ref This makes it possible to compensate for the ripple component with a relatively simple configuration.

[0064] Further, as in the fourteenth aspect of the present invention, a feedback control section is further provided in the secondary voltage control system, and the feedback control section is configured to control the secondary voltage V dc2 a secondary-side voltage control unit that generates a secondary-side DC link current command value required to control the secondary-side DC link current, and a zero-phase-sequence voltage command value v based on the secondary-side DC link current command value and the secondary-side DC link current, to control the secondary-side DC link current to the secondary-side DC link current command value. z ref Feedback control amount v z refFB A secondary DC link current control unit is provided to output a feedback control amount v z refFB , the secondary side zero-phase voltage command value v z2ref By adding the above, it becomes possible to prevent runaway of the secondary side DC link current by feedback control.

[0065] This makes it possible to perform feedforward control by the feedforward control unit and feedback control by the feedback control unit in parallel, thereby realizing a power conversion device that combines the high-speed response performance of feedforward control with the disturbance suppression performance of feedback control, and is therefore both responsive and accurate.

[0066] Here, when the above-described feedforward control is performed, the secondary voltage command value V dc2 ref When changes occur, the secondary voltage V dc2 Therefore, as in the fifteenth aspect of the present invention, the control device controls the secondary side voltage command value V dc2 ref If the secondary voltage V dc2 This reduces the excitation of vibrations, making it possible to achieve both high responsiveness and low vibration.

[0067] 1 is an electrical circuit diagram of a power conversion device with a common-GND dual inverter according to an embodiment of the present invention. FIG. 1 is a block diagram of a control device for the power conversion device of FIG. 1. FIG. 2 is a diagram illustrating an equivalent circuit of a zero-phase-sequence component of the power conversion device of FIG. 1. FIG. 3 is a diagram modeling secondary-side voltage control (feedforward control) of the power conversion device of FIG. 1 (Example 1). FIG. 4 is a block diagram of the secondary-side voltage control system, primary-side modulation unit, and secondary-side modulation unit of FIG. 2. FIG. 5 is a diagram illustrating each voltage command value and voltage when feedforward control is not executed. FIG. 6 is an enlarged view of FIG. 6 showing changes in the secondary-side voltage when the secondary-side voltage command value changes. FIG. 7 is a diagram illustrating each voltage command value and voltage when feedforward control of the control device of FIG. 2 is executed. FIG. 8 is an enlarged view of FIG. 8 showing changes in the secondary-side voltage when the secondary-side voltage command value changes. FIG. 9 is a diagram illustrating a state after vibration countermeasures have been implemented in FIG. 8. FIG. 10 is an enlarged view of FIG. 10 showing changes in the secondary-side voltage when the secondary-side voltage command value changes. FIG. 11 is a diagram modeling secondary-side voltage control (feedback control) of the power conversion device of FIG. 1 (Example 2). FIG. 12 is a block diagram of the secondary-side voltage control system, primary-side modulation unit, and secondary-side modulation unit of FIG. 2 when a feedback control unit is added. 14 is a block diagram of the secondary-side voltage control system, primary-side modulation unit, and secondary-side modulation unit of FIG. 2 when two-phase modulation is performed in the primary-side inverter (Example 3). FIG. 14 is a diagram explaining superscript two-phase modulation performed in the primary-side inverter of FIG. 14. FIG. 14 is a diagram explaining superscript two-phase modulation performed in the primary-side inverter of FIG. 14. FIG. 14 is a diagram explaining sub ... each voltage command value and voltage when feedforward control of the control device of FIG. 2 is executed in the case of FIG. 14. FIG. 21 is an enlarged view of FIG. 21 showing a change in secondary-side voltage when the secondary-side voltage command value is changed. FIG. 21 is a diagram showing a state after vibration countermeasures have been implemented in FIG. 21. FIG. 23 is an enlarged view of FIG. 23 showing a change in secondary-side voltage when the secondary-side voltage command value is changed.29 is a block diagram of the secondary-side voltage control system, primary-side modulation unit, and secondary-side modulation unit of FIG. 2 when a feedback control unit is added in FIG. 14 (Example 4). It is a diagram modeling vector control of a general power conversion device. It is an electrical circuit diagram of a power conversion device of a conventional common power supply type dual inverter. It is an electrical circuit diagram of a power conversion device of a conventional isolated power supply type dual inverter. It is an electrical circuit diagram of a power conversion device of a conventional floating capacitor type dual inverter. It is a diagram defining active power, reactive power, active voltage, and reactive voltage for explaining the operation of the floating capacitor type dual inverter power conversion device of FIG. 29. It is a block diagram for explaining a drive control method of the floating capacitor type dual inverter power conversion device of FIG. 29. It is a diagram explaining the charge mode and discharge mode of the capacitor of the floating capacitor type dual inverter power conversion device of FIG. 29.

[0068] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0069] (1) Power Conversion Device 1 Fig. 1 is an electrical circuit diagram of a power conversion device 1 of a common ground type dual inverter according to an embodiment of the present invention. The power conversion device 1 of the embodiment converts a DC voltage V dc (for example, DC 500V) is converted into a three-phase AC voltage (AC output) and supplied to the motor M. The motor M in this embodiment is a three-phase permanent magnet synchronous motor (Interior Permanent Magnet Synchronous Motor) that is composed of a stator with windings and a rotor with a built-in magnet that rotates inside the stator, and drives an electric compressor used in an air conditioning system for an electric vehicle such as an electric car or a hybrid car. dc is the primary voltage V dc1 is.

[0070] In this embodiment, the power conversion device 1 is configured with a three-phase primary-side inverter INV1 consisting of upper and lower arm switching elements 3A to 3F, a secondary-side inverter INV2 also consisting of upper and lower arm switching elements 4A to 4F, a control device 6 (FIG. 2), etc. In this embodiment, each of the switching elements 3A to 3F and 4A to 4F is configured with an insulated gate bipolar transistor (IGBT) incorporating a MOS structure in the gate portion.

[0071] In this invention, the DC voltage V of the DC power source 2 is generated by the primary side inverter INV1 and the secondary side inverter INV2. dc is converted into a three-phase AC voltage (AC output), and the difference voltage between the primary inverter INV1 and the secondary inverter INV2 is applied to the windings (stator windings) 7U, 7V, and 7W of the motor M. Here, the windings 7U, 7V, and 7W of the motor M have an open-ended structure that is not bundled at the neutral point.

[0072] (2) Primary-Side Inverter INV1 The primary-side 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, and each of the half-bridge circuits 9U to 9W for each phase has the above-mentioned upper-arm switching elements 3A to 3C and lower-arm switching elements 3D to 3F. Furthermore, each of the switching elements 3A to 3F has a built-in freewheeling diode connected in antiparallel.

[0073] The collector electrodes of the upper arm switching elements 3A to 3C, which are the positive input terminals of the primary side inverter INV1, are connected to a positive side 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 to 3F, which are the negative input terminals of the primary side inverter INV1, are connected to a negative side power supply line 12 (HV-) of the DC power supply 2. In the figure, reference numeral 13 denotes a capacitor connected between the positive side power supply line 11 and the negative side power supply line 12, which constitutes a noise filter.

[0074] In the primary inverter INV1, the emitter electrode of the upper arm switching element 3A and the collector electrode of the lower arm switching element 3D of the U-phase half-bridge circuit 9U are connected, and their connection point (arm midpoint: output end of the primary inverter INV1) is connected to one end of the U-phase winding 7U of the motor M.

[0075] In addition, the emitter electrode of the upper arm switching element 3B and the collector electrode of the lower arm switching element 3E of the V-phase half-bridge circuit 9V are connected, and their connection point (arm midpoint: output end of the primary side inverter INV1) is connected to one end of the V-phase winding 7V of the motor M.

[0076] Furthermore, the emitter electrode of the upper arm switching element 3C and the collector electrode of the lower arm switching element 3F of the W-phase half-bridge circuit 9W are connected, and their connection point (arm midpoint: output end of the primary side inverter INV1) is connected to one end of the W-phase winding 7W of the motor M.

[0077] (3) Secondary-side inverter INV2 The secondary-side inverter INV2 also includes three half-bridge circuits 16U, 16V, and 16W corresponding to the phases U, V, and W. The neutral points of the phases of the motor M are not bundled together, and the windings 7U to 7W of the motor M are sandwiched between the half-bridge circuits 9U to 9W of the primary-side inverter INV1 and the half-bridge circuits 16U to 16W of the secondary-side inverter INV2.

[0078] The half-bridge circuits 16U to 16W of the secondary-side inverter INV2 also have upper-arm switching elements 4A to 4C and lower-arm switching elements 4D to 4F, respectively. Each of the switching elements 4A to 4F also incorporates a free-wheeling diode connected in antiparallel.

[0079] A capacitor C is connected between the collector electrodes of the upper arm switching elements 4A to 4C, which are the positive input terminals of the secondary inverter INV2, and the emitter electrodes of the lower arm switching elements 4D to 4F, which are the negative input terminals of the secondary inverter INV2.

[0080] However, the collector electrodes of the upper arm switching elements 4A to 4C, which are the positive input terminals of the secondary side inverter INV2, are not connected to but separated from the positive power supply line 11 of the DC power supply 2. On the other hand, in the present invention, the emitter electrodes of the lower arm switching elements 4D to 4F, which are the negative input terminals of the secondary side inverter INV2, are connected to the negative power supply line 12 of the DC power supply 2.

[0081] The emitter electrode of the upper arm switching element 4A and the collector electrode of the lower arm switching element 4D of the U-phase half-bridge circuit 16U are connected, and their connection point (arm midpoint: output terminal of the secondary side inverter INV2) is connected to the other end of the U-phase winding 7U of the motor M.

[0082] In addition, the emitter electrode of the upper arm switching element 4B and the collector electrode of the lower arm switching element 4E of the V-phase half bridge circuit 16V are connected, and their connection point (arm midpoint: output end of the secondary side inverter INV2) is connected to the other end of the V-phase winding 7V of the motor M.

[0083] Furthermore, the emitter electrode of the upper arm switching element 4C and the collector electrode of the lower arm switching element 4F of the W-phase half-bridge circuit 16W are connected, and their connection point (arm midpoint: output end of the secondary-side inverter INV2) is connected to the other end of the W-phase winding 7W of the motor M. In other words, the power conversion device 1 of the present invention has the above-mentioned common-GND dual inverter configuration.

[0084] (4) Control Device 6 Next, Fig. 2 shows a block diagram of the control device 6. The control device 6 of the embodiment is composed of a microcomputer having a processor, and receives a speed command value ω from the ECU of the electric vehicle. rm ref and the secondary voltage command value V dc2 ref and the phase current of the motor M is input from a current sensor (not shown), and based on these, the ON / OFF states of the switching elements 3A to 3F and 4A to 4F of the primary inverter INV1 and the secondary inverter INV2 are controlled (switching).

[0085] Specifically, it controls the gate voltages applied to the gates of the switching elements 3A to 3F and 4A to 4F. The control device 6 of the embodiment includes a speed control unit 21, a dq-axis current control unit 22, a secondary-side voltage control system 23, a primary-side modulation unit 24, a secondary-side modulation unit 26, etc.

[0086] The speed control unit 21 performs PI calculation and q-axis current i q and torque, the q-axis current command value i q ref The dq-axis current control unit 22 calculates and outputs the d-axis voltage command value v d ref and the q-axis voltage command value v q ref In this case, the d-axis current control unit 22 basically calculates and outputs the d-axis current command value i d ref and d-axis current i d (estimated value), q-axis current command value i q ref and q-axis current i q The d-axis voltage command value v in the direction that eliminates the deviation from the (estimated value) d ref and the q-axis voltage command value v q ref is calculated.

[0087] The secondary voltage control system 23 controls the secondary voltage V dc2 is the secondary voltage command value V dc2 ref The secondary DC link current required for controlling the z The zero-phase voltage command value v z ref Then, the d-axis current i d (estimated value) and q-axis current i q (estimated value), the d-axis voltage command value v output by the dq-axis current control unit 22 d ref and the q-axis voltage command value v q ref , the zero-phase voltage command value v z refto the primary side output voltage command value v for switching each of the switching elements 3A to 3F of the primary side inverter INV1. u1 ref , v v1 ref , v w1 ref and a secondary-side output voltage command value v for switching the respective switching elements 4A to 4F of the secondary-side inverter INV2. u2 ref , v v2 ref , v w2 ref The configuration and operation of the secondary side voltage control system 23 will be described in detail later.

[0088] In this embodiment, the primary side modulation unit 24 modulates the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref The primary inverter INV1 generates and outputs a primary inverter switching signal (PWM signal) for switching (PWM control) each of the switching elements 3A to 3F of the primary inverter INV1 by performing general three-phase modulation.

[0089] In this embodiment, the secondary side modulation unit 26 also converts the secondary side output voltage command value v u2 ref , v v2 ref , v w2 ref The inverter circuit 100 generates and outputs a secondary inverter switching signal (PWM signal) for switching (PWM control) each of the switching elements 4A to 4F of the secondary inverter INV2 by performing general three-phase modulation from the input signal.

[0090] (5) Secondary-side voltage control system 23 Next, the detailed configuration and operation of the secondary-side voltage control system 23 of the embodiment will be described with reference to Figures 3 to 11. In this embodiment, the secondary-side voltage control system 23 is configured to include a secondary-side voltage / zero-phase voltage command conversion unit 27 and an output voltage command generation unit 29.

[0091] Here, the equivalent circuit of the zero-phase component of the power conversion device 1 in Fig. 1 is shown in the lower part of Fig. 3. This equivalent circuit in the lower part of Fig. 3 can be regarded as a chopper circuit of a step-down chopper and a step-up chopper. dc1 is the primary voltage, which is the DC voltage of the DC power supply 2. dc2 is the capacitance of the capacitor C, and L z is the self-inductance of the z-axis of the motor M, R a is the internal resistance.

[0092] From this equivalent circuit, the zero-phase voltage v of the primary inverter INV1 z1 and the zero-phase voltage v of the secondary inverter INV2 z2 The zero-phase voltage V is the potential difference z (=v z1 -v z2 ) to calculate the zero-phase current i z By controlling the secondary voltage v dc2 Therefore, the control device 6 of this embodiment can control the zero-phase current i z is used as an index of the secondary DC link current. This is the zero-phase current i z is approximately equal to the secondary DC link current.

[0093] As described above, assuming that the zero-phase component (z-axis) of the power conversion device 1 can be expressed equivalently to a chopper circuit, the feedforward control controller and the controlled object (plant model) for the power conversion device 1 in FIG. 1 are modeled as shown in FIG. 4. In this case, the plant model of the controlled object is expressed as the voltage (v z -e z ) to the current (zero-phase current i z ) model (shown as 31 in the figure), an LR load is assumed as in the dq axis, and the zero-phase current i z to the secondary voltage V dc2 The model for e (shown as 32 in the figure) is modeled as a simple capacitor. z is the induced voltage component excited on the z-axis by the rotation of the motor M, ω re is the electrical angular velocity, θ re is the rotor position.

[0094] Regarding the control system, a feedforward control system 25 constituting a feedforward control unit 20 (FIG. 5) that controls the secondary side voltage is z ref The feedforward control amount v z refFF The feedforward control unit 20 is included in the secondary side voltage / zero-phase voltage command conversion unit 27 shown in FIG.

[0095] The feedforward control system 25 controls the secondary voltage command value V dc2 ref and the primary voltage V dc1 Based on this, the zero-phase voltage command value v is calculated using the following formula (VI): z ref The feedforward control amount v z refFF is calculated and output. G in this formula (VI) V is the secondary voltage command value V dc2 ref , the zero-phase voltage command value v z ref The feedforward control amount v z refFF This function is superior in responsiveness to feedback control and is calculated directly by the feedforward control system 25.

[0096]

[0097] The aforementioned induced voltage component e excited on the z-axis by the rotation of the motor M z The feedforward control amount v z refFF and the zero-phase voltage command value v is output from the feedforward control unit 20. z ref This makes it possible to design a controller for the power conversion device 1 of FIG.

[0098] A block diagram of the secondary voltage control system 23 designed by the above modeling is shown in Fig. 5. In the upper left of Fig. 5, the feedforward control system 25 of Fig. 4 constitutes the feedforward control unit 20 of the secondary voltage / zero-phase voltage command conversion unit 27 of Fig. 2, and this feedforward control unit 20 controls the zero-phase current i z (secondary DC link current in the present invention) is expressed as a zero-phase current command value i z ref (Secondary voltage V dc2 (the secondary DC link current command value required to control the zero-phase voltage command value v z ref Output.

[0099] The block shown below is the output voltage command generating unit 29 of Fig. 2. The basic control block of this output voltage command generating unit 29 is the same as that of the floating capacitor type dual inverter power conversion device shown in Fig. 31. That is, the output voltage command generating unit 29 of this embodiment has an active / inactive decomposition unit 36, which calculates the d-axis voltage command value v d ref and the q-axis voltage command value v q ref , the effective voltage V real and reactive voltage V imag This effective voltage V real is an example of a primary side output voltage vector command value in the present invention, and the reactive voltage V imag is an example of a secondary side output voltage vector command value in the present invention.

[0100] The output voltage command generator 29 calculates the effective voltage V decomposed as above using the above-mentioned formula (V). real is the d-axis voltage command value v of the primary inverter INV1. d1 ref and the q-axis voltage command value v of the primary inverter INV1 q1 ref is set to 0. In addition, the d-axis voltage command value v d2 ref is set to 0, and the reactive voltage V imag The q-axis voltage command value v of the secondary inverter INV2 q2ref Let's say.

[0101] Next, the dq-uvw conversion unit 37 of the output voltage command generation unit 29 converts the d-axis voltage command value v d1 ref and the q-axis voltage command value v of the primary side inverter INV1. q1 ref is converted into the output voltage command values ​​of the u, v, and w phases of the primary inverter INV1, and the d-axis voltage command value v of the secondary inverter INV2 is converted into the output voltage command values ​​of the u, v, and w phases of the secondary inverter INV2 by the dq-uvw conversion unit 38. d2 ref and the q-axis voltage command value v of the secondary inverter INV2. q2 ref are converted into output voltage command values ​​for each phase uvw of the secondary side inverter INV2.

[0102] The output voltage command generator 29 also includes a zero-phase-sequence voltage distributor 39. The zero-phase-sequence voltage distributor 39 distributes the zero-phase-sequence voltage command value v z ref to the primary inverter INV1 and the secondary inverter INV2 with a gain M1 for distributing to the primary inverter INV1 and a gain M2 for distributing to the secondary inverter INV2. Then, an adder 41 multiplies the output voltage command value of each uvw phase of the primary inverter INV1 output from the dq-uvw conversion unit 37 by the gain M1 to obtain the zero-phase voltage command value v z ref and the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref and an adder 42 multiplies the output voltage command values ​​of the uvw phases of the secondary inverter INV2 output from the dq-uvw conversion unit 38 by a gain M2 to obtain a zero-phase voltage command value v z ref and the secondary output voltage command value v u2 ref , v v2 ref , v w2 ref Output as

[0103] That is, the effective voltage V as the primary side output voltage vector command value real and the reactive voltage V as the secondary output voltage vector command value imag (Actually, these are converted into output voltage command values ​​for each phase of u, v, and w) z ref By distributing and adding, the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref and the secondary output voltage command value v u2 ref , v v2 ref , v w2 ref Generate and output.

[0104] Here, gain M1 + gain M2 = 1. The zero-phase voltage distribution unit 39 has two cases: gain M1 = 1 and gain M2 = 0, and gain M1 = 0 and gain M2 = 1. Therefore, the zero-phase voltage command value v is added to the output voltage command values ​​of the u, v, and w phases of either one of the inverters INV1 and INV2. z ref In some cases, one is added to the other and the other is not.

[0105] Basically, the zero-phase voltage command value v z ref to the output voltage command values ​​of each uvw phase of the inverters INV1 and INV2 output by the dq-uvw conversion units 37 and 38, respectively. However, since a zero-phase voltage is added, it is better that the primary-side inverter INV1, which has a higher voltage, should bear the zero-phase voltage, taking into consideration the operating range, etc. In this case, the zero-phase voltage distribution unit 39 sets the gain M1=1 and the gain M2=0, and calculates the zero-phase voltage command value v only for the primary-side inverter INV1. z ref to impose a burden.

[0106] The zero-phase voltage command value v multiplied by the gain M2 added in the adder 42 is z ref The reason why the sign of is set to - (i.e., subtraction) is that the zero-phase voltage v zThis is because it is necessary to create a potential difference of v, and the adder 42 actually becomes a subtractor, and the zero-phase voltage command value v multiplied by the gain M2 is z ref The negative value of is added to the output voltage command value of each phase uvw.

[0107] In this way, the output voltage command generating unit 29 generates the zero-phase voltage command value v z ref Based on this, the primary side output voltage command value v for switching the primary side inverter INV1 is u1 ref , v v1 ref , v w1 ref and a secondary-side output voltage command value v for switching the secondary-side inverter INV2. u2 ref , v v2 ref , v w2 ref Generate and output.

[0108] The primary side modulator 24 modulates the primary side output voltage command value v outputted by the output voltage command generator 29. u1 ref , v v1 ref , v w1 ref The secondary-side modulator 26 generates and outputs a primary-side inverter switching signal (PWM signal) for performing three-phase modulation from the output voltage command generator 29 to switch (PWM control) each of the switching elements 3A to 3F of the primary-side inverter INV1. u2 ref , v v2 ref , v w2 ref The inverter circuit 100 generates and outputs a secondary inverter switching signal (PWM signal) for performing three-phase modulation from the input signal to switch (PWM control) each of the switching elements 4A to 4F of the secondary inverter INV2.

[0109] Next, the effect of the feedforward control by the control device 6 of the power conversion device 1 described above will be described with reference to Figures 6 to 11. Figure 6 is a diagram showing voltage command values ​​and voltages when feedforward control is not executed, and Figure 7 is a diagram showing the secondary side voltage command value V dc2 ref When the secondary voltage V changes dc2 6 is an enlarged view of FIG. 6 showing the change in the voltage command value V. FIG. 8 is a view showing the voltage command values ​​and voltages when the feedforward control of the control device 6 of FIG. 2 is executed. FIG. 9 is a view showing the change in the secondary side voltage command value V. dc2 ref When the secondary voltage V changes dc2 8 showing the change in .times. ...

[0110] The top row of each diagram shows the voltages v of each phase of the UVW of the primary inverter INV1. u1 , v v1 , v w1 and the zero-phase voltage v z1 The second row from the top shows the voltages v of each phase of the UVW of the secondary inverter INV2. u2 , v v2 , v w2 and the zero-phase voltage v z2 The third row from the top shows the zero-phase voltage v of the primary inverter INV1. z1 and the zero-phase voltage v of the secondary inverter INV2 z2 The second row from the bottom shows the primary voltage (primary DC link voltage) V dc1 , the bottom row is the secondary voltage (secondary DC link voltage) V dc2 and the secondary voltage command value V dc2 ref This shows:

[0111] As is clear from a comparison of FIG. 7 and FIG. 9, when feedforward control is performed (FIG. 9), the secondary-side voltage command value V dc2 ref Changes in the secondary voltage V dc2 It can be seen that the response is extremely high.

[0112] However, as is clear from FIG. 9, the secondary voltage V dc2 Therefore, the control device 6 controls the secondary side voltage command value Vdc2 ref 10 and 11. Note that FIG. 10 shows a case where the feedforward control of the control device 6 in FIG. 2 is executed and the secondary side voltage command value V dc2 ref 11 shows the voltage command values ​​and voltages when the rate of change of the secondary side voltage command value V dc2 ref When the secondary voltage V changes dc2 10 showing the change in

[0113] However, this limitation is based on the secondary voltage V dc2 As a result, the secondary voltage V dc2 The vibrations can be eliminated or suppressed.

[0114] As described above, according to the present invention, by configuring the power conversion device 1 as the aforementioned common-GND dual inverter, the capacitor C is charged by the secondary-side inverter INV2 from the DC power source 2 via the motor M, and an AC output is applied to the motor M using the voltage charged in the capacitor C by the secondary-side inverter INV2, thereby making it possible to expand the drivable range in response to changes in the input voltage.

[0115] Furthermore, in the power conversion device 1 of the common GND type dual inverter, the positive input terminal of the secondary side inverter INV2 is not connected to the positive power supply line 11 of the DC power supply 2 as in the embodiment, and the negative input terminal of the secondary side inverter INV2 is connected to the negative power supply line 12 of the DC power supply 2, so the secondary side inverter INV2 does not have a floating potential, and the reference voltages of the primary side inverter INV1 and the secondary side inverter INV2 are the same.

[0116] This eliminates the need to create a gate drive power supply (insulated power supply) for the switching elements 4A to 4F of the secondary side inverter INV2 in addition to the gate drive power supply (insulated power supply) for the switching elements 3A to 3F of the primary side inverter INV1, and the switching elements 3A to 3F of the primary side inverter INV1 and the switching elements 4A to 4F of the secondary side inverter INV2 can be switched by a common gate drive power supply, making it possible to expand the drivable range in response to changes in input voltage without using a separate boost converter or the like.

[0117] Furthermore, since there is no longer a need to create a gate drive power supply for each inverter INV1, INV2, the increase in component mounting area can be suppressed, and miniaturization and cost reduction can be achieved. This is extremely effective for devices such as automotive electric compressors, where the input voltage varies greatly, there is a strong demand for cost reduction, and the board area is limited, requiring the miniaturization of the power conversion device.

[0118] Furthermore, in the present invention, the secondary voltage V, which is the charging voltage of the capacitor C, dc2 A control device 6 is provided to control the secondary side voltage V dc2 is the secondary voltage command value V dc2 ref The zero-phase voltage command value v z ref Since the secondary voltage control system 23 is configured to generate the secondary voltage V dc2 It is now possible to model and design a control system for the secondary voltage V dc2 This makes it possible to design the response of the secondary voltage and the motor M in a stable manner.

[0119] In particular, the secondary voltage V dc2 and designing a control system. In the present invention, the secondary voltage control system 23 is provided with a secondary voltage command value V dc2 ref and the primary voltage V dc1 Based on this, the zero-phase voltage command value v z ref The feedforward control amount v zrefFF Since the feedforward control section 20 that outputs the signal is provided, it is possible to realize even faster response by the feedforward control.

[0120] In the embodiment, the control device 6 determines the secondary voltage command value V dc2 ref Since the rate of change of the secondary voltage V dc2 This reduces the excitation of vibrations, making it possible to achieve both high responsiveness and low vibration.

[0121] (6) Feedback Control Next, another embodiment of the present invention will be described with reference to Figs. 12 and 13. In this embodiment, the secondary voltage V dc2 12 is a diagram modeling the secondary-side voltage control (feedback control) of the power conversion device 1 of FIG. 1, and FIG. 13 is a block diagram of the secondary-side voltage control system 23, the primary-side modulation unit 24, and the secondary-side modulation unit 26 of FIG. 2 when a feedback control unit 30 is added.

[0122] The feedback control controller and the controlled object (plant model) of the power conversion device 1 in Fig. 1 are modeled as shown in Fig. 12. In this figure, the same reference numerals as in Fig. 4 denote the same or similar functions. In this case, the plant model of the controlled object is the same as that in Fig. 4.

[0123] On the other hand, in the control system, the voltage PI control system 33 that controls the secondary side voltage controls the zero-phase current command value i z ref and outputs the zero-phase current i z The current PI control system 34 controls the zero-phase voltage command value v z ref Feedback control amount v z refFB The induced voltage component e is generated on the z-axis by the rotation of the motor M. z The non-interfering voltage command value e z est The feedback control amount v z refFBThis similarly makes it possible to design a feedback control controller for the power conversion device 1 of FIG.

[0124] In addition, the secondary voltage V dc2 The control of the zero-phase current i z In the model of Figure 12, PI control is applied, so the secondary voltage V dc2 However, the non-interacting voltage command value e z est Due to parameter errors, etc., the zero-phase current i z When a ripple occurs in the secondary voltage V dc2 Since ripples are also excited, advanced current control can be achieved by adopting a controller that suppresses AC components (periodic disturbance components) from the viewpoint of voltage quality, such as periodic disturbance suppression control, sine wave tracking control, or repetitive control.

[0125] Fig. 13 shows a block diagram in which a feedback control unit 30 is added to the secondary side voltage / zero-phase sequence voltage command conversion unit 27 of the embodiment in Fig. 5. In the figure, the same reference numerals as in Fig. 5 denote the same or similar functions. In the upper left of Fig. 13, the feedback control unit 30 of the secondary side voltage control system 23 in this case has a secondary side voltage control unit 35 and a secondary side DC link current control unit 28. The voltage PI control system 33 in Fig. 12 constitutes the secondary side voltage control unit 35, and this secondary side voltage control unit 35 controls the zero-phase sequence current command value i z ref (Secondary voltage V dc2 The secondary DC link current command value required to control the

[0126] 12 constitutes the secondary side DC link current control unit 28, and this secondary side DC link current control unit 28 controls the zero-phase current i z (secondary DC link current in the present invention) is expressed as a zero-phase current command value i z ref (the secondary DC link current command value in the present invention) z refFeedback control amount v z refFB Output.

[0127] In this embodiment, the current PI control system 34 constituting the secondary side DC link current control unit 28 receives the zero-phase current command value i z ref From the zero-phase current i z Then, the current PI control system 34 of the secondary side DC link current control unit 28 receives the zero-phase current command value i z ref and zero-phase current i z The zero-phase voltage command value v in the direction of eliminating the difference z ref Feedback control amount v z refFB Calculate the zero-phase current i z The zero-phase current command value i z ref It operates to control the

[0128] The zero-phase voltage command value v output by the feedforward control unit 20 z ref The feedforward control amount v z refFF and the zero-phase voltage command value v output by the feedback control unit 30. z ref Feedback control amount v z refFB , the non-interfering voltage command value e z est is added, and the zero-phase voltage command value v z ref Thereafter, the effective voltage V as the primary side output voltage vector command value is output as in the case of FIG. real and the reactive voltage V as the secondary output voltage vector command value imag (Actually, these are converted into output voltage command values ​​for each phase of u, v, and w) z ref By distributing and adding, the primary side output voltage command value v u1 ref , v v1 ref , v w1 refand the secondary output voltage command value v u2 ref , v v2 ref , v w2 ref Generate and output.

[0129] As in this embodiment, a feedback control unit 30 is provided in the secondary voltage control system 23, and the feedback control unit 30 controls the secondary voltage V dc2 a secondary-side voltage control unit 35 that generates a secondary-side DC link current command value required to control the zero-phase current command value (secondary-side DC link current command value) i z ref and the zero-phase current (secondary DC link current) i z Based on this, the zero-phase current i z The zero-phase current command value i z ref The zero-phase voltage command value v z ref Feedback control amount v z refFB By providing a secondary side DC link current control unit 28 that outputs a zero-phase current i z This will make it possible to prevent runaway.

[0130] This allows feedforward control by the feedforward control unit 20 and feedback control by the feedback control unit 30 to be performed in parallel, making it possible to realize a power conversion device 1 that combines the high-speed response performance of feedforward control with the disturbance suppression performance of feedback control, thereby providing both responsiveness and accuracy.

[0131] (7) Two-Phase Modulation Next, another embodiment of the present invention will be described with reference to Figures 14 to 24. In this embodiment, two-phase modulation is performed by either the primary-side modulator 24 or the secondary-side modulator 26, and three-phase modulation is performed by the other. In each figure, components designated by the same reference numerals as in Figures 1 to 13 perform the same or similar functions. In the following description, it is assumed that two-phase modulation is performed by the primary-side modulator 24, and three-phase modulation is performed by the secondary-side modulator 26.

[0132] (7-1) During Boost Operation First, the superscript two-phase modulation performed by the primary side modulation unit 24 will be described with reference to Figures 15 and 16. When the secondary side inverter INV2 performs boost operation, the primary side modulation unit 24 performs superscript two-phase modulation. Note that the numerical values ​​shown in each figure are plus or minus V. dc1 This is a value normalized to plus or minus 1 by / 2.

[0133] The superscript two-phase modulation in the primary side modulation unit 24 is performed by using the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref , the same primary side zero-phase voltage command value v z1 ref is the modulation value V com As shown in FIG. 16, the primary side output voltage command value v u1 2ph , v v1 2ph , v w1 2ph By generating the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref is maximized, the upper arm switching elements 3A to 3C are fixed to the ON state, and the lower arm switching elements 3D to 3F are fixed to the OFF state, and switching (PWM operation) is stopped. This reduces the number of switching operations of the switching elements compared to three-phase modulation, and makes it possible to significantly reduce switching loss.

[0134] Modulation value V in general superscript biphase modulation com is the difference between the primary output voltage command value of the maximum phase and "1" (FIG. 15), and is used as the primary output voltage command value v of all phases. u1 ref , v v1 ref , v w1 ref By adding to the modulation value V com, that is, the primary side zero-phase voltage command value v z1 ref Therefore, in this embodiment, the primary side modulation unit 24 takes on part of the function of the secondary side voltage / zero-phase sequence voltage command conversion unit 27.

[0135] However, when the primary side modulation unit 24 performs two-phase modulation, the calculated primary side zero-phase voltage command value v z1 ref As shown in Figs. 15 and 16, the zero-phase current i z (secondary DC link current) and secondary voltage V dc2 A large ripple is excited in the

[0136] Therefore, in this embodiment, a ripple component canceling control unit 46 is provided in the secondary voltage control system 23. Figure 14 shows a block diagram of the secondary voltage control system 23, the primary side modulation unit 24, and the secondary side modulation unit 26 in this case. In this case, the secondary side voltage V dc2 is the primary side output voltage amplitude v of the primary side inverter INV1 m ref (FIG. 15), the feedforward control system 25 constituting the feedforward control unit 20 of the secondary side voltage / zero-phase voltage command conversion unit 27 in this embodiment is dc2 ref and the primary voltage V dc1 Based on this, the primary side output voltage amplitude v m ref Calculate and output.

[0137]

[0138] This primary side output voltage amplitude v m ref is the zero-phase voltage command value v z ref The reason is that the primary side output voltage amplitude v m ref is the primary side output voltage command value v u1 ref , v v1 ref , v w1ref are used to generate the primary-side zero-phase voltage command value v z1 ref is the modulation value V com By adding the above, the primary side output voltage command value v u1 2ph , v v1 2ph , v w1 2ph That is, the zero-phase voltage command value v z ref (v z ref =v z1 ref +v z2 ref ) The primary side zero-phase voltage command value v z1 ref is the primary side output voltage amplitude v m ref This is because it is determined by

[0139] In addition, in formula (VII), the primary side output voltage amplitude v m ref When it is 0, the voltage is doubled, and when it is 1.2, the voltage is increased by one.

[0140] Then, the output voltage command generating unit 29 calculates the primary side output voltage amplitude v m ref Based on this, the primary side output voltage command value v is calculated using the following formula (VIII). u1 ref , v v1 ref , v w1 ref is calculated and output to the primary side modulation unit 24. re is the rotor position, θ Vm is the voltage phase difference with respect to rotor position.

[0141]

[0142] As described above, the primary side modulator 24 calculates the primary side output voltage command value v u1 ref , v v1 ref , v w1ref , the primary side zero-phase voltage command value v z1 ref is the modulation value V com By adding as above, the primary side output voltage command value v u1 2ph , v v1 2ph , v w1 2ph Furthermore, the uvw-αβ conversion unit 47 generates the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref to the primary side α-axis voltage command value vα1 ref and the primary side β-axis voltage command value vβ1 ref Generate.

[0143] Furthermore, the dq-αβ conversion unit 48 included in the output voltage command generation unit 29 converts the d-axis voltage command value v d ref and the q-axis voltage command value v q ref is converted to the αβ axis, and the converted value is the primary side α axis voltage command value vα1 ref and the primary side β-axis voltage command value vβ1 ref The value obtained by the subtraction is converted into a secondary side output voltage vector command value by an αβ-uvw converter 49.

[0144] On the other hand, the ripple component cancellation control unit 46 of the embodiment of FIG. 14 is configured to cancel the primary side output voltage command value v u1 2ph , v v1 2ph , v w1 2ph After adding these, the primary side zero-phase voltage command value v z1 ref (feedforward control amount). Then, this primary side zero-phase sequence voltage command value v z1 ref From the above, the primary side zero-phase voltage command value v z1 ref By subtracting the value that has passed through the low-pass filter 51 (resulting in the effect of a high-pass filter), the secondary-side zero-phase sequence voltage command value v z2 ref(which also serves as a feedforward control variable) is derived.

[0145] Next, the derived secondary side zero-phase voltage command value v z2 ref is added to the secondary-side output voltage vector command value output by the αβ-uvw conversion unit 49 in the adder 52, thereby obtaining the secondary-side output voltage command value v u2 ref , v v2 ref , v w2 ref is generated and output to the secondary side inverter INV2.

[0146] FIG. 17 shows the secondary side zero-phase voltage command value v z2 ref and the primary side output voltage command value v of the two-phase modulation u1 2ph , v v1 2ph , v w1 2ph and the primary side zero-phase voltage command value v z1 ref The secondary side zero-phase voltage command value v z2 ref is the primary side zero-phase voltage command value v z1 ref Since it is added negatively to the zero-phase voltage command value v z ref is constant at 0.5 in the figure, and the primary side zero-phase voltage command value v z1 ref That is, the secondary side inverter INV2 is supplied with the secondary side zero-phase sequence voltage command value v so as to cancel out the ripple component superimposed by the primary side inverter INV1. z2 ref will be superimposed.

[0147] In this way, the ripple component cancellation control unit 46 outputs the primary side zero-phase sequence voltage command value v z1 ref and the primary side zero-phase voltage command value v z1 ref The difference between this and the secondary side zero-phase voltage command value v z2 refBy outputting the signal as a ripple component, it becomes possible to compensate for the ripple component with a relatively simple configuration.

[0148] The ripple component cancellation control unit 46 shown in FIG. 14 uses a low-pass filter 51 to cancel the secondary side zero-phase voltage command value v z2 ref However, the primary side zero-phase voltage command value v z1 ref and the primary side output voltage amplitude V m ref Based on this, the secondary side zero-phase voltage command value v is calculated using the following formula (IX). z2 ref may be calculated.

[0149]

[0150] In this way, the ripple component cancellation control unit 46 controls the primary side zero-phase voltage command value v z1 ref and the primary side output voltage amplitude V m ref Based on this, the secondary side zero-phase voltage command value v z2 ref If the above formula is calculated and output, it becomes possible to instantaneously compensate for the ripple component.

[0151] (7-2) During Step-Down Operation Next, the subscript two-phase modulation performed by the primary-side modulation unit 24 will be described with reference to Figures 18 and 19. When step-down operation is performed by the secondary-side inverter INV2, the primary-side modulation unit 24 performs subscript two-phase modulation. Similarly, each figure shows the plus and minus V dc1 This is a value normalized to plus or minus 1 by / 2.

[0152] The subscripted two-phase modulation in the primary side modulation unit 24 is performed by using the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref , the same primary side zero-phase voltage command value v z1 ref is the modulation value V com By adding the above, the primary side output voltage command value v u12ph , v v1 2ph , v w1 2ph By generating the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref The lower arm switching elements 3D to 3F of one phase for which the voltage is minimum are fixed to the ON state, and the upper arm switching elements 3A to 3C are fixed to the OFF state, and switching (PWM operation) is stopped.

[0153] Modulation value V in general subscript biphase modulation com is the difference between the primary output voltage command value of the minimum phase and "-1" (Fig. 18), and is used as the primary output voltage command value v of all phases. u1 ref , v v1 ref , v w1 ref By adding to the primary side zero-phase voltage command value v z1 ref 18 and 19, the ripple component is cancelled by the ripple component cancellation control section 46.

[0154] In this case, the secondary voltage V dc2 is the primary side output voltage amplitude v of the primary side inverter INV1 m ref (FIG. 18), the feedforward control system 25 constituting the feedforward control unit 20 of this embodiment determines the secondary side voltage command value V dc2 ref and the primary voltage V dc1 Based on this, the primary side output voltage amplitude v m ref Calculate and output.

[0155]

[0156] In addition, the primary side output voltage amplitude v m refWhen it is 0, it is 0V, when it is 1.2, it is a 1x voltage drop, and when it is 0.6, it is a 1 / 2x voltage drop.

[0157] Then, the output voltage command generating unit 29 calculates the primary side output voltage amplitude v m ref Based on this, the primary side output voltage command value v is calculated using the above-mentioned formula (VIII). u1 ref , v v1 ref , v w1 ref and outputs it to the primary side modulation unit 24.

[0158] Hereinafter, as in the above, the primary side modulator 24 calculates the primary side output voltage command value v u1 ref , v v1 ref , v w1 ref , the primary side zero-phase voltage command value v z1 ref is the modulation value V com By adding as above, the primary side output voltage command value v u1 2ph , v v1 2ph , v w1 2ph Furthermore, the ripple component cancellation control unit 46 generates the secondary side zero-phase sequence voltage command value v z2 ref The secondary side zero-phase voltage command value v z2 ref is added to the secondary-side output voltage vector command value output by the αβ-uvw conversion unit 49 in the adder 52, thereby obtaining the secondary-side output voltage command value v u2 ref , v v2 ref , v w2 ref is generated and output to the secondary side inverter INV2.

[0159] FIG. 20 shows the secondary side zero-phase voltage command value v z2 ref and the primary side output voltage command value v of the two-phase modulation u1 2ph , v v1 2ph , v w12ph and the primary side zero-phase voltage command value v z1 ref The secondary side zero-phase voltage command value v z2 ref is the primary side zero-phase voltage command value v z1 ref Since it is added negatively to the zero-phase voltage command value v z ref is constant at -0.5 in the figure, and the primary side zero-phase voltage command value v z1 ref The ripple component of

[0160] During this voltage step-down operation, the ripple component cancellation control unit 46 in FIG. 14 does not use the low-pass filter 51 but instead calculates the secondary side zero-phase sequence voltage command value v z2 ref Similarly, when calculating the primary side zero-phase voltage command value v z1 ref and the primary side output voltage amplitude V m ref Based on this, the secondary side zero-phase voltage command value v z2 ref Calculate.

[0161]

[0162] Next, the effect of the feedforward control by the control device 6 of the power conversion device 1 of this embodiment will be described with reference to Figures 21 to 24. Figure 21 shows the voltage command values ​​and voltages when the feedforward control of the control device 6 of this embodiment is executed, and Figure 22 shows the secondary side voltage command value V dc2 ref When the secondary voltage V changes dc2 21 showing the change in the parameter values ​​of the temperature, the temperature, and the like. The parameters in each figure are the same as those in FIGS. 6 to 11.

[0163] As is clear from a comparison of FIG. 7 and FIG. 22, when the feedforward control of this embodiment is executed (FIG. 22), the secondary side voltage command value V dc2 ref Changes in the secondary voltage V dc2 It can be seen that the response is extremely high.

[0164] However, as is clear from FIG. 22, in this case too, the secondary voltage V dc2 Therefore, in this case, the control device 6 also vibrates at the secondary side voltage command value V dc2 ref 23 and 24. Note that FIG. 23 shows the control device 6 of this embodiment that performs feedforward control and limits the rate of change of the secondary side voltage command value V dc2 ref 24 shows the voltage command values ​​and voltages when the rate of change of the secondary side voltage command value V dc2 ref When the secondary voltage V changes dc2 23 showing the change in

[0165] However, this limitation also applies to the secondary voltage V shown in FIGS. dc2 As a result, the secondary voltage V dc2 The vibrations can be eliminated or suppressed.

[0166] As described above, if the primary side modulation unit 24 of the control device 6 performs two-phase modulation in which the upper arm switching elements 3A to 3C of one phase are turned on to stop switching, or the lower arm switching elements 3D to 3F of one phase are turned on to stop switching, the number of times that the upper and lower arm switching elements 3A to 3F of the primary side inverter INV1 are switched can be reduced compared to the case of three-phase modulation, thereby significantly reducing switching losses and suppressing heat generation.

[0167] In addition, the secondary side voltage control system 23 receives the primary side zero-phase voltage command value v z1 ref The secondary side zero-phase voltage command value v z2 ref A ripple component cancellation control unit 46 is provided to generate a d-axis voltage command value v d ref and the q-axis voltage command value v q ref The secondary side zero-phase voltage command value vz2 ref Adding this, the secondary side output voltage command value v u2 ref , v v2 ref , v w2 ref Since the primary side zero-phase voltage command value v z1 ref This compensates for the ripple component of the rectifier, making it possible to suppress the generation of electromagnetic noise and noise due to the ripple current.

[0168] In this case, the control device 6 also calculates the secondary voltage command value V dc2 ref By providing a function to limit the rate of change of the secondary voltage V dc2 This reduces the excitation of vibrations, making it possible to achieve both high responsiveness and low vibration.

[0169] (8) Two-phase modulation + feedback control Next, another embodiment of the present invention will be described with reference to Fig. 25. In this embodiment, the secondary side zero-phase sequence voltage command value v z2 ref A control amount of feedback control is added to the feedforward control amount. Figure 25 is a block diagram of the secondary side voltage control system 23, primary side modulation unit 24, and secondary side modulation unit 26 of Figure 2 when a feedback control unit 30 is added. In this figure, components denoted by the same reference numerals as those in Figures 13 and 14 have the same or similar functions.

[0170] In this case, the zero-phase voltage command value v outputted by the secondary side DC link current control unit 28 configured by the current PI control system 34 z ref Feedback control amount v z refFB , the secondary side zero-phase voltage command value v z2 ref In this case, the secondary DC link current control unit 28 also adds the zero-phase current i z (secondary DC link current in the present invention) is expressed as a zero-phase current command value i z ref (the secondary DC link current command value in the present invention)z ref Feedback control amount v z refFB Also, the feedback control amount v z refFB is set to a negative value (-) for the same reason as above, and the secondary side zero-phase voltage command value v z2 ref (feedforward control amount).

[0171] In this way, the control device 6 is further provided with a feedback control section 30, and the feedback control section 30 is dc2 The zero-phase current command value i required to control z ref and a secondary voltage control unit 35 that generates a zero-phase current command value i z ref and zero-phase current i z Based on this, the zero-phase current i z The zero-phase current command value i z ref The zero-phase voltage command value v z ref Feedback control amount v z refFB a secondary DC link current control unit 28 that outputs a feedback control amount v z refFB , the secondary side zero-phase voltage command value v z2 ref By adding to the zero-phase current i z This will make it possible to prevent runaway.

[0172] This makes it possible to perform feedforward control by the feedforward control unit and feedback control by the feedback control unit in parallel, thereby realizing a power conversion device that combines the high-speed response performance of feedforward control with the disturbance suppression performance of feedback control, and is therefore both responsive and accurate.

[0173] In each embodiment, the zero-phase current i is used as an index indicating the secondary DC link current. zHowever, the present invention is not limited to this, and a capacitor current may be used as the secondary DC link current. However, when a capacitor current is used, a separate sensor is required to detect the current flowing through the capacitor C. However, the zero-phase current i z If so, each phase current i u , i v , i w From i z = (i u +i v +i w ) / 3, which can be detected by the control device 6.

[0174] Furthermore, in the second and fourth embodiments, the secondary side DC link current control unit 28 is provided in the secondary side voltage control system 23, but this is also effective for a power conversion device that does not have the secondary side DC link current control unit 28.

[0175] Furthermore, in the first and second embodiments, the output voltage command generating unit 29 generates an effective voltage V real and reactive voltage V imag However, the method for determining the primary side output voltage vector command value and the secondary side output voltage vector command value is not limited to this, and various modifications are possible. That is, the zero-phase voltage command value v z ref As one of the methods for determining the primary side output voltage vector command value and the secondary side output voltage vector command value before adding real and reactive voltage V imag There is a method to divide it into

[0176] Furthermore, in the third and fourth embodiments, two-phase modulation is performed in the primary-side modulation unit 24 and three-phase modulation is performed in the secondary-side modulation unit 26, but this is not limiting, and three-phase modulation may be performed in the primary-side modulation unit 24 and two-phase modulation may be performed in the secondary-side modulation unit 26. In this case, the voltage step-up operation is performed with subscript two-phase modulation and the voltage step-down operation is performed with superscript two-phase modulation.

[0177] In addition, although the switching elements in the embodiments are IGBTs, MOSFETs may also be used. In particular, the specific configurations and numerical values ​​shown in the embodiments are not limited to these and may be changed within the scope of the present invention.

[0178] REFERENCE SIGNS LIST 1 Power conversion device 2 DC power supplies 3A to 3F, 4A to 4F Switching element 6 Control device 7U, 7V, 7W Winding 11 Positive power supply line 12 Negative power supply line 20 Feedforward control section 21 Speed ​​control section 22 dq axis current control section 23 Secondary side voltage control system 24 Primary side modulation section 25 Feedforward control system 26 Secondary side modulation section 27 Secondary side voltage / zero-phase voltage command conversion section 28 Secondary side DC link current control section 29 Output voltage command generation section 30 Feedback control section 33 Voltage PI control system 34 Current PI control system 35 Secondary side voltage control section 36 Effective / reactive decomposition section 39 Zero-phase voltage distribution section 46 Ripple component cancellation control section 51 Low-pass filter C Capacitor INV1 Primary side inverter INV2 Secondary side inverter M Motor

Claims

1. A power conversion device comprising a primary-side inverter connected to one end of an open-ended winding of a motor, and a secondary-side inverter connected to the other end of the winding, and applying a differential voltage between the primary-side inverter and the secondary-side inverter to the motor, wherein the primary-side inverter is connected to a DC power source, the secondary-side inverter is connected to a capacitor, and a negative power supply line of the primary-side inverter and the secondary-side inverter is shared, and the power conversion device comprises a control device that controls the secondary-side voltage, which is the charging voltage of the capacitor, and the control device has a secondary-side voltage control system that generates a zero-phase sequence voltage command value that causes a secondary-side DC link current required to control the secondary-side voltage to a secondary-side voltage command value to flow, and the secondary-side voltage control system has a feedforward control unit that outputs a feedforward control amount of the zero-phase sequence voltage command value or a control amount for deriving it, based on the secondary-side voltage command value and the primary-side voltage.

2. The power conversion device according to claim 1, wherein the primary side inverter and the secondary side inverter are each composed of upper and lower arm switching elements of each phase connected in series, the positive side input terminal of the primary side inverter is connected to the positive side power line of the DC power supply, the negative side input terminal of the primary side inverter is connected to the negative side power line of the DC power supply, the output terminal of the primary side inverter is connected to one end of the winding, the output terminal of the secondary side inverter is connected to the other end of the winding, the capacitor is connected between the positive side input terminal and the negative side input terminal of the secondary side inverter, the positive side input terminal of the secondary side inverter is not connected to the positive side power line of the DC power supply, and the negative side input terminal of the secondary side inverter is connected to the negative side power line of the DC power supply, and the control device generates an AC output from the DC power supply by switching the upper and lower arm switching elements of each phase.

3. The power conversion device according to claim 1, wherein the secondary voltage control system further comprises a feedback control unit, the feedback control unit comprising: a secondary voltage control unit that generates a secondary DC link current command value required to control the secondary voltage; and a secondary DC link current control unit that outputs a feedback control amount of the zero-phase sequence voltage command value based on the secondary DC link current command value and the secondary DC link current, so as to control the secondary DC link current to the secondary DC link current command value.

4. The power conversion device according to claim 3, characterized in that the control device employs a capacitor current flowing through the capacitor as the secondary side DC link current, or employs a zero-phase current as an index indicating the secondary side DC link current.

5. A power conversion device as described in any one of claims 1 to 4, characterized in that the secondary side voltage control system further comprises an output voltage command generation unit that generates a primary side output voltage command value for switching the primary side inverter and a secondary side output voltage command value for switching the secondary side inverter based on the zero-phase sequence voltage command value, which is the feedforward control amount, or the zero-phase sequence voltage command value obtained by adding the feedback control amount to the feedforward control amount.

6. The power conversion device according to claim 5, characterized in that the output voltage command generation unit generates a primary side output voltage vector command value and a secondary side output voltage vector command value from dq axis voltage command values, generates the primary side output voltage command value from the primary side output voltage vector command value, generates the secondary side output voltage command value from the secondary side output voltage vector command value, and generates the primary side output voltage command value and the secondary side output voltage command value by adding the zero-phase sequence voltage command value to the primary side output voltage vector command value and / or the secondary side output voltage vector command value.

7. The power conversion device according to claim 6, wherein the control device further comprises: a primary side modulation unit that generates a primary side inverter switching signal for switching the primary side inverter from the primary side output voltage command value; and a secondary side modulation unit that generates a secondary side inverter switching signal for switching the secondary side inverter from the secondary side output voltage command value.

8. The power conversion device according to claim 2, wherein the control device has a primary side modulation unit that generates a primary side inverter switching signal for switching the primary side inverter, and a secondary side modulation unit that generates a secondary side inverter switching signal for switching the secondary side inverter, and the primary side modulation unit or the secondary side modulation unit performs two-phase modulation in which the upper arm switching element of one phase is turned on to stop switching, or the lower arm switching element of one phase is turned on to stop switching.

9. The power conversion device according to claim 8, wherein the primary-side modulation unit or the secondary-side modulation unit adds the same primary-side zero-phase sequence voltage command value or secondary-side zero-phase sequence voltage command value as a modulation value to the primary-side output voltage command value of each phase for switching the primary-side inverter or the secondary-side output voltage command value of each phase for switching the secondary-side inverter, thereby turning on the upper arm switching element of the phase where the primary-side output voltage command value or the secondary-side output voltage command value is maximum to stop switching, or turning on the lower arm switching element of the phase where the primary-side output voltage command value or the secondary-side output voltage command value is minimum to stop switching.

10. The power conversion device according to claim 9, characterized in that the primary side modulation unit performs the two-phase modulation by adding the primary side zero-phase voltage command value as the modulation value to the primary side output voltage command value of each phase, and the control quantity for deriving the feedforward control quantity of the zero-phase voltage command value output by the feedforward control unit is the primary side output voltage amplitude for generating the primary side output voltage command value.

11. The power conversion device according to claim 10, characterized in that the secondary side voltage control system has a ripple component cancellation control unit that generates a secondary side zero-phase sequence voltage command value that cancels the ripple component of the primary side zero-phase sequence voltage command value, and generates the secondary side output voltage command value by adding the secondary side zero-phase sequence voltage command value to a secondary side output voltage vector command value generated based on the dq axis voltage command value.

12. The power conversion device according to claim 11, characterized in that the ripple component cancellation control unit calculates and outputs the secondary side zero-phase sequence voltage command value based on the primary side zero-phase sequence voltage command value and the primary side output voltage amplitude.

13. The power conversion device according to claim 11, characterized in that the ripple component cancellation control unit outputs the difference between the value of the primary side zero-phase sequence voltage command value that has passed through a low-pass filter and the primary side zero-phase sequence voltage command value that has not passed through the low-pass filter as the secondary side zero-phase sequence voltage command value.

14. The power conversion device according to any one of claims 11 to 13, wherein the secondary side voltage control system further comprises a feedback control unit, the feedback control unit comprising: a secondary side voltage control unit that generates a secondary side DC link current command value required to control the secondary side voltage; and a secondary side DC link current control unit that outputs a feedback control amount of the zero-phase sequence voltage command value based on the secondary side DC link current command value and the secondary side DC link current so as to control the secondary side DC link current to the secondary side DC link current command value, and the feedback control amount is added to the secondary side zero-phase sequence voltage command value.

15. The power conversion device according to claim 1, wherein the control device has a function of limiting the rate of change of the secondary side voltage command value.

Images