WO2024057913A1 - Power conversion device - Google Patents

Abstract

[Problem] To suppress common-mode noise without changing the modulation method by outputting an identical voltage vector by using only a region capable of modulating a voltage vector outside the region capable of modulation in a modulation method for suppressing excitation of common-mode noise for which the region capable of modulation is limited. [Solution] A power conversion device 1 equipped with an inverter circuit 27 and a control device 21 for controlling the switching of a switching element. The control device 21 is equipped with: a modulation unit 50 which sets a partial region in a base voltage space, which is a voltage vector region capable of outputting in an inverter circuit, as a region capable of modulation; and a phase voltage command correction unit 40 for calculating a corrected voltage vector obtained by correcting the voltage vector to within the region capable of modulation when the voltage vector falls inside the base voltage space and outside the region capable of modulation. As a result, the modulation unit 50 outputs by using the corrected voltage vector.

Description

power converter

The present invention relates to a power conversion device that converts DC voltage to AC voltage.

Conventionally, various pulse width modulation (PWM) methods have been proposed for suppressing conduction noise propagating to a power supply, but the methods can be broadly divided into two. One is a method that completely suppresses fluctuations in the common mode voltage that cause common mode noise, and the other is a method that partially suppresses fluctuations in the common mode voltage while allowing the fluctuations.

The former method includes pulse width modulation that outputs only odd voltage vectors or only even voltage vectors. According to this method, it is possible to completely suppress fluctuations in common mode voltage within a carrier period. There is also pulse width modulation that switches between outputting only odd-numbered voltage vectors and outputting only even-numbered voltage vectors depending on the electrical angle phase. Also by this method, fluctuations in the common mode voltage can be largely suppressed (see, for example, Patent Document 1).

The latter method includes pulse width modulation in which the timing of the rise and fall of the phase voltage of a specific phase is matched with the fall and rise of the phase voltage of other phases in a PWM pattern (for example, see Patent Document 2). Furthermore, fluctuations in the common mode voltage can also be suppressed by pulse width modulation of two-phase modulation in which switching of one phase is fixed and switching of the other two phases is fixed (see, for example, Patent Document 3).

Patent No. 5397448 WO2019/180763 Patent No. 5298003

Although the former method (Patent Document 1) is the most effective method for suppressing common mode voltage fluctuations, it has limitations on the voltage vectors used, so it is limited to the linear output region (where the voltage vector can rotate once with a constant radius). The disadvantage is that the maximum value of amplitude) is limited, and the modulation rate that can be output is limited. Therefore, it is difficult to apply this method when driving a compressor motor, or when the rotational speed and modulation rate are high, it is necessary to switch the modulation method as in Patent Document 3. However, when the modulation method is switched, there is a problem in that the common mode voltage fluctuates at the time of switching, and the effect of suppressing common mode voltage fluctuation is degraded in a modulation method having a wider linear output region.

On the other hand, although the latter method (Patent Document 2, Patent Document 3) can utilize the linear output region to the normal maximum and achieve a high modulation rate, the effect of suppressing common mode voltage fluctuation is still lower than that of the former method. method.　

Here, in Patent Document 3, two-phase modulation and three-phase modulation are switched depending on the operating region, and it is possible to switch between the former method and the latter method described above in the same way, but switching of the pulse width modulation method A shock problem arises.　

The present invention has been made in order to solve such conventional technical problems, and provides a power conversion device that enables high modulation rate operation in pulse width modulation, which has a high noise suppression effect but has a limited modulation rate. The purpose is to provide.

The present invention provides a power conversion device that converts a DC voltage into an AC voltage, and includes an inverter circuit that applies phase voltages generated at connection points of switching elements of each phase to a load, and that controls switching of the switching elements of the inverter circuit. a control device, the control device includes a modulator whose modulation region is a part of a basic voltage space that is a voltage vector region that can be output in the inverter circuit; a phase voltage command correction unit that calculates a corrected voltage vector in which the command voltage vector is corrected to be within the modulation possible area when the command voltage vector is within the modulation possible area and outside the modulation possible area; This is a power conversion device characterized by outputting power using a power converter.

In relation to the power conversion device, the modulation unit includes a first modulation processing unit having a first modulation area that is the modulation area, and an area that is the modulation area and is different from the first modulation area. a second modulation processing section having a second modulation possible region, wherein the phase voltage command modification section has a second modulation processing section having a second modulation possible region; It may also be a feature to modify the vector.

In relation to the power conversion device, the phase voltage command modification section includes a modulation region selection section that selects either the first modulation possible region or the second modulation possible region as a modification destination of the command voltage vector. The modulation area selection unit may switch between the first modulation possible area and the second modulation possible area based on the phase of the command voltage vector.

In relation to the power conversion device, the first modulation processing section executes pulse width modulation that outputs only odd voltage vectors, and the second modulation processing section executes pulse width modulation that outputs only even voltage vectors. It may also be characterized by executing.

In relation to the power conversion device, the phase voltage command modification section includes a modulation region selection section that selects either the first modulation possible region or the second modulation possible region as a modification destination of the command voltage vector. and the modulation area selection unit does not switch the first modulation area and the second modulation area immediately after switching the first modulation area and the second modulation area. may be a feature.

In relation to the power conversion device, when defining a phase that is a boundary for switching between the first modulation possible region and the second modulation possible region in the modulation region selection section as a switching boundary phase, the modulation region selection section , when the voltage vector passes through the switching boundary phase in the reverse rotation direction, switching between the first modulation possible region and the second modulation possible region may not be performed.

In relation to the power conversion device, the modulation region selection unit estimates continuous switching of the first modulation possible region and the second modulation possible region by predicting the future command voltage vector; As a result of the estimation, if it is estimated that switching will be performed continuously, switching of the first modulation possible region and the second modulation possible region is not performed when the command voltage vector arrives in the future. Good too.

In relation to the power conversion device, a command calculation unit that generates the command voltage vector is provided, and the command calculation unit is configured to combine the corrected voltage vector calculated by the phase voltage command correction unit and the command voltage vector before correction. The present invention may be characterized in that the error in the command voltage vector is compensated for in the calculation of the command voltage vector from the next time onwards.

In relation to the power conversion device, the phase voltage command correction unit may set the corrected voltage vector on a boundary line that defines the modifiable region.

In relation to the power conversion device, the phase voltage command correction unit sets the relationship between the voltage vector and the corrected voltage vector so that the lengths thereof are the same and the phases thereof are different from each other. You can also use it as

In relation to the power conversion device, the phase voltage command correction unit sets the relationship between the voltage vector and the corrected voltage vector so that they have the same phase and different lengths. You can also use it as

According to the present invention, the modulator can perform modulation control after correcting a voltage vector that is outside the operable region to within the operable region, so a modulation method that always suppresses the excitation of common mode noise is used. This makes it possible to achieve an excellent effect of comprehensively suppressing common mode noise. Further, according to another invention related to the present invention, the next voltage vector to be output is calculated by taking into account the error between the corrected voltage vector and the voltage vector before correction. However, even when the inverter circuit is within the output range and outside the modulation unit's operable range, it is possible to output a voltage vector equivalent to the immediately previous command voltage vector.

FIG. 1 is an electrical circuit diagram of a power conversion device according to an embodiment of the present invention. FIG. 3 is a diagram showing three-phase AC voltage command values. FIG. 3 is a diagram showing a basic voltage space for explaining a linear output region. FIG. 3 is a diagram showing the relationship between voltage vectors and phase voltages. It is a figure showing a voltage vector (basic voltage vector). It is a flowchart explaining the operation of the control device of the power converter. FIG. 3 is a diagram showing a voltage space for explaining an output region of an odd voltage RSPWM. FIG. 3 is a diagram showing a correlation between an output region and a function value. FIG. 3 is a diagram illustrating a linear output region of an odd voltage RSPWM. It is a figure which shows the output vector and output time of odd number voltage RSPWM. FIG. 6 is a diagram showing an example of an output vector of odd voltage RSPWM. It is a figure which shows the PWM pattern of odd voltage RSPWM. FIG. 7 is a diagram showing a modulation waveform of an odd voltage RSPWM at a low modulation rate. FIG. 3 is a diagram showing a voltage space for explaining an output region of an even voltage RSPWM. FIG. 3 is a diagram showing a correlation between an output region and a function value. FIG. 3 is a diagram illustrating a linear output region of an even voltage RSPWM. It is a figure which shows the output vector and output time of even number voltage RSPWM. FIG. 7 is a diagram showing an example of an output vector of even voltage RSPWM. FIG. 7 is a diagram showing an example of an output vector of even voltage RSPWM. It is a figure which shows the PWM pattern of even number voltage RSPWM. FIG. 7 is a diagram showing a modulation waveform of an even voltage RSPWM at a low modulation rate. FIG. 13 is a diagram showing the operating region of the full voltage RSPWM. FIG. 7 is a diagram showing in voltage space the application range of odd voltage RSPWM and even voltage RSPWM in the total voltage RSPWM of the phase determination formula. FIG. 7 is a diagram showing each phase range to which an odd voltage RSPWM and an even voltage RSPWM are applied in the total voltage RSPWM of a phase determination formula. FIG. 6 is a diagram showing a modulation waveform at a low modulation rate of full voltage RSPWM. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 7 is a diagram showing the correspondence between each phase range of the voltage vector, the operable region to which the voltage vector is corrected, and the line segment of the boundary selected in the correction destination in full voltage RSPWM. FIG. 2 is a block diagram showing the functional configuration of a phase voltage command modification section in the control device. It is a flowchart explaining operation of a common mode voltage command modification part. FIG. 6 is a diagram showing a voltage vector correction destination in a voltage space for an inoperable region in full voltage RSPWM. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. It is a block diagram showing a modification of the functional configuration of a phase voltage command modification section in the control device. It is a flowchart explaining the modification of the operation of a common mode voltage command modification part. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram representing a voltage vector correction method in voltage space. FIG. 3 is a diagram showing a modulation waveform at a high modulation rate of the present power conversion device. (A) is a conceptual diagram that averages the movement locus of three-phase voltage command values generated by the present power converter, and (B) is a conceptual diagram that shows a part of the same movement locus in an enlarged manner. FIG. 3 is a diagram showing a modulation waveform at a high modulation rate of the present power conversion device. FIG. 7 is a diagram representing a modification of a voltage vector correction method in a voltage space.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

A power conversion device 1 according to an embodiment of the present invention drives a motor 8 (load) of a so-called inverter-integrated electric compressor that constitutes a refrigerant circuit of a vehicle air conditioner installed in a vehicle such as an electric vehicle. It is something.

(1) Circuit configuration of power converter 1 In FIG. 1, the power converter 1 of the embodiment includes a three-phase inverter circuit 27 and a control device 21. The inverter circuit 27 is a circuit that converts the DC voltage Vdc of a DC power source (vehicle battery: for example, 350V) 29 into a three-phase AC voltage and applies it to the motor 8 . In this case, the motor 8 of the embodiment is an IPMSM (Interior Permanent Magnet Synchronous Motor).

The inverter circuit 27 includes a U-phase half-bridge circuit 19U, a V-phase half-bridge circuit 19V, and a W-phase half-bridge circuit 19W. Each phase half-bridge circuit 19U to 19W is connected to an upper arm switching element 18A to 18C, respectively. and lower arm switching elements 18D to 18F. Further, a free wheel diode 31 is connected in antiparallel to each of the switching elements 18A to 18F. In the embodiment, each of the upper and lower arm switching elements 18A to 18F is composed of an insulated gate bipolar transistor (IGBT) in which a MOS structure is incorporated in the gate portion.

The collectors of the upper arm switching elements 18A to 18C of the inverter circuit 27 are connected to the DC power supply 29 and the upper arm power supply line (positive bus) 10 of the smoothing capacitor 32. On the other hand, the emitters of the lower arm switching elements 18D to 18F of the inverter circuit 27 are connected to the lower arm power supply line (negative bus) 15 of the DC power supply 29 and the smoothing capacitor 32.

In this case, the emitter of the upper arm switching element 18A of the U-phase half bridge circuit 19U and the collector of the lower arm switching element 18D are connected in series, and the emitter of the upper arm switching element 18B and the lower arm switching element of the V-phase half bridge circuit 19V are connected in series. 18E are connected in series, and the emitter of the upper arm switching element 18C and the collector of the lower arm switching element 18F of the W-phase half bridge circuit 19W are connected in series.

The connection point (U phase voltage Vu) between the upper arm switching element 18A and the lower arm switching element 18D of the U phase half bridge circuit 19U is connected to the U phase armature coil of the motor 8, and the V phase half bridge circuit 19U is connected to the U phase armature coil of the motor 8. The connection point (V-phase voltage Vv) between the upper arm switching element 18B and the lower arm switching element 18E is connected to the V-phase armature coil of the motor 8, and the connection point between the upper arm switching element 18C and the lower arm switching element 18B of the W-phase half bridge circuit 19W is connected to the V-phase armature coil of the motor 8. A connection point (W-phase voltage Vw) of the arm switching element 18F is connected to the W-phase armature coil of the motor 8.

(Basic configuration of control device)
Next, the control device 21 is composed of a microcomputer having a processor, and in the embodiment, inputs a rotation speed command value from the ECU of the vehicle, obtains a motor current (phase current) from the motor 8, and based on these, , controls the ON/OFF state (switching) of each switching element 18A to 18F of the inverter circuit 27. Specifically, the gate voltage applied to the gate of each switching element 18A to 18F is controlled.

The control device 21 of the embodiment includes a dq-axis current command calculation section 28, a phase voltage command value calculation section 33, a phase voltage command modification section 40, a modulation section 50, a PWM signal generation section 36, and a gate driver 37. , has current sensors 26A, 26B, and 26C comprising current transformers for measuring the motor currents (phase currents) of each phase flowing through the motor 8, such as U-phase current iu, V-phase current iv, and W-phase current iw. There is. Each current sensor 26A to 26C is connected to a phase voltage command calculation section 33.

In the embodiment, the current sensor 26A measures the U-phase current iu, the current sensor 26B measures the V-phase current iv, and the current sensor 26C measures the W-phase current iw. The V-phase current iv may be measured by the current sensor 26B, and the W-phase current iw may be calculated from these. In addition, as for the method of detecting the motor current of each phase, in addition to measuring with the current sensors 26A to 26C as in the embodiment, the current value of the lower arm power supply line 15 is detected with a shunt resistor, and the current value and the motor 8 There is no particular limitation on the method of detecting and estimating each phase current, as there is a method for the phase voltage command calculation unit 33 to estimate it from the operating state of the phase voltage command calculation unit 33.

(dq-axis current command calculation section)
The dq-axis current command calculation unit 28 outputs a d-axis current command value and a q-axis current command value as target values for controlling the motor 8.

(Phase voltage command calculation section)
The phase voltage command calculation unit 33 calculates the electrical angle of the motor 8, the d-axis current command value Id ^ref , the q-axis current command value Iq ^ref , and the d-axis current obtained by converting the three-phase current detected by the current sensor 26B into the dq-axis. Phase voltage command for three-phase modulation to generate U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw to be applied to the armature coil of each phase of motor 8 by vector control based on Id and q-axis current Iq. The values Vu ^ref (hereinafter referred to as U-phase voltage command value Vu ^ref ), Vv ^ref (hereinafter referred to as V-phase voltage command value Vv ^ref ), and Vw ^ref (hereinafter referred to as W-phase voltage command value Vw ^ref ) are calculated and output. Specifically, the phase voltage command calculation unit 33 includes a dq-axis current controller 34 and a coordinate conversion unit 35. Note that although a case is exemplified here in which the phase voltage command calculation unit 33 outputs a three-phase AC phase voltage command value (command voltage vector), the present invention is not limited to this. Other forms of output may be used as long as the command calculation unit can calculate some command voltage vector.

The dq-axis current controller 34 outputs a d-axis current Id and a q-axis current Iq obtained by converting the three-phase current flowing through the motor 8 into dq-axes, and a d-axis current command value Id ^ref output from the dq-axis current command calculation unit 28. and q-axis current command value Iq ^ref are compared, and the current is feedback-controlled (for example, PI control) so that the two match. Furthermore, this dq-axis current controller 34 has a d-axis correction amount converted into a dq-axis voltage by a correction amount (Vm'-Vm) of a corrected voltage vector Vm' outputted from a phase voltage command correction unit 40, which will be described later. It is fed back in the form of Vd ^err and q-axis correction amount Vq ^err , and these values are also reflected in the above-mentioned PI control. As a result, the dq-axis current controller 34 outputs the d-axis voltage command value Vd ^ref and the q-axis voltage command value Vq ^ref . As a specific example, the dq-axis current controller 34 may perform PI control using the following formula (I).

The coordinate conversion unit 35 converts the α-axis voltage command value Vα ^ref and the β-axis voltage command value Vα ^ref and the β-axis voltage command value using the following formula (II) from the d-axis voltage command value Vd ref and the q-axis voltage command value Vq ^ref obtained from the dq-axis current controller 34. The voltage command value Vβ ^ref is calculated, and the voltage command values Vu ^ref , Vv ^{ref ,} Vw ^{ref (} phases voltage command value).

If the above formula (III) is rewritten as a voltage vector (command voltage vector) Vm composed of a phase θm with the α axis as a reference, an α axis voltage command value Vα ^ref , and a β axis voltage command value Vβ ^ref , the following formula ( IV).

FIG. 2 shows the waveforms of the voltage command values Vu ^ref , Vv ^ref , and Vw ^ref for each phase calculated using formula (IV), and FIG. 3 shows the linear output region kH. The linear output region is the maximum value of the amplitude at which the voltage vector can make one complete rotation (draw a circle) in the diagram representing the voltage space in FIG. 3. Since the voltage space of a three-phase inverter is hexagonal as shown in FIG. 3, the linear output region is theoretically the inscribed circle of the hexagon. In this application, the linear output region kH in general three-phase modulation is expressed as 1, and the linear output regions of other modulation methods are normalized and discussed.

Furthermore, when the High and Low states of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw are summarized, they are expressed in the states of eight voltage vectors (basic voltage vectors) from V0 to V7 as shown in Figure 4. be able to. Among these, V1, V3, and V5 are odd voltage vectors, V2, V4, and V6 are even voltage vectors, and V0 and V7 are zero voltage vectors. When each voltage vector is shown in voltage space, it becomes as shown in FIG.

The coordinate conversion unit 35 of the embodiment further calculates voltage command values Vu ^ref2 , Vv ^ref2 , and Vw ^ref2 for two-phase modulation of each phase using the following formula (V) and formula (VI).

Note that Vmod in each formula (V) and (VI) calculates the voltage command values Vu ^ref2 , Vv ref2 , ^{Vw ref2} for two-phase modulation from the voltage command values Vu ^ref , Vv ^ref , Vw ^ref for three-phase modulation. In formula (V), it is the value obtained by adding the minimum value (min) of the three-phase voltage command values Vu ^ref , Vv ^ref , and Vw ^ref to Vdc/2, and in formula (VI), it is the correction value for The value is obtained by subtracting the maximum value (max) of the phase voltage command values Vu ^ref , Vv ^ref , and Vw ^ref from Vdc/2.

If the sign of the phase with the maximum amplitude among the three-phase modulation voltage command values Vu ^ref , Vv ^ref , and Vw ^ref (phase voltage command values) is negative, the amplitude is determined to be the maximum using formula (VI). The ^{upper arm} switching element of the ^phase of Two-phase modulation is used in which the lower arm switching element of the phase with the maximum amplitude is fixed ON. If the sign of the phase with the maximum amplitude is positive, use formula (VI) to perform two-phase modulation in which the upper arm switching element of the phase with the maximum amplitude is fixed ON, and if the sign of the phase with the maximum amplitude is negative. In this case, two-phase modulation may be performed in which the lower arm switching element of the phase in which the amplitude is maximum is fixed to ON using equation (V).

(Phase voltage command correction section)
The phase voltage command correction unit 40 corrects the voltage vector Vm composed of the α-axis voltage command value Vα ^ref and the β-axis voltage command value Vβ ^ref , which are temporarily converted by the coordinate conversion unit 35, to obtain a modified α-axis voltage. A corrected voltage vector Vm' composed of the command value Vα' ^ref and the corrected β-axis voltage command value Vβ' ^ref is generated, and this is passed to the coordinate conversion unit 35 . Further, the phase voltage command correction unit 40 uses equation (III) to calculate a corrected phase voltage command value Vu' for three-phase modulation from the corrected α-axis voltage command value Vα' ^ref and the corrected β-axis voltage command value Vβ' ^ref . Calculate ^ref , Vv' ^ref , and Vw' ^ref , and use formula (V) and formula (VI) to calculate corrected voltage command values Vu' ^ref2 , Vv' ^ref2 , and Vw' ^ref2 for two-phase modulation for each phase. Then, this is passed to the coordinate transformation section 35. Note that since the specific modification method in the phase voltage command modification section 40 is closely related to the modulation method in the modulation section 50, the modulation section 50 will be explained first here, and the modification method of the phase voltage command modification section 40 will be explained first. Details will be described later.

(Modulation section)
The modulation section 50 includes an odd voltage modulation processing section 52 and an even voltage modulation processing section 54. The odd voltage modulation processing unit 52 uses the above-mentioned modified voltage vector Vm' to perform odd side pulse width modulation in which only the odd voltage vectors V1, V3, and V5 of the basic voltage vectors are output during one control period. do. The even voltage modulation processing unit 54 executes even-number side pulse width modulation in which only the even voltage vectors V2, V4, and V6 of the basic voltage vectors are output during one control period. In odd-number side pulse width modulation, the ON times tu, tv, and tw of the upper arm switching elements of each phase are directly generated from the modified α-axis voltage command value Vα' ^ref and the modified β-axis voltage command value Vβ' ^ref , and the voltage Output vectors (V1, V3, V5) and their output times. In even-number side pulse width modulation, the ON times tuv, tvw, and twu of the two-phase upper arm switching elements are directly generated from the corrected α-axis voltage command value Vα' ^ref and the corrected β-axis voltage command value Vβ' ^ref , and the voltage vector (V2, V4, V6) and their output times are output. In this application, this odd-numbered pulse width modulation is hereinafter referred to as odd-numbered voltage RSPWM (Remote State PWM), and the even-numbered side pulse width modulation is hereinafter referred to as even-numbered voltage RSPWM (Remote State PWM). Note that such pulse width modulation is based on the concept of instantaneous space vector modulation in which space vector modulation is performed without waiting for the next sampling point.

The modulation unit 50 switches between the odd voltage RSPWM and the even voltage RSPWM by determining whether the maximum phase is positive or negative. In this application, this pulse width modulation is hereinafter referred to as the total voltage RSPWM of the maximum phase determination formula.

(PWM signal generation section)
The PWM signal generation section 36 inputs the voltage vector and output time output by the modulation section 50, and compares the magnitude with the carrier signal, thereby generating signals between the U-phase inverter 19U, V-phase inverter 19V, and W-phase inverter of the inverter circuit 27. A PWM signal serving as a 19W drive command signal is generated and output.

(gate driver)
Based on the PWM signal output from the PWM signal generation section 36, the gate driver 37 outputs the gate voltages of the switching elements 18A and 18D of the U-phase inverter 19U, the gate voltages of the switching elements 18B and 18E of the V-phase inverter 19V, and W. Gate voltages of switching elements 18C and 18F of phase inverter 19W are generated.

Then, each of the switching elements 18A to 18F of the inverter circuit 27 is driven ON/OFF based on the gate voltage output from the gate driver 37. That is, when the gate voltage is in an ON state (predetermined voltage value), the switching element is turned on, and when the gate voltage is in an OFF state (zero), the switching element is turned off. When the switching elements 18A to 18F are the above-mentioned IGBTs, the gate driver 37 is a circuit for applying a gate voltage to the IGBTs based on a PWM signal, and is composed of a photocoupler, a logic IC, a transistor, etc. Ru.　

Then, the voltage at the connection point between the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half bridge circuit 19U is applied (output) to the U-phase armature coil of the motor 8 as the U-phase voltage Vu (phase voltage). , the voltage at the connection point between the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V is applied (output) to the V-phase armature coil of the motor 8 as a V-phase voltage Vv (phase voltage), The voltage at the connection point between the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W is applied (output) to the W-phase armature coil of the motor 8 as the W-phase voltage Vw (phase voltage).　

(Detailed explanation of the operation of the modulation section)
Next, the operation of the modulation section 50 in this embodiment will be explained with reference to FIG. 6 and subsequent figures. FIG. 6 is a flowchart illustrating the overall flow of pulse width modulation performed by the modulation section 50. In step S1, a modified α-axis voltage command value Vα' ^ref and a modified β-axis voltage command value Vβ' ^ref modified by the phase voltage command modification unit 40, the details of which will be described later, and a modified phase voltage command value Vu of three-phase modulation. The modulator 50 receives ' ^ref , ^Vv'ref , and ^Vw'ref .

Then, in step S2, it is determined whether the sign of the phase with the maximum amplitude is positive or negative among the modified phase voltage command values Vu' ^ref , Vv' ^ref , and Vw' ^ref of the three-phase modulation described above. do. Then, if the sign of the phase with the maximum amplitude among the corrected phase voltage command values Vu' ^ref , Vv' ^ref , Vw' ^ref of the three-phase modulation is positive, the process proceeds to step S3, and odd voltage RSPWM is performed.

(odd voltage RSPWM)
In step S3 of the odd voltage RSPWM, the modulation unit 50 calculates each phase from the corrected α-axis voltage command value Vα' ^ref and the corrected β-axis voltage command value Vβ' ^ref using the following formula (VII) and formula (VIII). The ON times tu, tv, and tw of the upper arm switching elements 18A, 18B, and 18C are calculated. Note that V1, V3, and V5 in formula (VII) are odd voltage vectors, and Ts is one control period. This control period Ts may be one carrier period. However, this one control period Ts is a period sufficiently shorter than one period of electrical angle. Further, Su, Sv, and Sw are functions corresponding to output regions (sectors) A to C of the voltage space shown in FIG. 7, and the correspondence between each output region and the functions Su, Sv, and Sw is shown in FIG. These functions Su, Sv, and Sw select voltage vectors in space vector modulation. Note that since the calculation result of formula (VIII) is the same as that of formula (V), either one may be used in step S3.

Next, in step S4, the zero voltage output time _t0 , which is the time to output the zero voltage vector V0, is calculated using formula (IX). Note that here, since the modified α-axis voltage command value Vα' ^ref and the modified β-axis voltage command value Vβ' ^ref that have been modified in advance through the modulation range determination unit 42, which will be described later, are adopted, this zero voltage output Time t0 always takes a value greater than or equal to zero.

In step S5, based on the calculated zero voltage output time _t0 , the ON time of the upper arm switching element of each phase is corrected using the following formula (X). This is done by adding t ₀ /3 to all of the ON times tu, tv, and tw. This eliminates the zero voltage output time and eliminates fluctuations in the common mode voltage Vc of the motor 8.

Then, in step S6, as shown in FIG. 10, the modulation unit 50 determines the odd voltage vectors (V1, V3, V5) and their output times based on each output region (Sector). These values are finally output to the PWM signal generation section 36 in step S14. Note that FIG. 10 shows the relationship among the output region (sector), voltage vector, and output time of the odd voltage RSPWM.　

A circle Q1 in FIG. 9 indicates a linear output region when odd voltage RSPWM (odd RSPWM) is used alone. On the other hand, in this embodiment, the entire range of the triangular region Z1 (hereinafter referred to as the odd-number side operable region) connecting the vertices of the odd-numbered voltage vectors (V1, V3, V5) is used for output. Note that the odd-numbered operable region Z1 has three line segments Z1a, Z1b, and Z1c that define the region. FIG. 11 shows the output times of odd voltage vectors V1, V3, and V5 calculated based on the corrected voltage vector Vm' in the output region A, for example. Further, FIG. 12 shows output patterns of odd voltage vectors V1, V3, and V5 in output region A.

Note that if the corrected voltage vector Vm' falls within the range of the circle Q1 in FIG. 9, it means that the control state in which the modulation rate is low continues. For example, assuming a case where modulation is performed with "only" the odd voltage RSPWM at a low modulation rate, the modulation waveform of each UVW phase will be as shown in Figure 13, and there will be no fluctuation in the common mode voltage Vc (at a low modulation rate). (Modulation waveform of odd voltage RSPWM only).

On the other hand, if the corrected voltage vector Vm' does not fall within the range of the circle Q1, it means that the modulation rate is in a high control state. Details of the modulation waveform in this case will be described later.

(Even voltage RSPWM)

On the other hand, if in step S2 the sign of the phase with the maximum amplitude among the corrected phase voltage command values Vu' ^ref , Vv' ^ref , Vw' ^ref of the three-phase modulation is negative, the process proceeds to step S8 and the even number voltage RSPWM is set. Execute. In this step S8, the modulation unit 50 uses the following formula (XI) and formula (XII) to determine the two-phase upper arm switching from the modified α-axis voltage command value Vα′ ^ref and the modified β-axis voltage command value Vβ′ ^ref . The ON times tuv, tvw, and twu of the elements are calculated.

In addition, tuv is the ON time of the upper arm switching elements 18A and 18B of the U phase and V phase, tvw is the ON time of the upper arm switching elements 18B and 18C of the V phase and W phase, and twu is the upper arm of the W phase and U phase. This is the ON time of the switching elements 18C and 18A. In addition, V2, V4, and V6 in formula (XI) are even voltage vectors, Suv, Svw, and Swu are functions corresponding to output regions (Sectors) A to C of the voltage space shown in FIG. 14, and each output region and function The correspondence between Suv, Svw, and Swu is shown in FIG. 15. These functions Suv, Svw, and Swu select voltage vectors in space vector modulation.

Furthermore, the modulation unit 50 calculates the OFF times tu (upper bar), tv (upper bar), and tw (upper bar) of the upper arm switching elements 18A, 18B, and 18C of each phase using the following formula (XIII). do. Note that since the calculation result of formula (XIII) is the same as formula (XII), either one may be used in step S8.

Next, in step S9, the zero voltage output time _t7 , which is the time to output the zero voltage vector V7, is calculated using formula (XIV). Note that here, since the modified α-axis voltage command value Vα' ^ref and the modified β-axis voltage command value Vβ' ^ref that have been modified in advance through the modulation range determination unit 42, which will be described later, are adopted, this zero voltage output The time _t7 always takes a value greater than or equal to zero.

In step S10, based on the calculated zero voltage output time _t7 , the OFF time of the upper arm switching element of each phase is corrected using the following formulas (XV) and (XVI). This is performed by adding t ₇ /3, which is the OFF time, to all of the OFF times tu (upper bar), tv (upper bar), and tw (upper bar). This eliminates the zero voltage output time and eliminates fluctuations in the common mode voltage Vc of the motor 8.

Then, in step S11, as shown in FIG. 17, the modulation unit 50 determines the even voltage vectors (V2, V4, V6) and their output times based on each output region (sector). Then, those values are finally output to the PWM signal generation section 36 in step S14. Note that FIG. 17 shows the relationship among the output region (sector), voltage vector, and output time of the even voltage RSPWM.　

Circle Q2 in FIG. 16 indicates the linear output region when this even voltage RSPWM (even RSPWM) is used alone. On the other hand, in this embodiment, the entire range of the triangular region Z2 (hereinafter referred to as even-number side operable region) connecting the vertices of the even-numbered voltage vectors (V2, V4, V6) is used for output. Note that the even-numbered operable region Z2 has three line segments Z2a, Z2b, and Z2c that define the region. FIG. 18 shows the output times of even voltage vectors V2, V4, and V6 based on the modified voltage vector Vm' in the output region A, for example, and FIG. The output times of the even voltage vectors V2, V4, and V6 based on the graph are shown. Further, FIG. 20 shows the output pattern of each voltage vector V4, V2, and V6 in the output region C.

Note that if the corrected voltage vector Vm' falls within the range of the circle Q2, it means that the control state with a low modulation rate continues. For example, assuming that in a low modulation rate state, modulation is performed with "only" the even voltage RSPWM, the modulation waveform of each phase of UVW will be as shown in Figure 21, and there will be no fluctuation in the common mode voltage Vc (low modulation rate (Modulation waveform of only even voltage RSPWM).　

On the other hand, if the corrected voltage vector Vm' does not fall within the range of the circle Q2, it means that the modulation rate is in a high control state. Details of the modulation waveform in this case will be described later.

(Total voltage RSPWM of maximum phase determination formula)
Note that in this embodiment, since modulation control is performed while switching between the odd voltage RSPWM and the even voltage RSPWM, the result is RSPWM that uses all voltage vectors. This is called the total voltage RSPWM. Among the total voltage RSPWM, in this embodiment, among the corrected phase voltage command values Vu' ^ref , Vv' ^ref , Vw' ^ref , the odd number is determined depending on whether the sign of the phase with the maximum amplitude is positive or negative. Since the voltage RSPWM and the even voltage RSPWM are switched, the total voltage RSPWM is the maximum phase determination formula.

FIG. 22 shows the operable region Z3 of the total voltage RSPWM of the maximum phase determination formula. The full-voltage RSPWM operable region (hereinafter referred to as full-voltage operable region) Z3 is a region in which the odd-number side operable region Z1 and the even-number side operable region Z2 overlap. Further, there are a total of six areas X (hereinafter referred to as inoperable areas) that surround the full voltage operable area Z3 and are outside the range of the full voltage operable area Z3. The inoperable region X is an isosceles triangle.

Note that the circle Q3 in FIG. 22 indicates the linear output region when the total voltage RSPWM of the maximum phase determination formula is used alone. Circle Q3, which is the linear output region due to the total voltage RSPWM, is enlarged compared to circles Q1 and Q2, which are the linear output regions when odd voltage RSPWM or even voltage RSPWM is performed alone. On the other hand, in this embodiment, output is performed using the entire range of the full voltage operable region Z3 beyond this linear output region (circle Q3).

Note that if the corrected voltage vector Vm' falls within the range of the circle Q3, it means that the control state with a low modulation rate continues. On the other hand, if the corrected voltage vector Vm' does not fall within the range of the circle Q3, it means that the modulation rate is in a high control state.

(Total voltage RSPWM of phase judgment formula)
In the total voltage RSPWM of the maximum phase determination formula described above, the modulation unit 50 selects the corrected phase voltage command values Vu' ^ref , Vv' ^ref , Vw' ^ref of the three-phase modulation, in which the sign of the phase with the maximum amplitude is positive. The positive and negative cases are determined, and the odd voltage RSPWM and the even voltage RSPWM are switched accordingly. On the other hand, the present invention is not limited thereto. For example, the odd voltage RSPWM and the even voltage RSPWM may be switched depending on the phase θm' of the corrected voltage vector with respect to the α axis of the corrected voltage vector Vm'. In this application, this pulse width modulation is hereinafter referred to as phase-determined total voltage RSPWM.

FIG. 23 shows a phase region odd to which an odd voltage RSPWM is applied and a phase region even to which an even voltage RSPWM is applied in the operation region of the total voltage RSPWM of the phase determination formula. Note that FIG. 24 shows the correspondence between each phase range and the odd voltage RSPWM and even voltage RSPWM applied thereto. As shown in FIGS. 23 and 24, one period of electrical angle is divided into six regions (330°<θm'≦30°, 30°<θm'≦90°, 90°<θm'≦150°, 150°<θm '≦210°, 210°<θm'≦270°, 270°<θm'≦330°), and the odd voltage RSPWM and the even voltage RSPWM are alternately switched.

Note that the operable region output region Z3 of the total voltage RSPWM of the phase determination formula is the same as the total voltage RSPWM of the maximum phase determination formula in FIG. In other words, the full voltage RSPWM operable region (hereinafter referred to as full voltage operable region) Z3 is a region in which the odd-number side operable region Z1 and the even-number side operable region Z2 overlap. Further, there are a total of six regions (hereinafter referred to as inoperable regions) X that surround the full voltage operable region Z3 and are outside the range of the full voltage operable region Z3.

Note that if the corrected voltage vector Vm' falls within the range of the circle Q3, it means that the control state with a low modulation rate continues. In a situation where the corrected voltage vector Vm' is within the range of the circle Q3, the modulation waveform of each phase of UVW by the total voltage RSPWM is as shown in FIG. In this case, the common mode voltage Vc fluctuates when switching between the odd voltage RSPWM and the even voltage RSPWM (modulation waveform due to the total voltage RSPWM at a low modulation rate).

On the other hand, if the corrected voltage vector Vm' does not fall within the range of the circle Q3, it means that the modulation rate is in a high control state. Details of the modulation waveform in this case will be described later.

(Explanation of detailed operation of phase voltage command correction section)
Returning to FIG. 1, the phase voltage command correction unit 40 adjusts the voltage vector Vm composed of the α-axis voltage command value Vα ^ref and the β-axis voltage command value Vβ ^ref (before modification) to the full voltage operable region Z3. Determine whether it is within the range. Note that when the voltage vector Vm falls within the full voltage operable region Z3, there is no need to correct the voltage vector Vm, so the voltage vector Vm is set to be equal to the corrected voltage vector Vm'. On the other hand, as shown in FIG. 26, when the voltage vector Vm is located outside the full voltage operable region Z3, that is, in the inoperable region , a voltage vector within the full voltage operable region Z3 is calculated, and this is set as a corrected voltage vector Vm'. Note that the inoperable area X means an area within the hexagonal basic voltage space B surrounded by the V1 to V6 basic voltage vectors in vector control and outside the full voltage operable area Z3. Note that this approximation range is, for example, a range in which the vector length N' of the corrected voltage vector Vm' is 0.3N≦N'≦1.7N with respect to the vector length N of the voltage vector Vm, or 0.5N≦ Examples include a range where N'≦1.5N and a range where 0.7N≦N'≦1.3N. The approximation range is, for example, a range in which the voltage phase θm' of the corrected voltage vector Vm' satisfies θm-120°≦θm'≦θm+120° with respect to the voltage phase θm of the voltage vector Vm, or θm-90°≦θm Examples include a range where '≦θm+90°, a range where θm-60°≦θm'≦θm+60°, and a range where θm-45°≦θm'≦θm+45°.

As methods for calculating the corrected voltage vector Vm' in this approximation range K, there are, for example, the following (method A) to (method E).

(Method A: Correction to the boundary between the inoperable region and the voltage operable region)
For example, as shown in FIG. 27, arbitrary coordinates on the boundary lines Y1 and Y2 between the inoperable region X to which the voltage vector Vm belongs and the full voltage operable region Z3 are set as the corrected voltage vector Vm'. Although a case is illustrated here in which the correction is made on the boundary lines Y1 and Y2 of the full voltage operable region Z3, the present invention is not limited to this, and the correction is made on the boundary line between the inoperable region X and the odd-number side operable region Z1. The correction may be made within the odd operable region Z1, or may be made on the boundary line between the inoperable region X and the even operable region Z2, or within the even operable region Z2.

(Method B: Voltage phase correction)
As shown in FIG. 28, only the phase θm of the voltage vector Vm is modified without changing the length of the voltage vector Vm, and the location where it intersects with the boundary lines Y1 and Y2 of the inoperable region X and the full voltage operable region Z3 is shown. is the modified voltage vector Vm'. When there are two correction voltage vector candidates, one for forward rotation (correction in the positive direction) and the other for rotation (correction in the negative direction) of the phase θm, select the one with the smaller absolute value of the amount of correction of the voltage phase θm. It is preferable to do so. Although a case is illustrated here in which the correction is made on the boundary lines Y1 and Y2 of the full voltage operable region Z3, the present invention is not limited to this, and the correction is made on the boundary line between the inoperable region X and the odd-number side operable region Z1. The correction may be made within the odd operable region Z1, or may be made on the boundary line between the inoperable region X and the even operable region Z2, or within the even operable region Z2.

(Method C: Voltage vector length correction)
As shown in FIG. 29, only the length of the voltage vector Vm is corrected without changing the phase θm of the voltage vector Vm, and the location where it intersects with the boundaries Y1 and Y2 of the inoperable region X and the full voltage operable region Z3 is is the modified voltage vector Vm'. Although a case is illustrated here in which the correction is made on the boundary lines Y1 and Y2 of the full voltage operable region Z3, the present invention is not limited to this, and the correction is made on the boundary line between the inoperable region X and the odd-number side operable region Z1. The correction may be made within the odd operable region Z1, or may be made on the boundary line between the inoperable region X and the even operable region Z2, or within the even operable region Z2.

(Method D: Correct the coordinates of the voltage vector by moving it parallel to the outermost line of the inoperable area X)
As shown in FIG. 30, by moving the α-axis coordinate Vα and the β-axis coordinate Vβ of the voltage vector Vm parallel to the outermost line Y3 (outline of the basic voltage space B) of the inoperable region X, full voltage operation is possible. The location where the region Z3 intersects with the boundaries Y1 and Y2 is defined as a corrected voltage vector Vm'. When there are two correction voltage vector candidates, one for forward rotation (correction in the positive direction) and the other for rotation (correction in the negative direction) of the phase θm, select the one with the smaller absolute value of the amount of correction of the voltage phase θm. It is preferable to do so. Although a case is illustrated here in which the correction is made on the boundary lines Y1 and Y2 of the full voltage operable region Z3, the present invention is not limited to this, and the correction is made on the boundary line between the inoperable region X and the odd-number side operable region Z1. The correction may be made within the odd operable region Z1, or may be made on the boundary line between the inoperable region X and the even operable region Z2, or within the even operable region Z2.

(Method E: Combination modification of the above (Method A) to (Method D))
The corrected voltage vector Vm' may be calculated by appropriately combining the above (Method A) to (Method D).

In the above (Methods A) to (Method E), the case where the voltage vector Vm is corrected to be on the boundary of the full voltage operable region Z3 is illustrated, but in advance, as the correction destination region, the odd number side operable region Z1 and the even number side The modification may be performed by selecting one of the side operable areas Z2 and narrowing down to the boundary of either the odd-number side operable area Z1 or the even-number side operable area Z2. For example, when applying the total voltage RSPWM of the maximum phase determination formula, if the sign of the phase with the maximum amplitude among the three-phase modulation phase voltage command values Vu ^ref , Vv ^ref , and Vw ^ref before modification is negative, , the modification to the even-numbered operable region Z2 may be selected, and if the sign of the phase with the maximum amplitude is positive, the modification to the odd-numbered side operable region Z1 may be selected.

For example, when applying the total voltage RSPWM of the phase determination formula, as shown in FIG. The modification to the side operable area Z1 may be switched. Note that FIG. 31 shows a line segment of the boundary selected when correcting the voltage vector Vm on the neighboring boundary line of the even-number side operable region Z2 or the odd-number side operable region Z1 based on the phase θm. ).

(Method B: Explanation of detailed operation of voltage phase correction)

Next, a detailed operation example of the phase voltage command modification unit 40 in the case where the above (method B) is adopted will be described on the premise that the phase determination type total voltage RSPWM is applied. FIG. 33 is a flowchart illustrating the flow of operation of the phase voltage command modification section 40. As shown in FIG. 32, the phase voltage command modification section 40 includes a modulation range determining section 42, a modulation region selection section 44, a modification command calculation section 46, a modification command selection section 48, and a feedback processing section 49.

The modulation range determining unit 42 determines whether the coordinates of the voltage vector Vm are within the full voltage operable region Z3 (step S41). If the voltage vector Vm falls within the full voltage operable region Z3, there is no need to correct the voltage vector Vm, so the process proceeds to step S42, where the correction command calculation unit 46 changes the voltage vector Vm itself to a corrected voltage. Set to vector Vm'. Next, the process proceeds to step S80, and this modified voltage vector Vm' is output to the modulation section 50.

On the other hand, in step S41, if the coordinates of the voltage vector Vm are located outside the full voltage operable region Z3, that is, in the inoperable region X, the voltage vector Vm needs to be corrected, so the process proceeds to step S44. , the modulation area selection unit 44 is activated.

In step S44, the modulation region selection unit 44 refers to the phase θm of the voltage vector Vm with respect to the α axis, and according to the relationship shown in FIG. Select one of the modifications to. When the relationship in FIG. 31 is illustrated in FIG. 34, the inoperable region It will have X2. If the voltage vector Vm belongs to the odd modification region X1, the modulation region selection unit 44 modifies the voltage vector so that it falls within the odd operable region Z1. When the voltage vector Vm belongs to the even number modification region X2, the modulation region selection unit 44 modifies the voltage vector so that it falls within the even number side operable region Z2. At this time, the correction destination of the voltage vector Vm of the odd correction area X1 is an isolated triangular area that is adjacent to the odd correction area It is preferable to correct the area Zlt. Similarly, the correction destination of the voltage vector Vm of the even correction region It is preferable to correct the area Z2t.

Note that when the three line segments Z1a, Z1b, and Z1c that partition the odd-number side operable region Z1 are expressed as functions of the α and β axes, the following equation (XVII) is obtained. This function is used when calculating the correction destination coordinates of the voltage vector Vm.

Similarly, when the three line segments Z2a, Z2b, and Z2c that partition the even-number side operable region Z2 are expressed as functions of the α and β axes, the following equation (XVIII) is obtained. This function is used when calculating the correction destination coordinates of the voltage vector Vm.

For convenience of explanation, hereinafter, the following formula (XVII) and formula (XVIII) will be generalized as the following formula (XIX).

In step S44, when the voltage vector Vm is in the state shown in FIG. 35, that is, the phase θm is within the range of 330°<θm≦30°, the odd-number side operable region Z1 is selected based on the correlation table shown in FIG. Ru. After that, the process proceeds to step S50, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the odd-number side operable region Z1.

Prior to modification, the modification command calculation unit 46 defines a perfect circle P having a radius equal to the coordinates of the voltage vector Vm as a function of the α and β axes, as shown in FIG. As a result, the perfect circle P is expressed by the following formula (XX).

Next, since the phase θm of this voltage vector Vm belongs to 0°<θm≦30°, a function representing the line segment Z1a is selected from formula (XVIII) based on the correlation table in FIG. Then, the two intersection points (VAα', VAβ') and (VBα', VBβ') of this and the function representing the perfect circle P of formula (XX) are calculated. Note that the reason why the line segment Z1a is selected is that when this voltage vector Vm is rotated in both forward and reverse directions, it intersects this line segment Z1a first.

When a function generalized by formula (XIX) is used, the coordinates of the two intersection points are expressed by formula (XXI) below.

As a result of the above, in step S50, the modification command calculation unit 46 calculates first and second voltage vectors (hereinafter referred to as first and second modification candidate voltage vectors) VAm', VBm' is calculated.

Next, the process proceeds to step S52, and the modification command selection unit 48 selects one voltage vector from the first and second modification candidate voltage vectors VAm' and VBm', and sets this as the modified voltage vector Vm'. . Prior to this selection, the modification command selection unit 48 selects a first phase modification amount θAmod of the first modification candidate voltage vector VAm' based on the voltage vector Vm, and a second modification candidate voltage vector based on the voltage vector Vm. The second phase modification amount θBmod of VBm' is calculated using the following formula (XXII).

The modification command selection unit 48 compares the first phase modification amount θAmod and the second phase modification amount θBmod, and selects the smaller modification candidate voltage vector VAm', VBm' (here, the first modification candidate voltage vector VAm'). , the modified voltage vector Vm' is determined. Thereafter, the process proceeds to step S80, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S82, and the feedback processing unit 49 converts the modification amount (Vm'-Vm) of the modified voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis modification amount Vd ^err and the q-axis modification amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

Returning to step S44, when the voltage vector Vm is in the state shown in FIG. 36, that is, the phase θm is within the range of 30°<θm≦90°, the even-number side operable region Z2 is determined based on the correlation table of FIG. selected. After that, the process proceeds to step S60, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the even number side operable region Z2.

Prior to the modification, the modification command calculation unit 46 defines a perfect circle P whose radius is the coordinates of the voltage vector Vm using the above formula (XX), as shown in FIG. Furthermore, since the phase θm of this voltage vector Vm belongs to 30°<θm≦60°, a function representing the line segment Z2a is selected from formula (XVIII) based on the correlation table of FIG. , and the two intersection points (VAα', VAβ') and (VBα', VBβ') of the function representing the perfect circle P of formula (XX) are calculated. Note that the reason why line segment Z2a is selected is that when this voltage vector Vm is rotated in both forward and reverse directions, it intersects line segment Z2a first.

As a result of the above, in step S60, the modification command calculation unit 46 calculates the first and second voltage vectors (hereinafter referred to as first and second modification candidate voltage vectors) VAm′, which are candidates for modification to the even-number side operable region Z2. VBm' is calculated.

Next, the process proceeds to step S62, and the modification command selection unit 48 selects one voltage vector from the first and second modification candidate voltage vectors VAm' and VBm', and sets this as the modified voltage vector Vm'. . Prior to this selection, the modification command selection unit 48 selects a first phase modification amount θAmod of the first modification candidate voltage vector VAm' based on the voltage vector Vm, and a second modification candidate voltage vector based on the voltage vector Vm. The second phase modification amount θBmod of VBm' is calculated using the above formula (XXII).

The modification command selection unit 48 compares the first phase modification amount θAmod and the second phase modification amount θBmod, and selects the smaller modification candidate voltage vector VAm', VBm' (here, the second modification candidate voltage vector VBm'). , the modified voltage vector Vm' is determined. Thereafter, the process proceeds to step S80, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S82, and the feedback processing unit 49 converts the modification amount (Vm'-Vm) of the modified voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis modification amount Vd ^err and the q-axis modification amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

(Method C: Detailed explanation of voltage vector length correction)

Next, a detailed operation example of the phase voltage command modification unit 40 in the case where the above (Method C) is adopted will be described on the premise that the phase determination type total voltage RSPWM is applied. FIG. 38 is a flowchart illustrating the flow of operation of the phase voltage command modification section 40. As shown in FIG. 37, the phase voltage command modification section 40 includes a modulation range determining section 42, a modulation region selection section 44, a modification command calculation section 46, and a feedback processing section 49.

The modulation range determination unit 42 determines whether the coordinates of the voltage vector Vm are within the full voltage operable range Z3 (step S71). If the voltage vector Vm is within the full voltage operable range Z3, there is no need to modify the voltage vector Vm, so the process proceeds to step S72, where the correction command calculation unit 46 sets the voltage vector Vm itself to the modified voltage vector Vm'. Next, the process proceeds to step S100, where the modified voltage vector Vm' is output to the modulation unit 50.

On the other hand, in step S71, if the coordinates of the voltage vector Vm are located outside the full voltage operable area Z3, that is, in the inoperable area X, the voltage vector Vm needs to be corrected, so the process proceeds to step S74. , the modulation area selection section 44 is activated.

In step S74, the modulation area selection unit 44 refers to the phase θm of the voltage vector Vm with respect to the α axis, and according to the correlation table of FIG. Select one of the modifications to Z1. For example, when the voltage vector Vm is in the state shown in FIG. 39, that is, when the phase θm is within the range of 330°<θm≦30°, the odd-number side operable region Z1 is selected based on the correlation table shown in FIG. After that, the process proceeds to step S80, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the odd-number side operable region Z1.

Prior to the modification, the modification command calculation unit 46 defines a radial line segment E having the same phase as the voltage vector Vm as a function of the α and β axes, as shown in FIG. As a result, the radial line segment E becomes the following formula (XXIII).

Next, since the phase θm of this voltage vector Vm belongs to 0°<θm≦30°, a function representing the line segment Z1a is selected from formula (XVII) based on the correlation table in FIG. Then, the intersection point (Vα', Vβ') between this and the function representing the radial line segment E of formula (XXIII) is calculated. Note that the line segment Z1a is selected because it is the closest boundary line to the voltage vector Vm.

For the sake of convenience, the above formulas (XVII) and (XVIII) are generalized by the following formula (XXIV).

The coordinates of the intersection of this generalized formula (XXIV) and formula (XXIII) are expressed by formula (XXV) below.

As a result of the above, in step S80, the modification command calculation unit 46 calculates the modified voltage vector Vm' that is the result of modification to the odd-number side operable region Z1. Thereafter, the process proceeds to step S100, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S102, and the feedback processing unit 49 converts the correction amount (Vm'-Vm) of the correction voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis correction amount Vd ^err and the q-axis correction amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

Returning to step S74, when the voltage vector Vm is in the state shown in FIG. 40, that is, the phase θm is within the range of 30°<θm≦90°, the even-number side operable region Z2 is determined based on the correlation table of FIG. selected. After that, the process proceeds to step S90, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the even number side operable region Z2.

Prior to modification, the modification command calculation unit 46 defines a radial line segment E having the same phase as the voltage vector Vm as a function of the α and β axes, as shown in FIG. As a result, the radial line segment E becomes the above formula (XXIII).

Next, since the phase θm of this voltage vector Vm belongs to 30°<θm≦60°, a function representing the line segment Z2a is selected from formula (XVIII) based on the correlation table in FIG. Then, the intersection point (Vα', Vβ') between this and the function representing the radial line segment E of formula (XXIII) is calculated. Note that the line segment Z2a is selected because it is the closest boundary line to the voltage vector Vm.

As a result of the above, in step S90, the modification command calculation unit 46 calculates the modified voltage vector Vm' that is the result of modification to the even-number side operable region Z2. Thereafter, the process proceeds to step S100, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S102, and the feedback processing unit 49 converts the correction amount (Vm'-Vm) of the correction voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis correction amount Vd ^err and the q-axis correction amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

(Method D: Explanation of detailed operation when moving the coordinates of the voltage vector in parallel with the outermost line of the inoperable region X)
Next, a detailed operation example of the phase voltage command modification unit 40 in the case of employing the above (Method D) will be described on the premise that the total voltage RSPWM of the phase determination formula is applied. Note that the internal configuration and operation flowchart of the phase voltage command modification unit 40 are the same as those in FIGS. 37 and 38, so these will be referred to.

The modulation range determining unit 42 determines whether the coordinates of the voltage vector Vm are within the full voltage operable region Z3 (step S71). If the voltage vector Vm falls within the full voltage operable region Z3, there is no need to modify the voltage vector Vm, so the process proceeds to step S72, where the modification command calculation unit 46 changes the voltage vector Vm itself to a modified voltage. Set to vector Vm'. Next, the process proceeds to step S100, and this modified voltage vector Vm' is output to the modulation section 50.

On the other hand, in step S71, if the coordinates of the voltage vector Vm are located outside the full voltage operable area Z3, that is, in the inoperable area X, it is necessary to correct the voltage vector Vm, so the process proceeds to step S74. , the modulation area selection section 44 is activated.

In step S74, the modulation area selection unit 44 refers to the phase θm of the voltage vector Vm with respect to the α axis, and according to the correlation table of FIG. Select one of the modifications to Z1.

In step S74, when the voltage vector Vm is in the state shown in FIG. 41, that is, the phase θm is within the range of 330°<θm≦30°, the odd-number side operable region Z1 is selected based on the correlation table shown in FIG. Ru. After that, the process proceeds to step S80, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the odd-number side operable region Z1.

Prior to the modification, the modification command calculation unit 46 calculates the ON time of the upper arm switching elements 18A, 18B, and 18C of each phase by applying formula (VIII) to the voltage vector Vm, as shown in FIG. Calculate command values tu, tv, and tw. Note that adjustments using formulas (VIX) and (X) are not performed here. As a result, one of tu, tv, and tw is always zero. Note that in the case of the voltage vector Vm in FIG. 41, tw is always zero.

Since the phase θm of the voltage vector Vm belongs to 0°<θm≦30°, tu>tv always holds true. Therefore, while maintaining the larger value tu, the tv side is modified using the relational expression tv'=Ts-tu. That is, tv is corrected to tv' using the relational expression Ts=tu+tv'. As a result, as shown in FIG. 41, a corrected voltage vector Vm' that falls within the odd-number side operable region Z1 is calculated based on the corrected ON time command values (tu, tv').

Note that the coordinates (Vα', Vβ') of this corrected voltage vector Vm' on the α and β axes pass through the coordinates of the voltage vector Vm before correction, and are parallel to the outermost line Y3 of the inoperable region X. This is the intersection of the line segment F and the function representing the line segment Z1a selected from the formula (XVII) based on the correlation table of FIG.

In addition, in order to generalize the above explanation, the remaining two non-zero command values among the ON times tu, tv, and tw calculated by applying formula (VIII) to the voltage vector Vm are Define t1 and t2. In this case, the coordinates (t1', t2') that fall within the odd-numbered operable region Z1 of the corrected voltage vector Vm' are determined by maintaining the larger command value of t1 and t2 as is, and by changing the remaining smaller command value. , the following formula (XXVI) is obtained.

As a result of the above, in step S80, the modification command calculation unit 46 calculates the modified voltage vector Vm' that is the result of modification to the odd-number side operable region Z1. Thereafter, the process proceeds to step S100, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S102, and the feedback processing unit 49 converts the correction amount (Vm'-Vm) of the correction voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis correction amount Vd ^err and the q-axis correction amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

Returning to step S74, when the voltage vector Vm is in the state shown in FIG. 42, that is, the phase θm is within the range of 30°<θm≦90°, the even-number side operable region Z2 is determined based on the correlation table of FIG. selected. After that, the process proceeds to step S90, and the modification command calculation unit 46 modifies the voltage vector Vm to be within the even number side operable region Z2.

Prior to the modification, the modification command calculation unit 46 calculates the OFF time of the upper arm switching elements 18A, 18B, and 18C of each phase by applying formula (XIII) to the voltage vector Vm, as shown in FIG. Command values tu (upper bar), tv (upper bar), and tw (upper bar) are calculated. Note that adjustment using formula (XIV) is not performed here. As a result, one of tu (upper bar), tv (upper bar), and tw (upper bar) is always zero. Note that in the case of the voltage vector Vm in FIG. 42, tu (upper bar) is always zero.

Since the phase θm of the voltage vector Vm belongs to 30°<θm≦60°, tw (upper bar)>tv (upper bar) always holds true. Therefore, while maintaining the larger value tw (upper bar), the tv (upper bar) side is modified using the relational expression tv' (upper bar)=Ts-tw (upper bar). That is, tv (upper bar) is corrected to tv' (upper bar) using the relational expression Ts=tw (upper bar) + tv' (upper bar). As a result, as shown in FIG. 42, a corrected voltage vector Vm' within the even-number side operable area Z2 is calculated based on the corrected OFF time command values (tv' (upper bar), tw (upper bar)). Note that the coordinates (Vα', Vβ') of this corrected voltage vector Vm' on the α and β axes pass through the coordinates of the voltage vector Vm before correction, and are parallel to the outermost line Y3 of the inoperable region X. This is the intersection of the line segment F and the function representing the line segment Z2a selected from the formula (XVIII) based on the correlation table of FIG.

As a result of the above, in step S90, the modification command calculation unit 46 calculates the modified voltage vector Vm' that is the result of modification to the even-number side operable region Z2. Thereafter, the process proceeds to step S100, and this modified voltage vector Vm' is output to the modulation section 50. Furthermore, the process proceeds to step S102, and the feedback processing unit 49 converts the correction amount (Vm'-Vm) of the correction voltage vector Vm' into a dq-axis voltage, thereby obtaining the d-axis correction amount Vd ^err and the q-axis correction amount Vq ^err. is generated and fed back to the dq-axis current controller 34.

In addition, in order to generalize the above explanation, among the OFF times tu (upper bar), tv (upper bar), and tw (upper bar) calculated by applying formula (XIII) to the voltage vector Vm, The remaining two non-zero command values are defined as t1 (upper bar) and t2 (upper bar). In this case, the coordinates (t1' (upper bar), t2' (upper bar)) within the even number side operable region Z2 of the corrected voltage vector Vm' are the larger of t1 (upper bar) and t2 (upper bar). Since the command value of is left and the smaller command value is corrected, the following formula (XXVII) is obtained.

As described above, according to the power conversion device 1 of the present embodiment, the phase voltage command correction unit 40 converts the voltage vector Vm belonging to the inoperable region X to the corrected voltage vector Vm' in the full voltage operable region Z3. Since the modulation section 50 then performs modulation control, it is possible to always perform modulation using the same modulation method. As a result, when controlling at a high modulation rate, even if the voltage vector Vm partially deviates from the full voltage operable region Z3, it is all corrected to within the full voltage operable region Z3, so common mode noise is always eliminated. Since it is driven using a modulation method that does not excite, common mode noise is significantly suppressed overall.

In the power conversion device 1, when converting the voltage vector Vm into the corrected voltage vector Vm' within the full-voltage operable region Z3 in the phase voltage command modification unit 40, the voltage vector Vm is close to the inoperable region X to which the voltage vector Vm belongs. The range is selected. In addition, since control is performed by feeding back the amount of correction of the corrected voltage vector Vm', it is possible to suppress the amount of correction of the corrected voltage vector Vm'. , Vv, and Vw can be stabilized.

FIG. 43 shows the waveform B (reference) of the three-phase voltage commands Vu, Vv, and Vw output from the modulation unit 50 by the power conversion device 1 of this embodiment and the common mode voltage waveform Vc. It can be seen that fluctuations in the common mode voltage waveform Vc are suppressed to a greater extent than in the conventional power converter 1.

(Correction control of selection method of operable area in modulation area selection unit)
As already mentioned, the modulation region selection unit 44 refers to the phase θm of the voltage vector Vm with respect to the α axis, and according to the correlation table of FIG. In the method of selecting one of the modifications to the region Z1, as long as the rotational speed of the phase θm is always positive, the modulation region selection unit 44 selects the even-number side operable region Z2 and the phase θm at every phase interval of 60°. The odd number side operable region Z1 is alternately switched.

By the way, in this embodiment, in order to stabilize the output control of the motor 8, the amount of correction of the corrected voltage vector Vm' is fed back to the dq-axis current controller 34 to perform current control, as shown in equation (I). ing. Since the corrected voltage vector Vm' moves forward or backward in phase θm or increases or decreases in vector length with respect to the original voltage vector Vm, information regarding these correction amounts is fed back to the dq-axis current controller 34. When the current is controlled using the d-axis voltage command value Vd ^ref and the q-axis voltage command value Vq ^ref that are output, the influence thereof is reflected.

FIG. 44(A) shows the influence on the phase voltage command value due to the modification of the voltage vector Vm. Line D in FIG. 44(A) indicates the α-axis voltage command value Vα ^ref and the β-axis obtained by coordinate-converting the d-axis voltage command value Vd ^ref and the q-axis voltage command value Vq ^ref to the αβ-axis using formula (II). It is a conceptual diagram which averages and expresses the movement locus of voltage command value Vβ ^ref (voltage vector Vm). Note that this "averaging of the movement locus" means that the voltage vector Vm actually output from the dq-axis current controller 34 oscillates greatly in the rotational direction and radial direction on the αβ axis, so it is difficult to illustrate it. Therefore, the concept is to virtually smooth out the movement trajectory by applying filters in the rotational direction and the radial direction. As shown in the region D1 of the line D, the voltage vector Vm has the switching boundary phase (30°, 90°, 150° , 210°, 270°, 330°).

FIG. 44(B) is a conceptual diagram showing a part of the movement locus in this area D1 enlarged without smoothing. Since the actual voltage vector Vm vibrates finely, the movement locus of the voltage vector Vm reciprocates in the circumferential direction before and after the switching boundary phase of 270°. If the movement locus of the voltage vector Vm is defined by the control timing time series k1 to k7 for each control cycle Ts, and if the correlation table of FIG. Z1, k2: Odd number side operable area Z1, k3: Even number side operable area Z2, k4: Odd number side operable area Z1, k5: Even number side operable area Z2, k6: Odd number side operable area Z1, k7: Even number Side operable area Z2, k8: Even number side operable area Z2. As a result, during the short control period (5 control cycles) from k3 to k7, the odd-number side operable area Z1 and the even-number side operable area Z2 are alternately switched, and as shown in the area indicated by the dotted line C in FIG. Common mode voltage fluctuations that do not occur will be excited.

Therefore, the modulation area selection unit 44 modifies the correlation table of FIG. 31. Specifically, the voltage vector Vm rotates in the opposite direction, passes through the switching boundary phase (270° in FIG. 44(B)) in the reverse rotation direction, and enters the operable region of the reverse rotation destination (in FIG. 44(B)). When the odd-number side operable area Z1) is about to be selected, it is forcibly replaced with the operable area before reverse rotation (even-number side operable area Z2 in FIG. 44(B)). In other words, when the voltage vector Vm reversely rotates and can be selected from the even-numbered operable region Z2 before the reverse rotation to the odd-numbered operable region Z1 after the reverse rotation, as in k3→k4 in the control timing time series, , k4 is forcibly replaced with the even number side operable region Z2 before reverse rotation. Similarly, as in k5→k6 in the control timing time series, when the voltage vector Vm is reversely rotated and the even number side operable region Z2 before the reverse rotation can be selected as the odd number side operable region Z1 after the reverse rotation. Forcibly replaces the selection in k6 with the even number side operable region Z2 before reverse rotation. In other words, the switching at the switching boundary phase is made to have a unidirectional characteristic in the forward rotation direction, and switching in the reverse rotation direction is prohibited.

In order to execute this correction control, the modulation area selection unit 44 selects the d-axis voltage command value Vd output from the dq-axis current controller 34 from the current control timing k to the next (future) control timing k+1. ^ref and the q-axis voltage command value Vq ^ref are estimated using the following formula (XXVIII).

By calculating the phase θm from the estimated d-axis voltage command value Vd ^ref and q-axis voltage command value Vq ^ref , the voltage vector Vm is reversely rotated at the next control timing k+1, and the switching boundary phase is also reversely rotated. It is possible to determine whether or not to pass in the direction. Only when the vehicle passes in the reverse rotation direction, the operable region before reverse rotation may be selected.

FIG. 45 shows the waveform B (reference) of the three-phase voltage commands Vu, Vv, and Vw output from the modulation section 50 and the common mode voltage waveform Vc when correction control is applied in the modulation region selection section 44. It can be seen that fluctuations in the common mode voltage waveform Vc are suppressed compared to the fluctuations in FIG. 43.

As described above, in this embodiment, odd voltage RSPWM, even voltage RSPWM, or full voltage RSPWM has been exemplified as a modulation method using a part of the basic vector area B, but the present invention is not limited to this. , other modulation schemes can be adopted. Furthermore, in the present embodiment, the modulation unit 50 has two modulation methods: the odd voltage modulation processing unit 52 that performs odd voltage RSPWM, and the even voltage modulation processing unit 54 that performs even voltage RSPWM. However, the present invention is not limited to this. Modulation section 50 may have a single modulation method. Furthermore, the modulation section 50 may include a first modulation processing section that executes another first modulation method and a second modulation processing section that executes another second modulation method, and these may be switched as appropriate. Furthermore, in the present invention, the modulation section 50 can employ three or more types of modulation methods and switch between them as appropriate.

Furthermore, in the present embodiment, as (Method A) in the phase voltage command modification unit 40, the case where the voltage vector Vm is modified to be on the boundary between the inoperable region and the voltage operable region is illustrated, but the present invention is limited to this. It is also possible to modify it inside this boundary. Further, (Method A), (Method B), (Method C), and (Method D) which are voltage vector correction methods are examples, and other correction methods can be adopted. For example, as an example of combining (Method A), (Method B), and (Method C), as shown in FIG. It is also preferable to correct the corrected voltage vector Vm' at the intersection of G and the boundary line Y1.

Further, in each of the above embodiments, the driving of the motor (load) of an electric compressor has been explained as an example, but the present invention is not limited thereto, and is also effective when driving a motor other than the motor of the electric compressor. Furthermore, the present invention is applicable to various power conversion devices that convert DC voltage into AC voltage using an inverter and apply the voltage to a load.

1 Power converter 8 Motor 18A to 18F Upper and lower arm switching elements 19U U-phase inverter 19V V-phase inverter 19W W-phase inverter 21 Control device 27 Inverter circuit 28 dq-axis current command calculation unit 33 Phase voltage command calculation unit 34 dq-axis current controller 35 Coordinate conversion section 36 PWM signal generation section 37 Gate driver 40 Phase voltage command modification section 42 Modulation range inside determination section 44 Modulation region selection section 46 Modification command calculation section 48 Modification command selection section 49 Feedback processing section 50 Modulation section

Claims (11)

1. In a power conversion device that converts DC voltage to AC voltage,
   an inverter circuit that applies phase voltages generated at the connection points of switching elements of each phase to a load;
   a control device that controls switching of the switching element of the inverter circuit,
   The control device includes:
   a modulator whose modulation region is a part of a basic voltage space that is a voltage vector region that can be output in the inverter circuit;
   a phase voltage command correction unit that calculates a corrected voltage vector in which the command voltage vector is corrected to be within the modulation possible region when the command voltage vector belongs to the basic voltage space and outside the modulation possible region;
   The power converter device, wherein the modulation unit outputs the modified voltage vector using the modified voltage vector.
2. The modulation section is
   a first modulation processing section having a first modulation possible area that is the modulation possible area;
   a second modulation processing unit having a second modulation area that is the modulation area and is different from the first modulation area;
   The phase voltage command correction unit includes:
   The power conversion device according to claim 1, wherein the modified voltage vector is modified within either the first modulatable region or the second modulatable region.
3. The phase voltage command modification section includes a modulation region selection section that selects either the first modulation possible region or the second modulation possible region as a modification destination of the command voltage vector,
   The power conversion device according to claim 2, wherein the modulation area selection unit switches between the first modulation possible area and the second modulation possible area based on the phase of the command voltage vector.
4. The first modulation processing unit executes pulse width modulation that outputs only odd voltage vectors,
   The power conversion device according to claim 2, wherein the second modulation processing unit executes pulse width modulation that outputs only even voltage vectors.
5. The phase voltage command modification section includes a modulation region selection section that selects either the first modulation possible region or the second modulation possible region as a modification destination of the command voltage vector,
   The modulation area selection unit is characterized in that immediately after switching between the first modulation area and the second modulation area, the modulation area selection unit does not switch between the first modulation area and the second modulation area. The power conversion device according to claim 2.
6. When defining a phase serving as a boundary for switching between the first modulation possible area and the second modulation possible area in the modulation area selection section as a switching boundary phase,
   The modulation area selection unit is characterized in that when the voltage vector passes through the switching boundary phase in a reverse rotation direction, the modulation area selection unit does not perform switching between the first modulation possible area and the second modulation possible area. 3. The power conversion device according to 3.
7. In the modulation area selection unit, by predicting the future command voltage vector, continuous switching of the first modulation possible area and the second modulation possible area is estimated, and as a result of the estimation, continuous switching is performed. If it is estimated that the power conversion will be performed, switching of the first modulation possible region and the second modulation possible region is not performed when the command voltage vector arrives in the future. Device.
8. comprising a command calculation unit that generates the command voltage vector,
   The command calculation unit is
   The electric power according to claim 1, wherein an error between the corrected voltage vector calculated by the phase voltage command correction unit and the command voltage vector before correction is compensated for in subsequent calculations of the command voltage vector. conversion device.
9. The power conversion device according to claim 1, wherein the phase voltage command correction unit sets the corrected voltage vector on a boundary line that defines the modifiable region.
10. 8. The phase voltage command modification unit sets the relationship between the voltage vector and the modified voltage vector so that they have the same length and different phases. power converter.
11. 8. The phase voltage command modification unit sets the relationship between the voltage vector and the modified voltage vector so that their phases are the same and their lengths are different. power converter.

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