JP4715449B2 - Inverter - Google Patents

Description

  The present invention relates to an inverter for supplying a rotating electric machine with a composite current for independently driving the two rotors.

In an inverter as an example of a power conversion device that has two three-phase bridge circuits and performs power conversion with independent PWM signals, triangular wave generation means for generating a triangular wave is provided, and the triangular wave generation means includes two three-phase generation means. There is known a configuration capable of outputting two triangular waves having a predetermined phase difference to the PWM signal generating means of the bridge circuit. When the load of the two three-phase bridge circuits is a motor and both the motors are in a power running operation or a regenerative operation, the phase difference of the triangular wave is set to 45 ° to 135 °. When one motor is in power running operation and the other motor is in regenerative operation, the phase difference is set to 0 °. Due to the phase difference of the triangular wave, the phase difference of the ripple current generated in each bridge circuit is shifted by 180 °, and the ripple currents canceling each other and flowing through the current smoothing capacitor can be suppressed to a small value (for example, see Patent Document 1).
JP 2002-300800 A

  In such a conventional inverter, the number of phases of the two motors is the same. Therefore, if the phase difference of the triangular wave is controlled according to the power running operation and regenerative operation of both motors, the ripple current can be kept small. It was. However, the composite current generated by the inverter is composed of m-phase and n-phase, the relative phase of at least two of the m-phase currents is 180 °, and the relative phase of at least two of the n-phase currents is 0 °. In this case, the triangular wave phase difference that maximizes the ripple current reduction effect depends on the phase current amplitude, power factor, and modulation factor. Therefore, in the conventional method of controlling the phase difference of the triangular wave only from the power running operation and the regenerative operation state, it is difficult to maximize the ripple current reduction effect.

  An object of the present invention is to solve the above-described problems and to provide an inverter capable of maximizing the ripple current reduction effect even when the composite current to be generated is different from that of the m-phase and the n-phase. .

The inverter of the present invention is an inverter for supplying a rotating electrical machine with a composite current for independently driving the two rotors, and more specifically, combining the two rotors from a multi-phase inverter. The rotating electric machine that is driven independently by the current and the stator coil of the rotating electric machine are divided into sets in which the total current is zero, the neutral points of the stator coils in each set are connected to each other, and PWM drive pulse signals to the inverter arm of the multi-phase inverter energizing the stator coil and the inverter arm energizing the other set of stator coils are independent from each other, and the triangular wave generating means for generating a triangular wave is also independent from each other, A bridge circuit connected to one set of stator coils and a bridge circuit connected to another set of stator coils have their DC ends connected to each other. An inverter connected to a DC power supply in a row, wherein the composite current is composed of m-phase and n-phase, the relative phase of at least two phase currents of the m-phase current is 180 °, and at least 2 of the n-phase currents When the relative phase of two phase currents is 0 °, a triangular wave that is used to obtain a PWM drive pulse signal and that can output a triangular wave having a predetermined phase difference from each other is provided independently for each of the two rotors. Generating means, and operating state detecting means for detecting phase current amplitude, power factor, and modulation factor for controlling the driving of each rotor of the rotating electrical machine , wherein the triangular wave generating means is the operating state detecting means. Based on the detected phase current amplitude, power factor, and modulation factor, the relative phase difference of the triangular wave is brought close to the upper limit or lower limit, and the phase difference of the triangular wave is switched to minimize the generated ripple current. It is characterized by being configured to control the phase difference.

  In the present invention, since the triangular wave generating means generates two triangular waves having a predetermined phase difference, the independent PWM signal generating means creates a PWM signal based on triangular waves having different phases, and each switching circuit operates during operation. The phase difference of the generated ripple current can be shifted. As a result, each ripple current is canceled and the ripple current flowing in the current smoothing capacitor is reduced. Therefore, a capacitor having a small rated ripple current can be used, and the apparatus can be reduced in size and cost. Moreover, the Joule heat generated in the capacitor is reduced by reducing the ripple current, and the capacitor temperature is kept low, thereby extending the life of the electrolytic capacitor.

  Note that, as a preferred example of the inverter according to the present invention, the rotating electrical machine and operating state detecting means for detecting the operating state of the inverter are provided, and the triangular wave generating means is arranged based on the detected operating state. It can be configured to switch the phase difference. With this configuration, the phase of the triangular wave used for PWM signal generation is switched according to the power supply state of the m-phase current and n-phase current, so even if the power supply state of the m-phase current and n-phase current changes. The phase of the ripple current can be appropriately shifted, and the ripple current can be reduced.

  As a preferred example of the inverter according to the present invention, the operating state detecting means can be configured to detect a phase current, a power factor, and a modulation factor for controlling each motor. With this configuration, only the phase current, power factor, and modulation factor for driving the two rotors need to be detected, so that the operating state of the motor can be easily determined.

  Furthermore, as a preferred example of the inverter according to the present invention, when the inverter generates only m-phase current or only n-phase current, the triangular wave phase difference is 0 ° lower limit and 180 ° upper limit, and any one of 0 to 180 The relative phase difference can be set as follows. With this configuration, when the inverter generates only m-phase current or only n-phase current, the ripple current can be reduced by shifting the phase of the triangular wave by 0 ° to 180 °. As a result, a current smoothing capacitor having a small rated ripple current can be used, and the size and cost of the apparatus can be reduced. Moreover, the Joule heat generated in the capacitor is reduced by reducing the ripple current, and the capacitor temperature is kept low, thereby extending the life of the electrolytic capacitor.

  Furthermore, as a preferred example of the inverter of the present invention, when the inverter supplies a composite current of m-phase and n-phase to the motor, the relative phase difference of the triangular wave is set as an upper limit based on the phase current amplitude, power factor, and modulation factor. Or it can comprise so that it may approach a minimum. With this configuration, when the inverter supplies a composite current of m phase and n phase to the motor, the ripple current can be reduced by determining the phase difference of the triangular wave from the phase current amplitude, power factor, and modulation factor. . As a result, a current smoothing capacitor having a small rated ripple current can be used, and the size and cost of the apparatus can be reduced. Moreover, the Joule heat generated in the capacitor is reduced by reducing the ripple current, and the lifetime of the electric field capacitor is extended by keeping the capacitor temperature low.

  As a preferred example of the inverter according to the present invention, a temperature sensor is attached to the capacitor so that the above-described control can be performed when the capacitor temperature exceeds a predetermined temperature. With this configuration, it is possible to reduce the load on the control system and prevent the electrolytic capacitor from increasing in temperature due to the ripple current, thereby preventing the life of the electrolytic capacitor from being reduced.

  Further, as a preferred example of the inverter according to the present invention, in order to change the relative phase of the triangular wave, the amplitude fluctuation of at least one phase of the triangular wave is stopped for a certain period of time, and then the amplitude fluctuation of the triangular wave is restarted, and at least one trapezoidal wave Can be configured to obtain a desired phase difference. With this configuration, a triangular wave phase difference can be suitably created.

  Furthermore, as a preferred example of the inverter of the present invention, in order to change the relative phase of the triangular wave, it is possible to obtain a desired phase difference by temporarily changing the triangular wave frequency of at least one phase. . With this configuration, a triangular wave phase difference can be suitably created.

  Further, as a preferred example of the inverter of the present invention, in order to change the relative phase of the triangular wave, it is possible to obtain a desired phase difference by temporarily changing at least one phase of the triangular wave amplitude. With this configuration, a triangular wave phase difference can be suitably created.

Embodiments of the present invention will be described below in detail with reference to the drawings.
The inverter of the present invention will be described by taking as an example a rotating electric machine (for example, see Patent Document 2) in which two rotors driven independently by a composite current are arranged coaxially.
JP 2001-103717 A

  In this example, the outer rotor has a three-phase and six-pole pair, and the inner rotor has a six-phase and three-pole pair. Each of the stator coils is connected to a 6-phase inverter. There are a total of six feeder lines 1 to 6 connected to the stator coil. At this time, the phase of the current passing through each feeder line is as shown in Table 1 below. The sum of currents of the pair of feeder lines 1, 3, 5 and the pair of feeder lines 2, 4, 6 is 0, and there is no electrical problem even if the neutral point is divided.

  As shown in Table 1, when one side of the composite current is three-phase (outer rotor) and the other is six-phase (inner rotor), the phase of the feed line 1 and the feed line 4 is 180 ° different from the 6-phase current. The phase of the ripple current generated from the feeder line 1 and the feeder line 4 differs by 180 °, and the ripple current cancels out on the inner rotor side. On the other hand, since the phases of the feed line 1 and the feed line 4 are the same in the three-phase current, the ripple current generated from the feed line 1 and the feed line 4 has the same phase, and the ripple current is superimposed on the outer rotor side.

  The phase of the triangular wave used when creating the PWM signal of the set including the feed line 1 (feed lines 1, 3, 5) and the PWM signal of the set including the feed line 4 (feed lines 2, 4, 6) are created. When the phase of the triangular wave used at the time is shifted by 180 °, the phase of the ripple current generated from the feed line 1 and the phase of the ripple current generated from the feed line 4 are also shifted by 180 °. Therefore, in this case, the ripple current generated from the feeder line 1 and the feeder line 4 of the six-phase current (inner rotor side) is superimposed, and the ripple current generated from the feeder line 1 and the feeder line 4 of the three-phase current (outer rotor side). Cancel each other.

  In the case of the above example, in the present invention, the ripple current caused by the three-phase current (outer current) on the outer rotor side is larger than the ripple current caused by the six-phase current (inner current) on the inner rotor side. The mutual phase of the triangular wave is set to 180 ° so that the ripple current caused by the outer current cancels out. As a result, it is possible to cancel more ripple currents than when ripple currents caused by the inner currents cancel each other. Conversely, when the ripple current caused by the inner current is larger than the ripple current caused by the outer current, the mutual phase of the triangular wave is set to 0 ° so that the ripple current caused by the inner current cancels out. As a result, more ripple currents can be canceled than when ripple currents caused by outer currents cancel each other. In this way, the phase difference is controlled so that the ripple current caused by the composite current supplied to the two rotors is minimized.

  Here, the magnitude of the ripple current caused by the outer current depends on the outer phase current amplitude, the outer power factor, and the outer modulation factor. Similarly, the magnitude of the ripple current caused by the inner current depends on the inner phase current amplitude, the inner power factor, and the inner modulation factor.

  Next, the configuration of the inverter in the above-described example in which the outer rotor has three phases and six pole pairs and the inner rotor has six phases and three pole pairs will be described.

  1 and 2 are diagrams for explaining an example of a drive pulse generator for generating a drive pulse. In the example shown in FIG. 1, the drive pulse generator 19 compares the signal wave 7 and the triangular wave 8 with the comparator 9 to generate drive pulses on the feeder lines 1, 3, and 5. Similarly, in the example illustrated in FIG. 2, the drive pulse generator 20 compares the signal wave 10 and the triangular wave 11 with the comparator 12 to generate drive pulses on the feeder lines 2, 4, and 6.

  FIG. 3 is a block diagram showing an example of a configuration when a six-phase inverter of a drive system that realizes the inverter of the present invention is used. In the example shown in FIG. 3, the drive system 21 receives the target torque and the target rotation speed from the host controller 13. The drive system 21 commands the microcomputer 14 that generates the modulation rate, the microcomputers 16 and 17 that generate the drive pulses, the communication means 15 that communicates between the microcomputer 14, the microcomputer 16, and the microcomputer 17, and the phase difference of the triangular wave. And a microcomputer 18.

  The target torque and target rotational speed are first input to the microcomputer 14. Further, the microcomputer 14 receives a DC power supply voltage and a phase current. The microcomputer 14 generates a modulation rate for achieving the target torque and the target rotational speed. Next, the generated modulation factor and the amplitude of the captured phase current are sent to the communication means 15, and the microcomputer 18 captures them. A power factor is sent to the microcomputer 18 from the operating state. The modulation rate is sent from the communication means 15 to the microcomputers 16 and 17.

  For example, the microcomputer 18 stores the relationship shown in FIG. In the example shown in FIG. 4, the X axis indicates the outer phase current amplitude, the Y axis indicates the inner phase current amplitude, and the Z axis indicates the outer modulation rate. The plurality of curved surfaces are curved surfaces having a constant inner modulation rate. When the inner modulation factor is A, if the outer modulation factor is below the curved surface of the inner modulation factor A, the relative phase of the triangular wave is 0 °, and if it is above, the relative phase is 180 °. The phase difference can be controlled so that the ripple current to be minimized. This curved surface is created using simulation or the like. In this example, the curved surface of the inner modulation factor is shown discontinuously as A, 2A, 3A, and 4A, but the effect of control can be further enhanced by interpolating between the curved surfaces. In the example described above, the relative phase of the triangular wave is switched between 0 ° and 180 °. However, the ripple current can be further reduced by controlling the angle of the relative phase more finely.

  When performing control in consideration of the power factor, a curved surface having a constant inner modulation factor is prepared in advance for each power factor.

Next, a method for actually shifting the relative phase of the triangular wave will be described.
FIG. 5 is a diagram for explaining a method of shifting the relative phase of the triangular wave by the microcomputer 18. In FIG. 5, when it is desired to shift the phase of the triangular wave 23 with respect to the triangular wave 22, the amplitude change of the triangular wave 23 is stopped for a certain period of time, and then restarted. As a result, the triangular wave 22 and the triangular wave 23 are out of phase. FIG. 6 is a diagram for explaining another method for shifting the relative phase of the triangular wave by the microcomputer 18. In FIG. 6, when it is desired to shift the phase of the triangular wave 25 with respect to the triangular wave 24, the frequency of the triangular wave 23 is temporarily changed. As a result, the triangular wave 24 and the triangular wave 25 are out of phase. FIG. 7 is a diagram for explaining still another method of shifting the relative phase of the triangular wave by the microcomputer 18. In FIG. 7, when it is desired to shift the phase of the triangular wave 27 with respect to the triangular wave 26, the amplitude of the triangular wave 27 is temporarily changed. As a result, the triangular wave 26 and the triangular wave 27 are out of phase.

  The microcomputer 18 determines the relative phase of the triangular wave from the inner and outer phase current amplitudes, the power factor, and the modulation factor by the method shown in FIG. In order to generate the determined phase difference, the microcomputer 18 shifts the phase of the triangular wave sent to the microcomputer 16 or 17 by a predetermined angle by the method of FIG. 5, FIG. 6 or FIG. Thereby, the phase difference can be controlled so that the ripple current generated in the two rotors is minimized.

  Next, examples other than the above-described example in which the outer rotor has a three-phase and six-pole pair and the inner rotor has a six-phase and three-pole pair will be described.

  Table 2 shows the case where one of the composite currents has four phases and the other has eight phases. In this case, the four-phase feed line 1 and feed line 3, the feed line 2 and feed line 4, the feed line 5 and feed line 7, and the feed line 6 and feed line 8 are 180 degrees out of phase and sent to each feed line. If the phase difference of the triangular wave is the same, the ripple currents of the divided feeder lines cancel each other. If the phases of the eight-phase feeder 1 and the feeder 5 are 180 degrees different from each other and the phase difference of the triangular wave sent to each feeder is the same, ripple currents generated from the feeder 1 and the feeder 5 cancel each other. Therefore, in this example, when the triangular wave sent to each feeder line has the same phase, the amount of ripple current cancellation is the largest, and the phase difference can be controlled so that the ripple current generated in the two rotors is minimized. In this example, there is little or no ripple current reduction effect of the relative phase control of the triangular wave. When one of the composite currents is an odd phase and the other is an even phase, the effect of the relative phase control of the triangular wave is increased.

  Table 3 shows the case where one of the composite currents has three phases and the other has 12 phases. In this case as well, when the number of phases on one side is twice the number of phases on the other side, as in the case of three phases and six phases, it is used to generate a current flowing through the feeder line 1 and the feeder line 7. By changing the relative phase of the triangular wave between 0 ° and 180 °, the ripple currents can be canceled or overlapped, and the phase difference can be reduced so that the ripple current generated in the two rotors is minimized. Can be controlled.

  According to the inverter of the present invention, the composite current is composed of m-phase and n-phase, the relative phase of at least two of the m-phase currents is 180 °, and the relative phase of at least two of the n-phase currents is 0. When it is °, a ripple current generated in the two rotors can be obtained by providing independently provided triangular wave generating means that can output triangular waves having a predetermined phase difference, which are used to obtain a PWM drive pulse signal. It can be suitably used for applications in which the phase difference is controlled to be minimized.

It is a figure for demonstrating an example of the drive pulse generator which produces | generates a drive pulse in the inverter of this invention. It is a figure for demonstrating the other example of the drive pulse generator which produces | generates a drive pulse in the inverter of this invention. It is a block diagram which shows an example of a structure at the time of using the 6-phase inverter of the drive system which implement | achieves the inverter of this invention. In the inverter of the present invention, a graph for determining whether the relative phase of two triangular waves is 0 ° or 180 °, with the inner phase current amplitude, inner modulation factor, outer phase current amplitude, and outer modulation factor as variables. It is an example. In the inverter of this invention, it is a figure for demonstrating one method of shifting the relative phase of a triangular wave with a microcomputer. In the inverter of this invention, it is a figure for demonstrating the other method of shifting the relative phase of a triangular wave with a microcomputer. In the inverter of this invention, it is a figure for demonstrating the further another method of shifting the relative phase of a triangular wave with a microcomputer.

Explanation of symbols

7, 10 Signal wave 8, 11, 22, 23, 24, 25, 26, 27 Triangle wave 9, 12 Comparator 13 Host controller 14, 16, 17, 18 Microcomputer 15 Communication means 19, 20 Drive pulse generator

Claims (5)

An inverter for supplying a rotating electrical machine with a composite current for independently driving the two rotors, the composite current comprising an m-phase and an n-phase, and at least two of the m-phase currents When the relative phase is 180 ° and the relative phase of at least two phase currents of the n-phase current is 0 °, a triangular wave having a predetermined phase difference can be output, which is used to obtain a PWM drive pulse signal. a triangular wave generating means provided independently in correspondence with each of the two rotors, the phase current amplitude for controlling the driving of each rotor of the rotary electric machine, power factor, operating condition detecting means for detecting the modulation factor, wherein the triangular wave generating means, the phase current amplitude detected by the operating condition detecting means, power factor, close to the relative phase difference between the triangular wave on the basis of the modulation factor to the upper limit or the lower limit, the phase difference of a triangular wave By replacing it Ri, inverter, wherein a ripple current generated is configured to control the phase difference to be a minimum. The inverter according to claim 1 , wherein the control according to claim 1 is performed when the temperature of the capacitor exceeds a predetermined temperature by attaching a temperature sensor to the capacitor. In order to change the relative phase of the triangular wave, the amplitude fluctuation of at least one phase of the triangular wave is stopped for a certain time, and then the amplitude fluctuation of the triangular wave is restarted to produce at least one trapezoidal wave, thereby obtaining a desired phase difference. The inverter according to claim 1 . To alter the relative phase of the triangular wave, by temporarily changing a triangular wave frequency of at least one phase, the inverter according to claim 1, characterized in that to obtain the desired phase difference. To alter the relative phase of the triangular wave, by temporarily changing a triangular wave amplitude of at least one phase, the inverter according to claim 1, characterized in that to obtain the desired phase difference.

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