JP2007236080A - Power conversion device for magneto system synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems, wherein when a motor having a high induced voltage is used with an increased output, a voltage supplied to an inverter on a failure becomes so high that risk for elements to destruct, and wherein, to prevent the destruction of the element, the elements having high withstand performance need to be used, but this results in high cost, a bulky inverter, and the like. <P>SOLUTION: A magneto system synchronous motor (10) is constituted, in such a way that each phase of power source side arm (Ah) of at least one side of the arms (Ah, Al), making up of a power converter has opposite direction switching elements (SW-u2, SW-v2, SW-w2). By placing the opposite direction elements at the one side of a half bridge, it can be structured to block the induced voltage supplied from the motor side on control failure and the like, and not to apply voltage to the DC side of the inverter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power converter for a magnet type synchronous motor.

Conventionally, an inverter having a booster circuit has been developed (see Patent Document 1). FIG. 1 shows a circuit diagram of an inverter configuration having such a booster circuit. FIG. 3 is a diagram showing the characteristics of a conventional motor used with such a conventional inverter. In such a conventional technique, the battery voltage (Vbatt) shown in FIG. 3 can be made variable by the booster circuit, so that the optimum β angle can be maintained even in a wider output region than when the battery voltage is fixed. is there. That is, since it can be driven without a field weakening, it is efficient. Also, by providing such a booster circuit, the DC voltage increases and a motor with a large induced voltage can be mounted.
JP 2005-245067

  However, in an application such as an electric vehicle, for example, all the electric power necessary for driving the vehicle is supplied from the battery, so that the inductance L (coil) necessary for the step-up / step-down circuit becomes very large (see FIG. 1). In parallel hybrid vehicles, the same problem occurs in increasing the output. In addition, if the motor is increased in accordance with the increase in output, the voltage applied to the inverter at the time of failure increases, which may cause destruction of the element. In order to prevent the destruction of the element, it is necessary to use an element having high breakdown voltage performance, but there are problems such as high cost and bulky inverter.

In order to solve the above-described problems, a power converter for a magnet-type synchronous motor according to a first invention
Each phase of at least one power supply side arm (P (positive) side or N (negative) side) among the arms constituting the power converter is a reverse switching element (switching the conduction in the reverse direction on and off) Element).

A power converter for a magnet type synchronous motor according to a second invention
A high-voltage compatible section including a part of elements constituting the power converter is provided.
Moreover, the power converter for magnet type synchronous motors according to the third invention provides:
The high-voltage corresponding section is an element (such as a switching element or a diode) that constitutes the reverse switching element and an arm on the side where the reverse switching element is not provided, and the rest of the power converter The withstand voltage is higher than that of the element.

Moreover, the power converter for magnet type synchronous motors according to the fourth aspect of the present invention provides:
The reverse switching element is a normally-off element (that is, during normal control, a gate voltage is applied to control conduction).

Moreover, the power converter for magnet type synchronous motors according to the fifth aspect of the present invention provides:
When the inverter is stopped when the motor induced voltage is higher than the battery voltage, a first control means (such as a circuit) that controls the reverse direction element to turn off the reverse direction switching element of the corresponding phase when the phase current crosses zero. In addition,
It is characterized by that.

Moreover, the power converter for magnet type synchronous motors according to the sixth invention provides:
It further comprises a second control means for controlling the motor operating voltage with the maximum torque at the motor base rotational speed so as to match the battery voltage.
As described above, the solution of the present invention has been described as an apparatus, but the present invention can be realized as a method substantially corresponding to these, and the scope of the present invention also includes these. I want you to understand.

  According to the first aspect of the invention, by inserting a reverse element on one side of the half bridge, it is possible to block the induced voltage applied from the motor side due to control failure or the like and not apply it to the inverter DC side. More specifically, at least one arm element is doubled so that a high voltage is not applied to the smoothing capacitor or the high-power battery, and the switching element on one side is configured in the reverse direction. ). This backflow prevention element is a forward element with respect to the motor. As a result, the induced voltage of the motor can be designed to be higher than the conventional voltage (the number of turns of the coil can be increased).

Further, according to the second invention, the withstand voltage performance in the inverter sections other than the high-voltage compatible section can be relaxed, which contributes to cost reduction. That is, only a part of the elements included in the high-voltage compatible section can be increased in cost, so that cost reduction can be achieved.
Further, the third invention is a more specific embodiment of the second invention. According to this, the loss of the element can be reduced by making a part of the elements constituting the power converter compatible with a high voltage. For example, if the breakdown voltage is doubled for only some element groups, the current can be halved and the chip area is halved. However, since the number of elements increases to 3/2, the total element area is 3/4. Similarly, when the withstand voltage is tripled, the total element area becomes 1/2 (the element area is 1/3, the number of elements is 3/2), and a great effect can be obtained in cost reduction.

  In addition, according to the fourth invention, even if the device is in a non-energized state for some reason such as a control failure, a normally-off element is used, so that the high voltage on the motor side cannot be applied to the DC side. . According to the fifth aspect of the present invention, when the reverse direction element is turned off, the voltage can be prevented from rising by cutting near the current zero. Further, according to the sixth aspect, the phase current peak can be lowered most, and the element can be designed to be small.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Before explaining the present invention, a general motor design will be described to help understand the principle of the present invention. In general, the withstand voltage design of the motor (see FIG. 2) is a withstand voltage design that can withstand the induced voltage at the maximum rotation speed Nmax. Assuming that the induced voltage at Nmax is 600V, and the base rotational speed Nr of the motor is 1/6 of the maximum rotational speed Nmax, the induced voltage at Nr is 100V. That is, if the required power of the motor is P1 [kW], the phase current is determined as in the following equation.
Practical current V = 600 [V] × Nb / Nmax
Phase current (Irms) ∝ Tmax
= P1 [kW] / (Practical voltage execution value / (Line voltage / Phase voltage)) / Number of phases

  FIG. 4 is a diagram showing motor characteristics of a motor suitable for use in the power converter according to the present invention. The induced voltage line L2 of the motor used in the present invention has a slope twice that of the induced voltage line L1 of the motor used in the prior art of FIG. That is, in the motor of FIG. 3, the number of coil turns is doubled and the gradient of the induced voltage is doubled. As shown in the figure, the same magnetomotive force can be obtained when the peak of the phase current is 1/2. Thereby, size reduction of an inverter element and size reduction of an inverter can be achieved. During normal motor control, voltage control is performed so as not to exceed the battery voltage as described above.

  However, in the magnetic synchronous motor having the characteristics as shown in FIG. 4, if the motor current (voltage) control is stopped due to failure or the like, a large induced voltage is generated, and an excessive voltage may be applied to the battery or the capacitor. It is possible. Therefore, in the present invention, in order to avoid this, an inverter switching circuit having a configuration that blocks the induced voltage from the motor from being applied to the battery side is used. FIG. 5 is an example of a circuit diagram of the power converter according to the present invention. As shown in the figure, a power converter 10 according to the present invention includes a power converter (inverter) 12 and is connected to a battery Vb, a smoothing capacitor C, and a permanent magnet synchronous motor PM. The power converter 12 includes a high side arm Ah on the P side and a low side arm Al on the N side. The high side arm Ah is a forward switching element such as IGBT SW-u1, SW-v1, SW-w1, and diodes D-u1, D-v1, D- Has w1. Similarly, the low-side arm Al includes forward switching elements SW-u3, SW-v3, SW-w3 such as IGBTs, and diodes D-u3, D-v3 that enable conduction in the reverse direction in parallel to these. Contains D-w3.

  The high-side arm Ah (P side) further includes reverse switching elements SW-u2, SW-v2, SW-w2, and diodes D-u2, D-v2, and D-w2 for preventing backflow. It is arranged in the U, V, W phase, and is configured to prevent the voltage from being applied to the DC side when the voltage between terminals rises.

  FIG. 6 is a system configuration diagram of the power conversion apparatus according to the present invention. As shown in the figure, the power conversion device 10 includes a power converter 12 and is connected to a permanent magnet synchronous motor PM, and a current measuring means AM is disposed therebetween. The motor PM is equipped with a phase sensor PS such as an encoder, and converts the measured electrical angle θ into a motor rotation speed ω. A control device 14 is connected to the power converter 12, and the control device 14 includes a target torque generation unit 16, a current command generation unit 18, a voltage command generation unit 20, a three-phase / two-phase coordinate conversion unit 22, and a two-phase. A three-phase coordinate converter 24 and a switch open / close signal generator 26 are provided.

  A torque target value T ~ is given from the host circuit (controller), and the target torque generator 16 sets the torque target value T * according to the operation mode state. Vector control is the same as general motor control. Then, the switch open / close signal generation unit 26 provides the power converter 12 with an open / close signal for each switching element for each phase.

  FIG. 7 is a diagram showing a control sequence when the power converter according to the present invention is applied to an electric vehicle. In such control, ready mode 1, CPU standby mode 2, operation control mode (zero torque hold) 3, operation control mode (torque control) 4 according to input signals such as stop signal, torque command signal, emergency stop signal, etc. , Transition to stop mode 5 and emergency stop mode 6. When the battery voltage decreases, the field weakening region increases, that is, the field weakening must be performed at the base rotation speed or lower, so the motor output decreases. However, since the decrease in output decreases linearly with the battery voltage, it also changes gradually in the motion performance of the vehicle, and is smaller than the inverter volume reduction effect.

  FIG. 8 is a circuit diagram showing a modification of the power converter (inverter switching circuit) according to the present invention. The power converter 30 of this modification includes a power converter (inverter) 32, and the circuit arrangement of the high side arms is in series. The power converter (inverter) 32 is provided with a high voltage corresponding part (high voltage corresponding section) 34. The element included in the high voltage corresponding part 34 is designed to withstand a higher voltage than other parts.

  FIG. 9 is a flowchart showing an operation sequence of the reverse switching element of the power converter according to the present invention, FIG. 9A is a flowchart, and FIG. 9B is a conceptual diagram showing rotation of a current vector. . In step S1, it is determined whether the voltage threshold value V1 has become larger than Vbatt or whether an emergency stop flag has been set. If the condition of step S1 is not satisfied, the reverse switching element is turned on (step S7). If satisfied, the process proceeds to step S3, and it is determined whether the phase current has zero-crossed, that is, whether the phase current is near zero. If the condition is satisfied, the reverse switching element of the corresponding phase is turned off (step S5). It is determined whether or not the phase current has been turned off by two phases (step S9). If the phase current can be turned off, the reverse element stop sequence ends (step S11).

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each member, each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of members, means, steps, etc. can be combined or divided into one. Is possible. For example, the first control unit and the second control unit may be a single control circuit.

It is a circuit diagram of an inverter configuration having a conventional booster circuit. It is a figure which shows the motor characteristic of a motor. It is a figure which shows the motor characteristic of a motor. It is a figure which shows the motor characteristic of the motor suitable for use with the power converter device by this invention. It is a circuit diagram of the power converter device by this invention. It is a system configuration figure of the power converter by the present invention. It is a figure which shows the control sequence at the time of applying a power converter device to an electric vehicle. It is a circuit diagram which shows the modification of the power converter device (inverter switching circuit) by this invention. 3 is a flowchart illustrating an operation sequence of a reverse switching element of a power converter according to the present invention.

Explanation of symbols

1 Ready mode
2 Standby mode
3 Operation control mode (zero torque hold)
4 Operation control mode (torque control)
5 Stop mode
6 Emergency stop mode
10 Power converter
12 Power converter
30 Power converter
34 High pressure part
Ah high side arm
Al low side arm
C smoothing capacitor
D-u1, D-u2, D-u3 diode
Nmax maximum speed
Nr base rotation speed
PM permanent magnet synchronous motor
SW-u1, SW-u2, SW-u3 Switching element

Claims (6)

A power converter for a magnet-type synchronous motor,
Each phase of the arm on the power source side of at least one of the arms constituting the power converter includes a reverse switching element.
A power converter for a magnet type synchronous motor. In the power converter for magnet type synchronous motors according to claim 1,
Provided a high-voltage compatible section including a part of the elements constituting the power converter,
A power converter for a magnet type synchronous motor. In the power converter for magnet type synchronous motors according to claim 1,
The high voltage corresponding section is an element constituting the reverse switching element and an arm on the side where the reverse switching element is not provided, and has a higher withstand voltage than the remaining elements constituting the power converter,
A power converter for a magnet type synchronous motor. In the power converter for magnet type synchronous motors according to any one of claims 1 to 3,
The reverse switching element is a normally-off element;
A power converter for a magnet type synchronous motor. In the power converter for magnet type synchronous motors according to any one of claims 1 to 4,
When the inverter is stopped when the motor induced voltage is higher than the battery voltage, the inverter further includes first control means for controlling the reverse direction element to turn off the reverse direction switching element of the corresponding phase when the phase current crosses zero.
A power converter for a magnet type synchronous motor. In the power converter for magnet type synchronous motors according to any one of claims 1 to 5,
A second control means for controlling the motor operating voltage of the maximum torque at the motor base rotational speed to match the battery voltage;
A power converter for a magnet type synchronous motor.

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