WO2009101859A1

WO2009101859A1 - Inverter device and method for controlling the same

Info

Publication number: WO2009101859A1
Application number: PCT/JP2009/051414
Authority: WO
Inventors: Kenji Yamada
Original assignee: Kabushiki Kaisha Yaskawa Denki
Priority date: 2008-02-13
Filing date: 2009-01-29
Publication date: 2009-08-20
Also published as: JPWO2009101859A1

Abstract

It is possible to provide an inverter device which can protect electronic parts of both of a battery and an inverter with a sufficient reliability. Provided also is a method for controlling the inverter device. The inverter device includes a battery (3) for power supply backup in a DC bus of the inverter separately from a power supply system and drives an AC motor (2). The inverter device includes: a voltage level judgment device (4) which detects a transient voltage of the inverter DC bus and a transient voltage of the battery; a comparison circuit (9) which compares the transient voltage of the inverter DC bus to the transient voltage of the battery; and an inverter control unit (6) which switches a reduction operation pattern of the AC motor according to a differential voltage as the comparison result obtained by the comparison circuit.

Description

Inverter device and control method thereof

The present invention relates to an inverter device for driving and controlling an AC motor and a control method thereof.

Conventionally, there is a system that provides a backup function by connecting a battery to a direct current portion of an inverter device for driving a motor. Moreover, in an electric vehicle, a battery is used as a main power source instead of a backup. When the battery is considered as an absorption element for the regenerative energy of the AC motor, a predetermined regenerative braking force may not be obtained when the AC motor is decelerating and the battery is nearly fully charged. In order to avoid this problem, there is a method of monitoring the state of charge of the battery and adjusting the operating state of the AC motor according to the state of charge of the battery (see, for example, Patent Document 1). As the adjustment of the operation state, when the battery is fully charged, a recirculation mode is created by the inverter, the electric charge charged in the battery is discharged by the motor, and then the chargeable state is made. In contrast to this, there is a method of monitoring the terminal voltage of the battery and operating the torque limit value of the motor (see, for example, Patent Document 2). In either case, countermeasures are taken assuming that regenerative braking power cannot be absorbed depending on the state of charge of the battery when the motor is decelerated.
FIG. 5 is a block diagram of a conventional inverter device. In FIG. 5, 1 is an inverter, 2 is a motor, 3 is a battery connected in parallel to the DC bus of the inverter, 4 is a voltage level determination unit, 5 is a regenerative / reflux mode selector, 6 is an inverter control unit, and 7 is a speed detection. It is a vessel. P is a positive DC bus of the inverter 1, and N is a negative DC bus of the inverter 1. The voltage level determination unit 4 determines whether or not the battery 3 is in an overcharged state where the regenerative energy of the motor 2 cannot be absorbed. When the regeneration / reflux mode selector 5 determines that the battery is in an overcharge state, the regeneration mode is switched to the reflux mode that consumes energy. During this operation, the torque current is reduced and the excitation current component is increased to consume the energy of the battery 3 as a heat loss inside the motor.
FIG. 6 is another configuration diagram of a conventional inverter device. In FIG. 6, 1 is an inverter, 2 is a motor, 3 is a battery, 6 is an inverter control unit, 7 is a speed detector, and 8 is a voltage detector. The terminal voltage of the battery 3 is detected by the voltage detector 8, and the motor torque command is selected or the stop operation of the inverter 1 is selected in the inverter control unit 6 according to the voltage level.
Thus, the conventional apparatus determines the operation of the inverter 1 while detecting and monitoring the terminal voltage of the battery 3.
Japanese Patent Application Publication No. 2002-95105 (FIG. 1) Japanese Patent No. 3195879 (FIG. 1)

In a conventional inverter device equipped with a battery in the direct current section, the terminal voltage of the battery is detected and monitored, and when the battery is almost fully charged, the motor is decelerated or stopped, or the motor torque is changed. The battery voltage is controlled so that it does not become an abnormal value.
However, when the DC bus of the inverter and the battery are directly connected, charging / discharging is greatly influenced by the impedance characteristics of the battery, and this characteristic determines the response and redundancy of the inverter drive system.
Normally, a smoothing capacitor is installed on the DC bus of the inverter, and the smoothing capacitor and the battery have an overwhelmingly low impedance. Therefore, even if the motor deceleration or stop method is changed or the motor torque is changed using only the battery voltage as a criterion, the terminal voltage of the smoothing capacitor is higher than the battery terminal voltage. There is a risk of exceeding the withstand voltage of the electronic components mounted on the inverter. That is, although the battery terminal and the smoothing capacitor terminal are electrically connected and have the same potential in a steady state, a potential difference occurs transiently. The conventional technique is a method that considers the safety of the battery. However, even if the battery is actually protected, the main circuit IGBT, smoothing capacitor, and the like, which are the electronic components of the inverter, cannot be protected with sufficient reliability.

The present invention has been made in view of such problems, and detects a transient potential difference between a battery terminal and a smoothing capacitor terminal to determine the operating state of the inverter, and An object of the present invention is to provide an inverter device that can protect both with sufficient reliability and a control method thereof.

In order to solve the above problem, the present invention is configured as follows.
Separately from the power supply system, the inverter has a battery for power backup on the DC bus of the inverter, and in the inverter device that drives the AC motor,
Voltage level determination device for detecting the transient voltage of the DC bus of the inverter and the transient voltage of the battery, a comparison circuit for comparing the transient voltage of the DC bus of the inverter and the transient voltage of the battery, and a comparison result of the comparison circuit And an inverter control unit that switches a deceleration operation pattern of the AC motor based on the difference voltage.
Further, in claim 1, the deceleration operation pattern has any one of a normal deceleration pattern that decelerates at a preset deceleration rate, a pattern that extends the deceleration rate more than the normal deceleration pattern, and a zero vector output pattern. It is.
The inverter control unit according to claim 1, wherein the inverter controller decelerates the deceleration operation pattern of the AC motor at a preset deceleration rate based on the differential voltage, a pattern for extending the deceleration rate over the normal deceleration pattern, and a zero vector The output patterns are switched in order.
In addition, when 0 ≦ difference voltage V ≦ first set value, the vehicle decelerates at a preset deceleration rate. When first set value ≦ difference voltage V <second set value, the deceleration rate is longer than the normal deceleration. When the second set value ≦ the difference voltage V <the third set value, a zero voltage vector is output, and when the third set value ≦ the difference voltage V, the inverter is gate-blocked. .
Further, when the differential voltage exceeds a predetermined protection level, the inverter is gate-blocked.
Further, in the case of the AC motor in which the winding of the AC motor has a low-speed high-speed winding and a high-speed winding and can switch between these windings, when the inverter is gate-blocked, It is characterized by opening the switch.
In the second to fourth aspects of the present invention, the zero vector output pattern is such that only the P-side (positive side) or N-side (negative side) transistors are turned on simultaneously.

According to the present invention, since the difference between the battery terminal voltage and the inverter DC bus voltage can be detected, for example, when the potential difference becomes large to some extent during motor deceleration, before the breakdown voltage of the electronic components mounted on the inverter is exceeded. The electronic components mounted on the inverter can be protected by switching the deceleration method.
Further, for example, when the difference between the terminal voltage of the battery and the DC bus voltage of the inverter becomes large when the motor is decelerated, it is possible to avoid a situation in which an overvoltage is applied to the electronic components of the inverter.
Also, for example, when the motor decelerates, when the difference between the battery terminal voltage and the inverter DC bus voltage becomes large, the motor is free-run stopped (coast-to-stop). As a result, the backflow of energy to the smoothing capacitor of the DC bus of the battery or inverter can be minimized. Here, the free-run stop is an operation in which the drive signal to the main circuit transistor is interrupted by an external signal and the power supply to the motor is stopped during the inverter operation. In this case, the motor does not generate a braking force and stops spontaneously while coasting.

The block diagram of the inverter apparatus which shows 1st Example of this invention Behavior of smoothing capacitor and battery terminal voltage during motor deceleration according to the present invention Operation explanatory diagram at the time of motor deceleration of the present invention Gate block operation (motor free run) in the case of the winding switching type motor according to the present invention Configuration diagram of conventional inverter device Configuration diagram of conventional inverter device Explanatory drawing of zero vector output (reflux mode) of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter 2 Motor 3 Battery 4 Voltage level determination device 5 Regenerative / reflux mode selector 6 Inverter control unit 7 Speed detector 8 Voltage detector 9 Comparison circuit 10 SW pattern generation unit 11 Drive circuit 12 Winding switching unit 13 P side transistor 14 N-side transistor 15 Current at zero vector 16 Smoothing capacitor
SSW1, SSW2 Semiconductor switch
MSW1, MSW2 mechanical switch

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of the inverter device of the present invention. In the figure, 1 is an inverter, 2 is a motor, 3 is a battery connected in parallel to the DC bus of the inverter, 6 is an inverter control unit, 7 is a speed detector, 8 is a voltage detector, 9 is a comparison circuit, and 10 is a switching pattern. A generating unit, 11 is a drive circuit, and 16 is a smoothing capacitor. The inverter control unit 6 includes a switching pattern generation unit 10 and a drive circuit 11. P is a positive side DC bus and N is a negative side DC bus, and is connected to the smoothing capacitor 16. The output side of the inverter 1 is connected to a motor 2 serving as a load to supply electric power. The voltage detector 8 is connected to each of the battery 3 and the positive / negative DC bus PN, measures the voltage every predetermined sampling, and outputs the measurement data to the comparison circuit 9. The comparison circuit 9 is connected to the inverter control unit 6. The inverter control unit 6 inputs the data of the comparison circuit 9 and the speed detector 7 and gives a gate drive signal to the main circuit switching element of the inverter 1 to drive the inverter 1.

Next, the operation will be described. At the time of regenerative braking of the motor, power is regenerated from the motor to the smoothing capacitor 16 arranged at the DC bus voltage of the inverter 1 and the battery 3. The impedance of the smoothing capacitor 16 and the battery 3 is overwhelmingly low. When the regenerative power is absorbed, only the terminal voltage of the smoothing capacitor 16 rises transiently and is between the terminal voltage of the battery 3. A potential difference occurs. The terminal voltage of the smoothing capacitor 16 and the terminal voltage of the battery 3 are detected by the voltage detector 8, and this potential difference is calculated by the comparison circuit 9. A switching pattern generated by a switching pattern generation unit (for example, an ASIC (Application Specific IC) that is an application specific IC) is selected according to the level of the potential difference calculated by the comparison circuit 9. As a switching pattern to be selected, a normal regenerative braking switching pattern, a switching pattern in which the deceleration rate is increased and the regenerative braking energy is reduced, and a zero vector (reflux mode) are selected. The main circuit switching element of the inverter 1 is switched through the drive circuit 11 according to the selected switching pattern.

FIG. 2 is a diagram illustrating a transient behavior of the terminal voltage of the smoothing capacitor of the inverter and the terminal voltage of the battery during regenerative braking of the motor. In the figure, the horizontal axis represents time, and the vertical axis represents DC voltage. Time ta is a deceleration start time, and from this moment, the motor becomes a generator and the smoothing capacitor terminal voltage gradually increases from Va due to regenerative power. Since the smoothing capacitor is overwhelmingly low in impedance between the smoothing capacitor and the battery, as a transient phenomenon during regenerative braking, only the terminal voltage of the smoothing capacitor rises and a large potential difference occurs between the terminal voltage of the battery.
The time te is the time when the transient phenomenon ends and becomes a steady state, and after the time te, the smoothing capacitor terminal voltage and the battery terminal voltage have the same value Ve.

FIG. 3 is an explanatory diagram showing the relationship between the smoothing capacitor voltage and the deceleration method (deceleration operation pattern of the inverter) during regenerative braking of the motor in the inverter device of the present invention. In the figure, the horizontal axis represents the time axis, and the vertical axis represents the DC voltage of the smoothing capacitor. The motor 2 starts decelerating at time ta, which is the constant battery voltage Va, and the electric motor operates as a generator to start supplying regenerative power to the smoothing capacitor and the battery. The voltage difference at the time of transition between the smoothing capacitor and the battery voltage is hereinafter simply referred to as a difference voltage V. The values of the differential voltages (Vb-Va), (Vc-Va), and (Vd-Va) are set in advance before actual operation in consideration of the withstand voltages of the main circuit IGBT and smoothing capacitor that are the electronic components of the inverter. deep. The differential voltages (Vb−Va), (Vc−Va), and (Vd−Va) are defined as a first set value, a second set value, and a third set value, respectively.
(1) When 0 ≦ differential voltage V ≦ (Vb−Va), normal deceleration is performed. Here, normal deceleration means decelerating at a preset deceleration rate.
(2) If (Vb−Va) ≦ difference voltage V <(Vc−Va), the deceleration rate is made longer than the normal deceleration. The deceleration rate represents the rate of deceleration that is the speed per unit time.
(3) When (Vc−Va) ≦ difference voltage V <(Vd−Va), a zero voltage vector is output.
(4) When (Vd−Va) ≦ the difference voltage V, the gate of the main circuit transistor of the inverter 1 is cut off (gate block).
Here, the acceleration / deceleration rate used when controlling the motor is simply the slope (set in normal time) until the speed is reached from the stop state and the slope during reverse operation. This is the time required to accelerate or decelerate the motor with respect to the load. Setting in actual use is almost always done in seconds with respect to the set maximum speed. For example, if the maximum speed is set to 60Hz for an inverter and the motor uses a 60Hz rated 1800rpm, and the acceleration time is set to 2 seconds and the deceleration time is set to 1.5 seconds, it will reach 0 to 1800rpm in 2 seconds, and 1800rpm to stop 1.5 seconds.
As described above, during regenerative braking of the motor, if a difference voltage occurs between the terminal voltage of the smoothing capacitor of the inverter and the terminal voltage of the battery, the difference voltage causes (1) normal deceleration and (2) deceleration rate. (3) Zero vector output (reflux mode), (4) Protection operation (motor free run) by IGBT gate block.

FIG. 4 shows a case where the motor is a winding switching type motor having a low speed winding and a high speed winding. Here, the low speed winding uses all of the motor windings W1 and W2. On the other hand, the high-speed winding is a short circuit of W2 of a part of the motor winding and uses only the remaining winding W1. In this protection operation, a free-run state is created by opening the winding changeover switch. The winding changeover switch is indicated by 12 in the figure as a winding changeover unit, and is an example of a combination of semiconductor switches (SSW1, SSW2) and mechanical switches (MSW1, MSW2). The configuration of the winding switching unit is not limited to this.
In this way, in the present invention, since the difference between the terminal voltage of the battery and the terminal voltage of the smoothing capacitor of the DC bus of the inverter is detected, the deceleration method is selected by changing the switching pattern of the inverter based on the potential difference. If a potential difference occurs due to the difference in regenerative braking power absorption capability during motor deceleration, the deceleration method is switched according to the level, and the electronic components mounted on the inverter are protected before the breakdown voltage of the electronic components mounted on the inverter is exceeded. be able to.

In addition, when the motor is a winding switching type motor having a low speed winding and a high speed winding, the difference between the terminal voltage of the battery and the terminal voltage of the smoothing capacitor of the DC bus of the inverter increases, and the motor is decelerated by the deceleration method described above. However, the difference in the terminal voltage is still large, and the motor free-run operation when the voltage exceeds a certain level is created by opening the winding switching switch.
FIG. 7 is an example of zero vector output (reflux mode). The figure shows a state where only the P-side (positive side) transistors 13 are simultaneously turned on. In this state, the regenerative power of the motor flows in a closed loop between the motor and the P-side (positive side) transistor 13, and the regenerative power is mainly consumed by the windings in the motor.
On the other hand, the N-side zero vector can be created by simultaneously turning on only the N-side (negative-side) transistor 14.

The present invention relates to a machine tool spindle drive, a hoisting / lowering machine drive, a crane, an elevator, an electric vehicle, a hybrid vehicle equipped with both an electric vehicle and a gasoline engine, an electric motor for a wind power generation system, and an electric motor thereof. It can be applied to a drive inverter.

Claims

Separately from the power supply system, the inverter has a battery for power backup on the DC bus of the inverter, and in the inverter device that drives the AC motor,
Voltage level determination device for detecting the transient voltage of the DC bus of the inverter and the transient voltage of the battery, a comparison circuit for comparing the transient voltage of the DC bus of the inverter and the transient voltage of the battery, and a comparison result of the comparison circuit An inverter device comprising an inverter control unit that switches a deceleration operation pattern of the AC motor based on the differential voltage.
2. The inverter according to claim 1, wherein the deceleration operation pattern has one of a normal deceleration pattern that decelerates at a preset deceleration rate, a pattern that extends the deceleration rate more than the normal deceleration pattern, and a zero vector output pattern. apparatus.
The inverter control unit is configured in the order of a normal deceleration pattern that decelerates the deceleration operation pattern of the AC motor based on the differential voltage at a preset deceleration rate, a pattern that extends the deceleration rate over the normal deceleration pattern, and a zero vector output pattern. The inverter device according to claim 1, wherein the inverter device is switched.
When “0 ≦ Differential voltage V ≦ First set value”, the vehicle decelerates at a preset deceleration rate. When “First set value ≦ Differential voltage V <Second set value”, the deceleration rate is set to the normal deceleration rate. If “second setting value ≦ difference voltage V <third setting value”, a zero voltage vector output pattern is output. If “third setting value ≦ difference voltage V”, the main circuit transistor of the inverter is output. 2. The inverter device according to claim 1, wherein the inverter block is gate-blocked.
The inverter device according to claim 1, wherein when the differential voltage exceeds a predetermined protection level, the main circuit transistor of the inverter is gate-blocked.
In the case of an AC motor in which the winding of the AC motor has a low-speed high-speed winding and a high-speed winding, and these windings can be switched, a switch for winding switching when the main circuit transistor of the inverter is gate-blocked 6. The inverter device according to claim 5, wherein the inverter device is opened.
The inverter device according to any one of claims 2 to 4, wherein the zero vector output pattern is configured to simultaneously turn on only the P-side (positive side) or N-side (negative side) transistors.
In the control method of the inverter device that includes a battery for power backup on the DC bus of the inverter separately from the power system, and drives the AC motor,
The transient voltage of the DC bus of the inverter and the transient voltage of the battery are detected, the transient voltage of the DC bus of the inverter and the transient voltage of the battery are compared, and the AC is based on the difference voltage which is a comparison result of the comparison circuit A control method for an inverter device, characterized by switching a motor deceleration operation pattern.
9. The inverter according to claim 8, wherein the deceleration operation pattern includes any one of a normal deceleration pattern that decelerates at a preset deceleration rate, a pattern that extends the deceleration rate more than the normal deceleration pattern, and a zero vector output pattern. Control method of the device.
The inverter control unit switches the deceleration operation pattern of the AC motor based on the differential voltage in the order of a normal deceleration pattern that decelerates at a preset deceleration rate, a pattern that extends the deceleration rate over the normal deceleration pattern, and a zero vector output pattern The method for controlling an inverter device according to claim 8.
When “0 ≦ Differential voltage V ≦ First set value”, the vehicle decelerates at a preset deceleration rate. When “First set value ≦ Differential voltage V <Second set value”, the deceleration rate is set to the normal deceleration rate. If “second setting value ≦ difference voltage V <third setting value”, a zero voltage vector output pattern is output. If “third setting value ≦ difference voltage V”, the main circuit transistor of the inverter is output. 9. The method of controlling an inverter device according to claim 8, wherein the gate block is performed.
9. The method of controlling an inverter device according to claim 8, wherein when the differential voltage exceeds a predetermined protection level, the main circuit transistor of the inverter is gate-blocked.
In the case of an AC motor in which the winding of the AC motor has a low-speed high-speed winding and a high-speed winding, and these windings can be switched, the winding switching switch is opened when the inverter is gate-blocked. The method of controlling an inverter device according to claim 12.
12. The method of controlling an inverter device according to claim 9, wherein the zero vector output pattern is such that only the P-side (positive side) or N-side (negative side) transistors are turned on simultaneously.