Electric vehicle control device

Abstract

To effectively reduce loss of a motor at a continuous rated operating point of the motor.SOLUTION: An electric vehicle control device comprises: a converter that converts an AC voltage into a DC voltage; an inverter that is connected to a motor and converts the DC voltage into a three-phase AC voltage; and a control device that controls the converter and the inverter. The control device controls the converter by setting an output voltage of the converter to a first DC voltage at a continuous rated point of the motor, and controls the inverter through synchronous multi-pulse control according to a firing angle command by setting an output voltage of the inverter to a first inverter output voltage that is lower than an inverter maximum voltage that can be set with the first DC voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an electric vehicle control device for driving a railway vehicle. [Background technology]

[0002] In systems such as locomotives where the continuous rated operating point of the motor is specified, the temperature rise of the motor at the continuous rated operating point must be below the allowable value in the motor specifications. In particular, locomotive motors generally have a larger motor output than ordinary train motors, and tend to be larger in size. However, there are also restrictions on vehicle equipment, so reducing motor loss is important for systems such as locomotives.

[0003] Common techniques for reducing motor loss include those disclosed in Patent Documents 1 and 2. Patent Document 1 focuses on the fact that in the low-speed range of a motor, copper loss is greater than iron loss, while in the medium-speed and high-speed ranges, iron loss is greater than copper loss, and controls the motor to minimize the sum of iron loss and copper loss. In Patent Document 2, in order to reduce the overall loss, which is a combination of fundamental wave loss and harmonic loss, a voltage amplitude command value is generated using a PWM current distortion factor as an index representing the level of current harmonics generated by PWM control, and the PWM current distortion factor is maintained low and the pulse mode is transitioned so as not to change suddenly, thereby reducing harmonic loss and motor loss. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-166349 [Patent Document 2] International Publication No. 2014 / 174597 Summary of the Invention [Problem to be solved by the invention]

[0005] However, to reduce motor loss, which is the sum of iron loss and copper loss, or motor loss, which is the sum of fundamental wave loss and harmonic loss, it is necessary to implement control that minimizes iron loss and copper loss based on the motor's loss characteristics, or control that reduces fundamental wave loss and harmonic loss based on the harmonic distribution.To do this, it is necessary to analyze the motor and obtain characteristic diagrams of the motor's loss characteristics and harmonic distribution, which is difficult to implement easily and also makes motor control complicated.

[0006] In general, in systems such as locomotives, the continuous rated operating point is the region where motor losses are most severe. This is because, in the speed region below the continuous rated operating point, there is no need to guarantee continuous operation even if motor losses are greater than at the continuous rated point, and because the speed region above the continuous rated point is a constant power region, output torque and motor current decrease, resulting in lower motor losses. Therefore, in systems such as locomotives, there is no need to implement detailed control to reduce motor losses across the entire speed range, and the important practical technology is to reduce motor losses at the continuous rated operating point.

[0007] The present invention has been made in view of the above, and has as its object to effectively reduce motor losses at the continuous rated operating point of the motor. [Means for solving the problem]

[0008] An electric vehicle control device according to an embodiment includes a converter that converts AC voltage into DC voltage, an inverter connected to a motor that converts the DC voltage into three-phase AC voltage, and a control device that, at a continuous rating point of the motor, controls the converter by setting the converter output voltage to a first DC voltage, and sets the inverter output voltage to a first inverter output voltage that is lower than the maximum inverter voltage that can be set at the first DC voltage, and controls the inverter by synchronous multi-pulse control using an arc angle command. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic block diagram of an AC overhead line driven electric railcar system. [Figure 2] FIG. 2 is a graph showing the motor rotation speed, inverter input voltage / motor input voltage, and control method. [Figure 3] FIG. 3 is a diagram showing an example of an inverter output voltage waveform during synchronous three-pulse control. [Figure 4] FIG. 4 is a diagram showing an example of an inverter output voltage waveform during synchronous one-pulse control. [Figure 5] FIG. 5 is a graph showing the relationship between the motor temperature rise and the elapsed time for each control method. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described with reference to the drawings, in which: Fig. 1 is a schematic block diagram of an AC overhead line driven electric railcar system. The electric vehicle control device 1 includes a converter 11, an inverter 12, a capacitor 13, and a control device 50.

[0011] The converter 11 converts the single-phase AC power of the AC overhead line 5 via the pantograph 4 and the transformer 2 into DC power having a predetermined inverter input voltage. The inverter 12 has a capacitor 3 connected to its DC side and converts the DC power output by the converter 11 into three-phase AC power having a predetermined frequency and voltage. The motor 3 is connected to the AC side of the inverter 12 and is driven by the three-phase AC power output by the inverter 12.

[0012] The control device 50 outputs control signals to the converter 11 and the inverter 12. The control device 50 switches between a plurality of control methods to control the inverter. In this embodiment, a system that receives power from an AC overhead line will be described, but the present invention can also be applied to a system that receives power from a DC overhead line or a system that receives power from a storage battery mounted on a vehicle. In such a system that receives DC power, the converter controls the inverter input voltage using a DC transformer such as a DC / DC converter or a step-up / step-down chopper.

[0013] FIG. 2 is a graph showing the motor rotation speed and motor torque / inverter input voltage / motor input voltage and control method. As shown in Figure 2, as the motor speed shifts from a low range to a high range, the control method switches between asynchronous multi-pulse control, synchronous multi-pulse control (synchronous 9-pulse control), synchronous 3-pulse control (synchronous 3-dash pulse control, synchronous 3DP control), and synchronous 1-pulse control.

[0014] Asynchronous multi-pulse control is, for example, triangular wave comparison PWM control, which generates a gate signal by comparing a carrier wave and a modulating wave. Note that in asynchronous multi-pulse control, the ratio of the carrier wave frequency to the modulating wave frequency is not fixed, so the number of pulses per unit time does not depend on the speed range. Synchronous multi-pulse control is, for example, triangular wave comparison PWM control, which generates a gate signal by comparing the carrier wave and modulating wave. In synchronous multi-pulse control, the ratio of the carrier wave frequency to the modulating wave frequency is fixed, thereby suppressing waveform distortion in the output.

[0015] Synchronous three-pulse control generates a gate signal at a specified firing angle. With triangular wave comparison PWM control, if the output voltage increases and the modulated wave becomes larger than the amplitude of the triangular wave carrier, which is the carrier wave, it enters an overmodulation state. When an overmodulation state occurs, switching cannot be performed near the peak of the voltage command value, making it difficult to output voltage according to the command value and increasing harmonic components. Therefore, when an overmodulation state occurs, the system switches from triangular wave comparison PWM control to firing angle command PWM control, which maximizes the output voltage by turning the gate on and off at the firing angle timing determined for each speed.

[0016] FIG. 3 is a diagram showing an example of an inverter output voltage waveform during synchronous three-pulse control. Unlike triangular wave comparison PWM control, synchronous 3-pulse control controls the on / off of pulses at a fixed firing angle. In particular, synchronous 3-dash pulse control determines the firing angle so that the voltage change is small when switching to 1-pulse control. It is also possible to reduce harmonic components.

[0017] Synchronous one-pulse control generates a gate signal at a predetermined firing angle. FIG. 4 is a diagram showing an example of an inverter output voltage waveform during synchronous one-pulse control. In synchronous 1-pulse control, the on / off of the pulse is controlled at a fixed firing angle, just like in synchronous 3-pulse control, resulting in a single pulse waveform.

[0018] Here, we will explain control near the continuous rated operating point of the motor using the graph in Figure 2, which shows motor rotation speed and motor torque / inverter input voltage / motor input voltage and the control method. Near the continuous rated operating point of the motor, synchronous 3-dash pulse control is performed using the firing angle command, and the inverter output voltage is controlled to be the maximum relative to the inverter input voltage (first DC voltage). That is, the control device 50 provides a gate signal to the converter 11 so that the converter 11 outputs the first DC voltage, and provides a gate signal to the inverter 12 so that the inverter 12 performs synchronous three-pulse control and achieves the maximum inverter output voltage for the first DC voltage.

[0019] Note that, although the maximum inverter output voltage is described here for the first DC voltage, if the modulation factor is 1, it will result in synchronous 1-pulse control, so the modulation factor is smaller than 1, which does not result in synchronous 1-pulse control, and it will be the maximum inverter output voltage in 3-pulse control with a predetermined firing angle. Also, the modulation factor that results in the maximum inverter output voltage is preferably a modulation factor that is larger than the modulation factor that results in an overmodulation state in triangular wave comparison PWM control, so long as it is larger than the modulation factor that results in an overmodulation state in triangular wave comparison PWM control.

[0020] By performing this type of control, the motor input voltage can be made as high as possible at the continuous rated operating point, which makes it possible to reduce the motor current.In addition, by using synchronous three-pulse control that turns the motor on and off at a timing determined by the firing angle for each speed, the harmonic current of the motor can be reduced, and motor loss at the continuous rated operating point can be reduced.

[0021] Next, control of the speed range higher than the continuous rated operating point of the motor and the speed range lower than the continuous rated operating point of the motor will be described. As shown in Figure 2, in the range higher than the motor's continuous rated operating point, the inverter performs synchronous one-pulse control, and the converter increases the DC voltage from the first to the second, and when the specified speed is reached, it controls it to be constant at the second DC voltage. The second DC voltage is the maximum voltage that the inverter can output according to its specifications. The region higher than the continuous rated operating point of the motor is the constant output region, in which the output torque and inverter current decrease, and therefore the motor loss decreases.

[0022] Furthermore, as shown in Figure 2, in the speed range lower than the continuous rated operating point of the motor, the inverter performs synchronous multi-pulse control and asynchronous multi-pulse control, and the converter controls the first DC voltage to a constant value. Of the synchronous and asynchronous multi-pulse control of the inverter, asynchronous multi-pulse control is used in the lower speed range. In speed ranges lower than the motor's continuous rated operating point, for example, triangular wave comparison PWM control is used to produce an inverter output voltage that corresponds to the motor's rotation speed.In addition, with synchronous multi-pulse control, the ratio between the carrier wave frequency and the modulating wave frequency is fixed, which suppresses output waveform distortion, while with asynchronous multi-pulse control, the ratio between the carrier wave frequency and the modulating wave frequency is not fixed, so the number of pulses per unit time does not depend on the speed range and the number of on / off times can be reduced.

[0023] FIG. 5 is a graph showing the relationship between the motor temperature rise and the elapsed time for each control method. As shown in FIG. 5, in this embodiment, synchronous three-pulse control (synchronous multi-pulse control, which is PWM control using firing angle commands) used near the continuous rated operating point of the motor tends to result in smaller motor temperature rise, i.e., smaller motor loss, compared to synchronous nine-pulse control (synchronous multi-pulse control, which is PWM control using triangular wave comparison) in the overmodulation region or synchronous one-pulse control.

[0024] This is because, in the overmodulation region of synchronous 9-pulse control, which is PWM control based on triangular wave comparison, the motor input voltage is smaller and the motor current, which includes harmonic components, increases compared to synchronous 1-pulse control or synchronous 3-pulse control, which is PWM control based on firing angle commands. Furthermore, during synchronous 1-pulse control, the motor input voltage is equivalent to that during synchronous 3-pulse control, which is PWM control using an arc angle command, but the number of pulses is less than that during synchronous 3-pulse control, which increases the harmonic components of the motor current.

[0025] Thus, according to this embodiment, in a system such as a locomotive in which the continuous rated operating point is the region in which motor loss is most severe, for control near the continuous rated operating point, synchronous three-pulse control is performed at the maximum modulation rate, which is smaller than 1 and does not result in synchronous one-pulse control, thereby making it possible to reduce motor loss at the continuous rated operating point.

[0026] Furthermore, in a system configuration that transitions from a constant torque region to a constant output region, by controlling to minimize the PWM current distortion rate, harmonic losses are reduced and motor losses are reduced. In this control, switching from synchronous multi-pulse control to synchronous three-pulse control requires determining the characteristics of the PWM current distortion rate and switching at a modulation rate that minimizes the PWM current distortion rate.

[0027] In contrast, in systems such as locomotives, there is no constant torque region, and from the perspective of prioritizing starting torque from a stop, the motor torque is not constant, but gradually increases from the continuous rated operating point toward the zero speed region, as shown in Figure 4. Therefore, the motor current in each speed range varies for each system according to the motor torque curve, and the modulation factor at which motor loss is minimized at the continuous rated operating point is not uniquely determined by the PWM current distortion factor. In other words, the modulation factor for the timing of switching to synchronous three-pulse control can also be changed for each system, and there is no need to determine the characteristics of the PWM current distortion factor and set the modulation factor at which the PWM current distortion factor is minimized.

[0028] Therefore, in a system such as a locomotive in which the motor torque gradually increases from the continuous rated operating point toward the zero speed region, by using synchronous three-pulse control at the maximum modulation rate with a modulation rate smaller than 1 that does not result in synchronous one-pulse control for control near the continuous rated operating point, there is no need to implement fine control to reduce motor loss across the entire speed range, and motor loss can be easily reduced at the continuous rated operating point.

[0029] Furthermore, since iron loss can be reduced by using three synchronous pulses to control near the continuous rated operating point and reducing the harmonic components of the control motor current, this method is also useful from the perspective of improving the accuracy of temperature monitoring in systems where a temperature monitoring sensor is installed in the motor.

[0030] Systems such as locomotives often have temperature monitoring sensors attached to monitor the motor temperature, but to simplify motor design and manufacturing, they are often attached to the external core.Motors used in systems such as locomotives experience the most severe motor loss at the continuous rated operating point, so monitoring the motor temperature at the continuous rated operating point is important, but iron loss is generally larger than copper loss at the continuous rated operating point, and the heat generated by iron loss has a significant impact on the temperature monitoring sensor.

[0031] Therefore, by minimizing iron loss at the continuous rated operating point, in a system in which a temperature monitoring sensor is provided in the motor, it is possible to improve the accuracy of temperature monitoring and drive the motor up to the upper limit of the allowable motor loss. Therefore, in addition to reducing the motor loss itself, it is possible to drive the motor up to the upper limit of the allowable motor loss, which makes it possible to reduce the size and simplify the motor and its cooling system, such as the motor cooling blower.

[0032] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0033] 1. Electric vehicle control device 2. Transformer 3. Motor 11. Inverter 12 Converter 13. Capacitor 50...Control device

Claims

1. a converter that converts AC voltage into DC voltage; an inverter connected to the motor to convert the DC voltage into a three-phase AC voltage; and a control device that, at a continuous rated point of the motor, controls the converter by setting the output voltage of the converter to a first DC voltage, and controls the inverter by synchronous multi-pulse control using an arc angle command by setting the output voltage of the inverter to a first inverter output voltage that is lower than a maximum inverter voltage that can be set at the first DC voltage.

2. a DC transformer that converts DC power into DC voltage; an inverter connected to the motor to convert the DC voltage into a three-phase AC voltage; and a control device that, at a continuous rated point of the motor, controls the DC transformer by setting the output voltage of the DC transformer to a first DC voltage, and controls the inverter by synchronous multi-pulse control using an arc angle command by setting the output voltage of the inverter to a first inverter output voltage that is lower than a maximum inverter voltage that can be set at the first DC voltage.

3. In a speed range below a continuous rated operating point, the converter outputs a first DC voltage; 3. An electric vehicle control device according to claim 1 or 2, wherein in a speed range equal to or higher than a continuous rated operating point, the inverter output voltage is increased from a first inverter output voltage in accordance with the speed, to control the inverter with synchronous one-pulse control, and when a predetermined speed is reached, the converter output voltage is increased from a first DC voltage to a second DC voltage in accordance with the speed, and the converter output voltage is controlled so as to be constant at the second DC voltage.

4. 3. The electric vehicle control device according to claim 1, wherein the motor has a temperature monitoring sensor provided in a motor core.

Images