JP2023042118A - Power converter control device and control method - Google Patents

Abstract

To suppress overvoltage of a DC-side voltage of a power converter by controlling a torque command value for an electric motor during regenerative operation, so that stable regenerative operation is performed.SOLUTION: A power converter control device includes a control unit that outputs a switching command to a power converter for driving an electric motor on the basis of a torque command value for the electric motor, and a regenerative operation unit that corrects the torque command value by outputting a torque operation amount to the control unit during regenerative operation of the electric motor. In the case where a detection value of the DC voltage of the power converter is greater than a DC voltage target value, the regenerative operation unit outputs the torque operation amount to adjust the torque command value to a power running torque command value which is such an infinitesimal value that the electric motor cannot perform a power running operation.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a power converter control device and control method, and is particularly suitable for power converters for railway vehicles.

During regenerative operation, railcars operate their motors as generators, return the generated electric power to overhead lines, and use it to accelerate other trains, thereby making effective use of electric power. However, when there are few load vehicles (power running vehicles) around the own vehicle, or when other load vehicles are regenerating and the overhead wire voltage is high, if the regenerative brake is applied, the overhead wire voltage and FC (Filter Capacitor) : filter capacitor) will increase the voltage, leading to overvoltage.

Therefore, in a control device for a power converter (inverter) for railway vehicles, when the voltage value detected by the FC voltage detector provided in the control device exceeds the FC voltage target value, torque is applied to reduce the regenerative braking torque. It is equipped with light load regeneration control that calculates the amount of operation.

In a no-load state in which there is no power equipment that consumes regenerative power, a no-load regenerative state in which the regenerative braking torque is reduced to zero by light-load regenerative control. In this no-load regeneration state, even if the torque command value after the torque operation by the light load regeneration control is set to zero, in reality, there is a voltage output error, CT (Current Transformer: current detector), voltage detection error by DCPT (Direct Current Potential Transformer: DC voltage detector), torque error due to motor loss, and several Nm during operation. of braking torque is generated, which may lead to overvoltage detection.

Various improvement techniques have been proposed for the problem of preventing overvoltage during regenerative operation.
In Patent Document 1, when the detected FC voltage exceeds the FC voltage target value during regenerative operation, the torque current command is narrowed down to match the voltage value with a predetermined FC voltage target value, thereby preventing overvoltage. Techniques are disclosed.

In addition, Patent Document 2 discloses a technique that calculates a frequency adjustment amount according to the FC voltage during regenerative operation, and if the frequency adjustment amount is positive, shifts the motor from the regeneration state to the power running state to prevent overvoltage. It is

JP-A-2004-88974 U.S. Pat. No. 7,126,297

The inventors of the present application made extensive studies with the aim of preventing overvoltage during regenerative operation, and as a result, obtained the following knowledge.
The technology described in Patent Document 1 calculates the light load regeneration control torque current value based on the voltage value detected by the voltage detection unit, and when the voltage value exceeds the FC voltage target value, the light load regeneration control calculation is performed. The means has a function of narrowing down the torque current command in order to output the light load regeneration control torque current value. As a result, the voltage value detected by the voltage detection means can be matched with the predetermined FC voltage target value, and as a result, the overhead line voltage is stabilized.

However, when it matches the FC voltage target value, even if the torque command value after the torque operation of the light load regeneration control is set to zero, due to the current detection error due to the PWM mode, the DCPT detection error and the motor loss, during operation There is a problem that a brake torque of about several Nm is generated at the time, which may lead to overvoltage detection.

Further, the technique described in Patent Document 2 is characterized by calculating the output frequency according to the FC voltage during regenerative operation, and performing power running operation when the FC voltage is rising.

However, there is a problem that regenerative power cannot be utilized to the maximum extent because the system shifts to the power running state when the FC voltage is rising regardless of the voltage leading to overvoltage detection.

Therefore, the present invention has been made in consideration of the above points. It is an object of the present invention to provide a technique for preventing overvoltage while maximally utilizing regenerative electric power during regenerative operation by changing the pattern of the manipulated variable so as to output minute power running torque.

In order to solve the above-described problems, one typical power converter control device according to the present invention outputs a switching command to a power converter that drives the electric motor based on a torque command value for the electric motor. and a regeneration operation unit that outputs a torque operation amount to the control unit during regenerative operation of the electric motor to correct the torque command value. exceeds the DC voltage target value, the torque operation amount is output so that the torque command value is a very small powering torque command value that does not cause the motor to power.

According to the present invention, for example, when a railway vehicle is in regenerative operation, there are few load cars in the vicinity, or even in a state where other load cars are regenerating and the overhead line voltage is high, the generation of overvoltage is prevented and regenerative power is generated. can be driven to the maximum.
Problems, configurations, and effects other than those described above will be clarified by the description in the following embodiments.

1 is a block diagram showing a configuration example of a driving unit of an electric vehicle and its control device according to the present invention; FIG. It is a figure which shows the equivalent circuit containing an overhead wire and an LC filter circuit. FIG. 4 is a diagram showing an input/output mode of a light load regeneration manipulated variable calculation unit according to the first embodiment; FIG. 4 is a diagram showing an example of a manipulated variable table for light load regeneration control (proportional control); FIG. 10 is a diagram showing a modified example of a manipulated variable table for light load regenerative control (proportional control); FIG. 10 is a diagram showing an input/output mode of a light load regeneration manipulated variable calculation unit of Example 2; FIG. 5 is a diagram showing an example of characteristics of a voltage detection value and a brake torque command in Examples 1 and 2; FIG. 11 is a block diagram showing an example of using PI control for the control device according to the second embodiment; FIG. 11 is a block diagram showing an example of a control device according to Example 3; FIG. 12 is a block diagram showing an example of a control device according to a fourth embodiment; FIG.

Hereinafter, Examples 1 to 4 will be described as modes for carrying out the present invention with reference to the drawings. It should be noted that the present invention is not limited by these examples. Moreover, in the description of the drawings, the same parts are denoted by the same reference numerals.

FIG. 1 is a block diagram showing a configuration example of an electric vehicle driving unit and its control device according to the present invention.
In FIG. 1 , overhead wire 107 is connected to the positive potential point of DC filter capacitor 105 via pantograph 108 and DC filter reactor 106 . Also, the negative side potential point of DC filter capacitor 105 is grounded to rail 110 via wheel 109 . Also, the left side of the drawing schematically shows an electric car 111 equipped with the above configuration.

The power converter 102 is connected between the positive side potential point and the negative side potential point of the DC filter capacitor 105, converts the DC power from the overhead wire 107 into AC power, and supplies the AC power to the electric motor 103 to drive the electric motor 103. do.

The control device 101 is composed of a command generator 113 , a light load regeneration manipulated variable calculator 112 and a vector controller 114 , and controls the power converter 102 based on the output from the vector controller 114 .

In order to detect the DC voltage or overhead line voltage input to the power converter 102, in FIG. It is input to the load regeneration operation amount calculation unit 112 .

Phase current detector 115 detects AC currents iu and iw flowing from power converter 102 to electric motor 103 . This phase current detection unit 115 is realized by, for example, a current sensor using a Hall element. In FIG. 1, two-phase detection is performed using the U phase and the W phase, but any two phases of the U, V, and W phases may be used, or three-phase detection may be performed. Detected currents iu and iw are input to vector control unit 114 .

A command generator 113 generates a torque command value Tm* for the electric motor 103 .
Light load regeneration manipulated variable calculation unit 112 calculates and outputs a torque manipulated variable ΔTm* for correcting the torque command value when the voltage value of the detected voltage Ecf exceeds the target value.

Vector control unit 114 performs switching of power converter 102 based on alternating current detection values Iu and Iw from phase current detection unit 115 and value Tm** obtained by adding torque operation amount ΔTm* to torque command value Tm*. A switching command for driving the elements is generated and input to the power converter 102 .
Power converter 102 converts DC power into three-phase AC power based on the switching command generated by vector control unit 114 , and supplies the converted three-phase AC power to electric motor 103 .

In the electric train control apparatus as described above, when the electric train 111 decelerates from a certain speed during operation, the electric motor 103 which is given rotational force by the adhesive force between the rails 110 and the wheels 109 operates as a generator. do. The DC power generated by this generator operation is returned to overhead line 107 as regenerated power via DC filter capacitor 105, DC filter reactor 106 and pantograph .

FIG. 2 is a diagram showing an equivalent circuit including overhead wire 107 and an LC filter circuit.
Let RL be a regenerative load resistance simulating how the other vehicle behaves during regeneration of the own vehicle. Also, since the overhead line voltage is produced by full-wave rectification of the three-phase AC voltage, the diode is shown.

When another vehicle that is electrically connected to the overhead wire consumes a large amount of power in power running mode, the regenerative load resistance becomes sufficiently small, so the own vehicle returns a large amount of regenerated power to the overhead wire. No increase in catenary voltage occurs.

On the other hand, when other vehicles that are electrically connected via overhead lines do not consume power, the regenerative load resistance becomes a large value. The current causes an increase in overhead line voltage. Furthermore, when the elevated catenary voltage exceeds a certain voltage value, the electric car control system shuts down due to overvoltage protection.

FIG. 3 is a diagram showing an input/output mode of the light load regeneration manipulated variable calculator 112 of the first embodiment.
The light load regeneration operation amount calculation unit 112 detects the light load when the voltage detection value Ecf exceeds the voltage target value Ecf* based on the voltage detection value Ecf in order to prevent overvoltage protection of the overhead line voltage. A torque operation amount ΔTm* for narrowing down the regenerative braking torque is output as regenerative control.

When the voltage detection value Ecf matches the voltage target value Ecf*, the torque command value Tm** after the torque operation of the light load regeneration control becomes zero. At this time, due to the current detection error caused by the PWM mode, the DCPT detection error, and the motor loss, a brake torque of several Nm is generated during operation, which may lead to overvoltage detection.

In particular, power converters (inverters) for railway vehicles are driven in synchronous PWM mode with a small number of voltage pulses in order to increase the voltage utilization rate for the purpose of reducing power consumption and effectively using regenerated power. have. On the other hand, in the synchronous PWM mode, in which the number of voltage pulses is small, the harmonic component contained in the current waveform tends to increase, and an error tends to occur when detecting the current.

FIG. 4 is a diagram showing an example of a manipulated variable table for light load regeneration control (proportional control).
As shown in FIG. 4, when the voltage detection value Ecf exceeds the voltage target value Ecf* (ii shown in FIG. 4), an operation Change the quantity pattern. As a result, an increase in overhead line voltage can be suppressed, and overvoltage can be prevented. However, due to the output of this minute powering torque, the vehicle does not reach powering operation.

Further, when the overhead wire voltage is reduced by the above change operation, or when the overhead wire voltage is lowered as a result of another vehicle starting power running operation, regenerative torque is output again according to the voltage detection value Ecf.
Here, the operation amount table is not limited to the form shown in FIG. 4, and can be modified in various ways without departing from the gist of the invention at the stage of implementation.

FIG. 5 is a diagram showing a modified example of the manipulated variable table for light load regeneration control (proportional control) shown in FIG.
5, when the voltage detection value Ecf exceeds the voltage target value Ecf* (ii shown in FIG. 5), when the operation amount table shown in FIG. Although the point of outputting (b) shown in FIG. 5 is the same, the curve of the manipulated variable up to that point is different. For example, if the control is performed like the solid quadratic curve, the torque can be quickly reduced. On the other hand, it is possible to make effective use of the regenerative electric power by controlling as indicated by the dotted quadratic curve.

As described above, according to the first embodiment, even when there are few load cars in the vicinity during regenerative operation of the railway vehicle, or when the overhead line voltage is high due to the regeneration of other load cars, the simple configuration with little computational load can be used. , the occurrence of overvoltage can be prevented, and regenerative operation can be stably performed.

Unlike the first embodiment, the second embodiment outputs the torque manipulated variable according to the difference between the voltage target value Ecf* and the voltage detection value Ecf.
In the following, differences from the first embodiment will be mainly described.

FIG. 6 is a diagram showing an input/output mode of the light load regeneration manipulated variable calculator 112 of the second embodiment.
In the second embodiment, the light load regeneration manipulated variable calculation unit 112 calculates the torque manipulated variable ΔTm* according to the difference obtained by subtracting the voltage detection value Ecf detected by the voltage detection unit 104 from the voltage target value Ecf*. Output. At this time, when the voltage detection value Ecf exceeds the voltage target value Ecf*, the light load regeneration operation amount calculation unit 112 controls the voltage detection value Ecf to match the voltage target value Ecf*. As a result, the overhead wire voltage is narrowed down to a certain constant value.

FIG. 7 is a diagram showing an example of characteristics of a voltage detection value and a brake torque command in Examples 1 and 2. FIG.
(a) of FIG. 7 is a diagram showing a manipulated variable table (lower side) and a voltage detection value Ecf (upper side) of light load regeneration control (proportional control) according to the first embodiment, and (b) of FIG. FIG. 9 is a diagram showing a break torque command (lower side) and a voltage detection value ECF (upper side) in light load regeneration control (PI control) according to example 2;

In the second embodiment, the brake torque command is not narrowed down until the voltage detection value Ecf exceeds the voltage target value Ecf*, and the voltage is maintained at a high voltage within a range that does not cause an overvoltage. As a result, compared with the first embodiment, it is possible to make maximum use of the regenerative electric power (the hatched portion in FIG. 7(b)).

FIG. 8 is a block diagram showing an example of using PI control for the control device according to the second embodiment. Moreover, in the second embodiment, a maximum powering torque setting unit 116 is added as compared with the first embodiment.
Light load regeneration operation amount calculation unit 112 outputs torque operation amount ΔTm* as light load regeneration control. A value Tm** obtained by adding this torque operation amount ΔTm* to the torque command value Tm* output from the command generator 113, and the power running torque b set by the maximum power running torque setting unit 116 output during light load regeneration are calculated. The smaller one (MIN) is output as the torque compensation amount.

As described above, according to the second embodiment, when the railway vehicle is in regenerative operation, even in a state where there are few load cars in the vicinity, or in a state where the overhead line voltage is high due to regeneration of other load cars, overvoltage is prevented. , stable regenerative operation can be performed while maximizing the regenerative electric power.

Also, in the above-described second embodiment, PI control has been described, but the present invention is not limited to this, and PID control may be used. Also, although the maximum powering torque to be output is limited by MIN, it may be limited by a limit or a table. These are the same in Examples 3 and 4, which will be described later.

Example 3 increases the amount of power running torque output when overvoltage is detected a plurality of times.
In the following, differences from the first and second embodiments will be mainly described.

FIG. 9 is a block diagram illustrating an example of a control device according to the third embodiment; The third embodiment differs from the first and second embodiments in that the powering torque setting by the maximum powering torque setting unit 116 can be changed.

The initial value b of the maximum powering torque set by the maximum powering torque setting unit 116 to be output during light load regeneration is set in advance. At this time, if power running torque more than necessary is output, the control may become unstable when switching from regeneration to power running, so it is necessary to set the minimum required power running torque.

However, there is a possibility that the required powering torque value will change due to changes in the temperature of the motor, variations in individual motors, temperature fluctuations in detectors such as CT and DCPT, and overvoltage may be detected.

Therefore, when overvoltage is detected multiple times during light load regeneration control, the maximum powering torque b is increased. Also, the maximum powering torque b is changed depending on the occurrence frequency and situation of overvoltage.

As described above, according to the third embodiment, the maximum powering torque is increased even when the required powering torque value changes due to changes in the temperature of the motor, errors in measurement equipment, individual variations in the motors, and the like. As a result, generation of overvoltage can be prevented, and regenerative operation can be stably performed.

The fourth embodiment changes the maximum powering torque b not only when overvoltage is detected as in the third embodiment, but also by using temperature information.
In the following, differences from the third embodiment will be mainly described.

FIG. 10 is a block diagram illustrating an example of a control device according to the fourth embodiment;
By using temperature information separately for the overvoltage detection information, overvoltage can be detected even if the required powering torque value changes due to at least one of the temperature fluctuations of the electric motor and detectors such as CT and DCPT. Detection can be prevented in advance.

The temperature information is mainly used as the overvoltage detection information and the temperature information, and the temperature information may be used alone. As the temperature information to be used, a detection signal from an external sensor or an estimated value inside the device is used. It is possible to implement.

As described above, according to the fourth embodiment, even if the constant of the electric motor changes due to a change in the temperature of the electric motor, by adjusting the output powering torque, generation of overvoltage can be prevented and stable regenerative operation can be performed. can.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to the above-described respective embodiments, and various modifications can be made without departing from the gist of the present invention.

101 control device, 102 power converter, 103 electric motor, 104 voltage detector,
105 DC filter capacitor, 106 DC filter reactor, 107 overhead wire,
108 pantograph, 109 wheel, 110 rail, 111 electric car,
112 light load regeneration operation amount calculation unit, 113 command generator, 114 vector control unit,
115 phase current detector, 116 maximum powering torque setting unit

Claims (9)

a control unit that outputs a switching command to a power converter that drives the electric motor based on a torque command value for the electric motor;
a regeneration operation unit that outputs a torque operation amount to the control unit during regenerative operation of the electric motor to correct the torque command value;
When the DC voltage detection value of the electric power converter exceeds a DC voltage target value, the regeneration operation unit treats the torque command value as a powering torque command value of a minute value that does not cause the motor to power running. A control device for a power converter, characterized in that it outputs the torque manipulated variable. A power converter control device according to claim 1,
The regenerative operating unit is characterized in that the rate of change of the torque command value is kept constant or varied based on the magnitude of the DC voltage detection value until the DC voltage detection value reaches the DC voltage target value. A control device for a power converter. The power converter control device according to claim 1 or 2,
The regeneration operation unit outputs the torque operation amount according to a difference between the DC voltage target value and the DC voltage detection value, and the torque operation amount is such that the DC voltage detection value is equal to the DC voltage target value. A control device for a power converter, wherein the operation amount is such that the DC voltage detection value is maintained at a high voltage within a range in which the DC voltage detection value does not become an overvoltage until the torque command value is exceeded. A power converter control device according to any one of claims 1 to 3,
The regeneration operation unit sets a maximum powering torque to be output during the regeneration operation, outputs the torque operation amount when the torque operation amount is smaller than the maximum powering torque, and outputs the torque operation amount when it is equal to or higher than the maximum powering torque. A control device for a power converter, characterized by outputting the maximum powering torque. A power converter control device according to claim 4,
The control device for a power converter, wherein the regeneration operation unit increases the setting of the maximum powering torque according to the frequency of occurrence of overvoltage including multiple overvoltage occurrences of the DC voltage detection value. A power converter control device according to claim 4 or 5,
The power converter, wherein the regeneration operation unit changes the setting of the maximum powering torque based on at least one of temperature information of the electric motor and temperature information of a detector installed in the power converter. controller. An electric vehicle equipped with the power converter control device according to any one of claims 1 to 6. A control method for a power converter that drives an electric motor, comprising:
outputting a switching command to the electric power converter based on a value obtained by manipulating a torque operation amount to a torque command value for the electric motor;
When the DC voltage detection value of the electric power converter exceeds the DC voltage target value during regenerative operation of the electric motor, the torque command value is set to a minute powering torque command value that does not cause the electric motor to power running. A control method for a power converter, characterized in that the torque manipulated variable is output as . A power converter control method according to claim 8,
The torque operation amount is changed based on at least one of overvoltage information of the DC voltage detection value, temperature information of the electric motor, and temperature information of a detector installed in the power converter. A method of controlling a power converter.

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