The present invention relates to an electric rolling stock control device which controls a power converter for supplying power to an electric motor that drives an electric rolling stock without a sensor.
Patent Literature 1 discloses an electric rolling stock control device including a car speed frequency converter which uses an output of a car speed sensor permanently installed in a vehicle of the electric rolling stock as a backup speed (definition of “backup speed” will be described later) and converts the output into a rotation frequency of an induction motor and a limiter which prevents an estimation value of a rotor rotation frequency of a rotor rotation frequency calculation unit from departing from a control range based on an output from the car speed frequency converter.
According to the electric rolling stock control device disclosed in Patent Literature 1, the limiter can prevent the estimation value of the rotor rotation frequency from departing from the control range. Therefore, instability of control in a process from coasting of the electric rolling stock to restart is eliminated, and driving characteristics with high stability and high reliability can be obtained.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2003-324998
However, the electric rolling stock control device disclosed in Patent Literature 1 has a system using the backup speed even though the electric rolling stock control device performs sensorless control. The electric rolling stock control device has had a problem in that when an error between the backup speed and an actual speed (referred to as “actual motor speed” below) of the electric motor for driving the electric rolling stock (appropriately referred to as “motor” below) increases, limit processing of an estimated speed originally performed to improve reliability of speed estimation prevents accurate speed estimation, and this causes deterioration in accuracy of the speed estimation.
The present invention has been made in view of the above. An object of the present invention is to obtain an electric rolling stock control device capable of suppressing deterioration in accuracy of speed estimation even with a system using a backup speed.
To solve the above problem and achieve the object, an electric rolling stock control device for controlling a power converter that supplies power to an electric motor for driving an electric rolling stock without a sensor according to the present invention includes: a voltage controlling unit that controls an output voltage of the power converter; and a speed estimating unit that calculates a rotation speed estimation value of the electric motor. The speed estimating unit includes: an initial speed estimating unit that outputs an initial speed estimation value; a steady speed estimating unit that outputs a steady speed estimation value; a correction coefficient calculating unit that calculates a correction coefficient based on the steady speed estimation value and a backup speed that is speed information from outside that is stored in a set of electric rolling stocks; and a correction speed calculating unit that stores the correction coefficient in a storage unit and calculates a correction speed by multiplying the correction coefficient by the backup speed.
According to the present invention, an effect to suppress deterioration in accuracy of speed estimation even with a system using a backup speed can be obtained.
First, before starting to describe the electric rolling stock control device according to the present embodiment, meanings of major terms used herein will be clarified.
(Backup Speed)
A backup speed is a speed obtained from a car speed sensor permanently installed in a vehicle of an electric rolling stock. As the car speed sensor, a Pulse Generator (PG) sensor attached to a non-driving wheel of the vehicle referred to as a trailing wheel is generally used. Speed information obtained by the PG sensor is stored by a train information managing system for managing train information as speed information of a set of electric rolling stocks, and the speed information is used for an operation or security of the train. From the viewpoint of the electric rolling stock control device, the backup speed is positioned as speed information obtained from the outside. Since wheel diameters of the trailing wheel and a driving wheel which is a main driving wheel are different from each other, strictly speaking, the backup speed does not necessarily coincide with a rotation speed of the motor (appropriately referred to as “motor speed” below). Therefore, the backup speed is not sufficient to control the motor speed with high accuracy, and the motor is controlled by estimating a speed by additionally detecting a current flowing in the motor (appropriately referred to as “motor current” below). In some cases, the car speed sensor is attached to the driving wheel to directly detect the speed of the driving wheel. This method is referred to as a sensor control method. A method to which the present invention is applied is a method which does not directly detect the speed of the driving wheel and is referred to as a sensorless control method.
(Steady Speed Estimation)
In the sensorless control method, a steady speed estimation is a processing or a method of estimating the motor speed by using a voltage command of the motor and the motor current obtained from a current sensor. When an inverter for driving the motor is gating on and is continuously in a power running state or a regenerative state, an algorithm sequence for steady speed estimation is applied. The term “steady” is used to distinguish the term from “initial speed estimation” described below.
(Initial Speed Estimation)
When the electric rolling stock is in a coasting state, the inverter is in a gate-off state. When the inverter is restarted from this state, it is necessary to gate on the inverter while adjusting an output voltage frequency of the inverter to be equal to the motor speed. During coasting, since the motor is not excited and the speed cannot be estimated, an algorithm sequence for the initial speed estimation is prepared to restart the inverter so as not to generate overcurrent and the like.
(Wheel Diameter Error)
Since the driving wheel may idly rotate when power is transmitted to a rail, wear of the driving wheel is increased. However, the wear of the trailing wheel is less than that of the driving wheel. In addition, maintenance for cutting the wheels may be performed so as not to cause a difference between diameters of the wheels of the single vehicle. For these reasons, the difference between the diameters, that is, the wheel diameter error is caused in the wheels of the set of the vehicles.
Hereinafter, the electric rolling stock control device according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment below. In the following description, a case where an electric motor is an induction motor will be described as an example. However, it goes without saying that main parts of the present invention can be applied to a synchronous electric motor.
Next, the electric rolling stock will be described. A high-potential-side connection end of the inverter 1 is electrically connected to an overhead contact line 11 via a pantagraph 15, and a low-potential-side connection end of the inverter 1 is electrically connected to a rail 18 via a wheel 16. The inverter 1 is a power converter which converts a direct current to an alternate current with a variable voltage and a variable frequency. An AC-side of the inverter 1 is connected to the electric motor 2 which is an induction motor. The inverter 1 drives the electric motor 2. The electric motor 2 drives a driving wheel 17 coupled to the electric motor 2 via a gear 10 to apply a driving force to the electric rolling stock. A current detector 4 is provided between the inverter 1 and the electric motor 2. The current detector 4 detects motor currents iu, iv, and iw which are phase currents flowing in the electric motor 2. The phase currents iu, iv, and iw detected by the current detector 4 are input to the voltage controlling unit 3. In
A detailed configuration of the voltage controlling unit 3 is illustrated in
The coordinate converter 36 converts the motor currents iu, iv, and iw detected by the current detector 4 into two axes of a dq-axis rotational coordinate system and calculates a d-axis current id and a q-axis current iq. Here, the d-axis and the q-axis are respectively referred to as a magnetic flux axis and a torque axis, and both axes are orthogonal to each other in terms of vectors.
The current command generating unit 31 calculates a q-axis current command iq* which is a torque axis current command and a d-axis current command id* which is a magnetic flux axis current command based on a magnetic flux command Φ* and a torque command Tm* according to the following formulas (1) and (2).
i
d
*=Φ*/M (1)
i
q*=(L2×Tm*)/(M×Φm*) (2)
In the formulas (1) and (2), the reference character M indicates a mutual inductance, and the reference character L2 indicates a secondary inductance.
The slip frequency calculating unit 32 calculates a slip frequency fs to be applied based on the d-axis current command id* and the q-axis current command iq* output from the current command generating unit 31 according to the formula (3). In the example in
f
s=(R2×iq*)/(2π×L2×iq*) (3)
In the formula (3), the reference character R2 indicates a secondary resistance, and the reference character L2 indicates a secondary inductance.
According to the formulas (4) and (5), the voltage command calculating unit 33 receives the d-axis current command id* and the q-axis current command iq* calculated by the current command generating unit 31, the d-axis current id and the q-axis current iq output from the coordinate converter 36, an angular frequency ωi generated by the voltage controlling unit 3 and used in the voltage controlling unit 3 as inputs and calculates a d-axis voltage command vd* and a q-axis voltage command vq* based on these inputs. The angular frequency ωi will be described later in detail.
v
d
*=R1×id*−ωi×σ×L1×iq*+(Kp+Ki/s)×(id*−id*) (4)
v
q
*=R1×iq*+ωi×σ×L1×id*+(Kp+Ki/s)×(iq*−iq*) (5)
In the formulas (4) and (5), the reference character R1 indicates a primary resistance, the reference character L1 indicates a primary inductance, and the reference character L2 indicates a secondary inductance. Furthermore, the reference character Kp indicates a current control proportional gain, and the reference character Ki indicates a current control integral gain. In addition, the reference character σ is a leakage inductance indicated by the following formula (6).
σ=1−(M×M)/(L1×L2) (6)
The integrator 34 calculates a phase σi by integrating an input angular frequency ωi. As illustrated in
Based on the phase θi calculated by the integrator 34 and the d-axis voltage command vd* and the q-axis voltage command vq* calculated by the voltage command calculating unit 33, the PWM controlling unit 35 generates the PWM signal used to perform PWM control to the switching element 1a of the inverter 1.
Next, the speed estimating unit 20 will be described. The speed estimating unit 20 receives the d-axis voltage command vd* and the q-axis voltage command vq* calculated by the voltage command calculating unit 33, the d-axis current id and the q-axis current iq which are outputs of the coordinate converter 36, and the backup speed ωb as inputs and generates the speed estimation value ωe of the electric motor 2 based on these inputs and outputs the generated value to the voltage controlling unit 3. As described above, the backup speed ωb is input as the speed information of a train of electric rolling stocks. Speed information managed by a train information managing system which is not illustrated, speed information from a car speed sensor which is not illustrated attached to the trailing wheel, and the like are exemplified. In the following description, a case where the speed information from the car speed sensor attached to the trailing wheel is input will be described as an example.
The initial speed estimating unit 201 receives the d-axis voltage command vd*, the q-axis voltage command vq*, the d-axis current id, and the q-axis current iq as inputs and estimates an initial speed estimation value ωx based on these inputs. Note that a method for estimating the initial speed estimation value ωx is well known, and the detailed description thereof will be omitted.
The steady speed estimating unit 202 receives the d-axis voltage command vd*, the q-axis voltage command vq*, the d-axis current id, and the q-axis current iq as inputs and estimates a steady speed estimation value ωy based on these inputs. Note that a method for estimating the steady speed estimation value ωy is well known, and the detailed description thereof will be omitted.
The correction coefficient calculating unit 203 receives the backup speed ωb and the steady speed estimation value ωy as inputs. The correction coefficient calculating unit 203 calculates a correction coefficient k and stores the correction coefficient k in the storage unit 204. The latest correction coefficient k is stored in the storage unit 204 and is output to the multiplier 205. A typical example of the correction coefficient k is a ratio between the steady speed estimation value ωy and the backup speed ωb, that is, ωy/ωb calculated as the correction coefficient k. Note that the correction coefficient k may be obtained by performing integration processing as described later. Furthermore, the correction coefficient calculating unit 203 does not need to calculate the correction coefficient k in real time, a calculation frequency of the correction coefficient k may be set to about once a day. Furthermore, since it can be considered that the wheel diameter of the driving wheel significantly changes in several days or weeks, the calculation frequency of the correction coefficient k may be set to the several days or weeks. The points of attention in a case where the train runs will be described later.
Returning back to the description of
The limiter 206 receives the initial speed estimation value ωx and the correction speed ωb′ as inputs and determines a threshold of the limiter 206 based on these inputs. Based on the determined threshold, the limiter 206 generates an initial speed estimation value ωx′ limited within a limit range. In the present embodiment, regarding the function of the limiter 206, a method disclosed in Patent Literature 1 is used. Detail of the processing is disclosed in Patent Literature 1. Therefore, detailed description thereof is omitted. All or a part of the contents disclosed in Patent Literature 1 are incorporated herein and forms a part of the present specification.
The output of the limiter 206, that is, the initial speed estimation value ωx′ and the steady speed estimation value ωy limited within the limit range are input to the output switch 207. The output switch 207 selects one of the initial speed estimation value ωx′ and the steady speed estimation value ωy limited within the limit range and outputs the selected value as the speed estimation value ωe.
Supplemental description regarding a part of the processing will be made. Since the correction coefficient k which is an output of the storage unit 204 can be obtained by the ratio of the steady speed estimation value ωy and the backup speed ωb, even if there is no accurate wheel diameter information at the time of calculation, it is possible to lessen an influence of the wheel diameter error. Actually, if only standard wheel diameter information before cutting the wheel is input, even when the wheel wears when the train runs or the wheel is cut for maintenance, the value of the steady speed estimation value ωy follows the wear or cut. Therefore, the correction coefficient is constantly updated to be appropriate.
Next, the meaning of the term “speed” will be described.
In addition, there is a case where the car speed is converted into units of the rotation speed of the driving wheel by using the wheel diameter of the driving wheel. As a unit of the rotation speed of the driving wheel, “Hz”, “rad/s”, and the like are used. In addition, there is a case where the rotation speed of the driving wheel is converted into units of a motor mechanical speed and a motor electrical speed by using the wheel diameter of the driving wheel, a gear ratio, and the number of pairs of motor poles. As units of the motor mechanical speed and the motor electrical speed, “Hz”, “rad/s”, and the like are used.
As described above, in the display or the control of the electric rolling stock, a plurality of terms having the concept of the speed exists. However, the terms are corresponding to each other one by one, and units are converted between the terms. Therefore, any term may be used as the backup speed.
Next, an operation of main parts of the electric rolling stock control device according to the present embodiment and an effect of the electric rolling stock control device will be described with reference to
First, the operation profile illustrated in
In contrast, in the operation profile illustrated in
In addition, in the operation profile in
Especially, in the embodiment in which the speed information managed by an external system, not the information of the car speed sensor, is received as the backup speed, a backup speed update involves a time lag due to a transmission delay. Therefore, if the calculation processing of the correction speed is performed during acceleration, the error of the correction speed may increase. Even in such a case, when the car speed is constant, the correction speed is not affected by the transmission delay. Accordingly, an increase in the error of the correction speed can be avoided.
In a case where the calculation processing of the correction speed is performed in the coasting section, in
Next, a processing flow regarding the calculation of the correction coefficient will be described with reference to
In
It is determined in step S103 whether the electric rolling stock is coasting. If the electric rolling stock is not coasting (step S103, No), the procedure proceeds to step S102 to reset the integral values. Then, the procedure returns to the processing in step S101. On the other hand, if the electric rolling stock is coasting (step S103, Yes), the procedure proceeds to step S104.
In step S104, it is determined whether the smaller one of the steady speed estimation value ωy and the backup speed ωb is larger than or equal to a determination value. In a case where one of the steady speed estimation value ωy and the backup speed ωb is smaller than the determination value (step S104, No), the procedure proceeds to step S102, and the reset processing of the integral values is performed. Then, the procedure proceeds to the processing in step S101. On the other hand, in a case where both of the steady speed estimation value ωy and the backup speed ωb are larger than or equal to the determination value (step S104, Yes), the procedure proceeds to step S105.
In step S105, whether idle rotation of the electric rolling stock occurs is detected. If the idle rotation of the electric rolling stock is detected (step S105, Yes), the procedure proceeds to step S102, and the reset processing of the integral values is performed. Then, the procedure returns to the processing in step S101. On the other hand, if the idle rotation of the electric rolling stock is not detected (step S105, No), the procedure proceeds to step S106.
In step S106, the integral value of the steady speed estimation value ωy which is a first integral value and the integral value of the backup speed ωb which is a second integral value are updated.
In step S107, an elapsed integration time is determined. If the integration time does not reach a desired elapsed time (step S107, No), the procedure returns to the processing in step S101. On the other hand, if the integration time reaches the desired elapsed time (step S107, Yes), the procedure proceeds to step S108, and a ratio between the integral value of the steady speed estimation value ωy and the integral value of the backup speed ωb is calculated as the correction coefficient k. Then, the processing flow in
According to the processing flow in
In the processing flow in
Furthermore, in a case where the inverter stops the operation by an operation command during the calculation of the correction coefficient, it is preferable that the correction coefficient be calculated by using only the integral value before stopping the operation of the inverter to update the correction coefficient. In this way, it is possible to update the correction coefficient without wasting the integrated data.
Finally, a hardware configuration of the voltage controlling unit 3 and the speed estimating unit 20 will be described.
Central Processing Unit (CPU) 100 for performing calculations, a memory 102 for storing a program to be read by the CPU 100, and an interface 104 for inputting and outputting signals. The CPU 100 may be a device referred to as a computing device, a microprocessor, a microcomputer, a processor, a Digital Signal Processor (DSP), or the like. Furthermore, the memory 102 is, for example, a non-volatile or volatile semiconductor memory such as a Random Access Memory (RAM), a Read Only Memory (ROM), a flash memory, an Erasable Programmable ROM (EPROM), and an Electrically EPROM (EEPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a Digital Versatile Disc (DVD), a Blu-ray (registered trademark) Disc (BD), and the like.
Specifically, the memory 102 stores programs for executing the functions of the voltage controlling unit 3 and the speed estimating unit 20. The CPU 100 receives information of the motor currents iu, iv, and iw, the d-axis current command id*, the q-axis current command iq*, the d-axis current id, the q-axis current iq, the angular frequency ωi, the d-axis voltage command vd*, the q-axis voltage command vq*, the backup speed ωb, and the speed estimation value ωe via the interface 104.
In a case where the function of the voltage controlling unit 3 is realized, a program for the voltage controlling unit 3 is stored in the memory 102, and the CPU 100 executes the stored program to realize the function of the voltage controlling unit 3.
In a case where the function of the speed estimating unit 20 is realized, a program for the speed estimating unit 20 is stored in the memory 102, and the CPU 100 executes the stored program to realize the function of the speed estimating unit 20.
In a case where the functions of the voltage controlling unit 3 and the speed estimating unit 20 are realized with the hardware, the configuration illustrated in
The processing circuit 103 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an application specific integrated circuit (ASiC), a field-programmable gate array (FPGA), or a combination thereof. By constructing the functions of the voltage controlling unit 3 and the speed estimating unit 20 in the processing circuit 103, the functions of the voltage controlling unit 3 and the speed estimating unit 20 can be realized.
The structures indicated in the above embodiment indicate exemplary contents of the present invention and can be combined with other known technology. Furthermore, the structures indicated in the embodiment can be partially omitted and changed without departing from the scope of the present invention.
1 inverter; 1a switching element; 2 electric motor; 3 voltage controlling unit; 4 current detector; 8 gate driving circuit; 10 gear; 11 overhead contact line; pantagraph; 16 wheel; 17 driving wheel; 18 rail; 20 speed estimating unit; 22 correction speed calculating unit; 31 current command generating unit; 32 slip frequency calculating unit; 33 voltage command calculating unit; 34 integrator; 35 PWM controlling unit; 36 coordinate converter; 100 CPU; 102 memory; 103 processing circuit; 104 interface; 201 initial speed estimating unit; 202 steady speed estimating unit; 203 correction coefficient calculating unit; 204 storage unit; 205 multiplier; 206 limiter; 207 output switch.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2016/050842 | 1/13/2016 | WO | 00 |