DESCRIPTION
ELECTRIC VEHICLE CONTROLLER
Field
[0001] The present invention relates to an electric vehicle controller having an overvoltage suppression function.
Background
[0002] In the event that a voltage applied from a substation becomes excessive, an electric vehicle controller stops the operation of an inverter, opens a line breaker usually provided on a power supply path to an electric vehicle, and electrically separates the substation and the inverter in order to protect a switching device used in the inverter and a brake chopper circuit against the overvoltage. At this time, an overvoltage suppression thyristor is ignited to discharge an electrical charge in a filter capacitor via an overvoltage suppression resistor connected in series with the overvoltage suppression thyristor. As a result of these controls, the electrical charge in the filter capacitor is consumed in the overvoltage suppression resistor, thus the voltage of the filter capacitor drops.
[0003] Patent Literature 1 is an example of a conventional technology pertaining to the electric vehicle controller having the overvoltage suppression function. According to Patent Literature 1, current flowing through the overvoltage suppression resistor is commensurate with regenerative power at the time of regenerative braking, which can thus be continued without voltage being excessive. [0004] Note that while Patent Literature 1 only

aiscioses trie overvoicage suppression lunciioa, ±L ±S common for an ordinary electric vehicle to have a configuration including a brake chopper circuit consuming the regenerative power together with an overvoltage suppression circuit as disclosed in Patent Literature 2, for example.
Citation List
Patent Literature
[0005] Patent Literature 1: Japanese Patent Application
Laid-Open No. H3-159501
Patent Literature 2: Japanese Patent Application Laid-Open No. 2000-358384
Summary
Technical Problem
[0006] Patent Literature 2 discloses a configuration of achieving commonality between the overvoltage suppression resistor and a generated energy absorbing resistor but has not achieved commonality between the overvoltage suppression circuit and the brake chopper circuit, namely has not achieved an omission of either one of the overvoltage suppression circuit and the brake chopper circuit. The commonality between the overvoltage suppression circuit and the brake chopper circuit can greatly contribute to reduction in size of a device and is thus much desired in terms of cost reduction, improved maintainability and the like.
[0007] Moreover, the current flowing through the overvoltage suppression resistor is restricted as describee above in Patent Literature 1 for the reason of not unnecessarily operating a device detecting an amount of change in the current AI that is usually provided in a

substation (such device will be hereinafter referred to as a "AI detector"). The operation of the AI detector leads to tripping of a breaker in the substation. Tripping of the breaker in the substation causes a considerable influence on the vehicle operation since the operation of not only an own vehicle but also other vehicles are stopped [0008] The unnecessary operation of the AI detector is caused not only at the time of the regenerative braking but also by a sudden change in voltage of an overhead line, for example. When overvoltage is generated by the sudden change in voltage of the overhead line, the operation of the inverter is stopped, the line breaker is opened, and the brake chopper circuit is operated as described above. In reality, however, the brake chopper circuit is turned on before the line breaker is opened due to a delayed mechanical operation of the line breaker. This causes current to flow from a power supply source to the brake chopper circuit through the line breaker at the same time as the brake chopper circuit being turned on so that the AI detector in the substation may be operated to possibly cause unnecessary tripping of the breaker in the substation where this event has been a problem. [0009] The present invention has been made in consideration of the aforementioned problem, where an object of the invention is to obtain an electric vehicle controller capable of preventing an unintended and unnecessary operation of the breaker in the substation while achieving commonality between the overvoltage suppression circuit and the brake chopper circuit.
Solution to Problem
[0010] To solve the above described problem and achieve
the object an electric vehicle controller according to the present invention includes: an inverter to drive a motor receiving power supplied via a line breaker and a DC bus power consumption circuit to be connected in parallel wi¬the inverter while including a switching device and a poi consumption resistor connected in series with the switch. device; a voltage detector to detect a bus voltage applii to the DC bus; and a control unit to perform power consumption control that causes the power consumption resistor to consume regenerative power supplied from the motor and overvoltage suppression control that suppresse: the bus voltage from being excessive. The control unit controls the switching device in order for a second duty ratio used at the time of performing the overvoltage suppression control to be lower than a first duty ratio used at the time of performing the power consumption control.
Advantageous Effects of Invention
[0011] The effect of the present invention is that th< unintended and unnecessary operation of the breaker in tl substation can be prevented while achieving commonality between the overvoltage suppression circuit and the brak< chopper circuit.
Brief Description of Drawings
[0012] FIG. 1 is a diagram illustrating an example of the configuration of an electric vehicle controller according to an embodiment.
FIG. 2 is a diagram illustrating an example of the configuration of a control unit in the electric vehicle controller according to an embodiment.
FIG. 3 is a time chart used to describe an operatior of the electric vehicle controller according to an

embodiment.
FIG. 4 is a diagram illustrating the configuration of a general electric vehicle controller employing an overvoltage suppression circuit.
Description of Embodiments
[0013] There will now be described an electric vehicle
controller according to an embodiment of the present
invention with reference to the drawings. Note that the
present invention is not to be limited by the following
embodiment.
[0014] Embodiment.
FIG. 1 is a diagram illustrating an example of the configuration of an electric vehicle controller according to an embodiment. As illustrated in FIG. 1, an electric vehicle controller 50 according to the embodiment is configured to receive DC (direct current) power from an overhead line 1 via a current collector 2 and a line breaker 3, convert the received DC power into AC (alternative current) power by using an inverter 11, and drive a motor 12 being a load.
[0015] In addition to the inverter 11, the electric vehicle controller 50 is configured to include a brake chopper circuit 8 in which a switching device 6,and a braking resistor 7 are connected in series, and a filter capacitor 10 that accumulates power supplied from the overhead line 1. One end of the brake chopper circuit 8 is connected to a DC bus 4a on a high potential side, while another end of the brake chopper circuit 8 is connected to a DC bus 4b on a low potential side. Likewise, the filter capacitor 10 is connected between the DC buses 4a and 4b. Also a voltage detector 9 which detects applied voltage from the overhead line or voltage of the filter capacitor

6 10 is provided between the DC buses 4a and 4b. A filter
capacitor voltage FCV being information of the voltage
across the filter capacitor 10 detected by the voltage
detector 9 is input to a control unit 13. The control unit
13 uses the filter capacitor voltage FCV to control the
inverter 11, the brake chopper circuit 8, and the line
breaker 3.
[0016] FIG. 4 is an example of the configuration of an
electric vehicle controller illustrated as a comparative
example, the configuration being illustrated as a
conventional configuration in Patent Literature 2, for
example. In FIG. 4, a part identical or eguivalent to a
part in FIG. 1 is indicated with the same reference numeral
as that assigned to the part in FIG. 1. As is apparent
from a comparison between FIG. 1 and FIG. 4, an overvoltage
suppression circuit 5 is omitted in the electric vehicle
controller 50 according to the embodiment. In the electric
vehicle controller 50 according to the embodiment, a
function that the overvoltage suppression circuit 5 takes
charge of is substituted by the brake chopper circuit 8
operated under control of the control unit 13. That is,
the brake chopper circuit 8 of the embodiment operates as a
power consumption circuit having a combination of an
overvoltage suppression function and a regenerative power
consumption function included in an original brake chopper
circuit, while the braking resistor 7 provided in the brake
chopper circuit 8 operates as a power consumption resistor.
Note that the function substituted by the brake chopper
circuit 8 will be described in detail later on.
[0017] Next, there will be described differences between
the overvoltage suppression circuit 5 and the brake chopper
circuit 8 with reference to the configuration in FIG. 4.
The design concept is different in the first place between

the overvoltage suppression circuit 5 and the brake chopper circuit 8, where this difference in the design concept is expressed as a difference between the overvoltage suppression resistor 5a and the braking resistor 7. The overvoltage suppression resistor 5a is provided for the purpose of discharging an electrical charge in the filter capacitor 10 when voltage applied from the overhead line 1 becomes excessive. The operation of the overvoltage suppression circuit 5 is designed while considering coordination with a substation, specifically such that a AI detector in the substation does not operate even when an overvoltage suppression thyristor 5b is ignited before opening the line breaker 3.
[0018] On the other hand, the braking resistor 7 is designed such that surplus power of regenerative power supplied from the motor 12 can be consumed quickly without waste. At this time, a resistance value Rl of the overvoltage suppression resistor 5a and a resistance value R2 of the braking resistor 7 are generally in a relationship of Rl > R2. This causes larger current to flow in from the substation when the brake chopper circuit 8 is used in performing overvoltage suppression control, thereby possibly causing the AI detector to operate to be a cause of the problem in the electric vehicle controller having the overvoltage suppression function. [0019] Therefore, the electric vehicle controller 50 according to the embodiment realizes the configuration of a control system not allowing the AI detector to operate even when the brake chopper circuit 8 is used as the overvoltage suppression circuit, where FIG. 2 is a diagram illustrating an example of the configuration of the control system. [0020] FIG. 2 illustrates the configuration including a first control system 13a pertaining to brake chopper

control in an upper tier and a second control system 13b pertaining to overvoltage suppression control in a lower tier. The first control system 13a includes a first comparator 13al, a first duty ratio calculation unit 13a2 and a first drive signal generation unit 13a3, while the second control system 13b includes a second comparator 13bl a second duty ratio calculation unit 13b2 and a second drive signal generation unit 13b3. Moreover, an output unit 13c is provided in an output stage of the control unit 13.
[0021] There will now be described the operation of each of the first control system 13a and the second control system 13b. [0022] (First comparator)
The first comparator 13al receives the filter capacitor voltage FCV detected by the voltage detector 9 at a B terminal and a first overvoltage determination value Val indicating a starting voltage of brake chopper control at an A terminal. The first comparator 13al compares the filter capacitor voltage FCV with the first overvoltage determination value Val and outputs a brake chopper control command BCHC to the first duty ratio calculation unit 13a2 when the filter capacitor voltage FCV is higher than or equal to the first overvoltage determination value Val. [0023] (Second comparator)
The second comparator 13bl receives the filter capacitor voltage FCV at a B terminal similarly to the first comparator 13al, and receives a second overvoltage determination value Va2 indicating a starting voltage of overvoltage protection control at an A terminal of the second comparator 13bl. The second comparator 13bl compares the filter capacitor voltage FCV with the second overvoltage determination value Va2 and outputs an

overvoltage protection command VPC to the second duty ratio calculation unit 13b2 when the filter capacitor voltage FCV is higher than or equal to the second overvoltage determination value Va2. Note that the first overvoltage determination value Val and the second overvoltage determination value Va2 are in a relationship of Val < Va2. Accordingly, the brake chopper control command BCHC is generated before the overvoltage protection command VPC is generated while the filter capacitor voltage FCV is in the process of increasing, for example. [0024] (First duty ratio calculation unit)
The first duty ratio calculation unit 13a2 receives the filter capacitor voltage FCV and the brake chopper control command BCHC generated by the first comparator 13al. tfhile receiving the brake chopper control command BCHC, the first duty ratio calculation unit 13a2 calculates a duty ratio CUR1 being a first duty ratio corresponding to the nagnitude of the filter capacitor voltage FCV and outputs ;he duty ratio to the first drive signal generation unit L3a3. Note that the duty ratio represents a ratio of an 3n-period occupying the duration of one cycle of an on-Dulse and an off-pulse at the time of controlling the switching device 7. [0025] (Second duty ratio calculation unit)
The second duty ratio calculation unit 13b2 receives ;he overvoltage protection command VPC generated by the second comparator 13bl and a line breaker state signal LBS from the line breaker 3. Note that the line breaker state signal LBS in this case will be described as one that is >utput when the line breaker 3 is closed. While receiving :he overvoltage protection command VPC and the line breaker ;tate signal LBS, the second duty ratio calculation unit _3b2 calculates a duty ratio CUR2 being a second duty ratio

±u and outputs it to the second drive signal generation unit
13b3 while at the same time outputting a line breaker
release command LBR provided to release the line breaker 3
and an inverter operation stop command INVS provided to
stop the operation of the inverter 11 to the line breaker 3
and the inverter 11, respectively. Note that the duty
ratio CUR2 output by the second duty ratio calculation unit
13b2 and the duty ratio CUR1 output by the first duty ratio
calculation unit 13a2 are in a relationship of CUR2 < CUR1.
[0026] The line breaker 3 is opened when a line breaker
release command LBR is input to the line breaker 3. The
line breaker state signal LBS is not output once the line
breaker 3 is opened. When the line breaker state signal
LBS is lost from the state in which both the overvoltage
protection command VPC and the line breaker state signal
LBS are input, the second duty ratio calculation unit 13b2
sets the duty ratio CUR2 to a third duty ratio higher in
value than the duty ratio CUR1. It suffices the third duty
ratio is higher than the duty ratio CUR1 being the first
duty ratio. Note that the line breaker 3 is open at the
time the third duty ratio is generated, whereby no current
flows in from the overhead line 1. Accordingly, the
braking resistor 7 can consume power quickly by setting the
third duty ratio to 100%, for example, unless the
regenerative power of the motor 12 is excessive.
[0027] (First drive signal generation unit)
The first drive signal generation unit 13a3 receives
the duty ratio CUR1 calculated by the first duty ratio
calculation unit 13a2. The first drive signal generation
unit 13a3 generates a control pulse to drive the switching
device 6 of the brake chopper circuit 8 according to the
duty ratio CUR1.
[0028] (Second drive signal generation unit)

The second drive signal generation unit 13b3 receives ;he duty ratio CUR2 calculated by the second duty ratio calculation unit 13b2. The second drive signal generation init 13b3 generates a control pulse to drive the switching ievice 6 of the brake chopper circuit 8 according to the iuty ratio CUR2. [0029] (Output unit)
The control pulse generated by the first drive signal jeneration unit 13a3 and the control pulse generated by the second drive signal generation unit 13b3 are input to the output unit 13c. When both of the control pulses are generated, the output unit 13c performs processing by prioritizing the control pulse generated by the second irive signal generation unit 13b3 and outputs the processed ;ontrol pulse to the brake chopper circuit 8 as a brake ;hopper operation command BCX, whereby the switching device > of the brake chopper circuit 8 is controlled. ^0030] Next, an operation performed when the overvoltage .s detected by the electric vehicle controller of the :mbodiment will be described with reference to FIGS. 1, 2 ind 3. FIG. 3 is a time chart used to describe the iperation performed when the overvoltage is detected by the ilectric vehicle controller. The time chart of FIG. 3 llustrates the waveform of each of the filter capacitor -oltage FCV, the brake chopper control command BCHC, the ivervoltage protection command VPC, the line breaker state ignal LBS, the brake chopper operation command BCX, and an nput current lb flowing in from the overhead line 1 in rder from the upper side.
0031] When the voltage applied from the overhead line 1 ecomes excessive, the voltage detector 9 detects an vervoltage state. Since the control unit 13 of the lectric vehicle controller 50 according to the embodiment

is configured as illustrated in FIG. 2, it is determined at time ta that the filter capacitor voltage FCV exceeds a brake chopper control starting voltage (corresponding to the first overvoltage determination value Val in FIG. 2) . At this time, the control unit 13 performs the aforementioned operation to output the brake chopper operation command BCX expressed as a control pulse signal that is turned on and off with the duty ratio CUR1, whereby filter capacitor current la from the filter capacitor 10 flows into the brake chopper circuit 8 as illustrated in FIG. 1. On the other hand, the switching device 6 being controlled to be turned-on and turned-off suppresses the influx of the input current lb from the overhead line 1 into the brake chopper circuit 8, whereby the AI detector does not operate.
[0032] When the filter capacitor voltage FCV further increases, it is determined at time tb that the filter capacitor voltage FCV exceeds an overvoltage protection starting voltage (corresponding to the second overvoltage determination value Va2 in FIG. 2) so that the overvoltage protection command VPC is output. The line breaker release command LBR is output when the overvoltage protection command VPC is output, but the line breaker 3 is not opened immediately due to a delay in a mechanical operation as expressed by the line breaker state signal LBS. Until the line breaker 3 is opened (from time tb to time tc) , the control unit 13 controls the switching device 6 by outputting the brake chopper operation command BCX expressed as a control pulse signal that is turned-on and turned-off with the duty ratio CUR2 having a reduced duty ratio. At this time, the input current lb flows from the overhead line 1 but can be suppressed so as not to exceed a AI set value being a determination threshold since the duty

ratio is reduced.
[0033] The input current lb does not flow after time tc at which the line breaker 3 is opened, so that the duty ratio is changed to 100% to quickly discharge the electrical charge in the filter capacitor 10. [0034] Note that the duty ratio during the time from when the line breaker release command LBR is output to when the line breaker 3 is opened can be determined according to the AI set value, the resistance value of the braking resistor 7, an overvoltage set value, and the number of electric vehicle controllers. With Rb denoting the resistance value of the braking resistor 7 and n denoting the number of electric vehicle controllers per formation, the resistance value Rb of the braking resistor can be determined on the basis of the following expression, for example.
[0035] Rb > n x Va2/(AI set value)
[0036] As has been described, the electric vehicle controller according to the embodiment can realize commonality between the overvoltage suppression circuit and the brake chopper circuit, thus it becomes possible to reduce size and cost of the controller. [0037] Moreover, according to the electric vehicle controller of the embodiment, the switching device is controlled such that the second duty ratio at the time of performing overvoltage suppression control is lower than the first duty ratio at the time of performing brake chopper control, whereby an unintended and unnecessary operation of the breaker in the substation can be suppressed while realizing commonality between the overvoltage suppression circuit and the brake chopper circuit. [0038] Furthermore, the electric vehicle controller

14 according to the embodiment performs control to increase
the duty ratio after making sure that the line breaker is
opened, whereby the electrical charge in the filter
capacitor can be discharged guickly while suppressing the
unintended and unnecessary operation of the breaker in the
substation.
[0039] Note that the configuration illustrated in the
aforementioned embodiment is merely an example of the
configuration of the preset invention, where it is needles
to say that the configuration can be combined with another
known technigue or modified by omitting a part of the
configuration or the like without departing from the gist
of the present invention.
Industrial Applicability
[0040] As has been described, the present invention is useful as the electric vehicle controller having the overvoltage suppression function.
Reference Signs List
[0041] 1 overhead line, 2 current collector, 3 line breaker, 4a, 4b DC bus, 5 overvoltage suppression circui 6 switching device, 7 braking resistor (power consumptio resistor), 8 brake chopper circuit (power consumption circuit), 9 voltage detector, 10 filter capacitor, 11 inverter, 12 motor, 13 control unit, 13a first control system, 13al first comparator, 13bl second comparator, 13a2 first duty ratio calculation unit, 13b2 second duty ratio calculation unit, 13a3 first drive signal generatio unit, 13b3 second drive signal generation unit, 13c output unit, 50 electric vehicle controller, BCHC brake chopper control command, CUR1 duty ratio (first duty ratio), CUR2 duty ratio (second duty ratio), FCV filter

l^djJctl^X LU L VUlLdyB, XJ.MVO X11 V fci J_ L. ti J_ UpeidLlUll SLUp CUIlLULcUlU,
LBR line breaker release command, LBS line breaker state signal, VPC overvoltage protection command, Val first overvoltage determination value, Va2 second overvoltage 5 determination value.

An electric vehicle controller comprising:
an inverter to drive a motor by receiving power upplied via a line breaker and a DC bus;
a power consumption circuit to be connected in arallel with the inverter while including a switching evice and a power consumption resistor connected in series ith the switching device;
a voltage detector to detect a bus voltage applied to he DC bus; and
a control unit to perform power consumption control hat causes the power consumption resistor to consume egenerative power supplied from the motor and overvoltage uppression control that suppresses the bus voltage from eing excessive, wherein
the control unit controls the switching device in rder for a second duty ratio used at the time of erforming the overvoltage suppression control to be lower han a first duty ratio used at the time of performing the ower consumption control.
The electric vehicle controller according to claim 1, herein
the control unit includes a first control system to erform the power consumption control and a second control ystem to perform the overvoltage suppression control,
the control unit starts an operation of the first ontrol system when the bus voltage is higher than or egual o a first determination value and starts an operation of le second control system when the bus voltage is higher nan or equal to a second determination value that is arger than the first determination value, and
the operation of the second control system is

prioritized when the tirst control system and the second control system are operated at the same time.
3. The electric vehicle controller according to claim 2,
wherein
the second control system receives information to open or close the line breaker, and
the second control system calculates a third duty ratio larger than the first duty ratio when acknowledging the information to open or close the line breaker and controls the switching device according to the third duty ratio.
4. The electric vehicle controller according to claim 3,
wherein the third duty ratio equals 100%.