Electrically driven vehicle

Abstract

The purpose of the present invention is to make more effective use of regenerative electric power. This electrically driven vehicle comprises a battery, a DC / DC converter which accepts the output voltage of the battery as an input, an inverter which accepts the voltage output from the DC / DC converter or the voltage from overhead wires as an input to drive an electric motor, and a brake chopper device which is connected to the DC side of the inverter, and the electrically driven vehicle is provided with an overhead wire load determiner which determines whether there is a load consuming power on the overhead wires or not on the basis of a detected voltage value on the DC side of the inverter and a detected current value of a current flowing from the inverter to the overhead wires.

Description

Electrically powered vehicles

[0001] The present invention relates to an electrically powered vehicle that runs on power supplied from an overhead line.

[0002] Electrically powered vehicles are known that run on electricity supplied via a current collector such as a pantograph in sections where overhead lines are installed, and run on electricity stored in batteries installed on the vehicle in sections where overhead lines are not installed.

[0003] In such vehicles, the regenerative power generated when the brakes are applied is stored in a battery installed on the vehicle, or stored in a ground-based power storage facility via overhead lines, or supplied to other vehicles in motion via overhead lines.

[0004] Patent Document 1 discloses a technology for improving regenerative efficiency by ensuring a supply destination for regenerative power when electric brakes are in use, controlling the load on the onboard load device, and maintaining the overhead line voltage at a value suitable for regenerative operation.

[0005] JP 2013-70611 A

[0006] When regenerating power, if there is no power storage facility on the ground or if there are no other vehicles running on the overhead lines, supplying regenerated power to the overhead lines can cause problems such as an increase in overhead line voltage. Patent Document 1 does not take such problems into consideration. This is fine if the batteries installed in the vehicles can absorb all of the regenerated power, but if there is surplus power that cannot be absorbed by the batteries, such problems occur.

[0007] A known measure is to suppress the regenerative power supplied to the overhead line when the overhead line voltage rises. This is because supplying regenerative power to the overhead line when there is no load consuming power on the overhead line generally causes the overhead line voltage to rise. However, this is not the only factor that causes the overhead line voltage to rise. When the magnitude of the system voltage supplied from the power system to the substation rises, the magnitude of the overhead line voltage supplied by the substation also rises. If the regenerative power supplied to the overhead line is suppressed in response to this rise, even if there is a load on the overhead line that can consume power, the regenerative power supplied to the overhead line will be suppressed, resulting in the problem of ineffective use of regenerative power.

[0008] An object of the present invention is to make more effective use of regenerative power.

[0009] In order to solve the above problems, in an electrically driven vehicle having a battery, a DC / DC converter that receives the output voltage of the battery as an input, an inverter that drives an electric motor using the voltage output by the DC / DC converter or the voltage from an overhead line as an input, and a brake chopper device connected to the DC side of the inverter, the electrically driven vehicle is provided with an overhead line load determiner that determines whether or not there is a load consuming power on the overhead line based on the detected voltage value on the DC side of the inverter and the detected current value of the current flowing from the inverter to the overhead line.

[0010] According to the present invention, when there is a load on the overhead line, power is supplied to the overhead line, making effective use of regenerative power. When there is no load, the power is consumed by the brake chopper device, making it possible to suppress an increase in overhead line voltage. This makes it possible to stabilize the overhead line voltage and make even more effective use of regenerative power.

[0011] 1 is a diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the brake chopper device of FIG. 1. FIG. 3 is a diagram showing the configuration of the controller of FIG. 1. FIG. 4 is a diagram showing the configuration of the overhead line load determiner of FIG. 3. FIG. 5 is a diagram showing the configuration of the chopper controller of FIG. 3. FIG. 6 is a diagram showing the configuration of the chopper operation determiner of FIG. 5. FIG. 7 is a diagram showing an example of operating waveforms in an embodiment of the present invention. FIG. 8 is a diagram showing another configuration of an electrically driven vehicle. FIG. 9 is a diagram showing another configuration of an electrically driven vehicle.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrically driven vehicle according to the present invention will be described below with reference to the drawings.

[0013] 1 shows the configuration of a first embodiment of an electrically powered vehicle. The electrically powered vehicle 1 of this embodiment includes pantographs 101A and 101B, a reactor 102, an inverter 103, an electric motor 104, a DC / DC converter 105, a battery 106, a brake chopper device 107, a smoothing capacitor 108, a voltage sensor 109, a current sensor 110, and a controller 111.

[0014] When electrically powered vehicle 1 travels in a section where overhead lines 2A, 2B supplying DC voltage are installed, pantograph 101 is connected to overhead line 2. DC power supplied to electrically powered vehicle 1 from overhead lines 2A, 2B is supplied to the DC side of inverter 103 via pantograph 101 and reactor 102. Inverter 103 converts the DC power into three-phase AC power and supplies it to electric motor 104 from the AC side of inverter 103. Electric motor 104 is driven by the three-phase AC power, causing electrically powered vehicle 1 to travel. The DC voltage of inverter 103 is approximately equal to the DC voltage of overhead line 2, and the DC voltage of inverter 103 is maintained by overhead line 2. The DC / DC converter 105 operates in a power control mode that controls the charging and discharging power of the battery 106, and in preparation for future travel in sections where the overhead lines 2A and 2B are not installed, the battery 106 is normally charged with a constant current, and when the battery 106 approaches full charge, it is charged with a constant voltage.

[0015] On the other hand, when electrically powered vehicle 1 travels in a section where overhead lines 2A, 2B are not installed, DC / DC converter 105 supplies the electrical energy stored in battery 106 to the DC side of inverter 103 as DC power, inverter 103 converts the DC power into three-phase AC power and supplies it from the AC side of inverter 103 to electric motor 104, and electric motor 104 is driven by the three-phase AC power to travel electrically powered vehicle 1. In order to maintain the DC voltage of inverter 103 at a predetermined value, DC / DC converter 105 operates in a voltage control mode that controls the DC voltage of inverter 103. That is, DC / DC converter 105 charges and discharges battery 106 so as to maintain the DC voltage of inverter 103.

[0016] The brake chopper device 107 is connected to the DC side of the inverter 103 and is a device for discharging electrical energy stored on the DC side of the inverter 103. The brake chopper device 107 operates upon receiving a gate pulse signal from a controller 111, which will be described later.

[0017] A smoothing capacitor 108 is connected to the DC side of the inverter 103 , and a voltage sensor 109 detects the DC voltage of the inverter 103 .

[0018] The current sensor 110 is connected in series with the reactor 102 and detects the current flowing through the reactor 102. In the following description, the direction of the current flowing from the reactor 102 to the overhead wire 2A is defined as positive.

[0019] The controller 111 receives the voltage detection value 36 detected by the voltage sensor 109 and the current detection value 37 detected by the current sensor 110, and outputs a gate pulse signal 59 to the brake chopper device 107. Note that in this embodiment, only the controller 111 that controls the brake chopper device 107 is shown. In reality, controllers that control the inverter 103 and DC / DC converter 105 are also required, but their description is omitted in this embodiment.

[0020] Fig. 2 is a diagram showing the configuration of the brake chopper device 107 of Fig. 1. The brake chopper device 107 has a resistor 21, a diode 22, a switching element 23 such as an IGBT or SiC, and a diode 24. The resistor 21 and the switching element 23 are connected in series, and the diode 22 and the diode 24 are connected to the resistor 21 and the switching element 23, respectively. When the switching element 23 receives a gate pulse signal from the controller 111 and becomes conductive, a current flows through the resistor 21, and the electrical energy stored on the DC side of the inverter 103 is discharged.

[0021] Fig. 3 is a diagram showing the configuration of the controller 111 in Fig. 1. The controller 111 has an overhead line load determiner 31 and a chopper controller 32. The overhead line load determiner 31 determines whether or not a load that consumes the power regenerated by the electrically driven vehicle 1 to the overhead line 2 exists on the overhead line 2, and outputs the result as a load determination result. The chopper controller 32 receives as inputs a load determination result 35 output by the overhead line load determiner 31 and a voltage detection value 36 detected by the voltage sensor 109, and outputs a gate pulse signal 59 to the brake chopper device 107.

[0022] Fig. 4 is a diagram showing the configuration of the overhead line load determiner 31 in Fig. 3. The overhead line load determiner 31 has a voltage change rate calculator 41, a first sign determiner 42, a second sign determiner 43, and a multiplier 44.

[0023] The voltage change rate calculator 41 receives the voltage detection value 36 detected by the voltage sensor 109 and calculates the rate of change.

[0024] The first sign determiner 42 receives the rate of change output by the voltage change rate calculator 41 and determines the sign of the rate of change to determine whether the voltage detection value detected by the voltage sensor 109 is increasing or decreasing. If the sign of the rate of change is positive and the detected voltage value is increasing, it outputs a determination result of 1. If the sign of the rate of change is zero or negative and the detected voltage value is constant or decreasing, it outputs a determination result of 0.

[0025] If the sign of the rate of change is positive and exceeds a predetermined threshold, the determination result may be set to 1. In this case, it is possible to reduce the risk of false detection.

[0026] The second sign determiner 43 receives the current detection value 37 detected by the current sensor 110 as input, and determines the sign of the value to determine the direction of the current flowing through the reactor 102. If the sign is positive, i.e., if the current is flowing from the reactor 102 to the overhead line 2A, it outputs 1 as the determination result. If the sign is zero or negative, i.e., if no current is flowing through the reactor 102 or if the current is flowing from the reactor 102 to the DC side of the inverter 103, it outputs 0 as the determination result.

[0027] The multiplier 44 receives the determination results output by the first sign determiner 42 and the second sign determiner 43 as input, calculates the multiplied value, and outputs the result as the load determination result. The load determination result is 1 when both the determination results output by the first sign determiner 42 and the second sign determiner 43 are 1. Therefore, the load determination result is 1 only when the voltage of the overhead line 2 is rising and power is being regenerated to the overhead line 2, and the load determination result is 0 in all other cases. Note that a load determination result of 1 means that there is no other load on the overhead line 2 that consumes the power being regenerated from the electrically driven vehicle 1, and a load determination result of 0 means that power is not being regenerated to the overhead line 2 or there is another load on the overhead line 2 that consumes the power being regenerated.

[0028] Fig. 5 is a diagram showing the configuration of the chopper controller 32 of Fig. 3. The chopper controller 32 has a chopper operation determiner 51, a subtractor 52, a multiplier 53, a duty ratio calculator 54, and a PWM calculator 55.

[0029] The chopper operation determiner 51 receives as input the load determination result 35 output by the overhead line load determiner 31 and the voltage detection value 36 detected by the voltage sensor 109. Then, it outputs a chopper operation determination result 57 indicating whether or not to operate the brake chopper device 107 and a voltage command Vref 58 for operating the brake chopper device 107. The chopper operation determination result 57 outputs 1 when the brake chopper device 107 is to be operated, and 0 when it is not to be operated.

[0030] The subtractor 52 outputs the difference between the voltage detection value 36 detected by the voltage sensor 109 and the voltage command Vref 58 output by the chopper operation determiner 51 .

[0031] The multiplier 53 receives the chopper operation determination result 57 output by the chopper operation determiner 51 and the difference value output by the subtractor 52 as inputs, and outputs the product thereof.

[0032] The duty ratio calculator 54 receives the multiplied value output by the multiplier 53 and calculates a duty ratio 71, which serves as a command for turning on / off the switching element 23. The duty ratio output by the duty ratio calculator 54 is limited to a range of 0 to 1. The duty ratio calculator 54 is configured, for example, by proportional-integral control.

[0033] The PWM calculator 55 receives the duty ratio output by the duty ratio calculator 54 as an input, compares the duty ratio with the carrier signal, and outputs a gate pulse signal 59 to the switching element 23 .

[0034] Fig. 6 is a diagram showing the configuration of the chopper operation determiner 51 of Fig. 5. The chopper operation determiner 51 has a comparator 61, a multiplier 62, a signal rising edge detector 63, and a sample-and-hold calculator 64.

[0035] Comparator 61 receives a predetermined voltage threshold Vth 66 and a voltage detection value 36 detected by voltage sensor 109 as inputs, and outputs the comparison result. If the voltage detection value is greater than voltage threshold Vth, it outputs 1 as the comparison result, and if the voltage detection value is equal to or smaller than voltage threshold Vth, it outputs 0 as the comparison result.

[0036] Multiplier 62 receives as input the load determination result 35 output by overhead line load determiner 31 and the comparison result output by comparator 61, and outputs the multiplied value as the chopper operation determination result. If the load determination result is 1 and the comparison result is 1, the chopper operation determination result is 1. In all other cases, the chopper operation determination result is 0. When the load determination result is 1, this means that there is no other load on the overhead line 2 that consumes the power being regenerated by the electrically driven vehicle 1. In this state, if the voltage detection value 36 detected by voltage sensor 109 exceeds a predetermined voltage threshold Vth, it is necessary to operate brake chopper device 107 to suppress a voltage rise on the overhead line 2. Therefore, the chopper operation determination result is set to 1 at this time.

[0037] The signal rising edge detector 63 detects the rising edge of the chopper operation determination result output from the multiplier 62, and outputs a pulse signal at the timing when the rising edge is detected.

[0038] The sample-and-hold calculator 64 receives as input the pulse signal output by the signal rising edge detector 63 and the voltage detection value 36 detected by the voltage sensor 109, samples and holds the voltage detection value detected by the voltage sensor 109 at the timing when the pulse signal is input, and outputs the result as a voltage command Vref 69. When it is determined that the brake chopper device 107 needs to be operated and the chopper operation determination result changes from 0 to 1, the signal rising edge detector 63 outputs a pulse signal, and the voltage detection value detected by the voltage sensor 109 at the timing when the pulse signal is output is output as the voltage command Vref 69. In other words, the voltage detection value when the brake chopper device 107 starts to operate is set as the voltage command Vref 69, and therefore the brake chopper device 107 discharges the electrical energy stored on the DC side of the inverter 103 so that the voltage detection value detected by the voltage sensor 109 does not rise any further.

[0039] 7 is a diagram showing an example of operating waveforms in one embodiment of the present invention. This case is an example in which the load on the overhead line 2 decreases while power is being regenerated on the overhead line 2.

[0040] Until time T1, the current detection value 37 detected by the current sensor 110 is negative, and current is flowing from the overhead line 2 to the DC side of the inverter 103, so the electrically powered vehicle 1 is running while receiving power from the overhead line 2.

[0041] Next, from time T1, the detected current value begins to change in the positive direction, and becomes positive from time T2. From time T2, power is regenerated from the DC side of inverter 103 to overhead line 2, and at time T3, the increase in the regenerated power stops and becomes constant. However, even though power is being regenerated to overhead line 2 from time T2, the detected voltage value 36 detected by voltage sensor 109 has not changed, and therefore the power regenerated to overhead line 2 is being consumed by the load on overhead line 2.

[0042] Next, from time T4, the load on the overhead line 2 decreases, and the power consumed by the overhead line 2 decreases, causing the voltage detection value 36 detected by the voltage sensor 109 to start rising. Since the voltage detection value rises while power is being regenerated to the overhead line 2, the overhead line load determiner 31 outputs 1 as the load determination result at time T5.

[0043] Next, at time T6, when the voltage detection value 36 reaches the voltage threshold value Vth, the chopper operation determiner 51 outputs 1 as the chopper operation determination result and sets the voltage detection value at that time as the voltage command Vref. Therefore, the chopper controller 32 adjusts the duty ratio so that the voltage detection value does not exceed the voltage command Vref, thereby suppressing an increase in the voltage detection value.

[0044] As described above, when the load on the overhead line 2 decreases while power is being regenerated to the overhead line 2 and the load is no longer able to consume all of the power being regenerated to the overhead line 2, the brake chopper device 107 operates to suppress the voltage rise on the overhead line 2.

[0045] 8 is a diagram showing another example of operating waveforms in one embodiment of the present invention. In this case, the voltage of the overhead line 2 is rising from the beginning, and the load on the overhead line 2 decreases while power is being regenerated to the overhead line 2.

[0046] Until time T1, the current detection value 37 detected by the current sensor 110 is negative, and current is flowing from the overhead line 2 to the DC side of the inverter 103, so the electrically powered vehicle 1 is running while receiving power from the overhead line 2.

[0047] Next, from time T1, the detected current value begins to change in the positive direction, and becomes positive from time T2. From time T2, power is regenerated from the DC side of inverter 103 to overhead line 2, and at time T3, the increase in the regenerated power stops and becomes constant. However, even though power is being regenerated to overhead line 2 from time T2, the detected voltage value 36 detected by voltage sensor 109 has not changed, and therefore the power regenerated to overhead line 2 is being consumed by the load on overhead line 2.

[0048] Next, from time T4, the load on the overhead line 2 decreases, causing a decrease in the power consumed by the overhead line 2, and the voltage detection value 36 detected by the voltage sensor 109 begins to rise. Since the voltage detection value rises while power is regenerated to the overhead line 2, the overhead line load determiner 31 outputs 1 as the load determination result at time T5. At this time, the voltage detection value exceeds the voltage threshold value Vth, so the chopper operation determiner 51 outputs 1 as the chopper operation determination result and sets the voltage detection value at that time as the voltage command Vref. The chopper controller 32 adjusts the duty ratio 71 so that the voltage detection value does not exceed the voltage command Vref, thereby suppressing the rise in the voltage detection value.

[0049] As described above, in a case where the voltage of the overhead line 2 is rising from the beginning, if the number of other loads connected to the overhead line 2 decreases while power is being regenerated to the overhead line 2 and the other loads are no longer able to consume all of the power that the electrically driven vehicle 1 is regenerating to the overhead line 2, the brake chopper device 107 will operate and the voltage rise on the overhead line 2 can be suppressed.

[0050] FIG. 9 shows a modified example of another configuration of an electrically powered vehicle. The electrically powered vehicle 1 of this embodiment basically includes pantographs 101A and 101B, a reactor 102, an inverter 103, an electric motor 104, a brake chopper device 107, a smoothing capacitor 108, a voltage sensor 109, a current sensor 110, and a controller 111, similar to the first embodiment and FIG. 1 . The difference from the electrically powered vehicle 1 of FIG. 1 is that the electrically powered vehicle 1 of this embodiment does not include a DC / DC converter 105 or a battery 106. Therefore, the electrically powered vehicle 1 of this embodiment is always operated while connected to the overhead line 2. Otherwise, similar to the electrically powered vehicle 1 of the first embodiment, the electrically powered vehicle 1 determines whether or not there is a load capable of consuming power on the overhead line 2. If there is a load, the electric power is supplied to the overhead line. If there is no load, the electric power is consumed by the brake chopper device 107. As a result, even an electrically powered vehicle without a DC / DC converter 105 or a battery 106 can achieve the same effects as the configuration of the first embodiment.

[0051] FIG. 10 shows a modified example of another configuration of an electrically powered vehicle. The electrically powered vehicle 1 of this embodiment basically includes pantographs 101A and 101B, a reactor 102, an inverter 103, an electric motor 104, a brake chopper device 107, a smoothing capacitor 108, a voltage sensor 109, a current sensor 110, and a controller 111, similar to the first embodiment and FIG. 1 . The difference from the electrically powered vehicle 1 of FIG. 1 is that an AC / DC converter 112 and a generator 113 are provided instead of the DC / DC converter 105 and the battery 106. Although not described in detail in this embodiment, the generator 113 generates electricity by being driven by an engine or the like. Even with this configuration, similar to the electrically powered vehicle 1 of FIG. 1 , it is possible to determine whether or not there is a load capable of consuming power on the overhead line 2, and if there is a load, power is supplied to the overhead line. If there is no load, the power is consumed by the brake chopper device 107. As a result, even in an electrically driven vehicle having an AC / DC converter 112 and a generator 113 instead of the DC / DC converter 105 and the battery 106, the same effects as those of the configuration of the first embodiment can be achieved.

[0052] As described above, the present invention described using the first to third embodiments can be widely applied to electrically driven vehicles. Among these, a particularly suitable application is a dump truck, which is operated in a limited area such as a mine and can contribute to environmental friendliness by efficiently utilizing regenerative power. Another suitable application is a trolley bus, and a configuration in which a large number of electrically driven vehicles are operated within a narrow route is also suitable.

[0053] The various inventions disclosed in the specification of this application as described above can also be expressed as follows, by way of example. <1> An electrically powered vehicle including a battery, a DC / DC converter that receives as its input the output voltage of the battery, an inverter that receives as its input the voltage output by the DC / DC converter or the voltage from an overhead line to drive an electric motor, and a brake chopper device connected to the DC side of the inverter, the electrically powered vehicle further including an overhead line load determiner that determines whether or not there is a load consuming power on the overhead line based on a detected voltage value on the DC side of the inverter and a detected current value of a current flowing from the inverter to the overhead line. <2> The electrically powered vehicle in <1>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the detected voltage value is positive and the detected current value is positive. <3> The electrically powered vehicle in <2>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the detected voltage value. <No. 4> The electrically powered vehicle in <No. 1>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive. <No. 5> The electrically powered vehicle in <No. 4>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the voltage detection value. <No. 6> The electrically powered vehicle includes an inverter that drives an electric motor using voltage from an overhead line as input, and a brake chopper device connected to the DC side of the inverter, and further includes an overhead line load determiner that determines whether there is a load consuming power on the overhead line based on the voltage detection value on the DC side of the inverter and the current detection value of the current flowing from the inverter to the overhead line. <No. 7> The electrically powered vehicle in <No. 6>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive and the current detection value is positive. <No. 8> The electrically driven vehicle according to <No. 7>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the voltage detection value.<No. 9> The electrically powered vehicle in <No. 6>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive. <No. 10> The electrically powered vehicle in <No. 9>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the voltage detection value. <No. 11> The electrically powered vehicle includes a generator, an AC / DC converter that receives as input the output voltage of the generator, an inverter that receives as input the voltage output by the AC / DC converter or the voltage from the overhead line to drive an electric motor, and a brake chopper device connected to the DC side of the inverter, and further includes an overhead line load determiner that determines whether there is a load consuming power on the overhead line based on the voltage detection value on the DC side of the inverter and the current detection value of the current flowing from the inverter to the overhead line. <No. 12> The electrically powered vehicle in <No. 11>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive and the current detection value is positive. <No. 13> The electrically powered vehicle in <No. 12>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the voltage detection value. <No. 14> The electrically powered vehicle in <No. 11>, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive. <No. 15> The electrically powered vehicle in <No. 14>, wherein the brake chopper device is operated based on the determination result of the overhead line load determiner and the voltage detection value.

[0054] 1: Electrically driven vehicle 2: Overhead wire 21: Resistor 22: Diode 23: Switching element 24: Diode 31: Overhead wire load determiner 32: Chopper controller 35: Load determination result 36: Voltage detection value 37: Current detection value 41: Voltage change rate calculator 42: First sign determiner 43: Second sign determiner 44: Multiplier 51: Chopper operation determiner 52: Subtractor 53: Multiplier 54: Duty ratio calculator 55: PWM calculator 61: Comparator 62: Multiplier 63: Signal rising edge detector 64: Sample and hold calculator 101: Pantograph 102: Reactor 103: Inverter 104: Electric motor 105: DC / DC converter 106: Battery 107: Brake chopper device 108: Smoothing capacitor 109: Voltage sensor 110: Current sensor 111: Controller 112: AC / DC converter 113: Generator

Claims

1. An electrically powered vehicle comprising a battery, a DC / DC converter which receives as its input the output voltage of the battery, an inverter which receives as its input the voltage output by the DC / DC converter or the voltage from an overhead line to drive an electric motor, and a brake chopper device connected to the DC side of the inverter, characterized in that the electrically powered vehicle also comprises an overhead line load determiner which determines whether or not there is a load consuming power on the overhead line based on the detected voltage value on the DC side of the inverter and the detected current value of the current flowing from the inverter to the overhead line.

2. An electrically powered vehicle as claimed in claim 1, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive and the current detection value is positive.

3. An electrically powered vehicle according to claim 2, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the voltage detection value.

4. An electrically powered vehicle as claimed in claim 1, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive.

5. An electrically powered vehicle according to claim 4, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the detected voltage value.

6. An electrically powered vehicle equipped with an inverter that uses voltage from an overhead line as input to drive an electric motor and a brake chopper device connected to the DC side of the inverter, the electrically powered vehicle further comprising an overhead line load determiner that determines whether or not there is a load consuming power on the overhead line based on a voltage detection value on the DC side of the inverter and a current detection value of the current flowing from the inverter to the overhead line.

7. An electrically powered vehicle according to claim 6, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive and the current detection value is positive.

8. An electrically powered vehicle according to claim 7, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the voltage detection value.

9. An electrically powered vehicle as claimed in claim 6, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive.

10. An electrically powered vehicle according to claim 9, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the voltage detection value.

11. An electrically powered vehicle comprising a generator, an AC / DC converter which receives as input the output voltage of the generator, an inverter which receives as input the voltage output by the AC / DC converter or the voltage from an overhead line to drive an electric motor, and a brake chopper device connected to the DC side of the inverter, the electrically powered vehicle further comprising an overhead line load determiner which determines whether or not there is a load consuming power on the overhead line based on the detected voltage value on the DC side of the inverter and the detected current value of the current flowing from the inverter to the overhead line.

12. An electrically powered vehicle according to claim 11, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive and the current detection value is positive.

13. An electrically powered vehicle according to claim 12, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the voltage detection value.

14. An electrically powered vehicle as claimed in claim 11, wherein the overhead line load determiner determines that there is a load consuming power on the overhead line when the rate of change of the voltage detection value is positive, the value exceeds a predetermined threshold, and the current detection value is positive.

15. An electrically powered vehicle according to claim 14, wherein the brake chopper device is operated based on the result of determination by the overhead line load determiner and the voltage detection value.

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