Electric vehicle, generator control device and generator control method

Abstract

electric vehicle (1), comprising: a machine for generating torque (2), an electric generator (3) driven by the machine to generate torque, for outputting a generated alternating current, an excitation unit (15) for outputting an excitation current to the electrical generator on the basis of a command signal, a rectifier (7) for converting the alternating current output by the electric generator into direct current, a pantograph (5) for drawing direct current from overhead lines (6), a power converter (11) connected to connection points (20) for receiving direct current from the rectifier and direct current from the current collector, for converting the direct current output at the connection points into alternating current, an electric motor (4) driven by the alternating current output by the power converter, Wheels (13) driven by the electric motor, a control unit (14) for supplying the command signal to the excitation unit (15) in a time period for switching between a first mode in which the direct current supplied by the rectifier (7) is output to the power transformer (11) and a second mode in which the direct current supplied by the overhead lines (6) is output to the power transformer (11), and a changeover switch (16) which is connected between the pantograph (5) and the connection points (20) to block the direct current supplied by the overhead lines (6) in the first mode and to output the direct current supplied by the overhead lines (6) from the connection points (20) to the power converter (11) in the second mode, characterized by a first current detector (8) for detecting a current value between the rectifier (7) and one of the connection points (20), wherein the control unit (14) is set up: In the first mode of the excitation unit (15), a command signal is supplied, which, when executing a PI control, is obtained from a DC voltage value taken between the rectifier (7) and the power converter (11) and a generator DC voltage command, in order to control the DC voltage output by the electric generator (3), In the second mode of the excitation unit (15), a command signal is supplied, which, when executing PI control, is obtained from the DC value detected by the current detector (8) between the rectifier (7) and the connection point (20), and a generator DC command, in order to control the DC current output by the electric generator (3), and During the time period for switching between the first and second modes of the excitation unit (15), a command signal is to be supplied based on the detected current value, such that the sum of the direct current supplied by the rectifier (7) and the direct current supplied by the overhead lines (6) is equal to a value of the direct current supplied by the rectifier (7) in the first mode.

Description

TECHNICAL AREA

[0001] The present invention relates to an electric vehicle powered by an electric motor. This invention also relates to a method and a device for controlling or regulating an electric generator. STATE OF THE ART

[0002] Traditionally, electric vehicles are known to be capable of powering an electric motor by switching between power from a diesel engine and power from an overhead line. Examples of such electric vehicles include overhead-line-powered dump trucks. This type of overhead-line dump truck is constructed with a diesel engine, an electric generator or dynamo that converts the diesel engine's output into electrical energy, a power converter (or inverter) that converts the electrical energy supplied by the generator or overhead line, and an electric motor to drive the wheels. Furthermore, if the electric motor is used as a wheel hub motor integrated into a wheel, an axle is no longer required to rotate the wheel.

[0003] This type of dump truck is used in various scenarios, such as in an open-pit quarry. In the quarry, the land surface is excavated until a mineral deposit is exposed; therefore, the dump truck, carrying a load of ore, must travel up and down a steep hill leading from the mineral deposit to the surface. On level roads, the electrical energy generated by the diesel engine's generator powers the electric motor without the need for overhead power lines, thus moving the dump truck. In the following explanation, the operating mode in which the diesel engine is used as the energy source without drawing power from the overhead line is referred to as the "non-overhead-line mode (first mode)."

[0004] In some cases, however, the total weight of the ore load on the bed of a dump truck exceeds several tens of tons, in addition to the truck's own weight. Using only the diesel engine as a power source would lead to a noticeable increase in fuel consumption. A common countermeasure is as follows: Two parallel contact wires or overhead lines are laid across the slope of the quarry, and as the dump truck travels uphill, the energy supplied by these overhead lines is used to power the electric motor, thus moving the truck. The operating mode in which the energy supplied to move the dump truck is obtained from the overhead line is called the "overhead line mode (second mode)."

[0005] Several documents are currently known regarding overhead line electric vehicles. Patent literature 1 JP 2002 - 067 776 A) describes, for example, a method with a motor-generator that is switched on when no power supply from an overhead line is available in order to enable the propulsion or operation of a vehicle. US 2003 / 0 025 399 A1 discloses a similar method in which the excitation of the generator is controlled in such a way as to result in a smooth transition between the operating modes. The preamble of claim 1 is based on this prior art. SUMMARY OF THE INVENTION

[0006] Furthermore, in overhead line electric vehicles, the DC voltage supplied to the power converter is determined by the overhead line voltage. The overhead line voltage is higher than the generator's output voltage. Therefore, when switching back and forth between overhead line and non-overhead line modes, it becomes difficult to control the excitation current for the generator's output voltage using a DC voltage. If the excitation current is not controlled accordingly, abrupt load fluctuations occur during mode switching, overloading the electric motor.An example of this "shock" is as follows: When switching from non-overhead line mode to overhead line mode, a drive unit performs a rapid rotation by applying an overhead line voltage that is higher than the generator's output voltage, resulting in an unintended acceleration of the dump truck. Conversely, when switching from overhead line mode to non-overhead line mode, a different type of shock occurs, such as a sudden deceleration of the dump truck.

[0007] Furthermore, the method described in patent literature 1 is silent on how the generator is controlled by the excitation current.

[0008] The present invention was made in view of the situation described above and its aim is to reduce the influence on the electric vehicle when switching between the first mode and the second mode.

[0009] This problem is solved by the invention specified in the claims.

[0010] Exemplary embodiments of the invention include a rectifier to convert the alternating current generated by a machine for torque production into direct current. A power converter is connected to connection points that receive direct current from the rectifier and direct current from a current collector, which draws direct current from an overhead line, in order to convert the direct current output at the connection point into alternating current, which is used to activate and operate an electric motor.

[0011] Next, during a switching period between a first mode, in which the direct current supplied by the rectifier is output to the power converter, and a second mode, in which the direct current supplied by the overhead line is output to the power converter, a control unit performs the following control functions. Based on a current value detected between the electric generator and a connection point, the control unit sends a command signal to an excitation unit, causing the excitation unit to output an excitation current to the generator. The control unit ensures that the sum of the direct current supplied by the rectifier and the direct current supplied by the overhead line equals the value of the direct current supplied by the rectifier in the first mode.

[0012] Furthermore, a changeover switch, which is connected between the pantograph and the connection point, works as follows: In the first mode, this switch blocks the direct current supplied by the overhead line, and in the second mode, the switch outputs the direct current supplied by the overhead line to the power converter.

[0013] According to this invention, the control unit is designed to control the excitation current to be output by the excitation unit to the electric generator on the basis of the current value detected between the generator and the connection point, thereby making it possible to switch smoothly between the first mode and the second mode and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows an explanatory diagram of an exemplary model with overhead line and non-overhead line mode zones according to an embodiment of the present invention. Fig. Figure 2 shows a block diagram of an exemplary internal structure of an overhead line tipper truck according to an embodiment of the present invention. Fig. Figure 3 shows an explanatory diagram of a control procedure for preparing an excitation current command that must be supplied by a control unit to an excitation unit, according to an embodiment of the present invention. Fig. Figure 4 shows an explanatory diagram of an exemplary control of DC voltage and DC current when switching from overhead line mode to non-overhead line mode according to an embodiment of the present invention. Fig. Figure 5 shows an explanatory diagram of an exemplary control of DC voltage and DC current when switching from non-overhead line mode to overhead line mode according to an embodiment of the present invention. Fig. 6A to Fig. Figure 6D shows explanatory diagrams of a modified example for the stepwise increase / decrease of the direct current output by the generator and the direct current supplied by the overhead line according to an embodiment of the present invention. DESCRIPTION OF THE EXECUTION FORMS

[0014] An exemplary embodiment of the present invention is described below with reference to the accompanying drawings. It should be noted that in the description and in the drawings, components or elements that have essentially the same functions or structure are designated by the same reference numerals, thus avoiding repetitive and lengthy explanations.

[0015] First, a tipper truck type 1 of the overhead line type is briefly described.

[0016] Fig. Figure 1 shows an explanatory diagram of an example with an overhead line mode zone and non-overhead line mode zones.

[0017] The overhead line dump truck 1 is used as an example of an electric vehicle. The dump truck 1 has a pantograph 5, which serves as a current collector. Inside this dump truck, there is also a motor 2, which serves as a torque-generating machine, an electric generator 3, which outputs the alternating current generated by the motor 2, and an electric motor 4 driven by the alternating current. For this motor 2, a diesel engine is used as an example of the torque-generating machine.

[0018] The dump truck 1 can move forwards and backwards and switch between two operating modes (i.e., overhead line mode and non-overhead line mode).

[0019] A land zone, where the dump truck 1 is driving on a level road, for example, is a non-overhead line mode zone, where it operates in non-overhead line mode. During this time, engine 2 is activated to drive electric generator 3 and thereby generate electrical energy. This current, output by generator 3, is then supplied to electric motor 4 to power the wheels, thus propelling the dump truck 1.

[0020] A section of track where the dump truck 1 climbs a steep incline is an overhead line mode zone, where it operates in overhead line mode. On this incline, using only the power of engine 2 would cause the dump truck 1 to slow down. To avoid this, the truck is switched to overhead line mode to draw current from the overhead lines 6. The pantograph 5 makes contact with the overhead lines 6 to draw direct current. The pantograph 5 then supplies the direct current drawn from the overhead lines 6 to the electric motor 4. In the overhead line mode zone, engine 2 is either deactivated or can alternatively be idled at a minimal speed. Because the overhead line dump truck 1 can operate without the assistance of engine 2 and generator 3, fuel consumption can be reduced.After overcoming the incline, the dump truck 1 travels again on a level road; at this point, it switches from overhead line mode to non-overhead line mode.

[0021] Fig. Figure 2 shows a block diagram of an exemplary internal structure of the overhead line tipper truck 1.

[0022] The dump truck 1 comprises a motor 2, an electric generator 3, a rectifier 7, a current detector 8, a voltage detector 9, a smoothing capacitor 10, a power converter 11, an electric motor 4, a gearbox 12, and wheels 13. The dump truck 1 also comprises a control unit 14, an excitation unit 15, a changeover switch 16, a voltage detector 17, a current detector 18, connection points 20, and an operating mode switching command unit 21.

[0023] A rectifier station 19 is planned and connected to the overhead lines 6.

[0024] Furthermore, the rectifier 7, the power converter 11, the control unit 14 and the switch 16 are also used as a generator control device that regulates the operation of the electric generator 3, although this is not shown in detail.

[0025] Examples of engine 2 also include an internal combustion engine, for example a diesel engine.

[0026] Generator 3 generates electric current by means of the rotation of a shaft (not shown) or similar device coupled to motor 2, in order to output alternating current. The alternating current output by generator 3 is rectified by rectifier 7.

[0027] Rectifier 7 converts the alternating current input from generator 3 into direct current. Rectifier 7 applies a DC voltage of a defined value to two output terminals (not shown).

[0028] The current detector 8 (first current detector) is connected between an output terminal of the rectifier 7 and the connection point 20. In non-overhead line mode, the current detector 8 outputs a DC current value, detected between the rectifier 7 and the connection point 20, to the control unit 14.

[0029] The voltage detector 9 is connected to the two output terminals of the rectifier 7. When the voltage detector 9 detects a DC voltage, the detected DC voltage value is transmitted to the control unit 14.

[0030] The smoothing capacitor 10 is connected in parallel to the rectifier 7. The smoothing capacitor 10 charges either the DC voltage supplied by the rectifier 7 or the DC voltage supplied via the switch 16 from the overhead line 6 and smooths the voltage.

[0031] The power converter 11 is connected in parallel to the smoothing capacitor 10 to convert the smoothed direct current output by the smoothing capacitor 10 into alternating current.

[0032] The electric motor 4 is driven by the alternating current output by the power converter 11 to drive the gearbox 12.

[0033] The wheels 13 are driven by the electric motor 4 via the gearbox 12, which makes the dump truck 1 move.

[0034] The control unit 14 receives a DC current value from the current detector 8 and a DC voltage value from the voltage detector 9. Based on these DC current and voltage values, the control unit 14 then determines the excitation current to be supplied by the excitation unit 15 to the generator 3. The control unit 14 outputs a command signal to the excitation unit 15 indicating the determined excitation current value. In electric vehicles such as the overhead line dump truck 1, the excitation current to be supplied to the generator 3 is regulated by feeding back the DC voltage obtained by rectifying the output voltage of the generator 3 using the rectifier 7.

[0035] The excitation unit 15 outputs the excitation current to the generator 3 based on the command signal received from the control unit 14 and controls the generator 3. It should be noted that the excitation current output by the excitation unit 15 to the generator 3 is monitored by the control unit 14. Therefore, if the excitation current becomes too high, the control unit 14 quickly detects the occurrence of a fault and issues a command to limit the excitation current to the excitation unit 15.

[0036] The changeover switch 16 is connected between the pantographs 5 and the connection points 20 to switch the energy source fed into the power converter 11 either to the overhead line 6 or the generator 3. In non-overhead line mode, the changeover switch 16 interrupts or disconnects the direct current supplied from the overhead line 6, while in overhead line mode it allows the output of the direct current supplied by the overhead line 6 to the power converter 11 via the connection points 20.

[0037] The voltage detector 17 detects the DC voltage between two current collectors 5 that are in contact with the overhead line 6 and outputs this DC voltage value to the control unit 14.

[0038] The current detector 18 (second current detector) is connected between a current collector 5, which is in contact with the overhead line 6, and the changeover switch 16. In overhead line mode, the current detector 18 outputs a DC current value, detected between the overhead line 6 and the changeover switch 16, to the control unit 14.

[0039] Rectifier station 19 remains in operation to rectify the direct current fed into the overhead lines 6.

[0040] The connection points 20 are used to receive the direct current from the rectifier 7 and the direct current from the current collectors 5. The changeover switch 16 is connected in parallel to the rectifier 7 and the smoothing capacitor 10 via the connection points 20.

[0041] The operating mode switching command unit 21 instructs the control unit 14 to switch between the non-overhead line mode, in which the direct current supplied by the rectifier 7 is output to the power transformer 11, and the overhead line mode, in which the direct current supplied by the overhead line 6 is output to the power transformer 11.

[0042] The following are operating examples of the respective parts of the dump truck 1.

[0043] In non-overhead line mode, switch 16 is off. At this time, motor 2 drives generator 3, which in turn outputs alternating current (AC). Generator 3 is connected to rectifier 7. This rectifier converts the AC output by generator 3 into direct current (DC) and outputs the converted DC. The DC output by rectifier 7 is smoothed by smoothing capacitor 10 and then converted back into AC by power converter 11. This AC is supplied to electric motor 4. Electric motor 4, connected to power converter 11, is coupled to wheels 13 via gearbox 12. When motor 4 drives gearbox 12, wheels 13 rotate, causing dump truck 1 to move forward and backward or accelerate.

[0044] In overhead line mode, the changeover switch 16 is switched on. At this time, the pantographs 5 are connected to the overhead line 6, whereby rectifier station 19 supplies directed direct current to the power converter 11 via the connection points 20. The power converter 11 converts the direct current supplied by overhead line 6 into alternating current. The power converter 11 then drives the electric motor 4. The electric motor 4 is coupled to the wheels 13 via the gearbox 12, which is why the motor 4 rotates the wheels 13. At this point, the motor 2 is idling, and no alternating current is output by the generator 3.

[0045] The voltage of the overhead line is detected by the voltage detector 17, and the current of the overhead line is detected by the current detector 18. The control unit 14 uses the voltage of the overhead line detected by the voltage detector 17 and the current of the overhead line detected by the current detector 18 to predict fluctuations in the direct current supplied by the overhead line, which is received by the overhead line 6, thus enabling smooth switching of the operating mode.

[0046] The following procedure has been used in overhead line electric vehicles. When switching from overhead line mode to non-overhead line mode, the motor 2, which is in its idle state, is switched on or activated, causing the generator 3 to output alternating current. The switching process then continues to gradually increase the direct current supplied by the rectifier 7 and, essentially simultaneously, to gradually decrease the direct current supplied by the overhead line 6, thus achieving a smooth change of operating mode.

[0047] In contrast, when switching from non-overhead line mode to overhead line mode, a control process is implemented to allow generator 3 to output alternating current and to gradually reduce the direct current supplied by rectifier 7. Subsequently, the switching process is carried out to gradually increase the direct current supplied by overhead line 6, thus ensuring a smooth change of operating mode.

[0048] However, when switching between overhead line mode and non-overhead line mode, the switch 16 is switched on. Because the connection points 20 are connected to the overhead line 6 via the switch 16 and the pantographs 5, the DC voltage detected by the voltage detector 9 is determined by the overhead line voltage.

[0049] A current output by known excitation units is regulated by the control unit 14 such that the DC voltage, directed by a rectifier corresponding to the rectifier 7 in the exemplary embodiment, is detected by the voltage detector 9 and the desired power can be output by the generator 3. Therefore, it was difficult to regulate the excitation current of the generator 3 solely by using the DC voltage reflecting the overhead line voltage detected by the voltage detector 9, in order to regulate the desired power output by the generator 3.

[0050] In contrast to the prior art, according to the present embodiment, the control unit 14, when switching from overhead line mode to non-overhead line mode, sends a command signal to the excitation unit 15 by means of an output current value detected by the current detector 8 between the generator 3 and the connection point 20. The control unit 14 thus regulates the excitation current supplied by the excitation unit 15 to the generator 3. This regulation ensures that the sum of the direct current supplied by the rectifier 7 and the direct current supplied by the overhead line 6 is equal to the value of the direct current that must be supplied by the rectifier 7 in non-overhead line mode.

[0051] The following is a detailed explanation of a control process to be executed by control unit 14 for generator 3.

[0052] Fig. Figure 3 shows an explanatory diagram of a control procedure to cause the output of an excitation current command from the control unit 14 to the excitation unit 15.

[0053] The control unit 14 has a subtractor 31, a proportional-integral controller (PI controller) 32, a subtractor 33, a PI controller 24 and a selector switch 35 with two inputs.

[0054] In non-overhead line mode, the control unit 14 performs the control by supplying an excitation current, derived from a generator DC control loop (using a DC voltage value detected by the voltage detector 9) to the generator 3, from the excitation unit 15. Conversely, in overhead line mode, the control unit 14 performs the control by supplying an excitation current, derived from a generator DC control loop (using a DC current value detected by the current detector 8) to the generator 3, from the excitation unit 15. Furthermore, the processing for the generator DC control loop, using the DC current value detected by the current detector 8, is also carried out during the transition periods from non-overhead line mode to overhead line mode.

[0055] Specifically, the generator DC voltage command for controlling the DC voltage output by generator 3 is supplied to the subtractor 31 as a positive or "plus" value. Simultaneously, a negative or "minus" value for the DC voltage output by generator 3, detected by voltage detector 9, is supplied as a DC feedback signal. A difference value obtained by subtracting the DC feedback signal from the generator DC voltage command is input to the PI controller 32. The PI controller 32 performs the PI control of a generator excitation current command (an example of the command signal). The generator excitation current command output by the PI controller 32 is transmitted to the two-input selector switch 35.

[0056] On the other hand, the generator DC command for controlling the DC current output by generator 3 is supplied as a positive value to the subtractor 33; a negative value for the DC current output by generator 3, detected by the current detector 8, is supplied as a DC feedback signal. A difference value obtained by subtracting the DC feedback signal from the generator DC command is input to the PI controller 34. The PI control is performed in the PI controller 34, which then outputs a generator excitation current command to the two-input selector switch 35.

[0057] A switching command is fed to the two-input selector switch 35, which is received by the operating mode switching command unit 21. This command specifies the currently set driving mode (i.e., overhead line mode or non-overhead line mode). Based on this switching command, the excitation unit 15 switches to one of the two PI controllers 32 or 34 and then receives an excitation current command according to the selected operating mode. For example, if the tipper 1 is in non-overhead line mode, the generator excitation current command, which has passed through the subtractor 31 and the PI controller 32, is fed to the excitation unit 15, causing the excitation unit 15 to output an excitation current.Alternatively, if the tipper is in overhead line mode, the generator excitation current command, which has passed through the subtractor 33 and the PI controller 34, is supplied to the excitation unit 15, resulting in the excitation current being output by the excitation unit 15 and then supplied to the generator 3.

[0058] The following is an example of the temporal sequence of voltage and current values ​​in the case of alternating switching between overhead line mode and non-overhead line mode, with reference to Fig. 4 and Fig. 5 described.

[0059] Fig. Figure 4 shows an explanatory diagram of an exemplary control of direct current and direct voltage when switching from overhead line mode to non-overhead line mode.

[0060] Typically, a switching time of a few seconds is required to switch from overhead line mode to non-overhead line mode and from non-overhead line mode to overhead line mode.

[0061] In overhead line mode, the switch 16 is turned on according to the instruction of the control unit 14. At this time, the DC voltage applied to the power converter 11 is essentially equal to the overhead line voltage. On the other hand, the generator 3 is only producing a minimum of its current, so that the DC voltage output by the generator 3 and rectified by the rectifier 7 is almost zero. At this time, the DC current supplied by the overhead line, fed in by the overhead line 6, has a constant value determined by the overhead line voltage, while the DC current output by the generator 3 is almost zero.

[0062] At the beginning of the switchover from overhead line mode to non-overhead line mode, the direct current supplied by the overhead line is forcibly and gradually reduced, while conversely, the direct current output by the generator is gradually and gradually increased. In this context, the point at which the reduction of the direct current supplied by the overhead line begins precedes the point at which the increase of the direct current output by the generator occurs. This is done to prevent a sudden change in the current applied to electric motor 4 during the rapid switchover from the direct current supplied by the overhead line to the direct current output by the generator, given that the direct current supplied by the overhead line is greater than the direct current output by the generator.

[0063] In a Fig. In the first switching period 41 shown in Figure 4, the direct current supplied by the overhead line is forcibly reduced stepwise. At the beginning of this stepwise reduction of the direct current supplied by the overhead line, the direct current supplied to the power converter 11 is subject to turbulence.

[0064] Subsequently, in a second switching period 42, when the power value of the DC current supplied by the overhead line drops to the target power value of generator 3 in non-overhead line mode, the DC current output by the generator is forcibly increased. It should be noted that at the moment of transition between the first and second switching periods 41 and 42, the directed output voltage of generator 3 is potentially increased until it is essentially equal to the overhead line voltage. The control unit 14 provides the regulation in the second switching period 42, such that the sum of the DC current supplied by the overhead line and the DC current output by the generator is kept stably equal to a value 43 of the DC current output by the generator that is to be supplied by generator 3 in non-overhead line mode.

[0065] Then, at the point in time when the direct current supplied by the overhead line becomes almost zero (that is, after the second switching period 42 has elapsed), the switch 16 changes its state from on to off. The switching from overhead line mode to non-overhead line mode is thus complete.

[0066] Fig. Figure 5 shows an explanatory diagram of an exemplary control of DC voltage and DC current when switching from non-overhead line mode to overhead line mode.

[0067] In non-overhead line mode, motor 2 is activated or "woken up" so that generator 3 can generate current, causing it to output a DC voltage. At this point, the DC voltage supplied to power converter 11 has a lower potential value than the overhead line voltage.

[0068] When switching from non-overhead line mode to overhead line mode, the switch 16 changes from off to on at the point when the DC voltage is essentially equal to the overhead line voltage. This switching point of the switch 16 becomes the start time of the first switching period 44. During the first switching period 44, the directed output voltage of the generator 3 is increased until it is almost equal to the overhead line voltage. During the first switching period 44, the DC current output by the generator is forcibly and gradually decreased, while the DC current supplied by the overhead line is gradually increased.When switching from non-overhead line mode to overhead line mode, the point in time at which the direct current supplied by the overhead line is caused to begin to decrease is essentially the same as the point in time at which the direct current output by the generator is caused to begin to increase.

[0069] Then a second switching period 45 occurs, close to the switchover point for the overhead line mode. During this second switching period 45, motor 2 is switched off. Fig. Generator 1 is switched to its no-load position at the point when the direct current output by the generator becomes almost zero. This allows generator 3 to perform a minimal current generation, thus enabling the output voltage of generator 3 to become almost zero.

[0070] On the other hand, in overhead line mode, the DC voltage supplied to the power converter 11 becomes almost equal to the overhead line voltage. In the second switching period 45, the DC current supplied by the overhead line is approximated to a value that can be obtained from the overhead line voltage, as shown in Fig. 5 shown.

[0071] While switch 16 is energized, the DC voltage is essentially equal to the overhead line voltage. Consequently, during the increase / decrease of the generator output power, the generator excitation current is regulated by feeding back the DC current output by the generator, thus controlling the magnitude of the DC current output by the generator. Optionally, the regulation of the generator excitation current can also be achieved by feeding back the DC current supplied by the overhead line instead of the DC current from generator 3.

[0072] The dump truck 1 according to the embodiment described above is specifically designed to regulate the excitation current based on a current value that is detected between the generator 3 and the connection point 20 at the time of switching between the overhead line mode and the non-overhead line mode and vice versa. This enables a smooth switching between these operating modes.

[0073] In particular, the control unit 14 regulates the excitation current supplied to the generator 3 by the excitation unit 15, based on a current value recorded between the generator 3 and the connection point 20 during the switching periods between the non-overhead line mode and the overhead line mode. This regulation is intended to ensure that the sum of the direct current supplied by the rectifier 7 and the direct current supplied by the overhead line 6 is essentially equal to the value of the direct current supplied by the rectifier 7 in the non-overhead line mode. This ensures that no rapid fluctuations are transmitted to the electric motor 4 during the switch between the non-overhead line mode and the overhead line mode.

[0074] Control unit 14 is also configured to output the generator excitation current command in non-overhead line mode, which is obtained by PI control of the generator DC command using a DC feedback signal. Alternatively, in overhead line mode, this control unit outputs the generator excitation current command, which is obtained by PI control of the generator DC command using a DC feedback signal. By selecting a suitable feedback signal according to the mode activated in this way, it is possible to successfully control the excitation current supplied to generator 3.

[0075] Furthermore, the current detector 8 is provided between the rectifier 7 and the connection point 20 to output the current value of any current flowing between the rectifier 7 and the connection point 20 to the control unit 14. This makes it possible to reliably distinguish between current values ​​to be detected in non-overhead line mode and in overhead line mode. This, in turn, makes it possible to control the generator 3 according to the activated mode.

[0076] Furthermore, it is important that the control unit 14 supplies the command signal to the excitation unit 15 to ensure that the output power between the connection points 20 from the generator 3 increases or decreases gradually. This makes it easier to keep the sum of the DC current supplied by the overhead line and the DC current output by the generator at a constant value during switching events in overhead line mode / non-overhead line mode. This prevents the sum from fluctuating abruptly, so that no rapid changes or "shocks" are transmitted to the electric motor 4.

[0077] Although the embodiment described above is designed to carry out a stepwise increase / decrease of the direct current output by the generator and the direct current supplied by the overhead line, it is also permissible to vary the direct current continuously at a constant rate of change.

[0078] Fig. 6A to Fig. Figure 6D shows explanatory diagrams of a modified example illustrating the stepwise increase / decrease of the direct current output by the generator and the direct current supplied by the overhead line. These diagrams explain the changes in electrical energy during the switchover from overhead line mode to non-overhead line mode.

[0079] Fig. 6A and Fig. 6B shows explanatory diagrams for examples where the step change amount varies over time during the step increase / decrease.

[0080] In these examples, the control unit 14 delivers its command signal to the excitation unit 15, while simultaneously varying the stepwise change amount during the execution of the stepwise increase / decrease.

[0081] In the Fig. In the example shown in Figure 6A, the control unit 14 first reduces the direct current supplied by the overhead line by a specific amount and then, in the next step, increases the reduction by a factor greater than the specified amount. Subsequently, the control unit increases the reduction amount of the direct current supplied by the overhead line once per step until the direct current supplied by the overhead line approaches zero. By varying the reduction amount of the direct current supplied by the overhead line in this way, it is possible to prevent the electric motor 4 from being undesirably affected during operating mode switching events.

[0082] In the Fig. In the example shown in Figure 6B, the control unit 14 first reduces the direct current supplied by the overhead line by a specific amount and then, in the next step, increases the reduction by a factor greater than the amount specified above. Subsequently, the reduction is increased once per step. Then, when the direct current supplied by the overhead line approaches zero, the reduction is decreased. With this system, even in cases where the difference between the direct current supplied by the overhead line and the direct current output by the generator is relatively large, the time required for switching power can be reduced by ensuring smooth power switching.

[0083] Fig. Figure 6C shows an explanatory diagram for an example where the rate of change of electrical energy is kept constant over time.

[0084] In the Fig. In the example shown in Figure 6C, the control unit 14 provides the command signal to the excitation unit 15 by increasing or decreasing the output power between the connection points 20 of the generator 3, while keeping the rate of change of the output power constant. For example, the control unit 14 causes the direct current supplied by the overhead line to decrease moderately at a constant rate of change. It also causes the direct current output by the generator to increase gradually at a fixed rate of change. With this approach, it is possible to reduce the influence on the electric motor 4 when switching between the direct current supplied by the overhead line and the direct current output by the generator.

[0085] Fig. Figure 6D shows an explanatory diagram for an example where the rate of change of electrical energy varies over time.

[0086] In the Fig.In the example shown in Figure 6D, the control unit 14 sends the command signal to the excitation unit 15, while subsequently varying the rate of change for the output power between the connection points 20 of the generator 3. For example, the control unit 14 varies the rate of change for the reduction of the DC current supplied by the overhead line midway through. The control unit 14 varies the rate of change such that the gradient of a curve is increased at the beginning and then decreased again halfway through. As the gradient decreases, the DC current output by the generator is regulated to increase moderately at a constant rate of change. With this approach, even in cases where the difference between the DC current supplied by the overhead line and the DC current output by the generator is large, it is possible to shorten the time required for switching power by rapidly switching the power.

[0087] Although the dump truck 1 described above has been mentioned as an example of electrically powered vehicles with an internal combustion engine, the principles of this invention can also be applied to various other types of land vehicles, including buses, crane trucks, etc.

[0088] Furthermore, it should be noted that although the control unit 14 is set up to perform PI control based on generator DC voltage / DC current commands in order to output the generator excitation current command, this control unit can also be modified to work with other control methods for outputting the generator excitation current command.

[0089] Although a specific example has been described where a diesel engine is used as engine 2, other types of engines can also be used, including gasoline engines, hydrogen engines, fuel cells and battery-powered engines.

[0090] Furthermore, current detectors 8 and 18 are designed so that at least one of them is used. This makes it possible to reduce the weight of the dump truck 1 while simultaneously reducing the electrical energy required for it.

[0091] While the present invention has been shown and described with particular reference to the currently preferred embodiments thereof, it is evident to the person skilled in the art that the foregoing and other changes relating to form and details can be made to it without deviating from the idea of ​​the invention as defined in the attached patent claims.

[0092] For example, the embodiments mentioned above are those used to provide a detailed and concrete explanation of the system or device configurations, in order to explain the concepts of the disclosed invention in an easily understandable way, and the invention should not be limited to the single embodiment that includes all the components described herein. Furthermore, a part of one embodiment is interchangeable with the corresponding part of another embodiment, and it is also possible to add a configuration from one embodiment to that of another. Naturally, with respect to any part of the configuration of each embodiment, it is possible to add, omit, or exchange other configurations.

[0093] The aforementioned configurations, functions, processing units, and other elements can be implemented wholly or partially, for example, by hardware with integrated circuits. Alternatively, each configuration and function can also be implemented by software, using a processor to interpret and execute the programs that perform the respective functions. These programs for implementing the respective functions, along with their associated data such as tables and files, can be stored in storage devices such as semiconductor memory, hard disk drives (HDDs), solid-state drives (SSDs), etc., or alternatively, stored on data carriers such as chip cards, SD cards, DVDs, or the like.

[0094] The control lines and / or data lines shown indicate those lines that are assumed to be necessary for the explanation; it is not necessarily intended to represent all control and data lines used in actually manufactured products. It can also be assumed that almost all configurations are interconnected in practical implementations.

Claims

[1] Electric vehicle (1) comprising: a machine for generating torque (2), an electric generator (3) driven by the machine to generate torque, for outputting a generated alternating current, an excitation unit (15) for outputting an excitation current to the electrical generator on the basis of a command signal, a rectifier (7) for converting the alternating current output by the electric generator into direct current, a pantograph (5) for drawing direct current from overhead lines (6), a power converter (11) which is connected to connection points (20) for receiving direct current from the rectifier and direct current from the current consumer, for converting the direct current output at the connection points into alternating current, an electric motor (4) driven by the alternating current output by the power converter, Wheels (13) driven by the electric motor, a control unit (14) for supplying the command signal to the excitation unit (15) in a time period for switching between a first mode in which the direct current supplied by the rectifier (7) is output to the power transformer (11) and a second mode in which the direct current supplied by the overhead lines (6) is output to the power transformer (11), and a changeover switch (16) which is connected between the pantograph (5) and the connection points (20) to block the direct current supplied by the overhead lines (6) in the first mode and to output the direct current supplied by the overhead lines (6) from the connection points (20) to the power converter (11) in the second mode, characterized by a first current detector (8) for detecting a current value between the rectifier (7) and one of the connection points (20), wherein the control unit (14) is set up: In the first mode of the excitation unit (15), a command signal is supplied, which, when executing a PI control, is obtained from a DC voltage value taken between the rectifier (7) and the power converter (11) and a generator DC voltage command, in order to control the DC voltage output by the electric generator (3), In the second mode of the excitation unit (15), a command signal is supplied, which, when executing PI control, is obtained from the DC value detected by the current detector (8) between the rectifier (7) and the connection point (20), and a generator DC command, in order to control the DC current output by the electric generator (3), and During the time period for switching between the first and second modes of the excitation unit (15), a command signal is to be supplied based on the detected current value, such that the sum of the direct current supplied by the rectifier (7) and the direct current supplied by the overhead lines (6) is equal to a value of the direct current supplied by the rectifier (7) in the first mode. [2] Electric vehicle according to claim 1, comprising: the first current detector (8) which is connected between the rectifier (7) and the connection point (20), and a second current detector (18) which is connected between the overhead lines (6) and the changeover switch (16), wherein the first current detector (8) in the first mode outputs a DC current value detected between the rectifier (7) and the connection point (20) to the control unit (14), and In the second mode, the second current detector (18) outputs a direct current value, detected between the overhead lines (6) and the switch (16), to the control unit (14). [3] Electric vehicle according to claim 2, wherein the control unit (14) provides the command signal such that the output power of the generator (3) increases or decreases stepwise between the connection points (20). [4] Electric vehicle according to claim 3, wherein the control unit (14) provides the command signal while causing the amount of change of each step to vary in the middle. [5] Electric vehicle according to claim 2, wherein the control unit (14) provides the command signal such that the output power of the generator (3) increases or decreases between the connection points (20) while ensuring that the output power remains constant in its rate of change. [6] Electric vehicle according to claim 2, wherein the control unit (14) provides the command signal by varying the rate of change for the output power of the generator (3) between the connection points (20) in the middle. [7] Generator control device comprising: a rectifier (7) for converting alternating current generated by an electric generator (3) driven by a torque-generating machine (2) into direct current, a power converter (11) connected to connection points (20) for receiving direct current from the rectifier and direct current from a current collector (5) that draws direct current from overhead lines (6), for converting the direct current output from the connection points into alternating current and for using the alternating current to drive an electric motor (4), a control unit (14) for supplying a command signal to an excitation unit (15) in a time period for switching between a first mode in which the direct current supplied by the rectifier (7) is output to the power transformer (11) and a second mode in which the direct current supplied by the overhead lines (6) is output to the power transformer (11), wherein: In the first mode, a command signal is supplied to the excitation unit (15), which, when executing a PI control, is obtained from a DC voltage value tapped between the rectifier (7) and the power converter (11) and a generator DC voltage command in order to control the DC voltage output by the electric generator (3), In the second mode, a command signal is supplied to the excitation unit (15), which, when executing PI control, is obtained from a DC value detected by a current detector (8) between the rectifier (7) and one of the connection points (20), and a generator DC command to control the DC current output by the electric generator (3), and The excitation unit (15) receives a command signal based on the detected current value during the time period for switching between the first and second modes, such that the sum of the direct current supplied by the rectifier (7) and the direct current supplied by the overhead lines (6) is equal to a value of the direct current supplied by the rectifier (7) in the first mode. which causes the excitation unit (15) to output an excitation current to the electrical generator (3), and a changeover switch (16) which is connected between the pantograph (5) and the connection points (20) to block the direct current supplied by the overhead lines (6) in the first mode, and to output the direct current supplied by the overhead lines (6) from the connection points (20) to the power converter (11) in the second mode. [8] Generator control method comprising the steps: Causing a rectifier (7) to convert alternating current generated by an electric generator (3) driven by a torque-generating machine (2) into direct current, Causing a power converter (11), which is connected to connection points (20) for receiving direct current from the rectifier and direct current from a current collector (5) that draws direct current from overhead lines (6), to convert the direct current output from the connection points (20) into alternating current and to drive an electric motor (4) with the alternating current, Supplying a command signal to an excitation unit (15) in a time period to switch between a first mode in which the direct current supplied by the rectifier (7) is output to the power transformer (11) and a second mode in which the direct current supplied by the overhead lines (6) is output to the power transformer (11), wherein: In the first mode, a command signal is supplied to the excitation unit (15), which, when executing a PI control, is obtained from a DC voltage value tapped between the rectifier (7) and the power converter (11) and a generator DC voltage command in order to control the DC voltage output by the electric generator (3), In the second mode, a command signal is supplied to the excitation unit (15), which, when executing PI control, is obtained from a DC value detected by a current detector (8) between the rectifier (7) and one of the connection points (20), and a generator DC command to control the DC current output by the electric generator (3), and The excitation unit (15) receives a command signal based on the detected current value during the time period for switching between the first and second modes, such that the sum of the direct current supplied by the rectifier (7) and the direct current supplied by the overhead lines (6) is equal to a value of the direct current supplied by the rectifier (7) in the first mode. which causes the excitation unit (15) to output an excitation current to the electrical generator (3), and Causing a changeover switch (16) which is connected between the pantograph (5) and the connection points (20) to operate in the first mode in such a way that the direct current supplied by the overhead lines (6) is blocked, and in the second mode in such a way that the direct current supplied by the overhead lines (6) is output from the connection points (20) to the power converter (11).

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