Control circuits, electric vehicles, control methods, and programs

Abstract

The present invention provides a control circuit capable of improving wheel slippage in electric vehicles. [Solution] The control circuit includes a control unit configured to control an inverter corresponding to the axle connected to a wheel that is slipping among the wheels of the electric vehicle.

Description

Technical Field

[0001] The present disclosure relates to a control circuit, an electric vehicle, a control method, and a program.

Background Art

[0002] As an electric vehicle in a transportation system such as an Automated Guideway Transit (AGT) or an Automated People Mover (APM), there is an electric vehicle that runs using electric power supplied from an overhead line. Patent Document 1 discloses a technique related to voltage switching control of an electric vehicle as a related technique.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an electric vehicle that runs using electric power supplied from an overhead line, a technique capable of improving wheel spin for safe running is required.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a control circuit, an electric vehicle, a control method, and a program.

Means for Solving the Problems

[0006] In order to solve the above problems, a control circuit according to the present disclosure includes a control unit configured to control an inverter corresponding to an axle connected to a wheel that is spinning among the wheels provided in an electric vehicle.

[0007] The electric vehicle relating to this disclosure comprises the above-described control circuit and an inverter controlled by the control circuit.

[0008] The control method relating to this disclosure includes controlling an inverter corresponding to the axle connected to a wheel that is slipping among the wheels of an electric vehicle.

[0009] The program relating to this disclosure causes a computer to control an inverter corresponding to the axle connected to a wheel that is slipping among the wheels of an electric vehicle. [Effects of the Invention]

[0010] According to the control circuit, electric vehicle, control method, and program relating to this disclosure, it is possible to improve wheel slippage of an electric vehicle. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the configuration of the transportation system according to the first embodiment of this disclosure. [Figure 2] This figure shows an example of the configuration of a control circuit according to the first embodiment of this disclosure. [Figure 3] This figure shows an example of the configuration of a transportation system according to a first modification of the first embodiment of the present disclosure. [Figure 4] This figure shows an example of the configuration of a control circuit according to a first modification of the first embodiment of the present disclosure. [Figure 5] This figure shows an example of the processing flow of a traffic system according to a first modification of the first embodiment. [Figure 6] This figure shows an example of the configuration of a DAB circuit according to a second modification of the first embodiment of the present disclosure. [Figure 7] This is the first diagram to illustrate the problems that arise when controlling a typical DAB-type DC-DC converter. [Figure 8] This is the second diagram, illustrating the problems that arise when controlling a typical DAB-type DC-DC converter. [Figure 9] It is the third figure for explaining the problems that occur when controlling a general DAB - type DC - DC converter. [Figure 10] It is the first figure for explaining the control content of the control unit according to the third modification example of the first embodiment. [Figure 11] It is the second figure for explaining the control content of the control unit according to the third modification example of the first embodiment. [Figure 12] It is the third figure for explaining the control content of the control unit according to the third modification example of the first embodiment. [Figure 13] It is the fourth figure for explaining the control content of the control unit according to the third modification example of the first embodiment. [Figure 14] It is the fifth figure for explaining the control content of the control unit according to the third modification example of the first embodiment. [Figure 15] It is the first figure showing an example of the waveform of the simulation for charging the capacitor according to the third modification example of the first embodiment. [Figure 16] It is the second figure showing an example of the waveform of the simulation for charging the capacitor according to the third modification example of the first embodiment. [Figure 17] It is the third figure showing an example of the waveform of the simulation for charging the capacitor according to the third modification example of the first embodiment. [Figure 18] It is a figure showing an example of the configuration of a traffic system according to the second embodiment of the present disclosure. [Figure 19] It is a figure showing an example of the configuration of a DC - DC converter according to the second embodiment of the present disclosure. [Figure 20] It is a schematic block diagram showing the configuration of a computer according to at least one embodiment. [Figure 21] It is a figure showing an example of the configuration of a traffic system that is a comparison target of the traffic systems according to the respective embodiments of the present disclosure. [Figure 22] It is a figure showing an example of the configuration of a VFD inverter used in a traffic system that is a comparison target of the traffic systems according to the respective embodiments of the present disclosure. [Modes for carrying out the invention]

[0012] First, we will describe the transportation system 1a that is used as a comparison for each embodiment of the transportation system 1.

[0013] (Configuration of the transportation systems being compared) Figure 21 shows an example of the configuration of a comparable transportation system 1a to the transportation system 1 according to each embodiment of the present disclosure. As shown in Figure 21, the transportation system 1a comprises an overhead line 10, an electric vehicle 20a, and a higher-level system 30.

[0014] The overhead line 10 supplies power to the electric vehicle 20a. For example, the overhead line 10 supplies power to the electric vehicle 20a at a predetermined DC voltage (for example, a DC voltage (nominal voltage) of 750V). This predetermined DC voltage can fluctuate significantly. For example, Section 5.2.1 of the Japanese Industrial Standards (JIS) lists Table 0A, the standard voltage and frequency of overhead lines and their fluctuation ranges, with Type 1 specifying a maximum voltage of 900V and a minimum voltage of 500V for a DC voltage of 750V. In other words, for an overhead line voltage with a standard DC voltage of 750V, the voltage can fluctuate from 500V to 900V. The higher-level system 30 outputs a torque command to the electric vehicle 20a.

[0015] The electric vehicle 20a operates using power supplied from the overhead line 10 via the pantograph 203a. As shown in Figure 21, the electric vehicle 20a comprises a vehicle body 201a, wheels 202a1, 202a2, pantograph 203a, motors 204a1, 204a2, a VVVF (Variable Voltage Variable Frequency) inverter 205a, an APU (Auxiliary Power Unit) 206a, transformers 207a1, 207a2, 207a3, motors 208a1, 208a2, 208a3, an HVAC (Heating, Ventilation, and Air Conditioning) compressor 209, a brake air compressor 210, a cooling fan 211, accessories 212, a rectifier circuit 213a, a control power supply 214a, and a control circuit 215a.

[0016] The vehicle body 201a houses motors 204a1 and 204a2, VVVF inverters 205a, APU 206a, transformers 207a1, 207a2, and 207a3, motors 208a1, 208a2, and 208a3, HVAC compressor 209a, brake air compressor 210a, cooling fan 211a, accessories 212a, rectifier circuit 213a, control power supply 214a, and control circuit 215a.

[0017] Wheel 202a1 is, for example, two front wheels. Wheel 202a2 is, for example, two rear wheels. Each of wheels 202a1 and 202a2 has, for example, a rubber tire.

[0018] Pantograph 203a receives power supplied from the overhead line 10. The power received by pantograph 203a is supplied to the VVVF inverter 205a and APU 206a.

[0019] Motors 204a1 and 204a2 drive wheels 202a1 and 202a2. For example, motor 204a1 rotates wheel 202a1 in accordance with the AC voltage output from VVVF inverter 205a. Similarly, motor 204a2 rotates wheel 202a2 in accordance with the AC voltage output from VVVF inverter 205a.

[0020] The VVVF inverter 205a converts DC voltage to AC voltage. The VVVF inverter 205a is a VVVF inverter for railway vehicles and is composed of electronic components with a higher voltage rating (e.g., 1700V) compared to the electronic components used in inverters for EVs (Electric Vehicles) and general-purpose inverters (e.g., 1200V). Examples of electronic components include resistors, capacitors, inductors, and semiconductor elements such as diodes and transistors.

[0021] Figure 22 shows an example of the configuration of a VVVF inverter 205a used in a comparative traffic system 1a according to each embodiment of the present disclosure. As shown in Figure 22, the VVVF inverter 205a comprises a switching circuit 2051a and a control circuit 2052a.

[0022] The switching circuit 2051a, under the control of the control circuit 2052a, performs a switching operation to convert the DC voltage supplied from the overhead line 10 into AC voltage for supplying to the motors 204a1 and 204a2.

[0023] As shown in Figure 22, the control circuit 2052a comprises a detection unit 2052a1 and a control unit 2052a2. The detection unit 2052a1 detects the change in rotational speed (acceleration) of motors 204a1 and 204a2. For example, the detection unit 2052a1 detects these changes in rotational speed as a change in the frequency of the motor current flowing through motors 204a1 and 204a2. Alternatively, the detection unit 2052a1 may detect the change in rotational speed (acceleration) of motors 204a1 and 204a2 using a rotational speed sensor capable of detecting the rotational speed of the motors.

[0024] The control unit 2052a2 switches the switching circuit 2051a to obtain a torque corresponding to the torque command from the higher-level system 30. The VVVF inverter 205a has a function to improve wheel slippage when it detects that the wheels 202a1 and 202a2 are slipping. The function to improve wheel slippage is performed when the control unit 2052a2 detects wheel slippage (i.e., when it is determined that the change in the frequency of the motor current flowing to motors 204a1 and 204a2 exceeds an allowable value, or when it is determined that the difference in rotational speed between multiple motors (in this case, motors 204a1 and 204a2) exceeds an allowable value), and controls the motor 204a1 or motor 204a2 whose change in the frequency of the motor current is determined to exceed an allowable value to reduce the current value (i.e., reduce the torque of motor 204a1 or motor 204a2). Control that reduces the motor speed to improve wheel slippage when such slippage is detected is called "slip-re-adhesion control" or "slip-detection / re-adhesion control."

[0025] The APU206a converts DC voltage to AC voltage. The converted AC voltage output by the APU206a has a fixed amplitude and frequency. The APU206a is used as an auxiliary power supply. Like the VVVF inverter 205a, the APU206a is composed of electronic components with a higher voltage rating (e.g., 1700V) than the electronic components used in inverters for EVs and general-purpose inverters (e.g., 1200V). Since high-voltage (e.g., 1700V) electronic components are expensive, the manufacturing cost of the APU206a is reduced by combining the auxiliary power supply units that use high-voltage electronic components used in electric vehicles 20a into a single unit, the APU206a shown in Figure 21.

[0026] Transformer 207a1 converts the AC voltage output by APU 206a into an AC voltage capable of driving motors 208a1, 208a2, and 208a3. Transformer 207a2 converts the AC voltage output by APU 206a into an AC voltage capable of supplying to accessory 212a. Transformer 207a3 converts the AC voltage output by APU 206a into an AC voltage such that the DC voltage rectified by rectifier circuit 213a is large enough to supply to control power supply 214a.

[0027] Motor 208a1 drives the HVAC compressor 209a. Motor 208a1 rotates in accordance with the AC voltage output by transformer 207a1, which has a fixed amplitude and frequency. In other words, motor 208a1 rotates at a fixed rotational speed.

[0028] Motor 208a2 drives the brake air compressor 210. Motor 208a2 rotates at a fixed speed, similar to motor 208a1.

[0029] Motor 208a3 drives the cooling fan 211. Motor 208a3 rotates at a fixed speed, similar to motors 208a1 and 208a2.

[0030] The HVAC compressor 209a draws in the refrigerant evaporated in the air conditioner of the electric vehicle 20a and converts it back into a liquid. The brake air compressor 210a generates compressed air to operate the pneumatic equipment for braking the electric vehicle 20a. The cooling fan 211a cools the heat-generating parts within the vehicle body 201a by circulating air around them.

[0031] Accessory 212a operates using a fixed amplitude and frequency AC voltage output by transformer 207a1 as its power source. Examples of accessory 212a include communication equipment, defrosters, and other devices that operate by being powered via an electrical outlet.

[0032] The rectifier circuit 213a rectifies the AC voltage with fixed amplitude and frequency output by the transformer 207a3 and outputs a DC voltage after rectification. An example of the rectifier circuit 213a is a diode bridge circuit.

[0033] The control power supply 214a generates a voltage (for example, 110V) for the control circuit 215a from the DC voltage output by the rectifier circuit 213a, and supplies the generated voltage to the control circuit 215a.

[0034] The control circuit 215a controls the electric vehicle 20a. As shown in Figure 21, the control circuit 215a includes a control unit 215a1. For example, the control unit 215a1 controls the VVVF inverter 205a and the APU 206a. Specifically, the control unit 215a1 generates a PWM (Pulse Width Modulation) signal for each of the VVVF inverter 205a and the APU 206a, and controls the AC voltage output by the VVVF inverter 205a and the APU 206a by controlling them with the generated PWM signal. The control unit 215a1 also controls communication between the electric vehicle 20a and the higher-level system 30.

[0035] The higher-level system 30 controls the movement of the electric vehicle 20a in the traffic system 1a. For example, the higher-level system 30 outputs a torque command to the electric vehicle 20a, and the electric vehicle 20a moves according to that torque command.

[0036] The above describes the comparison of the transportation system 1a with respect to each embodiment of the transportation system 1 of this disclosure. The electric vehicle 20a described above is composed of high-voltage (e.g., 1700V) electronic components such as the VVVF inverter 205a and APU 206a. In addition, the VVVF inverter 205a has a function to improve wheel slippage, which is not normally provided in inverters. As a result, the VVVF inverter 205a is expensive, and consequently the electric vehicle 20a is also expensive. Furthermore, as described above, since the auxiliary power supply unit using high-voltage electronic components used in the electric vehicle 20a is combined into one APU 206a, the motors 208a1, 208a2, and 208a3 rotate at a fixed rotational speed. As a result, the driving efficiency of the motors 208a1, 208a2, and 208a3 is lower than the driving efficiency when the motors 208a1, 208a2, and 208a3 are driven by an inverter with a variable frequency.

[0037] <First Embodiment> The embodiments will be described in detail below with reference to the drawings. First, the traffic system 1 according to the first embodiment of this disclosure will be described.

[0038] (Configuration of the transportation system) Figure 1 shows the configuration of a traffic system 1 according to a first embodiment of the present disclosure. As shown in Figure 1, the traffic system 1 comprises an overhead line 10, an electric vehicle 20, and a higher-level system 30. The traffic system 1 is a system in which an isolated DC-DC converter is provided between the overhead line 10 and the electric vehicle 20, and only the electronic components on the overhead line 10 side of the DC-DC converter are high-voltage (e.g., 1700V), thereby reducing the number of high-voltage electronic components to that of a comparable electric vehicle 20a.

[0039] The overhead line 10 supplies power to the electric vehicle 20. For example, the overhead line 10 supplies power to the electric vehicle 20 at a predetermined DC voltage (for example, a DC voltage (nominal voltage) of 750V). This predetermined DC voltage can fluctuate significantly. For example, in an overhead line with a standard voltage of DC 750V, the voltage can fluctuate from 500V to 900V.

[0040] The electric vehicle 20 operates using power supplied from the overhead line 10 via the pantograph 203a. As shown in Figure 1, the electric vehicle 20 comprises a vehicle body 201a, wheels 202a1, 202a2, pantograph 203a, motors 204a1, 204a2, motors 208a1, 208a2, 208a3, HVAC compressor 209a, brake air compressor 210a, cooling fan 211a, accessories 212a, control power supply 214a, control circuit 215, DC-DC converter 216a, inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a.

[0041] The vehicle body 201a houses motors 204a1, 204a2, motors 208a1, 208a2, 208a3, HVAC compressor 209a, brake air compressor 210a, cooling fan 211a, accessory 212a, control power supply 214a, DC-DC converter 216a, inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a, respectively.

[0042] Wheel 202a1 is, for example, two front wheels. Wheel 202a2 is, for example, two rear wheels. Each of wheels 202a1 and 202a2 has, for example, a rubber tire.

[0043] The pantograph 203a receives power supplied from the overhead wire 10. The power received by the pantograph 203a is supplied to the DC-DC converter 216a.

[0044] Motors 204a1 and 204a2 drive wheels 202a1 and 202a2. For example, motor 204a1 rotates wheel 202a1 in accordance with the AC voltage output from inverter 217a1. Similarly, motor 204a2 rotates wheel 202a2 in accordance with the AC voltage output from inverter 217a2.

[0045] Motor 208a1 drives the HVAC compressor 209a. Motor 208a1 rotates in accordance with the AC voltage output by inverter 217a3.

[0046] Motor 208a2 drives the brake air compressor 210a. Motor 208a2 rotates in accordance with the AC voltage output by inverter 217a4.

[0047] Motor 208a3 drives the cooling fan 211a. Motor 208a3 rotates in accordance with the AC voltage output by inverter 217a5.

[0048] The HVAC compressor 209a draws in the refrigerant evaporated in the air conditioner of the electric vehicle 20 and converts it back into a liquid. The brake air compressor 210a generates compressed air to operate the pneumatic equipment for braking the electric vehicle 20. The cooling fan 211 cools the heat-generating parts within the vehicle body 201a by circulating air around them.

[0049] Accessory 212a operates using the AC voltage output from inverter 217a6 as its power source. Examples of accessory 212a include communication equipment, defrosters, and other devices that operate by being powered via an electrical outlet.

[0050] The control power supply 214a generates a voltage for the control circuit 215 from the DC voltage output by the DC-DC converter 218a, and supplies the generated voltage to the control circuit 215.

[0051] The control circuit 215 controls the electric vehicle 20. Figure 2 shows an example of the configuration of the control circuit 215 according to the first embodiment of the present disclosure. As shown in Figure 2, the control circuit 215 includes a control unit 2151.

[0052] The control unit 2151 controls the DC-DC converter 216a, inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a. Specifically, the control unit 2151 generates a PWM signal for each of the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and controls the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6 using the generated PWM signals, thereby controlling the AC voltage output by each of the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6. Specifically, the control unit 2151 controls the DC voltage output by the DC-DC converter 218a by chopper-controlling the switching elements of the DC-DC converter 218a.

[0053] Furthermore, the control unit 2151 controls communication between the electric vehicle 20 and the higher-level system 30. The control operations performed by the control unit 2151 are, for example, carried out via CAN (Controller Area Network) communication.

[0054] The DC-DC converter 216a is an isolated bidirectional DC-DC converter capable of transmitting voltage in both directions: from the overhead line 10 to the motor vehicle 20, and from the motor vehicle 20 to the overhead line 10.

[0055] For example, a DC-DC converter 216a used to transmit power from the overhead line 10 to the electric vehicle 20 comprises an inverter 216a1, a converter 216a2, and a transformer 216a3. The inverter 216a1 converts the DC voltage of the overhead line 10 to an AC voltage. The inverter 216a1 is composed of high-voltage (e.g., 1700V) electronic components.

[0056] The converter 216a2 converts the AC voltage transmitted from the primary side (i.e., the overhead line 10 side) to the secondary side (the electric vehicle 20 side) of the transformer 216a3 into a DC voltage. The converter 216a2 is composed of electronic components with a lower voltage rating (e.g., 1200V) than the inverter 216a1.

[0057] Transformer 216a3 converts the AC voltage output by inverter 216a1 into an AC voltage corresponding to the primary and secondary winding ratio, such that the DC voltage output by converter 216a2 is a DC voltage of a size suitable for inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a, using a primary and secondary winding ratio.

[0058] Furthermore, when power is transmitted from the electric vehicle 20 to the overhead line 10 (for example, when the electric vehicle 20 applies electric brakes and regenerative power is generated in the electric vehicle 20), the DC-DC converter 216a will have the inverter and converter swapped, and will consist of an inverter 216a2, a converter 216a1, and a transformer 216a3. The operation of the DC-DC converter 216a when power is transmitted from the electric vehicle 20 to the overhead line 10 can be considered in the same way as the operation of the DC-DC converter 216a when power is transmitted from the overhead line 10 to the electric vehicle 20, by replacing the inverter 216a1 with the converter 216a2 and the converter 216a2 with the converter 216a1, and further swapping the primary and secondary sides of the transformer 216a3.

[0059] The inverter 217a1 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that drives the motor 204a1. The inverter 217a1 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a1 are not fixed but can be changed as needed.

[0060] The inverter 217a2 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that drives the motor 204a2. The inverter 217a2 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a2 are not fixed but can be changed as needed.

[0061] The inverter 217a3 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that drives the motor 208a1. The inverter 217a3 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a3 are not fixed but can be changed as needed.

[0062] The inverter 217a4 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that drives the motor 208a2. The inverter 217a4 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a4 are not fixed but can be changed as needed.

[0063] The inverter 217a5 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that drives the motor 208a3. The inverter 217a5 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a5 are not fixed but can be changed as needed.

[0064] The inverter 217a6 converts the DC voltage output by the DC-DC converter 216a into an AC voltage that can be supplied to the accessory 212a. The inverter 217a6 is composed of low-voltage (e.g., 1200V) electronic components. The amplitude and frequency of the AC voltage output by the inverter 217a6 are not fixed but can be changed as needed.

[0065] The DC-DC converter 218a converts the DC voltage output by the DC-DC converter 216a into a DC voltage that can be supplied to the control power supply 214a.

[0066] The higher-level system 30 controls the movement of the electric vehicle 20 in the traffic system 1. For example, the higher-level system 30 outputs a torque command to the electric vehicle 20, and the electric vehicle 20 moves according to that torque command.

[0067] (advantage) The first embodiment of the traffic system 1 of this disclosure has been described above. In the DC-DC converter 216a of the traffic system 1, the inverter 216a1 is made of high-voltage (e.g., 1700V) electronic components, and the converter 216a2 is made of low-voltage (e.g., 1200V) electronic components. By configuring the DC-DC converter 216a of the traffic system 1 in this way, it is possible to provide a bidirectional DC-DC converter that can achieve the same functionality as when using high-voltage electronic components, even when replacing an electrical component containing high-voltage electronic components with an electrical component containing lower-voltage electronic components.

[0068] <First modified example of the first embodiment> Next, a traffic system 1 according to a first modification of the first embodiment of the present disclosure will be described. The traffic system 1 according to the first modification of the first embodiment is a system that has a function to improve wheel slippage, similar to the VVVF inverter 205a of the electric vehicle 20a used for comparison.

[0069] In the first modified example of the first embodiment, the function of improving wheel slippage is realized by the control circuit 215, the higher-level system 30, and the wheel rotation sensors 40a1 and 40a2, which will be described later. The differences between the traffic system 1 according to the first modified example of the first embodiment and the traffic system 1 according to the first embodiment will be explained below.

[0070] (Configuration of the transportation system) Figure 3 shows an example of the configuration of a traffic system 1 according to a first modification of the first embodiment of the present disclosure. The traffic system 1 according to the first modification of the first embodiment includes a vehicle body 201a, wheels 202a1, 202a2, pantograph 203a, motors 204a1, 204a2, motors 208a1, 208a2, 208a3, HVAC compressor 209a, brake air compressor 210a, cooling fan 211a, accessory 212a, control power supply 214a, control circuit 215, DC-DC converter 216a, inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a, similar to the traffic system 1 of the first embodiment shown in Figure 1. Furthermore, the traffic system 1 according to the first modified example of the first embodiment further includes rotation sensors 40a1 and 40a2.

[0071] The rotation sensor 40a1 detects the number of rotations per unit time of the wheel 202a1. The rotation sensor 40a2 also detects the number of rotations per unit time of the wheel 202a2.

[0072] The control circuit 215 controls the electric vehicle 20. Figure 4 shows an example of the configuration of the control circuit 215 according to a first modification of the first embodiment of the present disclosure. As shown in Figure 4, the control circuit 215 includes a control unit 2151, an acquisition unit 2152, and a determination unit 2153.

[0073] The acquisition unit 2152 acquires the rotation speed detection results from the rotation sensors 40a1 and 40a2, respectively.

[0074] The determination unit 2153 calculates the rate of change of the rotations per unit time of wheel 202a1 and the rate of change of the rotations per unit time of wheel 202a2 from the respective detection results acquired by the acquisition unit 2152 (i.e., the rotations per unit time of wheel 202a1 and the rotations per unit time of wheel 202a2), compares them, and determines whether the axles (i.e., the front and rear axles) are slipping based on the comparison result. For example, the determination unit 2153 determines that the axle to which the wheel with the higher rate of change of rotations per unit time is connected is slipping if the rate of change of the rotations per unit time of wheel 202a2 is outside the range of the rate of change of the rotations per unit time of wheel 202a2 predetermined based on the rate of change of the rotations per unit time of wheel 202a1, i.e., the allowable value of the rate of change of rotations. Furthermore, the determination unit 2153 determines that the axle is not slipping if the rate of change of the rotational speed does not fall outside the range, i.e., the allowable value of the rate of change of the rotational speed. The determination unit 2153 may also determine whether the axle is slipping by using "the number of rotations per unit time of wheel 202a1 and the number of rotations per unit time of wheel 202a2" instead of "the rate of change of the rotational speed per unit time of wheel 202a1 and the rate of change of the rotational speed per unit time of wheel 202a2".

[0075] The control unit 2151 controls the DC-DC converter 216a, inverters 217a1, 217a2, 217a3, 217a4, 217a5, 217a6, and DC-DC converter 218a, similar to the control unit 2151 according to the first embodiment. Specifically, the control unit 2151 generates PWM signals for each of the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, and 217a6, and controls the AC voltage output by each of the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, and 217a6 by controlling the DC voltage output by each of the DC-DC converters 216a and inverters 217a1, 217a2, 217a3, 217a4, 217a5, and 217a6 with the generated PWM signals. Furthermore, the control unit 2151 controls the DC voltage output by the DC-DC converter 218a by chopper control of the switching elements of the DC-DC converter 218a.

[0076] Furthermore, the control unit 2151 controls communication with the higher-level system 30 in the electric vehicle 20, similar to the control unit 2151 in the first embodiment. However, in the first modified example of the first embodiment, the control unit 2151 controls the inverters 217a1 and 217a2 respectively based on the determination result of the determination unit 2153. Specifically, if the determination unit 2153 determines that an axle is slipping (i.e., at least one of the front and rear axles), the control unit 2151 controls the inverter corresponding to each individual axle (i.e., inverter 217a1 or inverter 217a2) to reduce the torque of the wheel connected to the axle that was determined to be slipping (i.e., wheel 202a1 or wheel 202a2). The degree to which the torque is reduced is determined by a combination of the control content of the inverter by the control unit 2151 and the rate of change of the rotational speed of the wheel per unit time. In this way, the control unit 2151 controls the inverters 217a1 and 217a2 respectively based on the determination result from the determination unit 2153, so that even if at least one of the front and rear axles slips, the slippage of the axle can be immediately corrected.

[0077] In addition to the functions of the higher-level system 30 according to the first embodiment, the higher-level system 30 has the function of detecting the change in rotational speed (acceleration) of motors 204a1 and 204a2, similar to the detection unit 2051a1 and control unit 2052a2 of the VVVF inverter 205a of the electric vehicle 20a used for comparison. Furthermore, the higher-level system 30 has the function of detecting slippage of both axles (front and rear axles) (in this example, when it is determined that the change in the frequency of both motor currents flowing to motors 204a1 and 204a2 exceeds an allowable value), and transmitting a torque command value to the electric vehicle 20 to reduce the current value of motors 204a1 and 204a2 whose change in motor current frequency has been determined to exceed an allowable value (i.e., to reduce the torque of motors 204a1 and 204a2).

[0078] Specifically, the higher-level system 30 controls the movement of the electric vehicle 20 in the traffic system 1. For example, the higher-level system 30 outputs a torque command to the electric vehicle 20, and the electric vehicle 20 moves according to that torque command. However, the higher-level system 30 detects the change in rotational speed (acceleration) of each of the motors 204a1 and 204a2. For example, the higher-level system 30 detects these changes in rotational speed as a change in the frequency of the motor current flowing through motors 204a1 and 204a2. The higher-level system 30 determines whether the change in the frequency of both motor currents flowing through motors 204a1 and 204a2 exceeds an allowable value, and if it determines that the change in the frequency of both motor currents exceeds an allowable value, it determines that both axles are slipping. Also, if the higher-level system 30 determines that the change in the frequency of at least one of the motor currents does not exceed an allowable value, it determines that both axles are not slipping.

[0079] Then, if the higher-level system 30 detects slippage on both axles (in this example, if it determines that the change in the frequency of both motor currents flowing to motors 204a1 and 204a2 exceeds an allowable value), it transmits a torque command value to the electric vehicle 20 that reduces the current value of motors 204a1 and 204a2 whose change in motor current frequency has been determined to exceed an allowable value (i.e., reduces the torque of motors 204a1 and 204a2). In this case, the control unit 2151 of the electric vehicle 20 controls inverters 217a1 and 217a2 respectively according to the torque command transmitted from the higher-level system 30.

[0080] (Processing performed by the transportation system) Figure 5 shows an example of the processing flow of a traffic system according to a first modification of the first embodiment. Next, the process for improving wheel slippage by the traffic system 1 according to the first modification of the first embodiment will be described with reference to Figure 5.

[0081] Traffic system 1 sets a slip tolerance value (step S1). Specifically, for example, the determination unit 2153 sets and maintains a predetermined range of the rate of change of the rotational speed per unit time of wheel 202a2, i.e., a tolerance value for the rate of change of rotational speed, based on the rate of change of the rotational speed per unit time of wheel 202a1. In addition, the higher-level system 30 sets and maintains tolerance values ​​for the amount of change in the rotational speed (acceleration) of motors 204a1 and 204a2 respectively (for example, tolerance values ​​for the amount of change in the frequency of the motor current flowing through motors 204a1 and 204a2).

[0082] The traffic system 1 detects axle slippage (step S2). Specifically, in the electric vehicle 20, the acquisition unit 2152 acquires the rotation speed detection results from the rotation sensors 40a1 and 40a2, respectively. The determination unit 2153 calculates the rate of change of the rotation speed per unit time of wheel 202a1 and the rate of change of the rotation speed per unit time of wheel 202a2 from the respective detection results acquired by the acquisition unit 2152 (i.e., the rotation speed per unit time of wheel 202a1 and the rotation speed per unit time of wheel 202a2), compares them, and determines axle slippage based on the comparison result. For example, the determination unit 2153 determines that the axle to which the wheel with the higher rate of change in rotations per unit time is connected is slipping if the rate of change in rotations per unit time of wheel 202a2 falls outside the range of the rate of change in rotations per unit time of wheel 202a2 predetermined based on the rate of change in rotations per unit time of wheel 202a1, i.e., the allowable value of the rate of change in rotations. Conversely, the determination unit 2153 determines that the axle is not slipping if the rate of change in rotations does not fall outside the range of the rate of change in rotations per unit time, i.e., the allowable value of the rate of change in rotations.

[0083] Specifically, the higher-level system 30 determines whether the change in frequency of both motor currents flowing through motors 204a1 and 204a2 exceeds an allowable value. If it determines that the change in frequency of both motor currents exceeds an allowable value, it determines that both axles (front and rear axles) are slipping. If the higher-level system 30 determines that the change in frequency of at least one motor current does not exceed an allowable value, it determines that neither axle is slipping.

[0084] In step S2, if the traffic system 1 determines that it has detected slippage on at least one of the front and rear axles (in step S2, "control for each individual axle"), it controls the inverter corresponding to each individual axle to reduce the torque of the wheel connected to the axle that is determined to be slipping (step S3). Specifically, if the determination unit 2153 determines that an axle is slipping, the control unit 2151 controls the inverter corresponding to each individual axle (i.e., inverter 217a1 or inverter 217a2) to reduce the torque of the wheel connected to the axle that is determined to be slipping (i.e., wheel 202a1 or wheel 202a2).

[0085] In step S2, if the traffic system 1 determines that it has detected slippage on both the front and rear axles, it controls the inverters corresponding to each axle to reduce the torque of the wheels connected to both axles. Specifically, if the higher-level system 30 detects slippage on both axles (in this example, if it determines that the change in the frequency of both motor currents flowing to motors 204a1 and 204a2 exceeds an allowable value), it transmits a torque command value to the electric vehicle 20 that reduces the current value of motors 204a1 and 204a2 whose change in motor current frequency has been determined to exceed an allowable value (i.e., reduces the torque of motors 204a1 and 204a2). In this case, the control unit 2151 of the electric vehicle 20 controls inverters 217a1 and 217a2 respectively according to the torque command transmitted from the higher-level system 30.

[0086] Furthermore, in the process of step S2, if the traffic system 1 determines that neither axle is slipping (i.e., "within the slippage tolerance limit" in step S2), it returns to the determination in step S2.

[0087] Furthermore, in the traffic system 1, if the determination unit 2153 determines that the axle is slipping and the higher-level system 30 transmits a torque command value to the electric vehicle 20, the control unit 2151 prioritizes the torque command value transmitted by the higher-level system 30 to the electric vehicle 20 and controls the inverters corresponding to each of the axles. In other words, the traffic system 1 executes the process in step S4 with priority over the process in step S3.

[0088] (advantage) The traffic system 1 according to the first modification of the first embodiment has been described above. In the traffic system 1 according to the first modification of the first embodiment, the processing of steps S2 and S4 described above makes it possible to improve wheel slippage to the same extent as that of the VVVF inverter 205a of the electric vehicle 20a to be compared. Since this improvement in wheel slippage to the same extent as that of the VVVF inverter 205a can be achieved by the higher-level system 30 that already exists in the traffic system 1, the inverter of the electric vehicle 20 does not need to have a function to improve wheel slippage like that of the VVVF inverter 205a, and a lower-function inverter can be used. As a result, a reduction in the manufacturing cost of the electric vehicle 20 can be expected.

[0089] Furthermore, in the traffic system 1 according to the first modified example of the first embodiment, the processing of steps S2 and S3 described above makes it possible to determine slippage of the front and rear axles based on the comparison result of comparing the rate of change of the rotation speed of the front and rear wheels, which is not present in the electric vehicle 20a being compared, and to improve the slippage of the wheels connected to the slipping axles.

[0090] <Second variation of the first embodiment> Next, a traffic system 1 according to a second modification of the first embodiment of this disclosure will be described. The traffic system 1 according to the second modification of the first embodiment is a traffic system that includes a DAB (Dual Active Bridge) type DC-DC converter (hereinafter referred to as DAB circuit 216a) as a specific example of the DC-DC converter 216a, which is an isolated bidirectional DC-DC converter provided in the traffic system 1 of the first embodiment. The traffic system 1 according to the second modification of the first embodiment is a traffic system that improves upon the problems that arise when controlling a general DAB type DC-DC converter.

[0091] (DAB circuit configuration) Figure 6 shows an example of the configuration of a DAB circuit 216a according to a second modification of the first embodiment of the present disclosure. As shown in Figure 6, the DAB circuit 216a comprises a primary side (overhead line 10 side) circuit 216a1, a secondary side (electric vehicle 20 side) circuit 216a2, and a transformer 216a3. For the sake of explanation, the circuit on the overhead line 10 side is referred to as the primary side circuit 216a1, and the circuit on the electric vehicle 20 side is referred to as the secondary side circuit 216a2. However, since the DAB circuit 216a is an isolated bidirectional DC-DC converter, it goes without saying that in actual operation, the electric vehicle 20 side is the primary side and the overhead line 10 side is the secondary side, and power can be transmitted from the electric vehicle 20 to the overhead line 10.

[0092] As shown in Figure 6, the primary circuit 216a1 comprises four switching elements 709, 710, 711, and 712, four diodes 717, 718, 719, and 720, five capacitors 725, 726, 727, 728, 729, and 733, and a reactor 735. The switching elements 709, 710, 711, and 712 are, for example, power semiconductors. Examples of power semiconductors include MOS (Metal Oxide Semiconductor) transistors, IGBTs (Insulated Gate Bipolar Transistors), and SiC (Silicon Carbide) transistors.

[0093] For example, if the switching elements 709, 710, 711, and 712 are MOS transistors, then diode 717 is the body diode (i.e., the source-drain parasitic diode) of switching element 709. Also, diodes 718, 719, and 720 are the body diodes of switching elements 710, 711, and 712, respectively. Furthermore, capacitors 725, 726, 727, and 728 are snubber capacitors.

[0094] Furthermore, as shown in Figure 6, the secondary circuit 216a2 includes four switching elements 713, 714, 715, and 716, four diodes 721, 722, 723, and 724, and five capacitors 729, 730, 731, 732, and 734. The switching elements 713, 714, 715, and 716 are, for example, power semiconductors. Note that the switching elements 713, 714, 715, and 716 may be different types of power semiconductors from the switching elements 709, 710, 711, and 712. For example, the switching elements 709, 710, 711, and 712 may be IGBTs, and the switching elements 713, 714, 715, and 716 may be MOS transistors.

[0095] For example, if switching elements 713, 714, 715, and 716 are MOS transistors, then diode 721 is the body diode of switching element 713. Also, diodes 722, 723, and 724 are the body diodes of switching elements 714, 715, and 716, respectively. Furthermore, capacitors 729, 730, 731, and 732 are snubber capacitors.

[0096] As shown in Figure 6, the transformer 216a3 includes a primary coil 736 and a secondary coil 737.

[0097] Note that the connections between elements in the DAB circuit 216a shown in Figure 6 are the same as those in a typical DAB type DC-DC converter. In the traffic system 1 according to the second modification of the first embodiment, the switching elements 709, 710, 711, 712, 713, 714, 715, and 716 are controlled to be on or off by the control unit 2151 of the control circuit 215. In the traffic system 1 according to the second modification of the first embodiment, the control of the switching elements 709, 710, 711, 712, 713, 714, 715, and 716 by the control unit 2151 differs from the general control performed on a DAB type DC-DC converter.

[0098] Here, we will explain the problems that arise when controlling a typical DAB-type DC-DC converter. Figure 7 is the first diagram illustrating the problems that arise when controlling a typical DAB-type DC-DC converter. Figure 8 is the second diagram illustrating the problems that arise when controlling a typical DAB-type DC-DC converter. Figure 9 is the third diagram illustrating the problems that arise when controlling a typical DAB-type DC-DC converter. Note that Figure 8 is an enlarged view of a portion of Figure 7(a). Also, Figure 9 is an enlarged view of a portion of Figure 7(b) that includes one cycle of operation.

[0099] Part 7(a) of Figure 7 shows the simulation results when the control unit 2151 switches the switching elements 709, 710, 711, and 712 of the DAB circuit 216a with a constant period signal with a duty cycle of 50% (in this example, a constant period of 20kHz) to transmit 5kW of power from the primary circuit 216a1 to the secondary circuit 216a2. When power is transmitted from the primary circuit 216a1 to the secondary circuit 216a2, the switching elements 713, 714, 715, and 716 of the secondary circuit 216a2 are in the off state, and the voltage transmitted from the primary circuit 216a1 to the secondary circuit 216a2 via the transformer 216a3 is rectified by the bridge circuit composed of diodes 721 to 724. Furthermore, the input voltage of the primary circuit 216a1 is 800V, and the output voltage of the secondary circuit 216a2 is 500V. A dead time is provided for the switching of the switching elements to prevent switching elements 709 and 710, which are connected in series above and below, from being turned on simultaneously, and also to prevent switching elements 711 and 712 from being turned on simultaneously (i.e., to prevent through-current from flowing).

[0100] Controlling switching elements with a constant-period signal with a 50% duty cycle is a commonly performed control method. In a typical DAB-type DC-DC converter, if the control unit 2151 controls the switching elements with a constant-period signal with a 50% duty cycle, for example, even if switching elements 709 and 712 are controlled to be ON and switching elements 710 and 711 to be OFF, a dead time is provided, resulting in a state where both switching elements 709 and 710 are OFF. However, even when switching element 710 is OFF, current flows through diode 718, via the path diode 718, reactor 735, primary coil 736, and switching element 712. In this state, when the dead time ends and switching element 709 turns ON, a voltage approximately equal to the input voltage of the primary circuit 216a1 due to the DC voltage of the overhead line 10 is applied to diode 718, causing a phenomenon called recovery in which current flows in the reverse direction through diode 718. In this case, the switching element 710 also turns on, causing a problem where a through-current flows from the switching element 709 to the switching element 710 (i.e., hard switching). When the control unit 2151 controls the switching elements with a constant period signal with a duty cycle of 50%, a phenomenon called recovery occurs every half-cycle. The reason why the phenomenon called recovery occurs when the control unit 2151 controls the switching elements with a constant period signal with a duty cycle of 50% is, as shown in Figure 8, that the transformer current changes from a positive current to a negative current and crosses zero during the period when the transformer voltage is at a high level, and the transformer current changes from a negative current to a positive current and crosses zero during the period when the transformer voltage is at a low level. When the input voltage of the primary circuit 216a1 and the output voltage of the secondary circuit 216a2 are equal, there is almost no change in the transformer current and no zero-crossing occurs, so the phenomenon called recovery does not occur.

[0101] To prevent the phenomenon known as recovery described above, an operating method called intermittent operation has been proposed. Intermittent operation is a control method in which the switching element is switched before the transformer current changes and crosses zero. In part 7(b) of Figure 7, the constant period (20kHz in this case) is not changed, and the period during which the transformer voltage is at a high level and the period during which it is at a low level are changed, thereby switching between high and low levels before the transformer current crosses zero. However, the power transmitted from the primary circuit 216a1 to the secondary circuit 216a2 must be the same as before the change (in this example, it must be 5kW), so the transmitted power is adjusted by providing a period during which the transformer voltage is zero. However, if intermittent operation is performed without changing the constant period (20kHz in this case), hard switching may occur as shown in Figure 9, that is, the phenomenon known as recovery may not be completely eliminated.

[0102] Therefore, in the traffic system 1 according to the second modification of the first embodiment, the constant period is shortened (for example, to 40 kHz, which corresponds to half the period), and a period is provided during which the transformer voltage is set to zero so that the power transmitted from the primary circuit 216a1 to the secondary circuit 216a2 is the same as before the modification. The control unit 2151 eliminates hard switching, that is, the phenomenon called recovery, by controlling the switching elements 709, 710, 711, and 712 of the DAB circuit 216a with such signals. Part 7(c) of Figure 7 shows an example of the signals used by the control unit 2151 when controlling the switching elements 709, 710, 711, and 712 of the DAB circuit 216a. As shown in Figure 7(c), as described above, by shortening the constant period (for example, to 40 kHz, which corresponds to half the period) and using a signal that provides a period during which the transformer voltage is set to zero so that the power transmitted from the primary circuit 216a1 to the secondary circuit 216a2 remains the same as before, the control unit 2151 controls the switching elements 709, 710, 711, and 712 of the DAB circuit 216a. This makes it possible to switch between the High level and Low level before the transformer current crosses zero, thereby eliminating hard switching, or the phenomenon known as recovery. Generally, when the constant period is shortened, the frequency increases, meaning the number of switching cycles increases, and efficiency tends to decrease due to heat generated by switching. However, in the traffic system 1 according to the second modification of the first embodiment, even if the constant period is shortened, a corresponding rest period is also set, making it possible to keep the number of switching cycles per period the same as or less than before the constant period was shortened. Therefore, the traffic system 1 according to the second modification of the first embodiment can improve efficiency.

[0103] Furthermore, when the load on the DC-DC converter 216a is light, such as when the air conditioner is stopped in the electric vehicle 20, the transformer current becomes small. When the transformer current is small, if it changes due to noise or some other reason, the proportion of that change to the transformer current becomes large, and the change in transformer current, which would be negligible when the transformer current is large, becomes negligible. In other words, when the transformer current is small, the transformer current changes, and a phenomenon called recovery may occur, similar to when the input voltage of the primary circuit 216a1 and the output voltage of the secondary circuit 216a2 are different. Therefore, when the transformer current is small, the control unit 2151 should shorten the constant period and set the rest period so that the power transmitted per unit time is the desired power, and control the switching elements 709, 710, 711, and 712 of the DAB circuit 216a.

[0104] Furthermore, if the input voltage of the primary circuit 216a1 and the output voltage of the secondary circuit 216a2 can be considered to be the same, or if the load can be considered to be heavy, the control unit 2151 may control the switching elements 709, 710, 711, and 712 to switch with a constant period signal with a duty cycle of 50% (in this example, a constant period of 20 kHz) as shown in part (a) of Figure 7.

[0105] Furthermore, when transmitting power from the electric vehicle 20 to the overhead line 10 (for example, when the electric vehicle 20 applies electric brakes and regenerative power is generated in the electric vehicle 20), if the voltage of the power generated on the electric vehicle 20 side (an example of a third voltage) is different from the voltage of the overhead line 10 (an example of a first voltage), or if the load on the overhead line 10 is light, the switching elements 709, 710, 711, and 712 should be turned off, and the control unit 2151 should perform the same control on the switching elements 713, 714, 715, and 716 as the control on the switching elements 709, 710, 711, and 712 described above.

[0106] (advantage) The traffic system 1 according to the second modification of the first embodiment has been described above. When the input voltage of the primary circuit 216a1 (an example of the first voltage) and the output voltage of the secondary circuit 216a2 (an example of the second voltage) are different, or when the load on the DC-DC converter 216a in the electric vehicle 20 is light, the control unit 2151 shortens the switching period of the switching elements 709, 710, 711, and 712 and provides a period during which no switching occurs. Furthermore, when the voltage of the power generated on the electric vehicle 20 side (an example of the third voltage) and the voltage of the overhead line 10 (an example of the first voltage) are different, or when the load on the overhead line 10 is light, the control unit 2151 shortens the switching period of the switching elements 713, 714, 715, and 716 and provides a period during which no switching occurs. By configuring the DC-DC converter 216a of the traffic system 1 in this way, the occurrence of hard switching can be suppressed.

[0107] <Third Modification of the First Embodiment> Next, a traffic system 1 according to a third modification of the first embodiment of this disclosure will be described. The traffic system 1 according to the third modification of the first embodiment is a traffic system that charges the capacitor 734 of the secondary circuit 216a2 when the DAB circuit 216a of the traffic system 1 according to the second modification of the first embodiment is started up, thereby reducing the possibility of malfunctions occurring in the electronic components of the DAB circuit 216a.

[0108] (Configuration of the transportation system) The configuration of the DAB circuit 216a in the third modification of the first embodiment is the same as the configuration of the DAB circuit 216a in the second modification of the first embodiment shown in Figure 6. The traffic system 1 in the third modification of the first embodiment differs from the traffic system 1 in the second modification of the first embodiment in the content of the control unit 2151's control of the switching elements 709, 710, 711, and 712.

[0109] Figure 10 is the first diagram illustrating the control content of the control unit 2151 according to a third modification of the first embodiment. Figure 11 is the second diagram illustrating the control content of the control unit 2151 according to a third modification of the first embodiment. Figure 12 is the third diagram illustrating the control content of the control unit 2151 according to a third modification of the first embodiment. Figure 13 is the fourth diagram illustrating the control content of the control unit 2151 according to a third modification of the first embodiment. Figure 14 is the fifth diagram illustrating the control content of the control unit 2151 according to a third modification of the first embodiment.

[0110] Figure 10 shows an example of a control signal used by the control unit 2151 to switch the switching elements 709, 710, 711, and 712. Figure 11 shows the current path in the DAB circuit 216a during the period indicated as 1 in Figure 10. During the period indicated as 1 in Figure 10, the control unit 2151 controls the switching elements 709 and 712 to the ON state and the switching elements 710 and 711 to the OFF state. During the period indicated as 1 in Figure 10, current flows through the path of the overhead wire 10, switching element 709, reactor 735, primary coil 736, switching element 712, and overhead wire 10, as shown in Figure 11.

[0111] Figure 12 shows the current path in the DAB circuit 216a during the period indicated as 2 in Figure 10. During the period indicated as 2 in Figure 10, the control unit 2151 controls the switching element 712 to the ON state and controls the switching elements 709, 710, and 711 to the OFF state. During the period indicated as 2 in Figure 10, current flows through the reactor 735, primary coil 736, switching element 712, and diode 718, as shown in Figure 12.

[0112] Figure 13 shows the current path in the DAB circuit 216a during the period indicated as 3 in Figure 10. During the period indicated as 3 in Figure 10, the control unit 2151 controls the switching elements 710 and 711 to the ON state and the switching elements 709 and 712 to the OFF state. During the period indicated as 3 in Figure 10, as shown in Figure 13, current flows through the path of the overhead wire 10, switching element 711, primary coil 736, reactor 735, switching element 710, and overhead wire 10.

[0113] Figure 14 shows the current path in the DAB circuit 216a during the period indicated as 4 in Figure 10. During the period indicated as 4 in Figure 10, the control unit 2151 controls the switching element 711 to the ON state and controls the switching elements 709, 710, and 712 to the OFF state. During the period indicated as 4 in Figure 10, as shown in Figure 14, current flows through the switching element 711, the primary coil 736, the reactor 735, and the diode 717.

[0114] When the DAB circuit 216a is started, the periods shown as 1 to 4 in Figure 10 are repeated, and current flows repeatedly through the paths shown in Figures 11 to 14. In this case, the direction of the current flowing through the reactor 735 changes; that is, alternating current flows through the reactor 735. This alternating current is transmitted to the secondary circuit 216a2 via the transformer 216a3 and rectified by the bridge circuit of diodes 721 to 724. As a result, the capacitor 734 is charged. As shown in Figure 10, the period during which switching elements 709 and 710 are ON is shorter than the period during which switching elements 711 and 712 are ON. Therefore, the charging of the capacitor 734 consists of repeated small charges over short periods. In other words, the possibility of the capacitor 734 being overcharged by overcurrent is reduced.

[0115] Furthermore, when the capacitor 734 reaches a predetermined charge state (for example, when it is determined that it has been charged to 80% of its full charge), the control unit 2151 may extend the period during which the switching elements 709 and 710 are ON, similar to the period during which the switching elements 711 and 712 are ON.

[0116] Figure 15 is the first figure showing an example of the waveform in a simulation of charging capacitor 734. Figure 16 is the second figure showing an example of the waveform in a simulation of charging capacitor 734. Figure 17 is the third figure showing an example of the waveform in a simulation of charging capacitor 734.

[0117] Figure 15 shows an example of the waveform during the initial charging of capacitor 734. From the waveform shown in Figure 15, it can be seen that the voltage across capacitor 734 is slowly increasing.

[0118] Figure 16 shows an example of a simulation waveform during the middle of charging capacitor 734. From the waveform shown in Figure 16, it can be seen that the voltage change of capacitor 734 is rising even more slowly than at the start of charging.

[0119] Figure 17 shows an example of a simulation waveform when the capacitor 734 has reached a predetermined charge state (in this example, 80% of its full charge), and the control unit 2151 extends the period during which switching elements 709 and 710 are ON, similar to the period during which switching elements 711 and 712 are ON. From the waveform shown in Figure 17, it can be seen that when the control unit 2151 extends the period during which switching elements 709 and 710 are ON, similar to the period during which switching elements 711 and 712 are ON, the voltage of capacitor 734 rises rapidly from that timing.

[0120] Furthermore, when transmitting power from the electric vehicle 20 to the overhead line 10 (for example, when the electric vehicle 20 applies electric brakes and regenerative power is generated in the electric vehicle 20), the switching elements 709, 710, 711, and 712 are turned off, and the control unit 2151 performs the same control on the switching elements 713, 714, 715, and 716 as the control on the switching elements 709, 710, 711, and 712 described above.

[0121] (advantage) The traffic system 1 according to the third modification of the first embodiment has been described above. In the traffic system 1 according to the third modification of the first embodiment, the control unit 2151 shortens the ON state period of some switching elements (for example, switching elements 709 and 710) compared to the ON state period of other switching elements (for example, switching elements 711 and 712), thereby switching these switching elements and charging the capacitor 734 without causing an overcurrent to flow through it.

[0122] <Second Embodiment> Next, a traffic system 1 according to a second embodiment of the present disclosure will be described. Figure 18 is a diagram showing an example of the configuration of the traffic system 1 according to a second embodiment of the present disclosure. Unlike the traffic system 1 according to the first embodiment, the DC-DC converter 216a in the traffic system 1 according to the second embodiment of the present disclosure is a bidirectional DC-DC converter with chopper control. In the DC-DC converter 216a, the circuit that handles the voltage of the overhead line 10 is made up of high-voltage (e.g., 1700V) electronic components. Also, in the DC-DC converter 216a, the circuit that handles the voltage supplied to the electric vehicle 20, or the voltage generated in the electric vehicle 20 (e.g., the voltage indicated by regenerative power), is made up of low-voltage (e.g., 1200V) electronic components. The chopper control of the switching elements in the DC-DC converter 216a can be performed by the control circuit 215.

[0123] The DC-DC converter 216a according to the second embodiment is, for example, a bidirectional chopper circuit. Figure 19 is a diagram showing an example of the configuration of the DC-DC converter 216a according to the second embodiment of this disclosure. As shown in Figure 19, the DC-DC converter 216a comprises switching elements 709, 710, capacitors 733, 734, and a reactor 735. The DC-DC converter 216a shown in Figure 19 has a configuration equivalent to the general bidirectional chopper circuit described in Figure 4 of Japanese Patent Application Publication No. 2006-006061.

[0124] The switching elements 709 and 710 are, for example, power semiconductors. For example, if the switching elements 709 and 710 are MOS transistors, then diode 717 is the body diode of switching element 709. Also, diode 718 is the body diode of switching element 710. The DC-DC converter 216a shown in Figure 19 can step down the voltage between the left ground GND terminal and terminal a1 and output it as the voltage between the right ground GND terminal and terminal a2. The DC-DC converter 216a shown in Figure 19 can also step up the voltage between the right ground GND terminal and terminal a2 and output it as the voltage between the left ground GND terminal and terminal a1. In the case of the DC-DC converter 216a shown in Figure 19, the switching elements 709 and 710, capacitor 733, and reactor 735 are high-voltage (e.g., 1700V) electronic components that constitute a circuit that handles the voltage of the overhead line 10. Furthermore, in the case of the DC-DC converter 216a shown in Figure 19, the capacitor 734 is a low-voltage (e.g., 1200V) electronic component that constitutes a circuit that handles the voltage generated in the electric vehicle 20.

[0125] Furthermore, the DC-DC converter 216a is not limited to the bidirectional chopper circuit shown in Figure 19. Any DC-DC converter that can convert the voltage on the overhead line 10 side to the voltage on the electric vehicle 20 side when supplying power from the overhead line 10 to the electric vehicle 20, and that can convert the regenerative power generated in the electric vehicle 20 when, for example, electric braking is applied, from the voltage on the electric vehicle 20 side to the voltage on the overhead line 10 side and transmit it, may be used.

[0126] (advantage) The traffic system 1 according to the second embodiment has been described above. In the DC-DC converter 216a of the traffic system 1 according to the second embodiment, the circuit that handles the voltage of the overhead line 10 is composed of high-voltage (e.g., 1700V) electronic components. In addition, the circuit that handles the voltage supplied to the electric vehicle 20, or the voltage generated in the electric vehicle 20 (e.g., the voltage indicated by regenerative power), is composed of low-voltage (e.g., 1200V) electronic components. By configuring the DC-DC converter 216a of the traffic system 1 in this way, even if an electrical component containing a high-voltage electronic component is replaced with an electrical component containing a lower-voltage electronic component, the same functionality as when using a high-voltage electrical component can be achieved.

[0127] In addition, the order of processing in the embodiments of this disclosure may be changed, as long as appropriate processing is performed.

[0128] Each of the storage units and memory devices (including registers and latches) in the embodiments of this disclosure may be located anywhere within the scope of appropriate information transmission and reception. Furthermore, each of the storage units and memory devices may be multiple in number, storing data in a distributed manner within the scope of appropriate information transmission and reception.

[0129] While embodiments of this disclosure have been described, the electric vehicle 20, control circuit 215, control unit 2151, higher-level system 30, and other control devices described above may each have a computer system internally. The above-described processing steps are stored in program form on a computer-readable recording medium, and the above processing is performed by the computer reading and executing this program. A specific example of a computer is shown below.

[0130] Figure 20 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. As shown in Figure 20, the computer 5 comprises a CPU 6, main memory 7, storage 8, and interface 9. For example, the electric vehicle 20, control circuit 215, control unit 2151, higher-level system 30, and other control devices are each implemented in the computer 5. The operation of each of the above-mentioned processing units is stored in the storage 8 in the form of a program. The CPU 6 reads the program from the storage 8 and loads it into the main memory 7, and executes the above-mentioned processing according to the program. The CPU 6 also allocates storage areas in the main memory 7 corresponding to each of the above-mentioned storage units according to the program.

[0131] Examples of storage 8 include HDDs (Hard Disk Drives), SSDs (Solid State Drives), magnetic disks, magneto-optical disks, CD-ROMs (Compact Disc Read Only Memory), DVD-ROMs (Digital Versatile Disc Read Only Memory), and semiconductor memory. Storage 8 may be an internal medium directly connected to the bus of computer 5, or an external medium connected to computer 5 via interface 9 or a communication line. Furthermore, if this program is distributed to computer 5 via a communication line, computer 5, upon receiving the program, may expand it into main memory 7 and execute the above processing. In at least one embodiment, storage 8 is a tangible storage medium that is not temporary.

[0132] Furthermore, the above program may implement some of the functions described above. Moreover, the above program may be a file that can implement the above functions in combination with a program already recorded in the computer system, a so-called differential file (differential program).

[0133] While several embodiments of this disclosure have been described, these embodiments are examples and do not limit the scope of the disclosure. These embodiments may be modified in various ways, without departing from the gist of the disclosure.

[0134] <Note> The electric vehicle (20), traffic system (1), control method, and program described in each embodiment of this disclosure can be understood, for example, as follows:

[0135] (1) The bidirectional DC-DC converter (216a) according to the first embodiment is: A first voltage, which is the DC voltage of the overhead line (10), is processed by a first circuit (216a1) which is composed of first electronic components including a first switching element, A second circuit (216a2) is composed of a second electronic component that includes a second switching element and has a lower voltage rating than the first electronic component, which processes a second voltage that is a DC voltage supplied to the electric vehicle (20) or a third voltage that is a DC voltage generated in the electric vehicle (20), A control circuit (215) that controls the switching of at least one of the first switching element and the second switching element, Equipped with, Convert the first voltage to the second voltage, or convert the third voltage to the first voltage.

[0136] As a result, the bidirectional DC-DC converter (216a) can achieve the same functionality as when using high-voltage electronic components, even when replacing an electronic component containing high-voltage electronic components with one containing lower-voltage electronic components.

[0137] (2) The bidirectional DC-DC converter (216a) according to the second embodiment is the bidirectional DC-DC converter of (1), A transformer provided between the first circuit (216a1) and the second circuit (216a2), It may also be equipped with

[0138] This allows the bidirectional DC-DC converter (216a) to isolate the first circuit (216a1) from the second circuit (216a2).

[0139] (3) The bidirectional DC-DC converter (216a) according to the third embodiment is the bidirectional DC-DC converter (216a) of (1), The control circuit (215) is At least one of the first switching element and the second switching element may be controlled by a chopper.

[0140] As a result, the bidirectional DC-DC converter (216a) can separate the voltage on the overhead line 10 from the voltage on the electric vehicle (20) without using a transformer.

[0141] (4) The bidirectional DC-DC converter (216a) according to the fourth embodiment is any one of the bidirectional DC-DC converters (216a) from (1) to (3), The control circuit (215) is If the first voltage and the second voltage are different, or if the first voltage and the third voltage are different, the switching period of at least one of the first switching element and the second switching element may be shortened, and a period during which no switching occurs may be provided.

[0142] This allows the bidirectional DC-DC converter (216a) to suppress hard switching.

[0143] (5) The bidirectional DC-DC converter (216a) according to the fifth embodiment is any one of the bidirectional DC-DC converters (216a) from (1) to (4), The control circuit (215) is When the bidirectional DC-DC converter (216a) is started up, the switching of the first and second switching elements may be controlled by making the period during which a specific switching element among the first and second switching elements is ON shorter than the period during which the other switching elements are ON.

[0144] This allows the bidirectional DC-DC converter (216a) to suppress overcurrent during startup and safely charge the capacitor to which it transmits power.

[0145] (6) The traffic system (1) relating to the sixth type is, A bidirectional DC-DC converter (216a) described in any one of the first to fifth embodiments, A higher-level system that transmits torque commands to the bidirectional DC-DC converter (216a), It is equipped with.

[0146] As a result, the traffic system (1) can achieve the same functionality as when using high-voltage electrical components, even when replacing electrical components containing high-voltage electronic components with electrical components containing lower-voltage electronic components.

[0147] (7) The control method relating to the seventh aspect is: A control method performed by a bidirectional DC-DC converter comprising: a first circuit (216a1) which processes a first voltage, which is the DC voltage of an overhead line (10), and is composed of a first electronic component including a first switching element; and a second circuit (216a2) which processes a second voltage, which is the DC voltage supplied to an electric vehicle (20), or a third voltage, which is the DC voltage generated by the electric vehicle (20), and is composed of a second electronic component including a second switching element and having a lower voltage rating than the first electronic component, wherein the control method is performed by the bidirectional DC-DC converter. Control the switching of at least one of the first switching element and the second switching element, Convert the first voltage to the second voltage, or convert the third voltage to the first voltage.

[0148] As a result, the control method allows electrical components containing high-voltage electronic components to be replaced with electrical components containing lower-voltage electronic components, while still achieving the same functionality as when high-voltage components are used.

[0149] (8) The program relating to the eighth aspect is: A computer in a bidirectional DC-DC converter comprising: a first circuit (216a1) which processes a first voltage, which is the DC voltage of the overhead line (10), and is composed of a first electronic component including a first switching element; and a second circuit (216a2) which processes a second voltage, which is the DC voltage supplied to the electric vehicle (20), or a third voltage, which is the DC voltage generated by the electric vehicle (20), and is composed of a second electronic component including a second switching element and having a lower voltage rating than the first electronic component, Control the switching of at least one of the first switching element and the second switching element. Convert the first voltage to the second voltage, or convert the third voltage to the first voltage.

[0150] This allows the program to perform the same functions as when using high-voltage electronic components, even when replacing an electronic component containing high-voltage components with one containing lower-voltage components. [Explanation of Symbols]

[0151] 1. Transportation System 5. Computers 6..CPU 7. Main Memory 8. Storage 9. Interface 10... Overhead wires 20, 20a... Electric vehicles 30... Higher-level system 40a1, 40a2... Rotation sensors 201a... Vehicle body 202a1, 202a2...wheels 203a...Pantograph 204a1, 204a2, 208a1, 208a2, 208a3... motors 205a...VVVF Inverter 206a···APU 207a1, 207a2, 207a3...transformers 209...HVAC compressor 210... Brake air compressor 211... Cooling fan 212...Accessories 213a... Rectifier circuit 214a... Control power supply 215, 215a... control circuits 215a1, 2052a2, 2151... Control Units 216a...DC-DC converter, DAB circuit 216a1...Primary side circuit 216a2...Secondary side circuit 217a1, 217a2, 217a3, 217a4, 217a5, 217a6... Inverters 218a...DC-DC converter 709, 710, 711, 712, 713, 714, 715, 716... Switching elements 717, 718, 719, 720, 721, 722, 723, 724... Diodes 725, 726, 727, 728, 729, 730, 731, 732, 733, 734... Capacitors 2051a1, 2052a1...Detection unit 2153...Judgment section 2152...Acquisition Department

Claims

1. A control unit configured to control the inverter corresponding to the axle connected to a wheel that is slipping among the wheels of an electric vehicle. A control circuit equipped with the following features.

2. A determination unit configured to determine whether the wheels of the electric vehicle are slipping based on the detection result of the rotational speed per unit time of the wheels of the electric vehicle, Equipped with, The control unit, Based on the determination result by the determination unit, the inverter is controlled. The control circuit according to claim 1.

3. An acquisition unit configured to acquire the detection result from at least one rotation sensor that detects the number of rotations per unit time of the wheels provided on the electric vehicle, Equipped with, The determination unit, Based on the detection results obtained by the acquisition unit, the slippage of the wheels of the electric vehicle is determined. The control circuit according to claim 2.

4. The control unit, The inverter is controlled to reduce the torque of the wheels of the electric vehicle that the determination unit has determined are slipping. The control circuit according to claim 2.

5. The control circuit according to claim 1, An inverter controlled by the aforementioned control circuit, An electric vehicle equipped with [a specific feature / equipment].

6. DC-DC converter connected to the inverter, The electric vehicle according to claim 5, comprising:

7. Controlling the inverter corresponding to the axle connected to the wheel that is slipping among the wheels of an electric vehicle. A control method including

8. On the computer, Controlling the inverter corresponding to the axle connected to the wheel that is slipping among the wheels of an electric vehicle. A program that executes the command.

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