Regenerative braking system and electric drive work vehicle using the same

Abstract

In the case where the regenerative operation is in progress, the electric power from the main machine side is supplied to the sub machine side, the voltage of the sub machine side is made to be a first voltage value which is prescribed in advance based on the operation voltage specification of the sub machine device, the electric power to the sub machine side is stopped by stopping the electric generator of the sub machine side, and the electric power of the sub machine side is supplied to the electric storage device. In the case where the regenerative operation has ended, the supply of the electric power from the main machine side to the sub machine side is stopped, and the electric generator of the sub machine side is controlled so that the electric generator of the sub machine side is started, the voltage of the sub machine side is made to be the first voltage value, and the electric power of the electric storage device is controlled so that the electric power of the electric storage device is supplied to the sub machine side and the voltage of the sub machine side is made to be a second voltage value which is higher than the first voltage value. Thus, it is possible to suppress the variation of the supply voltage supplied to the sub machine at the time of switching the regenerative operation based on the traveling motor.

Description

TECHNICAL FIELD

[0001] The present application relates to a regenerative braking system and an electric drive work vehicle using the same. BACKGROUND

[0002] In recent years, against the background of depletion of fossil fuels and worsening of the earth's environment, interest in electric vehicles that utilize electric power, such as hybrid vehicles and electric vehicles, has been rising, and they have been put into practical use. For example, various electric drive work vehicles are used in mine sites, and as work vehicles for transport purposes, large electric drive work vehicles, such as electric drive dump trucks, are also used. For electric drive dump trucks, there are cases where an electric drive system is used that converts the electric power generated by a main engine generator connected to an engine by an inverter to drive a travel motor. For dump trucks equipped with such an electric drive system, it is considered that by equipping a so-called regenerative braking system that supplies regenerative electric power generated by the travel motor when decelerating (braking) to auxiliary machines, energy saving and fuel consumption reduction can be achieved.

[0003] As a technology related to such a regenerative braking system, for example, Patent Literature 1 discloses a power supply system having: a power supply circuit that outputs a first voltage to a first power supply line; an electric storage unit that is connected to the first power supply line and charged by receiving the first voltage; a voltage conversion circuit that has a step-down function that steps down the first voltage from the first power supply line to a second voltage and outputs the second voltage to a second power supply line; and an electric load that is connected to the second power supply line and driven by receiving the second voltage, the electric load further having a voltage drop protection mechanism that takes the second voltage as a lower limit value of an operation voltage that ensures normal operation, and when the step-down function of the voltage conversion circuit is impaired, stops the step-down operation in the voltage conversion circuit, and fixes the voltage conversion ratio to substantially 1.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2010-74913 SUMMARY

[0007] For the regenerative braking system, during a regenerative operation in which the travel motor generates regenerative electric power (during a regenerative period), the regenerative electric power of the travel motor is supplied to the auxiliary machines via the DC / DC converter. On the other hand, during other periods in which the regenerative operation is not performed, electric power generated by an auxiliary machine generator driven by the engine or the like is supplied to the auxiliary machines. Here, in order to obtain a greater energy saving effect by the regenerative braking system, it is desirable to set the output of the auxiliary machine generator to zero during the regenerative period, and to supply all of the consumed electric power of the auxiliary machines from the DC / DC converter. Therefore, in such a case, switching of the supply source of the electric power supplied to the auxiliary machines occurs at the start or end of the regenerative period. The output of the auxiliary machine generator is slow to respond compared to the electric power converter such as the DC / DC converter, so in the transient state immediately after the start and end of the regenerative period, the voltage supplied to the auxiliary machines fluctuates sharply, and it is possible that the normal operation of the auxiliary machines will be hindered. In particular, immediately after the end of the regenerative period, since the auxiliary machine generator is started from a state in which the output is zero, there is concern that the voltage supplied to the auxiliary machines will decrease sharply. Although, for example, a large-capacity smoothing capacitor is connected to the auxiliary machine DC line to suppress fluctuations in the auxiliary machine DC voltage, in addition to problems such as the large size and cost increase of the system, there is also the problem that time is required for the first charge at the time of start and the discharge at the time of stop.

[0008] The present application was made in view of the above problems, and has as its object to provide a regenerative braking system capable of suppressing fluctuations in the supply voltage supplied to auxiliary machines at the time of switching of a regenerative operation based on a travel motor, and an electrically driven work vehicle using the regenerative braking system.

[0009] The present application includes a plurality of modes that solve the above problems, but if one example is given, the regenerative braking system has: a first generator and a second generator connected to an engine; a first rectifier circuit connected to the first generator, which rectifies the output of the first generator and outputs it as direct current to a first direct current line; an inverter connected between the first direct current line and a motor; a power consumption device connected to the first direct current line, which can consume the power of the first direct current line; a second rectifier circuit connected to the second generator, which rectifies the output of the second generator and outputs it as direct current to a second direct current line; an auxiliary machine device connected to the second direct current line; a first power conversion device that converts the power of the first direct current line and supplies it to the second direct current line; an electric storage device; a second power conversion device that switches between a discharging operation that converts the power of the electric storage device and supplies it to the second direct current line, and a charging operation that converts the power of the second direct current line and supplies it to the electric storage device; and a control device, wherein the control device is configured to determine whether the motor is performing a regenerative operation based on information related to a drive target of the motor, in the case where it is determined that the motor is in the regenerative operation, control the first power conversion device so that the power of the first direct current line is supplied to the second direct current line, and the voltage of the second direct current line becomes a first voltage value that is predetermined based on the operating voltage specification of the auxiliary machine device, and control the second generator so that the second generator is stopped to stop the supply of power to the second direct current line, and control the second power conversion device so that the power of the second direct current line is supplied to the electric storage device, and the voltage of the second direct current line becomes a second voltage value that is predetermined based on the operating voltage specification of the auxiliary machine device and is higher than the first voltage value, in the case where it is determined that the regenerative operation has ended, control the first power conversion device so that the supply of power from the first direct current line to the second direct current line is stopped, and control the second generator so that the second generator is started to start the supply of power to the second direct current line, and the voltage of the second direct current line becomes the first voltage value, and control the second power conversion device so that the power of the electric storage device is supplied to the second direct current line, and the voltage of the second direct current line becomes the second voltage value.

[0010] Inventive Effects

[0011] According to the present application, the variation in the supply voltage supplied to the auxiliary machine when switching the regenerative operation based on the traveling motor can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a side view schematically showing the appearance of the electric drive dump truck of the first embodiment.

[0013] Figure 2 is a diagram schematically showing an electric drive system including the regenerative braking system of the electric drive dump truck of the first embodiment.

[0014] Figure 3 is a diagram schematically showing an example of a configuration of a power conversion device between a host system and an auxiliary system.

[0015] Figure 4 is a diagram showing an example of an operation waveform of the power conversion device between the host system and the auxiliary system.

[0016] Figure 5 is a diagram schematically showing an example of a configuration of a power conversion device between an electric storage device and an auxiliary DC line.

[0017] Figure 6 is a diagram showing an example of an operation waveform of the power conversion device between the electric storage device and the auxiliary DC line, and is a diagram showing a pattern at the time of discharging of the electric storage device.

[0018] Figure 7 is a diagram showing an example of an operation waveform of the power conversion device between the electric storage device and the auxiliary DC line, and is a diagram showing a pattern at the time of charging of the electric storage device.

[0019] Figure 8 is a functional block diagram showing a processing content of the auxiliary voltage control section.

[0020] Figure 9 is a flowchart showing a processing content of switching on and off of the power conversion device and the auxiliary generator based on the regenerative period determination section.

[0021] Figure 10 is a timing chart showing an example of an operation waveform of the electric drive system, and is a diagram showing a pattern at the time of start of the regenerative period.

[0022] Figure 11 is a timing chart showing an example of an operation waveform of the electric drive system, and is a diagram showing a pattern at the time of end of the regenerative period.

[0023] Figure 12 is a functional block diagram showing a processing content of the upper limit value setting section.

[0024] Figure 13 is a diagram showing an example of an operation waveform of the upper limit value setting section.

[0025] Figure 14 is a functional block diagram showing a processing content of the auxiliary voltage control section of the second embodiment.

[0026] Figure 15is a flowchart showing the processing contents of switching between the electric power conversion device and the auxiliary generator performed by the regeneration period determination section of the second embodiment.

[0027] Figure 16 is a timing chart showing an example of the operation waveform of the electric drive system of the second embodiment, and is a chart showing the state at the start of the regeneration period.

[0028] Figure 17 is a timing chart showing an example of the operation waveform of the electric drive system of the second embodiment, and is a chart showing the state at the end of the regeneration period. DETAILED DESCRIPTION

[0029] Embodiments of the present application will be described below with reference to the accompanying drawings. In this embodiment, an electric drive dump truck is exemplified as an example of an electric drive work vehicle, but the present application can also be applied to other electric drive work vehicles such as an electric drive wheel loader.

[0030] <First Embodiment>

[0031] Reference will be made to Figures 1-13 to describe the first embodiment of the present application.

[0032] Figure 1 is a side view schematically showing the appearance of the electric drive dump truck of the present embodiment. In addition, Figure 2 is a diagram schematically showing the electric drive system including the regenerative braking system of the electric drive dump truck. Furthermore, Figure 1 In the drawings, only one of the left and right pair of components is illustrated and the reference numerals are attached, and for the other, only the reference numerals are indicated by parentheses in the drawings, and the illustration is omitted.

[0033] Figure 1 and Figure 2 In the drawings, the schematic configuration of the electric drive dump truck 100 includes: a vehicle body frame 1 extending in the front-rear direction and forming a support structure; a cargo box (dump body) 5 disposed on the upper portion of the vehicle body frame 1 in such a manner as to extend in the front-rear direction and having its rear end lower portion pivotably provided to the vehicle body frame 1 via a pin coupling portion 5a; a pair of driven wheels (front wheels) 2L, 2R disposed on the lower front side left and right of the vehicle body frame 1; a pair of drive wheels (rear wheels) 3L, 3R disposed on the lower rear side left and right of the vehicle body; a cab 4 disposed on the upper front side of the vehicle body frame 1; a fuel tank 9 disposed on the lower portion of the vehicle body frame 1; an engine 11 disposed on the vehicle body frame 1 and driven by fuel supplied from the fuel tank 9 (see Figure 2 ); and an electric drive system (see Figure 2), the electric drive system has a main generator 12 (first generator) connected to the engine 11 to be driven, and travel motors 10L, 10R and the like that drive the wheels (drive wheels 3L, 3R) using the electric power output from the main generator 12. The travel motors 10L, 10R are housed together with a reduction mechanism not shown in the rotating shaft portion of the drive wheels 3L, 3R. The vehicle body frame 1 and the cargo box 5 are connected by a hydraulic lifting cylinder 6, and the cargo box 5 is rotated about the pin joint portion 5a by the extension and contraction of the hydraulic lifting cylinder 6.

[0034] On the vehicle body frame 1, a deck on which an operator can walk is installed, and the operator can move to the cab 4 via the deck. In the interior of the cab 4, an accelerator pedal, a brake pedal, a lift pedal, a steering wheel, and the like not shown are provided. The operator controls the acceleration force and the braking force of the electric drive dump truck 100 by the amount of depression of the accelerator pedal and the brake pedal in the cab 4, performs a steering operation based on hydraulic drive by rotating the steering wheel to the left and right, and performs a cargo box 5 unloading operation based on hydraulic drive by depressing the lift pedal.

[0035] At the rear of the cab 4, a control cabinet 8 in which various electric power equipment is housed, and a plurality of grid boxes 7 for dissipating heat as heat from the remaining energy through the electric power consumption device 15 (refer to Figure 2 ) are mounted. In addition, Figure 1 Although not shown, on the vehicle body frame 1 between the left and right front wheels 2L, 2R, in addition to the engine 11 and the main generator 12 shown in Figure 2 , an auxiliary generator 41 as a power source for an auxiliary system and a main pump (not shown) as a hydraulic source for hydraulic equipment and the like are mounted.

[0036] Figure 2In the present embodiment, the regenerative braking system of the electric drive dump truck 100 has: a main machine generator 12 (first generator) connected to the engine 11 and an auxiliary machine generator 41 (second generator); a main machine rectifier circuit 14 (first rectifier circuit) connected to the main machine generator 12 and rectifying the output of the main machine generator 12 to output as direct current to a main machine direct current line 16 (first direct current line); inverter 13L, 13R for the traveling motor connected between the main machine direct current line 16 and the traveling motors 10L, 10R; a power consumption device 15 capable of consuming the electric power of the main machine direct current line 16; an auxiliary machine rectifier circuit 42 (second rectifier circuit) connected to the auxiliary machine generator 41 and rectifying the output of the auxiliary machine generator 41 to output as direct current to an auxiliary machine direct current line 43 (second direct current line); an auxiliary machine device 44 connected to the auxiliary machine direct current line 43; a power conversion device 21 (first power conversion device) converting the electric power of the main machine direct current line 16 and supplying to the auxiliary machine direct current line 43; an electric storage device 31; a power conversion device 32 (second power conversion device) switching between a charging operation of converting the electric power of the auxiliary machine direct current line 43 and supplying to the electric storage device 31 and a discharging operation of converting the electric power of the electric storage device 31 and supplying to the auxiliary machine direct current line 43; and a control device 50 controlling the operations of the engine 11 and the main machine generator 12, the auxiliary machine generator 41, the power consumption device 15, the power conversion device 21, the power conversion device 32, and the like.

[0037] The main machine rectifier circuit 14 rectifies the output of the main machine generator 12 and outputs as direct current to the main machine direct current line 16. Also, the auxiliary machine rectifier circuit 42 rectifies the output of the auxiliary machine generator 41 and outputs as direct current to the auxiliary machine direct current line 43. The main machine rectifier circuit 14 and the auxiliary machine rectifier 42 are each configured using, for example, a diode. Alternatively, an AC / DC converter configured using a switching element can be used instead of the main machine rectifier circuit 14 and the auxiliary machine rectifier circuit 42. Here, the output current of the auxiliary machine generator 41 rectified by the auxiliary machine rectifier circuit 42 is defined as (IG). In the following description, the output current IG is treated as the output current of the auxiliary machine generator 41.

[0038] The main machine generator 12 and the auxiliary machine generator 41 are each, for example, a synchronous generator of a coil excitation type, and each has an excitation device as an actuation device attached thereto. However, other types of generators can be applied to the main machine generator 12 and the auxiliary machine generator 41. For example, an AC / DC converter can be used as the main machine rectifier circuit 14 or the auxiliary machine rectifier circuit 42, and a permanent magnet synchronous generator can be used.

[0039] The inverters 13L, 13R are configured using, for example, IGBTs (Insulated Gate Bipolar Transistors) as switching elements. The DC input of the inverters 13L, 13R is connected to the main DC line 16, and the AC output is connected to the drive motors 10L, 10R.

[0040] The power consumption device 15 consumes the electric power of the main DC line 16 (that is, converts it into heat energy and dissipates it) based on the command signal from the control device 50, and has switching elements 152 and diodes 153 configured as a chopper connected in series between the positive and negative poles of the main DC line 16, and a resistor 151 connected in parallel to the switching elements 152. The resistor 151 is mounted on the grid box 7. As the switching elements 152, IGBTs are used, for example.

[0041] The auxiliary devices 44 are, for example, inverters and compressor motor systems for air conditioning, inverters and blower motor systems for equipment cooling, and the like. Therefore, the consumed electric power of the auxiliary devices 44 (auxiliary consumed electric power) varies depending on the running state of the electric drive dump truck 100. In addition, Figure 2 These are illustrated as an equivalent impedance for the auxiliary devices 44.

[0042] The power conversion device 21 is a so-called DC / DC converter that converts the main DC voltage Vi of the main system (main DC line 16) into an auxiliary DC voltage Vo during the regeneration period described later and supplies it to the auxiliary system (auxiliary DC line 43). Here, the output current of the power conversion device 21 output to the auxiliary DC line 43 is defined as ID.

[0043] A voltage detector 17 that detects the voltage (main DC voltage Vi) of the main DC line 16 is connected between the positive and negative poles of the main DC line 16. The voltage value (detection value) detected by the voltage detector 17 is output to the control device 50.

[0044] A voltage detector 45 that detects the auxiliary DC voltage (second DC voltage: Vo) generated in the auxiliary DC line 43 is connected between the positive and negative poles of the auxiliary DC line 43. In addition, a current detector 29 that detects the DC current (ID) generated in the auxiliary DC line 43 is inserted at one of the positive and negative poles of the auxiliary DC line 43. The voltage value (detection value) detected by the voltage detector 45 and the current value (detection value) detected by the current detector 29 are output to the control device 50.

[0045] The electric power conversion device 32 is a so-called bidirectional DC / DC converter that switches between a discharging operation of converting the electric power (voltage VB) stored in the electric storage device 31 into (Vo) and supplying it to the auxiliary machine DC line 43 and a charging operation of converting the electric power (voltage Vo) of the auxiliary machine DC line 43 into (VB) and supplying it to the electric storage device 31. Here, the direct current voltage between the positive and negative poles of the electric storage device 31 is defined as VB, the output current output from the electric storage device 31 to the electric power conversion device 32 is defined as IB, and the current converted by the electric power conversion device 32 and output to the auxiliary machine DC line 43 is defined as IB'. In addition, with respect to the current IB and the current IB', the flow in the direction from the electric storage device 31 to the auxiliary machine DC line 43, that is, the flow in the direction in which the electric storage device 31 discharges is set to be positive, and the flow in the direction from the auxiliary machine DC line to the electric storage device 31, that is, the flow in the direction in which the electric storage device 31 charges is set to be negative. In the following description, the current IB' is treated as the output current of the electric power conversion device 32. As described later, a capacitor is connected to each of the two terminals on the electric storage device 31 side and the auxiliary machine DC line 43 side of the electric power conversion device 32. If it is assumed that the electrostatic capacity of these capacitors is sufficiently large and the loss of the electric power conversion device 32 can be ignored, IB' = IB x VB / Vo holds in the steady state.

[0046] The current detector 33 that detects the direct current (IB) generated between the electric storage device 31 and the electric power conversion device 32 is inserted in one of the positive and negative poles of the electric storage device 31. The current value (detection value) detected by the current detector 33 is output to the control device 50. In addition, between the electric storage device 31 and the electric power conversion device 32, a fuse, a relay, a breaker, or the like can be inserted in addition to the current detector 33.

[0047] As described above, in the regenerative braking system of the embodiment, Figure 1 The electric power supplied from the main generator 12 via the electric power conversion device 21, the electric power supplied from the electric storage device 31 via the electric power conversion device 32, and the electric power supplied from the auxiliary generator 41 become the power source of the electric power supplied to the auxiliary device 44. Here, the resultant current of the currents ID, IB', and IG is defined as the auxiliary power current IA (= ID + IB' + IG) as the power current of the auxiliary device 44.

[0048] The detection value Vi from the voltage detector 17, the detection value Vo from the voltage detector 45, and the detection value IB from the current detector 33 are input to the control device 50, respectively. In addition, a vehicle information signal SV is input to the control device 50. The vehicle information signal SV includes a plurality of information such as the vehicle body speed information of the electrically driven work vehicle, i.e., the electrically driven dump truck 100, the operator's operation input information (the operation amount of the accelerator pedal and the brake pedal, etc.), and the like. Further, although not illustrated in the Figure 1

[0049] The control device 50 outputs control signals to the above-described respective devices based on the detection signals, and controls the energy flow within the electric drive system. Figure 1 In the figure, control signals output from the control device 50 to the engine 11, the main machine generator 12, the inverters 13L, 13R, the electric power consumption device 15, the electric power conversion device 21, the electric power conversion device 32, and the auxiliary machine generator 41 are indicated. The control signals that control the operation of the main machine generator 12 and the auxiliary machine generator 41 are command values of the field voltage or current. That is, the field devices of the main machine generator 12 and the auxiliary machine generator 41 control the field voltage or current in accordance with the command values from the control device 50.

[0050] Figure 3 is a diagram schematically indicating an example of the configuration of the electric power conversion device between the main machine system and the auxiliary machine system.

[0051] On the input terminal of the main machine direct current line 16 side of the electric power conversion device 21, the direct current input terminal of the inverter 22 and the capacitor 23 are connected. The alternating current output terminal of the inverter 22 is connected to the primary coil of the transformer 24. The secondary coil of the transformer 24 is connected to the alternating current input terminal of the rectifier circuit 25. The direct current output terminal of the rectifier circuit 25 is connected to the output terminal of the auxiliary machine direct current line 43 side of the electric power conversion device 21 via a filter circuit configured by the choke coil 26 and the capacitor 27.

[0052] The drive control device 28 outputs drive voltages of the elements Q1 to Q4 that configure the inverter 22 based on the control signal input from the control device 50. The inverter 22 converts the main machine direct current voltage Vi input to the electric power conversion device 21 into an alternating current voltage Vtr, and applies it to the primary coil of the transformer 24. The transformer 24, while insulating between the input and output of the electric power conversion device 21, transforms the voltage applied to the primary coil, and generates an alternating current voltage in the secondary coil. This alternating current voltage is converted into a direct current voltage by the rectifier circuit 25, and is output from the electric power conversion device 21 via the filter circuit.

[0053] ​Further, as the power conversion device 21, other circuit configurations can be used as long as it is a DC / DC converter. Also, as the circuit configuration of the inverter 22, a full-bridge inverter circuit having four elements Ql to Q4 is exemplified, but other circuit configurations can be used. For example, Figure 2 In the above, the case where the elements Ql to Q4 are IGBTs is exemplified, but other types of elements such as MOSFETs can be used. Also, as the circuit configuration of the rectifier circuit 25, a full-bridge rectifier circuit composed of four diodes Dl to D4 is exemplified, but other circuit configurations can be used. Also, the power conversion device 21 can have, in addition to the above elements, control components such as short-circuiters and relays, protection components such as fuses and surge protectors, and noise filters.

[0054] Figure 4 is a view showing an example of an operation waveform of the power conversion device between the host system and the auxiliary system.

[0055] Figure 4 In the above, the case where the elements Ql to Q4 are IGBTs is exemplified, but other types of elements such as MOSFETs can be used. Also, as the circuit configuration of the rectifier circuit 25, a full-bridge rectifier circuit composed of four diodes Dl to D4 is exemplified, but other circuit configurations can be used. Also, the power conversion device 21 can have, in addition to the above elements, control components such as short-circuiters and relays, protection components such as fuses and surge protectors, and noise filters. Figure 4 The vertical axis items of the view of FIG. 6 show the drive signals (on-off signals) of the elements Ql to Q4, the primary coil voltage Vtr of the transformer 24, the output current ID, and the current ILd of the choke coil 26. The output current ID and the current ILd are shown superimposed, and the output current ID is shown as a broken line. Further, in the view of FIG. 6, the output current ID is shown as a broken line, and the current ILd is shown as a solid line. Figure 4 In the above, the case where the elements Ql to Q4 are IGBTs is exemplified, but other types of elements such as MOSFETs can be used. Also, as the circuit configuration of the rectifier circuit 25, a full-bridge rectifier circuit composed of four diodes Dl to D4 is exemplified, but other circuit configurations can be used. Also, the power conversion device 21 can have, in addition to the above elements, control components such as short-circuiters and relays, protection components such as fuses and surge protectors, and noise filters. Figure 4 In the above, the case where the elements Ql to Q4 are IGBTs is exemplified, but other types of elements such as MOSFETs can be used. Also, as the circuit configuration of the rectifier circuit 25, a full-bridge rectifier circuit composed of four diodes Dl to D4 is exemplified, but other circuit configurations can be used. Also, the power conversion device 21 can have, in addition to the above elements, control components such as short-circuiters and relays, protection components such as fuses and surge protectors, and noise filters.

[0056] In the period when the elements Ql and Q4 are on, the absolute value of the voltage Vtr is equal to the voltage Vi, and the polarity of the voltage Vtr is positive. In the period when the elements Q2 and Q3 are on, the absolute value of the voltage Vtr is equal to the voltage Vi, but the polarity of the voltage Vtr is negative. In these periods, the current ILd increases with time. In the period when all the elements (Ql to Q4) are off, the voltage Vtr is zero, and the current ILd decreases with time. The current ILd thus repeatedly increases and decreases, and the average value thereof is the output current ID. Here, as shown in the view of FIG. 6, the output current ID is shown as a broken line, and the current ILd is shown as a solid line. Figure 4As shown, the switching period is defined as Tsw, and the on-time of the elements Ql, Q4 (or the elements Q2, Q3) is defined as Ton. At this time, the duty ratio dD in pulse width modulation (PWM) is (2Ton) / Tsw. That is, by controlling the duty ratio dD, the output voltage Vo of the power conversion device 21 can be controlled. If the voltage Vi is fixed, the greater the duty ratio dD is made, the higher the output voltage Vo of the power conversion device 21 is made.

[0057] Figure 5 is a view schematically showing a configuration example of a power conversion device between the electric storage device and the auxiliary machine DC line.

[0058] The power conversion device 32 is constituted by an upper and lower bridge arm (half bridge circuit) 34 formed based on two elements Q5, Q6, a choke coil 35, capacitors 36, 37. A drive control device 38 outputs a drive voltage of the elements Q5, Q6 based on a control signal input from the control device 50.

[0059] Figure 6 and Figure 7 is a view showing an example of an operation waveform of the power conversion device between the electric storage device and the auxiliary machine DC line, Figure 6 shows the appearance at the time of discharging of the electric storage device, Figure 7 shows the appearance at the time of charging of the electric storage device.

[0060] Figure 6 and Figure 7 in which operation waveforms of two periods of the switching operation of the elements Q5, Q6 are shown. As Figure 6 and Figure 7 the vertical axis items of the graphs show the drive signal (on-off signal) of the elements Q5, Q6, the output voltage Vch of the upper and lower bridge arm 34, the charge-discharge current IB, the current ILb of the choke coil 35. The current IB and the current ILb are shown superimposed, and the current IB is shown as a broken line. Further, in Figure 6 and Figure 7 the voltage and current oscillations caused by the parasitic capacitance and the parasitic inductance of the circuit and the voltage drop of the elements are ignored. In addition, in Figure 6 and Figure 7 the voltage VB of the electric storage device 31 and the auxiliary machine DC voltage Vo are respectively set to be fixed during the periods shown. In addition, the static capacitance of the capacitor 36 is assumed to be sufficiently large, and the current IB is set to be fixed. In addition, although not shown in the graphs, the static capacitance of the capacitor 37 is also sufficiently large, and the current IB' is also fixed.

[0061] Figure 6 in which the power conversion device 32 discharges the electric storage device 31, and the current IB is positive. At this time, the side of the power conversion device 32 to which the capacitor 36 is connected (Figure 5 The terminal on the left side is the input, and the side connected to capacitor 37 is the input side. Figure 5 The terminal on the right side is the output. Component Q5 is normally closed. During the period when component Q6 is open, the voltage Vch is 0 (zero), and a voltage VB is applied to the choke coil 35. The current ILb increases over time, and energy is stored in the choke coil 35. During the period when component Q6 is closed, the energy stored in the choke coil 35 is released to the output side through the reverse diode of component Q5, and the current ILb decreases over time. At this time, the voltage Vch is the output voltage (auxiliary DC voltage Vo). The current ILb increases and decreases repeatedly as described above, and its average value is the current IB. Here, as... Figure 6 As shown, the conversion period is defined as Tsw, and the on-time of component Q6 is defined as Ton6. At this time, the duty cycle dB6 in the PWM is Ton6 / Tsw. The duty cycle dB6 is the operating quantity of the power conversion device 32 during discharge. If the voltage VB is set to a fixed value, increasing the duty cycle dB6 will result in a higher output voltage Vo of the power conversion device 32.

[0062] Figure 7 In this process, the power conversion device 32 charges the energy storage device 31, and the current IB is negative. At this time, the side of the power conversion device 32 connected to the capacitor 37 ( Figure 5 The right-side terminal is the input, connected to the side of capacitor 36. Figure 5 The terminal on the left side is the output. Component Q6 is normally closed. During the period when component Q5 is open and voltage Vch is voltage Vo, current flows from the input side to the output side through component Q5 and choke coil 35. The absolute value of current ILb increases with time. If component Q5 is turned off, the reverse diode of component Q6 conducts, making voltage Vch 0 (zero), and the absolute value of current ILb decreases with time. Here, as... Figure 7 As shown, the conversion period is defined as Tsw, and the on-time of component Q5 is defined as Ton5. At this time, the duty cycle dB5 in the PWM is Ton5 / Tsw. The duty cycle dB5 is the operating quantity of the power conversion device 32 during charging. If the voltage Vo is set to a fixed value, increasing the duty cycle dB5 will result in a higher output VB.

[0063] Here, the duty cycles dB5 and dB6 are combined into one, defined as a duty cycle dB with positive and negative polarities. For the drive control device 38, dB is input as a control signal from the control device 50. When the control signal dB is positive, the drive control device 38 uses a duty cycle dB6 = dB. Figure 6 The control element Q6 is shown to be turned on and off. On the other hand, when the control signal dB is negative, the duty cycle dB5 = |dB| is used as follows... Figure 7The opening and closing of the control element Q5 is shown. That is, in the case where the control signal dB is positive, discharge is performed, and in the case where it is negative, charge is performed. Furthermore, in the steady state, the average value of the current ILb is the current IB. That is, Figure 2 In the above, a configuration in which the control device 50 uses the detection value (current IB) of the current detector 33 is exemplified, but a configuration in which the current ILb is detected instead of the current IB and the average value thereof is used can also be configured.

[0064] Returning Figure 2 .

[0065] As Figure 2 shown, the control device 50 has a drive control section 51, a main machine voltage control section 52, and an auxiliary machine voltage control section 53.

[0066] The drive control section 51 outputs control signals to the engine 11 and the inverter 13 in accordance with the operation amounts of the accelerator pedal and the brake pedal included in the vehicle information signal SV. As will be described later, the voltage Vi is controlled by the main machine generator 12 at the time of acceleration and by the power consumption device 15 at the time of braking.

[0067] The main machine voltage control section 52 judges acceleration or deceleration (braking) from the input vehicle information signal SV to output control signals to the main machine generator 12 or the power consumption device 15 in such a manner that the voltage Vi coincides with a prescribed command value.

[0068] The auxiliary machine voltage control section 53 outputs control signals to the auxiliary machine generator 41, the power conversion device 21, and the power conversion device 32 as auxiliary machine power sources in such a manner that the auxiliary machine direct current voltage Vo coincides with a prescribed command value. That is, the voltage Vo is controlled by the three auxiliary machine power sources of the auxiliary machine generator 41, the power conversion device 21, and the power conversion device 32. As with the drive control section 51 and the main machine voltage control section 52, the vehicle information signal SV is also input to the auxiliary machine voltage control section 53.

[0069] Furthermore, as will be described later, the control device 50 detects and controls the current IB, but a configuration in which the current IB' is detected instead of the current IB and controlled can also be configured. In this case, the connection position of the current detector 33 is changed to a position at which the current IB' can be detected, and the current command value is converted using the above-described relationship (IB' = IB x VB / Vo).

[0070] The implementation method of the control device 50 is arbitrary, but as an example, a method in which electronic circuits are mounted on a substrate is used. In this case, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a microcomputer, an FPGA (Field-Programmable Gate Array), or the like is mounted on the substrate. The operation content of the auxiliary machine voltage control section 53 described later is implemented by a program or the like executed by these devices. Furthermore, since the control device 50 has a plurality of operation modules, each operation module can be mounted on an independent substrate or device, or these can be aggregated to constitute the control device 50. Alternatively, one operation module can be distributed to and mounted on a plurality of substrates or devices. For example, the auxiliary machine voltage control section 53 generates control signals of the auxiliary machine generator 41, the power conversion device 21, and the power conversion device 32, but the generation of each control signal can be distributed to other substrates or devices.

[0071] Here, the basic energy flow of the electric drive system is described.

[0072] First, the energy flow of the electric drive system at the time of acceleration is described. When the main machine generator 12 is driven by the engine 11, the alternating current voltage output from the main machine generator 12 is converted into the main machine direct current voltage Vi by the main machine rectifier circuit 14, and is input to the inverter 13. If the operator steps on the accelerator pedal, alternating current power is supplied from the inverter 13 to the running motor 10, and the running motor 10 drives the wheels to accelerate the vehicle body. In this case, the main machine direct current voltage Vi is controlled by the main machine generator 12. When the auxiliary machine generator 41 is driven by the engine 11, the alternating current voltage output from the auxiliary machine generator 41 is converted into direct current by the auxiliary machine rectifier circuit 42, and is input to the auxiliary machine device 44. In addition, the power conversion device 32 discharges the storage device 31, and the discharged power can be supplied to the auxiliary machine device 44.

[0073] Next, the energy flow during braking, that is, during regeneration of the traveling motor 10 will be described. When the operator steps on the brake pedal, the traveling motor 10 converts the kinetic energy of the vehicle body into electric power and outputs the regenerated electric power to the main machine DC line 16 via the inverter 13. That is, the traveling motor 10 operates as a generator. The electric power consumption device 15 converts the regenerated electric power into heat and prevents the main machine DC voltage Vi from becoming excessively large. Therefore, the main machine DC voltage Vi in this case is controlled by the electric power consumption device 15. The electric power conversion device 21 converts the main machine DC voltage Vi into the auxiliary machine DC voltage Vo and outputs a part of the regenerated electric power to the auxiliary machine DC line 43. The electric power output to the auxiliary machine DC line 43 is consumed by the auxiliary machine device 44 or stored in the electric storage device 31 via the electric power conversion device 32. Thus, electric braking is implemented by consuming the regenerated electric power, and the vehicle body is decelerated. In addition, for braking of the vehicle body, electric braking and a not-shown mechanical brake can be used in combination.

[0074] Since the electric power conversion device 21 supplies electric power to the auxiliary machine device 44 when braking, the load of the auxiliary machine generator 41, and further the load of the engine 11, are reduced in correspondence therewith. By such an operation, it is possible to effectively utilize the regenerated electric power generated during braking by the auxiliary machine, and in correspondence therewith, it is possible to achieve energy saving and fuel consumption reduction of the dump truck. This is the regenerative braking system of the present application.

[0075] Next, the processing content of the auxiliary machine voltage control section 53 of the control device 50 will be described.

[0076] Figure 8 is a functional block diagram showing the processing content of the auxiliary machine voltage control section.

[0077] Figure 8 In the auxiliary machine voltage control section 53, there are a voltage control system 60 (first voltage control system) for controlling the auxiliary machine DC voltage Vo, a voltage control system 70 (second voltage control system), and a voltage control system 80 (third voltage control system).

[0078] The voltage control system 60 performs an operation for controlling the auxiliary machine generator 41 so that the voltage Vo coincides with a first voltage command value. In addition, the voltage control system 70 performs an operation for controlling the electric power conversion device 32 so that the voltage Vo coincides with a second voltage command value. In addition, the voltage control system 80 performs an operation for controlling the electric power conversion device 21 so that the voltage Vo coincides with a third voltage command value.

[0079] In this embodiment, the first voltage command value and the third voltage command value are set to VI, and the second voltage command value is set to V2. At this time, V2 > VI is set. Further, with respect to the voltage Vo, an allowable range (operation voltage specification) for normally operating the auxiliary machinery 44 is predetermined based on the withstand voltage characteristics and the operation characteristics, and the voltages VI and V2 are set to values within the allowable range.

[0080] The auxiliary machinery voltage control section 53 performs the regeneration period determination, and performs the on-off control of the power conversion device 21 and the auxiliary machinery generator 41 based on the determination result. The regeneration period determination section 54 performs the regeneration period determination based on the vehicle information signal SV, and generates a regeneration period determination signal SR. As an example of the regeneration period determination signal SR, a digital signal such as an H level (high level) during the regeneration period and an L level (low level) during a period other than the regeneration period (hereinafter referred to as a non-regeneration period) can be conceived. The regeneration period determination signal SR is output to the on-off switching section 81 (second on-off switching section), the on-off switching section 61 (first on-off switching section), and the upper limit value setting section 71 (first upper limit value setting section) described later.

[0081] The vehicle information signal SV includes the vehicle body speed information and the operator's operation input information. For example, from the information of the operator's brake pedal operation or deceleration of the vehicle body, it is possible to determine whether or not it is in the regeneration period. Further, although not illustrated, it is also possible to detect the alternating current output current of the inverter 13 and calculate the torque of the running motor 10, and to calculate the regenerative electric power from the torque and the rotational speed of the running motor 10, thereby performing the regeneration period determination. At this time, in a case where the regenerative electric power is greater than a predetermined threshold value, it is determined that it is in the regeneration period. Instead of using the detected alternating current output current of the inverter 13, it is also possible to use the current command value calculated by the drive control section 51. According to the above, the regeneration period determination section 54 can be input not only the vehicle information signal SV but also other information necessary for the regeneration period determination.

[0082] The on-off switching section 81 is associated with the on-off control of the power conversion device 21, and generates an on-off signal SD in such a manner that the power conversion device 21 is operated (becomes an on state) during the regeneration period. The generated on-off signal SD is output to the on-off control section 82 (second on-off control section) described later. As an example of the on-off signal SD, a digital signal such as an H level (high level) in the on state and an L level (low level) in the off state can be conceived. In this case, the on-off signal SD is the same as the regeneration period determination signal SR.

[0083] The on-off switching section 61 generates an on-off signal SG in a manner that the auxiliary generator 41 is operated (becomes an on state) during the non-regeneration period in association with on-off control of the auxiliary generator 41. The generated on-off signal SG is output to the on-off control section 62 (first on-off control section) described later. As an example of the on-off signal SG, a digital signal such as a signal that becomes an H level (high level) in the on state and becomes an L level (low level) in the off state can be conceived. In this case, the on-off signal SG is the same as the signal SP after the regeneration period judgment signal SR is inverted.

[0084] Figure 9 is a flowchart showing the processing content of the on-off switching of the power conversion device and the auxiliary generator based on the regeneration period judgment section. In the case where the operation of the auxiliary voltage control section 53 is realized by a program or the like in the CPU, the processing of the on-off switching based on the flowchart shown in Figure 9 is periodically executed.

[0085] Figure 9 In the regeneration period judgment section 54, first, whether or not it is in the regeneration period is judged based on the vehicle information signal SV, and a regeneration period judgment signal SR corresponding to the judgment result is generated (step S100). Next, whether or not it is in the regeneration period is judged, that is, whether or not the regeneration period judgment signal SR is on is judged (step S110), and in the case where the judgment result is yes, H (high level) is output as the on-off signal SD, whereby the power conversion device 21 is controlled to the on state, and L (low level) is output as the on-off signal SG, whereby the auxiliary generator 41 is controlled to the off state (step S111), and the processing is ended. In addition, in the case where the judgment result in step S110 is no, that is, in the case where it is judged that it is not in the regeneration period, L level (low level) is output as the on-off signal SD, whereby the power conversion device 21 is controlled to the off state, and H level (high level) is output as the on-off signal SG, whereby the auxiliary generator 41 is controlled to the on state (step S112), and the processing is ended.

[0086] Here, the control operation of the power conversion device 21 is described. The voltage control system 80 calculates the operation amount of the power conversion device 21 by the voltage control operation section 83 after calculating the deviation (V1-V0) of the voltage V1 and the voltage Vo, and outputs it to the on-off control section 82. Specifically, the operation amount is changed in a manner that the deviation becomes small based on a control rule such as proportional integral (PI: Proportional Integral) control. In the configuration of the power conversion device 21, the duty ratio dD of the PWM is the operation amount. The on-off control section 82 outputs the operation amount generated by the voltage control operation section 83 directly based on the on-off signal SD if it is in the on state. If it is in the off state, the operation amount is changed to zero and output. The output of the on-off control section 82 is output as a control signal to the power conversion device 21.

[0087] Next, the control operation of the auxiliary generator 41 will be described. The voltage control system 60 calculates the operation amount of the auxiliary generator 41 by the voltage control operation section 63 after calculating the deviation (V1-V0) of the voltage V1 from the voltage Vo, and outputs it to the on-off control section 62. As described above, a synchronous generator of the coil excitation type is assumed as the auxiliary generator 41, and the command value of the excitation voltage or current is taken as the operation amount. The on-off control section 62 directly outputs the operation amount generated by the voltage control operation section 63 based on the on-off signal SG if it is in the on state. If it is in the off state, the operation amount is changed to zero and output. The output of the on-off control section 62 is output as a control signal to the auxiliary generator 41.

[0088] Next, the control operation of the power conversion device 32 will be described. The voltage control system 70 has a current control system 72 for controlling the charge / discharge current IB of the electric storage device 31 as a local hysteresis loop. As described above, the current IB' and the current ILb can also be controlled instead of the current IB. In the voltage control system 70, the current command value is generated by the voltage control operation section 73 after calculating the deviation (V2-V0) of the voltage V2 from the voltage Vo. This current command value is defined as the pre-limit current command value IBrefl (first current command value). Specifically, the pre-limit current command value IBrefl is changed in such a way that the deviation becomes smaller based on a control rule such as PI control. The pre-limit current command value IBrefl is input to the variable limiter 74 of the rear stage. The current upper limit value IBmax described later is also input to the variable limiter 74. The variable limiter 74 sets the upper limit value to IBmax and performs a limiting process on the pre-limit current command value IBrefl, and generates a post-limit current command value IBref2 (second current command value). The post-limit current command value IBref2 is input to the current control system 72.

[0089] In the current control system 72, the operation amount of the power conversion device 32 is calculated by the current control operation section 75 after calculating the deviation (IBref2-IB) of the post-limit current command value IBref2 from the current IB, and output. Specifically, the operation amount is changed in such a way that the deviation becomes smaller based on a control rule such as PI control. In the configuration of the power conversion device 32, the duty ratio dB of the PWM is the operation amount. The operation amount generated by the current control operation section 75 is output as a control signal to the power conversion device 32. The upper limit value setting section 71 generates the upper limit value IBmax of the pre-limit current command value IBrefl from the regeneration period judgment signal SR and outputs it to the variable limiter 74. The specific generation method of IBmax is described in the action timing chart and the block diagram of the voltage control system 70 of FIG. 6. Figure 1The same as the subsequent description. In addition, although not illustrated, with respect to the voltage control system 80 of the electric power conversion device 21, a current control system as a local hysteresis loop can also be provided, similarly to the voltage control system 70, to control the output current ID and the current ILd of the electric power conversion device 21.

[0090] Figure 10 and Figure 11 is a timing chart showing an example of an operation waveform of the electric drive system, Figure 10 shows the appearance at the start of the regeneration period, Figure 11 shows the appearance at the end of the regeneration period.

[0091] Figure 10 and Figure 11 The vertical axis items of the graph are the on-off signals SD, SG of the electric power conversion device 21 and the auxiliary generator 41, the auxiliary direct-current voltage Vo, the output current ID of the electric power conversion device 21, the charge-discharge current IB of the electric storage device 31, and the output current IG of the auxiliary generator 41. With respect to the current IB, the upper limit value IBmax of the current is indicated by a dotted line. In addition, the current input to the auxiliary device 44 during the period illustrated is fixed, and the value thereof is set to the current I1 and is indicated in the graph. Furthermore, Figure 10 and Figure 11 show the approximate shapes of the changes in voltage and current, and these items are illustrated as linear changes, but the actual voltage and current are not limited to linear changes.

[0092] First, the operation at the start of the regeneration period will be described. As shown in Figure 10 , the times t1, t2 are defined, and the regeneration period starts at the time t1. That is, the regeneration period determination section 54 determines that the regeneration period has started at the time t1. Hereinafter, using Figure 11 , the operation of each of the period before the time t1, the period from the time t1 to t2, and the period after the time t2 will be described in order. Furthermore, Figure 10 , the current IB and the current IBmax almost overlap. This case implies that the current IB is limited by the variable limiter 74, as will be described later.

[0093] The period before the time t1 is a non-regeneration period, the electric power conversion device 21 is in the closed state, and the auxiliary generator 41 is in the open state. Since the electric power conversion device 21 is in the closed state, the current ID is 0 (zero). In addition, according to the reason described later, the voltage Vo is controlled to the voltage V1 by the auxiliary generator 41.

[0094] The upper limit value setting portion 71 sets the current IBmax to I3. I3 is a positive value or 0 (zero). That is, the power conversion device 32 is in a state where the discharge current IB is limited to the current I3 although the electric storage device 31 can be discharged. Here, in the case where the current IB is controlled to the current I3, the output current IB' of the power conversion device 32 is defined to become the current I3'. Since the mutual conversion between the current IB and the current IB' has been described, the description is omitted. The current I3 is set to satisfy I3' < I1. Therefore, the state where the entire auxiliary power cannot be supplied by only the power conversion device 32 is present. The deficient amount of power is I1-I3'.

[0095] The voltage control system 70 for the power conversion device 32 operates in such a manner that the voltage Vo is increased to the voltage V2. However, in the voltage control system 70, the post-limit current command value IBref2 is limited to IBmax = I3 by the variable limiter 74 regardless of how much the pre-limit current command value IBrefl is increased by the voltage control operation portion 73. As described above, the entire auxiliary power cannot be supplied by only the discharge of the electric storage device 31 at the current I3. In the state limited by the variable limiter 74, the power conversion device 32 operates in a constant current (CC) mode and cannot control the voltage Vo to the voltage V2. The current command value in the constant current mode becomes IBmax = I3. The current IB is controlled to the current I3 by the current control system 72, and the current IB' becomes the current I3'.

[0096] The voltage control system 60 for the auxiliary generator 41 operates in such a manner that the voltage Vo is controlled to the voltage VI. As a result, the voltage Vo becomes a state where the voltage VI is controlled by the auxiliary generator 41, and the current IG becomes the deficient current I1-I3' described above.

[0097] Further, Figure 10 In the above, although the current IBmax is fixed at the current I3, the current IBmax can be changed by the charge remaining amount of the electric storage device 31. For example, if a voltage detector for detecting the voltage VB of the electric storage device 31 is added with respect to the electric drive system in the present embodiment, the charge remaining amount can be calculated from the detected value of the voltage VB. Alternatively, the charge remaining amount can be calculated by the integration of the current IB. In the case where the charge remaining amount reaches a lower limit value, the current IBmax can be set to zero. If the current IBmax is zero, the current IG is I1, and the state where the entire auxiliary power can be supplied by only the auxiliary generator 41 is present.

[0098] During the period from time tl to t2, the regeneration period starts at time tl, the power conversion device 21 becomes the ON state, and the auxiliary generator 41 becomes the OFF state. Even if the field coil voltage of the auxiliary generator 41 is set to 0 (zero), the field current gradually decreases due to the inductance of the field coil. Therefore, the current IG also gradually decreases to 0 (zero).

[0099] During the period from time tl to t2, the upper limit value setting portion 71 gradually decreases the current IBmax to a negative value (-I2). At this point, it is important to note that the current I2 > 0 (zero). Figure 10 The current IBmax is gradually decreased linearly, but it is not limited thereto. The limited post-current command value IBref2 decreases in conjunction with the current IBmax, and the current IB also decreases in conjunction with the current IBmax by the action of the current control system 72. That is, the above-described constant current mode continues, and becomes an action such that the current command value gradually decreases. If the current IB and the current IBmax are reversed from positive to negative, the power storage device 31 changes from discharging to charging. The current IB' also decreases in conjunction with the current IB. At this point, it is defined that when the current IB is controlled to (-I2), the current IB' becomes a current (-I2').

[0100] The voltage control system 80 for the power conversion device 21 starts to act so as to control the voltage Vo to the voltage VI. As a result, the power conversion device 21 gradually increases the ID in response to the above-described decrease in IG and IB', so that the auxiliary power supply current IA (= ID + IB' + IG) coincides with I1. When IG becomes zero and IB' becomes -I2', ID becomes I1 + I2'. By gradually decreasing IB as described above, it is possible to suppress the load variation of the power conversion device 21, and the transient variation of Vo becomes small. Furthermore, in practice, the gradually decreasing IG and IB' become external disturbances, and Vo becomes slightly lower than VI. In Figure 8 In (a), this case is ignored, and Vo coincides with VI.

[0101] During the period after time t2, the voltage Vo is controlled to the voltage VI by the power conversion device 21. The current ID becomes I1 + I2', the current IB becomes (-I2), and the current IG becomes 0 (zero). At this point, the power storage device 31 is in a charging state, and the size of the charging current is the current I2. In this way, during the regeneration period, the power conversion device 21 supplies all of the auxiliary consumption power, and also supplies power for charging the power storage device 31 by the power conversion device 32. After the start of the regeneration period, the auxiliary power supply is switched from the auxiliary generator 41 to the power conversion device 21.

[0102] Furthermore, Figure 10Although the current IBmax is fixed at the current (-I2), it can also be varied by the remaining charge of the energy storage device 31. For example, when the remaining charge reaches its upper limit, the current IBmax can be set to zero. By charging the energy storage device 31 during the regeneration period, the energy necessary for the discharge described later can be stored.

[0103] Next, the actions at the end of the regeneration period will be explained. For example... Figure 11 As shown, times t3, t4, and t5 are defined. It is assumed that the regeneration period ends at time t3. The following uses... Figure 11 The actions during the periods t3 to t4 and t4 to t5 are described sequentially. Furthermore, the actions before time t3 and after time t2 are described (see [reference]). Figure 10 Similarly, the actions during the period after time t5 and the actions during the period before time t1 (refer to...) Figure 10 Similarly, explanations are omitted here.

[0104] During the period from time t3 to t4, assuming the regeneration period ends at time t3, the power conversion device 21 is closed, and the current ID decreases to 0 (zero). On the other hand, the auxiliary generator 41 is open.

[0105] The upper limit setting unit 71 changes the current IBmax to a positive value I4. By making the current IBmax positive, the power conversion device 32 can discharge the energy storage device 31. Here, it is defined that when the current IB is controlled to be current I4, the current IB' becomes I4'. The current I4 is set such that I4' > I1. That is, the power conversion device 32 is allowed to supply all auxiliary equipment power independently. Furthermore, the current IB' when the current IB is controlled to be I1' is defined as current I1. Since I4' > I1, I1' < I4.

[0106] The voltage control system 70 used in the power conversion device 32 increases the current command value IBref2 after limitation to a positive value in order to increase the voltage Vo to V2. The operation of the current control system 72 increases the current IB, reversing from negative to positive. That is, the energy storage device 31 switches from charging to discharging. The current IB' also reverses from negative to positive along with the current IB.

[0107] Immediately after time t3, the current IA(=ID+IB'+IG) is smaller than the current II, and thus the voltage Vo decreases from VI. The voltage control system 60 for the auxiliary generator 41 operates in such a manner that the voltage Vo increases toward VI, and thus the current IG starts to flow. In this way, both the power conversion device 32 and the auxiliary generator 41 output the current in order to prevent the voltage Vo from decreasing. However, since the response of the auxiliary generator 41 is slower than that of the power conversion device 32, the current IG hardly increases, and the voltage Vo hardly increases due to the current IB' alone.

[0108] If the voltage Vo is smaller than V2 even after the voltage Vo reaches VI, the power conversion device 32 wants to increase the current IB'. Thus, when the voltage Vo is higher than VI, the auxiliary generator 41 wants to decrease the current IG. As a result, the power conversion device 32 alone supplies all of the auxiliary power, the current IB' becomes II, and the current IB becomes II'. In addition, the current IG decreases to zero. If this state is reached, the voltage Vo is controlled by the power conversion device 32 to the voltage V2. At this time, the power conversion device 32 operates in a constant voltage (CV) mode.

[0109] In this way, both the auxiliary generator 41 and the power conversion device 32 want to control the voltage Vo, but since V2>Vl, the power conversion device 32 preferentially outputs the power.

[0110] From time t4, which is the time at which a predetermined time elapses from the end of the regeneration period, to time t5, the upper limit value setting section 71 gradually decreases the current IBmax from I4 to the above-mentioned I3. In addition, Figure 11 In this way, both the auxiliary generator 41 and the power conversion device 32 want to control the voltage Vo, but since V2>Vl, the power conversion device 32 preferentially outputs the power.

[0111] Here, the processing content of the upper limit value setting section 71 will be described in detail.

[0112] Figure 12is a functional block diagram showing the processing contents of the upper limit value setting section. In addition, Figure 13 is a graph showing an example of the action waveform of the upper limit value setting section.

[0113] As shown in Figure 12 , the upper limit value setting section 71 generates the current upper limit value IBmax based on the regeneration period judgment signal SR input from the regeneration period judgment section 54. In the following description, regarding the values of the regeneration period judgment signal SR and its inverted signal SP, 1 is set in the case of the H level (high level), and 0 (zero) is set in the case of the L level (low level).

[0114] The current upper limit value IBmax output from the upper limit value setting section 71 is a value obtained by adding the current upper limit value IBR for the regeneration period and the current upper limit value IBP for the non-regeneration period, which is generated by passing through the drop rate limiter 711.

[0115] The current upper limit value IBR for the regeneration period is generated by multiplying the regeneration period judgment signal SR by the value (-I2) in the multiplier 714. That is, since the regeneration period judgment signal SR = 1 during the regeneration period, the current upper limit value IBR = -I2. In addition, since the regeneration period judgment signal SR = 0 (zero) during the non-regeneration period, the current upper limit value IBR = 0 (zero).

[0116] The current upper limit value IBP for the non-regeneration period is generated based on the inverted signal SP generated by the logic inverter (logical negator) 715 of the regeneration period judgment signal SR. The decay current command generation section 712 generates the decay current command value IBdec from the signal SP by the following principle. The decay current command generation section 712 takes the end point of the regeneration period as a trigger point, that is, takes the activation of the signal SP as a trigger point, and the decay current command generation section 712 increases the decay current command value IBdec to the positive value IBM. Then, the decay current command generation section 712 decays the decay current command value IBdec to zero. The value IBM is set to a value larger than the current I4.

[0117] The decay current command value IBdec is input to the limiter 713. The limiter 713 performs a limiting process on the decay current command value IBdec in such a way that the upper limit value becomes I4 and the lower limit value becomes I3. The current upper limit value IBP is generated by multiplying the output from the limiter 713 by the signal SP in the multiplier 716. Since the signal SP = 0 (zero) during the regeneration period, the current upper limit value IBP = 0 (zero). During the non-regeneration period, the signal SP = 1, in which case the upper limit value of the current upper limit value IBP becomes I4, and the lower limit value becomes I3. In addition, Figure 13In this case, the upper limit value of the current IBP and the decay current command value IBdec are overlapped, and the decay current command value IBdec is indicated by the dotted line.

[0118] The decrease rate limiter 711 is a rate limiter that acts only with respect to the decrease of the input current value (IBR + IBP). Figure 13 In this case, the current IBmax and the current value (IBR + IBP) are overlapped, and the current value (IBR + IBP) is indicated by the dotted line.

[0119] The effects of the present embodiment configured as described above will be described.

[0120] In the present embodiment, after the start of the regeneration period, the auxiliary power source is switched from the auxiliary generator 41 to the power conversion device 21. That is, the output of the auxiliary generator 41 is set to zero, and the entire auxiliary power is supplied from the power conversion device 21. Thus, the energy saving effect of the regenerative braking system can be improved.

[0121] In addition, at the end of the regeneration period, the power conversion device 32 discharges the electric storage device 31 on the basis of the auxiliary generator 41, whereby the sharp decrease of the auxiliary DC voltage Vo can be suppressed. At this time, by setting the voltage command value V2 of the power conversion device 32 higher than the voltage command value VI of the auxiliary generator 41, the power is preferentially output from the power conversion device 32 that responds faster than the auxiliary generator 41, and thus the sharp decrease of the auxiliary DC voltage Vo can be more reliably suppressed. Since the power conversion device 32 operates in the constant voltage mode, even after the end of the regeneration period, if the auxiliary power increases or decreases, the voltage control system 70 can automatically increase or decrease the current command values (IBrefl, IBref2) in response thereto, and control the voltage Vo to V2. In this way, even if there is a variation in the auxiliary power consumption, the sharp variation of the voltage Vo can be prevented.

[0122] In addition, after a predetermined time elapses from the end of the regeneration period, the upper limit value setting portion 71 decreases the current IBmax. Thus, in the case where the capacity of the electric storage device 31 is insufficient, the remaining amount of the charge of the electric storage device 31 can be prevented from being too small. In addition, by gradually decreasing the current IBmax, the auxiliary generator 41 can increase the output in response thereto, and the sharp variation of the voltage Vo can be prevented.

[0123] In addition, since the variation of the voltage Vo can be suppressed, the capacity of the smoothing capacitor connected to the auxiliary DC line 43 can be reduced, the system can be downsized and the cost can be reduced, and the time taken for the first charge at the start and the discharge at the stop can be shortened.

[0124] Further, although the variation of the voltage Vo is suppressed by discharging the electric storage device 31, when charging the electric storage device 31 with the energy necessary for discharging, the output of the auxiliary generator 41 (i.e., the output of the engine 11) is not used, but the regenerative energy of the traveling motor 10 is used, so that the energy saving efficiency can be improved. Moreover, if the capacity of the electric storage device 31 is sufficient, the electric storage device 31 can be charged during the regenerative period, and the auxiliary devices can be supplied with power from the electric storage device 31 during the non-regenerative period, so that the energy saving effect can be further improved.

[0125] <2nd Embodiment>

[0126] A 2nd embodiment of the present application will be described with reference to the drawings. Figures 14-17

[0127] In the present embodiment, the auxiliary generator 41 is set to the ON state regardless of whether or not the regenerative period is present.

[0128] Figure 14 is a functional block diagram showing the processing contents of the auxiliary voltage control section of the present embodiment. In the drawing, the same reference numerals are attached to the same parts as those of the 1st embodiment, and the description thereof will be omitted.

[0129] Figure 14 In the present embodiment, the auxiliary voltage control section 53 has a voltage control system 60 (1st voltage control system) for controlling the auxiliary DC voltage Vo, a voltage control system 70 (2nd voltage control system), a voltage control system 80 (3rd voltage control system), a regenerative period judging section 54, an upper limit value setting section 71 (1st upper limit value setting section), an ON / OFF switching section 81, and an ON / OFF control section 82. In the present embodiment, the 1st voltage command value is set to VI, the 2nd voltage command value is set to V2, and the 3rd voltage command value is set to V3. At this time, V3 > V2 > VI is set. Further, the command values VI to V3 are values within the allowable range for the normal operation of the auxiliary devices 44.

[0130] Here, the control operation of the auxiliary generator 41 will be described. The auxiliary voltage control section 53 does not perform the ON / OFF control of the auxiliary generator 41 based on the result of the judgment of the regenerative period. That is, the operation amount generated by the voltage control operation section 63 is outputted to the auxiliary generator 41 as a control signal regardless of the result of the judgment of the regenerative period.

[0131] Figure 15 is a flowchart showing the processing contents of the ON / OFF switching of the power conversion device and the auxiliary generator based on the judgment of the regenerative period.

[0132] Figure 15 ​In the middle of the regeneration period, the regeneration period judging section 54 first judges whether or not it is in the regeneration period based on the vehicle information signal SV, generates a regeneration period judging signal SR corresponding to the judging result (step S200). Next, it judges whether or not it is in the regeneration period, that is, whether or not the regeneration period judging signal SR is ON (step S210), and in the case where the judging result is YES, outputs H (high level) as the opening / closing signal SD, thereby controlling the power conversion device 21 to the ON state (step S211), and ends the processing. At this time, the auxiliary generator 41 is in the always ON state, and is controlled by the operation amount generated by the voltage control operation section 63. In the case where the judging result of step S210 is NO, that is, in the case where it is judged that it is not in the regeneration period, L (low level) is output as the opening / closing signal SD, thereby controlling the power conversion device 21 to the OFF state (step S212), and the processing is ended. In this case, the auxiliary generator 41 is also in the always ON state, and is controlled by the operation amount generated by the voltage control operation section 63.

[0133] Next, the control operation of the power conversion device 32 will be described. The voltage control system 70 has a voltage control operation section 73 and a current control system 72 of a local hysteresis loop. Since the operation of these is the same as in the first embodiment, the description will be omitted. The voltage control system 70 has a variable limiter 76. To the variable limiter 76, the current lower limit value IBmin is further input in addition to the pre-limit current command value IBrefl and the current upper limit value IBmax. The variable limiter 76 sets the upper limit value to IBmax, sets the lower limit value to IBmin, and performs a limiting process on the pre-limit current command value IBrefl, thereby generating a post-limit current command value IBref2. The voltage control system 70 generates the operation amount of the power conversion device 32, and outputs it as a control signal to the power conversion device 32.

[0134] Figure 16 and Figure 17 is a time chart showing an example of the operation waveform of the electric drive system, Figure 16 shows the appearance at the start of the regeneration period, Figure 17 shows the appearance at the end of the regeneration period.

[0135] Figure 16 and Figure 17 The vertical axis items of the graphs are the opening / closing signals SD, SG of the power conversion device 21 and the auxiliary generator 41, the auxiliary direct current voltage Vo, the output current ID of the power conversion device 21, the charge / discharge current IB of the electric storage device 31, and the output current IG of the auxiliary generator 41. As for the charge / discharge current IB of the electric storage device 31, the current upper limit value IBmax and the lower limit value IBmin are indicated by overlapping dotted lines.

[0136] In this embodiment, the opening / closing control of the auxiliary generator 41 is not performed. Therefore, as a comparison with the first embodiment, the opening / closing signal SG of the auxiliary generator 41 is always set to the open state. The current input to the auxiliary device 44 is fixed, and its value is denoted as Ii in the drawing. Further, the voltage Vo is denoted as V2 in the drawing. Figure 16 and Figure 17 The approximate shapes of the changes in voltage and current are indicated by straight lines, but the actual voltage and current are not limited to straight-line changes.

[0137] First, the operation at the start of the regeneration period is described. As shown in FIG. 7, the times t1 and t2 are defined, and it is assumed that the regeneration period starts at the time t1. Hereinafter, the operation of each of the periods from the time t1 to the time t2 and after the time t2 is described in order. Figure 16 The operation of the period before the time t1 is the same as that of the first embodiment (refer to FIG. 6), and thus the description is omitted. The auxiliary voltage control section 53 sets the current value IBmin to (-I2) during the entire period. Figure 16 Figure 10 During the period from the time t1 to the time t2, the regeneration period starts at the time t1, and the power conversion device 21 becomes the open state. The voltage control system 80 for the power conversion device 21 operates in such a manner that the voltage Vo increases from V1 to V3, and the output current ID increases. On the other hand, when the voltage Vo is higher than V1, the voltage control system 60 for the auxiliary generator 41 operates in such a manner that the voltage Vo decreases to V1, and the output current IG decreases. In this way, although both the power conversion device 21 and the auxiliary generator 41 want to control the voltage Vo, since V3 > V1, the power conversion device 21 preferentially performs the output. As a result, the voltage Vo is controlled to V3 by the power conversion device 21, and the current IG decreases to 0 (zero). That is, even in the case where the auxiliary generator 41 is set to the always-on state, it is possible to suppress the output of the auxiliary generator 41.

[0138] During the period from the time t1 to the time t2, the regeneration period starts at the time t1, and the power conversion device 21 becomes the open state. The voltage control system 80 for the power conversion device 21 operates in such a manner that the voltage Vo increases from V1 to V3, and the output current ID increases. On the other hand, when the voltage Vo is higher than V1, the voltage control system 60 for the auxiliary generator 41 operates in such a manner that the voltage Vo decreases to V1, and the output current IG decreases. In this way, although both the power conversion device 21 and the auxiliary generator 41 want to control the voltage Vo, since V3 > V1, the power conversion device 21 preferentially performs the output. As a result, the voltage Vo is controlled to V3 by the power conversion device 21, and the current IG decreases to 0 (zero). That is, even in the case where the auxiliary generator 41 is set to the always-on state, it is possible to suppress the output of the auxiliary generator 41.

[0139] During the period after the time t1, the upper-limit value setting section 71 gradually decreases the current value IBmax. On the other hand, the voltage control system 70 for the power conversion device 32 operates in such a manner that the voltage Vo decreases to V2, and the current IB gradually decreases. Figure 16 ​The text indicates that the decrease in current IB, implemented based on the voltage control system 70, is faster than the decrease in current value IBmax. When current IB reverses from positive to negative, the energy storage device 31 switches from discharging to charging. Unlike the first embodiment, which forces the switch to charging based on current value IBmax, the switch occurs because V3 > V2. Furthermore, even when current IB decreases rapidly from IBmax, IBmax will not decrease to (-I2), and even if the decrease is stopped midway (e.g., at zero), the behavior of current IB will not change. As current IB decreases, current IB' also decreases.

[0140] The power conversion device 21 gradually increases the current ID relative to the reduction of currents IG and IB', so that the auxiliary power supply current IA (=ID+IB'+IG) matches the current I1. In practice, the gradually decreasing currents IG and IB' become external disturbances, and the voltage Vo decreases slightly from V3. However, Figure 16 This situation is ignored, and it is assumed that the voltage Vo is the same as V3.

[0141] During the period after time t2, at time t2, the current IB decreases to (-I2). During the period after time t2, the voltage control system 70 used by the power conversion device 32 also operates to reduce the voltage Vo to V2. However, since the variable limiter 76 prevents the current command value IBref2 from being less than IBmin = -I2, the reduction of the current IB also stops at IBmin = -I2. As defined in the first embodiment, the current IB' becomes (-I2'). In addition, the current ID becomes I1 + I2'. Based on the above, except that the voltage Vo is controlled to V3, the states of each current (ID, IB', IG) are the same as in the first embodiment (see Figure 10 The same applies to the period after time t2 in the original text.

[0142] Next, the actions at the end of the regeneration period will be explained. For example... Figure 11 As shown, times t3, t4, and t5 are defined. It is assumed that the regeneration period ends at time t3. The following uses... Figure 11 The actions during the periods t3 to t4 and t4 to t5 will be described sequentially. Furthermore, the actions performed before time t3 are the same as those in the first embodiment (see [reference]). Figure 10 The operation after time t2 is the same, so the explanation is omitted. Furthermore, the operation during the period from time t4 to t5 is also the same as in the first embodiment (see [reference]). Figure 11 Similarly, the explanation is omitted here. The auxiliary voltage control unit 53 sets the current value IBmin to (-I2) throughout the entire period.

[0143] During the period from time t3 to t4, if the regeneration period ends at time t3, the power conversion device 21 becomes the closed state, and the current ID decreases to 0 (zero).

[0144] The upper limit value setting portion 71 changes the current value IBmax to a positive value I4. Immediately after time t3, the current IA (= ID + IB' + IG) is smaller than the input current II of the auxiliary device 44, and thus the voltage Vo decreases from V3. If the voltage Vo becomes smaller than V2, the power conversion device 32 increases the current IB to the positive, and the electric storage device 31 shifts from charging to discharging. The voltage Vo is increased from the decrease to the increase by this discharging. The current IB' is increased to II, and the power conversion device 32 supplies the auxiliary power alone, at this time, the voltage Vo is controlled to V2. Figure 17 In this way, when time t4 is reached, the voltage Vo becomes V2, the current IB becomes II', and the currents ID and IG become 0 (zero).

[0145] The other configurations are the same as those of the first embodiment.

[0146] In the present embodiment configured as described above, the same effects as those of the first embodiment can be obtained.

[0147] In addition, by setting the voltage command value V3 of the power conversion device 21 higher than the voltage command value VI of the auxiliary generator 41, even after the start of the regeneration period, the output of the auxiliary generator 41 can be suppressed by operating the power conversion device 21, without stopping the auxiliary generator 41. Further, as in the first embodiment, the auxiliary power supply is switched from the auxiliary generator 41 to the power conversion device 21.

[0148] In addition, because the auxiliary generator 41 is not stopped, the fluctuation of the voltage Vo can be suppressed. That is, in the case where the auxiliary generator 41 is stopped at the start of the regeneration period, a time difference occurs between the stop and the start of the operation of the power conversion device 21. In the case where the start of the operation of the power conversion device 21 is delayed, the auxiliary direct-current voltage Vo decreases from VI. Therefore, the present embodiment is configured to suppress the output of the auxiliary generator 41 by the operation of the power conversion device 21, and thus the decrease of the voltage Vo does not occur. In this way, by switching the auxiliary power supply without stopping the auxiliary generator 41, the fluctuation of the voltage Vo can be prevented.

[0149] In addition, by increasing the voltage Vo to V3 during the regeneration period, the decrease of the voltage Vo after the end of the regeneration period can be more reliably suppressed.

[0150] Next, the features of the above-described embodiments will be described.

[0151] (1) In the above embodiment, the regenerative braking system has: a first generator (e.g., the main generator 12) connected to the engine 11 and a second generator (e.g., the auxiliary generator 41); a first rectifier circuit (e.g., the main rectifier circuit 14) connected to the first generator, rectifying the output of the first generator and outputting the rectified output as direct current to a first direct current line (e.g., the main direct current line); inverters 13L, 13R connected between the first direct current line and the electric motor; a power consumption device 15 connected to the first direct current line, capable of consuming the power of the first direct current line; a second rectifier circuit (e.g., the auxiliary rectifier circuit 42) connected to the second generator, rectifying the output of the second generator and outputting the rectified output as direct current to a second direct current line (e.g., the auxiliary direct current line 43); an auxiliary device 44 connected to the second direct current line; a first power conversion device 21 converting the power of the first direct current line and supplying the second direct current line; an electric storage device 31; a second power conversion device 32 switching between a discharging operation of converting the power of the electric storage device and supplying the second direct current line and a charging operation of converting the power of the second direct current line and supplying the electric storage device; and a control device 50, in which the control device is configured to determine whether the electric motor is performing a regenerative operation based on information related to a drive target of the electric motor, in the case where it is determined that the regenerative operation is being performed, control the first power conversion device so that the power of the first direct current line is supplied to the second direct current line and the voltage of the second direct current line becomes a first voltage value that is predetermined based on the operating voltage specification of the auxiliary device, and control the second generator so that the second generator is stopped to stop the supply of power to the second direct current line, and control the second power conversion device so that the power of the second direct current line is supplied to the electric storage device, in the case where it is determined that the regenerative operation has ended, control the first power conversion device so that the supply of power from the first direct current line to the second direct current line is stopped, control the second generator so that the second generator is started to start the supply of power to the second direct current line and the voltage of the second direct current line becomes the first voltage value, and control the second power conversion device so that the power of the electric storage device is supplied to the second direct current line and the voltage of the second direct current line becomes a second voltage value that is predetermined based on the operating voltage specification of the auxiliary device and is higher than the first voltage value.

[0152] Thus, the variation in the supply voltage supplied to the auxiliary device when switching the regenerative operation based on the traveling motor can be suppressed.

[0153] (2) In addition, in the regenerative braking system of (1) in the above embodiment, the control device 50 controls the second power conversion device 32 so that the current supplied from the electric storage device to the second direct current line decreases with the passage of time after a predetermined time elapses from the point in time at which the regenerative operation has ended, in the case where it is determined that the regenerative operation has ended.

[0154] (3) In addition, in the above embodiment, there is provided the regenerative braking system of (1), and drive wheels 3L, 3R that operate by the electric power output to the first direct current line (e.g., the main machine direct current line 16) from the first generator (e.g., the main machine generator 12) of the regenerative braking system via the first rectifier circuit (e.g., the main machine rectifier circuit 14), and the electric motor that outputs regenerative electric power to the first direct current line is driven as a travel motor 10L, 10R.

[0155] <Notes>

[0156] Further, the present application is not limited to the above embodiment, and includes various modifications and combinations within the scope of the gist thereof. In addition, the present application is not limited to the one provided with all the configurations described in the above embodiment, and includes the one in which a part of the configurations is deleted. In addition, a part or all of the above configurations, functions, and the like can be realized, for example, by an integrated circuit design or the like. In addition, the above configurations, functions, and the like can be interpreted as a program for realizing each function by a processor, and realized by software execution.

[0157] Explanation of Reference Numerals

[0158] 1 … vehicle body frame, 2L, 2R … driven wheels (front wheels), 3L, 3R … drive wheels (rear wheels), 4 … cab, 5 … cargo box (hopper), 5a … pin joint, 6 … hydraulic lift cylinder, 7 … grid box, 8 … control cabinet, 9 … fuel tank, 10L, 10R … travel motors, 11 … engine, 12 … main machine generator, 13L, 13R … inverters, 14 … rectifier circuit, 15 … electric power consumption device, 16 … main machine direct current line, 17 … voltage detector, 21 … power conversion device, 41 … auxiliary machine generator, 42 … rectifier circuit, 43 … auxiliary machine direct current line, 44 … auxiliary machine device, 50 … control device, 51 … drive control section, 52 … main machine voltage control section, 53 … auxiliary machine voltage control section, 100 … electric drive dump truck, 151 … resistor, 152 … conversion element, 153 … diode.

Claims

1. A regenerative braking system having: a first generator and a second generator connected to an engine; a first rectifier circuit connected to the first generator, rectifying an output of the first generator and outputting the output as direct current to a first direct current line; an inverter connected between the first direct current line and a motor; a power consumption device connected to the first direct current line, capable of consuming power of the first direct current line; a second rectifier circuit connected to the second generator, rectifying an output of the second generator and outputting the output as direct current to a second direct current line; an auxiliary machine device connected to the second direct current line; a first power conversion device converting power of the first direct current line and supplying the power to the second direct current line; an electric storage device; a second power conversion device switching between a discharging operation of discharging the electric storage device and supplying power to the second direct current line and a charging operation of converting a voltage of the second direct current line to a voltage of the electric storage device and charging the electric storage device; and a control device, the regenerative braking system characterized in that the control device is configured to: judge whether the motor is in a regenerative operation based on information related to a drive target of the motor, in a case where it is judged that the motor is in the regenerative operation, control the second generator so that a voltage of the second direct current line becomes a first voltage value predetermined based on an operation voltage specification of the auxiliary machine device, and control the second power conversion device so that the voltage of the second direct current line becomes a second voltage value that is a voltage value predetermined based on the operation voltage specification of the auxiliary machine device and higher than the first voltage value, and control the first power conversion device so that the voltage of the second direct current line becomes a third voltage value that is a voltage value predetermined based on the operation voltage specification of the auxiliary machine device and higher than the second voltage value, in a case where it is judged that the regenerative operation has ended, stop the first power conversion device and control the second generator and the second power conversion device as in the regenerative operation.

2. The regenerative braking system according to claim 1, characterized in that the control device, in a case where it is judged that the regenerative operation has ended, sets an upper limit value of a discharging current of the electric storage device so that the auxiliary machine device can be driven only by discharging of the electric storage device during a period from a time point when the regenerative operation ends to a prescribed time elapses, and controls the second power conversion device so that the upper limit value of the discharging current of the electric storage device decreases as time elapses after the prescribed time elapses. having: an engine; the regenerative braking system according to claim 1; and a drive wheel that operates by power output to the first direct current line from the first generator of the regenerative braking system via the first rectifier circuit and is driven with the motor that outputs regenerative power to the first direct current line as a traveling motor. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 3. An electrically driven work vehicle, characterized in that ​ ​ ​ ​ ​

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