Electric drive system

Abstract

The purpose of the present invention is to provide an electric drive system capable of maintaining a DC voltage on an auxiliary winding side by means of a single power converter provided on the auxiliary winding side regardless of the rotational speed of a duplex-winding induction generator and the magnitude of a load on the auxiliary winding side. To this end, a control device calculates a first d-axis current command value for an auxiliary winding on the basis of a first DC voltage and a command value for the first DC voltage, and calculates a second d-axis current command value for the auxiliary winding on the basis of the rotational speed of a generator and the required power of an auxiliary machine, and a control unit that controls the power converter such that the d-axis current value of the auxiliary winding matches the first d-axis current command value in a slowing state or an idle state, and controls the power converter such that the d-axis current value of the auxiliary winding matches the second d-axis current command value in a slowing state or an idle state.

Description

Technical Field

[0001] The present invention relates to an electric drive system having a dual-winding induction generator. Background Art

[0002] A system for controlling a rotating machine using multiple windings is known. For example, Patent Document 1 discloses "an auxiliary battery charging device for a series hybrid vehicle, characterized by comprising: a rotating electric machine, mounted on an engine output shaft, having a main winding and an auxiliary winding; a power generation control unit, which rotates the rotating electric machine via the engine, thereby generating driving power for a vehicle driving motor and / or charging power for a main battery in the main winding; and an auxiliary charging control unit, which charges the auxiliary battery using a voltage induced in the auxiliary winding when the rotating electric machine is rotated."

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 8-289406 Summary of the Invention

[0006] For an induction generator with a stator consisting of a main winding and an auxiliary winding (a dual-winding induction generator), if the d-axis auxiliary winding current (excitation current) is determined based on the DC voltage command value on the main winding when the load on the main winding (the power required by the main machine) is close to zero and the dual-winding induction generator's rotational speed is low, this can lead to excessive or insufficient excitation depending on the magnitude of the auxiliary winding load (the power required by the auxiliary machine), resulting in reduced power generation efficiency. Furthermore, insufficient excitation can prevent the auxiliary winding DC voltage from being maintained, making it impossible to supply the auxiliary winding load.

[0007] In Patent Document 1, when the rotating electrical machine's rotational speed is below a specified value, an excitation current is supplied to the main winding to increase the excitation flux of the permanent magnets. This allows the auxiliary battery to be charged regardless of the rotating electrical machine's rotational speed, even at low rotational speeds, by inducing a voltage in the auxiliary winding that exceeds the operable voltage of the step-down chopper circuit. However, since the main winding's excitation current is determined solely by the rotating electrical machine's rotational speed, the excitation may become insufficient if the load on the auxiliary winding (the power required by the auxiliary battery) increases.

[0008] The present invention has been proposed in view of the above-mentioned problems, and its object is to provide an electric drive system that can maintain the DC voltage on the auxiliary winding side by using a single power converter provided on the auxiliary winding side, regardless of the rotational speed of the dual-winding induction generator and the load on the auxiliary winding side.

[0009] In order to achieve the above-mentioned object, the present invention provides an electric drive system comprising: a travel motor; an auxiliary machine; a generator having a stator including a main winding and an auxiliary winding; a rectifier connected to the main winding, converting the AC voltage generated by the main winding into a first DC voltage; a travel inverter connected to the rectifier, converting the first DC voltage into an AC voltage and supplying it to the travel motor; a power converter connected to the auxiliary winding, controlling the voltages of the main winding and the auxiliary winding, and converting the AC voltage generated by the auxiliary winding into a second DC voltage and supplying it to the auxiliary machine; and a control device for controlling the power converter. The electric drive system is characterized in that the control device is based on the The control device calculates a first d-axis current command value for the auxiliary winding based on a first DC voltage and a command value of the first DC voltage. The control device calculates a second d-axis current command value for the auxiliary winding based on the rotational speed of the generator and the required power of the auxiliary machine. In a traction state in which electric power is supplied from the traction inverter to the traction motor, the control device controls the power converter so that the d-axis current value of the auxiliary winding coincides with the first d-axis current command value. In a state in which the traction motor slows down the generation of regenerative electric power or in an idling state in which the traction motor is stopped, the control device controls the power converter so that the d-axis current value of the auxiliary winding coincides with the second d-axis current command value.

[0010] Effects of the Invention

[0011] According to the present invention, in an electric drive system including a dual-winding induction generator, a single power converter provided on the auxiliary winding side can maintain a DC voltage on the auxiliary winding side regardless of the rotational speed of the dual-winding induction generator and the magnitude of the load on the auxiliary winding side. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing the structure of a dump truck in an embodiment of the present invention.

[0013] Figure 2 It is a diagram showing the configuration of an electric drive system according to an embodiment of the present invention.

[0014] Figure 3 It is a side view and a partially enlarged cross-sectional view showing the structure of a dual-winding induction generator in an embodiment of the present invention.

[0015] Figure 4 This is a functional block diagram of a control device in an embodiment of the present invention.

[0016] Figure 5 This is a block diagram showing the processing of the current command calculation unit and the voltage command calculation unit in the embodiment of the present invention.

[0017] Figure 6 This is a block diagram showing the processing of the frequency command calculation unit in the embodiment of the present invention.

[0018] Figure 7 This is a block diagram showing the processing of the voltage command compensating unit in the embodiment of the present invention.

[0019] Figure 8 This is a block diagram showing a modified example of the processing of the voltage command compensating unit in the embodiment of the present invention.

[0020] Figure 9 This is a block diagram showing the processing of the auxiliary machine required power estimation unit in the embodiment of the present invention.

[0021] Figure 10 This is a diagram showing an example of the relationship between the auxiliary machine required power, the generator rotation speed, and the second d-axis auxiliary winding current command value in the embodiment of the present invention.

[0022] Figure 11 This is a diagram showing time-series changes in various parameters of the electric drive system in the embodiment of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. In the drawings, identical elements are denoted by the same reference numerals, and duplicate descriptions are omitted as appropriate.

[0024] Figure 1 : is a diagram showing the structure of a dump truck in an embodiment of the present invention. Figure 1 In the figure, the dump truck includes a vehicle body 30, a prime mover 1, a platform 31 mounted vertically and rotatably on the upper rear side of the vehicle body 30, and a driver's seat 32 located on the upper front side of the vehicle body 30. Furthermore, a pair of left and right driven wheels 33 are disposed on the lower front side of the vehicle body 30, and a pair of left and right drive wheels 34 are disposed on the lower rear side of the vehicle body 30. The drive wheels 34 are driven by a travel motor 5. Dump trucks used in mines repeatedly perform a series of operation cycles: loading soil and sand at a loading site, traveling from the loading site to an unloading site, unloading at the unloading site, and traveling from the unloading site to the loading site.

[0025] Figure 2 It means it is installed on Figure 1 The structure of the electric drive system of the dump truck is shown in the figure. Figure 2In the embodiment, the electric drive system includes: a prime mover 1; a dual-winding induction generator 2 having a stator with a main winding and an auxiliary winding; a rectifier 3; a travel inverter 4; a travel motor 5; a regenerative discharge resistor 6; a power converter 7; a travel motor cooling inverter 8a; a regenerative discharge resistor cooling inverter 8b; a pump inverter 8c; a generator cooling inverter 8d; a travel motor cooling motor 9a; a regenerative discharge resistor cooling motor 9b; a pump motor 9c; a generator cooling motor 9d; a starting battery 10; a control device 11; an auxiliary machine side DC voltage sensor 12; an auxiliary winding current sensor 13; a generator speed sensor 14; a main winding voltage sensor 15; a main winding current sensor 16; a main machine side DC voltage sensor 17; a travel motor speed sensor 50; an accelerator operating device 53a; an accelerator operating amount sensor 53b; a brake operating device 54a; and a brake operating amount sensor 54b. Here, the prime mover 1, the two-winding induction generator 2, the rectifier 3, the power converter 7, the control device 11, the auxiliary machine-side DC voltage sensor 12, the auxiliary winding current sensor 13, the generator speed sensor 14, the main winding voltage sensor 15, the main winding current sensor 16, and the main machine-side DC voltage sensor 17 constitute the power generation system 40 in this embodiment. The travel inverter 4 and the travel motor 5 constitute the main machine, which is a load on the main winding side. The travel motor cooling inverter 8a, the regenerative discharge resistor cooling inverter 8b, the pump inverter 8c, the generator cooling inverter 8d, the travel motor cooling motor 9a, the regenerative discharge resistor cooling motor 9b, the pump motor 9c, and the generator cooling motor 9d constitute the auxiliary machine 41, which is a load on the auxiliary winding side.

[0026] Prime mover 1 rotates the rotor of a two-winding induction generator 2. The main winding of the two-winding induction generator 2 is connected to a travel inverter 4 via a rectifier 3. The travel inverter 4 is connected to a travel motor 5. A regenerative discharge resistor 6 is connected to the rectifier 3 and the travel inverter 4 when the travel motor 5 is generating electricity. The auxiliary winding of the two-winding induction generator 2 is connected to an auxiliary machine 41 via a power converter 7. A starting battery 10 is connected to the power converter 7 and the auxiliary machine 41 when the two-winding induction generator 2 is started. Since the power required by the travel motor 5 is greater than that required by the auxiliary machine 41, the power converter, which is more expensive than the rectifier, is connected to the auxiliary machine 41, which has a lower power requirement, rather than to the travel inverter 4. This reduces the capacity of the power converter and reduces the cost of the power generation system 40.

[0027] The travel motor cooling inverter 8a is connected to the travel motor cooling motor 9a. The regenerative discharge resistor cooling inverter 8b is connected to the regenerative discharge resistor cooling motor 9b. The pump inverter 8c is connected to the pump motor 9c. The generator cooling inverter 8d is connected to the generator cooling motor 9d. The travel motor cooling motor 9a is controlled by the travel motor cooling inverter 8a, the regenerative discharge resistor cooling motor 9b is controlled by the regenerative discharge resistor cooling inverter 8b, the pump motor 9c is controlled by the pump inverter 8c, and the generator cooling motor 9d is controlled by the generator cooling inverter 8d. The control device 11 calculates the required rotational speeds for the travel motor cooling motor 9a, the regenerative discharge resistor cooling motor 9b, the pump motor 9c, and the generator cooling motor 9d and transmits these speeds to each inverter.

[0028] Here, the scenario in which the issues contemplated by the present invention arise will be described using the operation of a dump truck as an example. As the dump truck repeats the aforementioned operating cycle, the temperatures of the two-winding induction generator 2, the travel motor 5, and the regenerative discharge resistor 6 gradually rise. To suppress this temperature rise, the travel motor cooling motor 9a, the regenerative discharge resistor cooling motor 9b, and the generator cooling motor 9d are driven for the two-winding induction generator 2, the travel motor 5, and the regenerative discharge resistor 6, respectively, thereby cooling them. During loading and unloading, the dump truck is parked, idling at a low generator speed. However, when temperatures are high, the travel motor cooling motor 9a, the regenerative discharge resistor cooling motor 9b, and the generator cooling motor 9d must be driven at high output even at idle, increasing the power required by the auxiliary equipment 41. In such situations, if the excitation current of the two-winding induction generator 2 is inappropriately determined, the excitation amount may be excessive or insufficient, potentially leading to reduced efficiency and an inability to supply the required power to the auxiliary equipment 41.

[0029] Figure 3 The figure shows a side view and a partially enlarged cross-sectional view of the structure of a dual-winding induction generator 2 according to this embodiment. The dual-winding induction generator 2 includes a stator 210 and a rotor 220. The stator 210 has primary windings 213 disposed in stator slots 212 formed by a stator core 211. The primary windings 213 include a main winding 2131 and an auxiliary winding 2132. The primary windings 213 are retained in the stator slots 212 by wedges 214. The rotor 220 has rotor bars 2231 disposed in rotor slots 222 formed by the rotor core 221. The ends of the rotor bars 2231 are short-circuited by end rings 2232. The secondary conductors 223 include rotor bars 2231 and end rings 2232. The gap 230 is the space between the stator 210 and the rotor 220.

[0030] Figure 4 FIG. 1 is a functional block diagram of the control device 11 for controlling the power converter 7. Figure 4In the embodiment, the control device 11 comprises three-phase / two-phase conversion units 18a, 18b, and 18c, a current command calculation unit 19, a frequency command calculation unit 20, a voltage command calculation unit 21, a voltage command compensation unit 22, a turns ratio conversion unit 23, an auxiliary machine required power estimation unit 24, a two-phase / three-phase conversion unit 25, and a control signal generation unit 26. The control device 11 comprises a controller with computational processing capabilities and an input / output interface for signal input and output with external devices. The functions of each unit are achieved by executing programs stored in a storage device such as a ROM. In this embodiment, the control device 11 controls the voltage and current of the main and auxiliary windings via the power converter 7 so that the main machine-side DC voltage VmDC and the auxiliary machine-side DC voltage VaDC match the main machine-side DC voltage command value VmDC* and the auxiliary machine-side DC voltage command value VaDC*, respectively.

[0031] Voltage control is performed by the current command calculation unit 19, for example, by performing a proportional integral operation using the values ​​obtained from the main engine-side DC voltage sensor 17 and the auxiliary engine-side DC voltage sensor 12 (main engine-side DC voltage VmDC and auxiliary engine-side DC voltage VaDC) to calculate auxiliary winding current command values ​​Iad* and Iaq*. Current control is performed by the voltage command calculation unit 21, for example, by performing a proportional integral operation using the values ​​obtained from the auxiliary winding current sensor 13 (the three-phase auxiliary winding currents Iau, Iav, and Iaw) converted to the d / q axes by the three-phase / two-phase conversion unit 18c (the d-axis auxiliary winding current Iad and the q-axis auxiliary winding current Iaq). The generator speed ωr and frequency command value ω1* obtained by the voltage command calculation unit 21 from the generator speed sensor 14 are used to compensate for the induced voltage generated by the rotor rotation of the dual-winding induction generator 2 and the interference component between the d / q axes.

[0032] Figure 5 This is a block diagram showing the processing of the command current calculation unit 19 and the command voltage calculation unit 21. The command current calculation unit 19 performs a proportional integration on the difference between the host-side DC voltage command value VmDC* and the host-side DC voltage VmDC to calculate the first d-axis auxiliary winding current command value Iad_1*. In the figure, Kmv_p represents the host-side voltage control proportional gain, and Kmv_i represents the host-side voltage control integral gain.

[0033] The current command calculation unit 19 also includes a second d-axis auxiliary winding current command calculation unit 19a, a current command switching determination unit 19b, and a current command switching unit 19c. The second d-axis auxiliary winding current command calculation unit 19a calculates a second d-axis auxiliary winding current command value Iad_2* based on the generator speed ωr and the auxiliary power Pa_req estimated by the auxiliary power estimation unit 24. The current command switching determination unit 19b determines whether a current command switching flag FL_Iad_ref is on or off based on the accelerator operation amount Aa, the brake operation amount Ab, the travel motor speed ωm, and the generator speed ωr. The current command switching unit 19c outputs either the first d-axis auxiliary winding current command value Iad_1* or the second d-axis auxiliary winding current command value Iad_2* as the d-axis auxiliary winding current command value Iad* based on the current command switching flag FL_Iad_ref.

[0034] Furthermore, the current command calculation unit 19 performs a proportional integration on the difference between the auxiliary machine-side DC voltage command value VaDC* and the auxiliary machine-side DC voltage VaDC, outputting this value as the q-axis auxiliary winding current command value Iaq*. In the figure, Kav_p represents the auxiliary machine-side voltage control proportional gain, and Kav_i represents the auxiliary machine-side voltage control integral gain.

[0035] The voltage command calculation unit 21 subtracts the interference component generated between the d-axis and q-axis axes from the proportional integral of the difference between the d-axis auxiliary winding current command value Iad* and the d-axis auxiliary winding current Iad, outputting the resulting d-axis auxiliary winding voltage command value Vad*. The interference component generated between the d-axis and q-axis axes is calculated by multiplying the integral of the difference between the d-axis auxiliary winding current command value Iad* and the d-axis auxiliary winding current Iad by ω1*Lσm / Rσa. In the figure, Kmc_p represents the main-side current control proportional gain, and Kmc_i represents the main-side current control integral gain.

[0036] Furthermore, the voltage command calculation unit 21 adds the interference component generated between the d-axis and q-axis axes and the induced voltage ωr*μ*φ2d to the proportional integral of the difference between the q-axis auxiliary winding current command value Iaq* and the q-axis auxiliary winding current Iaq, outputting the resulting q-axis auxiliary winding voltage command value Vaq*. The interference component generated between the d-axis and q-axis axes is obtained by multiplying the integral of the difference between the q-axis auxiliary winding current command value Iaq* and the q-axis auxiliary winding current Iaq using the auxiliary current control integral gain Kac_i by ω1*Lσm / Rσa. In the figure, Kac_p represents the auxiliary current control proportional gain, and Kac_i represents the auxiliary current control integral gain.

[0037] Figure 6: is a block diagram showing the processing of the frequency command calculation unit 20. The frequency command calculation unit 20 adds the generator rotation speed ωr to the frequency command value ωs* calculated by the slip frequency command calculation unit 20a, and outputs the result as the frequency command value ω1*.

[0038] return Figure 4 The function of the voltage command compensator 22 will now be described. In a two-winding induction generator 2, the main winding and the auxiliary winding are magnetically coupled, generating interference components between the windings. This phenomenon can be explained using the differential equation for the auxiliary winding portion of the two-winding induction generator 2, shown in Equation 1.

[0039] [Formula 1]

[0040]

[0041] The symbols in Formula 1 are as follows.

[0042] Rσm: Main winding resistance related to the auxiliary winding in the dq-axis model

[0043] Rσa: Auxiliary winding resistance related to the auxiliary winding in the dq-axis model

[0044] Lσm: Main winding self-inductance related to the auxiliary winding in the dq-axis model

[0045] Lσa: Auxiliary winding self-inductance related to the auxiliary winding in the dq axis model

[0046] μ: primary conversion factor related to auxiliary winding

[0047] τ2: Secondary time constant (=secondary inductance / secondary resistance)

[0048] p: differential operator

[0049] Imd, Imq: d-axis main winding current, q-axis main winding current

[0050] Vmd, Vmq: d-axis main winding voltage, q-axis main winding voltage

[0051] Vad, Vaq: d-axis auxiliary winding voltage, q-axis auxiliary winding voltage

[0052] φ2d, φ2q: d-axis secondary magnetic flux, q-axis secondary magnetic flux

[0053] ω1: primary frequency

[0054] Arrange equation 1 to obtain equation 2.

[0055] [Formula 2]

[0056]

[0057] As can be seen from Equation 2, the auxiliary winding voltage includes the main winding currents Imd and Imq on the dq axes and the main winding voltages Vmd and Vmq. The terms related to the main winding current and voltage represent interference components of the main winding with respect to the auxiliary winding, causing instability in the control of the two-winding induction generator 2. Therefore, the control device 11 compensates for this interference component, enabling stable control of the two-winding induction generator 2 even when magnetic coupling exists between the main and auxiliary windings. Specifically, the auxiliary winding voltage command values ​​Vad* and Vaq* calculated by the voltage command calculation unit 21 are added with voltage compensation amounts ΔVad* and ΔVaq*, respectively, calculated by the voltage command compensation unit 22. These compensated auxiliary winding voltage command values ​​Vad** and Vaq** are then input to the turns ratio conversion unit 23.

[0058] The turns ratio conversion unit 23 multiplies the compensated auxiliary winding voltage command values ​​Vad** and Vaq** by the ratio of the main winding self-inductance Lσm associated with the auxiliary winding in the dq-axis model to the auxiliary winding self-inductance Lσa associated with the auxiliary winding in the dq-axis model. The auxiliary winding voltage command values ​​Vad*** and Vaq***, after the turns ratio conversion, are input by the turns ratio conversion unit 23 to the two-phase to three-phase conversion unit 25. The converted three-phase voltage command values ​​Vau*, Vav*, and Vaw* are input to the control signal generation unit 26. In the three-phase to two-phase conversion units 18a, 18b, and 18c and the two-phase to three-phase conversion unit 25, the phase used for coordinate conversion uses, for example, a value obtained by integrating the frequency command value ω1*. The control signal generating unit 26 generates a control signal to be transmitted to the power converter 7 based on, for example, a comparison between a duty ratio signal calculated based on the three-phase voltage command values ​​Vau*, Vav*, and Vaw* and a carrier wave.

[0059] Figure 7This is a block diagram illustrating the processing of the voltage command compensation unit 22. The values ​​obtained from the main winding voltage sensor 15 and the main winding current sensor 16 (the main winding's three-phase currents Imu, Imv, and Imw, and the main winding's three-phase voltages Vmu, Vmv, and Vmw) are converted to coordinates by the three-phase / two-phase conversion units 18a and 18b, respectively. The converted values ​​(Imd, Imq, Vmd, and Vmq) are used as inputs to the voltage command compensation unit 22. The d-axis voltage compensation amount ΔVad* is the difference between the d-axis main winding voltage Vmd and the d-axis main winding current Imd multiplied by the auxiliary winding's main winding resistance Rσm. The q-axis voltage compensation amount ΔVaq* is the difference between the q-axis main winding voltage Vmq and the q-axis main winding current Imq multiplied by the auxiliary winding's main winding resistance Rσm. By directly using the values ​​acquired from the main winding voltage sensor 15 and the main winding current sensor 16 in this manner, the compensation voltage amounts ΔVad* and ΔVaq* can be calculated without slowing down the calculation.

[0060] Figure 8 It means being able to Figure 7 The block diagram of the process of the voltage command compensator 22 in the case where the main winding voltage sensor 15 is not used is considered in the modification of the process shown. Figure 8 In the embodiment, instead of the main winding voltages Vmd and Vmq detected by the main winding voltage sensor 15, the auxiliary winding voltage command values ​​Vad* and Vaq* output from the voltage command calculation unit 21 are input to the voltage command compensation unit 22. The voltage command compensation unit 22 utilizes the property that the voltage of the main winding and the voltage of the auxiliary winding of the dual-winding induction generator 2 are approximately proportional to each other, and multiplies the auxiliary winding voltage command values ​​Vad* and Vaq* by the correction gain K (the ratio of the main winding voltage to the auxiliary winding voltage) to calculate the estimated values ​​of the main winding voltages Vmd and Vmq. In such a configuration, it is also possible to achieve the same Figure 7 The same effect as the structure of is achieved, and since the main winding voltage sensor 15 for detecting the main winding voltages Vmd and Vmq is not required, the structure of the power generation system 40 can be simplified.

[0061] return Figure 4 Next, the auxiliary machine required power estimation unit 24 will be described. The auxiliary machine required power Pa_req, which is the output of the auxiliary machine required power estimation unit 24, is the power required by the auxiliary machine 41. In the present embodiment, it is the total power required to drive the travel motor cooling motor 9a, the regenerative discharge resistor cooling motor 9b, the pump motor 9c, and the generator cooling motor 9d at the desired rotational speed.

[0062] Figure 9This is a block diagram illustrating the processing of the auxiliary equipment required power estimation unit 24. The travel motor cooling motor power estimation unit 24a calculates the power required when the travel motor cooling motor 9a rotates at the travel motor cooling motor speed command ωa_mot* (travel motor cooling motor required power), Pa_mot_req. The regenerative discharge resistor cooling motor power estimation unit 24b calculates the power required when the regenerative discharge resistor cooling motor 9b rotates at the regenerative discharge resistor cooling motor speed command ωa_grid* (regenerative discharge resistor cooling motor required power), Pa_grid_req. The pump motor power estimation unit 24c calculates the power required when the pump motor 9c rotates at the pump motor speed command ωa_pump* (pump motor required power), Pa_pump_req. The generator cooling motor power estimation unit 24d calculates the power required when the generator cooling motor 9d rotates at the generator cooling motor speed command ωa_gen* (generator cooling motor required power), Pa_gen_req. The auxiliary machine required power Pa_req is calculated by summing the travel motor cooling motor required power Pa_mot_req, the regenerative discharge resistor cooling motor required power Pa_grid_req, the pump motor required power Pa_pump_req, and the generator cooling motor required power Pa_gen_req calculated above. This is input to the second d-axis auxiliary winding current command calculation unit 19a.

[0063] Figure 5 The second d-axis auxiliary winding current command calculation unit 19a shown is as follows Figure 10 The characteristics shown are shown in that the second d-axis auxiliary winding current command value Iad_2* is calculated based on the auxiliary machine required power Pa_req and the generator rotation speed ωr calculated by the auxiliary machine required power estimation unit 24 . Figure 10 : is a diagram showing an example of the relationship between the auxiliary machine required power Pa_req, the generator speed ωr, and the second d-axis auxiliary winding current command value Iad_2*. Figure 10 In the example, the second d-axis auxiliary winding current command value Iad_2* increases in direct proportion to the auxiliary power required Pa_req. The greater the generator speed ωr, the smaller the degree of increase in the second d-axis auxiliary winding current command value Iad_2* relative to the auxiliary power required Pa_req (the slope of the graph in the figure). When the auxiliary power required Pa_req is zero, the second d-axis auxiliary winding current command value Iad_2* remains at a predetermined minimum value Iad_2_min, regardless of the generator speed ωr. Figure 10 The characteristics of are determined by precalculation or experimentation.

[0064] return Figure 5Next, the current command switching determination unit 19b will be described. The current command switching determination unit 19b sets the current command switching flag FL_Iad_ref to on (FL_Iad_ref = 1) when the travel motor speed ωm is less than the predetermined value ωm_th and the generator speed ωr is less than the predetermined value ωr_th; when the accelerator operating device 53a is not operated and the travel motor speed ωm is greater than or equal to the predetermined value ωm_th; or when the brake operating device 54a is being operated.

[0065] Here, the predetermined value ωm_th is the travel motor speed threshold, used to determine whether the vehicle body is in a driving state. The predetermined value ωr_th is the generator speed threshold, used to determine whether the vehicle body is in an idling state. A state in which the travel motor speed ωm is less than the travel motor speed threshold ωm_th and the generator speed ωr is less than the generator speed threshold ωr_th corresponds to an idling state in which the travel motor 5 is stopped. Furthermore, a state in which the accelerator operating device 53a is not operated and the travel motor speed ωm is greater than the travel motor speed threshold ωm_th, or a state in which the brake operating device 54a is being operated, corresponds to a state in which the regenerative power generation of the travel motor 5 is slowed down. The travel motor speed threshold ωm_th and the generator speed threshold ωr_th are each determined by calculation or experimentation.

[0066] When the current command switching flag FL_Iad_ref is off (FL_Iad_ref=0), the current command switching unit 19c outputs the first d-axis auxiliary winding current command value Iad_1* as the d-axis auxiliary winding current command value Iad*. When the current command switching flag FL_Iad_ref is on (FL_Iad_ref=1), the current command switching unit 19c outputs the second d-axis auxiliary winding current command value Iad_2* as the d-axis auxiliary winding current command value Iad*.

[0067] Below, refer to Figure 11 , the main actions and effects of the electric drive system in this embodiment are explained. Figure 11This diagram shows the time-series changes in various parameters of the electric drive system in this embodiment (travel motor speed ωm, generator speed ωr, current command switching flag FL_Iad_ref, auxiliary machine required power Pa_req, d-axis auxiliary winding current Iad, main engine-side DC voltage VmDC, and auxiliary machine-side DC voltage VaDC). The following describes an example of operation when the travel motor speed ωm, generator speed ωr, and auxiliary machine required power Pa_req change. Furthermore, to clarify the effects of this embodiment, a comparison is made with a case where the first d-axis auxiliary winding current command value Iad_1* is always set as the d-axis auxiliary winding current command value Iad*, rather than the second d-axis auxiliary winding current command value Iad_2* calculated by the second d-axis auxiliary winding current command calculation unit 19a. The electric drive system of this embodiment and the electric drive system of the comparative example assume that the changes in the travel motor speed ωm, generator speed ωr, and auxiliary machine required power Pa_req are the same.

[0068] exist Figure 11 In FIG. 1 , the time series change of each parameter of the present embodiment is represented by a solid line, and the time series change of each parameter of the comparative example is represented by a dotted line. Figure 11 The horizontal axes of (a) to (g) represent time (elapsed time). Figure 11 The vertical axis of (a) represents the driving motor speed ωm, Figure 11 The vertical axis of (b) represents the generator speed ωr, Figure 11 The vertical axis of (c) represents the current instruction switching flag FL_Iad_ref, Figure 11 The vertical axis of (d) represents the auxiliary machine required power Pa_req, Figure 11 The vertical axis of (e) represents the d-axis auxiliary winding current Iad, Figure 11 The vertical axis of (f) represents the host-side DC voltage VmDC detected by the host-side DC voltage sensor 17. Figure 11 The vertical axis of (g) represents the auxiliary machine side DC voltage VaDC detected by the auxiliary machine side DC voltage sensor 12 .

[0069] exist Figure 11 In the example, time t0 is the time when the travel motor speed ωm starts to change. Time t1 is the time when the current command switching flag FL_Iad_ref is switched from off to on based on the travel motor speed ωm and the generator speed ωr in this embodiment. Time t2 is the time when the travel motor 5 is stopped in this embodiment.

[0070] like Figure 11 As shown in (a) of FIG. 2 , in the case of this embodiment, the travel motor 5 starts to decrease at time t0 and stops at time t2 .

[0071] like Figure 11 As shown in (b), in the case of this embodiment, the generator rotation speed ωr decreases from time t0 to time t2, and rotates at the idling speed after time t2.

[0072] like Figure 11 As shown in (c), in the case of this embodiment, the current command switching determination unit 19b determines that the travel motor speed ωm becomes less than the travel motor speed threshold ωm_th and the generator speed ωr becomes less than the generator speed threshold ωr_th at time t1, and sets the current command switching flag FL_Iad_ref from off to on.

[0073] like Figure 11 As shown in (d) of FIG. 2 , in the case of the present embodiment, after time t0 , the auxiliary machine required electric power Pa_req is reduced to a predetermined value.

[0074] like Figure 11 As shown in (e), in the comparative example, the d-axis auxiliary winding current Iad decreases to a predetermined value after time t0. This is because the travel motor speed ωm decreases, and the host-side DC voltage VmDC no longer needs to be maintained high.

[0075] In contrast, in the case of this embodiment, until time t1, Figure 11 The comparative example (e) has the same waveform, but at time t1, after the set value of the d-axis auxiliary winding current command value Iad* is switched from the first d-axis auxiliary winding current command value Iad_1* to the second d-axis auxiliary winding current command value Iad_2*, the d-axis auxiliary winding current Iad rises to the specified value because the power converter 7 outputs the d-axis auxiliary winding current Iad that takes into account the generator speed ωr and the auxiliary machine required power Pa_req.

[0076] like Figure 11 As shown in (f), in the comparative example, after time t0, the master-side DC voltage VmDC decreases to a predetermined value. This is because the master-side DC voltage VmDC no longer needs to be maintained high due to the decrease in the travel motor speed ωm, so the master-side DC voltage command value VmDC* is reduced.

[0077] In contrast, in the case of this embodiment, until time t1, Figure 11Comparative example (f) shows the same waveform, but at time t1, after the d-axis auxiliary winding current command value Iad* is switched from the first d-axis auxiliary winding current command value Iad_1* to the second d-axis auxiliary winding current command value Iad_2*, the d-axis auxiliary winding current Iad rises to a predetermined value, exciting the main winding and increasing the host-side DC voltage VmDC. Furthermore, the upper limit of the d-axis auxiliary winding current command value Iad* at this time is determined by the maximum voltage that the host-side DC voltage VmDC can take, preventing the host-side DC voltage VmDC from exceeding the maximum voltage. Furthermore, if the host-side DC voltage VmDC exceeds the maximum voltage, the regenerative discharge resistor 6 is connected to discharge the voltage below the maximum voltage.

[0078] like Figure 11 As shown in (g), in the comparative example, the auxiliary machine side DC voltage VaDC decreases after time t0. This is because the first d-axis auxiliary winding current command value Iad_1*, which does not take into account the generator speed ωr and the auxiliary machine required power Pa_req, is set as the d-axis auxiliary winding current command value Iad*. Consequently, a sufficient excitation amount cannot be obtained for the auxiliary machine required power Pa_req, and the auxiliary machine side DC voltage VaDC cannot be maintained at the auxiliary machine side DC voltage command value VaDC*.

[0079] In contrast, in the case of this embodiment, until time t1, Figure 11 The comparative example (g) has the same waveform, but at time t1, the power converter 7 outputs the d-axis auxiliary winding current Iad taking into account the generator speed ωr and the auxiliary machine required power Pa_req, so that the auxiliary machine side DC voltage VaDC can be restored to the auxiliary machine side DC voltage command value VaDC*.

[0080] Next, we will describe a method for verifying whether the structure of this embodiment is correctly installed in the electric drive system. Since the structure of this embodiment is likely installed in software (the program of the control device 11), verification based on the appearance of the electric drive system is expected to be difficult. Therefore, the electric drive system is activated and verification is performed based on its behavior.

[0081] When performing verification, for example, in the power generation system 40 ( Figure 2 Voltage sensors are connected to the DC links on the main engine side and the auxiliary engine side (as shown in FIG). A load device is connected to the DC link on the auxiliary engine side. The voltage sensors measure the DC voltage on the main engine side and the DC voltage on the auxiliary engine side when the speed of the prime mover 1 and the load of the load device are changed. At this time, it is assumed that there is no load on the main engine side.

[0082] When the speed of the prime mover 1 is reduced and the load on the auxiliary machine side is increased, if the DC voltage on the main machine side increases while the DC voltage on the auxiliary machine side maintains a constant value, it can be confirmed that the structure of this embodiment has been implemented. Conversely, if the structure of this embodiment is not implemented, the DC voltage on the main machine side does not increase, and the DC voltage on the auxiliary machine side cannot maintain a constant value. Thus, by measuring the DC voltages on the main machine side and the auxiliary machine side of the power generation system 40 with voltage sensors, it is possible to verify whether the structure of this embodiment has been implemented.

[0083] (Summarize)

[0084] In this embodiment, the electric drive system includes: a travel motor 5; an auxiliary machine 41; a generator 2 having a stator 210 including a main winding 2131 and an auxiliary winding 2132; a rectifier 3 connected to the main winding 2131, converting the AC voltage generated by the main winding 2131 into a first DC voltage VmDC; a travel inverter 4 connected to the rectifier 3, converting the first DC voltage VmDC into an AC voltage and supplying it to the travel motor 5; a power converter 7 connected to the auxiliary winding 2132, controlling the voltages of the main winding 2131 and the auxiliary winding 2132, and converting the AC voltage generated by the auxiliary winding 2132 into a second DC voltage VaDC and supplying it to the auxiliary machine 41; and a control device 11 that controls the power converter 7. In this electric drive system, the control device 11 A first d-axis current command value Iad_1* of the auxiliary winding 2132 is calculated based on the first DC voltage VmDC and the command value VmDC* of the first DC voltage VmDC. A second d-axis current command value Iad_2* of the auxiliary winding 2132 is calculated based on the rotational speed ωm of the generator 2 and the required power Pa_req of the auxiliary device 41. In a traction state in which power is supplied from the traction inverter 4 to the traction motor 5, the power converter 7 is controlled so that the d-axis current value of the auxiliary winding 2132 coincides with the first d-axis current command value Iad_1*. In a deceleration state in which the traction motor 5 generates regenerative power or an idling state in which the traction motor 5 is stopped, the power converter 7 is controlled so that the d-axis current value of the auxiliary winding 2132 coincides with the second d-axis current command value Iad_2*.

[0085] According to the present embodiment configured as described above, in an electric drive system equipped with a dual-winding induction generator 2, even in a state (idling or decelerating) where the generator speed ωr decreases due to a reduction in the load on the main engine (the power required by the traction inverter 4 and the traction motor 5), the auxiliary machine-side DC voltage VaDC can be maintained at the voltage (auxiliary machine-side DC voltage command value VaDC*) required to supply the required power to the auxiliary machine 41 by the single power converter 7 provided on the auxiliary winding side. Consequently, regardless of the speed ωr of the dual-winding induction generator 2 and the load on the auxiliary winding side (the auxiliary machine-side power required Pa_req), the auxiliary winding-side DC voltage VaDC can be maintained by the single power converter 7 provided on the auxiliary winding side.

[0086] The electric drive system of this embodiment also includes an accelerator operating device 53a for instructing acceleration of the travel motor 5, a brake operating device 54a for instructing deceleration of the travel motor 5, and a first rotational speed sensor 50 for detecting the rotational speed ωm of the travel motor 5. The control device 11 determines a deceleration state when the accelerator operating device 53a is not being operated and the travel motor rotational speed ωm detected by the first rotational speed sensor 50 is greater than or equal to a first predetermined value ωm_th, or when the brake operating device 54a is being operated. This allows accurate determination of a deceleration state.

[0087] Furthermore, the electric drive system of this embodiment includes a first rotational speed sensor 50 for detecting the rotational speed ωm of the travel motor 5 and a second rotational speed sensor 14 for detecting the rotational speed ωr of the generator 2. The control device 11 determines that a state in which the travel motor rotational speed ωm detected by the first rotational speed sensor 50 is less than a first predetermined value ωm_th and the rotational speed ωr of the generator 2 detected by the second rotational speed sensor 14 is less than a second predetermined value ωr_th is an idle state. This allows accurate idle state determination.

[0088] The embodiments of the present invention have been described in detail above. However, these embodiments have been described in detail to facilitate understanding of the present invention, and the present invention is not necessarily limited to having all of the described structures. For example, the control lines and information lines shown in the figures are those deemed necessary for illustration and do not necessarily represent all of the control lines and information lines required for the product. In practice, it is assumed that almost all of the components are interconnected.

[0089] In addition, the present invention is not limited to the above-mentioned embodiments. For example, the following modified examples are also within the scope of the present invention. It is also possible to combine the structure shown in the modified examples with the structure described in the above-mentioned embodiments, or to combine the structures described in the following different modified examples with each other.

[0090] <Variation 1>

[0091] In the above embodiment, the transition between the first d-axis auxiliary winding current command value Iad_1* and the second d-axis auxiliary winding current command value Iad_2* can be made smoother. For example, by providing a rate-of-change limiter at the output of the current command switching unit 19c, the fluctuation of the d-axis auxiliary winding current command value Iad* associated with the switching between the first d-axis auxiliary winding current command value Iad_1* and the second d-axis auxiliary winding current command value Iad_2* can be made smoother. This can suppress transient fluctuations in the auxiliary winding current, the main machine-side DC voltage VmDC, and the auxiliary machine-side DC voltage VaDC.

[0092] <Variation 2>

[0093] In the above-described embodiment, in order to avoid the influence of interference and noise, the control device 11 may perform moving average processing or low-pass filtering processing on the values ​​used for various judgments and calculations.

[0094] <Variation 3>

[0095] Part or all of the functions of the control device 11 described in the above embodiment may be realized by hardware (for example, logic for executing each function is designed by an integrated circuit).

[0096] <Variation 4>

[0097] In the above embodiment, an electric drive system mounted on a dump truck is described as an example, but the application of the present invention is not limited thereto. The present invention can be applied to various vehicles equipped with a power generation system having two load systems.

[0098] Description of Reference Numerals

[0099] 1 Prime mover; 2 Generator; 2 Two-winding induction generator; 3 Rectifier; 4 Travel inverter; 5 Travel motor; 6 Regenerative discharge resistor; 7 Power converter; 8a Travel motor cooling inverter; 8b Regenerative discharge resistor cooling inverter; 8c Pump inverter; 8d Generator cooling inverter; 9a Travel motor cooling motor; 9b Regenerative discharge resistor cooling motor; 9c Pump motor; 9d Generator cooling motor; 10 Starting battery; 11 Control unit; 12 Auxiliary machine side DC voltage sensor; 13 Auxiliary winding current sensor; 14 Generator speed sensor (second speed sensor); 15 Main winding voltage sensor; 16 Main winding current sensor; 17 Main machine side DC voltage sensor; 19 Current command calculation unit; 19a Second d-axis auxiliary winding current command calculation unit; 19b Current command switching determination unit; 19c Current command switching unit; 20 Frequency command calculation unit; 20a Frequency command calculation unit; 21 Voltage command Calculation unit; 22 Voltage command compensation unit; 23 Turns ratio conversion unit; 24 Auxiliary machine required power estimation unit; 24a Travel motor cooling motor power estimation unit; 24b Regenerative discharge resistor cooling motor power estimation unit; 24c Pump motor power estimation unit; 24d Generator cooling motor power estimation unit; 26 Control signal generation unit; 30 Vehicle body; 31 Carriage; 32 Driver's seat; 33 Driven wheels; 34 Drive wheels; 40 Power generation system; 41 Auxiliary machine; 50 Travel motor speed sensor (first speed sensor); 53a accelerator operating device; 53b accelerator operating amount sensor; 54a brake operating device; 54b brake operating amount sensor; 210 stator; 211 stator core; 212 stator slot; 213 primary winding; 214 wedge; 220 rotor; 221 rotor core; 222 rotor slot; 223 secondary conductor; 230 gap; 2131 main winding; 2132 auxiliary winding; 2231 rotor bar; 2232 end ring.

Claims

1. An electric drive system comprising: Travel motor; Auxiliary engines; a generator having a stator including a main winding and an auxiliary winding; a rectifier connected to the main winding, and converting the AC voltage generated by the main winding into a first DC voltage; a driving inverter connected to the rectifier, converting the first DC voltage into an AC voltage and supplying the AC voltage to the driving motor; a power converter connected to the auxiliary winding, controlling the voltages of the main winding and the auxiliary winding, and converting the AC voltage generated by the auxiliary winding into a second DC voltage and supplying the DC voltage to the auxiliary machine; and a control device for controlling the power converter, The electric drive system is characterized in that: The control device calculates a first d-axis current command value of the auxiliary winding based on the first DC voltage and a command value of the first DC voltage. The control device calculates a second d-axis current command value of the auxiliary winding based on the rotational speed of the generator and the required power of the auxiliary machine. In a traction state in which electric power is supplied from the traction inverter to the traction motor, the control device controls the power converter so that the d-axis current value of the auxiliary winding coincides with the first d-axis current command value. In a decelerating state in which the traction motor generates regenerative electric power or an idling state in which the traction motor is stopped, the control device controls the power converter so that the d-axis current value of the auxiliary winding matches the second d-axis current command value.

2. The electric drive system according to claim 1, characterized in that: have: an accelerator operating device for instructing acceleration of the travel motor; a brake operating device for instructing deceleration of the travel motor; and A first speed sensor detects the speed of the travel motor. The control device determines a state in which the accelerator operating device is not operated and the rotation speed of the travel motor detected by the first rotation speed sensor is equal to or greater than a first predetermined value, or a state in which the brake operating device is being operated, as the deceleration state.

3. The electric drive system according to claim 1, characterized in that: have: a first rotation speed sensor, detecting the rotation speed of the travel motor; and A second rotation speed sensor detects the rotation speed of the generator, The control device determines that a state in which the rotation speed of the travel motor detected by the first rotation speed sensor is less than a first predetermined value and the rotation speed of the generator detected by the second rotation speed sensor is less than a second predetermined value is the idle state.

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