On-vehicle powertrain for AGV

Abstract

This document presents an on-vehicle powertrain for an automated guided vehicle (AGV). The on-vehicle powertrain includes a split-source inverter (SSI) having at least one midpoint pole, a positive DC link pole, and a negative DC link pole, a battery (21) and an inductor (22) connected in series between the positive or negative DC link pole and the midpoint pole, and a supercapacitor (20) connected between the positive DC link pole and the negative DC link pole.

Description

Technical Field

[0001] The present disclosure relates to an on-vehicle powertrain for an automated guided vehicle. Background Art

[0002] Automated guided vehicles (AGVs) use batteries to supply power to different motors in the AGV. Figure 1A An example of a powertrain for an AGV is shown. A battery 1 having a voltage V B is connected to a DC link (shown as a voltage source inverter VSI) through a DC / DC converter (shown as a boost converter BC). Alternatively, the battery 1 can be directly connected to the VSI. In electric vehicle (EV) applications, supercapacitors have been used to extend the battery life and thus the life of the entire system. In Figure 1A , a supercapacitor 5 is provided in the BC and / or a supercapacitor 6 is provided in the VSI for buffering high power peaks from acceleration and regenerative braking. The BC includes an inductor 2 connected to the battery 1 and a MOSFET 4, and the MOSFET 4 is connected to the VSI and the supercapacitor 5. The inductor 2 is also connected to a MOSFET 3. The VSI includes MOSFETs 7-12 arranged to provide a motor voltage V a -V c . Thus, integrating a supercapacitor unit into the on-vehicle energy storage unit has high potential in reducing the total cost of the system and extending its life. In this case, it is common practice to use another DC / DC converter to interface the supercapacitor, i.e., use two BCs as follows: one BC for the battery and one BC for the supercapacitor, where the outputs of the two DC / DC converters will be connected in parallel to the VSI, as Figure 1B shown. In Figure 1B , a supercapacitor BC is added in parallel with the Figure 1A shown powertrain for buffering high power peaks from acceleration and regenerative braking. The supercapacitor BC includes an inductor 14 connected to a battery 13 and a MOSFET 16, and the MOSFET 16 is connected to the VSI and a supercapacitor 17. The inductor 14 is also connected to a MOSFET 15.

[0003] In AGV applications, the cost and compactness of the on-vehicle powertrain are highly evaluated. For Figure 1B the conventional solution shown, there are two DC / DC converters BC and one VSI, which results in a higher cost and limits a more compact system design.

[0004] As described in https: / / en.wikipedia.org / wiki / Supercapacitor, a supercapacitor (SC), also known as an ultracapacitor, is a high-capacity capacitor that lies between electrolytic capacitors and rechargeable batteries, with a capacitance value far higher than other capacitors but a lower voltage limit. Supercapacitors typically store 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries with a much higher current capacity, and can withstand more charge-discharge cycles than rechargeable batteries.

[0005] Unlike ordinary capacitors, supercapacitors do not use traditional solid dielectrics but instead use electrostatic double-layer capacitance and electrochemical pseudocapacitance, both of which contribute to the total capacitance of the capacitor but have some differences.

[0006] Electrostatic double-layer capacitors (EDLCs) use carbon or its derivatives as electrodes, with an electrostatic double-layer capacitance far higher than that of electrochemical pseudocapacitance, thus achieving charge separation in the Helmholtz double layer at the interface between the conductive electrode surface and the electrolyte. The separation of charges is on the order of a few angstroms (0.3 - 0.8 nm), much smaller than in conventional capacitors.

[0007] Electrochemical pseudocapacitors use metal oxide or conductive polymer electrodes with a large amount of electrochemical pseudocapacitance added to the double-layer capacitance. Pseudocapacitance is achieved by utilizing Faraday electron charge transfer, intercalation, or electroadsorption of redox reactions.

[0008] Hybrid capacitors such as lithium-ion capacitors use electrodes with different characteristics: one mainly exhibits electrostatic capacitance, and the other mainly exhibits electrochemical capacitance.

[0009] The electrolyte forms an ion-conductive connection between the two electrodes, which differentiates them from conventional electrolytic capacitors where there is always a dielectric layer, and the so-called electrolyte (such as MnO2 or conductive polymer) is actually part of the second electrode (the cathode, or more precisely the positive electrode). Supercapacitors are polarized through the design of asymmetric electrodes or, for symmetric electrodes, through the potential applied during manufacturing. Summary of the Invention

[0010] An object of the present invention is to integrate a battery and a supercapacitor into an on-vehicle powertrain for an automated guided vehicle (AGV) without the need for an additional DC / DC converter to achieve a compact system design.

[0011] According to a first aspect, a vehicle-mounted power-train for an AGV is provided. The vehicle-mounted power-train includes a split-source inverter (SSI) having at least one midpoint pole, a positive DC link pole, and a negative DC link pole, a battery and an inductor connected in series between the positive DC link pole or the negative DC link pole and the midpoint pole, and a supercapacitor connected between the positive DC link pole and the negative DC link pole.

[0012] The vehicle-mounted power-train can be configured to generate a plurality of electrical phases, such as three electrical phases.

[0013] Each electrical phase can be connected to a separate midpoint pole. The vehicle-mounted power-train can further include a battery and an inductor connected in series between the positive or negative DC link pole and each midpoint pole.

[0014] All electrical phases can be connected to a common midpoint pole. The vehicle-mounted power-train can further include semiconductor elements between the common midpoint pole and each electrical phase. The semiconductor elements can be diodes or MOSFETs.

[0015] The battery can be connected closer to the positive or negative DC link pole than to the inductor.

[0016] The vehicle-mounted power-train can further include a supercapacitor for each electrical phase of the SSI, each supercapacitor being connected between a common negative DC link pole for the SSI and a separate positive DC link pole for each phase of the SSI.

[0017] The vehicle-mounted power-train can further include an off-vehicle charger having a step-down transformer. The vehicle charger can be connected to an electrical phase of the SSI via a switch and an inductor. The vehicle charger can be connected to individual midpoint poles separately. The vehicle charger can be connected to the common midpoint pole.

[0018] The capacitance of at least one supercapacitor can be at least 1 mJ / mm 3 .

[0019] The capacitance of each supercapacitor can be at least 1 farad (F), such as at least 10 F or at least 100 F.

[0020] With the proposed vehicle-mounted power-train, the supercapacitor is connected to the DC link terminals to allow for peak load shaving and buffering for the battery. By integrating the switch into the SSI, a modular design is also feasible. The motor can also be driven to change the DC link voltage. The DC link will further have a smaller voltage variation because the battery is directly connected to the DC link and the supercapacitor is arranged to inject only high currents.

[0021] Generally, all terms used in the claims will be interpreted according to their ordinary meaning in the technical field, unless otherwise expressly defined herein. All references to "an element, apparatus, component, device, step, etc." will be construed broadly to refer to at least one instance of the element, apparatus, component, device, step, etc., unless otherwise expressly stated. Unless expressly stated, the steps of any method disclosed herein need not be performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Aspects and embodiments will now be described by way of example with reference to the drawings, in which:

[0023] Figure 1A and 1B schematically shows a known on-vehicle powertrain for an AGV; and

[0024] FIGS. 2-6 are diagrams schematically showing embodiments of an on-vehicle powertrain for an AGV. DETAILED DESCRIPTION

[0025] Aspects of the present disclosure will now be described more fully hereinafter with reference to the drawings, in which certain embodiments of the present disclosure are shown.

[0026] However, these aspects may be embodied in many different forms and should not be construed as limited; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of all aspects to those skilled in the art. Throughout the specification, like reference numerals refer to like elements.

[0027] Reference Figure 2A and 2B , shows an embodiment of an on-vehicle powertrain for an AGV. This embodiment presents an efficient topology that integrates a battery and a supercapacitor with a diode-inductor assembly to provide a split-source inverter (SSI), thereby leveraging the two-level converter available on the rack.

[0028] The supercapacitor 20 is connected to the DC link of the three-phase SSI, i.e., between the positive and negative poles of the DC link. The battery 21 configured to drive the three-phase AGV is connected between the midpoint of the SSI (via inductor 22) and the negative pole ( Figure 2A ) or the positive pole ( Figure 2B ) of the DC link for the motor drive of the AGV.

[0029] The midpoint of the SSI is connected to the diode 23 of each phase of the three-phase SSI, and each phase is connected to the corresponding AC terminals Va, Vb, Vc of the motor. The SSI also includes MOSFETs 7-12 arranged to provide the motor voltages Va - Vc.

[0030] Therefore, both the battery current and the supercapacitor current can be controlled by the SSI, such that only smooth DC current is extracted from or fed to the battery, and the fluctuating current is buffered by the supercapacitor, which has better cycling ability and smaller internal losses. The battery life can be extended, while the life of the supercapacitor is significantly longer than that of the battery and is no longer a problem. In addition, the energy from regenerative braking can be buffered to extend the charging range. The energy from regenerative braking is buffered in the supercapacitor, the voltage of the supercapacitor will build up and the supercapacitor is designed to handle this situation. Then, the energy stored in the supercapacitor is reinjected into the load during acceleration.

[0031] At a battery voltage V B of 12 V and a supercapacitor rated voltage V SC of 48 V, the DC link voltage of the system can vary between 48 V and 24 V to allow high current injection or absorption from the electric motor.

[0032] Therefore, energy flow between the supercapacitor 20, the battery 21 and the electric motor is allowed. There are two main advantages: by using the supercapacitor to buffer the load peaks and absorb the regenerative energy, the battery life and the charging range can be extended; and the cost of the diodes and inductors may be lower than the cost of the DC / DC converter in the traditional solution.

[0033] The SSI, the battery and the supercapacitor can all be made of standardized commercial products. The inductor with diodes can alternatively be integrated as a single piece instead of being a standard product connected to the standard SSI. Only minor design modifications to the typical on-vehicle powertrain of the AGV are required to implement the topology.

[0034] Figure 3 An embodiment with the topology is shown, where Figure 2A and 2B the diodes 23 and 24 are replaced by MOSFETs 25 to allow bidirectional power flow. When pushing energy into the battery, the MOSFET 25 operates in the synchronous rectification mode and switches at the fundamental frequency according to the motor requirements.

[0035] Figure 4 An embodiment with the topology is shown, where Figure 3 the battery 21 is divided into 3 modules V B1 、V B2 、V B3 , where each module is connected to the negative DC link pole and the AC terminals V a 、26 b 、26 c via switches 26 a 、V b 、Vc between one of the terminals in. Switch 26 a 、26 b 、26 c can be a diode, a MOSFET, or a diode with series MOSFETs to achieve full controllability. Switch 26 a 、26 b 、26 c can also be a relay to activate only one of these batteries.

[0036] Figure 5 shows an embodiment with a topology where the supercapacitor 20 is also divided into 3 modules V in the same way as the batteries shown Figure 4 such that each phase of the motor is connected to a half-bridge. SC1 、V SC2 、V SC3 ,so that each phase of the motor is connected to a half-bridge.

[0037] Figure 6 shows an embodiment of an on-vehicle charger with a Figure 3 topology. The external AC power supply can be connected to phase V of the SSI via the step-down transformer 29, the switch 28, and the inductor 27 a 、V b 、V c . The motor can be connected via the switch 30. When the battery 21 is charged via the external AC power supply, the motor is disconnected. The on-vehicle charger is illustrated as being connected to a three-phase terminal, but alternatively can be connected to a common midpoint pole as a single-phase charger. A relay or contactor can be used to avoid a direct connection between the transformer and the motor. As an alternative option, the switch can be a MOSFET, in which case the on-vehicle charger can be just a step-down transformer without much complexity, thus reducing the system cost.

[0038] The choice of the topology of a particular implementation can depend on the internal layout design (i.e., space requirements) of the AGV and the required functions.

[0039] Refer to Figure 4 and Figure 5 , which shows an embodiment of an on-vehicle powertrain for an AGV. The on-vehicle powertrain includes an SSI, a midpoint pole of each electrical phase of the SSI, a positive DC link pole and a negative DC link pole, a battery 21 and an inductor 22 connected in series between the positive or negative DC link pole and the midpoint pole, and a supercapacitor 20 connected between the positive and negative DC link poles.

[0040] The on-vehicle powertrain can be configured to generate multiple electrical phases. There can be three electrical phases V a 、V b 、V c .

[0041] Each electrical phase V a 、V b 、V c is connected to a separate midpoint pole.

[0042] The on-vehicle power-train may also include a battery 21 and an inductor 22, which are connected in series between a positive or negative DC-link pole and each midpoint pole.

[0043] (A plurality of) batteries may be connected closer to the positive or negative DC-link pole than to the inductor.

[0044] The on-vehicle power-train may also include a supercapacitor for each electrical phase V of the SSI a 、V b 、V c , each supercapacitor being connected between the common negative DC-link pole of the SSI and the separate positive DC-link pole of each phase of the SSI.

[0045] The on-vehicle power-train may also include an off-vehicle charger having a step-down transformer.

[0046] The on-vehicle charger may be connected to the electrical phases V of the SSI via a switch and an inductor a 、V b 、V c 。

[0047] The on-vehicle charger may be connected separately to the respective midpoint poles.

[0048] The capacitance of at least one supercapacitor 20 may be at least 1 mJ / mm3.

[0049] The capacitance of each supercapacitor 20 may be at least 1 farad (F), or may be at least 10 F, or at least 100 F.

[0050] Referring to FIGS. 2, 3 and 6, an embodiment of an on-vehicle power-train for an AGV is shown. The on-vehicle power-train includes an SSI having a common midpoint pole, a positive DC-link pole and a negative DC-link pole, a battery 21 and an inductor 22 connected in series between the positive or negative DC-link pole and the common midpoint pole, and a supercapacitor 20 connected between the positive and negative DC-link poles.

[0051] The on-vehicle power-train may be configured to generate a plurality of electrical phases. There may be three electrical phases V a 、V b 、V c 。

[0052] All electrical phases are connected to the common midpoint pole.

[0053] The on-vehicle power-train may also include between the common midpoint pole and each electrical phase V a, V b , V c The semiconductor components 23, 24, 25 between

[0054] The semiconductor components may be diodes 23, 24 or MOSFET 25.

[0055] The battery 21 may be connected to the positive or negative DC link pole closer than to the inductor 22.

[0056] The vehicle powertrain may also include each electrical phase V of the SSI a , V b , V c The supercapacitor 20, with each supercapacitor connected between the common negative DC link pole of the SSI and the individual positive DC link poles of each phase of the SSI.

[0057] The vehicle powertrain may also include an off-vehicle charger with a step-down transformer 29.

[0058] The vehicle charger may be connected to the electrical phases V of the SSI via a switch 28 and an inductor 27 a , V b , V c .

[0059] The vehicle charger may be connected to the common midpoint pole.

[0060] The capacitance of at least one supercapacitor 20 may be at least 1 mJ / mm3.

[0061] The capacitance of each supercapacitor 20 is at least 1 F, or at least 10 F, or at least 100 F.

[0062] The various aspects of the present invention have been described above mainly with reference to some embodiments and their examples. However, as can be easily understood by those skilled in the art, within the scope of the present invention defined by the appended patent claims, other embodiments besides the above-disclosed embodiments are equally feasible.

Claims

1. An on-vehicle power-train for an Automated Guided Vehicle (AGV), said on-vehicle power-train comprising: - A Split-Source Inverter (SSI) having at least one midpoint pole, a positive DC-link pole and a negative DC-link pole; - A battery (21) and an inductor (22) connected in series between said positive or negative DC-link pole and said midpoint pole; And - A supercapacitor for each electrical phase (Va, Vb, Vc) of said SSI, each supercapacitor being connected between a common negative DC-link pole for said SSI and a separate positive DC-link pole for each phase of said SSI.

2. The vehicle powertrain according to claim 1, configured to generate a plurality of electrical phases (V a , V b , V c ).

3. The vehicle powertrain according to claim 1, configured to generate three electrical phases (V a , V b , V c ).

4. The vehicle powertrain according to claim 2, wherein each electrical phase (V a , V b , V c ) is connected to a separate midpoint pole.

5. The on-vehicle power-train according to claim 4, further comprising a battery (21) and an inductor (22), said battery (21) and said inductor (22) being connected in series between said positive or negative DC-link pole and each midpoint pole.

6. The on-vehicle power-train according to claim 2, wherein all electrical phases are connected to a common midpoint pole.

7. The on-vehicle power-train according to claim 6, further comprising semiconductor elements (23; 24; 25) between said common midpoint pole and each electrical phase.

8. The on-vehicle power-train according to claim 7, wherein said semiconductor elements are diodes (23; 24) or MOSFETs (25).

9. The on-vehicle power-train according to any one of claims 1-8, wherein said battery is connected closer to said positive or negative DC-link pole than to said inductor.

10. The on-vehicle power-train according to any one of claims 1-8, further comprising an off-vehicle charger having a step-down transformer (29).

11. The vehicle powertrain according to claim 10, wherein the on-vehicle charger is connected to the electrical phases (V a , V b , V c ) of the SSI via a switch (28) and an inductor (27).

12. The on-vehicle power-train according to claim 10, wherein said on-vehicle charger is connected individually to respective midpoint poles.

13. The on-vehicle power-train according to claim 10, wherein said on-vehicle charger is connected to a common midpoint pole.

14. The vehicle powertrain according to any one of claims 1-8, wherein the energy storage per unit volume of at least one supercapacitor (20) is at least 1 mJ / mm 3 .

15. The on-vehicle power-train according to claim 14, wherein the capacitance of each supercapacitor (20) is at least 1 Farad (F), at least 10 F or at least 100 F.

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