DESC:DUAL POWER CONVERTER ENERGY PACK FOR ELECTRIC VEHICLE
TECHNICAL FIELD
The present disclosure generally relates to a power electronics system for electric vehicles (EVs). In particular, the present disclosure relates to a dual power converter energy pack capable of storing excess regenerative braking energy in electric vehicles (EVs).
BACKGROUND
Regenerative braking is a braking technique employing electromagnetic torque by which some part of the energy present in the vehicle can be recovered and fed back to the energy storage elements. This energy can be reused again, thereby providing more energy efficiency and improved range. There are certain limitations to the extent by which the energy can be recovered with regenerative braking due to the power handling capabilities of different components, especially the battery. Regenerative Braking is generally usually used in conjunction with mechanical braking in order to provide a controlled, safe, and reliable braking system.
In conventionally available electric vehicles (EVs), regenerative electric power is generated at deceleration of the electric vehicles. The regenerative electric power is retrieved by the traction inverter present in the vehicle and the retrieved electric power is stored in a DC link capacitor of the traction inverter and battery.
Typically, in electric vehicles (EVs), an on-board charger (OBC) refers to a charging system integrated within the electric vehicle. The OBC takes AC input voltage from the grid and supplies a controlled DC voltage in order to charge the traction battery. Also, the EV includes a power conversion module that converts the DC voltage supplied by the traction battery into a variable voltage variable frequency AC voltage required to drive and control the electric motor of the vehicle.
Traditionally, OBC hardware is utilized only during charging the vehicle when it is not in driving mode, at all other times the OBC hardware is left unused.
Further, in a situation where the battery pack of the EV is in a high state of charge (SOC) and/or non-receptive conditions, the regenerative braking is disabled by the system as the battery cannot store more energy.
Thus, there exists a need for a novel architecture for a regenerative braking energy recovery system that enhances the energy recovery capability and stores the energy when the battery pack is in the non-receptive (high state of charge) condition.
SUMMARY
The main object of the present invention is to provide a dual power converter energy pack capable of storing excess regenerative braking energy in electric vehicles (EVs).
Another object of the present invention is to provide an on-board charger (OBC) capable of storing regenerative braking energy, in a situation where the battery pack of the EV is in high state of charge (SOC) and/or non-receptive conditions.
Another object of the present disclosure is to provide a dual power converter energy pack capable of enhancing regenerative braking energy recovery capability of the EV by utilising the existing OBC of the EV.
In accordance with an embodiment of the present disclosure, there is provided a dual power converter (DPC) energy pack for electric vehicles capable of storing excess regenerative braking energy in an electric vehicle (EV), the dual power converter energy pack for electric vehicle comprising:
- at least one battery pack;
- a drive-train unit (DTU); and
- an energy recovery and storage system (ERSS) including an input rectifier, at least one energy storage device and a DC-DC converter,
wherein the DC-DC converter is bi-directional and facilitates flow of the excess regenerative braking energy to the energy storage device, when the EV is in operation and the at least one battery pack is in high charge stage.
The present disclosure provides a dual power converter (DPC) energy pack for electric vehicle (EV). The dual power converter (DPC) energy pack, as disclosed in the present disclosure, is advantageous in terms of providing an additional storage space for the regenerative braking energy without incorporating bulky energy storage medium to the existing EV. Among other advantages, the energy recovery and storage system (ERSS), as disclosed in the present disclosure, is advantageous in terms of redirecting the surplus regenerative energy to a secondary storage available in the OBC of the EV.
Other objects and advantages of the dual power converter (DPC) energy pack of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 is a diagram illustrating a dual power converter (DPC) energy pack including a battery pack, an energy recovery and storage system (ERSS), DTU and a traction motor in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The detailed description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a dual power converter (DPC) energy pack 100 for electric vehicle capable of storing excess regenerative braking energy in electric vehicles and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
Figure 1 depicts a dual power converter (DPC) energy pack 100 for storing excess regenerative braking energy in an electric vehicle (EVs) (not shown in figure), in accordance with an embodiment of the present disclosure. The dual power converter (DPC) energy pack 100 includes at least one battery pack 102, a drive-train unit (DTU) 104 and an energy recovery and storage system (ERSS) 106. The energy recovery and storage system (ERSS) 106 further includes an active rectifier 112, at least one energy storage device 114 and a DC-DC converter 116. Specifically, the DC-DC converter 116 is bi-directional and facilitates flow of the excess regenerative braking energy to the at least one energy storage device 114, when the EV is in operation and the at least one battery pack 102 is in high charge stage.
Optionally, the dual power converter (DPC) energy pack 100 is connected to a traction motor 118 through the DC-AC converter 110 of the DTU 104.
As used herein, the terms ‘input rectifier’ and ‘active rectifier’ are used interchangeably and refers to power factor correction AC to DC converter.
As used herein, the terms ‘electric vehicle’, ‘2W-EVs’, ‘electric two-wheeler’, ‘EV’, ‘EVs’ and ‘two-wheel electric vehicle’ are used interchangeably and refer to any vehicle having stored electrical energy, including those vehicles capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source.
As used herein, the terms ‘dual power converter energy pack’, ‘dual power converter’, ‘DPC energy pack’ and ‘energy pack’ are used interchangeably and refer to a combination of a battery pack, an on-board charger and traction inverter, of the electric vehicle. Further, the DPC energy pack 100 may include an auxiliary power supply unit. The auxiliary power supply unit, when in operation, is operable to supply electrical energy to the low voltage components of the EV.
As used herein, the terms ‘battery pack’ and ‘battery unit’ are used interchangeably and refer to a set of identical batteries or individual battery cells, that may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The battery pack 102 may further include a battery management system (BMS). The BMS is an electronic system that manages a rechargeable battery to ensure it operates safely and efficiently, and designed to monitor the parameters associated with the battery pack and its individual cells, apply the collected data to eliminate safety risks and optimise the battery performance.
As used herein, the terms ‘drive-train unit’, ‘DTU’ and ‘traction inverter’ are used interchangeably and refer to an inverter that converts energy from the vehicle's battery in order to drive the motors in the drive-train. Typically, the DTU, when in operation, converts dc power from an on-board high voltage (HV) battery into ac power to drive the main motor of the electric vehicle.
As used herein, the terms ‘energy recovery and storage system’, ‘ERS system’, ‘ERSS’, ‘on-board charger’ and ‘OBC’ are used interchangeably and refer to a charging module integrated with the battery pack 102 and DTU 104 of the EV, and capable of allowing flow of the surplus regenerative energy to a secondary storage available therein.
As used herein, the terms ‘at least one energy storage device’, ‘at least one energy storage device’, ‘energy storage device’, ‘OBC DC link capacitor’ and ‘DC link capacitor’ are used interchangeably and refers to an energy storage device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other.
In an embodiment, there is provided a dual power converter 100 capable to storing the regenerative braking energy in electrical vehicle having battery pack 102 that is integrated with the drive train unit (DTU) 104. The drive train unit 104 comprises a DC link capacitor 108 and a DC to AC converter 110 which are connected with each other in drive train unit 104 and the drive train unit 104 is integrated with traction motor 118.
In another embodiment, there is provided a traction motor 118 which provides the AC supply (during the regeneration) to the DTU 104. The converted DC supply is stored in the energy storage device 114 (which acts as an energy storage device). Optionally, the energy storage device includes at least one of a DC Link capacitor, super-capacitor, ultra-capacitor or a combination thereof.
In an embodiment, the ERSS 106 comprises at least one bleed resistor 120 for discharging the at least one energy storage device 114. Specifically, the bleed resistor is integrated with the at least one energy storage device 114 for discharging the same. In other words, the bleed resistor 120 is connected to energy storage device and is capable of discharging the at least one energy storage device. The bleed resistor discharge capacitors to safe voltage levels after power is removed.
In an embodiment, the DPC energy pack 100 further comprises primary battery unit 102 including a plurality of individual cells connected electrically. In an embodiment, the ERSS 106 facilitates charging of the battery pack 102, when the EV is not in operation and connected to an external energy source or power grid.
In another embodiment, there is provided an ERSS 106 which is capable to convert the current, and power, that is stored in the energy storage device 114 through the bi-directional DC-DC converter 116. The bidirectional DC/DC converter 116 is changed into the charging mode when the battery pack 102 is required to be charged. The switching is performed on the bidirectional DC/DC converter 116 such that when the regenerative braking is applied, the bidirectional DC/DC converter 116, converts the applied voltage into the rated voltage of the energy storage device 114.
In an exemplary embodiment, there is provided a dual power converter energy pack 100 having drive train unit 104. The drive train unit 104 includes DC link capacitor 108 and DC to AC converter 110. The bidirectional DC-DC converter 116 is connected with the DC link capacitor 108. The energy storage device 114 stores the power through DC-DC converter 116. During driving there is no input from the grid side, hence the DC link capacitor 114 of OBC remains in a zero-charge condition. In such a situation, the bi-directional DC-DC converter allows flow of the regenerative braking energy to an uncharged high voltage capacitance (the DC link capacitor of OBC) 114. Thus, enabling the DPC energy pack to utilise the DC link capacitor 114 of the OBC 106 as a secondary energy storage unit, other than the battery pack 102.
Further, when regenerative braking is performed, the limitation relating to the battery pack 102 SOC and the maximum current rates of the battery pack 102 are eliminated. The availability of an additional path via bidirectional DC-DC converter 116 of the ERSS 106 to the DC link capacitor provides 108 an additional storage to recover more power from the motor 118 than the battery pack 102 may store.
Alternatively, this surplus energy may be fed to the OBC DC link capacitor 114 which, being at higher voltage level, has much more energy storage capacity than the DC link capacitor 108 of the DTU 104.
For example, for the same capacitance value if the voltage level is increased to around 8 times (48V to 390V), the energy storage capacity increases to 64 times, while the increase in volume or weight is very less comparatively. Moreover, this additional storage is provided without adding any new component to the OBC.
In a specific embodiment, the excess energy generated in the DTU 104 is dumped in the ERSS 106 OBC DC link capacitor 114 via the DC-DC converter 116 of the ERSS 106, thus discharging the Inverter DC link capacitor 108 to safer voltage limits even without requirement of stopping the vehicle by going into active short circuit, for a temporary and/or less magnitude safety event.
In another specific embodiment, when the battery pack 102 is in high SOC conditions and the regenerative braking is disabled by system, due to limited capacity of the battery pack 102, and electromagnetic braking is required, the braking at high SOC may be done without braking resistor just by directing the power flow towards the OBC DC link capacitor 114. Further, the surplus energy stored in the OBC DC link capacitor 114 may be taken back to the DC link capacitor 108 of the DTU, the battery pack 102 or slowly dissipated via compact bleeder resistor 120.
In an embodiment, when the battery 102 is not fully charged, the electric vehicle is in operation, and regenerative breaking is applied the voltage produced by the traction motor 118 is supplied to the DTU 104.
In another embodiment, when the battery 102 is fully charged, the electric vehicle is in operation, and regenerative breaking is applied, the power supplied from traction motor 118 is passed through the DTU 104 and stored in the OBC link capacitor 114.
Further, the bidirectional DC/DC converter 116 is present in the ERSS 106 and is integrated with the DTU 104 and the facilitates flow of the excess regenerative braking energy to the energy storage device 114, when the EV is in operation and at least one battery pack 102 is in high charge stage. Specifically, the energy storage device 114 stores the power supplied (received) through DC-DC converter 116. The bidirectional DC-DC converter 116 is a device for performing oscillation between several tens of KHz to several hundreds of KHz inside, and raising and dropping voltage.
Optionally, the bidirectional DC/DC converter 116 includes the first and second transistor, which are turned on or turned off under the control of Pulse Width Modulation (PWM), and bidirectional converts DC voltage into specific DC voltage while the first and second transistor is switched on or off.
Furthermore, the dual power converter energy pack 100 which being capable of regenerative power storage system mounted on an electric vehicle according to the present invention is provided between the inverter and the traction motor 118.
In a situation, when uncontrolled regeneration happens due to momentary loss means short time loss of control and battery pack is disconnected. In this situation another path allows energy storage and thus avoids overcharging of inverter dc link capacitor 108.
Example
Below example explains the conditions when the regenerative braking of the electric vehicle occurs:
Regeneration Power = 1 kW
Minimum DTU DC Link Voltage
Vdc_DTU_min = 40 V
Maximum DTU DC Link Voltage
Vdc_DTU_max = 60 V
DTU Capacitance
CDTU = 4700 µF
DTU DC Link Capacitance Energy at 40V
EDTU_40 = 0.5 x C x V2
EDTU_40 = 3.76 J
DTU DC Link Capacitance Energy at 60V
EDTU_60 = 0.5 x C x V2
EDTU_60 = 8.46 J
DTU DC Link Capacitance Energy Difference (60V to 40V)
?EDTU_Cap = 8.46 – 3.76
?EDTU_Cap = 4.7 J
The time taken by 1 kW regeneration power to charge DTU capacitors from 40V to 60V = 4.7/1000 = 4.7 milliseconds (ms).
Hence, maximum time for which DTU 104 can handle uncontrolled regeneration of 1kW is 4.7 ms, beyond which the DC Link capacitors 108 can get damaged. This is best case scenario where capacitors were initially at 40V. If initial voltage is taken as 55V the time comes down to 1.35 ms.
Now if this power is redirected to DC Link capacitors 114 of OBC 106.
OBC Capacitance
COBC = 680µF
OBC Capacitance Energy at 400V
EOBC_400 = 0.5 x C x V2
EOBC_400 = 54.4 J
OBC Capacitance Energy at 300V
EOBC_300 = 0.5 x C x V2
EOBC_300 = 30.6 J
OBC Capacitance Energy Difference (400V to 300V)
?EOBC_Cap = 54.4 – 30.6
?EOBC_Cap = 23.8 J
So, initially uncharged DC Link capacitors 114 of OBC 106 can take 1kW regeneration power for 54.4 ms. even when DC Link capacitors 114 of OBC 106 are initially at 300V, taking them to 400V still takes 23.8 ms for 1kW of power source.
Therefore, the additional path, as provided by the present disclosure, increases the ability of the vehicle to handle loss of control and uncontrolled regeneration in terms of time duration by 6 to 50 times. This time may further be increased to very high levels by turning on bleeding/braking resistor at HVDC link. Other than time, it also provides added safety and avoids DTU capacitor damage in such scenarios.
Further, when extra energy storage is added the regenerative braking energy recovery capability increases and its available irrespective of the SOC of battery, and this energy is used back to charge main battery, or to feed auxiliary loads.
So, only with the DC Link capacitors 114 of OBC 106 the 54 J (exact value depends upon exact system parameters) energy storage capabilities is added, this can be further increased several times if more energy storage is added.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

WE CLAIM:
1. A dual power converter DPC energy pack (100) for electric vehicle, the DPC energy pack (100) comprising:
- at least one battery pack (102);
- a drive-train unit DTU (104); and
- an energy recovery and storage system ERSS (106) including an input rectifier (112), at least one energy storage device (114) and a DC-DC converter (116),
characterized in that the DC-DC converter (116) is bi-directional and facilitate flow of the excess regenerative braking energy to the energy storage device (114), when the EV is in operation and the at least one battery pack (102) is in high charge stage.
2. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) is connected to a traction motor (118) of the EV.
3. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DTU (104) comprises at least one DC Link capacitor (108) and a DC-AC converter (110).
4. The DPC energy pack (100) for electric vehicle EV as claimed in claim 3, wherein the DC-AC converter (110) facilitates the flow of regenerative braking energy from the traction motor (118) to the DTU (104) of the DPC energy pack (100).
5. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the at least one energy storage device (114) includes at least one of a DC Link capacitor, super-capacitor, ultra-capacitor or a combination thereof.
6. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the ERSS (106) further includes at least one bleed resistor (120) for discharging the at least one energy storage device (114).
7. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) further comprises the at least one battery pack (102) including a plurality of individual cells connected electrically.
8. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) facilitates charging of the plurality of individual cells, when the EV is not in operation and connected to an external energy source.

Dated 10 March 2023 Kumar Tushar Srivastava
IN/PA- 3973
Agent for the Applicant

ABSTRACT
DUAL POWER CONVERTER ENERGY PACK FOR ELECTRIC VEHICLE
There is disclosed a dual power converter (DPC) energy pack 100 capable for storing excess regenerative braking energy in an electric vehicle (EV) comprising at least one battery pack 102, a drive-train unit (DTU) 104, and an energy recovery and storage system (ERSS) 106 including an active rectifier 112, at least one energy storage device 114 and a DC-DC converter 116. Specifically, the DC-DC converter 116 is bi-directional and facilitates flow of the excess regenerative braking energy to the at least one energy storage device 114, when the EV is in operation and the at least one battery pack 102 is in high charge stage.

,CLAIMS:WE CLAIM:
1. A dual power converter DPC energy pack (100) for electric vehicle, the DPC energy pack (100) comprising:
- at least one battery pack (102);
- a drive-train unit DTU (104); and
- an energy recovery and storage system ERSS (106) including an input rectifier (112), at least one energy storage device (114) and a DC-DC converter (116),
characterized in that the DC-DC converter (116) is bi-directional and facilitate flow of the excess regenerative braking energy to the energy storage device (114), when the EV is in operation and the at least one battery pack (102) is in high charge stage.
2. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) is connected to a traction motor (118) of the EV.
3. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DTU (104) comprises at least one DC Link capacitor (108) and a DC-AC converter (110).
4. The DPC energy pack (100) for electric vehicle EV as claimed in claim 3, wherein the DC-AC converter (110) facilitates the flow of regenerative braking energy from the traction motor (118) to the DTU (104) of the DPC energy pack (100).
5. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the at least one energy storage device (114) includes at least one of a DC Link capacitor, super-capacitor, ultra-capacitor or a combination thereof.
6. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the ERSS (106) further includes at least one bleed resistor (120) for discharging the at least one energy storage device (114).
7. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) further comprises the at least one battery pack (102) including a plurality of individual cells connected electrically.
8. The DPC energy pack (100) for electric vehicle as claimed in claim 1, wherein the DPC energy pack (100) facilitates charging of the plurality of individual cells, when the EV is not in operation and connected to an external energy source.