DESC:Filed of Invention:
The present invention relates to a protection system for an electric or hybrid vehicle and more particularly relates to a protection system for various electronic/ electric components from regenerated power in electric or hybrid vehicle.

Cross reference to Related Invention
This invention takes priority from an earlier filed provisional patent application no. 202021002125 filed on January 17, 2020; which is incorporated herein as reference.

Background of Invention:
Electric or hybrid vehicles are provided with number of electrical and electronic components. Some of these components are vital for operation of the vehicle like a Motor Control Unit (MCU), DC-DC converter. These components are very costly. Hence, their protection and safety is an important aspect of the vehicle. The electric vehicle includes an electric motor as a drive member of vehicle and a battery to supply necessary power to the electric motor. A rotor or a shaft of the motor starts rotating to produce required drive upon receiving power from battery, which is further transmitted to the wheels of the vehicle to move forward.

In a reverse way, when the vehicle is driven by some external force like during towing or while vehicle is running on downhill, in such situations wheel of the vehicle drives the motor i.e. the rotor or shaft of the motor is rotated by the wheel. As an inherent property of any motor, when the shaft of the motor is rotated an alternating current in developed the stator coils due to rotating magnetic field created by rotor magnets. The motor starts acting as a generator and generates the electric current/ power. This generated power is sent back to the battery or other electric components connected across the system bus. The regenerative power of an electric motor assists in charging the battery, thereby improves the overall efficiency of the system. However, there exists a condition during regeneration wherein, if the battery is disconnected from system (for ex vehicle is in Ignition OFF condition), a large regenerated voltage is developed across various electrical components. This regenerated power is dumped in capacitors across MCU input, DC-DC converter input, charger output etc. However, the regenerated power is not used for any other useful work, thus the total capacitance would continue charging, taking the system voltage level beyond permissible levels and resulting in damage to some or all of the components connected across the system bus. This will be a major loss for the vehicle owner and may also lead to an unsafe condition.

This situation is more prone and dangerous when the vehicle is running on a downhill or during towing with the battery in disconnected condition, because when the battery is disconnected the regenerated power cannot go back to the battery, rather it goes into other electric components like MCU, DC-DC converter etc. The MCU is provided with number of capacitors having a specific capacity to store the regenerated power however; their capacity is limited. If the regenerated power exceeds the storage capacity of the capacitors then it may destroy the components connected directly across the system bus (e.g. MCU, DC-DC converter, charger etc). This could also result in a safety hazard and calls for replacement of these costly components.

There are number of solutions available to protect the components of electric/ hybrid vehicle. The available systems use the regenerative current to fully charge the battery, once the battery is fully charged a separation switch is used to disconnect/ separate the battery such that the regenerative current is no more sent to the battery and it is controlled within inverter circuit. Such separation switches come at heavy cost as well as it increases the overall size of the system and reduces system reliability as a series switch is getting added in the power chain. The use of switch causes higher electrical losses, which reduces the overall efficiency of the system.

According to another prior art system available, the regenerated current is supplied to number of resistors, where it is converted into heat. This excessive heat requires cooling system to effectively manage the heat. It is very costly and has high losses.

Hence, there is a need to provide an effective system to protect the components from regenerative current even when the battery is in disconnected condition and the system needs to be reliable, cost effective, simple, compact and with minimal losses.

Therefore, in view of above mentioned drawbacks and challenges of existing systems; the object of the present invention is to provide an effective protection system for electrical/ electronic components of electric or hybrid vehicle from regenerative current.

Another objective of the present invention is to provide a protection system for electric or hybrid vehicle, which is reliable, cost effective, simple, compact and with minimal losses.

SUMMARY OF THE INVENTION:

With this object in view, the present invention provides a protection system for electric or hybrid vehicle comprising:
a battery source to supply electric power to electric motor;
said electric motor is used to drive the vehicle;
a control unit to regulate the electric power generated by the electric motor during regeneration phase wherein; the control unit regulates said electric power when the battery source is in disconnected condition and the vehicle or motor speed or regenerated voltage exceeds a pre-defined threshold limit.

According to first embodiment of present invention, the control unit regulates the electric power by applying a controlled braking with the help of at least a switching device. According to second embodiment of present invention, a controlled braking is applied based on current speed of the vehicle or motor and a pre-defined map of speed v/s torque stored in the control unit.

The battery source is connected to the electric motor through said control unit using a system bus. The other electric/ electronic components are connected to the battery source over said system bus including DC-DC converter, Charger, Auxiliary battery etc.

A DC to AC converter configured to convert DC supply of said battery source into AC supply, which is further supplied to said electric motor. The DC to AC converter may be a part of the control unit or may be provided as a separate unit.

The battery source gets disconnected from the DC to AC converter, electric motor and other electric/ electronic components when the vehicle is in OFF condition. While in OFF condition, if the vehicle is in motion (downhill, towing etc.), the motor starts regenerating.

The DC to AC converter comprises plurality of switching devices configured to control the voltage and current through frequent commuting. The DC to AC converter further comprises at least a capacitor configured to store electric power and supply said power to the motor in a form of ripple current during commuting of the switching devices. Other electric/ electronic components including DC-DC converter, charger may be connected on same system bus.

The control unit is stored with a pre-defined limit of maximum and minimum regenerated voltage that said system could sustain without any damage to electrical/electronic components wherein; said regenerated voltage is a voltage generated by the electric motor during regeneration phase. The pre-defined limits are stored in a hysteresis controller, which is a part of said control unit. The pre-defined limits may be calibrated for any electric/ hybrid vehicle based on its architecture.

The control unit is configured to identify the battery is in disconnected condition, and motor is in regeneration phase. According to first embodiment of present invention, the control unit comprises a high pass filter configured to generate a trigger signal to enable the regulation of regenerated voltage if the motor or vehicle speed exceeds a predefined speed threshold limit. Alternatively, the vehicle or motor speed may be measured using a speed sensor.

According to second embodiment of present invention, the control unit is further configured to measure the rate of change of regenerated voltage. The hardware module could be a DC bus measurement and a clamping module that identifies motor is in regeneration phase if the capacitors have stored certain charge in battery-disconnected condition.

The hysteresis controller is interfaced with said high pass filter to receive the trigger signal according to first embodiment or in communication with said DC bus measurement and clamping module according to second embodiment to receive measured regenerated voltage and configured to enable/disable the control of regulating regenerated voltage based on the comparison of measured regenerated voltage with pre-defined limits.

According first embodiment of present invention; the hysteresis controller is interfaced with said high pass filter through a rectifier and latch unit. The rectifier and latch unit is configured to send an enable signal to hysteresis controller enable/disable the control of regulating regenerated voltage if the regenerated voltage exceeds the pre-defined threshold limits stored in the hysteresis controller.

The rectifier and latch unit is configured to verify the power supply from battery is disconnected and send an enable signal to activate at least a hysteresis controller and a DC-DC converter. The DC-DC converter is configured to supply regenerated power to the gate controller and to the hysteresis controller by stepping it down to a regulated voltage upon receiving enable signal from the rectifier and latch circuit.

According to second embodiment of the present invention, the control unit comprises a PWM controller configured to receive a signal from hysteresis controller that the regenerated voltage has exceeded the pre-defined threshold limit and further configured to regulate the regenerated voltage by modulating the pulse width or duty cycle of the switching devices. The PWM controller may be provided as a separate unit or may be a part of a control unit.

A speed sensor of the vehicle and/ or motor reads the current vehicle/motor speed. The PWM controller is in communication with a map of speed v/s torque to compute allowed braking torque value for current speed of the vehicle/ motor and configured to generate a signal to modulate the pulse width or duty cycle of said switching devices based on computed allowed braking torque which helps to maintain the voltage under pre-defined limit. The PWM controller provides a means to control the braking torque so that wheel locking is prevented. The PWM controller verifies that the computed torque is well within pre-defined limits of maximum and minimum safe braking torque limits. A safe braking limit is identified for current speed of the motor and it is ensured that the identified braking torque is within acceptable limits and then PWM controller proportionately increases the duty cycle at else, the duty cycle is reduced. The PWM controller is configured to ensure that the duty cycle of switching devices is applied in small discrete steps such that controlled braking is applied and wheel locking and/or skidding of the vehicle is avoided. The map of speed v/s torque comprise set of ideal data of acceptable braking torque at various speed levels.

The PWM controller is configured to proportionately modulate the pulse width or duty cycle of switching devices by recirculating a portion of regenerated power by commutating the switching devices at certain duty cycle dependent on computed ideal torque thereby ensuring that only a fraction of the regenerated power is used to charge the capacitors, thus reducing the rate at which the system voltage increases.

A gate controller interfaced with hysteresis controller and configured to control the switching devices of the DC to AC converter for directing the flow of regenerated power. .

After, modulating the duty cycle, the regenerated voltage level and/or rate of change of voltage are checked continuously by the hysteresis controller. As only, a portion of regenerative power is utilised by applying a controlled braking, the rate of change of regenerated voltage drops. As the voltage drops below the lower control limit of hysteresis controller, the PWM controller turns off the control signal.

During regulation of regenerated voltage, if the battery is reconnected as the vehicle is turned ON, the control unit stops further regulation of regenerated voltage. The regenerated voltage may be supplied directly to the battery for battery charging purpose if the battery is not fully charged.

According to another embodiment of the present invention, the control unit is configured to register last state of charge (SOC) of battery source and/ or capacitor before the vehicle is turned OFF. If the battery/ capacitor SOC is below a pre-defined threshold limit then the regenerated power is first utilised to charge the battery and/or capacitors and when the battery and/or capacitors are charged to the set threshold limit, then the protection system is activated and the regenerated voltage is regulated to protect the components from any damage due to increasing DC voltage. If the last registered SOC of battery and/or capacitor is above the threshold limit then the protection system immediately starts regulating the regenerated voltage without further charging the battery and/ or capacitor. The battery is charged by reconnecting the battery with system bus. The control unit configured to keep all other vehicle components in OFF state, even though battery is reconnected with the system bus in vehicle OFF condition.

According to another embodiment of the present invention, the switching device explained herein above are MOSFET or IGBT switches preferably, MOSFET type switches, six in number are used. There are plurality of capacitors provided as a part of DC-AC converter or may be provided separately. DC to AC converter is a voltage source inverter (VSI) which may be a part of control unit. The vehicle may be provided with a single electric motor or plurality of electric motors to drive the vehicle. A Motor Control Unit (MCU) is provided to control various functions of motor and/or vehicle. The control unit may be a part of said Motor Control Unit or may be provided as a separate unit. The battery source may comprise a single battery or a set of batteries.

Present invention provides a method for regulating the regenerated voltage of electric motor using a control unit comprising steps of measuring a motor or vehicle RPM or measuring a regenerated voltage and comparing with a predefined threshold limit; generating a trigger signal if the measured vehicle or motor RPM or regenerated voltage exceeds predefined speed threshold limit; enabling the regulation of regenerated voltage by controlling atleast one switching device of a DC to AC converter; measuring the regenerated voltage and comparing with predefined maximum and minimum threshold limits in a hysteresis controller; disabling the regulation if the measured regenerated voltage drops below predefined threshold limit.

The above explained protection system is applicable to any electric or hybrid vehicle irrespective of its type i.e. the system is applicable to any two-wheeled, three-wheeled or four-wheeled vehicle.

Brief Description of Drawings:
The system of the present invention may be more fully understood from the following description of preferred embodiments thereof, made with reference to the accompanying drawings in which:

FIG. 1 illustrates a block diagram of complete vehicle system architecture according to the present invention;

FIG.2 illustrates a block diagram of protection system according to first embodiment of the present invention;

FIG.3 illustrate a flow chart of control methodology of the protection system according to first embodiment of the present invention;

FIG.4 illustrates a block diagram of protection system according to second embodiment of the present invention;

FIG.5 illustrate a flow chart of control methodology of the protection system according to second embodiment of the present invention; and

FIG.6 illustrate a flow chart of methodology used to charge the battery according to an alternate embodiment of the present invention.

Detail Description of Drawings:
A preferred embodiment will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

Referring to FIG.. 1 illustrating the block diagram of vehicle architecture involving various electrical/ electronic components. A battery source 100 supply required electric power to all the components over a system bus (135). A battery source 100 may comprise a single battery or a set of batteries. An electric motor (125) is connection with the battery source (100) to receive the required electric motor and configured to drive the vehicle using received power. A control unit (120) is used to connect the battery source (100) to the motor (125) which performance various functions including controlling of various components such as motor (125). The battery source (100) is charged using a charger (150). The charger (150) may be externally provided to the vehicle or may be provided as an on-board component. All other vehicle electrical/ electronic components such as headlamp, tail lamp, indicators, horn are connected over a same system bus (135). These components are connected to the battery source (100) through a DC-DC converter (140) and an auxiliary battery (170). The function of the DC-DC convertor (140) is to charge the auxiliary battery (170) by taking current from the main battery (100). Since the auxiliary battery (170) operates at much lower voltage than battery (100), a direct current of 48 volt from main battery (100) cannot directly be used to charge the auxiliary battery (170). DC-DC converter (140) steps down the voltage. All other electric/ electronic components are connected across auxiliary battery, which operates at lower voltage range. When the vehicle is turned to ON condition the connector switch (110) gets closed, thereby supplying the power from battery (100) to all the components and when the vehicle is turned to OFF condition, the connector switch (110) gets open, thereby stopping the power supply from the battery (100) to all the components. The control unit (120) comprises DC to AC converter (165), which is configured to convert the DC supply from battery (100) into AC supply as required by the motor (125).

The problem of overvoltage due to regeneration occurs when a battery (100), accidently or otherwise, is disconnected from the system bus (135) (in Vehicle OFF condition) and the vehicle is in motion (downhill, towing etc.). In such scenario, motor (125) acts like a generator, generating electric power. In the absence of the battery (100), the regenerated voltage may swell beyond safe values, which may cause failure of DC to AC converter (165) and/or failures of other electronic components that are connected on system bus (135) such as DC-DC converter (140), Charger (150) etc. The proposed invention disclosure provides an intelligent protection system for limiting the system bus voltage to a safe value by regulating the power flow from the motor in to the system bus. The safe value may be calibrated for any electric or hybrid vehicle based on its architecture. The control unit (120) is provided with said protection system of the present invention, which is configured to protect all the components from over voltage caused by the motor (125) during regeneration phase, which is explained in detail herein below.

Referring to FIG.. 2 illustrating the block diagram of various components and their inter-relation used in the protection system according to first embodiment of the present invention. The protection system is a part of control unit (120). A motor (125) is in connection with a Control Unit (120). The control unit (120) may be a part of Motor Control Unit (MCU), which is configured to control the operation motor (125). The control unit (120) comprises a DC to AC converter (165) in a form of a voltage source inverter (VSI). The VSI circuitry (165) has at least a capacitor (C), preferably plurality of capacitors and plurality of switching devices (M1- M6) in the form of MOSFET switches. The capacitors (C) are configured to store the power and supply the ripple current to motor (125) whenever required. The MOSFET switches (M1-M6) are configured to control the voltage and current and do necessary conversion of DC supply to AC and vice-versa. The MOSFET switches (M1- M6) are operated according to a control logic stored in the control unit (120).

During regenerative braking wherein, if the battery is disconnected from the VSI (165), a large voltage is developed across the VSI (165) and other components connected on system bus(135). Such high voltages can result into added stress on the devices in the VSI (165), reducing their reliability and durability. The control unit (120) is configured to control the regenerated voltage in order to prevent in consequences due to excessive regeneration voltage. The control unit (120) is connected to the VSI (165).

Speed of motor is directly proportional to the regenerated voltage. As the speed increases the regenerated voltage increases. The components of electronic circuitry have a certain capacity up to which they can safely store/ sustain the regenerated voltage. The control unit (120) comprises a high pass filter (11) to detect whether vehicle or motor speed has exceeds a predefined speed threshold limit. The predefined speed threshold limit is a limit up to which the electronic components can safely sustain the regenerated voltage. If the speed of the vehicle exceed the speed threshold limit then the high pass filter (11) generates a trigger signal to activate further components of control unit (120) for regulating the regenerated voltage.
The high pass filter (11) is interfaced with a rectifier and latch circuit (44) configured to provide an enable signal to DC-DC converter (140), and a hysteresis controller (3). The rectifier and latch circuit (44) verifies that the supply from battery is disconnected before providing enable signal to other components. The Gate controller (8) and Hysteresis controller (3) are configured to receive regulated power from the DC-DC converter (140) upon getting enable signal from rectifier and latch circuit (44). A hysteresis controller (3) is stored with a pre-defined limit of maximum and minimum regenerated voltage that said system may sustain without any damage to electrical/electronic components wherein; the pre-defined limits are calibrated for any electric/ hybrid vehicle based on its architecture. The hysteresis controller (3) measures the voltage built up across system bus (135). The hysteresis controller (3) is configured to enable/disable the control of regulating regenerated voltage based on the comparison of measured regenerated voltage with pre-defined limits. The Gate controller (8) is connected to the switches of the VSI (165) and configured to operate the switches (M1-M6) for regulating the regenerated voltage. The regenerated power is circulated within the VSI circuitry (165), which helps in reducing the regenerated voltage built up in circuitry up to a safe limit. For example, the maximum limit may be 36V at which hysteresis controller sends signal to enable regulation of regenerated voltage. This helps in dropping the regenerated built up voltage. Once the voltage reaches a minimum limit, which may be 32V, regulation of regenerated voltage, is disabled. The number of switches to be operated, its frequency and sequence may be predefined. According to one of the embodiment of present invention, three switches of inverter are operated.

According to the first embodiment, the complete hardware based circuitry is used to regulate the voltage and no specialized controller is required. This also eliminates need to use any software or algorithm based control logic, thereby minimising overall cost and complexity of the system. The above-described strategy to control the regenerated voltage continues until the battery (100) is reconnected. Whenever Key power signals from battery (100) is triggered i.e. when the battery supply is restored the above-described control methodology is disable and the control is handed over to a microcontroller used in MCU of the vehicle.

Referring to FIG. 3, illustrating a flow chart of detail steps involved in regulating the regenerated voltage according to first embodiment of present invention. The control unit is configured to measure motor or vehicle RPM at step 210. A high pass filter is used for this purpose. The measured RPM is then compared it with predefined speed threshold limit by the high pass filter at step 220 and a trigger signal is generated by the high pass filter if the measured RPM exceeds predefined speed threshold limit to activate a rectifier and latch unit at step 230. The regenerated voltage is measured and compared with a predefined threshold limits stored in the hysteresis controller at step 240. It is also verified battery supply is disconnected at step 240. A signal is generate to enable the function of hysteresis controller and DC-DC converter at step 250 if the measured regenerated voltage exceeds the predefined threshold limit. The gate controller is instructed by the hysteresis controller to operate the switching devices of DC to AC converter to regulate the regenerated voltage. At step 260, the built up voltage across system bus is compared with maximum limit of voltage stored in the hysteresis controller and the regulation of regenerated voltage is disabled if the built up voltage is less than maximum limit.

Referring to FIG. 4, illustrating the block diagram of various components and their inter-relation used in the protection system according to second embodiment of the present invention. As explained above, during regeneration phase, wherein motor (125) acts as a generator to produce electric power. While the vehicle is in OFF state but is in motion, the DC bus measurement and clamping module (1) wakes up if the capacitors (C) have stored certain charge. The control unit (120) starts monitoring the rate of change of voltage generated due to regeneration.

A hysteresis controller (3) is provided with pre-defined limits of maximum and minimum voltage that the vehicle components can sustain without any damage. The hysteresis controller is also configured to enable/disable the control based on a comparison of regenerated voltage with the pre-defined limits. If the regenerated voltage exceeds the pre-defined limits, the hysteresis controller enables the regulation of regenerated voltage. This input is given to a PWM controller (4). The control unit (120) is further provided with a speed v/s torque map (7) comprising ideal data of acceptable braking torque at various speed levels. This may comprise maximum and minimum torque that may be applied for a current speed level. Vehicle/ motor output speed is sensed and based on the ideal map data, an acceptable braking torque at current speed level is determined. Based on the inputs, the PWM controller (4) generates the required control signal, which is given to the Gate Control (8) that drives the switching devices (M1-M6) (MOSFETs) of the VSI (5). The duty cycle of the MOSFET devices (M1-M6) is adjusted to maintain the voltage under safe operating limits and avoid wheel locking. By applying PWM control to the MOSFET devices (M1-M6), a portion of the regenerated power is recirculated by commutating the MOSFET devices (M1-M6) at certain duty cycles dependent on the acceptable braking torque. A portion of regenerated power is utilized in braking. This ensures that only a fraction of the regenerated power is used to charge the capacitors, thus reducing the rate at which the system voltage increases. According to another embodiment, the MOSFET switches may be replaced by IGBT type switches.

The PWM controller (4) provides a means to control the braking torque so that wheel locking is prevented. The PWM controller (4) verifies that the computed torque is well within pre-defined limits of maximum and minimum safe braking torque limits. The PWM controller (4) is configured to ensure that the duty cycle of switching devices (M1-M6) is applied in small discrete steps such that controlled braking is applied and wheel locking and/or skidding of the vehicle is avoided. The map of speed v/s torque comprise set of ideal data of acceptable braking torque at various speed levels.

Speed v/s map data (7) plays an important role in applying a controlled braking and helps in avoiding wheel locking. In addition, sudden braking of the motor (125) with full duty cycle can be dangerous as it may result in wheel locking and/or skidding of the vehicle. Therefore, the braking needs to be in small discrete steps instead of providing a complete braking at a single instance.

Referring to FIG.5, showing a flow chart of detail steps involved while applying the control methodology according to second embodiment of the present invention. Once, it is detected that the motor is in regeneration phase, the system bus voltage is monitored (1) throughout the operation of the VSI by DC bus measurement and clamping module (1). If certain charge is stored in the capacitor the protective system of present, invention wakes up at the step (300). The hysteresis controller (3) is stored with upper and lower control limit of safe regenerated voltage that the system can sustain. The regenerated voltage is compared with pre-defined limits set in the control unit (120) at step (302). If the regenerated voltage is within safe limit and has not exceeded the pre-defined limits then no further action is taken. As the regeneration voltage level crosses the pre-set limit, the protection system is activated (302). In such scenario, a hysteresis controller (3) triggers the PWM controller block (4) which outputs a control signal of fixed initial duty cycle to the Gate Control (8) at step (304). After an initial duty signal is applied, the rate of change of the system bus voltage is monitored (2) at step (306). If the system bus voltage is still increasing, then it is decided to further increase the duty cycle based on current speed of the motor (6) and/or vehicle at step (308). The speed of the motor (6) is continuously measured. The speed is compared with ideal map data of Speed v/s Torque map (7) and a safe braking limit is identified for current speed of the motor (6) at step (310). It is ensured that the identified braking torque is within acceptable limits at step (312) and then PWM controller (4) proportionately increases the duty cycle at (308) else, the duty cycle is reduced (314). The duty cycle is reduced if the identified braking torque is towards maximum safe braking limit and the duty cycle is increased if the identified braking torque is towards minimum safe braking limit. The PWM control logic adjusts the duty cycle to limit the braking torque as per the speed v/s torque map. After, increasing or decreasing the duty cycle, the voltage level as well as rate of change of voltage are checked continuously till the regenerated voltage level drops below the pre-defined limits. As only, a portion of regenerative power is utilised by applying a controlled braking, the rate of change of regenerated voltage drops. If the system bus voltage drops below the lower control limit of hysteresis controller (3) at step (316) then the PWM controller (4) turns off the control signal.

Now referring to FIG. 6, which is illustrating an another embodiment of the present invention, wherein; the control unit (120) is configured to first check whether battery (100) and/ or capacitor (C) has a capacity to store any regenerated voltage before regulating the regenerated voltage. The control unit (120) is configured to identify the motor (125) is in regeneration phase and the battery (100) is in disconnected condition i.e. vehicle is in OFF condition. The control unit (120) at step (402) registers Battery/ capacitor (C) last state of charge (SOC) of battery source (100) and/ or capacitor (C) before the vehicle is turned OFF. Maximum threshold value of SOC level is stored in the control unit (120), which is a maximum charge that may be stored in the battery (100) and/ or capacitor (C). The control unit (120) continuously monitors the system bus voltage at step (404). If the battery (100)/ capacitor (C) SOC is identified as below a pre-defined threshold limit at step (406), then the regenerated power is first utilised to first charge the battery (100) and/or capacitors (C) at step (408). This is done by closing the connector (110), thereby connecting the battery source (100) with the motor (125). However, if the connector (110) is closed the battery source (100) may get reconnected with all the vehicle components. This situation needs to be avoided, as the vehicle is in OFF condition. The control unit (120) disconnects all the vehicle components. Therefore, even though the battery (100) is reconnected in vehicle OFF condition, all other components remains OFF. SOC level of battery (100) and/or capacitors (C) is continuously monitored at frequent time intervals and it is compared with the pre-defined threshold limit at step (410) by the control unit (120). If the battery (100) and /or capacitor (C) are charged to the set threshold limit, then the protection system is activated and regulation of regenerated power continues as explained herein above according to the flow chart of FIG.3 or FIG. 5. However, if the battery (100) and /or capacitor (C) are not charged up to the threshold limit then the charging continues until the SOC level crosses the threshold limit. If the last registered SOC of battery (100) and/or capacitor (C) is above the threshold limit then the protection system immediately starts regulating the regenerated voltage without further charging the battery and/ or capacitor.

During regulation of regenerated voltage as explained herein above, if the vehicle is turned ON, the battery source (100) gets reconnected. In such scenario, the control unit (120) stops further regulation of regenerated voltage. The regenerated voltage may be supplied directly to the battery (100) for battery charging purpose if the battery is not up to threshold SOC level. The regenerated power may be regulated by the protection system, if the battery (100) is already fully charged up to its threshold limit.

According to another embodiments of the present invention, there are plurality of capacitors (C) provided as a part of DC-AC converter (165) or may be provided separately. DC to AC converter (165) may be a part of control unit (120) or provided separately. The vehicle may be provided with a single electric motor or plurality of electric motors to drive the vehicle. A Motor Control Unit (MCU) is provided to control various functions of motor and/or vehicle. The control unit (120) may be a part of said Motor Control Unit or may be provided as a separate unit. The battery source (100) may comprise a single battery or a set of batteries.

The above explained protection system is applicable to any electric or hybrid vehicle irrespective of its type i.e. the system is applicable to any two-wheeled, three-wheeled or four-wheeled vehicle.
,CLAIMS:CLAIMS
We Claim:
1. A protection system for an electric or hybrid vehicle, the system comprising:
a battery source (100) to supply electric power to an electric motor (125);
the electric motor (125) is used to drive the vehicle;
a control unit (120) to regulate the electric power generated by the electric motor (125) during regeneration phase wherein; the control unit (120) regulates the electric power when the battery source (100) is in disconnected condition and the vehicle/ motor speed or regenerated voltage exceeds a pre-defined threshold limit.

2. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the control unit (120) regulates the electric power by applying braking with the help of at least one switching device (M1-M6).

3. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein braking is controlled based on current speed of the vehicle or motor and a pre-defined map of speed v/s torque stored in the control unit (120).

4. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the electric motor (125) is connected to a DC to AC converter (165) comprising
at least a capacitor (C) configured to store the electric power; and
plurality of switching devices (M1-M6); wherein
the control unit (120) is configured to control atleast one switching device of the DC to AC converter (165) to regulate the regenerated voltage once the regenerated voltage exceeds a predefined threshold limit.

5. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the DC to AC converter (165) is a part of the control unit (120) or is provided as a separate unit.

6. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the control unit (120) comprises a hysteresis controller (4) stored with a pre-defined limit of maximum and minimum level of sustainable regenerated voltage wherein the pre-defined limits are calibrated for any electric/ hybrid vehicle based on its architecture.

7. The protection system for electric or hybrid vehicle as claimed in claim 6, wherein the control unit (120) comprises a high pass filter (11) configured to generate a trigger signal to enable the regulation of regenerated voltage if the motor or vehicle speed exceeds a predefined speed threshold limit.

8. The protection system for electric or hybrid vehicle as claimed in claim 7, wherein the hysteresis controller (3) is interfaced with the high pass filter (11) to receive the trigger signal and configured to enable/disable the control of regulating regenerated voltage based on the comparison of measured regenerated voltage with pre-defined limits.

9. The protection system for electric or hybrid vehicle as claimed in claim 8, wherein the hysteresis controller (3) is interfaced to the high pass filter (11) through a rectifier and latch unit (22) configured to send a signal to enable/disable the control of regulating regenerated voltage if the regenerated voltage exceeds the pre-defined threshold limit stored in the hysteresis controller (3).

10. The protection system for electric or hybrid vehicle as claimed in claim 9, wherein the rectifier and latch unit (44) is configured to verify the power supply is disconnected from battery (100) and to send an enable signal to activate at least a hysteresis controller (3), and a DC-DC converter (140).

11. The protection system for electric or hybrid vehicle as claimed in claim 10, wherein the DC-DC converter (140) is configured to supply regenerated power to the gate controller (8) and to the hysteresis controller (3) upon receiving enable signal from the rectifier and latch circuit (44).

12. The protection system for electric or hybrid vehicle as claimed in claim 10, wherein the gate controller (8) interfaced to the hysteresis controller (3) and configured to operate atleast one switching device (M1-M6) of the DC to AC converter (165).

13. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the vehicle or motor speed is measured using a speed sensor.

14. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein the control unit (120) comprises a DC bus measurement and a clamping module (1) configured to identify motor (125) is in regeneration phase if the capacitors (C) have stored pre-defined charge in battery-disconnected condition, and
a hysteresis controller (3) in communication with the DC bus measurement and clamping module (1) to receive measured regenerated voltage and configured to enable/disable the control of regulating regenerated voltage based on the comparison of measured regenerated voltage with pre-defined limits.

15. The protection system for electric or hybrid vehicle as claimed in claim 14,wherein the control unit (120) comprises a PWM controller (4) configured to receive a signal from hysteresis controller (3) if the regenerated voltage exceeds the pre-defined threshold limit and further configured to regulate the regenerated voltage by modulating the pulse width or duty cycle of the switching devices (M1-M6), wherein the PWM controller (4) is provided as a separate unit or as a part of a control unit (120).

16. The protection system for electric or hybrid vehicle as claimed in claim 15, wherein the PWM controller (4) is in communication with a map of speed v/s breaking torque to compute allowed safe braking torque value for current speed of the vehicle/ motor and configured to generate a signal to modulate the pulse width or duty cycle of the switching devices (M1-M6) based on computed allowed braking torque to maintain the regenerated voltage under pre-defined limit.

17. The protection system for electric or hybrid vehicle as claimed in claim 16, wherein the PWM controller (4) is configured to ensure that computed breaking torque is within predefined maximum and minimum safe breaking torque limits and to adjust the duty cycle of switching devices (M1-M6) accordingly wherein; the duty cycle is applied in small discrete steps such that controlled braking is applied and wheel locking and/or skidding of the vehicle is avoided.

18. The protection system for electric or hybrid vehicle as claimed in claim 17, wherein the PWM controller (4) is configured to proportionately modulate the pulse width or duty cycle of switching devices (M1-M6) by circulating a portion of regenerated power by commutating the switching devices (M1-M6) dependent on computed ideal torque to use only a fraction of the regenerated power to charge the capacitor/s (C).

19. The protection system for electric or hybrid vehicle as claimed in claim 16, wherein the signal generated by PWM controller (4) to modulate the duty cycle of switching devices (M1-M6) is sent to the DC to AC converter (165) through a gate controller (8) wherein; the gate controller (8) adjusts the voltage level of signal produced by the PWM controller (4) and transmits the signal to the switching devices (M1-M6).

20. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein the control unit (120) stops regulation of regenerated voltage if the battery (100) is reconnected as the vehicle is turned ON and the stored regenerated voltage is optionally supplied directly to the battery (100) for battery charging purpose if the battery (100) is not fully charged.

21. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein the control unit (120) is configured to first charge the battery source (100) before activating regulation of regenerated voltage if the battery/ capacitor SOC is below a pre-defined threshold limit.

22. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein the switching devices are MOSFET or IGBT switches, six in number.

23. A method for regulating the regenerated voltage of electric motor (125) in a battery disconnected condition using a control unit (120) comprising steps of;
measuring a motor or vehicle speed or regenerated voltage and comparing with a predefined threshold limit;
generating a trigger signal if the measured vehicle or motor RPM or regenerated voltage exceeds predefined speed threshold limit;
enabling the regulation of regenerated voltage by controlling atleast one switching device of a DC to AC converter (165);
measuring the regenerated voltage and comparing it with predefined maximum and minimum threshold limits in a hysteresis controller; and
disabling the regulation if the measured regenerated voltage drops below the predefined threshold limit.

24. The protection system for electric or hybrid vehicle as claimed in claim 2, wherein the control unit (120) is a part of a Motor Control Unit (MCU) configured to control various functions of motor and/or vehicle or provided as a separate unit.

25. The protection system for electric or hybrid vehicle as claimed in claim 1, wherein the battery source (100) is connected to the electric motor through the control unit (120) using a system bus wherein the system bus is further used to connect the other electric/ electronic components to the battery source (100) including DC-DC converter (140), Charger (150), Auxiliary battery such that the electric/ electronic components get disconnected from the battery source (100) when the vehicle is in OFF condition