System and method for active discharge of an electric vehicle inverter

Abstract

Systems and methods for active discharge of an electric vehicle inverter. A system includes: an inverter configured to convert DC power from a battery to AC power to drive a motor, where the inverter includes: one or more switches; and one or more controllers configured to: determine a gate voltage for operating the one or more switches of the inverter based on a temperature of the inverter; operating the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate an active discharge of a bus voltage of the inverter; and accelerating the active discharge of the bus voltage by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a pulse of the PWM signal when the bus voltage is greater than a first threshold voltage.

Description

Technical Field

[0001] Various embodiments of the present disclosure relate generally to systems and methods for controlling active discharge of an electric vehicle inverter, and more particularly, to systems and methods for accelerating active discharge of an electric vehicle inverter. Background Art

[0002] For example, the inverter used to drive an electric vehicle motor is responsible for converting high-voltage direct current (HVDC) into alternating current (AC) to drive the motor. Within the inverter, bulk capacitors discharge in the event of a fault condition to reduce the risk of exposure to high voltage. This active discharge of bulk capacitors can stress the power switches.

[0003] The present disclosure is directed to overcoming one or more of these aforementioned challenges. Summary of the Invention

[0004] In certain aspects, the technology described herein relates to a system comprising: an inverter configured to convert DC power from a battery into AC power to drive a motor, wherein the inverter comprises: one or more switches; and one or more controllers configured to: determine a gate voltage for operating the one or more switches of the inverter based on a temperature of the inverter; operate the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate active discharge of a bus voltage of the inverter; and accelerate the active discharge of the bus voltage by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal when the bus voltage is greater than a first threshold voltage.

[0005] In certain aspects, the technology described herein relates to a system wherein the one or more controllers are further configured to: determine an amount of voltage reduction in the bus voltage based on operation of the one or more switches; and in response to determining that the amount of voltage reduction in the bus voltage is less than a second threshold voltage, perform one or more of increasing the gate voltage or determining whether a contactor of the inverter has failed.

[0006] In certain aspects, the technology described herein relates to a system wherein performing one or more of increasing the gate voltage or determining whether a contactor of the inverter is faulty includes: incrementing a fault count; increasing the gate voltage when the fault count is less than a fault threshold; and determining whether a contactor of the inverter is faulty when the fault count is greater than or equal to the fault threshold.

[0007] In certain aspects, the technology described herein relates to a system wherein determining a gate voltage further comprises: determining a temperature of the inverter; determining a threshold voltage for the one or more switches; and determining the gate voltage based on the threshold voltage for the one or more switches, wherein the gate voltage is less than the threshold voltage for the one or more switches.

[0008] In certain aspects, the technology described herein relates to a system wherein performing one or more of increasing the gate voltage or decreasing the wait time after a pulse of the PWM signal further comprises: starting a timer; when the timer is greater than a threshold time, increasing the gate voltage and resetting the timer; and when the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and setting the wait time after the first PWM signal based on the bus voltage.

[0009] In certain aspects, the technology described herein relates to a system wherein performing one or more of increasing the gate voltage or decreasing the waiting time after a pulse of the PWM signal further comprises: when the timer is less than the threshold time: operating the one or more switches based on the first PWM signal; determining whether a PWM cycle count of the first PWM signal is greater than a threshold cycle count; and when the PWM cycle count is greater than the threshold cycle count, resetting the PWM cycle count, turning off the one or more switches, and determining the first threshold voltage.

[0010] In certain aspects, the technology described herein relates to a system wherein setting the wait time after the first PWM signal based on the bus voltage includes: when the bus voltage is in a first voltage range, setting the wait time to a first value, delaying operation of the one or more switches by the first value of the wait time, and determining whether the timer is less than a threshold time; and when the bus voltage is in a second voltage range less than the first voltage range, setting the wait time to a second value less than the first value, delaying operation of the one or more switches by the second value of the wait time, and determining whether the timer is less than the threshold time, wherein a lower limit value of the second voltage range is equal to the first threshold voltage.

[0011] In certain aspects, the technology described herein relates to a system, further comprising: the battery configured to supply the DC power to the inverter; and the motor configured to receive the AC power from the inverter to drive the motor, wherein the system is provided as a vehicle, the vehicle including the inverter, the battery, and the motor.

[0012] In certain aspects, the technology described herein relates to a system comprising one or more controllers configured to: determine a gate voltage for operating one or more switches of an inverter based on a temperature of the inverter; operate the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate active discharge of a bus voltage of the inverter; and accelerate the active discharge of the bus voltage by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal when the bus voltage is greater than a first threshold voltage.

[0013] In certain aspects, the technology described herein relates to a system wherein performing one or more of increasing the gate voltage or decreasing the wait time after a pulse of the PWM signal further comprises: starting a timer; when the timer is greater than a threshold time, increasing the gate voltage and resetting the timer; and when the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and setting the wait time after the first PWM signal based on the bus voltage.

[0014] In certain aspects, the technology described herein relates to a system wherein setting the wait time after the first PWM signal based on the bus voltage includes: when the bus voltage is in a first voltage range, setting the wait time to a first value, delaying operation of the one or more switches by the first value of the wait time, and determining whether the timer is less than a threshold time, and when the bus voltage is in a second voltage range less than the first voltage range, setting the wait time to a second value less than the first value, delaying operation of the one or more switches by the second value of the wait time, and determining whether the timer is less than the threshold time.

[0015] In certain aspects, the technology described herein relates to a method comprising: performing, by one or more controllers, operations for controlling an inverter, the operations comprising: receiving a request to initialize active discharge of a bus voltage of the inverter; determining a gate voltage for operating one or more switches of the inverter based on a temperature of the inverter; operating the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate the active discharge of the bus voltage; and accelerating the active discharge of the bus voltage by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal when the bus voltage is greater than a first threshold voltage.

[0016] In certain aspects, the technology described herein relates to a method, wherein the operation further includes: operating the one or more switches; determining a voltage drop in the bus voltage; and in response to determining that the voltage drop in the bus voltage is less than a second threshold voltage, performing one or more of increasing the gate voltage or determining whether a contactor of the inverter has failed.

[0017] In certain aspects, the technology described herein relates to a method wherein performing one or more of increasing the gate voltage or determining whether a contactor of the inverter is faulty includes: incrementing a fault count; when the fault count is less than a fault threshold, increasing the gate voltage; and when the fault count is greater than or equal to the fault threshold, determining whether a contactor of the inverter is faulty.

[0018] In certain aspects, the technology described herein relates to a method wherein determining a gate voltage further comprises: determining a temperature of the inverter; determining a threshold voltage for the one or more switches; and determining the gate voltage based on the threshold voltage for the one or more switches, wherein the gate voltage is less than the threshold voltage for the one or more switches.

[0019] In certain aspects, the technology described herein relates to a method wherein performing one or more of increasing the gate voltage or decreasing the waiting time after a pulse of the PWM signal further comprises: starting a timer; and when the timer is greater than a threshold time, increasing the gate voltage and resetting the timer.

[0020] In certain aspects, the technology described herein relates to a method wherein performing one or more of increasing the gate voltage or decreasing the wait time after a pulse of the PWM signal further comprises: when the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and setting the wait time after the first PWM signal based on the bus voltage.

[0021] In certain aspects, the technology described herein relates to a method wherein performing one or more of increasing the gate voltage or decreasing the waiting time after a pulse of the PWM signal further comprises: when the timer is less than the threshold time: operating the one or more switches based on the first PWM signal; determining whether a PWM cycle count of the first PWM signal is greater than a threshold cycle count; and when the PWM cycle count is greater than the threshold cycle count, resetting the PWM cycle count, turning off the one or more switches, and determining the first threshold voltage.

[0022] In certain aspects, the technology described herein relates to a method wherein setting the wait time after the first PWM signal based on the bus voltage includes: when the bus voltage is in a first voltage range, setting the wait time to a first value, delaying operation of the one or more switches by the first value of the wait time, and determining whether the timer is less than a threshold time, and when the bus voltage is in a second voltage range less than the first voltage range, setting the wait time to a second value less than the first value, delaying operation of the one or more switches by the second value of the wait time, and determining whether the timer is less than the threshold time.

[0023] In certain aspects, the technology described herein relates to a method wherein a lower limit value of the second voltage range is equal to the first threshold voltage.

[0024] Other objects and advantages of the disclosed embodiments will be set forth in part in the following description, and in part will become apparent from the description, or may be learned by practicing the disclosed embodiments. The objects and advantages of the disclosed embodiments will be realized and obtained by means of the elements and combinations particularly pointed out in the appended claims.

[0025] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and, together with the description, serve to explain the principles of the disclosed embodiments.

[0027] Figure 1 Depicted are exemplary system infrastructures for a vehicle including a combined inverter and converter according to one or more embodiments.

[0028] Figure 2 Depicted is a power schematic diagram of a three-phase inverter module in a connected system according to one or more embodiments.

[0029] Figure 3 Depicted are implementations of a computer system that can perform the techniques presented herein, in accordance with one or more embodiments.

[0030] Figure 4 Depicted are exemplary methods for operating an inverter to perform active discharge according to one or more embodiments.

[0031] Figure 5 Depicted are exemplary methods of initializing an inverter according to one or more embodiments.

[0032] Figure 6 Depicted are exemplary methods for memory device threshold voltage and temperature according to one or more embodiments.

[0033] Figure 7 Depicted are exemplary methods for initiating active discharge according to one or more implementations.

[0034] Figure 8 Depicted are exemplary methods for initiating pulse and measurement functionality in accordance with one or more implementations.

[0035] Figure 9 Depicted are exemplary methods for increasing gate-to-source voltage and fault checking in accordance with one or more embodiments.

[0036] Figure 10 Depicted are exemplary methods for accelerating active discharge according to one or more embodiments.

[0037] Figure 11 Depicted are exemplary plots of voltage and temperature of an inverter during active discharge according to one or more embodiments. DETAILED DESCRIPTION

[0038] The foregoing general description and the following detailed description are exemplary and explanatory only and do not limit the claimed features. As used herein, the terms "comprises," "comprising," "having," or other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but may also include other elements not expressly listed or inherent in such process, method, article, or apparatus. In this disclosure, unless otherwise stated, relative terms (such as "about," "substantially," and "approximately") are used to indicate that the value being described may vary by ±10%. In this disclosure, unless otherwise stated, any numerical value may include a variation of ±10% that the value being described may vary.

[0039] The terminology used hereinafter is to be interpreted in the broadest reasonable manner, even though it is used in conjunction with the detailed description of certain specific examples of the present disclosure. Indeed, certain terms may even be emphasized hereinafter; however, any term that is intended to be interpreted in any limiting manner will be clearly and specifically defined in this detailed description section. For example, in the context of the present disclosure, a switching device may be described as a switch or a device, but may refer to any device used to control the flow of power in a circuit. For example, a switch may be a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), an insulated gate bipolar transistor (IGBT), or a relay, or any combination thereof, but is not limited thereto.

[0040] Various embodiments of the present disclosure relate generally to systems and methods for controlling active discharge of an electric vehicle inverter, and more particularly, to systems and methods for accelerating active discharge of an electric vehicle inverter.

[0041] An inverter, such as one used to drive a motor in an electric vehicle, is responsible for converting high voltage direct current (HVDC) into alternating current (AC) to drive the motor. A three-phase inverter may include a bridge having six power device switches (e.g., power transistors such as IGBTs or MOSFETs) that are controlled by pulse width modulation (PWM) signals generated by a controller. The inverter may include three half-H-bridge switches to control the phase voltages, an upper gate driver and a lower gate driver to control the switches, a PWM controller, and glue logic between the PWM controller and the gate driver. The PWM controller may generate signals to define the desired state of the system. The gate driver may send signals from the PWM controller to the half-H-bridge switches. The half-H-bridge switches may drive the phase voltages. Six-phase (or other phase) inverters and multi-level inverters are not excluded from this concept and will follow similar principles.

[0042] Due to system design, the inverter's high-voltage bus bulk / DC link capacitors may store a significant amount of energy. This stored high-voltage energy must be dissipated to prevent human exposure to hazardous voltage levels. An inverter feature called "active discharge" allows for controlled dissipation of energy stored in system capacitors. System capacitors are typically referred to as bulk capacitors in inverter systems. Before initiating active discharge of the bus, the high-voltage battery supplying energy to the inverter is disconnected to prevent battery discharge. The active discharge feature rapidly dissipates high-voltage bus energy to ensure safety during events such as vehicle maintenance and a crash. The discharge rate depends on the initial bus voltage, capacitance, and energy dissipation mechanism. Government / OEM regulations also dictate the required discharge rate. For example, regulations may require that the high-voltage bus must be discharged to below 60V within 2.5 seconds.

[0043] Inverters often have safety requirements that require that bulk capacitors on the inverter be discharged within a short period of time (e.g., 1 to 3 seconds) in the event of a crash or other fault condition. Some systems use the motor windings to discharge the bulk capacitors, which requires that the motor is not short-circuited and the main microcontroller is available. Other systems use a dedicated resistive discharge device to discharge the bulk capacitors, which is typically a combination of a high-power resistor, a switch, and a controller.

[0044] Therefore, the inverter can use the switching losses in the inverter power device switches (IGBT / FET) to release energy. Controlling the on / off (also called enabling / disabling) of the power devices results in predictable losses. Switching them multiple times at a high frequency will result in a significant amount of these cumulative losses. The discharge rate (loss) can be proportional to the switching frequency. These losses can be used to quickly discharge the HVDC bus as a backup or without the cost and complexity of using motor windings or dedicated resistive discharge devices. Additionally, by eliminating the resistive element from certain methods, significant cost, circuit board area, and unnecessary heat can be saved.

[0045] For example, the inverter used to drive an electric vehicle motor is responsible for converting high-voltage direct current (HVDC) into alternating current (AC) to drive the motor. Within the inverter, bulk capacitors are discharged in the event of a fault condition to reduce the risk of exposure to high voltage. Active discharge of the bulk capacitors can stress the power switches. During active discharge, the SiC semiconductor is biased with a low gate voltage and operates in the ohmic region, acting as a resistor.

[0046] Some systems use gate drivers to discharge bulk capacitors, operating one power switch in a half-H-bridge in linear mode. This effectively uses the power switch as a resistor by controlling the gate positive bias voltage and / or switching. In this approach, one power switch (e.g., the upper switch) is turned on as in normal operation, while the other power switch (e.g., the lower switch) is pulsed on with a reduced gate voltage. The HVDC bus and bulk capacitors can be discharged via specific PWM pulses. The drain current of the power switch can increase eightfold or more with temperature variations. For example, this temperature variation can be due to self-heating of the power switch in linear mode or the initial temperature of the power switch during the initialization of active discharge. During active discharge, if the temperature is not controlled, the power switch may experience a significant temperature increase sufficient to cause failure.

[0047] The transfer characteristics of the power switches may vary significantly with temperature, especially in the linear mode region for DC link discharge. The temperature difference may be based on the ambient temperature and may include, for example, operating temperatures such as -40°C to 100°C.

[0048] Some systems use threshold detection to discharge the bulk capacitor, which requires turning off the opposing device. The sensed threshold can be optionally increased by a step size (e.g., 390mV) and can have a voltage that is fixed at the beginning of the discharge operation and cannot be changed during the discharge operation. Some systems use a pre-programmed voltage to discharge the bulk capacitor, where the voltage is fixed at power-up during configuration mode and cannot be changed during inverter operation.

[0049] For example, the specification might specify 4A per die. At a die temperature of 100°C, the gate voltage might be 3.08V, resulting in a die current of 4A. At a temperature of 25°C and a gate voltage of 3.08V, the die current might be 0.8A (approximately 20% of the rated value). At a temperature of 125°C and a gate voltage of 3.08V, the die current might be 5.3A (approximately 133% of the rated value). At a temperature of 140°C and a gate voltage of 3.08V, the die current might be 5.8A (approximately 145% of the rated value). At a temperature of 175°C and a gate voltage of 3.08V, the die current might be 12.13A (approximately 300% of the rated value). Additional errors arise when the drain voltage varies. For example, at a drain-source voltage of 950V, the SiC FET transconductance is much higher, resulting in significantly higher drain-source current. This must be taken into account during the process of estimating the required gate voltage.

[0050] Some systems for performing DC link capacitor discharge use large, high-power resistors that are activated via FETs to resistively discharge the DC link capacitors. Some systems perform discharge by using gate driver ICs in conjunction with inverter power switches, typically used to drive motors. Some gate drivers implement hard switching of power devices connected across a capacitive load. The upper and lower devices are turned on, effectively shorting the current from HV+ to HV- for a short period of time to discharge the DC link capacitors (i.e., a punch-through current mode of active discharge). Some gate drivers turn on the power semiconductors in a resistive linear mode by setting the VGS voltage to a defined value, thereby discharging with a current value low enough to avoid damaging or overheating the power switches operating in linear mode (i.e., a controlled punch-through current mode of active discharge). In addition, the current may vary as the power semiconductors heat up, without taking into account positive feedback to discharge at the intended low current.

[0051] However, some methods may not be able to actively discharge while the vehicle is in motion and / or the wheels are rotating, as this will result in EMF generation during the discharge event and eliminate the possibility of accurately sensing the Vgs threshold voltage. Since multiple (e.g., one to three) modules may need to be discharged and coordination may not be possible, the value of the capacitor to be discharged may be unknown. The discharge may need to accommodate a higher system voltage than expected by the gate driver, and the energy stored in the capacitor increases with the square of the voltage (E=1 / 2*C*V^2). The protection mechanisms assumed to be available by the gate driver (e.g., temperature sensing) may not be applicable to fast, high-power discharge pulses. Timely discharge of the DC link capacitor may require regular adjustment of the discharge curve so that discharge can be achieved within the allowable time range specified by the safety standards interpreted by the vehicle manufacturer. Typical protection mechanisms such as current sensing may not be available. When operating in linear mode, some active discharge methods may not take into account current sharing between devices in the die. Some methods may not take into account the required VGS threshold estimation error, which can quickly lead to damage to the power switch.

[0052] One or more embodiments may overcome the issues with some of the active discharge methods discussed above. For example, one or more embodiments may address one or more of the following issues: insufficient resolution of Vgs setting to control the punch-through current to a safe level; insufficient pulse width control; insufficient discharge period control; insufficient resolution of Vgs measurement; inability to predict the resulting current at high Vds voltages; inability to detect which inverter is performing the active discharge and which bulk capacitor is being discharged; inability to predict the value of the capacitor being discharged; or inability to predict SiC FET transconductance and its effects.

[0053] One or more embodiments may provide an algorithm that systematically estimates the power switch bias voltage, programmatically increments the gate voltage, and ensures safe operating compliance in an active short-circuit mode of active discharge with optimized bulk capacitor discharge time. One or more embodiments may utilize a gate driver operating in a current-limited mode, resulting in a large voltage drop across the device during the discharge event. One or more embodiments may precisely control the power dissipation caused by the discharge event, thereby limiting the temperature rise in the power device (e.g., IGBT / SiC power switch) and maintaining the temperature within a specified safe operating area. One or more embodiments may control the on and off times to allow the power device to cool between pulses and limit the temperature rise during each cycle so that the maximum junction temperature of the power semiconductor is not exceeded. One or more embodiments may provide an upper layer algorithm that controls the PWM curve and manages the temperature rise in the power device during the active discharge event to complete the capacitor discharge in a safe, timely, and reliable manner.

[0054] One or more embodiments may use a dynamic algorithm that depends on the HVDC bus voltage, the SiC threshold voltage estimate, and the desired discharge time. One or more embodiments may accelerate the active discharge time as a function of the HVDC bus voltage by using a constant on-time variable frequency approach. One or more embodiments may provide an algorithm that incorporates variations in the bias of the gate voltage as a function of the initial threshold and temperature variation. One or more embodiments may provide an algorithm that exploits expected differences in current sharing between dies by using bias voltage and cool-down time, which can take advantage of the thermal capacity of the cooling system. One or more embodiments may provide a retry strategy to meet customer requirements under open-loop operating limits and may determine the condition of the battery contactor. One or more embodiments may provide an algorithm designed to operate within a defined safe operating region for the power switch.

[0055] One or more embodiments may be optimized for high capacitance, high voltage, and subsequently high energy systems requiring an open loop approach. One or more embodiments may allow the vehicle's wheels to rotate during a discharge event. One or more embodiments may provide an algorithm that does not monitor power switch current during a discharge event.

[0056] The algorithm can generate a lookup table that characterizes the expected power switch package temperature and the gate threshold voltage of the power switch. The algorithm can update the lookup table whenever the inverter is in six-switch off operation and no current is flowing in the system (due to back EMF). The algorithm can receive a request to initiate active discharge and can determine the temperature and compare the determined temperature with the previous temperature to adjust the gate voltage threshold. The algorithm can use the following formula to determine the new threshold voltage: VTH(T) = VTH0-kVT(T-T0).

[0057] For example, a 1V systematic error could be caused by one or more of a measurement error in the threshold detection in the gate driver, a difference in low current threshold detection versus conduction current, or a threshold variation with temperature. The initial temperature used should be related to the coolant temperature, as the thermal time constant will allow the starting temperature to be relative to the coolant temperature. Based on the calculated ideal threshold voltage and the subtracted error, the algorithm can determine the closest gate voltage setting provided by the gate driver and round down to the nearest value in the lookup table.

[0058] One or more embodiments may apply short duration pulses in the discharge circuit to limit temperature rise. For example, the pulse may be limited to an on-time of 6.4 μs within a 600 μs period. The algorithm may generate a pulse train that enables 3 ms, for example, with a variable off-time for cooling. The on-time sequence will be referred to as applying a pulse. After the initial pulse, the algorithm may generate a cool-down time of, for example, 174 ms, where the switch is biased off. The algorithm may then increment the gate voltage by a set point step. The algorithm may recycle this operation twice, for example for a total of 3 pulses, and may clamp the maximum allowable gate voltage. If no voltage decay of, for example, 20 V or more is detected, the algorithm may repeat the pulse a total of 3 times, for example, with an off-time of 174 ms between discharge event pulses. For example, if no voltage decay of 20 V is detected, the algorithm may determine that the contactor used to disconnect the battery has failed in the closed position.

[0059] For example, if a 20V drop is detected, the algorithm can apply another pulse and, for example, increment the gate voltage setting every 150ms. The algorithm can measure the HVDC during the pulse and set a different off-time. This process can continue until the voltage discharge is complete (for example, until the HVDC reaches 60V). For example, if the cycle count reaches 67 cycles (which may be associated with 10 seconds) and the discharge is not complete, the algorithm can read the threshold, initiate a gate voltage threshold reading, and begin another discharge cycle.

[0060] One or more embodiments can accommodate limitations such as a rotating wheel or open-loop algorithm. One or more embodiments can utilize an algorithm to account for alternative system conditions. For example, one or more embodiments can interpolate and adjust threshold changes based on associated temperature rises.

[0061] System limitations may prevent measuring the gate threshold before a discharge event, and the system may be in run mode or active short-circuit mode. One or more embodiments may model and track the threshold in software, and the algorithm may account for temperature variations. One or more embodiments may estimate the threshold voltage to remain below the expected gate threshold voltage. One or more embodiments may estimate the threshold voltage to be higher than the expected gate threshold voltage. One or more embodiments may compensate by using longer pulse widths to dynamically increase the cooling time based on system voltage conditions. One or more embodiments may accelerate discharge based on a decrease in the HVDC bus voltage.

[0062] One or more embodiments may utilize an open loop algorithm with the wheels spinning (inverter in generator mode) without knowledge of the switch current in the loop. One or more embodiments may accelerate discharge based on the HVDC voltage. One or more embodiments may incorporate bias voltage adjustments based on initial values ​​and temperature. One or more embodiments may incorporate a retry strategy that complies with open loop constraints. One or more embodiments may incorporate bias adjustment timing and values ​​to ensure that individual dies within the power switch comply with safe operating area requirements. One or more embodiments may apply multiple phases in parallel to accelerate discharge.

[0063] One or more embodiments may programmatically adjust the applied bias voltage, duty cycle, and duration of the intermittent discharge pulse sequence. One or more embodiments may operate in active short-circuit mode. One or more embodiments may reduce the period between discharge pulses to reduce the discharge time based on a decrease in the HVDC bus voltage. One or more embodiments may manage the temperature rise within the power semiconductor for a given discharge requirement (C, V, t). As the HVDC decreases, one or more embodiments may incrementally increase the gate voltage to increase the discharge rate. One or more embodiments may programmatically apply an intermittent discharge sequence rather than a continuous pulse train. One or more embodiments may operate without testing the threshold voltage during discharge. One or more embodiments may use a threshold voltage estimate and offset function to safely initiate a discharge event. One or more embodiments may monitor the HVDC and adjust the cooldown time between discharge sequences.

[0064] One or more embodiments may be optimized for high voltage, high capacitance, SiC-based systems. One or more embodiments may discharge a 3mF bus capacitor at 950V in less than 2.5 seconds. One or more embodiments may provide safe discharge without knowledge of the switch current (SiC die). One or more embodiments may provide non-simultaneous discharge initiation using multiple controllers. One or more embodiments may accommodate operation of the inverter in generating mode (e.g., wheel rotation, etc.). One or more embodiments may accommodate inter-die threshold variations within the switch. One or more embodiments may ensure a safe operating area for each individual die within the power switch. One or more embodiments may ensure survival of the SiC die in the event of a stuck contactor. One or more embodiments may be applied to multiple phases in parallel to accelerate discharge. One or more embodiments may utilize an upper or lower switch in linear mode with an appropriate active short circuit mode.

[0065] One or more embodiments may be performed with the inverter in power generation mode or with the reverse switch closed when a high voltage is present. One or more embodiments may provide an algorithm that starts with a gate voltage that does not result in conduction and incrementally increases the gate voltage in a programmable manner while monitoring the HVDC voltage. One or more embodiments may incorporate bias voltage adjustment based on an initial value and temperature. One or more embodiments may perform active discharge without knowing the current in the switch. One or more embodiments may apply pulses with a duration shorter than the system thermal time constant (i.e., intermittent). One or more embodiments may modify the off time based on the HVDC voltage to remain within a safe operating area to achieve rapid discharge. One or more embodiments may incorporate a retry strategy that complies with open-loop constraints. One or more embodiments may be applied to multiple phases in parallel to accelerate discharge.

[0066] Figure 1 An exemplary system infrastructure of a vehicle including a combined inverter and converter according to one or more embodiments is depicted. Alternatively, the inverter may be an inverter without a converter. In the context of this disclosure, an inverter without a converter or a combined inverter and converter may be referred to as an inverter. Figure 1As shown, the electric vehicle 100 may include an inverter 110, a motor 190, and a battery 195. The inverter 110 may include a component for receiving power from an external source and outputting power to charge the battery 195 of the electric vehicle 100. For example, the inverter 110 may convert DC power from the battery 195 in the electric vehicle 100 into AC power to drive (e.g., rotate) the motor 190 of the electric vehicle 100, but embodiments are not limited thereto. The inverter 110 may be bidirectional and may convert DC power into AC power, or convert AC power into DC power, such as during regenerative braking. The inverter 110 may be a three-phase inverter, a single-phase inverter, or a multi-phase inverter.

[0067] Figure 2 A power schematic diagram of a three-phase inverter module according to one or more embodiments is depicted. Figure 1 and Figure 2 As shown, the inverter 110 can be connected to a battery or power source 195 and a motor or load 190. The inverter 110 can include a first three-phase switch group 210 and a second three-phase switch group 220. The first phase U can be associated with ΦA including switches Q1 and Q4, the second phase V can be associated with ΦB including switches Q3 and Q6, and the third phase W can be associated with ΦC including switches Q5 and Q2, as shown in FIG. Figure 2 As shown. The first three-phase switch group 210 may include a first-phase switch Q1, a second-phase switch Q3, and a third-phase switch Q5. The second three-phase switch group 220 may include a first-phase switch Q4, a second-phase switch Q6, and a third-phase switch Q2. Switches Q1 to Q6 may be metal oxide semiconductor field effect transistors (MOSFETs), but are not limited thereto.

[0068] The first three-phase switch group 210 and the second three-phase switch group 220 may be controlled by an inverter controller 300 (e.g. Figure 3 ) is driven by a PWM signal generated to convert the DC power delivered via the input terminal group 285 at the capacitor 230 into three-phase AC power output to the motor 190 at the output terminals U, V and W via the output terminal group 295. Additionally, although Figure 1 and Figure 2 A three-phase inverter is exemplified, but the present disclosure is not limited thereto and may include a single-phase or multi-phase inverter.

[0069] Figure 3 Depicted according to one or more embodiments Figure 2 FIG. 3 is an exemplary system infrastructure of an inverter controller 300 . The inverter controller 300 may include one or more controllers.

[0070] The inverter controller 300 may include a set of instructions that can be executed to cause the inverter controller 300 to perform any one or more of the methods or computer-based functions disclosed herein. The inverter controller 300 may operate as a standalone device or may be connected to other computer systems or peripheral devices (e.g., using a network).

[0071] In a networked deployment, the inverter controller 300 can operate as a server, as a client in a server-client user network environment, or as a peer computer system in a peer-to-peer (or distributed) network environment. The inverter controller 300 can also be implemented as or incorporated into various devices, such as a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile device, a palmtop computer, a laptop computer, a desktop computer, a communication device, a wireless phone, a landline phone, a control system, a camera, a scanner, a fax machine, a printer, a pager, a personal trusted device, a network appliance, a network router, a switch or a bridge, or any other machine capable of executing a set of instructions (sequential or otherwise) that specify the actions to be taken by the machine. In a specific implementation, the inverter controller 300 can be implemented using an electronic device that provides voice, video, or data communication. In addition, although the inverter controller 300 is illustrated as a single system, the term "system" should also be understood to include any collection of systems or subsystems that execute one or more sets of instructions, either individually or in combination, to implement one or more computer functions.

[0072] like Figure 3 As shown, the inverter controller 300 may include a processor 302, such as a central processing unit (CPU), a graphics processing unit (GPU), or both. The processor 302 may be a component in various systems. For example, the processor 302 may be part of a standard inverter. The processor 302 may be one or more general-purpose processors, digital signal processors, application-specific integrated circuits, field programmable gate arrays, servers, networks, digital circuits, analog circuits, combinations thereof, or other devices now known or later developed for analyzing and processing data. The processor 302 may implement a software program, such as manually generated (i.e., programmed) code.

[0073] Inverter controller 300 may include memory 304, which may communicate via bus 308. Memory 304 may be main memory, static memory, or dynamic memory. Memory 304 may include, but is not limited to, computer-readable storage media, such as various types of volatile and non-volatile storage media, including, but not limited to, random access memory, read-only memory, programmable read-only memory, electrically programmable read-only memory, electrically erasable read-only memory, flash memory, magnetic tape or disk, optical media, and the like. In one implementation, memory 304 comprises cache or random access memory for processor 302. In alternative implementations, memory 304 is separate from processor 302, such as a processor's cache memory, system memory, or other memory. Memory 304 may be an external storage device or database for storing data. Examples include a hard drive, a compact disc ("CD"), a digital video disc ("DVD"), a memory card, a memory stick, a floppy disk, a universal serial bus ("USB") memory device, or any other device operable to store data. Memory 304 is operable to store instructions executable by processor 302. The functions, actions, or tasks shown in the figures or described herein may be performed by processor 302 executing instructions stored in memory 304. The functions, actions, or tasks are not related to a particular type of instruction set, storage medium, processor, or processing strategy, and may be performed by software, hardware, integrated circuits, firmware, microcode, etc., alone or in combination. Likewise, processing strategies may include multi-processing, multi-tasking, parallel processing, etc.

[0074] As shown in the figure, the inverter controller 300 may further include a display 310, such as a liquid crystal display (LCD), an organic light emitting diode (OLED), a flat panel display, a solid state display, a cathode ray tube (CRT), a projector, a printer, or other display devices now known or later developed for outputting certain information. The display 310 may serve as an interface for a user to view the operation of the processor 302, or specifically serve as an interface with software stored in the memory 304 or the drive unit 306.

[0075] Additionally or alternatively, the inverter controller 300 may include an input device 312 configured to allow a user to interact with any component of the inverter controller 300. The input device 312 may be a numeric keypad, a keyboard, or a cursor control device (e.g., a mouse, a joystick, a touch screen display, a remote control, or any other device that operatively interacts with the inverter controller 300).

[0076] The inverter controller 300 may also or alternatively include a drive unit 306 implemented as a disk or optical drive. The drive unit 306 may include a computer-readable medium 322 in which one or more sets of instructions 324 (e.g., software) may be embedded. In addition, the instructions 324 may embody one or more methods or logic described herein. During execution by the inverter controller 300, the instructions 324 may reside entirely or partially within the memory 304 and / or within the processor 302. The memory 304 and the processor 302 may also include computer-readable media as described above.

[0077] In some systems, computer-readable medium 322 includes instructions 324, or receives and executes instructions 324 in response to a propagated signal, enabling devices connected to network 370 to transmit voice, video, audio, images, or any other data over network 370. Furthermore, instructions 324 can be sent or received over network 370 via communication port or interface 320 and / or sent or received using bus 308. Communication port or interface 320 can be part of processor 302 or a separate component. Communication port or interface 320 can be created in software or as a physical connection in hardware. Communication port or interface 320 can be configured to connect to network 370, external media, display 310, or any other component in inverter controller 300, or a combination thereof. The connection to network 370 can be a physical connection, such as a wired Ethernet connection, or can be established wirelessly, as described below. Similarly, additional connections to other components of inverter controller 300 can be physical connections or established wirelessly. Network 370 can alternatively be directly connected to bus 308.

[0078] Although the computer-readable medium 322 is shown as a single medium, the term "computer-readable medium" can include a single medium or multiple media, such as a centralized or distributed database, and / or associated caches and servers that store one or more sets of instructions. The term "computer-readable medium" can also include any medium that can store, encode, or carry a set of instructions for execution by a processor or cause a computer system to perform any one or more of the methods or operations disclosed herein. The computer-readable medium 322 can be non-transitory and can be tangible.

[0079] The computer-readable medium 322 may include solid-state memory, such as a memory card or other package that houses one or more non-volatile read-only memories. The computer-readable medium 322 may be a random access memory or other volatile rewritable memory. Additionally or alternatively, the computer-readable medium 322 may include magneto-optical or optical media, such as a disk or tape or other storage device, to capture carrier signals, such as signals transmitted via a transmission medium. Digital file attachments to emails or other self-contained information archives or archives may be considered distribution media (i.e., tangible storage media). Therefore, the present disclosure is considered to include any one or more of computer-readable media or distribution media and other equivalent and subsequent media in which data or instructions may be stored.

[0080] In alternative implementations, dedicated hardware implementations, such as application specific integrated circuits, programmable logic arrays, and other hardware devices, may be constructed to implement one or more of the methods described herein. Applications that may include devices and systems of various implementations may broadly include various electronic and computer systems. One or more implementations described herein may implement functionality using two or more specific interconnected hardware modules or devices having associated control and data signals that may be transmitted between and through the modules, or as part of an application specific integrated circuit. Thus, the present system encompasses software, firmware, and hardware implementations.

[0081] The inverter controller 300 can be connected to a network 370. The network 370 can define one or more networks, including wired or wireless networks. The wireless network can be a cellular telephone network, an 802.11, 802.16, 802.20, or WiMAX network. In addition, such networks can include public networks (e.g., the Internet), private networks (e.g., intranets), or combinations thereof, and can utilize various existing or later developed networking protocols, including but not limited to TCP / IP-based networking protocols. The network 370 can include a wide area network (WAN) such as the Internet, a local area network (LAN), a campus network, a metropolitan area network, a direct connection (e.g., via a universal serial bus (USB) port), or any other network that allows data communication. The network 370 can be configured to connect one computing device to another computing device to enable data to be transferred between the devices. The network 370 can generally use any form of machine-readable media to transfer information from one device to another. The network 370 can include communication methods for information to travel between computing devices. The network 370 can be divided into subnetworks. A subnetwork may allow access to all other components connected thereto, or a subnetwork may restrict access between components. Network 370 may be considered a public or private network connection and may include, for example, a virtual private network or encryption or other security mechanisms employed on the public Internet.

[0082] According to various implementations of the present disclosure, the methods described herein may be implemented by a software program executable by a computer system. In addition, in exemplary, non-limiting implementations, the implementation may include distributed processing, component or object distributed processing, and parallel processing. Alternatively, a virtual computer system process may be constructed to implement one or more methods or functions described herein.

[0083] Although this specification describes components and functions that can be implemented in specific implementations with reference to specific standards and protocols, the present disclosure is not limited to such standards and protocols. For example, the standards used for Internet and other packet-switched network transmission (e.g., TCP / IP, UDP / IP, HTML, HTTP) represent examples of the prior art. Such standards are regularly replaced by faster or more efficient equivalent standards with substantially the same functionality. Therefore, alternative standards and protocols having the same or similar functionality as those disclosed herein are considered equivalents thereof.

[0084] It should be understood that, in one embodiment, the operations of the methods discussed are performed by a suitable processor (or processors) of a processing (i.e., computer) system executing instructions (computer-readable code) stored in a memory portion. It should also be understood that the present disclosure is not limited to any particular implementation or programming technique, and that the present disclosure may be implemented using any suitable technique for implementing the functionality described herein. The present disclosure is not limited to any particular programming language or operating system.

[0085] It should be understood that any operation disclosed herein (e.g., with reference to Figures 4 to 10 The disclosed operations) are not limited to being performed in any particular order or sequence. Any order or sequence disclosed herein is disclosed only as an example, and those skilled in the art will appreciate that one or more operations (e.g., operations of a given process) may be performed in any applicable manner.

[0086] Figure 4 Depicted is an example method 400 for operating the inverter 110 to perform active discharge according to one or more embodiments. Figure 4 An overview of an exemplary method 400 is depicted, including operation of the inverter 110 in normal operating operation and active discharge operation, and Figures 5 to 10 Further depicted Figure 4 The various operations described in .

[0087] The exemplary method 400 may include initializing the inverter 110 (operation 405, see also Figure 5). The exemplary method 400 may include operating the inverter in a mission mode (operation 410), which may be a normal operating mode of converting DC power from the battery 195 in the electric vehicle 100 to AC power to drive (e.g., rotate) the motor 190 of the electric vehicle 100. The exemplary method 400 may include determining whether an active discharge request is valid (operation 415). For example, the inverter controller 300 may receive a command to perform an active discharge operation, or may determine that a condition for performing an active discharge operation is met. The exemplary method 400 may include, in response to determining that the active discharge request is invalid (no in operation 415), storing a threshold voltage and temperature of the inverter 110 (operation 420, see also Figure 6 ). The exemplary method 400 may include, in response to determining that the active discharge request is valid (yes in operation 415), initiating an active discharge mode and measuring a first voltage (operation 425, see also Figure 7 ).

[0088] The exemplary method 400 may include initiating a PWM pulse (eg, in one or more switches in the first three-phase switch group 210 or the second three-phase switch group 220) and measuring a second voltage (operation 430, see also Figure 8 ). The exemplary method 400 may include determining whether a voltage difference between the second voltage and the first voltage is greater than a threshold voltage difference (operation 435). The exemplary method 400 may include, in response to determining that the voltage difference is less than the threshold voltage difference (no in operation 435), increasing the gate-to-source voltage and performing a fault check (operation 450, see also Figure 9 ).

[0089] The exemplary method 400 may include, in response to determining that the voltage difference is greater than the threshold voltage difference (yes in operation 435), determining whether the bus voltage is less than the threshold voltage (operation 440). The exemplary method 400 may include, in response to determining that the bus voltage is less than the threshold voltage (yes in operation 440), ending the active discharge operation (operation 445). The exemplary method 400 may include, in response to determining that the bus voltage is greater than the threshold voltage (no in operation 440), accelerating the active discharge (operation 460, see also Figure 10 ). Exemplary method 400 may repeat operations 440 and 460 until it is determined that the bus voltage is less than the threshold voltage (YES in operation 440 ), thereby ending the active discharge operation (operation 445 ).

[0090] Figure 5 An exemplary method of initializing the inverter 110 according to one or more embodiments is depicted. Operation 405 (see also Figure 4) may include initializing the inverter 110 (operation 510), such as in an initial startup of the inverter 110 from an off to an on event. Operation 405 may include verifying that the inverter 110 is not faulty (operation 520). Operation 405 may include determining a device threshold voltage (operation 530). Operation 405 may include storing the determined threshold voltage in a lookup table (operation 540). For example, the algorithm may generate a lookup table that characterizes expected power switch package temperatures and gate threshold voltages. Operation 405 may include determining a device temperature (operation 550). Operation 405 may include storing the determined device temperature in a lookup table (operation 560). For example, the algorithm may update the lookup table as the device threshold voltage and temperature change over time. Operation 405 may continue to operation 410 (see Figure 4 ).

[0091] Figure 6 An exemplary method for measuring memory device threshold voltage and temperature according to one or more embodiments is depicted. Operation 420 (see also Figure 4 ) can be obtained from operation 415 (see also Figure 4 ) continues. For example, the algorithm may generate a lookup table that characterizes the expected power switch package temperature and the gate threshold voltage of the power switch. Whenever the inverter is in a six-switch off operation and there is no current flowing in the system (due to back EMF), the algorithm may update the lookup table. Operation 420 may include determining whether the inverter mode is in a state that allows reading the device threshold voltage (e.g., all six switches are off) (operation 610). Operation 420 may include, in response to determining that the inverter mode is not in a state that allows reading the device threshold voltage (no in operation 610), returning to operation 410. Operation 420 may include, in response to determining that the inverter mode is in a state that allows reading the device threshold voltage (yes in operation 610), reading the device threshold voltage (operation 620). Operation 420 may include storing the device threshold voltage (operation 630). Operation 420 may include reading the device temperature (operation 640). Operation 420 may include storing the device temperature (operation 650). For example, operation 420 may include updating and storing the device threshold voltage and temperature in the lookup table (see operation 560). Operation 420 may return to operation 410 (see Figure 4 ).

[0092] Figure 7 An exemplary method of initiating active discharge according to one or more embodiments is depicted. Operation 425 (see also Figure 4 ) can be obtained from operation 415 (see Figure 4) continues. For example, a systematic error of 1V could be caused by one or more of a measurement error in the threshold detection in the gate driver, a difference in low current threshold detection versus conduction current, or a change in the threshold with temperature. The initial temperature used should be related to the coolant temperature, as the thermal time constant will allow the starting temperature to be relative to the coolant temperature. Based on the calculated ideal threshold voltage and the subtracted error, the algorithm can determine the closest gate voltage setting provided by the gate driver and round down to the nearest value in the lookup table.

[0093] Operation 425 may include reading the temperature of inverter 110 (operation 710). Operation 425 may include determining a device threshold voltage (operation 720). Operation 425 may include determining a voltage setting (operation 730). Operation 425 may include adjusting for system errors (operation 740). Operation 425 may include determining a gate-to-source voltage (operation 750). Operation 425 may include applying the determined voltage setting (operation 760). For example, the algorithm may determine the closest gate voltage setting provided by the gate driver and round down to the closest value in the lookup table. Operation 425 may include waiting for the contactor to open (operation 770). For example, the wait time may be approximately 2.5 seconds. Operation 425 may include initializing variables (operation 780). For example, the variables may include setting a count and a clamped cycle to a value of zero. Operation 425 may include measuring a first voltage (operation 790), such as the voltage of the high voltage DC bus or capacitor 230. Operation 425 may continue to operation 430 (see also Figure 4 ).

[0094] Figure 8 An exemplary method of initiating pulse and measurement functions according to one or more embodiments is depicted. Operation 430 may continue from operation 425 (see also Figure 4 Operation 430 may be followed by operation 790 (see Figure 7 ) and operations 920 and 940 (see Figure 9 ) receives information. For example, operation 430 may receive the measured first voltage, the increased gate-to-source voltage, and the determination that the clamping period is equal to 2 from operation 790. Operation 430 (see Figure 4 ) may include executing a PWM cycle (operation 810). For example, operation 810 may include controlling inverter 110 to generate a pulse of 6.4 μs on and 600 μs off for 3 ms (e.g., 5 cycles). Operation 430 may include executing a wait time (operation 820). For example, the wait time may include a time of approximately 174 ms. Operation 430 may include measuring a second voltage (operation 830), such as a voltage of a high voltage DC bus or capacitor 230. Operation 430 may continue to operation 435 (see also Figure 4 ).

[0095] Figure 9 Depicts an exemplary method of increasing gate-to-source voltage and fault checking according to one or more embodiments. Operation 450 may continue from operation 435 (see Figure 4 ). For example, when the voltage difference is less than the threshold voltage, operation 450 may continue from operation 435. Operation 450 may include incrementing the count by 1 (operation 900). Operation 450 may include determining whether the count is greater than 2 (operation 910). Operation 450 may include, in response to determining that the count is not greater than 2 (no in operation 910) (e.g., a total of 3 iterations based on the initial count of 0), increasing the gate-to-source voltage (operation 920) and returning to operation 810. Operation 450 may include, in response to determining that the count is greater than 2 (yes in operation 910), incrementing the clamp cycle count by 1 (operation 930). Operation 450 may include determining whether the clamp cycle count is equal to 2 (operation 940). Operation 450 may include, in response to determining that the clamp cycle count is not equal to 2 (no in operation 940) (e.g., a total of 3 iterations based on the initial count of 0), returning to operation 810.

[0096] Operation 450 may include, in response to determining that the clamp cycle count is equal to 2 (yes in operation 940), determining that the contactor has faulted (e.g., shorted) (operation 950). Operation 450 may include waiting for a time t (operation 960). For example, the waiting time may be approximately 174 ms. Operation 450 may include executing a PWM cycle (operation 970). For example, operation 970 may include controlling the operation of inverter 110 to turn on with a pulse of 6.4 μs and off with a pulse of 600 μs for 3 ms (e.g., 5 cycles). Operation 450 may include determining whether a safe state for the contactor has been commanded (operation 980). Operation 450 may include, in response to determining that a safe state for the contactor has been commanded (yes in operation 980), executing a contactor safe state operation and ending the active discharge operation of inverter 110 (operation 990). Operation 450 may include, in response to determining that a safe state for the contactor has not been commanded (no in operation 980), returning to operation 940.

[0097] Figure 10 Depicted is an exemplary method for accelerating active discharge according to one or more embodiments. Operation 460 may continue from operation 440 (see also Figure 4). Operation 460 may include starting a timer (operation 1005). Operation 460 may include determining whether the timer is less than a threshold value (operation 1010). For example, the threshold value may be approximately 150 ms. Operation 460 may include, in response to determining that the timer is less than the threshold value (yes in operation 1010), starting a PWM cycle (operation 1015). For example, operation 1015 may include controlling the operation of inverter 110 to turn on with a pulse of 6.4 μs and turn off with a pulse of 600 μs for 3 ms (e.g., 5 cycles).

[0098] Operation 460 may include determining whether the PWM cycle count is greater than a threshold (operation 1020). For example, the PWM cycle count limit may be 67 cycles. Operation 460 may include, in response to determining that the PWM cycle count is not greater than the threshold (no in operation 1020), determining whether the voltage is greater than or equal to a first threshold (operation 1025). Determining whether the voltage is greater than or equal to the threshold may also be performed by determining whether the voltage is within a threshold range.

[0099] Operation 460 may include, in response to determining that the voltage is greater than or equal to the first threshold (Yes in Operation 1025), waiting (i.e., delaying the operation of the switches of the first three-phase switch group 210 and the second three-phase switch group 220) for a first time (Operation 1030), and returning to Operation 1010. Operation 460 may include, in response to determining that the voltage is not greater than or equal to the first threshold (No in Operation 1025), determining whether the voltage is greater than or equal to a second threshold (Operation 1026). Operation 460 may include, in response to determining that the voltage is greater than or equal to the second threshold (Yes in Operation 1026), waiting for a second time (Operation 1031), and returning to Operation 1010.

[0100] The first threshold value can be greater than the second threshold value, and the first time can be longer than the second time. Therefore, as the voltage (e.g., the voltage of capacitor 230) decreases, the waiting time between the pulses of operation 1015 can also be reduced, thereby accelerating the discharge of the voltage. Operations 1025 and 1026 are depicted as two operations, but operation 460 can include any number (n) of threshold operations and any number (n) of corresponding waiting times, thereby adjusting the acceleration of active discharge in increments of any number (n). The second threshold value (i.e., the nth threshold value) can be equal to the threshold value of operation 440, so that when the voltage approaches a safe voltage threshold (e.g., 60V), a final threshold reduction with a waiting time n occurs.

[0101] Operation 460 may include, in response to determining that the PWM cycle count is greater than the threshold value (No in operation 1020), resetting the cycle count (operation 1035). Operation 460 may include opening one or more switches of inverter 110 (operation 1040). Operation 460 may include measuring the threshold voltage (operation 1045) and returning to operation 440. Operation 460 may include, in response to determining that the timer is not less than the threshold value (No in operation 1010), increasing the gate to source voltage (operation 1050). Operation 460 may include resetting the timer (operation 1055). Operation 460 may continue to operation 440 (see Figure 4 ).

[0102] Figure 11 Depicted are exemplary plots of voltage and temperature of an inverter during active discharge according to one or more embodiments. Plot 1110 depicts voltage drop as a function of time, with accelerated voltage discharge. Plot 1120 depicts temperature of inverter 110 as a function of time, including temperature spikes during voltage discharge. Figure 11 As shown, as the voltage decreases over time, the waiting time between temperature spikes decreases, allowing more frequent pulses, thereby accelerating the voltage drop.

[0103] One or more embodiments may overcome the issues with some of the active discharge methods discussed above. For example, one or more embodiments may address one or more of the following issues: insufficient resolution of Vgs setting to control the punch-through current to a safe level; insufficient pulse width control; insufficient discharge period control; insufficient resolution of Vgs measurement; inability to predict the resulting current at high Vds voltages; inability to detect which inverter is performing the active discharge and which bulk capacitor is being discharged; inability to predict the value of the capacitor being discharged; or inability to predict SiC FET transconductance and its effects.

[0104] One or more embodiments may provide an algorithm that systematically estimates power switch bias voltage, programmatically increments gate voltage, and ensures safe operating compliance in active short-circuit mode with active discharge of optimized bulk capacitor discharge time.

[0105] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

1. A system, comprising: an inverter configured to convert DC power from a battery into AC power to drive a motor, wherein the inverter comprises: one or more switches; and One or more controllers, the one or more controllers configured to: determining a gate voltage for operating the one or more switches of the inverter based on a temperature of the inverter; operating the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate active discharge of a bus voltage of the inverter; and When the bus voltage is greater than a first threshold voltage, the active discharge of the bus voltage is accelerated by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal.

2. The system according to claim 1, wherein: The one or more controllers are further configured to: determining an amount of voltage reduction of the bus voltage based on operation of the one or more switches; as well as In response to determining that the voltage drop amount of the bus voltage is less than a second threshold voltage, one or more of increasing the gate voltage or determining whether a contactor of the inverter is faulty is performed.

3. The system according to claim 2, wherein: Performing one or more of increasing the gate voltage or determining whether a contactor of the inverter fails includes: Increment the fault count; When the fault count is less than a fault threshold, increasing the gate voltage; and When the fault count is greater than or equal to the fault threshold, it is determined whether a contactor of the inverter fails.

4. The system according to claim 1, wherein: Determining the gate voltage also includes: determining a temperature of the inverter; determining a threshold voltage for the one or more switches; and The gate voltage is determined based on the threshold voltage for the one or more switches, wherein the gate voltage is less than the threshold voltage for the one or more switches.

5. The system according to claim 1, wherein: Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: Start the timer; When the timer is greater than a threshold time, increasing the gate voltage and resetting the timer; and When the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and The waiting time after the first PWM signal is set based on the bus voltage.

6. The system according to claim 5, wherein: Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: When the timer is less than the threshold time: operating the one or more switches based on the first PWM signal; determining whether a PWM cycle count of the first PWM signal is greater than a threshold cycle count; and When the PWM cycle count is greater than the threshold cycle count, the PWM cycle count is reset, the one or more switches are turned off, and the first threshold voltage is determined.

7. The system according to claim 6, wherein: The waiting time after setting the first PWM signal based on the bus voltage includes: When the bus voltage is within a first voltage range, setting the waiting time to a first value, delaying operation of the one or more switches by the first value of the waiting time, and determining whether the timer is less than the threshold time, and When the bus voltage is in a second voltage range that is smaller than the first voltage range, setting the waiting time to a second value that is smaller than the first value, delaying operation of the one or more switches by the second waiting time, and determining whether the timer is less than the threshold time, The lower limit value of the second voltage range is equal to the first threshold voltage.

8. The system according to claim 1, further comprising: the battery configured to supply the DC power to the inverter; as well as the motor, the motor being configured to receive the AC power for driving the motor from the inverter, The system is provided as a vehicle, and the vehicle includes the inverter, the battery, and the motor.

9. A system comprising one or more controllers configured to: determining a gate voltage for operating one or more switches of the inverter based on a temperature of the inverter; operating the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage to initiate active discharge of a bus voltage of the inverter; as well as When the bus voltage is greater than a first threshold voltage, the active discharge of the bus voltage is accelerated by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal.

10. The system according to claim 9, wherein: Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: Start the timer; When the timer is greater than a threshold time, increasing the gate voltage and resetting the timer; and When the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and The waiting time after the first PWM signal is set based on the bus voltage.

11. The system according to claim 10, wherein: The waiting time after setting the first PWM signal based on the bus voltage includes: When the bus voltage is within a first voltage range, setting the waiting time to a first value, delaying operation of the one or more switches by the first value of the waiting time, and determining whether the timer is less than the threshold time, and When the bus voltage is in a second voltage range that is smaller than the first voltage range, the waiting time is set to a second value that is smaller than the first value, the operation of the one or more switches is delayed by the second value of the waiting time, and it is determined whether the timer is less than the threshold time.

12. A method comprising: One or more controllers are used to perform operations for controlling the inverter, including: receiving a request to initiate active discharge of a bus voltage of the inverter; determining a gate voltage for operating one or more switches of the inverter based on a temperature of the inverter; operating the one or more switches based on a pulse width modulation (PWM) signal and the gate voltage, to initiate active discharge of the bus voltage; and When the bus voltage is greater than a first threshold voltage, the active discharge of the bus voltage is accelerated by operating the one or more switches and by performing one or more of increasing the gate voltage or decreasing a wait time after a pulse of the PWM signal.

13. The method according to claim 12, further comprising: operating the one or more switches; determining a voltage drop of the bus voltage; as well as In response to determining that the voltage drop amount of the bus voltage is less than a second threshold voltage, one or more of increasing the gate voltage or determining whether a contactor of the inverter is faulty is performed.

14. The method according to claim 13, wherein: Performing one or more of increasing the gate voltage or determining whether a contactor of the inverter fails includes: Increment the fault count; When the fault count is less than a fault threshold, increasing the gate voltage; and When the fault count is greater than or equal to the fault threshold, it is determined whether a contactor of the inverter fails.

15. The method according to claim 12, wherein: Determining the gate voltage also includes: determining a temperature of the inverter; determining a threshold voltage for the one or more switches; and The gate voltage is determined based on the threshold voltage for the one or more switches, wherein the gate voltage is less than the threshold voltage for the one or more switches.

16. The method according to claim 12, wherein Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: Start the timer; and When the timer is greater than a threshold time, the gate voltage is increased and the timer is reset.

17. The method according to claim 16, wherein Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: When the timer is less than the threshold time: operating the one or more switches based on a first PWM signal; determining the bus voltage; and The waiting time after the first PWM signal is set based on the bus voltage.

18. The method according to claim 17, wherein Performing one or more of increasing the gate voltage or reducing the waiting time after the pulse of the PWM signal further includes: When the timer is less than the threshold time: operating the one or more switches based on the first PWM signal; determining whether a PWM cycle count of the first PWM signal is greater than a threshold cycle count; and When the PWM cycle count is greater than the threshold cycle count, the PWM cycle count is reset, the one or more switches are turned off, and the first threshold voltage is determined.

19. The method according to claim 17, wherein The waiting time after setting the first PWM signal based on the bus voltage includes: When the bus voltage is within a first voltage range, setting the waiting time to a first value, delaying operation of the one or more switches by the first value of the waiting time, and determining whether the timer is less than the threshold time, and When the bus voltage is in a second voltage range that is smaller than the first voltage range, the waiting time is set to a second value that is smaller than the first value, the operation of the one or more switches is delayed by the second value of the waiting time, and it is determined whether the timer is less than the threshold time.

20. The method according to claim 19, wherein A lower limit value of the second voltage range is equal to the first threshold voltage.

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