SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control method

Abstract

The present application relates to the technical field of fuel cell thermal management and electronic control, in particular to a low-temperature cold start variable frequency drive control method for a fuel cell solenoid valve based on SiC, comprising the following steps: S1, environment perception and initial state establishment; S2, intelligent strategy determination and mode shunting; S3, high-frequency micro-vibration preheating stage; S4, instantaneous strong current impact stage; S5, closed-loop maintenance and dynamic correction stage. The present application improves the solenoid valve start success rate at-30 DEG C extreme low temperature to more than 99%, shortens the start response time to within 200ms, controls the coil temperature rise within a safe range, effectively solves the low-temperature cold start problem of the fuel cell solenoid valve, and meets the commercial application needs in the northern alpine regions.

Description

Technical Field

[0001] This invention relates to the field of fuel cell thermal management and electronic control technology, specifically a SiC-based method for low-temperature cold start variable frequency drive control of fuel cell solenoid valves. Background Technology

[0002] With the rapid development of the hydrogen energy industry, fuel cell vehicles (FCVs) and hydrogen refueling station infrastructure are gradually moving from demonstration operations to commercial promotion. In hydrogen supply and air management systems, solenoid valves, as key fluid control actuators, directly determine the system's safety and overall vehicle performance through their response speed and reliability. However, in practical applications, especially under extreme conditions in northern winters and high-altitude regions (ambient temperatures below -20°C), existing solenoid valve drive technology still faces the following challenges: (1) At extremely low temperatures, the viscosity of the lubricating coating and sealing grease on the surface of the solenoid valve core will increase sharply. At the same time, the unavoidable trace amount of water vapor in the hydrogen flow path is very easy to condense into ice crystals at the gap between the valve seat and the valve core. This causes the static friction and viscous resistance of the valve core to soar to 3 to 5 times that at room temperature, forming a huge "cold start resistance".

[0003] (2) Existing drive circuits mostly use silicon-based IGBTs or MOSFETs. Due to their large switching losses, they are difficult to support high-frequency and high-current modulation above 20kHz. This means that the eddy current heating effect generated by the high-frequency alternating magnetic field cannot be used to quickly preheat the valve body, which limits the performance of the hardware.

[0004] (3) Traditional technologies generally adopt a "constant voltage start" or a simple "PWM sustain + direct start" strategy. This "one-size-fits-all" driving method often cannot provide enough instantaneous electromagnetic impact force to break through the ice crystal binding under low temperature and high resistance conditions, resulting in a valve opening response delay of more than 300ms, or even valve core jamming failure. In order to force opening, if the driving voltage is simply increased or the high current time is extended, the coil is very likely to overheat and burn out due to Joule heat accumulation. It is impossible to find a balance between "strong driving force required for ice breaking" and "coil thermal safety". Summary of the Invention

[0005] The purpose of this invention is to provide a SiC-based method for low-temperature cold start variable frequency drive control of fuel cell solenoid valves, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A SiC-based method for low-temperature cold-start variable frequency drive control of fuel cell solenoid valves includes the following steps: S1. Environmental perception and initial state establishment: After the system is powered on, the ambient temperature of the solenoid valve is collected, and the SiC drive bridge arm is self-checked to establish the initial safe state. S2. Intelligent Strategy Judgment and Mode Diversion: The operating condition is determined based on the collected ambient temperature. If the ambient temperature is greater than 0℃, the conventional PID control mode is entered, and the standard PWM drive strategy is used to stabilize the current and control energy consumption. If the ambient temperature is less than or equal to 0℃, the low temperature cold start frequency conversion drive mode is activated, and subsequent steps S3 to S5 are executed in sequence. S3, High-frequency micro-vibration preheating stage: Drive SiCMOSFET to output a high-frequency PWM signal of 20kHz-50kHz, control the PWM duty cycle to keep the average current of the coil in a subthreshold state, and generate an electromagnetic force less than the spring preload force, driving the valve core to generate micron-level high-frequency vibration in place. At the same time, the eddy current effect of the high-frequency alternating magnetic field and the Joule heat of the coil are used to preheat the valve core, reduce viscous resistance and break up micro ice crystals. S4, Instantaneous High Current Impact Stage: After the preheating stage, the driving frequency is switched from high frequency to low frequency, and an overdrive signal with a 100% duty cycle is applied. Utilizing the low internal resistance characteristics of SiC devices, the coil current rapidly rises to the peak value with a high di / dt slope, generating an explosive electromagnetic attraction force to overcome the residual resistance and pull the valve core open. S5, Closed-loop maintenance and dynamic correction stage: After the valve core is opened, the valve core status is confirmed by monitoring the characteristic changes of the coil current waveform. After confirming that it is open, the PWM duty cycle is reduced so that the current drops back to the maintenance current level. If no opening characteristic is detected, the enhanced retry mechanism is triggered, and stages S3 to S4 are re-executed. The preheating time is automatically extended and the impact pulse width is increased until the valve is successfully opened or the maximum number of safe retry attempts is reached.

[0007] Preferably, the duration of the high-frequency micro-vibration preheating stage is an adaptive parameter that is dynamically adjusted according to the ambient temperature. When the ambient temperature is -10℃, the preheating duration is 100ms, and when the ambient temperature is -30℃, the preheating duration is 300ms.

[0008] Preferably, the high-frequency micro-vibration preheating stage further includes preheating energy management, which uses an energy integral constraint model to perform closed-loop control of the input energy, satisfying:

[0009] in, This is the effective value of the coil current. For coil resistance, This refers to the power loss due to eddy currents in the valve core. This is the maximum allowed cumulative thermal energy threshold for the coil.

[0010] Preferably, the PWM duty cycle function is a piecewise frequency converter control law that satisfies:

[0011] In the formula, The preheating flutter frequency is set to 20kHz-50kHz; A is the flutter amplitude coefficient. The DC bias is applied so that the average value of the combined electromagnetic force is less than the spring preload. To achieve the desired duty cycle, a value of 100% is used. To maintain the duty cycle, it is used to stabilize the current at the maintenance current level; For the warm-up time, To impact duration.

[0012] Preferably, it also includes an adaptive variable parameter control step, in which the corresponding control parameters are obtained by means of a preset lookup table method based on the real-time collected ambient temperature. The lookup table method stores the PWM reference value, jitter frequency and jitter superposition amplitude corresponding to different temperature nodes. At the same time, linear compensation is performed according to the battery voltage to adjust the actual output PWM duty cycle.

[0013] Preferably, the temperature nodes of the lookup table method include -40℃, -20℃, 0℃, and 25℃, and the corresponding control parameters are as follows: At -40℃, the PWM reference value is 85%, the chatter frequency is 1000Hz, and the chatter superposition amplitude is 30%. At -20℃, the PWM reference value is 70%, the chatter frequency is 800Hz, and the chatter superposition amplitude is 20%. At 0℃, the PWM reference value is 50%, the dither frequency is 400Hz, and the dither superposition amplitude is 10%. At 25℃, the PWM reference value is 35%, the jitter frequency is 200Hz, and the jitter superposition amplitude is 5%.

[0014] A SiC-based fuel cell solenoid valve cryogenic cold start variable frequency drive control system includes: The environmental sensing unit is used to collect the ambient temperature where the solenoid valve is located and to perform fault self-checks on the SiC drive bridge arm. The working condition determination unit is connected to the environmental sensing unit and is used to determine the current working condition based on the collected ambient temperature. If the ambient temperature is greater than 0℃, the control enters the normal PID control mode; if the ambient temperature is less than or equal to 0℃, the low temperature cold start frequency conversion drive mode is activated. The SiC power drive unit is used to output a PWM drive signal to the solenoid valve coil according to the control signal. The frequency conversion control unit is connected to the operating condition determination unit and the SiC power drive unit respectively, and is used to sequentially execute the control of the high-frequency micro-vibration preheating, instantaneous strong current impact, closed-loop maintenance and dynamic correction stages in the low temperature cold start mode. The current sampling unit, connected to the frequency conversion control unit, is used to collect coil current in real time and provide feedback signals for closed-loop control and valve core status monitoring.

[0015] Preferably, the SiC power drive unit is an H-bridge topology, including four SiC MOSFET switches, with the solenoid valve coil connected between the midpoints of the two bridge arms. The H-bridge topology supports bidirectional current drive, enabling bidirectional flutter and active demagnetization control.

[0016] Preferably, the frequency converter control unit further includes an adaptive lookup table module, which is used to obtain the corresponding control parameters by looking up a preset parameter table according to the real-time ambient temperature, and to compensate according to the battery voltage to adjust the output PWM signal parameters.

[0017] Preferably, it also includes a thermal safety control unit for integral control of the input energy during the preheating stage, limiting the accumulated heat energy to not exceed the maximum safety threshold of the coil, and preventing the coil from overheating and burning out.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention uses SiC power devices, which breaks through the limitations of switching losses in silicon-based devices. It supports high-frequency PWM modulation of 20-50kHz and can achieve internal self-heating of the valve core by utilizing the eddy current effect of the high-frequency alternating magnetic field. Combined with the Joule heating of the coil, it achieves dual preheating. Compared with the traditional external PTC heating method, no additional heating element is required, the preheating speed is faster, and the energy consumption is lower. It can raise the valve core temperature to above the freezing point within hundreds of milliseconds, quickly softening solidified grease and melting microscopic ice crystals.

[0019] This invention proposes a segmented driving strategy of "high-frequency micro-vibration preheating + instantaneous strong impact". During the preheating stage, the valve core is driven by subthreshold current to vibrate at the micron level, which transforms the huge static friction force into dynamic friction force. At the same time, it breaks up the micro ice crystals at the valve seat, which greatly reduces the cold start resistance. Then, the low internal resistance characteristics of SiC are used to achieve a high di / dt instantaneous high current impact, which generates an explosive electromagnetic force to complete the ice breaking and opening. This not only solves the problem of low temperature jamming, but also avoids the coil overheating problem caused by long-term high current in traditional constant voltage drive, and achieves a balance between driving force and thermal safety.

[0020] This invention designs an adaptive variable parameter control and thermal safety management mechanism. It automatically adjusts the preheating time, chatter frequency, and PWM parameters by looking up the ambient temperature, adapting to all operating conditions from -40℃ to room temperature. At the same time, it uses an energy integral model to perform closed-loop management of the input energy during the preheating stage, strictly limiting the accumulated heat of the coil to not exceed the safety threshold, thus ensuring the ice-breaking capability while completely avoiding the risk of coil overheating and burning.

[0021] This invention introduces a closed-loop state monitoring and self-healing retry mechanism. It monitors the valve core opening status in real time by observing the characteristic changes in the coil current waveform. When the start-up fails, it automatically extends the preheating time and increases the impact pulse width for retrying, which greatly improves the start-up success rate at extreme low temperatures. Compared with the traditional driving method, the start-up success rate at -30℃ is increased from 72% to over 99%, and the start-up response time is shortened from over 500ms to less than 200ms.

[0022] This invention adopts an H-bridge SiC driving topology, supports bidirectional current driving, and realizes bidirectional chatter and active demagnetization control, further improving the effect of micro-chatter ice breaking, while accelerating the response speed of valve closing and improving the dynamic adjustment capability of the system. Attached Figure Description

[0023] Figure 1 This is a hardware architecture diagram of the present invention based on single-transistor low-side driving; Figure 2 This is a schematic diagram of strong excitation and unidirectional flutter in Embodiment 1 of the present invention; Figure 3 This is a hardware architecture diagram of the solenoid valve drive based on the H-bridge (full bridge) of the present invention; Figure 4 This is a current waveform diagram under the H-bridge mode of the present invention; Figure 5 This is a visualization diagram of the adaptive temperature control strategy logic of the present invention; Figure 6 This is a topology diagram of the driving circuit of the present invention; Figure 7 This is a flowchart illustrating the logic of the drive control strategy of this invention. Figure 8 This is a comparative analysis diagram of the driving waveform and response characteristics of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figure 1-8 As shown, the low-temperature cold start variable frequency drive control method for fuel cell solenoid valves based on SiC includes the following steps: Step S1, Environmental Perception and Initial State Establishment: After the system is powered on, the microcontroller (MCU) first reads the temperature sensor values ​​located at the valve body or system flow channel through the integrated A / D sampling interface to obtain the current ambient temperature. At the same time, the system will perform a self-test on the SiC drive bridge arm to ensure that there are no short circuit or open circuit faults and establish an initial safe state.

[0026] Step S2, Intelligent Strategy Determination and Mode Division: The controller determines the mode based on the acquired... Perform logical judgments: Step S21: If If the system is determined to be operating under normal temperature conditions, it will automatically enter the conventional PID control mode. At this time, the standard PWM drive strategy is adopted, focusing on the smooth regulation of current and the minimization of energy consumption.

[0027] Step S22: If (especially to reach) If the condition is low temperature (or below), the system will automatically activate the low temperature cold start inverter drive mode and execute subsequent steps S3 to S5 in sequence.

[0028] Step S3, High-frequency micro-vibration preheating stage one: This stage aims to solve the "cold stickiness" problem of the valve core through non-contact means.

[0029] Step S31: High-frequency modulation: The controller drives the SiC MOSFET output frequency to be... The high-frequency PWM signal (preferred range 20kHz to 50kHz) benefits from the extremely low switching losses of SiC devices, so even at this high frequency, the temperature rise of the drive module is negligible.

[0030] Step S32: Energy Conversion Mechanism: The high-frequency signal generates an alternating magnetic field in the electromagnetic coil. Utilizing the skin effect and eddy current effect of the high-frequency magnetic field, eddy current losses are generated inside the ferromagnetic valve core, causing the valve core to heat up rapidly from the inside; at the same time, the coil copper loss (Joule heating) is superimposed, achieving a dual heating effect and quickly softening the solidified lubricating coating.

[0031] Step S33: Mechanical micro-vibration: Control the PWM duty cycle to make the average current in a "subthreshold" state (i.e., the generated electromagnetic force is less than the spring preload). At this time, the high-frequency current component will drive the valve core to generate micro-amplitude high-frequency vibration (micrometer level) in place. This high-frequency mechanical wave can effectively break the micro-ice crystal structure at the valve seat joint, and transform the originally huge static friction force into a smaller dynamic friction force, thus preparing the physical conditions for subsequent opening.

[0032] Step S4, Instantaneous High Current Impact Phase Two: After the preheating phase ends (usually lasting 100ms-200ms), immediately switch to impact mode and implement the "ice-breaking" action.

[0033] Step S41: Frequency switching: The drive frequency instantly changes from high frequency. Switch to low frequency (e.g., 0Hz / DC, or <100Hz).

[0034] Step S42: Overdrive strategy: Apply an overdrive voltage of 100% duty cycle or higher than the rated voltage. Due to the low internal resistance of the SiC device, the total circuit impedance is significantly reduced, allowing the coil current to flow at extremely high speeds. The slope rapidly climbs to its peak (Over-current).

[0035] Step S43: Maximum Electromagnetic Force Output: According to the electromagnetic force formula A sudden surge of current will generate an explosive electromagnetic attraction force several times greater than the rated value. This force is sufficient to overcome the low-temperature viscous resistance and residual ice crystal resistance weakened by step S3, forcibly pulling the valve core to the fully open position quickly, controlling the opening response delay to the millisecond level.

[0036] Step S5, Closed-loop maintenance and dynamic correction stage three: After the valve is opened, the system does not simply remain open, but enters a closed-loop monitoring state.

[0037] Step S51: Status Confirmation: Confirm whether the valve is truly open by real-time monitoring of characteristic changes in the current waveform (such as the current dip caused by the sudden change in inductance due to the valve core being in position).

[0038] Step S52: Energy Management: After confirming that it is enabled, reduce the PWM duty cycle to allow the current to drop back to the holding current. This is to reduce coil heating and prevent overheating damage.

[0039] Step S53: Dynamic Correction (Self-Healing Mechanism): If no opening characteristic signal is detected after the end of step S4 (meaning there may be serious jamming), the system will automatically determine that the start-up has failed and immediately trigger the "enhanced retry mechanism", that is, return to the S3 stage, but automatically extend the preheating time and increase the impact pulse width of the S4 stage to make a second ice-breaking attempt until the valve is successfully opened or the maximum number of safe retry times is reached.

[0040] After the ambient temperature in the simulated environment chamber is stabilized at -20℃, the system is powered on and executes the "low-temperature adaptive startup" procedure as follows: Step 1, Environmental Awareness and Policy Matching (T=0ms): The MCU collects environmental data in real time through the onboard NTC temperature sensor. When the ADC sampling result shows that the ambient temperature is... At -20℃, the internal algorithm substitutes this value into a lookup table function for matching, determines that the current operating condition belongs to the "moderate freezing zone", and then automatically retrieves the relevant data. 150ms warm-up time and A specific set of parameters for the 30kHz flutter frequency is used to execute subsequent control strategies.

[0041] Step 2, High-frequency micro-vibration warm-up stage (0 <t≤150ms): Firstly, at the parameter setting and control execution level, the system fully utilizes the high-speed switching characteristics of SiC devices, setting the PWM carrier frequency to a level much higher than that of traditional drives (1-2kHz). The MCU outputs a PWM signal superimposed with a sinusoidal perturbation, and through closed-loop feedback, it precisely controls the current flowing through the coil to fluctuate at a high frequency between 0.2A and 0.4A, ensuring that its average current of 0.3A is far below the valve opening threshold, thereby preventing the valve from malfunctioning while generating excitation.

[0042] Secondly, high-frequency current physically induces a significant eddy current heating effect. A 30kHz high-frequency signal generates a "skin effect" on the surface of the metal valve core. This mechanism allows for rapid heating of the valve core's surface metal using eddy currents without significantly increasing coil copper losses. This targeted, localized heating method can directly act on the frozen interface, quickly melting the ice layer adhering between the valve core and the valve sleeve.

[0043] Finally, the alternating magnetic field force generated by the current fluctuation Mechanical thawing was achieved. A changing magnetic field drove the valve core to produce a tiny reciprocating displacement (i.e., high-frequency flutter) with an amplitude of about 50 μm. This micron-level vibration was sufficient to disrupt the lattice structure of the ice crystals, successfully converting the static friction between the valve core and the contact surface into dynamic friction, thereby physically thawing the mechanical freeze.

[0044] Step 3, Instantaneous overvoltage impact stage (150ms) <t≤200ms): First, after the warm-up phase, the MCU immediately executes a control strategy switch, adjusting the PWM frequency to 0Hz, i.e., outputting a control signal with a 100% duty cycle. This instruction signifies that the system has switched from high-frequency flutter mode to full-power drive mode, preparing the signal layer for valve opening.

[0045] Secondly, upon receiving the full-conduction signal, the SiC MOSFET quickly enters a fully conduction state. Thanks to the extremely low on-state voltage drop of the SiC device (close to 0V), voltage losses in the drive circuit are minimized, ensuring that the power supply voltage is applied almost entirely across the load coil.

[0046] Third, under full-voltage drive, the physical effect manifests as a momentary surge in coil current. The current spikes to 1.6A in a very short time, which is about 1.5 times the rated current, indicating that the system is intentionally in an overload drive state at this moment in order to obtain the maximum instantaneous drive energy.

[0047] Actual measurement data shows that, thanks to the reduced total circuit impedance caused by the low internal resistance of SiC, the current rise slope (di / dt) is improved by approximately 15% compared to traditional IGBT solutions. This enhances the electromagnetic attraction. It can burst at a faster speed, instantly overcoming the resistance of loosened ice crystals and viscous resistance during the preheating stage, and achieving decisive opening and complete engagement of the valve within a continuous strong drive time of 50ms.

[0048] Step 4, Low-power maintenance phase (t>200ms): First, in terms of parameter settings, after the valve completes the opening action, the MCU immediately adjusts the control strategy to enter the holding phase, switches the drive signal back to the 20kHz high-frequency PWM mode, and significantly reduces the duty cycle to 30%.

[0049] Secondly, at the control execution level, the system precisely controls the current flowing through the coil by reducing the duty cycle, so that it is stably maintained at a low power consumption level of about 0.5A.

[0050] Finally, from a physical perspective, the magnetic field force generated by the sustaining current is sufficient to overcome the mechanical restoring force of the spring, ensuring that the valve remains open. At the same time, it significantly reduces the steady-state power consumption and heat generation of the system, effectively preventing the risk of overheating of the coil during long-term operation.

[0051] To achieve adaptive and rapid start-up of the solenoid valve under extreme low-temperature conditions and ensure that the coil winding is not damaged while using high current for ice breaking, a precise low-temperature valve dynamic model and energy control equation were established based on the electromagnetic-thermodynamic coupling mechanism. Through a microcontroller (MCU), the critical dynamic model of valve opening at low temperature, the PWM generation control law of SiC frequency conversion drive, and the preheating energy management and thermal safety equations were used to generate precise control signals to drive silicon carbide (SiC) power devices.

[0052] The implementation method of the critical dynamic model for valve opening at low temperature is as follows: The opening process of a solenoid valve is essentially a dynamic balance process in which electromagnetic force overcomes mechanical resistance and environmental resistance. Under normal operating conditions, the main sources of resistance are spring preload and fluid pressure, but at low temperatures (… Under certain conditions, the sharp increase in the viscosity of the lubricating medium and the condensation of ice crystals introduce significant additional resistance, leading to the construction of a critical start-up condition model:

[0053] in, The attraction is electromagnetic, and this force is driven by the current in the coil. The function usually approximately satisfies ( (where the air gap is the distance between the air gap and the air gap), this invention achieves current flow during the impact phase by utilizing the low internal resistance characteristics of SiC devices. The instantaneous overshoot, thereby maximizing ; Spring preload (unit: N) is a constant determined by the mechanical structure and represents the minimum force required for valve reset; Temperature-dependent viscous resistance (unit: N) is one of the main sources of low-temperature hysteresis. This invention models it as a temperature-dependent viscous resistance. An exponentially decaying function, and related to the valve core movement speed Related:

[0054] in, This is the base viscosity coefficient of the lubricating coating at the reference temperature; Thermosensitive coefficient (unit: This reflects the sensitivity of the medium to temperature changes. The results show that the lower the temperature, the more exponentially the viscous resistance increases. Therefore, the core strategy of this invention lies in improving viscous resistance through preheating. This significantly reduces the resistance. The force of ice crystal adhesion (unit: N) is the rigid resistance that causes the valve to "stick." In traditional static actuation, Extremely difficult to overcome. This invention uses high-frequency dithering during the preheating stage to induce micro-displacement of the valve core, transforming the originally huge static friction-type ice crystal resistance into a smaller dynamic friction resistance. Combined with the thermal effect, this causes the ice crystal structure to disintegrate, thereby enabling the valve to open at the main opening moment... .

[0055] To meet the aforementioned dynamic requirements, this invention designs a segmented frequency conversion PWM control law based on the characteristics of SiC devices. This patent uses the PWM duty cycle function output by the controller... Defined as:

[0056] in, The preheating dithering frequency is set to 20kHz-50kHz. This is the key innovation of this invention. Traditional IGBTs / MOSFETs are limited by switching losses and cannot operate efficiently at this frequency. This invention utilizes the extremely low switching losses of SiCMOSFETs to achieve ultra-high frequency modulation. The selection of this frequency is based on the "skin effect" principle, which induces concentrated eddy currents on the valve core surface by the alternating magnetic field, greatly improving heating efficiency and achieving rapid defrosting "from the inside out". The flutter amplitude coefficient is the amplitude of the modulated AC component, which is set by... With DC bias This results in the generation of a combined electromagnetic force. Always has a value less than The average value, but includes high-frequency pulsation components, ensures that the valve core only experiences micron-level high-frequency vibrations in situ without accidentally opening; To achieve the desired duty cycle, 100% is typically used, or an overvoltage drive provided by a boost circuit is employed. This utilizes the low on-resistance of SiC. This makes the loop time constant Decrease the current ramp-up slope Extremely large, establishing explosive ice-breaking force; This parameter represents the preheating time and is not a fixed value; it is based on the ambient temperature. The lookup table function, for example, when hour, Set to 100ms; when hour, Extended to 300ms, enabling adaptive control.

[0057] The preheating energy management and thermal safety equation process is as follows: Although rapid heating is required, it is essential to prevent the coil insulation from burning out due to overheating. This invention introduces an energy integral constraint model to implement closed-loop control of the input energy during the preheating stage, i.e. (3-2-4) In the formula, Coil copper loss (Joule heating) is the main source of traditional heating; The power of eddy current loss and hysteresis loss of valve core and magnetic circuit materials at high frequency The percentage of this item increases significantly, which helps to target the heating of the metal valve core surface, the most critical area for ice crystal adhesion. This is the maximum allowable cumulative heat energy threshold for the coil, set according to the coil insulation class (e.g., Class H, 180°C). Another implicit meaning of expression (3-2-4) is that, thanks to the near-zero switching losses of SiC devices... This invention effectively avoids ineffective heat dissipation of the drive circuit itself, ensuring that the power input energy is converted into effective heat energy of the heating coil and valve core to the maximum extent; this efficient energy conversion mechanism enables the system to operate close to the maximum thermal safety threshold. It can operate stably under extreme conditions, thereby achieving cold start preheating that balances safety and optimal efficiency.

[0058] By combining the above three sets of models and formulas, this invention achieves closed-loop precise control from mechanical ice breaking, electrical drive to thermal management.

[0059] A SiC-based fuel cell solenoid valve cryogenic cold start variable frequency drive control system includes: The environmental sensing unit is used to collect the ambient temperature where the solenoid valve is located and to perform fault self-checks on the SiC drive bridge arm. The working condition determination unit is connected to the environmental sensing unit and is used to determine the current working condition based on the collected ambient temperature. If the ambient temperature is greater than 0℃, the control enters the normal PID control mode; if the ambient temperature is less than or equal to 0℃, the low temperature cold start frequency conversion drive mode is activated. The SiC power drive unit is used to output a PWM drive signal to the solenoid valve coil according to the control signal. The SiC power drive unit has an H-bridge topology and includes four SiC MOSFET switches. The solenoid valve coil is connected between the midpoints of the two bridge arms. The H-bridge topology supports bidirectional current drive and realizes bidirectional chatter and active demagnetization control. The frequency conversion control unit is connected to the operating condition determination unit and the SiC power drive unit respectively. It is used to sequentially execute the control of the high-frequency micro-vibration preheating, instantaneous strong current impact, closed-loop maintenance and dynamic correction stages in the low temperature cold start mode. The frequency conversion control unit also includes an adaptive lookup table module, which is used to obtain the corresponding control parameters by looking up the preset parameter table according to the real-time ambient temperature, and to compensate according to the battery voltage to adjust the output PWM signal parameters. The current sampling unit is connected to the frequency conversion control unit and is used to collect the coil current in real time to provide feedback signals for closed-loop control and valve core status monitoring. The thermal safety control unit is used to integrally control the input energy during the preheating stage, limiting the accumulated heat energy to not exceed the maximum safety threshold of the coil, and preventing the coil from overheating and burning out.

[0060] Figure 6 The diagram shows the topology of the drive circuit, which integrates SiC devices and includes the connection of the MCU, SiC drive bridge arm, current sampling, and valve coil.

[0061] based on Figure 6 The schematic diagram of the integrated SiC device driving circuit topology shown allows us to draw the following two important conclusions: (1) The hardware layout provides significant physical support for high-performance driving. The topology is specifically optimized for the high switching speed (high di / dt) characteristics of SiC devices. By significantly reducing stray inductance in the power circuit, it not only effectively suppresses voltage spikes and electromagnetic interference that may be generated during high-frequency operation, ensuring the safe and stable operation of SiC modules under extreme conditions, but also minimizes losses in the energy transmission path, providing a solid hardware foundation for the large instantaneous current injection required for low-temperature cold start.

[0062] (2) The perfect combination of closed-loop control architecture and device characteristics enables precise energy efficiency management. This circuit constructs a compact and efficient closed-loop control system through MCU, SiC drive bridge arm and high-precision current sampling resistor (R_shunt). The extremely low on-resistance and nanosecond-level response speed of SiC devices enable MCU to adjust the load current with extremely high resolution through PWM signal. This architecture provides the necessary hardware carrier for implementing the "segmented frequency conversion drive algorithm", thereby balancing strong torque output and thermal safety in millisecond time, and completely solving the problem of slow response and easy jamming of traditional solutions at low temperature.

[0063] Figure 7 The control logic flowchart corresponds to steps S1-S5 above.

[0064] based on Figure 7 The logic flowchart of the drive control strategy shown (S1-S5) can be analyzed to draw the following three core conclusions: (1) The adaptive hierarchical control based on environmental perception breaks the limitations of traditional single logic. The core watershed of the flowchart is the "temperature threshold determination" in step S3, which indicates that the system no longer blindly outputs constant power, but has the ability to identify operating conditions. By intelligently switching between two completely different control paths, "low temperature strong excitation" and "normal temperature normal drive", this logic ensures that the system can prioritize the "survival requirement" of overcoming static friction at extreme low temperatures, while focusing on the "efficiency requirement" of stability and energy saving at normal temperatures, thus achieving the optimal performance configuration across the entire temperature range.

[0065] (2) The software logic deeply explores and releases the physical potential of SiC hardware. In the logic design of the low-temperature branch, the "strong excitation mode" (high duty cycle and fast current building) is explicitly executed, which is actually a precise call to the high di / dt (current change rate) characteristics of SiC devices at the algorithm level. This logic transforms the hardware advantages of SiC in high voltage resistance and fast response into actual "ice-breaking" driving force, effectively solving the physical bottleneck of traditional silicon-based devices being unable to provide sufficient inrush current in milliseconds to overcome cold start lag due to the limitation of switching speed.

[0066] (3) The seamless integration of transient burst and steady-state accuracy ensures system reliability. The flowchart shows that no matter which startup branch is selected in the S3 stage, it will eventually converge to the "PID closed-loop regulation" in the S4 step. This means that the control strategy not only focuses on the "burst force" at the moment of startup (through open-loop strong excitation), but also pays more attention to the subsequent "control force". By introducing real-time current feedback, the system can quickly converge the violent startup current to the precise target value, prevent overcurrent damage to the device, and realize a smooth transition from aggressive startup to precise steady-state control.

[0067] Figure 8 For the comparative analysis of drive waveform and response characteristics, curve A (existing technology) represents a slow rise in current with a clear plateau period and a delayed start-up; curve B (this invention) has high-frequency ripples (flutter preheating) in the first part, followed by a steep current spike (impact), and the valve position signal quickly changes from 0 to 1.

[0068] based on Figure 3 A comparative analysis of the driving waveforms and response characteristics shown reveals four key conclusions based on the differences in shape between curve A (existing technology) and curve B: (1) The introduction of high-frequency chatter effectively lowers the physical threshold for startup. The unique sinusoidal ripples at the beginning of curve B indicate that the system was "preheated" before it was officially started. Although this small high-frequency current is not enough to directly open the valve, it is enough to make the valve core move slightly, transforming the difficult-to-overcome "static friction" into a smaller "dynamic friction". Compared with the rough approach of curve A, which starts from zero, this strategy clears the way for the subsequent large current impact from a physical perspective, which is especially valuable under the condition of low-temperature viscous oil.

[0069] (2) High performance of SiC devices This characteristic enables a "transient, powerful attack" of current on the inductor. Curve B, after preheating, exhibits a nearly vertical, steep rising edge, in stark contrast to the slow, exponential rise of curve A. This confirms that the present invention successfully establishes a huge magnetic field energy in an extremely short time by utilizing the advantages of SiC's low on-resistance and nanosecond-level switching speed. This explosive current impact force can quickly overcome mechanical hysteresis, solving the "soft-start" weakness problem caused by insufficient current rise rate in traditional silicon-based drive solutions.

[0070] (3) The powerful drive completely eliminates the "current plateau" effect of traditional solenoid valves. The obvious flat dip (plateau) in the middle of curve A is a typical characteristic of the back electromotive force canceling the drive voltage in traditional drives, which directly leads to the pause and lag in valve action. Curve B maintains a high slope throughout, completely covering and suppressing the influence of the back electromotive force. This shows that the drive power reserve of the present invention is sufficient to forcibly maintain the rate of increase of current, ensuring that the valve core always maintains maximum acceleration during the movement, thus eliminating the "hesitation time" during the action.

[0071] (4) The system response has achieved a qualitative leap from "millisecond delay" to "instantaneous response". As can be seen from the comparison of the displacement waveforms below, the valve position signal of curve B jumps to 1 almost immediately following the current spike, while curve A has a significant lag time ( This result quantifies the ultimate benefit of the control strategy: by eliminating static friction resistance, increasing current build-up speed, and overcoming back electromotive force, this invention significantly reduces the total response time of the actuator, enabling it to meet the demands of precision control scenarios with extremely high real-time requirements. Example 1: like Figure 1 As shown (based on a basic hardware architecture with a single transistor low-side drive), this circuit mainly consists of a DC power supply ( Inductive load (solenoid valve coil) ), freewheeling diode ( ) and main power switching transistor ( )composition.

[0072] One end of the solenoid valve coil is connected to the positive terminal of the power supply, and the other end is connected to the switching transistor. The drain of the transistor. The source of the switching transistor is grounded. The freewheeling diode. Connected in reverse parallel across the two ends of the coil.

[0073] Although the present invention preferably uses silicon carbide (SiC) MOSFETs, in this embodiment, High-performance silicon-based (Si) MOSFETs can also be used. If Si MOSFETs are used, to achieve a similar fast response, a low gate charge ( ) and low on-resistance ( (Model number)

[0074] like Figure 2 As shown (Working principle of Example 1: Strong excitation and unidirectional chatter), the control unit (MCU) sends... The gate sends a PWM signal. It consists of two typical driving stages: Strong excitation stage: When fully conductive (duty cycle close to 100%), the current rises rapidly to overcome static friction.

[0075] One-way dithering phase: After entering the hold phase, the MCU superimposes a low-frequency dithering signal. Since it is driven by a single transistor, the current cannot be reversed, and the dithering is manifested as "ripple fluctuation" of the current near the target value.

[0076] Under single-tube drive, the coil current The rise and fall follow the response of a first-order RL circuit. When When the circuit is turned on, the formula for the increase in coil current is: (S1-1) when When switched off, current flows through. During freewheeling, the current decay formula is: (S1-2) in, Battery voltage; This refers to the MOSFET's on-state voltage drop. The DC resistance of the coil varies with temperature. This is the on-resistance of the MOSFET; This refers to the forward voltage drop of the diode. This is the charging time constant; This is the freewheeling time constant (ignoring the diode's dynamic resistance).

[0077] Based on the analysis of the simulation waveforms of Example 1 (single-transistor low-side drive), the following conclusions can be drawn: ( ) The strong excitation strategy effectively overcomes the physical hysteresis of the inductive load, verifying the "ice-breaking" capability of the basic scheme. Simulation results show that during the strong excitation phase of 0-50ms, by applying a 100% duty cycle, the coil current not only does not rise slowly due to the time constant of the RL circuit, but also rises rapidly and reaches the design peak value. This proves that even the simplest single-tube hardware, combined with the strong excitation control logic of this invention, is sufficient to generate a huge electromagnetic force within milliseconds, thereby effectively overcoming the high viscous resistance of low-temperature oil and the static friction of the valve core, solving the core pain point of "slow cold start response" of solenoid valves.

[0078] (2) Although the unidirectional chatter is limited by the hardware and cannot be reversed, it can still maintain the dynamic micro-movement of the valve core, establishing the low-cost protection baseline of the present invention. In the waveform during the holding phase, the current exhibits a unidirectional ripple shape that is always greater than zero. This indicates that the circuit cannot generate a reverse current to achieve "active demagnetization" due to the unidirectional conduction characteristics of the freewheeling diode; however, the chatter signal superimposed by the MCU still successfully makes the current fluctuate continuously near the target value. This conclusion confirms that although the demagnetization effect of Example 1 is not as good as that of the H-bridge (Example 2), it can still keep the valve core in a "micro-oscillation" suspended state, significantly reducing the dynamic friction coefficient, which is sufficient to meet the needs of cost-sensitive applications with non-top-level precision requirements.

[0079] Example 2: like Figure 3 As shown, an H-bridge topology is used, containing four switching transistors ( The load (solenoid valve coil) is connected across the midpoint of the two bridge arms.

[0080] In this embodiment, All of them use SiCMOSFET as the key switching device, making full use of its excellent high voltage withstand characteristics to ensure the safety boundary of the system under high voltage environment. At the same time, with the core advantages of low reverse recovery charge (LowQrr) and extremely low switching loss, it can significantly reduce heat dissipation while achieving high frequency and high efficiency switching operation, thereby greatly improving the overall system energy efficiency and reliability.

[0081] Compared to Example 1, the H-bridge allows current to flow in reverse, which makes it possible to achieve "bidirectional flutter" and "active demagnetization," namely: (1) Bi-directional dither To address the problem of extremely high oil viscosity at low temperatures, where traditional unidirectional ripple current is insufficient to drive the valve core to produce sufficient mechanical micro-motion, this embodiment utilizes the full control characteristics of the H-bridge to periodically execute "forward conduction" during the forward current holding phase. ) Extremely short reverse pulse ( ) The control sequence for "positive recovery"; this strategy, by actively inserting reverse voltage pulses, not only significantly increases the peak-to-peak value of the current ripple ( This strengthens the mechanical chatter force and effectively eliminates the residual magnetism of the iron core by utilizing the alternating magnetic field at the zero-crossing point, completely solving the hysteresis phenomenon and ensuring the sensitive response of the valve core under extreme working conditions.

[0082] (2) Freewheeling control using the reverse recovery characteristics of SiC In a traditional H-bridge, freewheeling typically relies on the body diode. The body diode of a SiC MOSFET has an extremely short reverse recovery time ( The time to turn on is typically in the 15ns-30ns range, far lower than the hundreds of nanoseconds of SiMOSFETs. During the freewheeling phase, this embodiment does not rely solely on the body diode, but actively turns on the MOSFET channel on the freewheeling side (i.e., it employs synchronous rectification mode). For example, when... When shut down, immediately reactivate after the dead time. (or just the lower pipe) (Low-side freewheeling is performed). The power consumption of the SiC synchronous rectification is:

[0083] The freewheeling power dissipation of a traditional diode is:

[0084] Due to SiC Extremely small (e.g., 20m) At a current of 10A, ,and (Assuming) This low heat generation characteristic eliminates the need for additional heat sinks in high-temperature, sealed environments.

[0085] Figure 4 The current waveform in H-bridge mode is shown, where, For strong excitation, the current rises directly to ; To maintain the current during the holding phase, the current is... The frequency at Fluctuations occur between these points. As can be seen in the diagram, the key point is at the trough of the flutter, where the current can momentarily cross zero, using a reverse magnetic field to loosen the valve core.

[0086] based on Figure 4 The H-bridge mode current waveform shown (including zero-crossing chatter) leads to the following conclusions: The active zero-crossing mechanism completely eliminates the hysteresis effect and improves control accuracy. In the waveform diagram, the current periodically crosses the zero axis at the flutter trough (generating an instantaneous negative current), which directly proves that the H-bridge topology has the ability to generate a reverse magnetic field. Unlike traditional unidirectional drives that can only rely on spring reset, this mechanism, which uses reverse voltage to force the current to cross zero, plays a role similar to "demagnetization," effectively removing the residual magnetism accumulated in the iron core. This completely solves the common hysteresis problem of solenoid valves, making the valve core's response to control commands more linear and precise.

[0087] The significantly enhanced ripple energy effectively overcomes the high viscous friction at low temperatures. The figure shows the peak-to-peak value of the current ripple (…). It spans the positive and negative ranges, and its amplitude is significantly greater than the ripple in the traditional natural continuous flow mode. This large current fluctuation is transformed into a strong high-frequency mechanical micro-motion, which gives the valve core greater kinetic energy. Under the harsh working conditions of extremely low temperature oil viscosity, this strong flutter can effectively destroy the fluid boundary layer and static friction between the valve core and the valve body, so that the valve core always maintains a "dynamic suspension" state, thereby preventing valve core jamming or dead zone phenomenon caused by oil viscosity.

[0088] The "strong excitation-zero-crossing hold" strategy balances rapid response with low-heat operation. The waveform is clearly divided into two segments: The peak value of the stage current indicates that the system has extremely high dynamic response capability and can overcome inertia to open the valve instantly; The system then enters a low average current sustaining state. The conclusion is that by introducing zero-crossing chatter, the system can maintain valve core sensitivity without maintaining a high DC average current (using AC components to combat friction). This allows the system to maintain high-performance response while significantly reducing coil resistive heat loss, achieving an optimal balance between drive performance and thermal management.

[0089] Example 3: Examples 1 and 2 use SiCMOSFET as an example, but this control strategy is also applicable to the following devices, provided they meet the following specific physical characteristics: (1) Gallium nitride (GaN) HEMT devices This technical solution demonstrates highly forward-looking material compatibility and scalability. Its core architecture is not only perfectly compatible with silicon carbide (SiC) devices, but can also be seamlessly extended to next-generation power semiconductor applications such as gallium nitride (GaN). Because GaN materials have higher electron mobility than SiC, their theoretical switching speed and high-frequency characteristics are superior, providing a physical basis for further increasing the dithering frequency and achieving more precise valve core micro-motion control. However, in practical engineering applications, if the switching device is replaced with a GaNHEMT, the hardware circuitry requires targeted parameter adaptation: the drive voltage needs to be significantly reduced from the standard 15V-18V for SiC to the GaN-compatible 5V-6V logic level to prevent gate breakdown; simultaneously, given the extremely fast switching transients (dv / dt) of GaN, the design needs to incorporate more stringent gate loop impedance matching and buffer circuitry to effectively suppress gate ringing caused by parasitic inductance, ensuring the system's electromagnetic compatibility and operational reliability. Based on the commonality of the above technical logic, this embodiment makes a clear and broad patent declaration: any technical solution that uses wide bandgap semiconductor materials (including but not limited to SiC, GaN, gallium oxide, etc.) with a bandgap greater than 3.0eV to generate high-frequency chattering current by utilizing their high-frequency and low-loss characteristics, thereby solving the problem of viscous friction of hydraulic components under low-temperature and high-viscosity conditions, is considered to have utilized the core inventive concept of this invention and falls within the scope of protection of this patent without exception.

[0090] (2) Silicon-based (Si) MOSFETs with multiple transistors in parallel To address potential cost-avoidance strategies employed by competitors, such as attempting to reduce on-resistance by paralleling 3 to 4 low-cost silicon-based (Si) MOSFETs to mimic the low-heat performance of silicon carbide (SiC), this patent has pre-designed a robust defensive layout and technology coverage scheme. While, from a static perspective, paralleling multiple transistors can indeed reduce the equivalent on-resistance (Rds(on)) to a level similar to wide-bandgap devices, this "quantity for performance" physical stacking has significant dynamic performance limitations: the parallel structure causes the total gate input capacitance (Ciss) to multiply, thereby significantly increasing the load on the drive circuit, resulting in significantly slower switching rise / fall edges and limiting the system's high-frequency response. Therefore, the control architecture of this invention exhibits strong versatility. Specifically designed for such high-capacitance, slow-switching hardware environments, it integrates a "switching dead-time adaptive compensation" algorithm. This technology, as a key subordinate protection point of this patent, can dynamically adjust the PWM timing to offset the switching delay caused by the large capacitance and prevent H-bridge shoot-through. In terms of claim construction, this patent adopts a dual locking strategy of "physical features + algorithm logic": any switching module that uses an equivalent on-resistance lower than a certain threshold (XmΩ), regardless of whether it is a single-transistor SiC or multiple-transistor Si in parallel, falls within the scope of this patent's definition of high-performance hardware; at the same time, if competitors adopt similar dead-zone compensation logic to solve the timing lag problem caused by parallel connection, they will also violate the methodological protection boundary of this patent, thereby achieving a comprehensive technical blockade from high-end wide-bandgap solutions to low-cost silicon-based alternatives.

[0091] Example 4: Parameter setting group under specific working conditions This embodiment focuses on a specific automotive-grade solenoid valve (rated voltage 12V, resistance 4). (Inductance 8mH), three sets of typical control parameters are given.

[0092] Table 1. Control Parameter Setting Table

[0093] The physical meaning of the selected parameters is explained below: (1) Explanation of the selection of 800Hz: The mechanical natural frequency of a solenoid valve is usually between 50Hz and 150Hz. If the chatter frequency is too low, it is easy to cause mechanical resonance and noise. Setting it to 800Hz avoids the resonance zone and can also utilize the rate of change of current ( It generates sufficient high-frequency electromagnetic force to make the valve core be in a "suspended" micro-vibration state in the oil film, which greatly reduces the static friction coefficient.

[0094] (2) Formula for calculating strong excitation time: Set the target excitation current as Then the required time At least: (S3-1) At low temperatures, the increased internal resistance of the battery leads to... As the speed decreases, the MCU needs to calculate and extend the time in real time. This is precisely the theoretical basis for increasing ms from 50ms to 200ms in Table S4-1.

[0095] Example 5: Adaptive Variable Parameter Strategy Based on Look-up Table like Figure 5 (The logic visualization of the adaptive temperature control strategy (BatVolt=12V) is shown.)

[0096] The operating procedure is explained below: Step 1: Power on the system: Initialize the MCU.

[0097] Step 2, Temperature Sampling: Read the temperature value of the NTC thermistor embedded near the solenoid valve coil or on the PCB board. ).

[0098] Step 3: Interval Determination and Table Lookup: (1) If Enter energy-saving mode (low flutter amplitude, reduce heat generation).

[0099] (2) If Enter standard mode.

[0100] (3) If Enter icebreaking mode (maximum flutter amplitude, highest frequency).

[0101] Step 4, Parameter Compensation Calculation: In addition to looking up the table, linear compensation is also required based on the battery voltage.

[0102] Step 5, PWM generation and driving: output control signal.

[0103] based on Figure 5 From the simulation results and visualization curves, the following conclusions can be drawn: The hierarchical control logic exhibiting a significant negative correlation between temperature and output was verified. The graphs visually demonstrate that both the chatter amplitude (solid blue line) and chatter frequency (dashed red line) decrease in a stepwise manner as temperature increases. This design precisely matches the physical characteristic of hydraulic oil viscosity decreasing with increasing temperature: providing high-energy drive to overcome resistance in the low-temperature, high-viscosity range, while reducing output in the high-temperature, low-viscosity range to avoid interference control. This reverse matching mechanism ensures consistent mechanical response of the solenoid valve across the entire temperature range (-40°C to 40°C), resolving the pain point of "no response at low temperatures, overheating at high temperatures" caused by traditional fixed-parameter control.

[0104] The extreme operating conditions of "icebreaking mode" and "energy-saving mode" were clearly defined. The curves show steep parameter jumps between -20°C and 0°C, clearly delineating the system's safety boundaries. In "icebreaking mode" (T < -20°C), the system forces the output of maximum amplitude (>600mA) and highest frequency (200Hz) to instantly break the frozen oil film or ice crystals around the valve core through high-frequency, large-amplitude vibration, ensuring cold-start reliability under extreme cold conditions. In "energy-saving mode" (T > 0°C), the parameters drop back to the lowest level, effectively suppressing coil temperature rise and extending device life.

[0105] This embodies a dual adjustment mechanism of "table lookup and segmented adjustment + linear compensation." Observing the blue amplitude curve, it can be seen that it is not absolutely horizontal within each stepped plane, but has a slight slope or fluctuation (generated by the voltage compensation term in the code). This indicates that the system not only performs coarse adjustment based on the temperature range (table lookup), but also introduces battery voltage (BatVoltage) as a real-time compensation variable for fine adjustment. The conclusion is that this control strategy has extremely high robustness, and can dynamically maintain a constant electromagnetic force under battery voltage fluctuations, preventing insufficient driving force due to voltage drops.

[0106] Embedded programming parameter mapping table (LUTSpecification) Table S2 defines the control parameters at the critical temperature nodes. In actual programming, linear interpolation is usually used to calculate the parameters corresponding to the temperature between two nodes, or interval step control is used.

[0107] Table S2, Control Parameters at Key Temperature Nodes

[0108] Note: The PWM reference value assumes a timer period (ARR) of 1000 counts.

[0109] In conjunction with the above embodiments 1-4, the following is further disclosed: First, in a low-temperature environment of -20℃, it demonstrated excellent start-up reliability and response speed; the valve successfully improved the start-up rate and eliminated the "stuck" or "partially open" faults common in traditional drive solutions; at the same time, the total time from issuing the opening command to the valve being fully opened (including the preheating process) was strictly controlled to meet the stringent requirements of most industrial and automotive applications for rapid response.

[0110] Secondly, in terms of thermal safety, it demonstrates excellent energy management capabilities; throughout the entire high-dynamic startup process, the temperature rise inside the coil is always controlled within a safe range, and there is no risk of overheating. This result verifies the effectiveness of the energy management strategy of this invention from a physical perspective, ensuring the stability of the equipment under extreme operating conditions for a long time.

[0111] Finally, this embodiment powerfully demonstrates the advanced nature and practical value of this technical approach; the facts show that combining the low-resistance, high-speed characteristics of SiC devices with the segmented frequency conversion drive algorithm can perfectly balance the starting torque and heat loss, and is an efficient and reliable technical solution to the problem of low-temperature cold start of solenoid valves.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A SiC-based method for low-temperature cold-start variable frequency drive control of fuel cell solenoid valves, characterized in that, Includes the following steps: S1. Environmental perception and initial state establishment: After the system is powered on, the ambient temperature of the solenoid valve is collected, and the SiC drive bridge arm is self-checked to establish the initial safe state. S2. Intelligent Strategy Judgment and Mode Diversion: The operating condition is determined based on the collected ambient temperature. If the ambient temperature is greater than 0℃, the conventional PID control mode is entered, and the standard PWM drive strategy is used to stabilize the current and control energy consumption. If the ambient temperature is less than or equal to 0℃, the low temperature cold start frequency conversion drive mode is activated, and subsequent steps S3 to S5 are executed in sequence. S3, High-frequency micro-vibration preheating stage: Drive SiCMOSFET to output a high-frequency PWM signal of 20kHz-50kHz, control the PWM duty cycle to keep the average current of the coil in a subthreshold state, and generate an electromagnetic force less than the spring preload force, driving the valve core to generate micron-level high-frequency vibration in place. At the same time, the eddy current effect of the high-frequency alternating magnetic field and the Joule heat of the coil are used to preheat the valve core, reduce viscous resistance and break up micro ice crystals. S4, Instantaneous High Current Impact Stage: After the preheating stage, the driving frequency is switched from high frequency to low frequency, and an overdrive signal with a 100% duty cycle is applied. Utilizing the low internal resistance characteristics of SiC devices, the coil current rapidly rises to the peak value with a high di / dt slope, generating an explosive electromagnetic attraction force to overcome the residual resistance and pull the valve core open. S5, Closed-loop maintenance and dynamic correction stage: After the valve core is opened, the valve core status is confirmed by monitoring the characteristic changes of the coil current waveform. After confirming that it is open, the PWM duty cycle is reduced so that the current drops back to the maintenance current level. If no opening characteristic is detected, the enhanced retry mechanism is triggered, and stages S3 to S4 are re-executed. The preheating time is automatically extended and the impact pulse width is increased until the valve is successfully opened or the maximum number of safe retry attempts is reached.

2. The control method according to claim 1, characterized in that, The duration of the high-frequency micro-vibration preheating stage is an adaptive parameter that is dynamically adjusted according to the ambient temperature. When the ambient temperature is -10℃, the preheating time is 100ms, and when the ambient temperature is -30℃, the preheating time is 300ms.

3. The low-temperature cold start variable frequency drive control method for fuel cell solenoid valves based on SiC according to claim 1, characterized in that, The high-frequency micro-vibration preheating stage also includes preheating energy management, which uses an energy integral constraint model to control the input energy in a closed loop, satisfying the following: ; in, This is the effective value of the coil current. For coil resistance, This refers to the power loss due to eddy currents in the valve core. This is the maximum allowed cumulative thermal energy threshold for the coil.

4. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control method according to claim 1, characterized in that, The PWM duty cycle function is a piecewise frequency converter control law that satisfies: ; In the formula, The preheating flutter frequency is set to 20kHz-50kHz; A is the flutter amplitude coefficient. The DC bias is applied so that the average value of the combined electromagnetic force is less than the spring preload. To achieve the desired duty cycle, a value of 100% is used. To maintain the duty cycle, it is used to stabilize the current at the maintenance current level; For the warm-up time, To impact duration.

5. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control method according to claim 1, characterized in that, It also includes an adaptive variable parameter control step, which obtains the corresponding control parameters according to the real-time collected ambient temperature through a preset lookup table method. The lookup table method stores the PWM reference value, jitter frequency, and jitter superposition amplitude corresponding to different temperature nodes. At the same time, it performs linear compensation based on the battery voltage to adjust the actual output PWM duty cycle.

6. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control method according to claim 5, characterized in that, The temperature nodes for the table lookup method include -40℃, -20℃, 0℃, and 25℃, and the corresponding control parameters are as follows: At -40℃, the PWM reference value is 85%, the chatter frequency is 1000Hz, and the chatter superposition amplitude is 30%. At -20℃, the PWM reference value is 70%, the chatter frequency is 800Hz, and the chatter superposition amplitude is 20%. At 0℃, the PWM reference value is 50%, the dither frequency is 400Hz, and the dither superposition amplitude is 10%. At 25℃, the PWM reference value is 35%, the jitter frequency is 200Hz, and the jitter superposition amplitude is 5%.

7. A SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control system, characterized in that, include: The environmental sensing unit is used to collect the ambient temperature where the solenoid valve is located and to perform fault self-checks on the SiC drive bridge arm. The working condition determination unit is connected to the environmental sensing unit and is used to determine the current working condition based on the collected ambient temperature. If the ambient temperature is greater than 0℃, the control enters the normal PID control mode; if the ambient temperature is less than or equal to 0℃, the low temperature cold start frequency conversion drive mode is activated. The SiC power drive unit is used to output a PWM drive signal to the solenoid valve coil according to the control signal. The frequency conversion control unit is connected to the operating condition determination unit and the SiC power drive unit respectively, and is used to sequentially execute the control of the high-frequency micro-vibration preheating, instantaneous strong current impact, closed-loop maintenance and dynamic correction stages in the low temperature cold start mode. The current sampling unit, connected to the frequency conversion control unit, is used to collect coil current in real time and provide feedback signals for closed-loop control and valve core status monitoring.

8. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control system according to claim 7, characterized in that, The SiC power drive unit has an H-bridge topology, including four SiC MOSFET switches. The solenoid valve coil is connected between the midpoints of the two bridge arms. The H-bridge topology supports bidirectional current drive, enabling bidirectional flutter and active demagnetization control.

9. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control system according to claim 7, characterized in that, The frequency converter control unit also includes an adaptive lookup table module, which is used to obtain the corresponding control parameters by looking up a preset parameter table according to the real-time ambient temperature, and to compensate according to the battery voltage to adjust the output PWM signal parameters.

10. The SiC-based fuel cell solenoid valve low-temperature cold start variable frequency drive control system according to claim 7, characterized in that, It also includes a thermal safety control unit, which is used to integrally control the input energy during the preheating stage, limit the accumulated heat energy to not exceed the maximum safety threshold of the coil, and prevent the coil from overheating and burning out.

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