Control strategy using brake resistor

Abstract

The invention relates to the technical field of electric drive control, in particular to a control strategy utilizing a brake resistor, which comprises the steps of monitoring an electric drive vehicle control system, judging a working mode of the electric drive vehicle control system, dynamically scheduling a power path according to the working mode and optimizing brake resistor control. In the loading working mode, a dynamic prediction model including engine power output optimization control and brake resistor access optimization control which are built in a calculation controller is constructed; the dynamic prediction model is solved through an optimization algorithm, an optimal accelerator control sequence in a future control time domain and an optimal brake resistor control sequence in the future control time domain are obtained respectively, rolling optimization control is conducted, and collaborative optimization control over the engine accelerator and brake resistor access mode is achieved. And the stability of the bus voltage in the loading mode and the response speed and robustness of the system to the dynamic load are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric drive control, in particular to a control strategy utilizing a braking resistor. Background Art

[0002] Electric-powered special-equipment vehicles experience significant power fluctuations and voltage instability during towing, braking, and parking operations. Due to the unique operating conditions of these vehicles, batteries cannot be relied upon for energy management. Traditional systems struggle to coordinate energy distribution with voltage stability requirements, leading to significant bus voltage fluctuations during operation and compromising system stability.

[0003] Prior art energy management for electric vehicles in parked and mounted mode typically employs rule-based or traditional PID control strategies. These methods generally suffer from poor dynamic response performance when dealing with drastic fluctuations in load power demand and engine response lag. When load power demand suddenly increases, the engine's inherent lag prevents it from instantly delivering sufficient power, potentially leading to a significant drop in bus voltage or even undervoltage. Conversely, when the load decreases suddenly, the engine's output power is difficult to absorb quickly, potentially causing a sharp increase in bus voltage. Furthermore, traditional closed-loop voltage control (such as PID) often lags in regulating pulsed, intermittent high-power surges, making it difficult to effectively smooth out severe voltage fluctuations. Furthermore, to handle peak demand, the engine often needs to operate at a higher average power point. During load intervals, excess energy is dissipated by braking resistors, resulting in wasted energy and low overall energy efficiency.

[0004] Therefore, there is an urgent need for an advanced control strategy that can actively and efficiently smooth bus voltage fluctuations and coordinately optimize engine and brake resistor control to meet the dynamic power requirements of the superstructure while taking into account energy efficiency. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, the present invention aims to provide a control strategy using a brake resistor, which monitors the system status in real time, dynamically schedules the power path and optimizes the brake resistor control to actively smooth out voltage fluctuations and improve energy utilization efficiency.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a control strategy utilizing a brake resistor, comprising: monitoring an electric vehicle control system, controlling the on / off power supply to a drive motor, an upper assembly box, and a brake resistor via a computational controller, determining an operating mode of the electric vehicle control system, dynamically scheduling a power path based on the operating mode, and optimizing brake resistor control; The working modes include traction drive working mode, braking working mode and upper loading working mode; In the bodywork working mode, a dynamic prediction model is constructed, wherein the dynamic prediction model includes an engine power output optimization control model and a brake resistor access optimization control model built into the calculation controller; The engine power output is optimized and controlled through the engine power output optimization control model, and the brake resistor access is optimized and controlled through the brake resistor access optimization control model; The above dynamic prediction model is solved by the optimization algorithm to obtain the optimal throttle control sequence in the future control time domain and the optimal brake resistance control sequence in the future control time domain, respectively, and perform rolling optimization control.

[0007] The present invention is further configured as follows: the engine power output optimization control model takes the engine throttle opening as input and outputs the predicted busbar upstream power supply, and the mathematical expression can be: ; Where, Supply power to the predicted busbar load, is the reference value of the upper body power requirement, is the throttle control increment, , is the weight matrix, For the prediction time domain, is the control time domain, k is the control period; After solving the engine power output optimization control model to obtain the optimal throttle control sequence, only the first control variable is applied to the engine, and rolling optimization is performed in the next control cycle.

[0008] Objective function The aim is to minimize the deviation between the predicted power supplied by the upper equipment and the actual power demand, while taking into account the smoothness of throttle changes and avoiding overly frequent or drastic adjustments. The optimization solution must meet constraints such as engine throttle opening, speed and its change rate, generator output power capacity, and bus voltage safety range.

[0009] The present invention is further configured as follows: the braking resistor is connected to the optimization control model to control the braking resistor to connect the control signal is the input, the output is the predicted bus voltage, the access control signal is the duty cycle, taking into account the bus capacitance, line impedance, brake resistor value, switching device (IGBT, MOSFET) characteristics, etc., the output is the predicted bus voltage, which can be expressed mathematically as follows: ; Where, To predict the bus voltage, is the bus reference voltage, is the braking resistor control signal increment, To predict the power consumption of the braking resistor, 、 、 is the weight matrix, For the prediction time domain, To control the time domain, For the control cycle.

[0010] After the calculation controller solves and obtains the optimal brake resistor control sequence, only the first control variable is applied to the brake resistor switch calculation controller, and rolling optimization is performed in the next control cycle.

[0011] The present invention is further configured such that if the braking resistor is controlled by PWM, the PWM duty cycle is calculated by a calculation controller, the duty cycle is input into a PWM pulse generator, and a corresponding PWM control wave is generated and output to the IGBT transistor, thereby controlling the connection of the braking resistor and regulating the voltage and power. The duty cycle is calculated as follows: ; in, is the duty cycle, Indicates the equivalent power of the braking resistor, Indicates the impedance of the braking resistor; Indicates the bus voltage.

[0012] The present invention is further configured such that the duty cycle can be calculated by monitoring the deviation of the bus voltage, specifically: ; in, To predict the bus voltage, is the reference voltage of the bus; when ＞ , indicating that there is excess power and a braking resistor needs to be connected for regulation and control. for: ; ; in, is the duty cycle, is the total bus current.

[0013] When the duty cycle , it means that the engine power is insufficient and the power output needs to be increased; if the duty cycle , it means that the braking resistor cannot completely consume the excess power and the engine needs to reduce power output.

[0014] The present invention is further configured such that: the engine power output optimization control model and the brake resistor access optimization control model interact to achieve coordinated control; The engine power output optimization control model uses the bus supply power predicted in each optimization cycle as a known input and passes it to the brake resistor access optimization control model to improve the accuracy of its bus voltage prediction; When the engine power output optimization control model performs throttle optimization, it can stabilize the bus voltage within a wider desired range as one of the soft constraints or targets. Connecting the optimization control model through the brake resistor is responsible for stabilizing the bus voltage more accurately near the target value and quickly responding to power differences that the engine power output optimization control architecture cannot compensate for in time.

[0015] The present invention is further configured such that: the calculation controller has built-in weight dynamic adjustment logic.

[0016] The present invention is further configured such that: the computing controller has a built-in backup control strategy; when the engine power output optimization control model or the brake resistor access optimization control model fails to find a feasible solution within a preset time, or the predicted control strategy exceeds a safety threshold, the computing controller switches the control strategy to the backup control strategy and sends an alarm to the upper-level monitoring system.

[0017] The present invention is further configured as follows: in the traction drive working mode, the upper assembly switch box and the braking resistor are in a disconnected state, and the drive motor is powered and operates.

[0018] If the voltage sensor detects abnormal voltage fluctuations and the drive motor speed is abnormal, the calculation controller outputs a control signal to turn on the brake resistor switch brake, connecting the brake resistor to the circuit to consume excess energy and avoid bus overload.

[0019] The present invention is further configured as follows: in the braking working mode, a control signal is output to turn on the braking resistor switch calculation controller, and the braking resistor is connected to consume the braking energy.

[0020] In summary, the beneficial effects of the above technical solution of the present invention are as follows: 1. Significantly improves bus voltage stability in parked bodywork mode: Through collaborative optimization control based on model predictive control, this invention can more proactively and accurately predict and respond to the dynamic power demand of the bodywork load and the engine's response lag, making brake resistor adjustment more proactive and refined. This reduces bus voltage fluctuations to a smaller range, providing higher-quality power to the bodywork equipment.

[0021] 2. Improved system response speed and robustness to dynamic loads: The predictive capabilities of model predictive control enable the system to proactively intervene in impending power imbalances, optimizing the coordination between engine power output and brake resistors. This accelerates the system's response to load changes and enhances control robustness under parameter changes or unmodeled dynamic influences. By real-time monitoring of key parameters such as drive motor speed and voltage, brake resistors can be promptly connected to dissipate excess energy in the event of motor anomalies or reduced load power, effectively preventing system overloads and bus voltage anomalies.

[0022] 3. Enhanced intelligence and adaptability of the control strategy: This invention utilizes a predictive control framework based on an optimized control model for engine power output and a brake resistor access optimization model. This framework, combined with real-time data to update model states, enables the control strategy to possess certain self-learning and adaptive capabilities, enabling it to better adapt to changing operating conditions and system characteristics.

[0023] 4. The system control is highly integrated and scalable: Real-time communication and signal interaction are achieved between components via the CAN bus, making it easy to expand to different vehicle models or equipment structures, and possessing good engineering practicality and versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is a circuit diagram of the control strategy for power and voltage regulation using a braking resistor according to the present invention.

[0026] Figure 2 This is a structural diagram of the control strategy for power and voltage regulation using a braking resistor according to the present invention.

[0027] Figure 3 This is a control logic flow chart of a control strategy calculation controller for power and voltage regulation using a braking resistor according to the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, other similar embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of the present invention.

[0029] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0030] Example 1 like Figure 1-Figure 3 FIG. 1 shows a preferred embodiment of the present invention, a control strategy utilizing a brake resistor, including: monitoring an electric vehicle control system, controlling the power supply to a drive motor, a motor-mounted switch box, and a brake resistor via a computing controller, determining an operating mode of the electric vehicle control system, dynamically scheduling a power path based on the operating mode, and optimizing brake resistor control; The working modes include a traction drive working mode, a braking working mode and a bodywork working mode.

[0031] This embodiment implements the control strategy of utilizing a brake resistor as described in the present invention based on a control system. The control system mainly includes an engine, an AC generator, an AC / DC controlled rectifier, a DC / AC motor drive inverter, a drive motor, a high-voltage distribution box for a bodywork, a bodywork (vehicle load), a brake resistor switch calculation controller, a brake resistor, an engine speed sensor, a bodywork work demand signal, a voltage sensor, a bodywork current sensor, a drive motor speed sensor, and a calculation controller. The structural circuit diagram and structural diagram of the control system are shown in FIG. Figure 1-Figure 2 shown.

[0032] The calculation controller outputs a control signal to cut off the upper body high-voltage distribution box and the brake resistor switch brake, and the upper body and the brake resistor are in an open-circuit state. At the same time, the control signal connects the DC / AC drive inverter to the DC bus, and the engine drives the AC generator through a mechanical connection. The output AC power is converted into DC power through the AC / DC controlled rectifier, and then converted into AC power again through the DC / AC motor drive inverter to provide power for the drive motor.

[0033] In traction drive mode, if the bodywork demand signal is not sent to the computer controller, the computer controller outputs a control signal to disconnect the bodywork high-voltage distribution box and the brake resistor switch computer controller, connecting the DC / AC motor drive inverter and supplying bus current to the drive motor for driving. The engine output power is adjusted in real time based on the driver's accelerator pedal position.

[0034] Under this working condition, the drive motor speed sensor detects the drive motor speed signal, inputs it into the calculation controller, and monitors the working status of the drive motor in real time. At the same time, the voltage sensor detects the bus voltage data. When both the drive motor speed and the bus voltage show abnormal changes, the calculation controller determines that the drive motor has failed and cannot work normally, and outputs a control signal to the brake resistor switch controller and the engine, connecting the brake resistor to the circuit to consume excess energy and reduce the power output of the engine to ensure the safety of the main circuit operation and avoid bus overload.

[0035] When the drive motor transitions to generating mode and the drive motor speed sensor detects a rapid decrease in speed, it inputs this speed data into the calculation controller, determining that the motor is in braking mode. The braking energy generated by the motor is converted to DC power by the DC / AC motor drive inverter, which then outputs a control signal to turn on the brake resistor switch calculation controller, dissipating the braking energy through the brake resistor.

[0036] In the bodywork mode, the vehicle is stationary while the bodywork equipment is operating. Upon receiving the bodywork operation request signal, the computation controller disconnects the drive motor inverter and connects the bodywork high-voltage distribution box, allowing the engine to drive the generator to power the bodywork.

[0037] like Figure 3 As shown, in the upper installation working mode, a dynamic prediction model is constructed, which includes an engine power output optimization control model and a brake resistor access optimization control model built into the calculation controller; The engine power output is optimized and controlled through the engine power output optimization control model, and the brake resistor access is optimized and controlled through the brake resistor access optimization control model; The above dynamic prediction model is solved by the optimization algorithm to obtain the optimal throttle control sequence in the future control time domain and the optimal brake resistance control sequence in the future control time domain, respectively, and perform rolling optimization control.

[0038] The optimization control of the engine power output by the engine power output optimization control model specifically includes the following steps: S11: Preset the mathematical model parameters for the power flow from the engine to the upstream device in the calculation controller. Perform online or offline identification and calibration of the model parameters during initial operation or periodically to improve model accuracy. The model uses the engine throttle position as input and predicts the power supplied by the busbar to the upstream device over a period of time, while also considering intermediate variables such as engine speed and generator efficiency. S12: The calculation controller collects the current engine speed from the engine speed sensor, the actual load current from the load current sensor, and the current bus voltage from the voltage sensor in real time via the CAN bus. Combining the load operation demand signal with historical data, the load power demand prediction module within the calculation controller predicts the load power demand within the future prediction time domain. S13: In each control cycle, the calculation controller constructs an optimization problem based on the current system state and the predicted power demand of the upper equipment, with the objective function of minimizing the deviation between the predicted upper equipment supply power and the required power, while taking into account the smoothness of throttle control. The optimization problem is constructed with the engine throttle opening limit, engine speed limit, engine speed change rate constraint, and the expected stable range of the bus voltage as constraints. The mathematical expression can be: ; Where, Supply power to the predicted busbar load, is the reference value of the upper body power requirement, is the throttle control increment, , is the weight matrix, For the prediction time domain, To control the time domain, To control the cycle; S14: The computing controller uses an embedded efficient optimization algorithm to solve the engine power output optimization control model to obtain an optimal throttle control sequence in a future control time domain; The optimization algorithm can be quadratic programming, interior point method, etc. S15: The computation controller sends only the first element of the optimal throttle sequence to the engine controller via the CAN bus as the current throttle control command. At the next control cycle, the system state is re-collected, the prediction is updated, and steps S13 through S15 are repeated, forming a rolling optimization process.

[0039] The optimization control of the braking resistor access through the braking resistor access optimization control model specifically includes the following steps: S21: Preset the mathematical model parameters of the upper and brake resistor circuits in the calculation controller, including busbar equivalent capacitance, brake resistor resistance, line parameters, etc. The brake resistor is connected to the optimization control model to control the brake resistor connection signal. u 2 is the input, and the output is the predicted bus voltage; S22: The calculation controller collects the current bus voltage fed back by the voltage sensor, the upper body current fed back by the upper body current sensor, and the current flowing through the brake resistor in real time through the CAN bus; S23: In each control cycle, the objective function is to minimize the deviation between the predicted bus voltage and the target reference voltage, minimize the change in the brake resistor control signal, and minimize the instantaneous power dissipation of the brake resistor. The absolute safety upper and lower limits of the bus voltage, the range of the brake resistor control signal, and the maximum allowable power dissipation of the brake resistor are used as constraints. An optimization problem is constructed in the computational controller.

[0040] The mathematical expression can be: ; Where, To predict the bus voltage, is the bus reference voltage, is the braking resistor control signal increment, To predict the power consumption of the braking resistor, 、 、 is the weight matrix, For the prediction time domain, To control the time domain, k For the control cycle.

[0041] S24: The computing controller uses an efficient optimization algorithm suitable for embedded systems to solve and obtain the optimal braking resistor control sequence in the future control time domain.

[0042] S25: The calculation controller sends the first element of the optimal control sequence to the brake resistor switch controller. This controller precisely switches on the brake resistor by controlling the on and off of power electronic switches such as IGBTs and MOSFETs. At the next control cycle, steps S22 through S25 are repeated.

[0043] The access control signal u 2 is the duty cycle.

[0044] If the braking resistor is controlled by PWM, the PWM duty cycle is calculated by the calculation controller and input into the PWM pulse generator, which generates the corresponding PWM control wave and outputs it to the IGBT transistor, thereby controlling the connection of the braking resistor and regulating the voltage and power. The duty cycle is calculated as follows: ; in, is the duty cycle, Indicates the equivalent power of the braking resistor, Indicates the impedance of the braking resistor; Indicates the bus voltage.

[0045] The engine power output optimization control model and the brake resistor access optimization control model interact to achieve collaborative control; specifically including: The engine power output optimization control model and the brake resistor access optimization control model share prediction information. For example, the engine power output optimization control model uses the bus supply power predicted in each optimization cycle as a known input and passes it to the brake resistor access optimization control model to improve the accuracy of its bus voltage prediction.

[0046] Target coordinated compensation, for example, when the engine power output optimization control model performs throttle optimization, the bus voltage can be stabilized within a wider desired range as one of the soft constraints or targets. The optimization control model connected through the brake resistor is responsible for stabilizing the bus voltage more accurately near the target value and quickly responding to power differences that the engine power output optimization control architecture cannot compensate in time.

[0047] In some embodiments, the computation controller includes built-in dynamic weight adjustment logic. For example, when a large power step is detected in the load, the weight of the voltage tracking error in the brake resistor optimization control architecture can be temporarily increased, and the weight of the throttle smoothness in the engine power output optimization control architecture can be increased to prioritize voltage stability and smooth engine operation.

[0048] In some embodiments, the computing controller may also have a built-in backup control strategy; when the engine power output optimization control model or the brake resistor access optimization control model fails to find a feasible solution within a preset time, or the predicted control strategy exceeds a safety threshold, the computing controller will switch the control strategy to the backup control strategy and alarm the upper-level monitoring system.

[0049] Example 2 A control strategy using a braking resistor differs from the embodiment only in that a method other than PWM is used to control the braking resistor, and the duty cycle can be calculated by monitoring the deviation of the bus voltage, specifically: ; in, To predict the bus voltage, is the reference voltage of the bus; when ＞ , indicating that there is excess power and a braking resistor needs to be connected for regulation and control. The excess power is: ; ; in, is the duty cycle, is the total bus current.

[0050] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A control strategy using a braking resistor, characterized in that: include: Monitor the electric vehicle control system, control the power supply to the drive motor, upper generator box and brake resistor through the calculation controller, determine the operating mode of the electric vehicle control system, dynamically schedule the power path and optimize the brake resistor control according to the operating mode; The working modes include traction drive working mode, braking working mode and upper loading working mode; In the bodywork working mode, a dynamic prediction model is constructed, wherein the dynamic prediction model includes an engine power output optimization control model and a brake resistor access optimization control model built into the calculation controller; The engine power output is optimized and controlled through the engine power output optimization control model, and the brake resistor access is optimized and controlled through the brake resistor access optimization control model; The above dynamic prediction model is solved by the optimization algorithm to obtain the optimal throttle control sequence in the future control time domain and the optimal brake resistance control sequence in the future control time domain, respectively, and perform rolling optimization control.

2. A control strategy using a braking resistor according to claim 1, characterized in that: The engine power output optimization control model takes the engine throttle opening as input and outputs the predicted busbar mounted power. The mathematical expression is: Where, Supply power to the predicted busbar load, is the reference value of the upper body power requirement, is the throttle control increment, is the weight matrix, For the prediction time domain, To control the time domain, To control the cycle; After solving the engine power output optimization control model to obtain the optimal throttle control sequence, only the first control variable is applied to the engine, and rolling optimization is performed in the next control cycle.

3. A control strategy using a braking resistor according to claim 2, characterized in that: The braking resistor is connected to the optimization control model to control the braking resistor's connection signal As input, the access control signal is the duty cycle; the output is the predicted bus voltage, which is expressed mathematically as follows: Where, To predict the bus voltage, is the bus reference voltage, is the braking resistor control signal increment, To predict the power consumption of the braking resistor, 、 、 is the weight matrix, For the prediction time domain, To control the time domain, To control the cycle; After the calculation controller solves and obtains the optimal brake resistor control sequence, only the first control variable is applied to the brake resistor switch calculation controller, and rolling optimization is performed in the next control cycle.

4. A control strategy using a braking resistor according to claim 3, characterized in that: If the braking resistor is controlled by PWM, the PWM duty cycle is calculated by the calculation controller, and the duty cycle is input into the PWM pulse generator to generate the corresponding PWM control wave which is output to the switching device, thereby controlling the access of the braking resistor and adjusting the voltage and power.

5. The control strategy using a braking resistor according to claim 3, characterized in that: The duty cycle can be calculated by monitoring the deviation of the bus voltage, specifically: in, To predict the bus voltage, is the reference voltage of the bus; when > , indicating that there is excess power and a braking resistor needs to be connected for regulation and control. for: in, is the total current of the busbar, is the duty cycle.

6. A control strategy using a braking resistor according to claim 3, characterized in that: The engine power output optimization control model and the brake resistor access optimization control model interact to achieve coordinated control; The engine power output optimization control model uses the bus supply power predicted in each optimization cycle as a known input and passes it to the brake resistor access optimization control model to improve the accuracy of its bus voltage prediction; When the engine power output optimization control model performs throttle optimization, stabilizing the bus voltage within a certain desired range is used as one of the soft constraints or goals. The optimization control model connected through the brake resistor is responsible for stabilizing the bus voltage at the target value and quickly responding to power differences that the engine power output optimization control architecture cannot compensate for in time.

7. A control strategy using a braking resistor according to claim 6, characterized in that: The calculation controller has built-in weight dynamic adjustment logic.

8. The control strategy using a braking resistor according to claim 1, characterized in that: The computing controller has a built-in backup control strategy; when the engine power output optimization control model or the brake resistor access optimization control model fails to find a feasible solution within a preset time, or the predicted control strategy exceeds the safety threshold, the computing controller switches the control strategy to the backup control strategy and alerts the upper-level monitoring system.

9. The control strategy using a braking resistor according to claim 1, characterized in that: In the traction drive working mode, the upper generator box and the brake resistor are disconnected, and the drive motor is powered and running; If the voltage sensor detects abnormal voltage fluctuations and the drive motor speed is abnormal, the calculation controller outputs a control signal to turn on the brake resistor switch brake, connecting the brake resistor to the circuit to consume excess energy and avoid bus overload.

10. The control strategy using a braking resistor according to claim 1, characterized in that: In the braking working mode, a control signal is output to turn on the braking resistor switch calculation controller, and the braking resistor is connected to consume braking energy.

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