A new energy vehicle power supply assembly system based on waterproof battery

Abstract

The present invention relates to the technical field of braking kinetic energy recovery, and in particular to a power supply assembly system for a new energy vehicle based on a waterproof battery, which includes a detection recovery unit, a motor control unit, a DC-DC conversion unit and a balancing control unit. The present invention monitors the brake pedal and vehicle speed signals in real time through the detection recovery unit, calculates the braking energy value, and triggers subsequent work. Based on this, the motor control unit adopts a vector control algorithm to decompose the current through coordinate transformation, dynamically adjusts the current reference value according to the braking energy value and the battery charging state, so that the motor works at the best power generation efficiency point, and provides power input for the DC-DC conversion unit. After receiving the power, the DC-DC conversion unit adjusts the output through a voltage and current dual closed-loop control strategy. The balancing control unit performs balancing control based on the remaining battery power to ensure the performance of the battery pack. The units work together to improve the efficiency of braking kinetic energy recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of kinetic energy recovery, and in particular to a new energy vehicle power supply assembly system based on a waterproof battery. Background Art

[0002] Kinetic energy recovery is an important technology. With the improvement of environmental awareness and increasingly stringent emission restrictions on traditional fuel vehicles, the new energy vehicle market has developed rapidly. In the field of new energy vehicle technology, the application of waterproof batteries has become more and more extensive. Their safety and stability are crucial to the overall performance of the vehicle. However, the traditional new energy vehicle power supply system based on waterproof batteries has many problems in braking kinetic energy recovery.

[0003] Among them, when recovering braking kinetic energy, traditional systems are often unable to accurately detect braking conditions, resulting in insufficient braking energy recovery. In urban traffic with frequent starts and stops or long downhill sections, braking is frequent, but due to insufficient detection accuracy, a large amount of braking energy is wasted and cannot be effectively converted into electrical energy for storage. Moreover, even if some braking energy can be recovered, the motor control lacks precision and cannot optimize the direct-axis and quadrature-axis current reference values ​​according to the battery charging state and the amount of braking energy, making it impossible for the motor to operate at the optimal power generation efficiency point, reducing the energy recovery efficiency. In order to solve this technical problem, we provide a new energy vehicle power supply assembly system based on a waterproof battery. Summary of the invention

[0004] The purpose of the present invention is to provide a new energy vehicle power supply assembly system based on a waterproof battery to solve the problems raised in the above background technology.

[0005] To achieve the above purpose, a new energy vehicle power supply assembly system based on a waterproof battery is provided, including a detection recovery unit, a motor control unit, a DC-DC conversion unit and a balancing control unit;

[0006] The detection and recovery unit includes a braking detection module and an energy recovery module. The braking detection module monitors the brake pedal signal and the vehicle speed signal of the vehicle in real time. When the brake pedal is stepped on and the vehicle speed is greater than a set threshold, it is determined that the vehicle enters a braking condition and the energy recovery module is triggered to work. The energy recovery module calculates the vehicle braking energy value according to the brake pedal travel depth and the vehicle speed change rate;

[0007] The motor control unit controls the energy recovery motor using a vector control algorithm based on the maximum energy recovery principle, decomposes the three-phase AC current into a direct-axis current and a quadrature-axis current through coordinate transformation, and dynamically adjusts the direct-axis current and the quadrature-axis current reference values ​​according to the braking energy value and the battery charging state, so that the motor works at the best power generation efficiency point, and the power output at the best power generation efficiency point is used as the input basis of the DC-DC converter;

[0008] The DC-DC conversion unit receives the electric energy output of the motor control unit at the optimal power generation efficiency point, and adopts a voltage and current double closed-loop control strategy, wherein the outer voltage loop sets the target charging voltage according to the battery characteristics and compares it with the actual voltage to obtain the current loop reference current through the PI controller, and the inner current loop adjusts the switch device control pulse width accordingly;

[0009] The balancing control unit sets a battery remaining power difference threshold value based on the battery remaining power, and uses a balancing strategy to perform balancing control on the battery pack until the remaining power difference value of each single battery is within a preset range.

[0010] As a further improvement of the technical solution, the motor control unit includes a vector control module, and the coordinate transformation in the vector control module uses a combination of Clarke transformation and Park transformation to decompose the direct-axis current and the quadrature-axis current, as follows:

[0011] Assume that the three-phase currents in the three-phase stationary coordinate system are i a 、i b 、i c , and i a +i b +i c =0, change i a 、i b 、i c The three-phase current is converted to the two-phase stationary coordinate system by the Clarke transformation formula. α 、i β ;

[0012] Then, Park transformation is performed, assuming that the direct axis current in the two-phase rotating coordinate system is i d , the quadrature axis current is i q , the current i in the two-phase stationary coordinate system α 、i β , and the electrical angle θ of the rotating coordinate system are transformed by the Park transformation formula to decompose the three-phase AC current in the three-phase stationary coordinate system into the direct axis current i in the two-phase rotating coordinate system d and the quadrature axis current i q .

[0013] As a further improvement of the technical solution, the motor control unit includes a battery adjustment module, and the method for the battery adjustment module to dynamically adjust the direct-axis current and quadrature-axis current reference values ​​according to the braking energy value and the battery charging state is as follows:

[0014] A mapping relationship between braking energy and a direct-axis current reference value adjustment coefficient is established based on historical data, and based on this relationship, the direct-axis current reference value adjustment coefficient corresponding to different braking energy values ​​and the quadrature-axis current reference value adjustment coefficient under different battery states are determined, wherein the battery state is the battery charge state, indicating the percentage of the battery's current charge level relative to its full capacity;

[0015] During the operation of the vehicle, the detection and recovery unit calculates the braking energy value in real time and transmits it to the battery adjustment module. The battery adjustment module extracts the corresponding direct-axis current reference value adjustment coefficient according to the received braking energy value, and continuously monitors the battery charging state and provides it to the battery adjustment module. The battery adjustment module extracts the corresponding quadrature-axis current reference value adjustment coefficient according to the charging state;

[0016] Set the original direct-axis current reference value and the quadrature-axis current reference value, and multiply the original direct-axis current reference value and the quadrature-axis current reference value by the corresponding adjustment coefficients to obtain the direct-axis current reference value i d * and the quadrature axis current reference value i q * .

[0017] As a further improvement of the technical solution, when the vector control module uses the vector control algorithm to control the energy recovery motor, the control of the direct-axis current and the quadrature-axis current adopts a feedforward compensation control strategy, which is as follows:

[0018] The rotary transformer is used to obtain the position and speed of the motor rotor and the winding inductance of the motor, and the back electromotive force e is calculated by the formula d 、e q , and e d 、e q As feedforward compensation items for the direct-axis current controller and the quadrature-axis current controller respectively;

[0019] Then e d 、e q The direct axis current reference value and the quadrature axis current reference value are added to the output obtained by the PI controller to obtain the direct axis voltage command u d and the quadrature axis voltage command u q Finally, u is converted to d and u q Converted into a switching signal for a three-phase inverter to control the input voltage of the motor.

[0020] As a further improvement of the technical solution, the space vector pulse width modulation method in the vector control module is as follows:

[0021] Given a direct-axis voltage command and a quadrature-axis voltage command in a two-phase rotating coordinate system, a voltage space vector is calculated, wherein the voltage space vector is represented by converting the three-phase voltage into a vector on a complex plane to represent the magnitude and phase of the voltage, and the position of the corresponding voltage space vector on the complex plane is determined;

[0022] The complex plane is divided into six sectors and numbered. The switching order of the switch state is determined according to the sector where the voltage space vector is located, and the action time of two adjacent basic voltage space vectors and the zero vector in each sector is calculated.

[0023] According to the action time and sector information, the switching sequence of the three-phase inverter switching devices is determined. The determined switching sequence is generated according to the set switching frequency through the control circuit to generate corresponding pulse signals, drive the switching devices in the three-phase inverter, and control the input voltage of the motor.

[0024] As a further improvement of the technical solution, the outer loop voltage loop PI controller parameters are determined according to the capacity and internal resistance value of the new energy vehicle battery, and the parameters are proportional coefficients and integral coefficients. Different battery characteristics and corresponding PI controller parameters are constructed into a database to form a three-dimensional mapping relationship between battery capacity, internal resistance and PI controller proportional coefficients and integral coefficients, and the battery characteristics include battery capacity and internal resistance value;

[0025] The DC-DC conversion unit monitors the capacity and internal resistance of the battery in real time through sensors, and searches for the corresponding PI controller parameter K in the pre-established three-dimensional mapping relationship. p and K i Then, K p and K i It is applied to the PI controller of the outer voltage loop to control the voltage loop.

[0026] As a further improvement of the technical solution, the method for controlling the voltage loop is as follows:

[0027] By comparing the difference between the target charging voltage of the outer voltage loop and the actual battery voltage, the voltage error is obtained, and the proportional term output is calculated according to the proportional coefficient;

[0028] For the integral term, the integral coefficient is substituted into the rectangular integration method for calculation, and the proportional term output and the integral term output are added to obtain the final output of the PI controller, and the final output of the PI controller is used to control the voltage loop.

[0029] As a further improvement of the technical solution, in the voltage-current dual closed-loop control strategy of the DC-DC conversion unit, the inner current loop adopts a hysteresis control algorithm when adjusting the switching device control pulse width, as follows:

[0030] The hysteresis width is set, and the hysteresis width is the range of current fluctuation allowed in the current control system, and the output current of the DC-DC conversion unit is collected in real time, and the output current is calculated with the current reference value to obtain the difference;

[0031] The switching device is controlled according to the situation that the difference is within the hysteresis band width, and the output current is adjusted.

[0032] As a further improvement of the technical solution, the method for the balancing control unit to perform balancing control on the battery pack using a balancing strategy is as follows:

[0033] The remaining power of each single cell in the waterproof battery pack is obtained through the sensor, and the difference between the maximum and minimum remaining power of the single cells in the battery pack is calculated, and the difference is compared with the preset battery remaining power difference threshold, and it is determined whether equalization control is needed according to the result;

[0034] Assume that the normal operating voltage range of the battery is [V min , V max ], when it is detected that balancing is required, for a single cell with a charge greater than 70% of the total battery capacity, the DC-DC converter works as a step-down circuit, that is, converting the high voltage of the single cell into an intermediate voltage, the high voltage being at [70%V max , V max ], the intermediate voltage is [30%V max , 70% V max ];

[0035] For a single cell with a charge lower than 70% of the total battery capacity, the DC-DC converter works as a boost circuit, that is, boosting the low voltage to an intermediate voltage, where the low voltage is [V min , 30%V max ].

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In a new energy vehicle power supply assembly system based on a waterproof battery, a vector control algorithm is used in combination with Clarke transformation and Park transformation to achieve effective decomposition of three-phase AC current and precise control of direct-axis and quadrature-axis currents, so that the motor can operate at the optimal power generation efficiency point under different working conditions, thereby improving the efficiency of braking kinetic energy recovery. At the same time, the current reference value is dynamically adjusted based on the braking energy and the battery charging state, further optimizing the motor power generation performance. The application of the feedforward compensation control strategy effectively offsets the interference of back electromotive force, enhances the motor control accuracy and dynamic response capability, and improves the efficiency of energy recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is an overall block diagram of the present invention.

[0039] The meaning of each number in the figure is:

[0040] 1. Detection recovery unit; 11. Braking detection module; 12. Energy recovery module; 2. Motor control unit; 21. Vector control module; 22. Battery adjustment module; 3. DC-DC conversion unit; 4. Balance control unit. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The present invention provides a new energy vehicle power supply assembly system based on waterproof batteries, please refer to Figure 1 As shown, it includes a detection recovery unit 1, a motor control unit 2, a DC-DC conversion unit 3 and a balancing control unit 4;

[0043] The detection and recovery unit 1 includes a brake detection module 11 and an energy recovery module 12. The brake detection module 11 monitors the brake pedal signal and the vehicle speed signal of the vehicle in real time. When the brake pedal is stepped on and the vehicle speed is greater than a set threshold, it is determined that the vehicle enters a braking condition and the energy recovery module is triggered to work. The energy recovery module 12 calculates the vehicle braking energy value according to the brake pedal travel depth and the vehicle speed change rate;

[0044] The motor control unit 2 includes a vector control module 21. The vector control module 21 controls the energy recovery motor using a vector control algorithm based on the maximum energy recovery principle, and decomposes the three-phase AC current into a direct-axis current and a quadrature-axis current through coordinate transformation, as follows:

[0045] The mathematical model of the three-phase AC motor is a complex time-varying nonlinear model in the three-phase stationary coordinate system, and it is difficult to control it directly. However, after converting the three-phase stationary coordinate system to the two-phase rotating coordinate system through Clarke transformation and Park transformation, a relatively simple mathematical model can be obtained, which is convenient for controlling and analyzing the motor, as follows:

[0046] First, collect the three-phase current sensor to obtain the real-time value of the three-phase current i a 、i b 、i c , the Clarke transformation formula is as follows:

[0047]

[0048] Then calculate according to the above formula to obtain the current i in the two-phase stationary coordinate system α 、i β , and then the current i in the two-phase stationary coordinate system α 、i β The current i converted to the two-phase rotating coordinate system d 、i q , assuming that the electrical angle of the rotating coordinate system is θ, the electrical angle is determined by obtaining the rotor position information of the motor through the rotary transformer, then the Park transformation formula is as follows:

[0049] i d =i α cosθ+i β sinθ;i q =-i α sinθ+i β cosθ;

[0050] The complex three-phase AC motor model is simplified into a linear time-invariant model in a two-phase rotating coordinate system, which reduces the complexity of the control algorithm and makes the design and implementation of the controller easier. Through precise direct-axis current and quadrature-axis current control, the motor can operate near the optimal efficiency point under different working conditions.

[0051] The motor control unit 2 includes a battery adjustment module 22. The battery adjustment module 22 dynamically adjusts the direct-axis current and quadrature-axis current reference values ​​according to the braking energy value and the battery charging state, as follows:

[0052] Braking energy can vary greatly under different braking conditions. For example, the braking energy is larger during emergency braking, but smaller during slow braking. By constructing a mapping relationship between braking energy and the direct-axis current reference value adjustment coefficient, the direct-axis current can be reasonably adjusted according to the actual braking energy, thereby optimizing the motor's power generation efficiency and energy recovery effect. Similarly, based on the battery's charging characteristics and requirements, the quadrature-axis current reference value adjustment coefficient under different battery charging states can be determined.

[0053] During the operation of the vehicle, the detection recovery unit 1 calculates the braking energy value in real time and transmits it to the battery adjustment module 22. The battery adjustment module 22 extracts the corresponding direct axis current reference value adjustment coefficient K according to the received braking energy value. d , and continuously monitors the battery charging state and provides it to the battery adjustment module 22. The battery adjustment module 22 extracts the corresponding quadrature-axis current reference value adjustment coefficient K according to the charging state. q .

[0054] Set the original direct axis current reference value i d0 and the quadrature axis current reference value i q0 , then the adjusted direct-axis current reference value is id * =i d0 ×K d ;i q * =i q0 ×K q ; where K d , K q They are the direct-axis current reference value adjustment coefficient and the quadrature-axis current reference value adjustment coefficient respectively.

[0055] The battery regulation module 22 then controls the energy recovery motor based on these adjusted current reference values ​​using a vector control algorithm, decomposes the three-phase AC current into direct-axis current and quadrature-axis current through coordinate transformation, and adjusts the motor's operating state according to the new reference value, so that the motor operates at the optimal power generation efficiency point. Its electric energy output serves as the input basis of the DC-DC converter. Through precise current reference value adjustment, the motor's power generation and battery charging process are more stable.

[0056] When the vector control module 21 uses the vector control algorithm to control the energy recovery motor, the feedforward compensation control strategy is used to control the direct-axis current and the quadrature-axis current, as follows:

[0057] When the motor is running, the back EMF will interfere with the current control, especially when it is running at high speed or the load changes. The back EMF changes greatly. If it is not compensated, the output deviation of the current controller will increase, affecting the control accuracy and dynamic performance of the motor. Through feedforward compensation, the influence of the back EMF on the current control can be offset in advance, so that the current controller can track the current reference value more accurately, which can reduce the current error caused by the back EMF and improve the control accuracy of the motor. The details are as follows:

[0058] First, the rotary transformer is used to obtain the position and speed of the motor rotor and the winding inductance of the motor, and the back electromotive force is calculated by the formula. The expression of the back electromotive force in the two-phase rotating coordinate system is:

[0059]

[0060] Where L d , L q are the inductances of the direct axis and quadrature axis respectively, ω is the electrical angular velocity of the electrode, i d 、i q are the direct-axis and quadrature-axis currents, is the permanent magnet flux. In the current control loop, the calculated back electromotive force e d 、e q They serve as feedforward compensation items for the direct-axis current controller and the quadrature-axis current controller respectively.

[0061] For the direct-axis current controller, e d With the direct axis current reference value i d * The outputs obtained by the PI controller are added to form the direct axis voltage command u d .

[0062] For the quadrature-axis current controller, e q With the quadrature axis current reference value i q * The outputs obtained by the PI controller are added to form the quadrature axis voltage command u q , and then u is converted to d and u q It is converted into a switching signal of a three-phase inverter to control the input voltage of the motor, thereby achieving control of the direct-axis current and quadrature-axis current and compensating for the influence of back electromotive force.

[0063] Since the influence of back-EMF is compensated in advance, the current can track the reference value faster, thereby improving the dynamic response speed of the motor, helping to improve the stability of motor operation, reducing current fluctuations and torque pulsations caused by back-EMF interference, reducing motor vibration and noise, and extending the service life of the motor.

[0064] The space vector pulse width modulation method in the vector control module 21 is specifically as follows:

[0065] In motor control, especially for motor drive and energy recovery of new energy vehicles, it is necessary to accurately control the input voltage of the motor to adjust the torque and speed of the motor. Through space vector pulse width modulation technology, the voltage command in the two-phase rotating coordinate system can be converted into the switching signal of the three-phase inverter, thereby effectively controlling the three-phase input voltage of the motor and realizing decoupling control of the motor magnetic field and torque.

[0066] It is known that the direct axis voltage command u in the two-phase rotating coordinate system is d and the quadrature axis voltage command u q , using the voltage space vector synthesis formula where u a 、u b 、u c is the phase voltage in the three-phase stationary coordinate system. The amplitude and phase relationship of the three-phase voltage can be obtained by inverse transformation, and the corresponding voltage space vector can be determined. Position in the complex plane.

[0067] The entire complex plane is divided into six sectors, numbered I-VI, according to the voltage space vector The subsequent switch state switching sequence is determined by the sector in which it is located. Located in sector I, it involves the synthesis of the three basic voltage space vectors 000, 001, and 011. The three-bit binary number here represents the switching state of the three bridge arms in the three-phase inverter. 0 means that the lower tube is turned on and the upper tube is turned off, and 1 means that the upper tube is turned on and the lower tube is turned off.

[0068] After the sectors are determined, in order to synthesize the target voltage space vector It is necessary to calculate the action time of two adjacent basic voltage space vectors and the zero vector in each sector, as follows:

[0069] Assume that two adjacent basic voltage space vectors are The zero vector is According to the volt-second balance principle Where T s is a switching cycle, T x 、T y , T0 are By solving this equation, we can get T x 、T y , T0 value, and must satisfy T x +T y +T0=T s ; In sector I, T is calculated by the relevant formula x 、T y Then according to the known u d 、u q And the DC bus voltage is used to calculate the specific action time value.

[0070] According to the calculated action time and sector information, the switching sequence of the three-phase inverter switch device is determined. Taking sector I as an example, the switching sequence is 000-001-011-011-001-000, where the dwell time in the 000 state is Time, stay in 001 state T x Time, stay in 011 state T y time, and then switch back in the reverse direction, so that in one switching cycle T s The target voltage space vector is synthesized The determined switching sequence is controlled at the set switching frequency to generate a corresponding pulse signal through the control circuit to drive the switching devices in the three-phase inverter, thereby controlling the input voltage of the motor, making the motor run in the desired manner, and achieving precise control of motor parameters such as torque and speed, thereby improving the reliability of the entire new energy vehicle power supply assembly system.

[0071] The DC-DC conversion unit 3 receives the electric energy output of the motor control unit 2 at the optimal power generation efficiency point, and adopts a voltage and current dual closed-loop control strategy, in which the outer voltage loop sets the target charging voltage according to the battery characteristics and compares it with the actual voltage through a PI controller to obtain a current loop reference current, and the inner current loop adjusts the switching device to control the pulse width accordingly.

[0072] Among them, in the voltage-current dual closed-loop control strategy of the DC-DC conversion unit 3, the PI controller parameters of the outer voltage loop are adaptively adjusted according to the capacity and internal resistance characteristics of the battery, as follows:

[0073] Batteries of different types and specifications have different capacities and internal resistance characteristics. These characteristics will affect the battery's charging characteristics and charging voltage requirements. During the battery charging process, its capacity and internal resistance are not fixed, but will change with factors such as charging status, temperature, and battery aging. If the PI controller parameters are fixed, it will not be able to adapt to these dynamic changes in the battery during the charging process, which may lead to unstable voltage control and affect the battery's charging efficiency and life.

[0074] According to the capacity and internal resistance of the new energy vehicle battery, the parameters of the outer voltage loop PI controller are determined. The parameters are the proportional coefficient and the integral coefficient. Different battery characteristics and corresponding PI controller parameters are constructed into a database to form a three-dimensional mapping relationship between battery capacity, internal resistance and PI controller proportional coefficient and integral coefficient. Battery characteristics include battery capacity and internal resistance.

[0075] The DC-DC conversion unit 3 monitors the capacity and internal resistance of the battery in real time through sensors, and searches for the corresponding PI controller parameter K in the pre-established three-dimensional mapping relationship. p and K i Then, K p and K i It is applied to the PI controller of the outer voltage loop to control the voltage loop.

[0076] The outer voltage loop can better track the target charging voltage and reduce voltage errors. Whether in the early, middle or late stages of battery charging, it can maintain stable and accurate voltage control, making the voltage control more stable during the entire charging process and reducing voltage fluctuations and mutations.

[0077] The method for controlling the voltage loop is as follows:

[0078] The capacity and internal resistance of the battery are key factors affecting the charging process. Batteries with different capacities and internal resistances have different requirements for charging voltage. By pre-establishing a three-dimensional mapping relationship and finding the corresponding PI controller parameters, the control strategy can be adjusted according to the specific characteristics of the battery. This method can accurately adapt to the charging needs of the battery and ensure that the charging process is both efficient and safe.

[0079] By comparing the target charging voltage V ref and the actual detected battery voltage V sj , we get voltage error e(t) = V ref -V sj This error signal is the basis for the PI controller to make adjustments. It can adjust the PI parameters according to the battery characteristics so that the charging voltage can track the target voltage more accurately, thereby increasing the charging current and speeding up the charging speed while ensuring battery safety.

[0080] According to the proportionality factor K p , calculate the proportional output u p (t) = K p ×e(t), the role of the proportional term is to make the control signal proportional to the error signal and respond to the error quickly. In the actual digital implementation, the integral term is calculated using the rectangular integration method. In each control cycle T, the update formula of the integral term is u i (n) = u i (n-1)+K i ×e(n)×T; where n represents the current control cycle, u i (n-1) is the integral term output of the previous cycle, and e(n) is the voltage error of the current cycle. The function of the integral term is to eliminate the steady-state error and ensure that the system can accurately track the target voltage in a stable state.

[0081] Output the proportional term u p (t) and the integral output u i (t) is added to obtain the final output of the PI controller u(t) = u p (t)+u i (t); This output signal is used as the control signal of the outer voltage loop to control the on-time of the switching device, and then adjust the output voltage so that the battery voltage changes toward the target charging voltage. This not only helps to protect the battery, but also improves the reliability of the charging system and prolongs the battery life.

[0082] In the voltage and current dual closed-loop control strategy, the inner current loop uses a hysteresis control algorithm when adjusting the switching device control pulse width, as follows:

[0083] In the DC-DC conversion unit (3), the output current needs to be precisely controlled to meet the needs of battery charging or other loads. The hysteresis control algorithm is a simple and direct control method. It does not require complex proportional and integral operations like the traditional PI controller. It can quickly determine the state of the switching device by simply comparing the current difference with the hysteresis width. This simplicity enables it to respond to current changes in a shorter time, which is very suitable for application scenarios with high dynamic performance requirements, such as the power supply system of new energy vehicles.

[0084] First, according to the system's requirements for current control accuracy and circuit characteristics, the hysteresis loop width H is set, and the output current i of the DC-DC conversion unit (3) is collected in real time. out , and compare it with the current reference value i ref Compare and calculate the difference Δi=i ref -i out .

[0085] when When the switching device is in the off state, the switching device is turned on, causing the inductor to start storing energy and the current to rise.

[0086] when When the switching device is in the on state, the switching device is turned off, the inductor releases energy to the load and capacitor through the diode, and the current decreases.

[0087] when When the current state of the switching device is kept unchanged, a dynamic balance process is formed in which the current fluctuates within the hysteresis range. The switching device is continuously turned on and off according to the relationship between the current and the hysteresis boundary, thereby adjusting the output current so that it fluctuates around the current reference value within the set hysteresis width.

[0088] Through the hysteresis control algorithm, the output current can be effectively controlled to fluctuate within a smaller range near the reference current. This stable current output is crucial to the battery charging process. It can avoid damage to the battery due to excessive or insufficient current and extend the battery life. At the same time, for the power supply of other on-board electrical equipment, stable current can also ensure the normal operation of the equipment, reduce the probability of equipment failure, and improve the reliability of the entire new energy vehicle electrical system.

[0089] The balancing control unit sets a battery remaining power difference threshold based on the battery remaining power, and uses a balancing strategy to balance the battery pack until the remaining power difference of each single battery is within a preset range, as follows:

[0090] With the use of new energy vehicles, the remaining power of each single cell in the battery pack will gradually differ due to their different positions. If no balancing control is performed, this difference will continue to expand, causing the overall performance of the battery pack to decline. Through active balancing strategies, the electric energy of high-power single cells is transferred to low-power single cells, which can effectively maintain the consistency of the power of the single cells in the battery pack and enable the entire battery pack to work better together.

[0091] The remaining power of each single cell in the waterproof battery pack is obtained through the sensor, and the difference between the maximum and minimum remaining power of the single cells in the battery pack is calculated, and the difference is compared with the preset battery remaining power difference threshold, and it is determined whether equalization control is needed according to the result;

[0092] Assume that the normal operating voltage range of the battery is [V min , V max ], when it is detected that balancing is required, for a single cell with a charge greater than 70% of the total battery capacity, the DC-DC converter works as a step-down circuit, that is, converting the high voltage of the single cell into an intermediate voltage, and the high voltage is at [70%V max , V max ], the intermediate voltage is [30%V max , 70% V max ];

[0093] For single cells with a charge lower than 70% of the total battery capacity, the DC-DC converter works as a boost circuit, that is, boosting the low voltage to an intermediate voltage. The low voltage is [V min , 30%V max ].

[0094] The active balancing strategy can effectively avoid overcharging and over-discharging of single cells. Since the capacity of the battery pack is determined by the single cell with the lowest capacity, when the power of the single cells in the battery pack varies greatly, it is easy to cause the low-power single cells to be overcharged during the charging process, and the high-power single cells to be over-discharged during the discharge process. By balancing control to keep the power of each single cell relatively consistent, the damage to the single cell caused by this unbalanced charging and discharging can be reduced, thereby extending the overall service life of the battery pack and maintaining stable performance of the battery pack when new energy vehicles recover braking energy.

[0095] In the present invention, the brake pedal and vehicle speed signals are monitored in real time by detecting the recovery unit, the braking energy value is calculated, and subsequent work is triggered. Based on this, the motor control unit adopts a vector control algorithm, decomposes the current through coordinate transformation, and dynamically adjusts the current reference value according to the braking energy value and the battery charging state, so that the motor works at the optimal power generation efficiency point, and provides power input for the DC-DC conversion unit. After receiving the power, the DC-DC conversion unit adjusts the output through the voltage and current dual closed-loop control strategy. The balancing control unit performs balancing control based on the remaining battery power to ensure the performance of the battery pack. Each unit works in coordination to improve the braking kinetic energy recovery efficiency.

[0096] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A new energy vehicle power supply assembly system based on a waterproof battery, characterized in that: It comprises a detection recovery unit (1), a motor control unit (2), a DC-DC conversion unit (3) and a balancing control unit (4); The detection and recovery unit (1) comprises a braking detection module (11) and an energy recovery module (12); the braking detection module (11) monitors the brake pedal signal and vehicle speed signal of the vehicle in real time; when the brake pedal is stepped on and the vehicle speed is greater than a set threshold, it is determined that the vehicle enters a braking condition, and the energy recovery module (12) is triggered to operate; the energy recovery module (12) calculates the vehicle braking energy value according to the brake pedal travel depth and the vehicle speed change rate; The motor control unit (2) controls the energy recovery motor using a vector control algorithm based on the maximum energy recovery principle, decomposes the three-phase AC current into a direct-axis current and a quadrature-axis current through coordinate transformation, and dynamically adjusts the direct-axis current and the quadrature-axis current reference values ​​according to the braking energy value and the charging state of the battery, so that the motor operates at an optimal power generation efficiency point, and the power output at the optimal power generation efficiency point is used as the input basis of the DC-DC converter; The DC-DC conversion unit (3) receives the electric energy output at the optimal power generation efficiency point of the motor control unit (2), and adopts a voltage and current double closed-loop control strategy, wherein the outer voltage loop sets the target charging voltage according to the battery characteristics and compares it with the actual voltage to obtain the current loop reference current through the PI controller, and the inner current loop adjusts the switch device control pulse width accordingly; The balancing control unit (4) sets a battery remaining power difference threshold value based on the battery remaining power, and uses a balancing strategy to perform balancing control on the battery pack until the remaining power difference of each single battery is within a preset range.

2. According to claim 1, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: The motor control unit (2) comprises a vector control module (21), wherein the coordinate transformation in the vector control module (21) uses a combination of Clarke transformation and Park transformation to decompose the direct-axis current and the quadrature-axis current, specifically as follows: Assume that the three-phase currents in the three-phase stationary coordinate system are i a 、i b 、i c , and i a +i b +i c =0, change i a 、i b 、i c The three-phase current is converted to the two-phase stationary coordinate system by the Clarke transformation formula. α 、i β ; Then, Park transformation is performed, assuming that the direct axis current in the two-phase rotating coordinate system is i d , the quadrature axis current is i q , the current i in the two-phase stationary coordinate system α 、i β , and the electrical angle θ of the rotating coordinate system are transformed by the Park transformation formula to decompose the three-phase AC current in the three-phase stationary coordinate system into the direct axis current i in the two-phase rotating coordinate system d and the quadrature axis current i q .

3. According to claim 1, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: The motor control unit (2) comprises a battery adjustment module (22), and a method in which the battery adjustment module (22) dynamically adjusts the direct-axis current and quadrature-axis current reference values ​​according to the braking energy value and the battery charging state is specifically as follows: A mapping relationship between braking energy and a direct-axis current reference value adjustment coefficient is established based on historical data, and based on this relationship, the direct-axis current reference value adjustment coefficient corresponding to different braking energy values ​​and the quadrature-axis current reference value adjustment coefficient under different battery states are determined, wherein the battery state is the battery charge state, indicating the percentage of the battery's current charge level relative to its full capacity; During vehicle operation, the detection recovery unit (1) calculates the braking energy value in real time and transmits it to the battery adjustment module (22). The battery adjustment module (22) extracts the corresponding direct-axis current reference value adjustment coefficient according to the received braking energy value, and continuously monitors the battery charging state and provides it to the battery adjustment module (22). The battery adjustment module (22) extracts the corresponding quadrature-axis current reference value adjustment coefficient according to the charging state. Set the original direct-axis current reference value and the quadrature-axis current reference value, and multiply the original direct-axis current reference value and the quadrature-axis current reference value by the corresponding adjustment coefficients to obtain the direct-axis current reference value i d * and the quadrature axis current reference value i q * .

4. According to claim 3, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: When the vector control module (21) uses a vector control algorithm to control the energy recovery motor, a feedforward compensation control strategy is used to control the direct-axis current and the quadrature-axis current, as follows: The rotary transformer is used to obtain the position and speed of the motor rotor and the winding inductance of the motor, and the back electromotive force e is calculated by the formula d 、e q , and e d 、e q As feedforward compensation items for the direct-axis current controller and the quadrature-axis current controller respectively; Then e d 、e q The direct axis current reference value and the quadrature axis current reference value are added to the output obtained by the PI controller to obtain the direct axis voltage command u d and the quadrature axis voltage command u q Finally, u is converted to d and u q Converted into a switching signal for a three-phase inverter to control the input voltage of the motor.

5. According to claim 4, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: The space vector pulse width modulation method in the vector control module (21) is specifically as follows: Given a direct-axis voltage command and a quadrature-axis voltage command in a two-phase rotating coordinate system, a voltage space vector is calculated, wherein the voltage space vector is represented by converting the three-phase voltage into a vector on a complex plane to represent the magnitude and phase of the voltage, and the position of the corresponding voltage space vector on the complex plane is determined; The complex plane is divided into six sectors and numbered. The switching order of the switch state is determined according to the sector where the voltage space vector is located, and the action time of two adjacent basic voltage space vectors and the zero vector in each sector is calculated. According to the action time and sector information, the switching sequence of the three-phase inverter switching devices is determined. The determined switching sequence is generated according to the set switching frequency through the control circuit to generate corresponding pulse signals, drive the switching devices in the three-phase inverter, and control the input voltage of the motor.

6. According to claim 1, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: In the voltage-current dual closed-loop control strategy of the DC-DC conversion unit (3), the PI controller parameters of the outer voltage loop are adaptively adjusted according to the capacity and internal resistance characteristics of the battery, as follows: According to the capacity and internal resistance of the new energy vehicle battery, the outer loop voltage loop PI controller parameters are determined, the parameters are proportional coefficients and integral coefficients, and different battery characteristics and corresponding PI controller parameters are constructed into a database to form a three-dimensional mapping relationship between battery capacity, internal resistance and PI controller proportional coefficients and integral coefficients, and the battery characteristics include battery capacity and internal resistance; The DC-DC conversion unit (3) monitors the capacity and internal resistance of the battery in real time through sensors, and searches for the corresponding PI controller parameter K in the pre-established three-dimensional mapping relationship. p and K i Then, K p and K i It is applied to the PI controller of the outer voltage loop to control the voltage loop.

7. The new energy vehicle power supply assembly system based on a waterproof battery according to claim 6 is characterized in that: The method for controlling the voltage loop is specifically as follows: By comparing the difference between the target charging voltage of the outer voltage loop and the actual battery voltage, the voltage error is obtained, and the proportional term output is calculated according to the proportional coefficient; For the integral term, the integral coefficient is substituted into the rectangular integration method for calculation, and the proportional term output and the integral term output are added to obtain the final output of the PI controller, and the final output of the PI controller is used to control the voltage loop.

8. According to claim 1, a new energy vehicle power supply assembly system based on a waterproof battery is characterized in that: In the voltage-current dual closed-loop control strategy of the DC-DC conversion unit (3), the inner current loop adopts a hysteresis control algorithm when adjusting the switching device control pulse width, which is specifically as follows: Setting a hysteresis width, which is a range of current fluctuation allowed in a current control system, and collecting the output current of a DC-DC conversion unit (3) in real time, calculating the output current with a current reference value, and obtaining a difference; The switching device is controlled according to the situation that the difference is within the hysteresis band width, and the output current is adjusted.

9. The new energy vehicle power supply assembly system based on a waterproof battery according to claim 1 is characterized in that: The method in which the balancing control unit (4) uses a balancing strategy to perform balancing control on a battery pack is specifically as follows: The remaining power of each single cell in the waterproof battery pack is obtained through the sensor, and the difference between the maximum and minimum remaining power of the single cells in the battery pack is calculated, and the difference is compared with the preset battery remaining power difference threshold, and it is determined whether equalization control is needed according to the result; Assume that the normal operating voltage range of the battery is [V min , V max ], when it is detected that balancing is required, for a single cell with a charge greater than 70% of the total battery capacity, the DC-DC converter works as a step-down circuit, that is, converting the high voltage of the single cell into an intermediate voltage, the high voltage being at [70%V max , V max ], the intermediate voltage is [30%V max , 70% V max ]; For a single cell with a charge lower than 70% of the total battery capacity, the DC-DC converter works as a boost circuit, that is, boosting the low voltage to an intermediate voltage, where the low voltage is [V min , 30%V max ].

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