Converter current control method and system

Abstract

The present invention discloses a converter current control method and system, which belongs to the field of DC-DC conversion technology, and includes collecting speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of an electric vehicle and performing preprocessing to obtain a real-time data set; calculating a state value according to the real-time data set; judging the magnitude of the state value and a preset first threshold value and a second threshold value; if the state value is less than the first threshold value, switching to an SPWM control mode to control the current; if the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to a current tracking control mode to control the current; if the state value is greater than or equal to the second threshold value, switching to an SVPWM control mode to control the current. The present invention calculates the state value according to the real-time data set, and flexibly switches to different current control modes according to the magnitude relationship between the state value and the preset threshold value, so as to adapt to the current control requirements of the electric vehicle under different working conditions.

Description

Technical Field

[0001] The present invention relates to the field of DC-DC conversion technology, and in particular to a converter current control method and system. Background Art

[0002] In modern electric vehicles, DC-DC converters are key components responsible for converting the power of high-voltage batteries into low-voltage power for other devices in the vehicle. In order to ensure that electric vehicles work efficiently and safely, the current control strategy of the DC-DC converter is crucial.

[0003] At present, traditional current control methods are often based on fixed control strategies, such as PWM (pulse width modulation) control. Although this control method can achieve current regulation to a certain extent, during the operation of electric vehicles, their speed, load, acceleration rate, deceleration rate, ambient temperature and other parameters will change in real time. These changes put extremely high demands on the current control of the converter. Traditional fixed control strategies are difficult to flexibly adjust according to these real-time changing parameters, resulting in inaccurate current control, which in turn affects the performance and safety of electric vehicles.

[0004] Therefore, there is an urgent need for a converter current control method and system that can be flexibly adjusted according to the real-time operating status of an electric vehicle to improve the accuracy and efficiency of current control, thereby meeting the high performance requirements of modern electric vehicles. Summary of the invention

[0005] To solve the above problems, the present invention provides a converter current control method and system, which obtains a state value by calculating according to a real-time data set, and flexibly switches to different current control modes according to the relationship between the state value and a preset threshold value, so as to adapt to the current control requirements of electric vehicles under different working conditions.

[0006] The above objectives can be achieved through the following solutions:

[0007] A converter current control method includes: collecting speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of an electric vehicle and performing preprocessing to obtain a real-time data set; calculating a state value according to the real-time data set; judging the magnitude of the state value and a preset first threshold value and a second threshold value; if the state value is less than the first threshold value, switching to an SPWM control mode to control current; if the state value is greater than or equal to the first threshold value and the state value is less than the second threshold value, switching to a current tracking control mode to control current; if the state value is greater than or equal to the second threshold value, switching to an SVPWM control mode to control current.

[0008] Furthermore, the collecting of speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle and preprocessing to obtain a real-time data set includes: collecting speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle to obtain a preliminary data set; filtering the preliminary data set; and normalizing the preliminary data set after filtering to obtain a real-time data set.

[0009] Furthermore, the state value calculated according to the real-time data set includes: setting fuzzy sets for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively; setting corresponding membership functions for the fuzzy sets; selecting the corresponding fuzzy set according to the parameter values ​​in the real-time data set; inputting the parameter values ​​in the real-time data set into the membership function corresponding to the selected fuzzy set to obtain the corresponding fuzzy evaluation value; and calculating the state value according to the fuzzy evaluation value.

[0010] Further, the state value calculated according to the fuzzy evaluation value includes: setting weight coefficients for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively; establishing a state function for characterizing the operating state of the electric vehicle with respect to speed, load, acceleration rate, deceleration rate and ambient temperature according to the weight coefficients; inputting the fuzzy evaluation value into the state function to calculate the state value, and for the state value ,

[0011] have ,

[0012] In the formula, is the weight coefficient of the electric vehicle speed, is the fuzzy evaluation value of the electric vehicle speed, is the weight coefficient of the electric vehicle load, is the fuzzy evaluation value of the electric vehicle load, is the weight coefficient of the electric vehicle acceleration rate, is the fuzzy evaluation value of the electric vehicle acceleration rate, is the weight coefficient of the electric vehicle deceleration rate, is the fuzzy evaluation value of the electric vehicle deceleration rate, is the weight coefficient of the ambient temperature of the electric vehicle, is the fuzzy evaluation value of the ambient temperature of the electric vehicle.

[0013] Furthermore, if the state value is less than the first threshold, switching to the SPWM control mode to control the current includes: collecting the current state and operating requirements of the electric vehicle to obtain a first demand current value; setting SPWM wave parameters according to the first demand current value; generating an SPWM control signal according to the SPWM wave parameters; and outputting a first actual current value according to the SPWM control signal.

[0014] Furthermore, if the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current includes: collecting the current state and operating requirements of the electric vehicle to obtain a second demand current value; collecting the input current value of the DC-DC converter; outputting a second actual current value based on the input current value and the second demand current value; determining whether the deviation between the second actual current value and the second demand current value is less than a third threshold value; if not, adjusting the input current value based on the deviation between the second actual current value and the second demand current value to obtain a new input current value.

[0015] Furthermore, if the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current also includes: collecting the current state and operating requirements of the electric vehicle to obtain a first required voltage value; collecting the output voltage value of the DC-DC converter; determining whether the deviation between the output voltage value and the first required voltage value is less than a fourth threshold value; if not, adjusting the input voltage value according to the deviation between the output voltage value and the first required voltage value, thereby obtaining a new input current value.

[0016] Furthermore, if the state value is greater than or equal to the second threshold value, switching to the SVPWM control mode to control the current includes: establishing an equivalent space current vector diagram of the DC-DC converter; collecting the current state and operating requirements of the electric vehicle to obtain a third demand current value; collecting the current output current value of the DC-DC converter; determining the direction and magnitude of the equivalent current vector that currently needs to be adjusted based on the difference between the third demand current value and the output current value and the equivalent space current vector diagram; calculating the on-time and off-time of each switching element based on the direction and magnitude of the equivalent current vector; controlling the on and off of the switching element based on the on-time and the off-time, and then outputting a third actual current value.

[0017] Furthermore, the method also includes: collecting the current state and operating requirements of the electric vehicle to obtain a second required voltage value; collecting the current output voltage value of the DC-DC converter; determining whether the difference between the current output voltage value and the second required voltage value is greater than a fifth threshold; if so, triggering a safety alarm and stopping power supply.

[0018] Based on the same inventive concept, the present invention also provides a converter current control system, the system comprising: a data acquisition module, used to collect speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle; a data processing module, used to pre-process the speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle to obtain a real-time data set; a state calculation module, used to calculate the state value according to the real-time data set; a state analysis module, used to judge the size of the state value and the preset first threshold and second threshold; an SPWM control module, used to switch to the SPWM control mode to control the current if the state value is less than the first threshold; a current tracking control module, used to switch to the current tracking control mode to control the current if the state value is greater than or equal to the first threshold and the state value is less than the second threshold; an SVPWM control module, used to switch to the SVPWM control mode to control the current if the state value is greater than or equal to the second threshold.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The present invention collects real-time data such as the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle, calculates the state value based on these data, and then flexibly switches to different current control modes (SPWM control mode, current tracking control mode, SVPWM control mode) according to the size relationship between the state value and the preset threshold value; this control mode can more accurately adapt to the current control requirements of the DC-DC converter of the electric vehicle under different working conditions, thereby improving the accuracy and flexibility of the current control of the DC-DC converter;

[0021] 2. The present invention uses a current tracking control mode to monitor not only the current deviation value but also the voltage deviation value, and adjusts the input current by the current deviation value and the voltage deviation value to achieve dual closed-loop control of the output current of the DC-DC converter;

[0022] 3. The present invention realizes high-precision current control by establishing an equivalent space current vector diagram of the DC-DC converter and adjusting the on and off time of the switch element according to the difference between the demand current and the output current; this control method has the advantages of fast response and strong anti-interference, and can ensure the stable operation of the electric vehicle under different working conditions;

[0023] 4. The present invention also sets up a safety alarm mechanism during the current control process; when the difference between the collected current output voltage value and the required voltage value is greater than a certain threshold, a safety alarm will be triggered and the power supply will be stopped; this mechanism can effectively prevent safety accidents caused by improper current control and enhance the safety of electric vehicles.

[0024] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flowchart of a converter current control method according to an embodiment of the present invention.

[0027] Figure 2 It is an execution flow chart of a converter current control method according to an embodiment of the present invention.

[0028] Figure 3 It is an execution flow chart of controlling current in the current tracking control mode according to an embodiment of the present invention.

[0029] Figure 4 It is an execution flow chart of triggering a security alarm according to an embodiment of the present invention.

[0030] Figure 5 It is a structural schematic diagram of a converter current control system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0032] Reference Figure 1 An embodiment of the present invention proposes a converter current control method, which calculates a state value based on a real-time data set and flexibly switches to different current control modes according to the relationship between the state value and a preset threshold value to adapt to the current control requirements of an electric vehicle under different working conditions.

[0033] The method of this embodiment specifically includes:

[0034] The speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle are collected and pre-processed to obtain a real-time data set;

[0035] Exemplarily, five key parameters of an electric vehicle are collected: speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value; these parameters can fully reflect the current operating status and external environment of the electric vehicle; after these parameters are collected, they will be preprocessed to eliminate noise and interference to ensure the accuracy and reliability of the data; the preprocessed data set is called a real-time data set, which represents the current real status of the electric vehicle.

[0036] Calculate a status value according to the real-time data set;

[0037] Exemplarily, a state value is calculated based on a real-time data set; this state value is a comprehensive indicator that reflects the current overall operating state of the electric vehicle; the method for calculating the state value may involve complex algorithms such as fuzzy sets, membership functions, and weight coefficients, but the purpose is to obtain a value that can accurately reflect the state of the electric vehicle.

[0038] Determine the magnitude of the state value and a preset first threshold and a preset second threshold;

[0039] If the state value is less than the first threshold, switching to the SPWM control mode to control the current;

[0040] For example, Figure 2 As shown, after the state value is obtained, the current state of the electric vehicle will be judged according to the preset first threshold and second threshold, and the appropriate current control mode will be selected accordingly; if the state value is less than the first threshold, it means that the electric vehicle is in a relatively stable operating state. At this time, it will switch to the SPWM (sinusoidal pulse width modulation) control mode to control the current. In this mode, the current output is relatively stable, which is suitable for the operation of the electric vehicle in a stable state.

[0041] If the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current;

[0042] For example, Figure 2 As shown, if the state value is between the first threshold and the second threshold, it means that the electric vehicle is in a medium load or acceleration / deceleration state, and it will switch to the current tracking control mode. In this mode, the current demand of the electric vehicle will be tracked in real time, and the output current will be adjusted according to the demand to ensure the stable operation of the electric vehicle.

[0043] If the state value is greater than or equal to the second threshold, the current is controlled by switching to the SVPWM control mode.

[0044] For example, Figure 2 As shown, if the state value is greater than or equal to the second threshold, it means that the electric vehicle is in a high load or severe acceleration / deceleration state, and it will switch to the SVPWM (space vector pulse width modulation) control mode; in this mode, the output of current can be more accurately controlled to meet the needs of the electric vehicle under high load or severe change conditions.

[0045] Furthermore, the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle are collected and preprocessed to obtain a real-time data set including:

[0046] Collect the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle to obtain a preliminary data set;

[0047] Performing filtering on the preliminary data set;

[0048] Exemplarily, each parameter in the preliminary data set is filtered to remove noise and outliers; for example, speed data may be affected by road surface unevenness or sensor errors, and filtering can smooth these fluctuations to obtain a more accurate speed value.

[0049] The preliminary data set after filtering is normalized to obtain a real-time data set.

[0050] For example, since different parameters have different units and dimensions, in order to unify the processing, the filtered parameters need to be normalized; normalization is to scale the data so that it falls into a small specific interval (usually between 0 and 1); for example, speed data may be normalized to a speed ratio (current speed / maximum speed), load data may be normalized to a load rate (current load / maximum load), and so on; assuming that the maximum speed is 60km / h, then a speed of 45km / h will be normalized to 0.75 (45 / 60); similarly, the load, acceleration rate, deceleration rate and ambient temperature will also be normalized accordingly.

[0051] Further, the calculating the state value according to the real-time data set includes:

[0052] Set fuzzy sets for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively;

[0053] Exemplarily, the setting of fuzzy sets is to better describe the fuzziness and uncertainty of parameters; for example, the setting of speed "high", "medium" and "low" is to reflect the fuzzy characteristics of speed in different ranges.

[0054] For example, the fuzzy set of speed can be divided into "high", "medium" and "low", where "high" is set to be greater than 40 km / h, "medium" is set to be 20 to 40 km / h, and "low" is set to be less than 20 km / h;

[0055] Setting a corresponding membership function for the fuzzy set;

[0056] Exemplarily, a membership function is set for each fuzzy set based on actual conditions and expert experience; a membership function is a function that describes the degree to which a parameter value belongs to a fuzzy set, and can usually be in the form of trapezoidal distribution, triangular distribution, Gaussian distribution, etc.

[0057] Selecting the corresponding fuzzy set according to the parameter value in the real-time data set;

[0058] Exemplarily, according to the membership function, the actual value of each parameter is converted into a fuzzy evaluation value; the fuzzy evaluation value is a numerical value between 0 and 1, indicating the degree to which the parameter value belongs to a fuzzy set; according to the actual value of each parameter, the corresponding fuzzy set is selected.

[0059] Inputting the parameter value in the real-time data set into the membership function corresponding to the selected fuzzy set to obtain the corresponding fuzzy evaluation value;

[0060] A state value is calculated according to the fuzzy evaluation value.

[0061] Exemplarily, a corresponding fuzzy set is selected according to the actual value of each parameter, and the parameter value in the real-time data set is input into the membership function corresponding to the fuzzy set, and the corresponding fuzzy evaluation value is calculated; for example, the speed of the electric vehicle is collected to be 35 km / h at this time, which belongs to the fuzzy set of "medium speed". If the normalized value of the speed is 0.5 at this time, 0.5 is input into the membership function corresponding to "medium speed", and the fuzzy evaluation value of the speed is calculated to be 0.6; and so on, the fuzzy evaluation value of the load, the fuzzy evaluation value of the acceleration rate, the fuzzy evaluation value of the deceleration rate and the fuzzy evaluation value of the ambient temperature are obtained respectively, and these fuzzy evaluation values ​​are weightedly added to obtain the state value.

[0062] Further, the calculating the state value according to the fuzzy evaluation value includes:

[0063] Set weight coefficients for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively;

[0064] Specifically, according to actual needs, weight coefficients are set for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle, and these weight coefficients reflect the importance of each parameter in evaluating the state of the electric vehicle.

[0065] According to the weight coefficients, a state function is established for characterizing the running state of the electric vehicle with respect to speed, load, acceleration rate, deceleration rate and ambient temperature;

[0066] The fuzzy evaluation value is input into the state function to calculate the state value. ,

[0067] have ,

[0068] In the formula, is the weight coefficient of the electric vehicle speed, is the fuzzy evaluation value of the electric vehicle speed, is the weight coefficient of the electric vehicle load, is the fuzzy evaluation value of the electric vehicle load, is the weight coefficient of the electric vehicle acceleration rate, is the fuzzy evaluation value of the electric vehicle acceleration rate, is the weight coefficient of the electric vehicle deceleration rate, is the fuzzy evaluation value of the electric vehicle deceleration rate, is the weight coefficient of the ambient temperature of the electric vehicle, is the fuzzy evaluation value of the ambient temperature of the electric vehicle.

[0069] For example, assuming that =0.3, =0.2, =0.25, =0.15, =0.1; Assuming that the fuzzy evaluation value of each parameter has been calculated based on the real-time data set and membership function, =0.7, =0.5, =0.6, =0, =0.8; Substitute the fuzzy evaluation value and weight coefficient into the state function,

[0070] Calculate the status value = 0.3x0.7+0.2x0.5+0.25x0.6+0.15x0+0.1x0.8=0.54; this state value ( =0.54) indicates that the electric vehicle is currently in an above-average operating state. Through this method, multiple parameters of the electric vehicle can be comprehensively considered and appropriate weights can be assigned to them, thereby obtaining a state value that reflects the overall operating state of the electric vehicle. This state value can be used for subsequent control, decision-making or state monitoring.

[0071] Furthermore, if the state value is less than the first threshold, switching to the SPWM control mode to control the current includes:

[0072] Collect the current state and operation demand of the electric vehicle to obtain a first demand current value;

[0073] Exemplarily, the sensor network of the electric vehicle (such as speed sensors, current sensors, voltage sensors, etc.) collects the vehicle's operating data in real time, such as vehicle speed, battery voltage, motor temperature, etc.; based on the collected data and the driver's acceleration, deceleration and other operating instructions, the electric vehicle's current first demand current value is calculated; for example, assuming that the first demand current value is 10A, this is the current value required by the electric vehicle in the current state to meet the load demand.

[0074] Setting SPWM wave parameters according to the first required current value;

[0075] Exemplarily, in the SPWM control mode, the parameters of the SPWM wave (such as frequency, duty cycle, etc.) will directly affect the size and shape of the output current; in order to generate an SPWM control signal that meets the requirements, these parameters need to be set according to the first required current value; a fixed SPWM wave frequency (for example, 10kHz) is selected, and the duty cycle (for example, 50%) is determined by calculation to ensure that the output current can be close to the first required current value.

[0076] Generate an SPWM control signal according to the SPWM wave parameters;

[0077] For example, according to the set SPWM wave parameters, an SPWM control signal can be generated; this signal will be used to control the switch tube of the DC-DC converter, thereby adjusting the size and shape of the output current; in SPWM control, a sine wave is usually used as a modulation signal and compared with a high-frequency triangular wave; according to the comparison result, a series of pulse signals with varying widths can be generated, and these pulse signals will be used to control the switch tube of the DC-DC converter.

[0078] According to the SPWM control signal, a first actual current value is output.

[0079] Exemplarily, under the action of the SPWM control signal, the DC-DC converter will output an actual current value close to the first required current value; this actual current value will meet the current load demand of the electric vehicle and ensure that the electric vehicle can operate stably; the first actual current value can be obtained through measurement and monitoring; for example, assuming that the first required current value is 10A, the first actual current value is 9.8A, which means that the DC-DC converter successfully outputs an actual current close to the first required current value under the SPWM control mode; by collecting the current state and operating requirements of the electric vehicle, setting PWM wave parameters, generating SPWM control signals, and outputting the first actual current value, the current of the electric vehicle is successfully controlled; this control method not only improves the stability and performance of the electric vehicle, but also provides strong support for its operation under various working conditions.

[0080] Furthermore, if Figure 3 As shown, if the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current includes:

[0081] Collect the current state and operation demand of the electric vehicle to obtain a second demand current value;

[0082] Specifically, the current state of the electric vehicle may include battery power, motor temperature, vehicle speed, etc., while the operating requirements may include acceleration requirements, braking requirements, load changes, etc.; in order to determine the second demand current value of the electric vehicle, it is necessary to collect this information in real time through sensors and control systems.

[0083] Collect the input current value of the DC-DC converter;

[0084] Specifically, it is also necessary to collect the current input current value of the DC-DC converter, which reflects the current size currently provided by the DC-DC converter.

[0085] Outputting a second actual current value according to the input current value and the second required current value;

[0086] Specifically, in the current tracking control mode, the DC-DC converter will adjust the output current according to the difference between the input current value and the second required current value; but in this step, it temporarily only outputs an initial second actual current value, which may be close to the input current value, but is not necessarily completely equal to the second required current value.

[0087] Determining whether a deviation between the second actual current value and the second required current value is less than a third threshold;

[0088] Specifically, it is determined whether the deviation between the second actual current value and the second required current value is less than a preset third threshold value (eg, 1 A). This step is to check whether the accuracy of the current tracking control meets the requirements.

[0089] If not, the input current value is adjusted according to the deviation between the second actual current value and the second required current value to obtain a new input current value.

[0090] Specifically, since the deviation value is greater than the third threshold, it is necessary to adjust the input current value of the DC-DC converter according to the deviation value to reduce the deviation value and make the second actual current value closer to the second required current value; in the current tracking control mode, it is necessary to continuously monitor the deviation value between the second actual current value and the second required current value and adjust it as needed; this process is dynamic and will change according to the real-time status and operating requirements of the electric vehicle.

[0091] For example, suppose there is an electric car whose DC-DC converter has a current tracking control mode; the state value of the electric car is calculated by a combination of multiple parameters, and when the state value is greater than or equal to a first threshold (for example, 0.6) and less than a second threshold (for example, 0.9), the DC-DC converter will switch to the current tracking control mode to more accurately control the current; suppose the electric car is currently traveling at a medium speed, but the load suddenly increases, and more current is required to support the operation of the motor; by collecting and analyzing this information, the second demand current value is calculated to be 15A; suppose the current input current value of the DC-DC converter is 13A, which is less than the calculated second demand current value of 15A; suppose the initial second actual current The value is 13.5A, which is between the input current value of 13A and the second demand current value of 15A; the second actual current value is 13.5A, the second demand current value is 15A, and the deviation value is 1.5A, which is greater than the third threshold value of 1A; since the deviation value is greater than the third threshold value, the input voltage of the DC-DC converter can be increased or its control parameters can be adjusted to increase the output current; after adjustment, assuming that the new input current value increases to 14.5A, the second actual current value becomes 14.9A at this time, which also increases accordingly to a level close to 15A; through this process, it can be ensured that the DC-DC converter can accurately control the current in the current tracking control mode to meet the real-time needs of the electric vehicle and improve its performance and stability.

[0092] Furthermore, if Figure 3 As shown, if the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current also includes:

[0093] Collect the current state and operation requirements of the electric vehicle to obtain a first required voltage value;

[0094] Specifically, the current state and operating requirements of the electric vehicle determine not only the current demand but also the voltage demand; for example, when the electric vehicle needs to accelerate, not only more current is required to drive the motor, but also a higher voltage is required to provide sufficient power.

[0095] Collect the output voltage value of the DC-DC converter;

[0096] Specifically, it is necessary to collect the current output voltage value of the DC-DC converter; this value reflects the voltage currently provided by the DC-DC converter.

[0097] Determining whether a deviation between the output voltage value and the first required voltage value is less than a fourth threshold;

[0098] Specifically, it is necessary to determine whether the deviation between the output voltage value and the first required voltage value is less than a preset fourth threshold value; this step is to check whether the accuracy of voltage control meets the requirements.

[0099] If not, the input voltage value is adjusted according to the deviation value between the output voltage value and the first required voltage value, so as to obtain a new input current value.

[0100] Specifically, since the deviation value is greater than the fourth threshold, it is necessary to adjust the input current value of the DC-DC converter according to the deviation value to adjust the output voltage and make it closer to the first required voltage value; in the current tracking control mode, it is necessary to continuously monitor the deviation value between the output voltage value and the first required voltage value, and adjust it as needed; this process is dynamic and will change according to the real-time status and operating requirements of the electric vehicle; at the same time, it is also necessary to continue to monitor the second actual current value to ensure that it still meets the requirements of the second required current value; if necessary, the input current value can be adjusted at the same time to meet both current and voltage requirements.

[0101] For example, assuming that the electric vehicle is currently preparing to accelerate, by collecting and analyzing the current state of the electric vehicle (such as battery power, motor temperature, vehicle speed, etc.) and operating requirements (such as accelerator pedal position, load changes, etc.), it is calculated that the first required voltage value is 48V; assuming that the current output voltage value of the DC-DC converter is 46V, this value is less than the calculated first required voltage value of 48V; the output voltage value is 46V, the first required voltage value is 48V, and the deviation value is 2V, which is greater than the fourth threshold value of 1V; because the deviation value is greater than the fourth threshold value, it is necessary to adjust the input voltage of the DC-DC converter according to the deviation value. value; therefore, the input voltage value of the DC-DC converter is increased in the hope of increasing the output voltage; this will cause the input current value to increase accordingly, thereby obtaining a new input current value; after adjustment, it is assumed that the new input voltage value causes the output voltage value to increase to a level close to 48V, such as 47.8V; although this still has a certain deviation, it is already closer to the first required voltage value (less than the fourth threshold value 1V), and the second actual current value is output at this time; the current tracking mode has the advantages of high-precision control, fast response, strong anti-interference, strong adaptability and scalability through dual closed-loop control of voltage and current.

[0102] Furthermore, if the state value is greater than or equal to the second threshold, switching to the SVPWM control mode to control the current includes:

[0103] Establish the equivalent space current vector diagram of the DC-DC converter;

[0104] Specifically, the SVPWM control mode is based on the concept of space vectors, so it is first necessary to establish an equivalent space current vector diagram of the DC-DC converter; this vector diagram describes the current vector and its distribution that the converter can generate under different switching states.

[0105] Collect the current state and operation demand of the electric vehicle to obtain a third demand current value;

[0106] Collect the current output current value of the DC-DC converter;

[0107] Determining the direction and magnitude of the equivalent current vector that currently needs to be adjusted according to the difference between the third required current value and the output current value and the equivalent space current vector diagram;

[0108] Calculating the on-time and off-time of each switch element according to the direction and magnitude of the equivalent current vector;

[0109] The switch element is controlled to be turned on and off according to the on-time and the off-time, thereby outputting a third actual current value.

[0110] Specifically, in practical applications, it is necessary to detect the actual value of the DC-DC converter output current in real time and compare it with the expected value; according to the comparison result, adjust the parameters in the control algorithm to achieve accurate control of the output current.

[0111] Exemplarily, the electric vehicle is currently cruising at a speed of 60 km / h, and the third required current value required by the motor, such as 100 A, is calculated based on information such as vehicle speed and load; the current output current value of the DC-DC converter is 90 A; based on the difference (10 A) between the third required current value (100 A) and the output current value (90 A), and the equivalent space current vector diagram, the direction and magnitude of the current vector that needs to be adjusted are determined; this vector will point in a direction that can increase the output current, and its magnitude will correspond to the required current increment; based on the determined direction and magnitude of the equivalent current vector, the on-time and off-time of each switching element in the DC-DC converter are calculated; these times will ensure that the converter can generate the required current vector, thereby achieving precise control of the current; based on the calculated on-time and off-time, the on and off of the switching elements in the DC-DC converter are controlled by a PWM signal. This will cause the converter to generate the required current vector and output a third actual current value (for example, 100A) to meet the operating requirements of the electric vehicle; in the SVPWM control mode, the converter will continuously monitor the output current of the DC-DC converter and the operating status of the electric vehicle; if the output current deviates from the required current, the on and off time of the switching element will be adjusted again according to the equivalent space current vector diagram and the difference between the required current and the output current to maintain stable current control; this control method has the advantages of high precision, fast response and strong anti-interference, which can ensure the stable operation of electric vehicles under different working conditions.

[0112] Furthermore, if Figure 4 As shown, the method also includes:

[0113] Collect the current state and operation requirements of the electric vehicle to obtain a second required voltage value;

[0114] Collect the current output voltage value of the DC-DC converter;

[0115] Determine whether a difference between the current output voltage value and the second required voltage value is greater than a fifth threshold;

[0116] If so, a security alarm is triggered and power is shut off.

[0117] For example, the electric vehicle is currently traveling on a highway at a speed of 50 km / h. The second required voltage value, such as 48V, required by the motor and other electronic components is calculated based on information such as vehicle speed and load. The current output voltage value of the DC-DC converter is 55V, which is obtained through real-time monitoring by a voltage sensor. The difference between the output voltage value of 55V and the required voltage value of 48V is calculated to be 7V, and a safety threshold (the fifth threshold) is set to 5V. Because 7V is greater than 5V, it is determined that the current output voltage value exceeds the safety range. When the difference between the output voltage value and the required voltage value is greater than the fifth threshold, it is considered that there is a safety hazard, and therefore a safety alarm is immediately triggered. The safety alarm may include sound alarms, light alarms, or displaying warning information to the driver. At the same time, the DC-DC converter will be controlled to stop supplying power to prevent excessive voltage from damaging the electronic components of the electric vehicle or causing other safety problems.

[0118] Based on the same inventive concept, as shown in the figure, the present invention also provides a converter current control system, the system comprising:

[0119] A data acquisition module is used to collect speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle;

[0120] A data processing module is used to pre-process the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle to obtain a real-time data set;

[0121] A state calculation module, used for calculating a state value according to the real-time data set;

[0122] A state analysis module, used to determine the magnitude of the state value and a preset first threshold and a preset second threshold;

[0123] An SPWM control module, configured to switch to an SPWM control mode to control current if the state value is less than the first threshold;

[0124] A current tracking control module, configured to switch to a current tracking control mode to control current if the state value is greater than or equal to the first threshold and the state value is less than the second threshold;

[0125] The SVPWM control module is used to switch to the SVPWM control mode to control the current if the state value is greater than or equal to the second threshold.

[0126] It should be noted that the electrical connection between the above-mentioned units does not necessarily mean direct connection of the lines, and the indirect connection mode can be applied to the embodiments of the present invention as long as the purpose of the present invention is achieved. The above is only an exemplary embodiment of the present invention and cannot be used to limit the scope of the present invention.

[0127] That is, any equivalent changes and modifications made according to the teachings of the present invention are still within the scope of the present invention. After considering the disclosure of the specification and the truth of practice, those skilled in the art will easily think of other embodiments of the present invention. This application is intended to cover any variation, use or adaptive change of the present invention, which follows the general principles of the present invention and includes common knowledge or customary technical means in the art that are not described in the present invention.

Claims

1. A converter current control method, characterized in that: The method comprises: The speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle are collected and pre-processed to obtain a real-time data set; Calculate a status value according to the real-time data set; Determine the magnitude of the state value and a preset first threshold and a preset second threshold; If the state value is less than the first threshold, switching to the SPWM control mode to control the current; If the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current; If the state value is greater than or equal to the second threshold, switching to the SVPWM control mode to control the current; Among them, the current tracking control mode controls the current including: Collect the current state and operation demand of the electric vehicle to obtain a second demand current value; Collect the input current value of the DC-DC converter; Outputting a second actual current value according to the input current value and the second required current value; Determining whether a deviation between the second actual current value and the second required current value is less than a third threshold; If not, the input current value is adjusted according to the deviation between the second actual current value and the second required current value to obtain a new input current value.

2. A converter current control method according to claim 1, characterized in that: The real-time data set obtained by collecting and preprocessing the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle includes: Collect the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle to obtain a preliminary data set; Performing filtering on the preliminary data set; The preliminary data set after filtering is normalized to obtain a real-time data set.

3. The converter current control method according to claim 1, characterized in that: The calculating the state value according to the real-time data set comprises: Set fuzzy sets for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively; Setting a corresponding membership function for the fuzzy set; Selecting the corresponding fuzzy set according to the parameter value in the real-time data set; Inputting the parameter value in the real-time data set into the membership function corresponding to the selected fuzzy set to obtain the corresponding fuzzy evaluation value; A state value is calculated according to the fuzzy evaluation value.

4. A converter current control method according to claim 3, characterized in that: The calculating of the state value according to the fuzzy evaluation value comprises: Set weight coefficients for the speed, load, acceleration rate, deceleration rate and ambient temperature of the electric vehicle respectively; According to the weight coefficients, a state function is established for characterizing the running state of the electric vehicle with respect to speed, load, acceleration rate, deceleration rate and ambient temperature; The fuzzy evaluation value is input into the state function to calculate the state value. ,have ， In the formula, is the weight coefficient of the electric vehicle speed, is the fuzzy evaluation value of the electric vehicle speed, is the weight coefficient of the electric vehicle load, is the fuzzy evaluation value of the electric vehicle load, is the weight coefficient of the electric vehicle acceleration rate, is the fuzzy evaluation value of the electric vehicle acceleration rate, is the weight coefficient of the electric vehicle deceleration rate, is the fuzzy evaluation value of the electric vehicle deceleration rate, is the weight coefficient of the ambient temperature of the electric vehicle, is the fuzzy evaluation value of the ambient temperature of the electric vehicle.

5. The converter current control method according to claim 1, characterized in that: If the state value is less than the first threshold, switching to the SPWM control mode to control the current includes: Collect the current state and operation demand of the electric vehicle to obtain a first demand current value; Setting SPWM wave parameters according to the first required current value; Generate an SPWM control signal according to the SPWM wave parameters; According to the SPWM control signal, a first actual current value is output.

6. A converter current control method according to claim 1, characterized in that: If the state value is greater than or equal to the first threshold value, and the state value is less than the second threshold value, switching to the current tracking control mode to control the current also includes: Collect the current state and operation requirements of the electric vehicle to obtain a first required voltage value; Collect the output voltage value of the DC-DC converter; Determining whether a deviation between the output voltage value and the first required voltage value is less than a fourth threshold; If not, the input voltage value is adjusted according to the deviation value between the output voltage value and the first required voltage value, so as to obtain a new input current value.

7. The converter current control method according to claim 1, characterized in that: If the state value is greater than or equal to the second threshold, switching to the SVPWM control mode to control the current includes: According to the circuit topology and working principle of the DC-DC converter, the DC current is decomposed into a virtual space vector, and an equivalent space current vector diagram is established to describe the change of the current under different switching states; Collect the current state and operation demand of the electric vehicle to obtain a third demand current value; Collect the current output current value of the DC-DC converter; Determining the direction and magnitude of the equivalent current vector that currently needs to be adjusted according to the difference between the third required current value and the output current value and the equivalent space current vector diagram; Calculating the on-time and off-time of each switch element according to the direction and magnitude of the equivalent current vector; The switch element is controlled to be turned on and off according to the on-time and the off-time, thereby outputting a third actual current value.

8. The converter current control method according to claim 1, characterized in that: The method further comprises: Collect the current state and operation requirements of the electric vehicle to obtain a second required voltage value; Collect the current output voltage value of the DC-DC converter; Determine whether a difference between the current output voltage value and the second required voltage value is greater than a fifth threshold; If so, a security alarm is triggered and power is shut off.

9. A converter current control system, applied to a converter current control method according to any one of claims 1 to 8, characterized in that: The system comprises: A data acquisition module is used to collect speed values, load values, acceleration rate values, deceleration rate values ​​and ambient temperature values ​​of the electric vehicle; A data processing module is used to pre-process the speed value, load value, acceleration rate value, deceleration rate value and ambient temperature value of the electric vehicle to obtain a real-time data set; A state calculation module, used for calculating a state value according to the real-time data set; A state analysis module, used to determine the magnitude of the state value and a preset first threshold and a preset second threshold; An SPWM control module, configured to switch to an SPWM control mode to control current if the state value is less than the first threshold; A current tracking control module, for switching to a current tracking control mode to control current if the state value is greater than or equal to the first threshold value and the state value is less than the second threshold value; wherein the current tracking control mode to control current includes: collecting the current state and operation requirements of the electric vehicle to obtain a second demand current value; collecting the input current value of the DC-DC converter; outputting a second actual current value according to the input current value and the second demand current value; judging whether a deviation between the second actual current value and the second demand current value is less than a third threshold value; if not, adjusting the input current value according to the deviation between the second actual current value and the second demand current value to obtain a new input current value; The SVPWM control module is used to switch to the SVPWM control mode to control the current if the state value is greater than or equal to the second threshold.

Images