A new energy locomotive DCDC control method and system

Abstract

This invention provides a DC-DC control method for new energy locomotives, comprising: acquiring the input current signals of each DC-DC converter unit, the SOC value of each power battery, and the output bus voltage acquisition value; constructing a dual closed-loop control structure of voltage outer loop and current inner loop; wherein, the voltage outer loop takes the deviation between the preset target value of the bus voltage and the acquisition value as input, and generates a total current command through an active disturbance rejection controller (ADRC); determines the target value of each current inner loop based on each SOC value and the total current command, so that the SOC of each battery tends to be consistent; the current inner loop takes the deviation between the target value of the current inner loop and the corresponding input current acquisition value as input, and generates a modulation wave signal through a PI regulator; performs amplitude limiting processing on the modulation wave signal; compares the amplitude-limited modulation wave signal with a triangular carrier wave to generate a drive pulse, and controls the operation of the power switch.

Description

Technical Field

[0001] This application relates to the field of rail transit traction control technology, and in particular to a DC-DC control method and system for new energy locomotives. Background Technology

[0002] Traditional shunting locomotive platforms mostly use diesel generators as their power source. With the advancement of the national strategy for upgrading and transforming aging equipment, major locomotive manufacturers are accelerating the standardized design of new energy locomotives for four-axle / six-axle models. New energy locomotives have broad application prospects in industries such as steel and metallurgy, especially in furnace-front and in-plant shunting operations, where there is significant market demand.

[0003] In new energy vehicle systems, the DC-DC converter is a crucial link connecting the high-voltage battery and the low-voltage power supply, and its control strategy directly affects the vehicle's energy management efficiency, operational stability, and safety. However, existing DC-DC control technologies still face the following challenges: 1. Insufficient energy conversion efficiency and energy consumption optimization New energy locomotives have extremely high requirements for energy utilization efficiency, and DC-DC converters need to maintain high efficiency operation under different operating conditions. Although traditional PWM control and synchronous rectification technology can achieve basic voltage conversion, there is still considerable room for improvement in their energy conversion efficiency and dynamic response capability under complex operating conditions such as load fluctuations and ambient temperature changes.

[0004] 2. System stability and reliability issues under harsh operating conditions New energy locomotives often operate in harsh environments such as high temperature, vibration, shock, and strong electromagnetic interference. Existing DC-DC control systems still have shortcomings in terms of anti-interference capabilities, overvoltage, overcurrent, and short-circuit protection mechanisms, making it difficult to guarantee long-term stable operation of the system under extreme conditions.

[0005] 3. Insufficient control precision and adaptive adjustment capability With the development of intelligent technology, DC-DC control systems have placed higher demands on the accuracy and dynamic response of voltage / current closed-loop control. Existing solutions mostly use fixed-frequency PWM control or traditional analog circuits, which make it difficult to achieve adaptive adjustment based on real-time changes in load status and input voltage. This results in a difficulty in simultaneously achieving optimal dynamic response, control accuracy, and energy consumption control.

[0006] In summary, existing DC-DC control technologies have significant shortcomings in terms of conversion efficiency, control accuracy, system stability, and intelligent adjustment capabilities, making it difficult to meet the high-performance requirements of new energy locomotives under complex operating conditions. Therefore, there is an urgent need for a novel DC-DC control scheme with efficient energy conversion, adaptive adjustment capabilities, multiple protection mechanisms, and balanced energy control of the power battery to improve the overall energy management level and system reliability of new energy locomotives. Summary of the Invention

[0007] The purpose of this application is to provide a DC-DC control method and system for new energy locomotives to address the deficiencies in existing technologies and solve the problems existing in the prior art. To achieve the above objectives, this application provides a DC-DC control method for new energy locomotives, the method comprising: The system collects the input current signals of each DC-DC converter unit, the state of charge (SOC) value of each power battery, and the output bus voltage. A dual closed-loop control structure of voltage outer loop and current inner loop is constructed; wherein, the voltage outer loop takes the deviation between the preset target value of the output bus voltage and the sampled value of the output bus voltage as input, and performs closed-loop regulation through the active disturbance rejection controller (ADRC) to generate the total current command; Based on the SOC value of each power battery and the total current command, the target value of the inner current loop of each DC-DC converter unit is determined to make the SOC of each power battery more consistent. The inner current loop takes the deviation between the target value of the inner current loop of each DC-DC converter unit and the corresponding input current acquisition value as input, and performs amplitude limiting processing on the input current of each DC-DC converter unit according to the charging and discharging current or power limit. The input current is closed-loop regulated by a PI regulator to generate the modulation wave signal of each DC-DC converter unit. Each modulated wave signal is compared with its corresponding triangular carrier wave to generate a drive pulse for each DC-DC converter unit, thereby controlling the operation of the power switching transistors of each DC-DC converter unit.

[0008] In one possible implementation, determining the target value of the inner current loop for each DC-DC converter unit based on the SOC value of each power battery and the total current command specifically includes: Calculate the SOC equalization control coefficient of each DC-DC converter unit based on the SOC value of each power battery. The total current command is multiplied by the SOC equalization control coefficient of each DC-DC converter unit to obtain the target value of the inner current loop of each DC-DC converter unit.

[0009] In one possible implementation, the SOC equalization control mode includes a first mode and a second mode; the calculation method for the SOC equalization control coefficient includes: When the SOC equalization control mode is in the first mode, according to the formula Calculate the equilibrium coefficient; When the SOC equalization control mode is the second mode, according to the formula Calculate the equilibrium coefficient; Where, k iLet SOC be the SOC equalization control coefficient of the i-th DC-DC converter unit. i Let SOC be the SOC value of the i-th power battery group, i=1,2,…,N, where N is the total number of DC-DC conversion units.

[0010] In one possible implementation, the method further includes: The current operating condition of the DC-DC converter is identified based on the locomotive's operating status. The operating conditions include traction, braking, ground charging, and other conditions. Select the corresponding SOC equalization control mode based on the current operating conditions: When the current working condition is traction condition or other working condition, select the first mode to calculate the SOC balance control coefficient; When the current operating condition is braking or ground charging, select the second mode to calculate the SOC equalization control coefficient.

[0011] In one possible implementation, the limiting of the input current of each DC-DC converter unit specifically includes: Obtain the discharge current or discharge power limit value issued by the network as the upper limit of the amplitude; Obtain the inverse of the charging current or charging power limit value issued by the network as the lower limit of the amplitude limit; The input current of each DC-DC converter unit is limited between the upper and lower limits of the current limit.

[0012] In one possible implementation, the method further includes: Phase shifting is performed on the triangular carriers of each DC-DC converter unit so that the carrier phases of two adjacent DC-DC converter units differ by 360° / N, where N is the total number of DC-DC converter units.

[0013] In one possible implementation, the method further includes: The switching frequency is set according to the current operating condition of the DC-DC converter: when the current operating condition is the discharge mode, the first switching frequency is adopted; the discharge mode includes traction mode and other operating conditions. When the current operating condition is charging mode, a second switching frequency is used; wherein, the second switching frequency is greater than the first switching frequency; the charging mode includes braking mode and ground charging mode; When the operating conditions change, the switching frequency is adjusted using a step-by-step switching method; the step-by-step switching method includes: When switching from discharge mode to charging mode, the switching frequency increases in a stepwise manner: first switching frequency, first switching frequency + step value, first switching frequency + 2 × step value, ..., second switching frequency. When switching from charging mode to discharging mode, the switching frequency decreases in a stepwise manner: second switching frequency, second switching frequency - step value, second switching frequency - 2 × step value, ..., first switching frequency. A preset delay time is applied after each switch.

[0014] In one possible implementation, each DC-DC converter unit includes an upper bridge arm power switch and a lower bridge arm power switch; the generation of drive pulses for each DC-DC converter unit specifically includes: Generate drive pulses for the power switching transistors in the upper bridge arm; Generate a drive pulse for the lower bridge arm power switch that is complementary to the drive pulse for the upper bridge arm power switch.

[0015] In one possible implementation, the method further includes: When the operating conditions of the DC-DC converter change, the power switches of the upper and lower bridge arms of each DC-DC converter unit are driven in a pulse complementary manner to achieve a smooth transition of the output voltage.

[0016] Secondly, the present invention provides a DC-DC control system for a new energy locomotive, the system comprising: The signal acquisition module is used to acquire the input current signal of each DC-DC conversion unit in the multi-bidirectional Buck-Boost converter, the state of charge (SOC) value of each power battery, and the output bus voltage acquisition value. The multi-bidirectional Buck-Boost converter includes N parallel DC-DC conversion units, each DC-DC conversion unit is connected to a set of power batteries, and the output side of each DC-DC conversion unit is connected in parallel to supply power to the locomotive load. The voltage outer loop control module is used to take the deviation between the preset target value of the output bus voltage and the acquired value of the output bus voltage as input, and perform closed-loop regulation through the active disturbance rejection controller (ADRC) to generate a total current command. The current distribution module is used to determine the target value of the inner current loop of each DC-DC converter unit based on the SOC value of each power battery and the total current command, so that the SOC of each power battery tends to be consistent. The current limiting module is used to limit the input current of each DC-DC converter unit. The current inner loop control module is used to take the deviation between the target value of the current inner loop of each DC-DC converter unit and the corresponding input current acquisition value as input, and perform closed-loop regulation of the input current through a PI regulator to generate the modulation wave signal of each DC-DC converter unit. The drive generation module is used to compare the limited modulated wave signals with the corresponding triangular carrier waves, generate drive pulses for each DC-DC converter unit, and control the operation of the power switching transistors of each DC-DC converter unit.

[0017] By applying the DC-DC control method for new energy locomotives provided in this application, the key DC-DC control problem of new energy locomotives is solved. A new technical method for DC-DC control of new energy locomotives is provided, which adopts advanced digital control strategies, active disturbance rejection algorithms, variable switching frequency, power battery energy balance control and multiple protection mechanisms. This method has the advantages of high-efficiency energy conversion and optimal energy consumption, and stable and reliable control performance, providing a reliable technical solution for the high-performance operation of new energy locomotives under complex working conditions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the DC-DC control system for a new energy locomotive provided in an embodiment of this application; Figure 2 This is a structural diagram of the DC-DC control method for new energy locomotives provided in an embodiment of this application; Figure 3 A schematic diagram of the control strategy for an eight-fold DC-DC converter unit; Figure 4 Schematic diagram of the control effect of different SOCs; Figure 5 This is a diagram showing the switching between four operating conditions; Figure 6(A) is one of the schematic diagrams of the switching process between traction and braking conditions; Figure 6(B) is the second schematic diagram of the switching process between traction and braking conditions; Figure 7(A) is one of the schematic diagrams without carrier phase shifting; Figure 7(B) is a second schematic diagram without carrier phase shifting; Figure 7(C) is one of the schematic diagrams for carrier phase shifting; Figure 7(D) is the second schematic diagram of carrier phase shifting; Figure 8(A) is one of the schematic diagrams of direct switching of switching frequency; Figure 8(B) is the second schematic diagram of direct switching of switching frequency; Figure 8(C) is one of the schematic diagrams of switching frequency distribution; Figure 8(D) is the second schematic diagram of the switching frequency distribution; Figure 9 This is a structural diagram of the DC-DC control system for a new energy locomotive provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a schematic diagram of the DC-DC control system for a new energy locomotive provided in an embodiment of this application. The DC-DC (buck-boost) converter for new energy locomotives is divided into four-axle and six-axle series. Four-axle new energy locomotives include a quadruple DC-DC converter, while six-axle new energy locomotives include an octupple DC-DC converter. This application takes a six-axle new energy locomotive as an example; the control mechanism is the same for four-axle new energy locomotives.

[0022] like Figure 1 As shown, the system consists of eight buck-boost bidirectional DC-DC converters, namely DC-DC1, DC-DC2...DDC8. The input side of each DC-DC converter unit is powered by battery 1, battery 2...battery 8 respectively. The output sides of the eight DC-DC converter units are connected in parallel to supply power to the locomotive traction converter and auxiliary converter.

[0023] Each DC-DC converter unit is equipped with an input current sensor, named TA1, TA2...TA8, and a battery voltage sensor, named TV1, TV2...TV8. In addition, each DC-DC converter unit also includes a pre-charge circuit, a boost inductor, and two IGBT modules. Specifically, boost inductor L1 and IGBT modules S11 and S12 form the first Buck-Boost circuit; boost inductor L2 and IGBT modules S21 and S22 form the second Buck-Boost circuit; and so on, with boost inductor L8 and IGBT modules S81 and S82 forming the eighth Buck-Boost circuit. The output side is connected in parallel and equipped with an output voltage sensor TV and an output filter capacitor C. dc .

[0024] The DC-DC converter control unit (DCU) collects all the above voltage and current signals, and the collected input current sensor signals are I... 1_mes I 2_mes ...I 8_mes The battery voltage sensor signals collected are U1, U2...U8, and the collected output voltage is U. dc_mes .

[0025] Figure 2 The flowchart of the new energy locomotive DCDC control method provided in the embodiments of this application is as follows: Figure 2 As shown, the DC-DC control method for new energy locomotives includes the following steps: Step 210: Collect the input current signal of each DC-DC converter unit, the state of charge (SOC) value of each power battery, and the output bus voltage.

[0026] Specifically, the DCU acquires the input current signal (IC) of each DC-DC converter unit. 1_mes -I 8_mes The State of Charge (SOC) values ​​of each power battery (SOC1-SOC8) and the output bus voltage U are also collected. dc_mes .

[0027] Step 220: Construct a dual closed-loop control structure of voltage outer loop and current inner loop; wherein, the voltage outer loop takes the deviation between the preset target value of the output bus voltage and the acquired value of the output bus voltage as input, and performs closed-loop regulation through the active disturbance rejection controller (ADRC) to generate a total current command. Step 230: Based on the SOC value of each power battery and the total current command, determine the target value of the inner current loop for each DC-DC converter unit to make the SOC of each power battery more consistent; the inner current loop takes the deviation between the target value of the inner current loop of each DC-DC converter unit and the corresponding input current acquisition value as input, and performs amplitude limiting processing on the input current of each DC-DC converter unit according to the charging and discharging current or power limit, and performs closed-loop regulation of the input current through a PI regulator to generate the modulation wave signal of each DC-DC converter unit.

[0028] Among them, the eight-loop DC-DC converter employs a voltage outer loop and current inner loop control strategy to ensure that the DC-DC converter maintains stable output voltage while ensuring controllable power in all DC-DC circuits. Its control strategy is as follows: Figure 3 As shown, the voltage outer loop uses the target value and the voltage acquisition value for closed-loop control via an Active Disturbance Rejection Controller (ADRC), which enables the DC-DC converter to have strong system robustness and anti-interference ability when the output voltage is stable. The voltage outer loop output is multiplied by the SOC equalization control coefficient k. i (i=1, 2...8) is used as the target value for the inner current loop. The sampled value of the input current of each DC-DC converter is used as the feedback value. The PI regulator is used to control the inner current loop to ensure that the power of all DC-DC loops is controllable.

[0029] Specifically, determining the target value of the inner current loop for each DC-DC converter unit based on the SOC value and total current command of each power battery includes: Calculate the SOC equalization control coefficient of each DC-DC converter unit based on the SOC value of each power battery. The total current command is multiplied by the SOC equalization control coefficient of each DC-DC converter unit to obtain the target value of the inner current loop of each DC-DC converter unit.

[0030] The SOC equalization control mode includes a first mode and a second mode; the calculation method for the SOC equalization control coefficient includes: When the SOC equalization control mode is in the first mode, according to the formula Calculate the equilibrium coefficient; When the SOC equalization control mode is the second mode, according to the formula Calculate the equilibrium coefficient; Where, k i Let SOC be the SOC equalization control coefficient of the i-th DC-DC converter unit. i Let S be the SOC value of the i-th group of power batteries, i = 1, 2, ..., N, where N is the total number of DC-DC converter units. In the second mode, the lower the SOC value of the power battery, the larger its corresponding equalization control coefficient, thereby obtaining a larger charging current in charging conditions (braking conditions or ground charging conditions), which rapidly increases its SOC and achieves rapid equalization of the battery pack SOC.

[0031] Furthermore, the method also includes: The current operating condition of the DC-DC converter is identified based on the locomotive's operating status. The operating conditions include traction, braking, ground charging, and other conditions. Select the corresponding SOC equalization control mode based on the current operating conditions: When the current working condition is traction condition or other working condition, select the first mode to calculate the SOC balance control coefficient; When the current operating condition is braking or ground charging, select the second mode to calculate the SOC equalization control coefficient.

[0032] The above steps will be explained in detail. Specifically, the outer voltage loop uses a preset target value U for the output-side bus voltage. dc_ref The output bus voltage acquisition value U dc_mes The deviation is used as input, and closed-loop regulation is performed through an Active Disturbance Rejection Controller (ADRC) to generate a total current command I. total .

[0033] Then, based on the SOC value of each power battery and the total current command, the target value of the inner current loop for each DC-DC converter unit is determined to make the SOC of each power battery more consistent. Specifically, this includes: First, calculate the SOC equalization control coefficient k for each DC-DC converter unit based on the SOC value of each power battery. i In this application, the SOC equilibrium control mode includes a first mode and a second mode. The calculation method for the SOC equilibrium control coefficient is as follows: When the SOC equalization control mode is in the first mode, the equalization coefficient is calculated according to the following formula: When the SOC equalization control mode is the second mode, the equalization coefficient is calculated according to the following formula: Where, k i Let SOC be the SOC equalization control coefficient of the i-th DC-DC converter unit. i Let SOC be the SOC value of the i-th power battery group, i=1,2,…,N, where N is the total number of DC-DC conversion units (N=8 in this embodiment).

[0034] Then, the total current command I total Multiply by the SOC equalization control coefficient k of each DC-DC converter unit. i The target value I of the inner current loop of each DC-DC converter unit is obtained. i_ref .

[0035] Furthermore, this application also includes operating condition identification and mode selection steps: The current operating condition of the DC-DC converter is identified based on the locomotive's operating status. This operating condition includes traction, braking, ground charging, and other conditions. The corresponding State of Charge (SOC) equalization control mode is selected based on the current operating condition: when the current operating condition is traction or another condition, a first mode is selected to calculate the SOC equalization control coefficient; when the current operating condition is braking or ground charging, a second mode is selected to calculate the SOC equalization control coefficient. For example... Figure 4 As shown, the above-mentioned SOC equalization control strategy can make each battery tend to be consistent after running under different SOCs for a certain period of time, thus achieving the purpose of SOC equalization.

[0036] The following are the balanced control coefficients for each operating condition of the DCDC system: Table 1 The DCU receives the State of Charge (SOC) from each DC-DC battery system in the train network control system, defined as SOC1, SOC2...SOC8. The SOC equalization control is designed based on the received SOC, and the design method is as follows: The calculation methods for each equilibrium control coefficient in Mode 1 are as follows: The calculation methods for each equilibrium control coefficient in Mode 2 are as follows: The aforementioned SOC balancing control strategy allows the SOCs of the batteries to converge after a certain period of operation at different SOC levels, achieving SOC balancing. The control effect is shown in the figure; after repeated traction and braking operations, the SOCs of the eight batteries continuously converge.

[0037] This patented eight-fold DC-DC control process divides the DC-DC operating conditions into four types: 1. Traction condition; 2. Braking condition; 3. Ground charging condition; 4. Other conditions. The selection and switching methods for each condition are as follows: Figure 5 As shown.

[0038] Each DC-DC control employs a pulse complementarity method for pulse drive (e.g., the drive pulses of the two IGBTs S1 and S2 of DC-DC1 are complementary), which can achieve a smooth and shock-free transition of output voltage during the switching of each mode. As shown in Figures 6(A) and 6(B), the traction braking switching process is displayed, with a smooth transition of intermediate voltage.

[0039] Specifically, the limiting of the input current of each DC-DC converter unit includes: The system obtains the discharge current or discharge power limit value issued by the network as the upper limit; it obtains the inverse of the charging current or charging power limit value issued by the network as the lower limit; and limits the input current of each DC-DC converter unit between the upper and lower limits to prevent exceeding the network's charging and discharging current limits for the DC-DC converter. The inner loop output of the current of each DC-DC converter is used as a modulation wave, compared with a triangular carrier wave, and a drive pulse is output to complete the control of each DC-DC converter.

[0040] Step 240: Compare the limited modulated wave signals of each modulated wave with the corresponding triangular carrier wave to generate drive pulses for each DC-DC converter unit and control the operation of the power switching transistors of each DC-DC converter unit.

[0041] Specifically, each DC-DC converter unit includes an upper bridge arm power switch and a lower bridge arm power switch. The specific method for generating the drive pulse is as follows: a drive pulse for the upper bridge arm power switch is generated, and a drive pulse for the lower bridge arm power switch, which is complementary to the drive pulse of the upper bridge arm power switch, is also generated. Furthermore, a preset dead time is added when generating the complementary pulse to prevent shoot-through short circuits between the upper and lower bridge arms.

[0042] When the operating conditions of the DC-DC converter change, the power switches of the upper and lower bridge arms of each DC-DC converter unit are driven in a pulse complementary manner to achieve a smooth transition of the output voltage.

[0043] Each DC-DC converter unit includes an upper bridge arm power switch and a lower bridge arm power switch; the generation of drive pulses for each DC-DC converter unit specifically includes: generating drive pulses for the upper bridge arm power switch; and generating drive pulses for the lower bridge arm power switch that are complementary to the drive pulses for the upper bridge arm power switch.

[0044] Furthermore, as a preferred embodiment of this application, as shown in Figures 7(A), 7(B), 7(C) and 7(D), this application also includes a carrier phase shift control step: performing phase shift processing on the triangular carrier of each DC-DC converter unit so that the carrier phase difference between two adjacent DC-DC converter units is 360° / N, where N is the total number of DC-DC converter units.

[0045] Specifically, the eight-fold DC-DC carrier control adopts carrier phase shift control, with each carrier differing by 22.5°, which can cancel out the voltage ripple of the intermediate DC bus in each layer, thereby reducing the voltage ripple of the intermediate DC bus.

[0046] As can be seen from the above, when the carrier phase shift is not performed, the ripple of the intermediate DC bus is approximately ±5V, and after the carrier phase shift, the voltage ripple of the intermediate DC bus is approximately ±0.2V.

[0047] Furthermore, as a preferred embodiment of this application, as shown in Figures 8(A), 8(B), 8(C) and 8(D), this application also includes a switching frequency adaptive switching step: setting the switching frequency according to the current operating condition of the DC-DC converter: when the current operating condition is a discharge mode, a first switching frequency is adopted; the discharge mode includes traction mode and other operating conditions; When the current operating condition is charging mode, a second switching frequency is used; wherein, the second switching frequency is greater than the first switching frequency; the charging mode includes braking mode and ground charging mode; When operating conditions change, a step-by-step switching method is used to adjust the switching frequency to reduce impact and achieve a smooth transition. The step-by-step switching method includes: When switching from discharge mode to charging mode, the switching frequency increases in a stepwise manner: first switching frequency, first switching frequency + step value, first switching frequency + 2 × step value, ..., second switching frequency. When switching from charging mode to discharging mode, the switching frequency decreases in a stepwise manner: second switching frequency, second switching frequency - step value, second switching frequency - 2 × step value, ..., first switching frequency. A preset delay time is applied after each switch.

[0048] Because the current difference between discharge mode (traction / other operating conditions, higher current) and charging mode (braking / ground charging, lower current) is significant, different switching frequencies are configured for different operating conditions to minimize battery charging current ripple. The discharge switching frequency is set to 1200Hz, and the charging switching frequency to 2000Hz. Furthermore, to minimize impact during switching frequency transitions, the switching frequency is switched in steps: 1200Hz (100ms delay) -> 1400Hz (100ms delay) -> 1600Hz (100ms delay) -> 1800Hz (100ms delay) -> 2000Hz and 2000Hz (100ms delay) -> 1800Hz (100ms delay) -> 1600Hz (100ms delay) -> 1400Hz (100ms delay) -> 1200Hz, achieving a smooth transition between different switching frequencies.

[0049] As shown in the figure above, using step-by-step switching of the switching frequency can reduce the impact and make the switching smoother.

[0050] like Figure 9 As shown, this application also includes a new energy locomotive DCDC control system, the system comprising: The signal acquisition module 910 is used to acquire the input current signal of each DC-DC conversion unit in the multi-stage bidirectional Buck-Boost converter, the state of charge (SOC) value of each power battery, and the output bus voltage acquisition value; wherein, the multi-stage bidirectional Buck-Boost converter includes N parallel DC-DC conversion units, each DC-DC conversion unit is connected to a set of power batteries, and the output side of each DC-DC conversion unit is connected in parallel to supply power to the locomotive load; The voltage outer loop control module 920 is used to take the deviation between the preset target value of the output bus voltage and the acquired value of the output bus voltage as input, and perform closed-loop regulation through the active disturbance rejection controller ADRC to generate a total current command. The current distribution module 930 is used to determine the target value of the inner current loop of each DC-DC converter unit according to the SOC value of each power battery and the total current command, so that the SOC of each power battery tends to be consistent. Limiting module 940 is used to limit the input current of each DC-DC converter unit; The current inner loop control module 950 is used to take the deviation between the current inner loop target value of each DC-DC converter unit and the corresponding input current acquisition value as input, and perform closed-loop regulation through a PI regulator to generate the modulation wave signal of each DC-DC converter unit. The drive generation module 960 is used to compare the limited modulated wave signals with the corresponding triangular carrier waves, generate drive pulses for each DC-DC converter unit, and control the operation of the power switching transistors of each DC-DC converter unit.

[0051] By applying the DC-DC control method for new energy locomotives provided in this application, the key DC-DC control problem of new energy locomotives is solved. A new technical method for DC-DC control of new energy locomotives is provided, which adopts advanced digital control strategies, active disturbance rejection algorithms, variable switching frequency, power battery energy balance control and multiple protection mechanisms. This method has the advantages of high-efficiency energy conversion and optimal energy consumption, and stable and reliable control performance, providing a reliable technical solution for the high-performance operation of new energy locomotives under complex working conditions.

[0052] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0053] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented in hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0054] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A DC-DC control method for a new energy locomotive, characterized in that, The method includes: The system collects the input current signals of each DC-DC converter unit, the state of charge (SOC) value of each power battery, and the output bus voltage. A dual closed-loop control structure of voltage outer loop and current inner loop is constructed; wherein, the voltage outer loop takes the deviation between the preset target value of the output bus voltage and the sampled value of the output bus voltage as input, and performs closed-loop regulation through the active disturbance rejection controller (ADRC) to generate the total current command; Based on the SOC value of each power battery and the total current command, the target value of the inner current loop of each DC-DC converter unit is determined to make the SOC of each power battery more consistent. The inner current loop takes the deviation between the target value of the inner current loop of each DC-DC converter unit and the corresponding input current acquisition value as input, and performs amplitude limiting processing on the input current of each DC-DC converter unit according to the charging and discharging current or power limit. The input current is closed-loop regulated by a PI regulator to generate the modulation wave signal of each DC-DC converter unit. Each modulated wave signal is compared with its corresponding triangular carrier wave to generate a drive pulse for each DC-DC converter unit, thereby controlling the operation of the power switching transistors of each DC-DC converter unit.

2. The DC-DC control method for new energy locomotives according to claim 1, characterized in that, The determination of the target value of the inner current loop for each DC-DC converter unit based on the SOC value and total current command of each power battery specifically includes: Calculate the SOC equalization control coefficient of each DC-DC converter unit based on the SOC value of each power battery. The total current command is multiplied by the SOC equalization control coefficient of each DC-DC converter unit to obtain the target value of the inner current loop of each DC-DC converter unit.

3. The DC-DC control method for new energy locomotives according to claim 2, characterized in that, The SOC equalization control mode includes a first mode and a second mode; the calculation method for the SOC equalization control coefficient includes: When the SOC equalization control mode is in the first mode, according to the formula Calculate the equilibrium coefficient; When the SOC equalization control mode is the second mode, according to the formula Calculate the equilibrium coefficient; Where, k i Let SOC be the SOC equalization control coefficient of the i-th DC-DC converter unit. i Let SOC be the SOC value of the i-th power battery group, i=1,2,…,N, where N is the total number of DC-DC conversion units.

4. The DC-DC control method for new energy locomotives according to claim 3, characterized in that, The method further includes: The current operating condition of the DC-DC converter is identified based on the locomotive's operating status. The operating conditions include traction, braking, ground charging, and other conditions. Select the corresponding SOC equalization control mode based on the current operating conditions: When the current working condition is traction condition or other working condition, select the first mode to calculate the SOC balance control coefficient; When the current operating condition is braking or ground charging, select the second mode to calculate the SOC equalization control coefficient.

5. The DC-DC control method for new energy locomotives according to claim 1, characterized in that, The specific steps of limiting the input current of each DC-DC converter unit include: Obtain the discharge current or discharge power limit value issued by the network as the upper limit of the amplitude; Obtain the inverse of the charging current or charging power limit value issued by the network as the lower limit of the amplitude limit; The input current of each DC-DC converter unit is limited between the upper and lower limits of the current limit.

6. The DC-DC control method for new energy locomotives according to claim 1, characterized in that, The method further includes: Phase shifting is performed on the triangular carriers of each DC-DC converter unit so that the carrier phases of two adjacent DC-DC converter units differ by 360° / N, where N is the total number of DC-DC converter units.

7. The DC-DC control method for new energy locomotives according to claim 1, characterized in that, The method further includes: The switching frequency is set according to the current operating condition of the DC-DC converter: when the current operating condition is the discharge mode, the first switching frequency is adopted; the discharge mode includes traction mode and other operating conditions. When the current operating condition is charging mode, a second switching frequency is used; wherein, the second switching frequency is greater than the first switching frequency; the charging mode includes braking mode and ground charging mode; When the operating conditions change, the switching frequency is adjusted using a step-by-step switching method; the step-by-step switching method includes: When switching from discharge mode to charging mode, the switching frequency increases in a stepwise manner: first switching frequency, first switching frequency + step value, first switching frequency + 2 × step value, ..., second switching frequency. When switching from charging mode to discharging mode, the switching frequency decreases in a stepwise manner: second switching frequency, second switching frequency - step value, second switching frequency - 2 × step value, ..., first switching frequency. A preset delay time is applied after each switch.

8. The DC-DC control method for new energy locomotives according to claim 1, characterized in that, Each DC-DC converter unit includes an upper bridge arm power switch and a lower bridge arm power switch; the specific methods for generating the drive pulses for each DC-DC converter unit include: Generate drive pulses for the power switching transistors of the upper bridge arm; Generate a drive pulse for the lower bridge arm power switch that is complementary to the drive pulse for the upper bridge arm power switch.

9. The DC-DC control method for new energy locomotives according to claim 8, characterized in that, The method further includes: When the operating conditions of the DC-DC converter change, the power switches of the upper and lower bridge arms of each DC-DC converter unit are driven in a pulse complementary manner to achieve a smooth transition of the output voltage.

10. A DC-DC control system for a new energy locomotive, characterized in that, The system includes: The signal acquisition module is used to acquire the input current signal of each DC-DC conversion unit in the multi-bidirectional Buck-Boost converter, the state of charge (SOC) value of each power battery, and the output bus voltage acquisition value. The multi-bidirectional Buck-Boost converter includes N parallel DC-DC conversion units, each DC-DC conversion unit is connected to a set of power batteries, and the output side of each DC-DC conversion unit is connected in parallel to supply power to the locomotive load. The voltage outer loop control module is used to take the deviation between the preset target value of the output bus voltage and the acquired value of the output bus voltage as input, and perform closed-loop regulation through the active disturbance rejection controller (ADRC) to generate a total current command. The current distribution module is used to determine the target value of the inner current loop of each DC-DC converter unit based on the SOC value of each power battery and the total current command, so that the SOC of each power battery tends to be consistent. The current limiting module is used to limit the input current of each DC-DC converter unit. The current inner loop control module is used to take the deviation between the target value of the current inner loop of each DC-DC converter unit and the corresponding input current acquisition value as input, and perform closed-loop regulation of the input current through a PI regulator to generate the modulation wave signal of each DC-DC converter unit. The drive generation module is used to compare the limited modulated wave signals with the corresponding triangular carrier waves, generate drive pulses for each DC-DC converter unit, and control the operation of the power switching transistors of each DC-DC converter unit.

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