DC-dc converter power optimal current curve planning control method and system

Abstract

This invention discloses a method and system for planning and controlling the power-optimal current curve of a DC-DC converter. The method includes the following steps: obtaining power system parameters and task objectives; based on the power system parameters, controlling the load coil current within a given time period. T The value increases from 0 to the target value. I The current rise phase, and from I The current decrease phase, from zero to zero, is divided into multiple sub-phases, and the power value for each sub-phase is planned. Based on the power value of each sub-phase, the current curve for each sub-phase is recursively generated based on the differential relationship between power and current, thus forming the current curves for the current rise and current fall phases. The current curves for the current rise and current fall phases are output to a DC-DC converter to achieve closed-loop control of the load current. This invention can reduce instantaneous power demand and optimize power distribution, thereby reducing the requirements for power system capacity and improving system economy and reliability.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, specifically to a method and system for planning and controlling the optimal power current curve of a DC-DC converter. Background Technology

[0002] In applications involving strong magnetic fields, such as ship demagnetization, a high-power power supply is often required to provide precisely controlled current to coil loads with high inductive characteristics to establish the desired magnetic field. Due to the energy storage characteristics of inductance, the coil absorbs and stores energy from the power supply during the current rise phase (manifested as positive power), and feeds energy back to the system during the current fall phase (manifested as negative power). Using traditional linear or simple step current driving methods results in extremely high transient power demands and a highly uneven distribution of positive and negative power. Specifically, traditional linear or step current driving methods lead to extremely high transient power demands and uneven power distribution during the current rise phase, placing excessive demands on the instantaneous output capability of the power supply system; similarly, the energy feedback during the current fall phase exhibits power abrupt changes and imbalances, requiring high energy absorption capacity from the power supply system and affecting system stability and energy recovery efficiency.

[0003] As mentioned above, this places excessively high demands on the instantaneous output and recirculation capabilities of the power supply unit and the entire energy system, not only increasing the complexity of system design and manufacturing but also significantly driving up equipment costs. Therefore, how to generate specific time-varying current curves based on power planning and ensure that the target current is reached within a specified time is a key issue in practical control. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides a DC-DC converter power optimal current curve planning and control method and system that reduces instantaneous power demand and optimizes power distribution, thereby reducing the requirements for power system capacity and improving system economy and reliability.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for power-optimal current curve planning and control of a DC-DC converter includes the following steps: Obtain power system parameters and mission objectives; the power system parameters include DC bus voltage. U , load coil inductance L With equivalent series resistance R The task objective is: to complete the task within a given timeframe. T Within, the load coil current is increased from 0 to the target value. I , or from I Drop to 0; Based on the power system parameters, the load coil current is measured at a given time. T The value increases from 0 to the target value. IThe current rise phase, and from I The current drop phase to 0 is divided into multiple sub-phases, and the power value of each sub-phase is planned. Based on the power values ​​of each sub-stage, the current curves of each sub-stage are recursively generated based on the differential relationship between power and current, thereby forming the current curves of the current rising stage and the current falling stage, ensuring that the mission objectives are met. The current curves during the current rise and fall phases are output to the DC-DC converter to achieve closed-loop control of the load current.

[0006] Preferably, the specific process for calculating the power value of each sub-stage during the current rise phase is as follows: In the first stage, the load is driven with the maximum output voltage U, causing the power to rise linearly to the peak power. ; In the second stage, the output voltage is adjusted to maintain a constant power. until the current rises to near the target value; The third stage, from Linearly reduced to steady-state power To achieve a smooth transition; In the fourth stage, the drive continues with a small, constant power until the current precisely reaches the target value. I .

[0007] Preferably, peak power The calculation formula is:

[0008] in This is the sum of the time for the first and second phases.

[0009] Preferably, the power curve for the third stage of the current rise phase is as follows:

[0010] in The duration of the third phase; This is the first correction factor.

[0011] Preferably, the power curve for the fourth stage of the current rise phase is as follows:

[0012] in This is for adjusting the coefficient.

[0013] Preferably, the specific process for calculating the power value of each sub-stage in the current-decreasing phase is as follows: In the first stage, power changes from steady-state power. Decrease to negative peak power ; The second stage maintains constant power. To achieve energy feedback; In the third stage, the control current decreases linearly to zero at a fixed slope, and the power naturally drops to zero.

[0014] Preferably, The calculation formula is:

[0015] in , , This is the second correction factor.

[0016] Preferably, power With current The specific differential relation is as follows: .

[0017] The present invention also discloses a computer-readable storage medium having a computer program stored thereon, the computer program performing the steps of the method described above when run by a processor.

[0018] The present invention further discloses a power-optimal current curve planning and control system for a DC-DC converter, comprising a memory and a processor connected to each other, wherein the memory stores a computer program, and the computer program executes the steps of the method described above when run by the processor.

[0019] Compared with the prior art, the advantages of the present invention are as follows: The present invention relates to a power-optimal current curve planning and control method for DC-DC converters applied to high-energy inductive loads. By planning the current curve, the instantaneous power demand is reduced and the power distribution is optimized, thereby reducing the requirements for power system capacity and improving system economy and reliability.

[0020] The multi-stage power planning strategy proposed in this invention for the current rise phase divides the rise process into four stages: rapid rise to peak power, constant power, smooth transition, and fine-tuning. The parameters for each stage are determined through theoretical calculations to minimize peak power and achieve smooth power changes. This significantly reduces the instantaneous power peak during the current rise process, makes the power distribution more balanced, reduces the impact on the power supply system, and lowers the system design and manufacturing costs.

[0021] The multi-segment power planning strategy proposed in this invention for the current decline phase divides the decline process into power smooth decline, constant power feedback and linear decline phases. By optimizing and determining the constant power value and introducing a smooth transition, stable energy feedback is achieved, thereby reducing the absolute value of instantaneous power during the current decline process, making the power change smooth, reducing the burden of energy absorption on the power system, improving energy recovery efficiency and enhancing system reliability.

[0022] This invention is based on the power set at each stage determined by power planning, uses the power-current differential relationship to iteratively calculate the current curve, and introduces smooth switching processing to ensure that the current curve is continuous and strictly meets the time constraints, thereby realizing the accurate mapping of power planning to the actual current curve, ensuring control accuracy, avoiding power abrupt changes, and improving the dynamic performance and stability of the system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the magnetic field construction system in an embodiment of the present invention.

[0024] Figure 2 This is a graph showing the planned current versus planned power in an embodiment of the present invention.

[0025] Figure 3 In the embodiments of the present invention, when When set to 1, the planned current and planned power curves disappear in the fourth stage.

[0026] Figure 4 This is a flowchart of the control method for the current rising stage in an embodiment of the present invention.

[0027] Figure 5 This is a flowchart of the control method for the current decrease stage in an embodiment of the present invention.

[0028] Figure 6 The output current and output power waveforms are obtained using linear programming.

[0029] Figure 7 The output current and output power waveforms are shown after applying the method of the present invention.

[0030] Figure 8 This is a flowchart of the DC-DC converter power-optimal current curve planning and control method according to an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] In typical high magnetic field establishment tasks, the power supply equipment uses a four-quadrant DC-DC converter to adjust the amplitude and direction of the equivalent voltage applied across the load coil to generate a stable and precisely controllable coil current, thereby generating the required controllable magnetic field along the load coil axis. The system configuration is as follows: Figure 1 As shown.

[0033] Assume the input DC bus voltage is constant. U The inductance and equivalent series resistance of the load coil are respectively L and R The task requirement is: within a given time... T Within, the load coil current is increased from 0 to the target value. I , or from I Drops to 0. Instantaneous power output of the power supply. P With equivalent output voltage u The relationship between them is: (1) (2) in i This is the instantaneous value of the load current; Because the strong magnetic field requires the load coil to have a very high inductance, the instantaneous power of the power supply system changes drastically during the magnetic field charging process.

[0034] To achieve user-friendly control of power supply equipment, the instantaneous peak power output should be minimized, and the power change process should be smooth and continuous to reduce the demand on the instantaneous power capacity of the power system and minimize electrical shock. This invention provides a power-optimal current curve planning and control method for a DC-DC converter. Its core idea is to divide the current rise and fall processes into multiple stages, and plan each stage according to a specific power change law, so that the overall power curve satisfies the requirements of minimum peak value, smooth change, and strict time constraint. Figure 8 As shown, the specific steps of the optimal current curve planning and control method of the present invention are as follows: 1) Obtain power system parameters and mission objectives; the power system parameters include DC bus voltage. U , load coil inductance L With equivalent series resistance R The task objective is: to complete the task within a given timeframe. T Within, the load coil current is increased from 0 to the target value. I , or from I Drop to 0; 2) Based on the power system parameters, the load coil current is controlled within a given time. T The value increases from 0 to the target value. I The current rise phase, and from IThe current drop phase to 0 is divided into multiple sub-phases, and the power value of each sub-phase is planned. like Figure 2 As shown, the power planning during the current rise phase is as follows: During the current rise process, a strategy of "rapidly increasing the power to the peak value first, then operating at constant power, and finally smoothly transitioning to steady-state power" is adopted to achieve the desired result within a given time. T Internal target current I At the same time, to make peak power Minimization. Specifically, it is divided into the following four stages (corresponding to...). Figure 2 (S1 to S4) Phase 1 (S1): Power increases linearly from 0 to peak power. : During this stage, the converter unit operates at its maximum output voltage. U When driving a load, the current increases exponentially. (3) Set time Instantaneous power reached ,but satisfy: (4) Therefore, we can solve this. The expression: (5) Phase 2 (S2): Power remains constant : From time Initially, the converter unit adjusts the output voltage to keep the instantaneous power constant. The load current continues to rise. Let's assume that when the current rises to 0.95... I The time is According to the law of conservation of energy, within the time interval... Internally, the energy output by the power supply equals the sum of the energy consumed by the load resistor and the energy increment stored in the inductor, that is: (6) (7) Combining equations (5) to (7), we can obtain: , (8) According to the constraints, when time is At that time, the load current is 0.95I ,Right now: (9) Substituting into equation (4) We can obtain: (10) achievable for: (11) Phase 3 (S3): Power from Smooth linear decrease to steady-state power ; To avoid a sudden power drop when the current reaches the target value (from Jump to ） Set a smooth transition range. When the current rises to... 0.95I At that time, the output power begins to decrease linearly. ΔT Time to drop , ΔT The value of needs to ensure that the current is within T The moment just arrived I And the power change is smooth. exist ΔT Internally consumed resistive power The range of values ​​is:

[0035] During this period, the current curve rises sharply, indicating the power of the resistor. It can be estimated as follows: (12) First correction factor The value range is 0.9025~1, which is used to compensate for and correct the error in the power estimation of the resistor; During this period, the following occurred: (13) We can obtain: (14) The power curve for the third stage during the rising period is then: (15) To ensure that the total current rise time does not exceed the set time T It requires constant Apply constraints, that is: (16).

[0036] Phase 4 (S4): Fine-tuning phase when When the value is small, the approximate power consumed by the resistor may be less than the actual power consumed, and the power allocated for energy storage in the coil load may be insufficient to support the load current reaching the set current within the expected time. Therefore, when the power drops to slightly above [a certain value], At that time, the converter unit continues to drive with a small, constant power until the current precisely reaches the specified level. I The power setting for this stage is: (17) Adjustment coefficient The value ranges from 0.05 to 0.1 and is used to limit the minimum fine-tuning power.

[0037] When the first correction factor As the value increases, the duration of phase S4 will decrease, eventually disappear, and then... Further increases cause the load output current to reach its maximum ahead of schedule. I The magnitude of the sudden drop in output power increases. For example... Figure 3 As shown, When the value is 1, the planned current reaches the set current ahead of schedule. I The planned power output suddenly dropped to a lower level. The operating conditions.

[0038] like Figure 2 As shown, the power planning during the current decrease phase is as follows: The goal of the current drop phase is to achieve the following within a given time. T The internal current will flow from I Reduce to 0, while minimizing the absolute value of instantaneous power and ensuring smooth changes. The plan is divided into the following three stages (corresponding to...). Figure 2 (S6 to S8) Phase 1 (S6): Power from steady-state power Linearly decrease to negative peak power ;in The set constant power feedback value; the linear descent process ensures continuous power transition; Phase 2 (S7): Power remains constant. The converter unit operates at constant power. As energy is absorbed from the load, the current gradually decreases. Third stage (S8): Power decreases to 0 as current decreases; current decreases to 0 at a fixed slope, and output power decreases as current decreases.

[0039] in The power consumed by the resistor can be estimated using the energy balance relationship. When estimating the power consumption of the resistor, the load current is first considered to change linearly, and then a second correction factor is introduced. (Take a value of 1.2-1.5) to correct for the deviation in resistance power estimation caused by nonlinear changes in current.

[0040] (18) (19) (20) 3) Generation of the planned current curve The set power for each stage is obtained based on the above power planning. Then, the current curve is recursively generated using the differential relationship between power and current. From: (twenty one) The iterative formula for the current at the next moment can be obtained: (twenty two); During the current rise process: (twenty three); During the current decrease process: (twenty four) Numerical integration can yield the current curve that satisfies power planning and reaches the target value strictly within time T.

[0041] 4) Output the current curves during the current rise and current fall phases to the DC-DC converter to achieve closed-loop control of the load current.

[0042] In practical applications, based on the aforementioned power planning and current curve generation methods, the following can be formulated: Figure 4 , Figure 5 The method flow shown is used to generate the optimal current trajectory in real time in a digital controller.

[0043] The process of current rise is as follows: Figure 4 As shown: First, based on system parameters U, L, R and task requirements T, I, Calculate the peak power according to formula (11) Then it enters the first stage, driving the load with the maximum output voltage U until the power reaches its maximum. After entering the second stage, adjust the output voltage to maintain power. Constant, and real-time monitoring of the planned current. When planning current Rising to 0.95 I At that time, the smooth transition phase of the third stage begins, and the power is linearly reduced to [a certain value] according to equation (15). ； Finally, the fourth stage, the fine-tuning stage, is initiated by driving with minimal power according to equation (17) until the current precisely reaches the target value. I， The ascent process is complete.

[0044] In each of the above stages, the settings are based on formulas (15) and (17). Then calculate according to formula (23) Then, the real-time planning current is calculated according to formula (22). To plan current in real time Using the load current as feedback, a closed-loop PI control of the current is performed until... achieve I At that time, it ended.

[0045] The implementation process of the current decrease process is as follows: Figure 5 As shown: First, based on the energy balance relationship and correction coefficient... Estimated feedback power After entering the S6 stage, the output power changes from the steady-state power. Linearly decreases to constant power feedback value Then it enters the S7 constant power feedback phase to maintain power. The current remains constant and continues to decrease during the inductor energy storage feedback process. When it is detected that the current decrease slope remains stable and the current can decrease linearly to zero in the remaining time, the system enters the S8 stage. In the S8 stage, the control current decreases linearly to zero at a fixed slope, and the power naturally decreases to zero, completing the entire current decrease process.

[0046] In each of the above stages, calculations and updates are performed according to formula (24). The real-time planning current is calculated according to formula (22). To plan current in real time Using the load current as feedback, a closed-loop PI control of the current is performed until... It ends at midnight.

[0047] The present invention relates to a power-optimal current curve planning and control method for DC-DC converters applied to high-energy inductive loads. By planning the current curve, the instantaneous power demand is reduced and the power distribution is optimized, thereby reducing the requirements for power system capacity and improving system economy and reliability.

[0048] The multi-stage power planning strategy proposed in this invention for the current rise phase divides the rise process into four stages: rapid rise to peak power, constant power, smooth transition, and fine-tuning. The parameters for each stage are determined through theoretical calculations to minimize peak power and achieve smooth power changes. This significantly reduces the instantaneous power peak during the current rise process, makes the power distribution more balanced, reduces the impact on the power supply system, and lowers the system design and manufacturing costs.

[0049] The multi-segment power planning strategy proposed in this invention for the current decline phase divides the decline process into power smooth decline, constant power feedback and linear decline phases. By optimizing and determining the constant power value and introducing a smooth transition, stable energy feedback is achieved, thereby reducing the absolute value of instantaneous power during the current decline process, making the power change smooth, reducing the burden of energy absorption on the power system, improving energy recovery efficiency and enhancing system reliability.

[0050] This invention is based on the power set at each stage determined by power planning, uses the power-current differential relationship to iteratively calculate the current curve, and introduces smooth switching processing to ensure that the current curve is continuous and strictly meets the time constraints, thereby realizing the accurate mapping of power planning to the actual current curve, ensuring control accuracy, avoiding power abrupt changes, and improving the dynamic performance and stability of the system.

[0051] To verify the effectiveness of the method proposed in this invention, simulations and experiments were conducted under the following conditions: DC voltage U =2500V, coil parameters L =310MH, R =0.11Ω, the control target is: at T =Within 1 second, the output current will rise from 0A to I =5000A, then drops from 5000A to 0A within 1 second, completing one pulse magnetic field establishment task.

[0052] In contrast, a simulation was first performed using the traditional linear current programming method (i.e., the current rises / falls at a fixed slope), and the output current and output power waveforms are as follows: Figure 6 As shown. By Figure 6 As can be seen, under the linear programming method, the peak power output of the load is 10.55MW, the peak power feedback of the load is 10.75MW, and the maximum power fluctuation range is 13.68MW, which places extremely high demands on the instantaneous power capacity and energy feedback capability of the power supply system.

[0053] After applying the power-optimal current curve planning and control method proposed in this invention, the actual test results are as follows: Figure 7 As shown in the figure. The test results show that: the peak load output power decreased to 6.868MW, a decrease of 43% compared with the linear programming method; the peak load feedback power decreased to 5.078MW, a decrease of 52.7% compared with the linear programming method; there were no significant changes in output power throughout the process, and the power change amplitude was reduced by 100%, achieving smooth power switching and stable control.

[0054] This invention also discloses a computer-readable storage medium storing a computer program thereon, which, when run by a processor, executes the steps of the method described above. This invention further discloses a power-optimal current curve planning and control system for a DC-DC converter, comprising an interconnected memory and a processor, wherein the memory stores a computer program that, when run by a processor, executes the steps of the method described above. The medium and control system of this invention, corresponding to the methods described above, also possess the advantages described in the control methods above.

[0055] The present invention can implement all or part of the processes in the methods of the above embodiments, or it can be implemented by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above method embodiments. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium includes: any entity or device capable of carrying computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. The memory is used to store computer programs and / or modules. The processor implements various functions by running or executing the computer programs and / or modules stored in the memory, and by calling data stored in the memory. The memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0056] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for power-optimal current curve planning and control of a DC-DC converter, characterized in that, Including the following steps: Obtain power system parameters and mission objectives; the power system parameters include DC bus voltage. U , load coil inductance L With equivalent series resistance R ; The task objective is: within a given time... T Within, the load coil current is increased from 0 to the target value. I , or from I Drop to 0; Based on the power system parameters, the load coil current is measured at a given time. T The value increases from 0 to the target value. I The current rise phase, and from I The current drop phase to 0 is divided into multiple sub-phases, and the power value of each sub-phase is planned. Based on the power values ​​of each sub-stage, the current curves of each sub-stage are recursively generated based on the differential relationship between power and current, thereby forming the current curves of the current rising stage and the current falling stage, ensuring that the mission objectives are met. The current curves during the current rise and fall phases are output to the DC-DC converter to achieve closed-loop control of the load current.

2. The DC-DC converter power-optimal current curve planning and control method according to claim 1, characterized in that, The specific process for calculating the power values ​​of each sub-stage during the current rise phase is as follows: In the first stage, the voltage is equal to the DC bus voltage. U The maximum output voltage drives the load, causing the power to rise linearly to peak power. ; In the second stage, the output voltage is adjusted to maintain a constant power. until the current rises to near the target value; The third stage, from Linearly reduced to steady-state power To achieve a smooth transition; In the fourth stage, the drive continues with a small, constant power until the current precisely reaches the target value. I .

3. The DC-DC converter power-optimal current curve planning and control method according to claim 2, characterized in that, Peak power The calculation formula is: in This is the sum of the time for the first and second phases.

4. The DC-DC converter power-optimal current curve planning and control method according to claim 3, characterized in that, The power curve for the third stage of the current rise phase is as follows: in The duration of the third phase; This is the first correction factor.

5. The DC-DC converter power-optimal current curve planning and control method according to claim 4, characterized in that, The power curve for the fourth stage of the current rise phase is as follows: in This is for adjusting the coefficient.

6. The DC-DC converter power-optimal current curve planning and control method according to any one of claims 1-5, characterized in that, The specific process for calculating the power values ​​of each sub-stage during the current decrease phase is as follows: In the first stage, power changes from steady-state power. Decrease to negative peak power ; The second stage maintains constant power. To achieve energy feedback; In the third stage, the control current decreases linearly to zero at a fixed slope, and the power naturally drops to zero.

7. The DC-DC converter power-optimal current curve planning and control method according to claim 6, characterized in that, The calculation formula is: in , , This is the second correction factor.

8. The DC-DC converter power optimal current curve planning and control method according to any one of claims 1-5, characterized in that, power With current The specific differential relation is as follows: 。 9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-8.

10. A power-optimal current curve planning and control system for a DC-DC converter, comprising an interconnected memory and a processor, wherein the memory stores a computer program, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-8.

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