Dual-current closed-loop control method for magnetic power supply of steady-state magnetic field test device

Abstract

The present invention discloses a dual-current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device, the method comprising the following steps: constructing a mathematical model of an equivalent circuit model of a main circuit of the magnet power supply; determining the equivalent load of each branch in the equivalent circuit model; obtaining the transfer function of each branch according to the equivalent load of each branch and the proportional integral coefficient and current feedback coefficient of the inner loop of each branch; obtaining the main circuit transfer function, thereby constructing a dual-current closed-loop negative feedback control block diagram to achieve dual-current closed-loop control; analyzing the main circuit transfer function to obtain a dual-loop system Bode diagram, and analyzing the current accuracy, and adjusting the parameters of the main circuit transfer function when the expected effect is not achieved; the advantages of the present invention are: ensuring the high-precision requirements of the total output current, taking into account the current sharing of each branch, avoiding the imbalance of branch currents that causes excessive current in a certain branch to cause damage, and avoiding the problem of branch circulation.

Description

Technical Field

[0001] The present invention relates to the technical field of magnet power supplies, and more particularly to a dual-current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device. Background Art

[0002] Earth's fossil energy reserves are limited, so nuclear fusion research, aimed at solving humanity's energy needs, is a key approach to promoting sustainable development. Consequently, China, the European Union, India, South Korea, Japan, Russia, and the United States officially signed the International Thermonuclear Experimental Reactor (ITER) project in 2006, often referred to as the "ITER Project." During stable operation of the ITER project, interactions between various components can cause a unique steady-state magnetic field, with magnetic induction intensities exceeding 5 mT. This steady-state magnetic field can affect the performance of ITER equipment components according to theoretical analysis. Therefore, steady-state magnetic field qualification testing is required for equipment operating on-site at the ITER facility. Due to the limited space requirements of some operating components, there is currently no dedicated laboratory instrument internationally capable of performing electromagnetic compatibility testing on ITER equipment. Furthermore, the steady-state magnetic induction intensities required for testing large-scale equipment require larger, higher-power instruments. Based on these two requirements, the ITER Project is organizing the construction of a steady-state magnetic field test facility to conduct steady-state magnetic field testing experiments on ITER-related operating equipment.

[0003] When using a steady-state magnetic field test device to perform a qualified test on a steady-state magnetic field, the magnetic power supply has higher precision and faster response speed requirements. In order to achieve high-precision control of the power supply, the traditional single current closed-loop control structure, such as "A Single Closed-Loop Control Strategy for Aviation Inverter Power Supply [J]. Teng Guofei, Yu Yong, Wang Shanhu. Information Technology and Informatization. 2020 (10)", cannot meet the requirements of high-precision output current of the steady-state magnetic power supply. On the other hand, in the case of outputting ultra-large current, a single power module cannot meet the design requirements, and multiple branches are required to generate current for control, which also involves the problem of current sharing between the branches. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the power closing control scheme of the existing technology cannot meet the requirements of high-precision output current of the steady-state magnetic power supply, and it is difficult to take into account the current balance of each branch. It is easy for a branch current to be excessively large, causing damage and branch circulation problems.

[0005] The present invention solves the above technical problems by the following technical means: a dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device, the method comprising the following steps:

[0006] S1. Construct a mathematical model of the equivalent circuit model of the main circuit of the magnet power supply;

[0007] S2. Determine the equivalent load of each branch in the equivalent circuit model;

[0008] S3. Obtain the transfer function of each branch according to the equivalent load of each branch and the proportional integral coefficient and current feedback coefficient of the inner loop of each branch;

[0009] S4. Based on the transfer functions of each branch and the outer loop proportional integral coefficient and current feedback coefficient in the equivalent circuit model, the main circuit transfer function is obtained, thereby constructing a dual current closed-loop negative feedback control block diagram to achieve dual current closed-loop control;

[0010] S5. Analyze the main circuit transfer function to obtain the dual-loop system Bode plot, and build a steady-state magnet power supply operation model in MATLAB / Simulink simulation software to analyze the current accuracy to determine whether the dual current closed-loop control method achieves the expected effect. If the expected effect is not achieved, adjust the parameters of the main circuit transfer function.

[0011] The present invention constructs a mathematical model of the equivalent circuit model of the main circuit of the magnet power supply and obtains the main circuit transfer function, thereby constructing a dual-current closed-loop negative feedback control block diagram, realizing dual-current closed-loop control, and analyzing the current accuracy to determine whether the dual-current closed-loop control method achieves the expected effect. If the expected effect is not achieved, the parameters of the main circuit transfer function are adjusted so that the total output current of the magnet power supply can reach and track the expected target current value in a short time and ensure the high precision requirement of the total output current. At the same time, compared with the single closed-loop strategy, this dual closed-loop control strategy can take into account the current sharing of each branch, avoid the imbalance of branch current causing excessive current in a certain branch to cause damage, and avoid branch circulation problems.

[0012] Furthermore, the equivalent circuit model based on the main circuit of the magnetic power supply includes a communication power supply module, a Buck and synchronous rectification circuit, and a resistive-inductive load. There are multiple communication power supply circuits on each branch and they are connected in parallel to form a group of communication power supply modules. There is one resistive-inductive load, and a Buck and synchronous rectification circuit is connected between each group of communication power supply modules and the resistive-inductive load.

[0013] Furthermore, the resistive-inductive load in the equivalent circuit model includes the inductor L L , Ohmic resistance R L , then the equivalent load function of each branch is:

[0014] Furthermore, the transfer functions of the branches G1(s) to G n (s) is:

[0015]

[0016] Among them, K p2 , K i2 is the proportional integral coefficient of each branch inner loop in the equivalent circuit model, β1 is the negative feedback current feedback coefficient of each branch inner loop, i1~i n is the branch current output by each branch, I nref is the given branch current value of the inner loop, and s is a complex variable.

[0017] Furthermore, the main circuit transfer function G(s) is:

[0018]

[0019] Among them, K p1 , K i1 is the proportional integral coefficient of the outer loop in the equivalent circuit model, β is the negative feedback current feedback coefficient of the outer loop, I o is the total output current, I oref is the total current value given by the outer loop, and s is a complex variable.

[0020] Furthermore, the dual current closed-loop control includes: a current outer loop control composed of the target output total current of the magnet power supply as the current outer loop given instruction and the output total current feedback; and a current inner loop control composed of the current instruction obtained by the current outer loop being equally divided through each branch as the current inner loop given instruction and the output branch current feedback of each branch.

[0021] Furthermore, both the current inner loop control and the current outer loop control adopt a proportional-integral control structure.

[0022] Furthermore, the current outer loop control comprises the following steps:

[0023] (1) The total output current of the magnet power supply is given by I oref With the total output current I o Compare and find the deviation value e o ;

[0024] (2) Deviation e o The outer loop control signal I is amplified by proportional integral control eo .

[0025] Furthermore, the current inner loop control comprises the following steps:

[0026] (1) The outer loop control signal I eo Divide into n equal parts and obtain the inner loop given branch current value I after each branch is adjusted nref ;

[0027] (2) Set the inner loop given branch current value I nref The output currents I1~I of each Buck and synchronous rectification circuit are respectively obtained by sampling. n Compare and find the deviation value e1~e n ;

[0028] (3) Deviation value e1~e n After being amplified by the proportional controller, the inner loop control signal I is formed e1 ~I en ;

[0029] (4) Inner loop control signal I e1 ~I en After being processed by the sinusoidal pulse width modulation (SPWM) driving unit, an SPWM driving signal is generated. The Buck corresponding to the driving signal and the synchronous rectification circuit then generate the target current of each branch.

[0030] Furthermore, after obtaining the steady-state current waveform of each branch according to the Bode diagram of the dual-loop system, analyze whether the current waveform of each branch is the same; after obtaining the preset current I set After the steady-state current waveform is obtained, the maximum current I omax , minimum current I omin And calculate the actual current I o , output current accuracy λ I and ripple peak-to-peak fluctuation δ p-p , check whether I <0.5%、δ p-p <0.5%, if so, the dual current closed-loop control method achieves the expected effect, where

[0031]

[0032]

[0033]

[0034] The advantages of the present invention are: the present invention constructs a mathematical model of the equivalent circuit model of the main circuit of the magnet power supply and obtains the main circuit transfer function, thereby constructing a dual-current closed-loop negative feedback control block diagram, realizing dual-current closed-loop control, and analyzing the current accuracy to determine whether the dual-current closed-loop control method achieves the expected effect. If the expected effect is not achieved, the parameters of the main circuit transfer function are adjusted so that the total output current of the magnet power supply can reach and track the expected target current value in a short time and ensure the high precision requirements of the total output current. At the same time, compared with the single closed-loop strategy, this dual closed-loop control strategy can take into account the current sharing of each branch, avoid the imbalance of branch current causing excessive current in a certain branch to cause damage, and avoid branch circulation problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of a dual-current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device disclosed in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of an equivalent circuit model in a dual-current closed-loop control method for a magnetic power supply of a steady-state magnetic field testing device disclosed in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of a communication power supply module in a dual-current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device disclosed in an embodiment of the present invention;

[0038] Figure 4 A double current closed-loop negative feedback control block diagram of a double current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device disclosed in an embodiment of the present invention;

[0039] Figure 5 Bode diagram of a dual current closed-loop negative feedback control system of a dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device disclosed in an embodiment of the present invention.

[0040] Figure 6 A diagram of a steady-state magnetic power supply operation model constructed in MATLAB / Simulink simulation software for a dual-current closed-loop control method for a magnetic power supply of a steady-state magnetic field test device disclosed in an embodiment of the present invention;

[0041] Figure 7 This is a total current output waveform diagram of the simulation results of the dual-current closed-loop control method for the magnet power supply of the steady-state magnetic field testing device disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] like Figure 1 As shown, a dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device is provided, the method comprising the following steps:

[0044] S1. Construct the mathematical model of the equivalent circuit model of the main circuit of the magnet power supply; Figure 2As shown, the equivalent circuit model based on the magnet power supply main circuit includes a communication power supply module, a Buck and synchronous rectification circuit ( Figure 2 C1, V1, D1 and L1 form a Buck and synchronous rectification circuit), resistive and inductive loads ( Figure 2 Medium R L and L L ), there are multiple communication power supply circuits in each branch and they are connected in parallel to form a group of communication power supply modules, there is one resistive inductive load, and a Buck and synchronous rectification circuit is connected between each group of communication power supply modules and the resistive inductive load. For detailed circuit structure, please refer to Figure 2 , I will not elaborate on this. Figure 3 As shown, the telecommunications power module includes an uncontrolled rectifier, an interleaved parallel boost circuit, and a full-bridge LLC circuit. The uncontrolled rectifier and interleaved parallel boost circuit form a single-phase active power factor correction circuit to improve power factor; the full-bridge LLC circuit reduces switching losses and improves power efficiency. The total input is a three-phase, five-wire 220V AC power supply. It is divided into 24 branches. To ensure three-phase load balance, branches 1 to 8, branches 9 to 16, and branches 17 to 24 are connected between the live and neutral wires of phases A, B, and C, respectively. Each branch in the diagram consists of a telecommunications power module consisting of six 48V telecommunications power circuits connected in parallel, providing energy for the subsequent DC-DC circuit. The 24 buck converters and synchronous rectifier circuits are connected in parallel across the resistive and inductive loads of the steady-state magnet to generate very high currents.

[0045] S2. Determine the equivalent load of each branch in the equivalent circuit model; Specifically: the resistive and inductive loads in the equivalent circuit model include the inductor L L , Ohmic resistance R L , then the equivalent load function of each branch is: In this embodiment,

[0046]

[0047] Then the equivalent load function of each branch is:

[0048]

[0049] S3, according to the equivalent load of each branch and the proportional integral coefficient and current feedback coefficient of each branch inner loop, obtain the transfer function of each branch; wherein, the transfer function of each branch G1(s) to G n (s) is:

[0050]

[0051] Among them, K p2 , K i2is the proportional integral coefficient of each branch inner loop in the equivalent circuit model, β1 is the negative feedback current feedback coefficient of each branch inner loop, i1~i n is the branch current output by each branch, I nref is the given branch current value of the inner loop, and s is a complex variable.

[0052] S4. Based on the transfer functions of each branch and the outer loop proportional integral coefficient and current feedback coefficient in the equivalent circuit model, the main circuit transfer function is obtained, thereby constructing a dual current closed-loop negative feedback control block diagram to achieve dual current closed-loop control; wherein the main circuit transfer function G(s) is:

[0053]

[0054] Among them, K p1 , K i1 is the proportional integral coefficient of the outer loop in the equivalent circuit model, β is the negative feedback current feedback coefficient of the outer loop, I o is the total output current, I oref is the total current value given by the outer loop, and s is a complex variable.

[0055] like Figure 4 The dual current closed-loop control includes: a current outer loop control composed of the total output current of the magnet power supply target as the current outer loop given instruction and the output total current feedback; a current inner loop control composed of the current instruction obtained by the current outer loop and divided equally among the branches as the current inner loop given instruction and the output branch current feedback of each branch, taking the current outer loop given instruction I oref There are two cases: 6750A and 13500A respectively.

[0056] The current inner loop control and the current outer loop control both adopt proportional integral control structure. The proportional integral coefficient of the outer loop in the equivalent circuit model is K p1 =10, K i1 =0.0001, the outer loop negative feedback current feedback coefficient is β=1 / 800; the inner loop proportional integral coefficient of each branch in the equivalent circuit model is K p2 =5, K i2 =0.0005, and the negative feedback current feedback coefficient of each branch inner loop is β1=1 / 300.

[0057] The current outer loop control comprises the following steps:

[0058] (1) The total output current of the magnet power supply is given by I oref With the total output current I o Compare and find the deviation value e o ;

[0059] (2) Deviation e oThe outer loop control signal I is amplified by proportional integral control eo .

[0060] The current inner loop control comprises the following steps:

[0061] (1) The outer loop control signal I eo Divide it into 24 equal parts to obtain the inner loop given branch current value I after each branch is adjusted nref ;

[0062] (2) Set the inner loop given branch current value I nref The output currents I1~I of each Buck and synchronous rectification circuit are respectively obtained by sampling. n Compare and find the deviation value e1~e n ;

[0063] (3) Deviation value e1~e n After being amplified by the proportional controller, the inner loop control signal I is formed e1 ~I en ;

[0064] (4) Inner loop control signal I e1 ~I en After being processed by the sinusoidal pulse width modulation (SPWM) driving unit, an SPWM driving signal is generated. The Buck corresponding to the driving signal and the synchronous rectification circuit then generate the target current of each branch.

[0065] Figure 4 In the embodiment, carrier phase shift technology is added to each branch to achieve the effect of a higher equivalent switching frequency at a lower device switching frequency, thereby solving the problem of poor control effect caused by low system switching frequency due to large switching losses of high-power switching devices in high-power power electronic devices. The carrier phase shift technology is an existing technology and will not be described in detail here.

[0066] The Bode diagram of the dual-loop system described in step S5 is obtained from the closed-loop transfer function G(s), as shown in FIG. Figure 4 As shown in the figure, the dual-loop system basically maintains stable amplification gain and zero phase shift near the output DC value in the low-frequency band, and the system attenuation gain is 15.4dB in the high-frequency band near the switching frequency of 10kHz, with a large amplitude attenuation, which has a good suppression effect on interference in the switching frequency and above.

[0067] S5. Analyze the transfer function of the main circuit to obtain the Bode diagram of the dual-loop system, such as Figure 5As shown, the dual-loop system's low-frequency steady-state accuracy and low-frequency anti-interference capability, mid-frequency robustness, and high-frequency noise suppression capability are analyzed; a steady-state magnet power supply operation model is built in MATLAB / Simulink simulation software to analyze current accuracy and determine whether the dual-current closed-loop control method achieves the expected effect. If the expected effect is not achieved, the parameters of the main circuit transfer function are adjusted. After obtaining the steady-state current waveform of each branch based on the Bode diagram of the dual-loop system, analyze whether the current waveform of each branch is the same; after obtaining the preset current I set After the steady-state current waveform is obtained, the maximum current I omax , minimum current I omin And calculate the actual current I o , output current accuracy λ I and ripple peak-to-peak fluctuation δ p-p , check whether I <0.5%、δ p-p <0.5%. If so, the dual current closed-loop control method achieves the expected effect, where

[0068]

[0069]

[0070]

[0071] The following details the verification process: Figure 6 To verify the effectiveness of the dual-current closed-loop control method in achieving high-precision current target tracking, a 13.5kA steady-state magnet operation model was constructed in MATLAB / Simulink simulation software. The model includes two dual-current loop control modules, a carrier phase shift module, a main circuit module, and an equivalent inductive load module. The figure shows two power supply modules connected in parallel across the steady-state magnet load. Each group of 12 branches performs carrier phase shifting, for a total of 24 branches. Each main circuit consists of 12 parallel buck converter circuits with synchronous rectification. The DC voltage is set to 48V, and the load parameters are 4.5mH / 2.3mΩ.

[0072] As shown in Table 1, in the simulation, I oref The waveform of the total output current can be obtained in two cases: 6750A and 13500A. The steady-state current waveform for a period of time is now intercepted for analysis. Figure 7 Figure a in the middle is I oref =6750A current simulation waveform, the maximum current is 6750.006A, the minimum current is 6749.992A; Figure b is I oref=13500A current simulation waveform, the maximum current is 13500.004A, the minimum current is 13499.9955A. It can be easily seen from the waveform image that regardless of I oref No matter what the value is, the total output current can be kept stable near the target current.

[0073] Table 1 Simulated steady-state output current values

[0074]

[0075] like Figure 7 As shown, at the preset current I set =6750A, the actual current I o =6749.999A, output current accuracy λ I =2.07×10 -4 , ripple peak-to-peak fluctuation δ p-p =2.07×10 -4 , in accordance with λ I <0.5%、δ p-p <0.5%; at the preset current I set =13500A, the actual current I o =13499.999A, output current accuracy λ I =6.29×10 -5 , ripple peak-to-peak fluctuation δ p-p =6.29×10 -5 , which also meets λ I <0.5%、δ p-p <0.5%, achieving the goal of high-precision current control.

[0076] Continue reading Figure 7 , at the preset current I set =13500A, the output current waveform of branch 13-branch 18 is intercepted for illustration. The theoretical calculation shows that the steady-state current of each branch is 13500 / 24=562.5A. Figure 7 As shown, the output current waveforms of branches 13 to 18 are almost completely consistent, and the current values ​​in the steady-state stage are all stable at around 562.5A, achieving the effect of current sharing among the 24 branches.

[0077] Through the above technical scheme, the present invention constructs a mathematical model of the equivalent circuit model of the main circuit of the magnet power supply and obtains the main circuit transfer function, thereby constructing a dual-current closed-loop negative feedback control block diagram, realizing dual-current closed-loop control, and analyzing the current accuracy to determine whether the dual-current closed-loop control method achieves the expected effect. If the expected effect is not achieved, the parameters of the main circuit transfer function are adjusted so that the total output current of the magnet power supply can reach and track the expected target current value in a short time and ensure the high-precision requirements of the total output current. At the same time, compared with the single closed-loop strategy, this dual closed-loop control strategy can take into account the current sharing of each branch, avoid the imbalance of branch current causing excessive current in a certain branch to cause damage, and avoid branch circulation problems.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual current closed-loop control method for a magnet power supply in a steady-state magnetic field test device, characterized in that: The method comprises the following steps: S1. Construct a mathematical model of an equivalent circuit model of the main circuit of the magnet power supply; the equivalent circuit model of the main circuit of the magnet power supply includes a communication power supply module, a Buck and synchronous rectification circuit, and a resistive and inductive load. There are multiple communication power supply circuits on each branch and they are connected in parallel to form a group of communication power supply modules, there is one resistive and inductive load, and a Buck and synchronous rectification circuit is connected between each group of communication power supply modules and the resistive and inductive load; S2. Determine the equivalent load of each branch in the equivalent circuit model; S3. Obtain the transfer function of each branch according to the equivalent load of each branch and the proportional integral coefficient and current feedback coefficient of the inner loop of each branch; S4. Based on the transfer functions of each branch and the outer loop proportional integral coefficient and current feedback coefficient in the equivalent circuit model, the main circuit transfer function is obtained, thereby constructing a dual current closed-loop negative feedback control block diagram to achieve dual current closed-loop control; S5. Analyze the main circuit transfer function to obtain the dual-loop system Bode diagram, and build a steady-state magnet power supply operation model in MATLAB / Simulink simulation software to analyze the current accuracy, and determine whether the dual-current closed-loop control method achieves the expected effect. If the expected effect is not achieved, adjust the parameters of the main circuit transfer function.

2. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 1, characterized in that: The resistive-inductive load in the equivalent circuit model includes the inductor , ohmic resistance , then the equivalent load function of each branch is: .

3. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 2, characterized in that: The transfer functions of each branch to for: in, 、 is the proportional integral coefficient of the inner loop of each branch in the equivalent circuit model, is the negative feedback current feedback coefficient of the inner loop of each branch, ~ is the branch current output by each branch, is the current value of the given branch in the inner loop, is a complex variable.

4. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 3, characterized in that: The main circuit transfer function for: in, 、 is the proportional integral coefficient of the outer loop in the equivalent circuit model, is the outer loop negative feedback current feedback coefficient, is the total output current, is the total current value given by the outer loop, is a complex variable.

5. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 1, characterized in that: The dual current closed-loop control includes: a current outer loop control consisting of the total output current of the magnet power supply target as the current outer loop given instruction and the output total current feedback; and a current inner loop control consisting of the current instruction obtained by the current outer loop being equally divided among the branches as the current inner loop given instruction and the output branch current feedback of each branch.

6. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 5, characterized in that: The current inner loop control and the current outer loop control both adopt a proportional integral control structure.

7. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 5, characterized in that: The current outer loop control comprises the following steps: (1) Total output current given value of magnet power supply and the total output current Compare and find the deviation value ; (2) Bias The outer loop control signal is amplified by proportional integral control .

8. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 7, characterized in that: The current inner loop control comprises the following steps: (1) The outer loop control signal Divide into n equal parts to obtain the inner loop given branch current value after each branch is adjusted ; (2) Set the inner loop given branch current value The output current of each Buck and synchronous rectification circuit is obtained by sampling ~ Compare and find the deviation value ; (3) Deviation value Amplified by the proportional controller to form the inner loop control signal ~ ; (4) Inner loop control signal ~ After being processed by the sinusoidal pulse width modulation (SPWM) driving unit, an SPWM driving signal is generated. The Buck corresponding to the driving signal and the synchronous rectification circuit then generate the target current of each branch.

9. The dual current closed-loop control method for a magnet power supply of a steady-state magnetic field testing device according to claim 1, characterized in that: According to the Bode diagram of the dual-loop system, after obtaining the steady-state current waveform of each branch, analyze whether the current waveform of each branch is the same; after obtaining the preset current After the steady-state current waveform is obtained, the maximum current is obtained , minimum current And calculate the actual current , output current accuracy and ripple peak-to-peak fluctuations , check whether 、 If so, the dual current closed-loop control method achieves the expected effect, where 。

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