EAST fast control power supply output current fast balancing control method and system

Abstract

The present invention relates to the technical field of EAST fast control power supply, and provides a method for fast balanced control of the output current of an EAST fast control power supply based on a variable gain sliding mode, comprising: sampling the total output current and each branch current of the EAST fast control power supply, and obtaining a reference current signal value; extrapolating the output current i within k+1 cycles according to the constraint equation of the EAST fast control power supply structure and circuit. o (k+1), compensating for delays during the system's digital control process; adaptively adjusting the current balancing gain c of each branch; establishing a sliding mode surface function for rapid output current balancing and optimizing the traditional sliding mode exponential approach rate; discretizing and solving to obtain the control rate, and then generating a duty cycle PWM wave to control the on and off of the switching tube. This invention solves the problems of slow dynamic response of the total output current of the EAST fast-controlled power supply and unbalanced branch currents, improving the performance of plasma vertical displacement balance control.

Description

Technical Field

[0001] The present invention relates to the technical field of EAST fast control power supply operation, and in particular to an EAST fast control power supply output current fast balancing control method and system thereof. Background Art

[0002] The Experimental Advanced Superconducting Tokamak (EAST) is a Chinese-developed experimental device for controlled nuclear fusion power generation, playing a key role in alleviating contemporary energy challenges. During the fusion power generation process, the EAST fast-control power supply tracks the reference signal output current from the plasma control system (PCS) to control the excitation of the load coil, generating a corresponding magnetic field for rapid and stable magnetic balance control of the plasma's vertical displacement. For example, Bi Nanxia of Hefei University of Technology published her master's thesis, "Research and Optimization of the New Fast-Control Power Supply Control System for EAST," in April 2018. The EAST fast-control power supply utilizes six parallel inverter bridge branches. Each branch tracks the reference current signal from the PCS and outputs a rated current of 1500A, resulting in a total output current of 9000A at the load output. The total output current of the EAST fast-control power supply exhibits a linear amplification characteristic with respect to the PCS reference current signal and is the sum of the output currents of each branch, so the currents in each branch should remain consistent and balanced.

[0003] Achieving rapid tracking and control of the total output current is an important goal for ensuring rapid and stable magnetic balance control of the plasma. Therefore, high requirements are placed on the dynamic response speed of the output current of the EAST fast-control power supply. The EAST fast-control power supply adopts a multi-branch parallel structure, with current-sharing reactors connected to the output ends of each branch to achieve passive balancing of the currents in each branch. However, the passive balancing of branch currents is poor, and the imbalance of branch currents seriously damages the service life of the switching power devices in each branch, which is not conducive to the long-term stable operation of the EAST fast-control power supply. At present, the EAST fast-control power supply adopts a proportional control method to achieve output current tracking of the reference signal. However, the working environment of the EAST fast-control power supply is complex, and proportional control has major defects in achieving rapid control of the output current and balanced control of the currents in each branch. The rapid control of the total output current and the balanced robust control performance of the currents in each branch need to be further improved.

[0004] Sliding mode control has the advantages of strong anti-interference ability, fast dynamic response, and good robustness, and has been applied in many tracking control scenarios. For example, the Chinese invention patent with publication number CN114710080A, "Sliding Mode Control Method for Permanent Magnet Synchronous Motor Based on Improved Variable Gain Reaching Law," discloses a sliding mode control method for permanent magnet synchronous motors based on an improved variable gain reaching law. The method optimizes the exponential reaching law of the fixed gain, improves the fixed gain exponential reaching law to an adaptive gain reaching law based on the size of the sliding surface, and constructs an extended state observer for system disturbances and rotor angular velocity observations. Combining the improved variable gain reaching law with an integral sliding mode permanent magnet synchronous motor speed controller, the method achieves vector optimization tracking control of the permanent magnet synchronous motor. The paper "Model-free Parameter Adaptive Sliding Mode Control of Underwater Helicopters," published in the Journal of Ship Science and Technology in May 2022, proposes a model-free parameter adaptive sliding mode control method and designs an adaptive adjustment law for the sliding mode controller parameters to address the overshoot and oscillation problems of the sliding mode controller, achieving optimal control of underwater helicopter flight curve tracking.

[0005] The aforementioned patent application and paper improved the sliding mode control method, specifically proposing an adaptive control method based on a sliding mode controller. This improved the system's dynamic response performance, resolved the chattering problem associated with sliding mode control, and achieved excellent tracking control. However, the complex trigonometric function calculations and adaptive rate variation increased the controller's computational complexity, hindering the implementation of digital control in the rapid balanced control of the output current of the EAST fast-control power supply. Consequently, the improvement in the dynamic response speed of the output current of the EAST fast-control power supply and the improvement in branch current balanced control performance were limited. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to improve the output current response speed and branch current balancing control performance of the EAST fast-control power supply.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] The present invention provides an EAST fast control power supply output current fast balancing control method, comprising the following steps:

[0009] S1. Sample the total output current of the EAST fast control power supply and the current of each branch, and obtain the reference current signal value from the PCS;

[0010] S2, the total output current i obtained based on sampling within k cycles o (k), the output current i in the k+1 cycle is obtained by extrapolating the constraint equations of the EAST fast control power supply structure and circuit o (k+1), using i o (k+1) replaces i o(k) Delay compensation during digital control of the system;

[0011] S3. Adaptively adjust the current balancing gain value c of each branch according to the error between each branch current and the standard branch current;

[0012] S4, the output total current with unity gain quickly tracks the reference current and the branch currents with gain c balance the standard branch current, thereby establishing a sliding mode surface function for output current fast balance control;

[0013] S5. Improve and optimize the traditional sliding mode index approach rate;

[0014] S6. Based on the designed sliding surface function and the improved and optimized convergence rate, the control rate is obtained after discretization, and then the PWM wave of the duty cycle is obtained. The obtained PWM wave will act on the switch tubes of each inverter bridge branch of the EAST fast-control power supply to control the conduction and shutdown of the switch tubes.

[0015] Furthermore, in step S2, the output current i in the k+1 cycle is obtained by extrapolating the constraint equation of the EAST fast control power supply structure and circuit. o (k+1), specifically:

[0016] The constraint equation expression of the EAST fast control power supply circuit is:

[0017]

[0018] Where, L H is the current-sharing reactor value of the branch and the current-sharing reactor values ​​of each branch are equal, i j is the current of each branch, L o is the total load at the output, i o is the total output current, u j Control voltage at each branch output terminal;

[0019] Then, in the ideal case where the currents of the six branches of the EAST fast-control power supply are balanced and the total output current is evenly distributed during the balanced operation of the six branches, the constraint equation of the EAST fast-control power supply circuit is expressed as

[0020]

[0021] Discretizing formula (2) yields

[0022]

[0023] Where, T s is the switching period, i o (k+1) is the extrapolated value of the total output current in the next cycle, i o(k) is the total output current value of the current cycle, u j (k-1) is the control voltage of each branch output terminal in the previous cycle;

[0024] Arranging formula (3), the output current extrapolation prediction value of the next cycle of the total output current is:

[0025]

[0026] Furthermore, the adaptive adjustment of the current balancing gain value c of each branch in step S3 is specifically as follows:

[0027] During the balanced operation of the six branches of the EAST fast-control power supply, the ideal standard current expression of each branch is:

[0028]

[0029] According to the current i of each branch j With the branch standard current i j * The error e is adaptively adjusted to the c value, and the expression for the adaptive adjustment of the c value is:

[0030]

[0031] Where K b and K a The upper and lower limits of the e value are allowed.

[0032] Furthermore, the general expression for establishing the output current fast balancing control sliding mode function in step S4 is:

[0033] s=(i ref -i o )+c(i j * -i j ),j=1,2,…,6 (7)

[0034] Where i ref is the reference current.

[0035] Furthermore, the conventional sliding mode index approach rate is improved and optimized as described in step S5, specifically:

[0036] The traditional sliding mode exponential approach rate expression is:

[0037] s~=-εsgn(s)-qs (8)

[0038] Where ε and q are the convergence rate constants and ε>0, q>0, sgn(s) is the sign function, and the sign function expression is

[0039]

[0040] Then, the improved approach rate expression with the addition of higher-order terms is:

[0041] s~=-εsgn(s)-qs-f(s) (10)

[0042]

[0043] Where f(s) is a high-order term and R is the acceptable thickness of the sliding surface.

[0044] Furthermore, the designed sliding surface function and the improved optimized approach rate described in step S6 are discretized and solved to obtain the control rate, which is specifically:

[0045] Based on formula (10), the optimized improved approach rate is discretized to obtain

[0046]

[0047] Where s(k) and s(k+1) are the sizes of the sliding surface functions in periods k and k+1;

[0048] Based on formula (13), we can get

[0049] s(k+1)=s(k)-T s εsgn[s(k)]-qT s s(k)-T s f[s(k)] (14)

[0050] In the designed sliding surface function, combined with formula (7), it can be seen that the sliding surface function expression in the k+1 period is

[0051]

[0052] During the digital control process of EAST fast control power supply, after compensating the digital control delay, there is

[0053]

[0054] Where u j (k) is the number obtained after compensation o (k+1) required branch control amount;

[0055] Based on formula (2), under ideal conditions, the constraint equation of the EAST fast control power supply circuit is rewritten as

[0056]

[0057] After discretizing formula (17), the branch current extrapolation formula after digital delay compensation can be obtained as follows:

[0058]

[0059] Based on formulas (14) and (15), we can get

[0060]

[0061] Combining formulas (16), (18) and (19), we can obtain the branch control rate of the control output total current to quickly track the reference current and the branch current balance after digital delay compensation:

[0062]

[0063] The present invention also provides an EAST fast-control power supply output current fast balancing control system, which adopts the above method when the system is running, and includes the following modules:

[0064] The sampling module is used to sample the total output current of the EAST fast control power supply and the current of each branch, and obtain the reference current signal value from the PCS;

[0065] The current prediction module is used to calculate the total output current i based on the sampling within k cycles. o (k), the output current i in the k+1 cycle is obtained by extrapolating the constraint equations of the EAST fast control power supply structure and circuit o (k+1), using i o (k+1) replaces i o (k) Delay compensation during digital control of the system;

[0066] The branch gain module is used to adaptively adjust the current balancing gain value c of each branch according to the error between each branch current and the standard branch current;

[0067] A sliding surface function establishment module is used to quickly track the reference current by the output total current of unity gain and to evenly track the standard branch current by the currents of each branch with a gain of c, thereby establishing a sliding surface function for fast balanced control of the output current;

[0068] The approach rate optimization module is used to improve and optimize the traditional sliding mode exponential approach rate;

[0069] The output module is used to obtain the control rate after discretization based on the designed sliding surface function and the improved and optimized approach rate, and then obtain the PWM wave of the duty cycle. The obtained PWM wave will act on the switching tubes of each inverter bridge branch of the EAST fast-control power supply to control the conduction and shutdown of the switching tubes.

[0070] Furthermore, the current prediction module extrapolates the constraint equations of the EAST fast control power supply structure and circuit to obtain the output current i within the k+1 cycle. o(k+1), specifically:

[0071] The constraint equation expression of the EAST fast control power supply circuit is:

[0072]

[0073] Where, L H is the current-sharing reactor value of the branch and the current-sharing reactor values ​​of each branch are equal, i j is the current of each branch, L o is the total load at the output, i o is the total output current, u j Control voltage at each branch output terminal;

[0074] Then, in the ideal case where the currents of the six branches of the EAST fast-control power supply are balanced and the total output current is evenly distributed during the balanced operation of the six branches, the constraint equation of the EAST fast-control power supply circuit is expressed as

[0075]

[0076] Discretizing formula (2) yields

[0077]

[0078] Where, T s is the switching period, i o (k+1) is the extrapolated value of the total output current in the next cycle, i o (k) is the total output current value of the current cycle, u j (k-1) is the control voltage of each branch output terminal in the previous cycle;

[0079] Arranging formula (3), the output current extrapolation prediction value of the next cycle of the total output current is:

[0080]

[0081] Furthermore, the approach rate optimization module improves and optimizes the traditional sliding mode index approach rate, specifically:

[0082] The traditional sliding mode exponential approach rate expression is:

[0083] s~=-εsgn(s)-qs (8)

[0084] Where ε and q are the convergence rate constants and ε>0, q>0, sgn(s) is the sign function, and the sign function expression is

[0085]

[0086] Then, the improved approach rate expression with the addition of higher-order terms is:

[0087] s~=-εsgn(s)-qs-f(s) (10)

[0088]

[0089] Where f(s) is a high-order term and R is the acceptable thickness of the sliding surface.

[0090] Furthermore, the designed sliding surface function and the improved optimized approach rate described in the output module are discretized and solved to obtain the control rate, which is specifically:

[0091] Based on formula (10), the optimized improved approach rate is discretized to obtain

[0092]

[0093] Where s(k) and s(k+1) are the sizes of the sliding surface functions in periods k and k+1;

[0094] Based on formula (13), we can get

[0095] s(k+1)=s(k)-T s εsgn[s(k)]-qT s s(k)-T s f[s(k)] (14)

[0096] In the designed sliding surface function, combined with formula (7), it can be seen that the sliding surface function expression in the k+1 period is

[0097]

[0098] During the digital control process of EAST fast control power supply, after compensating the digital control delay, there is

[0099]

[0100] Where u j (k) is the number obtained after compensation o (k+1) required branch control amount;

[0101] Based on formula (2), under ideal conditions, the constraint equation of the EAST fast control power supply circuit is rewritten as

[0102]

[0103] After discretizing formula (17), the branch current extrapolation formula after digital delay compensation can be obtained as follows:

[0104]

[0105] Based on formulas (14) and (15), we can get

[0106]

[0107] Combining formulas (16), (18) and (19), we can obtain the branch control rate of the control output total current to quickly track the reference current and the branch current balance after digital delay compensation:

[0108]

[0109] The advantages of the present invention are:

[0110] (1) In step S2 of the present invention, in order to compensate for the inherent delay of the digital control of the EAST fast-control power supply, the output current prediction value of the next cycle is obtained by extrapolation based on the constraint equation of the EAST fast-control power supply structure and circuit, and the output current prediction value is used to track the reference current, so that the output total current tracks the reference current value in advance, further improving the output current response speed of the EAST fast-control power supply and optimizing the output current fast control process.

[0111] (2) In step S3 of the present invention, the gain value c of the control target item of the balance of each branch current is adaptively adjusted according to the error between each branch current and the standard branch current. When the error between the branch current and the standard branch current is large, the gain value c is adaptively adjusted to become larger. When the error between the branch current and the standard branch current is small, the gain value c is adaptively adjusted to become smaller. Under the premise of realizing rapid control of the total output current, balanced control of each branch current is realized, and the long-term stable operation of the EAST fast-control power supply under the parallel operation of each branch is maintained.

[0112] (3) In step S4 of the present invention, a sliding surface function is established based on the output total current quickly tracking the reference current and the balanced control of each branch current, and the branch current balanced control gain can be adaptively adjusted, ensuring that the balance of each branch current is also guaranteed under the premise that the output total current quickly tracks the reference current, achieving good control performance and further improving the stability of the EAST fast control power supply.

[0113] (4) In step S5 of the present invention, the traditional sliding mode exponential sliding mode approach rate is improved, and an optimized improved approach rate with high-order terms is designed so that when the sliding mode controller approaches the equilibrium point from a relatively far area, the high-order terms play a major role in accelerating the convergence speed of the system, so that the system quickly approaches the equilibrium point; when the system approaches the equilibrium point, the high-order terms in the designed optimized improved approach rate are adaptively reduced to near zero, ensuring that the sliding mode controller can jump back and forth near the equilibrium point with less jitter, thereby accelerating the convergence speed of the sliding mode control system and making the sliding mode control system have less jitter, further optimizing the control performance of the EAST fast control power supply.

[0114] (5) The optimal branch control quantity obtained in step S6 of the present invention realizes digital control delay compensation, and is only related to the total output current value and the current value of each branch, and has nothing to do with other branch control quantities. It not only realizes the optimal control of each branch, ensuring that the total output current quickly tracks the reference current, but also realizes balanced control of each branch current, thereby achieving the purpose of fast and robust control of the EAST fast-control power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0115] Figure 1 This is a flow chart of a method for rapidly balancing the output current of an EAST fast-control power supply according to an embodiment of the present invention;

[0116] Figure 2 This is a block diagram of the output current fast balancing control structure of the EAST fast control power supply of the present invention;

[0117] Figure 3 This is a schematic diagram of the output current tracking response waveform of the EAST fast-control power supply according to the present invention. DETAILED DESCRIPTION

[0118] 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 the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0119] Example 1

[0120] This embodiment provides a method for fast balancing control of the output current of an EAST fast control power supply. Figure 1 As shown, the following steps are included:

[0121] S1, the total output current i of the EAST fast control power supply o And each branch current i j The current is sampled by a 1:5000 current sensor, and the reference current signal i ref It is connected to the branch controller of the EAST fast-control power supply in the form of a voltage value, and the output total current, branch current and reference current value are connected to the corresponding branch controller through the ADC digital sampling chip.

[0122] S2, the total output current i obtained based on sampling within k cycles o(k) In order to compensate for the digital control delay of the EAST fast control power supply and further improve the dynamic response speed of the output current, the constraint equation of the EAST fast control power supply structure and circuit is extrapolated to obtain the predicted value of the output current of the next cycle in advance. The constraint equation expression of the EAST fast control power supply circuit is:

[0123]

[0124] Where, L H is the current-sharing reactor value of the branch and the current-sharing reactor values ​​of each branch are equal, i j is the current of each branch, L o is the total load at the output, i o is the total output current, u j Control voltage at each branch output.

[0125] During the balanced operation of the six branches of the EAST fast-control power supply, the currents of each branch are balanced and the total output current is evenly distributed. Therefore, under ideal conditions, the constraint equation of the EAST fast-control power supply circuit is expressed as follows:

[0126]

[0127] Discretizing formula (2) yields

[0128]

[0129] Where, T s is the switching period, i o (k+1) is the extrapolated value of the total output current in the next cycle, i o (k) is the total output current value of the current cycle, u j (k-1) is the control voltage at the output end of each branch in the previous cycle.

[0130] Arranging formula (3), the output current extrapolation prediction value of the next cycle of the total output current is:

[0131]

[0132] In the process of controlling the six branches of the EAST fast-control power supply separately, each branch samples the total output current and its own branch current. According to formula (4), the extrapolated prediction of the total output current in each branch is only related to the control voltage of each branch output terminal in the previous cycle and the total output current value collected in the current cycle, and is not related to the control of other branches. Therefore, formula (4) is used to realize the extrapolated prediction of the total output current, and i is used to calculate the total output current. o (k+1) instead of i o (k) Track the reference current value so that the total output current tracks the reference current in advance, achieving the purpose of rapid control of the total output current.

[0133] S3. Based on the purpose of fast control of the total output current of the EAST fast-control power supply and balanced control of each branch current, the gain value c of the control target item of each branch current balance is adaptively adjusted according to the error between each branch current and the standard branch current. Under the premise of ensuring that the total output current is quickly obtained, each branch current can be adaptively balanced and adjusted according to the error between itself and the standard branch current. During the balanced operation of the 6 branches of the EAST fast-control power supply, the ideal standard current expression of each branch is:

[0134]

[0135] According to the current i of each branch j With the branch standard current i j * The error e is adaptively adjusted to the c value, and the expression for the adaptive adjustment of the c value is:

[0136]

[0137] Where K b and K a The upper and lower limits of the e value are allowed.

[0138] During the adaptive adjustment process of the c value, the gain value is adaptively adjusted as the size of the e value remains within the range of 0.2 to 1, ensuring that the total current is output quickly as the primary control purpose. Secondly, when the deviation of each branch current from the branch standard current is large, the c value will be increased to ensure the balance of each branch current. When the deviation of each branch current from the branch standard current is small, the c value will be reduced to ensure that the dynamic response speed of the total output current is faster.

[0139] S4. Based on the purpose of fast control of the total output current of the EAST fast control power supply and balanced control of each branch current, a sliding surface function for fast balanced control of the output current is established. The sliding surface function consists of two items: the fast tracking reference current of the total output current with a unit gain and the balanced tracking standard branch current of each branch current with a gain of c. The two items together constitute the sliding surface function to ensure fast balanced control of the output current of the EAST fast control power supply. The general expression of the sliding surface function for fast balanced control of the output current is established as follows:

[0140] s=(i ref -i o )+c(i j * -i j ),j=1,2,…,6 (7)

[0141] Where i ref is the reference current.

[0142] In the sliding surface function design, the primary control objective is to quickly output the total current. Its gain is the standard unit gain, and the adaptive adjustment of the c value ensures that the currents of each branch can evenly track the standard branch current.

[0143] S5. Based on the traditional sliding mode exponential approach rate, a high-order term is added to improve and optimize the traditional sliding mode exponential approach rate to ensure that the sliding surface function can quickly reach the vicinity of the sliding surface, thereby improving the output current response speed of the entire EAST fast control power supply; the high-order term added in the improved approach rate can be adaptively adjusted according to the size of the sliding surface, ensuring that the sliding surface function converges quickly while having less jitter. The traditional sliding mode exponential approach rate expression is:

[0144] s~=-εsgn(s)-qs (8)

[0145] Where ε and q are the convergence rate constants and ε>0, q>0, sgn(s) is the sign function, and the sign function expression is

[0146]

[0147] In order to speed up the convergence of the sliding mode controller and make the system quickly approach the sliding surface while reducing the chattering near the sliding surface, the traditional exponential approach rate is improved based on the sliding surface function. The improved approach rate expression with the addition of high-order terms is:

[0148] s~=-εsgn(s)-qs-f(s) (10)

[0149]

[0150] Where f(s) is a high-order term and R is the acceptable thickness of the sliding surface.

[0151] According to the sliding mode stability theorem, the designed sliding mode controller can meet the stability conditions.

[0152] s ～ s<0 (12)

[0153] This proves that the designed improved optimized sliding mode control rate with high-order terms can be stably applied to the designed sliding mode controller.

[0154] The designed optimized improved approach rate with high-order terms enables the high-order terms to play a major role in the process of the sliding mode controller approaching the equilibrium point from a relatively distant area, accelerating the convergence speed of the system and making the system quickly approach the equilibrium point; when the system approaches the equilibrium point, the high-order terms in the designed optimized improved approach rate are adaptively reduced, and the high-order terms will gradually transform to near zero values, reducing the impact on the system, allowing the sliding mode controller to jump back and forth near the equilibrium point with less jitter, ensuring that the sliding mode control system has less jitter.

[0155] S6. Based on the designed sliding surface function and the improved approach rate, the optimal control rate is obtained after discretization, and then the PWM wave with the optimal duty cycle is obtained to control the on and off of the switch tubes of each inverter bridge branch. Based on formula (10), the optimized approach rate is discretized to obtain

[0156]

[0157] Where s(k) and s(k+1) are the sizes of the sliding surface functions in periods k and k+1.

[0158] Based on formula (13), we can get

[0159] s(k+1)=s(k)-T s εsgn[s(k)]-qT s s(k)-T s f[s(k)] (14)

[0160] In the designed sliding surface function, combined with formula (8), it can be seen that the sliding surface function expression in the k+1 period is

[0161]

[0162] There is a digital control delay in the digital control process of EAST fast control power supply. After compensating the digital control delay, there is

[0163]

[0164] Where u j (k) is the number obtained after compensation o (k+1) The optimal branch control quantity required.

[0165] Based on formula (2), under ideal conditions, the constraint equation of the EAST fast control power supply circuit is rewritten as

[0166]

[0167] After discretizing formula (17), the branch current extrapolation formula after digital delay compensation can be obtained as follows:

[0168]

[0169] Based on formulas (14) and (15), we can get

[0170]

[0171] Combining formulas (16), (18) and (19), we can obtain the optimal control rate of the branch with the total output current quickly tracking the reference current and branch current balance after digital delay compensation:

[0172]

[0173] The optimal control rate u obtained by solving j (k) is related to the sliding surface function s(k), that is, the optimal control rate of each branch is only related to the total output current value and branch current value collected by each branch, and has nothing to do with the control quantities of other branches. This not only realizes the optimal control of each branch and ensures that the total output current quickly tracks the reference current, but also realizes the balanced control of each branch current.

[0174] Based on the on and off conditions of the switches in each inverter bridge branch, the total output current is quickly controlled, achieving the goal of the EAST fast-control power supply output current quickly tracking the reference current. At the same time, the output current balance of each branch is more consistent, that is, they can all track the standard branch current, achieving the goal of balanced control of the EAST fast-control power supply branch current, and ensuring the long-term good and stable operation of the entire EAST fast-control power supply. Figure 2 As shown, each branch control structure has a certain control effect on the total output current i o and their respective branch currents i j (j=1,2,...,6) and the reference current signal i ref To compensate for the delay caused by the digital control process of the EAST fast control power supply and further improve the dynamic response speed of the output current, the constraint equation of the EAST fast control power supply structure and circuit is extrapolated to obtain the predicted output current value i of the next cycle in advance. o (k+1), using i o (k+1) instead of i o (k) Control is performed to achieve current delay compensation; in order to achieve the purpose of fast control of the total output current of the EAST fast control power supply and balanced control of the current of each branch, a sliding surface consisting of two items, the total current quickly tracks the reference current and the branch current evenly tracks the standard branch current, is established. The gain c value of the branch current evenly tracking the standard branch current in the established sliding surface can be adaptively adjusted according to the error between the current of each branch and the standard branch current, so as to ensure that the output current of each branch is more balanced; in order to ensure that the established sliding surface converges quickly and stably and reduces the vibration near the sliding surface, high-order terms are added to the traditional sliding mode exponential approach rate for improvement and optimization, so that the control system can converge quickly when it is far away from the sliding surface, and the vibration is smaller when sliding near the sliding surface; based on the designed gain adaptive sliding surface function and the sliding mode controller with improved optimized approach rate, the optimal control rate is obtained after discretization, so as to obtain the PWM wave with the optimal duty cycle to act on the switch tube of each inverter bridge branch of the EAST fast control power supply; the output end of each branch passes through the current sharing reactor L H Connect to common load L oAt the end, each branch controller controls each other independently, and only the output current of each branch is aggregated to the common load end; the designed sliding mode controller can converge quickly and has small jitter, which solves the problems of insufficient dynamic response speed of the output current of the EAST fast-control power supply and low branch current balance, and achieves the purpose of fast, balanced, stable and robust control of the output current of the EAST fast-control power supply.

[0175] This embodiment also simulates and analyzes the fast balancing control method for the output current of the EAST fast control power supply. The simulation parameters are as follows: the EAST fast control power supply is composed of 6 inverter bridge branches in parallel, each inverter bridge branch is composed of 3 single H-bridge inverter bridges in cascade, the DC supply voltage of each single H-bridge inverter bridge is 540V, the common load inductance value is 160μH, the common load inductance internal resistance value is 0.008Ω, the branch current sharing reactor value is 100μH, the switching frequency of the switching device is 5kHz, the total reference current is ±9000A / 100Hz AC square wave, the total output current rating is ±9000A / 100Hz, the output current of each branch is ±1500A / 100Hz, the 6 branches operate together, and the parameters of each branch controller are consistent. The fast balancing control method for the output current of the EAST fast control power supply based on variable gain sliding mode is used to achieve fast balancing control of the output current of the EAST fast control power supply, such as Figure 3 As shown, analysis of the simulation waveform shows that within a complete output current cycle, when the reference current signal is a ±9000A / 100Hz AC square wave, the total output current of the EAST fast-control power supply can quickly track the reference current signal output ±9000A / 100Hz AC square wave current, and the output current of each branch can reach ±1500A / 100Hz AC square wave current output. The currents in each branch are well balanced, and the current waveforms between each branch can maintain a high degree of consistency. The simulation waveform shows that the present invention can enable the EAST fast-control power supply to quickly and accurately follow the reference signal to output the corresponding current, and the currents in each branch are well balanced, which can achieve the performance of rapid balanced control of the vertical displacement of the plasma.

[0176] Example 2

[0177] It should be further explained that, based on the same inventive concept, this embodiment provides an EAST fast-control power supply output current fast balancing control system. When running, the system executes the method described in Example 1 and includes the following modules:

[0178] The sampling module is used to sample the total output current of the EAST fast control power supply and the current of each branch, and obtain the reference current signal value from the PCS;

[0179] The current prediction module is used to calculate the total output current i based on the sampling within k cycles. o(k), the output current i in the k+1 cycle is obtained by extrapolating the constraint equations of the EAST fast control power supply structure and circuit o (k+1), using i o (k+1) replaces i o (k) Delay compensation during digital control of the system;

[0180] The branch gain module is used to adaptively adjust the current balancing gain value c of each branch according to the error between each branch current and the standard branch current;

[0181] A sliding surface function establishment module is used to quickly track the reference current by the output total current of unity gain and to evenly track the standard branch current by the currents of each branch with a gain of c, thereby establishing a sliding surface function for fast balanced control of the output current;

[0182] The approach rate optimization module is used to improve and optimize the traditional sliding mode exponential approach rate;

[0183] The output module is used to obtain the control rate after discretization based on the designed sliding surface function and the improved and optimized approach rate, and then obtain the PWM wave of the duty cycle. The obtained PWM wave will act on the switching tubes of each inverter bridge branch of the EAST fast-control power supply to control the conduction and shutdown of the switching tubes.

[0184] The current prediction module is described in the EAST fast control power supply structure and circuit constraint equations to obtain the output current i within k+1 cycles o (k+1), specifically:

[0185] The constraint equation expression of the EAST fast control power supply circuit is:

[0186]

[0187] Where, L H is the current-sharing reactor value of the branch and the current-sharing reactor values ​​of each branch are equal, i j is the current of each branch, L o is the total load at the output, i o is the total output current, u j Control voltage at each branch output terminal;

[0188] Then, in the ideal case where the currents of the six branches of the EAST fast-control power supply are balanced and the total output current is evenly distributed during the balanced operation of the six branches, the constraint equation of the EAST fast-control power supply circuit is expressed as

[0189]

[0190] Discretizing formula (2) yields

[0191]

[0192] Where, T s is the switching period, i o (k+1) is the extrapolated value of the total output current in the next cycle, i o (k) is the total output current value of the current cycle, u j (k-1) is the control voltage of each branch output terminal in the previous cycle;

[0193] Arranging formula (3), the output current extrapolation prediction value of the next cycle of the total output current is:

[0194]

[0195] The approach rate optimization module improves and optimizes the traditional sliding mode index approach rate, specifically:

[0196] The traditional sliding mode exponential approach rate expression is:

[0197] s~=-εsgn(s)-qs (8)

[0198] Where ε and q are the convergence rate constants and ε>0, q>0, sgn(s) is the sign function, and the sign function expression is

[0199]

[0200] Then, the improved approach rate expression with the addition of higher-order terms is:

[0201] s~=-εsgn(s)-qs-f(s) (10)

[0202]

[0203] Where f(s) is a high-order term and R is the acceptable thickness of the sliding surface.

[0204] The output module is based on the designed sliding surface function and the improved optimized approach rate, which is discretized and solved to obtain the control rate, specifically:

[0205] Based on formula (10), the optimized improved approach rate is discretized to obtain

[0206]

[0207] Where s(k) and s(k+1) are the sizes of the sliding surface functions in periods k and k+1;

[0208] Based on formula (13), we can get

[0209] s(k+1)=s(k)-T s εsgn[s(k)]-qTs s(k)-T s f[s(k)] (14)

[0210] In the designed sliding surface function, combined with formula (7), it can be seen that the sliding surface function expression in the k+1 period is

[0211]

[0212] During the digital control process of EAST fast control power supply, after compensating the digital control delay, there is

[0213]

[0214] Where u j (k) is the number obtained after compensation o (k+1) required branch control amount;

[0215] Based on formula (2), under ideal conditions, the constraint equation of the EAST fast control power supply circuit is rewritten as

[0216]

[0217] After discretizing formula (17), the branch current extrapolation formula after digital delay compensation can be obtained as follows:

[0218]

[0219] Based on formulas (14) and (15), we can get

[0220]

[0221] Combining formulas (16), (18) and (19), we can obtain the branch control rate of the control output total current to quickly track the reference current and the branch current balance after digital delay compensation:

[0222]

[0223] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 various embodiments of the present invention.

Claims

1. The EAST fast control power supply output current fast balancing control method is characterized by: The following steps are involved: S1. Sample the total output current of the EAST fast control power supply and the current of each branch, and obtain the reference current signal value from the PCS; S2, based on k The total output current sampled during the cycle i o ( k ), extrapolated from the constraint equations of the EAST fast control power supply structure and circuit k + Output current within 1 cycle i o ( k +1), take advantage of i o ( k +1) Replace i o ( k ), to compensate for the delay in the digital control process of the system; The constraint equation expression of the EAST fast control power supply circuit is: （1） Where, L H is the current-sharing reactor value of the branch and the current-sharing reactor values ​​of each branch are equal. i j is the current of each branch, L o is the total load at the output, i o is the total output current, u j Control voltage at each branch output terminal; Then, in the ideal case where the currents of the six branches of the EAST fast-control power supply are balanced and the total output current is evenly distributed during the balanced operation of the six branches, the constraint equation of the EAST fast-control power supply circuit is expressed as （2） Discretizing formula (2) yields （3） Where, T s is the switching period, i o ( k +1) is the extrapolated value of the total output current in the next cycle, i o ( k ) is the total output current value of the current cycle, u j ( k -1) is the control voltage of each branch output terminal in the previous cycle; Arranging formula (3) to obtain the output current extrapolation prediction value of the next cycle of the total output current is （4） S3. Adaptively adjust the current balancing gain value c of each branch according to the error between each branch current and the standard branch current; S4, the output total current with unity gain quickly tracks the reference current and the branch currents with gain c balance the standard branch current, and establishes the output current fast balance control sliding mode function, which is expressed as （7） Where, i ref is the reference current; S5. Improve and optimize the traditional sliding mode index approach rate. The specific methods are as follows: The traditional sliding mode exponential approach rate expression is: （8） In the formula ε and q is the approach rate constant and ε >0, q >0,sgn( s ) is a symbolic function, and the symbolic function expression is （9） Then, the improved approach rate expression with the addition of higher-order terms is: （10） （11） Where, f ( s ) is a high-order term, R is the acceptable thickness of the sliding surface; S6. Based on the designed sliding surface function and the improved and optimized convergence rate, the control rate is obtained after discretization, and then the PWM wave of the duty cycle is obtained. The obtained PWM wave will act on the switch tubes of each inverter bridge branch of the EAST fast-control power supply to control the conduction and shutdown of the switch tubes; The designed sliding surface function and the improved optimized approach rate are discretized and solved to obtain the control rate, which is specifically: Based on formula (10), the optimized improved approach rate is discretized to obtain （13） Where, s ( k )and s ( k +1) k and k +1 period sliding surface function size; Based on formula (13), we can get （14） In the designed sliding surface function, combined with formula (7), we can know k The sliding surface function expression within the +1 period is: （15） During the digital control process of EAST fast control power supply, after compensating the digital control delay, there is （16） Where, u j ( k ) is obtained after digital compensation i o ( k +1) the required branch control amount; Based on formula (2), under ideal conditions, the constraint equation of the EAST fast control power supply circuit is rewritten as （17） After discretizing formula (17), the branch current extrapolation formula after digital delay compensation can be obtained as follows: （18） Based on formulas (14) and (15), we can get （19） Combining formulas (16), (18) and (19), we can get the branch control rate of the control output total current to quickly track the reference current and the branch current balance after digital delay compensation: （20）。 2. The method for rapidly balancing the output current of an EAST fast-control power supply according to claim 1, wherein: The adaptive adjustment of the current balancing gain value c of each branch in step S3 is specifically as follows: During the balanced operation of the six branches of the EAST fast-control power supply, the ideal standard current expression of each branch is: （5） According to the current of each branch i j and branch standard current i j * Error e Adaptive size adjustment c value, c The adaptive adjustment expression of value is （6） Where, K b and K a for e The upper and lower limits of the allowed values.

3. EAST fast control power supply output current fast balancing control system, characterized by: When the system is running, the method described in any one of claims 1 to 2 is adopted, including the following modules: The sampling module is used to sample the total output current of the EAST fast control power supply and the current of each branch, and obtain the reference current signal value from the PCS; Current prediction module, used based on k The total output current sampled during the cycle i o ( k ), extrapolated from the constraint equations of the EAST fast control power supply structure and circuit k + Output current within 1 cycle i o ( k +1), take advantage of i o ( k +1) Replace i o ( k ), to compensate for the delay in the digital control process of the system; The branch gain module is used to adaptively adjust the current balancing gain value c of each branch according to the error between each branch current and the standard branch current; A sliding surface function establishment module is used to quickly track the reference current by the output total current of unity gain and to evenly track the standard branch current by the currents of each branch with a gain of c, thereby establishing a sliding surface function for fast balanced control of the output current; The approach rate optimization module is used to improve and optimize the traditional sliding mode exponential approach rate; The output module is used to obtain the control rate after discretization based on the designed sliding surface function and the improved and optimized approach rate, and then obtain the PWM wave of the duty cycle. The obtained PWM wave will act on the switching tubes of each inverter bridge branch of the EAST fast-control power supply to control the conduction and shutdown of the switching tubes.

4. The EAST fast control power supply output current fast balancing control system according to claim 3 is characterized in that: The branch gain module adaptively adjusts the current balancing gain value c of each branch, specifically: During the balanced operation of the six branches of the EAST fast-control power supply, the ideal standard current expression of each branch is: （5） According to the current of each branch i j and branch standard current i j * Error e Adaptive size adjustment c value, c The adaptive adjustment expression of value is （6） Where, K b and K a for e The upper and lower limits of the allowed values.

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