CN-122001234-A - Double-frequency induction heating power inverter output frequency feedforward anti-interference control method

CN122001234ACN 122001234 ACN122001234 ACN 122001234ACN-122001234-A

Abstract

The invention discloses a feedforward anti-interference control method for the output frequency of a double-frequency induction heating power inverter. For the frequency transient deviation and current envelope oscillation caused by the abrupt in-out and the attitude change of a workpiece and the voltage fluctuation of a power grid, the output voltage and the load current of a high-frequency channel and a low-frequency channel are synchronously obtained in each control period, the discrete variation of the phase difference between active power and voltage and current is calculated, a disturbance observation vector is constructed, the high-frequency and low-frequency target frequency correction quantity is obtained through feedforward gain matrix mapping, and the high-frequency and low-frequency target frequency correction quantity is superimposed to the original target frequency after recursive filtering and amplitude limiting. The corrected target frequency is executed by a cascade frequency adjustment structure, wherein an outer loop generates a frequency increment instruction according to an improved increment adjustment rule, and the inner loop rapidly completes tracking update under the frequency increment and change rate constraint and double-frequency minimum frequency interval constraint. The method weakens the impact of strong interference on the double-frequency closed loop, inhibits the frequency impact, shortens the recovery time and keeps the frequency track smooth and the closed loop stable.

Inventors

CHEN XINGRU
DUAN ZHONGXIA
LI NINGNING
WANG SHUYU
MA BENDONG
Shang Yaru
WANG HOUSHENG

Assignees

中国科学院电工研究所

Dates

Publication Date: 20260508
Application Date: 20260112

Claims (10)

1. The feedforward anti-interference control method for the output frequency of the double-frequency induction heating power inverter is characterized by comprising the following steps of: step S1, defining control period, symbols and constraint parameters, and presetting parameters for frequency increment amplitude constraint, frequency increment change rate constraint and double-frequency minimum frequency interval constraint; S2, constructing disturbance observation vectors based on output voltage and load current sampling results of the high-frequency channel and the low-frequency channel; S3, taking the disturbance observation vector as input, calculating a high-frequency target frequency instruction correction amount and a low-frequency target frequency instruction correction amount, and correcting the target frequency instruction to form a feedforward compensation channel; And S4, performing closed-loop tracking on the target frequency instruction corrected in the step S3 through a cascade frequency control structure comprising an outer ring improved incremental frequency regulator and an inner ring frequency tracking link, wherein the outer ring calculates a frequency incremental instruction according to a frequency error between the target frequency instruction and an actual output frequency, the inner ring applies a frequency incremental amplitude constraint and a frequency incremental change rate constraint preset in the step S1 to the frequency incremental instruction to generate an intermediate output frequency, and applies a double-frequency minimum frequency interval constraint preset in the step S1 on the basis of the intermediate output frequency, and finally obtaining a high-frequency output frequency and a low-frequency output frequency by adjusting a low-frequency channel through a coordination strategy.
2. The method for feedforward anti-interference control of the output frequency of the inverter of the dual-frequency induction heating power supply according to claim 1, wherein the step S1 includes: Setting a discrete control period of the output frequency control, defined as The discrete time sequence number is defined as , Represent the first A control period; The high frequency output frequency is defined as Indicating that the inverter is at the first The high frequency output frequency corresponding to each control period is defined as Indicating that the inverter is at the first Low frequency output frequency corresponding to the control period; The high frequency target frequency command and the low frequency target frequency command are respectively defined as ; The feedforward compensation corrected high-frequency target frequency command and low-frequency target frequency command are respectively defined as ; The high frequency output frequency increment and the low frequency output frequency increment are respectively as follows: ; setting the lower limit and the upper limit of the high-frequency output frequency as respectively The lower limit and the upper limit of the low-frequency output frequency are respectively ; The maximum increment amplitude of the high-frequency output frequency and the maximum increment amplitude of the low-frequency output frequency are respectively The upper limit of the rate of change of the increment of the high-frequency output frequency and the upper limit of the rate of change of the increment of the low-frequency output frequency are respectively defined as ; Dual-frequency minimum frequency interval parameter: Indicating that the absolute value of the difference between the high-frequency output frequency and the low-frequency output frequency is not less than ; The sampling sequences of the output voltage and the load current of the high-frequency channel are respectively defined as The sampling sequences of the output voltage and the load current of the low-frequency channel are respectively defined as Wherein Representing the sample sequence number.
3. The method for feedforward anti-interference control of output frequency of dual-frequency induction heating power inverter according to claim 2, wherein a first step is provided The sampling window corresponding to each control period is The number of sampling points contained therein In the sampling window, the output voltage sampling sequence and the load current sampling sequence of the high-frequency channel are respectively 、 The low frequency channel corresponds to 、 Wherein The active power of the high-frequency channel is defined as: , The active power of the low frequency channel is defined as: , Based on the first Extracting voltage-current phase difference of high-frequency channel and low-frequency channel from voltage-current sampling data in each control period 、 The control unit calculates the voltage-current phase difference of the high-frequency channel and the low-frequency channel based on the sampling voltage and the load current 、 ; From the first Starting a control period, the active power variation and the phase difference variation of the high-frequency channel are respectively defined as: , the active power variation and the phase difference variation of the low-frequency channel are respectively defined as: , the differential feature quantities of the high-frequency channel and the low-frequency channel are uniformly combined into a double-frequency disturbance observation vector: 。
4. The method for feedforward anti-interference control of the output frequency of the inverter of the dual-frequency induction heating power supply of claim 3, wherein step S3 includes: S3.1, the double-frequency disturbance observation vector is calculated Mapping into a high-frequency target frequency command correction amount and a low-frequency target frequency command correction amount; and S3.2, filtering and clipping the target frequency command correction amount.
5. The method for feedforward anti-interference control of the output frequency of a dual-frequency induction heating power inverter of claim 4, wherein S3.1 comprises: , , Wherein, the Is shown in the first The high frequency target frequency command modifier generated by the feedforward compensation for each control period, Representing a low frequency target frequency command modifier generated by feed forward compensation; 、、、、、、、 The system is a constant coefficient preset according to the actual system characteristics and is used for describing the sensitivity of high-frequency and low-frequency target frequency instructions to disturbance observables of each component.
6. The method for feedforward anti-interference control of the output frequency of the dual-frequency induction heating power inverter of claim 5, wherein S3.2 comprises: , Wherein, the For the filtered feedforward correction amount vector, The feedforward filter coefficient is used for adjusting the smoothness of the feedforward correction quantity; Setting the maximum amplitude allowed by the high-frequency feedforward correction amount as The maximum amplitude allowed by the low frequency feedforward correction is The following steps are: , , Wherein the method comprises the steps of , Limiting threshold value for symmetrical limiting 0) For defining The maximum absolute value of the output, i.e. after clipping 。
7. The method for feedforward anti-interference control of the output frequency of the inverter of the dual-frequency induction heating power supply of claim 6, wherein step S4 includes: S4.1, superposing the target frequency instruction correction amount generated in the step S3 with an original target frequency instruction to form a disturbance corrected target frequency instruction, and defining a frequency error; S4.2, receiving the frequency error defined in the S4.1, calculating a frequency increment instruction through an outer ring improved increment type frequency adjustment rule, and outputting the frequency increment instruction to an inner ring S4.3; S4.3, the inner ring receives the increment instruction of S4.2, applies the constraint of the amplitude and the change rate defined in the step S1, generates a smooth actual frequency increment, and outputs the intermediate frequency to S4.4; s4.4, applying the minimum frequency interval constraint defined in the step S1 based on the intermediate frequency of the step S4.3, and adjusting a low-frequency channel through a coordination strategy to ensure that the double-frequency interval meets the requirement; And S4.5, based on the parameters, observables and control structures defined in the steps, the time scales and control parameters of the feedforward, the outer ring and the inner ring are coordinated, and the whole system is ensured to work rapidly, smoothly and stably under strong interference.
8. The method for feedforward anti-interference control of the output frequency of the dual-frequency induction heating power inverter of claim 7, wherein S4.5 includes: The cascade frequency control structure is composed of a feedforward compensation channel, an outer ring improved incremental frequency regulator and an inner ring frequency tracking link, wherein: the equivalent bandwidth of the inner loop frequency tracking link is higher than that of the outer loop improved incremental frequency regulator, so that the outer loop regards the inner loop as a controlled object of approximate first order during setting; The equivalent bandwidth of the feedforward compensation channel is not higher than the bandwidth of the inner loop frequency tracking link, and the feedforward correction quantity after filtering The rate of change of (c) should be within the range that the inner loop can follow, enabling the inner loop to perform feedforward-induced target frequency adjustment in each control period without disrupting the output frequency smoothness due to the feedforward changing too fast.
9. The method is characterized in that S4.5 comprises two stages of setting an inner loop frequency tracking link, wherein the first stage is used for determining an inner loop control parameter according to the frequency increment amplitude constraint and the frequency increment change rate constraint in the step S1 under the condition that the double frequency minimum frequency interval constraint is not introduced, so that the inner loop tracks a frequency increment instruction output by an outer loop and outputs an intermediate output frequency meeting the constraint, the second stage is used for incorporating the double frequency minimum frequency interval constraint into an inner loop updating result, and when the intermediate output frequency does not meet the double frequency minimum frequency interval constraint defined in the step S1, compensating and adjusting a low frequency channel according to the coordination strategy of the step S4.4, so that the updated high and low frequency output frequencies meet the double frequency minimum frequency interval constraint and the upper and lower working limit constraints of the high and low frequency output frequencies.
10. The dual-frequency induction heating power inverter output frequency feedforward anti-interference control method of claim 9, wherein S4.5 includes: On the basis that the inner loop frequency tracking link is already set, the outer loop parameter setting is preferably performed under the condition that the feedforward compensation channel is closed, namely, the feedforward gain matrix is made Only the closed loop formed by the cascade of the outer loop and the inner loop is considered; After the outer loop parameter setting is completed and a stable closed loop is formed, introducing a feedforward compensation channel; On the premise of confirming that the stability of an outer loop closed loop is not affected, gradually increasing elements related to main disturbance observables in a feedforward gain matrix, enabling a feedforward channel to bear more rapid correction tasks, properly reducing an outer loop proportional coefficient or an error variation term coefficient, avoiding the feedforward compensation and an outer loop regulator from excessively superposing the same disturbance, and thus keeping proper closed loop damping characteristics before frequency increment constraint is not triggered; The feedforward filter coefficient is selected as a value which can still act on disturbance in time within the range that the inner loop can follow, so that the equivalent bandwidth of the feedforward correction quantity is not higher than the bandwidth of the inner loop frequency tracking link.

Description

Double-frequency induction heating power inverter output frequency feedforward anti-interference control method Technical Field The invention relates to the technical field of induction heating power supplies and control thereof, in particular to a feedforward anti-interference control method for the output frequency of an inverter of a dual-frequency induction heating power supply. Background The dual-frequency induction heating power supply can give consideration to both superficial heating and deeper heating in the same set of equipment by simultaneously providing high-frequency output frequency and low-frequency output frequency, and is suitable for various industrial induction heating working conditions. Inverters of this type of power supply typically form a resonant circuit with the induction coil and workpiece, requiring high and low frequency output frequencies to operate near the respective resonant points to improve efficiency and reduce device stress. In industrial sites, abrupt in-out, gesture change and batch switching of workpieces in induction coils are quite common, and in addition, the superposition of power grid voltage fluctuation and upper-level power supply disturbance causes abrupt change of load equivalent resistance and equivalent inductance in a short time, high-frequency resonance points and low-frequency resonance points drift rapidly, instantaneous offset and oscillation of double-frequency output frequency are extremely easy to occur, and current envelope oscillation and even protection action are further caused. The existing double-frequency induction heating power inverter mostly adopts a feedback control mode based on output voltage, current and phase thereof, and high-frequency output frequency and low-frequency output frequency are enabled to operate in a closed loop near resonance through means such as frequency searching, phase approximation or power characteristic quantity adjustment. The method can maintain basic stability when the load change is slow or the disturbance is weaker, but the controller parameters and the adjustment bandwidth are limited by the system stability margin, the frequency step limit and the double-frequency minimum frequency interval constraint, so that the response speed and the smoothness are difficult to be considered under the strong interference effects of sudden workpiece in-out, rapid workpiece gesture change, power grid disturbance and the like. If the response speed is increased simply by increasing the feedback gain or shortening the adjustment period, the measurement noise and the model error are often amplified, so that the frequency closed loop is subjected to overshoot and oscillation, and even mutual disturbance between the high-frequency channel and the low-frequency channel is caused under the double-frequency coupling condition. In order to restrain noise and overshoot, part of the technical proposal adds links such as filtering, amplitude limiting and the like in a feedback loop, or reduces the adjusting strength through a fixed margin, so that the frequency change of the double-frequency output is more gentle. However, such measures further reduce the sensitivity to abrupt disturbances, and when strong disturbances occur, it is difficult for the high and low frequency output frequencies to get closer to the new resonance point in time, and under some conditions, the output frequencies may deviate from the optimal operating interval for a long time, resulting in current surge, voltage swing, and efficiency degradation. In a dual-frequency system, a high-frequency channel and a low-frequency channel often share part of a power device and a load structure, and frequency impact of one channel also influences current and power distribution of the other channel through load coupling, so that disturbance propagation between dual frequencies is more complex. In the prior art, although the scheme of utilizing active power or phase difference to carry out frequency adjustment exists, the quantities are still generally regarded as components of feedback errors, the output frequency is slowly corrected mainly through a feedback link, and a disturbance observation and feedforward compensation structure specially oriented to a strong interference scene is absent. Especially, under the discrete sampling control condition, how to construct disturbance observance by utilizing the variation of voltage, current and phase thereof between adjacent control periods, how to quickly map disturbance information into frequency command correction on the premise of not damaging the stability of the original frequency closed loop, and coordinate with frequency increment constraint and double-frequency interval constraint, and a feedforward anti-interference control method with a definite structure and parameter design principle is not yet available. Therefore, it is necessary to provide an output frequency feedforward anti-interference control method capa