Multi-feed-forward current loop control method

Abstract

The invention relates to a multi-feed-forward current loop control method, which comprises the steps of generating a frequency-variable square wave current reference signal, and taking a difference value between the square wave reference current signal and an inductive current sampling value as a current error signal; the resonance angular frequency of the PR controller is adjusted according to the change of the power grid frequency, and the repetitive control period is adjusted according to the change of the square wave current frequency; respectively determining the output of a PI controller, the output of a PR controller and the output of a repetitive controller according to the current error signal, the resonance angular frequency and the repetitive control period; calculating current feed-forward output and voltage feed-forward output; and outputting the duty ratio controlled by the current loop. And repeating the steps in the next control period. According to the multi-feed-forward current loop control method provided by the invention, rapid and accurate tracking and disturbance suppression of the square wave current can be realized.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly to a multi-feedforward current loop control method. Background Art

[0002] High-power dysprosium lamps are commonly used in film shooting and stage lighting scenarios. In actual work, dysprosium lamps are driven by square-wave currents generated by digital ballasts. The two-stage ballast includes two links: rectification and H-bridge inversion. The H-bridge inversion link controls both the amplitude and frequency of the square-wave current simultaneously. The two-stage inverter reduces the number of power conversion links, improves system efficiency, and reduces system costs. However, it has high requirements for its control characteristics. However, traditional PI control has problems such as slow tracking speed and low accuracy for alternating signals, and thus urgent improvement is needed. Summary of the Invention

[0003] Based on this, it is necessary to provide a multi-feedforward current loop control method that can achieve fast and accurate tracking of alternating square-wave currents.

[0004] This application provides a multi-feedforward current loop control method, including the following steps: S10. Generate a square-wave current reference signal with variable frequency, and use the difference between the square-wave current reference signal and the sampled value of the inductor current as the current error signal; S20. Adjust the resonant angular frequency of the PR controller according to the change of the grid frequency, and adjust the repetitive control period according to the change of the square-wave current frequency; S30. Determine the output of the PI controller, the output of the PR controller, and the output of the repetitive controller respectively according to the current error signal, the resonant angular frequency, and the repetitive control period; calculate the current feedforward output and the voltage feedforward output; S40. Output the duty cycle of the current loop control :

[0005] Among them, is the first feedforward gain coefficient, is the second feedforward gain coefficient, is the output of the PI controller, is the output of the PR controller, is the output of the repetitive controller, is the current feedforward output, is the voltage feedforward output; in the next control cycle, repeat the above steps S10 to S40.

[0006] Preferably, the output of the PI controller is:

[0007] Among them, is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient.

[0008] Preferably, the output of the PR controller is: {u}_{PR}\left ( {t} \right )={K}_{2}\times e\left ( {t} \right )+{K}_{r}\int ^{t}_{0} {e\left ( {\tau} \right )\sin {\left [ {{\omega}_{0}\left ( {t-\tau} \right )} \right ]}{e}^{-{\omega}_{c}\left ( {t-\tau} \right )}d\tau}

[0009] where is the second proportional gain coefficient, is the resonance gain coefficient, is the resonance angular frequency, is the cut-off frequency.

[0010] Preferably, the output of the repetitive controller is:

[0011] where is the repetitive control period, is the third proportional gain coefficient, is the sequence number of the control period, is the time constant of the low-pass filter, is the current error signal at time is the weighted function of the error signal by the low-pass filter in the time domain.

[0012] Preferably, the current feedforward output is:

[0013] The voltage feedforward output is:

[0014] where is the inductance, is the current feedforward control period, is the output voltage, is the input voltage.

[0015] Preferably, in the microcontroller, a timer interrupt is used to generate a square wave signal with variable frequency as the square wave reference current signal.

[0016] Preferably, the frequency of the square-wave current is 50 Hz, 60 Hz, 75 Hz, 270 Hz - 360 Hz, 900 Hz - 1200 Hz.

[0017] Preferably, the resonant angular frequency is:

[0018] where is the grid frequency.

[0019] Preferably, the repetition control period is:

[0020] where is the frequency of the square-wave current.

[0021] The multi-feedforward current loop control method provided by this application outputs the duty cycle of the current loop control D which is composed of the output of the PI controller, the output of the PR controller, the output of the repetitive controller, the current feedforward output, and the voltage feedforward output, realizing the fast and accurate tracking and disturbance suppression of the square-wave current. Among them, the multi-feedforward links of current and voltage significantly improve the fast tracking ability of the square-wave current; the PR control and repetitive control links effectively suppress the current deviation and external disturbance in the process of square-wave current tracking, realizing the precise control of the square-wave current. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 is the circuit topology diagram of a two-stage digital square-wave ballast.

[0024] Figure 2 is the state diagram of the BUCK circuit.

[0025] Figure 3 is the flowchart of the multi-feedforward current loop control method in the embodiments of this application.

[0026] Figure 4 is the control block diagram of the embodiments of this application.

[0027] Figure 5 is the voltage and current transient waveform diagram before the application of the multi-feedforward control in the embodiments of this application.

[0028] Figure 6 Voltage and current transient waveform diagram after applying multi-feedforward control in the embodiments of this application. Detailed implementation manners

[0029] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to the relevant drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0030] It can be understood that in the following embodiments, "connection", if there is an electrical signal or data transfer between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0031] This embodiment provides a multi-feedforward current loop control method. The hardware platform to which this control method is applied is a two-stage digital square wave ballast, and the circuit topology is as Figure 1 shown. In Figure 1 , the input is an AC power supply. One end of the PFC high-frequency tube module 1 is electrically connected to the AC power supply, and the other end of the PFC high-frequency tube module 1 is electrically connected to the PFC low-frequency tube module 2. The PFC high-frequency tube module 1 is composed of multiple high-frequency tubes and inductors in three-phase interleaving. Its main function is to control the AC current, thereby controlling the DC bus voltage. The PFC low-frequency tube module 2 is composed of two low-frequency tubes, and realizes rectification by switching the state of the switch tube by tracking the direction of the AC current. The combination of the two parts realizes the functions of rectification voltage regulation and power factor correction, and outputs a DC voltage. Then the DC voltage is filtered by a bus capacitor and connected to the BUCK high-frequency tube module 3. The BUCK high-frequency tube module 3 is composed of multiple high-frequency tubes and inductors in three-phase interleaving. Its main function is to control the amplitude of the DC current. Then the DC current is input to the BUCK low-frequency tube module 4. The BUCK low-frequency tube module 4 can realize the function of inversion by controlling the on-off state of the upper and lower tubes to adjust the output current direction.

[0032] The multi-feedforward current loop control method of this embodiment is an optimized method proposed for the current loop control of the BUCK part. The given value of the current loop is an AC square wave signal, the feedback is the inductor current, and the output is the duty cycle D . The circuit state on the BUCK side is as Figure 2 shown. S1 and S3 are high-frequency tubes, and S2 and S4 are low-frequency tubes. It is stipulated that the output current is positive from top to bottom. When the current reference value is positive, the low-frequency tube S4 is turned on and the low-frequency tube S2 is turned off. When the high-frequency tube S1 is turned on and the high-frequency tube S3 is turned off, the inductor is charged, as shown in Figure 2 (a) in; when the high-frequency tube S1 is turned off and the high-frequency tube S3 is turned on, the inductor discharges, as shown in Figure 2As shown in Fig. (b). When the current reference value is negative, the low-frequency transistor S2 conducts and the low-frequency transistor S4 turns off; when the high-frequency transistor S3 turns on and the high-frequency transistor S1 turns off, the inductor is charged, as shown in Figure 2 Fig. (c); when the high-frequency transistor S3 turns off and the high-frequency transistor S1 turns on, the inductor discharges, as shown in Figure 2 Fig. (d). Therefore, the output of the positive half-cycle current loop is the duty cycle of the high-frequency transistor S1, and the output of the negative half-cycle current loop is the duty cycle of the high-frequency transistor S3.

[0033] As shown in Figure 3 and Figure 4 Fig., Figure 4 is a control block diagram represented in the S domain or Z domain. This embodiment provides a multi-feedforward current loop control method, including:

[0034] Step S10: Generate a square-wave current reference signal with a variable frequency , and use the difference between the square-wave current reference signal and the sampled value of the inductor current as the current error signal . .

[0035] Preferably, in the microcontroller, use the timer interrupt to generate a square-wave signal with a variable frequency as the square-wave current reference signal . Here, according to the set frequency or the externally input frequency command, the parameters of the timer can be dynamically changed, so as to change the frequency of the square-wave current reference signal . In this embodiment, the square-wave current frequency

[0036] is 50Hz, 60Hz, 75Hz, 270Hz - 360Hz, 900Hz - 1200Hz. As an example, when the square-wave current frequency

[0037] is 75Hz, the timer interrupt frequency is 60KHz, then the timer count value.

[0038] Preferably, the sampled value of the inductor current is obtained by sampling through a Hall effect current sensor. The PI controller subtracts the square-wave current reference signal from the sampled value of the inductor current to obtain the current error signal .

[0039] Step S20: Adjust the resonant angular frequency of the PR controller according to the change of the power grid frequency , so that ​; Adjust the repetitive control period according to the frequency of the square-wave current to achieve precise control of the square-wave current. , so that , realizing precise control of the square-wave current.

[0040] Preferably, the grid frequency is 50Hz or 60Hz.

[0041] Step S30: Determine the output of the PI controller , the resonant angular frequency and the repetitive control period respectively, and calculate the current feedforward output , the output of the PR controller , the output of the repetitive controller ; Calculate the current feedforward output and the voltage feedforward output .

[0042] Specifically, the output of the PI controller consists of a proportional term and an integral term. The role of the proportional term is to quickly adjust the control output according to the current error, and the role of the integral term is to eliminate the steady-state error:

[0043] wherein is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient.

[0044] In the S domain, its transfer function:

[0045] The output of the PR controller consists of a proportional part and a resonant part. The proportional part is used to quickly respond to the error, and the resonant part is used to suppress the second-harmonic disturbance: {u}_{PR}\left ( {t} \right )={K}_{2}\times e\left ( {t} \right )+{K}_{r}\int ^{t}_{0} {e\left ( {\tau} \right )\sin {\left [ {{\omega}_{0}\left ( {t-\tau} \right )} \right ]}{e}^{-{\omega}_{c}\left ( {t-\tau} \right )}d\tau}

[0046] wherein is the second proportional gain coefficient, is the resonance gain coefficient, is the said resonance angular frequency, is the cut-off frequency.

[0047] In the S domain, its transfer function:

[0048] The output of the repetitive controller is:

[0049] wherein, is the repetitive control period, is the third proportional gain coefficient, is the sequence number of the control period, is the time constant of the low-pass filter, represents the current error signal of the control system at moment, is the weighting function of the low-pass filter for the error signal in the time domain.

[0050] In the Z domain, its transfer function:

[0051] wherein, , is the timer interrupt period; is the exponential decay factor per step, .

[0052] The current feedforward output is:

[0053] The voltage feedforward output is:

[0054] wherein, is the inductance, is the current feedforward control period, is the output voltage, is the input voltage.

[0055] As an example, the input voltage and the output voltage are measured by using a voltage sensor.

[0056] Step S40, output the duty cycle of the current loop control. Here, the preset duty cycle adjustment formula is:

[0057] Among them, is the first feedforward gain coefficient, is the second feedforward gain coefficient, is the output time.

[0058] In the next control cycle, the above steps S10 to S40 are repeatedly executed.

[0059] Figure 5 and Figure 6 are the voltage and current transient waveform diagrams before and after the multi-feedforward control is applied. Among them, the red curve is the output voltage waveform, and the blue curve is the output current waveform. Figure 5 is the waveform without feedforward control. There are obvious spikes in the initial stage of the voltage waveform after commutation, and the subsequent fluctuations are relatively large. The current waveform rises steeply and fluctuates violently before reaching the stable value. It shows that the voltage stability is poor during commutation, and the transient response of the current change is not ideal; while Figure 6 is the waveform under multi-feedforward control. After commutation, the voltage spike is significantly reduced, the subsequent fluctuation amplitude of the voltage waveform decreases, and it tends to be stable. The rising process of the current waveform becomes relatively gentle, the fluctuation amplitude is significantly reduced, and the speed of reaching the stable state is faster. It shows that the feedforward control effectively suppresses the voltage mutation, improves the voltage stability, and improves the transient response characteristics of the current.

[0060] The multi-feedforward control has a significant optimization effect on the output voltage and current waveforms of the system, effectively suppresses the mutation and fluctuation of the voltage, and at the same time improves the transient response of the current, making the current change more smoothly and quickly reach the stable value, and improving the dynamic performance and stability of the system.

[0061] For the multi-feedforward current loop control method provided in this embodiment, the duty cycle of the output current loop control D is composed of the output of the PI controller, the output of the PR controller, the output of the repetitive controller, the current feedforward output, and the voltage feedforward output, realizing the fast and accurate tracking and disturbance suppression of the square wave current. Among them, the multi-feedforward links of current and voltage significantly improve the fast tracking ability of the square wave current; the PR control and repetitive control links effectively suppress the current deviation and external disturbance during the tracking process of the square wave current, realizing the precise control of the square wave current.

[0062] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A multi-feedforward current loop control method, characterized in that, It includes the following steps: S10. Generate a square-wave current reference signal with variable frequency, and use the difference between the square-wave current reference signal and the sampled value of the inductor current as the current error signal; S20. Adjust the resonant angular frequency of the PR controller according to the change of the grid frequency, and adjust the repetitive control period according to the change of the square-wave current frequency; S30. Determine the outputs of the PI controller, the PR controller, and the repetitive controller respectively according to the current error signal, the resonant angular frequency, and the repetitive control period . The output of the PR controller . The output of the repetitive controller ; Calculate the current feedforward output and the voltage feedforward output ; S40, Duty cycle of output current loop control : Among them, is the first feedforward gain coefficient, is the second feedforward gain coefficient; In the next control period, repeat the above steps S10 to S40.

2. The multi-feedforward current loop control method according to claim 1, wherein The output of the PI controller is: Wherein, is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient.

3. The multi-feedforward current loop control method according to claim 2, wherein The output of the PR controller is: {u}_{PR}\left ( {t} \right )={K}_{2}\times e\left ( {t} \right )+{K}_{r}\int ^{t}_{0} {e\left ( {\tau} \right )\sin {\left [ {{\omega}_{0}\left ( {t-\tau} \right )} \right ]}{e}^{-{\omega}_{c}\left ( {t-\tau} \right )}d\tau} Among them, is the second proportional gain coefficient, is the resonance gain coefficient, is the resonance angular frequency for the said, is the cut-off frequency.

4. The multi-feedforward current loop control method according to claim 3, wherein The output of the repetitive controller is: wherein, is the repetition control period, is the third proportional gain coefficient, is the sequence number of the control period, is the time constant of the low-pass filter, is the current error signal at the moment of is the weighting function of the error signal by the low-pass filter in the time domain.

5. The multi-feedforward current loop control method according to claim 4, characterized in that, The current feedforward output is: The voltage feedforward output is: Among them, is the inductance, is the current feed-forward control period, is the output voltage, is the input voltage.

6. The multi-feedforward current loop control method according to claim 1, wherein In the microcontroller, use the timer interrupt to generate a square-wave signal with variable frequency as the square-wave reference current signal.

7. The multi-feedforward current loop control method according to claim 6, wherein The square-wave current frequencies are 50Hz, 60Hz, 75Hz, 270Hz - 360Hz, 900Hz - 1200Hz.

8. The multi-feedforward current loop control method according to claim 1, characterized in that The resonant angular frequency is: Among them, is the power grid frequency.

9. The multi-feedforward current loop control method according to claim 1, characterized in that The repetitive control period is: Among them, is the frequency of the square-wave current.

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