A multi-feedforward current loop control method

Abstract

The present application relates to a multi-feedforward current loop control method, comprising: generating a frequency-variable square wave current reference signal, and using the difference between the square wave reference current signal and the inductor current sampling value as a current error signal; adjusting the resonant angular frequency of the PR controller according to changes in the grid frequency, and adjusting the repetitive control period according to changes in the square wave current frequency; determining the output of the PI controller, the output of the PR controller, and the output of the repetitive controller according to the current error signal, the resonant angular frequency, and the repetitive control period; calculating the current feedforward output and the voltage feedforward output; and outputting the duty cycle of the current loop control. In the next control period, the above steps are repeated. The multi-feedforward current loop control method provided by the present application can achieve fast and accurate tracking and disturbance suppression of square wave current.

Description

Technical Field

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

[0002] High-power HMI lamps are commonly used in film and television productions and stage lighting. In practice, these lamps are driven by a square-wave current generated by a digital ballast. A two-stage ballast consists of two stages: rectification and H-bridge inverter. The H-bridge inverter controls both the amplitude and frequency of the square-wave current. This two-stage inverter reduces the number of power conversion steps, improving system efficiency and reducing system costs. However, it places high demands on its control characteristics. Traditional PI control, however, suffers from slow tracking speed and low accuracy for alternating signals, requiring urgent improvement. 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 current.

[0004] The present application provides a multi-feedforward current loop control method, comprising the following steps: S10, generating a frequency-variable square wave current reference signal, and using the difference between the square wave current reference signal and the inductor current sampling value as a current error signal; S20, adjusting the resonant angular frequency of the PR controller according to changes in the grid frequency, and adjusting the repetitive control period according to changes in the square wave current frequency; S30, determining the output of the PI controller, the output of the PR controller, and the output of the repetitive controller according to the current error signal, the resonant angular frequency, and the repetitive control period; calculating the current feedforward output and the voltage feedforward output; S40, outputting the duty cycle of the current loop control :

[0005]

[0006] in, 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, Current feedforward output, is the voltage feedforward output; in the next control cycle, the above steps S10 to S40 are repeated.

[0007] Preferably, the output of the PI controller is:

[0008]

[0009] in, is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient.

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

[0011] {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}

[0012] in, is the second proportional gain coefficient, is the resonant gain coefficient, is the resonant angular frequency, is the cutoff frequency.

[0013] Preferably, the output of the repetitive controller is:

[0014]

[0015] in, is the repetitive control cycle, is the third proportional gain coefficient, is the sequence number of the control cycle, is the time constant of the low-pass filter, for The current error signal at the moment, It is the weighting function of the low-pass filter on the error signal in the time domain.

[0016] Preferably, the current feedforward output is:

[0017]

[0018] The voltage feedforward output is:

[0019]

[0020] in, is the inductance, is the current feedforward control period, is the output voltage, is the input voltage.

[0021] Preferably, in the microcontroller, a timer interrupt is used to generate a frequency-variable square wave signal as the square wave reference current signal.

[0022] Preferably, the square wave current frequency is 50 Hz, 60 Hz, 75 Hz, 270 Hz to 360 Hz, or 900 Hz to 1200 Hz.

[0023] Preferably, the resonant angular frequency is:

[0024]

[0025] in, is the grid frequency.

[0026] Preferably, the repetitive control cycle is:

[0027]

[0028] in, is the square wave current frequency.

[0029] The multi-feedforward current loop control method provided by this application outputs a duty cycle of the current loop control D Comprising the outputs of the PI controller, the PR controller, and the repetitive controller, as well as current and voltage feedforward outputs, it achieves fast and accurate square-wave current tracking and disturbance suppression. The multiple current and voltage feedforwards significantly enhance the ability to quickly track square-wave currents. The PR and repetitive control stages effectively suppress current deviations and external disturbances during square-wave current tracking, achieving precise control of the square-wave current. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is the circuit topology diagram of a two-stage digital square wave ballast.

[0032] Figure 2 This is the BUCK circuit state diagram.

[0033] Figure 3 This is a flow chart of a multi-feedforward current loop control method according to an embodiment of the present application.

[0034] Figure 4This is a control block diagram of an embodiment of the present application.

[0035] Figure 5 This is a transient waveform diagram of voltage and current before the multi-feedforward control is applied according to an embodiment of the present application.

[0036] Figure 6 This is a transient waveform diagram of voltage and current after the multi-feedforward control is applied according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0038] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if there is transmission of electrical signals or data between the connected circuits, modules, units, etc.

[0039] This embodiment provides a multi-feedforward current loop control method. The hardware platform used in this control method is a two-stage digital square wave ballast. The circuit topology is as follows: Figure 1 As shown. Figure 1 In the example, the input is an AC power source. One end of the PFC high-frequency tube module 1 is electrically connected to the AC power source, and the other end is electrically connected to the PFC low-frequency tube module 2. PFC high-frequency tube module 1 consists of multiple high-frequency tubes and an inductor in a three-phase interlaced arrangement. Its primary function is to control the AC current, thereby controlling the DC bus voltage. PFC low-frequency tube module 2 consists of two low-frequency tubes, which switch the switching state to track the direction of the AC current to achieve rectification. These two components combine to implement rectification, voltage regulation, and power factor correction, outputting a DC voltage. This DC voltage is then filtered through bus capacitors and connected to the buck high-frequency tube module 3. Buck high-frequency tube module 3, consisting of multiple high-frequency tubes and an inductor in a three-phase interlaced arrangement, primarily controls the DC current amplitude. This DC current is then input to the buck low-frequency tube module 4, which adjusts the output current direction by controlling the switching states of the upper and lower tubes, thus achieving an inverter function.

[0040] The multi-feedforward current loop control method of this embodiment is an optimization method proposed for the current loop control of the BUCK part. The given current loop is an AC square wave signal, the feedback is the inductor current, and the output is the duty cycle. D The circuit status on the BUCK side is as follows: Figure 2As shown, S1 and S3 are high-frequency tubes, S2 and S4 are low-frequency tubes, and the output current is specified to be in the positive direction 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 the figure. Figure 2 As shown in (a); 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 2 As shown in (b). When the current reference value is negative, the low-frequency tube S2 is turned on and the low-frequency tube S4 is turned off; when the high-frequency tube S3 is turned on and the high-frequency tube S1 is turned off, the inductor is charged, as shown in Figure 2 As shown in (c); when the high-frequency tube S3 is turned off and the high-frequency tube S1 is turned on, the inductor discharges, as shown in Figure 2 As shown in (d), the output of the positive half-cycle current loop is the duty cycle of the high-frequency tube S1, and the output of the negative half-cycle current loop is the duty cycle of the high-frequency tube S3.

[0041] like Figure 3 and Figure 4 As shown, Figure 4 is a control block diagram expressed in the S domain or the Z domain. This embodiment provides a multi-feedforward current loop control method, including:

[0042] Step S10: Generate frequency Variable square wave current reference signal , the square wave current reference signal and the inductor current sampling value The difference is used as the current error signal .

[0043] Preferably, in the microcontroller, a timer interrupt is used to generate a frequency The variable square wave signal serves as the square wave current reference signal Here, the timer parameters can be dynamically changed according to the set frequency or external input frequency command, thereby changing the square wave current reference signal frequency.

[0044] In this embodiment, the square wave current frequency 50Hz, 60Hz, 75Hz, 270Hz~360Hz, 900Hz~1200Hz.

[0045] As an example, when the square wave current frequency When the timer interrupt frequency is 75Hz, If the frequency is 60KHz, the timer count value will be

[0046] Preferably, the inductor current sampling value is obtained by sampling the Hall effect current sensor The PI controller converts the square wave current reference signal and the inductor current sampling value Subtract and get the current error signal .

[0047] Step S20: According to the grid frequency The change of adjusts the resonant angular frequency of the PR controller ,make ; According to the square wave current frequency Adjust the repetitive control cycle according to the changes ,make , to achieve precise control of square wave current.

[0048] Preferably, the grid frequency 50Hz or 60Hz.

[0049] Step S30: According to the current error signal , resonant angular frequency and repeat control cycles Determine the output of the PI controller respectively , the output of the PR controller , repeat the controller output ; Calculate current feedforward output and voltage feed-forward output .

[0050] Specifically, the output of the PI controller is It consists of a proportional term and an integral term. The proportional term is used to quickly adjust the control output according to the current error, and the integral term is used to eliminate the steady-state error:

[0051]

[0052] in, is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient.

[0053] In the S domain, its transfer function is:

[0054]

[0055] Output of PR controller It consists of a proportional part and a resonant part. The proportional part is used to quickly respond to errors, and the resonant part suppresses double frequency disturbances:

[0056] {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}

[0057] in, is the second proportional gain coefficient, is the resonant gain coefficient, is the resonant angular frequency, is the cutoff frequency.

[0058] In the S domain, its transfer function is:

[0059]

[0060] Repeat the controller output for:

[0061]

[0062] in, To repeat the control cycle, is the third proportional gain coefficient, is the sequence number of the control cycle, is the time constant of the low-pass filter, Indicates that the control system is The current error signal at the moment, It is the weighting function of the low-pass filter on the error signal in the time domain.

[0063] In the Z domain, its transfer function is:

[0064]

[0065] in, , is the timer interrupt period; is the exponential decay factor per step, .

[0066] The current feedforward output is:

[0067]

[0068] The voltage feedforward output is:

[0069]

[0070] in, is the inductance, is the current feedforward control period, is the output voltage, is the input voltage.

[0071] As an example, a voltage sensor is used to measure the input voltage and output voltage .

[0072] Step S40: Output current loop control duty cycle Here, the preset duty cycle The adjustment formula is:

[0073]

[0074] in, is the first feedforward gain coefficient, is the second feedforward gain coefficient, is the output time.

[0075] In the next control cycle, the above steps S10 to S40 are repeatedly executed.

[0076] Figure 5 and Figure 6 The voltage and current transient waveforms before and after the multi-feedforward control is applied. The red curve is the output voltage waveform, and the blue curve is the output current waveform. Figure 5 This is a waveform without feedforward control. The voltage waveform has a significant spike in the initial stage after commutation, and the subsequent fluctuation is relatively large. The current waveform rises steeply and fluctuates violently before reaching a stable value. This indicates that the voltage is not stable during commutation and the transient response of the current change is not ideal. Figure 6 This is the waveform under multi-feedforward control. After commutation, the voltage spike is significantly reduced, and the subsequent fluctuation amplitude of the voltage waveform decreases, becoming more stable. The current waveform rises relatively smoothly, with a significantly reduced fluctuation amplitude, and reaches a stable state more quickly. This shows that feedforward control effectively suppresses voltage mutations, improves voltage stability, and enhances the transient response characteristics of the current.

[0077] Multi-feedforward control has a significant optimization effect on the system's output voltage and current waveforms, effectively suppressing voltage mutations and fluctuations, while improving the transient response of current, making the current change more smoothly and quickly reach a stable value, thereby improving the system's dynamic performance and stability.

[0078] The multi-feedforward current loop control method provided in this embodiment outputs a duty cycle of the current loop control. D Comprising the outputs of the PI controller, the PR controller, and the repetitive controller, as well as current and voltage feedforward outputs, it achieves fast and accurate square-wave current tracking and disturbance suppression. The multiple current and voltage feedforwards significantly enhance the ability to quickly track square-wave currents. The PR and repetitive control stages effectively suppress current deviations and external disturbances during square-wave current tracking, achieving precise control of the square-wave current.

[0079] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A multi-feedforward current loop control method, characterized in that: The steps include: S10, generating a frequency-variable square wave current reference signal, and taking the difference between the square wave current reference signal and the inductor current sampling value as a current error signal; S20, adjusting the resonant angular frequency of the PR controller according to the change of the grid frequency, and adjusting the repeated control period according to the change of the square wave current frequency; S30, determining the output of the PI controller according to the current error signal, the resonant angular frequency and the repeated control period , the output of the PR controller , repeat the controller output ; Calculate current feedforward output and voltage feed-forward output ; S40, duty cycle of output current loop control : in, is the first feedforward gain coefficient, is the second feedforward gain coefficient; In the next control cycle, the above steps S10 to S40 are repeatedly executed.

2. The multi-feedforward current loop control method according to claim 1, characterized in that: The output of the PI controller is: in, is the current error signal, is the first proportional gain coefficient, is the integral gain coefficient, for The current error signal at that moment.

3. The multi-feedforward current loop control method according to claim 2, characterized in that: 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 in, is the second proportional gain coefficient, is the resonant gain coefficient, is the resonant angular frequency, is the cutoff frequency.

4. The multi-feedforward current loop control method according to claim 3, characterized in that: The output of the repetitive controller is: in, is the repetitive control cycle, is the third proportional gain coefficient, is the sequence number of the control cycle, is the time constant of the low-pass filter, for The current error signal at the moment, It is the weighting function of the low-pass filter on the error signal 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: in, is the inductance, is the current feedforward control period, is the output voltage, is the input voltage.

6. The multi-feedforward current loop control method according to claim 1, characterized in that: In the microcontroller, a timer interrupt is used to generate a frequency-variable square wave signal as the square wave current reference signal.

7. The multi-feedforward current loop control method according to claim 6, characterized in that: The square wave current frequency is one of 50 Hz, 60 Hz, 75 Hz, 270 Hz to 360 Hz, and 900 Hz to 1200 Hz.

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

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

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