Apfc converter control method, apfc converter and industrial power supply

Abstract

The application relates to the technical field of industrial power supply power electronic control, and discloses an APFC converter control method, an APFC converter and an industrial power supply, the method comprising the following steps: acquiring an output voltage, an input voltage and an inductance current of the APFC converter; acquiring a voltage regulation value according to a voltage error value of a preset reference voltage and the output voltage; acquiring a reference current according to the voltage regulation value and the input voltage; acquiring a current error value according to the reference current and the inductance current; acquiring an adjustment coefficient of a proportional integral parameter; adjusting the integral parameter and the proportional parameter according to the adjustment coefficient; calculating an output control amount according to the integral parameter, the proportional parameter and the current error value; comparing the control amount with sawtooth harmonics to adjust a duty cycle and output a PWM signal. The application can change the adjustment coefficient of the APFC converter controller according to the waveform of the input voltage, thereby improving the power factor of the APFC converter and greatly reducing the harmonic content.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic control of industrial power supplies, and mainly relates to an APFC (Active Power Factor Correction) converter control method, an APFC converter and an industrial power supply. Background Art

[0002] In actual industrial production, most of the power generated is high-voltage alternating current. If we want to meet the power characteristics requirements of different users, we need to convert the industrial frequency alternating current into direct current and then supply it to the power-consuming equipment.

[0003] In existing technologies, conventional full-bridge rectifier and filter current conversion circuits are usually selected to achieve AC-to-DC functions. However, the input current only flows when the input voltage is greater than the output voltage, resulting in severe distortion and extremely high THD (Total Harmonic Distortion). Extensive use of this technology can affect the normal operation of the power grid. The use of APFC technology can improve the power factor of power electronic devices and reduce grid harmonic pollution. However, the adjustment coefficient of the controller used in the APFC converter is generally a fixed value, that is, the current waveform cannot track the input voltage waveform well, which affects the power factor of the APFC converter. Summary of the Invention

[0004] The embodiments of the present application provide an APFC converter control method, an APFC converter, and an industrial power supply, which can change the regulation coefficient of the APFC converter controller according to the waveform of the input voltage, thereby improving the power factor of the APFC converter and greatly reducing the harmonic content.

[0005] To solve the above technical problems, a technical solution adopted in an embodiment of the present invention is to provide an APFC converter control method, the method comprising: obtaining the output voltage, input voltage and inductor current of the APFC converter; performing error amplification processing based on a preset reference voltage and a voltage error value of the output voltage to obtain a voltage regulation value; obtaining a reference current based on the voltage regulation value and the input voltage; obtaining a current error value based on the reference current and the inductor current; obtaining an adjustment coefficient of a proportional-integral parameter; adjusting the integral parameter and the proportional parameter based on the adjustment coefficient; calculating an output control quantity based on the integral parameter, the proportional parameter and the current error value; comparing the control quantity with a sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to adjust the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform.

[0006] Optionally, obtaining the adjustment coefficient of the proportional-integral parameter includes obtaining the adjustment coefficient according to the following formula:

[0007] coeff=-k*|V in | / V max +b

[0008] Wherein, coeff is the adjustment coefficient, k and b are adjustment parameters, |V in | is the pulsating voltage, V max is the peak value of the grid voltage.

[0009] Optionally, adjusting the integral parameter and the proportional parameter according to the adjustment coefficient includes: adjusting the integral parameter and the proportional parameter according to the following formula, where the formula is:

[0010] k p =K p *coeff

[0011] k i =K i *coeff

[0012] Among them, k p is the adjusted proportional parameter, k i is the adjusted integral parameter, K p is the proportional parameter before adjustment, K i is the integral parameter before adjustment, and coeff is the adjustment coefficient.

[0013] Optionally, calculating the output control quantity according to the integral parameter, the proportional parameter, and the current error value includes: calculating the control quantity according to the following formula, which is:

[0014] y=k p *ΔI+k i *T s *1 / (z-1)*ΔI

[0015] Wherein, y is the control variable, ΔI is the current error value, Ts is the calculation period, 1 / (z-1) is the change characteristic of the zero-order holder, k p is the adjusted proportional parameter, k i is the adjusted integral parameter.

[0016] Optionally, after executing the step of obtaining the output voltage, input voltage and inductor current of the APFC converter, the method further includes: performing filtering and correction processing on the output voltage, the input voltage and the inductor current respectively.

[0017] Optionally, the APFC converter also includes an inductor and a rectifier capacitor. Before executing the step of obtaining the output voltage, input voltage and inductor current of the APFC converter, the method also includes: starting current limiting protection when the input voltage increases to the mains voltage; obtaining the pulsating voltage based on the input voltage; charging the inductor and the rectifier capacitor using the pulsating voltage; and cutting off the current limiting protection when the charging reaches the required voltage state.

[0018] To solve the above technical problems, another technical solution adopted in an embodiment of the present invention is to provide an APFC controller, the APFC controller comprising: a control circuit, the control circuit comprising a control unit, and an analog-to-digital converter, a first controller, a second controller, and a data processing unit respectively connected to the control unit, the control unit being configured to send a sampling signal to the analog-to-digital converter; the analog-to-digital converter being configured to obtain an output voltage, an input voltage, and an inductor current of the APFC converter by sampling the sampling signal; the first controller being configured to obtain a preset reference voltage and the output voltage, and to control an output voltage regulation value based on the preset reference voltage and the output voltage; The data processing unit is used to obtain the voltage adjustment value and the input voltage, and calculate the output reference current based on the voltage adjustment value and the input voltage; the second controller is used to: obtain a current error value based on the reference current and the inductor current; obtain an adjustment coefficient of a proportional-integral parameter, adjust the integral parameter and the proportional parameter based on the adjustment coefficient, and calculate an output control quantity based on the integral parameter, the proportional parameter and the current error value; compare the control quantity with the sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to adjust the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform.

[0019] Optionally, the control circuit further includes a sampling and filtering processing unit. After the analog-to-digital converter obtains the output voltage, the input voltage and the inductor current, the sampling and filtering processing unit is used to: perform filtering and correction processing on the output voltage, the input voltage and the inductor current respectively.

[0020] Optionally, the APFC converter also includes an inductor, a rectifier capacitor, a starting current limiting device and a rectifier bridge; the starting current limiting device is used to start current limiting protection when the input voltage increases to the mains voltage; the rectifier bridge is used to obtain the pulsating voltage according to the input voltage to charge the inductor and the rectifier capacitor; the starting current limiting device is also used to cut out the current limiting protection when the voltage is charged to the required voltage state.

[0021] In order to solve the above technical problems, another technical solution adopted in the embodiment of the present invention is to provide an industrial power supply, which includes the APFC converter as described above.

[0022] Different from the related art, the embodiments of the present invention provide an APFC converter control method, an APFC converter, and an industrial power supply. These methods obtain the output voltage, input voltage, and inductor current of the APFC converter; perform error amplification processing based on a voltage error value between a preset reference voltage and the output voltage to obtain a voltage regulation value; obtain a reference current based on the voltage regulation value and the input voltage; obtain a current error value based on the reference current and the inductor current; obtain an adjustment coefficient for a proportional-integral parameter; adjust the integral parameter and the proportional parameter based on the adjustment coefficient; calculate an output control variable based on the integral parameter, the proportional parameter, and the current error value; compare the control variable with a sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to regulate the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform. The APFC converter control method and APFC converter provided by the embodiments of the present invention change the regulator parameters based on the waveform of the mains voltage, improve the power factor of the APFC converter, and significantly reduce the harmonic content. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0024] Figure 1 Schematic diagram of an application environment of the APFC converter control method provided by an embodiment of the present invention;

[0025] Figure 2 is a control flow chart of a control circuit in an APFC converter provided by an embodiment of the present invention;

[0026] Figure 3 is a flow chart of an APFC converter control method provided by an embodiment of the present invention;

[0027] Figure 4 is a schematic diagram of a parameter coefficient change curve of a second controller provided by an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of PWM signal output provided by an embodiment of the present invention;

[0029] Figure 6This is a schematic diagram of a curve showing a reference current and an inductor current change without adding a variable parameter adjustment according to an embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of a curve showing a reference current and an inductor current change with adaptive variable parameters provided by an embodiment of the present invention;

[0031] Figure 8 A control circuit for an APFC converter is provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that, unless there is a conflict, the various features of the embodiments of the present invention may be combined with each other and are all within the scope of protection of the present invention. Furthermore, although the functional modules are divided in the device schematics and the logical order is shown in the flow charts, in some cases, the steps shown or described may be performed in a different order than the module division in the device schematics or the order in the flow charts. Furthermore, the terms "first," "second," and the like used herein do not limit the order of data or execution, but only distinguish between identical or similar items with substantially the same functions and effects.

[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are intended solely for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0035] In DC-to-AC conversion circuits, a stable output voltage is typically maintained by controlling the on / off switching of MOSFETs. However, due to the nonlinear switching characteristics of power electronic devices, these devices absorb non-sinusoidal currents when used in circuits, generating a large amount of harmonics. These harmonics can reduce the power factor of the equipment and cause severe power loss in the grid. To address the current waveform distortion caused by harmonics, power factor correction (PFC) technology has been introduced. This technology allows the current to track the voltage, correcting the distorted current to a sinusoidal state through PFC, bringing the current and voltage into phase. Currently, power factor correction technologies are primarily categorized into active power factor correction (APFC) and passive power factor correction (PPFC).

[0036] A PFC converter is a device that converts industrial frequency alternating current into direct current. During the conversion process, it can improve the power factor, increase the utilization rate of power grid electricity, and reduce the harmonic content, thereby reducing the voltage distortion, loss, and malfunction of the grid. This application uses active power factor correction, and the APFC control mode adopts a continuous current mode (CCM). The input current is continuous and the current ripple is small, making it more suitable for high-power applications. In addition, in order to improve the power factor and reduce the harmonic content, the current control method of this application adopts an average current control method. The control strategy of the APFC converter adopts a dual closed-loop control strategy of inner and outer loops. The outer loop is a voltage loop and the inner loop is a current loop. The voltage loop can control the output stable voltage, and the current loop can make the waveform of the inductor current closely follow the waveform of the input voltage, thereby improving the power factor of the industrial frequency alternating current converted to direct current.

[0037] The performance of APFC converters, such as power factor and harmonic content, is largely determined by the quality of current loop control. In engineering applications, the controller is typically adjusted to achieve parameters that meet these performance requirements, and these parameters are typically fixed. However, the input voltage is AC power from the mains, which varies sinusoidally over time, while the output voltage requires a stable DC voltage. Therefore, selecting fixed controller parameters is theoretically suboptimal.

[0038] Therefore, the embodiment of the present invention proposes a variable parameter adaptive regulation control method with an added dimension, which changes the regulator parameters according to the waveform of the mains voltage, improves the power factor of the APFC converter, and greatly reduces the harmonic content.

[0039] Specifically, Figure 1Schematic diagram of one application environment of the APFC converter control method provided by an embodiment of the present invention. The application environment includes: a mains power supply, a starting current limiting device, an EMI, a rectifier bridge, a filtering capacitor Cftr, a boost chopper circuit, a rectifying capacitor Co, a load RL, and a control circuit.

[0040] The topological structure shown in this application scenario is the main circuit of an APFC converter. When the input voltage V in increases to the mains voltage, the APFC converter starts, and the starting inrush current is relatively large. The current limiting device starts to limit the current. At this time, the control circuit does not start, that is, the switching MOS transistor does not generate waves. The mains voltage passes through the EMI to suppress the electromagnetic interference of the alternating current, and outputs a pulsating voltage after full-bridge rectification. The pulsating voltage passes through the inductor L and the diode VD, and directly charges the rectifying capacitor Co. When the charging voltage of the rectifying capacitor Co is greater than Kf*V in (0 < Kf < 0.3), and at the same time, when the timing unit of the main control DSP controller times greater than Ta (Ta > 1 s), the short-circuit cut-out control of the starting current limiting device is started. The main control DSP controller is a device that controls the circuit using a digital signal processor. The filtering capacitor Cftr plays a smoothing role when the voltage of the diode VD suddenly cuts off at 0.7V, making the voltage slowly drop from 0.7V to 0. The diode VD can prevent the voltage from flowing back in reverse when the rectifying capacitor Co is fully charged.

[0041] After the control circuit receives the cut-out control of the starting current limiting device, the control unit of the control circuit starts. Figure 2 Flowchart of the control circuit of the APFC converter provided by an embodiment of the present invention. The control circuit includes: a control unit, an analog-to-digital converter, a first controller, a second controller, and a data processing unit. The control unit is respectively connected to the analog-to-digital converter, the first controller, the second controller, and the data processing unit. The second controller is a PI controller.

[0042] In the prior art, the integral parameter and the proportional parameter of the second controller are fixed values. Although power factor correction can be achieved and the harmonic content can be reduced, theoretically, using fixed parameter values for control is not optimal. After being optimized by the APFC converter control method provided by the embodiments of the present application, the regulator parameters can be changed according to the waveform of the mains voltage, so that the parameters of the second controller are not fixed values, improving the power factor of the APFC converter and greatly reducing the harmonic content, achieving better control.

[0043] Embodiment 1

[0044] Specifically, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0045] The embodiment of the present invention provides an APFC converter control method, see Figure 3 , which shows a flow chart of an APFC converter control method provided by an embodiment of the present invention, the method includes but is not limited to the following steps:

[0046] S11. Obtain the output voltage, input voltage, and inductor current of the APFC converter.

[0047] The output voltage is the voltage value obtained after the voltage Vo at both ends of the capacitor is filtered and corrected. in The inductor current IL can be used for control after data conversion, while the output voltage Vo is filtered by a large capacitor, and there is a ripple voltage phase lead. The ripple voltage is the industrial frequency AC component contained in the output voltage. The control strategy will perform low-pass filtering on it to ensure phase consistency. The analog sampling values ​​need to be filtered and corrected.

[0048] The control quantity of the filter controller is calculated according to the following formula:

[0049] A Filt =(2*pi*fs*Ts) / (2*pi*fs*Ts+1);

[0050] B Filt =1-A Filt ;

[0051] y(k)=A Filt *x(k)+B Filt *y(k-1);

[0052] Among them, A Filt is the current input filter coefficient, B Filt is the previous output filter coefficient, pi is the constant π, x(k) is the current input, y(k) is the current output, y(k-1) is the previous output, fs is the cutoff frequency, Ts is the control frequency, and k in the above y(k) formula is the time discrete value.

[0053] The sampled values ​​are corrected according to the following correction function:

[0054] f(x)=k*x+b;

[0055] Where x is the input, f(x) is the output, k in the above f(x) formula is the correction coefficient, and b is the correction bias.

[0056] S12: Perform error amplification processing based on a voltage error between a preset reference voltage and the output voltage to obtain a voltage adjustment value. Specifically, the error amplification processing may utilize a voltage error amplifier. The preset reference voltage Vref may be set based on actual conditions and user needs, and may be specifically 400V. This disclosure does not impose any specific limitation on this.

[0057] S13, obtaining a reference current according to the voltage adjustment value and the input voltage. in After full-bridge rectification, it becomes a pulsating voltage, and the product of the pulsating voltage and the voltage adjustment value is used as the reference current Iref for current loop control. Specifically, a multiplier can be used. The pulsating voltage is a sinusoidal half-wave voltage waveform, and the waveform remains unchanged after multiplying with the voltage adjustment value, that is, the waveform of the reference current Iref is consistent with the waveform shape of the pulsating voltage.

[0058] S14. Obtain a current error value based on the reference current and the inductor current. The inductor current IL is the input current ultimately controlled by the current loop. The reference current Iref is compared with the inductor current IL, and the comparison result is subjected to error amplification to obtain a current error value ΔI. Specifically, the error amplification process may utilize a current error amplifier.

[0059] S15, obtaining the adjustment coefficient of the proportional integral parameter. The proportional integral parameter is divided into a proportional parameter kp and an integral parameter ki, and the adjustment coefficient is coeff, which can adjust the size of the proportional parameter kp and the integral parameter ki. For details, please refer to Figure 4 , which shows a schematic diagram of the change curve of the parameter coefficient of the second controller provided by the embodiment of the present invention. Curve 1 is the grid-side voltage waveform, that is, the pulsating voltage waveform. The pulsating voltage is the input voltage V in The full-wave rectified voltage after the rectifier bridge. In the prior art, the adjustment coefficient coeff of the second controller is a fixed value, as shown in curve 2. For the convenience of calculation, the adjustment coefficient coeff is generally set to 1. For details, see Figure 6 , which shows a schematic diagram of the reference current and inductor current change curve without adding variable parameters. According to this simulated change curve, it can be seen that the tracking effect is better when the reference current crosses the zero point, and is relatively poor when the current peaks. The adjustment coefficient coeff in this application changes with the change of the pulsating voltage waveform, such as Figure 4 As shown in curve 3, according to Figure 6 From the tracking effect shown, it can be seen that the proportional and integral parameters of the PI regulator need to be larger in the time period before and after the trough of the sine wave, while the proportional and integral parameters of the PI regulator need to be relatively smaller in the time period before and after the peak of the sine wave.

[0060] The adjustment coefficient is obtained according to the following formula:

[0061] coeff=-k*|V in | / V max +b

[0062] Wherein, coeff is the adjustment coefficient, k and b are adjustment parameters, |V in | is the pulsating voltage, V max is the peak value of the grid voltage. In this application, the preset coeff can be obtained by adjusting k and b. When the voltage value is less than Vp, coeff is not adjusted. When the voltage value is greater than or equal to Vp, k and b are adjusted so that coeff changes with the pulsating voltage. For example, when the angle of the pulsating voltage waveform is 90°, the target value of the adjustment coefficient coeff can be set to 0.5. At this time, the adjustment coefficient coeff can be adjusted to the target value by simply changing the adjustment parameters k and b. The target value of the adjustment coefficient coeff can be set according to demand, and this application does not impose specific restrictions on this.

[0063] S16, adjusting the integral parameter and the proportional parameter according to the adjustment coefficient. Adjust the integral parameter and the proportional parameter according to the following formula, which is:

[0064] k p =K p *coeff

[0065] k i =K i *coeff

[0066] Among them, k p is the adjusted proportional parameter, k i is the adjusted integral parameter, K p is the proportional parameter before adjustment, K i is the integral parameter before adjustment, and coeff is the adjustment coefficient.

[0067] S17, calculating the output control quantity according to the integral parameter, the proportional parameter and the current error value. The control quantity is calculated according to the following formula, which is:

[0068] y=k p *ΔI+k i *T s *1 / (z-1)*ΔI

[0069] Wherein, y is the control variable, ΔI is the current error value, Ts is the calculation period, 1 / (z-1) is the change characteristic of the zero-order holder, k p is the adjusted proportional parameter, k iis the adjusted integral parameter. The current error value ΔI is the error value between the reference current Iref and the inductor current IL. The calculation period Ts is the calculation period of the current loop. Because a digital system is actually used, the system needs to be discretized. This disclosure uses the zero-order holder method for discretization. The control variable y is the output value of the second controller, that is, the output value of the PI controller.

[0070] S18. Compare the control variable with the sawtooth harmonics to adjust the duty cycle and output a PWM signal. The PWM signal is used to regulate the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform. The sawtooth harmonics are generated by the repeated charging and discharging process of the rectifier capacitor Co.

[0071] See Figure 5 , which shows a schematic diagram of the PWM signal output provided by an embodiment of the present invention. If the control variable y is lower than the sawtooth harmonic, a low level is output. This low level controls the switching MOS transistor VT to conduct, causing the pulsating voltage to charge the inductor L and the inductor current IL to increase linearly. At this time, the diode VD is reverse-biased and cut off, preventing current from passing through. The rectifier capacitor Co uses the previously stored energy to power the load RL. If the control variable y is higher than the sawtooth harmonic, a high level is output. This high level controls the switching MOS transistor VT to turn off, preventing the current in the inductor L from changing suddenly, generating a reverse electromotive force. That is, the voltage on the inductor L is positive on the right and negative on the left. The voltage on the inductor L is superimposed on the pulsating voltage to charge the rectifier capacitor Co and power the load RL, causing the inductor current IL to decrease linearly. The second calculation cycle Ts then begins, and the above process repeats. The output PWM signal controls the on and off state of the switching MOS transistor VT, thereby maintaining a stable output voltage Vo. The input current waveform tracks the input voltage waveform, achieving power factor correction. When the control quantity y increases, the time of outputting high level increases, the off time Toff of the switch MOS tube VT increases, and the duty cycle D increases; when the control quantity y decreases, the time of outputting low level increases, the on time Ton of the switch MOS tube VT increases, and the duty cycle D decreases.

[0072] The voltage across the inductor L is calculated according to the formula:

[0073] U = L·(di / dt);

[0074] When the switch MOS tube VT is turned on, the voltage on the inductor is the pulsating voltage Vs, then:

[0075]

[0076] When the switch MOS tube VT is turned off, the voltage on the inductor is Vo-Vs, then:

[0077]

[0078] According to the volt-second balance principle, that is, the current flowing through the inductor L is equal when the switch MOS tube is turned on and off, it can be obtained:

[0079]

[0080]

[0081] The duty cycle is calculated according to the following formula:

[0082]

[0083] Arranged:

[0084] Among them, Ton is the on-time of the switch MOS tube VT, Toff is the off-time of the switch MOS tube VT, Vs is the pulsating voltage, Vo is the output voltage, and D is the on-duty cycle of the switch MOS tube VT.

[0085] After adjusting the parameters of the second controller, the PI regulator controls the inductor current to better track the reference current, that is, the inductor current can better track the input voltage waveform. For specific waveforms, see Figure 7 , which shows a schematic diagram of the reference current and inductor current curves using adaptive variable parameters, as provided by an embodiment of the present invention. The inductor current essentially coincides with the reference current, achieving good tracking. This control strategy significantly improves the power factor while significantly reducing the harmonic content of the power grid.

[0086] An embodiment of the present invention provides an APFC converter control method, which samples the output voltage, input voltage and inductor current of the APFC converter and performs filtering and correction processing, obtains a voltage regulation value based on a set reference voltage and the output voltage, obtains a reference current based on the voltage regulation value and the input voltage, obtains a current error value based on the reference current and the inductor current, outputs a control quantity based on the current error value, an integral parameter and a proportional parameter of a controller, compares the control quantity with a sawtooth ramp wave, thereby adjusting the duty cycle and outputting a PWM signal through a second controller, the PWM signal controls the inductor current waveform to track the input voltage waveform, changes the regulator parameters through the waveform of the mains voltage, improves the power factor of the APFC converter, and greatly reduces the harmonic content.

[0087] Example 2

[0088] An embodiment of the present invention provides an APFC converter, wherein the APFC converter includes a control circuit 20. Figure 8The control circuit 20 includes a control unit 201, and an analog-to-digital converter 202, a first controller 203, a data processing unit 204 and a second controller 205 respectively connected to the control unit 201.

[0089] The control unit 201 is used to send a sampling signal to the analog-to-digital converter;

[0090] The analog-to-digital converter 202 is used to obtain the output voltage, input voltage and inductor current of the APFC converter according to the sampling signal;

[0091] The first controller 203 is used to obtain a preset reference voltage and the output voltage, and control the output voltage adjustment value according to the preset reference voltage and the output voltage;

[0092] The data processing unit 204 is used to obtain the voltage adjustment value and the input voltage, and calculate the output reference current according to the voltage adjustment value and the input voltage;

[0093] The second controller 205 is used to obtain a current error value based on the reference current and the inductor current; obtain an adjustment coefficient of a proportional-integral parameter, adjust the integral parameter and the proportional parameter according to the adjustment coefficient, and calculate an output control quantity based on the integral parameter, the proportional parameter, and the current error value; compare the control quantity with the sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to adjust the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform.

[0094] In some embodiments, see Figure 8 The control circuit 20 further includes a sampling and filtering processing unit 206. After the analog-to-digital converter 202 obtains the output voltage, the input voltage, and the inductor current, the sampling and filtering processing unit 206 is used to perform filtering and correction processing on the output voltage, the input voltage, and the inductor current respectively.

[0095] In some embodiments, the APFC converter further includes an inductor, a rectifier capacitor, a startup current limiting device, and a rectifier bridge;

[0096] The starting current limiting device is used to start the current limiting protection when the input voltage increases to the mains voltage;

[0097] The rectifier bridge is used to obtain the pulsating voltage according to the input voltage to charge the inductor and the rectifier capacitor;

[0098] The startup current limiting device is also used to cut out the current limiting protection when the battery is charged to a required voltage state.

[0099] It should be noted that the APFC converter described above can execute the APFC control method provided in the embodiments of the present invention and has functional modules corresponding to the execution method. For technical details not fully described in the APFC converter embodiments, reference can be made to the APFC control method provided in the embodiments of the present invention. A sampling and filtering processing unit in the APFC converter control circuit samples the output voltage, input voltage, and inductor current of the APFC converter and performs filtering and correction processing. A first controller obtains a voltage regulation value based on a set reference voltage and the output voltage. A data processing unit obtains a reference current based on the voltage regulation value and the input voltage. A second controller obtains a current error value based on the reference current and the inductor current. A control variable is output based on the current error value, an integral parameter, and a proportional parameter of the controller. The control variable is compared with a sawtooth ramp to adjust the duty cycle and output a PWM signal through the second controller. The PWM signal controls the inductor current waveform to track the input voltage waveform. Therefore, the regulator parameters are changed by the grid voltage waveform, improving the power factor of the APFC converter and significantly reducing the harmonic content.

[0100] Example 3

[0101] An embodiment of the present invention provides an industrial power supply including the APFC converter described in the above embodiment. Thus, the industrial power supply can implement the APFC control method provided in the embodiment of the present invention and has functional modules corresponding to the APFC control method. Technical details not fully described in this embodiment can be found in the APFC control method and APFC converter provided in the embodiment of the present invention. The industrial power supply has the beneficial effects of improving the power factor and increasing the energy utilization rate during the conversion process of industrial frequency alternating current (AC) to direct current (DC), while also reducing harmonic content.

[0102] It should be noted that in each of the above embodiments, there is not necessarily a certain order between the above steps. A person skilled in the art can understand, based on the description of the embodiments of this application, that in different embodiments, the above steps may have different execution orders, that is, they may be executed in parallel, or may be executed interchangeably, etc.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Under the idea of ​​the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of this application.

Claims

1. An APFC converter control method, characterized in that: include: Obtain the output voltage, input voltage and inductor current of the APFC converter; performing error amplification processing according to a voltage error value between a preset reference voltage and the output voltage to obtain a voltage regulation value; obtaining a reference current according to the voltage adjustment value and the input voltage; Obtaining a current error value according to the reference current and the inductor current; Obtaining an adjustment coefficient of a proportional-integral parameter includes obtaining the adjustment coefficient according to the following formula: , where coeff is the adjustment coefficient, k and b are adjustment parameters, |V in | is the pulsating voltage, V max is the peak value of the grid voltage; Adjusting the integral parameter and the proportional parameter according to the adjustment coefficient includes adjusting the integral parameter and the proportional parameter according to the following formula, wherein the formula is: ; , where k p is the adjusted proportional parameter, k i is the adjusted integral parameter, K p is the proportional parameter before adjustment, K i is the integral parameter before adjustment, coeff is the adjustment coefficient; Calculating the output control quantity according to the integral parameter, the proportional parameter, and the current error value includes calculating the control quantity according to the following formula: , where y is the control variable, ∆I is the current error value, Ts is the calculation period, 1 / (z-1) is the change characteristic of the zero-order holder, k p is the adjusted proportional parameter, k i is the adjusted integral parameter; The control variable is compared with the sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to regulate the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform.

2. The APFC converter control method according to claim 1, characterized in that: After executing the step of obtaining the output voltage, input voltage and inductor current of the APFC converter, the method further includes: Filter correction processing is performed on the output voltage, the input voltage and the inductor current respectively.

3. The APFC converter control method according to claim 1, wherein: The APFC converter further includes an inductor and a rectifier capacitor. Before performing the step of obtaining the output voltage, input voltage, and inductor current of the APFC converter, the method further includes: When the input voltage increases to the mains voltage, the current limiting protection is activated; obtaining the pulsating voltage according to the input voltage; charging the inductor and the rectifier capacitor using the pulsating voltage; When the battery is charged to the required voltage, the current limiting protection is turned off.

4. An APFC converter, characterized in that: The APFC converter includes a control circuit, which includes a control unit, and an analog-to-digital converter, a first controller, a second controller, and a data processing unit respectively connected to the control unit. The control unit is used to send a sampling signal to the analog-to-digital converter; The analog-to-digital converter is used to obtain the output voltage, input voltage and inductor current of the APFC converter according to the sampling signal; The first controller is used to obtain a preset reference voltage and the output voltage, and control the output voltage adjustment value according to the preset reference voltage and the output voltage; The data processing unit is used to obtain the voltage adjustment value and the input voltage, and calculate the output reference current according to the voltage adjustment value and the input voltage; The second controller is used for: Obtaining the reference current and the inductor current, and obtaining a current error value according to the reference current and the inductor current; Obtaining an adjustment coefficient of a proportional-integral parameter, adjusting the integral parameter and the proportional parameter according to the adjustment coefficient, and calculating the output control quantity according to the integral parameter, the proportional parameter, and the current error value, including obtaining the adjustment coefficient according to the following formula, which is: , where coeff is the adjustment coefficient, k and b are adjustment parameters, |V in | is the pulsating voltage, V max is the peak value of the grid voltage; and further comprising adjusting the integral parameter and the proportional parameter according to the following formula, the formula being: ; , where k p is the adjusted proportional parameter, k i is the adjusted integral parameter, K p is the proportional parameter before adjustment, K i is the integral parameter before adjustment, coeff is the adjustment coefficient; and the control amount is calculated according to the following formula: , where y is the control variable, ∆I is the current error value, Ts is the calculation period, 1 / (z-1) is the change characteristic of the zero-order holder, k p is the adjusted proportional parameter, k i is the adjusted integral parameter; The control variable is compared with the sawtooth harmonic to adjust the duty cycle and output a PWM signal, wherein the PWM signal is used to regulate the inductor current of the APFC converter so that the inductor current waveform tracks the input voltage waveform.

5. The APFC converter according to claim 4, characterized in that: The control circuit further includes a sampling and filtering processing unit. After the analog-to-digital converter acquires the output voltage, the input voltage, and the inductor current, the sampling and filtering processing unit is configured to: Filter correction processing is performed on the output voltage, the input voltage and the inductor current respectively.

6. The APFC converter according to claim 5, characterized in that: The APFC converter also includes an inductor, a rectifier capacitor, a startup current limiting device and a rectifier bridge; The starting current limiting device is used to start the current limiting protection when the input voltage increases to the mains voltage; The rectifier bridge is used to obtain the pulsating voltage according to the input voltage to charge the inductor and the rectifier capacitor; The startup current limiting device is also used to cut out the current limiting protection when the battery is charged to a required voltage state.

7. An industrial power supply, characterized in that: The industrial power supply includes the APFC converter according to any one of claims 4 to 6.

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