CN111641333A

CN111641333A - Multi-carrier period PFC control method

Info

Publication number: CN111641333A
Application number: CN202010437944.0A
Authority: CN
Inventors: 朱绯; 石明杰; 王声纲; 石泽发
Original assignee: Sichuan Hongmei Intelligent Technology Co Ltd
Current assignee: Sichuan Hongmei Intelligent Technology Co Ltd
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2020-09-08
Anticipated expiration: 2040-05-21
Also published as: CN111641333B

Abstract

The embodiment of the invention discloses a multi-carrier period PFC control method, and relates to the field of household appliance control. The method is applied to a PFC circuit comprising a driving switch device, and comprises the following steps: dividing a carrier cycle of a PFC algorithm into at least two cycles; acquiring a PFC algorithm step which is originally required to be completed in a single carrier cycle, and acquiring a step required to be calculated in the PFC algorithm step; dividing steps required to be calculated in the PFC algorithm into at least two carrier wave periods for calculation, so that the calculation of the divided steps is completed in each carrier wave period of the at least two carrier wave periods, and other data are obtained in a non-calculation mode, and the calculation result of each carrier wave period is obtained. Therefore, the calculation which needs to be completed in a single carrier cycle is divided into a plurality of carrier cycles, the calculation pressure of each carrier cycle is relieved, and the calculation time of the PFC algorithm in each carrier cycle is reduced.

Description

Multi-carrier period PFC control method

Technical Field

The invention relates to the field of household appliance control, in particular to a multi-carrier period PFC control method.

Background

The variable frequency air conditioner compressor generally adopts a permanent magnet synchronous motor and has adjustable rotating speed, and the variable frequency air conditioner is generally controlled by adopting an alternating current-direct current-alternating frequency method. Therefore, when the frequency and load of the inverter air conditioner are increased, the voltage of the direct current bus is reduced, the current distortion is increased, the power factor is reduced, and the current waveform is shown in figure 1. In order to stabilize the dc voltage, improve the Power Factor, and reduce the electromagnetic interference, a PFC (Power Factor Correction) control technique is generally adopted. After PFC control is added, the current waveform in the ideal state is restored to a nearly sinusoidal state as shown in fig. 2.

The method for correcting the power factor mainly comprises a software PFC control method and a hardware PFC control method. An inductor and an Insulated Gate Bipolar Transistor (IGBT) are added on a circuit of the software PFC, and the PFC control is realized by controlling the on-off of the IGBT through the software; the hardware PFC control method needs to add an additional hardware circuit on the basis of a software PFC control circuit, and the circuit is complex and high in cost. Therefore, software PFCs are widely used on household appliances.

As technology develops, carrier frequency increases, which can reduce cost and heat generation with smaller inductance, and also shorten the time left for the PFC algorithm to run in the controller. Most of related patents (such as CN201611185290.7) focus on the improvement of algorithm structure, so as to shorten the computation time and complete the computation within one carrier period.

As the carrier frequency is higher and higher, the carrier frequency is gradually increased, and the situation that the calculation cannot be completed within one carrier period often occurs. For example, when the carrier frequency is 20kHz, there is 50 μ s time for the PFC algorithm to run; when the carrier frequency is increased to 40kHz, 25 mus time is provided for the PFC algorithm to run, and if the PFC algorithm needs 30 mus time for completing the operation, the PFC algorithm cannot run at 40 kHz.

Disclosure of Invention

The embodiment of the invention provides a multi-carrier period PFC control method, which can reduce the operation time of a PFC algorithm in each carrier period.

The embodiment of the invention adopts the following technical scheme:

a multi-carrier period PFC control method is applied to a PFC circuit comprising a driving switch device and comprises the following steps:

dividing a carrier cycle of a PFC algorithm into at least two cycles;

acquiring a PFC algorithm step which is originally required to be completed in a single carrier cycle, and acquiring a step required to be calculated in the PFC algorithm step;

dividing steps required to be calculated in the PFC algorithm into at least two carrier wave periods for calculation, so that the calculation of the divided steps is completed in each carrier wave period of the at least two carrier wave periods, and other data are obtained in a non-calculation mode, and the calculation result of each carrier wave period is obtained.

Optionally, the at least two cycles, the remaining data includes data that needs to be calculated except for the dividing step and sampling data that needs to be sampled, and the obtaining of the respective remaining data in a non-calculation manner includes:

the data which needs to be calculated in each carrier period except the dividing step directly obtains the data of the adjacent previous period;

and sampling in each carrier period to obtain respective sampling data.

Optionally, the sampled data includes an alternating voltage, a direct voltage, and a circuit current in the PFC circuit.

Optionally, the PFC algorithm steps originally required to be completed in a single carrier cycle include:

s11, sampling the alternating current voltage, the direct current voltage and the circuit current in the PFC circuit;

s12, filtering the sampled PFC circuit current to obtain an actual current;

s13, calculating a reference current according to the target direct-current voltage and the sampled direct-current voltage;

s14, calculating a reference rectified voltage according to the reference current and the actual current;

s15, calculating a duty ratio according to the reference rectified voltage and the sampled alternating voltage;

s16, generating PWM waves according to the duty ratio to drive a switching device to operate and control the PFC circuit;

optionally, the step of acquiring the PFC algorithm includes the following steps:

the obtaining of the S12, the S13, the S14 and the S15 is a step that needs to be calculated in the PFC algorithm step.

Optionally, the dividing the carrier cycle of the PFC algorithm into at least two cycles includes: converting the carrier period of the PFC algorithm into at least one cycle of carrier period A-carrier period B;

the carrier cycle a includes:

a11, sampling alternating current voltage, direct current voltage and circuit current in the PFC circuit;

a12, calculating a reference current according to the target direct-current voltage and the sampled direct-current voltage;

a13, directly using the reference rectified voltage obtained by calculation of the adjacent previous carrier cycle without calculating the reference rectified voltage;

a14, calculating a duty ratio according to the reference rectified voltage and the sampled alternating voltage;

a15, generating a PWM wave according to the duty ratio to drive a switching device to operate and control the PFC circuit;

the carrier cycle B includes:

b11, sampling the alternating voltage, the direct voltage and the current of the PFC circuit in the PFC circuit;

b12, filtering the sampled PFC circuit current to obtain an actual current;

b13, directly using the reference current obtained by calculation of the adjacent previous carrier cycle without calculating the reference current;

b14, calculating a reference rectified voltage according to the reference current and the actual current;

b15, directly calculating the duty ratio by using a carrier period without calculating the duty ratio;

and B16, generating a PWM wave according to the duty ratio to drive a switching device to operate and control the PFC circuit.

Optionally, the filtering the sampled PFC circuit current to obtain an actual current includes: according to i_LPF＝LPF(i_PFC) Filtering the sampled PFC circuit current to obtain the actual current, wherein i_LPFFor the actual current, i_PFCLPF represents low-pass filtering for the sampled PFC circuit current;

the calculating the reference current according to the target direct-current voltage and the sampled direct-current voltage comprises: according to i_PFC ^*＝PI(V_dc ^*-V_dc) Calculating a reference current, wherein i_PFC ^*Is a reference current, V_dc ^*Is a target DC voltage, V_dcPI represents a proportional-integral regulator for the sampled dc voltage.

Optionally, the calculating a reference rectified voltage according to the reference current and the actual current includes; according to | V_ac|^*＝PI(i_PFC ^*-i_LPF) Calculating a reference rectified voltage, wherein | V_ac|^*For reference to the rectified voltage, i_LPFFor the actual current, PI represents a proportional-integral regulator;

the calculating the duty ratio according to the reference rectified voltage and the sampled alternating voltage comprises: according to M1- (| Vac | - | V)_ac|^*)/V_dcCalculating the duty ratio, wherein M is the duty ratio, Vac is the alternating voltage obtained by sampling, | V_ac|^*For reference to rectified voltage, V_dcIs the sampled dc voltage.

Optionally, the PFC circuit further includes:

the rectifier bridge, filter capacitor, voltage stabilizing capacitor, converter, inductance coils, sampling resistor, diode, the rectifier bridge filter capacitor, drive switch device, voltage stabilizing capacitor, converter connect in parallel in proper order, filter capacitor with connect respectively on two connecting lines between the drive switch device inductance coils with sampling resistor, the diode sets up drive switch device with on the connecting line of voltage stabilizing capacitor.

Optionally, the sampling the ac voltage, the dc voltage, and the current of the PFC circuit in the PFC circuit includes:

sampling a current flowing through the sampling resistor as a circuit current in the PFC circuit;

sampling voltages at two ends of the voltage stabilizing capacitor to be used as direct-current voltages in the PFC circuit;

and sampling the voltage applied to two ends of the rectifier bridge to be used as the alternating voltage in the PFC circuit.

The multi-carrier cycle PFC control method applied to the PFC circuit comprising the driving switch device based on the technical scheme divides the carrier cycle of the PFC algorithm into at least two cycles, obtains the PFC algorithm step which is originally required to be completed in a single carrier cycle, obtains the steps required to be calculated in the PFC algorithm step, divides the steps required to be calculated in the PFC algorithm into at least two carrier cycles for calculation, enables the calculation of the divided steps to be completed in each carrier cycle of the at least two carrier cycles, and obtains the rest data of each carrier cycle in a non-calculation mode to obtain the calculation result of each carrier cycle. Therefore, the calculation which needs to be completed in a single carrier cycle is divided into a plurality of carrier cycles, the calculation pressure of each carrier cycle is relieved, and the calculation time of the PFC algorithm in each carrier cycle is reduced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

Fig. 1 is a schematic diagram of a current waveform without PFC according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a current waveform with PFC according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a PFC circuit according to an embodiment of the present invention;

fig. 4 is a flowchart of a multi-carrier-cycle PFC control method according to an embodiment of the present invention;

fig. 5 is a schematic diagram of carrier period division according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

Fig. 3 is a schematic diagram of a PFC circuit according to an embodiment of the present invention, as shown in fig. 3, the PFC circuit includes a rectifier bridge 100, a filter capacitor 200, a driving switching device 300(IGBT), a voltage stabilizing capacitor 400, a frequency converter 500, an inductor 600, a sampling resistor 700, and a diode 800, the rectifier bridge 100, the filter capacitor 200, the driving switching device 300(IGBT), the voltage stabilizing capacitor 400, and the frequency converter 500 are sequentially connected in parallel, two connection lines between the filter capacitor 200 and the driving switching device 300(IGBT) are respectively connected to the inductor 600 and the sampling resistor 700, and the diode 800 is disposed on the connection line between the driving switching device 300(IGBT) and the voltage stabilizing capacitor 400.

In the state without PFC (Power Factor Correction) control, since the ac voltage is periodically changed, when the instantaneous value of the ac voltage of the Power supply is lower than the dc voltage, no current flows to the voltage stabilizing capacitor, and when the instantaneous value of the ac voltage of the Power supply is higher than the dc voltage, the Power supply has a current flowing to the voltage stabilizing capacitor, and the current flows in the direction of the dotted arrow in fig. 3. I.e. a current waveform as shown in fig. 1, there is a waveform with a current of 0. After the PFC control is added, when the instantaneous value of the ac voltage of the power supply is lower than the dc voltage, the IGBT is turned on for a certain period of time, so that a loop is formed when the IGBT is turned on, and the current flows in the direction of the solid arrow in fig. 3, and when the IGBT is turned off, the current flows in the direction of the dotted arrow in fig. 3. Thereby avoiding the case where the current is 0 so that the current waveform approaches a sine wave as shown in fig. 2.

As shown in fig. 4, an embodiment of the present invention provides a multi-carrier-cycle PFC control method, which is applied to a PFC circuit including a driving switching device 300(IGBT) as shown in fig. 3, and includes:

101. the carrier cycle of the PFC algorithm is divided into at least two cycles.

102. Obtaining the PFC algorithm steps which are originally required to be completed in a single carrier cycle, and obtaining the steps required to be calculated in the PFC algorithm steps.

103. Dividing steps required to be calculated in the PFC algorithm into at least two carrier wave periods for calculation, so that the calculation of the divided steps is completed in each carrier wave period of the at least two carrier wave periods, and other data are obtained in a non-calculation mode, and the calculation result of each carrier wave period is obtained.

The multi-carrier cycle PFC control method applied to the PFC circuit comprising the driving switch device divides a carrier cycle of a PFC algorithm into at least two cycles, obtains a PFC algorithm step which is originally required to be completed in a single carrier cycle, obtains a step which is required to be calculated in the PFC algorithm step, divides the step which is required to be calculated in the PFC algorithm into at least two carrier cycles for calculation, enables the calculation of the divided steps to be completed in each carrier cycle of the at least two carrier cycles, and obtains the rest data of each carrier cycle in a non-calculation mode to obtain the calculation result of each carrier cycle. Therefore, the calculation which needs to be completed in a single carrier cycle is divided into a plurality of carrier cycles, the calculation pressure of each carrier cycle is relieved, and the calculation time of the PFC algorithm in each carrier cycle is reduced.

In one embodiment, the at least two periods of the above division as shown in fig. 5 are cycled, for example, the period a-period B-period a-period B … … as shown in fig. 5 is cycled, the rest data includes data to be calculated and sampled data to be sampled, and the non-calculation method for acquiring the rest data includes:

and directly acquiring the data of the adjacent previous period from the data which needs to be calculated in each carrier period except the dividing step. For example, the previous cycle of the cycle B in fig. 5 is the cycle a, the first cycle a has no previous cycle to acquire the jacket cycle data of 0, and other cycles are cyclically operated and all the other cycles can acquire the corresponding data of the previous adjacent cycle.

And sampling in each carrier period to obtain respective sampling data. For example, in fig. 5, the sampling at period a obtains the sampling data at period a, and the sampling at period B obtains the sampling data at period B.

In one embodiment, the sampled data includes an alternating voltage, a direct voltage, and a circuit current in the PFC circuit.

In one embodiment, the PFC algorithm steps that originally need to be completed within a single carrier cycle include:

s12, filtering the sampled PFC circuit current to obtain an actual current;

and S16, generating PWM waves according to the duty ratio to drive a switching device to operate and control the PFC circuit.

Specifically, when the ac voltage, the dc voltage, and the PFC circuit current in the PFC circuit are sampled in S11, the current flowing through the sampling resistor is sampled as the circuit current in the PFC circuit, the voltage across the voltage stabilizing capacitor is sampled as the dc voltage in the PFC circuit, and the voltage applied across the rectifier bridge is sampled as the ac voltage in the PFC circuit.

The filtering the sampled PFC circuit current to obtain an actual current in S12 includes: according to i_LPF＝LPF(i_PFC) Filtering the sampled PFC circuit current to obtain the actual current, wherein i_LPFFor the actual current, i_PFCLPF means low pass filtering for the sampled PFC circuit current. Low-pass filtering is understood to mean setting a frequency point above which the signal cannot pass, i.e. a cut-off frequency, and assigning all values to 0 in the digital signal above which the frequency domain is above. In this process, the low frequency signal may pass through all the way, so it is called low pass filtering.

The main purpose is to filter out interference in the sampled signal

In S13, the calculating the reference current according to the target dc voltage and the sampled dc voltage includes: according to i_PFC ^*＝PI(V_dc ^*-V_dc) Calculating a reference current, wherein i_PFC ^*For the reference current, is the target current, V, that the current needs to reach_dc ^*Is a target direct current voltage (V)_dc ^*Reference dc voltage, target voltage that dc voltage needs to reach), V_dcPI represents a proportional-integral regulator for the sampled dc voltage.

Said calculating a reference rectified voltage from said reference current and said actual current in S14 comprises; according to | V_ac|^*＝PI(i_PFC ^*-i_LPF) Calculating a reference rectified voltage, wherein | V_ac|^*For reference to the rectified voltage, i_LPFIs the actual current (i)_LPFLow pass filtered actual current) PI represents a proportional-integral regulator.

The calculating the duty ratio according to the reference rectified voltage and the sampled alternating voltage in S15 includes: according to M1- (| Vac | - | V)_ac|^*)/V_dcCalculating the duty ratio, wherein M is the duty ratio, Vac is the alternating voltage obtained by sampling, | Vac | is the absolute value of the alternating voltage, is the rectified voltage, | V |_ac|^*For reference to rectified voltage, V_dcFor sampling the resulting DC voltage, V_dcIs the DC voltage on the voltage-stabilizing capacitor.

When the PFC circuit is controlled by generating the PWM wave according to the duty ratio to drive the switching device to operate in S16, the PFC circuit is controlled by generating the PWM wave according to the duty ratio M to drive the switching device to operate, specifically, if one period is 50us and the duty ratio is 0.3, a PWM wave with a high level of 15us and a low level of 35us is generated in one period; at high level, the driving switching device 300(IGBT) in fig. 3 is turned on, and current flows in the solid arrow line; at low level, the drive switching device 300(IGBT) in fig. 3 is not conducting and current flows as indicated by the dashed arrow. Therefore, the current in fig. 1 can be converted into the current in fig. 2, the current is corrected, the Power Factor (PF) is higher, and the Power Factor Correction (PFC) is realized.

The specific calculation methods of the above steps S11-S16 may refer to the following steps corresponding to the period a and the period B, and the following steps corresponding to the period a and the period B may refer to the specific calculation methods of the above steps S11-S16.

In one embodiment, the step of obtaining the required calculation in the step of obtaining the PFC algorithm includes: the obtaining of the S12, the S13, the S14 and the S15 is a step that needs to be calculated in the PFC algorithm step.

In one embodiment, the dividing the carrier cycle of the PFC algorithm into at least two cycles includes: the carrier period of the PFC algorithm is translated into a loop of at least one carrier period a-carrier period B … as shown in fig. 5.

In one embodiment, the carrier cycle a includes:

and A15, generating a PWM wave according to the duty ratio to drive a switching device to operate and control the PFC circuit.

In one embodiment, the carrier cycle B includes:

b12, filtering the sampled PFC circuit current to obtain an actual current;

Through the period A and the period B division and the calculation step distribution, the corresponding data acquired by the adjacent previous period without corresponding to the carrier period of the first period A is 0, and other periods circularly run and have corresponding previous periods, so that the corresponding value of the previous period can be acquired, and the control is not influenced.

In the above steps S11-S16, in which the main computation amounts are concentrated in the steps S12-S15, a large amount of time is taken. After the calculation steps are divided, the carrier cycle A comprises 2 steps and occupies a large amount of time, and the carrier cycle B comprises 2 steps and occupies a large amount of time, so that the time occupied by each cycle is shortened, and the calculation task which cannot be completed originally can be completed.

In one embodiment, the filtering the sampled PFC circuit current to obtain the actual current includes: according to i_LPF＝LPF(i_PFC) Filtering the sampled PFC circuit current to obtain the actual current, wherein i_LPFFor the actual current, i_PFCLPF represents low-pass filtering for the sampled PFC circuit current;

in one embodiment, the calculating the reference current according to the target dc voltage and the sampled dc voltage includes: according to i_PFC ^*＝PI(V_dc ^*-V_dc) Calculating a reference current, wherein V_dc ^*Is a target DC voltage，V_dcPI represents a proportional-integral regulator for the sampled dc voltage.

In one embodiment, said calculating a reference rectified voltage from said reference current and said actual current comprises; according to | V_ac|^*＝PI(i_PFC ^*-i_LPF) Calculating a reference rectified voltage, wherein | V_ac|^*For reference to the rectified voltage, i_LPFFor the actual current, PI represents a proportional-integral regulator;

in one embodiment, the calculating the duty cycle from the reference rectified voltage and the sampled ac voltage includes: according to M1- (| Vac | - | V)_ac|^*)/V_dcCalculating the duty ratio, wherein M is the duty ratio, Vac is the alternating voltage obtained by sampling, | V_ac|^*For reference to rectified voltage, V_dcIs the sampled dc voltage.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A multi-carrier-cycle PFC control method is applied to a PFC circuit comprising a driving switching device, and comprises the following steps:

dividing a carrier cycle of a PFC algorithm into at least two cycles;

2. The method of claim 1, wherein the at least two cycles, the remaining data includes data to be calculated other than the dividing step and sampled data to be sampled, and the non-calculating obtaining of the respective remaining data includes:

and sampling in each carrier period to obtain respective sampling data.

3. The method of claim 2, wherein the sampled data comprises an alternating voltage, a direct voltage, and a circuit current in the PFC circuit.

4. The method according to claim 2 or 3, wherein the PFC algorithm steps that would have to be performed in a single carrier cycle comprise:

s12, filtering the sampled PFC circuit current to obtain an actual current;

5. The method of claim 4, wherein the step of obtaining the PFC algorithm includes the steps of:

6. The method of claim 2, wherein the dividing the carrier cycle of the PFC algorithm into at least two cycles comprises: converting the carrier period of the PFC algorithm into at least one cycle of carrier period A-carrier period B;

the carrier cycle a includes:

the carrier cycle B includes:

b12, filtering the sampled PFC circuit current to obtain an actual current;

7. The method according to any one of claims 4 to 6,

the step of filtering the sampled PFC circuit current to obtain the actual current comprises the following steps: according to i_LPF＝LPF(i_PFC) Filtering the sampled PFC circuit current to obtain the actual current, wherein i_LPFFor the actual current, i_PFCLPF represents low-pass filtering for the sampled PFC circuit current;

8. The method of claim 7,

said calculating a reference rectified voltage from said reference current and said actual current comprises; according to | V_ac|^*＝PI(i_PFC ^*-i_LPF) Calculating a reference rectified voltage, wherein | V_ac|^*For reference to the rectified voltage, i_LPFFor the actual current, PI represents a proportional-integral regulator;

9. The method of any of claims 3 to 8, wherein the PFC circuit further comprises: the device comprises a rectifier bridge, a filter capacitor, a voltage stabilizing capacitor, a frequency converter, an inductance coil, a sampling resistor and a diode;

the rectifier bridge, the filter capacitor, the drive switch device, the voltage stabilizing capacitor and the frequency converter are connected in parallel in sequence, two connecting lines between the filter capacitor and the drive switch device are respectively connected with the inductance coil and the sampling resistor, and the diode is arranged on the connecting line between the drive switch device and the voltage stabilizing capacitor.

10. The method of claim 9, wherein sampling the ac voltage, the dc voltage, and the PFC circuit current in the PFC circuit comprises: