阅读说明：本技术 一种dcac变换器的双前馈控制方法 (Double feedforward control method of DCAC converter ) 是由 李珣 李明阳 刘思佳 黄勇 李晓冬 于 2020-12-16 设计创作，主要内容包括：本发明提供一种DCAC变换器的双前馈控制方法,涉及新能源及电力电子技术领域,采用基于电压PI和电流PI结构,同时分别在电压和电流环上叠加电压有效值前馈和瞬时电压前馈,即保留了PI简单易用、鲁棒性高的优点,同时又能快速消除正弦波稳态静差,使输出更加稳定,系统的可靠性更高。(The invention provides a double feedforward control method of a DCAC converter, which relates to the technical field of new energy and power electronics, adopts a structure based on a voltage PI and a current PI, and simultaneously superposes a voltage effective value feedforward and an instantaneous voltage feedforward on a voltage loop and a current loop respectively, thereby retaining the advantages of simple and easy use of PI and high robustness, and simultaneously quickly eliminating the steady static difference of a sine wave, so that the output is more stable and the reliability of the system is higher.)

1. A method of dual feed forward control of a DCAC converter, comprising the steps of:

step 1: initializing a system and setting threshold parameters;

step 2: the method comprises the steps that an input direct-current bus voltage Vbus _ fbk, a load current iac _ fbk and a load voltage uac _ fbk are obtained through a signal acquisition module;

and step 3: judging whether the bus voltage reaches an alternating current output threshold value VBUS _ AC _ ON, if not, not enabling the full-bridge PWM output; if the driving output of the full bridge is enabled, entering a system soft start stage;

and 4, step 4: calculating a reference value iac _ ref of an alternating current loop PI _ iac module to complete first feedforward control superposed on a voltage loop reference end;

and 5: obtaining a current loop output signal iac _ duty;

step 6: obtaining a PWM control signal duty of the inverter full-bridge power tube to complete second feedforward control superposed on the output end of the current loop;

and 7: the real-time monitoring of Vbus _ fbk, UAC _ fbk and IAC _ fbk is realized through a timing monitoring unit, and the real-time monitoring is compared with preset corresponding thresholds VBUS _ MIN, VBUS _ MAX, UAC _ RMS _ MAX and IAC _ MAX to judge whether to alarm or close the driving output so as to achieve the purposes of undervoltage, overvoltage and overcurrent protection of the system.

2. A dual feed-forward control method for DCAC converter as claimed in claim 1, characterized in that in said step 3, the reference value UAC _ REF of the "PI _ UAC" module is set to the product of the output of the standard Sine generation module "Sine _ Gen" and K times the fixed value UAC _ REF by means of time-slicing during the start-up phase.

3. A dual feed-forward control method for DCAC converter as claimed in claim 2, wherein in step 3, after the soft start is finished, UAC _ REF is set to be the product of the output of the standard Sine generation module "Sine _ Gen" and the reference value UAC _ REF corresponding to the fixed output voltage, so that the duty ratio of the PWM output driving is gradually increased, K has a value range of [0.5,0.9], and K is gradually increased from 0 to its set value during the soft start.

4. A dual feedforward control method for a DCAC converter according to claim 1, wherein in step 4, the reference value iac _ ref of the ac current loop "PI _ iac" module is calculated to perform the first feedforward control superimposed on the reference end of the voltage loop, specifically:

uac-fbk is calculated by a Sine wave analysis module 'Sine _ An' to obtain An effective value uac _ rms of the current output voltage, the effective value is added with uac _ ref and then multiplied by a standard Sine generation module 'Sine _ Gen', the output is connected to the reference value input end of a 'PI _ uac' module, and after proportional integral calculation and saturation amplitude limiting processing, the reference value iac _ ref of An alternating current loop 'PI _ iac' module is obtained.

5. A method for dual feed forward control of a DCAC converter as claimed in claim 1, wherein in said step 5, a current loop output signal iac _ duty is obtained, in particular: and sending iac _ ref to a reference value input end of a PI _ iac module, sending iac _ fbk to a feedback input end, performing proportional integral calculation, and performing saturation amplitude limiting processing to obtain a current loop output signal iac _ duty.

6. A dual feedforward control method of a DCAC converter according to claim 1, wherein in step 6, a PWM control signal duty of the inverter full-bridge power transistor is obtained to perform a second feedforward control superposed on the output end of the current loop, specifically: and adding iac _ duty and uac _ fbk, and then dividing by Vbus _ fbk to obtain a PWM control signal duty of the inverter full-bridge power tube, and completing the second feed-forward control superposed on the output end of the current loop so as to realize the working state of alternating current stable output until a stop or fault interruption command is received.

Technical Field

The invention relates to the technical field of new energy and power electronics, in particular to a double feedforward control method of a DCAC converter.

Background

When the problems of energy crisis and environmental pollution are getting worse, it is important to develop renewable clean energy such as photovoltaic power generation.

The DC-AC converter is an inverter device for realizing direct current to alternating current, and the common DCAC converter control methods include PI (proportional integral), PR (resonance), slip film and repetitive control. Although the PI algorithm is simple, the steady-state error of the time-varying sinusoidal signal cannot be accurately tracked; PR has good steady-state characteristics, but a controller is required to be arranged for each harmonic wave; synovial control relies on building an accurate system model to obtain synovial surface functions and control fields; the repeated control can only delay one period to generate a control quantity, and the dynamic performance is poor; besides PI, other control methods have the problems of complex structure and difficult realization.

Disclosure of Invention

The invention provides a double feedforward control method of a DCAC converter, which adopts a structure based on a voltage PI and a current PI, and simultaneously superposes a voltage effective value feedforward and an instantaneous voltage feedforward on a voltage loop and a current loop respectively, thereby not only keeping the advantages of simple and easy use of PI and high robustness, but also quickly eliminating the steady static difference of a sine wave, ensuring more stable output and higher reliability of a system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method of dual feed forward control of a DCAC converter, comprising the steps of:

step 1: initializing a system and setting threshold parameters;

step 2: the method comprises the steps that an input direct-current bus voltage Vbus _ fbk, a load current iac _ fbk and a load voltage uac _ fbk are obtained through a signal acquisition module;

and step 3: judging whether the bus voltage reaches an alternating current output threshold value VBUS _ AC _ ON, if not, not enabling the full-bridge PWM output; if the driving output of the full bridge is enabled, entering a system soft start stage;

and 4, step 4: calculating a reference value iac _ ref of an alternating current loop PI _ iac module to complete first feedforward control superposed on a voltage loop reference end;

and 5: obtaining a current loop output signal iac _ duty;

step 6: obtaining a PWM control signal duty of the inverter full-bridge power tube to complete second feedforward control superposed on the output end of the current loop;

and 7: the real-time monitoring of Vbus _ fbk, UAC _ fbk and IAC _ fbk is realized through a timing monitoring unit, and the real-time monitoring is compared with preset corresponding thresholds VBUS _ MIN, VBUS _ MAX, UAC _ RMS _ MAX and IAC _ MAX to judge whether to alarm or close the driving output so as to achieve the purposes of undervoltage, overvoltage and overcurrent protection of the system.

In the step 3, in the starting phase, the reference value UAC _ REF of the PI _ UAC module is set to be the product of the output of the standard Sine generation module "Sine _ Gen" and K times of the fixed value UAC _ REF by a timing segmentation method.

In the step 3, after the soft start is finished, UAC _ REF is set to be the product of the output of the standard Sine generation module "Sine _ Gen" and the reference value UAC _ REF corresponding to the fixed output voltage, so that the duty ratio of the PWM output drive is gradually increased, the value range of K is [0.5,0.9], and K is gradually increased from 0 to its set value during the soft start.

In step 4, a reference value iac _ ref of the ac current loop "PI _ iac" module is calculated to complete a first feedforward control superimposed on the reference end of the voltage loop, specifically:

uac-fbk is calculated by a Sine wave analysis module 'Sine _ An' to obtain An effective value uac _ rms of the current output voltage, the effective value is added with uac _ ref and then multiplied by a standard Sine generation module 'Sine _ Gen', the output is connected to the reference value input end of a 'PI _ uac' module, and after proportional integral calculation and saturation amplitude limiting processing, the reference value iac _ ref of An alternating current loop 'PI _ iac' module is obtained.

In the step 5, the current loop output signal iac _ duty is obtained, specifically: and sending iac _ ref to a reference value input end of a PI _ iac module, sending iac _ fbk to a feedback input end, performing proportional integral calculation, and performing saturation amplitude limiting processing to obtain a current loop output signal iac _ duty.

In step 6, a PWM control signal duty of the inverter full-bridge power tube is obtained, and a second feedforward control superposed on the output end of the current loop is completed, specifically: and adding iac _ duty and uac _ fbk, and then dividing by Vbus _ fbk to obtain a PWM control signal duty of the inverter full-bridge power tube, and completing the second feed-forward control superposed on the output end of the current loop so as to realize the working state of alternating current stable output until a stop or fault interruption command is received.

Compared with the prior art, the invention has the beneficial effects that:

the voltage PI and current PI based structure is adopted, and voltage effective value feedforward and instantaneous voltage feedforward are respectively superposed on a voltage loop and a current loop at the same time, so that the advantages of simple and easy use of PI and high robustness are kept, and meanwhile, the steady static error of the sine wave can be quickly eliminated, the output is more stable, and the reliability of the system is higher.

Drawings

FIG. 1 is a control block diagram of the present invention;

FIG. 2 is a control flow chart of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples, which are intended to illustrate only some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments used by those skilled in the art without any creative effort belong to the protection scope of the present invention.

Example 1:

as shown in fig. 1 and 2, for a certain 3KW DCAC converter, the rated output is 220V, 50HZ sine wave, the main control chip adopts a certain brand 32bit microcontroller, and the dual feed-forward control method and steps are as follows:

(1) system initialization and threshold parameter settings VBUS _ MIN 180V, UAC _ REF 220V, VBUS _ MAX 400V, UAC _ RMS _ MAX 235V, IAC _ MAX 15A, K0.5;

(2) the input direct-current bus voltage Vbus _ fbk, the load current iac _ fbk and the load voltage uac _ fbk are obtained through a signal acquisition module.

(3) Judging whether the bus voltage reaches an alternating current output threshold value VBUS _ MIN or not, and if not, not enabling the full-bridge PWM output; and if the driving output of the full bridge is enabled, entering a system soft start stage.

(4) Uac-fbk is calculated by a Sine wave analysis module 'Sine _ An' to obtain An effective value uac _ rms of the current output voltage, the effective value is added with uac _ ref and then multiplied by a standard Sine generation module 'Sine _ Gen', the output is connected to the reference value input end of a 'PI _ uac' module, after proportional integral calculation and saturation amplitude limiting processing, a reference value iac _ ref of An alternating current loop 'PI _ iac' module is obtained, and the first feedforward control superposed on the reference end of a voltage loop is completed.

(5) And sending iac _ ref to a reference value input end of a PI _ iac module, sending iac _ fbk to a feedback input end, performing proportional integral calculation, and performing saturation amplitude limiting processing to obtain a current loop output signal iac _ duty.

(6) And adding iac _ duty and uac _ fbk, and then dividing by Vbus _ fbk to obtain a PWM control signal duty of the inverter full-bridge power tube, and completing the second feed-forward control superposed on the output end of the current loop so as to realize the working state of alternating current stable output until a stop or fault interruption command is received.

(7) The timing monitoring unit is used for realizing real-time monitoring on Vbus _ fbk, uac _ fbk and iac _ fbk, comparing the real-time monitoring with a preset corresponding threshold value, and judging whether to alarm or close the driving output so as to achieve the purposes of undervoltage, overvoltage and overcurrent protection of the system.

In the system starting stage, setting a reference value uac _ ref of a PI-uac module as the product of the output of a standard Sine generation module Sine-Gen and 0.5 times of a rated voltage per unit by a timing segmentation method; after the soft start is finished, UAC _ REF is set to be the product of the output of the standard Sine generation module "Sine _ Gen" and the reference value UAC _ REF corresponding to the fixed output voltage, so that the duty ratio driven by the PWM output is gradually increased, and the purpose of reducing the large current impact at the moment of switching on the switching tube is achieved. The value range of K is [0.5,0.9], and K is gradually increased from 0 to the set value during the soft start.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.