CN112993966A - Active filtering method applied to direct current system - Google Patents

Active filtering method applied to direct current system Download PDF

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CN112993966A
CN112993966A CN202110359412.4A CN202110359412A CN112993966A CN 112993966 A CN112993966 A CN 112993966A CN 202110359412 A CN202110359412 A CN 202110359412A CN 112993966 A CN112993966 A CN 112993966A
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current
signal
active filter
direct current
active
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CN112993966B (en
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窦文雷
姚钢
黄琛
周荔丹
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Shanghai Jiaotong University
China Ship Development and Design Centre
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Shanghai Jiaotong University
China Ship Development and Design Centre
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/02—Arrangements for reducing harmonics or ripples
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The active filtering method for DC system includes sampling and filtering the current in DC load to obtain the harmonic signal in the load current, taking the harmonic signal as compensation signal after inversion, subtracting the current signal from the current signal generated by active filter to obtain error signal, and using the error signal as negative feedback to regulate and isolate the output voltage and current range of DC/DC converter dynamically so as to minimize the loss of active filter. The invention greatly reduces the current harmonic of the direct current load through the compensation effect of the active filter, improves the electric energy quality of the voltage and the current at the load side, enables the load to run more stably and reliably, and effectively reduces the harm of the harmonic to a direct current system.

Description

Active filtering method applied to direct current system
Technical Field
The invention relates to a technology in the field of direct current filters, in particular to an active filtering method applied to a direct current system.
Background
In the prior art, active filters are increasingly gaining attention and being used to improve the quality of electric power. However, most active filters are designed for three-phase ac systems and cannot be applied directly to dc systems. Some control methods for an active filter in an ac system, although they can also be applied to an active filter in a dc system, do not make good use of the characteristics of the dc system, and thus are redundant and complicated. However, in the existing research on the dc active filter, most of the researches are on the current tracking control and the harmonic detection algorithm thereof, and the control of the dc side voltage of the active filter and the influence of the harmonic frequency change on the filtering effect are rarely considered, and a specific architecture of the whole dc active filter system is not given. Aiming at the characteristic that direct current is mainly used in a direct current system, the direct current active filter can be simplified in control, and the loss of the active filter can be reduced as much as possible.
Disclosure of Invention
Aiming at the problems of larger load harmonic current, fixed and unadjustable input voltage, unstable direct-current side voltage and larger loss in the existing direct-current system, the invention provides an active filtering method applied to the direct-current system, which greatly reduces the current harmonic of a direct-current load through the compensation effect of an active filter, improves the electric energy quality of the load side voltage and current and ensures that the load can operate more stably and reliably; the stable filtering effect can be still kept when the harmonic frequency changes through the PI controller and the self-adaptive quasi-PR controller; the isolated DC/DC converter directly takes electricity from the DC bus to provide stable DC voltage for the input end of the active filter, so that an additional DC power supply is not needed; the system can also estimate harmonic power according to the magnitude of load voltage and current, so as to intelligently regulate and control the output voltage of the DC/DC converter, namely the input voltage of the active filter, so that the output current of the DC/DC converter is kept in a certain range, devices are protected, meanwhile, the loss of the active filter can be reduced, the normal and stable operation of the load is ensured, and the harm of harmonic to a direct current system is effectively reduced.
The invention is realized by the following technical scheme:
the invention relates to an active filtering method applied to a direct current system, which is characterized in that a harmonic signal in load current is obtained after current at a direct current load is sampled and filtered, the harmonic signal is used as a compensation signal after being inverted and is subtracted from a current signal generated by an active filter to obtain an error signal, and the error signal is used as negative feedback to dynamically adjust and isolate the voltage output by a DC/DC converter and the range of the output current, so that the loss of the active filter is minimized.
The negative feedback generates a control signal through a parallel PI controller and a self-adaptive quasi-PR controller which are arranged between the direct current bus and the active filter, and the control signal is compared with a triangular carrier by a carrier pulse width modulation (CBPWM) unit to obtain a control signal for controlling the on and off of a switching tube in the active filter.
The active filter is arranged on a direct current bus through an isolation DC/DC converter and is connected with a load, and the active filter specifically comprises: the output end of the direct current active filter is connected with the direct current load in parallel through a blocking capacitor, the input end of the direct current active filter is connected with the output end of the isolation DC/DC converter, and the input end of the isolation DC/DC converter is connected with the direct current bus.
The active filter adopts a diode Neutral Point Clamped (NPC) three-level topology, and comprises: the active filter comprises eight switching tubes, two blocking capacitors and a second-order LC filter which is composed of an output filter capacitor and an output filter inductor and used for filtering harmonic waves in output current of the active filter.
The isolation DC/DC converter adopts a two-level dual-active full-bridge topology, and comprises: eight switching tubes, a high-frequency transformer, an input filter capacitor, two output filter capacitors and a resonant inductor.
The isolated DC/DC converter voltage loop is controlled with single phase shift PWM and the output voltage can be varied by varying the value of the reference voltage.
Technical effects
The invention integrally solves the harmonic problem of the direct current load in the existing direct current microgrid system. Compared with the prior art, the invention can quickly and effectively compensate the harmonic current of the direct current load and reduce the harmonic distortion rate of the load current to about 0.01 percent. The PI controller and the self-adaptive quasi-PR controller are adopted in the control of the active filter, so that good tracking and compensation effects can be still kept when the frequency or the load of the generator suddenly changes; the direct current side of the active filter adopts the mode that the isolation DC/DC converter directly supplies power, so that the voltage of the direct current side can be still ensured to be stable when the load power fluctuates.
Drawings
FIG. 1 is a schematic diagram of an embodiment of an active filter;
FIG. 2 is a flow chart of an embodiment active filtering method.
FIG. 3 is a flowchart of a voltage loop control method of an isolated DC/DC converter according to an embodiment.
Detailed Description
As shown in fig. 1, the present embodiment relates to a dc active filtering system with a harmonic frequency adaptive tracking function, which includes: direct current bus, direct current load, direct current active filter, isolated DC/DC converter, wherein: the input end and the output end of the isolated DC/DC converter are respectively connected with the DC bus and the DC side of the active filter, and the output end of the DC active filter passes through the inductor LfAnd a capacitor CfForm a second-order LC filter and a DC blocking capacitor CiThen the current is connected in parallel with the DC load to be compensated, thereby improving the current flowing through the load and further improving the voltage on the load.
The DC/DC converter adopts two-level full-bridge DAB topology and phase-shift PWM voltage closed-loop control to ensure the stability of output voltage and improve the voltage utilization rate, and the voltage and current stress of a switching device is small, so the cost is low, high efficiency can be achieved, and the problem of voltage stability of the direct current side of an active filter does not need to be considered.
The active filter adopts a diode neutral point clamped three-level topology, has a better compensation effect compared with two levels, has lower voltage stress of the switching tube, saves cost and reduces loss.
The embodiment relates to a direct current active filtering method of the system, which is characterized in that harmonic power is obtained through sampling voltage and current at a direct current load and estimating, and then the voltage output by an isolation DC/DC converter and the range of the output current are dynamically adjusted, so that the loss of an active filter is minimized.
The embodiment reduces the output voltage of the isolation DC/DC converter as much as possible on the premise of ensuring that the output current does not exceed the allowable maximum value, even if the input voltage of the active filter is as low as possible, thereby reducing the loss of the active filter.
As shown in fig. 2, the minimization of the loss of the active filter specifically includes:
the method comprises the following steps: sampling the current at the load to obtain a current signal I containing direct current and harmonic currentd+idAfter passing through a low-pass filter, a direct current I without harmonic waves is obtaineddAnd then using the collected current signal Id+idSubtracting the DC signal IdThe harmonic signal i in the load current can be obtainedd。
Step two: harmonic signal idObtaining the compensation signal needed to be generated by the active filter by taking the inverse, and then combining the compensation signal with the current signal i generated by the active filtercBy subtraction, i.e. obtaining the error signal e by negative feedbackiAnd then respectively inputting the signals into a PI controller and an adaptive quasi-PR controller.
Step three: and a carrier pulse width modulation (CBPWM) unit superposes signals output by the PI controller and the self-adaptive quasi-PR controller and compares the superposed signals with upper and lower paths of in-phase triangular carriers to obtain a control signal for controlling the on and off of a switching tube in the active filter.
As shown in fig. 3, the single phase shift PWM control of the isolated DC/DC converter specifically includes:
step i: sampling the output voltage of the converter to obtain UoutAnd using a set reference voltage UrefMinus the sampling voltage UoutBy using negative feedback to obtain the error signal euThe above signals are combinedAnd inputting the signals into a PI controller to generate a control signal of phase shift.
Step ii: the signal output by the controller is processed by a linearization unit and then compared with a triangular wave, namely a Pulse Width Modulation (PWM) strategy is adopted to obtain a control signal for controlling the on and off of a switching tube in the isolation DC/DC converter.
Through simulation, under the environment of MATLAB/Simulink, the direct current active filter system is built, the harmonic distortion rate of the load current before filtering is about 0.08%, the harmonic distortion rate of the load current after filtering is about 0.01%, the harmonic distortion rate can still be kept about 0.01% when the frequency of the generator fluctuates, and the voltage of the direct current side of the active filter is kept at 400V in the period.
In summary, the present invention utilizes a diode midpoint clamping type three-level topology and an isolation DC/DC converter to directly take power at a DC bus as an input voltage of an active filter, and adopts a PI + adaptive quasi-PR control strategy on a current tracking control strategy of the active filter, so that the system can still maintain a good compensation effect under the condition of harmonic frequency variation.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (7)

1. An active filtering method applied to a direct current system is characterized in that a harmonic signal in load current is obtained after current at a direct current load is sampled and filtered, the harmonic signal is used as a compensation signal after being inverted and is subtracted from a current signal generated by an active filter to obtain an error signal, the error signal is used as negative feedback, and then voltage output by a DC/DC converter and the range of output current are dynamically adjusted and isolated, so that the loss of the active filter is minimized;
the negative feedback generates a control signal through a parallel PI controller and a self-adaptive quasi-PR controller which are arranged between the direct current bus and the active filter, and the control signal is compared with a triangular carrier by a carrier pulse width modulation (CBPWM) unit to obtain a control signal for controlling the on and off of a switching tube in the active filter.
2. The active filtering method applied to the DC system according to claim 1, wherein the active filter is disposed on the DC bus via an isolation DC/DC converter and connected to a load, and specifically comprises: the output end of the direct current active filter is connected with the direct current load in parallel through a blocking capacitor, the input end of the direct current active filter is connected with the output end of the isolation DC/DC converter, and the input end of the isolation DC/DC converter is connected with the direct current bus.
3. The active filtering method applied to the dc system of claim 1, wherein the active filter adopts a diode midpoint clamped three-level topology, comprising: the active filter comprises eight switching tubes, two blocking capacitors and a second-order LC filter which is composed of an output filter capacitor and an output filter inductor and used for filtering harmonic waves in output current of the active filter.
4. The active filtering method applied to the DC system as claimed in claim 1, wherein the isolated DC/DC converter adopts a two-level dual-active full-bridge topology, comprising: eight switching tubes, a high-frequency transformer, an input filter capacitor, two output filter capacitors and a resonant inductor.
5. The active filtering method applied to the direct current system of claim 1, wherein the isolated DC/DC converter voltage loop is controlled by single phase shift PWM and the output voltage is varied by varying the value of the reference voltage.
6. The active filtering method applied to the dc system according to claim 1, wherein the minimizing of the loss of the active filter specifically comprises:
step (ii) ofFirstly, the method comprises the following steps: sampling the current at the load to obtain a current signal I containing direct current and harmonic currentd+idAfter passing through a low-pass filter, a direct current I without harmonic waves is obtaineddAnd then using the collected current signal Id+idSubtracting the DC signal IdThe harmonic signal i in the load current can be obtainedd；
Step two: harmonic signal idObtaining the compensation signal needed to be generated by the active filter by taking the inverse, and then combining the compensation signal with the current signal i generated by the active filtercBy subtraction, i.e. obtaining the error signal e by negative feedbackiThen, respectively inputting the signals into a PI controller and a self-adaptive quasi-PR controller;
step three: the carrier pulse width modulation unit superposes signals output by the PI controller and the self-adaptive quasi-PR controller and then compares the superposed signals with upper and lower paths of in-phase triangular carriers to obtain a control signal for controlling the on and off of a switching tube in the active filter.
7. The active filtering method applied to the direct current system as claimed in claim 5, wherein the single phase-shift PWM control of the isolated DC/DC converter specifically comprises:
step i: sampling the output voltage of the converter to obtain UoutAnd using a set reference voltage UrefMinus the sampling voltage UoutBy using negative feedback to obtain the error signal euInputting the signals into a PI controller to generate control signals of phase shift;
step ii: the signal output by the controller is processed by a linearization unit and then compared with a triangular wave, namely, a pulse width modulation strategy is adopted to obtain a control signal for controlling the on and off of a switching tube in the isolation DC/DC converter.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1658485A (en) * 2005-03-10 2005-08-24 上海交通大学 Counter control current tracking control method based on average current compensation
US20110057517A1 (en) * 2009-09-09 2011-03-10 Jinhui Zhang Hybrid Conditioner for a Power System
CN104269841A (en) * 2014-09-19 2015-01-07 中国舰船研究设计中心 Rectification harmonic suppression device for direct current power grid
CN104993470A (en) * 2015-06-29 2015-10-21 南京航空航天大学 Control mode for active filter in DC link
CN110912132A (en) * 2019-11-27 2020-03-24 天津瑞能电气有限公司 Harmonic compensation control method for single-phase cascade active power filter

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1658485A (en) * 2005-03-10 2005-08-24 上海交通大学 Counter control current tracking control method based on average current compensation
US20110057517A1 (en) * 2009-09-09 2011-03-10 Jinhui Zhang Hybrid Conditioner for a Power System
CN104269841A (en) * 2014-09-19 2015-01-07 中国舰船研究设计中心 Rectification harmonic suppression device for direct current power grid
CN104993470A (en) * 2015-06-29 2015-10-21 南京航空航天大学 Control mode for active filter in DC link
CN110912132A (en) * 2019-11-27 2020-03-24 天津瑞能电气有限公司 Harmonic compensation control method for single-phase cascade active power filter

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
WEI HUANG 等: "A Novel Recursive Integral PI Repetitive Control for Three-phase Three-wire Shunt Active Power Filter", 《2011 6TH IEEE CONFERENCE ON INDUSTRIAL ELECTRONICS AND APPLICATIONS》 *
刘文亚 等: "基于级联多电平的有源滤波器直流侧电压平衡控制", 《电力系统保护与控制》 *
孟鑫 等: "改进PR控制器在四桥臂有源滤波装置中的设计与实现", 《电测与仪表》 *
纪飞峰 等: "基于直流侧电压周期离散控制的单相并联有源滤波器", 《中国电机工程学报》 *

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