CN101895128A - Control method of voltage fluctuation feedback of grid-connected current transformer under asymmetric voltage - Google Patents

Control method of voltage fluctuation feedback of grid-connected current transformer under asymmetric voltage Download PDF

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CN101895128A
CN101895128A CN2010102186897A CN201010218689A CN101895128A CN 101895128 A CN101895128 A CN 101895128A CN 2010102186897 A CN2010102186897 A CN 2010102186897A CN 201010218689 A CN201010218689 A CN 201010218689A CN 101895128 A CN101895128 A CN 101895128A
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voltage
current
component
axle
grid
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CN101895128B (en
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赵紫龙
吴维宁
王伟
石磊
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State Grid Electric Power Research Institute
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Abstract

The invention relates to a control method of a grid-connected current transformer under asymmetric voltage, which comprises the following steps of: detecting direct current voltage udc by using a Hall element, detecting grid voltage by using a PT (Potential Transformer) and converting the grid voltage to a d-q coordinate system to acquire a d-axis component ud and a q-axis component uq; multiplying the output of direct current voltage closed loop by coefficients to be respectively used as first components in a d-axis given value and a q-axis given value of the current; respectively extracting the sum of duple work frequency fluctuation in the d-axis component ud and the q-axis component of the voltage, multiplying the voltage by a conversion coefficient of the current to be used as second components in the d-axis given value and the q-axis given value of the current; acquiring the d-axis given value and the q-axis given value of the current by adding two components to detect actual currents id and iq to form a current closed loop; and controlling the work of the current transformer through PWM modulation. The invention can maintain the active power of the current transformer to be stable under the condition of asymmetric grid voltage, inhibit the fluctuation of direct current-side voltage and reduce the distortion of the output current.

Description

The magnitude of a voltage fluctuation feedback of grid-connected converter under the asymmetrical voltage
Technical field
The present invention relates to a kind of feedback, especially relate to the magnitude of a voltage fluctuation feedback of grid-connected converter under a kind of asymmetrical voltage.
Background technology
In recent years, along with the fast development of power electronic device, increase gradually its application scenario, and range of application progressively enlarges, and particularly the current transformer based on electronic power switch has obtained extensive use.In occasions such as Electric Machine Control, power conversion, the application of current transformer makes control convenient flexibly.But the traditional control method of grid-connected converter is to be prerequisite with three symmetrical line voltages, and its variation to voltage is comparatively responsive, causes it can not to adapt to the asymmetric operating condition of line voltage.And under situations such as long transmission line transmission of electricity or electrical network generation unbalanced fault, the asymmetric phenomenon of voltage happens occasionally.In order to guarantee that grid-connected converter in particular cases still can operate as normal at these, people begin to pay close attention to line voltage not to the control method of grid-connected converter under the situation.
Grid-connected converter adopts two closed-loop controls usually, is that outer shroud, alternating current closed loop are interior ring with the direct voltage closed loop promptly.When electrical network is asymmetric, comprised negative sequence component in the voltage, cause the active power of grid side to produce 2 times to the fluctuation of power frequency, the active power fluctuation shows as the fluctuation of direct voltage in the current transformer DC side.This fluctuation threatens the stable operation of current transformer on the one hand; On the other hand dc bus capacitor is formed the process of repeated charge, shorten electric capacity useful life.The effect that strengthens voltage close loop can suppress fluctuation to a certain extent, but can reduce the stability margin of system, causes the distortion of electric current simultaneously.At this situation, scholars more both domestic and external have proposed double-current control [1], two vector current controls [2], internal model control [3]Deng current transformer control method under the asymmetric situation of voltage.But they all need the positive-negative sequence component of voltage and current is implemented to decompose, and control procedure realizes complexity simultaneously, and amount of calculation is big, is a potential threat to real-time system.
[1]Hong-seok?Song，Kwanghee?Nam.Dual?Current?Control?Scheme?for?PWMConverter?Under?Unbalanced?Input?Voltage?Conditions.IEEE?Transactions?on?Industrial?Electronics，Vol.46，No.5，October?1999：953-959
[2]Magueed?F?A，Sannino?A，Svensson?J.Transient?Performance?of?voltage?source?converter?under?unbalanced?voltage?dips.35 th?IEEE?Annual?Power?Electronics?Specialists?Conference(PESC?04).Aachen，Germany.2004(2)：1163-1168.
[3] Zhang Xing, Ji Jianqiang, Zhang Chongwei, etc. based on the uneven control strategy research of the Three-phase PWM Voltage Rectifier of internal model control. Proceedings of the CSEE .2005.25 (13): 51-56.
Summary of the invention
Goal of the invention
The object of the invention provides a kind of control method of comparatively simple grid-connected converter, guarantees that under the asymmetric situation of line voltage grid side active power is stable and dc voltage is stable.
Technical scheme
In order to realize the foregoing invention purpose, the present invention serves as the control basis with outer voltage, current inner loop, by extract in the line voltage negative sequence component and to its do to feed back to after the simple process electric current given in, make active power stable, thereby realize the stable of current transformer dc voltage.
The present invention adopts following technical scheme, and concrete steps comprise:
1) adopt Hall element to detect direct voltage u Dc, adopt voltage transformer pt (Potential Transformer) detection of grid voltage, and line voltage is transformed under the positive sequence synchronous rotating frame (d-q coordinate system), obtain d axle component u dWith q axle component u q
2) with the output of direct voltage closed loop
Figure BSA00000172905300021
Multiply by coefficient respectively as electric current d axle set-point
Figure BSA00000172905300022
With q axle set-point
Figure BSA00000172905300031
In first component;
3) extract two times of power frequency fluctuation amounts in voltage d axle component and the q axle component respectively With
Figure BSA00000172905300033
, multiply by voltage behind the conversion coefficient of electric current as electric current d axle set-point
Figure BSA00000172905300034
With q axle set-point In second component;
4) electric current d axle set-point
Figure BSA00000172905300036
With q axle set-point
Figure BSA00000172905300037
Obtain by aforementioned two component additions, detect actual current i dAnd i qForm current closed-loop;
5) by the work of pulse-width modulation PWM (Pulse-width Modulation) control current transformer.
Realize that further technical scheme of the present invention can be:
Above-mentioned steps 2) in, d shaft current set-point
Figure BSA00000172905300038
First component be voltage close loop output; Q shaft current set-point
Figure BSA00000172905300039
First component be that coefficient u is multiply by in voltage close loop output D+/ u Q+, this coefficient is positive sequence voltage d axle component u D+With q axle component u Q+Ratio.
Realize that further technical scheme of the present invention can be:
Above-mentioned steps 3) in, two times of power frequency fluctuation amounts of d axle and q shaft voltage With
Figure BSA000001729053000311
Extract by the 100Hz band pass filter, can obtain positive sequence voltage d axle component u simultaneously D+With q axle component u Q+
Realize that further technical scheme of the present invention can be:
Above-mentioned steps 3) in, d shaft current set-point Second component be two times of power frequency fluctuation amounts of d shaft voltage
Figure BSA000001729053000313
Multiply by coefficient
Figure BSA000001729053000314
/ u D+Q shaft current set-point
Figure BSA000001729053000315
Second component be two times of power frequency fluctuation amounts of q shaft voltage Multiply by coefficient / u D+
Beneficial effect
The present invention can realize, can keep current transformer active power stable under the asymmetric situation of line voltage, suppresses the dc voltage fluctuation, reduces the output current distortion.The newly-increased amount of calculation on classical two closed-loop control bases of the present invention simultaneously is little, realizes easily.
The major loop of grid-connected converter connects (wherein, Lg represents net side inductance, and C represents dc bus capacitor) as shown in Figure 1, the asymmetric situation of simulation line voltage between 0.16s to 0.24s.When adopting classical two closed-loop control effect as shown in Figure 2, active power and dc voltage fluctuation are bigger, the current waveform distortion; Control effect as shown in Figure 3 when adopting the method for the invention, active power and dc voltage fluctuation are less, the current waveform distortion.Aspect amount of calculation, by implementation procedure as can be known, the newly-increased amount of calculation of the method for the invention is less, realizes easily.
Description of drawings
Fig. 1 is a grid-connected converter major loop connection layout
Fig. 2 is classical two closed-loop control effect
Fig. 3 is a magnitude of a voltage fluctuation FEEDBACK CONTROL effect of the present invention
Fig. 4 is that the magnitude of a voltage fluctuation FEEDBACK CONTROL realizes block diagram
Embodiment
The magnitude of a voltage fluctuation feedback control method adopts outer voltage to cooperate the control mode of current inner loop, and it realizes block diagram as shown in Figure 4.This control at first needs each electric weight is detected, and comprises direct voltage, line voltage and three-phase current.
Adopt Hall element can record direct voltage u Dc
Adopt voltage transformer pt (Potential Transformer) to measure three phase network voltage,, carry out the d-q conversion, obtain voltage d axle component u with A phase voltage orientation d, q axle component u qAnd voltage phase angle θ +When line voltage contains negative sequence component, can be expressed as
Figure BSA00000172905300041
In the formula, subscript " d " and " q " represent d axle component and q axle component respectively, and subscript "+" and "-" represent positive sequence component and negative sequence component respectively, and ω is an electrical network angular speed,
Figure BSA00000172905300042
It is the negative phase-sequence initial phase angle.All comprise alternating current component on d, the q axle in the formula (1), be expressed as respectively
Figure BSA00000172905300051
With , asking for by the 100Hz band pass filter of they obtains.
Adopt current transformer CT (Current Transformer) to measure three-phase current, carry out the d-q conversion equally and obtain electric current d axle component i dWith q axle component i q
The closed-loop control outer shroud is the direct current pressure ring.Given direct voltage controlled target u Dc *(under 690V alternating voltage grade, the direct voltage desired value can be made as 1100V) utilizes desired value and direct voltage value of feedback u DcDifference carry out proportional integral PI (Proportional-Integral) and regulate, obtain output
Figure BSA00000172905300053
This output as the given base value of electric current, is used for current closed-loop and calculates.
The closed-loop control of electric current comprises d axle closed loop and two parts of q axle closed loop, need given desired value be set respectively to d axle and q axle With
Figure BSA00000172905300055
, its basis of design is formula (2), wherein u D+By u dDeduct
Figure BSA00000172905300056
Obtain u Q+By u qDeduct
Figure BSA00000172905300057
Obtain.Utilize the difference of desired value and current feedback value to carry out the PI adjusting, obtain corresponding control voltage v ' dAnd v ' q
i d * = i + * - i + * u d + u ~ d i q * = u q + u d + i + * - i + * u d + u ~ q - - - ( 2 )
Control voltage v ' dAnd v ' qAdd cross-couplings voltage compensation item Δ v dWith Δ v qCan obtain final d, q axle control component of voltage v dAnd v q, in conjunction with voltage phase angle θ +With direct voltage u DcBehind space voltage vector modulation SVPWM (Space Vector Pulse-width Modulation), can obtain the required PWM drive signal of grid-connected converter (this is identical with classical two closed-loop controls).
Under the magnitude of a voltage fluctuation feedback controling mode, active power can be expressed as formula (3), and the size of active power and the output of voltage close loop are linear, and control is simple.Have only DC component in the active power, fluctuation has not realized the stable control of active power of output under the asymmetric situation of line voltage.
P = 3 2 ( u d i d * + u q i q * ) (3)
= 3 2 ( u d + u q + 2 u d + - u - 2 u d + ) i + *

Claims (4)

1. the magnitude of a voltage fluctuation feedback of grid-connected converter under the asymmetrical voltage is characterized in that, may further comprise the steps:
1) adopt Hall element to detect direct voltage u Dc, adopt voltage transformer pt (Potential Transformer) detection of grid voltage, and line voltage is transformed under the positive sequence synchronous rotating frame (d-q coordinate system), obtain d axle component u dWith q axle component u q
2) with the output of direct voltage closed loop Multiply by coefficient respectively as electric current d axle set-point
Figure FSA00000172905200012
With q axle set-point
Figure FSA00000172905200013
In first component;
3) extract two times of power frequency fluctuation amounts in voltage d axle component and the q axle component respectively
Figure FSA00000172905200014
With
Figure FSA00000172905200015
, multiply by voltage behind the conversion coefficient of electric current as electric current d axle set-point
Figure FSA00000172905200016
With q axle set-point
Figure FSA00000172905200017
In second component;
4) electric current d axle set-point
Figure FSA00000172905200018
With q axle set-point
Figure FSA00000172905200019
Obtain by aforementioned two component additions, detect actual current i dAnd i qForm current closed-loop;
5) by the work of pulse-width modulation PWM (Pulse-width Modulation) control current transformer.
2. the magnitude of a voltage fluctuation feedback of grid-connected converter under the asymmetrical voltage according to claim 1 is characterized in that:
Described step 2) in, d shaft current set-point
Figure FSA000001729052000110
First component be voltage close loop output; Q shaft current set-point
Figure FSA000001729052000111
First component be that coefficient u is multiply by in voltage close loop output D+/ u Q+, this coefficient is positive sequence voltage d axle component u D+With q axle component u Q+Ratio.
3. the magnitude of a voltage fluctuation feedback of grid-connected converter under the asymmetrical voltage according to claim 1 is characterized in that:
In the described step 3), two times of power frequency fluctuation amounts of d axle and q shaft voltage
Figure FSA000001729052000112
With Extract by the 100Hz band pass filter, can obtain positive sequence voltage d axle component u simultaneously D+With q axle component u Q+
4. the magnitude of a voltage fluctuation feedback of grid-connected converter under the asymmetrical voltage according to claim 1 is characterized in that:
In the described step 3), d shaft current set-point
Figure FSA00000172905200021
Second component be two times of power frequency fluctuation amounts of d shaft voltage
Figure FSA00000172905200022
Multiply by coefficient
Figure FSA00000172905200023
/ u D+Q shaft current set-point
Figure FSA00000172905200024
Second component be two times of power frequency fluctuation amounts of q shaft voltage
Figure FSA00000172905200025
Multiply by coefficient
Figure FSA00000172905200026
/ u D+
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103595278A (en) * 2013-11-18 2014-02-19 河南师范大学 Power balance resonance control method for solar power generation system grid-side converter
CN105006828A (en) * 2015-07-28 2015-10-28 南京工程学院 Grid-connected converter negative sequence current compensation method
CN108307670A (en) * 2015-10-09 2018-07-20 通用电气航空系统有限责任公司 To reduce the control of total harmonic distortion and the unbalanced AC source inventers of output voltage
CN110138184A (en) * 2019-06-26 2019-08-16 哈尔滨工业大学 A kind of self-adaptation control method and control device of three phase power rectifier
CN112356741A (en) * 2020-11-20 2021-02-12 西安许继电力电子技术有限公司 Feedback control method and system based on PWM energy feedback converter

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CN101741096A (en) * 2009-12-22 2010-06-16 浙江大学 Delayless control method of rotor current of grid-connection, speed-change and constant-frequency double-fed induction wind driven generator

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CN101141110A (en) * 2007-09-07 2008-03-12 浙江大学 Variable speed constant frequency dual-feed asynchronous wind power generator rotor current non-delay control method
CN101741096A (en) * 2009-12-22 2010-06-16 浙江大学 Delayless control method of rotor current of grid-connection, speed-change and constant-frequency double-fed induction wind driven generator

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103595278A (en) * 2013-11-18 2014-02-19 河南师范大学 Power balance resonance control method for solar power generation system grid-side converter
CN105006828A (en) * 2015-07-28 2015-10-28 南京工程学院 Grid-connected converter negative sequence current compensation method
CN108307670A (en) * 2015-10-09 2018-07-20 通用电气航空系统有限责任公司 To reduce the control of total harmonic distortion and the unbalanced AC source inventers of output voltage
CN108307670B (en) * 2015-10-09 2020-07-28 通用电气航空系统有限责任公司 Control of AC source inverter to reduce total harmonic distortion and output voltage imbalance
CN110138184A (en) * 2019-06-26 2019-08-16 哈尔滨工业大学 A kind of self-adaptation control method and control device of three phase power rectifier
CN112356741A (en) * 2020-11-20 2021-02-12 西安许继电力电子技术有限公司 Feedback control method and system based on PWM energy feedback converter
CN112356741B (en) * 2020-11-20 2022-06-07 西安许继电力电子技术有限公司 Feedback control method and system based on PWM energy feedback converter

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