CN103219745A - Grid-connected inverter control algorithm based on orthogonal sine wave extractor - Google Patents
Grid-connected inverter control algorithm based on orthogonal sine wave extractor Download PDFInfo
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- CN103219745A CN103219745A CN2013101374765A CN201310137476A CN103219745A CN 103219745 A CN103219745 A CN 103219745A CN 2013101374765 A CN2013101374765 A CN 2013101374765A CN 201310137476 A CN201310137476 A CN 201310137476A CN 103219745 A CN103219745 A CN 103219745A
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Abstract
The invention discloses a grid-connected inverter control algorithm based on an orthogonal sine wave extractor. The grid-connected inverter control algorithm based on the orthogonal sine wave extractor can be used in control of photovoltaic three-phase grid-connected inverter, a wind-electricity three-phase grid-connected inverter and the like. The invention includes the orthogonal sine wave extractor and a grid-connected inverter current control method based on the orthogonal sine wave extractor. The orthogonal sine wave extractor is achieved through a second order discrete state equation, simultaneously has band-pass filtering and phase shifting action for an input signal and is used for conducting treatment on a sine alternating quantity such as a voltage and a current in grid-connected inverter control. Based on the grid-connected inverter current control method based on the orthogonal sine wave extractor, tracking conducted by three-phase alternating-current feedback on floating which is given by the method is achieved, and the grid-connected inverter control algorithm based on the orthogonal sine wave extractor has strong power grid adaptability, can effectively suppress entry network current harmonics and reduce entry network current total harmonic distortion.
Description
Technical field
The invention belongs to combining inverter control technology field, it can be applied in the grid-connected power generation systems such as photovoltaic, wind-powered electricity generation.
Background technology
In recent years, the new energy electric power such as photovoltaic, wind-powered electricity generation networks on a large scale, and generation of electricity by new energy accounts for the degree that the proportion of gross generation be can not ignore to reach, and continues to rise.If enter network electric energy quality it is not high if whole power system is had undesirable effect.Pure new energy can be just set really to promote the well-being of mankind to the stable electric power that power network is conveyed.Photovoltaic and wind-powered electricity generation etc. typically need to convey energy by inverter to power network, and this aspect requires that inverter has higher grid adaptability, can be still incorporated into the power networks in the case where Voltage Harmonic is heavier.On the other hand, it is desirable to which the current harmonic content that inverter is sent in itself is low, it is unlikely to further to influence power network.This requires that combining inverter current control has good performance.
The combining inverter of three-phase full-controlled bridge form has the advantages that power factor is adjustable, is the general choice of current high-power grid-connected inverting system.The circuit is mainly made up of 6 IGBT and its antiparallel diode, and each two IGBT is connected into a bridge.Controller need to send control signal to each IGBT, and different drive level dutycycles may be such that three-phase full-controlled bridge is operated in rectification, inversion, sends out idle, inhales the various states such as idle.Although the circuit topology has obtained large-scale application, its control performance need to be improved.At present, the current control method of three-phase grid-connected inverter main flow has controls two classes using the proportional plus integral control under rotating coordinate system and the ratio resonance under rest frame.The characteristics of the former is DC quantity using three-phase alternating current amount under rotating coordinate system, adoption rate integral controller just can realize the DAZ gene of electric current, but it has the disadvantage that each controlling cycle is required for progress to rotate forward conversion and reversely rotates conversion, trigonometric function operation is directed to, algorithm execution time is longer.The latter can directly realize the DAZ gene to of ac in rest frame, save real time rotation conversion, but its major defect is that the effective ratio resonant controller of design is highly difficult, traditional method for designing is to be determined under continuous domain after the performances such as filtering bandwidth, discretization is into numerical control system again, discretization process necessarily brings the phase shift of signal, influences control performance.
The present invention designs a kind of novel grid-connected inverter current control algolithm to make up some defects of ratio resonance control.
The content of the invention
To overcome the above not enough, the invention provides a kind of parallel network reverse control algolithm based on orthogonal sine wave extractor.
In order to solve the above problems, the present invention uses following technical scheme：
A kind of parallel network reverse control algolithm based on orthogonal sine wave extractor, it is characterized in that include orthogonal sine wave extractor, the discrete state equations that the orthogonal sine wave extractor is defined as：
Wherein
For the output result of orthogonal sine wave extractor, primary condition can be taken as
,；
For sinusoidal signal angular frequency to be extracted, referred to herein as centre frequency；
Referred to as forgetting factor, plays a part of controlling filtering bandwidth；
Then the given calculating of alternating current is realized using orthogonal sine wave extractor, the DAZ gene to current first harmonics component is realized under rest frame, and reduce the content of 3,5,7 subharmonic.
As one kind improvement, the utilization orthogonal sine wave extractor realizes given calculate of alternating current and realized by following steps：
Cosine is
, sine is, uα,uβCorrespond to
, it is the output result of orthogonal sine wave extractor； 
It is given for watt current,
It is given for reactive current.
It is used as one kind improvement, fundametal compoment in the given current error between calculated value and adopted value of alternating current is controlled, so as to realize the DAZ gene to current first harmonics component under rest frame, simultaneously to 3 in the current error between alternating current set-point and sampled value, 5,7 inferior harmonic components are controlled, reduction by 3, the content of 5,7 inferior harmonic waves, is comprised the following steps that：
uαFor voltage acquisition value, eαi(n) it is fundamental wave error,
,
,For inductance；
kriFor other each harmonic control coefrficients, the method that can be added using ascending examination, too big harmonic controling coefficient can make system unstable, and the proportionality coefficient for being added to 5-10 times then sufficiently achieves satisfied harmonic suppression effect.
QSE has following two characteristics：
1）, orthogonality
If input variableCentered on frequency
Sinusoidal signal, then when can calculate stable stateIt is equal with input, without the change of any amplitude and phase offset, and
It is delayed
It is 90 degree, i.e., mutually orthogonal.
2）, frequency-selecting
QSE input
Decay and phase shift to different frequency input signal are different.QSE amplitude versus frequency characte and phase-frequency characteristic can be drawn, as shown in Figure 2.It is seen that the amplitude characteristic at positive and negative centre frequency is 1, phase shift is 0, illustrates that it does not have amplitude attenuation and phase shift to centre frequency.And then there is very big decay and phase shift to other frequencies, decay more remote from centre frequency is bigger.So
It is right
With bandpass filtering effect, in other words with frequency-selecting.Forgetting factor
Play a part of control bandwidth, forgetting factorCloser to 1, passband is narrower, and closer to 0, then passband is wider.
QSE not only can be by
In centre frequency Sinusoidal retrieval come out, and can will be with
The signal that 90 degree of phase lag signal is also extracted simultaneously, therefore is called orthogonal sine wave extractor.
Brief description of the drawings
The QSE schematic diagrams of Fig. 1 present invention.
The QSE of Fig. 2 present invention amplitude versus frequency characte and phase-frequency characteristic.
The three-phase grid-connected inverter system of Fig. 3 present invention.
The parallel network reverse control algolithm block diagram based on QSE of Fig. 4 present invention.
The mains voltage signal extraction effect based on QSE of Fig. 5 present invention.
The current control effect based on QSE of Fig. 6 present invention.
Embodiment
Combining inverter current Control Algorithm is general in digital signal processor（DSP）It is middle to realize.Alternating voltage and electric current are after sensor sample, AD conversion, and the signal being input in digital processing chip is discrete sampling sequence.These discrete sample signals generally based on fundamental frequency and contain each harmonic.The component of specific frequency is extracted in these signals, that is, is divided, is significantly for inverter control.Although the method for traditional Fourier decomposition can realize that frequency dividing is acted on, need the sampled data of preservation more and real-time is bad.The method of bandpass filtering is general in continuous domain design, has certain error in discretization real process.
The present invention directly provides a kind of operator with division function i.e. orthogonal sine wave extractor in discrete domain（Quadrature Sinewave Extractor, hereinafter referred to as QSE）.
The interval of two neighboring sampling instant is referred to as the sampling period.Assuming that the sampling period is T, the
Individual sampled signal is
, the discrete state equations that QSE is defined as：
（1）
Wherein
For QSE output result, primary condition can be taken as,
；
For sinusoidal signal angular frequency to be extracted, referred to herein as centre frequency；
Referred to as forgetting factor, plays a part of controlling filtering bandwidth.QSE schematic diagram is as shown in Figure 1.The transfer matrix of the state equation is that the first row of spin matrix is multiplied by forgetting factor.The effect of the spin matrix is clapped according to the upper one output result prediction clapped is current.The purpose for being multiplied by forgetting factor is to allow current output result only to remember a certain proportion of upper one output result clapped, and current signal is updated output result in certain proportion.Fixed in the sampling period one, the only forgetting factor of the parameter in formula is to need to adjust.
QSE has following two characteristics：
1）, orthogonality
If input variable
Centered on frequencySinusoidal signal, then when can calculate stable state
It is equal with input, without the change of any amplitude and phase offset, and
It is delayed
It is 90 degree, i.e., mutually orthogonal.
2）, frequency-selecting
QSE input
Decay and phase shift to different frequency input signal are different.QSE amplitude versus frequency characte and phase-frequency characteristic can be drawn, as shown in Figure 2.It is seen that the amplitude characteristic at positive and negative centre frequency is 1, phase shift is 0, illustrates that it does not have amplitude attenuation and phase shift to centre frequency.And then there is very big decay and phase shift to other frequencies, decay more remote from centre frequency is bigger.So
It is rightWith bandpass filtering effect, in other words with frequency-selecting.Forgetting factor
Play a part of control bandwidth, forgetting factor
Closer to 1, passband is narrower, and closer to 0, then passband is wider.
QSE not only can be by
In centre frequency Sinusoidal retrieval come out, and can will be with
The signal that 90 degree of phase lag signal is also extracted simultaneously, therefore is called orthogonal sine wave extractor.
Hardware connection and input/output signal
The present invention based on hardware topology as shown in figure 3, for typical three-phase grid-connected inverting system.Direct current side joint photovoltaic PV cell panels in figure, therefore upper figure is typical grid-connected photovoltaic system.If in wind-powered electricity generation control, the right then connects the inverter of motor control needs.Three phase network is connected in the output of inverter three-phase alternating current by 380V to 270V isolating transformer.The three-phase full-controlled bridge that the nucleus module of direct current to ac converter constitutes for 6 IGBT is realized in inverter.Three-phase full-controlled bridge ac output end need to connect the high-frequency harmonic that LC wave filters are modulated to filter with transformer bay.The direct-flow input end of three-phase full-controlled bridge need to fill DC support electric capacity, and cushioning effect, stable DC voltage are played to the energy that direct current is inputted.
Grid voltage sensor gathers the electric current on the line voltage of step down side, current sensor collection inductance, and direct current voltage sensor gathers the voltage of positive and negative of DC support electric capacity.
These sampled signals are transmitted to DSP, DSP is handled these signals according to control method proposed by the present invention by appropriate conditioning, 6 IGBT of finally modulation output drive signal.
Three-phase current is simple alternating current amount, if directly carrying out proportional plus integral control to it under rest frame, will be unable to realize DAZ gene, because integration has floating ability of tracking only for DC quantity.Integral element is actually a low pass filter, and it is actually the DC component being extracted in error.If there is DAZ gene ability to the AC compounent of certain frequency, the AC compounent the frequency of this in error is needed to extract.And QSE can just realize this function, therefore obtain the current Control Algorithm based on QSE.
Parallel network reverse current Control Algorithm based on QSE realizes under rest frame, as shown in Figure 4.Compared with traditional control algorithm, the algorithm realizes the suppression of the given calculating of alternating current, the DAZ gene of current first harmonics and harmonic wave using QSE.Given value of current value is depending on the concrete application environment of inverter.But for universal, general watt current is given to be obtained by the PI outputs of direct current pressure ring, and the given power factor needed by power network of reactive current is determined, power factor if desired is 1, then reactive current is given as 0.Watt current is given and reactive current it is given be DC quantity, it is necessary to further determine that alternating current gives according to the phase of line voltage fundamental wave.
A phases line voltage sampled value is passed through into QSE processing, one group of orthogonal voltage signal u is obtainedαAnd uβ.Its centre frequency w takes power frequency 100
Rad/s, to extract the fundamental wave in line voltage.The phase cosine of an angle of line voltage is
, sine is
.The cosine and sine value for obtaining line voltage fundamental wave just can be used to given value of current and calculates, and need not calculate angle.It is given according to watt current
It is given with reactive current
, and line voltage fundamental wave cosine and sine value, converted from Park, be calculated as follows a, b biphase currents are given.
It can be seen that b phase currents give always delayed a phase currents and give 120 degree from formula, and amplitude is equal.Because three-phase current sum is 0, it is also 0 that three-phase current, which gives sum, only needs to calculate a here, b biphase currents give.
Second step：The realization of current control equation.
Illustrate by taking a phases as an example, as the control of b phases.
First, fundamental extraction.
The current feedback values that the set-point and current sensor obtained according to the first step is measured, calculating current error,
.Frequency in QSE is set to fundamental frequency, pressed（1）Formula is programmed, and is taken first of QSE to export, that is, is obtained fundamental wave error eαi(n)。
Secondly, harmonic wave is extracted.
Frequency in QSE is set to certain subfrequency, such as 5 subharmonic, QSE centre frequency is taken as 5 times of fundamental frequencies, pressed（1）Formula is programmed, its e exportedα5(n) it is 5 order harmonic components in error.Other subharmonic processing methods are similar.
Finally, current control equation is realized.
Overall error is multiplied by proportionality coefficient kpIt is used as proportional.Fundamental wave error is multiplied by kri, each harmonic error is multiplied by output of the respective control coefrficient as QSE controlling units.It is in addition the disturbance of counteracting line voltage, need to be in governing equation plus voltage feed-forward control.Proportional, QSE and feedforward term are added, a phase modulation voltages are used as.I.e.：
B phase modulation voltages can be calculated with same step, then c phase voltages are calculated by three-phase voltage sum for 0 relation.
3rd step：Three-phase voltage is modulated.
According to three-phase control voltage and the size of DC voltage, it may be determined that each IGBT dutycycle.The topology can carry out voltage modulated using modulator approaches such as SVPWM or SPWM.For example, the duty ratio calculation method using SPWM as modulation algorithm is：
Wherein
For the dutycycle of bridge arm in certain phase,
For the voltage on DC support electric capacity.Two IGBT drive signal is complementary above and below each bridge arm, and the dutycycle of lower bridge arm and the dutycycle sum of upper bridge arm are 1.According to dutycycle, the corresponding registers of DSP are filled in, DSP is the drive signal for exporting each bridge arm IGBT.
The selection of control parameter
The selection of forgetting factor：The big then good wave filtering effect of forgetting factor, but the tracking velocity of voltage-phase mutation is slower.According to mains frequency harmonic situation, by professional standard, line voltage frequency is fluctuated in the range of 50 ± 2.5Hz, takes a=0.99 to be well adapted for power network.
The selection of each control coefrficient：Proportionality coefficient kpWith inductance
Size and control system delay etc. it is relevant, take here
, preferable dynamic and steady-state behaviour can be obtained.The method added using ascending examination of other each harmonic control coefrficients, too big harmonic controling coefficient can make system unstable, and the proportionality coefficient for being added to 5-10 times then sufficiently achieves satisfied harmonic suppression effect.
The technique effect of the present invention is as follows：
The extraction effect of line voltage fundamental wave and its quadrature lagging signal based on QSE is as shown in Figure 5.It can be seen that the fundametal compoment of the component extracted based on QSE always floating voltage, also has good adaptability for the mutation of line voltage.Voltage signal is extracted based on QSE to give to calculate alternating current, major advantage is that grid adaptability is strong：1）, no matter whether line voltage balances, and it always obtains the fundametal compoment of A phase voltages, while obtaining the orthogonal signalling of delayed A phases fundametal compoment, equal by this group of amplitude, the signal that 90 degree of phase mutual deviation is as the basis of given value of current, and it is balance that can remain given value of current；2）, when line voltage contains harmonic wave, QSE can still extract fundametal compoment therein exactly, in the absence of delay；3）Because QSE has certain bandwidth, the occasion that mains frequency there are some to fluctuate so is adapted to.
Parallel network reverse current control effect based on QSE is as shown in Figure 6.This is 500kw combining inverters, and grid current waveform during 30% rated power of hair, three-phase current steadily exports and reached fundamental wave DAZ gene.The current waveform and its fft analysis result when not taking harmonics restraint, top half networking three-phase current are shown in left figure, the latter half is the result of a wherein phase fft analysis.Find out from waveform, current sinusoidal degree is bad, fft analysis understands wherein to contain larger 5 times and 7 subharmonic, wherein 5 subharmonic content 22.7dB, 7 subharmonic 11.7dB, account for fundamental wave ratio about 4.5% and 1.3%.Right figure is adds after the harmonics restraint based on QSE, the current waveform and its FFT result measured.Wherein 5 subharmonic content 7.4dB, 7 subharmonic -8dB, it is about 0.8% and 0.1% to account for fundamental wave ratio.Therefore, add after the harmonics restraint algorithm based on QSE, harmonic wave is substantially reduced, and current waveform sine degree improves.
Claims (3)
1. a kind of parallel network reverse control algolithm based on orthogonal sine wave extractor, it is characterized in that include orthogonal sine wave extractor, the discrete state equations that the orthogonal sine wave extractor is defined as：
Wherein
For the output result of orthogonal sine wave extractor, primary condition can be taken as
,
；
For sinusoidal signal angular frequency to be extracted, referred to herein as centre frequency；
Referred to as forgetting factor, plays a part of controlling filtering bandwidth；
Then the given calculating of alternating current is realized using orthogonal sine wave extractor, the DAZ gene to current first harmonics component is realized under rest frame, and reduce the content of 3,5,7 subharmonic.
2. the parallel network reverse control algolithm according to claim 1 based on orthogonal sine wave extractor, is realized it is characterized in that the utilization orthogonal sine wave extractor realizes given calculate of alternating current by following steps：
Cosine is
, sine is
, uα,uβCorrespond to, it is the output result of orthogonal sine wave extractor； 
It is given for watt current,
It is given for reactive current.
3. the parallel network reverse control algolithm according to claim 2 based on orthogonal sine wave extractor, it is characterized in that being controlled to the fundametal compoment in the given current error between calculated value and adopted value of alternating current, so as to realize the DAZ gene to current first harmonics component under rest frame, simultaneously to 3 in the current error between alternating current set-point and sampled value, 5,7 inferior harmonic components are controlled, reduction by 3, the content of 5,7 inferior harmonic waves, is comprised the following steps that：
uαFor voltage acquisition value, eαi(n) it is fundamental wave error,
,
,For inductance；
kriFor other each harmonic control coefrficients, the method that can be added using ascending examination, too big harmonic controling coefficient can make system unstable, and the proportionality coefficient for being added to 5-10 times then sufficiently achieves satisfied harmonic suppression effect.
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Cited By (5)
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| CN103825302A (en) * | 2014-03-12 | 2014-05-28 | 浙江埃菲生能源科技有限公司 | Improved discrete orthogonal signal generator |
| CN104201720A (en) * | 2014-09-12 | 2014-12-10 | 阳光电源股份有限公司 | Control method and control device for suppression of resonance of grid-connected power generation system |
| CN105629064A (en) * | 2015-12-30 | 2016-06-01 | 浙江埃菲生能源科技有限公司 | Novel sine-wave low-pass filtering and extraction method |
| US10003198B2 (en) | 2014-09-12 | 2018-06-19 | Sungrow Power Supply Co., Ltd. | Method and device for monitoring and suppressing resonance |
| CN110954749A (en) * | 2019-11-06 | 2020-04-03 | 许继电源有限公司 | Electric automobile wireless charging phase detection circuit for realizing frequency tracking |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103825302A (en) * | 2014-03-12 | 2014-05-28 | 浙江埃菲生能源科技有限公司 | Improved discrete orthogonal signal generator |
| CN104201720A (en) * | 2014-09-12 | 2014-12-10 | 阳光电源股份有限公司 | Control method and control device for suppression of resonance of grid-connected power generation system |
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| CN105629064A (en) * | 2015-12-30 | 2016-06-01 | 浙江埃菲生能源科技有限公司 | Novel sine-wave low-pass filtering and extraction method |
| CN110954749A (en) * | 2019-11-06 | 2020-04-03 | 许继电源有限公司 | Electric automobile wireless charging phase detection circuit for realizing frequency tracking |
| CN110954749B (en) * | 2019-11-06 | 2021-07-30 | 许继电源有限公司 | Electric automobile wireless charging phase detection circuit for realizing frequency tracking |
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