CN108879683A - A kind of control method of centralization photovoltaic DC-to-AC converter Harmonics elimination - Google Patents
A kind of control method of centralization photovoltaic DC-to-AC converter Harmonics elimination Download PDFInfo
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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
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Abstract
The present invention provides a kind of control methods of centralized photovoltaic DC-to-AC converter Harmonics elimination, belong to electronic technology field.It solves the problems, such as that the Harmonics elimination effect and system stability of centralized photovoltaic DC-to-AC converter in the prior art are bad.This method includes：A, to three-phase inversion current sample and the positive-negative sequence value of three-phase inversion electric current in the rotated coordinate system is acquired；B, PI control is carried out to three-phase inversion electric current positive-negative sequence value, filtering processing obtains preliminary current control output valve；C, sampling is carried out to the line voltage of grid-connected centralized inverter and line phase inversion obtains the three-phase voltage of grid-connected centralized inverter；D, three rank complex vector filter transforms, park transformation and iir filter is carried out to three-phase voltage to filter to obtain the rotating coordinate system positive-negative sequence value of three-phase voltage；E, three-phase voltage positive-negative sequence value and preliminary current control output valve are overlapped to obtain ultimate current control output valve.This method, which can effectively eliminate Voltage Harmonic bring, to be influenced, improves system stability.
Description
Technical field
The present invention relates to photovoltaic DC-to-AC converter harmonic controling technical field more particularly to a kind of centralized photovoltaic DC-to-AC converter harmonic waves
The control method of elimination.
Background technique
New Energy Industry is grown rapidly in recent years, and China's photovoltaic generating system installed capacity has reached a GW up to a hundred, is concentrated
Formula photovoltaic DC-to-AC converter is widely used in photovoltaic generating system.In the power system, with the continuous increase of photovoltaic power generation capacity, electricity
The harmonic pollution of net is increasingly severe, and higher harmonic wave will increase line loss, acceleration equipment aging, the shakiness for bringing equipment
Determine, cause equipment series parallel resonance etc..
For centralized photovoltaic DC-to-AC converter in the preferable situation of power grid quality, itself does not bring biggish harmonic wave, but works as
Power grid quality is poor, and when power grid background harmonics are very high, photovoltaic inverter grid-connected electric current can be attached to a part of harmonic current.It is existing
Have in technology, centralized gird-connected inverter is all based on the processing of voltage background harmonic wave to the control method of harmonic carcellation, to electricity
Pressure background harmonics are filtered to be handled with trap, which will affect the real-time response of gird-connected inverter and low-voltage is worn
More.If the topological structure of inverter is LCL structure, if can also lead-in road feel when the exchange cable of inverter is too long
Anti-, filtering trap processing at this time can be easy to cause inverter to cause resonance, and Harmonics elimination effect is unobvious and is easy to bring not
Stablize.On-the-spot test 500kw centralized inverter uses old control mode waveform as shown in Figure 1, a indicates that current waveform, b indicate
Voltage waveform, in power grid background harmonics 3%, current harmonics is close to 10% when power 300KW, as can be seen from Fig. for old control
Aging method is easy by electric network influencing, and introduces LCL resonance.
Summary of the invention
The purpose of the present invention is there is the above problem in view of the prior art, it is humorous to propose a kind of centralized photovoltaic DC-to-AC converter
The control method that wave is eliminated, the technical problem to be solved is that how to improve centralized photovoltaic DC-to-AC converter harmonic wave to disappear for the control method
Except effect and stability.
Object of the invention can be realized by the following technical scheme：A kind of control of centralization photovoltaic DC-to-AC converter Harmonics elimination
Method processed, includes the following steps：
A, to three-phase inversion current sample and carry out positive-negative sequence 3/2 transformation obtain three-phase inversion electric current in the rotated coordinate system
Positive-negative sequence value；
B, to the three-phase inversion electric current obtained in step a positive-negative sequence value in the rotated coordinate system carry out after PI control by
Trapper is filtered to obtain preliminary current control output valve；
C, sampling is carried out to the line voltage of grid-connected centralized inverter and line phase inversion obtains grid-connected centralized inverter
Three-phase voltage；
D, three rank complex vector filter transforms, park transformation and IIR is successively carried out to the three-phase voltage obtained in step c to filter
Wave device filters to obtain the rotating coordinate system positive-negative sequence value of three-phase voltage；
E, by the preliminary current control in the rotating coordinate system positive-negative sequence value and step b of the three-phase voltage obtained in step d
Output valve is overlapped to obtain ultimate current control output valve.
The present invention passes through three rank complex vector filter transforms high-frequency harmonic always, then passes through iir filter, IIR filtering
Device is also recursion filter, operating structure usually by delay, multiplied by coefficient with the basic operations such as be added and form recursion type structure,
Four kinds of Direct-type, positive pseudotype, cascade connection type, parallel connection type structure types can be combined into, all there is feedback loop, pass through feedback loop
It is more precisely reliable to make filter result for design, so that energy regenerative is more steady before exporting control, avoid because voltage ripple of power network and
Lead to control system overshoot；In addition, the good stationarity of system is able to maintain by PI control, once, there is overshoot in interference mutation
When, system can restore balance rapidly stable state.
In a kind of control method of above-mentioned centralized photovoltaic DC-to-AC converter Harmonics elimination, the transmitting of the three ranks complex vector
Function is as follows：
Wherein ω0For power grid rated frequency, s is the Laplace transform factor, and j is the complex vector imaginary part factor.
It can guarantee the extraction and fundamental wave negative sequence of network voltage fundamental positive sequence by three rank complex vector filter transforms
Elimination, so as to inhibit high-frequency harmonic well.
In a kind of control method of above-mentioned centralized photovoltaic DC-to-AC converter Harmonics elimination, the value of the k1 and k2 pass through
Zero-pole assignment method obtains.
In a kind of control method of above-mentioned centralized photovoltaic DC-to-AC converter Harmonics elimination, IIR filter is carried out in the step d
Discriminatory analysis also is carried out to three-phase voltage before wave：When three-phase voltage d axis positive sequence voltage value be less than setting minimum threshold or
When person is greater than preset max-thresholds, do not need to carry out IIR filtering；It is set when the positive sequence voltage value of three-phase voltage d axis is more than or equal to
Fixed minimum threshold and when being less than or equal to preset max-thresholds, needs to carry out IIR filtering.By to beyond power grid minimum threshold
Endless IIR filtering is carried out with the rotational coordinates set occurrence of the three-phase voltage of max-thresholds, so that the harmonic wave of network voltage does not introduce
Feedforward monitors the influence to power grid.
In a kind of control method of above-mentioned centralized photovoltaic DC-to-AC converter Harmonics elimination, the minimum threshold is 0.8 times
Power grid load voltage value, the max-thresholds are 1.2 times of power grid load voltage values.
In a kind of control method of above-mentioned centralized photovoltaic DC-to-AC converter Harmonics elimination, the trapper is sunken specific time
The mathematical model of wave device, the trapper is：
Wherein, Q is quality factor.Harmonic wave can effectively be inhibited by carrying out specific secondary trap by trapper, again to power grid
Real-time detection judgement avoids in high-low pressure crossing process to the stability of the interference of power grid, the centralized gird-connected inverter of raising.
Compared with prior art, the control method of this centralization photovoltaic DC-to-AC converter Harmonics elimination has the following advantages that：1, energy
The influence of Voltage Harmonic bring is effectively eliminated, in the case where not increasing any hardware cost, increases the stabilization of system
Property；2, suitable for each power section type of centralized inverter, 3, the control method can also complicated, three-phase be in background harmonics
The stable conditions high quality of balance is run.
Detailed description of the invention
Fig. 1 is the waveform that existing method test 500kw centralized inverter obtains.
Fig. 2 is to draw amplitude-frequency response song with MATLAB after specific secondary trapper handles harmonic wave in embodiment
Line.
Fig. 3 is to draw three rank complex vector filter amplitude-frequency responses with MATLAB in embodiment.
Fig. 4 is the waveform that the method test 500kw centralized inverter of the embodiment of the present invention obtains.
Specific embodiment
Following is a specific embodiment of the present invention in conjunction with the accompanying drawings, technical scheme of the present invention will be further described,
However, the present invention is not limited to these examples.
The control method of this centralization photovoltaic DC-to-AC converter Harmonics elimination includes the following steps：
Step a, to three-phase inversion current sample and carry out positive-negative sequence 3/2 transformation obtain three-phase inversion electric current in rotational coordinates
Positive-negative sequence value in system.
Wherein 3/2 transformation uses following step：
1. first carrying out clarke transformation to power network current Ia, Ib, Ic：
2. Ic three-phase, which carries out T/4, to postpone to store then to power network current Ia, Ib：
Ia_delay[n]=Ia
Ib_delay[n]=Ib
Ic_delay[n]=Ic
3. pair delayed current Ia, Ib, Ic three-phase carries out clarke transformation：
4. merging obtains positive-negative sequence value Ialphap, Ibetap, Ialphan, Ibetan of power network current：
5. positive-negative sequence Ialphap, Ibetap, Ialphan, Ibetan of pair power network current carry out park convert to obtain Idp,
Iqp、Idn、Iqn。
Idp=Ialphap*cos(θ)+Ibetap*sin(θ)
Iqp=Ibetap*cos(θ)-Ialphap*sin(θ)
Idn=Ialphan*cos(θ)-Ibe tan*sin(θ)
Iqn=Ibe tan*cos(θ)-Ialphan*sin(θ)
Step b, after carrying out PI control to the positive-negative sequence value of the three-phase inversion electric current obtained in step a in the rotated coordinate system
It is filtered to obtain preliminary current control output valve by trapper.
In this step, trapper is specific secondary trapper, and the mathematical model of trapper is：
Wherein, ω0For power grid rated frequency, ω0=2*3.14*50*4, s be the Laplace transform factor, Q be quality because
Number takes Q=10 by practical calculating debugging.Harmonic wave can effectively be inhibited by carrying out specific secondary trap by trapper, use MATLAB
It is as shown in Figure 2 to draw amplitude-frequency response.The judgement of power grid real-time detection is avoided in high-low pressure crossing process to power grid again
Interference, the stability for improving centralized gird-connected inverter.
Step c, sampling is carried out to the line voltage of grid-connected centralized inverter and line phase inversion obtains grid-connected centralized inversion
The three-phase voltage of device, line phase inversion predominantly carries out clarke transformation to line voltage herein；
Step d, three rank complex vector filter transforms, park transformation are successively carried out to the three-phase voltage obtained in step c, so
Discriminatory analysis is carried out to three-phase voltage afterwards：When the positive sequence voltage value of three-phase voltage d axis is less than the minimum threshold of setting or is greater than
When preset max-thresholds, do not need to carry out IIR filtering；When the positive sequence voltage value of three-phase voltage d axis is more than or equal to setting most
Small threshold value and be less than or equal to preset max-thresholds when, need to carry out IIR filtering.Minimum threshold is 0.8 times of power grid voltage rating
Value, max-thresholds are 1.2 times of power grid load voltage values.By to the three-phase voltage beyond power grid minimum threshold and max-thresholds
Rotational coordinates set occurrence carries out endless IIR filtering, so that the harmonic wave of network voltage does not introduce feedforward, monitors the influence to power grid.
It filters to obtain the rotating coordinate system positive-negative sequence value of three-phase voltage using iir filter after judgement.
The transmission function of three rank complex vectors of three rank complex vector filters is as follows in this step：
Wherein, j is the complex vector imaginary part factor, and the value of k1 and k2 are obtained by zero-pole assignment method, and the acquisition process is such as
Under：
For the undistorted extraction for guaranteeing network voltage fundamental positive sequence, H (jw0)=1 is enabled, is obtained by above formula：
Arrangement obtains：
j*2*k1*ω0=(k4-k2) * ω0 3+j*(k3-1)ω0 3
It enables the real and imaginary parts on equal sign both sides equal, obtains
K4=k2
K3=2*k1+1
K4, k3 are substituted into former formula, obtained
One group of three rank complex vector filter poles is chosen using the method for zero-pole assignment, i.e.,
P1=-274
p2,3=-363 ± j478
K1=2.33 is obtained at this time；K2=3.18.
It can guarantee the extraction and fundamental wave negative sequence of network voltage fundamental positive sequence by three rank complex vector filter transforms
Elimination, with MATLAB draw three rank complex vector filter amplitude-frequency responses as shown in figure 3, high-frequency harmonic is pressed down well
System.
Step e, by the preliminary electric current in the rotating coordinate system positive-negative sequence value and step b of the three-phase voltage obtained in step d
Control output valve is overlapped to obtain ultimate current control output valve.
Method of the invention passes through three rank complex vector filter transforms high-frequency harmonic always, then passes through iir filter,
Iir filter is also recursion filter, operating structure usually by delay, multiplied by coefficient with the basic operations such as be added and form recurrence
Type structure can be combined into four kinds of Direct-type, positive pseudotype, cascade connection type, parallel connection type structure types, all have feedback loop, pass through
Feedback loop design, it is more precisely reliable to make filter result, to improve the Harmonics elimination effect of centralized photovoltaic DC-to-AC converter and steady
It is qualitative；In addition, being able to maintain the good stationarity of system by PI control, once interference mutation, when there is overshoot, system can be rapidly
Restore balance stable state.Using the test waveform See Figure 4 after method of the invention, in power grid background harmonics 3%, power
Current harmonics only has 2.5% when 300KW, and method of the invention inhibits LCL resonance well, and makes power grid more stable.
Specific embodiment described herein is only an example for the spirit of the invention.The neck of technology belonging to the present invention
The technical staff in domain can make various modifications or additions to the described embodiments or replace by a similar method
In generation, however, it does not deviate from the spirit of the invention or beyond the scope of the appended claims.
Claims (6)
1. a kind of control method of centralization photovoltaic DC-to-AC converter Harmonics elimination, includes the following steps：
A, to three-phase inversion current sample and carry out positive-negative sequence 3/2 transformation obtaining three-phase inversion electric current in the rotated coordinate system just
Negative phase-sequence value；
B, the three-phase inversion electric current obtained in step a positive-negative sequence value in the rotated coordinate system is carried out after PI control by trap
Device is filtered to obtain preliminary current control output valve；
C, sampling is carried out to the line voltage of grid-connected centralized inverter and line phase inversion obtains the three-phase of grid-connected centralized inverter
Voltage；
D, three rank complex vector filter transforms, park transformation and iir filter are successively carried out to the three-phase voltage obtained in step c
Filtering obtains the rotating coordinate system positive-negative sequence value of three-phase voltage；
E, the preliminary current control in the rotating coordinate system positive-negative sequence value and step b of the three-phase voltage obtained in step d is exported
Value is overlapped to obtain ultimate current control output valve.
2. a kind of control method of centralized photovoltaic DC-to-AC converter Harmonics elimination according to claim 1, which is characterized in that institute
The transmission function for stating three rank complex vectors is as follows：
Wherein ω0For power grid rated frequency, s is the Laplace transform factor, and j is the complex vector imaginary part factor.
3. a kind of control method of centralized photovoltaic DC-to-AC converter Harmonics elimination according to claim 2, which is characterized in that institute
The value for stating k1 and k2 is obtained by zero-pole assignment method.
4. a kind of control method of centralized photovoltaic DC-to-AC converter Harmonics elimination according to claim 1 or 2 or 3, feature
It is, carries out also carrying out discriminatory analysis to three-phase voltage before IIR filtering in the step d：When the positive sequence electricity of three-phase voltage d axis
When pressure value is less than the minimum threshold of setting or is greater than preset max-thresholds, do not need to carry out IIR filtering；As three-phase voltage d
When the positive sequence voltage value of axis is more than or equal to the minimum threshold of setting and is less than or equal to preset max-thresholds, need to carry out IIR filter
Wave.
5. a kind of control method of centralized photovoltaic DC-to-AC converter Harmonics elimination according to claim 4, which is characterized in that institute
Stating minimum threshold is 0.8 times of power grid load voltage value, and the max-thresholds are 1.2 times of power grid load voltage values.
6. a kind of control method of centralized photovoltaic DC-to-AC converter Harmonics elimination according to claim 1 or 2 or 3, feature
It is, the trapper is specific secondary trapper, and the mathematical model of the trapper is：
Wherein, Q is quality factor.
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Cited By (1)
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| CN109557491A (en) * | 2018-12-17 | 2019-04-02 | 江苏固德威电源科技股份有限公司 | A kind of its inverter of three-phase voltage sampling correcting methods and applications |
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Application publication date: 20181123 |