CN106253337B - A kind of impedance adapter for more grid-connected inverters systems of calming - Google Patents
A kind of impedance adapter for more grid-connected inverters systems of calming Download PDFInfo
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- CN106253337B CN106253337B CN201610698115.1A CN201610698115A CN106253337B CN 106253337 B CN106253337 B CN 106253337B CN 201610698115 A CN201610698115 A CN 201610698115A CN 106253337 B CN106253337 B CN 106253337B
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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 the impedance adapters for more grid-connected inverters systems of calming, and are connected in parallel in point of common coupling with more grid-connected inverters systems, including power output circuit and control circuit, and power output circuit exports DC capacitor voltageV dc And grid-connected currenti g ；Control circuit detects PCC voltagesv pcc , its phase is obtained by phase locked-loop unitθ, and respectively by outer voltage unit and current inner loop unit to DC capacitor voltageV dc And grid-connected currenti g Closed-loop control is carried out, while by introducing PCC electric voltage feed forward units, the output impedance characteristic of impedance adapter is corrected.Advantage is：This method is influenced very little by digital control delay, and can fast and effeciently calm system, also has preferable calming effect to the case where appearance multiple resonance points, and have no need to change the control method and software and hardware parameter of each inverter in system.
Description
Technical field
The present invention relates to new energy grid-connected power fields more particularly to a kind of for the more grid-connected inverters systems of calming
Impedance adapter.
Background technology
In recent years, for response environment pollution and energy deficiency, using wind energy, solar energy as the regenerative resource of representative
Increasingly obtain the attention of people.Gird-connected inverter is always the country as the interface between renewable generator unit and power grid
The hot spot of outer scholar's research.
In order to inhibit the switch harmonic for including in gird-connected inverter bridge arm output voltage, usually using LCL filter.But
Include resonance spikes in the frequency response of LCL filter, system stability may be influenced.Currently, to the resonance of LCL filter
The damping method of spike and inverter control Parameters design based on this comparative maturity, but these methods are big
Mostly based on the grid-connected situation of single inverter.
And in actual renewable power generation, usually there are more inverters to pass through point of common coupling (Point of
Common Coupling, PCC) access power grid in parallel.As permeability is continuously improved regenerative resource in power grid, power grid is got over
More to show the characteristic of light current net, the possible wide scope variation of line impedance.In this case, even if every inverter is each
From stable system is designed to, their passive circuit and control loop is intercoupled by electric network impedance, still may
Cause entire more grid-connected inverters systems unstable.
It is relatively fewer that it is directed to more grid-connected inverters systematic researches at present.The prior art goes out from inverter itself mostly
Hair improves robustness of the inverter to electric network impedance by certain control strategy, or inverter itself is made to have resonance inhibition
Function.On the one hand, which increase the complexities of each inverter control algorithm in system；On the other hand, due to digital control
The influence of delay, these methods are relatively weak to the inhibiting effect of high-frequency resonant.
Invention content
In view of the above technical problems, the present invention provides a kind of impedance for more grid-connected inverters systems of calming
Device, the impedance adapter are influenced very little by digital control delay, and can fast and effeciently calm system, to there are multiple resonance points
The case where also have preferable calming effect, and have no need to change the control method and software and hardware parameter of each inverter in system.
To achieve the goals above, the specific technical solution that the present invention takes is：
The impedance adapter for more grid-connected inverters systems of calming, with more grid-connected inverters systems in public
Coupling point is connected in parallel, including：
Power output circuit, output DC capacitor voltage VdcAnd grid-connected current ig；
Control circuit, including outer voltage unit, phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward units,
Control circuit detects the voltage v of point of common couplingpcc, its phase theta is obtained by phase locked-loop unit, and respectively correspondingly pass through electricity
The outer ring element of pressure and current inner loop unit are to DC capacitor voltage VdcWith grid-connected current igCarry out closed-loop control；Meanwhile passing through
PCC electric voltage feed forward units, are corrected the output impedance characteristic of impedance adapter；Also, the v that control circuit will detectpcc
Each harmonic content is compared with the threshold value of setting, judges more grid-connected inverters system stability, more inverters simultaneously
When net system occurs unstable, impedance adapter is cut grid-connected；
The power output circuit and the phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward cell formations
The port equivalent model of impedance adapter, the port equivalent model include three admittance Y of parallel connectionPLL(s)、Ycon(s)、Yff
(s), total output impedance Z of port equivalent modelo(s) such as formula (1)：
Wherein, YPLL(s)、Ycon(s)、Yff(s) before indicating phase locked-loop unit, current inner loop unit and PCC voltages respectively
Present the admittance that unit introduces.
It is described for calm more grid-connected inverters systems impedance adapter it is further design be, the phaselocked loop
Unit, according to the voltage vpccObtain vpccFundamental voltage amplitude VpccWith phase cosine value cos θ, and then v is calculatedpccFundamental wave
Instantaneous value vpccfWith harmonic wave instantaneous value vpcch, such as formula (2), (3)；
vpccf=Vpcccosθ (2)
vpcch=vpcc-vpccf (3)
The further design of the impedance adapter for more grid-connected inverters systems of calming is, outside the voltage
Ring element, including voltage regulator Gv(s), the DC capacitor voltage V of impedance adapter is controlleddcFloating voltage benchmark V* dc；Institute
Current inner loop unit is stated, including current regulator Gi(s), the grid-connected current i of impedance adapter is controlledgFollow current benchmark i* g,
Current reference i* gBy voltage regulator Gv(s) output I* gThe PCC voltage-phase cosine value cos θ phases obtained with phase locked-loop unit
It is multiplied to arrive.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the PCC is electric
Pressure feed forward element include：
PCC voltage harmonics feedforward link, by PCC voltage harmonic instantaneous values vpcchBy proportionality coefficient Gh, bandpass filter
Gbp(s) and feedforward function Gff(s) feedforward is born to current regulator Gi(s) output end；
PCC voltage fundamentals feedforward link, by PCC voltage fundamental instantaneous values vpccfBy proportionality coefficient GfIt is positive to feedover to electric current
Adjuster Gi(s) output end.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the power is defeated
It includes DC bus capacitor, full-bridge, LCL filter and grid-connected switch, the DC bus capacitor, full-bridge, LCL filter to go out circuit
And grid-connected switch is sequentially connected.
It is described for calm more grid-connected inverters systems impedance adapter it is further design be, LCL filter
By two inductance L1、L2And capacitance C compositions, the inductance L1, inductance L2And the grid-connected switch series winding, the capacitance C connect
In inductance L1、L2Between node, the other end connects in the full-bridge.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the control is electric
Road includes：
A/D sampling modules, to voltage vpcc, DC capacitor voltage Vdc, grid-connected current ig, capacitance current iCIt carries out real-time
Sampling；
Digital operation module, including the phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward units, receive
The v of A/D sampling modules acquisitionpcc、Vdc、igAnd iC, each harmonic content of PCC voltages is calculated, preset control algolithm is passed through
The port equivalent model is built, and calculates modulating wave vm；
Self-adaptive control module, by vpccEach harmonic content be compared with the threshold value of setting, judge system stablize
Property, when decision-making system is unstable, control impedance adapter incision is grid-connected, and according to vpccMajor harmonic component adaptively adjust
The proportionality coefficient G of PCC voltage harmonics feedforward link in the whole digital operation moduleh, bandpass filter Gbp(s) low frequency turnover
Frequency fc1With bandpass filter Gbp(s) high frequency corner frequency fc2；
Pulse width modulation module, to the modulating wave vmIt is modulated, obtains full-bridge switch pipe Q in power output circuit1~Q4
Drive signal.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the number is transported
Calculating module further includes：
Harmonic detecting unit detects v in real time by fast fourier transform algorithmpccEach harmonic content, as from
Suitable solution module judges the foundation of system stability and self_adaptive adjusting parameter；
Capacitor current feedback unit, by the capacitance current i of impedance adapterCBy proportionality coefficient HiCNegative-feedback is to electric current tune
Save device Gi(s) output end carries out active damping for the resonance spikes to LCL filter.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the PCC is electric
Press the bandpass filter G in harmonic wave feedforward linkbp(s) transmission function is
Wherein, Q is quality factor；
Feedforward function Gff(s) transmission function is
Wherein, L1、L2, C be respectively LCL filter bridge side inductance value, net side inductance value and filtering capacitance；HigFor resistance
The grid-connected current feedback coefficient of anti-adapter；KPWMFor modulating wave vmTo bridge arm output voltage vABTransmission function, it is DC side
Capacitance voltage VdcWith triangular carrier amplitude VtriRatio.
The further design of the impedance adapter for more grid-connected inverters systems of calming is that the PCC is electric
Press the proportionality coefficient G in fundamental wave feedforward linkfExpression formula is：
Compared with prior art, the present invention its major advantage and remarkable result are as follows：
1) present invention is by cutting an additional impedance adapter come calm entire more inverter parallel systems, the party
Method haves no need to change the control method and software and hardware parameter of each inverter in system, does not increase its computational burden, does not influence it
Normal work has preferable compatibility.
2) major function of impedance adapter proposed by the present invention is the resonant energy in absorption system, and is translated into
Fundamental wave energy feedback.Device and line loss are removed, absorbs and the average active power of release is 0.Therefore, impedance adapter
Capacity much smaller than the capacity of each gird-connected inverter in system, allow using higher switching frequency and control frequency.In this way,
Compared with the control algolithm directly realized by gird-connected inverter, the control algolithm realized by impedance adapter is in resonant frequency
Range is influenced smaller by digital control delay, more preferable to the rejection of resonance, is more advantageous to the stability of raising system.
3) impedance adapter proposed by the present invention can detect the major harmonic component of PCC voltages automatically, determine resonance frequency
Rate range, and the port Impedance of itself is adaptively adjusted, it is allowed to all show as just in the entire resonant frequency range of PCC voltages
The characteristic of resistance.Therefore, impedance adapter all has preferable calming effect in entire resonant frequency range, is not limited solely to list
The case where a resonance point, this is for more grid-connected inverters and appearance multiple resonance points, is especially suitable.
4) present invention is monitored in real time by each harmonic content to PCC voltages, once occur not in confirmation system
Stable situation just cuts impedance adapter at once, and its port Impedance is adaptively adjusted, and enables in absorption system
Resonant energy, and convert resonant energy to fundamental wave energy feedback.This method can be in guarantee system resonance found early,
It handles as early as possible, there is higher reliability.
Description of the drawings
Fig. 1 is the structural schematic diagram of middle impedance adapter power output circuit of the present invention.
Fig. 2 is the structural schematic diagram of middle impedance Adapter control circuit of the present invention
Fig. 3 is middle impedance adapter of the present invention corresponding simplify control block diagram at fundamental frequency.
Fig. 4 is middle impedance adapter of the present invention corresponding simplify control block diagram at harmonic frequency.
Fig. 5 is the port equivalent model of middle impedance adapter of the present invention.
Fig. 6 is the specific embodiment schematic diagram of the present invention.
Fig. 7 is the specific embodiment oscillogram of the present invention.
Specific implementation mode
Its specific implementation mode will be illustrated below.
Such as Fig. 1, the impedance adapter for more grid-connected inverters systems of calming of the present embodiment, simultaneously with more inverters
Net system is connected in parallel in point of common coupling (Point of Common Coupling, PCC).The impedance adapter is mainly by work(
Rate output circuit is formed with control circuit.Power output circuit exports DC capacitor voltage VdcAnd grid-connected current ig；Control
Circuit detects PCC voltages vpcc, its phase theta is obtained by phase locked-loop unit, and pass through outer voltage unit and current inner loop respectively
Unit is to DC capacitor voltage VdcWith grid-connected current igClosed-loop control is carried out, while by introducing PCC electric voltage feed forward units, it is right
The output impedance characteristic of impedance adapter is corrected.By power output circuit and control circuit, the equivalent mould in port can be built
Type, including three admittance in parallel, collectively form total output impedance Z of impedance adaptero(s), such as formula (1)：
Wherein, YPLL(s)、Ycon(s)、Yff(s) indicate that phaselocked loop, current inner loop and PCC electric voltage feed forward units draw respectively
The admittance entered.
Also, control circuit is by vpccEach harmonic content is compared with the threshold value of setting, judges more grid-connected inverters
System stability is cut impedance adapter grid-connected when more grid-connected inverters systems are unstable.
Such as Fig. 1, power output circuit is made of DC bus capacitor 1, full-bridge 2, LCL filter 3 and grid-connected switch 4, is led to
It crosses and builds actual hardware circuit to realize.Wherein, LCL filter is by two inductance L1、L2And capacitance C compositions, the inductance
L1, inductance L2And the grid-connected switch series winding, the capacitance C are connected to inductance L1、L2Between node, the other end is in described complete
Bridging connects.
Such as Fig. 2, control circuit is by A/D sampling modules 5, digital operation module 6, self-adaptive control module 7 and pulsewidth modulation
Module 8 forms, and is realized by writing software and loading on dsp chip, TMS320F2812 chips can be used in dsp chip.
Digital operation module 6 includes such as lower part：
1) harmonic detecting link 9 utilizes Fast Fourier Transform (FFT) (Fast Fourier Transform, FFT) algorithm pair
PCC instantaneous voltages vpccIt is handled, each harmonic content of PCC voltages is calculated.The reference formula of fft algorithm is as follows：
Wherein, N is the sampling number in a primitive period, and x (n) is the time-domain signal that sampling obtains, and X (k) is to pass through
The frequency-region signal obtained after FFT operations.
2) phaselocked loop based on synchronous rotating frame can be used in phaselocked loop 10, by the instantaneous value v of PCC voltagespccIt can be with
Obtain the fundamental voltage amplitude V of PCC voltagespccWith phase cosine value cos θ, and PCC voltages further are calculated using following formula
Fundamental wave instantaneous value vpccfWith harmonic wave instantaneous value vpcch：
vpccf=Vpcccosθ (3)
vpcch=vpcc-vpccf (4)
3) outer voltage 11, the DC capacitor voltage V for controlling impedance adapterdcFloating voltage benchmark V* dc, voltage
Adjuster Gv(s) pi regulator usually can be used, export I* gAmplitude as grid-connected current benchmark.
4) current inner loop 12, the grid-connected current i for controlling impedance adaptergFollow current benchmark i* g, current reference i* g
By voltage regulator Gv(s) output I* gIt is multiplied to obtain with the PCC voltage-phase cosine value cos θ that phaselocked loop obtains, current regulation
Device Gi(s) pi regulator or PR adjusters usually can be used, illustrated by taking pi regulator as an example here.
5) capacitor current feedback link 13, by the capacitance current i of impedance adapterCBy proportionality coefficient HiCNegative-feedback to electricity
Throttle regulator Gi(s) output end carries out active damping for the resonance spikes to impedance adapter LCL filter.
6) PCC voltage harmonics feedforward link 14, by PCC voltage harmonic instantaneous values vpcchBy proportionality coefficient Gh=1/Rh, band
Bandpass filter Gbp(s) and feedforward function Gff(s) feedforward is born to current regulator Gi(s) output end；Bandpass filter Gbp(s)
Transmission function is
Wherein, Q is quality factor, fc1And fc2The respectively low frequency corner frequency and high frequency corner frequency of filter.
Feedforward function Gff(s) transmission function is
Wherein, HigFor the grid-connected current feedback coefficient of impedance adapter；KPWMFor modulating wave vmTo bridge arm output voltage vAB's
Transmission function, it is input voltage VdcWith triangular carrier amplitude VtriRatio.
7) PCC voltage fundamentals feedforward link 15, by PCC voltage fundamental instantaneous values vpccfBy proportionality coefficient Gf=1/KPWMJust
It feedovers to current inner loop adjuster Gi(s) output end.
Below by by the simplify control block diagram and port equivalent model of impedance adapter, illustrate that impedance adapter is adaptive
Ground adjusts the operation principle of the port Impedance of itself.
Impedance adapter is set forth in fundamental frequency and the corresponding simplify control block diagram of harmonic frequency in Fig. 3 and Fig. 4.Its
In, GPLL(s) it is from PCC voltages vpcc(s) transmission function of the PCC voltage phase angle cosine value cos θ of phaselocked loop output, expression are arrived
Formula is
Wherein, KpAnd KiThe respectively proportionality coefficient and integral coefficient of phaselocked loop pi regulator.Gd(s) it is digital control draw
The time delay process entered, including the computation delay that the 0.5 PWM delays clapped and λ are clapped, expression formula are
Wherein, TsFor the controlling cycle of impedance adapter.Usually with the difference of sample mode, there are λ ∈ [0,1] to differ, this
In illustrated by taking λ=1 as an example.GLCL(s) it is bridge arm output voltage vAB(s) grid-connected current i is arrivedg(s) transmission function, expression
Formula is
Yoo(s) it is the open loop output admittance of impedance adapter, expression formula is
Pay attention to omitting outer voltage in figure, this is because the usual bandwidth of outer voltage is far below power frequency f0, output can
Approximation regards DC quantity as.
From figs. 3 and 4 it can be seen that sharing three accesses from PCC voltage to grid-connected current, counterpart impedance adaptation can be distinguished
Three admittance in parallel in the equivalent model of device port, as shown in Figure 5.Wherein, YPLL(s) be phaselocked loop introduce admittance, expression formula
For
Ycon(s) it is admittance that current inner loop introduces, expression formula is
Yff(s) be PCC electric voltage feed forward units introduce admittance, at fundamental frequency and harmonic frequency, expression formula difference
For
Port equivalent model according to figure 5, total output impedance Z of impedance adaptero(s) it is
The capacity of impedance adapter is much smaller than each gird-connected inverter in system, allows to use higher switching frequency and control
Frequency processed.In order to avoid influence of the digital control delay to control algolithm, the impedance adapter control frequency of the present embodiment as far as possible
Rate is each inverter highest controls frequency in system 10 times or more.And in multi-inverter grid-connected system, system is unstable
The resonant frequency of timing is usually within the 1/2 of each inverter control frequency.Thus, it is believed that system resonance frequencies are far below
The control frequency of impedance adapter, in resonant frequency range [fr1,fr2], the digital control delay of impedance adapter can be ignored,
It is approximately considered Gd(s)≈1.Work as bandpass filter corner frequency again to meet
Then in resonant frequency range [fr1,fr2], G can be approximately consideredbp(s) 1 ≈ has according to formula (6), (9), (14)：
If proportionality coefficient GhValue is sufficiently large, in resonant frequency range [fr1,fr2] have | Yffh(s)|>>|YPLL(s)+Ycon
(s) |, according to formula (15), total output impedance Z of impedance adaptero(s) can be approximately
Therefore, by be added PCC voltage harmonics feedover link, can correct impedance adapter system resonant frequency model
Enclose [fr1,fr2] port Impedance, be allowed to show as the characteristic of positive resistance, and resistance value is equal to proportionality coefficient GhR reciprocalh.In this way,
Impedance adapter can be in absorption system resonant energy, play the role of to multi-inverter grid-connected system calm.
Due to power frequency f0Far below the control frequency of impedance adapter, therefore, in power frequency f0Impedance adapter can be ignored in place
Digital control delay, be approximately considered Gd(s)≈1.Meanwhile usually it is far above LCL resonant frequencies when designing LCL filter
Power frequency f0, to ensure that loop gain of the electric current loop at fundamental wave is sufficiently large.Had according to formula (9), (10)
Therefore, as the proportionality coefficient G of PCC voltage fundamentals feedforward linkf=1/KPWMWhen, had according to formula (12), (13)
Ycon(j2πf0)+Yfff(j2πf0)≈0 (22)
According to formula (7), (11), (15), (22), in power frequency f0Place, total output impedance Z of impedance adapteroIt (s) can be approximate
For
Therefore, by the way that PCC voltage fundamentals feedforward link is added, recoverable impedance adapter is in power frequency f0The port at place hinders
It is anti-, it is allowed to show as the characteristic of negative resistance, and the amplitude I of resistance value and grid-connected current benchmark* gIt is inversely proportional.In this way, impedance adapter
The resonant energy of absorption can be converted in fundamental wave energy feedback to power grid to, avoid introducing additional loss.
It will be based on above-mentioned impedance adapter below, provide a kind of calm method of adaptive multi-inverter grid-connected system, in detail
It is thin that steps are as follows：
1) under normal circumstances, impedance adapter is in off-grid state, by A/D sampling modules to PCC instantaneous voltages vpccInto
Row real-time sampling.Every n0A controlling cycle Ts, by the harmonic detecting link of digital operation module PCC electricity is calculated using fft algorithm
The each harmonic content of pressure judges system stability according to result of calculation by self-adaptive control module：If each time humorous
Wave content then judges that system is stablized, there is no need for cutting through impedance adapters within threshold value；If continuous n1Secondary result of calculation is all
There is any frequency harmonics content to exceed threshold value, then judges that unstable situation occurs in system, go to step 2.
2) before cutting impedance adapter, self-adaptive control module is first according to each harmonic content of PCC voltages, really
Determine the resonant frequency range [f of PCC voltagesr1,fr2], and it is adaptively adjusted bandpass filter in PCC voltage harmonics feedforward link
Gbp(s) two corner frequency fc1And fc2, ensure the port Impedance of impedance adapter in entire resonant frequency range [fr1,fr2]
All show the characteristic of positive resistance.Minimum harmonic frequency of the content beyond threshold value can be considered as resonance lower frequency limit fr1, exceed
The highest harmonic frequency of threshold value is considered as resonance upper limiting frequency fr2, corner frequency f is calculated further according to formula (16) and formula (17)c1
And fc2。
3) it is closed grid-connected switch S1, impedance adapter is cut into system.It can be by proportionality coefficient GhInitial value be set as Gh0.Often
Every n0A controlling cycle Ts, each harmonic of PCC voltages is calculated using fft algorithm by the harmonic detecting link of digital operation module
Content judges system stability according to result of calculation by self-adaptive control module：If still there is any frequency harmonics
Content exceeds threshold value, and proportionality coefficient GhUpper limit G is not reachedmax, then proportionality coefficient is enabled to increase △ Gh；If each harmonic content
Within threshold value, then G is maintainedhIt is constant；If continuous n2Secondary result of calculation each harmonic content is within threshold value, then it is assumed that
System is stable, terminates automatic adjusument process；If proportionality coefficient GhReach upper limit GmaxAfterwards, continuous n3Secondary result of calculation is still
So there is any frequency harmonics content to exceed threshold value, then sends out alarm, further take other calm measures.
One that the present invention is given below applies example.
As shown in fig. 6, inverter 16 and inverter 17 are incorporated to light current net 18 by PCC, a grid-connected system is constituted.Two
Inverter software and hardware parameter is identical, as shown in table 1.Power network line impedance ZgFor pure perception, and inductance value is 100 μ H.This is
When system work, it may occur that serious resonance.Using an additional impedance adapter 19 come the system of calming, impedance adapter
Software and hardware parameter is as shown in table 2.
The software and hardware parameter of 1 single-phase LCL type inverter of table
The software and hardware parameter of 2 impedance adapter of table
The oscillogram of the specific embodiment as shown in fig. 7, be followed successively by PCC voltages v from top to bottompccWaveform, inverter 16 are simultaneously
Net electric current ig1Waveform, 17 grid-connected current i of inverterg219 grid-connected current i of waveform and impedance adaptergAWaveform.
Before impedance adapter incision, it can be seen that in the grid-connected current waveform and PCC voltage waveforms of two inverters
All there is serious resonance, system is unstable, needs to cut impedance adapter with system of calming.It, can by fft analysis
Determine that the main resonant frequency section of system is [2600Hz, 3150Hz].The band in impedance adapter PCC voltage harmonics feedover link
Bandpass filter Gbp(s) when quality factor take Q=10, can find out its corner frequency according to formula (16) and formula (17) is：fc1=
867Hz, fc2=3534Hz.
In t1Moment is closed grid-connected switch S1, impedance adapter is cut, the proportionality coefficient of PCC voltage harmonics feedforward link is enabled
GhIt is gradually increased since 0, when the value of proportionality coefficient rises to 0.4, the grid-connected current and PCC point voltage waves of two inverters
Resonance in shape disappears substantially.It can be seen that scheme provided by the invention can fast and effeciently inhibit multi-inverter grid-connected
Resonance in system plays the role of calm.
Claims (10)
1. a kind of impedance adapter for more grid-connected inverters systems of calming, with more grid-connected inverters systems in public coupling
Chalaza is connected in parallel, it is characterised in that：Including：
Power output circuit, output DC capacitor voltage VdcAnd grid-connected current ig；
Control circuit, including outer voltage unit, phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward units, control
Circuit detects the voltage v of point of common couplingpcc, its phase theta is obtained by phase locked-loop unit, and respectively correspondingly by voltage outside
Ring element and current inner loop unit are to DC capacitor voltage VdcWith grid-connected current igCarry out closed-loop control；Meanwhile passing through PCC electricity
Feed forward element is pressed, the output impedance characteristic of impedance adapter is corrected；Also, the v that control circuit will detectpccEach time
Harmonic content is compared with the threshold value of setting, judges more grid-connected inverters system stability, in more grid-connected inverters systems
When system occurs unstable, impedance adapter is cut grid-connected；
The power output circuit and the phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward cell formation impedances
The port equivalent model of adapter, the port equivalent model include three admittance Y of parallel connectionPLL(s)、Ycon(s)、Yff(s), it holds
Total output impedance Z of mouth equivalent modelo(s) such as formula (1)：
Wherein, YPLL(s)、Ycon(s)、Yff(s) phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward lists are indicated respectively
The admittance that member introduces.
2. the impedance adapter according to claim 1 for more grid-connected inverters systems of calming, it is characterised in that：Institute
Phase locked-loop unit is stated, according to the voltage vpccObtain vpccFundamental voltage amplitude VpccWith phase cosine value cos θ, and then calculate
vpccFundamental wave instantaneous value vpccfWith harmonic wave instantaneous value vpcch, such as formula (2), (3)；
vpccf=Vpcccosθ (2)
vpcch=vpcc-vpccf (3)。
3. the impedance adapter according to claim 1 for more grid-connected inverters systems of calming, it is characterised in that：Institute
Outer voltage unit is stated, including voltage regulator Gv(s), the DC capacitor voltage V of impedance adapter is controlleddcFloating voltage base
Quasi- V* dc；The current inner loop unit, including current regulator Gi(s), the grid-connected current i of impedance adapter is controlledgFollow current
Benchmark i* g, current reference i* gBy voltage regulator Gv(s) output I* gThe PCC voltage-phase cosine obtained with phase locked-loop unit
Value cos θ are multiplied to obtain.
4. the impedance adapter according to claim 3 for more grid-connected inverters systems of calming, it is characterised in that：Institute
Stating PCC electric voltage feed forward units includes：
PCC voltage harmonics feedforward link, by PCC voltage harmonic instantaneous values vpcchBy proportionality coefficient Gh, bandpass filter Gbp(s)
With feedforward function Gff(s) feedforward is born to current regulator Gi(s) output end；
PCC voltage fundamentals feedforward link, by PCC voltage fundamental instantaneous values vpccfBy proportionality coefficient GfIt is positive to feedover to current regulation
Device Gi(s) output end.
5. the impedance adapter according to claim 1 for more grid-connected inverters systems of calming, it is characterised in that：Institute
It includes DC bus capacitor, full-bridge, LCL filter and grid-connected switch to state power output circuit, the DC bus capacitor, full-bridge,
LCL filter and grid-connected switch are sequentially connected.
6. the impedance adapter according to claim 5 for more grid-connected inverters systems of calming, it is characterised in that LCL
Filter is by two inductance L1、L2And capacitance C compositions, the inductance L1, inductance L2And the grid-connected switch series winding, it is described
Capacitance C is connected to inductance L1、L2Between node, the other end connect with the full-bridge.
7. the impedance adapter according to claim 4 for more grid-connected inverters systems of calming, it is characterised in that：Institute
Stating control circuit includes：
A/D sampling modules, to voltage vpcc, DC capacitor voltage Vdc, grid-connected current ig, capacitance current iCCarry out real-time sampling；
Digital operation module, including the phase locked-loop unit, current inner loop unit and PCC electric voltage feed forward units, receive A/D and adopt
The v of egf block acquisitionpcc、Vdc、igAnd iC, each harmonic content of PCC voltages is calculated, is built by preset control algolithm
The port equivalent model, and calculate modulating wave vm；
Self-adaptive control module, by vpccEach harmonic content be compared with the threshold value of setting, judge system stability, when
When decision-making system is unstable, control impedance adapter incision is grid-connected, and according to vpccMajor harmonic component adaptively adjustment described in
The proportionality coefficient G of PCC voltage harmonics feedforward link in digital operation moduleh, bandpass filter Gbp(s) low frequency corner frequency fc1
With bandpass filter Gbp(s) high frequency corner frequency fc2；
Pulse width modulation module, to the modulating wave vmIt is modulated, obtains full-bridge switch pipe Q in power output circuit1~Q4Drive
Dynamic signal.
8. the impedance adapter according to claim 7 for more grid-connected inverters systems of calming, it is characterised in that：Institute
Stating digital operation module further includes：
Harmonic detecting unit detects v in real time by fast fourier transform algorithmpccEach harmonic content, as adaptive
Control module judges the foundation of system stability and self_adaptive adjusting parameter；
Capacitor current feedback unit, by the capacitance current i of impedance adapterCBy proportionality coefficient HiCNegative-feedback is to current regulator
Gi(s) output end carries out active damping for the resonance spikes to LCL filter.
9. the impedance adapter according to claim 8 for more grid-connected inverters systems of calming, it is characterised in that：Institute
State the bandpass filter G in PCC voltage harmonics feedforward linkbp(s) transmission function is
Wherein, Q is quality factor；
Feedforward function Gff(s) transmission function is
Wherein, L1、L2, C be respectively LCL filter bridge side inductance value, net side inductance value and filtering capacitance；HigIt is suitable for impedance
The grid-connected current feedback coefficient of orchestration；KPWMFor modulating wave vmTo bridge arm output voltage vABTransmission function, it is DC bus capacitor
Voltage VdcWith triangular carrier amplitude VtriRatio.
10. the impedance adapter according to claim 9 for more grid-connected inverters systems of calming, it is characterised in that：
Proportionality coefficient G in the PCC voltage fundamentals feedforward linkfExpression formula is：
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| CN109149615A (en) * | 2018-08-21 | 2019-01-04 | 南方电网科学研究院有限责任公司 | A kind of power grid high-frequency resonance adaptive active damping system and method |
| CN109167385B (en) * | 2018-08-31 | 2020-12-29 | 合肥工业大学 | Control method of composite impedance adapter system |
| CN109149646B (en) * | 2018-09-29 | 2022-08-30 | 南京航空航天大学 | Active damper capable of improving stability of inverter grid-connected system and adjusting power |
| CN109802405B (en) * | 2019-01-30 | 2020-07-28 | 天津科林电气有限公司 | Inverter resonance suppression method based on power grid voltage abnormal state feedback |
| CN111245017B (en) * | 2020-03-06 | 2023-04-25 | 河南理工大学 | Capacitive voltage feedforward control method for grid-connected inverter under weak current network |
| CN113224760B (en) * | 2021-05-07 | 2022-04-12 | 南方电网科学研究院有限责任公司 | Parameter design method of series passive impedance adapter suitable for flexible direct current |
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| CN103354359A (en) * | 2013-08-02 | 2013-10-16 | 南京航空航天大学 | Phase angle margin compensation-based system impedance active control method of grid -connected inverter |
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