CN103259287B - Bi-directional grid-connected inversion device and bi-directional grid-connected inversion method for distributed type new energy power generation system - Google Patents
Bi-directional grid-connected inversion device and bi-directional grid-connected inversion method for distributed type new energy power generation system Download PDFInfo
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Abstract
The invention provides a bi-directional grid-connected inversion device and an inversion method for a distributed type new energy power generation system. The device comprises signal acquisition units, a main control unit, a rectification inverted unit and an electric power storage unit. The signal acquisition units comprise a first signal acquisition unit and a second signal acquisition unit. An input unit of the first signal acquisition unit is connected with a direct current input end of the rectification inverted unit. An input end of the second signal acquisition unit is connected with a power grid end of the rectification inverted unit. The rectification inverted unit comprises a bridge rectifier circuit, a bridge inverter circuit, a Boost circuit and a Cuk buck circuit. A storage battery of the electric power storage unit is connected with the distributed new energy power generation system through a storage battery controller. The bi-directional grid-connected inversion method can be used for carrying out rapid judgment, and is capable of rapidly removing the system from a power grid if the new energy power generation system is in an islanding state and then calling active detection to carry out detection on a result of passive detection. The bi-directional grid-connected inversion device gives full play to the advantages of being high in accuracy of active detection, and overcomes the defects that detection time is long and the degree of harmonic pollution to the power grid is large.
Description
Technical field
The invention belongs to distributed new generating and technical field of electricity, be specifically related to a kind of two-way parallel network reverse device and method of distributed new electricity generation system.
Background technology
The energy is the source of human economy and cultural activity.Electric energy relies on its status of waiting many advantages to be sure to occupy energy currency convenient for cleaning.Along with the fossil energy of all parts of the world is day by day exhausted, new forms of energy (as wind energy, solar energy etc.) distributed power generation more and more receives the concern of people with its exclusive feature.But island effect becomes the principal element of restriction distributed generation technology development.Its reason mainly distributed generation technology is different from the confession distribution technique of the generating of traditional high-power station, bulk power grid transmission of electricity, due to features such as himself generate output is little, scattered distributions, traditional scheduling mode can not control effectively, like this when access grid collapses will make grid-connected distributed generation system be absorbed in island state.In order to improve the grid-connected reliability of grid-connected distributed generation system, controllability, give full play to the advantage of distributed generation system, various countries all require to have island effect measuring ability for grid-connected distributed generation system.
The method of current islanding detect has a variety of, be mainly divided into active detecting, passive detection with based on the islanding detect communicated.But the shortcomings such as these methods respectively have deficiency, and such as active detecting can produce disturbance to electrical network, and passive detection threshold value chooses difficulty, and blind area is larger.
Meanwhile, due to the deficiency of distributed new interconnection technology, for avoiding distributed new to impact electrical network, the relevant laws and regulations causing user side grid-connected are comparatively strict, this severely limits the development of distributed new.
Summary of the invention
For the deficiency that prior art exists, the invention provides a kind of two-way parallel network reverse device and method of distributed new electricity generation system.
Technical scheme of the present invention is:
A two-way parallel network reverse device for distributed new electricity generation system, comprises signal gathering unit, main control unit, commutation inversion unit and electricity accumulating unit.
Described signal gathering unit comprises the first signal gathering unit and secondary signal collecting unit, first signal gathering unit loader is connected to the direct-flow input end of commutation inversion unit, secondary signal collecting unit input is connected to the electrical network end of commutation inversion unit, and the output of the first signal gathering unit is all connected main control unit with the output of secondary signal collecting unit.
Described commutation inversion unit comprises bridge rectifier, bridge inverter main circuit, Boost circuit and Cuk reduction voltage circuit, the input of Cuk reduction voltage circuit is all connected distributed new electricity generation system with the input of Boost circuit, the output of Cuk reduction voltage circuit connects the input of bridge rectifier, the output of Boost circuit connects the input of bridge inverter main circuit, the input of bridge rectifier, the input of bridge inverter main circuit also connects main control unit respectively, the output of bridge rectifier and the output of bridge inverter main circuit are connected to electrical network through circuit breaker.
Described electricity accumulating unit comprises storage battery and battery controller, and storage battery is connected to distributed new electricity generation system through battery controller.
The side be connected with distributed new system of described commutation inversion unit is connected with ultracapacitor.
Described first signal gathering unit and secondary signal collecting unit include voltage sensor, current sensor, Frequency tester, bandwidth-limited circuit, three-phase voltage sampled signal modulation circuit, three-phase current sampled signal modulation circuit and frequency sampling signal modulation circuit.
The output of voltage sensor, the output of current sensor are all connected with the input of bandwidth-limited circuit with the output of Frequency tester, the output of bandwidth-limited circuit connects the input of three-phase voltage sampled signal modulation circuit, the input of three-phase current sampled signal modulation circuit and the input of frequency sampling signal modulation circuit respectively, and the output of three-phase voltage sampled signal modulation circuit, the output of three-phase current sampled signal modulation circuit and the output of frequency sampling signal modulation circuit are all connected to the input of main control unit.
Described main control unit is connected with power module, communication module, memory module and display module.
The mode of operation of described commutation inversion unit comprises inverter mode and rectification mode; when the generating of distributed new electricity generation system is sufficient; commutation inversion cell operation is at inverter mode; when distributed new electricity generation system abnormal electrical power supply or when needing electrical network to be charge in batteries, commutation inversion cell operation is at rectification mode.
Described storage battery adopts lead acid accumulator, in parallel between each storage battery; Battery controller comprises voltage stabilizing chip, power supply control chip and exports pressure regulation chip, storage battery connects voltage stabilizing chip input, the output of voltage stabilizing chip connects the input of power supply control chip, export the output that pressure regulation chip input is connected to power supply control chip, export pressure regulation chip output and connect distributed new electricity generation system.
The method of the two-way parallel network reverse device of the distributed new electricity generation system described in employing, comprises the following steps:
Step 1: voltage, electric current, the frequency of the DC side of the voltage of the common coupling node PCC of Real-time Collection electrical network, electric current, frequency and commutation inversion unit, and carry out filtering, noise reduction and transformation process;
Step 2: the data of voltage, electric current and frequency after filtering, noise reduction and transformation process are normalized, the memory module transferring to main control unit is preserved;
Step 3: initialization distributed new electricity generation system parameter, comprises resistance value R, inductance value L and capacitance C;
Step 4: according to the data after the normalization that memory module is preserved, the active-power P of calculatingization distributed new electricity generation system and reactive power Q are also preserved stored in memory module;
Step 5: the data in memory module are sent into main control unit, utilizes overvoltage/undervoltage/mistake under-frequency detection method to carry out passive islanding detect;
Step 5.1: calculate the degree of unbalance of active power and the degree of unbalance of reactive power and be stored to memory module;
Step 5.2: the voltage signal V utilizing the method detection of grid point of common coupling of wavelet analysis
pCCsingular point;
Step 5.3: if V detected
pCCthere is singular point, and the imbalance of the degree of unbalance of active power and reactive power exceedes threshold value, then distributed new electricity generation system is in island state, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, to drive circuit breaker distributed new electricity generation system to be excised from electrical network, otherwise perform step 6;
Step 6: utilize active frequency shift method to carry out active islanding detect;
Step 6.1: according to voltage, the current value at the electrical network point of common coupling place gathered, the angular frequency of the PCC Nodes after the phase angle of the voltage after calculation perturbation, the phase angle of electric current and disturbance
pcc;
Step 6.2: the impedance angle of Computation distribution formula grid-connected power generation system;
Step 6.3: calculate frequency displacement maximum ω
maxwith frequency displacement minimum value ω
min;
Step 6.4: judge ω
min< ω
pcc< ω
maxwhether set up, that then passive islanding detect result is accurate, otherwise passive islanding detect result is inaccurate, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, drives circuit breaker distributed new electricity generation system to be excised from electrical network;
Step 7: the data stored in memory module are shown in real time by display module, provides maintenance foundation to maintainer.
Beneficial effect:
The two-way parallel network reverse device of distributed new electricity generation system of the present invention, compared to traditional isolated island detecting device, has the features such as check frequency is little, accuracy in detection is high, applicability is strong.The present invention adopts and carries out islanding detect based on the mode of pattern recognition wavelet analysis, and effective threshold value of eliminating sets the blind area of bringing.Compared to traditional employing tradition passive detection and the isolated island detecting device of active detecting, the rapidity of passive detection, the advantage little to harmonic pollution in electric power net are given full play to, achieve checkout gear first to judge fast system, if distributed generation system is in island state, then rapid system to be excised from electrical network, then call the result of active detecting to passive detection to detect, give full play to the advantage that active detecting accuracy in detection is high, overcome detection time long, the deficiency large to harmonic pollution in electric power net degree.Generally speaking, the inventive method is compared to traditional island detection method, check frequency reduces 24%, detection time shortens 38%, accuracy in detection improves 92%, reduces 93% to harmonic pollution in electric power net, compared to traditional synchronizing mode, the present invention can intelligence switch between grid-connect mode and island mode, provide possibility for user side generates electricity by way of merging two or more grid systems arbitrarily.
Accompanying drawing explanation
Fig. 1 is the work system schematic diagram of two-way parallel network reverse device in electrical network of the distributed new electricity generation system of the specific embodiment of the invention;
Fig. 2 is the two-way parallel network reverse apparatus structure schematic diagram of the distributed new electricity generation system of the specific embodiment of the invention;
Fig. 3 is the circuit theory diagrams of the bandwidth-limited circuit of the specific embodiment of the invention;
Fig. 4 is the circuit theory diagrams of the three-phase voltage sampled signal modulation circuit of the specific embodiment of the invention;
Fig. 5 is the circuit theory diagrams of the three-phase current sampled signal modulation circuit of the specific embodiment of the invention;
Fig. 6 is the circuit theory diagrams of the frequency sampling signal modulation circuit of the specific embodiment of the invention;
Fig. 7 is the DSP of the specific embodiment of the invention and the circuit theory diagrams of power module thereof;
Fig. 8 is the circuit theory diagrams of the memory module of the specific embodiment of the invention;
Fig. 9 is the circuit theory diagrams of the communication module of the specific embodiment of the invention;
Figure 10 is the circuit theory diagrams of the display module of the specific embodiment of the invention;
Figure 11 is the commutation inversion element circuit schematic diagram of the specific embodiment of the invention;
Figure 12 is the SPWM control flow chart of the specific embodiment of the invention;
Figure 13 is the two-way parallel network reverse method flow diagram of the distributed new electricity generation system of the specific embodiment of the invention.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is elaborated.
As shown in Figure 2, the two-way parallel network reverse device of distributed new electricity generation system, comprises signal gathering unit, main control unit, commutation inversion unit and electricity accumulating unit.
Signal gathering unit comprises the first signal gathering unit and secondary signal collecting unit, first signal gathering unit loader is connected to the direct-flow input end of commutation inversion unit, secondary signal collecting unit input is connected to the electrical network end of commutation inversion unit, and the output of the first signal gathering unit is all connected main control unit with the output of secondary signal collecting unit.
First signal gathering unit and secondary signal collecting unit include voltage sensor VT, current sensor CT, Frequency tester, bandwidth-limited circuit, three-phase voltage sampled signal modulation circuit, three-phase current sampled signal modulation circuit and frequency sampling signal modulation circuit.The model of voltage sensor is HNV500T, the model of current sensor is ACS712ELCTR-05A5ASOP-8, voltage sensor is for gathering the voltage at distributed new electricity generation system and grid nodes (i.e. PCC node) place, current sensor exports galvanic electric current for the voltage's distribiuting formula new forms of energy gathering distributed new electricity generation system and grid nodes (i.e. PCC node) place, model is adopted to be the Frequency tester of BT3C, gather distributed new electricity generation system and the frequency at grid nodes (PCC node) place and the frequency of distributed new electricity generation system DC output end respectively.
The output of voltage sensor, the output of current sensor are all connected with the input of bandwidth-limited circuit with the output of Frequency tester, the output of bandwidth-limited circuit connects the input of three-phase voltage sampled signal modulation circuit, the input of three-phase current sampled signal modulation circuit and the input of frequency sampling signal modulation circuit respectively, and the output of three-phase voltage sampled signal modulation circuit, the output of three-phase current sampled signal modulation circuit and the output of frequency sampling signal modulation circuit are all connected to the input of main control unit.
The bandwidth-limited circuit of present embodiment as shown in Figure 3, the output pin u of bandwidth-limited circuit
oexport 7 road signals, wherein, voltage signal is connected to the u of three-phase voltage sampled signal modulation circuit
ainterface, as shown in Figure 4, the output OUT of three-phase voltage sampled signal modulation circuit
aconnect the signal input part (ADCINA0, ADCINA2 as DSP hold) of main control unit respectively; The 3 road current signals that bandwidth-limited circuit exports are connected to the i of three-phase current sampled signal modulation circuit
ainterface, as shown in Figure 5, the output OUT of three-phase current sampled signal modulation circuit
a1connect the signal input part (ADCINA3, ADCINA5 as DSP hold) of main control unit respectively; Frequency signal is connected to the input f of frequency sampling signal modulation circuit
g, as shown in Figure 6, the output OUT of frequency sampling signal modulation circuit
fend connects the signal input part (ADCINA6 as DSP holds) of main control unit.
Commutation inversion unit as shown in figure 11, comprise bridge rectifier 2, bridge inverter main circuit 4, Boost circuit 3 and Cuk reduction voltage circuit 1, the input of Cuk reduction voltage circuit 1 is all connected distributed new electricity generation system with the input of Boost circuit 3, the output of Cuk reduction voltage circuit 1 connects the input of bridge rectifier 2, the output of Boost circuit 3 connects the input of bridge inverter main circuit 4, the input of bridge rectifier 2, the input of bridge inverter main circuit 4 also connects main control unit respectively, the output of bridge rectifier 2 and the output of bridge inverter main circuit 4 are connected to electrical network through circuit breaker.Wherein, Boost circuit without isolated connection bridge inverter main circuit, then is connected bridge rectifier parallel connection with Cuk reduction voltage circuit is isolated.
The two-way parallel network reverse device of distributed new electricity generation system produces PWM control wave signal by the I/O mouth of DSP, this control signal is after signal amplification circuit amplifies, the each thyristor be docked in the on off operating mode of the relay (model adopted in present embodiment is DW15 broken-circuit controller) of PCC point and commutation inversion unit controls, and realizes the excision operation of the island operation state of distributed new electricity generation system and the distributed generation system reclosing operation of island state.
The side that commutation inversion unit is connected with distributed new system is connected with ultracapacitor.
The mode of operation of commutation inversion unit comprises inverter mode and rectification mode; when the generating of distributed new electricity generation system is sufficient; commutation inversion cell operation is at inverter mode; when distributed new electricity generation system abnormal electrical power supply or when needing electrical network to be charge in batteries, commutation inversion cell operation is at rectification mode.
In present embodiment, model is adopted to be that the DSP of TMS320F2812 is as main control unit, A/D conversion is carried out for the phase voltage of the PCC point that collects signal gathering unit, phase current and frequency, and islanding detect is carried out to the signal after A/D conversion, according to the corresponding Trig control signal of detection triggers, actuator's (circuit breaker) at PCC point place is driven to carry out corresponding action.
As shown in Figure 7, the model of present embodiment is that the DSP of TMS320F2812 is connected with power module, communication module, memory module and display module, and this power module provides the 3.3V voltage meeting job requirement to DSP.
The output signal of DSP send memory module, communication module, display module and circuit breaker, memory module, display module realize storage to the critical data of distributed new operation of electric power system state and display respectively, so that operating personnel understand the running status of system, and make correct process operation according to the critical data of record.
In present embodiment, the model of memory module is CY7C1041BV33, and its data input pin DO ~ D15 pin is connected with XD0 ~ XD15 pin of DSP, and A0 ~ A17 pin is connected with XA0 ~ XA17 pin of dsp chip, as shown in Figure 8.
Communication module, for realizing this device and the network communication of host computer, is convenient to dispatcher and is made rational arrangement to distributed new electricity generation system, and the greatest benefit realizing distributed new electricity generation system runs.RS485 communications protocol and MAX232 driving chip is adopted to realize communication module in present embodiment, as shown in Figure 9, its R2OUT, T2IN, R1OUT, T1IN pin is connected with SCIRXDA, SCITXDA, SCIRXDB, SCITXDB pin of DSP its circuit theory respectively.
Display module adopts liquid crystal display to realize, model is LCM12864ZK, as shown in Figure 10, the RS pin of liquid crystal display is connected with the IOPF4 pin of TMS320LF2812 chip, the R/W pin of liquid crystal display is connected with the IOPF5 pin of DSP, the E pin of liquid crystal display is connected with the IOPF6 pin of DSP, and D0 ~ D7 pin is connected with IOPB1 ~ IDPB7 pin of DSP, liquid crystal display /RST pin is connected with the IOPC1 pin of DSP.
Electricity accumulating unit comprises storage battery and battery controller, and storage battery is connected to distributed new electricity generation system through battery controller.
Storage battery adopts lead acid accumulator, in parallel between each storage battery; Battery controller comprises voltage stabilizing chip, power supply control chip and exports pressure regulation chip, storage battery connects voltage stabilizing chip input, the output of voltage stabilizing chip connects the input of power supply control chip, export the output that pressure regulation chip input is connected to power supply control chip, export pressure regulation chip output and connect distributed new electricity generation system.
As shown in Figure 1, in the two-way parallel network reverse device of the distributed new electricity generation system work system in electrical network, it is local load supplying that the direct current that distributed new electricity generation system exports exports the alternating current all identical with line voltage frequency, amplitude and phase place through two-way parallel network reverse device, and namely island mode runs.The breaker closing when the electric energy that distributed new electricity generation system provides meets grid-connected requirement, distributed new electricity generation system grid-connect mode runs, for electrical network common load is powered.When distributed new electricity generation system abnormal the sudden change of light condition (in the such as photovoltaic generation), distributed new electricity generation system is excised from electrical network by circuit breaker fast.Ultracapacitor is used for providing to electrical network within the breaker operator time or accessing required electric energy, consistent with electrical network to adjust distributed new electricity generation system electric voltage frequency, amplitude and phase place, thus reduces the impact to electrical network.When restart after the long-term dead electricity of distributed new electricity generation system or storage battery need from grid charging time, two-way parallel network reverse device reverse operation at rectification state, for electricity accumulating unit provides electric energy.
Adopt the method for the two-way parallel network reverse device of above-mentioned distributed new electricity generation system, flow process as shown in figure 13, comprises the following steps:
Step 1: voltage u, current i, the frequency of the DC side of the voltage of the common coupling node PCC of Real-time Collection electrical network, electric current, frequency and commutation inversion unit, and carry out filtering, noise reduction and transformation process;
Step 2: the data of voltage, electric current and frequency after filtering, noise reduction and transformation process are normalized, the memory module transferring to main control unit is preserved;
Step 3: initialization distributed new electricity generation system parameter, comprises resistance value R, inductance value L and capacitance C;
Step 4: according to the data after the normalization that memory module is preserved, the active-power P of calculatingization distributed new electricity generation system and reactive power Q are also preserved stored in memory module;
Wherein,
for power-factor angle, Z is the total load of network system;
Step 5: the data in memory module are sent into main control unit, utilizes overvoltage/undervoltage/mistake under-frequency detection method to carry out passive islanding detect;
Step 5.1: the degree of unbalance calculating active power
with the degree of unbalance of reactive power
and be stored to memory module;
Calculate active power degree of unbalance
with reactive power
the formula of degree of unbalance is as follows:
Wherein, ω
gfor electrical network angular frequency, and there is ω
g=2 π f
g, f
gfor mains frequency; u
gfor line voltage; Q
zidle on resonant capacitance, and have
Step 5.2: the voltage signal V utilizing the method detection of grid point of common coupling of the wavelet analysis based on pattern recognition
pCC, the voltage signal V of point of common coupling
pCCthe i.e. voltage signal at the grid-connected place of circuit breaker;
Step 5.2.1: by V
pCCbe designated as u (t);
Step 5.2.2: judge the Sudden Changing Rate Δ V of the voltage signal of point of common coupling in isolated island moment
pCCor the frequency signal of point of common coupling is at the Sudden Changing Rate Δ f of isolated island moment
pCCwhether exceed threshold value, if exceed threshold value, then detect that current distributed new electricity generation system is in island state, otherwise perform step 5.2.3;
Step 5.2.3: carry out inflection point detection;
Concrete grammar is as follows; Definition u (t) ∈-L
2(R), θ (t) ∈-L
2(R) be Gaussian smoothing function ,-L
2(R) represent real number two-dimensional space, get the first derivative of Gaussian smoothing function respectively
second dervative
as wavelet transformation generating function,
then θ
sstretching under (t) expression θ (t) scale factor s, then wavelet transformation is carried out to u (t):
Wherein,
be the WAVELET TRANSFORM MODULUS of signal u (t);
Known by above formula, the WAVELET TRANSFORM MODULUS of signal u (t)
local modulus maxima reaction signal u (t) there is singular point (or catastrophe point); The WAVELET TRANSFORM MODULUS of signal u (t)
local zero crossing, there is singular point (or catastrophe point) in reaction signal u (t).Therefore, for the primary signal having singular point, wavelet modulus maxima is exactly the singular point of primary signal;
Step 5.2.4: if V detected
pCCthere is singular point, then postpone 50ms, treat V
pCCsignal is steady, carries out Fourier transform and calculate V to signal u (t)
pCCfrequency spectrum, in this frequency spectrum, the amplitude of front 18 odd harmonics is as characteristic parameter, and each characteristic parameter forms sample characteristics storehouse;
Step 5.2.5 utilizes neural network classification algorithm to carry out pattern recognition to current demand signal u (t), namely the characteristic parameter for the frequency spectrum of current demand signal u (t) carries out characteristic parameter screening in sample characteristics storehouse, whether island operation state is in: if the characteristic parameter of the frequency spectrum of current demand signal u (t) is present in sample characteristics storehouse with recognition system, then identifying distributed new electricity generation system current is island operation state, and perform step 5.3, otherwise distributed new electricity generation system current be the state of being incorporated into the power networks;
Present embodiment adopts the BP neural net of 18-36-1 to classify, and whether is in island operation state with recognition system;
Step 5.3: if neural network recognization distributed new electricity generation system is island operation state, and the imbalance of the degree of unbalance of active power and reactive power exceedes threshold value, then distributed new electricity generation system is in island operation state, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, drive circuit breaker distributed new electricity generation system to be excised from electrical network, otherwise perform step 6;
The process of inversion control is carried out as shown in figure 12 to distributed new electricity generation system, specific as follows:
Inner ring open current loop transfer function can be represented by the formula:
G
I(S)=(G
P(S)*G
INV(S)-U
net)*G
L(S)*e
-ωt
In formula, G
p(S) be PI adjustment function, G
iNV(S) be inversion link transfer function, G
l(S) be filtering link transfer function.
The adjustment process that current inner loop controls can be described as: relative to given reference current I
ref *, when inversion exports grid-connected current I
outwhen being less than reference current, both difference signals are just, regulate, after adding voltage feed-forward control value, increase the amplitude of sinusoidal modulation signal, therefore increase the duty ratio of inverter bridge, thus output grid-connected current is increased through PI; As inverter output current I
outwhen being greater than reference current, both difference signals are negative, and voltage feed-forward control value deducts the error signal regulated through PI, thus reduce Using Sinusoidal Pulse Width Modulation signal amplitude, reduce the duty ratio of inverter bridge, and then reduce inversion output grid-connected current.
Outer voltage controls, and be that control DC bus-bar voltage is constant, detailed process is; As bus voltage measurement value V
dclinkbe greater than given reference value V
dcreftime, now capacitance stores energy, regulates by PI and strengthens grid-connected reference current I
ref *, current inner loop regulable control inverter bridge duty ratio increases, and grid-connected power increases, and reduces capacitance voltage; As bus bar side voltage measuring value V
dclinkbe less than given reference value V
dcreftime, electric capacity releases energy, and can reduce reference current I
ref *, reduce grid-connected power, thus increase capacitance voltage.
It is export grid-connected current I according to inversion that PI regulates
outwith reference current I
ref *difference, make a response rapidly, to reach I
outquick tracking I
ref *change: to the DC bus-bar voltage V adopted
dclinkwith given V
dcrefcompare, the error signal (V obtained
dclinkwith V
dcrefdifference) through PI regulate process after output as inner ring reference current amplitude I
ref, this amplitude be multiplied by line voltage with after the unit sine wave of frequently homophase as inner ring given value of current signal I
ref *, given electric current and output grid-connected current instantaneous value I
outcompare, error signal regulates after process through PI, and as sine pulse modulation signal, signal pulse controls inverter bridge power switch pipe break-make, exports after filter circuit, obtains and the sinusoidal current feed-in electrical network of line voltage with frequency homophase.
Step 6: utilize active frequency shift method to carry out active islanding detect;
Step 6.1: the PWM wave frequency exported by changing main control unit changes the output current of commutation inversion unit;
Step 6.2: disturbance is added to the angular frequency changing inverter output current PWM ripple:
Step 6.2: according to voltage, the current value of the PCC Nodes gathered, the phase angle of the voltage after calculation perturbation
the phase angle of electric current
with the angular frequency of the PCC Nodes after disturbance
pcc, ω
pcc=2 π f
pcc;
Step 6.3: the impedance angle of Computation distribution formula grid-connected power generation system, formula is as follows:
If distributed new electricity generation system is in island state, then the phase angle of the voltage of PCC Nodes
the phase angle of electric current
difference equal load impedance angle
namely have:
Step 6.4: calculate frequency displacement maximum ω
maxwith frequency displacement minimum value ω
min;
Calculate frequency displacement maximum ω
maxwith frequency displacement minimum value ω
min, formula is as follows:
In formula,
for voltage phase angle;
for current phase angle;
Step 6.4: judge ω
min< ω
pcc< ω
maxwhether set up, that then passive islanding detect result is accurate, otherwise passive islanding detect result is inaccurate, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, drives circuit breaker distributed new electricity generation system to be excised from electrical network;
Step 7: the data stored in memory module are shown in real time by display module, provides maintenance foundation to maintainer.
Claims (1)
1. a two-way parallel network reverse method for distributed new electricity generation system, the two-way parallel network reverse device of the distributed new electricity generation system adopted, comprises signal gathering unit, main control unit, commutation inversion unit and electricity accumulating unit;
Described signal gathering unit comprises the first signal gathering unit and secondary signal collecting unit, first signal gathering unit loader is connected to the direct-flow input end of commutation inversion unit, secondary signal collecting unit input is connected to the electrical network end of commutation inversion unit, and the output of the first signal gathering unit is all connected main control unit with the output of secondary signal collecting unit;
Described commutation inversion unit comprises bridge rectifier, bridge inverter main circuit, Boost circuit and Cuk reduction voltage circuit, the input of Cuk reduction voltage circuit is all connected distributed new electricity generation system with the input of Boost circuit, the output of Cuk reduction voltage circuit connects the input of bridge rectifier, the output of Boost circuit connects the input of bridge inverter main circuit, the input of bridge rectifier, the input of bridge inverter main circuit also connects main control unit respectively, the output of bridge rectifier and the output of bridge inverter main circuit are connected to electrical network through circuit breaker,
Described electricity accumulating unit comprises storage battery and battery controller, and storage battery is connected to distributed new electricity generation system through battery controller;
It is characterized in that: the method comprises the following steps:
Step 1: voltage, electric current, the frequency of the DC side of the voltage of the common coupling node PCC of Real-time Collection electrical network, electric current, frequency and commutation inversion unit, and carry out filtering, noise reduction and transformation process;
Step 2: the data of voltage, electric current and frequency after filtering, noise reduction and transformation process are normalized, the memory module transferring to main control unit is preserved;
Step 3: initialization distributed new electricity generation system parameter, comprises resistance value R, inductance value L and capacitance C;
Step 4: according to the data after the normalization that memory module is preserved, the active-power P of Computation distribution formula grid-connected power generation system and reactive power Q are also preserved stored in memory module;
Step 5: the data in memory module are sent into main control unit, utilizes overvoltage/undervoltage/mistake under-frequency detection method to carry out passive islanding detect; Step 5.1: calculate the degree of unbalance of active power and the degree of unbalance of reactive power and be stored to memory module;
Step 5.2: the voltage signal V utilizing the method detection of grid point of common coupling of wavelet analysis
pCCsingular point;
Step 5.3: if V detected
pCCthere is singular point, and the imbalance of the degree of unbalance of active power and reactive power exceedes threshold value, then distributed new electricity generation system is in island state, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, to drive circuit breaker distributed new electricity generation system to be excised from electrical network, otherwise perform step 6;
Step 6: utilize active frequency shift method to carry out active islanding detect;
Step 6.1: according to voltage, the current value at the electrical network point of common coupling place gathered, the angular frequency of the PCC Nodes after the phase angle of the voltage after calculation perturbation, the phase angle of electric current and disturbance
pcc;
Step 6.2: the impedance angle of Computation distribution formula grid-connected power generation system;
Step 6.3: calculate frequency displacement maximum ω
maxwith frequency displacement minimum value ω
min;
Step 6.4: judge ω
min< ω
pcc< ω
maxwhether set up, that then passive islanding detect result is accurate, otherwise passive islanding detect result is inaccurate, now main control unit sends PWM ripple and carries out inversion control to distributed new electricity generation system, drives circuit breaker distributed new electricity generation system to be excised from electrical network;
Step 7: the data stored in memory module are shown in real time by display module, provides maintenance foundation to maintainer.
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| CN103441667B (en) * | 2013-09-18 | 2016-08-17 | 湘潭大学 | A kind of direct-flow controlling device being applied to multistage energy-storage system |
| CN103684028B (en) * | 2013-12-16 | 2016-08-03 | 华北电力大学（保定） | A kind of Multi-transformer push-pull type photovoltaic inverter |
| CN104319812A (en) * | 2014-11-06 | 2015-01-28 | 安徽启光能源科技研究院有限公司 | Comprehensive island detection method of photovoltaic energy storage system |
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| CN110501610B (en) * | 2019-08-26 | 2021-10-01 | 国网山东省电力公司莱芜供电公司 | Multi-inverter grid-connected oscillation feature real-time extraction method and device |
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