CN102624027A - Multiprocess island effect detection device and method - Google Patents

Abstract

The invention relates to a multiprocess island effect detection device and method and belongs to the field of fault detection of distributed power generation systems. Compared with the traditional island detection device, the multiprocess island effect detection device provided by the invention has the characteristics of small non-detection zone, high detection accuracy, strong applicability and the like; and island detection is carried out on a system by adopting a passive detection mode in which detection variables are mutually independent, and the island detection can be carried out on the system more comprehensively. Compared with the traditional island detection device which adopts single passive detection and active detection, the detection device provided by the invention has the characteristics that the advantages of less pollution to harmonic wave of a power grid and rapidity of passive detection are fully played, rapid judgement on the system is firstly realized, if the distributed power generation system is in an island state, the system is rapidly removed from the power grid. Besides, active detection is called to recheck the result of the passive detection, the advantage of high detection accuracy of the passive detection is fully played, and the defects that the detection time is long and the pollution level to the harmonic wave of the power grid is high can be overcome.

Description

A kind of island effect checkout gear and method of multi-process

Technical field

The invention belongs to distributed generation system fault detect field, be specifically related to a kind of island effect checkout gear and method of multi-process.

Background technology

Since twentieth century; Along with economy and fast development of society; Energy resource consumption grows with each passing day, and the increasing rapidly of electricity needs makes People more and more pay attention to the development of regenerative resource, and the distributed power generation technology causes the concern that People more and more is many with its exclusive characteristics.Along with the distributed generation system quantity that is incorporated into the power networks increases year by year; Island effect becomes the principal element of restriction distributed power generation technology; Its reason mainly is the confession distribution technique that the distributed power generation technology is different from the generating of traditional high-power station, big grid power transmission; Because characteristics such as himself generate output is little, layout dispersions, traditional scheduling mode can not control effectively, and breaks down and will make the distributed generation system that is incorporated into the power networks be absorbed in island state when inserting electrical network like this.In order to improve reliability, the controllability that the distributed power generation system that is incorporated into the power networks is incorporated into the power networks; Give full play to the advantage of distributed generation system; Various countries all require to have the island effect measuring ability for the distributed power generation system that is incorporated into the power networks; For example:, require to have at least a kind of passive detection method and a kind of active detecting method in Japan; In the North America, require manufacturer to adopt active alone island detection mode based on frequency, phase place or variation; In China, during requiring, GB/T19939-2005 photovoltaic system interconnection technology requires each a kind of active and passive island detection device at least.Therefore, become domestic and international electric power researcher's research focus for the research of the research of island effect detection technique and relevant apparatus thereof.

Now, many kinds have been arranged, mainly be divided into two big types of active detecting and passive detections about the distributed generation system island effect detection method.For now, passive detection possesses skills simple, easy to implement, need not inject disturbance to system, has reduced advantages such as harmonic effects.But passive detection can only be that electricity generation system detects to the distribution behind the island effect, and makes corresponding processing, and it can not find the isolated island phenomenon in advance, and the detection blind area of passive detection is big in addition.Have the accuracy of detection height though the active detecting method detects, to detect advantages such as the blind area is little, this method control is complicated, and because testing process need be injected disturbing signal, has reduced the quality of inverter output electric energy.No matter because be the merits and demerits that all there are self in passive type detection method or active detection method,, active detecting becomes the new direction that nowadays becomes the island detection technical research so combining with passive detection.The island detection technology that present active detecting combines with passive detection is of a great variety; As overvoltage/undervoltage/mistake under-frequency detection method combines with the frequency offset detection method, the voltage harmonic detection method is floated detection method frequently with sliding formwork and combined ... defective but these methods all possess skills, such as greatly, also there is bigger detection blind area in the technical application difficulty, control device is complicated, detection time is long etc.

Summary of the invention

To the deficiency that existing method exists, the present invention proposes a kind of island effect checkout gear and method of multi-process, to reach the purpose of more comprehensively system being carried out island detection.

Technical scheme of the present invention is achieved in that a kind of island effect detection method of multi-process, may further comprise the steps:

Step 1: the three-phase voltage that collects, electric current and frequency are carried out filtering, noise reduction, transformation processing and analog-to-digital conversion, and the digital signal after the conversion is carried out normalization handle, deliver to data memory unit and preserve;

Step 2: initialization system parameter, described system parameters comprise resistance value R, inductance value L and the capacitance C of system;

Step 3: utilize the data of step 1 storage, the active power P of computing system and reactive power Q, and deposit active power value and reactive power value in the data memory unit preservation;

Step 4: the data in the data storage are sent into the CPU of DSP, carry out passive island detection, judge whether isolated island takes place, and method is: (1) utilizes overvoltage/undervoltage/mistake under-frequency detection method to calculate the degree of unbalance of active power and reactive power; (2) utilize SPA sudden phase anomalies detection method calculating voltage current phase declinate; (3) utilize power/frequency rate of change detection method to calculate the interconversion rate of active power interconversion rate, reactive power interconversion rate and frequency; Utilize the result of above-mentioned (1) (2) (3); Calculate passive detection comprehensive evaluation index value,, explain that distributed generation system is the state that normally is incorporated into the power networks if this value is not more than 10; Utilization active island detection flow process is checked execution in step 5 to the result of passive island detection; This value explains that greater than 10 distributed generation system has been in island state, and this moment, the DSP of system sent PWM ripple driving broken-circuit controller, and distributed generation system is excised from electrical network;

Step 5: the active island detection, method is: utilize the initiatively maximum ω of shift frequency method calculating frequency shift _MaxWith minimum value ω _Min, the angular frequency at calculating distributed generation system and grid nodes place _PIf do not satisfy ω _Min＜ω _P＜ω _Max, explain that the result of passive detection is incorrect, this moment, DSP sent PWM ripple driving broken-circuit controller, and distributed generation system is excised from electrical network; Otherwise the result that passive detection is described is correct, execution in step 6;

Step 6: distributed generation system is in the islet operation state, utilizes communication unit and host computer to carry out telecommunication, excises from electrical network to operating personnel's prompt system;

Step 7: the data that are stored in data storage element show through the state that display unit carries out distributed generation system, to the system overhaul personnel maintenance foundation are provided;

Step 8: for the distributed generation system that has excised from electrical network; The island detection device can carry out active detecting to distributed generation system through the active island detection; Judge whether distributed generation system satisfies the requirement of being incorporated into the power networks again; If satisfy, then DSP sends the PWM ripple and drives broken-circuit controller distributed generation system is incorporated into the power networks again.

Realize the device of the island effect detection method of multi-process, comprising:

Signal gathering unit: be used to gather three-phase voltage, electric current and the frequency at distributed generation system and grid nodes place and the signal that collects is carried out filtering, noise reduction, transformation processing;

Main control unit: be used for the signal that signal gathering unit collects is further handled, carry out passive island detection and active island detection, and according to testing result, the control distributed generation system is connected and shutoff with electrical network;

Data memory unit: the interconversion rate that is used to store degree of unbalance, electric current and voltage phase angle, active power interconversion rate, reactive power interconversion rate and the frequency of active power and reactive power;

Communication unit: be used to realize the network communication of island effect checkout gear and host computer.

Advantage of the present invention: the island effect checkout gear of multi-process proposed by the invention has characteristics such as the blind area of detection is little, accuracy in detection is high, applicability is strong than traditional island detection device.This island detection device adopts the separate passive detection mode of multiple detection variable that system is carried out island detection, more comprehensively system is carried out island detection.Island detection device than single passive detection of Traditional use and active detecting; The rapidity of passive detection, the advantage little have been given full play to harmonic pollution in electric power net; Realized that checkout gear at first judges system fast; If distributed generation system is in island state, then rapidly system is excised from electrical network.Next calls active detecting the result of passive detection is checked, and has given full play to the high advantage of active detecting accuracy in detection, and it is long to have overcome detection time, the deficiency big to the harmonic pollution in electric power net degree.Generally speaking, the island effect checkout gear of the multi-process that the present invention proposes detects the blind area and has reduced by 25% than traditional island detection device, has shortened 40% detection time, and accuracy in detection has promoted 90%, to the reduction of harmonic pollution in electric power net 92%.

Description of drawings

Fig. 1 is the structured flowchart of the island effect checkout gear of one embodiment of the present invention multi-process;

Fig. 2 is the circuit theory diagrams of one embodiment of the present invention bandwidth-limited circuit;

Fig. 3 is the circuit theory diagrams of one embodiment of the present invention three-phase voltage sampled signal modulation circuit;

Fig. 4 is the circuit theory diagrams of one embodiment of the present invention three-phase current sampled signal modulation circuit;

Fig. 5 is the circuit theory diagrams of one embodiment of the present invention frequency sampling signal modulation circuit;

Fig. 6 is the circuit theory diagrams of one embodiment of the present invention DSP and power module thereof;

Fig. 7 is the circuit theory diagrams of one embodiment of the present invention data storage cell;

Fig. 8 is the circuit theory diagrams of one embodiment of the present invention communication module;

Fig. 9 is the circuit theory diagrams of one embodiment of the present invention LCD MODULE;

Figure 10 is the island effect testing process figure of one embodiment of the present invention multi-process;

Figure 11 is the passive island detection flow charts of one embodiment of the present invention;

Figure 12 is one embodiment of the present invention overvoltage/undervoltage/mistake under-frequency detection method flow chart;

Figure 13 is one embodiment of the present invention SPA sudden phase anomalies detection method flow chart;

Figure 14 is one embodiment of the present invention power-frequency rate of change detection method flow chart;

Figure 15 is initiatively island detection flow charts of one embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing execution mode of the present invention is further specified.

Fig. 1 is the structured flowchart of the island effect checkout gear of multi-process.The island effect checkout gear of multi-process mainly comprises: the power module of signal gathering unit, main control unit, data memory unit, communication unit, liquid crystal display, broken-circuit controller and main control unit.Wherein, signal gathering unit comprises: 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.

In this execution mode; Adopt 3 voltage sensors (VT), 3 current sensors (CT); Be used to gather three-phase voltage and electric current that distributed generation system and grid nodes (PCC node) are located; Wherein, the model of voltage sensor is HNV500T, and the model of current sensor is ACS712ELCTR-05A5ASOP-8.Adopt 1 Frequency tester to gather the frequency that distributed generation system and grid nodes (PCC node) are located, the model of Frequency tester is BT3C.

The signal that utilizes voltage sensor (VT), current sensor (CT) and Frequency tester to collect passes to bandwidth-limited circuit, and described bandwidth-limited circuit is as shown in Figure 2.Frequency signal (the comprising 1 road frequency signal) output of the current signal output end (comprising 3 road current signals) of the voltage signal output end of voltage sensor (VT) (comprising 3 road voltage signals), current sensor (CT) and Frequency tester connects the input u of bandwidth-limited circuit simultaneously _i, the signal that collects is carried out filtering.After filtered signal carries out noise reduction, transformation processing through signal modulation circuit (comprising three-phase voltage sampled signal modulation circuit, three-phase current sampled signal modulation circuit and frequency sampling signal modulation circuit); Output amplitude is the voltage signal of 3.3V, passes to main control unit (for example central processing unit DSP).

The output pin u of bandwidth-limited circuit _oExport 7 road signals, wherein, 3 road voltage signals are connected to the u of three-phase voltage sampled signal modulation circuit _a, u _b, u _cInterface, as shown in Figure 3, the output OUT of three-phase voltage sampled signal modulation circuit _a, OUT _bAnd OUT _cThe signal input part (like the ADCINA0 ADCINA2 end of DSP) that connects main control unit respectively; 3 road current signals are connected to the i of three-phase current sampled signal modulation circuit _a, i _b, i _cInterface, as shown in Figure 4, the output OUT of three-phase current sampled signal modulation circuit _A1, OUT _B1And OUT _C1The signal input part (like the ADCINA3 ADCINA5 end of DSP) that connects main control unit respectively; 1 road frequency signal is connected to the input f of frequency sampling signal modulation circuit _g, as shown in Figure 5, the output OUT of frequency sampling signal modulation circuit _fEnd connects the signal input part (like the ADCINA6 end of DSP) of main control unit.

This execution mode adopts DSP as main control unit; Three-phase voltage, electric current and the electric voltage frequency that is used for that the PCC that collects is ordered carries out the A/D conversion; And the signal after the conversion is carried out island detection detect; According to detection triggers relative trigger control signal, the actuator that drives PCC point place carries out corresponding action.

Its model is TMS320F2812, sees Fig. 6, and Fig. 6 also comprises the power module of DSP, and DSP electric power source pair of module DSP provides the 3.3V that satisfies job requirement voltage.

The output signal of DSP is delivered to data storage cell, communication unit, liquid crystal display and broken-circuit controller; Main respectively storage and the demonstration that realizes the critical data of distributed generation system running status of described data memory unit, liquid crystal display; So that operating personnel understand the running status of system, and make correct processing according to the critical data of record and operate.

In this execution mode, the model of data storage cell is CY7C1041BV, and its data input pin D0～D15 pin links to each other with XD0～XD15 pin of DSP, and A0～A17 pin links to each other with the XA0～XA17 pin of dsp chip.As shown in Figure 7.

Described communication unit is used to realize the network communication of island detection device and host computer, is convenient to the dispatcher distributed generation system is made rational arrangement, realizes the greatest benefit operation of distributed generation system.Adopt the RS485 communications protocol in this execution mode, adopt the MAX232 chip for driving to realize that its circuit theory diagrams are as shown in Figure 8.Its R2OUT, T2IN, R1OUT, T1IN pin link to each other with SCIRXDA, SCITXDA, SCIRXDB, the SCITXDB pin of dsp chip respectively.

Described liquid crystal display adopts LCD to realize; The model of described LCD is LCM12864ZK, and is as shown in Figure 9, and the RS pin of LCD is connected with the IOPF4 pin of TMS320LF2812 chip; The R/W pin of LCD is connected with the IOPF5 pin of DSP; The E pin of LCD is connected with the IOPF6 pin of DSP, and D0～D7 pin is connected with IOPB1～IOPB7 pin of DSP, LCD /the RST pin is connected with the IOPC1 pin of DSP.

Multi-process island detection device produces PWM control wave signal through the I/O mouth of DSP; After this control signal is amplified through signal amplification circuit; Be docked at the control relay that is incorporated into the power networks (model that adopts in this execution mode is the DW15 broken-circuit controller) that PCC orders and carry out the control of on off operating mode, realize the excision operation of distributed generation system islet operation state and the distributed generation system reclosing operation of island state.

One embodiment of the present invention provide the flow process of the island effect detection method of multi-process, and are shown in figure 10.This flow process starts from step 1001.In step 1002; The three-phase voltage, electric current and the frequency that collect are carried out analog-to-digital conversion (for example, utilizing the A/D converter of DSP to realize analog-to-digital conversion), be called the voltage signal that amplitude is 3.3V; And the digital signal after the conversion is carried out normalization handle, deliver to data memory unit and preserve;

In step 1003, initialization system parameter, described system parameters comprise resistance value R, inductance value L and the capacitance C of system;

In step 1004, utilize the data of step 1 storage, the active power P of computing system and reactive power Q, and deposit active power value and reactive power value in the data memory unit preservation;

Wherein, this execution mode adopts three-phase instantaneous power method to calculate active power, reactive power and power-factor angle, and process is following:

Three-phase phase voltage that step 1002 samples and triple line electric current are respectively u _a, u _b, u _c, i _a, i _b, i _c, after the conversion of alpha-beta two phases, obtain u through a, b, c three-phase _α, u _βAnd i _α, i _β

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{\α\β}}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right],$ $\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{\α\β}}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]---\left(1\right)$

In the formula $C_{\mathrm{\α\; \β}}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{3}& -\frac{\sqrt{3}}{2}\end{array}\right]$

In the α-β plane Admiral vector

and

were synthesized for the (rotating) voltage vector

and the current vector

U, i are respectively the mould of vector

in the formula, and is respectively the phase angle of vector .

Calculate instantaneous active current of three-phase circuit and instantaneous reactive current:

Where the power factor angle

U and i _pProduct be the three-phase circuit instantaneous active power, u and i _qProduct be the three-phase circuit instantaneous reactive power.Promptly

p＝ui _p q＝ui _q (3)

In wushu (2) the substitution formula (3):

$\left[\begin{array}{c}p\\ q\end{array}\right]=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{\mathrm{pq}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]---\left(4\right)$

In the formula $C_{\mathrm{Pq}}=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]$

In wushu (1) the substitution formula (4):

P＝u _ai _a+u _bi _b+u _ci _c $Q=\frac{1}{\sqrt{3}}[(u_b-u_c)i_a+(u_c-u_a)i_b+(u_a-u_b)i_c]$

In step 1005, the data in the data storage are sent into the CPU of DSP, carry out passive island detection, judge whether isolated island takes place, shown in figure 11.This flow process starts from 1101.In step 1102; (1) utilizes overvoltage/undervoltage/mistake under-frequency detection method; The active power degree of unbalance

that calculating distributed generation system and grid nodes (PCC node) are located and the degree of unbalance of reactive power , flow process is shown in figure 12.This flow process starts from step 1201.In step 1202; Calculate the degree of unbalance of active power degree of unbalance and reactive power

, formula is following:

$\frac{\mathrm{\ΔP}}{P}=1-\frac{u_p^2}{u_g^2},$ $\frac{\mathrm{\ΔQ}}{Q}=\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}\frac{\mathrm{\ΔP}}{P}-(\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}-1)\frac{Q_Z}{Q}-\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}+1$

In the formula: ω _gBe the electrical network angular frequency, and ω is arranged _g=2 π f _g, f _gBe mains frequency; ω _pBe PCC place angular frequency, and ω is arranged _p=2 π f _p, f _pBe PCC node place frequency; u _gBe line voltage; u _pBe PCC node place voltage; Q _ZIdle on the resonant capacitance, and have $Q_Z={\mathrm{\ω}}_g{\mathrm{Cu}}_g^2.$

In step 1203, active power degree of unbalance that calculates

and reactive power degree of unbalance

are stored to data memory unit.

(2) utilize the SPA sudden phase anomalies detection method, calculating voltage phase angle and current phase angle, its flow process is shown in figure 13.This flow process starts from step 1301.In step 1302, measure through voltage sensor and to be separated by

Two instantaneous voltage u _n, u _N-1, current sensor is measured and is separated by

Two current instantaneous value i _n, i _N-1Calculate voltage phase angle and current phase angle, formula is following:

In the formula,

is voltage phase angle;

is current phase angle.

In step 1303, substitution formula

that step 1302 is calculated obtains voltage and the upper phase angle θ of electric current.

In step 1304, the electric current and voltage phase angle θ that step 1103 is calculated deposits data storage cell in.

(3) utilize power/frequency rate of change detection method, calculate rate of change, the rate of change of reactive power and the rate of change of frequency of the active power at PCC node place, flow process is shown in figure 14.This flow process starts from step 1401.In step 1402, calculate rate of change, the rate of change of reactive power and the rate of change of frequency of the active power at PCC node place, formula is following:

$\frac{\∂P}{\∂t}=\frac{P_n-P_{n-1}}{\mathrm{\Δt}},$ $\frac{\∂Q}{\∂t}=\frac{Q_n-Q_{n-1}}{\mathrm{\Δt}},$ $\frac{{\∂f}_P}{\∂t}=\frac{f_{\mathrm{Pn}}-f_{\mathrm{Pn}-1}}{\mathrm{\Δt}}$

In the formula, the system data that n, n-1 represent respectively the n time and the n-1 time sampling obtains; Δ t representes the time interval of the n time and the n-1 time sampling;

is the frequency at the PCC node place that collects for the n time,

be the frequency at the PCC node place that collects for the n-1 time.

In Step 1403: the calculated rate of change of active power

reactive power change rate

and the frequency change rate

stored in the data storage unit.

In step 1103, the electric current and voltage phase angle θ that the active power that (1) step 1102 is calculated and degree of unbalance (2) step 1106 of reactive power calculate; (3) rate of change

of rate of change

reactive power of the active power that calculates of step 1108 and the interconversion rate

of frequency are updated to passive island detection overall target judgement schematics; Calculate overall target and estimate β, formula is following:

$\mathrm{\β}=\frac{{\mathrm{\θ}}^2}{\mathrm{\π}}\sqrt{\frac{{(\mathrm{\ΔP}/P)}^2}{\cos \mathrm{\θ}}(1+\frac{(\∂Q/\∂t)}{\ln (\∂P/\∂t)})+\frac{{(\mathrm{\ΔQ}/Q)}^2}{\cos \mathrm{\θ}}(1+\frac{(\∂f_P/\∂t)}{\ln (\∂P/\∂t)})}$

In step 1104, whether judge passive detection comprehensive evaluation index value β less than 10, if satisfy, then carry out 1105, otherwise execution in step 1106.

In step 1105, explain passive island detection to the distributed generation system testing result for normally being incorporated into the power networks, launch island detection flow process initiatively this moment the result of passive island detection checked execution in step 1006;

In step 1106, because of β＞10, explain that distributed generation system has been in island state, this moment, the DSP of system sent PWM ripple driving broken-circuit controller, and distributed generation system is excised from electrical network.

In step 1107, finish.

In step 1006, utilize active shift frequency method to carry out the active island detection, shown in figure 15.This flow process starts from step 1501.In step 1502, change inverter output current i _InvAngular frequency,

In step 1503, gather three-phase voltage, the current value at PCC node place, and calculate the voltage after the disturbance, the phase angle of electric current

Angular frequency value ω with PCC node place after the disturbance _P, wherein, ω _p=2 π f _p

In step 1504: calculate the impedance angle of distributed generation system, formula is following:

If distributed generation system is in island state, then the difference of the phase angle of PCC voltages at nodes, electric current

equals load impedance angle

promptly has:

In step 1505, calculate the initiatively frequency swing ω of shift frequency method _MaxAnd ω _Min, formula is following:

In step 1506, compare the angular frequency at PCC node place _PIf, ω _PDo not satisfy the normal ω of relation _Min＜ω _P＜ω _Max, explain that the result of passive detection is incorrect, execution in step 1508, otherwise execution in step 1507.

In step 1507, the result of bright passive detection is correct, execution in step 1509.

In step 1508, at this moment, DSP sends the PWM ripple and drives broken-circuit controller, distributed generation system is excised from electrical network, and execution in step 1509;

Finish in step 1509.

In step 1007, distributed generation system is in the islet operation state, utilizes communication unit and host computer to carry out telecommunication, excises from electrical network to operating personnel's prompt system.

In step 1008, the data that are stored in data storage element show through the state that display unit carries out distributed generation system, to the system overhaul personnel maintenance foundation are provided.

In step 1009; For the distributed generation system that has excised from electrical network; The island detection device can carry out active detecting to distributed generation system through the active island detection; Judge that whether distributed generation system satisfies the requirement of being incorporated into the power networks again, if satisfy, then DSP sends the PWM ripple and drives broken-circuit controller distributed generation system is incorporated into the power networks again.

On the basis of Figure 10 described perhaps more flow chart, need not creationary work for those skilled in the art in the present technique field and can develop one or more software to Figure 15.The software of developing like this will be carried out Figure 10 to the described passive island detection flow process of Figure 14, active island detection flow process shown in Figure 15.Described software is kept in the main control unit (DSP).

Though more than described embodiment of the present invention, the those of skill in the art in the present technique field should be appreciated that these only illustrate, and can make numerous variations or modification to these execution modes, and not deviate from principle of the present invention and essence.Scope of the present invention is only limited appended claims.

Claims (4)

1. the island effect detection method of a multi-process, process is following:

Step 1: the three-phase voltage that collects, electric current and frequency are carried out filtering, noise reduction, transformation processing and analog-to-digital conversion, and the digital signal after the conversion is carried out normalization handle, deliver to data memory unit and preserve;

Step 2: initialization system parameter, described system parameters comprise resistance value R, inductance value L and the capacitance C of system;

Step 3: utilize the data of step 1 storage, the active power P of computing system and reactive power Q, and deposit active power value and reactive power value in the data memory unit preservation;

It is characterized in that: further comprising the steps of:

Step 4: the data in the data storage are sent into the CPU of DSP, carry out passive island detection, judge whether isolated island takes place, and method is: (1) utilizes overvoltage/undervoltage/mistake under-frequency detection method to calculate the degree of unbalance of active power and reactive power; (2) utilize SPA sudden phase anomalies detection method calculating voltage current phase declinate; (3) utilize power/frequency rate of change detection method to calculate the interconversion rate of active power interconversion rate, reactive power interconversion rate and frequency; Utilize the result of above-mentioned (1) (2) (3); Calculate passive detection comprehensive evaluation index value,, explain that distributed generation system is the state that normally is incorporated into the power networks if this value is less than or equal to 10; Utilization active island detection flow process is checked execution in step 5 to the result of passive island detection; This value explains that greater than 10 distributed generation system has been in island state, and this moment, the DSP of system sent PWM ripple driving broken-circuit controller, and distributed generation system is excised from electrical network;

Step 5: the active island detection, method is: utilize the initiatively maximum ω of shift frequency method calculating frequency shift _MaxWith minimum value ω _Min, formula is following:

In the formula,

is voltage phase angle;

is current phase angle;

Calculate the angular frequency at distributed generation system and grid nodes place _P, and ω is arranged _p=2 π f _pIf do not satisfy ω _Min＜ω _P＜ω _Max, explain that the result of passive detection is incorrect, this moment, DSP sent PWM ripple driving broken-circuit controller, and distributed generation system is excised from electrical network; Otherwise the result that passive detection is described is correct, execution in step 6;

Step 6: distributed generation system is in the islet operation state, utilizes communication unit and host computer to carry out telecommunication, excises from electrical network to operating personnel's prompt system;

Step 7: the data that are stored in data storage element show through the state that display unit carries out distributed generation system, to the system overhaul personnel maintenance foundation are provided;

Step 8: for the distributed generation system that has excised from electrical network; The island detection device can carry out active detecting to distributed generation system through the active island detection; Judge whether distributed generation system satisfies the requirement of being incorporated into the power networks again; If satisfy, then DSP sends the PWM ripple and drives broken-circuit controller distributed generation system is incorporated into the power networks again.

2. the island effect detection method of multi-process according to claim 1, it is characterized in that: the described passive island detection of step 4 may further comprise the steps:

Step 4-1: utilize overvoltage/undervoltage/mistake under-frequency detection method; The active power degree of unbalance

that calculating distributed generation system and grid nodes (PCC node) are located and the degree of unbalance of reactive power

, formula is following:

$\frac{\mathrm{\ΔP}}{P}=1-\frac{u_p^2}{u_g^2},$ $\frac{\mathrm{\ΔQ}}{Q}=\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}\frac{\mathrm{\ΔP}}{P}-(\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}-1)\frac{Q_Z}{Q}-\frac{{\mathrm{\ω}}_g}{{\mathrm{\ω}}_P}+1$

In the formula: ω _gBe the electrical network angular frequency, and ω is arranged _g=2 π f _g, f _gBe mains frequency; ω _pBe PCC place angular frequency, and ω is arranged _p=2 π f _p, f _pBe PCC node place frequency; u _gBe line voltage; u _pBe PCC node place voltage; Q _ZIdle on the resonant capacitance, and have $Q_Z={\mathrm{\ω}}_g{\mathrm{Cu}}_g^2;$

Step 4-2: the calculated active power imbalance

and reactive power imbalance

Save to data memory unit;

Step 4-3: utilize the SPA sudden phase anomalies detection method, calculating voltage phase angle and current phase angle:

Measure through voltage sensor and to be separated by

Two instantaneous voltage u _n, u _N-1, current sensor is measured and is separated by

Two current instantaneous value i _n, i _N-1, calculating voltage phase angle and current phase angle, formula is following:

Step 4-4: Step 4-3 calculated

into the formula

get the upper phase angle of voltage and current θ;

Step 4-5: the electric current and voltage phase angle θ that step: 4-4 is calculated deposits data storage cell in;

Step 4-6: utilize power/frequency rate of change detection method, calculate rate of change, the rate of change of reactive power and the rate of change of frequency of the active power at PCC node place, formula is following:

$\frac{\∂P}{\∂t}=\frac{P_n-P_{n-1}}{\mathrm{\Δt}},$ $\frac{\∂Q}{\∂t}=\frac{Q_n-Q_{n-1}}{\mathrm{\Δt}},$ $\frac{{\∂f}_P}{\∂t}=\frac{f_{\mathrm{Pn}}-f_{\mathrm{Pn}-1}}{\mathrm{\Δt}}$

In the formula, the system data that n, n-1 represent respectively the n time and the n-1 time sampling obtains; Δ t representes the time interval of the n time and the n-1 time sampling;

is the frequency at the PCC node place that collects for the n time,

be the frequency at the PCC node place that collects for the n-1 time;

Step 4-7: The calculated rate of change of active power

reactive power change rate

and the frequency change rate stored in the data storage unit.

3. the island effect detection method of multi-process according to claim 1, it is characterized in that: the computing formula of the described passive detection comprehensive evaluation index value of step 4 is following:

$\mathrm{\β}=\frac{{\mathrm{\θ}}^2}{\mathrm{\π}}\sqrt{\frac{{(\mathrm{\ΔP}/P)}^2}{\cos \mathrm{\θ}}(1+\frac{(\∂Q/\∂t)}{\ln (\∂P/\∂t)})+\frac{{(\mathrm{\ΔQ}/Q)}^2}{\cos \mathrm{\θ}}(1+\frac{(\∂f_P/\∂t)}{\ln (\∂P/\∂t)})}$

4. realize the device of the island effect detection method of the described multi-process of claim 1, it is characterized in that: comprising:

Signal gathering unit: be used to gather three-phase voltage, electric current and the frequency at distributed generation system and grid nodes place and the signal that collects is carried out filtering, noise reduction, transformation processing;

Main control unit: be used for the signal that signal gathering unit collects is further handled, carry out passive island detection and active island detection, and according to testing result, the control distributed generation system is connected and shutoff with electrical network;

Data memory unit: the interconversion rate that is used to store degree of unbalance, electric current and voltage phase angle, active power interconversion rate, reactive power interconversion rate and the frequency of active power and reactive power;

Communication unit: be used to realize the network communication of island effect checkout gear and host computer.

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