CN103227478B - Controlling algorithm for anti-islanding detection test load device - Google Patents

Abstract

The invention provides a controlling algorithm for an anti-islanding detection test load device. The controlling algorithm comprises the steps of collecting the grid voltages ea, eb and ec, and converting the grid voltages ea, eb and ec under a polar coordinate to solve an amplitude E of the grid voltages; carrying out phase locked tracking on the grid voltages ea, eb and ec to obtain a grid angular frequency omega; calculating the active power and the reactive power which are output by the anti-islanding detection test load device by utilizing the grid amplitude E, the grid frequency omega and given values R, L and c; collecting the currents ia, ib and ic output by a B inverter bridge of the device, and carrying out coordinate conversion on the currents ia, ib and ic to obtain e alpha and e beta; respectively sending the two differences to a PI (Proportional Integral) regulator to obtain Ub and Uq; converting a two-phase rotary coordinate system to a three-phase rotary coordinate system to obtain Ua, Ub and Uc; and finally, obtaining a driving wave of each phase through SPWM (Sinusoidal Pulse Width Modulation), decomposing the driving waves to obtain twelve-path driving pulses, and sending the twelve-path driving pulses to each power tube in a three-phase H bridge inverter. By utilizing the controlling algorithm, the volume of the anti-islanding detection test load device is small, the thermal drift phenomenon and parasitic amount compensation do not exist, and the load characteristics can be automatically regulated by a program according to the grid-connected power, therefore, the accuracy is high, and the reaction is rapid.

Description

A kind of anti-islanding detect experiment load device control algolithm

Technical field

The present invention relates to electric and electronic technical field, refer in particular to a kind of anti-islanding detect experiment load device control algolithm.

Background technology

When mains supply trips because of failure accident or power failure maintenance, fail to detect power down mode in time due to each distributed grid-connected electricity generation system and self cut off electricity network, the isolated island electricity generation system being made up of a self-energizing distributed generation system and its connected load will be formed.Thus safety hazard can be caused to transmission line of electricity maintenance personal, also can cause damage to some electrical equipments.

Existing isolated island detecting device: RLC load box major loop by resistive load, inductive load and capacitive load three part form, three fractional loads are by load box built-in switch Discrete control, automatic, manual loading adjustment can be realized in remote software, resistive, perceptual, capacitive part all can independent assortment, and compensates the parasitic capacitance in RLC load, stray inductance, parasitic resistance values.

The function that existing RLC load box will possess usually has: one is that required precision is high, loading procedure resistance-inductance-capacitance value is not drifted about with temperature; Two is that stepping amplitude is little but the most important thing is that parasitic amount compensates and remote control function must have, otherwise can not be suitable for.Detect the RLC load of isolated island, the every deviation 3% of L and C, resonant frequency meeting deviation 0.8Hz, conventional load to meet, so RLC load must have parasitic amount to compensate, but the compensation of parasitic amount is difficult to accomplish real-time fine compensation, actual RLC load and calculated value can be caused to have certain deviation.The harmonic content being exactly RLC load itself is in addition less than 2%.During long-time test, load box resistance R heating causes resistance thermal drift to cause resistance value to change, and affects the precision of RLC load.Owing to will accomplish can to detect island effect simultaneously in order to the stepping amplitude meeting required precision RLC load is as far as possible little to the combining inverter of different capacity, so the volume of RLC load box is usually all very large.

The resistance of this load simulating device, electric capacity even load size adopt mechanical type adjustment to need the combination of a lot of components and parts, so expensive, and service life is low.Wherein the active power of load is completely by resistance consumption, so when carrying out high-power combining inverter test experience, can consume a large amount of electric energy, causing environmental pollution.

Adopt converter device to simulate the characteristic of RLC load in parallel, islanding detect is carried out to distributed power generation combining inverter.This device adopts three-phase H bridge construction inverter circuit, and the control inverter that needs according to fictitious load exports certain active power and reactive power.Utilize active power and reactive power and grid-connected point voltage can obtain external R, L, C characteristic of this device, therefore can be completely achieved the single or combined characteristic of resistance, inductance, electric capacity by controlling three-phase inverting circuit, thus the parallel network reverse device of RLC shunt load to different capacity can be replaced carry out islanding detect.

Summary of the invention

The object of the present invention is to provide a kind of inverter and low capacity RLC load box to replace the device that RLC load box also can embody RLC load characteristic, a kind of anti-islanding detect experiment load device control algolithm is mainly provided.By controlling active power that current transformer exports and reactive power and adjustment low capacity RLC load box regulate the characteristic accurately embodying RLC load, to meet the requirement of the parallel network reverse device islanding detect of different capacity.This device volume is little, there is not thermal drift phenomenon and parasitic amount compensation, can according to grid-connected power by the automatic regulating load characteristic of programme-control, and thus precision is high, and reaction is fast.

The present invention adopts following scheme:

A kind of anti-islanding detect experiment load device control algolithm, is made up of following steps:

Step one, collection line voltage e _a, e _b, e _c, under being transformed to polar coordinates, try to achieve the amplitude E of line voltage;

Step 2, to line voltage e _a, e _b, e _ccarry out phase locked track and obtain electrical network angular frequency;

Step 3, utilize voltage magnitude E, mains frequency ω and given R, L, C value to calculate the experiment of anti-isolated island to detect the active power and reactive power that load device exports, using this active power and the reactive power given reference value P as control section power ring ^*and q ^*;

Step 4, gather this device B inverter bridge export current i _a, i _b, i _c, coordinate transform is carried out to it, under transforming to two-phase rest frame, obtains i _a, i _β.To the line voltage e gathered _a, e _b, e _ccarry out identical coordinate transform, obtain e _α, e _β, active-power P and the reactive power q of actual this device output is calculated according to formula (8);

Step 5, the respectively given reference value P of calculating active power ^*with difference, the given reference value q of reactive power of actual active power p ^*with the difference of actual reactive power q, these two differences are sent into pi regulator respectively and obtains U _d, U _q;

Step 6, the conversion being tied to three-phase static coordinate system through a two-phase rotational coordinates obtain U _a, U _b, U _c;

Step 7, eventually pass SPWM modulation and obtain the driving ripple of each phase, obtain 12 road driving pulses send into each power tube in three-phase H bridge inverters through decomposing.

A kind of combined type anti-islanding detect experiment load device, is connected and composed successively by dc source, simulation RLC load device, low capacity RLC load device, wherein:

Described dc source, for the inverter of anti-islanding detect experiment load device provides direct current;

Described simulation RLC load device is three phase full bridge inverter structure or three-phase H bridge inverter structure, and according to the power requirement of actual islanding detect, control inverter exports certain active power and reactive power;

Described low capacity RLC load device, according to system requirements, can make up the deficiency of inverter control precision, carry out accurate adjustment to load.

Its principle of the control section of technical solution of the present invention as shown in Figure 6

6.1 gather line voltage e _a, e _b, e _c, under being transformed to polar coordinates, try to achieve the amplitude E of line voltage;

$\left(\begin{array}{c}{e}_{\mathrm{\α}}\\ e_{\mathrm{\β}}\end{array}\right)=\frac{2}{3}\×\left(\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right)\×\left(\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right)$ Formula (1)

$E=\sqrt{{e_{\mathrm{\α}}}^2+{e_{\mathrm{\β}}}^2}$ Formula (2)

6.2 couples of line voltage e _a, e _b, e _ccarry out phase locked track and obtain electrical network angular frequency; Figure 5 shows that phase lock control block diagram, be input as e _α, e _β, feedback phase angle output obtains electrical network angular frequency; In Fig. 5,1 is Park conversion, and transformation for mula is as follows

2 is proportional and integral controller, and 3 is integrator, works as e _qwhen=0, ω is the angular frequency of electrical network;

6.3 utilize voltage magnitude E, mains frequency ω and given R, L, C value to calculate the experiment of anti-isolated island detects the active power and reactive powers that load device exports, using this active power and the reactive power given reference value P as control section power ring ^*and q ^*.

$i_d=\frac{E}{R}$ Formula (4)

$i_q=\mathrm{E\ωC}-\frac{E}{\mathrm{\ωL}}$ Formula (5)

P ^*=i _d* E formula (6)

Q ^*=i _q* E formula (7)

The current i that 6.4 this device of collection B inverter bridge export _a, i _b, i _c, coordinate transform is carried out to it, under transforming to two-phase rest frame, obtains i _a, i _β.To the line voltage e gathered _a, e _b, e _ccarry out identical coordinate transform, obtain e _α, e _β, active-power P and the reactive power q of actual this device output is calculated according to formula (8).

P=e*i*cos θ=e*i*cos (θ ₁-θ ₂) formula (8)

q=e*i*cosθ=e*i*sin(θ ₁-θ ₂)

See Fig. 6, obtained by formula (8) abbreviation $\left(\begin{array}{c}P\\ q\end{array}\right)=\left(\begin{array}{cc}{e}_{\mathrm{\α}}& e_{\mathrm{\β}}\\ e_{\mathrm{\β}}& {-e}_{\mathrm{\α}}\end{array}\right)\left(\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right)$ Formula (9)

6.5 Fig. 7 calculate the given reference value P of active power respectively ^*with difference, the given reference value q of reactive power of actual active power p ^*with the difference of actual reactive power q, these two differences are sent into pi regulator respectively and obtains U _d, U _q.In Fig. 7,1 and 2 is error comparator, and 3 and 4 is proportional and integral controller.

6.6 conversion being tied to three-phase static coordinate system through a two-phase rotational coordinates obtain U _a, U _b, U _cnamely

Eventually pass the driving ripple that SPWM modulation obtains each phase, through decomposing each power tube obtained in 12 road driving pulses feeding three-phase H bridge inverters.

6.7 anti-island protect test methods

The experimental condition of table 1 isolated island effect prevention protection

Load not matching state table in table 2 experimental condition A situation

Load not matching state in 3 experimental condition B and experimental condition C situation

The deviation percent (%) of the active power of load consumption, reactive power and rated value in test
	0，-5
0，-4
	0，-3
0，-2
	0，-1
0，1
	0，2
0，3
	0，4
0，5

Fig. 1 gives isolated island effect prevention protection test platform, and air switch K1 is the net side separating switch of tested inverter, and K2 is the load separating switch of tested inverter.Load adopts three-phase H bridge inverter structure.Test should be carried out under the conditions specified in table 1, and test procedure is as follows:

A) closed K1, disconnects K2, starts inverter to be measured, by regulating direct current input source, makes the power output P of inverter equal specified output AC power, and measures the reactive power q of inverter output;

B) inverter is shut down, disconnect K1;

C) value of R, L, C is set by the host computer of anti-islanding detect experiment load device, makes load quality factor Q _f=1.0 ± 0.05;

D) closed K2 accesses anti-islanding detect experiment load device, closed K1, start inverter to be measured, confirm that its power output meets step regulation a), by anti-islanding detect experiment load device interface, the value of R, L, C arranged, when output current to differ with target current value be less than 2% time, startup low capacity RLC load regulation R, L, C until when the Fundamental-frequency Current that flows through K1 is less than stable state inverter output-current rating 1%;

E) disconnect K1, record K1 be disconnected to inverter output current decline and maintain output-current rating less than 1% between time;

F) the R value on anti-islanding detect experiment load device host computer and arbitrary L or C value is regulated, to obtain the load not matching state of dash area Parametric Representation in following table 2; Parametric Representation in table 2 be the percentage of deviation, what symbol represented is flow through the active power stream of K switch 1 and the direction of reactive power flow in Fig. 1, and positive sign represents that poower flow is from inverter to electrical network; After each adjustment, all should record K1 be disconnected to inverter output current decline and maintain output-current rating less than 1% between time; If the time of record has any one to exceed step e) the middle time of recording, then in table 2, non-shaded portion parameter also should be tested.

G) for experimental condition B and C, regulate arbitrary L or C value, make it to change 1% by the regulation of table 2 at every turn.Parametric Representation in table 3 be the direction of the reactive power flow flowing through K switch 1 in Fig. 1, positive sign represents that poower flow is from inverter to electrical network; After each adjustment, record K1 be disconnected to inverter output current decline and maintain output-current rating less than 1% between time; If the time of record is in rising trend, then should continue to expand adjustable range with the increment of 1%, until the time of record is on a declining curve.

Relative to existing RLC load box, the present invention has following characteristics:

A. the resistance value of this anti-islanding detect experiment load device, inductance value, capacitance can sets itself on host computer according to actual needs, easy to operate.

B. this device is with energy-feedback power grid of gaining merit, a large amount of energy loss reduced in experimentation; And due to the adjustment of load abandoning mechanical system, improve the service life of experimental facilities, decrease the maintenance cost of experimental facilities; Also obvious advantage will be had in addition in volume and weight.

C. replace RLC load box with current transformer, and accurately realize single characteristic or the combined characteristic of RLC.Control and regulation ratio adjusts actual resistance, inductance and electric capacity controls electric current, voltage direction is more convenient, and precision is more accurate, and speed is also faster.

D. because there is no the device consumed energies such as the high-power resistance of actual physics and produce amount of heat, therefore, green energy conservation.

E. semiconductor device application technology

Relative to simple inverter load simulating device:

A. be equipped with low capacity RLC load device in system, make load regulation meticulousr.

Beneficial effect of the present invention: use the anti-islanding detect experiment load device controlling this algorithm to have following beneficial effect: a. isolated island device volume is less, lighter in weight, and R, L, C add carried convenient, only just can accurately need realize by artificially setting.

B. there is not thermal drift, do not need parasitic amount to compensate, thus precision is higher.

C. because replace RLC load box with current transformer, do not need to carry out switch on-off in RLC load box according to power demand, thus response is fast.

D. control flexibly, easy to operate.

E. add low capacity RLC load in system, compensate in converterization control, the problem of control step limited precision, makes final control accuracy be better than the mode adopting merely inverter to simulate.

Accompanying drawing explanation

Fig. 1. system principle diagram;

Fig. 2. three phase full bridge inverter structure;

Fig. 3. three-phase H bridge inverter structure 1;

Fig. 4. three-phase inversion bridge construction 2;

Fig. 5 .RLC load circuit figure;

Fig. 6. control flow chart;

Fig. 7. phase lock control block diagram;

Fig. 8. Current Voltage polar plot;

Fig. 9 .PI adjuster.

Detailed description of the invention

Fig. 1 is the system principle diagram of anti-islanding detect experiment load device, by current transformer simulation RLC load characteristic, replaces the island effect that RLC load box detects photovoltaic power generation grid-connecting apparatus in practice.The main circuit diagram of this device mainly contains three parts: S dc source, for the inverter of anti-islanding detect experiment load device provides direct current; B is simulation RLC load device, three phase full bridge inverter structure (circuit diagram as shown in Figure 2) or three-phase H bridge inverter structure (circuit diagram as shown in Figure 3 and Figure 4) can be adopted, and according to the power requirement of actual islanding detect, control inverter exports certain active power and reactive power; C, D, E are low capacity RLC load device, and as shown in Figure 5, this part according to system requirements, can make up the deficiency of inverter control precision to circuit diagram, carries out accurate adjustment to load.

A kind of anti-islanding detect experiment load device control algolithm, is made up of following steps:

Step one, collection line voltage e _a, e _b, e _c, under being transformed to polar coordinates, try to achieve the amplitude E of line voltage;

Step 2, to line voltage e _a, e _b, e _ccarry out phase locked track and obtain electrical network angular frequency;

Step 3, utilize voltage magnitude E, mains frequency ω and given R, L, C value to calculate the experiment of anti-isolated island to detect the active power and reactive power that load device exports, using this active power and the reactive power given reference value P as control section power ring ^*and q ^*;

Step 4, gather this device B inverter bridge export current i _a, i _b, i _c, coordinate transform is carried out to it, under transforming to two-phase rest frame, obtains i _a, i _β.To the line voltage e gathered _a, e _b, e _ccarry out identical coordinate transform, obtain e _α, e _β, active-power P and the reactive power q of actual this device output is calculated according to formula (8);

Step 5, the respectively given reference value P of calculating active power ^*with difference, the given reference value q of reactive power of actual active power p ^*with the difference of actual reactive power q, these two differences are sent into pi regulator respectively and obtains U _d, U _q;

Step 6, the conversion being tied to three-phase static coordinate system through a two-phase rotational coordinates obtain U _a, U _b, U _c;

Step 7, eventually pass SPWM modulation and obtain the driving ripple of each phase, obtain 12 road driving pulses send into each power tube in three-phase H bridge inverters through decomposing.

Claims (1)

1. an anti-islanding detect experiment load device control algolithm, described anti-islanding detect experiment load device, connected and composed successively by dc source, simulation RLC load device, low capacity RLC load device, wherein: described dc source, for the inverter of anti-islanding detect experiment load device provides direct current; Described simulation RLC load device is three phase full bridge inverter structure or three-phase H bridge inverter structure, and according to the power requirement of actual islanding detect, control inverter exports certain active power and reactive power; It is characterized in that being made up of following steps:

Step one, collection line voltage e _a, e _b, e _c, under being transformed to polar coordinates, try to achieve the amplitude E of line voltage;

Step 2, to line voltage e _a, e _b, e _ccarry out phase locked track and obtain electrical network angular frequency;

Step 3, utilize voltage magnitude E, electrical network angular frequency and given simulation RLC load device R, L, C value to calculate the experiment of anti-isolated island to detect the active power and reactive power that load device exports, using this active power and the reactive power given reference value P as control section power ring ^*and q ^*;

Step 4, gather the current i that anti-islanding detect experiment load device inverter structure exports _a, i _b, i _c, coordinate transform is carried out to it, under transforming to two-phase rest frame, obtains i _α, i _β, to the line voltage e gathered _a, e _b, e _ccarry out identical coordinate transform, obtain e _α, e _β, according to formula (8) p=e*i*cos θ=e*i*cos (θ ₁-θ ₂), q=e*i*sin θ=e*i*sin (θ ₁-θ ₂), calculate active-power P and the reactive power q of the output of actual anti-islanding detect experiment load device, wherein e is the space voltage vector of electrical network three-phase voltage equivalence synthesis, i is the Space current vector exporting three-phase current equivalence synthesis, θ is the angle of e and i, θ 1 is e and e α angle, and θ 2 is the angle of e and e β;

Step 5, the respectively given reference value P of calculating active power ^*with difference, the given reference value q of reactive power of actual active power p ^*with the difference of actual reactive power q, these two differences are sent into pi regulator respectively and obtains U _d, U _q;

Step 6, the conversion being tied to three-phase static coordinate system through a two-phase rotational coordinates obtain U _a, U _b, U _c; Step 7, eventually pass SPWM modulation and obtain the driving ripple of each phase, obtain 12 road driving pulses send into each power tube in simulation RLC load devices through decomposing.