CN103235227A - Combined anti-island detection experiment load device - Google Patents

Abstract

The invention provides a combined anti-island detection experiment load device. The combined anti-island detection experiment load device comprises a direct-current power supply, a simulated RLC load unit and small-capacity RLC load units, which are sequentially connected; the direct-current power supply supplies direct-current power to an inverter of the anti-island detection experiment load device; the simulated RLC load unit is of a three-phase full-bridge inverter structure or a three-phase H-bridge inverter structure, and according to the power requirement of actual island detection, the inverter is controlled to output certain active power and reactive power; and the small-capacity RLC load units can make up for the deficiency of inverter control precision to accurately adjust load according to system requirements. The device is small, the phenomenon of thermal drift and parasitic compensation do not exist, and the device can be controlled by a program to automatically adjust load characteristics according to grid-connected power, so precision is high and response is fast.

Description

A kind of combined type is prevented isolated island test experience load device

Technical field

The present invention relates to electric and electronic technical field, refer in particular to the anti-isolated island test experience load device of a kind of combined type.

Background technology

When mains supply barrier accident or when having a power failure maintenance and tripping operation for some reason, because each distributed grid-connected system is failed in time to detect power down mode and will self be cut off electricity network, will form by the distributed generation system load that links to each other with it and form the isolated island electricity generation system of a self-energizing.Thereby can cause safety hazard to the transmission line of electricity maintenance personal, also can cause damage to some consumers.

Existing isolated island pick-up unit: RLC load box major loop is made up of resistive load, inductive load and capacitive load three parts, three fractional loads are controlled by the segmentation of load box built-in switch, can realize automatic, manual loading adjusting in remote software, but resistive, perceptual, capacitive part is independent assortment all, and the stray capacitance in the RLC load, stray inductance, parasitic resistance values are compensated.

The function that existing RLC load box will possess usually has: the one, and accuracy requirement height, loading procedure resistance inductance capacitance value are not drifted about with temperature; The 2nd, the stepping amplitude will be little but the most important thing is that parasitic amount compensation 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, resonance frequency meeting deviation 0.8Hz, conventional load is to satisfy, so the RLC load must have the parasitic amount compensation, but the compensation of parasitic amount is difficult to accomplish real-time fine compensation, can cause actual RLC load and calculated value that certain deviation is arranged.The harmonic content that is exactly RLC load itself in addition is less than 2%.The heating of load box resistance R causes that the resistance thermal drift causes resistance value to change, and influences the precision of RLC load during long-time the test.Owing to will accomplish to detect island effect simultaneously for the stepping amplitude that satisfies accuracy requirement RLC load is as far as possible little, so the volume of RLC load box is all very big usually to the combining inverter of different capacity.

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

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

Summary of the invention

The object of the present invention is to provide and a kind ofly replace the RLC load box and can embody the device of RLC load characteristic with inverter and low capacity RLC load box.Active power and reactive power by control current transformer output are regulated the characteristic that accurately embodies the RLC load with adjusting low capacity RLC load box, with the requirement of the parallel network reverse device isolated island detection of satisfying different capacity.This device volume is little, does not have the compensation of thermal drift phenomenon and parasitic amount, can be according to the power that is incorporated into the power networks by the automatic regulating load characteristic of programmed control, thereby the precision height, reaction is fast.

The present invention adopts following scheme: a kind of combined type is prevented isolated island test experience load device, connected and composed successively by direct supply, simulation RLC load device, low capacity RLC load device, wherein:

Described direct supply is for the inverter of preventing isolated island test experience 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 the power requirement that detects according to actual isolated island, active power and reactive power that control inverter output is certain;

Described low capacity RLC load device can remedy the deficiency of inverter control accuracy according to system requirements, and load is accurately adjusted.

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, it is transformed to the amplitude E that tries to achieve line voltage under the polar coordinates;

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

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

6.2 to line voltage e _a, e _b, e _cCarry out phase locked track and obtain the electrical network angular frequency; Figure 5 shows that phaselocked loop control block diagram, be input as e _α, e _β, the feedback phase angle Output obtains the electrical network angular frequency; 1 is the Park conversion among Fig. 5, and transformation for mula is as follows

Formula (3)

2 is proportional and integral controller, and 3 is integrator, works as e _q=0 o'clock, ω was the angular frequency of electrical network;

6.3 utilize voltage magnitude E, mains frequency ω and given R, L, C value to calculate active power and reactive power that anti-isolated island experiment detects load device output, with this active power and the reactive power given reference value P as the 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)

6.4 gather the current i of this device B inverter bridge output _a, i _b, i _c, it is carried out coordinate transform, transform under the two-phase rest frame and obtain i _a, i _βTo the line voltage e that gathers _a, e _b, e _cCarry out identical coordinate transform, obtain e _α, e _β, calculate active power P and the reactive power q that actual this device is exported 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)

Referring to Fig. 6, got 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 calculates the given reference value P of active power respectively ^*The given reference value q of difference, reactive power with actual active power p ^*With the difference of actual reactive power q, these two differences are sent into pi regulator respectively obtain U _d, U _q1 and 2 is error comparator among Fig. 7, and 3 and 4 is proportional and integral controller.

6.6 the conversion that is tied to the three phase static coordinate system through a two-phase rotational coordinates obtains U _a, U _b, U _cNamely

Formula (10)

Finally by crossing the driving ripple that the SPWM modulation obtains each phase, obtain ten two road driving pulses and send into each power tube in the three-phase H bridge inverter through decomposing.

6.7 anti-isolated island protection test method

The test condition of table 1 isolated island effect prevention protection

Load under the table 2 test condition A situation situation that do not match

Load under table 3 test condition B and the test condition C situation situation that do not match

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

0，-1
	0，1
0，2
	0，3
0，4
	0，5

Fig. 1 has provided 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.Three phase full bridge inverter structure or three-phase H bridge inverter structure are adopted in load.Test should be carried out under table 1 defined terms, and test procedure is as follows:

A) closed K1 disconnects K2, starts inverter to be measured, by regulating the direct current input source, makes the output power P of inverter equal specified interchange output 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-isolated island test experience load device, makes load quality factor Q _f=1.0 ± 0.05;

D) closed K2 inserts anti-isolated island test experience load device, closed K1, start inverter to be measured, confirm that its output power meets the regulation of step a), by anti-isolated island test experience load device interface, R, the L that arranges, the value of C, when output current and target current value differ less than 2% the time, startup low capacity RLC load regulation R, L, C up to the fundamental frequency electric current that flows through K1 during less than stable state the inverter output-current rating 1%;

E) disconnect K1, record K1 be disconnected to the inverter output current descend and maintain output-current rating below 1% between time;

F) regulate R value and arbitrary L or C value on the anti-isolated island test experience load device host computer, the load of representing with dash area parameter in the acquisition following table 2 situation that do not match; What the parameter in the table 2 was represented is the number percent of deviation, symbolic representation be the direction of active power stream and reactive power flow of K switch 1 of flowing through among Fig. 1, positive sign represents that power flows from inverter to electrical network; After each the adjusting, all should record K1 be disconnected to the inverter output current descend and maintain output-current rating below 1% between time; If the time of record has any one to surpass the time of recording in the step e), then the non-shaded portion parameter also should be tested in the table 2.

G) for test condition B and C, regulate arbitrary L or C value, make it to change 1% by the regulation of table 2 is each.Parameter in the table 3 is represented is the direction of reactive power flow of K switch 1 of flowing through among Fig. 1, and positive sign represents that power stream is from the inverter to the electrical network; After each the adjusting, record K1 be disconnected to the inverter output current descend and maintain output-current rating below 1% between time; If the time of record is in rising trend, the increment that then should continue with 1% enlarges range of adjustment, and is on a declining curve until the time of record.

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

A. should prevent that resistance value, inductance value, the capacitance of isolated island test experience load device can set up on their own at host computer according to actual needs, easy to operate.

B. this device reduces the energy loss in the experimentation in a large number with the energy feedback grid of will gaining merit; And owing to abandoned the load adjustment of mechanical system, in the serviceable life of having improved experimental facilities, reduced the maintenance cost of experimental facilities; Also will have remarkable advantages aspect volume and the weight in addition.

C. replace the RLC load box with current transformer, and accurately realize single characteristic or the combined characteristic of RLC.Actual resistance, inductance and electric capacity are controlled electric current to regulating and controlling, voltage direction is more convenient than adjusting, and precision is more accurate, and speed is also faster.

D. because do not have the device consumed energy such as high-power resistance of actual physics and produce a large amount of heats, therefore, green energy conservation.

E. semiconductor device application technology

With respect to simple inverter load simulating device:

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

Beneficial effect of the present invention: a. isolated island device volume is less, and weight is lighter, and R, L, C add carried convenient, only needs just can accurately realize by artificial setting.

B. there is not thermal drift, do not need the parasitic amount compensation, thereby precision is higher.

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

D. control is flexible, easy to operate.

E. added low capacity RLC load in the system, remedied in the inverter Digital Control, the problem that the control step precision is limited makes final control accuracy be better than adopting merely the inverter simulated mode.

Description of drawings

Fig. 1. system principle diagram;

Fig. 2. the 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. phaselocked loop control block diagram;

Fig. 8. the current/voltage polar plot;

Fig. 9 .PI regulator.

Embodiment

By reference to the accompanying drawings, the present invention is further elaborated, and Fig. 1 is the system principle diagram of technical solution of the present invention, with current transformer simulation RLC load characteristic, replaces the island effect that the RLC load box detects photovoltaic power generation grid-connecting apparatus in practice.The main circuit diagram of this device mainly contains three parts: the S direct supply, for the inverter of preventing isolated island test experience load device provides direct current; B is simulation RLC load device, can adopt 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), and the power requirement that detects according to actual isolated island, active power and reactive power that control inverter output is certain; C, D, E are low capacity RLC load device, circuit diagram as shown in Figure 5, this part can remedy the deficiency of inverter control accuracy according to system requirements, and load is accurately adjusted.

Claims (1)

1. the anti-isolated island test experience load device of combined type is characterized in that being connected and composed successively by direct supply, simulation RLC load device, low capacity RLC load device, wherein:

Described direct supply is for the inverter of preventing isolated island test experience 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 the power requirement that detects according to actual isolated island, active power and reactive power that control inverter output is certain;

Described low capacity RLC load device can remedy the deficiency of inverter control accuracy according to system requirements, and load is accurately adjusted.

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