CN203933050U - Power distribution network containing distributed power generation is unified power quality adjusting device - Google Patents

Abstract

According to the similitude of unified power quality adjusting device and synchronization inverter main circuit structure, propose a kind of power distribution network containing distributed power generation and unify power quality adjusting device, this device consists of testing circuit, control circuit, inverter circuit, passive filter and distributed power source.System configuration and operation principle to device are analyzed, and adopt a kind of modified model compound instruction electric current composition algorithm, have realized this device and can generate electricity by way of merging two or more grid systems and can administer harmonic wave and idle several functions, increase work efficiency and reduce cost of investment.Simulation and experiment result verification reasonability and the practicality of this device.

Description

Power distribution network containing distributed power generation is unified power quality adjusting device

Technical field

The utility model relates to a kind of power distribution network containing distributed power generation and unifies power quality adjusting device, and particularly, in containing the distribution network system of micro-electrical network, device highlights stronger practicality and novelty.

Background technology

Development along with power electronic technology, regenerative resource obtains increasing development and application, cause occurring in low-voltage network a large amount of distributed power generation devices and grid-connected power electronic equipment, in addition in original low-voltage network, there is a large amount of power electronic device and nonlinear load, to power distribution network, brought serious power quality problem.Meanwhile, the capacity of power distribution network is generally less, and the infiltration of the humorous wave direction low voltage electric network of upper level electrical network is also relatively serious.This just causes the low-voltage network harmonic problem under micro-electrical network high permeability even more serious than general distribution network.

Although distributed power source has brought many uncertainties to system, such as its fluctuation, may cause system voltage flickering and introduce a large amount of harmonic waves etc., some aspects of the quality of power supply are further worsened, also there are the potentiality of improving the quality of power supply in it.The technology of improving the quality of power supply because existing is based upon on power electronic technology basis, and distributed power generation is also based upon on the basis of power electronic technology just, novel electric power system makes to utilize the power electronics transducer of self to become possibility like this, utilize existing power electronic equipment to absorb or discharge meritorious, idle, thereby not only realize the transmission conversion of electric energy, and improved the quality of power supply of system, reduce the additional investment of system.The < < Electric Power Automation Equipment > > of the 1st phase in 2013 has set up the Mathematical Modeling of multi-functional combining inverter topology, utilize weighted current feedback method to design its grid-connected current tracking control unit, based on the relation between damping resistance power consumption and damping ratio in output filter, designed damping resistance.Provided and a kind ofly comprised grid-connected power tracking and the quality of power supply compensates two-part instruction current generating algorithm.But, this instruction current generating algorithm more complicated.The < < Proceedings of the CSEE > > of the 24th phase in 2013 uses the unified control thought of parallel network power generation and Active Power Filter-APF, utilize the two topological structure characteristic to carry out further expansion to systemic-function, the unified model of controlling of photovoltaic generation and active filter is proposed, this device can be realized parallel network power generation simultaneously, reactive power compensation and harmonic current suppress, and can realize off-line UPS function, can be promptly to important load supplying when electric power system has a power failure, guarantee that responsible consumer is not subject to the impact of system cut-off.Under the micro-electrical network high permeability of labor, the mechanism of action of distributed power source to original distribution network voltage, the electric current quality of power supply, distribution network electric energy quality adjuster under micro-electrical network high permeability has been proposed, it is brought into play and under this environment, can generate electricity by way of merging two or more grid systems and can administer harmonic wave and idle function, increase work efficiency and reduce cost of investment.

The affect mechanism of distributed power source on distribution network voltage

The mutability of distributed power source, intermittence and randomness impact other users' of power distribution network supply power voltage, make distribution network voltage occur the great quality of voltage problems such as fluctuation, flickering.The impact that distributed power source is incorporated to a little it is maximum, and the voltage influence that therefore research is incorporated to a little DG is the most representative.

With the power distribution network of distributed power source at the equivalent electric circuit of DG access point as shown in Figure 1.

When distributed power source injected system power changes, can make the electric current on circuit change.Equivalent electric circuit, can estimate that when distributed power source energy output fluctuates, the voltage change on DG access point is as shown in Figure 1

$\mathrm{\&Delta;u}={\stackrel{\&CenterDot;}{Z}}_s\&CenterDot;\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}---\left(1\right)$

Have again

${\stackrel{\&CenterDot;}{Z}}_s=R_s+j{X}_s=\left|Z_s\right|\&angle;\mathrm{\&alpha;}---\left(2\right)$

$\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}=\mathrm{\&Delta;}{I}_p+\mathrm{j\&Delta;}{I}_q=\left|\mathrm{\&Delta;I}\right|\&angle;\mathrm{\&beta;}---\left(3\right)$

Substitution formula (1), has

$\mathrm{\&Delta;u}=\frac{u^2}{S_k}\&CenterDot;\frac{\mathrm{\&Delta;}{S}_n}{u}\left[\cos (\mathrm{\&alpha;}+\mathrm{\&beta;})j\sin (\mathrm{\&alpha;}+\mathrm{\&beta;})\right]---\left(4\right)$

In formula, Δ S _ninjecting power variation for distributed power source; S _kfor DG access point place capacity of short circuit; Zs=(Rs+jXs) is electrical network equiva lent impedance; Δ I is line current variable quantity; α for from DG access point see into electric network impedance angle; β is distributed power source power-factor angle; U is DG access point voltage.

The phase shift at same circuit two ends is not-time, can ignore vertical component, has

$K=\frac{\mathrm{\&Delta;u}}{u}=\frac{{\mathrm{\&Delta;S}}_n}{S_k}\cos (\mathrm{\&alpha;}+\mathrm{\&beta;})---\left(5\right)$

In formula, K represents the impact degree of distributed power source to system voltage.

From formula (5), distributed power source to the variation of the impact of system power supply voltage and injecting power, be incorporated to the capacity of short circuit of system and the power factor of distributed power source is relevant, these factors are the main causes that cause the great quality of voltage problems such as distribution network voltage fluctuation, flickering.

The affect mechanism of distributed power source on power distribution network electric current

In micro-electrical network, contain numerous non-linear power electronics members, after access power distribution network, when energy is provided, certainly will bring negative effect to current quality.When the permeability of micro-electrical network at distribution network system increases, distributed power source scale is enough greatly time in power distribution network, the harmonic content that a plurality of harmonic source stacks cause can have a strong impact on distribution network electric energy quality, moreover, a plurality of humorous vibration sources also can excite the power resonance of high order harmonic component in system, cause the proportion of non-linear electrical equipment in power distribution network to increase rapidly, will cause the further deterioration of power distribution network Current harmonic distortion rate, the safety in operation that threatens original power distribution network.

Summary of the invention

Containing the power distribution network of distributed power generation, unifying power quality adjusting device consists of testing circuit, control circuit, inverter circuit, passive filter and distributed power source.Distributed power source is placed in device DC side, has two cover inverters, wherein a set of in parallel with power distribution network after inversion, compensation Distribution Network Harmonics electric current, and another set of inverter is connected with power distribution network after inversion, compensation Distribution Network Harmonics voltage; Passive filter is placed between inverter and power distribution network.When distribution network electric energy quality is stablized, by control inverter, realize distributed power generation function; Power quality controlling function and distributed power generation function can realize simultaneously.

Compare with the distributed power source device that generates electricity by way of merging two or more grid systems, this device has only increased harmonic wave, Detecting Reactive Current link, administers distribution network systems harmonic wave when system is generated electricity by way of merging two or more grid systems.When this device generates electricity by way of merging two or more grid systems, can control inverter output and the meritorious fundamental current of electrical network with frequency homophase.And distributed power source can directly be connected with combining inverter and no longer need boost conversion circuit, thereby improved the efficiency that distributed power source generates electricity by way of merging two or more grid systems.

In addition, electrical network fundamental voltage is all applied on combining inverter AC power capacitor, reduce to greatest extent the capacity of inverter, PPF assembling is simultaneously located at load-side and realizes local compensation, in APF, DC voltage is far below electrical network fundamental voltage, improved because load harmonic current injects the distribution points of common connection place power quality problem causing, improved system run all right.

Compare and only increased a DG unit with conventional active power quality adjusting device, both simple in structure, there is again the plurality of advantages of electric energy quality compensating device.When the used time of doing of this device performance quality of power supply adjusting of needs, as long as harmonic wave and the idle instruction current in control inverter.And after combining inverter must not own bypass because of fault, passive filter still can play certain harmonic wave to be suppressed and inactive power compensation.

Distributed power source power points is followed the tracks of link and is determined maximum power point voltage, through voltage regulator, obtain the amplitude of grid-connected current real component, after multiplying each other with electrical network phase-locked loop unit sinusoidal signal, obtain active current instruction, by the adjustment of active current, complete the exchange of DC side and distribution energy, and then keep DC-side Voltage Stabilization.

Accompanying drawing explanation

The grid-connected equivalent electric circuit of Fig. 1 distributed power source

Fig. 2 is containing the general frame of the unified power quality adjusting device of distributed power generation

The compose operation of Fig. 3 compound instruction electric current

Fig. 4 system power, voltage waveform

Figure 50-0.05s current distortion rate is analyzed

Figure 60 .05-0.1s current distortion rate is analyzed

Figure 70 .1-0.15s current distortion rate is analyzed

Figure 80 .15-0.2s current distortion rate is analyzed

System power voltage waveform when Fig. 9 device does not put into operation

System power voltage waveform after Figure 10 device drops into

System power voltage waveform when Figure 11 device generates electricity by way of merging two or more grid systems function

Embodiment

Accompanying drawing 2 is for containing the general frame of the unified power quality adjusting device of distributed power generation, and the unified power quality adjusting device that contains distributed power generation consists of testing circuit, control circuit, inverter circuit, passive filter and distributed power source.Distributed power source is placed in device DC side, then by after its inversion, through passive filter, exports power distribution network side to, and inverter adopts full-control type device.In main circuit, have two cover inverters, wherein a set of in parallel with power distribution network after inversion, compensation Distribution Network Harmonics electric current, another set of inverter is connected with power distribution network after inversion, compensation Distribution Network Harmonics voltage; When distribution network electric energy quality is stablized, by controlling corresponding inverter, realize distributed power generation function; Power quality controlling function and distributed power generation function can realize simultaneously.

Inverter instruction current is synthetic

Traditional p-q detection method based on instantaneous reactive power theory has a wide range of applications, but the method is only applicable to the distortionless balance sysmte of three-phase voltage, and when voltage waveform has distortion, accuracy of detection will can not be guaranteed.Harmonic current detection method based on phase-demodulating principle is the phase place discrimination method based in mechanics of communication, is characterized in each phase harmonic wave of independent detection, thereby can accurately detect harmonic current when three phase network voltage fluctuation or distortion.But the harmonic current detection method of tradition based on phase-demodulating principle is open cycle system, its accuracy of detection and dynamic response performance depend on the design of low pass filter parameter to a great extent.And cut-off frequency and the exponent number of design low pass filter are more difficult, and open loop harmonics detection circuit system stability performance is low, and poor robustness is subject to the impact of other parameters of system.In order to improve stability and the dynamic property of system, detecting phase demodulation branch road increase proportional and integral controller herein, consider that a n rank low pass filter and integral unit can construct n+1 rank low pass filter by closed loop, open loop circuit model is arranged to closed loop circuit and improves its robustness, adopt integral element to replace low pass filter, reduce the difficulty of design.Synthesizing as shown in Figure 3 of compound instruction electric current.

One covering device is realized and is generated electricity by way of merging two or more grid systems and administer the several functions such as the quality of power supply, certainly will greatly reduce installation cost, and improve system run all right, operating efficiency and dynamic property.

Simulation and experiment interpretation of result

Distribution network systems voltage 380V/50Hz, distributed electrical output machine mouth voltage is equivalent to 800V; Switching frequency is 10KHz; Load is uncontrollable rectification resistance inductive load, load resistance R=20 Ω, L=25mH; Combining inverter Inductor Lo=11mH.In simulation process, distribution power-supply system side electric current, voltage waveform are as shown in Figure 4.

In simulation process, distribution power supply is surveyed current-voltage waveform as shown in Figure 4.Between 0-0.05s, this customizing device does not put into operation as seen from the figure, current waveform is typical rectification load waveform, has more serious distortion, and its corresponding current distortion rate analysis as shown in Figure 5, electric current resultant distortion rate is up to 23.93%, severe overweight.Between 0.05-0.1s, this device puts into operation, now control in the instruction current of this device and do not add the active current of generating electricity by way of merging two or more grid systems, the required active energy of load all derives from distribution power supply, by waveform, can be found out, customization this device now brought into play preferably the function of original power quality adjusting device, current waveform trend towards sine wave and with voltage waveform with frequency homophase, now aberration rate analysis is as shown in Figure 6, aberration rate is reduced to 4.33%, meets GB.In 0.1-0.15s device compound instruction electric current, add the instruction of 10A active current, between distribution mains side current amplitude and 0.05-0.1s, compare to some extent and reduce, and aberration rate as shown in Figure 7, size is 4.53%, show that device is on the basis of the original power quality adjusting device function of performance, realized and having generated electricity by way of merging two or more grid systems simultaneously, now electric current and voltage is with homophase frequently, and load power demand is provided jointly by distribution power supply and grid-connected distributed power source.The meritorious instruction of 0.15-0.2s is controlled electric current and is increased to 40A, now current waveform and voltage waveform are reverse, show that distributed power source passes through this device and powers to power distribution network and load simultaneously, and now grid-connected current aberration rate analysis as shown in Figure 8, size is 4.05%, meets the demands.

In order to verify the feasibility of the power quality adjusting device design of putting forward herein, carried out related experiment, 32 TMS320F2812 of fixed point of experiment control chip selection TI company.Mainly comprise power quality controlling experiment, generate electricity by way of merging two or more grid systems and two aspects of power quality controlling experiment.

(1) power quality controlling experiment

This power quality adjusting device is input coefficient when operation, and as shown in Figure 9, in figure, first figure is voltage waveform (400V/div) for the experimental system mains side electric current of actual measurement, voltage waveform, and second figure is current waveform (20A/div).

As shown in Figure 9, system power supply side electric current and voltage waveform, with frequently in the same way, are analyzed and can be obtained mains side electric current by FLUKE (43B type) power quality analyzer, and the total percent harmonic distortion of electric current (THD) is up to 24.9%, current distortion is comparatively serious, seriously surpasses GB.

After this device input coefficient operation, as shown in Figure 10, first figure is voltage waveform (400V/div) to experimental system mains side current-voltage waveform, and second figure is current waveform (20A/div).

From accompanying drawing 10, this device can better be brought into play power quality controlling function after putting into operation and stablizing, and current waveform is close to sine wave.It is known that same employing power quality analyzer carries out aberration rate analysis to electric current, and the total percent harmonic distortion size of electric current is now 4.51%, and effect above has improved significantly.

(2) power quality controlling and the experiment of generating electricity by way of merging two or more grid systems

This device is brought into play power quality controlling function and the experimental system current-voltage waveform that generates electricity by way of merging two or more grid systems as shown in figure 11 simultaneously, and first figure is voltage waveform (400V/div), and second figure is current waveform (20A/div).

From accompanying drawing 11, can find out that the aberration rate value that the later system power waveform of this timer operation is tending towards sine wave and electric current is 4.37%, can meet relevant national standard, illustrate that now this device still can be brought into play harmonic wave control and the no-power compensation function of original power quality adjusting device preferably.

Accompanying drawing 10 can obviously find out that with accompanying drawing 11 contrasts now current waveform direction is just in time contrary, show that now the electric current of system power supply side installs effluent to mains side by load and this, show that this device carried meritorious energy to electrical network, its size not only can meet the meritorious demand of load, can also be by the unnecessary meritorious electric network source side that is transported to.Now this device has not only been brought into play the function of reactive power compensation and harmonic treating apparatus, also to electric network source side and load, provides active energy simultaneously, has realized the function of generating electricity by way of merging two or more grid systems of distributed power source.System power aberration rate not only meets national utility mains by harmonics standard and has also reached micro-electrical network distributed power source aberration rate standard-required that generates electricity by way of merging two or more grid systems.

This device, by distributed power source being placed in to unified power quality adjusting device DC side, has been realized several functions.This device can either be administered the power quality problem in micro-electrical network, can realize the function of generating electricity by way of merging two or more grid systems again.Emulation and experiment show feasibility and the practicality of this device.

Claims (1)

1. containing the power distribution network of distributed power generation, unify a power quality adjusting device, by testing circuit, control circuit, inverter circuit, passive filter and distributed power source, formed; It is characterized in that, distributed power source is placed in device DC side, has two cover inverters, and wherein a set of in parallel with power distribution network after inversion, another set of inverter is connected with power distribution network after inversion, and passive filter is placed between inverter and power distribution network.