CN101593980A - A kind of novel neutral line triple harmonic current suppressor - Google Patents

Abstract

A kind of novel neutral line triple harmonic current suppressor, comprise two lc circuit I, II and a tortuous transformer 5 of forming by electric capacity, reactance, lc circuit I series connection inserts the neutral line, the reactance end of lc circuit I is connected with the neutral line of low-voltage network input, the capacitance terminal of lc circuit I is connected with the neutral line of load-side, three terminations of A, B, C of tortuous transformer are connected with the triple line of low-voltage network, the N end of tortuous transformer joins with the reactance end of lc circuit II, and the capacitance terminal of lc circuit II is connected with the capacitance terminal of lc circuit I.Can effectively suppress to have solved the influence of residual voltage on the basis of neutral current, and this device is very little to the influence of user's quality of power supply to tortuous transformer.Of the present invention to have a circuit structure simple, and cost is low, easy to implement, be subjected to electrical network to exist residual voltage to influence advantages such as inhibition little, neutral line triple harmonic current is effective.

Description

A kind of novel neutral line triple harmonic current suppressor

Technical field

The invention belongs to the power technology field, be specifically related to a kind of novel neutral line triple harmonic current suppressor that can be used for low-voltage network, suppresses neutral line triple harmonic current.

Background technology

Along with science and technology and expanding economy, medium-and-large-sized market, office building, residential quarter, city continues to bring out, and illumination wherein, computer, photocopier, air-conditioning are main power consumption equipment.Present lighting apparatus mostly is novel power electronics light fixtures such as LED, is generally single-phase rectifier equipment or thyristor voltage regulation mode; Computer and photocopier also are single-phase equipment, also are rectifying installation; Along with the development of air-conditioning technical, convertible frequency air-conditioner more and more is subjected to the parent and looks at, and its main circuit also is the rectification-inverter circuit of AC-DC-interchange.Therefore these equipment all are non-linear, and mostly are single-phase load, and they will produce a large amount of harmonic waves when work, electrical network is caused certain influence.Zero-sequence component will constitute path, particularly 3 order harmonic components flowing in the neutral line by the neutral line and power supply in the three-phase current, often make the electric current of the neutral line surpass the electric current in the phase line.When power distribution network designed, the lead radius of the neutral line was usually identical even littler with the radius of each phase conductor, will cause the overload of the neutral line like this even burnt.In large-scale market and office building low-voltage distribution system, neutral line overload causes the accident of power failure to happen occasionally.Phase line is transshipped, is burnt the power supply that only influences this phase, compares with it, and the influence that neutral line overload causes is even more serious, because center line will make the single-phase load in the whole system work after disconnecting.Therefore reducing neutral current is called the problem that work about electric power person needs solution badly.Analyze discovery by the composition to neutral current, wherein triple-frequency harmonics accounts for major part, and inhibition how to carry out triple harmonic current is the key that reduces neutral current.

Neutral current inhibition method has methods such as passive filtering, active filter, tortuous transformer.The cost of active filter is higher relatively, and because the restriction of the withstand voltage level of switching device, big capacity active filter manufacturing is difficulty comparatively.Tortuous transformer is used relative more with passive filtering.

The series compensation mode is exactly to adopt the device of electric capacity and reactance series connection, and this device series connection inserts the neutral line.For first-harmonic, electric capacity and inductance are in the state near resonance, and the impedance that presents is very little, and be therefore very little with distribution influence to flowing of fundamental current; For this device rendered very big impedance of triple-frequency harmonics, suppress flowing of 3 subharmonic.When adopting this mode, the access point of this equipment is bigger near the triple-frequency harmonics of user side, and causing of user's quality of power supply had a strong impact on, and causes the subscriber equipment cisco unity malfunction even causes the damage of subscriber equipment.

Tortuous transformer method is to the not influence of voltage of access point, but exists filter effect undesirable, and when there is zero-sequence component in supply voltage, causes tortuous transformer overcurrent easily even burns.In low-voltage network, the asymmetric situation of voltage often exists, and causes equipment not come into operation or can not normally move.

Summary of the invention

The technical problem to be solved in the present invention is at the deficiencies in the prior art, triple harmonic current in a kind of effectively filtering neutral line has been proposed, and little to user's power consumption equipment influence, be subjected to the power supply residual voltage to influence little novel neutral line triple harmonic current suppressor.

The technical problem to be solved in the present invention is achieved through the following technical solutions, a kind of novel neutral line triple harmonic current suppressor, be characterized in: comprise by electric capacity, two lc circuit I that reactance is formed, II and a tortuous transformer, lc circuit I series connection inserts the neutral line, the reactance end of lc circuit I is connected with the neutral line of low-voltage network input, the capacitance terminal of lc circuit I is connected with the neutral line of load-side, the A of tortuous transformer, B, three terminations of C are connected with the triple line of low-voltage network, the N end of tortuous transformer joins with the reactance end of lc circuit II, and the capacitance terminal of lc circuit II is connected with the capacitance terminal of lc circuit I.

The present invention is based on basic tortuous transformer and series resonant circuit, both are combined, can effectively suppress to have solved the influence of residual voltage on the basis of neutral current, and this device is very little to the influence of user's quality of power supply to tortuous transformer.The present invention has the following advantages: (1) its circuit structure is simple, and cost is low; (2) utilize common device to make up, easy to implement; When (3) there was residual voltage in electrical network, the electric current of tortuous transformer was little, and load equipment can safe and stable operation; (4) inhibition of neutral line triple harmonic current is effective.

Description of drawings

Fig. 1 is circuit theory diagrams of the present invention.

Fig. 2 is an equivalent circuit diagram of the present invention

Embodiment

A kind of novel neutral line triple harmonic current suppressor, comprise by electric capacity, two lc circuit I that reactance is formed, II and a tortuous transformer 5, reactance 1, electric capacity 2 constitutes lc circuit I, reactance 3, electric capacity 4 constitutes lc circuit II, lc circuit I series connection inserts the neutral line, the reactance end of lc circuit I is connected with the neutral line of low-voltage network input, the capacitance terminal of lc circuit I is connected with the neutral line of load-side, the A of tortuous transformer, B, three terminations of C are connected with the triple line of low-voltage network, the N end of tortuous transformer joins with the reactance end of lc circuit II, and the capacitance terminal of lc circuit II is connected with the capacitance terminal of lc circuit I.

Lc circuit I will satisfy first-harmonic near resonance among the present invention on parameter is provided with, and lc circuit II satisfies triple-frequency harmonics resonance on parameter.The capacity of reactance 1, electric capacity 2, electric capacity 3, reactance 4, tortuous transformer 5 and withstand voltage level design during by practical application as the case may be.

Wherein lc circuit I is to first-harmonic resonance, and is bigger to the triple-frequency harmonics impedance; Lc circuit II presents higher resistance to triple-frequency harmonics resonance to first-harmonic.This device can adopt two kinds of mounting meanss: (1) lc circuit I is located near mains side, and tortuous transformer and lc circuit II disperse to be installed in each load-side; (2) lc circuit I, lc circuit II and tortuous transformer are installed in load-side, disperse to install.Lc circuit I is public in the mode (1), and whole cost is lower, but influence is bigger if lc circuit I breaks down; Each device all has a lc circuit I in the mode (2), the cost height, and the mounting cost height is if a plant failure only influences its affiliated part power supply, reliability height.

The equivalence of triple harmonic current in the load is become current source, can draw equivalent electric circuit Fig. 7 of triple-frequency harmonics equivalent electric circuit Fig. 6 and fundamental wave zero sequence, as shown in Figure 2.Z among the figure _3s, Z _3ZImpedance when representing system side and tortuous transformer 150Hz respectively, Z _3LC1Electric capacity, the impedance of inductor combination when 150Hz of expression lc circuit I are for Z is taken into account in the impedance of convenient hypothesis center line _3LC2Electric capacity, the impedance of inductor combination when 150Hz of expression lc circuit II; Equally, Z _s, Z _Z, Z _LC1, Z _LC2Impedance when representing relative 50Hz; I _3fZero sequence triple harmonic current in the expression load; U _3sThree background harmonicses of zero sequence in the expression system; U _0sZero-sequence fundamental voltage in the expression system voltage.

According to the triple-frequency harmonics circuit, utilize superposition theorem, can calculate the electric current of tortuous transformer

$I_{3z}=\frac{(Z_{3s}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1})I_{3f}}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{<figure-callout\; id="1"\; label="LC"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">LC</figure-callout>}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}-\frac{U_{3s}}{Z_{2z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}---\left(1\right)$

$I_{3s}=\frac{(Z_{3z}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2})I_{3f}}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{<figure-callout\; id="1"\; label="LC"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">LC</figure-callout>}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}+\frac{U_{3s}}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}$

The system side electric current I _3sWith tortuous transformer current I _3ZIn the expression formula first is the shunting action by the zero sequence triple-frequency harmonics in the load current, and according to parameter designing, lc circuit I presents high impedance to triple-frequency harmonics, and lc circuit II is to triple-frequency harmonics resonance, i.e. Z _3LC1＞＞Z _3LC2≈ 0, and Z _3s, Z _3ZAll less, therefore:

$\frac{(Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1})I_{3f}}{Z_{3z}{+Z}_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}>>\frac{(Z_{3z}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2})I_{3f}}{Z_{3z}+Z_{3s}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}---\left(2\right)$

I then _3sAnd I _3ZIn second be that 3 background harmonicses of zero sequence by system cause, same because Z _3LC1Numerical value is bigger, and second numerical value is all less, to I _3sAnd I _3ZInfluence little.Can get by above-mentioned analysis:

I _3z＞＞I _3s (3)

Three Zero-pharse harmonic electric currents of load mainly flow through tortuous transformer, have effectively suppressed neutral current.

In like manner, the third harmonic voltage that calculates tortuous transformer access point can get:

$U_{3z}=\frac{(Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1})(Z_{3z}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2})I_{3f}}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{<figure-callout\; id="1"\; label="LC"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">LC</figure-callout>}1}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}---\left(4\right)$

$-\frac{(Z_{3z}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2})U_{3s}}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}$

First is that load zero sequence triple harmonic current flows through tortuous transformer circuit impedance Z in the following formula _3z+ 3Z _3LC2With the system circuit impedance Z _3s+ 3Z _3LV1The voltage that back in parallel produces.Know according to parameter characteristic:

$\frac{(Z_{3s}+{3\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1})(Z_{3z}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2})}{Z_{3z}+Z_{3s}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}1}+3{\mathrm{<figure-callout\; id="3"\; label="Z"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{3\mathrm{LC}2}}\&ap;Z_{3z}---\left(5\right)$

According to the characteristics of tortuous transformer Z as can be known _3zLess.Same because Z _3LC1＞＞0, so second numerical value is also smaller in the formula (4).This proof neutral current suppresses new method and causes the very little variation of load side voltage triple-frequency harmonics, and is little to the load influence.

Equally, calculate when containing the fundamental wave zero sequence component in the system voltage according to the first-harmonic circuit, the electric current that flows through tortuous transformer is:

$I_z=\frac{U_s}{Z_z+Z_s+3{\mathrm{<figure-callout\; id="1"\; label="Z\; LC"\; filenames="A2009100325260008H1.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{LC}}+3Z_{\mathrm{LC}2}}---\left(6\right)$

Because lc circuit I is to first-harmonic resonance, impedance is less, and lc circuit II presents capacitive to first-harmonic, the big Z of impedance _LC2＞＞Z _LC1≈ 0, then I _zBe subjected to Z _LC2Restriction, numerical value is less.Therefore this method is effectively during the resolution system Voltage unbalance, the excessive problem of tortuous transformer current that zero-sequence fundamental voltage causes.

By above-mentioned analysis as can be known, the present invention not only combines the series connection and the characteristics of shunt compensation, efficiently solves series compensation simultaneously and tortuous transformer compensates existing problem.

Claims (1)

1. novel neutral line triple harmonic current suppressor, it is characterized in that: comprise two lc circuit I, II and a tortuous transformer of forming by electric capacity, reactance, lc circuit I series connection inserts the neutral line, the reactance end of lc circuit I is connected with the neutral line of low-voltage network input, the capacitance terminal of lc circuit I is connected with the neutral line of load-side, three terminations of A, B, C of tortuous transformer are connected with the triple line of low-voltage network, the N end of tortuous transformer joins with the reactance end of lc circuit II, and the capacitance terminal of lc circuit II is connected with the capacitance terminal of lc circuit I.

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