CN101567565A - System for compensating combined negative sequence current of power regulator and static var compensator - Google Patents

Abstract

The invention discloses a system for compensating the combined negative sequence current of a power regulator and a static var compensator. The system consists of a railway power regulator and the static var compensator. The railway power regulator is installed between two power supplying arms at a secondary side of a traction transformer by two single-phase three-winding reducing transformer. The static var compensator consists of two groups of thyristor switched capacitors which are connected in parallel and a group of thyristor controlled reactors. The thyristor switched capacitors and the thyristor controlled reactors are respectively connected with two traction power supplying arms by single-phase three-winding reducing transformers, wherein the thyristor switched capacitors are installed below the single-phase three-winding reducing transformer which is connected with the power supplying arms with relatively advanced voltage phases, and the thyristor controlled reactors are installed below the single-phase three-winding reducing transformer of the power supplying arms with relatively hysteretic voltage phases. The system can maximally reduce the capacity of the railway power regulator while also satisfying the requirement of a railway system on the unbalancedness degree of three phase current.

Description

Power governor and Static Var Compensator associating negative-sequence current bucking-out system

Technical field

The present invention relates to a kind of electrified high-speed railway negative-sequence current bucking-out system, particularly a kind of power governor and Static Var Compensator associating negative-sequence current bucking-out system that is applicable to electrified high-speed railway.

Background technology

China electric railway traction transformer station adopts special-purpose traction transformer to give two single-phase traction circuits of on-load separately with the electric energy transmitting of three-phase electrical power system mostly, because the regulatory function of locomotive self, the traction load of two supply arms of traction substation is separate, random fluctuations, because traction load has this asymmetry, so the three-phase current unbalance of traction transformer high-low pressure both sides, and on the system side bus, produce negative-sequence current.Negative-sequence current in the trailer system can produce negative sequence voltage at the points of common connection place, and flows to other loads by points of common connection.Negative-sequence current in the trailer system can produce serious influence and disturbs protective relaying device, electric power system major component such as the transformer of generator, asynchronous motor, reflection negative sequence component and power transmission line and communication system etc.

For suppressing the negative-sequence current in the electric railway, the current measure of generally adopting is to carry out commutation at traction substation to connect, and each section inserts the not homophase of electric power system by turns.The method is simple, does not need to increase in addition equipment, and cost is low, easy care, but, influenced the speed-raising of locomotive owing to must in electrical network, make the electricity consumption phase-splitting, reduced the reliability of electrical network.Railway power regulator (RPC) is a kind of compensation arrangement that occurred in recent years, it transfers to heavily loaded side by the dual H-bridge inverter of common DC lateral capacitance with the energy of underloading one side, realizing the balance of two supply arm active power, thereby reach the purpose that suppresses the three-phase side negative-sequence current.When a side supply arm has the locomotive load, and opposite side is when unloaded, for reaching two supply arm active power balances, the capacity that must make RPC is half of locomotive bearing power, the electric locomotive that with power is 8MVA is an example, the capacity of RPC is minimum at this moment is 4MVA, and big capacity makes the cost of RPC higher, and manufactures and designs the difficulty increasing; Because the inherent characteristic of V/V traction transformer has determined to be at two supply arm power-balances and power factor, and the three-phase side negative-sequence current still has 50% with the ratio of forward-order current amplitude, adopt the RPC structure on negative-sequence current suppresses, to run into bottleneck merely at 1 o'clock simultaneously.

Summary of the invention

In order to solve the above-mentioned technical problem that the compensation of railway power controller negative-sequence current exists in the electrified high-speed railway system, the invention provides a kind of railway power regulator and Static Var Compensator associating negative-sequence current bucking-out system.The present invention is satisfying the capacity that Railway System reduces RPC under to the situation of the requirement of three-phase current unbalance degree to greatest extent.

The technical scheme that the present invention solves the problems of the technologies described above is: comprise railway power regulator and Static Var Compensator, railway power regulator is installed between two supply arms of traction transformer secondary side by two single-phase three winding step-down transformers, Static Var Compensator is made up of two groups of thyristor switchable capacitors that are connected in parallel and one group of thyristor-controlled reactor, respectively by the single-phase three winding step-down transformers two traction power supply arms that insert in parallel, wherein thyristor switchable capacitor is connected to the single-phase three winding step-down transformers under the leading relatively supply arm of voltage-phase, and thyristor-controlled reactor is connected to the single-phase three winding step-down transformers under the supply arm that voltage-phase relatively lags behind.

A kind of railway power regulator and Static Var Compensator associating negative-sequence current bucking-out system, comprise railway power regulator and Static Var Compensator, railway power regulator is installed between two supply arms of traction transformer secondary side by two single phase step-down transformers, Static Var Compensator is made up of two groups of thyristor switchable capacitors that are connected in parallel and one group of thyristor-controlled reactor, respectively by the single phase step-down transformer two traction power supply arms that insert in parallel, wherein thyristor switchable capacitor is connected to the single phase step-down transformer under the leading relatively supply arm of voltage-phase, and thyristor-controlled reactor is connected to the single phase step-down transformer under the supply arm that voltage-phase relatively lags behind.

Technique effect of the present invention is:

(1) improvement is to the compensation effect of the former limit of traction transformer three-phase current negative sequence component.By the introducing Static Var Compensator, the size of current phase and amplitude in the appropriate change two traction power supply arms, indirect regulation traction transformer three-phase side electric current reduces its contained negative sequence component, thereby reaches the purpose of improving the three-phase current unbalance degree.

(2) capacity of reduction railway power regulator.Because Static Var Compensator is to the regulating action of current phase and amplitude in the two traction power supply arms, little when reaching the same needed railway power regulator Capacity Ratio of degree of unbalance and using railway power regulator merely, therefore can reduce the capacity of railway power regulator device, reduce equipment cost.

The present invention is further illustrated below in conjunction with accompanying drawing.

Description of drawings

Fig. 1 is the structure chart of the embodiment of the invention 1.

Fig. 2 is the structure chart of the embodiment of the invention 2.

Fig. 3 is compensation principle figure of the present invention.

Fig. 4 is the present invention and the independent three-phase current unbalance degree of railway power regulator and the relation curve of RPC capacity of using.

Embodiment

Referring to Fig. 1, Fig. 1 is the structure chart of the embodiment of the invention 1.The present invention includes railway power regulator 1 and Static Var Compensator 2.Railway power regulator 1 adopts two single-phase H bridge inverters based on switching device, form " back-to-back " structure by the common DC lateral capacitance, two inverter AC side are by two single-phase three winding step-down transformers traction transformer secondary side two-phase supply arm that inserts in parallel respectively.Static Var Compensator 2 is made up of two groups of thyristor control switched capacitor 4 (TSC) and one group of thyristor-controlled reactors 3 (TCR) that are connected in parallel, respectively by the single-phase three winding step-down transformers two traction power supply arms that insert in parallel.Wherein TSC is connected to the single-phase three winding step-down transformers under the leading supply arm of voltage-phase, and TCR is connected to the single-phase three winding step-down transformers under the supply arm that voltage-phase lags behind.There is a winding on the former limit of single-phase three winding step-down transformers, and secondary has two windings, plays buffer action; The former secondary of single phase step-down transformer respectively has only a winding.

Referring to Fig. 2, Fig. 2 is the structure chart of the embodiment of the invention 2.Only replace single-phase three winding step-down transformers among the embodiment 1 in the present embodiment with single phase step-down transformer.

Two supply arms when having only uplink or downlink that locomotive is arranged, must have one to be zero mutually as the power supply unit descending locomotive power supply that makes progress independently mutually in the three-phase side electric current, this moment the negative sequence component maximum.The effect of RPC is by the dual H-bridge inverter of common DC lateral capacitance the energy of underloading one side to be transferred to heavily loaded side, to realize the balance of two supply arm active power.The balance of load active power can produce certain inhibition effect to the negative sequence component of three-phase current, but still can't eliminate.SVC introduces in order to reach this purpose.By dropping into electric capacity at the leading relatively supply arm of voltage, another supply arm that relatively lags behind at voltage drops into inductance, further increased the phase difference of two supply arms, making the three-phase side electric current more level off to amplitude equates, the balanced three-phase current that the phase place mutual deviation is 120 °, thus reduce even eliminate its negative sequence component.Simultaneously, because SVC is to the compensating action of negative phase-sequence, under the situation of the index that reaches identical three-phase current unbalance degree, the Capacity Ratio of the RPC that comprehensive compensation system is required is little when using RPC merely, thereby has reduced the capacity requirement of RPC.When the transfer capacity of RPC is less than normal capacity, the situation when being positioned at different supply arm, the capacitor and inductor value that comprehensive compensation system need drop into different parameters respectively in leading arm and lagging leg side at electric locomotive.The dynamic input of capacitor and inductor is to be finished by the switching signal controlling of TSC and TCR, and TSC is at dynamic constantly input of voltage peak and the corresponding electric capacity of excision, thereby TCR changes its access inductance value by adjusting the thyristor trigger angle.When electric locomotive was positioned at wherein a supply arm, the TSC of leading arm side dropped into accordingly a wherein group capacitor; Change the equivalent susceptance value of TCR at TCR that lagging leg adopted by the trigger angle of regulating thyristor, thus the inductance value of dynamic adjustments place in circuit.The acting in conjunction of TSC and TCR makes when locomotive is positioned at different supply arm to reach identical compensation effect.

Principle below in conjunction with 3 pairs of comprehensive compensation systems of accompanying drawing is further elaborated.

With

As with reference to vector, suppose that locomotive loads on a supply arm, the zero load of b supply arm.If two supply arm electric currents are respectively

The locomotive load current is

Before the compensation, ${\stackrel{\·}{I}}_a={\stackrel{\·}{I}}_l,{\stackrel{\·}{I}}_b=0.$ The voltage change ratio that makes the V/V transformer is K,

Be respectively three-phase current positive sequence, negative sequence component, a=e ^{J120 °}Be twiddle factor, then the three-phase side electric current can be expressed as:

$\left\{\begin{array}{c}{\stackrel{\·}{I}}_A=\frac{-{\stackrel{\·}{I}}_a}{K}\\ {\stackrel{\·}{I}}_B=-\frac{{\stackrel{\·}{I}}_b}{K}\\ {\stackrel{\·}{I}}_C=-({\stackrel{\·}{I}}_A+{\stackrel{\·}{I}}_B)=\frac{1}{K}({\stackrel{\·}{I}}_a+{\stackrel{\·}{I}}_b)\end{array}\right.---\left(1\right)$

According to electric current positive-negative sequence representation in components formula:

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">A</figure-callout>}1}=\frac{1}{3}({\stackrel{\&CenterDot;}{I}}_A+a{\stackrel{\&CenterDot;}{I}}_B+a^2{\stackrel{\&CenterDot;}{I}}_C)\\ {\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">A</figure-callout>}2}=\frac{1}{3}({\stackrel{\&CenterDot;}{I}}_A+a^2{\stackrel{\&CenterDot;}{I}}_B+a{\stackrel{\&CenterDot;}{I}}_C)\end{array}\right.---\left(2\right)$

Can get:

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">A</figure-callout>}1}=\frac{1}{3K}(a^2-1){\stackrel{\&CenterDot;}{I}}_a\\ {\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">A</figure-callout>}2}=\frac{1}{3K}(a-1){\stackrel{\&CenterDot;}{I}}_a\end{array}\right.$

Definition $K_I=\frac{\left|{\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">A</figure-callout>}2}\right|}{\left|{\stackrel{\&CenterDot;}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">A</figure-callout>}1}\right|},$ Be the three-phase current unbalance degree, promptly the ratio of three-phase current negative sequence component and positive sequence component can be got by above analysis, at this moment $K_I=\left|\frac{\frac{1}{3K}(a^2-1){\stackrel{\&CenterDot;}{I}}_a}{\frac{1}{3K}(a-1){\stackrel{\&CenterDot;}{I}}_a}\right|=1,$ Be that the three-phase current negative sequence component equates with the positive sequence component amplitude.

After dropping into the RPC device, the b supply arm provides part meritorious to a supply arm, and two supply arms are born the active power of load jointly, therefore have ${\stackrel{\&CenterDot;}{I}}_l={\stackrel{\&CenterDot;}{I}}_a+{\stackrel{\&CenterDot;}{I}}_b.$ Because the V/V transformer is 60 ° of tie lines forms, U _AcPhase place be ahead of U _Bc60 °, the electrified high-speed railway locomotive power-factor of load is often higher, and be similar at this and be taken as 1, so

In advance

After if RPC drops into

With

Amplitude than for n, then

Substitution (1) (2) Shi Kede:

$K_I=\frac{\sqrt{n^2-n+1}}{n+1}---\left(3\right)$

Can find out that by following formula when n=1, i.e. the active power of RPC transfer is a half of bearing power, ab two supply arms load complete equipilibrium, at this moment $K_I=\frac{\sqrt{n^2-n+1}}{n+1}=50\%,$ That is to say that the three-phase current negative sequence component still exists, and be positive sequence component half.

Continue to drop into the SVC device, because TSC and the electric capacity of TCR equivalence and the effect of inductance, two supply arm electric currents further change mutually.Suppose that it is α that TSC makes the leading angle of electric current of a supply arm, it is β that TCR makes the angle after the current hysteresis of b supply arm,

With

The ratio of real component be n, then two supply arm current relationships can be expressed as:

With this moment

Be the reference phasor, promptly

Then

According to (1) (2) Shi Kede:

Be not difficult to find out by formula (4), work as n=1, K during α=β=30 ° _I=0, the negative sequence component of three-phase current is by full remuneration, so RPC and SVC combined compensation system can improve the compensation effect to the three-phase current negative sequence component better, gets active power that this moment, RPC shifted and shifts capacity as the standard of RPC, represents with Cs.

Come the design of the parameter of SVC device in the illustrative system below in conjunction with accompanying drawing 2.With the locomotive load only the situation when a supply arm be example.If load current is I _La, suppose that still RPC drops into I afterwards _aWith I _bThe ratio of real component be n, the capacity that RPC shifts is lower than normal capacity, n＞1 is promptly arranged, then

$\frac{I_a\cos \mathrm{\&alpha;}}{I_b\cos \mathrm{\&beta;}}=n---\left(5\right)$

Ignore the loss of switching tube in the current transformer, the current balance type relation then arranged:

I _la＝I _acosα+I _bcosβ (6)

(5) formula substitution (6) is got:

$\left\{\begin{array}{c}{I}_a=\frac{n{I}_{\mathrm{la}}}{(n+1)\cos \mathrm{\&alpha;}}\\ I_b=\frac{I_{\mathrm{la}}}{(n+1)\cos \mathrm{\&beta;}}\end{array}\right.---\left(7\right)$

If the single-phase three winding step-down transformer step-downs of a buffer action when step-down ratio of step-down transformer are K _t, according to the effect of TSC and TCR as can be known:

$\left\{\begin{array}{c}{I}_{\mathrm{TSC}}=K_t{I}_a\cos \mathrm{\&alpha;}\tan \mathrm{\&alpha;}\\ I_{\mathrm{TCR}}=K_t{I}_b\cos \mathrm{\&beta;}\tan \mathrm{\&beta;}\end{array}\right.---\left(8\right)$

Make ab supply arm phase voltage be respectively U _Ac, U _Bc, the capacitance of TSC switching is C ₁, the equivalent inductance value of establishing TCR is L _1equ, then

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">C</figure-callout>}}_1=\frac{K_t{I}_{\mathrm{<figure-callout\; id="2"\; label="TSC"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">TSC</figure-callout>}}}{2\mathrm{\&pi;f}{U}_{\mathrm{ac}}}\\ {\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">L</figure-callout>}}_{1\mathrm{equ}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; bc"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">U</figure-callout>}}_{\mathrm{bc}}}{2\mathrm{\&pi;f}{K}_t{I}_{\mathrm{TCR}}}=\frac{U_{\mathrm{ac}}}{2\mathrm{\&pi;f}{K}_t{I}_{\mathrm{TCR}}}\end{array}\right.---\left(9\right)$

Wherein f is a fundamental frequency.

Simultaneous (7)-(9) can get:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">C</figure-callout>}}_1=\frac{n{I}_{\mathrm{la}}{{\mathrm{<figure-callout\; id="2"\; label="K\; t"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">K</figure-callout>}}_t}^2\tan \mathrm{\&alpha;}}{2\mathrm{\&pi;f}(n+1)U_{\mathrm{ac}}}\\ {\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A20091004355100112.png,A20091004355100122.png"\; state="\{\{state\}\}">L</figure-callout>}}_{1\mathrm{equ}}=\frac{U_{\mathrm{ac}}(n+1)}{2{\mathrm{\&pi;f}{K}_t}^2{I}_{\mathrm{la}}\tan \mathrm{\&beta;}}\end{array}\right.---\left(10\right)$

When locomotive load during only at the b supply arm, I after RPC drops into _aWith I _bThe ratio of real component be

The electric capacity that this moment, TSC dropped into is C ₂, the equivalent inductance value of TCR is L _2equ, in like manner can obtain:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">C</figure-callout>}}_2=\frac{I_{\mathrm{la}}{{\mathrm{<figure-callout\; id="2"\; label="K\; t"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">K</figure-callout>}}_t}^2\tan \mathrm{\&alpha;}}{2\mathrm{\&pi;f}(n+1)U_{\mathrm{ac}}}\\ {\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A20091004355100112.png"\; state="\{\{state\}\}">L</figure-callout>}}_{2\mathrm{equ}}=\frac{U_{\mathrm{ac}}(n+1)}{2\mathrm{\&pi;f}{{\mathrm{nK}}_t}^2{I}_{\mathrm{la}}\tan \mathrm{\&beta;}}\end{array}\right.---\left(11\right)$

Can obtain capacitor C by (10), (11) formula ₁And C ₂Value, and the equivalent reactance value that drops into of TCR.The value of L should be less than L _1equAnd L _2equIn smaller value, that is:

L＜min{L _1equ，L _2equ} (12)

So that TCR has bigger adjusting space.

Three-phase current unbalance degree when accompanying drawing 4 is to use independent use RPC that Matlab draws out and uses RPC and SVC association system and the relation curve of RPC capacity, the capacity of wherein getting RPC is C, abscissa is represented the ratio of RPC capacity and normal capacity, ordinate is represented three-phase current unbalance degree Ki, the curve when red line and blue line represent independent use RPC and association system in power-factor angle α=β=15 ° respectively.From figure, be not difficult to find out, when get the three-phase current unbalance degree be 50% by way of compensation during target the capacity of simple RPC identical with normal capacity, and the capacity of the required RPC of association system has only 57.31% of normal capacity, reduced 42.69% than the former, therefore, for identical compensation target, simple RPC is little for the required RPC capacity of association system, thereby reaches the purpose of relative reduction RPC capacity.

Claims (2)

1, a kind of power governor and Static Var Compensator associating negative-sequence current bucking-out system, it is characterized in that: comprise railway power regulator and Static Var Compensator, railway power regulator is installed between two supply arms of traction transformer secondary side by two single-phase three winding step-down transformers, Static Var Compensator is made up of two groups of thyristor switchable capacitors that are connected in parallel and one group of thyristor-controlled reactor, respectively by the single-phase three winding step-down transformers two traction power supply arms that insert in parallel, wherein thyristor switchable capacitor is connected to the single-phase three winding step-down transformers under the leading relatively supply arm of voltage-phase, and thyristor-controlled reactor is connected to the single-phase three winding step-down transformers under the supply arm that voltage-phase relatively lags behind.

2, a kind of power governor and Static Var Compensator associating negative-sequence current bucking-out system, it is characterized in that: comprise railway power regulator and Static Var Compensator, railway power regulator is installed between two supply arms of traction transformer secondary side by two single phase step-down transformers, Static Var Compensator is made up of two groups of thyristor switchable capacitors that are connected in parallel and one group of thyristor-controlled reactor, respectively by the single phase step-down transformer two traction power supply arms that insert in parallel, wherein thyristor switchable capacitor is connected to the single phase step-down transformer under the leading relatively supply arm of voltage-phase, and thyristor-controlled reactor is connected to the single phase step-down transformer under the supply arm that voltage-phase relatively lags behind.

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