CN106353637A - Method for fault analysis and location of thyristor controlled reactor of static var compensator - Google Patents

Abstract

The invention discloses a method for fault analysis and location of thyristor controlled reactor of static var compensator,which comprises the step of identifying and locating a fault source gradually by analyzing and calculating the waveform recorded during the fault period,analyzing the abnormalities of the bus line voltage to distinguish the internal fault from the external fault, distinguishing the main link fault or other link/equipment faults in the control system by analyzing whether the three-phase current is abnormal at the same time, and calculating the third-harmonic component in the current to distinguish thyristor valve block control failure from reactor failure. The invention analyzes and locates the fault source of the static var compensator rapidly without relying on laboratory detection or fault simulation, and has the advantages of simplified fault analysis, shortened outage time, improved efficiency, reduced cost and wide application range.

Description

SVC thyristor-controlled reactor accident analysis localization method

Technical field

The present invention relates to electrical engineering field is and in particular to a kind of SVC thyristor-controlled reactor fault Analyzing and positioning method.

Background technology

SVC (svc) has been developed as very ripe facts device, and it is widely used in modern electricity Force system send out, defeated, distribution links.It is one of reactive power compensator the most advanced as current technology, Static Synchronous Reactive-load compensator no longer to produce required reactive power using jumbo capacitor, inducer, but passes through power electronics device The HF switch of part is realized to reactive power compensation technology qualitative leap, and the dynamic reactive being particularly well-suited in median and high voltage power system is mended Repay.There is no rotary part as one kind, quickly, smooth controlled dynamic reactive power compensation equipment, SVC is Will be used in parallel to controlled reactor and power capacitor.Wherein capacitor can send reactive power, and controlled reactor can absorb Reactive power.By being adjusted to reactor, whole device can be made smoothly to change to absorbing no from sending reactive power Work(power, and response quickly.

Thyristor-controlled reactor (hereinafter referred to as tcr) branch road is as the core of SVC, existing electricity Anti- device, has thyristor controlled series compensation, complex structure again.A lot of tcr branch road reactor damage faults are there are in recent years.Accordingly, it would be desirable to A kind of can quick analyzing and positioning svc Reactor Fault method.The existing analyzing and positioning method for svc fault is less, A kind of svc analogue simulation dress based on realtime digital simulation platform as disclosed in the patent of Application No. 201120163744.7 Put, these detection means and method are applied to analyzing and positioning svc fault, the detection under laboratory environment or emulation mould must be carried out Intend, excessively complicated loaded down with trivial details, it is not suitable for the quick analyzing and positioning of svc fault.

In SVC life cycle, unavoidably need the crystalline substance to its core thyristor control branch road Brake tube control performance carries out Site Detection.Accordingly, it would be desirable to a kind of be applied to simple, the effective detection that svc runs site environment Device and method.The existing detection method for SVC (svc) is more, but is typically only applicable to laboratory ring The disclosed SVC based on multimode fibre in border, the such as Chinese patent literature of Application No. cn200510102658.4 Triggered quiet with a kind of wind energy turbine set disclosed in detecting system, the Chinese patent literature of Application No. cn201310495202.3 with photoelectricity The only parameter detection method of reactive-load compensator and system etc..But, these detection means and method are all excessively complicated loaded down with trivial details, detection Environment is higher with site requirements, is not suitable for svc and runs site environment.

Content of the invention

The technical problem to be solved in the present invention: for the problems referred to above of prior art, provide one kind need not rely on laboratory Detection or fault simulation simulation, can the quick analyzing and positioning source of trouble, accident analysis can be simplified, shorten idle time, improve and imitate Rate, reduces cost, the SVC thyristor-controlled reactor accident analysis localization method of wide accommodation.

In order to solve above-mentioned technical problem, the technical solution used in the present invention is:

A kind of SVC thyristor-controlled reactor accident analysis localization method, step includes:

1) obtain the record waveform during SVC fault, SVC is determined according to record waveform The angle of tcr branch road in three-phase current i_ab、i_bc、i_caAnd bus line voltage u_ab、u_bc、u_ca；

2) current waveform is found out according to record waveform and substantially abnormal timing node t occurs, when contrast judges timing node t Voltage waveform before and after quarter whether there is significant change, if there is significant change and consistent with current anomaly in voltage waveform, Then execution step 3), otherwise redirect execution step 4)；

3) whether the change of investigation voltage waveform is led to if it is determined that voltage waveform change turns to external fault and leads by external fault Cause, then judge that the source of trouble of SVC fault as external fault and exits；Otherwise, redirect execution step 4)；

4) determine that SVC fault leads to for internal fault, contrast judges the electricity before and after timing node t Whether exception to stream waveform simultaneously in three-phase, if three-phase occurs extremely, redirecting execution step 5 simultaneously)；Otherwise redirect execution Step 6)；

5) judge that the source of trouble of SVC fault as SVC control system main ring section and exits, Described main ring section includes the sampling element of control system, Trigger Angle calculates link and three-phase phase-locked loop section；

6) judge that current waveform is different normally due to Trigger Angle change causes or because the change of specified equivalent inductance causes, such as Fruit current waveform is different normally due to Trigger Angle change causes, then redirect execution step 7), otherwise redirect execution step 8)；

7) determine that SVC fault is to control fault to lead to by tcr thyristor controlled series compensation, judge static var compensation The source of trouble repaying device fault is the phaselocked loop section of the thyristor controlled series compensation of abnormal phase and valve control and abnormal phase and exits；

8) determine that SVC fault is to be led to by tcr Reactor Fault, judge SVC fault The source of trouble be the reactor body of abnormal phase and exit.

Preferably, described step 6) detailed step include:

6.1) timing node t tcr branch road exception phase current is obtained fundametal compoment i' by Fourier transformation₀, three Order harmonic components i'₃, non-for timing node t tcr branch road abnormal phase current is obtained fundametal compoment i by Fourier transformation₀；

6.2) assume one: Trigger Angle change causes current anomaly, abnormal mutually specified equivalent inductance is constant；Counted according to formula (1) Evaluation time node t is conducted angle α extremely₁, calculate timing node t further according to formula (2) and assume one theoretic for three times Harmonic component i'_3α；

${i^{\′}}_0=\frac{u}{\mathrm{\ω}l\·\mathrm{\π}}(2\mathrm{\π}-2{\mathrm{\α}}_1+sin2{\mathrm{\α}}_1)---\left(1\right)$

${i^{\′}}_{3\mathrm{\α}}=\frac{u}{\mathrm{\ω}l}\frac{4}{\mathrm{\π}}\[\frac{{\mathrm{sin\α}}_{1}cos3{\mathrm{\α}}_1-3{\mathrm{cos\α}}_{1}sin3{\mathrm{\α}}_1}{3*(3^2-1)}\]---\left(2\right)$

In formula (1) and (2), α₁Express time node t is conducted angle extremely, i'_3αExpress time node t is assumed One theoretic third-harmonic component, i'₀Express time node t tcr branch road exception phase current is obtained by Fourier transformation To fundametal compoment, u express time node t tcr branch road bus line voltage virtual value, l represents that tcr branch road is abnormal mutually former specified Equivalent inductance, ω is frequency；

6.3) two are assumed: specified equivalent inductance change causes current anomaly；First, when timing node t being calculated according to formula (3) Carve the angle of flow α of non-abnormal phase₀；

$i_0=\frac{u}{{\mathrm{\ωl}}_0\·\mathrm{\π}}(2\mathrm{\π}-2{\mathrm{\α}}_0+sin2{\mathrm{\α}}_0)---\left(3\right)$

In formula (3), i₀The non-abnormal phase current of express time node t tcr branch road obtains fundamental wave by Fourier transformation Component, u express time node t tcr branch road bus line voltage virtual value, l₀Represent the mutually specified equivalence of the non-exception of tcr branch road Inductance, ω is frequency, α₀The angle of flow of the non-abnormal phase of express time node t.

Assume in two that abnormal the be conducted angle and non-exception angle that is conducted is consistent, timing node t is conducted angle extremely For α₀, the abnormal mutually specified equivalent inductance l' of timing node t is calculated according to formula (4), calculates timing node t further according to formula (5) Moment assumes two theoretic third-harmonic component i'_3l；

$i_0^{\′}=\frac{u}{{\mathrm{\ωl}}^{\′}\·\mathrm{\π}}(2\mathrm{\π}-2{\mathrm{\α}}_0+sin2{\mathrm{\α}}_0)---\left(4\right)$

$i_{3l}^{\′}=\frac{u}{{\mathrm{\ωl}}^{\′}}\frac{4}{\mathrm{\π}}\[\frac{{\mathrm{sin\α}}_{0}cos3{\mathrm{\α}}_0-3{\mathrm{cos\α}}_{0}sin3{\mathrm{\α}}_0}{3*(3^2-1)}\]---\left(5\right)$

In formula (4) and formula (5), the abnormal mutually specified equivalent inductance of l' express time node t, i'_3lExpress time node t Moment assumes two theoretic third-harmonic components, α₀The angle of flow of express time node t exception phase, i'₀Express time section Point t tcr branch road exception phase current obtains fundametal compoment, u express time node t tcr branch road by Fourier transformation Bus line voltage virtual value, ω is frequency；

6.4) judge whether condition shown in formula (6) is set up, if set up, judge in angle current waveform different normally due to tactile Send out angle change cause, if in angle current waveform different normally due to Trigger Angle change cause, redirect execution step 7)；Otherwise jump Turn execution step 8)；

|i'_3α-i'₃|<|i'_3l-i'₃| (6)

In formula (6), i'_3αExpress time node t assumes a theoretic third-harmonic component, i'_3lExpress time section Point t assumes two theoretic third-harmonic components, i'₃Express time node t tcr branch road exception phase current passes through Fu In the third-harmonic component that obtains of leaf transformation.

SVC thyristor-controlled reactor accident analysis localization method of the present invention is by recording during to fault The analytical calculation of waveform, progressively recognizes positioning failure source, by isolated-phase buses electric voltage exception situation, differentiates internal fault or outer Portion's fault；By analyzing whether three-phase current occurs extremely, differentiating control system main ring section fault or other link/equipment simultaneously Fault, can differentiate thyristor controlled series compensation and control fault or Reactor Fault, need not rely on test in laboratory or fault simulation simulation, It is capable of the tcr source of trouble of quick analyzing and positioning SVC, have an advantage that

1st, simplify malfunction analysis procedure.The control system that SVC need not be dismantled is carried out test in laboratory or is taken Build phantom and carry out fault simulation, by the analytical calculation to recorder data, quick positioning failure source.

2nd, shorten equipment idle time.By the quick analyzing and positioning for the source of trouble, change trouble unit, improve fault SVC overhaul of the equipments efficiency, shortens equipment idle time.

3rd, improve failure investigation efficiency.By the analytical calculation to recorder data, can positioning failure part, such as need to enter one Step finds out fault concrete reason, can be directed to trouble unit again and carry out detection or fault simulation simulation, effectively shorten whole fault The investigation and analysis time, improve efficiency.

4th, reduce trouble shooting cost.Shorten faulty equipment recovery time and failure investigation analysis time, decrease equipment Test in laboratory, the work of fault simulation simulation, will reduce failure investigation and overhaul of the equipments cost.

5th, wide accommodation.Only need the record waveform such as three-phase current in tcr branch road angle, connect bus line voltage, you can open Exhibition accident analysis positioning, this is also one of key point of the present invention.

6th, detection environment and site requirements are low, are particularly suited for the operation site environment of SVC.

Brief description

Fig. 1 is the system structure diagram of detected SVC (prior art).

Fig. 2 is the basic procedure schematic diagram of present invention method.

Fig. 3 be present invention method step 6) basic procedure schematic diagram.

Specific embodiment

Hereafter will be, to SVC IGCT control of the present invention taking SVC shown in Fig. 1 (svc) as a example Reactor Fault analyzing and positioning method processed is further described.

Referring to Fig. 1, this SVC includes the three-phase being connected in parallel on the bus of 35kv power circuit respectively Thyristor control branch road, every phase thyristor control branch road has 24 thyristor controlled series compensation (being referred to as valve group in Fig. 1), static var compensation The control system repaying device is connected with the control end of each thyristor controlled series compensation respectively, for controlling three-phase thyristor controlling brancher to carry out Reactive-load compensation, this control system locks phase for split-phase.Every phase thyristor control has two Controlled Reactor, every equal value inductance ratings It is about 0.0275h (dispatch from the factory measured value).This tcr branch road a phase breaks down.

As shown in Fig. 2 the step of the present embodiment SVC thyristor-controlled reactor accident analysis localization method Rapid inclusion:

1) obtain the record waveform during SVC fault, SVC is determined according to record waveform The angle of tcr branch road in three-phase current i_ab、i_bc、i_caAnd bus line voltage u_ab、u_bc、u_ca；

2) current waveform is found out according to record waveform and substantially abnormal timing node t occurs, when contrast judges timing node t Voltage waveform before and after quarter whether there is significant change, if there is significant change and consistent with current anomaly in voltage waveform, Then execution step 3), otherwise redirect execution step 4)；In the present embodiment, substantially abnormal, voltage waveform in aforementioned currents waveform There is significant change and be three-phase current waveform, variable quantity before and after timing node t for the bus line voltage waveform in finger angle Beyond the threshold value being given；

3) whether the change of investigation voltage waveform is led to if it is determined that voltage waveform change turns to external fault and leads by external fault Cause, then judge that the source of trouble of SVC fault as external fault and exits；Otherwise, redirect execution step 4)；Investigation Whether voltage waveform change when being led to by external fault, can inquire about this moment whether electrical network occur the catastrophe failures such as near region short circuit with And near region electric network protection action situation, to determine whether voltage waveform change is that external fault leads to；

4) determine that SVC fault leads to for internal fault, contrast judges the electricity before and after timing node t Whether exception to stream waveform simultaneously in three-phase, if three-phase occurs extremely, redirecting execution step 5 simultaneously)；Otherwise redirect execution Step 6)；

5) judge that the source of trouble of SVC fault as SVC control system main ring section and exits, Described main ring section includes the sampling element of SVC control system, Trigger Angle calculates link and three-phase phase-locked loop Section；After link based on the judgement source of trouble, can check that the sampling element of SVC control system, Trigger Angle calculate one by one Link and three-phase phase-locked loop section, with further positioning failure source；

6) judge that current waveform is different normally due to Trigger Angle change causes or because the change of specified equivalent inductance causes, such as Fruit current waveform is different normally due to Trigger Angle change causes, then redirect execution step 7), otherwise redirect execution step 8)；

7) determine that SVC fault is to control fault to lead to by tcr thyristor controlled series compensation, judge static var compensation The source of trouble repaying device fault is the phaselocked loop section of the thyristor controlled series compensation of abnormal phase and valve control and abnormal phase and exits；Judge the source of trouble After the phaselocked loop section of the thyristor controlled series compensation for abnormal phase and valve control and abnormal phase, can check one by one abnormal phase thyristor controlled series compensation and Valve control, the phaselocked loop section with abnormal phase, with further positioning failure source；

8) determine that SVC fault is to be led to by tcr Reactor Fault, judge SVC fault The source of trouble be the reactor body of abnormal phase and exit；Judge the source of trouble as after the reactor body of abnormal phase it should check The reactor body of abnormal phase, emphasis investigates turn-to-turn short circuit.

As shown in figure 3, step 6) detailed step include:

6.1) timing node t tcr branch road exception phase current is obtained fundametal compoment i' by Fourier transformation₀, three Order harmonic components i'₃, non-for timing node t tcr branch road abnormal phase current is obtained fundametal compoment i by Fourier transformation₀；

6.2) assume one: Trigger Angle change causes current anomaly, abnormal mutually specified equivalent inductance is constant；Counted according to formula (1) Evaluation time node t is conducted angle α extremely₁, calculate timing node t further according to formula (2) and assume one theoretic for three times Harmonic component i'_3α；

${i^{\&prime;}}_0=\frac{u}{\mathrm{\&omega;}l\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_1+sin2{\mathrm{\&alpha;}}_1)---\left(1\right)$

${i^{\&prime;}}_{3\mathrm{\&alpha;}}=\frac{u}{\mathrm{\&omega;}l}\frac{4}{\mathrm{\&pi;}}\&lsqb;\frac{{\mathrm{sin\&alpha;}}_{1}cos3{\mathrm{\&alpha;}}_1-3{\mathrm{cos\&alpha;}}_{1}sin3{\mathrm{\&alpha;}}_1}{3*(3^2-1)}\&rsqb;---\left(2\right)$

In formula (1) and (2), α₁Express time node t is conducted angle extremely, i'_3αExpress time node t is assumed One theoretic third-harmonic component, i'₀Express time node t tcr branch road exception phase current is obtained by Fourier transformation To fundametal compoment, u express time node t tcr branch road bus line voltage virtual value, l represents that tcr branch road is abnormal mutually former specified Equivalent inductance, ω is frequency；

6.3) two are assumed: specified equivalent inductance change causes current anomaly；First, when timing node t being calculated according to formula (3) Carve the angle of flow α of non-abnormal phase₀；

$i_0=\frac{u}{{\mathrm{\&omega;l}}_0\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_0+sin2{\mathrm{\&alpha;}}_0)---\left(3\right)$

In formula (3), i₀The non-abnormal phase current of express time node t tcr branch road obtains fundamental wave by Fourier transformation Component, u express time node t tcr branch road bus line voltage virtual value, l₀Represent the mutually specified equivalence of the non-exception of tcr branch road Inductance, ω is frequency, α₀The angle of flow of the non-abnormal phase of express time node t.

Assume in two that abnormal the be conducted angle and non-exception angle that is conducted is consistent, timing node t is conducted angle extremely For α₀, the abnormal mutually specified equivalent inductance l' of timing node t is calculated according to formula (4), calculates timing node t further according to formula (5) Moment assumes two theoretic third-harmonic component i'_3l；

$i_0^{\&prime;}=\frac{u}{{\mathrm{\&omega;l}}^{\&prime;}\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_0+sin2{\mathrm{\&alpha;}}_0)---\left(4\right)$

$i_{3l}^{\&prime;}=\frac{u}{{\mathrm{\&omega;l}}^{\&prime;}}\frac{4}{\mathrm{\&pi;}}\&lsqb;\frac{{\mathrm{sin\&alpha;}}_{0}cos3{\mathrm{\&alpha;}}_0-3{\mathrm{cos\&alpha;}}_{0}sin3{\mathrm{\&alpha;}}_0}{3*(3^2-1)}\&rsqb;---\left(5\right)$

In formula (4) and formula (5), the abnormal mutually specified equivalent inductance of l' express time node t, i'_3lExpress time node t Moment assumes two theoretic third-harmonic components, α₀The angle of flow of express time node t exception phase, i'₀Express time section Point t tcr branch road exception phase current obtains fundametal compoment, u express time node t tcr branch road by Fourier transformation Bus line voltage virtual value, ω is frequency；

6.4) judge whether condition shown in formula (6) is set up, if set up, judge in angle current waveform different normally due to tactile Send out angle change cause, if in angle current waveform different normally due to Trigger Angle change cause, redirect execution step 7)；Otherwise jump Turn execution step 8)；

|i'_3α-i'₃|<|i'_3l-i'₃| (6)

In formula (6), i'_3αExpress time node t assumes a theoretic third-harmonic component, i'_3lExpress time section Point t assumes two theoretic third-harmonic components, i'₃Express time node t tcr branch road exception phase current passes through Fu In the third-harmonic component that obtains of leaf transformation.

Referring to Fig. 1, u before and after t in the present embodiment_ab、u_bc、u_caNo significant change is it is believed that fault is drawn for internal fault source Rise；Only has i before and after t_abAbnormal, i in waveform_bc、i_caWaveform is normal, and investigation fault is led by control system main ring section fault Cause；U=36kv, i are obtained by recorder data₀≈1010a、i'₀≈1675a、i'₃≈ 580a, brilliant according to SVC Brake tube controls reactor simulated failure computational methods, is calculated α₀=130 °, α₁≈119°、i'_3α≈176a、l'≈ 0.0166h、i'_3l≈596a；|i'_3α-i'₃|>|i'_3l-i'₃|, current anomaly is that specified equivalent inductance change causes.Therefore, recognize Led to by tcr Reactor Fault for fault.By check a phase reactor body, find reactor interturn short circuit vestige it was demonstrated that therefore Barrier analyzing and positioning is correct.

The above is only the preferred embodiment of the present invention, and protection scope of the present invention is not limited merely to above-mentioned enforcement Example, all technical schemes belonging under thinking of the present invention belong to protection scope of the present invention.It should be pointed out that for the art Those of ordinary skill for, some improvements and modifications without departing from the principles of the present invention, these improvements and modifications Should be regarded as protection scope of the present invention.

Claims (2)

1. a kind of SVC thyristor-controlled reactor accident analysis localization method is it is characterised in that step includes:

1) obtain the record waveform during SVC fault, SVC is determined according to record waveform Three-phase current i in the angle of tcr branch road_ab、i_bc、i_caAnd bus line voltage u_ab、u_bc、u_ca；

2) current waveform is found out according to record waveform and substantially abnormal timing node t occurs, before contrast judges timing node t Voltage waveform afterwards whether there is significant change, if voltage waveform has significant change and consistent with current anomaly, holds Row step 3), otherwise redirect execution step 4)；

3) whether the change of investigation voltage waveform leads to if it is determined that voltage waveform change turns to external fault and leads to by external fault, Then judge that the source of trouble of SVC fault as external fault and exits；Otherwise, redirect execution step 4)；

4) determine that SVC fault leads to for internal fault, contrast judges the current wave before and after timing node t Whether exception to shape simultaneously in three-phase, if three-phase occurs extremely, redirecting execution step 5 simultaneously)；Otherwise redirect execution step 6)；

5) judge that the source of trouble of SVC fault as SVC control system main ring section and exits, described Main ring section includes the sampling element of control system, Trigger Angle calculates link and three-phase phase-locked loop section；

6) judge that current waveform is different normally due to Trigger Angle change causes or because the change of specified equivalent inductance causes, if electric Stream Wave anomaly is because Trigger Angle change causes, then redirect execution step 7), otherwise redirect execution step 8)；

7) determine that SVC fault is to control fault to lead to by tcr thyristor controlled series compensation, judge SVC The source of trouble of fault is the phaselocked loop section of the thyristor controlled series compensation of abnormal phase and valve control and abnormal phase and exits；

8) determine that SVC fault is to be led to by tcr Reactor Fault, judge the event of SVC fault Barrier source is the reactor body of abnormal phase and exits.

2. SVC thyristor-controlled reactor accident analysis localization method according to claim 1, it is special Levy and be, described step 6) detailed step include:

6.1) timing node t tcr branch road exception phase current is obtained fundametal compoment i' by Fourier transformation₀, triple-frequency harmonics Component i'₃, non-for timing node t tcr branch road abnormal phase current is obtained fundametal compoment i by Fourier transformation₀；

6.2) assume one: Trigger Angle change causes current anomaly, abnormal mutually specified equivalent inductance is constant；When being calculated according to formula (1) Intermediate node t is conducted angle α extremely₁, calculate timing node t further according to formula (2) and assume a theoretic triple-frequency harmonics Component i'_3α；

${i^{\&prime;}}_0=\frac{u}{\mathrm{\&omega;}l\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_1+sin2{\mathrm{\&alpha;}}_1)---\left(1\right)$

${i^{\&prime;}}_{3\mathrm{\&alpha;}}=\frac{u}{\mathrm{\&omega;}l}\frac{4}{\mathrm{\&pi;}}\&lsqb;\frac{{\mathrm{sin\&alpha;}}_{1}cos3{\mathrm{\&alpha;}}_1-3{\mathrm{cos\&alpha;}}_{1}sin3{\mathrm{\&alpha;}}_1}{3*(3^2-1)}\&rsqb;---\left(2\right)$

In formula (1) and (2), α₁Express time node t is conducted angle extremely, i'_3αExpress time node t assumes a reason By upper third-harmonic component, i'₀Express time node t tcr branch road exception phase current obtains base by Fourier transformation Wave component, u express time node t tcr branch road bus line voltage virtual value, l represents the abnormal mutually former specified equivalence of tcr branch road Inductance, ω is frequency；

6.3) two are assumed: specified equivalent inductance change causes current anomaly；First, timing node t is calculated according to formula (3) non- The angle of flow α of abnormal phase₀；

$i_0=\frac{u}{{\mathrm{\&omega;l}}_0\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_0+sin2{\mathrm{\&alpha;}}_0)---\left(3\right)$

In formula (3), i₀The non-abnormal phase current of express time node t tcr branch road obtains fundametal compoment, u by Fourier transformation Express time node t tcr branch road bus line voltage virtual value, l₀Represent the mutually specified equivalent inductance of the non-exception of tcr branch road, ω For frequency, α₀The angle of flow of the non-abnormal phase of express time node t.

In hypothesis two, the abnormal angle that is conducted is conducted with non-exception, and angle is consistent, and timing node t is conducted angle extremely also for α₀, The abnormal mutually specified equivalent inductance l' of timing node t is calculated according to formula (4), calculates timing node t further according to formula (5) false If two theoretic third-harmonic component i'_3l；

$i_0^{\&prime;}=\frac{u}{{\mathrm{\&omega;l}}^{\&prime;}\&centerdot;\mathrm{\&pi;}}(2\mathrm{\&pi;}-2{\mathrm{\&alpha;}}_0+sin2{\mathrm{\&alpha;}}_0)---\left(4\right)$

$i_{3l}^{\&prime;}=\frac{u}{{\mathrm{\&omega;l}}^{\&prime;}}\frac{4}{\mathrm{\&pi;}}\&lsqb;\frac{{\mathrm{sin\&alpha;}}_{0}cos3{\mathrm{\&alpha;}}_0-3{\mathrm{cos\&alpha;}}_{0}sin3{\mathrm{\&alpha;}}_0}{3*(3^2-1)}\&rsqb;---\left(5\right)$

In formula (4) and formula (5), the abnormal mutually specified equivalent inductance of l' express time node t, i'_3lExpress time node t Assume two theoretic third-harmonic components, α₀The angle of flow of express time node t exception phase, i'₀Express time node t Moment tcr branch road exception phase current obtains fundametal compoment, u express time node t tcr branch road bus by Fourier transformation Line voltage virtual value, ω is frequency；

6.4) judge whether condition shown in formula (6) is set up, if set up, judge in angle current waveform different normally due to Trigger Angle Change causes, if in angle current waveform different normally due to Trigger Angle change cause, redirect execution step 7)；Otherwise redirect and hold Row step 8)；

|i'_3α-i'₃|<|i'_3l-i'₃| (6)

In formula (6), i'_3αExpress time node t assumes a theoretic third-harmonic component, i'_3lDuring express time node t Carve and assume two theoretic third-harmonic components, i'₃Express time node t tcr branch road exception phase current passes through Fourier Convert the third-harmonic component obtaining.