CN103105583A - Low voltage failure rapid detection method - Google Patents

Abstract

The invention discloses a low voltage failure rapid detection method which comprises the following steps: detecting the current of a double-fed motor stator and the instantaneous value of frequency converter direct current bus voltage in real time, and judging the occurring of a network voltage drop failure when the current of the stator or the voltage of the direct current bus exceeds a set threshold value and a frequency converter is in a normal starting state. The low voltage failure rapid detection method is mainly applied to a doubly-fed type wind turbine system and can improve the low voltage traversing capacity of a wind turbine generator set.

Description

A kind of low voltage failure method for quick

Technical field

The invention belongs to wind power generation field, be specifically related to a kind of low voltage failure method for quick that is applied to double-fed type wind generator system.

Background technology

There is larger defective in aerogenerator aspect reply electric network fault ability.Electrical network breaks down and causes the aerogenerator set end voltage to fall, and causes the generator unit stator electric current to increase.Due to the strong coupling between rotor and stator, the stator current that increases fast can cause rotor current to rise.When rotor current rise to surpass the maximum current that frequency converter can bear, frequency converter caused the unit off-grid with out of service.In addition, because the wind energy conversion system governing speed is slower, the wind energy of fault wind energy conversion system in early stage absorption can obviously not reduce, and genset reduces due to set end voltage, can not be normally to the electrical network transmission of electric energy, be that some energy can't defeated people's electrical network, these energy are digested by internal system, will cause the series of problems such as capacitor charging, DC voltage raise fast, rotor acceleration, electromagnetic torque sudden change.And the national grid requirement, wind power generating set should have low voltage ride-through capability, and namely when electric network fault or disturbance caused that the voltage of wind farm grid-connected point falls, in the scope that voltage falls, the wind-powered electricity generation unit can uninterruptedly be incorporated into the power networks.Frequency converter must adopt certain method to assist whole wind power generating set to complete low voltage crossing in the electric network fault situation, the prerequisite of taking measures is that frequency converter first detects the line voltage fault, so the low voltage failure detection speed directly affects the low voltage ride-through capability of unit.Existing research is fallen fault detect for line voltage and is proposed solution, patent " a kind of low-voltage traversing and device " (CN201110392986.8) and patent " double-fed fan motor unit low-voltage ride-through method " all relate to fault detection algorithm in (CN201210029338.0).The fault detection method of above patent is to adopt rotor current or line voltage as the fault detect criterion.

Angle from generator, the double feedback electric engine stator side directly is connected with electrical network, it is direct impact that stator current rises, due to the strong coupling between rotor and stator, the stator current that increases fast can cause rotor current to rise, therefore, it is indirectly that rotor current rises, and there is certain time-delay in detection algorithm.

Adopt the network voltage detection criterion, although this detection method can correctly realize voltage is fallen the detection of fault, detection algorithm need to be converted into DC quantity with the alternating voltage instantaneous value, still has certain time-delay.

Summary of the invention

Purpose of the present invention is to provide a kind of low voltage failure method for quick, and it is mainly used in double-fed type wind generator system, can improve low voltage ride-through capability of wind turbine generator system.

In order to reach above-mentioned purpose, solution of the present invention is:

A kind of low voltage failure method for quick comprises the steps:

(1) detect in real time double feedback electric engine stator current and frequency changer direct current bus instantaneous voltage;

(2) when stator current or DC bus-bar voltage surpass the threshold value of setting, enter step (3);

(3) if frequency converter is in normal starting state, judge that line voltage falls fault and occurs.

The threshold value I of said stator electric current _{Ds_lim}Satisfy formula:

0.85I _{ds_max}>I _{ds_lim}>1.2I _{ds_nom}

Wherein, I _{Ds_max}For system allows maximum stator current, I _{Ds_nom}Be rated secondary current.

The threshold value U of above-mentioned DC bus-bar voltage _{Dc_lim}Satisfy formula:

0.85U _{dc_max}>U _{dc_lim}>1.2U _{dc_nom}

Wherein, U _{Dc_max}For system allows maximum DC bus-bar voltage, U _{Dc_nom}Specified DC bus-bar voltage when normally moving for system.

After adopting such scheme, the present invention adopts motor double feedback electric engine stator current and frequency changer direct current bus instantaneous voltage to fall judgment basis as line voltage, namely when frequency converter normally starts, control system detects that DC voltage surpass to be set threshold value or the double feedback electric engine stator current surpasses when setting threshold value, think that line voltage falls generation, control system begins to carry out the low voltage crossing steering logic.Detection method of the present invention is applied to double-fed type frequency converter low voltage crossing control strategy, can improve line voltage fault detect speed, improves the low voltage ride-through capability of wind power generating set.

Description of drawings

Fig. 1 is the entire block diagram of the applied double-fed type wind generator system of the present invention;

Fig. 2 is that the present invention carries out the logical diagram that low voltage failure detects;

Wherein, arrow representative data flow path direction.

Embodiment

Below with reference to accompanying drawing, technical scheme of the present invention is elaborated.

The invention provides a kind of low voltage failure method for quick, be applied to double-fed type wind generator system, can coordinate shown in Figure 1ly, wherein, Udc represents frequency changer direct current bus voltage, and Ids represents the double feedback electric engine stator current; Described detection method comprises the steps:

(1) detect in real time double feedback electric engine stator current and frequency changer direct current bus instantaneous voltage;

(2) when stator current or DC bus-bar voltage surpass the threshold value of setting, enter step (3);

(3) if frequency converter is in normal starting state, judge that line voltage falls fault and occurs.

The threshold value I of stator current _{Ds_lim}Satisfy formula:

0.85I _{ds_max}>I _{ds_lim}>1.2I _{ds_nom}

Wherein, I _{Ds_max}For system allows maximum stator current, I _{Ds_nom}Be rated secondary current.

The threshold value U of DC bus-bar voltage _{Dc_lim}Satisfy formula:

0.85U _{dc_max}>U _{dc_lim}>1.2U _{dc_nom}

Wherein, U _{Dc_max}For system allows maximum DC bus-bar voltage, U _{Dc_nom}Specified DC bus-bar voltage when normally moving for system.

Below will the present invention is further described by specific embodiment.

The explanation threshold value U as an example of a kind of double feedback electric engine type example _{Dc_lim}And I _{Ds_lim}Computing method.Unit parameter is as shown in table 1:

Table 1

Generator rating power P N	1500kW
		Generator rated voltage U N	690V
The specified DC bus-bar voltage U of frequency converter dc_nom	1070V
		Synchronous rotational speed n	1500RPM
Rated speed n N	1800RPM

Can directly obtain threshold value U by above-mentioned parameter _{Dc_nom}Be 1070V.The computing method of stator current ratings are as follows:

Revolutional slip s calculates:

$s=\frac{n_N-n}{n}=0.2$

Stator rated power P _SCalculate:

P _S=P _N(1-s)=1200kW

Rated secondary current I _{Ds_nom}Calculate:

$I_{\mathrm{ds}\_\mathrm{nom}}=P_s/\sqrt{3}\·U_N=1004A$

U _{Dc_max}And I _{Ds_max}Can bear the maximal value estimation according to system:

U _{dc_max}=1600V

I _{ds_max}=2000A

Substitution threshold value formula can draw span after calculating:

1360V>U _{dc_lim}>1284V

1700A>I _{ds_lim}>1204A

Choose suitable threshold value in this span, when DC bus-bar voltage or stator current have one to satisfy operation condition, and frequency converter is in normal starting state, namely is judged to be voltage and falls generation, control system is completed low voltage crossing with rapid switching control strategy.

To sum up, a kind of low voltage failure method for quick of the present invention, adopt double feedback electric engine stator current and frequency changer direct current bus instantaneous voltage to fall criterion as line voltage, motor stator electric current and DC bus-bar voltage instantaneous value are logically the relation of "or", as long as one of them condition is met, and frequency converter is in normal starting state, thinks that namely line voltage falls.

Fall instantaneously at voltage, line voltage descends, but the stator built-in potential can not suddenly change, and can cause instantaneous voltage poor, because stator reactance is very little, be m Ω rank, so stator side will produce very large momentary current.Because reactance is little, Current rise speed is very fast, has improved fault detect speed.

Adopting DC voltage criterion main cause is that DC voltage has directly reflected the unit energy magnitude relation.When line voltage fell, whole unit generation power descended, but prime mover power input can not suddenly change, and unnecessary energy can be embodied in DC bus-bar voltage and rise rapidly.Therefore, adopt stator current combined with DC bus voltage instantaneous value can effectively improve fault detect speed and accuracy as fault generation criterion.Utilize the double feedback electric engine stator reactance little on the detection principle of stator current, the feature that the current transformation rate is large, equivalent fault occurs on amplitude; DC bus-bar voltage criterion equivalent fault on energy occurs; Choose reasonable stator current and DC bus-bar voltage threshold value can effectively promote unit low voltage failure detection speed and then accuracy.

Above embodiment only for explanation technological thought of the present invention, can not limit protection scope of the present invention with this, every technological thought that proposes according to the present invention, and any change of doing on the technical scheme basis is within all falling into protection domain of the present invention.

Claims (3)

1. a low voltage failure method for quick, is characterized in that comprising the steps:

(1) detect in real time double feedback electric engine stator current and frequency changer direct current bus instantaneous voltage;

(2) when stator current or DC bus-bar voltage surpass the threshold value of setting, enter step (3);

(3) if frequency converter is in normal starting state, judge that line voltage falls fault and occurs.

2. a kind of low voltage failure method for quick as claimed in claim 1, is characterized in that: the threshold value I of described stator current _{Ds_lim}Satisfy formula:

0.85I _{ds_max}>I _{ds_lim}>1.2I _{ds_nom}

Wherein, I _{Ds_max}For system allows maximum stator current, I _{Ds_nom}Be rated secondary current.

3. a kind of low voltage failure method for quick as claimed in claim 1, is characterized in that: the threshold value U of described DC bus-bar voltage _{Dc_lim}Satisfy formula:

0.85U _{dc_max}>U _{dc_lim}>1.2U _{dc_nom}

Wherein, U _{Dc_max}For system allows maximum DC bus-bar voltage, U _{Dc_nom}Specified DC bus-bar voltage when normally moving for system.

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