CN104078999B - The computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time - Google Patents

Abstract

The present invention is the computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time, be characterized in: start with from setting up the disturbed rear electromechanical transient Mathematical Modeling of DFIG herein, analyze DFIG initial operating condition, the effects of factor in electromechanical transient such as strength of turbulence and Crowbar protection act, DFIG unit of having derived reaches the condition of overspeed protection action, and by proposed method by the analysis to certain wind energy turbine set wind-powered electricity generation group of planes off-grid example, the time of overspeed protection action definite value is accelerated to according to calculated each machine group rotor, correctly identify the Wind turbines of overspeed protection action.The method calculates simple, has advantages such as calculating fast, evaluation precision is high, using value is high, application on site prospect is large.

Description

The computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time

Technical field

The present invention relates to double-fed fan motor unit hypervelocity off-grid field; propose the computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time; the method is by the analysis to certain wind energy turbine set wind-powered electricity generation group of planes off-grid example; accelerate to the time of overspeed protection action definite value according to calculated each machine group rotor, correctly identify the Wind turbines of overspeed protection action.

Background technology

Along with global wind-powered electricity generation fast development, China has planned eight ten million multikilowatt wind power base, now become the maximum country of global installed capacity, under the Wind Power Development pattern of extensive concentrated exploitation, Wind turbines large area off-grid causes comparatively serious safety problem, connect electrical network and bring impact to institute, guarantee safe operation of wind turbine and become the emphasis of electric power enterprise and scientific research personnel's concern, be of great significance.

The inducement of large-scale wind power unit off-grid accident is a lot, traditional research mainly concentrates on line voltage and subsides in the analysis of Wind turbines electromagnetic transient and low voltage crossing problem that disturbance causes, in fact, Crowbar protects, be mainly used in the low voltage crossing technology of wind power generation inverter, it is used in wind power generator rotor side, for bypass rotor-side converter, although Crowbar protection act protects the security of operation of electromagnetic transient rotor side converter, but after its action, break the original torque balance condition of double-fed wind power generator, cause electromechanical transient process, if new torque balance can be set up in follow-up electromechanical transient process, then double-fed wind power generator rotating speed can be stablized, if can not reach new torque balance, then double-fed wind power generator still has the risk of hypervelocity off-grid.The English name of crowbar is Crowbar; The English name of double-fed wind power generator is Double-FedInductionGenerator, is abbreviated as DFIG.This area adopts English name usually, or English name abbreviation.

Summary of the invention

The object of the invention is, provide a kind of scientific and reasonable, simple, computational speed is fast, precision is high, can to the computational methods of the double-fed fan motor unit hypervelocity off-grid crash time that off-grid Wind turbines identifies because of overspeed protection action.

The object of the invention is to be realized by following technical scheme: the computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time, it is characterized in that, it comprises the following steps:

1). set up DFIG electromechanical transient Mathematical Modeling

DFIG equation of rotor motion is:

$\frac{{\mathrm{d\ω}}_r}{\mathrm{dt}}=\frac{{\mathrm{\ω}}_N}{T_j}(T_m^{*}-T_e^{*})---\left(1\right)$

$\left\{\begin{array}{c}{T^{*}}_m={P^{*}}_m/{{\mathrm{\Ω}}^{*}}_r\\ {T^{*}}_e={T^{*}}_{\mathrm{es}}-{T^{*}}_{\mathrm{er}}\end{array}\right.---\left(2\right)$

In formula (1) and (2): subscript * represents perunit value; ω _rfor rotor electrical angular speed; Ω _rfor rotor mechanical angular speed; ω ₁for synchronous angular velocity; ω _nfor electrical network angular frequency; P _mfor mechanical output; T _jfor inertia time constant, T _mfor machine torque; T _efor electromagnetic torque, by synchronous torque component T _eswith asynchronous torque component T _erform,

If Crowbar protection act, rotor windings is through resistance R _cbshort circuit, DFIG enters asynchronous machine running status, now electromagnetic torque mean value T _eavfor:

$T_{\mathrm{eav}}=\frac{{3\mathrm{pU}}_1^2\×(R_r+R_{\mathrm{cb}})/s}{2\mathrm{\π}{f}_N[{(R_s+(R_r+R_{\mathrm{cb}})/s)}^2+{(X_s+X_r)}^2]}---\left(3\right)$

In formula (3): p is number of pole-pairs, U ₁for stator phase voltage effective value; S=(ω ₁-ω _r)/ω ₁for revolutional slip; f _nfor mains frequency; R _sfor stator winding resistance; R _rfor rotor windings resistance; X _sfor stator winding leakage reactance; X _rfor rotor windings leakage reactance; R _cbfor Crowbar protective resistance, usual value is 0.6p.u. ~ 1.5p.u.,

When electrical network generation unbalanced fault, due to DFIG stator winding isolated neutral, only there is positive sequence component and negative sequence component in stator voltage, and without zero-sequence component, the voltage positive sequence component reduction that fault causes can make T _eavreduce, cause rotor to accelerate; The negative sequence component of voltage makes to occur 2 harmonics in electromagnetic torque, but to T _eavaffect very little,

When analyzing unbalanced fault, with U in stator voltage positive sequence component effective value substituted (3) ₁, formula (3) shows: the Voltage Drop that grid disturbance causes is darker, electromagnetic torque mean value T _eavfall is larger;

2) rotor speed that .Crowbar protection act causes changes

The double-fed fan motor unit of normal operation can be divided into supersynchronous and metasynchronism two kinds of running statuses; supersynchronously be greater than in rotating magnetic field angular speed for generator angular speed; metasynchronism is generator angular speed and is less than rotating magnetic field angular speed; when double-fed fan motor unit is in supersynchronous running status, apart from overspeed protection definite value ω _rlimnargin is lower, more easily triggers overspeed protection action by after electrical network fault disturbance,

Because analyzed process time is shorter, <1s, then consider that the inertia of wind energy conversion system is comparatively large, can T be supposed _mremain unchanged in transient process after disturbed, before disturbed, T _mwith T _eequal, rotor speed remains unchanged, and after disturbed, stator voltage positive sequence component reduces, and causes T _eavthere is saltus step;

3). rotor accelerates to the time Tcr of overspeed protection action

By any initial state ω _r0start, after Crowbar protection act, rotor speed can be represented by following integration type over time,

${\mathrm{\&omega;}}_r\left(t\right)={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^t(T_m^{*}-T_{\mathrm{eav}}{\left(u\right)}^{*})\mathrm{du}---\left(4\right)$

Work as ω _rreach overspeed protection definite value ω _rlimtime, the corresponding time is the time T that rotor accelerates to overspeed protection action _cr,

So have:

${\mathrm{\&omega;}}_{\mathrm{rlim}}={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^{T_{\mathrm{cr}}}(T_m^{*}-T_{\mathrm{eav}}{\left(t\right)}^{*})\mathrm{dt}---\left(5\right)$

Formula (5) shows: the mean value T of electromagnetic torque after Crowbar action _eavless, T _crless; The initial speed ω of unit _r0larger, T _crit is also less,

Consider T in the of short duration process of Crowbar protection act _eav(t) ^*change is little, is set to constant T _eav ^*, then rotor accelerates to the time T of overspeed protection action _crapproximate expression is:

$T_{\mathrm{cr}}=\frac{T_j({\mathrm{\&omega;}}_{\mathrm{rlim}}-{\mathrm{\&omega;}}_{r0})}{{\mathrm{\&omega;}}_N(T_m^{*}-{T_{\mathrm{eav}}}^{*})}---\left(6\right).$

The computational methods of a kind of double-fed fan motor unit hypervelocity off-grid crash time of the present invention, start with from setting up the disturbed rear electromechanical transient Mathematical Modeling of DFIG, by analyzing DFIG initial operating condition, the effects of factor in electromechanical transient such as strength of turbulence and Crowbar protection act, DFIG unit of having derived reaches the condition of overspeed protection action, and by proposed method by the analysis to certain wind energy turbine set wind-powered electricity generation group of planes off-grid example, the time of overspeed protection action definite value is accelerated to according to calculated each machine group rotor, correctly identify the Wind turbines of overspeed protection action, there is methodological science, calculate simple, fast, evaluation precision is high, the advantages such as application on site effect is good.

Accompanying drawing explanation

Fig. 1 is double-fed fan motor set structure schematic diagram;

Fig. 2 is electromagnetic torque and machine torque relation schematic diagram before and after Crowbar action;

Fig. 3 is 1.5MW double-fed fan motor unit networking operation simulating schematic diagram;

Fig. 4 is wind energy turbine set electric main wiring diagram.

Embodiment

The computational methods of drawings and Examples to a kind of double-fed fan motor unit hypervelocity off-grid crash time of the present invention are utilized to be described in detail below.

The computational methods of double-fed fan motor unit hypervelocity off-grid crash time, it comprises the following steps:

1. double-fed fan motor unit hypervelocity off-grid Analysis on Mechanism

1). set up DFIG electromechanical transient Mathematical Modeling

Fig. 1 gives a kind of typical double-fed fan motor set structure, and DFIG equation of rotor motion is:

$\frac{{\mathrm{d\&omega;}}_r}{\mathrm{dt}}=\frac{{\mathrm{\&omega;}}_N}{T_j}(T_m^{*}-T_e^{*})---\left(1\right)$

$\left\{\begin{array}{c}{T^{*}}_m={P^{*}}_m/{{\mathrm{\&Omega;}}^{*}}_r\\ {T^{*}}_e={T^{*}}_{\mathrm{es}}-{T^{*}}_{\mathrm{er}}\end{array}\right.---\left(2\right)$

In formula (1) and (2): subscript * represents perunit value; ω _rfor rotor electrical angular speed; Ω _rfor rotor mechanical angular speed; ω ₁for synchronous angular velocity; ω _nfor electrical network angular frequency; P _mfor mechanical output; T _jfor inertia time constant, T _mfor machine torque; T _efor electromagnetic torque, by synchronous torque component T _eswith asynchronous torque component T _erform.

If Crowbar protection act, rotor windings is through resistance R _cbshort circuit, DFIG enters asynchronous machine running status, now electromagnetic torque mean value T _eavfor:

$T_{\mathrm{eav}}=\frac{{3\mathrm{pU}}_1^2\&times;(R_r+R_{\mathrm{cb}})/s}{2\mathrm{\&pi;}{f}_N[{(R_s+(R_r+R_{\mathrm{cb}})/s)}^2+{(X_s+X_r)}^2]}---\left(3\right)$

In formula (3): p is number of pole-pairs, U ₁for stator phase voltage effective value; S=(ω ₁-ω _r)/ω ₁for revolutional slip; f _nfor mains frequency; R _sfor stator winding resistance; R _rfor rotor windings resistance; X _sfor stator winding leakage reactance; X _rfor rotor windings leakage reactance; R _cbfor Crowbar protective resistance, usual value is 0.6p.u. ~ 1.5p.u..

When electrical network generation unbalanced fault, due to DFIG stator winding isolated neutral, only there is positive sequence component and negative sequence component in stator voltage, and without zero-sequence component, the voltage positive sequence component reduction that fault causes can make T _eavreduce, cause rotor to accelerate; The negative sequence component of voltage makes to occur 2 harmonics in electromagnetic torque, but to T _eavaffect very little.

When analyzing unbalanced fault, with U in stator voltage positive sequence component effective value substituted (3) ₁, formula (3) shows: the Voltage Drop that grid disturbance causes is darker, electromagnetic torque mean value T _eavfall is larger.

2) rotor speed that .Crowbar protection act causes changes

The double-fed fan motor unit of normal operation can be divided into supersynchronous and metasynchronism two kinds of running statuses, when double-fed fan motor unit is in supersynchronous running status, rotor speed higher than synchronous speed, apart from overspeed protection definite value ω _rlimnargin is lower, more easily triggers overspeed protection action by after electrical network fault disturbance.

Because analyzed process time is shorter, <1s, then consider that the inertia of wind energy conversion system is comparatively large, can T be supposed _mremain unchanged in transient process after disturbed, before disturbed, T _mwith T _eequal, rotor speed remains unchanged, and after disturbed, stator voltage positive sequence component reduces, and causes T _eavthere is saltus step, disturbed front and back, T _eand T _mrelation as shown in Figure 2.

3). rotor accelerates to the time Tcr of overspeed protection action

By any initial state ω _r0start, after Crowbar protection act, rotor speed can be represented by following integration type over time.

${\mathrm{\&omega;}}_r\left(t\right)={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^t(T_m^{*}-T_{\mathrm{eav}}{\left(u\right)}^{*})\mathrm{du}---\left(4\right)$

Work as ω _rreach overspeed protection definite value ω _rlimtime, the corresponding time is the time T that rotor accelerates to overspeed protection action _cr.

So have:

${\mathrm{\&omega;}}_{\mathrm{rlim}}={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^{T_{\mathrm{cr}}}(T_m^{*}-T_{\mathrm{eav}}{\left(t\right)}^{*})\mathrm{dt}---\left(5\right)$

Formula (5) shows: the mean value T of electromagnetic torque after Crowbar action _eavless, T _crless; The initial speed ω of unit _r0larger, T _cralso less.

Consider T in the of short duration process of Crowbar protection act _eav(t) ^*change is little, is set to constant T _eav ^*, then rotor accelerates to the time T of overspeed protection action _crapproximate expression is:

$T_{\mathrm{cr}}=\frac{T_j({\mathrm{\&omega;}}_{\mathrm{rlim}}-{\mathrm{\&omega;}}_{r0})}{{\mathrm{\&omega;}}_N(T_m^{*}-{T_{\mathrm{eav}}}^{*})}---\left(6\right).$

2. the disturbed rear electromagnetic transient simulation analysis of double-fed fan motor unit

For verifying the above analysis to double-fed fan motor unit hypervelocity off-grid mechanism, based on PSCAD/EMTDC platform, build certain model 1.5MW double-fed fan motor unit networking operation simulation model, connection principle as shown in Figure 3, DFIG through 0.69/10.5kv box type transformer through current collection connection to 35/220kv factory owner's transformer, then through sending connection outside to electrical network, unit parameter is in table 1.

During table 1t=0,33 unit operation parameters

Wind turbines overspeed protection definite value is 1880rpm, i.e. ω _rlim=196.8rad/s, R _cb=1.5p.u., before fault, running of wind generating set is in rated wind speed 12m/s, power output 1.5MW, and generating unit speed is 1760rpm,

During t=1.0s, bus U _gthere is AB two-phase short-circuit fault, bus U _gvoltage positive sequence component drops to 0.85p.u., and stator voltage positive sequence component drops to 0.8p.u., Crowbar protection act; Fault clearance during t=1.110s, line voltage recovers.Can calculate by formula (6) the time T that rotor accelerates to overspeed protection action according to above-mentioned parameter _cr=325ms.

3. a wind energy turbine set windy unit off-grid event analysis

On December 18th, 2012, there is AB two-phase short-circuit fault in the 220kV networking lines of Northeast Area of China wind energy turbine set, trouble duration is about 110ms, and fault causes a collection of unit off-grid of this wind energy turbine set.

This wind energy turbine set basic condition is as follows:

1) wind energy turbine set is equipped with 33 1.5MW double-fed fan motor units altogether, and the important technological parameters of unit is in table 2.

2) 33 units access electrical network through the step-up transformer of 1 220kV/35kV, 50MVA.

Certain model 1.5MWDFIG important technological parameters of table 2

The electric main wiring diagram of this wind energy turbine set as shown in Figure 4.

The action situation that after Wind turbines master control system have recorded fault, Wind turbines is protected; the fault message of record shows 14 typhoon group of motors protection act; wherein 12 units are that machine is cut in overspeed protection action; 2 unit current transformer protection act cut machine, have recorded the machine group number of protection act information and the generator protection classification of motion in table 3.

Table 3 has Wind turbines and the classification of protection act information

Export 220kV busbar fault recorder data from wind energy turbine set to analyze: before fault, wind energy turbine set exports meritorious 44.16MW, reaches 89.2% of specified installed capacity.

Getting the fault generation moment is t=0, and fault main time, in table 4, according to the condition of Voltage Drop after electric network fault disturbance, can calculate the time T that disturbed rear each machine group rotor accelerates to overspeed protection action _cr, result of calculation is in table 5.

Table 4 major failure sequential

The Tcr result of calculation of table 531 unit

4. interpretation of result

Return liter because wind energy turbine set power after 430ms only falls, the Wind turbines of still networking after showing 430ms can not continue raising speed, and therefore, t<430ms is the risk period of Wind turbines hypervelocity.

In fact, all T in table 5 _crthe rotating speed of 18 units of <430ms has all crossed overspeed protection threshold value within the hypervelocity risk period; overspeed protection action all should be judged as; wherein completely covers in table 3 have sufficient evidence be hypervelocity off-grid 12 typhoon group of motors; all the other 6 units also should be hypervelocity off-grids, just do not have fault message to prove.

The time T of overspeed protection action is accelerated to rotor _cras criterion, correctly identify disturbed rear whole 12 the hypervelocity off-grid Wind turbines having a record of this wind energy turbine set.

The specific embodiment of the present invention is also non exhaustive, and those skilled in the art, without the simple copy of creative work and improvement, should belong to the protection range of the claims in the present invention.

Claims (1)

1. the computational methods of double-fed fan motor unit hypervelocity off-grid crash time, it is characterized in that, it comprises the following steps:

1). set up DFIG electromechanical transient Mathematical Modeling

DFIG equation of rotor motion is:

$\frac{{\mathrm{d\&omega;}}_r}{dt}=\frac{{\mathrm{\&omega;}}_N}{T_j}(T_m^{*}-T_e^{*})---\left(1\right)$

$\left\{\begin{array}{c}{T^{*}}_m={P^{*}}_m/{{\mathrm{\&Omega;}}^{*}}_r\\ {T^{*}}_e={P^{*}}_{es}-{T^{*}}_{er}\end{array}\right.---\left(2\right)$

In formula (1) and (2): subscript * represents perunit value; ω _rfor rotor electrical angular speed; Ω _rfor rotor mechanical angular speed; ω ₁for synchronous angular velocity; ω _nfor electrical network angular frequency; P _mfor mechanical output; T _jfor inertia time constant, T _mfor machine torque; T _efor electromagnetic torque, by synchronous torque component T _eswith asynchronous torque component T _erform,

If Crowbar protection act, rotor windings is through resistance R _cbshort circuit, DFIG enters asynchronous machine running status, now electromagnetic torque mean value T _eavfor:

$T_{eav}=\frac{3{\mathrm{pU}}_1^2\&times;(R_r+R_{cb})/s}{2{\mathrm{\&pi;f}}_N\&lsqb;{(R_s+(R_r+R_{cb})/s)}^2+{(X_s+X_r)}^2\&rsqb;}---\left(3\right)$

In formula (3): p is number of pole-pairs, U ₁for stator phase voltage effective value; S=(ω ₁-ω _r)/ω ₁for revolutional slip; f _nfor mains frequency; R _sfor stator winding resistance; R _rfor rotor windings resistance; X _sfor stator winding leakage reactance; X _rfor rotor windings leakage reactance; R _cbfor Crowbar protective resistance, usual value is 0.6p.u. ~ 1.5p.u.,

When electrical network generation unbalanced fault, due to DFIG stator winding isolated neutral, only there is positive sequence component and negative sequence component in stator voltage, and without zero-sequence component, the voltage positive sequence component reduction that fault causes can make T _eavreduce, cause rotor to accelerate; The negative sequence component of voltage makes to occur 2 harmonics in electromagnetic torque, but to T _eavaffect very little,

When analyzing unbalanced fault, with U in stator voltage positive sequence component effective value substituted (3) ₁, formula (3) shows: the Voltage Drop that grid disturbance causes is darker, electromagnetic torque mean value T _eavfall is larger;

2) rotor speed that .Crowbar protection act causes changes

The double-fed fan motor unit of normal operation can be divided into supersynchronous and metasynchronism two kinds of running statuses; supersynchronously be greater than rotating magnetic field angular speed for generator angular speed; metasynchronism is generator angular speed and is less than rotating magnetic field angular speed; when double-fed fan motor unit is in supersynchronous running status, apart from overspeed protection definite value ω _rlimnargin is lower, more easily triggers overspeed protection action by after electrical network fault disturbance,

Because analyzed process time is shorter, the process time <1s that 0< analyzes, then consider that the inertia of wind energy conversion system is comparatively large, can T be supposed _mremain unchanged in transient process after disturbed, before disturbed, T _mwith T _eequal, rotor speed remains unchanged, and after disturbed, stator voltage positive sequence component reduces, and causes T _eavthere is saltus step;

3). rotor accelerates to the time Tcr of overspeed protection action

By any initial state ω _r0start, after Crowbar protection act, rotor speed can be represented by following integration type over time,

${\mathrm{\&omega;}}_r\left(t\right)={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^t(T_m^{*}-T_{eav}{\left(u\right)}^{*})du---\left(4\right)$

Work as ω _rreach overspeed protection definite value ω _rlimtime, the corresponding time is the time T that rotor accelerates to overspeed protection action _cr,

So have:

${\mathrm{\&omega;}}_{r\lim }={\mathrm{\&omega;}}_{r0}+\frac{{\mathrm{\&omega;}}_N}{T_j}{\&Integral;}_0^{T_{cr}}(T_m^{*}-T_{eav}{\left(t\right)}^{*})dt---\left(5\right)$

Formula (5) shows: the mean value T of electromagnetic torque after Crowbar action _eavless, T _crless; The initial speed ω of unit _r0larger, T _crit is also less,

Consider T in the of short duration process of Crowbar protection act _eav(t) ^*change is little, is set to constant T _eav ^*, then rotor accelerates to the time T of overspeed protection action _crapproximate expression is:

$T_{cr}=\frac{T_j({\mathrm{\&omega;}}_{r\lim }-{\mathrm{\&omega;}}_{r0})}{{\mathrm{\&omega;}}_N(T_m^{*}-{T_{eav}}^{*})}---\left(6\right).$