CN104617598A - Wind power plant low voltage riding through method based on dynamic direct current leakage resistor - Google Patents

Abstract

The invention provides a wind power plant low voltage riding through method based on a dynamic direct current leakage resistor. The method includes the following steps: building a wind power plant direct current grid connection model; determining the resistance of the dynamic direct current leakage resistor; setting the action protection judgment basis of the dynamic direct current leakage resistor; determining the action lasting time of the dynamic direct current leakage resistor; stopping the dynamic direct current leakage resistor after faults are removed. The method solves the technical problem in the prior art that a fan is directly and electrically connected with a fault alternating current system, and surplus wind power is consumed in a fan during the fault period. The dynamic direct current leakage resistor formed by connecting high power switching devices and dissipation resistors is arranged at the wire outlet position at the close end of the direct current end of the GAMMC to achieve smooth riding through during the fault period of the fan by means of flexible direct current grid connection. Meanwhile the dynamic direct current leakage resistor is in coordination control with the GSMMC to ensure that the output power of the wind power plant is recovered quickly after the faults are removed, and the recovery rate is far larger than the relevant technical index of the standard in the power system industry.

Description

A kind of wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current

Technical field

The invention belongs to electric and electronic technical field, be specifically related to a kind of wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current.

Background technology

Along with whole world reply climate change requires that lifting, energy shortage and energy resource supply security situation are increasingly severe day by day, regenerative resource is clean with it, safety, forever continuous feature, and the status in various countries' energy strategy improves constantly.In numerous renewable energy power generation mode, wind power generation is lower with its cost, technology is more ripe, the more high advantage of reliability, is able to fast development and starts to play an increasingly important role in energy resource supply.Between 2005 to 2010, the accumulative installed capacity of wind-driven power average growth rate per annum in the whole world is 27%, and existing 83 countries realize the commercial development of wind-powered electricity generation.2011, China became the country that installed capacity of wind-driven power is maximum in the world.

Large-scale developing and utilizing of wind resource proposes new challenge to power network safety operation, and outstanding behaviours is that grid connected wind power is dissolved problem and unit operation integrity problem, and basic reason is that the intermittent nature of wind energy determines the fluctuation of wind power.When wind energy turbine set adopts direct current grid-connected, though wind energy turbine set low voltage crossing can be realized when especially flexible direct current is grid-connected, but mostly to gain merit fan-out capability or locking flexible direct current converter based on wind energy turbine set during the reduction system failure.Obvious above-mentioned low voltage crossing scheme all changes the running status that front wind-electricity integration system occurs fault.In fact after the system failure is removed, no matter wind energy turbine set or converter, any damage switches to nominal situation all needs extra time, also proposes requirements at the higher level to the robustness of controller simultaneously.

Summary of the invention

Blower fan is not all overcome and fault AC system is directly electrically connected for acrossing schemes such as prior art rotor excitation regulation, between age at failure, unnecessary wind power consumption is at the technical barrier of blower interior, the invention provides a kind of wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current, by flexible direct current grid-connected and arrange in the DC terminal near-end outlet of GSMMC that the dynamic direct current be in series by high-power switch device and resistance for dissipation lets out can resistance, pass through smoothly during realizing fan trouble, after the cooperation control that dynamic direct current rushes down energy resistance and GSMMC simultaneously will guarantee fault clearance, Power Output for Wind Power Field is recovered rapidly, and regeneration rate is much larger than electric power system industry standard Specifications.

In order to realize foregoing invention object, the present invention takes following technical scheme:

The invention provides a kind of wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current, said method comprising the steps of:

Set up wind energy turbine set direct current and pessimistic concurrency control;

Determine that dynamic direct current lets out the resistance of energy resistance;

Set the action protection criterion that dynamic direct current lets out energy resistance;

Determine that dynamic direct current is let out and can drop into duration by resistance;

After fault clearance, dynamic direct current is let out and can be moved back fortune control by resistance.

Described wind energy turbine set direct current pessimistic concurrency control comprises wind energy turbine set, WFMMC, GSMMC and AC system; Described wind energy turbine set is connected to AC system successively by WFMMC and GSMMC; Between described wind energy turbine set and WFMMC, described WFMMC and GSMMC arranges the first circuit breaker Q F1 and the second circuit breaker Q F2 respectively.

Dynamic direct current lets out the resistance R of energy resistance _choprepresent, have:

$R_{\mathrm{chop}}=\frac{V_{\mathrm{PN}}^2}{P_{\mathrm{diss}}}=\frac{{(k*V_{\mathrm{PN}}^{*})}^2}{P_{\mathrm{wf}}-P_{\mathrm{GS}}^{\mathrm{fal}}}---\left(1\right)$

Wherein, V _pNfor DC line virtual voltage, for DC line rated voltage, P _dissfor dynamic direct current lets out the dissipation power of energy resistance, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, P _wffor the active power that wind energy turbine set exports, for the active power that fault in ac transmission system period GSMMC exports.

Break down when supposing AC system 0 second and cause GSMMC output voltage U _gSMMCfall, GSMMC output current i _dqrise immediately to improve GSMMC active power fan-out capability, thus maintain U _gSMMCconstant; If t ₁moment, i _dqreach GSMMC output current limiting value i _dq-lim, then the active power of fault in ac transmission system period GSMMC output reach the upper limit, simultaneously because wind energy turbine set continues, to DC line input active power, so charge respectively to the DC capacitor in WFMMC and GSMMC, thus to cause DC line virtual voltage V _pNrise; If t ₂moment, V _pNreach DC line virtual voltage protection threshold value V _{pN_max}, then start dynamic direct current and let out energy resistance to consume unnecessary active power.

If dynamically direct current lets out the rated power of energy resistance is P _chop, be expressed as:

$P_{\mathrm{chop}}={(k*V_{\mathrm{PN}}^{*})}^2/R_{\mathrm{chop}}---\left(2\right)$

Wherein, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, for DC line rated voltage, R _chopfor dynamic direct current lets out the resistance of energy resistance;

1) active-power P that wind energy turbine set that and if only if exports _wfwhen equaling wind energy turbine set rated power, dynamic direct current lets out the dissipation power P of energy resistance _dissequal the rated power P that dynamic direct current lets out energy resistance _chop, V _pNmaintain V _{pN_max}constant;

2) P is worked as _wfwhen being less than wind energy turbine set rated power, there is P _dissbe less than P _chop, dynamic direct current lets out energy resistance still constant conduction, and now the DC capacitor of WFMMC and GSMMC will be let out and can maintain its rated power P by resistance to make dynamic direct current let out by conductive discharge dynamic direct current _chop, thus cause V _pNreduce, namely have:

$C_{\mathrm{eq}}[{(k*V_{\mathrm{PN}}^{*})}^2-V_{\mathrm{PN}\_\mathrm{low}}^2]=(P_{\mathrm{chop}}-P_{\mathrm{diss}})*2T_S---\left(3\right)$

Wherein, C _eqfor submodule equivalent capacitys all in WFMMC and GSMMC, V _{pN_low}for DC line minimum voltage, T _slet out can drop into duration by resistance for dynamic direct current.

According to Instantaneous Power Theory, the active-power P that under dq synchronous rotating frame, GSMMC and AC system exchange _gSand reactive power Q _gSbe expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_{\mathrm{dGS}}{i}_{\mathrm{dGS}}+u_{\mathrm{qGS}}{i}_{\mathrm{qGS}}\\ Q_{\mathrm{GS}}=u_{\mathrm{qGS}}{i}_{\mathrm{dGS}}-u_{\mathrm{dGS}}{i}_{\mathrm{qGS}}\end{array}\right.---\left(4\right)$

Wherein, u _dGSand u _qGSbe respectively GSMMC output voltage d axle component and q axle component, i _dGSand i _qGSbe respectively GSMMC output current d axle component and q axle component;

When d axle is directed and AC system voltage u _srotating vector in the same way time, have u _dGS=u _sand u _qGS=0, so have:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_s{i}_{\mathrm{dGS}}\\ Q_{\mathrm{GS}}={-u}_s{i}_{\mathrm{qGS}}\end{array}\right.---\left(5\right)$

By control i _dGSthe active power that GSMMC exports to AC system can be limited.

Compared with prior art, beneficial effect of the present invention is:

A, utilize to arrange in the near-end outlet of GSMMC that dynamic direct current lets out can resistance, letting out at dynamic direct current can after the cooperation control of resistance and GSMMC guarantees fault clearance, Power Output for Wind Power Field is recovered rapidly, and regeneration rate is much larger than electric power system industry standard Specifications;

B, the invention provides that dynamic direct current lets out can the coordination control strategy of resistance and GSMMC, thus realizes Power Output for Wind Power Field non-overshoot and return to fault presteady state operation level fast, and versatility is good;

Dynamic direct current is let out and the range of application of resistance can be extended to whole fan operation interval and all can realize low voltage crossing by C, the method.

Accompanying drawing explanation

Fig. 1 is the grid-connected model structure figure of wind energy turbine set direct current in the embodiment of the present invention;

Fig. 2 is GSMMC inner ring current limit curve chart when fault clearance rear fan power output reduces in the embodiment of the present invention;

Fig. 3 is fault clearance rear fan power output constant GSMMC inner ring current limit curve chart in the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

The invention provides a kind of wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current, said method comprising the steps of:

Set up wind energy turbine set direct current and pessimistic concurrency control;

Determine that dynamic direct current lets out the resistance of energy resistance;

Set the action protection criterion that dynamic direct current lets out energy resistance;

Determine that dynamic direct current is let out and can drop into duration by resistance;

After fault clearance, dynamic direct current is let out and can be moved back fortune control by resistance.

As Fig. 1, described wind energy turbine set direct current pessimistic concurrency control comprises wind energy turbine set, WFMMC (Wind farm side modular multileverconverter, uncontrollable rectifier stage wind farm side modular multi-level flexible direct current converter), GSMMC (Grid side modularmultilevel converter, high-frequency rectification stage system side modular multi-level flexible direct current converter) and AC system; Described wind energy turbine set is connected to AC system successively by WFMMC and GSMMC; Between described wind energy turbine set and WFMMC, described WFMMC and GSMMC arranges the first circuit breaker Q F1 and the second circuit breaker Q F2 respectively.

GSMMC output voltage U is caused when AC system breaks down _gSMMCwhen falling, GSMMC active power fan-out capability declines thereupon, and is directly proportional to AC system residual voltage.Made output current limiting value be 1.2pu in GSMMC controller in addition, thus between age at failure GSMMC active power fan-out capability higher than AC system residual voltage level.

Dynamic direct current lets out the resistance R of energy resistance _choprepresent, have:

$R_{\mathrm{chop}}=\frac{V_{\mathrm{PN}}^2}{P_{\mathrm{diss}}}=\frac{{(k*V_{\mathrm{PN}}^{*})}^2}{P_{\mathrm{wf}}-P_{\mathrm{GS}}^{\mathrm{fal}}}---\left(1\right)$

Wherein, V _pNfor DC line virtual voltage, for DC line rated voltage, P _dissfor dynamic direct current lets out the dissipation power of energy resistance, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, P _wffor the active power that wind energy turbine set exports, for the active power that fault in ac transmission system period GSMMC exports.

Break down when supposing AC system 0 second and cause GSMMC output voltage U _gSMMCfall, GSMMC output current i _dqrise immediately to improve GSMMC active power fan-out capability, thus maintain U _gSMMCconstant; If t ₁moment, i _dqreach GSMMC output current limiting value i _dq-lim, then the active power of fault in ac transmission system period GSMMC output reach the upper limit, simultaneously because wind energy turbine set continues, to DC line input active power, so charge respectively to the DC capacitor in WFMMC and GSMMC, thus to cause DC line virtual voltage V _pNrise; If t ₂moment, V _pNreach DC line virtual voltage protection threshold value V _{pN_max}, then start dynamic direct current and let out energy resistance to consume unnecessary active power.

If dynamically direct current lets out the rated power of energy resistance is P _chop, be expressed as:

$P_{\mathrm{chop}}={(k*V_{\mathrm{PN}}^{*})}^2/R_{\mathrm{chop}}---\left(2\right)$

Wherein, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, for DC line rated voltage, R _chopfor dynamic direct current lets out the resistance of energy resistance;

1) active-power P that wind energy turbine set that and if only if exports _wfwhen equaling wind energy turbine set rated power, dynamic direct current lets out the dissipation power P of energy resistance _dissequal the rated power P that dynamic direct current lets out energy resistance _chop, V _pNmaintain V _{pN_max}constant;

2) P is worked as _wfwhen being less than wind energy turbine set rated power, there is P _dissbe less than P _chop, dynamic direct current lets out energy resistance still constant conduction, and now the DC capacitor of WFMMC and GSMMC will be let out and can maintain its rated power P by resistance to make dynamic direct current let out by conductive discharge dynamic direct current _chop, thus cause V _pNreduce, namely have:

$C_{\mathrm{eq}}[{(k*V_{\mathrm{PN}}^{*})}^2-V_{\mathrm{PN}\_\mathrm{low}}^2]=(P_{\mathrm{chop}}-P_{\mathrm{diss}})*2T_S---\left(3\right)$

Wherein, C _eqfor submodule equivalent capacitys all in WFMMC and GSMMC, V _{pN_low}for DC line minimum voltage, T _slet out can drop into duration by resistance for dynamic direct current.

After fault in ac transmission system is removed, the fast quick-recovery of fault point voltage, therefore GSMMC is to AC system conveying active power ability also fast quick-recovery thereupon.Now i _dqstill be in i _dq-lim, then a certain moment before system voltage returns to rated value (is assumed to be t ₃), GSMMC power output has returned to level before fault.Consider that this recovery capability is determined by AC system impedance operator, as t > t ₃after, GSMMC has little time to adjust i _dq-lim, namely continue to export more active power to AC system.The power that simultaneously wind energy turbine set is input to DC line does not increase, and the active power overload that obvious fault recovery later stage GSMMC exports will cause AC line voltage to reduce, therefore fault recovery phase GSMMC current limit link i _dq-limneed to redesign.

According to Instantaneous Power Theory, the active-power P that under dq synchronous rotating frame, GSMMC and AC system exchange _gSand reactive power Q _gSbe expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_{\mathrm{dGS}}{i}_{\mathrm{dGS}}+u_{\mathrm{qGS}}{i}_{\mathrm{qGS}}\\ Q_{\mathrm{GS}}=u_{\mathrm{qGS}}{i}_{\mathrm{dGS}}-u_{\mathrm{dGS}}{i}_{\mathrm{qGS}}\end{array}\right.---\left(4\right)$

Wherein, u _dGSand u _qGSbe respectively GSMMC output voltage d axle component and q axle component, i _dGSand i _qGSbe respectively GSMMC output current d axle component and q axle component;

When d axle is directed and AC system voltage u _srotating vector in the same way time, have u _dGS=u _sand u _qGS=0, so have:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_s{i}_{\mathrm{dGS}}\\ Q_{\mathrm{GS}}={-u}_s{i}_{\mathrm{qGS}}\end{array}\right.---\left(5\right)$

By control i _dGSthe active power that GSMMC exports to AC system can be limited.When same up-to-date style (5) also explains that described employing flexible direct current is grid-connected above, after fault, wind energy turbine set active power of output regeneration rate is much larger than the reason of electric power system industry standard 10% rated power/second.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit; those of ordinary skill in the field still can modify to the specific embodiment of the present invention with reference to above-described embodiment or equivalent replacement; these do not depart from any amendment of spirit and scope of the invention or equivalent replacement, are all applying within the claims of the present invention awaited the reply.

Claims (6)

1. let out a wind energy turbine set low-voltage ride-through method for energy resistance based on dynamic direct current, it is characterized in that: said method comprising the steps of:

Set up wind energy turbine set direct current and pessimistic concurrency control;

Determine that dynamic direct current lets out the resistance of energy resistance;

Set the action protection criterion that dynamic direct current lets out energy resistance;

Determine that dynamic direct current is let out and can drop into duration by resistance;

After fault clearance, dynamic direct current is let out and can be moved back fortune control by resistance.

2. according to claim 1 letting out based on dynamic direct current can the wind energy turbine set low-voltage ride-through method of resistance, it is characterized in that: described wind energy turbine set direct current pessimistic concurrency control comprises wind energy turbine set, WFMMC, GSMMC and AC system; Described wind energy turbine set is connected to AC system successively by WFMMC and GSMMC; Between described wind energy turbine set and WFMMC, described WFMMC and GSMMC arranges the first circuit breaker Q F1 and the second circuit breaker Q F2 respectively.

3. the wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current according to claim 1, is characterized in that: dynamically direct current lets out the resistance R of energy resistance _choprepresent, have:

$R_{\mathrm{chop}}=\frac{V_{\mathrm{PN}}^2}{P_{\mathrm{diss}}}=\frac{{(k*V_{\mathrm{PN}}^{*})}^2}{P_{\mathrm{wf}}-P_{\mathrm{GS}}^{\mathrm{fal}}}---\left(1\right)$

Wherein, V _pNfor DC line virtual voltage, for DC line rated voltage, P _dissfor dynamic direct current lets out the dissipation power of energy resistance, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, P _wffor the active power that wind energy turbine set exports, for the active power that fault in ac transmission system period GSMMC exports.

4. according to claim 1 letting out based on dynamic direct current can the wind energy turbine set low-voltage ride-through method of resistance, it is characterized in that: breaking down when supposing AC system 0 second causes GSMMC output voltage U _gSMMCfall, GSMMC output current i _dqrise immediately to improve GSMMC active power fan-out capability, thus maintain U _gSMMCconstant; If t ₁moment, i _dqreach GSMMC output current limiting value i _dq-lim, then the active power of fault in ac transmission system period GSMMC output reach the upper limit, simultaneously because wind energy turbine set continues, to DC line input active power, so charge respectively to the DC capacitor in WFMMC and GSMMC, thus to cause DC line virtual voltage V _pNrise; If t ₂moment, V _pNreach DC line virtual voltage protection threshold value V _{pN_max}, then start dynamic direct current and let out energy resistance to consume unnecessary active power.

5. the wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current according to claim 1, is characterized in that: set dynamic direct current to let out the rated power of energy resistance as P _chop, be expressed as:

$P_{\mathrm{chop}}={(k*V_{\mathrm{PN}}^{*})}^2/R_{\mathrm{chop}}---\left(2\right)$

Wherein, k is the protection act threshold coefficient that dynamic direct current lets out energy resistance, for DC line rated voltage, R _chopfor dynamic direct current lets out the resistance of energy resistance;

1) active-power P that wind energy turbine set that and if only if exports _wfwhen equaling wind energy turbine set rated power, dynamic direct current lets out the dissipation power P of energy resistance _dissequal the rated power P that dynamic direct current lets out energy resistance _chop, V _pNmaintain V _{pN_max}constant;

2) P is worked as _wfwhen being less than wind energy turbine set rated power, there is P _dissbe less than P _chop, dynamic direct current lets out energy resistance still constant conduction, and now the DC capacitor of WFMMC and GSMMC will be let out and can maintain its rated power P by resistance to make dynamic direct current let out by conductive discharge dynamic direct current _chop, thus cause V _pNreduce, namely have:

$C_{\mathrm{eq}}[{(k*V_{\mathrm{PN}}^{*})}^2-V_{\mathrm{PN}\_\mathrm{low}}^2]=(P_{\mathrm{chop}}-P_{\mathrm{diss}})*2T_S---\left(3\right)$

Wherein, C _eqfor submodule equivalent capacitys all in WFMMC and GSMMC, V _{pN_low}for DC line minimum voltage, T _slet out can drop into duration by resistance for dynamic direct current.

6. the wind energy turbine set low-voltage ride-through method letting out energy resistance based on dynamic direct current according to claim 1, is characterized in that: according to Instantaneous Power Theory, the active-power P that under dq synchronous rotating frame, GSMMC and AC system exchange _gSand reactive power Q _gSbe expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_{\mathrm{dGS}}{i}_{\mathrm{dGS}}+u_{\mathrm{qGS}}{i}_{\mathrm{qGS}}\\ Q_{\mathrm{GS}}=u_{\mathrm{qGS}}{i}_{\mathrm{dGS}}-u_{\mathrm{dGS}}{i}_{\mathrm{qGS}}\end{array}\right.---\left(4\right)$

Wherein, u _dGSand u _qGSbe respectively GSMMC output voltage d axle component and q axle component, i _dGSand i _qGSbe respectively GSMMC output current d axle component and q axle component;

When d axle is directed and AC system voltage u _srotating vector in the same way time, have u _dGS=u _sand u _qGS=0, so have:

$\left\{\begin{array}{c}{P}_{\mathrm{GS}}=u_s{i}_{\mathrm{dGS}}\\ Q_{\mathrm{GS}}=-u_s{i}_{\mathrm{qGS}}\end{array}\right.---\left(5\right)$

By control i _dGSthe active power that GSMMC exports to AC system can be limited.