CN101877488A - Device for realizing low voltage ride-through capability of wind turbine generator system - Google Patents

Abstract

The invention discloses a device for realizing low voltage ride-through capability of a wind turbine generator system, which is characterized by comprising a voltage-4-quadrant converter, a DC side capacitor, a bi-directional DC converter and a super capacitor bank, wherein the voltage-4-quadrant converter is cascaded with the bi-directional DC/DC converter. The device is connected to a common connection point of a wind power station; when the wind speed change causes the fluctuation of the output power of the wind power station, the super capacitor bank outputs or absorbs certain active power through the voltage converter so as to level the fluctuation of the power; and when the failure of a power network causes voltage drop, the power of the wind power station output to the power network is reduced, the mechanical power input to the wind power station is basically unchanged, the super capacitor bank is controlled to absorb certain active power, and a series of problems of DC link capacitor charging, DC voltage quick rise, motor rotor acceleration, electromagnetic torque sudden change and the like caused by inner digestion of excess power are avoided.

Description

A kind of device that is used to realize low voltage ride-through capability of wind turbine generator system

Technical field

The present invention relates to a kind of device that is used to realize the wind turbine generator low voltage ride-through capability.

Background technology

Along with the attention of the development of wind-powered electricity generation machine set technology and China to the regenerative resource development, there is increasing large-scale wind electricity field to insert electrical network, each province's grid company inserts the influence that electrical network brought to large-scale wind power, and the safety and stablization problem of electrical network is paid much attention to after especially wind-powered electricity generation being inserted.

Because the generator techniques that the wind-powered electricity generation unit adopts is compared with the conventional synchronization generator different static state and transient characterisitics are arranged, especially aspect voltage control capability, also can't compare with the conventional synchronization generator, therefore the preceding under the technical merit no matter wind energy turbine set installed capacity size, adopt which kind of wind-powered electricity generation machine set technology, wind-powered electricity generation inserts electrical network all can bring in various degree influence to the voltage stability that inserts area power grid; In addition, a large amount of wind-powered electricity generations insert the after wind group of motors certainly will substitute part synchronous motor group in the electrical network, the pressure regulation of this part synchronous unit, fm capacity must be born by other synchronous units or wind-powered electricity generation unit, therefore, external increasing grid company also proposes higher requirement for the large-scale wind electricity field of inserting electrical network: the low voltage ride-through capability LVRT of active power control ability, reactive power ability and wind-powered electricity generation unit (Low voltage Ride Through) for example.

The low voltage ride-through capability of wind-powered electricity generation unit is meant that in the scope that certain voltage is fallen, the wind-powered electricity generation unit can uninterruptedly be incorporated into the power networks when electric network fault or disturbance cause the electric voltage dropping of wind farm grid-connected point.

When electrical network is short-circuited fault, in the unit rotor, cause the transient state overcurrent, this electric current current transformer of flowing through; Simultaneously, from conservation of energy angle analysis, system short-circuit causes the rapid drawdown of unit set end voltage, and unit can't continue to the electrical network transmission of electric energy, and its unbalanced energy can cause that the wind-powered electricity generation unit quickens and the DC link charging, and voltage raises.The transient state overcurrent or the overvoltage of DC link that are rotor-side all can cause adverse effect to power electronic device.So how to make the wind-powered electricity generation unit pass through low voltage failure smoothly, and can protect its power electronic device not to be damaged to seem particularly important.Low voltage ride-through capability of wind turbine generator system is to guarantee wind energy turbine set off-the-line not under system failure situation, the mandatory attribute that can continue to generate electricity by way of merging two or more grid systems.

Summary of the invention

Technical problem to be solved by this invention is, overcomes the shortcoming of prior art, provides a kind of wind energy turbine set off-the-line not under system failure situation, the device that is used to realize low voltage ride-through capability of wind turbine generator system that can continue to generate electricity by way of merging two or more grid systems.

The technical solution adopted for the present invention to solve the technical problems is as follows: a kind of device that is used to realize low voltage ride-through capability of wind turbine generator system, it is characterized in that: it comprises bank of super capacitors, four-quadrant voltage-type current transformer, two-way DC converter and dc capacitor, bank of super capacitors and two-way DC converter cascade, two-way DC converter is by dc capacitor and the cascade of four-quadrant voltage-type current transformer, and the opposite side of four-quadrant voltage-type current transformer is connected in the wind energy turbine set points of common connection by transformer.

Beneficial effect of the present invention is as follows: wind speed changes when causing the Power Output for Wind Power Field fluctuation, and for reducing the impact of wind energy turbine set to electrical network, bank of super capacitors is by the output of voltage-type current transformer or absorb certain active power to stabilize power fluctuation; When electric network fault causes electric voltage dropping, the power that wind energy turbine set outputs to electrical network descends, and the mechanical output of input wind energy turbine set is constant substantially, the control bank of super capacitors absorbs certain active power, avoids a series of problems such as DC link electric capacity charging that the inner digestion of excess power causes, direct voltage fast rise, rotor acceleration, electromagnetic torque sudden change.

Description of drawings

Fig. 1 contains a kind of apparatus structure schematic diagram that is used to realize low voltage ride-through capability of wind turbine generator system.

Fig. 2 is voltage fluctuation of wind-powered electricity generation unit and time curve.

Fig. 3 is the energy flow graph of blower fan system when normally moving.

Fig. 4 is the energy flow graph of blower fan system under the low voltage condition.

Embodiment

The invention will be further described to utilize drawings and Examples below.

With reference to Fig. 2, it is the voltage that is limited by instruction under the condition that wind turbine generator must keep with system is connected that low-voltage is passed through operation characteristic, shown in Fig. 2 section part.In order to adapt to this requirement, necessary Correction and Control system and hardware are so that manage the energy that is produced by wind turbine generator in the low pressure event.When fault, there is not the management of energy, the power that wind turbine generator produces will still be stayed in the motor, cause the increase of mechanical speed.

With reference to Fig. 2, China has formulated wind energy turbine set access electric power network technique regulation according to actual electric network structure and wind-powered electricity generation development, and the wind energy turbine set low-voltage of regulation is passed through requirement and is:

(1) the wind-powered electricity generation unit in the wind energy turbine set 1 have and the site, and the site can keep being incorporated into the power networks 625ms for boosting to uprise with public electric wire net 2 direct-connected wind energy turbine set 1 when pressing side bus electric voltage dropping to 20% rated voltage.

(2) wind energy turbine set 1 point voltage that is incorporated into the power networks can return to 90% o'clock of rated voltage in the 3s falling the back, and the wind-powered electricity generation unit in the wind energy turbine set keeps being incorporated into the power networks.

With reference to Fig. 1, a kind of device 3 that is used to realize low voltage ride-through capability of wind turbine generator system of the present invention, it comprises bank of super capacitors C _Sc, four-quadrant voltage-type current transformer VSC, two-way DC converter DC/DC and dc capacitor C _Dc, bank of super capacitors C _ScWith two-way DC converter VSC cascade, two-way DC converter DC/DC is by dc capacitor C _DcWith four-quadrant voltage-type current transformer VSC cascade, the opposite side of four-quadrant voltage-type current transformer VSC is connected in wind energy turbine set points of common connection PCC by transformer.Bank of super capacitors C _Sc, four-quadrant voltage-type current transformer VSC, two-way DC converter DC/DC and dc capacitor C _DcBe the commercially available prod.

Bank of super capacitors C _ScMemory capacity be so selected: during the given whole low pressure operating mode of LVRT requirement, with whole capacity ratings of the system of being stored in as energy substantially.The specification E of energy storage device _LVRT, can by more than the LVRT curve and the area that defined below the 0.9pu calculate:

E _LVRT＝P _base[(0.9-V _min)t ₁+0.5(t ₂-t ₁)(0.9-V _min)]

In the formula, P _BaseBe prime power, V _MinGet 0.15pu, t ₁Get 0.625s, t ₂Get 3s, see Fig. 2.Can obtain bank of super capacitors C between age at failure thus _ScThe energy that must manage.

Suppose that the ceiling voltage across energy storage device is dc voltage reference value V _{Dc, ref}, capacitance is then pressed following formula and is determined

$C_{\mathrm{cs}}=\frac{{2E}_{\mathrm{LVRT}}}{V_{\mathrm{dc},\mathrm{<figure-callout\; id="2"\; label="ref"\; filenames="HSA00000194315400011.png,HSA00000194315400021.png"\; state="\{\{state\}\}">ref</figure-callout>}}^2}$

With reference to Fig. 3, the mechanical output of input wind energy turbine set 1 is P _m, its most of power outputs to electrical network when normally moving, i.e. power P shown in the figure _s, remainder is then by bank of super capacitors C _ScStore, be power P shown in the figure _Cs

With reference to Fig. 4, the mechanical output P of input wind energy turbine set 1 _mSubstantially constant, when electrical network 2 is short-circuited fault when causing that voltage reduces, wind energy turbine set 1 outputs to the power P of electrical network 2 _sTo descend, the power imbalance, this can cause a series of problems such as the charging of DC link electric capacity, direct voltage fast rise, rotor acceleration, electromagnetic torque sudden change, controls bank of super capacitors C this moment _ScAbsorb most of active power, avoid the inner digestion of excess power.

Claims (1)

1. device that is used to realize low voltage ride-through capability of wind turbine generator system, it is characterized in that: it comprises bank of super capacitors, four-quadrant voltage-type current transformer, two-way DC converter and dc capacitor, bank of super capacitors and two-way DC converter cascade, two-way DC converter is by dc capacitor and the cascade of four-quadrant voltage-type current transformer, and the opposite side of four-quadrant voltage-type current transformer is connected in the wind energy turbine set points of common connection by transformer.

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