Full power combination converter for megawatt wind power generation
(1) technical field
The utility model relates to technical field of wind power generation, particularly a kind of wind-force generating converter.
(2) background technology
Wind energy more and more is subjected to people's attention as a kind of cleaning, non-pollution of renewable energy, and wind power generation will become one of new forms of energy of 21 century maximum-norm exploitation.Present wind-driven generator single-machine capacity constantly increases, and variable speed constant frequency, Variable Pitch type wind energy conversion system have occupied leading position gradually.Gear box is to transship and the higher parts of premature damage rate in the MW grade wind driven generator unit at present, and since last century Mo, the wind-powered electricity generation unit manufacturer with headed by the German Enercon has released a series of non-gear box direct-drive wind power system.The mode that this unit adopts multistage aerogenerator and impeller directly to be of coupled connections and to drive, remove this legacy device of gear box from, multiple advantage such as high efficiency has very big development space when possessing low noise, improve unit durability, reduce unit volume, reducing operation expense, lower noise, low wind speed in wind energy conversion system development from now on.Can estimate that the direct-drive wind power system of saving gear box will become the main direction of following wind generating technology development.
The grid-connected converter power grade and the generating set of direct-drive aerogenerator group are suitable, the electric energy that generator sends all needs to be transformed to by current transformer the alternating current feed-in electrical network of frequency, voltage constant, and, make it to realize maximum power output by electromagnetic torque is controlled in the control of motor side current transformer electric current.Compare with the wind generator system that motor directly is incorporated into the power networks, the use of current transformer between generating set and electrical network, realized the isolation between generating set and electrical network, coupled problem between rotating speed and the mains frequency will be solved, also avoided to a certain extent because of power network fluctuation to generating set stable operation adverse effect.
American-European countries maintains the leading position on wind power technology, much enters the company in blower fan market, and such as ABB, Vestas etc. have released the Related product of 2MW-5MW.At present in the high-power especially occasion more than the MW class, blower fan system mainly is divided three classes: 1. cage-type induction machine constant-speed and constant-frequency wind generator system; 2. AC excitation double-fed electrical motor gearshift constant frequency wind generator system; 3. permanent magnet direct driving motor variable-speed constant-frequency wind power generation system.
In the double feedback electric engine system, because power converter is positioned at rotor-side, only handle slip power, power converter volume power is about 1/3rd of its generator capacity, and also belongs to low volage current transformer, so the cost of current transformer, volume reduce greatly.Because the double feedback electric engine system, objectively need low pressure and power converter that can four quadrant running.Traditional AC-DC-AC two level current transformers are with its superior performance, are generally adopted in the current transformer product of present different wind-powered electricity generation producer, as shown in Figure 1.What do in this respect the most successfully is the Vestas company of Hispanic Gamesa company and Denmark.
In the permanent magnet direct-drive variable-speed constant-frequency wind power generation system, magneto links to each other with electrical network by the power converter of full capacity, realizes variable speed constant frequency generator.It is needed to be a full power convertor.The SEG company of Hispanic MADE company and Germany adopts main circuit structure as shown in Figure 2, be that energy arrives DC side via uncontrollable AC-DC current transformer, because change of wind velocity, caused the fluctuation of dc voltage, adopting booster converter that voltage is fixed to the dc bus side of DC-AC current transformer, is to be incorporated into the power networks after meeting the alternating current of mains frequency by the inversion of DC-AC current transformer then.The cost of sort circuit structure is very low, but it does not possess the ability of four quadrant running, thereby is in operation and is very restricted.The power converter that possesses two PWW controls of four quadrant running ability has then obtained good application (as shown in Figure 3) in the blower fan giant Enercon of Germany company.This also is that a kind of technology is the most ripe, move the most reliably, and accommodation is technical scheme the most widely, so four-quadrant in service being widely adopted.
In addition, ABB AB of Switzerland adopts the main circuit structure of three level to solve the above wind power system (as shown in Figure 4) of high-power especially MW class.Owing to adopted Hair Fixer motor in the permanent magnetism, the voltage of its generation is the 4KV grade, is optimal selection so adopt the scheme of formula back-to-back of three level.Though three-level current transformer can produce very low current/voltage percent harmonic distortion, and need very little filter, the increase of the IGCT switching device that adopts and the drift of the neutral point voltage between discrete capacitor have limited the application of this main circuit structure.Have the bibliographical information neutral point drifting can adopt the mode of control to be resolved in addition recently, but because the technical parameter of the blower fan manufacturer of China is 690VAC mostly, this limit the application of many level structure in China more.
Traditional current mode AC-DC-AC converter adopts the nature commutated thyristor as switching device, and its DC side inductance is relatively more expensive, because its low frequency performance is poor, thereby seldom uses in the wind power generation.The PowerFlex7000 of Rockwell company is the current source converter (as shown in Figure 5) that adopts SGCT, be applicable to Middle pressure draught fan, and wind-driven generator is 690VAC, therefore electric pressure is inapplicable, if be applied in the double feedback electric engine, voltage matches needs to adjust, and near the performance need of PowerFlex7000 low speed and zero-speed improves in addition.
Because various factorss such as control method and hardware designs, the voltage-type current transformer is used more extensive.By 2003 ends, the wind-driven generator unit of all installations of China all is the low pressure unit of 690VAC, does not have the mesohigh unit, and the current transformer overwhelming majority that is adopted in the speed change unit is two level voltage type AC-DC-AC converter (as shown in Figure 3).The voltage-type AC-DC-AC converter, have excellent characteristics such as simple in structure, that harmonic content is few, power factor is adjustable, can significantly improve the output quality of power supply, and this structure has realized separating of net side and motor side fully by the dc bus lateral capacitance, also is that of present variable-speed constant-frequency wind power generation represents direction.
Just present, domesticly be in the starting stage generally with the research and the manufacture view of power converter, especially 2MW and above power used for wind power generation power converter blank out especially at megawatt level wind power generation.Because MW class variable speed constant frequency wind-powered electricity generation control panel is the external import of the long-term dependence of power converter especially, is restricting China's wind-powered electricity generation industrialization process.The high-power wind turbine power converter that development has independent intellectual property right, not only reduce the cost of wind power equipment greatly, and can improve the competitiveness of China in world's wind-powered electricity generation industry, and being China's wind power technology outlet, the status that is lifted on world's wind-power market lays the foundation.
(3) summary of the invention:
The utility model purpose provides a kind of power converter main circuit of the novel used for wind power generation that is used for the above power grade of MW class.
The utility model purpose is achieved in that it comprises wind-driven generator and low voltage electric network or step-up transformer, it also comprises at least two basic current transformer power cells, each basic current transformer power cell composes in parallel the power converter main circuit, wherein basic current transformer power cell comprises by the generating pusher side three-phase PWM of dc bus connection controls current transformer and PWM net side grid-connected converter entirely, the output of power converter main circuit connects low voltage electric network or step-up transformer, and the input of power converter main circuit connects wind-driven generator.
The utility model also has some architectural features like this:
1, described basic current transformer power cell also comprises three pole reactor and three phase capacitance, three-phase grid inductance and three-phase filter capacitor, wind-driven generator is connected to the electric capacity of the star-like connection of three-phase by cable, connect three pole reactor then, three pole reactor connects generating pusher side three-phase PWM and controls current transformer entirely, generating pusher side three-phase PWM links to each other with PWM net side grid-connected converter after controlling current transformer one group of flat wave capacitor in parallel entirely, PWM net side grid-connected converter connects the input of three-phase grid inductance, its output process and the star-like filter capacitor parallel connection that is connected of three-phase;
2, to control current transformer entirely be to control three-phase bridge entirely to described generating pusher side three-phase PWM, constitutes the three-phase brachium pontis by six switching devices and be formed in parallel, and device for power switching adopts IGBT;
3, described PWM net side grid-connected converter is made of three-phase full-controlled bridge, constitutes the three-phase brachium pontis by six switching devices and composes in parallel, and device for power switching is IGBT.
For reaching the purpose of the higher power grade of current transformer, the utility model adopts modular main circuit structure parallel connection, promptly control current transformer and PWM net side grid-connected converter entirely by two identical in structure generating pusher side three-phase PWMs, the flat-out friendship orthogonal of the big capacity voltage-type two way convertor that connects and composes by dc bus as shown in Figure 3, and with this as a basic current transformer power cell, adopt modular mode that two or more basic current transformer power cells are together in parallel then, realize higher current transformer power grade.
Advantage of the present utility model:
● the generating pusher side is controlled current transformer entirely can be so that wind turbine generator be moved by optimum efficiency in very big wind speed range, even under low wind speed, the control of boosting of controlling current transformer entirely also can the assurance system be satisfied the condition that is incorporated into the power networks;
● the generating pusher side is controlled current transformer entirely and can be controlled the generator output current, obtains maximum electromagnetic torque under the situation of minimum current, and has reduced the copper loss and the iron loss of generator;
● the generating pusher side is controlled current transformer entirely can provide the electric current that is almost sine, has reduced the harmonic wave of generator unit stator side, the torque control of generator inside is improved, thereby has further alleviated drive system stress;
● net side grid-connected converter has realized that the system power factor is adjustable on the basis that has guaranteed the grid-connected current quality.
● modular basic current transformer power cell parallel-connection structure can be realized the power grade of higher used for wind power generation current transformer on the basis of the switching device of equal switching voltage current stress, and the seriation of realization product that can be more convenient.
The used for wind power generation power converter main circuit of the above power grade of MW class of the present utility model is characterized in that comprising the wind-driven generator of an above power grade of MW class, two or more basic current transformer power cell and low voltage electric network or step-up transformer.The alternating current that wind-driven generator sends is connected to the circuit that constitutes after the parallel connection of two or more basic current transformer power cell by cable, the output of this circuit transformer or the low voltage electric network of being incorporated into the power networks that then directly be incorporated into the power networks to.
The principal character of basic current transformer power cell is to comprise that three pole reactor and three phase capacitance, generating pusher side PWM control current transformer, net side grid-connected converter and three-phase grid inductance and three-phase filter capacitor entirely.The three-phase alternating current that is sent by wind-driven generator is connected to the electric capacity of the star-like connection of three-phase by cable, be connected to the input of three pole reactor then, be directly connected to the full control PWM current transformer of generating pusher side from the output of three pole reactor, this current transformer is to control three-phase bridge entirely, be to be formed in parallel by the three-phase brachium pontis that six switching devices constitute, that device for power switching adopts is IGBT.The direct current output of the full control current transformer of generating pusher side links to each other with net side grid-connected converter behind one group of flat wave capacitor in parallel, the net side converter structurally circuit structure with the generator side converter is identical, promptly be made of three-phase full-controlled bridge, device for power switching equally also is IGBT.The output of the three-phase alternating current of net side grid-connected converter is directly connected to the input of three-phase grid inductance, its output through with the star-like filter capacitor parallel connection that is connected of three-phase after finish output.
During work, wind energy conversion system drive wind-driven generator sends the three-phase frequency and amplitude all changes alternating current, through entering the flat ripple inductance of generator side after the filtering of generating pusher side filter capacitor.Flat ripple inductance both can play the effect of flat ripple to three-phase electricity, can control current transformer entirely with the generating pusher side again and constitute booster converter, so just can be so that wind turbine generator is pressed the optimum efficiency operation in very big wind speed range, even under low wind speed, the control of boosting of full control current transformer also can guarantee the stable of DC bus-bar voltage, and the collateral security system satisfies the condition that is incorporated into the power networks.After the alternating current that is come by the output of flat ripple inductance is controlled the filtering of the rectification of current transformer and DC side filter capacitor entirely through the generating pusher side, as the dc bus direct feed of net side grid-connected converter to the net side converter.Export the three-phase alternating current of the permanent width of cloth of constant frequency through the net side converter of PWM control, via the flat ripple of three-phase grid inductance again by after the filtering of three-phase grid filter capacitor, can obtain the three-phase quasi sine alternating current of the permanent width of cloth of constant frequency and electrical network homophase, satisfy the condition that is incorporated into the power networks, can directly incorporate being connected to the grid after 690VAC low voltage electric network or process step-up transformer boost into.Wherein the three-phase grid inductance is regulated the effect of the phase place of grid-connected current in addition except having flat ripple effect, enables to satisfy the alternating current condition that is incorporated into the power networks.Parasitic fly-wheel diode among the switching device IGBT in addition, it is except having the afterflow effect, or the passage of reactive power, also is known as feedback diode.
The utility model full power combination converter for megawatt wind power generation main circuit structure is not only applicable to the permanent magnet direct-drive wind-force generating system, but also is applicable to double-fed type wind generator system.The utility model not only can be so that wind turbine generator be moved by optimum efficiency in very big wind speed range, even under low wind speed, the control of boosting of controlling current transformer entirely also can the assurance system be satisfied the condition that is incorporated into the power networks; But also can control the generator output current, under the situation of minimum current, obtain maximum electromagnetic torque, and reduced the copper loss and the iron loss of generator; In addition, modular basic current transformer power cell parallel-connection structure can be realized the power grade of higher wind-force generating converter on the basis of the switching device of equal switching voltage, current stress, and the seriation of realization product that can be more convenient.
(4) description of drawings:
Fig. 1 is a double feedback electric engine converter structure schematic diagram;
Fig. 2 is the permanent magnet direct-drive converter structure schematic diagram that adopts uncontrollable rectification;
Fig. 3 is a formula permanent magnet direct-drive converter structure schematic diagram back-to-back;
Fig. 4 is three level formula permanent magnet direct-drive converter structure schematic diagrames back-to-back;
Fig. 5 is the current source type converter structural representation;
Fig. 6 is a grid-connected converter structural representation of the present utility model;
Fig. 7 is the basic current transformer power cell structure of a current transformer schematic diagram;
Fig. 8 is a grid-connected converter structure principle chart of the present utility model.
(5) embodiment
For a more detailed description below in conjunction with Fig. 6-8 and specific embodiment to the utility model:
In conjunction with Fig. 6, main circuit structure of the present utility model mainly comprises: wind-driven generator Gen, at least two basic current transformer power cell current transformer, 690VAC low voltage electric network or step-up transformers that form in parallel.Basic current transformer power cell comprises generating pusher side three phase capacitance C
1f, three pole reactor L
1N, the generating pusher side control current transformer (VT entirely
11~VT
16) contain fly-wheel diode (D
11~D
16), DC side filter capacitor C
1, net side grid-connected converter (VT
21~VT
26) contain fly-wheel diode (D
21~D
26), the three-phase grid inductance L
2n, three-phase filter capacitor C
2f
Embodiment:
1. at first make up basic current transformer power cell.In conjunction with Fig. 7 with three filter capacitor C
1fBe parallel to three equal ripple inductance L after connecting according to star-like mode
1nAn end, then with flat ripple inductance L
1nThe other end be connected to the V of generator side converter
11~V
13The place.The concrete implementation of generator side converter is with six switching device (VT
11~VT
16) contain fly-wheel diode (D
11~D
16) (the utility model adopts IGBT but is not limited to IGBT) two two group, be respectively VT
11And VT
14, VT
13And VT
16, VT
15And VT
12, two devices in every group join end to end and form three groups of brachium pontis then, and its tie point is respectively V
11, V
12, V
13Three groups of brachium pontis three-phase fully-controlled current transformer main circuits that promptly form parallel with one another, the generating pusher side is controlled the dc output end of current transformer entirely at filter capacitor C in parallel
1After, directly feeder line is to the dc bus side of net side grid-connected converter, the direct current that provides inversion to use for grid-connected converter.For filter effect and the useful life that strengthens filter capacitor, filter capacitor can adopt when an electric capacity three strings two filter capacitor group structure also.The embodiment that net side grid-connected converter constitutes is similar with the execution mode that the generating pusher side is controlled current transformer entirely, is about to six switching device (VT
21~VT
26) contain fly-wheel diode (D
21~D
26) two two one group, be respectively VT
21And VT
24, VT
23And VT
26, VT
25And VT
22, two devices in every group join end to end then, form three groups of brachium pontis then, and its tie point is respectively V
21, V
22, V
23The three-phase alternating current output of net side grid-connected converter is directly connected to the three-phase grid inductance L
2n, pass through then and three-phase filter capacitor C
2fLink electrical network after the parallel connection.The execution mode of Here it is basic current transformer power cell.
2. in conjunction with Fig. 8 two or more basic current transformer power cells (basic current transformer power cell 1~basic current transformer power cell n) are together in parallel then, form the full power convertor main circuit.Be directly connected to the A of full power convertor main circuit then in conjunction with Fig. 6, Fig. 7 wind-driven generator
1, B
1, C
13 points, and the output A of full power convertor main circuit
2, B
2, C
2Directly receive 690VAC low voltage electric network or step-up transformer at 3.