Summary of the invention
Problem to be solved by this invention is, overcomes the above-mentioned defective that the technology of taking over exists, and a kind of telescope double rotor fan variable speed constant frequency control system is provided.
Technical solution problem of the present invention takes following technical scheme to realize, according to a kind of telescope double rotor fan variable speed constant frequency control system provided by the invention,
Comprise generator, wherein, configuration is by the permanent magnetism internal rotor of the driven off by shaft relative stator rotation of this auxiliary driving on the counter drive shaft of generator; Configuration is by the ring-shaped rotor of the driven off by shaft relative stator rotation of this main transmission on the final drive shaft of generator; This ring-shaped rotor is again encircles permanent magnetism internal rotor and can be around the structure configuration of permanent magnetism internal rotor rotation; The number of pole-pairs of the inboard winding of the ring-shaped rotor of described ring-shaped rotor and the consistent Pe that is set to of permanent magnetism internal rotor number of pole-pairs are to the utmost point; The consistent Pg that is set to the stator winding number of pole-pairs of number of pole-pairs of ring-shaped rotor outside winding is to the utmost point, and described ring-shaped rotor outside winding is connected by connecting line negative-phase sequence between the ring-shaped rotor winding with inboard winding; Be provided with on the major and minor wind wheel and the signal of rotating speed can be sent to the main air wheel speed measurement mechanism of unit centralized control equipment, secondary wind speed round measurement mechanism; The port that the unit centralized control equipment has the port that connects with the wind speed checkout gear, connect with the wind direction checkout gear, with the port of host computer transmission data; Yawer and unit centralized control equipment connect in the mode of wind direction rotation under the control main air wheel; Described main air is taken turns main air wheel variable propeller pitch adjusting mechanism, the secondary wind wheel variable propeller pitch adjusting mechanism with secondary wind wheel difference configuration adjustment propeller pitch angle, and described major and minor wind wheel variable propeller pitch adjusting mechanism and unit centralized control equipment all connect in the mode of control wind wheel variable propeller pitch adjusting mechanism change oar;
Connect successively at the voltage output end of generator can be limited generator output voltage, with after date softly be incorporated into the power networks, the grid-connection control device and the step-up transformer of off-grid when shutting down, connect with external power grid again; The output voltage measurement mechanism that connects of configuration and unit centralized control equipment, the detecting device for output current that connects with the unit centralized control equipment, the mains frequency checkout gear that connects with the unit centralized control equipment successively between grid-connection control device and step-up transformer; The unloaded checkout gear that configuration and unit centralized control equipment connect between generator and grid-connection control device;
The main air wheel (3) of generator is configured on the final drive shaft, and the stator (16) that has the Pg number of pole-pairs under the wind-force effect relatively is with the rotation of Nzr speed, and the main air wheel speed satisfies following relational expression:
Wherein: Nzr represents the main air wheel speed; Pg represents the stator winding number of pole-pairs; Pe represents the number of pole-pairs of permanent magnetism internal rotor; Fg represents stator frequency; Fe represents permanent magnetism internal rotor reduced frequency.
This case technical solution problem can also further realize according to following technical measures:
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, generator secondary wind wheel be configured on the counter drive shaft, this pair wind wheel drives permanent magnetism internal rotor with respect to the reverse rotation of the relative main air wheel of stator rotational speed N e speed, and permanent magnetism internal rotor reduced frequency satisfies following relational expression:
Wherein: Ne vice wind wheel relative stator rotating speed.
Aforementioned telescope double rotor fan variable speed constant frequency control system wherein, is configured to the permanent magnetism internal rotor that the Nzre rotating speed is counterrotating, have the Pe number of pole-pairs on counter drive shaft, the rotating speed of the relative ring-shaped rotor rotation of permanent magnetism internal rotor satisfies following relational expression:
Nzre=Nzr+Ne is wherein: Nzre represents the rotating speed of the relative ring-shaped rotor rotation of permanent magnetism internal rotor.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, described major and minor wind wheel variable propeller pitch adjusting mechanism structure is identical, and it is formed with change oar control device by becoming the oar servomechanism.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, described unit centralized control equipment connects with the mode that change oar servomechanism is according to detected propeller pitch angle variation carrying out main air is taken turns and secondary wind speed round is regulated by becoming the oar control device.
Aforementioned telescope double rotor fan variable speed constant frequency control system wherein, disposes secondary wind wheel propeller pitch angle measurement mechanism, main air wheel propeller pitch angle measurement mechanism respectively in described main air wheel and the secondary wind wheel.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, the blade wind sweeping area of described main air wheel is set to blade wind sweeping area 2-5 times of secondary wind wheel.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, described ring-shaped rotor outside winding number of pole-pairs Pg is set to greater than the inboard winding number of pole-pairs of ring-shaped rotor Pe.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, described major and minor wind wheel variable propeller pitch adjusting mechanism is by driven by servomotor; This change oar servomechanism and unit centralized control equipment are and can carry out the electric connection of mode of rotational speed regulation to main air wheel and secondary wind wheel according to the variation of propeller pitch angle; 3 times of the blade wind sweeping area that described main air impeller blade wind sweeping area is secondary wind wheel approximately.
Aforementioned telescope double rotor fan variable speed constant frequency control system, wherein, described wind sweeping area is the area that the wind wheel rotation forms; The wind direction rotation down of described main air wheel, the reverse rotation of secondary wind wheel upwind; Brake and unit centralized control equipment connect with the electric means that can start work when secondary wind speed round is 0.
The present invention compared with prior art has significant advantage and beneficial effect.By above technical scheme as can be known, the present invention has following advantage at least under the structural arrangements of excellence:
The generator of two wind wheel organizations is adopted in this case, wherein larger-diameter main air wheel is generating usefulness, than the secondary wind wheel of minor diameter for regulating the excitation frequency generating usefulness of holding concurrently, the two on same axis, opposite spin mutually, yawer is responsible for controlling the following wind direction of main air wheel and wind is rotated main force's generating; Secondary wind wheel upwind is to the wind reverse rotation, and auxiliary power generation improves usefulness greatly; The configuration of two wind wheel structure settings of this case and Yawing mechanism makes the simpler, reliable of set yaw control change;
Brushless double-fed machine rotor and rotary permanent-magnet internal rotor birotor cover stack structure are adopted in this case, realize the operation of unit variable speed constant frequency excitation, quite reduce 1/3 at least, thereby shorten the generator diameter, convenient transportation, reduction unit weight with capacity single rotor power generator electrode logarithm;
This case unit can be realized variable speed constant frequency operation, variable pitch adjusting, the two more single wind wheel variable speed constant frequency of the wind wheel generation unit unit wind energy utilizations of the following this case of rated wind speed improve a lot, non-gear box, can realize directly driving, the worry of no slip ring fault, do not need big capacity convertor assembly, unit reliability improves greatly; The present invention contrasts prior art significant contribution and progress, is really to have novelty, creativeness, practical good technology.
The specific embodiment of the present invention is provided in detail by following examples and accompanying drawing thereof.
Embodiment
Below in conjunction with accompanying drawing and preferred embodiment, to according to embodiment provided by the invention, structure, feature and effect thereof, describe in detail as after.
Shown in Fig. 1-4, a kind of telescopic double-rotor vscf generator comprises the generator main body 1 that is packed on the base 10, and generator unit stator 16 is installed in the generator main body casing 11, wherein,
Permanent magnetism internal rotor 17 by auxiliary driving 12 through-drive, be the constructing apparatus of relative stator 16 rotation in generator main body casing;
Ring-shaped rotor 14 is by final drive shaft 13 transmissions, and this ring-shaped rotor is to be encircled and can be around the constructing apparatus of permanent magnetism internal rotor rotation, and this ring-shaped rotor 14 is the structure configuration of relative stator 16 rotations; This ring-shaped rotor 14 is encircled aforementioned permanent magnetism internal rotor 17 devices on final drive shaft 13 by ring-shaped rotor support unit 140; Generator unit stator 16 is provided with ring-shaped rotor 14 couplings, and the stator winding 161 of outwards exporting electric energy is contained on the stator core 162 that is installed in the motor casing;
Described ring-shaped rotor 14 is made up of the ring-shaped rotor of encircling the permanent magnetism internal rotor unshakable in one's determination 141 and the inboard winding 142 of ring-shaped rotor that combines with ring-shaped rotor coupling unshakable in one's determination, ring-shaped rotor outside winding 143, the two ends of described ring-shaped rotor are provided with ring-shaped rotor support unit 140 respectively, the position that this ring-shaped rotor support unit combines with power transmission shaft is provided with bearing part 1401, so that ring-shaped rotor rotates with final drive shaft;
Ring-shaped rotor forms the dual rotor configuration of telescopiform of generator as brushless double-fed machine rotor and the permanent magnetism internal rotor by counter drive shaft transmission rotation thus; Thereby can realize the operation of unit variable speed constant frequency, quite reduce 1/3 at least, thereby can shorten the generator diameter greatly, make things convenient for the equipment transportation, reduce motor weight with capacity single rotor power generator electrode logarithm;
Secondary wind wheel 2 is the relative main air of upwind by its wheel hub 21 by known techniques and takes turns the external part 121 that the drive structure of reverse rotation is assemblied in counter drive shaft; The brake 15 that is used for secondary wind wheel brake is arranged between generator ' s cover and the secondary wind wheel wheel hub;
Described counter drive shaft supports by the clutch shaft bearing 115 that is configured in 111 ones of generator first end caps, stretch out the secondary wind wheel of casing 11 devices, pair wind wheel 2 relative main airs wheels are the reverse drive structure device that wind is rotated in the axle body end of counter drive shaft 12, and this pair wind wheel is upwind to wind rotation installation with known techniques by the F2 direction by its wheel hub 21;
By known techniques, will by the counter drive shaft 12 of secondary wind wheel transmission with by 13 one-tenths coaxial installations of the bind mode that can rotate mutually of final drive shaft of main air wheel transmission, by counter drive shaft with the transmission of power of secondary wind wheel to the permanent magnetism internal rotor; Described major and minor power transmission shaft all has the hollow via-hole 120,130 of preset diameters, so that the Generator Set power transmission shaft is satisfying under the specification requirement condition more lightweight, thereby reduces body weight;
One end of described final drive shaft supports by second bearing 116 that is configured in 112 ones of generator second end caps and stretches out casing and the assembling of main air wheel, this main air wheel 3 is assemblied on the final drive shaft 13 by the drive structure that its wheel hub 31 is wind direction rotation down, and the other end of this final drive shaft stretches into casing and is the configuration of power transmission structure by ring-shaped rotor support unit 140 by known techniques and ring-shaped rotor; This main air wheel is down with known techniques by the F3 direction by its wheel hub 31, and wind direction rotates installation to wind;
A kind of telescope double rotor fan variable speed constant frequency excitation control system, comprise aforementioned generator M, wherein, the main air of generator wheel 3 is configured on the final drive shaft, the stator 16 that has the Pg number of pole-pairs under the wind-force effect relatively is with the rotation of Nzr speed, and the main air wheel speed satisfies following relational expression:
Wherein: Nzr represents the main air wheel speed; Pg represents the stator winding number of pole-pairs; Pe represents the number of pole-pairs of permanent magnetism internal rotor; Fg represents stator frequency; Fe represents permanent magnetism internal rotor reduced frequency;
The inboard winding number of pole-pairs of described ring-shaped rotor and the consistent Pe that is set to of permanent magnetism internal rotor number of pole-pairs are to the utmost point; The consistent Pg that is set to the stator winding number of pole-pairs is to the utmost point for described ring-shaped rotor outside winding number of pole-pairs; Described ring-shaped rotor outside winding is connected by connecting line 123 negative-phase sequences between the ring-shaped rotor winding with inboard winding; Described ring-shaped rotor outside winding number of pole-pairs Pg is set to greater than the inboard winding number of pole-pairs of ring-shaped rotor Pe, and described ring-shaped rotor outside winding number of pole-pairs can be 3 times the inboard winding number of pole-pairs of ring-shaped rotor;
Generator secondary wind wheel 2 be configured on the counter drive shaft, this pair wind wheel drives permanent magnetism internal rotor with the reverse rotation of the relative main air wheel of Ne speed, and permanent magnetism internal rotor reduced frequency satisfies following relational expression:
Wherein: Ne vice wind wheel relative stator rotating speed;
Be configured to the permanent magnetism internal rotor that the Nzre rotating speed is counterrotating, have the Pe number of pole-pairs on counter drive shaft, the rotating speed of the relative ring-shaped rotor rotation of permanent magnetism internal rotor satisfies following relational expression: Nzre=Nzr+Ne
Wherein: Nzre represents the rotating speed of the relative ring-shaped rotor rotation of permanent magnetism internal rotor;
Be provided with on the aforesaid major and minor wind wheel and the signal of rotating speed can be sent to the main air wheel speed measurement mechanism G of unit centralized control equipment 5, secondary wind speed round measurement mechanism G1, the wind speed that the port D1 that connects via the wind speed checkout gear records and by the wind speed round that rotation-speed measuring device records is transferred to unit centralized control equipment 5; Unit centralized control equipment and yawer 6 connect, and wind direction is to wind rotation rotation down for control main air wheel, and yawer 6 can be installed on the engine room inside 101 under the base;
Described main air wheel is taken turns variable propeller pitch adjusting mechanism 38, secondary wind wheel variable propeller pitch adjusting mechanism 28 with the main air of the hub portion difference configuration adjustment propeller pitch angle of secondary wind wheel, this main air wheel, secondary wind wheel variable propeller pitch adjusting mechanism and the 5 electric connections of unit centralized control equipment are sent the instruction of change oar by 5 pairs of main air wheels of unit centralized control equipment variable propeller pitch adjusting mechanism 38; Dispose secondary wind wheel propeller pitch angle measurement mechanism G28, main air wheel propeller pitch angle measurement mechanism G38 in described main air wheel and the secondary wind wheel respectively;
Described major and minor wind wheel variable propeller pitch adjusting mechanism structure is identical, it is made up of change oar servomechanism 381,281 that drives with servomotor M38, M28 and change oar control device 382,282, and described unit centralized control equipment 5 is by becoming oar control device 382,282 and connecting with the change oar servomechanism 381,281 that servomotor M38, M28 drive; This change oar servomechanism changes the rotational speed regulation of carrying out main air wheel and secondary wind wheel according to detected propeller pitch angle under the control of unit centralized control equipment 5, realize that wind direction rotates wind under the main air wheel, and secondary wind wheel upwind is to the wind reverse rotation; Brake 15 is arranged between generator ' s cover and the secondary wind wheel wheel hub;
Voltage output end at generator connects grid-connection control device 7 and step-up transformer 8 successively, connects with external power grid W again; Between grid-connection control device and step-up transformer successively the output voltage measurement mechanism G4 that connects of configuration and unit centralized control equipment 5, the detecting device for output current G3 that connects with the unit centralized control equipment, and with the mains frequency checkout gear G2 of unit centralized control equipment connection; The unloaded checkout gear G5 that configuration and unit centralized control equipment connect between generator M and grid-connection control device; The unit centralized control equipment also have the port D1 that connects with wind speed checkout gear (not shown), with wind direction checkout gear (not shown) connect port D2, with the port D3 of host computer transmission data; Described major and minor wind wheel blade is pressed known technology mode device on the wind wheel wheel hub, described main air impeller blade wind sweeping area is greater than blade wind sweeping area 2-5 times of secondary wind wheel, especially be that 3 times of left and right sides of blade wind sweeping area of secondary wind wheel are preferable with main air impeller blade wind sweeping area, described wind sweeping area is the area that the wind wheel rotation forms;
The output voltage of the output current of the generator that records via detecting device for output current G3 and the generator that records via output voltage measurement mechanism G4 is transferred to unit centralized control equipment 5, and the output of a generator value that calculates via unit centralized control equipment 5 is right with default rated power numeric ratio; Imposing a condition down, wind speed that unit centralized control equipment 5 will be recorded by the connection port D1 of wind speed checkout gear and the main air wheel rated speed that records by rotation-speed measuring device G, collection calculates the adjusting numerical value of the propeller pitch angle of main air wheel rated speed under this wind speed, compare with the propeller pitch angle value of main air wheel propeller pitch angle measurement mechanism G38 collection again, send the instruction of change oar by 5 pairs of main airs wheels of unit centralized control equipment variable propeller pitch adjusting mechanism 38; Can realize that thus the main air wheel moves, and prevents the generator overload under firm power;
When intussusception permanent-magnet variable-speed constant frequency excitation birotor generator is incorporated into the power networks, the main air wheel speed is between default rated speed and minimum speed the time, secondary wind wheel under unit centralized control equipment 5 is regulated by the reverse rotation of pre-conditioned relative main air wheel, make the generator unit stator electric voltage frequency be always 50Hz by this rotation speed change; Secondary wind speed round is minimum to zero, brake 15 work when secondary wind speed round is 0 speed,
To sum up, the generator of two wind wheel organizations, wherein larger-diameter main air wheel is used for generating, secondary wind wheel than minor diameter is used for regulating the double generating of excitation frequency, the two on same axis, mutually opposite spin, yawer be responsible for controlling the main air wheel down wind direction wind is rotated main force's generating; Secondary wind wheel upwind is to the wind reverse rotation, and auxiliary power generation improves usefulness greatly.
Configurations such as the voltage output end grid-connection control device of described generator can be limited generator output voltage, with after date softly be incorporated into the power networks, off-grid when shutting down, can effectively reduce the impact of the reactive current that is incorporated into the power networks, guarantee unit safety operation; When generator reached rated output power, power of the assembling unit factor was controlled at operation about cos θ=1; When the generator active power of output hour, the lagging reactive power of unit output cos θ<1; When generator speed was lower than specified minimum speed or output of a generator and is higher than peak power output, off-the-line generator from the electrical network was finished soft off-the-line by configurations such as grid-connection control devices.
A kind of constant frequency exciting method for telescope double rotor fan speed changing and control system thereof:
1. be configured in the stator that has the Pg number of pole-pairs under the wind-force effect relatively main air wheel on the final drive shaft, and the main air wheel speed satisfies following relational expression with the rotation of Nzr speed:
Wherein: Nzr represents the main air wheel speed; Pg represents ring-shaped rotor outside winding number of pole-pairs; Pe represents the number of pole-pairs of permanent magnetism internal rotor; Fg represents stator frequency; Fe represents permanent magnetism internal rotor reduced frequency;
2. the secondary wind wheel in the configuration of counter drive shaft 12 ends drives the permanent magnetism internal rotor with the reverse rotation of the relative main air wheel of Ne speed, and permanent magnetism internal rotor reduced frequency satisfies following relational expression:
Wherein: Ne vice wind wheel relative stator rotating speed
3. be configured to the permanent magnetism internal rotor that the Nzre rotating speed is counterrotating, have the Pe number of pole-pairs on counter drive shaft, the rotating speed of the relative excitation internal rotor rotation of permanent magnetism internal rotor satisfies following relational expression:
Nzre=Nzr+Ne is wherein: Nzre represents the rotating speed of the relative ring-shaped rotor rotation of permanent magnetism internal rotor;
4. the inboard winding number of pole-pairs of described ring-shaped rotor and the consistent Pe that is set to of permanent magnetism internal rotor number of pole-pairs are to the utmost point; The consistent Pg that is set to the stator winding number of pole-pairs is to the utmost point for described ring-shaped rotor outside winding number of pole-pairs; Described ring-shaped rotor outside winding is connected by connecting line 123 negative-phase sequences between the ring-shaped rotor winding with inboard winding;
5. the wind speed that records of the port D1 that connects via the wind speed checkout gear and by the main air wheel speed that rotation-speed measuring device G records is transferred to unit centralized control equipment 5,
It is right that the unit centralized control equipment carries out main air vane tip speed ratio numeric ratio when the main air wheel is lower than rated speed, warp is right with the main air vane tip speed ratio numeric ratio that the unit centralized control equipment is preset, calculate the adjusting numerical value of propeller pitch angle, compare with the propeller pitch angle value of main air wheel propeller pitch angle measurement mechanism G38 collection again, send the instruction of change oar by 5 pairs of main airs wheels of unit centralized control equipment variable propeller pitch adjusting mechanism 38; Can realize that thus the main air wheel moves with its best tip speed ratio, reaches the purpose that makes full use of wind energy below rated speed;
When the main air wheel reaches rated speed, the output voltage of the output current of the generator that records via detecting device for output current G3 and the generator that records via output voltage measurement mechanism G4 is transferred to unit centralized control equipment 5, and the output of a generator value that calculates via this unit centralized control equipment is right with default rated power numeric ratio; When meeting preset value, wind speed that the port D1 that is connect by the wind speed checkout gear that unit centralized control equipment 5 will collect records and the main air wheel rated speed that records by rotation-speed measuring device G, calculate the adjusting numerical value of the propeller pitch angle of main air wheel rated speed under this wind speed, compare with the propeller pitch angle value of main air wheel propeller pitch angle measurement mechanism G38 collection again, send the instruction of change oar by 5 pairs of main airs wheels of unit centralized control equipment variable propeller pitch adjusting mechanism 38; Can realize that thus the main air wheel moves, and prevents the generator overload under firm power;
6. the wind speed that records of the port D1 that connects via the wind speed checkout gear and the secondary wind speed round that records by secondary wind speed round measurement mechanism G1 are transferred to unit centralized control equipment 5; By unit centralized control equipment 5 according to
Relational expression is carried out speed Control, makes generator in rated speed and the operation of the following 50Hz of remaining constant frequency;
When the main air wheel is lower than rated speed, the generator output voltage frequency numerical value comparison that secondary wind speed round calculates under the frequency numerical value of unit centralized control equipment collection mains frequency checkout gear G2 and this main air wheel speed, calculate the adjusting numerical value of propeller pitch angle under this rotating speed of secondary wind wheel, compare with the propeller pitch angle value of secondary wind wheel propeller pitch angle measurement mechanism G28 collection again, by the unit centralized control equipment secondary wind wheel variable propeller pitch adjusting mechanism 28 is sent the instruction of change oar, make generator below rated speed, keep the operation of 50Hz constant frequency;
When main air wheel reached rated speed, the port D1 that connects via the wind speed checkout gear was transferred to unit centralized control equipment 5 from the wind speed that records with by the secondary rated rotation speed of rotor that rotation-speed measuring device G records,
When the main air wheel reaches rated speed, unit centralized control equipment 5 is gathered the generator output voltage frequency numerical value comparison that calculates under mains frequency checkout gear G2 frequency numerical value and the secondary rated rotation speed of rotor, calculate the adjusting numerical value of secondary wind wheel propeller pitch angle under this wind speed, compare with the propeller pitch angle value of secondary wind wheel propeller pitch angle measurement mechanism G28 collection again, send the instruction of change oar by 5 pairs of secondary wind wheel variable propeller pitch adjusting mechanisms 28 of unit centralized control equipment; Make generator when rated speed, keep the operation of 50Hz constant frequency; With the generator output voltage frequency serves as to regulate target, and to limit stator frequency fg be 50Hz by regulating rotating speed that secondary wind wheel propeller pitch angle controls secondary wind wheel, and the static fe of permanent magnetism internal rotor is considered as 0;
7. described ring-shaped rotor outside winding number of pole-pairs Pg is set to greater than the inboard winding number of pole-pairs of ring-shaped rotor Pe, and described ring-shaped rotor outside winding number of pole-pairs can be 3 times the inboard winding number of pole-pairs of ring-shaped rotor;
Thereby, two rotor windings of intussusception have identical power frequency, mutual reciprocal rotating magnetic field during work, the rotary speed Nzre of the relative intussusception rotor of generator amature winding excitation field superposes, cooperates with the speed Nzr of main air wheel shaft mechanical rotation, all the time form synchronous excitation magnetic field, this synchronous field produces the 50Hz electromotive force in to the stator winding of the utmost point having Pg, realizes the variable speed constant frequency excitation operation of generating set.
8. being assemblied in main air wheel and the secondary wind wheel 2 that is assemblied in counter drive shaft on the power transmission shaft 13 regulates by the relative opposite direction at blade pitch angle and is relative reverse rotation and disposes.
9. when the main air wheel speed was between default rated speed and minimum speed, secondary wind wheel made the generator unit stator electric voltage frequency be always the variation rotating speed of 50Hz by default rule reverse rotation, formation under unit centralized control equipment 5 is regulated; When the main air wheel speed reached 1.2-1.5 times of rated speed, when secondary wind speed round reached minimum speed 0 speed simultaneously, brake 15 started; Both this, when the main air wheel speed reached specified minimum speed, secondary wind wheel reverse speed reached the highest, unit can be realized the variable speed constant frequency operation.
The above, it only is preferred embodiment of the present invention, be not that the present invention is done any pro forma restriction, every foundation technical spirit of the present invention all still belongs in the scope of technical solution of the present invention any simple modification, equivalent variations and modification that above embodiment did.