Double-unit wind power-generating grid-connected system and control method thereof
Technical field
The present invention relates to wind power-generating grid-connected system and the control method thereof of a kind of power electronics application technology and generation of electricity by new energy interconnection technology, particularly a kind of double-unit.
Background technology
Progress along with wind technology and power electronic technology, vane propeller-changing is widely used in the megawatt-level wind unit apart from technology and wind turbine variable speed constant frequency technology, in the new wind-powered electricity generation unit of installing in the whole world, there is the wind-powered electricity generation unit more than 90% to adopt the variable-pitch variable-speed constant-frequency technology, to realize the maximal wind-energy tracking, satisfy the high-efficiency operation of wide velocity interval.
In order to catch to greatest extent wind energy, wind generator system often adopts maximal power tracing control: according to the Wind Turbine, and under a certain wind speed, so that generator operation is in a certain rotating speed, thus capturing wind energy to greatest extent, the electrical power that output is maximum.At present, the variable speed constant frequency generator system that is used for wind power generation has multiple, and it is typically asynchronous dual feedback wind power generation system, electric excitation synchronous wind generating system and direct drive permanent magnetic synchronous wind generating system.
From the structure of power major loop, at present still take the form of two PWM, uncontrollable rectification-DC/DC-PWM inversion grid connection as main, to improve the current on line side quality, to improve the power factor of grid-connected system.
In July, 2009, Huang Surong, Zhang Qi, Hong Wencheng, fourth Xuan are bright, Xie Guodong proposes " independent magnetic circuit mixed excitation electric engine ", Chinese invention patent (No.ZL 200810032392.4).In June, 2010, Huang Surong, Hong Wencheng, Zhang Qi, Zou Haiyan propose " maximal power tracing of mixed field excitation wind power generation system and bus-bar voltage coordination control method ", Chinese invention patent (No.200810200814.4).
Summary of the invention
The object of the invention is to propose a kind of double-unit wind power-generating grid-connected system and control method thereof for novel dual armature independent magnetic circuit mixed excitation synchronous generator.Adopt the double-unit operating mode switching device of power electronic device composition, can change online neatly the operational mode of dual rectification and inversion unit.
When wind speed when fluctuating among a small circle, by regulating the electric exciting current of hybrid excitation generator, when wind speed when fluctuating in a big way, by changing operational mode, reach the constant purpose of direct current commutating voltage, effectively enlarged the wind energy catching range, realize maximal power tracing.
For achieving the above object, design of the present invention is:The double-unit wind power-generating grid-connected system adopts dual armature winding mixed excitation synchronous generator directly to link to each other with wind turbine, the alternation induced potential that each armature winding of synchronous generator sends output dc voltage behind uncontrollable rectifier bridge.Regulate by regulating electric exciting current air-gap field size, realize that magnetic field is smoothly adjustable.Make dual uncontrollable rectifier bridge be operated in independent working mode or tandem working pattern, dual parallel network reverse cell operation in independent working mode or parallel operation pattern by the double-unit operating mode switching device.
When wind speed is higher, generator speed is higher, and the induced electromotive force of dual armature mixed excitation synchronous generator is higher through the direct voltage of uncontrollable rectifier bridge output, and two cover parallel network reverse unit independently generate electricity by way of merging two or more grid systems.Along with rotating speed reduces, progressively drop into electric excitation, to guarantee sufficiently high dc voltage, make the grid side inversion unit can be normally, work reliably.
After dropping into maximum electric excitation, all can't make the parallel network reverse cell operation, two cover armature winding are connected through output dc voltage after the uncontrollable rectifier bridge, raise DC bus-bar voltage, make the parallel network reverse unit continue operation, the wind speed range of positive operation of expansion system.
According to the foregoing invention design, the present invention adopts following technical proposals:
A kind of pair of unit wind power-generating grid-connected system as shown in Figure 1, comprise wind energy conversion system (1), dual armature winding mixed excitation synchronous generator (2), the first and second uncontrollable rectification units (3,4), the first and second parallel network reverse unit (5,6), double-unit operating mode switching device (7) and electric excitation control unit (8) is characterized in that:
1) armature winding of the generating set of described wind energy conversion system (1) and dual armature winding mixed excitation synchronous generator (2) composition, be connected to the described first and second uncontrollable rectification units (3,4), the output voltage of the first and second uncontrollable rectification units (3,4) is through multiple units operating mode switching device (7), be connected to the first and second parallel network reverse unit (5,6), the energy that generating set is sent by the first and second parallel network reverse unit (5,6) is fed to electrical network (9).
2) described electric excitation control unit (8) is connected directly to the electric excitation winding of dual armature winding mixed excitation synchronous generator (2), adopts the DC PWM mode to control electric exciting current.
Above-mentioned double-unit operating mode switching device, as shown in Figure 2, its circuit structure:
1) composes in parallel respectively the first and second dynamic current limiting unit (U1, U2) by the first and second current-limiting resistances (R1, R2) and the first and second short-circuiting contactors (J1, J2).
2) first a gate-controlled switch device (G1) connects the negative terminal (-) of the first uncontrollable rectification unit (3) and the anode (+) of the second uncontrollable rectification unit (4); Second gate-controlled switch device (G2) connects the anode (+) of the first uncontrollable rectification unit (3) and the anode (+) of the second parallel network reverse unit (6) with after the first uncontrollable Power Diode Pumped (D5) is connected through the first dynamic current limiting unit (U1); The 3rd gate-controlled switch device (G3) connects the negative terminal (-) of the second uncontrollable rectification unit (4) and the negative terminal (-) of the first parallel network reverse unit (5) with after the second uncontrollable Power Diode Pumped (D6) is connected through the second dynamic current limiting unit (U2).
A kind of control method for above-mentioned grid-connected system is characterized in that the method may further comprise the steps:
1) when wind speed is higher, the double-unit operating mode switching device is in independent operation mode, the energy of dual armature winding mixed excitation synchronous generator (2) armature winding output is through the first and second uncontrollable rectification units (3 and 4) the first and second parallel network reverse unit (5 and 6), with energy feed-in three phase network;
2) when wind speed was low, the first and second uncontrollable rectification units (3 and 4) were in the series operation pattern, and the first and second parallel network reverse unit (5 and 6) are in single cover operational mode or parallel running pattern;
3) when wind speed when fluctuating among a small circle, regulate the electric exciting current of mixed excitation synchronous generator, keep the rectification unit output dc voltage constant.
In the said method, the control method that described double-unit operating mode switching device is in various operational modes is:
1) the first gate-controlled switch device (G1), the second gate-controlled switch device (G2) and the 3rd gate-controlled switch device (G3) all turn-off, the first uncontrollable rectification unit (3) is connected with the first parallel network reverse unit (5), the second uncontrollable rectification unit (4) is connected with the second parallel network reverse unit (6), and two cover rectifications and parallel network reverse unit are in independent operation mode;
2) the first gate-controlled switch device (G1) is open-minded, and the first and second uncontrollable rectification units (3 and 4) are in the series operation pattern, and the output voltage of equivalent rectification unit (3 and 4 series connection) is 2 times of single rectification unit output voltage.
3) rectification unit is in the series operation pattern, the second or the 3rd gate-controlled switch device (G2 or G3) is opened, the 3rd or second gate-controlled switch device (G3 or G2) turn-offs, equivalence rectification unit (3 and 4 series connection) is given the first or second parallel network reverse unit (5 or 6) power supply, and another second or first parallel network reverse unit (6 or 5) should be in closed condition, and the parallel network reverse unit is in single cover operational mode.
4) rectification unit is in the series operation pattern, and (G2 and G3) is open-minded for the second and the 3rd gate-controlled switch device, and equivalent rectification unit (3 and 4 series connection) is given the first and second parallel network reverse unit 5 and 6 power supplies, and two cover parallel network reverse unit are in the parallel running pattern.
5) rectification unit is in the handoff procedure of independent operation mode and series operation pattern, should drop into the first or second dynamic current limiting unit (U1 or U2), the first or second short-circuiting contactor (J1 or J2) disconnects, access the first or second current-limiting resistance (R1 or R2).To be switched finishing, rectification unit output voltage and parallel network reverse unit supply power voltage balance, the first or second short-circuiting contactor (J1 or J2) closure, excision the first or second current-limiting resistance (R1 or R2).
The present invention's outstanding substantive distinguishing features and remarkable advantage compared with prior art:
1) scheme of employing mixed excitation synchronous generator, by electric excitation regulation generator output voltage, the rectifier bridge that the generating pusher side only need adopt Power Diode Pumped to form need not DC to DC converter, and line construction is simple.Adopt electric exciting current closed-loop control, dynamic property is good, and stable state accuracy is high.
2) adopt the scheme of dual armature winding, dual rectification and dual inversion unit, avoided the direct parallel connection of power electronic device, improved the reliability of system, increased the redundancy of system.
3) consist of the double-unit operating mode switching device with power electronic device, have the advantages such as switch speed is fast, safe and reliable, can adapt to wind speed frequently, change fast.
4) adopt such scheme, effectively enlarged the catching range of wind energy, realize maximal power tracing.
Description of drawings
Fig. 1 is double-unit wind power-generating grid-connected system structure chart.
Fig. 2 is double-unit operating mode switching device figure.
Fig. 3 is the independent working mode equivalent circuit diagram.
Fig. 4 is uncontrollable rectification unit series connection, parallel network reverse unit list cover mode of operation equivalent circuit diagram.
Fig. 5 is uncontrollable rectification unit series connection, parallel network reverse unit parallel operation pattern equivalent circuit diagram.
Embodiment
The preferred embodiments of the present invention accompanying drawings is as follows:
Embodiment one:
This double-unit wind power-generating grid-connected system as shown in Figure 1, the first and second uncontrollable rectification units (3,4) are pressed three-phase bridge by 6 Power Diode Pumped and are connected, the first and second parallel network reverse unit (5,6) are pressed three-phase bridge by 6 IGBT modules with the inverse parallel Power Diode Pumped and are connected, the first and second parallel network reverse unit (5,6) output series connection three-phase reactor.Wind energy conversion system (1) be connected the mechanical coaxial connection of armature winding mixed excitation synchronous generator (2), the armature winding of generating set, be connected to the first and second uncontrollable rectification units (3,4), the output voltage of the first and second uncontrollable rectification units (3,4) is through double-unit operating mode switching device (7), be connected to the first and second parallel network reverse unit (5,6), the energy that generating set is sent by the first and second parallel network reverse unit (5,6) is fed to electrical network (9).Electricity excitation control unit (8) is connected directly to the electric excitation winding of dual armature winding mixed excitation synchronous generator (2).
Embodiment two:
Present embodiment and embodiment one are basic identical, special feature is described double-unit operating mode switching device (7) as shown in Figure 2, and first, second, and third gate-controlled switch device (G1, G2 and G3) is selected the IGBT module with the inverse parallel Power Diode Pumped.The first and second current-limiting resistances (R1, R2) compose in parallel the first and second dynamic current limiting unit (U1, U2) with the first and second short-circuiting contactors (J1, J2) respectively, and the first gate-controlled switch device (G1) connects the negative terminal (-) of the first uncontrollable rectification unit (3) and the anode (+) of the second uncontrollable rectification unit (4); The second gate-controlled switch device (G2) connects the anode (+) of the first uncontrollable rectification unit (3) and the anode (+) of the second parallel network reverse unit (6) with after the first uncontrollable Power Diode Pumped (D5) is connected through the first dynamic current limiting unit (U1); The 3rd gate-controlled switch device (G3) connects the negative terminal (-) of the second uncontrollable rectification unit (4) and the negative terminal (-) of the first parallel network reverse unit (5) with after the second uncontrollable Power Diode Pumped (D6) is connected through the second dynamic current limiting unit (U2).
Embodiment three:
The control method of this double-unit wind power-generating grid-connected system is: wind energy conversion system (1) drives dual armature winding mixed excitation synchronous generator (2) rotation, the induced potential of synchronous generator (2) armature winding output alternation, through the first and second uncontrollable rectifier bridges (3,4) the AC sine induced potential is become direct current, after dc bus capacitor filtering, obtain comparatively straight direct voltage.The first and second parallel network reverse unit (5 and 6) with the direct voltage inversion are and the same alternating voltage frequently of electrical network, and enforcement control current on line side, with energy feed-in three phase network.
1) when wind speed is higher, synchronous generator reaches rated speed, and electric excitation control unit (8) output current is zero, and only permanent magnet partly works.First, second, and third gate-controlled switch device (G1, G2 and G3) in the double-unit operating mode switching device (7) all turn-offs.The first uncontrollable rectification unit (3) is connected with the second parallel network reverse unit (5), and the second uncontrollable rectification unit (4) is connected with the second parallel network reverse unit (6), is in independent operation mode, equivalent circuit Fig. 3.
2) when wind speed reduces, the synchronous generator rotating speed will progressively strengthen electric excitation control unit (8) output current along with the synchronous reduction of wind speed, and will be constant to keep synchronous generator (2) armature winding output induced potential, keep direct voltage constant.First, second, and third gate-controlled switch device (G1, G2 and G3) in the double-unit operating mode switching device (7) keeps off state, and system still is in independent operation mode.
3) if wind speed and synchronous generator rotating speed continue to reduce, and electric excitation control unit (8) output current reaches maximum, in the time of still can not keeping direct voltage constant, arrives the mode of operation switching point.The first gate-controlled switch device (G1) is open-minded in the double-unit operating mode switching device (7), the first and second uncontrollable rectification units (3 and 4) are in the series operation pattern, and the output voltage of equivalent rectification unit (3 and 4 series connection) is 2 times of single rectification unit output voltage.When rectification unit was in the series operation pattern, can there be two kinds of mode of operations the parallel network reverse unit.
A. second (or 3rd) gate-controlled switch device G2(or G3 in the double-unit operating mode switching device (7)) open, the 3rd (or second) gate-controlled switch device G3(or G2) turn-off, equivalence rectification unit (3 and 4 series connection) is given first (or second) parallel network reverse unit 5(or 6) power supply, and second (or first) parallel network reverse unit 6(or 5) should be in closed condition, the parallel network reverse unit is in single cover operational mode, equivalent circuit Fig. 4.
B. the second and the 3rd gate-controlled switch device (G2 and G3) is open-minded simultaneously in the double-unit operating mode switching device (7), equivalence rectification unit (3 and 4 series connection) is given the first and second parallel network reverse unit (5 and 6) power supply, two cover parallel network reverse unit are in parallel running pattern, equivalent circuit Fig. 5.
4) because the raising of combining inverter direct voltage, can make that exciting current is zero.Along with wind speed continues to lower, progressively strengthen again exciting current.Combining inverter can be operated in single cover operational mode, also may operate in paralleling model.
5) effect of uncontrollable Power Diode Pumped D1 to D6 is to suppress reverse current, the first and second dynamic current limiting resistance (R1 and R2) play the effect of transient suppression equalizing current in work-mode switching process, after the mode of operation switching is finished, the first and second short-circuiting contactors (J1 or J2) closure is excised the first and second current-limiting resistances (R1 or R2).
When 6) wind speed was by low uprising, operation principle was same as described above, and its switching is opposite with adjustment process.