Background technology
In three-phase medium voltage converter speed governing field, the concatenated frequency changer of a kind of plural serial stage voltage source inverter commonly used belongs to the high type of height, and maximum input voltage is 10kV, the prime of present every step voltage source inventer unit generally adopts not control rectifier, and minority adopts three-phase controlled rectifier.The concatenated frequency changer of the high type of height, universal architecture comprises several three-phases of 3x level not control rectifier, several single-phase voltage source inventers of 3x level, the step-down transformer that high pressure input, low pressure are exported, being characterized as of step-down transformer elementaryly connects three phase windings, secondary for several tortuous three phase windings of 3x level for Y, the basic differential seat angle that tortuous three phase windings connect group is (60 °/progression), it is identical that per three three phase windings connect group, the supporting inverter of rectifier.
Through the retrieval of prior art document is found, Chinese patent application number: 02104140.7, name is called the patent of " no-harmonic wave pollution high voltage large power frequency converter "; It is the application of plural serial stage certain limit that doctor Jiang Youhua also discloses cascaded multiple at " research of high-power Asynchronous Motor Driving blower fan, load of the pumps speed adjusting technique " (doctorate paper .2006 of Shanghai University 02 month), frequency conversion voltage adjusting speed governing, energy-saving and cost-reducing effect have been brought into play, theory and practice has proved that all the concatenated frequency changer structure of plural serial stage is a kind of feasible circuit structure, but the still existing very important problem of power structure, for example: the design complexity of step-down transformer shows as secondary tortuous design of Windings complexity; Three-phase rectifier quantity is many; The laod unbalance of rectifier needs jumbo electrochemical capacitor; Machine volume is big, efficient is low, cost is high, control is complicated, poor-performing; More high voltage output needs more inverter series connection progression.
Summary of the invention
The present invention is directed to the prior art above shortcomings, the medium voltage frequency converter of a kind of friendship Direct Transform is provided, have novel, highly versatile, general structure is simple and improves the characteristics of net side power factor.
The present invention is achieved by the following technical solutions, the present invention includes: step-down transformer and three transducer arrays, wherein: three three-phase secondary winding of step-down transformer are connected with the input of three transducer arrays respectively.
The initial phase of described step-down transformer is 0 °, and the adjacent three-phase secondary winding of this step-down transformer has different phase places, and the absolute value of master phase difference is 20 °.
The elementary winding of described step-down transformer and the secondary winding of 0 ° of phase place adopt the Yg connection, and the secondary winding of the secondary winding of+20 ° of phase places and-20 ° of phase places adopts interconnected star connection.
Described transducer array comprises: three matrixers and three step-up transformers, wherein: the input of three matrixers is connected with three three-phase secondary winding respectively, and the output of three matrixers is connected with the single-phase elementary winding of three step-up transformers respectively.
Described step-up transformer is a single-phase step-up transformer.
The single-phase secondary winding of the step-up transformer in described three transducer arrays is connected in series respectively successively, forms three-phase high-voltage frequency conversion output, and the catenation sequence position of the step-up transformer of corresponding same phase three-phase secondary winding is identical; The not series connection end of the single-phase secondary winding of first step-up transformer links to each other in each transducer array, forms mid point N.
Described matrixer is formed three brachium pontis structures by six two-way gate-controlled switches, the mid point of three brachium pontis and corresponding three-phase secondary winding connection, one end of three two-way gate-controlled switches of one end of three two-way gate-controlled switches of last brachium pontis and following brachium pontis is connected with the single-phase elementary winding of corresponding step-up transformer respectively, this matrixer is the three-phase alternating voltage input, the output of single phase alternating current (A.C.) voltage.
The present invention adopts the step-down transformer output of phase shift to differ 20 ° three-phase secondary winding, and each three-phase secondary winding is three matrixer power supplies, and these three matrixers adhere to different transducer arrays separately, and the desired output voltage-phase differs 120 °.Matrixer adopts the matrix converter operation principle, and the output first-harmonic is sinusoidal wave high-frequency pulse voltage.When the bearing power balance of whole device, the load balance of each three-phase secondary winding, electric current are sinusoidal waveform and synchronous with three-phase secondary winding output voltage.For whole device, input and output is the unit's of showing as input power factor all like this, does not have harmonic current to pollute to electrical network, and line loss is lower, and the present invention is simple in structure, and is with low cost.Adopt the step-up transformer output series connection of single-phase high frequency can further realize the function that electrical isolation and step-up ratio increase arbitrarily.
Embodiment
Below in conjunction with accompanying drawing embodiments of the invention are elaborated, present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
Embodiment 1
As shown in Figure 1, present embodiment comprises: step-down transformer 1 and three transducer arrays 2,3,4, wherein: three three-phase secondary winding of step-down transformer 1 are connected with the input of three transducer arrays 2,3,4 respectively.
The initial phase of described step-down transformer is 0 °, the adjacent three-phase secondary winding of this step-down transformer has different phase places, and the absolute value of master phase difference is 20 ° of i.e. secondary winding 6 of 5,0 ° of phase place of secondary winding of+20 ° of phase places and secondary winding 7 of-20 ° of phase places.
The elementary winding of described step-down transformer and the secondary winding of 0 ° of phase place 6 adopt the Yg connection, and the secondary winding 5 of+20 ° of phase places and the secondary winding of-20 ° of phase places 7 adopt interconnected star connection.
Described transducer array 2 comprises: three matrixer M1, M2, M3 and three step-up transformer T1, T2, T3, wherein: the input of three matrixer M1, M2, M3 is connected with three three-phase secondary winding respectively, the output of three matrixer M1, M2, M3 is connected with the single-phase elementary winding of three step-up transformer T1, T2, T3 respectively, three step-up transformer T1, T2, T3 are connected in series successively, form the output of U phase high-pressure frequency-conversion.
Described transducer array 3 comprises: three matrixer M4, M5, M6 and three step-up transformer T4, T5, T6, wherein: the input of three matrixer M4, M5, M6 is connected with three three-phase secondary winding respectively, the output of three matrixer M4, M5, M6 is connected with the single-phase elementary winding of three step-up transformer T4, T5, T6 respectively, three step-up transformer T4, T5, T6 are connected in series successively, form the output of V phase high-pressure frequency-conversion.
Described transducer array 4 comprises: three matrixer M7, M8, M9 and three step-up transformer T7, T8, T9, wherein: the input of three matrixer M7, M8, M9 is connected with three three-phase secondary winding respectively, the output of three matrixer M7, M8, M9 is connected with the single-phase elementary winding of three step-up transformer T7, T8, T9 respectively, three step-up transformer T7, T8, T9 are connected in series successively, form the output of W phase high-pressure frequency-conversion.
The not series connection end of described step-up transformer T1, T4, T7 links to each other, and forms mid point N.
As shown in Figure 2, described matrixer M1, M2, M3, T4, T5, T6, M7, M8, M9 form three brachium pontis structures by six two-way gate-controlled switch BS1, BS2, BS3, BS4, BS5, BS6, the mid point of three brachium pontis and corresponding three-phase secondary winding connection, three two-way gate-controlled switch BS4 of an end and following brachium pontis of three two-way gate-controlled switch BS1 of last brachium pontis, BS2, BS3, the end of BS5, BS6 are connected with the single-phase elementary winding of corresponding step-up transformer respectively, this matrixer is the three-phase alternating voltage input, the output of single phase alternating current (A.C.) voltage.
Described two-way gate-controlled switch BS1, BS2, BS3, BS4, BS5, BS6 are made up of against leading switch two differential concatenations, against leading switch for to be composed in parallel by an insulated gate bipolar transistor and a diode reverse.
The three-phase alternating current output voltage of present embodiment is 6kV, and whole device desired output alternating voltage maximum is 6kV.The step-down transformer primary voltage is 6kV, and the step-down transformer secondary voltage is 690V.Transducer array is a matrixer, and electric pressure is for exchanging 690V.Series connection progression is 3 in each transducer array, and the transformation multiple of step-up transformer is 2 times, then can satisfy the frequency control requirement of 6kV high-pressure frequency-conversion motor fully.