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IPC classes for russian patent Multilevel frequency converter with differential voltage levels and bypass semiconductor keys (RU 2510769):
H02P27/08 - CONTROL OR REGULATION OF ELECTRIC MOTORS, GENERATORS, OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS (structure of the starter, brake, or other control devices, see the relevant subclasses, e.g. mechanical brake F16D, mechanical speed regulator G05D, variable resistor H01C, starter switch H01H; systems for regulating electric or magnetic variables using transformers, reactors or choke coils G05F; arrangements structurally associated with motors, generators, dynamo-electric converters, transformers, reactors or choke coils, see the relevant subclasses, e.g. H01F, H02K; connection or control of one generator, transformer, reactor, choke coil, or dynamo-electric converter with regard to conjoint operation with similar or other source of supply H02J; control or regulation of static converters H02M)
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FIELD: electricity.
SUBSTANCE: invention pertains to electrical engineering and can be used in high voltage regulated electrical drives. Multilevel frequency converter with differential voltage levels and bypass semiconductor keys contains input multi-winding transformer, control system and several levels of power cells in each phase. Output voltage of cells for each level is different: output voltage of the first level cells is equal to half of the rated output voltage of frequency converter and each next level is twice less than voltage of the previous level. In parallel to output of each power cell there's bypass semiconductor key, one semiconductor key of power cell is connected to the first control output of the control system by commutator switch in case of the cell failure, while its other control input is connected to the second control output of the control system by commutator switch in operating modes to change output voltage of the frequency converter.
EFFECT: obtaining a larger number of voltage levels at output of the frequency converter with less number of secondary windings of input multiphase transformer and with less number of power cells, providing possibility of control for bypass keys position not only in case of failure.
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The invention relates to the field of electrical engineering and can be used in high-voltage variable frequency drives.
Known multi-level transistor frequency Converter for control of an induction motor is proposed in U.S. patent No. 5625545 priority from 29.04.1997 "Device and method for pulse-width frequency Converter" ("Medium voltage PWM drive and method"), containing the input winding of the power transformer and connected in series power cells, each of which is made in the form of single-phase transistor inverter frequency control block cell, with three-phase bridge rectifier connected to the conclusions of the AC output of the secondary winding, the input winding of the power transformer, and the conclusions of the constant current through the power of the output filter with the input pins DC transistor single-phase of the inverter.
The disadvantages of this multilevel inverter frequency are the complexity of the design of the input winding of the power transformer, due to the presence of a large number of secondary windings, the significant dimensions of the frequency Converter due to the large number of low-voltage power cells and loss of use of the frequency Converter with elektrodvigatel the mi different nominal voltages. These drawbacks are due to the fact that all of the secondary winding, the input winding of the transformer and all the power cell of the frequency Converter have the same nominal voltage.
Closest to the claimed technical solution is a multi-level transistor frequency Converter to control the AC motor (patent No. 2411629 from 19.10.2009)containing the input winding of the power transformer, connected in series power cells, each of which is made in the form of single-phase transistor inverter frequency control unit cell and three-phase bridge rectifier connected to the conclusions of the AC outputs of the secondary winding of the power transformer, and the conclusions of the constant current through the power of the output filter with the input pins DC transistor single-phase inverter.
The drawbacks are the complexity of the design of the input winding of the power transformer, due to the presence of a large number of secondary windings, the significant dimensions of the frequency Converter, caused by a large number of low-voltage cells, and loss of use of the frequency Converter with electric motors of different nominal voltages. Other nedostatki the known device is the limited number of levels of the output voltage, which corresponds to the number of power cells in each phase that affects the degree of sinusoidality output voltage and makes impossible the use of the frequency Converter with electric motors of different nominal voltages.
These drawbacks due to the fact that all of the secondary winding, the input winding of the transformer and all the power cell of the frequency Converter is made with the same nominal voltage.
In order to obtain a larger number of voltage levels at the output of the frequency Converter in the known device, it is necessary to increase the number of secondary windings of the input transformer and increase the number of power cells in each phase, which complicates the design as input winding of the transformer and the electronic part of the frequency Converter.
An object of the invention is to simplify the design of a multilevel Converter, increasing the number of voltage levels at the output and the extension of its functionality by allowing use with motors of different nominal voltages.
This objective is achieved in that the device containing the multi-winding power transformer, connected in series power cells, each of which is made in the form of single-phase t is insisting frequency Converter with a control unit cell and three-phase bridge rectifier United conclusions AC outputs of the secondary winding of the power transformer, and the conclusions of the constant current through the power of the output filter with the input pins DC transistor single-phase inverter according to the invention the secondary winding of the input winding of the transformer and connected with them the power cell is made with a variety of secondary voltage, namely, the nominal voltage of the power cells of the first level is half of the nominal output voltage of the frequency Converter and the nominal voltage of the power cells in each subsequent level is two times lower than the nominal voltage of the power cells of the previous level, and parallel to the output of each power cell installed bypass semiconductor keys, one control input of which is connected to first control the output of the control system, the switching key in case of failure of the cell, and the other control input connected to the second control the output of the control system, the switching key in the operating modes for the output voltage of the frequency Converter.
The essence of the proposed technical solution is that the output voltage of the cells of the first level is half of the nominal output voltage of the Converter cha is toty U 1=UH/2, the cells of the second level - quarter U2=UH/4, cells of the third level - eighth U3=UH/8, cells of the fourth level - sixteenth U4=UH/16, the output voltage level cell n is 1/2" from the nominal output voltage of the frequency Converter Un=UH/(2n), and in parallel to the output of each power cell installed bypass semiconductor keys, one control input of which is connected to first control the output of the control system, the switching key in case of failure of the cell, and the other control input connected to the second control the output of the control system, the switching key in the operating modes for the output voltage of the frequency Converter.
Figure 1 presents the scheme of multi-level frequency Converter with various voltage levels and bypass semiconductor keys containing the input winding of the transformer T, the control system SU control the output OW, switching keys in case of failure of the power cells, and control the output OW, switching keys in the operating modes for the output voltage of the frequency Converter, and multiple levels of power cells in each phase: power cell of the first level 1 power cell of the second layer 2, a power cell of the third is level 3, and so forth, in parallel to the output of each power cell bypass connected semiconductor key K.
The device operates as follows. The output phase voltage of the frequency Converter is equal to the sum of the output voltages included power cell all levels from 1 to n:
Depending on what power cell is enabled and what is disabled, you can get the 2nvalues (levels) of the output voltage UO=Un(when the n-th cell and turned off all other cells) to UO=2n·Unwhen all the cells, and the level change of the output voltage is equal to Un.
In case of failure of any of the cell control system SU bypasses the defective cell by shorting the corresponding bypass semiconductor key To the cell output by the signal on the control output UV. When this is corrected in the other cells, so as to preserve the symmetry of the voltage on phases. In the proposed device control inputs bypass key not connected tol the to to control the output OW management system, switching keys in case of failure of the power cells, but also to control the output OW, switching keys in the operating modes for the output voltage of the frequency Converter. This allows us to control the position of the bypass key and includes the power cells not only in case of failure of the power cell, but also in operating modes: start-up modes and speed control of motors.
When starting in the initial state of the circuit power cell all levels are disabled, and all-pass semiconductor keys To open, and on the frequency inverter output voltage is missing. When you receive the command to start the motor M control system SU calculates the instantaneous value of the voltage of each phase for the desired frequency and delivers the commands to enable and disable the power cell and the bypass keys so that the discreteness of change of the output voltage of the frequency Converter is equal to the output voltage of the cell of the upper level n.
In the operating mode, speed control mode, the rotation number of enabled cells and the level of the output voltage is selected depending on the nominal voltage of the motor and method of frequency control. If there is an opportunity to connect to the frequency Converter electrode of the motor M, rated voltage which can be obtained from equation (1) by selecting on/off of the power cells.
Due to the fulfillment of cells with different nominal voltage of the opportunity with the same number of cells to form the output voltage from a larger number of voltage levels than in the known device. So, if all of the cells of the frequency Converter of the known devices have the same output voltage, when the number of levels n=4 it is possible to get only 4-level voltage of each polarity. In the proposed device the differential voltages of each level when n=4 is 2n=16 levels.
Figure 2 shows the output waveform of the multilevel Converter, if all cells have the same output voltage, and the number of levels and cells n=4.
Figure 3 shows the output waveform of the multilevel inverter frequency when the differentiated voltage of each level and the number of cells n=4. It is seen that the shape of the voltage figure 3 is much closer to a sine wave.
Thus, in the proposed device provides an increased number of voltage levels at the output of the frequency Converter with a smaller number of secondary windings of the input winding of the transformer and with fewer power cell. In addition to the CSO, by connecting the control inputs bypass key not only to the diagnostic findings of the management system, but also to the control, you can control the position of the bypass key not only in case of failure of the power cell, but also in the operating conditions such as start up mode or the frequency control mode. This allows to simplify the design of multi-level frequency Converter and to extend the functionality by allowing use with motors of different nominal voltages.
Multi-level frequency Converter with various voltage levels and bypass semiconductor keys containing the input winding of the power transformer, connected in series power cells, each of which is made in the form of single-phase transistor inverter frequency control unit cell and three-phase bridge rectifier connected to the conclusions of the AC outputs of the secondary winding of the power transformer, and the conclusions of the constant current through the power of the output filter with the input pins DC transistor single-phase inverter, characterized in that the secondary winding, the input winding of the transformer and connected with them the power cell is made with different the m secondary voltage, namely, the nominal voltage of the power cells of the first level is half of the nominal output voltage of the frequency Converter and the nominal voltage of the power cells in each subsequent level is two times lower than the nominal voltage of the power cells of the previous level, while the output of each power cell installed bypass semiconductor keys, one control input of which is connected to first control the output of the control system, the switching key in case of failure of the cell, and the other control input connected to the second control the output of the control system, the switching key in the operating modes for the output voltage of the frequency Converter.
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