Three-level midpoint potential balance control method based on zero sequence voltage injection
A zero-sequence voltage and potential balance technology
Inactive Publication Date: 2012-06-27
NORTH CHINA UNIVERSITY OF TECHNOLOGY
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Problems solved by technology
[0006] The technology of the present invention solves the problem: it overcomes the complexity of the existing SVPWM midpoint potential balance control method, and the existing point potential balance control method based on zero-sequence voltage injection requires complex calculations and high-precision acquisition circuits. In the modulation mode, a novel and simple neutral point potential balance control method based on zero-sequence voltage injection is proposed
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[0118] figure 1 It is a structural diagram of a three-level inverter control system, which mainly includes two main loops 80 and a control loop 85 . Main circuit 80 is made up of transformer 77, bridge rectifier 78, three-level inverter 79, motor load 86; A receiving circuit 81 and a power module 82 . The transformer 77 in the main circuit 80 is connected with the rectifier bridge 78, and the rectifier bridge 78 converts the three-phase AC power provided by the transformer 77 into a DC power supply for the use of the three-level inverter 79, and the rectifier bridge 78 is connected with the three-level inverter 79 , the inverter 79 is connected with the motor 86, and the three-level inverter 79 converts the DC power outputted by the rectifier bridge 78 into a three-phase AC with a desired frequency f, and supplies it to the motor load 86; 12 channels of PWM optical fiber sending and receiving circuits 83 and 12 fault signal optical fiber sending and receiving loops 81 are c...
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The invention provides a three-level midpoint potential balance control method based on zero sequence voltage injection, which is a control method capable of effectively controlling the balance of the midpoint potential in a high-power diode clamped three-level inverter. The control method comprises: collecting to obtain voltage values and three-phase output current values of two capacitors on the two sides of a direct current bus through voltage and current sampling circuits, calculating the voltage difference of two capacitors, judging whether the midpoint level is balanced and judging the relation of the three-phase output current and midpoint current during vector output under multi-carrier wave PWM modulation policy, calculating to generate a three-phase modulation voltage by using azero sequence voltage injection method according to a zero sequence voltage selection principle, comparing with carrier waves to generate a needed switching sequence so as to achieve the purpose of controlling the midpoint level balance in the three-level inverter. The invention not only controls the midpoint level effectively, but also has the advantages of simple control method and strong robustness, and can ensure the inverter to work stably in a total range.
Description
technical field [0001] The invention relates to a three-level midpoint potential balance control method based on zero-sequence voltage injection, which is used for the balance control of the midpoint potential of a high-power diode-clamped three-level inverter, and is especially suitable for low switching frequency and calculation For simple high-voltage and high-power applications, this control method is also suitable for midpoint potential balance control of PWM rectifiers and active power filters with the same main circuit structure. Background technique [0002] The three-level inverter has been widely used in high-voltage and high-power occasions due to its mature topology and low harmonic content in the output voltage. Compared with the two-level inverter, the three-level inverter has the following advantages: when the DC bus voltage is constant, the withstand voltage level of the switching device is reduced by half; at the same switching frequency, the three-level inv...
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IPC IPC(8): H02M5/458H02M7/537
Inventor 周京华章小卫刘辉臣
Owner NORTH CHINA UNIVERSITY OF TECHNOLOGY