Novel two-stage multi-level power inversion system

Abstract

The invention discloses a novel two-stage multi-level power inversion system. A front-stage multi-way output DC-DC (Direct Current-Direct Current) convertor and a diode clamping multi-level inverter are cascaded to serve as power topology. Voltage boosting of a power supply and active control on neutral-point voltage of the multi-level inverter can be realized by closed-loop control on voltage of the front-stage DC-DC convertor; and the back-stage clamping multi-level inverter can realize functions of motor driving, grid-connected inversion, isolated grid operation and the like. A method can realize the voltage boosting by the front-stage DC-DC convertor at the same withstand voltage of switching tubes; limitation of a voltage class of a DC power supply can be overcome; a high voltage class load can be adapted; the front-stage DC-DC convertor overcomes an influence of interrupted current input or low-frequency pulsation of the traditional inverter on the DC power supply; the problem of difficult balance of the neutral-point voltage of the clamping multi-level inverter can be overcome by utilizing the active control ability of the front-stage DC-DC convertor on the voltage; and multi-level inverter control of variable neutral-point voltage can be realized to acquire low current.

Description

Technical field [0001] The invention relates to a novel two-stage multi-level power inverter system, which belongs to the technical field of electric energy conversion. Background technique [0002] The power inverter system (also known as the frequency converter) is the core component of the motor drive, grid connection, island grid and other systems. Traditional motor drive, grid-connected, island grid and other systems are powered by a DC power supply connected to a full-bridge inverter, and the inverter output is realized through PWM modulation of the full-bridge inverter. [0003] However, the traditional full-bridge inverter control effect is not good, mainly due to the following four reasons: [0004] 1. The traditional DC power supply connected to the full-bridge inverter can only achieve step-down output. If the load terminal voltage level is higher, the traditional full-bridge inverter cannot meet its output requirements; [0005] 2. The input current of the traditional ful...

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Problems solved by technology

[0003] However, the control effect of the traditional full-bridge inverter is not good, mainly due to the following four reasons:

[0004] 1. The traditional DC power supply connected to the full-bridge inverter can only achieve step-down output. If the voltage level of the load terminal is high, the traditional full-bridge inverter cannot meet its output requirements;

[0005] 2. The input current of the traditional full-bridge inverter is discontinuous current and there are low-frequency ripples, which will increase the output ripple of the DC power supply and reduce the reliability of the DC power supply;

[0006] 3. When using a two-level full-bridge inverter, if the switching frequency is low, the current harmonics will be large, which will seriously increase system loss and reduce system reliability;

[0007] 4. When the clamp type multi-level inverter is used, there is a defect that the midpoint voltage oscillates and even tends to be unbalanced

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