Five-level double step-down full bridge inverter

Abstract

The invention relates to a five-potential dual-reduction full-bridge inverter, wherein it comprises power circuit (1), two reduction circuits (2, 3) whose inputs are connected to power circuit (1) and outputs are connected to filter capacitor and load circuit (4), work-frequency switch circuit (5) connected to all circuits. The switch tubes (Q51, Q52) are reversely connected into bidirectional baffle switch (S5); the source of filter capacitor (Cf) via added switch tubes (S3, S4, S5) are connected to the anode, cathode and middle point of direct-current bus voltage; the external bus voltage is reduced from +-Ud to +-Ud / 2. The invention has simple structure and low harmonic component, etc.

Description

1. Technical field [0001] The invention relates to a five-level double step-down full-bridge inverter, which belongs to the inverter in an electric energy conversion device. 2. Background technology [0002] In recent years, multilevel converters have attracted more and more attention in high-voltage and high-power applications, and have received a lot of research. Multilevel converters have many outstanding advantages: [0003] 1. Since the output voltage before filtering is a multi-level synthesized ladder wave, the harmonic content is very small, which greatly reduces the size of the required filter; [0004] 2. Compared with the traditional two-level converter, the switching frequency of the device is low, the switching loss is small; the stress of the device is small; [0005] 3. No need for output transformer and dynamic voltage equalizing circuit. [0006] On the other hand, the defects of multilevel converters are also prominent. To sum up, multilevel converters ...

AI Technical Summary

Problems solved by technology

[0007] 1. Multilevel converters generally have the problem of complex circuit structure and excessive use of devices: diode clamp type requires a large number of clamp diodes; flying capacitor type requires a large number of clamp capacitors; cascaded type also requires a large number of switching tubes and capacitors, and as the number of levels increases, many independent DC power supplies are required; the higher the number of levels, the lower the harmonic content of the output voltage of the multilevel converter, but its complexity and overhead also increase exponentially; It is for this reason that current research is still focused on levels 3 to 5;

[0008] 2. Based on the complexity of its circuit, the multilevel converter is also very complicated and difficult to control. People have also conducted a lot of research on this, and the various PWM control strategies proposed are generally very complicated;

[0009] 3. The flying capacitor type and the diode clamp type have the difficult problem of unbalanced capacitor voltage on the DC side; the cascaded type does not have the problem of unbalanced capacitor voltage, but the multi-channel independent DC power supply necessary to generate it is also difficult. difficult;

[0010] 4. The single module topology of the cascaded multilevel converter almost all adopts the H-bridge circuit. There are a large number of switching tubes directly connected in series at both ends of the power supply in the circuit, and the hidden danger of the bridge arm through-circuit is serious.

For MOS devices, measures to improve MOSFET performance often lead to poor body diode performance, and it is difficult to optimize both

Studies have shown that as the switching frequency increases, the reverse recovery problem of the body diode of the switching device tends to be serious, and the proportion of reverse recovery loss in the total loss of the converter increases significantly

Images