Mixed clamping type four-level converter

Abstract

The invention relates to a mixed clamping type level converter, which is characterized by comprising a DC (direct current) bus and three four-level bridge arms, wherein two ends of the DC bus are sequentially connected with the three four-level bridge arms in parallel; each four-level bridge arm is provided with an output end; and three output ends of the three four-level bridge arms output three-phase AC (alternating current) voltages together. The four-level converter comprises the DC bus and the three four-level bridge arms; the DC bus is formed by connecting three capacitors in series; each capacitor bears 1 / 3 of a DC bus voltage; each four-level bridge arm is formed by eight switching elements and one clamping capacitor; and the clamping capacitor also bears 1 / 3 of the DC bus voltage, therefore, the different switching modes are used to realize voltage balance control of all capacitors, thus the number of the clamping elements and the number of the clamping capacitors are reduced and the phenomenon that the switching elements are directly connected in series does not exist. The four-level converter is widely applied to the topological structures of power electronic multi-level converters.

Description

technical field [0001] The invention relates to a topological structure of a power electronic multilevel converter, in particular to a hybrid clamp type four-level converter. Background technique [0002] High-voltage and large-capacity AC motors are widely used in industrial fields such as steel rolling, papermaking, cement, coal, railways, and ships. The frequency conversion and speed regulation of AC motors by multi-level technology can not only achieve the purpose of energy saving, but also improve the process conditions, production efficiency and product quality. [0003] At present, common clamped multilevel topologies mainly include diode clamped, capacitor clamped, active neutral point clamped, and general clamped multilevel topologies. Among them, the diode-clamped structure is widely used in industry, such as the diode-clamped multi-level topology of the five-level bridge arm structure (such as figure 1 shown), but it has the following disadvantages: 1. With the ...

AI Technical Summary

Problems solved by technology

Among them, the diode-clamped structure is widely used in industry, such as the diode-clamped multi-level topology of the five-level bridge arm structure (such as figure 1 shown), but it has the following disadvantages: 1. With the increase of the number of output levels, the number of clamping diodes will increase rapidly according to the second power of the number of levels, the circuit structure is complex, the cost increases, and the reliability is low

2. It is difficult to achieve the voltage balance of the bus capacitors at all levels for five levels and above, and additional hardware circuits are required

These shortcomings limit the development of diode-clamped topologies to higher levels

like figure 2 As shown, the multi-level topology of the capacitor-clamped topology bridge arm structure also has similar disadvantages: a large number of clamping capacitors must be used, and the number is proportional to the square of the number of levels, causing system control Complexity, increased cost, and greatly reduced reliability

But its main disadvantage is that the number of switching devices and capacitors used is very high, and the cost is very high, which is not suitable for industrial promotion and use.

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