A DC conversion system and its control method

Abstract

The invention discloses a direct current conversion system and a control method thereof. The direct current conversion system includes a plurality of three-port direct current transformer sub-modules, and the input negative terminal of each sub-module is connected with the output positive terminal to form a common terminal. The input terminals of each sub-module are connected in series, and the output terminal of the last sub-module can be used as the output terminal of the converter to achieve high transformation ratio step-down; the output terminals of each sub-module are connected in series, and the input terminal of the first sub-module can be used as the output terminal of the converter. The input terminal realizes high transformation ratio boost. Each sub-module includes an inverter circuit, a resonance circuit, a high-frequency transformer and a rectifier circuit. The invention does not need a high-insulation transformer; the voltage equalization on the high-voltage side of the sub-module is easy to achieve; After the capacitor is powered off, the bypass switch malfunctions and the input capacitor voltage diverges during startup.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a self-equalizing high-DC conversion ratio DC converter based on a three-port DC transformer and a control method thereof. Background technique [0002] In high-voltage DC generators, medical power supplies and other low-voltage input and high-voltage output applications, as well as medium-voltage DC distribution networks, submarine observation network power supply systems and other high-voltage input and low-voltage output applications, DC converters with high DC conversion ratios are key equipment for power transmission. one. High DC conversion ratio DC converters in low voltage input and high voltage output applications often adopt a modular input parallel output series structure, and high DC conversion ratio DC converters in high voltage input and low voltage output applications often adopt a modular input series output parallel structure. In the above two structur...

AI Technical Summary

Problems solved by technology

Compared with conventional transformers, the leakage inductance and distributed capacitance of high-insulation transformers are more difficult to control, and the production cost is relatively high

In the closed-loop control of the output voltage, since the output voltage sampling circuit and the control circuit of the sub-module are located on both sides of the high and low voltage, the control system cannot avoid high-voltage feedback, which greatly increases the structure and control complexity of the converter when the number of sub-modules is large Spend

The input series output parallel structure also has the following problems: 1) the control circuit of the sub-module is difficult to obtain

The energy harvesting method of external power supply requires an expensive high-insulation auxiliary power supply, and often requires an additional uninterruptible power supply to improve the reliability of energy harvesting

The reliability of the self-energy harvesting method is low, and there are many problems when starting up and sub-module bypassing

2) The faulty sub-module is difficult to bypass, and the bypass will generate a huge inrush current instantaneously, which is not conducive to the rapid removal of the fault

3) In the self-energy mode, the power failure of the input capacitor of the sub-module will cause the sub-module controller to fail to send status information to the main controller

5) At start-up, due to the nature of the auxiliary power source with constant power, the voltage of the input capacitor of the sub-module diverges

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