Abstract
This paper presents a novel multi-stage coupled inductors (MCIs) dual-bridge converter using phase-shifted control strategy with arc current feedforward compensated, aiming to meet the demands of low frequency arc ignition, arc transfer process and multi-mode cutting in plasma cutting power supply. Compared to the conventional half-bridge and full-bridge converters, the proposed (MCIs) dual-bridge converter can significantly suppress the output current ripple, which benefits from inductance coupling and double control frequency. Then, the mathematical model of a multi-stage coupled dual-bridge was built, and phase-shifted control method was studied. Combined with the advantages of (MCIs) dual-bridge converter, the proposed control algorithm with arc current feedforward can solve the arc problems of ignition failure via plasma arc current compensation and pneumatic circuit compensation, which caused by serious current fluctuation during sudden change of air pressure and arc transform frequently in cutting process. To verify the feasibility of the proposed multi-stage coupled dual-bridge converter and control scheme, a 20kW experimental prototype for plasma cutting power supply has been built. The experimental results show that the proposed topology and control scheme help to improve the success rate of arc ignition, reduce the probability of cutting arc breaking, increase the stability of the power supply and enhance the cutting effect.
Highlights
Since influenced by pneumatic circuit, magnetic field and high temperature, the plasma cutting arc presents the characteristics of nonlinear and time-varying
The single-loop control cannot response to the nonlinear and time-varying characteristics, which will affect the cutting quality directly
The proposed converter consists of two groups of full bridge circuits, which are connected to the nozzle and electrode via two multi-stage coupled inductors
Summary
With the rapid development of thermal processing technology and the active promotion of market, high precision cutting equipment has achieved intensivedevelopment in the application of various fields. The single-loop control cannot response to the nonlinear and time-varying characteristics, which will affect the cutting quality directly To resolve this problem, [6] proposed that a control scheme switching between closed-loop with current and the open-loop with voltage. [7] proposed a control method of command current with feedforward for dual closed-loop control with outer current loop and inner voltage loop This control scheme can achieve good adaptability in nonlinear load, but the dynamic performance of voltage loop is not obviously improved. Combined with the advantages of (MCIs) dual-bridge converter, the proposed control algorithm with arc current feedforward via plasma arc current compensation and pneumatic circuit compensation, which can improve the dynamic response ability and make the system establish a good adaptability of nonlinear load. A novel control scheme about the topology of MCIs dual-bridge and the control strategy has been studied, and the novel control scheme has been verified effectively under the conditions of low-frequency arc ignition, arc transfer and multi-mode cutting in experiments
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