Power Supply Control and Adaptation System for Plasma Discharge Equipment

Abstract

Systems based on plasma electrolytic reactors or nonthermal reactors offer many technological advantages. They are used in a wide variety of applications to improve the anti-corrosion properties of materials, increasing micro-hardness and tribological properties. Plasma electrolytic oxidation (PEO) is an electrochemical and environmentally friendly process that improves the surface quality of metal parts. The surface characteristics of the metal substrate are heavily modified by electrochemical reactions accompanied by plasma micro - discharges. A modern power supply system based on power electronics is proposed in this paper. More precisely, two switching DC power sources and an adaptive two-position static switch (as a power switch) are used, made with modern transistors, with low losses. Furthermore, a proportional-integral (PI) controller with saturation elimination is designed for this system. The saturation occurs when the error has a very large value change (such as a large increase in the case of a discharge that can be equated to a limited short circuit). In this situation, the integrator induces a high overshoot value due to the large increase of the error and can no longer control the value of the output voltage of the direct current sources. An increasing error that accumulates permanently during the transient mode produces the saturation of the component corresponding to the integrator, causing a large overshoot. When the error becomes negative, the overshoot will remain at a positive value for a period of time before returning to normal. The realization of the power supplies requires that they be immune, fully protected, to the short circuits in the reactor, and their operation in the imposed conditions can be ensured. The system allows the supply with positive and / or negative direct current voltage as well as with positive and / or negative, symmetrical and /or asymmetric pulses with limitation of the current slope. The paper presents the principles of operation, simulations, and testing of the main characteristics of the complex power supply system of equipment that use plasma discharging.