Generator Source Impedance Emulation for Stable Plasma Loads
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Solution Overview
Problem
Interactions between a generator and a nonlinear load, such as a plasma load, can lead to instabilities due to mismatched impedance, particularly in highly sensitive plasma systems where the impedance presented by the plasma changes sharply with applied power.
Innovation Solution
A method and system for controlling a generator connected to a load, involving adjusting the generator output to maintain a measured value related to forward power calculated with respect to a reference impedance, while also adjusting setpoints to control conventional measures of generator output, effectively emulating a desired source impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the generator source impedance is matched to the plasma system impedance, then maximum power transfer is achieved, but plasma stability deteriorates due to sharp impedance changes in highly sensitive plasma systems
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the generator source impedance to offset the plasma system impedance. Instead of using a fixed matched impedance, the system continuously monitors plasma impedance changes and adjusts the generator's source impedance parameters (resistance and reactance) to maintain optimal stability conditions. This is achieved through control circuits that modify the generator operating parameters in real-time, transforming the static impedance matching approach into a dynamic parameter adjustment strategy that prioritizes plasma stability while maintaining acceptable power transfer.
2Stability of the object's composition
If different length cables are used to physically change the generator source impedance, then plasma stability improves, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical/physical approach of using different length cables to change source impedance with an electronic control system. Instead of physically reconfiguring cable lengths, the invention uses control circuits that electronically adjust the generator's output impedance through feedback mechanisms. This substitution of mechanical impedance adjustment with electronic control reduces device complexity while achieving the same plasma stability improvement, as electronic adjustment is more flexible and requires fewer physical components.
Solution Approach 2:
The patent transforms the static cable length approach into a dynamic control system where the generator source impedance can be continuously adjusted in real-time. Rather than requiring multiple fixed cable lengths, the system dynamically modifies the generator's impedance characteristics through control circuits that respond to changing plasma conditions. This dynamic approach reduces device complexity by replacing multiple physical configurations with a single adaptable electronic control mechanism.
3Stability of the object's composition
If the generator source impedance is offset from the plasma system impedance to improve stability, then plasma stability improves, but power transfer efficiency decreases
Solution Approach 1:
The patent applies partial action by adjusting the generator source impedance to the extent necessary for stability without completely sacrificing power transfer efficiency. The control system determines the optimal offset point where sufficient plasma stability is achieved while minimizing power loss. This involves partially matching the impedance rather than complete offsetting, finding a balance point that provides adequate stability improvement while maintaining acceptable power transfer. The adjustment is applied selectively and proportionally to the stability requirements.
Data Source
AI summary
A method for emulating a reactive source impedance for a generator connected to a load. The method comprises adjusting an output of the generator, wherein, in response to adjustment of the output, a first measured value M1 calculated with respect to a weighted sum of voltage v, current i and derivatives of the voltage v and the current i tends to a first setpoint S1 for M1. The method also includes receiving a second setpoint S2 for a second measured value M2 and adjusting S1 to adjust the second measured value M2 of a conventional measure of generator output towards the second setpoint S2 for M2, wherein holding M1 constant emulates a desired source impedance of the generator.