Inverter Frequency Control for Plasma Generator Stability
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Solution Overview
Problem
Plasma generators with capacitive loads face challenges in stable operation due to nonlinear impedance, leading to inefficiencies and equipment breakdowns, requiring large and costly power supply apparatuses to maintain stable ozone and radical gas production.
Innovation Solution
A power supply apparatus that automatically determines the driving frequency of the inverter to match the capacitive load's resonance frequency, using a controller and current-limiting reactor to regulate short circuits and maintain stable output, thereby reducing the need for oversized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power supply apparatus supplies voltage to a plasma generator with capacitive load, then the plasma generator can generate ozone gas and radical gas, but the nonlinear impedance causes unstable operation and difficulty in long-term operation
Solution Approach 1:
The power supply apparatus measures the actual power factor of the capacitive load and automatically adjusts the series reactor parameters to improve the power factor to a predetermined range (0.7-0.9). This closed-loop feedback control stabilizes the load impedance, enabling reliable and stable operation of the plasma generator without requiring complex manual intervention or oversized equipment.
2Power
If the power factor is small due to phase lag between voltage and current, then a very-large-scale power supply apparatus is required to increase active power, but this increases device size and cost
Solution Approach 1:
The invention dynamically changes the parameters of the series reactor (inductance value) based on the measured power factor. By adjusting the reactor parameters to optimize the power factor to a predetermined range, the system maximizes the active power output for a given apparent power capacity, thereby reducing the required size of the power supply apparatus while maintaining high active power delivery.
3Reliability
If a power factor improvement apparatus is mounted on the output unit to improve power factor, then the power factor improves, but the apparatus becomes more complex and requires additional components
Solution Approach 1:
The series reactor is designed to serve multiple functions simultaneously: it limits inrush current during startup, improves the power factor by compensating for capacitive reactance, and provides adjustable impedance matching. By combining these functions into a single adjustable component, the invention avoids the need for separate power factor correction devices while achieving reliable power factor improvement.
4Reliability
If the plasma generator operates with inconstant impedance, then it is difficult to control the output stably, but adding control mechanisms increases device complexity
Solution Approach 1:
The system continuously measures the power factor and automatically adjusts the series reactor parameters in real-time to maintain optimal operating conditions. This feedback control compensates for impedance variations in the plasma generator, ensuring stable output control without requiring complex manual intervention or multiple separate control devices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables stable operation of plasma generators by automatically adjusting the inverter frequency, preventing equipment breakdowns and reducing the size and cost of power supply apparatuses while maintaining high-purity ozone and radical gas production.
Implementation Method 1
a frequency which creates a resonance state between the load and the power supply apparatus
Implementation Method 2
a reactor inserted in series in a power line of the plasma generator
Implementation Method 3
a transformer connected to an alternating-current power-supply
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention provides a power supply apparatus that automatically determines a driving frequency of an inverter in a system including a plasma generator and the power supply apparatus. A power supply apparatus (10) according to the present invention includes a controller (6) that performs the following action and resonance means (7) for creating a resonance state between the power supply apparatus (10) and a plasma generator (5). That is, the controller (6) changes, when a value of electric power input equal to 100% (or a value of electric power input equal to or more than a threshold % and equal to or less than 100%) of a rated power is instructed, an inverter frequency and obtains an inverter output power factor for each of a plurality of inverter frequencies. Then, the controller (6) determines, as a driving frequency of the inverter, one of the plurality of inverter frequencies at which the inverter output power factor is maximized.