Grid Inverter Filter Inductor Identification for Nonlinear Control
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Solution Overview
Problem
Existing inverter control systems face challenges in accurately determining the inductance profile of filter coils, especially when operating in non-linear ranges, due to deviations from stored profiles caused by aging, environmental changes, and manufacturing tolerances, leading to suboptimal control quality and potential component damage.
Innovation Solution
A method involving precise measurement of coil current and voltage at multiple points during current ripples to determine the actual inductance profile, allowing continuous adaptation of control parameters to match the momentary inductance values, thereby improving control quality and enabling the use of cheaper, smaller inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If filter coils are operated in the non-linear inductor range to allow for a smaller design, then the size and cost of filter coils are reduced, but the control characteristics deteriorate due to non-linear behavior
Solution Approach 1:
The control system dynamically adapts to the non-linear inductance behavior by continuously determining the actual inductance profile during operation and adjusting control parameters accordingly. This allows the system to maintain optimal control characteristics even when operating with smaller, non-linear filter coils.
Solution Approach 2:
The invention changes the control approach from assuming constant linear inductance to actively tracking and adapting to variable non-linear inductance parameters. By determining inductance values at multiple operating points and using this information for control, the system achieves reliable performance with reduced coil size.
2Device complexity
If a fixed inductance profile from laboratory measurements is used for control, then the control process is simplified, but accuracy deteriorates due to deviations from actual inductance under operating conditions
Solution Approach 1:
The system implements feedback by continuously determining the actual inductance profile during operation using measured current and voltage values. This feedback loop allows the control system to adapt to real-world variations in inductance caused by aging, temperature, and manufacturing tolerances, maintaining high accuracy without excessive complexity.
Solution Approach 2:
The inverter performs self-characterization by automatically determining its own inductance profile during normal operation. This eliminates the need for separate laboratory measurements and calibration procedures, allowing the system to adapt to its specific components and operating conditions autonomously.
3Weight of moving object
If inductors are operated in non-linear range to enable miniaturization, then weight and size are reduced, but control precision deteriorates due to non-linear characteristics
Solution Approach 1:
The system performs preliminary characterization by determining the inductance profile at multiple operating points before using it for control. This advance knowledge of the non-linear characteristics allows the control algorithm to compensate for non-linearity, maintaining precision while enabling the use of lighter, smaller inductors operating in the non-linear range.
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
This approach ensures precise control of inverter output, maintaining ideal sinusoidal shapes and preventing component damage by accurately accounting for inductance variations, while allowing the use of less expensive and lighter inductors, thus enhancing miniaturization and cost optimization.
Implementation Method 1
Filter coils are increasingly being operated in the non-linear inductor range in order to allow for a smaller design, or because the core materials cause a non-linear profile of the inductor
Implementation Method 2
The reason for this lies in the presence of a hysteresis effect in the magnetization of the core materials of inductors and/or filter inductors
Data Source
AI summary
A method for operating an inverter includes applying, via a switching unit of the inverter, an AC voltage to a phase line in which a filter inductor is arranged, determining a coil current (iL) of the filter inductor and determining a coil voltage (uL) of the filter inductor, determining a first value (L(Ix)) of the filter inductor for a first value of the coil current (Ix), determining an inductance profile of the filter inductor with respect to the coil current, using the determined first value of the filter inductance and optionally using the at least one determined further value of the filter inductance, and controlling the switching unit of the inverter, via a control unit, to generate an alternating current in the phase line. At least one parameter of the control process is continuously adapted to the momentary coil current according to the determined current-dependent inductance profile.