Sensorless Current Estimation in VSCF Generator Control
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Solution Overview
Problem
Existing aircraft generators require constant speed inputs and heavy hydro-mechanical devices to maintain constant frequency output, which add unwanted loads to the aircraft and are inefficient over varying operating conditions.
Innovation Solution
A variable speed constant frequency (VSCF) generator system that estimates current through a filter capacitor using a bandpass filter, allowing for sensor-less operation and control of the generator, thereby eliminating the need for heavy mechanical devices and maintaining constant frequency output across varying engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heavy hydro-mechanical devices are used to maintain constant frequency output, then constant frequency output is achieved, but device weight and complexity increase
Solution Approach 1:
The patent replaces heavy hydro-mechanical devices with an electronic control system that uses power electronic converters (rectifier and inverter) to maintain constant frequency output. The controller measures actual frequency and adjusts the inverter switching accordingly, eliminating the need for mechanical constant speed drives while achieving the same frequency stability goal.
2Measurement precision
If sensors are used to measure current for control, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing filter capacitor in the output filter circuit to generate the current measurement signal. The controller measures the voltage across the filter capacitor and uses this information, combined with the known capacitor characteristics, to determine the current without requiring separate current sensors. The system essentially uses its own existing components to provide the measurement function.
3Adaptability or versatility
If variable speed operation is implemented, then adaptability to operating conditions is improved, but frequency output stability deteriorates
Solution Approach 1:
The controller continuously monitors the actual frequency output of the VSCF generator and uses this feedback to adjust the inverter switching parameters. By comparing the measured frequency with the desired constant frequency and dynamically adjusting the control signals, the system maintains stable frequency output despite variations in engine speed and loading conditions.
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
The system effectively regulates output voltage and frequency without sensors, reducing load on the aircraft and improving efficiency across a wide range of operating conditions.
Implementation Method 1
an estimate based on a frequency domain representation of the filter capacitor as an ideal differentiator being passed through a bandpass filter with a center frequency equal to the operating frequency of the VSCF generator system
Data Source
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AI summary
A VSCF generator system (100) includes a generator and electronics configured to control operations of the generator and a housing. The system (100) also includes a power converter connected to the generator that receives AC current from the generator and converts it to DC current, the power converter including: an output filter that includes a filter capacitor; a sensor assembly (220) that measures a voltage across the filter capacitor; and a controller (208) that receives the measured voltage across the filter capacitor and creates an estimate of a current through the filter capacitor based on the filter capacitor. The estimate is based on a frequency domain representation of the filter capacitor as an ideal differentiator being passed through a bandpass filter with a center frequency equal to the operating frequency of the VSCF generator system (100) and the controller (208) controls operation of the generator portion based on the estimate of current through the filter capacitor.