Aircraft Inverter Frequency Control to Reduce Subharmonic Oscillations
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Solution Overview
Problem
Existing methods for controlling electrical consumers in aircraft onboard networks face challenges in reducing subharmonic and interharmonic oscillations, which can lead to resonance and mechanical oscillations, requiring complex inverter control and increasing switching losses.
Innovation Solution
A method that determines and adjusts the rotational frequency of electric motors to prevent undesirable subharmonic and interharmonic oscillations by changing the frequency to a range where such oscillations do not occur, using pulse-width modulation (PWM) in inverters to produce a supply voltage that operates the motor at a frequency outside the oscillation range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex inverter switching processes are used to reduce subharmonic and interharmonic oscillations, then oscillation reduction is improved, but device complexity and switching losses increase
Solution Approach 1:
The patent changes the rotational frequency parameter of the electric motor to a frequency that does not coincide with the inverter switching frequency and its harmonics. This parameter change avoids the resonance conditions that cause subharmonic and interharmonic oscillations, thereby reducing harmful oscillations without requiring complex inverter control strategies.
Solution Approach 2:
The patent determines the inverter switching frequency and its harmonics in advance, then selects a rotational frequency for the electric motor that avoids coincidence with these frequencies. By performing this frequency selection beforehand, the patent prevents oscillations from occurring in the first place, rather than attempting to suppress them through complex control during operation.
2Object-affected harmful factors
If complex inverter switching processes are used to reduce subharmonic and interharmonic oscillations, then oscillation reduction is improved, but energy losses increase
Solution Approach 1:
The patent changes the rotational frequency parameter of the electric motor to avoid resonance with inverter switching frequencies. This simple parameter adjustment eliminates the need for complex switching processes, thereby reducing both harmful oscillations and the associated switching energy losses simultaneously.
3Object-affected harmful factors
If rotational frequency is adjusted to avoid oscillations, then harmful oscillations are reduced, but control complexity increases
Solution Approach 1:
The patent determines the safe rotational frequency range in advance by analyzing the inverter switching frequency and its harmonics. Once this frequency information is known, the control system simply needs to select a rotational frequency that does not coincide with these predetermined harmful frequencies, which is a straightforward control task rather than a complex one.
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 simplifies the control of electrical consumers by preventing undesirable oscillations without complex inverter operation, reducing wear, noise, and maintenance costs, while maintaining efficient and lightweight inverter architectures.
Implementation Method 1
The electrical consumer may also comprise a control unit by means of which the inverter may be operated, for example by pulse-width modulation (PWM)
Implementation Method 2
The electrical consumer comprises an electric motor and an inverter for producing an alternating voltage for the electric motor
Data Source
AI summary
An electrical consumer of an aircraft comprises an electric motor and an inverter for producing an alternating voltage for the electric motor. A method for controlling the electrical consumer comprises determining a rotational frequency for the electric motor. The method also includes establishing whether the rotational frequency leads to oscillations in the input current of the inverter which are below a predefined threshold, the oscillations being produced by the inverter when producing a supply voltage for the electric motor, and changing the rotational frequency if it has been established that the rotational frequency leads to oscillations below the predefined threshold.