Inverter Control Module Reducing Parasitic Voltage Harmonics
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Solution Overview
Problem
Aircraft fans generate parasitic voltage harmonics that are not compatible with the electrical network, causing disturbances and requiring restrictive operating points that may hinder optimal performance, and existing solutions to mitigate these harmonics are inefficient.
Innovation Solution
A control method for an inverter system that includes a control module with a cyclic digital signal and synchronization module to manage the switching of controlled switches in the inverter, reducing parasitic harmonics by allowing a continuous range of rotor rotational speeds without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan operates at unrestricted rotational speeds, then the fan performance and operational efficiency are optimized, but parasitic voltage harmonics are generated that disrupt the aircraft electrical network
Solution Approach 1:
The invention changes the timing parameter of the PWM control signal relative to the motor phase currents. By adjusting the phase relationship between the switching signal and the current waveform, the control module modifies the harmonic content of the generated voltage, eliminating parasitic frequencies that disrupt the electrical network while maintaining fan performance.
Solution Approach 2:
The control module continuously monitors the motor phase currents and adjusts the PWM switching timing based on this feedback. This closed-loop control ensures that the inverter generates minimal voltage harmonics while maintaining optimal fan operation across varying speed conditions.
2Object-generated harmful factors
If restrictive operating points are programmed to avoid parasitic harmonics, then voltage harmonics are reduced, but the fan cannot operate at optimal rotational speeds for cooling or ventilation
Solution Approach 1:
Instead of restricting operational speeds, the invention dynamically adjusts the PWM timing parameter across the entire speed range. This allows the fan to operate at any rotational speed while the control module compensates by optimizing the switching phase to minimize harmonics at each operating point.
Solution Approach 2:
The control module dynamically adapts the PWM switching timing in real-time based on the motor's instantaneous operating conditions. This dynamic adjustment enables the system to maintain low harmonic emissions across the full operational spectrum without requiring pre-programmed speed restrictions.
3Ease of operation
If known inverter control methods are used, then the inverter can operate the motor, but parasitic voltage harmonics at specific frequencies are generated that are incompatible with the aircraft electrical system
Solution Approach 1:
The invention modifies the timing parameter of the standard PWM control method by introducing a phase shift relative to the motor phase currents. This parameter adjustment transforms the harmonic spectrum of the generated voltage, eliminating the parasitic frequencies that make known control methods incompatible with aircraft electrical systems.
Data Source
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AI summary
The method involves generating a cyclic digital control signal for controlling switches (30A, 30B, 32A, 32B, 34A, 34B) of an inverter (18), at a predetermined frequency, to regulate electrical supply of a motor (12). The cyclic digital control signal is transmitted to one of the switches. A phase shift of a rotor of the motor with respect to a stator is detected. Temporal synchronization of the cyclic digital control signal over a moment of detection of the phase shift is carried out. Independent claims are also included for the following: (1) a module for controlling an inverter to electrically supply a motor (2) an electrical supply system.