AC Motor Control Apparatus Resolving LC Resonance Voltage Fluctuations
Solution Overview
Problem
Existing control apparatuses for AC motors experience voltage fluctuation due to resonance when the frequency of the bus current's amplitude spectrum coincides with the LC resonance frequency, leading to increased system losses, particularly when using the sine-waveform control method.
Innovation Solution
A power converter control apparatus that includes a converter, inverter, converter control unit, and inverter control unit, which calculates and adjusts voltage command values to switch between boost and non-boost states based on the spectrum amplitude of the bus current, effectively suppressing voltage fluctuations by transitioning to the boost state when the amplitude exceeds a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sine-waveform control method is applied when the target operating point comes within the LC resonance region, then voltage fluctuation is suppressed, but system losses increase
Solution Approach 1:
The patent dynamically switches between rectangular-waveform control and sine-waveform control based on real-time detection of the operating point's position relative to the LC resonance region. When the operating point enters the resonance region, the control method transitions to sine-waveform control to suppress voltage fluctuation; when outside, it returns to rectangular-waveform control to minimize losses. This dynamic adaptation resolves the contradiction by applying sine-waveform control only when necessary.
Solution Approach 2:
The patent changes the control parameter (waveform type) based on the operating conditions. By detecting whether the target operating point is within the LC resonance region and switching the waveform control method accordingly, the system optimizes both voltage stability and efficiency, avoiding continuous use of sine-waveform control and its associated energy losses.
2Loss of energy
If rectangular-waveform control method is used, then system losses are reduced, but voltage fluctuation occurs when frequency coincides with LC resonance frequency
Solution Approach 1:
The control system dynamically adjusts the waveform type based on real-time operating conditions. When the operating point is outside the LC resonance region, rectangular-waveform control is used to minimize losses; when it enters the resonance region, the system switches to sine-waveform control to suppress voltage fluctuation. This dynamic switching strategy resolves the contradiction between loss reduction and voltage stability.
Solution Approach 2:
The patent implements a feedback mechanism that continuously monitors the target operating point's position relative to the LC resonance region. Based on this feedback information, the control method is adjusted in real-time, switching between rectangular and sine waveforms as needed. This feedback-driven approach ensures optimal performance by adapting to changing operating 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
This solution effectively suppresses voltage fluctuations without relying on continuous sinusoidal waveform control, thereby reducing system losses when the AC motor operates within the LC resonance region.
Implementation Method 1
the frequency of the bus current's amplitude spectrum coincides with the LC resonance frequency of the converter
Data Source
AI summary
In a control apparatus for an AC motor, a voltage waveform specifying unit of an inverter control unit specifies a voltage waveform for operating the inverter, based on a voltage vector calculated by a voltage command calculation unit. A spectrum amplitude extraction unit acquires values of bus current of the inverter and extracts the spectrum amplitude of the specific frequency that corresponds to the LC resonance frequency of the converter. A boost/non-boost state judgement unit of a converter control unit determines whether the state required by the converter in the next control cycle is the boost state or the non-boost state. When the spectrum amplitude of the specific frequency, correlated with the voltage waveform, is higher than the judgement threshold value and the converter is in the non-boost state, a voltage command value alteration unit changes the voltage command reference value such that the converter transitions to the boost state.