Power Conversion Controller LC Resonance Compensation
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Solution Overview
Problem
In power conversion devices, the LC resonant circuits formed by reactors and capacitors cause distortion in output current or voltage waveforms, leading to increased harmonics and deviations from command values, which are difficult to counteract, especially with smaller capacitance capacitors.
Innovation Solution
A power conversion device with a controller that uses a compensator to store deviations in a storage system, allowing for real-time compensation of current and voltage values based on stored values, reducing distortion by adjusting the power converter's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor with small capacitance is used as DC link capacitor, then the power factor is improved, but the LC resonant frequency increases making it more difficult to reduce current deviation
Solution Approach 1:
The controller performs preliminary action by storing deviation values in advance in a storage unit before they affect the output. The deviation between command values and actual values is calculated and stored for each phase, then used for compensation in subsequent cycles, preventing the harmful effects of LC resonance from manifesting in the output waveform.
Solution Approach 2:
The invention implements feedback control by calculating the deviation between command values and actual current/voltage values, storing these deviations, and using them to generate compensated command values. This closed-loop feedback mechanism continuously reduces the deviation caused by LC resonance, maintaining current waveform quality even with small capacitance capacitors.
2Power
If reactors are provided on input or output side of converter circuit, then power conversion is enabled, but LC resonant circuit is formed causing distortion in output current waveform
Solution Approach 1:
The controller measures the actual current waveform, calculates deviation from command values, stores these deviations, and uses them to generate compensated command values. This feedback loop specifically targets and eliminates the distortion caused by LC resonance while maintaining the power conversion function enabled by the reactors.
Solution Approach 2:
The invention converts the harmful LC resonance phenomenon into a measurable and compensatable deviation. By storing the deviation values and using them for compensation, the system transforms the resonance-induced distortion into correctable data, effectively eliminating the harmful effect while preserving the necessary reactor components for power conversion.
3Reliability
If capacitance of DC link capacitor is reduced, then power factor increases, but harmonics in output current increase due to higher LC resonant frequency
Solution Approach 1:
The controller calculates and stores deviation values in advance for each phase before the harmonics can significantly distort the output waveform. This preliminary storage of deviation data enables proactive compensation that prevents harmonic generation rather than merely reacting to it.
Solution Approach 2:
The feedback mechanism continuously monitors the output current, calculates deviation from command values, stores these deviations, and generates compensated command values to eliminate harmonics. This closed-loop control specifically targets the harmonic distortion caused by high LC resonant frequency, maintaining clean waveforms even with reduced capacitance.
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 solution effectively reduces deviations from command values, minimizing distortion and harmonics in the output current waveform, particularly effective with smaller capacitance capacitors where LC resonant frequency is higher.
Implementation Method 1
This reactor and the DC link capacitor together form an LC resonant circuit, the resonance of which may cause distortion in the output current or voltage waveform of the converter circuit
Data Source
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AI summary
Disclosed herein is a power conversion device including a storage (62) and a power conversion controller (50, 60). The storage (62) stores multiple values, each correlated to a disturbance that causes distortion in a current (Iin) to a power converter (13), in association with a phase angle (θin) of a voltage (Vin) of an AC power supply (30). The power conversion controller (50, 60) controls ON/OFF operations by using the values stored in the storage (62) to compensate for a manipulated variable (iT*) of control performed by the power converter (13) in association with the phase angle (θin) of the voltage (Vin) of the AC power supply (30).