Inverter Ripple Compensation via Synchronous Frame Filtering
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Solution Overview
Problem
Existing methods for compensating for current ripples in inverters are inefficient and require high effort, leading to distorted AC waveforms and increased transformer temperatures due to signal offset issues in Balance of Plant (BOP) systems, particularly in fuel cell power generation systems.
Innovation Solution
An apparatus and method that senses DC and AC currents, converts them into synchronous coordinate systems, extracts ripple components using filters, and generates compensation values to remove ripples from the DC input to the inverter, preventing waveform distortion and reducing offset components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional ripple compensation methods are used, then ripple components can be reduced, but the system complexity and computational effort increase significantly
Solution Approach 1:
The patent extracts only the essential ripple compensation function by directly sensing DC current and using simple coordinate conversion to synchronous reference frame, then extracting ripple components through basic filtering operations. This selective extraction of the core compensation function eliminates unnecessary system complexity while maintaining effective ripple reduction.
Solution Approach 2:
The patent uses coordinate transformation to create a synchronous reference frame copy of the DC current signal, which simplifies ripple extraction. By transforming the sensed DC current into synchronous coordinates (dq-frame), the ripple components become easily identifiable and removable through simple filtering, avoiding complex analysis of the original three-phase signals.
2Device complexity
If offset components are not compensated, then the system operates simpler, but waveform distortion occurs and transformer temperature increases
Solution Approach 1:
The patent implements feedback by continuously sensing the DC current, transforming it to synchronous coordinates, extracting ripple components, and using this information to generate compensation signals that are fed back to eliminate the ripple. This closed-loop feedback mechanism effectively reduces waveform distortion and prevents transformer overheating without requiring overly complex systems.
Solution Approach 2:
The patent changes the parameter representation of the current signal by transforming from three-phase stationary coordinates to synchronous rotating coordinates. This parameter transformation simplifies the identification and removal of ripple components, as they appear as distinct frequency components in the synchronous frame, enabling effective compensation with minimal system complexity.
3Measurement precision
If detailed ripple analysis is performed on three-phase signals, then accurate compensation can be achieved, but computational effort and processing time increase
Solution Approach 1:
The patent performs preliminary coordinate transformation of the DC current signal into synchronous reference frame before ripple extraction. This preliminary action pre-organizes the signal in a form where ripple components are easily separable, eliminating the need for complex real-time analysis of three-phase signals and significantly reducing processing time while maintaining high detection accuracy.
Solution Approach 2:
The patent replaces complex mechanical signal analysis methods with electrical coordinate transformation and digital filtering operations. By substituting mathematical transformation (Park transformation to synchronous frame) for traditional time-domain analysis, the system achieves accurate ripple detection with minimal computational effort and processing delay.
Data Source
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AI summary
The present invention relates to an apparatus for compensating for a ripple and offset of an inverter and a method thereof, and more particularly, to an apparatus for compensating for a ripple and offset of an inverter which removes a ripple component by compensating for an offset component included in a signal that is input to the inverter from an inverter controller and a method thereof. Examples of a method of compensating for an offset in a signal for controlling an inverter in the present invention include: a method that senses a direct current (DC) that is input to an inverter from an inverter controller and an alternating current (AC) that is output from the inverter and removes a ripple component that is included in the DC based on the sensed currents; a method that removes a ripple component that is included in a reference voltage that is output from an inverter controller and is input to an inverter; and a method that compensates for an offset component of an AC voltage/AC that is used for inverter control and reduces a ripple component corresponding to an output frequency of an inverter.