Harmonic Cancellation in Series Power Delivery via Cross-Linked Rectifiers
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Solution Overview
Problem
Load commutated inverters generate undesired electrical harmonics that can cause pulsating torques in motor-driven machinery, leading to potential torsional damage, and existing harmonic suppression techniques are inadequate, especially for subharmonics on the DC link and across different fundamental frequencies.
Innovation Solution
A power delivery system with multiple rectifiers and inverters coupled in series through an inductor, where rectifiers and inverters are connected in a cross-linked configuration to cancel harmonics and subharmonics, effectively reducing their impact on both AC and DC channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a series inductor is disposed on the DC link to filter harmonics, then harmonic current signals are suppressed, but the inductor size is limited and cannot completely remove subharmonics
Solution Approach 1:
The patent combines multiple rectifiers and inverters into a multi-leg configuration where the rectifiers are coupled in series through an inductor. This merging of multiple power conversion units creates a system where harmonic currents from different legs cancel each other out, achieving complete removal of subharmonics that a single inductor cannot accomplish alone.
Solution Approach 2:
The patent converts the harmful harmonic currents generated by each rectifier-inverter unit into a beneficial cancellation effect. By synchronizing multiple units with appropriate phase relationships and coupling them through the inductor, the harmonic currents that would normally cause damage are transformed into canceling waveforms that eliminate each other, turning the harm into a benefit for harmonic suppression.
2Object-affected harmful factors
If multiple rectifiers and inverters are coupled in series through an inductor in a cross-linked configuration, then harmonics and subharmonics are canceled across different frequency operations, but the device complexity increases
Solution Approach 1:
The patent segments the power conversion system into multiple independent rectifier-inverter units (legs), each capable of operating at different frequencies. This segmentation allows each unit to be designed and controlled independently while achieving overall harmonic cancellation when combined in series through the inductor, making the complex system more manageable and scalable.
Solution Approach 2:
The patent creates a universal configuration where the same rectifier-inverter unit can operate at different fundamental frequencies depending on the application requirements. The cross-linked series configuration provides multi-functionality by enabling harmonic cancellation across various frequency operations, making the system adaptable to different power conversion needs without requiring completely different designs.
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 configuration significantly reduces harmonics and subharmonics, mitigating the risk of torsional damage by ensuring cancellation across different frequency operations, enhancing system stability and machinery safety.
Implementation Method 1
The two or more rectifiers and the two or more inverters are coupled in series with each other through an inductor
Data Source
AI summary
Embodiments described herein provide a power delivery system, as well as a method of configuring the power delivery system. The power delivery system includes two or more rectifiers electrically coupled to an AC power source and configured to generate a direct current. The power delivery system also includes two or more inverters configured to receive the direct current and generate an alternating current waveform for powering a load. Moreover, the two or more rectifiers and the two or more inverters are coupled in series with each other through an inductor.