Split Phase Inverter Control Without Center-Tapped Transformers
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Solution Overview
Problem
Existing split phase power conversion systems face issues such as harmonic distortion, output ripple, performance limitations with imbalanced loads, and complexity in inverter controls, particularly in eliminating the need for center-tapped transformers.
Innovation Solution
A split phase power conversion system comprising a generator, AC/DC converter, DC bus, and inverter with multiple legs and controllers that provide control signals based on voltage and current differences to achieve balanced and phased AC outputs without center-tapped transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If center-tapped transformers are used to provide split phase output, then two AC voltages 180 degrees out of phase can be provided, but device complexity and performance limitations with imbalanced loads occur
Solution Approach 1:
The patent extracts and eliminates the center-tapped transformer from the system by using a three-leg inverter configuration where the neutral leg directly provides the split phase outputs through PWM control, removing the need for transformer-based phase splitting
Solution Approach 2:
The patent replaces the electromagnetic transformer-based phase splitting mechanism with an electronic PWM control system that generates 180-degree out-of-phase voltages through switching control of the inverter legs
2Device complexity
If center-tapped transformers are eliminated to simplify the system, then device complexity is reduced, but harmonic distortion and output ripple increase
Solution Approach 1:
The patent implements feedback control through controllers that monitor the output voltages and currents from each inverter leg, adjusting the PWM duty cycles to maintain balanced split phase outputs and minimize harmonic distortion under varying load conditions
Solution Approach 2:
The patent uses dynamic PWM control where the duty cycles of the inverter switches are continuously adjusted based on real-time load conditions to maintain voltage balance and reduce output ripple across different operating scenarios
3Device complexity
If simple inverter control is used to reduce control complexity, then ease of operation is improved, but performance limitations with imbalanced loads occur
Solution Approach 1:
The patent applies independent control to each inverter leg with dedicated controllers that monitor and adjust the voltage and current of each leg individually, allowing optimized performance for each phase regardless of load imbalance conditions
Data Source
AI summary
Split phase power conversion apparatuses, methods and systems are disclosed. One exemplary embodiment includes a generator, an AC/DC converter coupled with the generator, a DC bus coupled with the AC/DC converter, and an inverter coupled with the DC bus. The inverter includes first, second, and third legs each including a plurality of switches. A first controller provides a control signal to the first leg based upon a voltage between a first system output and a second system output and a first current provided to the first system output. A second controller provides a second control signal to the second leg based upon a voltage between the second system output and a third system output and a second current provided to the third system output. A third controller controls the third leg to provide an output equal to one half of the DC bus voltage.