Neutral-Forming Converter for Islanded Split-Phase Voltage Balance
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Solution Overview
Problem
Residential power systems with a split-phase connection cannot be directly supplied by bidirectional EV chargers or other single-phase sources without a neutral reference, leading to uneven voltage distribution across loads, which is typically addressed by bulky and expensive autotransformers.
Innovation Solution
A neutral forming converter that includes a neutral forming circuit and controller to generate a center point neutral reference voltage, balancing voltage across loads using a semiconductor arrangement and capacitors, even when the system is islanded from the electrical grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an autotransformer is used to convert 2-wire 240V supply to split phase 3-wire output, then a neutral reference is provided for 120V loads, but the device becomes heavy, bulky, expensive, and occupies significant space
Solution Approach 1:
The patent replaces the mechanical autotransformer system with an electronic power conversion system using semiconductor switches (MOSFETs or IGBTs), capacitors, and a microcontroller. The neutral forming converter uses electronic switching and capacitive voltage division to generate the neutral reference, eliminating the need for heavy magnetic components while maintaining the split-phase output functionality.
Solution Approach 2:
The invention changes the operating parameters by using high-frequency electronic switching instead of low-frequency magnetic transformation. The system dynamically adjusts switching frequencies and capacitor charging/discharging cycles to maintain stable neutral reference voltage, replacing the static magnetic field-based voltage transformation with dynamic electronic parameter control.
2Reliability
If an autotransformer is used to provide neutral reference, then voltage balance across loads is achieved, but the device becomes expensive and occupies significant space
Solution Approach 1:
The patent replaces the mechanical autotransformer system with an electronic power conversion system using semiconductor switches (MOSFETs or IGBTs), capacitors, and a microcontroller. The neutral forming converter uses electronic switching and capacitive voltage division to generate the neutral reference, eliminating the need for heavy magnetic components while maintaining the split-phase output functionality.
Solution Approach 2:
The neutral forming converter integrates multiple functions into a single compact unit: it performs AC-AC voltage conversion, generates the neutral reference point, provides isolation, and ensures voltage balance across both legs of the split-phase system. This multi-functional integration replaces what would traditionally require separate components.
3Reliability
If a center-tapped transformer is used to convert 2-wire output to split phase 3-wire output, then neutral reference is provided, but the device becomes heavy and occupies significant space
Solution Approach 1:
The patent replaces the mechanical autotransformer system with an electronic power conversion system using semiconductor switches (MOSFETs or IGBTs), capacitors, and a microcontroller. The neutral forming converter uses electronic switching and capacitive voltage division to generate the neutral reference, eliminating the need for heavy magnetic components while maintaining the split-phase output functionality.
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 converter effectively balances voltage across loads, providing a neutral reference that is more compact, cost-effective, and efficient than traditional autotransformers, ensuring voltage stays within tolerance ranges.
Implementation Method 1
The neutral forming circuit is structured to receive a single-phase AC voltage across a first line conductor and a second line conductor as input and is configured to output the single-phase AC voltage with a center point neutral reference voltage, the center point neutral reference voltage being voltage at the midpoint between voltage of the first line conductor and voltage of the second line conductor
Data Source
AI summary
A neutral forming converter provides a center point neutral reference when a single-phase power source supplies power to a load center in a split-phase power system islanded from the electrical grid. When a load center is islanded and the center-tapped utility transformer cannot provide a neutral reference, a single-phase power source such as a bidirectional electric vehicle charger can supply power to the load center but will require a neutral reference for loads that operate on only half the line-to-line voltage. Without a neutral reference, loads with different impedances can cause the single-phase power system to become unbalanced. The neutral forming converter connects circuitry forming a neutral reference node between the two line voltages of the single-phase power supply. The converter actively balances the voltage between the loads connected across Line 1 and the neutral reference and that between the loads connected across Line 2 and the neutral reference.