Neutral-Forming Converter for Balanced Islanded Split-Phase Power
Find Innovative SolutionsGenerate Solutions
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 unsuitable for 120V loads and requires bulky, expensive autotransformers.
Innovation Solution
A neutral forming converter that uses a neutral forming circuit and controller to generate a center point neutral reference voltage, balancing voltage across loads connected to a load center when islanded from the grid, utilizing a semiconductor arrangement and capacitors to filter and balance AC voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an autotransformer is used to form a neutral reference for a single-phase power source, then a neutral reference can be provided to enable 120V loads to operate, but the device becomes heavy, bulky, expensive, and occupies significant space
Solution Approach 1:
The patent replaces the mechanical autotransformer system with an electronic circuit implementation. The neutral reference is generated using electronic components including capacitors, resistors, and operational amplifiers that create a virtual neutral point from the single-phase input, eliminating the need for heavy magnetic transformer components while achieving the same electrical function of providing a balanced neutral reference for 120V loads
Solution Approach 2:
The invention changes the fundamental approach from passive magnetic transformation to active electronic generation. By using electronic circuits to synthesize the neutral reference voltage through parameter control (capacitor values, resistor ratios, op-amp gain settings), the system achieves neutral reference provision without the physical constraints of transformer design, resulting in a compact, lightweight solution
2Reliability
If an autotransformer is used to form a neutral reference, then voltage balance across loads can be achieved, but the device becomes expensive and occupies significant space
Solution Approach 1:
The patent replaces the mechanical autotransformer system with an electronic circuit implementation. The neutral reference is generated using electronic components including capacitors, resistors, and operational amplifiers that create a virtual neutral point from the single-phase input, eliminating the need for heavy magnetic transformer components while achieving the same electrical function of providing a balanced neutral reference for 120V loads
Solution Approach 2:
The electronic neutral reference generator serves multiple functions within a compact footprint: it provides the neutral reference point, balances voltage across unequal loads, and can be integrated into existing single-phase power systems. This multi-functionality is achieved through the versatile electronic circuit topology that can be adapted to various power levels and load configurations without requiring separate components
3Device complexity
If a single-phase power source is used without a neutral reference, then the system is simpler to implement, but voltage divides unevenly across loads causing voltage to go out of normal tolerance range
Solution Approach 1:
The patent introduces an intermediary electronic circuit between the single-phase power source and the loads. This circuit acts as a mediator that creates a virtual neutral point, enabling proper voltage division across parallel loads. The intermediary circuit includes capacitors and operational amplifiers that synthesize the missing neutral reference, allowing 120V loads to receive balanced voltage without requiring a physical three-wire service or bulky autotransformer
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
Provides a compact, cost-effective solution to balance voltage across loads, ensuring compliance with voltage tolerance ranges and reducing the need for bulky autotransformers.
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
Implementation Method 2
utilizing a semiconductor arrangement and capacitors to filter and balance AC voltage
Data Source
Figure 1
Figure 2
Figure 3
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.