Transformerless Photovoltaic Power Converter Circuitry
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Solution Overview
Problem
Transformer-less power converter circuitry for photovoltaic devices faces challenges such as safety hazards due to lack of isolation, parasitic capacitance issues, and inefficiency due to reliance on unreliable electrolytic capacitors, which affect the conversion of DC power to AC for grid or load usage.
Innovation Solution
The power converter circuitry employs a boost converter and half-bridge converter topology with a link capacitor and control circuitry to maintain a constant power draw from photovoltaic panels, effectively grounding one terminal to reduce parasitic capacitance and using a smaller, more reliable film capacitor, while controlling switching elements to optimize power conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transformer-less power converter circuitry is used to eliminate isolation components, then cost and complexity are reduced, but safety hazards increase due to lack of isolation between photovoltaic panels and AC electrical grid
Solution Approach 1:
The patent introduces an intermediary isolation mechanism through the power converter circuitry's internal grounding system and parasitic capacitance management. By strategically grounding one terminal of the photovoltaic panel and managing the parasitic capacitance between panels and chassis, the system creates an effective isolation barrier without using traditional transformers, thus reducing complexity while maintaining safety.
2Object-generated harmful factors
If one terminal of photovoltaic panels is grounded to nullify parasitic capacitance, then capacitor currents are reduced, but short-circuiting occurs during operation with transformer-less circuitry
Solution Approach 1:
The patent applies local quality by selectively grounding only one terminal of the photovoltaic panel rather than both terminals. This localized grounding approach nullifies the parasitic capacitance effect and prevents short-circuiting, as the ungrounded terminal maintains the necessary voltage potential for operation while the grounded terminal eliminates capacitive coupling issues.
3Productivity
If large electrolytic capacitors are used to compensate for power pulsations, then efficiency is maintained, but reliability decreases due to capacitor failure
Solution Approach 1:
The patent replaces large, unreliable electrolytic capacitors with smaller, more reliable film capacitors. By redesigning the power converter topology to use film capacitors in a bridge configuration, the system achieves the necessary power pulsation compensation with components that have longer lifetimes and higher reliability, effectively substituting short-living electrolytic capacitors with longer-living film capacitors.
4Object-affected harmful factors
If transformer is used to isolate photovoltaic panels from AC grid, then safety is improved, but cost, size, and weight increase
Solution Approach 1:
The patent extracts and removes the transformer component from the power converter system. By implementing isolation and grounding functions through circuit topology and parasitic capacitance management rather than through a physical transformer, the system eliminates the heavy magnetic component while maintaining safety requirements, thus significantly reducing weight and cost.
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 enhances safety, reduces capacitor size and weight, increases reliability, and achieves high efficiency with minimal ripple and harmonic distortion, improving overall performance and energy harvesting from photovoltaic devices.
Implementation Method 1
Photovoltaic devices provide a direct current (DC) output signal
Implementation Method 2
The difference in output power requirements from photovoltaic devices and input power requirements of an AC electrical grid or AC load can be compensated for with a storage element such as a capacitor
Data Source
AI summary
Power converter circuitry includes a direct current (DC) input comprising a first DC input node and a second DC input node, an alternating current (AC) output comprising a first AC output node coupled to the first DC input node and a second AC output node, a first boost switch coupled between the second DC input node and a boost intermediate node, a second boost switch coupled between the boost intermediate node and a common node, a boost inductor coupled between the boost intermediate node and the first DC input node, a link capacitor coupled between the second DC input node and the common node, a first half-bridge switch coupled between the second DC input node and a half-bridge intermediate node, a second half-bridge switch coupled between the half-bridge intermediate node and the common node, and a half-bridge inductor coupled between the half-bridge intermediate node and the second AC output node.