Power Converter Segmentation for Photovoltaic Efficiency
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Solution Overview
Problem
In grid-connected power generation systems, particularly with photovoltaic cells, power pulsation leads to reduced efficiency due to the need for large electrolytic capacitors for decoupling, which increases size, weight, and cost, and poses voltage stress on the inverter.
Innovation Solution
A power converter system with a high side and low side input point, using a capacitor across these points, a chopper circuit for voltage conversion to high frequency AC, and an isolating transformer to minimize oscillations, along with a controller for pulse width modulation and maximum power point tracking to optimize power extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large electrolytic capacitors are used for power decoupling to minimize output power pulsation effects on input operating point, then power extraction efficiency is improved, but device volume, weight, cost, and lifetime are worsened
Solution Approach 1:
The patent divides the power conversion process into multiple stages: a first power conversion stage that converts input voltage to an intermediate voltage, and a second power conversion stage that converts the intermediate voltage to output voltage. This segmentation allows each stage to operate at optimized voltage levels, reducing the need for large decoupling capacitors while maintaining efficient power extraction.
Solution Approach 2:
The patent introduces an intermediate voltage stage as a mediator between the input and output stages. This intermediate stage acts as a buffer that decouples the power pulsations without requiring large capacitors, thereby improving power extraction efficiency while minimizing the volume and weight of energy storage components.
2Quantity of substance
If high DC voltage is generated to reduce energy storage component size, then capacitance requirements are reduced, but voltage stress on inverter and passive filters increases
Solution Approach 1:
The patent segments the voltage conversion into two stages with an intermediate voltage level. Neither stage operates at excessively high voltages, distributing the voltage stress across multiple components rather than concentrating it in a single inverter stage. This reduces the voltage stress on individual components while maintaining reasonable energy storage requirements.
Solution Approach 2:
The patent changes the voltage parameter through multiple conversion stages, using an intermediate voltage that is neither too high nor too low. This parameter transformation allows the system to achieve reduced capacitance requirements without subjecting any single component to excessive voltage stress.
3Power
If voltage source inverter with high DC bus voltage is employed, then power conversion capability is improved, but high frequency ripples on output current increase requiring larger passive filters
Solution Approach 1:
The patent divides the power conversion into sequential stages, with each stage processing a portion of the power at optimized voltage levels. This segmentation reduces the amplitude of high-frequency ripples at each stage compared to a single high-voltage stage, thereby reducing the size of passive filters required for ripple compensation.
4Productivity
If transformer-based energy buffer is used for power decoupling, then power extraction efficiency is improved, but device weight and volume increase
Solution Approach 1:
The patent extracts the energy storage function from traditional large-capacitor or transformer-based solutions and distributes it across multiple power conversion stages. Each stage uses smaller energy storage components optimized for its specific voltage and power level, achieving effective power decoupling without the weight and volume of a single large transformer or capacitor bank.
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 solution reduces the need for large capacitors, minimizes voltage stress, and enhances efficiency by decoupling power pulsations effectively, allowing for compact and cost-effective micro-inverter design.
Implementation Method 1
a chopper circuit for voltage conversion to high frequency AC
Implementation Method 2
an isolating transformer to minimize oscillations
Implementation Method 3
using a capacitor across these points... Energy storage in the circuit may supply oscillatory power and reduce power pulsation
Data Source
AI summary
Provided are methods, circuits, and systems for obtaining power from a power generator such as a photovoltaic cell or a fuel cell. The methods, circuits, and systems comprise converting substantially DC output power from the power generator into a high frequency AC voltage while rejecting or minimizing oscillations in the output power from the power generator; converting the high frequency AC voltage into a high frequency substantially sinusoidal voltage or current; and converting the high frequency substantially sinusoidal AC voltage or current into (i) a DC voltage or current, and (ii) a low frequency substantially sinusoidal AC voltage or current; wherein the high frequency substantially sinusoidal AC voltage or current is isolated from the DC voltage or current or the low frequency substantially sinusoidal AC voltage or current.