Solar PV System Maximizing Ripple Voltage on Storage Capacitor
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Solution Overview
Problem
Existing photovoltaic power generation systems face inefficiencies in maximum power point tracking (MPPT) when using multiple solar panels, particularly under shading conditions, and require significant inverter uprating, leading to increased costs and reduced efficiency.
Innovation Solution
A photovoltaic power generation system with a power conditioning unit that connects multiple solar panels in parallel, utilizing an energy storage capacitor and a dc-to-ac converter to perform MPPT by sensing power flow at the dc link, allowing for optimal power harvesting and reduced inverter overhead, without directly measuring panel voltage or current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple photovoltaic panels are connected in parallel to a single power conditioning unit, then device complexity is reduced and cost is lowered, but power harvesting efficiency deteriorates under shading conditions
Solution Approach 1:
An energy storage capacitor is introduced as an intermediary component on the DC link between parallel-connected photovoltaic panels and the power conditioning unit. This capacitor enables independent power contribution from each panel while maintaining a unified control architecture, resolving the contradiction by allowing cost-effective parallel connection without sacrificing power harvesting efficiency under varying shading conditions
2Productivity
If separate MPPT control is implemented for each photovoltaic panel, then power harvesting efficiency is maximized, but device complexity and cost increase significantly
Solution Approach 1:
The power conditioning unit implements a universal MPPT control algorithm that monitors the DC link voltage ripple and infers the power output of parallel-connected photovoltaic panels. This single control mechanism serves multiple panels simultaneously, achieving near-optimal power harvesting efficiency without requiring separate MPPT controllers for each panel, thus reducing device complexity and cost
3Power
If inverter capacity is increased to handle multiple photovoltaic panels, then power handling capability is improved, but cost per watt increases and efficiency decreases
Solution Approach 1:
The energy storage capacitor on the DC link is designed to provide partial energy storage and buffering capability, just sufficient to enable effective MPPT control for parallel-connected photovoltaic panels. This partial action approach allows the use of a smaller, more cost-effective power conditioning unit while maintaining optimal power handling capability and efficiency, avoiding the need for excessive inverter capacity that would increase cost per watt
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 approach achieves nearly optimal power harvesting with minimal performance difference compared to separate MPPT for each panel, reduces ac mains power generation costs per watt, and maintains inverter efficiency under cloudy conditions, with a small uprating of the energy storage capacitor.
Implementation Method 1
a power conditioning unit including an energy storage capacitor to store energy from the photovoltaic panels
Implementation Method 2
at least two photovoltaic panels each having a dc power output
Data Source
AI summary
We describe a photovoltaic (PV) power generation system comprising at least two PV panels and a power conditioning unit. The dc power outputs of the PV panels are connected in parallel to a dc power input of the power conditioning unit. The power conditioning unit comprises a dc-to-dc converter having an input coupled to the dc power input and an output coupled to a dc link of the unit, a dc-to-ac converter having an input coupled to the dc link and an ac mains power supply output, and an energy storage capacitor coupled to the dc link. The power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into the dc power input, and the level of power flowing into said dc power input is sensed at the dc link. In preferred implementations the energy storage capacitor is a non-electrolytic capacitor.