PV Storage Retrofit via DC-Link Control Without MPPT Disruption
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Solution Overview
Problem
Existing photovoltaic systems face inefficiencies and potential failures when integrating electrical storage due to the need for complex AC-to-DC conversions, which disrupt the Maximum Power Point Tracking (MPPT) algorithm and require significant modifications, especially when retrofitting systems without storage.
Innovation Solution
A photovoltaic system incorporating a photovoltaic panel, a DC-to-AC converter, a bidirectional DC-to-DC converter, and an electrical storage unit, controlled by a system that manages current flow using a control signal to charge or discharge the storage based on power balance and state of charge, ensuring seamless integration without altering the MPPT algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrical storage is implemented on the AC side of the photovoltaic system, then the storage can be integrated with existing AC-grid infrastructure, but the system requires an AC-to-DC converter and intricate implementation that increases device complexity
Solution Approach 1:
The patent introduces a DC-link bus as an intermediary connection point between the photovoltaic panels and the storage system. This DC-link serves as a mediator that allows the storage system to connect to the PV system at the DC side without requiring AC-to-DC conversion, thereby reducing device complexity while maintaining adaptability to existing PV systems
Solution Approach 2:
The patent segments the photovoltaic system into distinct functional modules: PV panels, DC-link bus, bidirectional DC-DC converter, and storage system. This segmentation allows the storage component to be independently integrated at the DC side, avoiding the need for complex AC-side integration while maintaining system modularity and adaptability
2Device complexity
If electrical storage is implemented on the DC-side of the photovoltaic system, then the integration is simpler without AC-to-DC conversion, but the storage represents a drain or addition of current that disrupts the MPPT algorithm and reduces productivity
Solution Approach 1:
The patent implements a feedback control mechanism where the bidirectional DC-DC converter continuously monitors the current and voltage at the DC-link and adjusts its operation to maintain the PV panels at their maximum power point. This feedback loop ensures that the storage system's current draw does not disrupt the MPPT algorithm, thereby maintaining system productivity while enabling simple DC-side integration
Solution Approach 2:
The patent employs a dynamic bidirectional DC-DC converter that can adapt its operating mode in real-time. The converter dynamically adjusts its duty cycle and current flow to balance the storage charging/discharging requirements with the PV system's power generation, ensuring that the MPPT algorithm remains effective while allowing flexible storage integration
3Adaptability or versatility
If electrical storage is retrofitted to an existing photovoltaic system, then the storage can be added to existing installations, but significant modifications to the installed photovoltaic systems are required
Solution Approach 1:
The patent designs a universal DC-link bus interface that can be integrated with various types of photovoltaic systems regardless of their specific configuration. The bidirectional DC-DC converter is designed with universal compatibility to work with different PV panel arrangements and storage technologies, enabling easy retrofitting without significant modifications to existing systems while maintaining ease of installation
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 enables efficient and reliable electrical storage within photovoltaic systems, optimizing power usage and minimizing grid power consumption by allowing the storage to act as an apparent extension of the photovoltaic panel, thus maintaining system performance and allowing for retrofitting without modifying existing systems.
Implementation Method 1
a photovoltaic panel that may have an output terminal for outputting current produced by the photovoltaic panel
Implementation Method 2
a bidirectional DC-to-DC converter that may have a first terminal for in-/outputting DC current and a second terminal for in-/outputting DC current
Implementation Method 3
an electrical storage; wherein the first terminal of the bidirectional DC-to-DC converter may be electrical connected with the photovoltaic panel and with the DC-to-AC converter, and the second terminal of the bidirectional DC-to-DC converter may be electrically connected with the electrical storage
Data Source
AI summary
The present invention relates to a system for electrical energy storage. More specifically, the system comprises an energy storage retrofitted to an existing photovoltaic system. The present invention further relates to a method for control such a system for electrical energy storage.