Dynamic Grounding Control in PV-Battery Energy Storage
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Solution Overview
Problem
Energy storage systems face a trade-off between system efficiency and safety due to differing grounding methods used by photovoltaic and battery systems, leading to inefficiencies and potential safety hazards.
Innovation Solution
A control system with switches and fault detectors is implemented to dynamically adjust grounding structures based on the state of the photovoltaic and battery systems, using floating and grounding modes to minimize Potential Induced Degradation (PID) and fault currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a photovoltaic system uses a grounding method optimized for system efficiency, then system efficiency is improved, but safety deteriorates
Solution Approach 1:
The patent implements a dynamic grounding structure that can switch between different grounding configurations based on system operating conditions. The controller dynamically adjusts the grounding state of the photovoltaic system and battery system, transitioning between a first grounding structure (when photovoltaic system is connected) and a second grounding structure (when battery system is connected), thereby optimizing both efficiency and safety for different operational modes
Solution Approach 2:
The patent applies different grounding configurations to different parts of the system based on their specific requirements. The photovoltaic system and battery system can have different grounding states simultaneously, with each subsystem optimized for its operational characteristics while maintaining overall system safety through localized grounding adjustments
2Reliability
If a battery system uses a grounding method optimized for safety, then safety is improved, but system efficiency deteriorates
Solution Approach 1:
The controller dynamically switches the grounding configuration of the battery system based on whether it is connected to or disconnected from the photovoltaic system. When the battery system operates independently, the grounding structure is adjusted to optimize efficiency; when connected to the photovoltaic system, the grounding structure is adjusted to prioritize safety, thereby resolving the efficiency-safety trade-off
3Device complexity
If a fixed grounding structure is used in the energy storage system, then device complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent employs switches and controllers that enable dynamic reconfiguration of the grounding structure without adding significant complexity. The system transitions between predefined grounding configurations (first grounding structure and second grounding structure) based on operational mode, achieving high adaptability through simple binary switching rather than complex continuous adjustment
Solution Approach 2:
The grounding structure is designed to serve multiple functions through a single configurable system. The same grounding infrastructure supports both photovoltaic system operation and battery system operation with different grounding requirements, eliminating the need for separate grounding systems and reducing overall device complexity while maintaining versatility
Data Source
AI summary
An energy storage system, including a photovoltaic (PV) system and a battery system and connected with a power grid, may comprise a power conversion system (PCS) connected with the power grid and selectively connected to at least one of the photovoltaic system and the battery system; a first switch selectively connecting the photovoltaic system and a direct current (DC) link of the power conversion system; a second switch selectively connecting the battery system and a DC link of the power conversion system; and a controller for controlling a ground structure of at least one of the photovoltaic system, the battery system, and the power conversion system by controlling the first switch and the second switch based on a state of the photovoltaic system and a state of the battery system.