DC-Coupled PV-BESS Inverter Layout to Reduce Power Clipping
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Solution Overview
Problem
Current solar photovoltaic (PV) systems with battery energy storage systems (BESS) face inefficiencies due to limitations in capturing and storing all generated power, leading to energy loss and system constraints, particularly when inverter ratings are exceeded or insufficient.
Innovation Solution
A hybrid system is introduced with a DC/DC converter connecting a PV system and BESS on the DC side, alongside separate AC-side inverters, allowing for direct power transfer between the two and enabling energy storage and grid feeding through two inverters, optimizing power management and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single inverter is used to connect PV system to grid, then the system structure is simple, but the inverter rating limit causes energy loss when power generation exceeds inverter capacity
Solution Approach 1:
The system divides the single inverter function into two separate inverters: a first inverter connecting the PV system to the grid, and a second inverter connecting the BESS to the grid. This segmentation allows each inverter to operate within its optimal rating, preventing energy loss when PV generation exceeds the first inverter's capacity, as excess power can be routed through the BESS via the second inverter.
Solution Approach 2:
The BESS acts as an intermediary component between the PV system and the grid. When PV generation exceeds the first inverter's rating, the DC/DC converter transfers excess power to the BESS, which then feeds it to the grid through the second inverter. This intermediary mechanism resolves the contradiction by providing an additional power pathway without requiring a single oversized inverter.
2Productivity
If PV system and BESS are connected independently to grid, then each component operates independently, but power transfer between PV and BESS is inefficient
Solution Approach 1:
The DC/DC converter serves as a direct intermediary connection between the PV system and BESS on the DC side. This enables efficient bidirectional power transfer without requiring conversion to AC and back to DC, significantly improving power transfer efficiency while maintaining a relatively simple connection structure through direct DC coupling.
Solution Approach 2:
The DC/DC converter enables continuous and efficient power transfer between the PV system and BESS regardless of the grid connection status. This continuous useful action ensures that power can be transferred directly between components at high efficiency, maintaining productivity while the dual inverter configuration manages the overall system complexity.
3Loss of energy
If excess PV power is not stored in BESS, then the system operation is simple, but energy is lost due to clipping
Solution Approach 1:
The control system continuously monitors PV generation levels and BESS state of charge, providing feedback to the DC/DC converter and inverters. When PV generation exceeds the first inverter's rating, the feedback mechanism automatically activates the DC/DC converter to transfer excess power to the BESS, preventing energy loss without requiring complex manual intervention, thus maintaining ease of operation while reducing energy loss.
Solution Approach 2:
The system proactively transfers excess PV power to the BESS before it would be lost through clipping. The DC/DC converter and control system are configured to automatically capture and store surplus energy in advance, ensuring that energy loss is minimized while the system operates autonomously, maintaining ease of operation.
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 hybrid approach maximizes energy harvesting, reduces clipping, enhances reliability, and allows for time-shifting of grid feeding, providing increased flexibility and efficiency in power generation and storage.
Implementation Method 1
A DC/DC converter is electrically arranged in between the DC source port and the DC connection port
Implementation Method 2
the DC connection port is electrically connected to a DC input port of a second inverter
Data Source
AI summary
A system including at least one renewable energy power plant with a DC source port. The DC source port is electrically connected to a DC input port of a first inverter and at least one battery energy storage system (BESS) with a DC connection port. The DC connection port is electrically connected to a DC input port of a second inverter. A DC/DC converter is electrically arranged in between the DC source port and the DC connection port.