Direct Grid-Connected Battery Converter Without Central PCS
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Solution Overview
Problem
Existing battery energy storage systems face high costs and losses due to the need for a power conversion system for AC/DC conversion between battery energy storage and AC systems, which is inefficient and costly.
Innovation Solution
The implementation of a power conversion method for an AC direct grid-connected type battery energy storage system that eliminates the centralized power conversion system by using full current-controlled battery circuits with upper and lower bridge arms, allowing direct AC/DC conversion through controlled power electronic devices and energy storage capacitors, reducing system costs and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a traditional power conversion system with two-level or three-level voltage source converter is used for AC/DC conversion, then power conversion between battery energy storage and AC system is achieved, but system cost and energy loss increase significantly
Solution Approach 1:
The patent extracts and eliminates the traditional centralized power conversion system (voltage source converter, AC filter, etc.) from the battery energy storage system. By removing these components and directly connecting the battery stack to the AC system through simplified circuitry, the invention achieves power conversion with dramatically reduced loss and complexity while maintaining the essential AC/DC conversion function.
Solution Approach 2:
The patent replaces expensive, complex power conversion equipment with simpler, more economical circuit components. The invention uses basic electronic components such as switches, diodes, and capacitors instead of costly voltage source converters and AC filters, achieving the same power conversion function at much lower cost and with reduced energy loss.
2Ease of manufacture
If a centralized power conversion system is used, then AC/DC power conversion is achieved, but system cost increases due to additional components like AC filter
Solution Approach 1:
The patent removes the AC filter and other auxiliary components from the traditional power conversion system. By extracting these unnecessary elements, the invention reduces system cost and manufacturing complexity while maintaining reliable power conversion through the core battery-direct connection architecture.
Solution Approach 2:
The battery energy storage system performs its own power conversion function directly without relying on external power conversion equipment. The system uses its inherent electrical characteristics and simple control circuitry to achieve AC/DC conversion, making the system both more cost-effective and reliable by eliminating dependency on complex external conversion systems.
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 method enables efficient AC/DC power conversion between the battery energy storage system and the AC system, reducing system costs and losses by eliminating the need for a traditional power conversion system, while ensuring accurate active and reactive power control.
Implementation Method 1
the intermediate energy unit includes an energy storage capacitor, the energy storage capacitor is connected with the battery module in parallel
Data Source
AI summary
A power conversion method for an AC direct grid-connected type battery energy storage system is provided. The AC direct grid-connected type battery energy storage system includes at least one energy storage module, each energy storage module includes A, B and C three phase units composed of upper bridge arms and/or lower bridge arms, each bridge arm includes series-connected full-controlled battery modules and an inductor connected in series. High-voltage terminals of all the upper bridge arms of the energy storage module are connected to form a positive DC bus, and low-voltage terminals of all the lower bridge arms of the energy storage module are connected to form a negative DC bus. A low-voltage terminal of the upper bridge arm and a high-voltage terminal of the lower bridge arm of each phase unit are connected to form an AC terminal of the phase unit to connect with an external AC system.