Energy Storage Converter Topology for Full Cell Voltage Utilization
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Solution Overview
Problem
The existing energy storage systems for photovoltaic power generation suffer from inefficiencies due to a narrow direct current input voltage range of energy storage converters and a wide operating voltage range of cell strings, leading to underutilization of cell capacity and increased energy waste.
Innovation Solution
The proposed energy storage system incorporates a DC/DC conversion topology that adapts voltages between cell strings and DC/AC conversion units, allowing for full utilization of cell capacity by coupling multiple cell strings with energy storage converters, and includes a controller to manage charging and discharging based on grid feed-in power and voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct current/alternating current (DC/AC) power conversion topology is used in the energy storage converter, then the system structure is simple, but the direct current input voltage range is narrow and cell capacity is not fully used
Solution Approach 1:
The energy storage converter is divided into two independent modules: a DC/DC conversion module and a DC/AC conversion module. The DC/DC module handles voltage matching between the wide-range cell voltage and the narrow-range DC/AC input voltage, while the DC/AC module performs power conversion to the grid. This segmentation allows each module to be optimized for its specific function, resolving the contradiction between structural simplicity and voltage adaptability.
Solution Approach 2:
The DC/DC conversion module acts as an intermediary between the cell string and the DC/AC conversion module. It buffers the voltage mismatch by converting the wide cell voltage range to the narrow DC/AC input voltage range, enabling the DC/AC module to operate within its optimal voltage range while the cell can utilize its full voltage range.
2Ease of manufacture
If the direct current input voltage range of the energy storage converter is kept narrow for simplicity, then the converter structure is simple, but cell capacity is wasted
Solution Approach 1:
The DC/DC conversion module provides dynamic voltage adjustment capability, allowing the system to adapt to the wide voltage range of the cell string. The converter can dynamically match the cell voltage to the optimal DC/AC input voltage range, ensuring full cell capacity utilization while maintaining the simplicity of the DC/AC module design.
Solution Approach 2:
The system changes the voltage parameter through the DC/DC conversion module, which transforms the wide cell voltage range into the narrow DC/AC input voltage range. This parameter transformation allows the DC/AC converter to maintain its simple narrow-voltage-range design while the overall system achieves full cell capacity utilization.
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 enhances the utilization of cell capacity, reduces energy waste, and improves the stability and efficiency of energy storage and release in photovoltaic energy storage systems, enabling better integration with the power grid.
Implementation Method 1
the first DC/DC conversion unit is configured to perform adaptation between a voltage of the DC/AC conversion unit and a voltage of at least one of the Q cell strings
Data Source
AI summary
The present disclosure discloses an energy storage system. The energy storage system includes M cell strings, N energy storage converters, first ends of the N energy storage converters are coupled to at least one of the M cell strings, and second ends of the N energy storage converters are configured to connect to a power grid. A first end of a first energy storage converter is coupled to Q cell strings in the M cell strings, and the first energy storage converter includes a DC/AC conversion unit and at least one DC/DC conversion unit. A first DC/DC conversion unit is coupled to at least one of the Q cell strings by using the first end of the first energy storage converter, the first DC/DC conversion unit is coupled to the DC/AC conversion unit, and the DC/AC conversion unit is coupled to the power grid by using a second end of the first energy storage converter. The first DC/DC conversion unit is configured to perform adaptation between a voltage of the DC/AC conversion unit and a voltage of a cell string. Therefore, a cell capacity is fully used, and a waste of the cell capacity is reduced.