Pump-Turbine Power Transfer with Shared Converter Energy Storage
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Solution Overview
Problem
The use of hybridization systems in power transfer systems for reversible hydraulic turbines is costly, limiting their commercial development.
Innovation Solution
Integrating an energy storage system with reduced costs by sharing AC/DC converters with a variable frequency converter, allowing efficient energy transfer during both pump starting and operational phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a hybridization system with an energy storage system is used to improve power transfer flexibility and dynamic adaptation, then system adaptability and energy management capability are improved, but system cost increases significantly
Solution Approach 1:
The patent merges the energy storage system with the variable frequency converter by sharing the DC link and AC/DC converters between them. This integration allows the energy storage system to be incorporated into the existing power transfer infrastructure without requiring separate dedicated components, thereby improving power transfer flexibility while avoiding the significant cost increase that would result from a fully independent hybridization system
Solution Approach 2:
The AC/DC converters and DC link are designed to serve dual purposes: functioning as part of the variable frequency converter for motor control during pump starting, and simultaneously serving as the interface for the energy storage system during normal operation. This multi-functionality enables the same hardware to provide both motor control and energy storage capabilities, improving adaptability without proportionally increasing system cost
2Speed
If a variable frequency converter is used to accelerate the pump-turbine from null speed to synchronization speed, then pump-turbine starting capability is improved, but device complexity increases
Solution Approach 1:
The variable frequency converter is designed to perform multiple functions: it provides variable speed control during pump-turbine starting from null speed to synchronization speed, and subsequently serves as the interface for the energy storage system during normal operation. This multi-functionality reduces the need for separate dedicated devices, thereby improving starting capability without proportionally increasing device complexity
Solution Approach 2:
The patent combines the variable frequency converter with the energy storage system interface by sharing the AC/DC converters and DC link. This merging allows the same converter system to handle both the high-complexity task of accelerating the pump-turbine from standstill and the ongoing energy storage functions, thereby achieving improved starting capability while managing overall system complexity through component sharing
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 approach reduces the overall cost of the power transfer system while maintaining efficient energy transfer capabilities, allowing for improved system performance without significant cost increases.
Implementation Method 1
The variable frequency converter comprises first and second AC/DC converters. The AC interfaces of these AC/DC converters are connected respectively to the AC network and to the pump-turbine.
Implementation Method 2
an energy storage system connected to the DC interface of the AC/DC converter. This energy storage system is a reversible DC source which is able to store electrical energy from the AC network and feed energy back into the AC network
Data Source
AI summary
A power transfer system includes a first branch including a controlled switch and a second branch including a variable frequency converter, in parallel between an AC network and a reversible pump-turbine, the variable frequency converter includes: a first AC/DC converter having a first DC interface, and a second AC/DC converter having a second DC interface, the first and second DC interfaces being connected by a DC link, a control circuit having a first mode wherein it simultaneously opens the switch and it transfers electrical power until it reaches the same frequency on two AC interfaces, and having a second mode wherein it closes the switch of the first branch; an energy storage system; and a switching system for selectively connecting the energy storage system to the DC link.