Renewable Energy Converter System Using Medium-Frequency Transformers
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Solution Overview
Problem
Existing renewable energy power station converter systems face inefficiencies, higher costs, and challenges in complying with grid code standards due to multiple conversion stages and the use of heavy, expensive transformers, particularly in offshore applications.
Innovation Solution
A converter system comprising an isolated DC-to-DC converter connected with a non-isolated DC-to-DC converter, where the non-isolated converter controls power flow and the isolated converter operates in open loop, eliminating the need for low-frequency transformers and reducing weight and size by using a medium-frequency transformer for galvanic isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple conversion stages with low frequency transformers are used, then voltage can be stepped up to high voltage, but weight, size and power density are penalized
Solution Approach 1:
The patent changes the operating frequency parameter from low frequency (50/60 Hz) to medium frequency (2-20 kHz), enabling the use of smaller, lighter transformers while achieving the same voltage transformation ratio. This frequency parameter change allows compact transformer design without sacrificing power transmission capability
Solution Approach 2:
The patent extracts and eliminates the need for large low-frequency transformers by replacing them with medium-frequency transformers combined with DC-to-AC converters, thereby removing the weight and size penalty associated with traditional transformer-based voltage stepping
2Power
If multiple conversion stages are used, then voltage conversion from medium voltage to high voltage is achieved, but efficiency decreases and costs increase
Solution Approach 1:
The patent merges the functions of multiple separate conversion stages into a single integrated DC-to-AC converter stage. Instead of using separate DC-to-DC converters and low-frequency transformers, the invention combines these functions into one converter that directly produces high-voltage AC output, thereby reducing the number of stages and improving overall efficiency
Solution Approach 2:
The DC-to-AC converter is designed to perform multiple functions simultaneously: voltage transformation, frequency conversion, and power factor correction, eliminating the need for dedicated separate components for each function and thereby reducing system complexity while maintaining high efficiency
3Power
If low frequency transformers are used for voltage stepping, then voltage transformation is achieved, but the system becomes heavier and more expensive
Solution Approach 1:
The patent changes the frequency parameter from low frequency (50/60 Hz) to medium frequency (2-20 kHz), enabling the use of smaller, lighter transformers while achieving the same voltage transformation ratio. This frequency parameter change allows compact transformer design without sacrificing power transmission capability
Solution Approach 2:
The patent replaces the traditional mechanical transformer-based voltage transformation system with an electronic DC-to-AC conversion system, eliminating the need for large low-frequency transformers and thereby reducing weight while maintaining power transmission capability
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 configuration enhances efficiency, reduces costs, and simplifies the connection of renewable energy sources to a DC distribution grid while maintaining optimal power extraction and compliance with grid standards, particularly beneficial for offshore installations.
Implementation Method 1
an isolated DC-to-DC converter (26) for galvanic isolation
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A converter system (14) for interconnecting renewable energy sources (12) with a DC distribution bus (20) comprises a converter unit (18) which comprises an isolated DC-to-DC converter (26) connectable to the renewable energy source (12), and a non-isolated DC-to-DC converter (28) connectable to the DC distribution bus (20), which is cascade connected with the isolated DC-to-DC converter (26).