Integrated Three-Port Bidirectional DC-DC Converter for Renewable Energy
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Solution Overview
Problem
Conventional renewable energy systems with battery backup require complex and costly power management due to separate converters for battery backup and renewable energy sources, leading to inefficiencies and increased complexity, particularly due to unidirectional power flow and circulating currents in existing DC-DC converters.
Innovation Solution
An integrated three-port bidirectional DC-DC converter using a dual active bridge (DAB) topology with phase-shift angle control and a boost converter with duty cycle control, allowing for decoupled power control of battery backup and renewable energy systems, and enabling efficient power flow management without additional components, thus simplifying the system and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate power converters are used for battery backup system and renewable energy system, then each system can be independently controlled, but the system complexity and cost increase due to requiring multiple converters and complex power management
Solution Approach 1:
The patent combines the battery backup converter and renewable energy converter into a single integrated three-port bidirectional DC-DC converter. This single converter includes a first bidirectional DC-DC converter for battery backup and a second bidirectional DC-DC converter for renewable energy, both sharing common components (transformer, switches, capacitors) while maintaining independent control capabilities through separate control circuits.
Solution Approach 2:
The integrated converter serves multiple functions simultaneously: it acts as a battery charger, battery discharger, renewable energy interface, and grid interface all through one device. The converter can operate in multiple modes (charging, discharging, power generation, grid interaction) without requiring different hardware configurations.
2Device complexity
If conventional DC-DC converters are used, then the structure is simple, but power flow is unidirectional and circulating currents occur between ports
Solution Approach 1:
The patent implements bidirectional power flow capability in both DC-DC converter stages, allowing power to flow in either direction depending on operating conditions. The first converter enables bidirectional flow between battery and DC link, while the second enables bidirectional flow between renewable energy and DC link, eliminating circulating currents through active control.
Solution Approach 2:
The control system monitors power flow directions and magnitudes, and adjusts the switching operations of both DC-DC converters to prevent circulating currents. The control circuits coordinate the operation of the converters based on real-time system conditions, ensuring power flows only when needed and in the correct direction.
3Loss of energy
If additional components are added to achieve bidirectional power flow and eliminate circulating currents, then system efficiency improves, but cost and complexity increase
Solution Approach 1:
The patent merges two separate DC-DC converter systems into one integrated converter that shares common magnetic components (transformer), capacitors, and control infrastructure. This consolidation achieves bidirectional power flow and eliminates circulating currents without proportionally increasing component count, as the integrated design allows shared resources.
Data Source
AI summary
A three-port bidirectional DC-DC converter for grid-interactive renewable energy source system applications. The three-phase topology is suitable for residential power requirements. The control of the backup battery system and the renewable energy source system are naturally decoupled. In addition, the port interface with the renewable energy is current type, which can implement maximum power point tracking (MPPT) and soft switching under wide variations in the renewable energy source terminal voltage.