Bidirectional 3-Level Converter for DC Bus Voltage Balancing
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Solution Overview
Problem
Conventional welding-type power systems face challenges in balancing the DC power bus, particularly when auxiliary loads are imbalanced, leading to potential capacitor failure and power unavailability during extended use.
Innovation Solution
A bi-directional 3-level converter is employed to balance the DC power bus by adjusting the duty cycles of switches connected to a power source, energy storage device, and sensors, allowing power flow between the DC power bus and energy storage device to maintain voltage balance and charge levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple converters are used to convert power between the DC power bus and the energy storage unit, then power conversion capability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple converter functions into a single bi-directional 3-level converter that can simultaneously perform power conversion in both directions (charging and discharging) and provide auxiliary power output. This integration eliminates the need for separate converters, reducing device complexity while maintaining full power conversion capability.
Solution Approach 2:
The bi-directional 3-level converter is designed to perform multiple functions: it can convert power from the DC power bus to charge the energy storage unit, convert power from the energy storage unit to supply the DC power bus, and provide auxiliary power output. This multi-functionality replaces what would traditionally require multiple separate converters.
2Productivity
If auxiliary power is provided without a balancing mechanism, then power availability is improved, but reliability deteriorates due to DC power bus unbalance
Solution Approach 1:
The patent implements a control mechanism that monitors the DC power bus balance and adjusts the converter operation accordingly. The controller detects unbalance conditions and modulates the converter switches to restore balance, providing feedback control that maintains reliability while allowing auxiliary power delivery.
Solution Approach 2:
The converter uses dynamic duty cycle adjustment of its switches to actively balance the DC power bus during auxiliary power delivery. By dynamically changing the switching patterns, the system can respond to unbalance conditions in real-time, maintaining both power availability and reliability.
3Ease of operation
If the DC power bus is allowed to operate without balancing during extended use, then operational simplicity is improved, but reliability deteriorates due to potential capacitor failure
Solution Approach 1:
The converter system performs self-balancing of the DC power bus through its inherent control mechanism. The system automatically detects and corrects unbalance conditions without requiring external intervention or complex external balancing equipment, maintaining reliability while keeping operation simple.
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
The bi-directional 3-level converter effectively balances the DC power bus, preventing capacitor failure and ensuring continuous power supply by dynamically adjusting power flow based on load characteristics and charge levels, even during extended use.
Implementation Method 1
a bi-directional 3-level converter configured to convert power between a power bus and an energy storage device
Data Source
AI summary
A welding-type power system than includes a power supply, a DC power bus, an energy storage device, and a bi-directional converter. The bi-directional converter configured to connect the DC power bus to the energy storage device, and further configured to convert power from the DC power bus to the energy storage device to charge the energy storage device, and to convert power from the energy storage device to the DC power bus in response to a power demand on the DC power bus. The bi-directional converter further configured to balance the DC power bus. A controller is configured to control the duty cycle of the bi-directional converter in order to balance the DC power bus, and control the flow of power between the energy storage device and the DC power bus.