Multilevel Converter Circulating Current Regulation
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Solution Overview
Problem
Existing power converter devices with multi-level topology face challenges in managing and regulating circulating currents, especially at low switching frequencies and with small inductances, leading to inefficiencies and asymmetrical voltage distribution.
Innovation Solution
Incorporating inductances in each phase module and using closed-loop control means to regulate circulating currents, with the option of coupling inductances to reduce the required inductance values and enhance regulation, while maintaining symmetry and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If circulating currents are not regulated in multi-level power converters, then the device complexity is reduced, but circulating currents cause inefficiencies and asymmetrical voltage distribution
Solution Approach 1:
The patent implements closed-loop control means that continuously measure circulating currents and adjust the switching of power semiconductors accordingly. This feedback mechanism detects circulating current magnitudes and modulates the pulse width modulation signals to actively dampen and regulate these currents, resolving the contradiction by using controlled complexity to reduce energy losses.
Solution Approach 2:
The control system dynamically adjusts the switching states of power semiconductors based on real-time circulating current conditions. By making the control adaptive and time-varying rather than static, the system can effectively regulate circulating currents across different operating conditions while maintaining manageable device complexity.
2Loss of energy
If inductances are increased to reduce circulating currents, then circulating current regulation improves, but the device size and cost increase
Solution Approach 1:
The patent replaces passive inductive elements with active electronic control. Instead of relying on large physical inductors to limit circulating currents, the system uses controlled switching of power semiconductors with closed-loop feedback to actively regulate circulating currents, substituting mechanical/electromagnetic components with electronic control mechanisms.
Solution Approach 2:
The control system changes the switching parameters (duty cycles, switching timing) of power semiconductors to regulate circulating currents. By dynamically adjusting these electrical parameters rather than relying on fixed inductance values, the system achieves circulating current reduction without increasing inductor size.
3Reliability
If inductances are increased to improve circulating current regulation, then circulating current control improves, but the device complexity and cost increase
Solution Approach 1:
The closed-loop control means measure voltage asymmetries and circulating currents, then adjust power semiconductor switching to maintain voltage symmetry. This feedback-based approach achieves reliable voltage balance without requiring complex passive inductor configurations.
Solution Approach 2:
The system uses dynamic control of power semiconductor switching states to adapt to changing operating conditions and maintain voltage symmetry. This active dynamic regulation replaces the need for complex fixed inductor arrangements, achieving reliability through controlled adaptability.
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 effectively controls and reduces circulating currents, ensures symmetrical regulation, and allows for the use of smaller inductors, improving the efficiency and cost-effectiveness of the power converter system.
Implementation Method 1
each phase module has at least one inductance, the closed-loop control means being designed to regulate a circulating current, which flows via the phase modules
Data Source
AI summary
A device for converting an electrical current includes at least one phase module with an AC voltage connection and at least one DC voltage connection, a phase module branch disposed between each DC voltage connection and the AC voltage connection and each phase module branch having a series circuit of submodules, each of which has an energy accumulator and at least one power semiconductor and closed-loop control means for regulating the device. The device can regulate circulating currents in a targeted manner by providing each phase module with at least one inductance and configuring the closed-loop control means to regulate a circulating current that flows through the phase modules.