Adaptive Node Balancing in Power Converter Apparatus
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Solution Overview
Problem
Conventional balancer circuits in power converter systems generate undesirable ripple currents even when loads are balanced, due to unbalanced loads causing voltage imbalances in DC bus systems.
Innovation Solution
A switching circuit with windings on a common magnetic core, where taps are coupled to nodes of an inverter circuit, and controlled switches operate at synchronized duty cycles to balance voltages between DC buses and a neutral, allowing flux to return to zero during switch off periods, and optionally using multiple balancer circuits in an interleaved manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional balancer circuit is used to address DC bus imbalance, then voltage balance between DC buses is improved, but ripple currents are generated even when load is balanced
Solution Approach 1:
The balancer circuit operates by periodically switching the coupling between DC buses and neutral through controlled switching intervals. The circuit alternates between coupling and decoupling states, with duty cycles adjusted to balance voltages while minimizing ripple. This periodic operation allows the system to achieve voltage balance without continuous connection that would generate constant ripple currents.
Solution Approach 2:
The invention dynamically adjusts the duty cycle parameter of the switching circuit based on detected voltage imbalances. By changing the duty cycle ratio between different switching intervals, the system adapts to varying load conditions and maintains voltage balance while optimizing ripple current characteristics. The duty cycle is modified according to the magnitude and direction of voltage imbalance.
2Productivity
If switches operate at high duty cycles to balance voltages quickly, then voltage balance response is improved, but flux in the core cannot return to zero
Solution Approach 1:
The switching circuit operates with periodic on-off cycles that provide sufficient off-time for core flux to return to zero. Each switching period includes both active balancing intervals and reset intervals where switches are open, allowing magnetic flux to demagnetize completely. This periodic structure ensures both rapid voltage balance response and proper core flux management.
Solution Approach 2:
The duty cycle is dynamically adjusted to maintain an optimal balance between active balancing time and flux reset time. The system adapts switching parameters in real-time based on voltage imbalance magnitude and core flux state, ensuring that sufficient time is allocated for flux recovery while maintaining effective voltage balancing performance.
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 balances voltages between DC buses and neutral, reducing ripple currents and improving performance by ensuring balanced operation even under unbalanced loads.
Implementation Method 1
A first winding and a second winding on a core and having first taps coupled in common to a first node of an inverter circuit
Implementation Method 2
The first and second duty cycles may each be less than or equal to about 50%, and may be configured to allow a flux in the core to return to substantially zero during periods in which the first and second switches are open
Data Source
AI summary
An apparatus includes a first winding and a second winding on a core and having first taps coupled in common to a first node of an inverter circuit. The apparatus further includes a switching circuit configured to selectively couple a second tap of the first winding to a second node of the inverter circuit and to selectively couple a second tap of the second winding to a third node of the inverter circuit. The switching circuit may be configured to provide a desired balance of first and second voltages at respective ones of the second and third nodes with respect to the first node. Related methods are also described.