Three-Level Inverter Neutral Point Voltage Balance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In three-level power conversion devices, voltage unbalance between capacitors can occur due to varying AC power supply conditions, leading to inefficiencies and harmonic issues in the output.
Innovation Solution
A control method and device that adjusts the pulse width of gate pulse signals and controls the charging and discharging of capacitors to maintain voltage balance, using a fixed pulse pattern and a control unit to manage the charging voltages of the capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed pulse pattern is used to control the three-level converter, then the control simplicity is improved, but voltage unbalance between capacitors occurs
Solution Approach 1:
The patent applies dynamics by transitioning from a static fixed pulse pattern to a dynamic control method where pulse widths are continuously adjusted based on real-time voltage difference detection between capacitors, enabling the system to adapt to varying operating conditions while maintaining voltage balance
Solution Approach 2:
The patent changes the parameter of pulse width in the gate pulse signals based on the detected voltage difference between capacitors. By dynamically modifying this parameter, the control method achieves voltage balance suppression without requiring complete redesign of the control architecture
2Stability of the object's composition
If the pulse width of gate pulse signals is adjusted to suppress voltage unbalance, then voltage balance is improved, but control complexity increases
Solution Approach 1:
The patent applies local quality by selectively adjusting only the pulse widths of specific gate pulse signals associated with capacitors exhibiting voltage imbalance, rather than uniformly modifying all pulse signals. This targeted approach suppresses voltage unbalance while minimizing overall control complexity
Solution Approach 2:
The patent implements feedback by continuously detecting the voltage difference between capacitors and using this information to dynamically adjust gate pulse signal parameters, creating a closed-loop control system that automatically maintains voltage balance without requiring complex manual intervention
3Stability of the object's composition
If voltage unbalance suppression control is implemented, then voltage balance is improved, but harmonic components in AC current increase
Solution Approach 1:
The patent applies partial action by implementing voltage balance suppression only when the voltage difference between capacitors exceeds a predetermined threshold. This selective approach addresses voltage unbalance issues without continuously modifying pulse patterns, thereby reducing the generation of harmonic components in AC current
Data Source
AI summary
A three-level power conversion device includes a three-level converter and a three-level inverter. When the voltage unbalance at a neutral point of the three levels between a + side voltage and a − side voltage is greater than or equal to a threshold value, the three-level power conversion device changes the pulse width of a gate pulse at a specific timing of a gate pulse signal for operating a switching element of the three-level converter. The three-level power conversion device performs control so that the voltage at the neutral point approaches zero.