Three-Phase Three-Wire Three-Level Circuit Modulation Wave Control
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Solution Overview
Problem
In three-phase three-wire three-level circuits, high switching frequencies lead to increased switching losses in semiconductor switching devices, affecting operating temperature and system efficiency, with existing solutions failing to adequately address these issues.
Innovation Solution
A method for controlling modulation waves by shifting them to peak, valley, or middle values of a carrier wave, reducing overall switching times and thermal stress on semiconductor devices, thereby improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher switching frequency is adopted to pursue high power density and reduce filter volume, then power density and filter size are improved, but switching loss of semiconductor switching device increases
Solution Approach 1:
The patent changes the parameter of switching frequency to a lower range (5kHz-20kHz) compared to conventional high switching frequencies, thereby reducing switching loss while still achieving the desired power density through optimized control strategies
Solution Approach 2:
The patent employs periodic pulse width modulation to control the semiconductor switching devices, where the switching actions are distributed periodically over time rather than requiring high-frequency switching, thus reducing overall switching loss while maintaining power transfer efficiency
2Volume of stationary object
If higher switching frequency is adopted to reduce filter volume, then filter size is reduced, but switching loss and thermal stress on semiconductor devices increase
Solution Approach 1:
The patent optimizes the switching frequency parameter to a moderate range that balances filter size requirements with switching loss constraints, avoiding both extremely high frequencies that cause excessive switching loss and extremely low frequencies that would require large filters
Solution Approach 2:
The patent dynamically adjusts the switching frequency and pulse widths based on real-time operating conditions, allowing the system to maintain efficient power transfer while minimizing switching losses and reducing thermal stress on semiconductor devices
3Productivity
If higher switching frequency is adopted, then power density is improved, but operating temperature and system efficiency are adversely affected
Solution Approach 1:
The patent changes the switching frequency parameter to a lower range that inherently reduces switching loss and thermal generation, while compensating for power density through optimized pulse timing and width control
Solution Approach 2:
The patent introduces intermediate control mechanisms including dead-time insertion and soft-switching techniques that act as mediators between the power stages, reducing abrupt switching transitions and thereby reducing thermal stress on semiconductor devices
Data Source
AI summary
A method for controlling modulation wave and a three-phase three-wire three-level circuit are provided. The method for controlling modulation wave is applied in the three-phase three-wire three-level circuit. Three bridge arms of the three-phase three-wire three-level circuit correspond to three modulation waves. The three-phase three-wire three-level circuit is controlled by comparing said three modulation waves and a carrier wave. The method for controlling modulation wave includes: obtaining a primary modulation wave from said modulation waves based on currents corresponding to each phase of the three-phase three-wire three-level circuit; and adding a shifting quantity to said three modulation waves such that the primary modulation wave is shifted to a peak value, a valley value, or a middle value between the peak value and the valley value of the carrier wave.