Multilevel Converter Modulation for Balanced Conduction Times
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multilevel converter modulation techniques, such as phase shifted carrier PWM and level shifted carrier PWM, either fail to evenly distribute conduction times among power converter modules or do not provide active control over these times, leading to inefficiencies and potential stability issues in output signals.
Innovation Solution
A novel modulation technique that groups power converter modules into multiple groups, with each group having its own phase-shifted carrier signals. This technique allows for both phase-shifted operation to increase the effective switching rate and balancing capability, while avoiding additional distortion in the output signal and its harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phase shifted carrier PWM is used, then the effective output switching rate is increased, but the conduction times of individual power converter modules cannot be actively controlled for balancing
Solution Approach 1:
The patent segments the power converter modules into multiple groups, where each group is controlled by a separate carrier signal. This segmentation enables independent control of conduction times for different groups while maintaining high switching rates through phase shifting between groups.
Solution Approach 2:
The patent dynamically adjusts the conduction times of power converter modules by varying the phase shifts between carrier signals of different groups. This dynamic control allows active balancing of workload distribution while maintaining high effective switching rates.
2Ease of operation
If level shifted carrier PWM is used, then active control of conduction times is provided, but the conduction times are not evenly distributed among modules
Solution Approach 1:
The patent applies different phase shift values to different groups of power converter modules, creating local variations in conduction patterns. This local quality approach ensures that each group can be optimized independently while collectively achieving even distribution across all modules.
Solution Approach 2:
The patent employs feedback mechanisms to monitor and adjust the conduction times of power converter modules. By measuring actual conduction times and adjusting phase shifts accordingly, the system achieves both active control capability and even distribution of workload.
3Ease of operation
If carrier waveform signals swapping is used for balancing, then workload distribution can be adjusted, but additional distortion is introduced in the output signal
Solution Approach 1:
The patent uses periodic phase shifting of carrier signals between different groups of power converter modules. This periodic action enables workload balancing through time-based distribution rather than signal swapping, thereby avoiding the introduction of additional distortion in the output signal.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
There is provided a a method for controlling a multilevel converter for generating a multilevel output signal, the multilevel converter comprising a plurality of energy sources and a plurality of power converter modules, each power converter module comprising at least two switching elements, the method comprising: providing a carrier signal for each of the plurality of power converter modules; assigning, based on at least one first variable parameter, a first number N of the plurality of power converter modules to a first group of power converter modules; assigning, based on the at least one first variable parameter, at least one second number M of the plurality of power converter modules to at least one second group of power converter modules; controlling the switching state of each of the first number N of the plurality of power converter modules assigned to the first group based on the carrier signal provided for each of the first number N of the plurality of power converter modules for generating a first output signal; and controlling the switching state of each of the at least one second number M of the plurality of power converter modules assigned to the at least one second group based on the carrier signal provided for each of the at least one second number M of the plurality of power converter modules for generating a second output signal, wherein the carrier signals provided for each of the first number N of the plurality of power converter modules form a first group of carrier signals and the carrier signals provided for each of the at least one second number M of the plurality of power converter modules form a second group of carrier signals, wherein the first group of carrier signals is phase shifted with respect to the second group of carrier signals for a group phase shift.