Modular Multilevel Converter Voltage Balancing for Stable UPS Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The stability and applicability of output voltages in modular multilevel converters (MMC) are compromised due to the simple series connection of input and common conversion modules, leading to unstable output voltages and reduced applicability.
Innovation Solution
A modular multilevel converter design that incorporates a common bridge arm and shared bus capacitor, along with DC/DC converters and a balanced circuit module, to adjust and balance voltages across bus capacitors, ensuring stable and proper output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the input conversion module and common conversion module are simply connected in series to form the rectifier loop, then the circuit structure is simplified and device quantity is reduced, but the output voltage stability deteriorates
Solution Approach 1:
The patent introduces a feedback control mechanism where the control module detects the output voltage of each conversion module and adjusts the switching duty cycle accordingly. This feedback loop ensures that the output voltage of each module remains stable despite the simplified series connection structure, resolving the contradiction between circuit simplicity and voltage stability.
Solution Approach 2:
The patent dynamically adjusts the switching duty cycle parameter of the conversion modules based on real-time voltage detection. By changing this control parameter, the system maintains stable output voltage from each module while preserving the simplified series connection architecture, thus resolving the contradiction between structural simplicity and voltage stability.
2Volume of moving object
If the input conversion module and common conversion module are simply connected in series, then the circuit volume is reduced, but the output voltage properness and stability deteriorate
Solution Approach 1:
The control module implements voltage detection and feedback control for each conversion module, adjusting switching parameters in real-time to ensure stable and proper output voltages while maintaining the compact series connection structure that reduces circuit volume.
Solution Approach 2:
The common conversion module serves dual functions as part of both the rectifier loop (with input conversion module) and the inverter loop (with output conversion module). This multi-functionality reduces the overall circuit volume while the control system ensures voltage stability through coordinated control of both loops.
3Loss of energy
If the common conversion module is shared by both rectifier and inverter loops, then power consumption is reduced, but the voltage balance and stability deteriorate
Solution Approach 1:
The common conversion module is designed to function in both the rectifier loop and the inverter loop, reducing the total number of conversion modules and thus lowering power consumption. The control module coordinates the operation of the common module in both loops to maintain voltage stability.
Solution Approach 2:
The control module dynamically adjusts the switching duty cycle parameters of the common conversion module based on the operational requirements of both the rectifier and inverter loops, ensuring proper voltage output and stability while utilizing the module's multi-functional capability to reduce overall power consumption.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This application provides a modular multilevel converter. The MMC includes an input conversion module, an output conversion module, a common conversion module, and a common bridge arm. One end of the input conversion module is connected to Vin, the other end of the input conversion module is connected to the common conversion module through the common bridge arm, and the common conversion module is connected to Vin and Vout. One end of the output conversion module is connected to the common conversion module through the common bridge arm, and the other end of the output conversion module is connected to Vout. The input conversion module and the output conversion module share one bus capacitor. The common conversion module includes at least one multilevel unit connected in series, and one multilevel unit includes one bus capacitor. A balanced circuit module in the MMC includes a plurality of DC/DC converters, where one ends of the plurality of DC/DC converters are connected in parallel, and one DC/DC converter is connected in parallel to one bus capacitor in the MMC. According to this application, properness of an output voltage of the MMC can be improved, and stability of a circuit of the MMC can be improved.