MMC Converter Frequency Control via Output Level Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MMC converters connected to power grids face challenges in reducing frequency fluctuations due to disturbances, limiting their ability to maintain grid stability and inject inertial energy effectively.
Innovation Solution
A method that detects real-time power grid frequency deviations, adjusts the number of output levels of the MMC converter using specific equations, and transfers voltage differences to the AC or DC terminal to stabilize frequency and inject inertial energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MMC converter output levels are adjusted in response to power grid frequency changes, then grid frequency stability is improved, but device complexity increases
Solution Approach 1:
The control system continuously monitors power grid frequency and adjusts MMC converter output levels based on detected frequency deviations. The controller calculates frequency deviation (Δf) and uses this feedback to dynamically adjust the number of output levels, creating a closed-loop control system that maintains grid frequency stability
Solution Approach 2:
The MMC converter transitions from a static operating mode to a dynamic adaptive mode where the number of output levels changes in real-time based on grid frequency conditions. The control method enables dynamic adjustment of converter characteristics to match varying grid requirements, improving responsiveness to frequency disturbances
2Speed
If the number of output levels is adjusted to reduce frequency deviation, then response speed to frequency changes is improved, but manufacturing precision requirements increase
Solution Approach 1:
The control method changes the operating parameters of the MMC converter by adjusting the number of output levels based on frequency deviation. The controller calculates the required number of output levels using the formula: Number of output levels = N - k×Δf, where N is the maximum number of levels, k is a control coefficient, and Δf is the frequency deviation. This parameter adjustment enables rapid response to frequency changes
3Reliability
If inertial energy is injected into the grid by adjusting submodule voltage, then grid stability during disturbances is improved, but energy loss increases
Solution Approach 1:
The control method converts the voltage difference that would normally represent energy loss into beneficial inertial energy injection. When submodule voltage differs from rated DC voltage, instead of dissipating this difference, the system transfers it to the AC or DC terminal to provide inertial support to the grid, transforming what would be wasted energy into a stabilizing resource
Data Source
AI summary
A method of controlling output levels of an MMC converter to reduce fluctuation in a power grid frequency, which adjusts an output level of the MMC converter in response to a change in a power grid frequency of a power grid system in the MMC converter connected to a grid system, is proposed. The method includes a detection step of detecting a power grid frequency of a grid connected to the MMC converter in real time, a comparison step of comparing the detected power grid frequency with a preset reference power grid frequency, and an adjustment step of adjusting a number of output levels of the MMC converter to reduce a difference between the detected power grid frequency and the reference power grid frequency when the detected power grid frequency and the reference power grid frequency are different from each other.