Modular Multilevel Converter Energy Control
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Solution Overview
Problem
Modular multilevel power converters require high capacitance values for energy storage, leading to increased space and mechanical requirements, which limits their applications due to high costs and safety concerns.
Innovation Solution
A method to control and regulate the energy stored in capacitors of a multi-phase modular multilevel power converter based on the operating point and mode of the load, allowing for reduced capacitance values by storing energy values in a table and generating setpoints for each power converter cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high capacitance values are used for energy storage in modular multilevel power converters, then energy storage capacity is improved, but space requirements and mechanical complexity increase
Solution Approach 1:
The patent implements dynamic energy management by controlling the energy stored in capacitor banks based on the operating point and mode of the converter. The control system adjusts capacitor energy dynamically rather than maintaining constant high energy storage, allowing reduced capacitance values while meeting energy storage requirements during operation. This resolves the contradiction by making the energy storage system adaptive to actual operational needs rather than statically oversized.
Solution Approach 2:
The patent changes the parameter of capacitor energy from a fixed high value to a dynamically adjustable value based on operating conditions. By monitoring the operating point and mode of the modular multilevel converter, the control system adjusts the energy stored in capacitors to match actual requirements, thereby reducing the necessary capacitance values and associated space requirements while maintaining adequate energy storage capacity during operation.
2Use of energy by moving object
If high capacitance values are used for energy storage in modular multilevel power converters, then energy storage capacity is improved, but device complexity and safety requirements increase
Solution Approach 1:
The control system dynamically adjusts capacitor energy based on operating point and mode, eliminating the need for oversized static capacitor banks. This dynamic management reduces the number of capacitors required and simplifies the overall device structure while maintaining adequate energy storage capacity for safe and reliable operation under varying conditions.
Solution Approach 2:
By changing the energy parameter from fixed high value to dynamically controlled value, the patent reduces the scale and complexity of the capacitor bank system. The control system monitors operating conditions and adjusts capacitor energy accordingly, reducing mechanical complexity and safety requirements associated with handling large amounts of stored energy.
3Reliability
If constant high energy is stored in capacitors, then energy storage reliability is improved, but adaptability to different operating conditions deteriorates
Solution Approach 1:
The patent implements dynamic energy management that adapts capacitor energy levels to different operating points and modes of the modular multilevel converter. The control system continuously monitors operating conditions and adjusts capacitor energy accordingly, ensuring reliable energy storage for each specific operating condition rather than maintaining constant oversized energy storage. This improves adaptability while maintaining reliability through condition-appropriate energy levels.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for operating a multi-phase modular multi-level power converter (2), having AC voltage terminals (U, V, W) to which a load (14) is connected, wherein a series circuit of a plurality of power converter cells (4), having a capacitor (CSM)) and a half-bridge with two semiconductor switches (SR, SF), and a throttle (Lz) are connected between each AC voltage terminal (U, V, W) and one of the two DC voltage terminals (6, 8) thereof, and wherein the semiconductor switches (SR, SF) of each power converter cell (4), which can be switched off, are controlled by means of a device depending on multiple setpoints. According to the invention at least one setpoint is generated in a manner such that the averages over time of the energies (formula I) stored in the capacitors (CSM) of the power converter cells (4) are specified by the operating point (AP) of the load (14) and/or the operating mode of the modular multi-level power converter (2). As a result, the required minimum capacitance values of the capacitors of all power converter cells (4) of a three-phase modular multi-level power converter (2) are significantly reduced, whereby the installation size of the power converter cells (4) is reduced and therefore also the installation size of the modular multi-level power converter (2).