Modular Multilevel Converter Reduces Transformer Volume
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Solution Overview
Problem
Conventional transformers are large, heavy, and lack redundancy, with fixed voltage waveforms and high costs due to the need for phase-shifting transformers to manage changing load demands and harmonic loads.
Innovation Solution
A modular multilevel converter (MMC) and power electronic transformer design utilizing multiple IGBT half-bridge circuits in series for low-frequency AC to DC and DC to high-frequency AC conversion, eliminating the need for phase-shifting transformers and allowing adjustable output voltages, with redundant output ends for increased stability and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional transformer is used, then the structure is simple and cost is low, but the volume is large, weight is heavy, and the voltage waveform cannot be controlled or adjusted
Solution Approach 1:
The transformer is divided into multiple independent cascaded modules, each capable of independent operation. This segmentation allows the system to achieve voltage control and adjustment capabilities while maintaining a modular structure that can be scaled and configured based on specific requirements, thereby reducing overall volume and weight compared to a single large transformer.
Solution Approach 2:
The patent introduces controllable switches (IGBTs) and capacitors in each module, enabling dynamic adjustment of voltage waveform, frequency, and quality. This transforms the static transformer into a dynamic system that can adapt to changing load demands and eliminate the need for phase-shifting transformers, reducing volume and cost.
2Adaptability or versatility
If a phase-shifting transformer is added to manage changing load demands and harmonic loads, then the adaptability improves, but the volume and cost increase significantly
Solution Approach 1:
Each cascaded module is designed with universal functionality to handle multiple tasks: voltage regulation, harmonic filtering, and load adaptation. The modular design with controllable switches and capacitors allows each module to independently manage load demands and harmonic loads without requiring additional phase-shifting transformers, thereby achieving adaptability while reducing volume.
Solution Approach 2:
The patent enables dynamic change of electrical parameters (voltage, frequency, waveform) through controlled switching of IGBTs and charging/discharging of capacitors in each module. This allows the system to adapt to varying load demands and harmonic conditions by adjusting parameters in real-time, eliminating the need for bulky phase-shifting transformers.
3Ease of manufacture
If a conventional transformer is used, then the manufacturing cost is low, but the system lacks redundancy and must be shut down for overhauls when problems occur
Solution Approach 1:
The system is divided into multiple independent cascaded modules, each with its own switches and capacitors. This segmentation creates inherent redundancy - if one module fails, the others can continue operating independently. The modular design allows for easier maintenance and replacement of individual modules without shutting down the entire system, improving reliability while maintaining cost-effectiveness.
Solution Approach 2:
The modular design with independent modules provides built-in redundancy that cushions against failures. Each module can operate independently, and the system can tolerate the failure of one or more modules without complete shutdown. This prior cushioning against failures improves system reliability and stability without requiring expensive redundant backup systems.
4Device complexity
If the voltage waveform of the primary side is determined, then the control is simple, but the voltage waveform of the secondary side is also determined and cannot be controlled or regulated
Solution Approach 1:
The patent transforms the static transformer into a dynamic system by introducing controllable IGBT switches and capacitors in each module. This allows independent control of the secondary voltage waveform, frequency, and quality regardless of the primary side waveform. The dynamic switching capability enables regulation and adaptation of output parameters while maintaining relatively simple control architecture through modular design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces volume and cost, enhances stability by allowing voltage adjustments and redundant operation, and eliminates the need for immediate shutdowns due to faults, effectively addressing the limitations of conventional transformers.
Implementation Method 1
a low-frequency AC to DC conversion module, comprising three branch circuits connected in parallel between output ends V1, V2, each branch circuit being formed of multiple IGBT half-bridge circuits connected in series
Implementation Method 2
a DC to high-frequency AC conversion module, connected between the output ends V1, V2, the DC to high-frequency AC conversion module being formed of multiple IGBT half-bridge circuits connected in series
Data Source
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AI summary
The present invention provides a modular multilivel converter and a power electronic transformer, the modular multilevel converter comprising: a low- frequency AC to DC conversion module, comprising three branch circuits connected in parallel between output ends V1, V2, each branch circuit being formed of multiple IGBT half -bridge circuits connected in series, and an electric coupling point N0 of two adjacent IGBT half -bridge circuits in a middle position of the branch circuit being connected to a voltage input end Vin; a DC to high-frequency AC conversion module, connected between the output ends V1 V2, the DC to high-frequency AC conversion module being formed of multiple IGBT half -bridge circuits connected in series, the DC to high-frequency AC conversion module having multiple sets of output ends. The MMC and power electronic transformer of the present invention have a smaller volume, lower cost and better stability in use.