Modular Multi-Level Converter for Asynchronous Machine Grid Integration
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Solution Overview
Problem
Existing electricity generating installations with synchronous machines are limited by fixed mechanical turbine frequencies, leading to inefficiencies, high costs, and the need for costly full converters to transmit power effectively.
Innovation Solution
A double-fed asynchronous machine configuration using a modular multi-stage converter in a matrix configuration, allowing for flexible operation and reduced converter rating by short-circuiting the rotor or stator for start-up, enabling efficient energy injection into an AC voltage grid with reduced thermal stresses and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous machines are used for electricity generation, then reliable power transmission to the AC voltage grid is achieved, but the mechanical turbine frequency is fixed and costs increase due to full converters
Solution Approach 1:
The converter system is segmented into a modular multi-stage converter with multiple converter stages, where each stage handles a portion of the power conversion. This allows the system to maintain reliability through distributed conversion while enabling frequency flexibility by independently controlling each stage. The modular structure replaces the single full converter with multiple smaller converter units that can operate semi-independently.
2Power
If full converters are used for power transmission, then complete power capacity is transmitted, but converter costs and rating requirements increase
Solution Approach 1:
The modular multi-stage converter implements partial power conversion by dividing the total power transmission task across multiple stages. Each converter stage handles a portion of the total power, allowing the system to achieve full power transmission capacity without requiring each individual converter to be rated for the complete power. This reduces the rating and cost of individual converter components while maintaining overall power transmission capability.
3Ease of operation
If additional start-up converters are added to enable start-up operation, then start-up capability is achieved, but device complexity and costs increase
Solution Approach 1:
The modular multi-stage converter is designed with multi-functionality to serve both start-up and normal operation modes. The same converter stages that enable start-up operation by short-circuiting the rotor or stator are also used for power transmission during generation. This eliminates the need for separate start-up converters, reducing device complexity while maintaining ease of operation across different operational phases.
4Device complexity
If conventional converters are used without modular design, then simpler structure is achieved, but adaptability to different applications and machines is reduced
Solution Approach 1:
The converter is segmented into identical or similar modular stages that can be replicated and scaled. Each stage has a standardized structure with power semiconductor circuits and energy stores, maintaining relative simplicity while enabling adaptability. The modular architecture allows the system to be scaled by adding or removing stages to match different power requirements and application scenarios without redesigning the entire converter.
Solution Approach 2:
The modular multi-stage converter enables parameter changes in system capacity by adjusting the number of converter stages or the rating of individual stages. This allows the same basic converter design to be adapted to different power levels and application requirements, achieving versatility without sacrificing structural simplicity. The standardized modular units can be configured in different quantities and arrangements to match specific application needs.
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
This solution provides a cost-effective and flexible means to optimize drive systems, reduce thermal stresses, and eliminate the need for additional start-up converters, while allowing for variable-frequency operation and scalable design.
Implementation Method 1
each switching module comprises a power semiconductor circuit and a dedicated energy store
Implementation Method 2
each switching module comprises a power semiconductor circuit and a dedicated energy store
Implementation Method 3
the asynchronous machine is operable in a double-fed configuration... designed to operate in a motor mode of the arrangement for the start-up of the asynchronous machine
Implementation Method 4
set up to operate in a generator mode for the injection of electrical energy into an AC voltage grid
Data Source
AI summary
An arrangement contains an asynchronous machine having a rotor and a stator. The arrangement is set up in a generator mode for feeding electrical energy into an AC voltage network. The arrangement is characterized in that the asynchronous machine can be doubly fed. The asynchronous machine can be connected in a matrix configuration to the AC voltage network by a modular multi-level converter, and the modular multi-level converter is set up in a motor mode of the arrangement for starting up the asynchronous machine while short-circuiting the rotor or the stator.