Comprehensive Documentation for Three-Phase Modular Multilevel Converter (MMC) Simulation

System Overview

What is a Modular Multilevel Converter (MMC)?

An MMC is a multi-level power converter topology consisting of multiple submodules per phase, allowing for:

• High voltage operation with modular scalability.
• Reduced harmonic content and improved power quality.
• Enhanced redundancy and fault tolerance for increased reliability.

Purpose of the Simulation

The simulation aims to:

• Demonstrate the working principles of a three-phase MMC.
• Validate voltage balancing and capacitor charge control.
• Analyze efficiency, harmonic performance, and dynamic response.

Key Features

Scalable Multi-Level Voltage Generation

The MMC topology enables high-voltage operation with multiple submodules per phase, reducing the need for bulky transformers. ➡️ HIL/PHIL Benefit: Real-time simulation validates submodule balancing and system performance under varying grid conditions.

Low Harmonic Distortion

By using a multi-level voltage waveform, MMCs achieve lower THD compared to traditional two-level and three-level converters. ➡️ HIL/PHIL Benefit: Harmonic analysis and compliance testing ensure the converter meets grid code requirements.

Fault-Tolerant Operation

MMC’s modular structure allows for redundant operation, improving system reliability in case of submodule failures. ➡️ HIL/PHIL Benefit: Real-time fault injection and testing enhance converter robustness under fault scenarios.

Bidirectional Power Flow

Enables energy regeneration and grid support.

Simulation Objectives

This simulation helps evaluate:

• Performance of different modulation strategies (Phase-Shifted PWM, Nearest Level Control).
• Voltage and current balancing across submodules.
• Efficiency analysis under various load and grid conditions.
• Dynamic response to grid disturbances and faults. ➡️ HIL/PHIL Benefit: These evaluations transition smoothly from simulation to real hardware testing, ensuring practical implementation feasibility.

Technical Description

System Configuration

• Input: Three-phase AC or DC supply (depending on AC-DC or DC-AC operation).
• Output: Regulated three-phase AC or DC voltage for HVDC, motor drives, or grid applications.
• Power Stage: Multiple submodules per phase (half-bridge or full-bridge cells with capacitors and switching devices).

Control Methodology

• Modulation Techniques: Nearest Level Control (NLC), Phase-Shifted PWM, or Model Predictive Control.
• Voltage Balancing: Ensuring equal capacitor voltages across all submodules.
• Fault Management: Detection and mitigation of submodule failures. ➡️ HIL/PHIL Benefit: Control logic validation and fine-tuning of parameters using real-time HIL testing before hardware deployment.

Advantages of MMC Simulation

• Higher Efficiency: Reduced switching losses and improved waveform quality.
• Scalability: Modular structure enables expansion for higher voltage applications.
• Improved Power Quality: Lower THD and better waveform synthesis. ➡️ HIL/PHIL Benefit: Each feature can be tested across the full development cycle (RCP → HIL → PHIL) using Impedyme’s platforms.

Applications

• HVDC Transmission: High-voltage AC-DC and DC-AC conversion.
• Flexible AC Transmission Systems (FACTS)‎: Static Synchronous Compensator (STATCOM): MMCs are used in STATCOMs to ‎provide reactive power compensation, improving voltage stability and power ‎quality in transmission networks.‎

Unified Power Flow Controller (UPFC): MMCs enable precise control of power ‎flow in transmission lines, enhancing grid stability and efficiency.‎

•  Electric Traction Systems: Railway Electrification: MMCs are used in electric trains and trams for efficient AC-to-DC and DC-to-AC power conversion, enabling regenerative breaking and reducing energy consumption.

High-Speed Trains: MMCs provide high power density and reliability, making them suitable for high-speed rail systems.

•  Marine and Offshore Applications: Shipboard Power Systems: MMCs are used in electric propulsion systems for ships, providing efficient power conversion and reducing fuel consumption.

Offshore Oil and Gas Platforms: MMCs are employed in power distribution systems on offshore platforms, ensuring reliable and efficient operation in harsh environments.

• Renewable Energy Integration: Grid connection for offshore wind farms and solar power plants.
• Industrial Motor Drives: High-power adjustable-speed drives for heavy industries. ➡️ HIL/PHIL Benefit: Real-time emulation and testing accelerate the development of tailored solutions for each application.