Optimized Fractional Order Fuzzy Type-II PI Control for Enhancing the Performance of Grid-Connected Modular Multilevel Converters

Основні поняття

A novel control strategy for grid-connected modular multilevel converters (GC-MMCs) using a Fractional Order Fuzzy Type-II PI (FOFPI) controller optimized by the Whale Optimization Algorithm (WOA) to achieve improved performance and robustness under various operating conditions.

Анотація

This paper proposes a novel control strategy for grid-connected modular multilevel converters (GC-MMCs) using a Fractional Order Fuzzy Type-II PI (FOFPI) controller. The key highlights are:

Design of a Fractional Order Proportional-Integral (FOPI) current controller to control GC-MMCs under unbalanced voltage conditions and model uncertainties.
Development of a Type-II FOFPI current controller to further improve the control performance of GC-MMCs. The FOFPI controller utilizes a type-II Fuzzy Inference System (FIS) to adaptively adjust the proportional and integral gains during the control process, enabling effective control under diverse operating conditions.
Optimization of the controller parameters, including the gains of proportional and integral terms, the order of integral in the FOPI controller, and the parameters of membership functions in the FOFPI controller, using the Whale Optimization Algorithm (WOA).
Simulation study to validate the effectiveness of the proposed control strategy under normal and unbalanced fault conditions, demonstrating the potential of the recommended control strategy for GC-MMCs.

The results show that the FOFPI controller outperforms the FOPI controller, achieving a smoother output line-line voltage with reduced ripple and total harmonic distortion (THD). The FOFPI controller's adaptability to changing gains in response to faults and varying operating conditions enables it to surpass the FOPI controller's performance, ensuring system stability across different operating conditions, even in the presence of uncertainties and faults.

Статистика

The THD of the output voltage using the FOPI controller is 0.33 at 400 volts input and 0.31 at 500 volts input.
The THD of the output voltage using the FOFPI controller is 0.28 at 400 volts input and 0.26 at 500 volts input.

Цитати

"The FOFPI controller's adaptability to changing gains in response to faults and varying operating conditions enables it to surpass the FOPI controller's performance, ensuring system stability across different operating conditions, even in the presence of uncertainties and faults."
"The results show that the FOFPI controller outperforms the FOPI controller, achieving a smoother output line-line voltage with reduced ripple and total harmonic distortion (THD)."

Ключові висновки, отримані з

Whale Optimization Algorithm-based Fractional Order Fuzzy Type-II PI Control for Modular Multilevel Converters

by Mohammad Ali... о arxiv.org 04-30-2024

https://arxiv.org/pdf/2404.18782.pdf

Глибші Запити

How can the proposed FOFPI controller be extended to other converter topologies, such as cascaded H-bridge converters or modular multilevel converters with different configurations?

The proposed Fractional Order Fuzzy Type-II Proportional-Integral (FOFPI) controller can be extended to other converter topologies by adapting its structure and parameters to suit the specific requirements of different configurations. For cascaded H-bridge converters, the FOFPI controller can be modified to accommodate the multiple levels of voltage in each phase. This may involve adjusting the membership functions in the Fuzzy Inference System (FIS) to account for the increased complexity of the converter topology. Additionally, the controller's tuning parameters, such as the gains of the proportional and integral terms, can be optimized using meta-heuristic algorithms like the Whale Optimization Algorithm (WOA) to ensure optimal performance in cascaded configurations.
In the case of modular multilevel converters with different configurations, the FOFPI controller can be customized to handle the unique characteristics of each configuration. For example, if the MMC has a different number of submodules or a varied capacitor arrangement, the FOFPI controller's FIS can be adjusted to reflect these changes. By fine-tuning the center and sigma values of the membership functions in the FIS, the controller can effectively regulate the converter under diverse operating conditions. Furthermore, the WOA can be utilized to optimize the parameters of the FOFPI controller for specific modular multilevel converter configurations, ensuring stability and optimal performance.

How does the performance of the proposed FOFPI controller compare to other advanced control strategies, such as Model Predictive Control (MPC) or Sliding Mode Control (SMC)?

The performance of the proposed FOFPI controller can be compared to other advanced control strategies like Model Predictive Control (MPC) and Sliding Mode Control (SMC) in terms of stability, robustness, and adaptability.
In comparison to MPC, the FOFPI controller offers a simpler implementation while still providing adaptive control capabilities. The FOFPI controller's ability to adjust its gains based on the system's operating conditions through the Type-II Fuzzy Inference System (FIS) makes it well-suited for handling uncertainties and nonlinearities. On the other hand, MPC requires a detailed model of the system and involves solving optimization problems at each control step, which can be computationally intensive.
When compared to SMC, the FOFPI controller offers smoother control action and reduced chattering due to its fuzzy logic-based approach. SMC, while robust to disturbances and uncertainties, can exhibit high-frequency oscillations in the control signal, known as chattering. The FOFPI controller's fractional-order characteristics and adaptive tuning through the FIS make it more suitable for applications where precise and smooth control is required.
Overall, the FOFPI controller strikes a balance between complexity and performance, offering robust and adaptive control for systems like Modular Multilevel Converters (MMCs) while being easier to implement than MPC and exhibiting less chattering than SMC.

What are the potential applications and benefits of the FOFPI controller in renewable energy systems, HVDC transmission, or medium-voltage drives beyond the GC-MMC application discussed in the paper?

The FOFPI controller holds significant potential for various applications in renewable energy systems, HVDC transmission, and medium-voltage drives beyond its current application in Grid-Connected Modular Multilevel Converters (GC-MMCs).
In renewable energy systems, the FOFPI controller can be utilized for controlling the power flow from sources like solar panels or wind turbines. By accurately tracking power references and maintaining harmonic performance, the controller can enhance the efficiency and stability of renewable energy integration into the grid. Its adaptability to changing operating conditions and ability to mitigate uncertainties make it well-suited for dynamic renewable energy environments.
For HVDC transmission systems, the FOFPI controller can play a crucial role in regulating the voltage and current levels, ensuring smooth power transfer over long distances. By optimizing the controller's parameters using meta-heuristic algorithms, the FOFPI controller can enhance the overall performance of HVDC systems, improving efficiency and stability.
In medium-voltage drives, the FOFPI controller can be employed to control the speed and torque of motors in industrial applications. Its fractional-order characteristics allow for more precise and flexible control, leading to improved motor performance and energy efficiency. By adapting the FOFPI controller to different medium-voltage drive configurations, it can cater to a wide range of industrial automation requirements.
Overall, the FOFPI controller's versatility, adaptability, and robustness make it a valuable asset in various energy systems and drive applications, offering benefits such as enhanced performance, stability, and efficiency beyond the scope of GC-MMCs.