Electromagnetic design of a Thyristor-Controlled Transformer for Dynamic Reactive Power Control

This document outlines the preliminary electromagnetic design of a 32 MVA TCT rated 135/6.6 kV, intended to supply a 24-pulse bridge for harmonic mitigation. The configuration features a primary star-connected winding with external neutral and four secondary windings providing angular phase shifts of ±15°, 0°, and +30°, ensuring magnetic decoupling and compliance with harmonic requirements [3].

The design aimed to meet electromagnetic specifications under technical and operational constraints. A key characteristic is the high short-circuit impedance (78%), enhancing leakage inductance for precise reactive power control. This was achieved through optimized magnetic configuration and winding arrangement to improve flux dispersion and dynamic response. Advanced simulations confirmed inductive behavior and stable flux distribution under nominal conditions, supporting feasibility for high-voltage integration.

An equivalent electrical model was developed in EMTP Software for detailed analysis under various operating conditions, such as no-load voltages, short-circuit currents, phase shifts, and flux density, providing a basis for future dynamic and harmonic studies.

Alongside core and winding design, the study includes thyristor valve architecture, standardized across voltage and power levels to ensure modularity and scalability. This approach simplifies manufacturing and supports future deployments. The proposed TCT solution represents a significant step toward innovative reactive power compensation in high-voltage networks, reducing footprint and implementation time compared to conventional technologies, while supporting European decarbonization targets and enhancing system stability amid growing renewable penetration.