Mohan Anitha Asha Rani

Grid-connected Permanent Magnet Synchronous Generators (PMSGs) exhibit significant sensitivity to unbalanced grid voltages, particularly during voltage sags, which introduce negative sequence components that lead to undesirable oscillations in grid currents, active/reactive power, and DC link voltage at twice the grid frequency. This study aims to enhance the dynamic performance of PMSGs under such adverse conditions by developing a novel reference current generation strategy that mitigates these fluctuations without relying on dual vector control. The approach estimates the stator flux angular frequency in the α–β frame using voltage and current signals, eliminating the need for a PLL or voltage differentiation. The Machine-Side Converter (MSC) manages active power, while the Grid-Side Converter (GSC) maintains constant DC link voltage and Unity Power Factor (UPF). Extensive simulations and real-time validation using OPAL-RT OP4510 demonstrate the scheme’s robustness. For instance, in Case I, oscillations in active power, reactive power, grid current, and DC voltage were reduced from 12.05%, 4.22%, 13.07%, and 0.422% to 0.497%, 1.73%, 7.37%, and 0.0152%, respectively. In Case IV with a severe phase-A fault, oscillations dropped from 86.56% to 12.32% in active power and from 87.23% to 32.23% in grid current. Across all test cases, total harmonic distortion in grid current was consistently brought below 5%, proving the method’s superiority over conventional techniques. Simulations conducted on a 2.5kW PMSG under various unbalanced grid voltage conditions using PSCAD/EMTDC confirm the suggested method's efficacy and its edge over current control techniques.

Ensuring stable and efficient power transfer from an offshore doubly fed induction generator based wind power plant to the onshore grid through a high voltage direct current (HVDC) link presents a complex control challenge due to dynamic grid conditions, system nonlinearities, and the need for precise coordination between converter stations. The offshore converter of the test HVDC system employs a line-commutated converter for efficient bulk power delivery, while a voltage source converter (VSC) at the onshore terminal enables decoupled real and reactive power exchange. Perturbations in onshore grid voltage directly impact the receiving end VSC station, inducing fluctuations in its operating parameters and compromising overall system performance due to grid imperfections. Under imbalanced grid voltage conditions, the conventional vector control approach results in significant power oscillations and harmonic distortions. To address this challenge, this paper proposes a reinforced current control (RCC) strategy, which injects dynamically computed compensating currents into the VSC control loop, effectively suppressing double frequency oscillations and maintaining power quality. The proposed scheme enables independent regulation of real and reactive power, mitigating power oscillations and minimizing the grid current total harmonic distortion (THD) induced by onshore grid voltage deviations. The system's performance is validated through simulations in power systems computer aided design/electromagnetic transients, including direct current and hardware-in-the-loop testing on the OP4510 real-time digital simulator developed by optimal algorithm for real-time. The proposed RCC strategy effectively suppresses active power oscillations to below 5% and maintains grid current THD within 3.5%, even under onshore voltage imbalances. The proposed strategy enhances system stability, fault ride-through capability, and compliance with Institute of Electrical and Electronics Engineers (IEEE) grid interconnection standards.

This paper proposes a novel backup protection to realize reliable numerical protection using the current index and power factor quantities. These quantities, estimated by the synchrophasor measurement units (PMUS), placed nearer to the generator bus, are used to detect and classify the disturbances into stressed conditions and different faults. The proposed backup protection has been implemented on the two-bus power system with a source and load at Bus-1 and Bus-2, respectively, in the MATLAB/Simulink platform. The result analysis of various disturbance scenarios shows that the proposed backup protection (in case the existing protection (over current protection) fails) detects and classifies the disturbances accurately, regardless of the current direction. Thus, the proposed protection is suitable to realize reliable numerical protection.

The offshore wind farm is one of the green energy technologies for power production in remote areas. The effective medium of power transmission from the offshore to the far away shore grid of more than 50 Km is feasible only with the help of the HVDC link for economical purposes. This paper proposes a novel power control technique of an offshore DFIG wind power farm (ODWPF) by injection of mitigating current at the shore VSC station of an HVDC link along with constant voltage/frequency ($\mathrm{V} / \mathrm{f}$) operation at the auxiliary grid. The HVDC link connected offshore wind farm is equipped with a line commutated converter (LCC) at the sending end and a voltage source converter (VSC) at the end terminal. The offshore substation is operated at variable frequency and voltage, which allows the ODWPF to be operated at constant V/f operation. The speed of each turbine varies with respect to other turbines. The DFIG wind turbine can adjust the small variations in the wind speed, and thus the frequency at the offshore auxiliary grid can be controlled according to the HVDC system voltage and frequency. The complete system is simulated in the PSCAD/EMTDC environment.

Voltage sags can lead to equipment malfunction, decreased performance, and operational disruptions. They are typically caused by short circuits, motor start-ups, or sudden load increases, affecting power system reliability. Voltage stability of the proposed system has been improved by implementing modified Static Synchronous Compensator (m-STATCOM) by reducing voltage sags resulting power quality of the proposed system has been enhanced during breakdowns in electrical systems. The Voltage-Source Inverter (VSI) technology of m-STATCOM allows for quick reaction. At the Point of Common Coupling (PCC), it stabilizes voltage to avoid equipment damage from voltage fluctuations. m-STATCOM boosts reactive power regulation, renewable energy stability, and fault ride-through for dependable grid performance. Hybrid Incremental Conductance and Ripple Correlation Control (INC-RCC) for MPPT in PV and wind farms tracks Maximum Power Point Tracking (MPPT) under diverse situations to reduce power losses and fluctuations resulting improve efficiency and reaction speed as compared to Penguin Search (PS) optimization. System stability and performance improve with the Solar Photovoltaic (SPV)-Wind farm and Sinusoidal Pulse Width Modulation (SPWM)-Voltage Source Inverter (VSI)-based m-STATCOM controller. This integrated solution assists in minimizing LLG failure voltage drops.1KW SPV and 2.5 kW wind farm hybrid system connected to 400 V, 50 Hz utility grid integrated to the SPWM-VSI based m-STATCOM controller has been designed using MATLAB/Simulink.

This paper proposes a Power Harmonic Suppression (Damping) (PHS) based reference current generation scheme, which focuses on simultaneous mitigation of harmonic pulsations in electromagnetic torque, stator real and reactive powers, and DC‐link voltage while retaining sinusoidal stator and grid currents and unity power factor at grid side. The crux of this PHS method lies in its ability to eliminate the harmonic powers developed in the DFIG stator and grid at 100Hz, 200Hz, 300Hz, 400Hz, and 600 Hz owing to second, fifth, and seventh harmonic grid voltages. This is achieved as a result of the elimination of natural fluxes developed in the DFIG air gap due to second, fifth, and seventh harmonic distortions in grid voltage. For this, a single concurrent reference current generation technique is developed for RSC and GSC to mitigate the oscillations of electromagnetic torque, stator real and reactive powers, and ripples in DC‐link voltage. Further, the reference rotor currents (positive, negative, fifth, and seventh sequence) are compared with the actual rotor currents using a PI controller to retain sinusoidal stator and grid currents. The proposed scheme's efficacy is validated with PSCAD/EMTDC simulations and using OPAL‐RT OP4510 real‐time simulator, on a 2.3 kVA DFIG.