Multimode control of a variable-speed wind energy system coupled to standalone DC microgrid

In this paper, the active front-end (AFE) converter topology for the total harmonic distortion (THD) reduction in a wind energy system (WES) is used. A higher THD results in serious pulsations in the wind turbine (WT) output power and several power losses at the WES. The AFE converter topology improves the capability, efficiency, and reliability in the energy conversion devices; by modifying a conventional back-to-back converter, from using a single voltage source converter (VSC) to use pVSC connected in parallel, the AFE converter is generated. The THD reduction is achieved by applying a different phase shift angle at the carrier of digital sinusoidal pulse width modulation (DSPWM) switching signals of each VSC. To verify the functionality of the proposed methodology, the WES simulation in Matlab-Simulink® (Matlab r2015b, Mathworks, Natick, MA, USA) is analyzed, and the experimental laboratory tests using the concept of rapid control prototyping (RCP) and the real-time simulator Opal-RT Technologies® (Montreal, QC, Canada) is achieved. The obtained results show a type-4 WT with a total output power of 6 MVA, generating a THD reduction up to 5.5 times of the total WES current output by Fourier series expansion.

Multi level inverter technology is being incorporated in various renewable energy based power generation technologies like wind and solar for higher voltage and power applications. Doubly fed induction generator (DFIG) based wind energy conversion systems is the leading technology in wind power market as they tender a variable speed, economically feasible and efficient substitute to the fossil fuel. The present paper comprises of a wind energy conversion system which is simulated using two-level pulse width modulation (PWM) converter as well as three level PWM converter. The performance of DFIG is compared using these technologies under normal and fault conditions. It is observed that multi-level inverters generate purer sinusoidal voltage with reduced total harmonic distortion thus bringing an upgrading in the quality of power produced by DFIG.

Deregulation of the electric power industry is making power quality a topic of increasing importance. Suitable corrective actions for the reduction of total harmonic distortion introduced into the distribution network by industrial loads are more necessary than ever. For the design of these corrective actions simulation has been proved to be a very useful tool. In this paper, the simulation of an active filter for the reduction of the voltage total harmonic distortion created by a steel plant is presented.

In areas of surplus wind availability, wind becomes an imperative source, and wind power generation at all possible conditions of wind velocity is a confronting task. This study emphasizes the evaluation of various control methods for the Rotor Side Converter (RSC) in a standalone Doubly Fed Induction Generator (DFIG) based Wind Energy System (WES). The stator voltage and frequency are regulated by controlling the RSC. Voltage control, Cascaded Voltage-Current Control, and Sequence-based Voltage-Current Control are deployed for RSC, and the performance is compared. The primary merit of this work, along with its comparative analysis, lies in ensuring efficient power transmission within the system across all operational modes, regardless of fluctuations in wind velocity. The comparative analysis is conducted using the Simpower Systems toolbox of MATLAB, and the validation, along with effective power transfer in various modes, is performed in real time using the Software-in-Loop (SIL) OPAL-RT (OP4510) real-time simulator. The findings demonstrate the effective performance of the DFIG-based WECS within a standalone DC microgrid across various operational modes, employing different control strategies.

The present paper puts forth a state-of-the-art control strategy for a Doubly Fed Induction Generator (DFIG)-based wind energy conversion system that supplies a multi-pump irrigation network. In order to surmount the power quality limitations inherent to conventional Direct Torque Control (DTC), a Fuzzy Logic–based Improved Direct Reactive Power Control (F-IDRPC) approach has been developed. The conventional hysteresis comparators and switching table are substituted by a fuzzy inference system, a modification that results in a substantial reduction of torque, flux, and current ripples, while ensuring the maintenance of near-sinusoidal stator currents. Furthermore, a Reliability-Aware Permutation Strategy (RAPS) is integrated into the Smart Energy Management Approach (SEMA) algorithm. By replacing a single high-power pump with a modular five-pump architecture, the proposed method increases system reliability by 226% (MTBF) and equalizes mechanical wear through cyclic duty cycling. The MATLAB/Simulink simulation. The MATLAB/Simulink simulation results demonstrate a 99.15% reduction in Total Harmonic Distortion (THD), an 48.25% reduction in active power ripples, and a 55.23% reduction in local reactive power compensation ripples, with a 90.04% reduction in frequency ripples compared with conventional control. These findings substantiate the efficacy of the proposed strategy in enhancing power quality, system stability, and irrigation reliability under variable wind conditions.

<p>This paper represents a comparative study of three different types of DC-DC<br />converter that can be used for reduction of Total Harmonic Distortion (THD)<br />in stator current, back electromotive force (EMF) and torque of brush less<br />DC motor. In addition, the topologies of these converters are analysed, and<br />the THD of the output characteristics have also been studied. In this work,<br />SEPIC, Zeta and Flyback converters are considered and their outputs are fed<br />to the BLDCM with the help of universal bridge or six step inverter.<br />Moreover the THD of the output voltages are not only measured for three<br />converters but also reduced by tuning the parameters. At first these three<br />converters are modeled in MATLAB/ Simulink based simulation platform<br />and studied the performance individually and further executed with hardware<br />circuitry. Finally the output parameters from both software simulation and<br />real time hardware are compared for these three converters separately and got<br />satisfactory similar results. Again we studied the performance with these<br />converters in terms of efficiency while fed in the commutation drive circuitry<br />of BLDCM by considering minimum THD. From this comparative<br />simulation results, it has been observed that Zeta converter showed maximum<br />efficiency. Therefore, in real time hardware implementation, the<br />commutation drive circuitry of BLDCM is studied with Zeta converter. With<br />this configuration, a comparatively low THD of stator current, back EMF and<br />electromagnetic torque have been achieved in BLDCM with PID controller.</p>

This paper presents an intelligent coordination strategy for enhancing the dynamic performance of doubly-fed induction generator (DFIG)-based wind energy systems through real-time reactive power optimization using Twin Delayed Deep Deterministic Policy Gradient (TD3) reinforcement learning. The proposed Reinforcement Learning Coordinated Transient Controller (RL-CTC) coordinates reactive power sharing between DFIG wind farms and Static Synchronous Compensator (STATCOM) devices, eliminating the need for explicit system models or fixed control parameters. The approach integrates artificial neural network (ANN)-based wind farm placement (with Bus 5 identified as optimal), rotor angle stability-based power system stabilizer (PSS) selection, and voltage stability-based STATCOM sizing. Comprehensive validation on the IEEE 14-bus test system demonstrates a 74.3% reduction in Sum of Maximum Rotor Angle Deviations (SMRAD), 50.0% improvement in voltage regulation, 57.1% reduction in total harmonic distortion, and 32.1% faster settling times compared to conventional methods. The system maintains frequency deviations within ±0.25 Hz and achieves full compliance with international grid codes, including Zero, Low, and High Voltage Ride-Through (ZVRT, LVRT, HVRT) requirements. Economic analysis indicates annual operational savings of $945k, representing a 40.6% improvement over existing control methods. The results confirm the proposed strategy’s effectiveness in improving grid stability, voltage support, and operational efficiency in power systems with high renewable energy penetration.

The reduction in total harmonic distortion of miniature loudspeaker is reported by investigating the force factor (Bl(x)). Micro tensile testing is employed to get Bl(x) vs x curves, which verify finite element simulation. Furthermore, magnetic system of miniature loudspeaker is modified to obtain tailor made Bl(x) vs x curves. Based on it, prototypes are fabricated, which is followed by total harmonic distortion and sound pressure level measurements in an anechoic chamber. Measurements reveal a significant reduction in total harmonic distortion without affecting the sound pressure level.

Novel control approach for enhancing multi-performance of two-stage converter during power transfer from solar photo-voltaic array to AC grid

This paper proposes a novel modulation scheme to reduce the harmonic content of voltages and currents caused by modular multilevel converters with embedded battery cell when employed for application in battery energy storage systems in the grid. The reduction in total harmonic distortion (THD) is obtained by injecting selected harmonics in modulating wave for phase disposition sinusoidal pulse width modulation. The main innovation is in the frequency of these injected harmonics, most of which are kept considerably higher than the carrier frequency. The injection has further been improved using closed-loop control for optimum reduction in the harmonic content of output. The simulations are performed and tested on MATLAB-SIMULINK and demonstrate a satisfactory reduction in both voltage and current THD without any counter effect.

This paper deals with design of permanent magnet synchronous generators (PMSG) for diesel engine generators. The PMSG is required to reduce the total harmonic distortion (THD) reduction of the induced electromotive force (EMF) for the enhancement of power quality. In this paper, a design method is proposed to reduce the THD of the induced EMF for power quality enhancement in the PMSG. First, the selection process for the number of poles and slots is described. Second, the rotor shape design is proposed using an eccentric curve and slit shape. Based on the results of the first process, the optimal rotor shape is selected to achieve the additional THD reduction of the induced EMF. Finally, the performance for the optimal rotor shape is verified through a 2-dimensional finite element analysis (2D FEA) and prototype.

Effective performance and power transfer operation of a current controlled WRIG based WES in a hybrid grid

Multilevel inverter has numerous features for high and medium voltage applications. The size and complexity of multilevel inverter topologies limits its applications. In this paper performance comparison of seven and five levels inverter is presented. For both inverters cascaded H-bridge and reduced switched topologies are used. Performance of the inverters is compared topological and by reduction in total harmonics distortion (THD) using the sinusoidal pulse width modulation (SPWM) control techniques. These techniques are phase disposition (PD), phase opposition disposition (POD), alternate phase opposition disposition (APOD), phase shift (PS) and hybrid PWM. Models are implemented in Matlab Simulink environment and results are compared. In reduced switch topologies increasing the output voltage level by minimizing the number of switching devices produce significant reduction in total harmonic distortion. Thus the conventional topology can be replaced with proposed reduced switched structure with the benefit of reducing losses, size and cost.

This paper presents analysis and control techniques for a doubly-fed induction generator (DFIG) used in wind energy systems under unbalanced grid conditions. The rotor currents and electromagnetic torque of the DFIG under unbalanced conditions are first analyzed. Negative sequence circuit models are investigated. Control strategies implementing negative sequence compensation from either the grid-side converter (GSC) or the rotor-side converter (RSC) are developed. The control objective of the GSC compensation is to provide the negative sequence currents for the grid to keep the stator currents free of negative sequence component. The control objective of the RSC compensation is to eliminate the rotor current harmonics. The main contribution of the paper is i) the analysis of the root cause of the high frequency harmonics in rotor currents and the electromagnetic torque and, ii) the comparison of the two control techniques frequently used in research. Matlab/Simulink tests for a 2MW DFIG are performed to confirm the analysis.

In linear resistor-inductor circuits, minimization of source rms current according to S. Fryze causes increase of total harmonic distortion (THD) and increase of source active powers resulting from higher harmonics of voltage and current. The authors of the present paper have proposed a method of the reduction of THD and rms value of the source current on the basis of the components of instantaneous power of the source. It has been demonstrated that the even component of that power secures a supply of the given active power from the source to the load. The odd component may be excluded from the instantaneous power of the source. Components of instantaneous power are the sums of the products of the even and odd components of source voltage and current. On the basis of these sums the voltage and current components have been determined, the compensation of which enables excluding the odd component of source instantaneous power, and in the same way– reduction of THD and rms value of the source current. The authors of the paper have presented the way of making use of the method in the situation when supply voltage is only odd or even function. It has been found out that it is possible to reduce THD of the source current several times in relation to THD of the source current while minimizing the source rms current according to Fryze, with negligible increase in the effective value of the source current in relation to the minimum value. Decrease of THD also causes significant decrease of active power of the source caused by higher harmonics of voltage and current.