Adaptive control universality of STATCOM for efficient wind energy conversion systems

Comparative analysis of controllers for stability enhancement for wind energy system with STATCOM in the grid connected environment

This article proposes a model reference adaptive control (MRAC) of static synchronous compensator (STATCOM) for enhancing the integration of driven wind turbine‐based self‐excited induction generator (SEIG) into electrical grids. An MRAC‐based Massachusetts Institute of Technology adaptive mechanism is utilised to control the reactive power flow of grid‐integrated SEIG. The voltage‐source inverter sinusoidal pulse width modulation of the STATCOM is used to overcome the abnormal operating conditions in the wind energy conversion system. This accordingly increases the low‐voltage ride through (LVRT) capability. The abnormal operating conditions are faults occurring at the point of common coupling between the generator and the grid. The proposed MRAC is compared to proportional‐integral (PI) controllers tuned by genetic algorithm (GA). To evaluate the proposed control of STATCOM for enhancing grid‐integrated SEIG, a part of the Egyptian 220 kV network integrated with Zafarana Wind Energy System is used. The results provide evidence of an efficient and robust proposed adaptive control performance rather than static PI controller whose parameters tuned by GA in the voltage, currents, and wind generator speed responses. Moreover, the proposed controller increases the capability of continuous operation of the wind turbines under different abnormal operating conditions and also increases the LVRT capability.

Introduction. Nowadays, the most widely used wind energy conversion system in wind farms is based on a doubly fed induction generator (DFIG); it has a large speed range and can function in multiple modes. Problem. Harmonic distortion in wind energy conversion system can degrade output waveform quality, reduce power conversion efficiency. Goal. This study investigates the dynamic performance of a wind energy conversion system comprising a grid-connected load, a 13-level hybrid multilevel converter and a doubly fed induction generator (DFIG), using a PI controller. The study aims to evaluate the dynamic performance and power quality of wind energy conversion systems, and to develop a novel hybrid metaheuristic method combining differential evolution (DE) and grey wolf optimization (GWO)-based selective harmonic elimination pulse-width modulation (SHEPWM) control strategies. This method reduces total harmonic distortion (THD) and ensures compliance with IEEE 519 standards, while increasing the power transferred to the grid. Methodology. The system, which includes a grid-connected load, a 13-level converter, and a DFIG, is modeled and simulated in MATLAB/Simulink under steady-state wind conditions. Vector control via stator flow orientation was used to modify the energy quality provided by the DFIG, making the system comparable to the DC machine. Our approach was to use a PI controller in order to directly control the active and reactive DFIG power through multi-level converter then a hybrid metaheuristic algorithm combining DE and GWO is implemented to solve the SHEPWM nonlinear transcendental equations. The proposed algorithm is evaluated based on its ability to suppress lower-order harmonics and improve THD performance, these converters increase the power transmitted to the power grid by reducing harmonic content of the output voltages. Results. By using the DE-GWO hybrid method and a PI controller, lower-order harmonics were effectively removed and THD was reduced to meet IEEE 519 standards. Simulations showed an improvement in output wave quality and better energy conversion efficiency compared to conventional optimization methods. Scientific novelty of the proposed work lies in the fact that the study introduces a novel DE-GWO hybrid optimization method for PWM (SHEPWM) in 13-level hybrid multilevel converter applied to wind energy systems. Practical value. The novel method demonstrates that constant high performance in wind energy systems may be achieved by combining intelligent optimization algorithms with complex multilevel converter designs This means it can be effectively integrated into contemporary wind farms where meeting grid standards, adjusting to varying sizes, and ensuring long-term reliability are crucial. References 26, table 1, figures 19.

This paper deals with the simultaneous tuning of proportional integral controller of static synchronous compensator (STATCOM) associated with lead-lag controller (LL) in order to improve the stability performance of combined wind farm (CWF). This type of farms has been developed to summarize the main benefits of Squirrel-Cage Induction Generator (SCIG) and doubly fed induction generators (DFIG). The performance of CWF with the tuned STATCOM is studied during line-to-line and three-phase faults. Multi-objective Lightning Attachment Procedure Optimization Algorithm (LAPO) is used as an intelligent optimization technique to determine the control parameters which can achieve the specified objective functions; minimizing the error signal and maximizing the output signal. The multi-objective LAPO is used to obtain the optimized values of AC voltage regulator, DC voltage regulator, current regulator, gains and time constant of LL. The ability of STATCOM tuned by multi-objective LAPO is examined by studying the performance of three wind farms. The first one is CWF and two other wind farms; one of them is based only on SCIG (SCIG-WF) and the other based only on DFIG (DFIG-WF) when they associated with the tuned STATCOM LAPO during grid fault. The results show that CWF associated with the tuned STATCOM LAPO has the best performance during grid faults compared with the other wind farms.

A Static Synchronous Compensator (STATCOM) is one of the Flexible AC Transmission System (FACTS) device which plays an vital role in power system network in alleviation of small and large transient disturbances and better voltage regulation. This paper proposed a self tuning Proportional-Integral (PI) controller for STATCOM which provided a voltage support at point of common coupling (PCC). Self tuning of PI controller was achieved by adapting PI controller gains with system parameters by using Bats Echolocation controller which mimics the Bats Echolocation behavior. In the proposed controller, the system voltage (parameter) at point of common coupling compared with reference voltage and then Bats Echolocation Controller updates the PI controller gains according to the variation obtained between them. This paper also proposed a Cascaded Multilevel Inverter (CMLI) instead of conventional Voltage Source Inverter (VSI) for STATCOM to obtain better voltage regulation at point of common coupling. The voltage imbalance between H-bridge cells in CMLI was rectified by prosing Multicarrier Pulse Width Modulation (PWM) techniques, The proposed controller was validated by comparing the simulation results with fixed gain PI controller and Self tuning PI controller using Neural controller and Particle Swarm Optimization.

This paper presents a novel nonlinear control scheme for designing static synchronous compensators (STATCOM). A passivity-based approach is proposed for designing robust nonlinear STATCOM controller. The mathematical model of STATCOM will be represented by a Euler-Lagrange (EL) system corresponding to a set of EL parameters. By employing the Park's transformation, the differential geometry approach is used to investigate the power system dynamics with considering STATCOM under the synchronous d-q frame. The STATCOM controller based on passivity is obtained with a feedback control law from linear system models. Digital computer simulation for a large operation point variations have been studied the STATCOM controller design. Simulation results show that the proposed STATCOM controller can effectively enhance transient stability of the power system even in the presence of large operation point variations

For the recent expansion of renewable energy applications, Wind Energy System (WES) is receiving much interest all over the world. However, area load change and abnormal conditions lead to mismatches in frequency and scheduled power interchanges between areas. These mismatches have to be corrected by the LFC system. This paper, therefore, proposes a new robust frequency control technique involving the combination of conventional Proportional-Integral (PI) and Model Predictive Control (MPC) controllers in the presence of wind turbines (WT). The PI-MPC technique has been designed such that the effect of the uncertainty due to governor and turbine parameters variation and load disturbance is reduced. A frequency response dynamic model of a single-area power system with an aggregated generator unit is introduced, and physical constraints of the governors and turbines are considered. The proposed technique is tested on the single-area power system, for enhancement of the network frequency quality. The validity of the proposed method is evaluated by computer simulation analyses using Matlab Simulink. The results show that, with the proposed PI-MPC combination technique, the overall closed loop system performance demonstrated robustness regardless of the presence of uncertainties due to variations of the parameters of governors and turbines, and loads disturbances. A performance comparison between the proposed control scheme, the classical PI control scheme and the MPC is carried out confirming the superiority of the proposed technique in presence of doubly fed induction generator (DFIG) WT.

Comparison of MPC based advanced hybrid controllers for STATCOM in medium scale PEM fuel cell systems

This paper presents the development of the wind power system and low voltage ride through (LVRT) techniques for doubly -fed induction generator (DFIG) wind energy system. In recent years, wind power has been developing rapidly. As the wind power penetration from large scale wind turbines has been increasing rapidly in the transmission system, there is a higher requirement for the frequency stability and power generation efficiency of the wind power generation system, and the power grid puts forward higher continuous operation requirements for the grid connected wind turbine in the power grid fault and demand that the wind power generator has to ride through the grid faults, especially the grid voltage dips. This overview mainly introduces DFIG and low voltage ride through technology in the wind power generation system. This paper introduces respectively their development, control strategies and future trend.

Electricity generation from the wind and solar photovoltaic (PV) systems are highly dependent upon weather conditions. Their intermittent nature leads to fluctuations in their output. Therefore, the need for rapid compensation for energy transmission and distribution systems is increasingly important. Static Synchronous Compensator (STATCOM) can be adopted for reactive power compensation and for decreasing the voltage fluctuation caused by the system and renewable energy sources. This study presents modelling of a Solar PV -Wind Hybrid Micro-grid and the increase of the stable operating limit of the system in case of the incorporation of STATCOM is examined. The major contribution of this paper is the optimization of gain parameters of four PI controllers in STATCOM based on genetic algorithms (GA) and therefore obtaining better responses and voltage stability in terms of nonlinear nature of solar-wind hybrid micro-grid. The Simulink models of the system architecture include a 2 MW wind turbine model based on a doubly fed induction generator (DFIG), 0.4 MW solar PV power system model and a STATCOM rated at 3 MVAR. It is certified that the voltage fluctuation at the end of the bus bar is reduced by 8 % using conventional PI controller. The results obtained by GA-based optimization of PI controllers are compared with that of the conventional controller and better results attained.

This paper aims to develop a coordinated controller to enhance the low voltage ride through (LVRT) performance of a permanent magnet synchronous generator (PMSG) based variable speed wind energy conversion system (WECS). This coordinated control comprises of a pitch angle control, a flux weakening control and a static synchronous compensator (STATCOM) control. The pitch angle control is adjusted to smooth the WECS output power fluctuations or to enhance the LVRT performance. The flux weakening controller is used to reduce the overvoltage of DC-link capacitor, and the STATCOM control is used to ensure continuous operation of WECS during symmetrical and asymmetrical grid faults. The proposed coordinated control method is compared with the conventional LVRT strategy based on the braking chopper (BC) via time series simulation results and effectiveness of the proposed control is verified.

Using the FACTS controllers, such as static synchronous compensator (STATCOM), as it provides continuous reactive power, in the grid including wind turbine (WT) equipped with doubly fed induction generator, for improving voltage profile (under normal circumstances) and providing a transition ability from inductor generator transition state has been proposed. In this paper, in order to control the controllers and explained goals, nonlinear controller, as a substitute for the traditional controller, is presented. Replacing STATCOM controller in wind farm, which is equipped with doubly fed induction generator (DFIG) using input-output feedback linearization controller, the needed reactive power in order to stable wind farm equipped with DFIG is considered when error is occurred. The proposed control method has been simulated for IEEE-9 Bus, bus No 5, and the achievability to the desired targets in STATCOM efficiency for its reactive power has been investigated. The reasons of using these controllers in bus 5 are voltage dropping and reducing reactive power in this bus. It can be seen by compensating for voltage and reactive power in this bus that these two parameters have improved in other buses. The results show that with the proposed controller, STATCOM has done its duty well and the network bus voltage and reactive power to sustain the wind farm equipped with DFIG in transient mode is provided.

The Vector controlled doubly fed induction generator (DFIG) wind energy system in a multi-machine power system is very sensitive to faults on transmission lines and thus affects the stability of the system. The performance of vector controlled DFIG highly depends on PI controller parameters. The objective of this paper is to optimize the performance of vector controlled DFIG in multi-machine power systems under faulty conditions by tuning the parameters using advanced differential evolution algorithm. An objective function is formulated, which drives the system with good voltage profile, reduced power oscillations under faulty conditions. The parameters of PI controller are tuned using Composite Differential Evolution algorithm. Simulations are performed on a two area benchmark problem in Matlab/Simulink. The simulation results of the optimized DFIG wind energy system are compared with the actual existed system. The simulation results show that the overall performance and stability of the optimized system are enhanced.

The present article demonstrates the design of a nonlinear optimal FACTS controller based on Hamiltonian function method. Static Synchronous Compensator (STATCOM), a most popular FACTS device has been selected for this purpose. A suitable Hamiltonian function has been formulated to optimize the desired cost functional. The act of the executed controller is correlated with a customary linear model STATCOM controller based upon investigation of the transient stability of a SMIB power system. The designable parameters of the traditional controller are estimated by a stochastic optimization method, Particle Swarm optimization (PSO). The study of investigated results reveals that the proposed optimal nonlinear controller is substantially good and works better than the customary model traditional STATCOM controller even during contingencies like earth fault incidents.

In this paper a nonlinear controller has been designed for Static Synchronous Compensator (STATCOM) in order to improve transient stability of a power system. The nonlinear model of the power system is exactly linearized via state feedback linearization technique. The optimal gain constants of the nonlinear controller are determined applying a special class of non-cooperative dynamic game theory. The performance of this proposed nonlinear STATCOM controller is compared with a fixed structure lead-lag based conventional STATCOM controller. The set of tuning parameters of the conventional controller are optimized through heuristic optimization technique, Genetic Algorithm (GA). The performance of both nonlinear and the conventional controllers are validated with application of a typical transient disturbance to a SMIB test power system. It has been revealed that the proposed nonlinear controller is more effective in the face of contingency in comparison to the GA based controller.