Fixed Speed Squirrel Cage Induction Research Articles

Determination of Minimum Reactive Power Compensation for the Stable Operation of Type-1 WTG in Grid-Connected mode

The current energy demand scenario leads to tremendous increase in the renewable energy sector, but the integration of these renewable causes various stability issues of the system. Increasing share Wind energy has several shortages due to its energy harnessed from the wind. These shortages can be improved by compensating reactive power into the wind plant. The wind farm consist of fixed speed squirrel cage Induction generator absorbs reactive power from the grid for stable operation and it can be injected using reactive power compensator. In this context, the main aim of the research is to find the minimum reactive power compensation required for stable operation for different rating of Type-1 WTG in grid connected mode. In this paper, a detailed model of constant speed Squirrel Cage Induction Generator is carried out in MATLAB/SIMULINK-2017a to analyze the need of reactive power compensation to maintain voltage and frequency stability of the system during normal condition. The work also focuses on to investigate the impact of induction generator inertia level on compensation level. The modified IEEE 5-bus radial distribution system is used to conduct these investigations and the simulation results clearly show that: (1) The necessity and minimum additional reactive power support to the wind farm to improve and maintain stability of the system; (2) the inertia level of wind farm and reactive power compensator level both are independent each other.

Improving the dynamic performance of grid connected wind farm using new SMES switching technique

Due to the uncertain nature of wind energy, the effective operation of grid connected wind farms is quite a challenge for grid operators. The stipulated grid requirements for frequency and voltage control must be satisfied to avoid the shutdown of grid networks during periods of dynamic grid disturbance. This paper tends to improve the dynamic performance of a grid network consisting of nuclear and thermal turbines that are tied to a wind farm that is made up of fixed speed squirrel cage induction generator wind turbine type. A supermagnetic energy storage (SMES) system is connected to the terminal of the wind farm in order to achieve smoothing of the distorted wind turbine variables so that steady power supply could be maintained during periods of grid disturbance. A new control strategy to improve the performance of the traditional SMES is proposed by integrating a parallel DC-DC chopper in the circuitry of the voltage source converter. The responses of the proposed control strategy for SMES were compared with the traditional SMES scheme during grid disturbance under the same conditions of wind speed. The simulation results in power system computer aided design and electromagnetic transient including the DC platform show the improved performance of the grid variables considering the proposed scheme for SMES.

A Methodology to Synthesize Gearbox and Control Design for Increased Power Production and Blade Root Stress Mitigation in a Small Wind Turbine1

Large wind turbines typically have variable rotor speed capability that increases power production. However, the cost of this technology is more significant for small turbines, which have the highest cost-per-watt of energy produced. This work presents a low-cost system for applications where cost and reliability are of concern. The configuration utilizes the fixed-speed squirrel cage induction generator. It is combined with a variable ratio gearbox (VRG) that is based on the automated-manual automotive transmission. The design is simple, low cost and implements reliable components. The VRG increases efficiency in lower wind speeds through three discrete rotor speeds. In this study, it is implemented with active blades. The contribution of this work is a methodology that synthesizes the selection of the gearbox ratios with the control design. The design objectives increase the power production while mitigating the blade stress. Top-down dynamic programming reduces the computational expense of evaluating the performance of multiple gearbox combinations. The procedure is customizable to the wind conditions at an installation site. A case study is presented to demonstrate the ability of the strategy. It employs a 300 kW wind turbine drivetrain model that simulates power production. Two sets of wind data representing low and high wind speed installation sites were used as the input. The results suggest a VRG can improve energy production by up to 10% when the system operates below the rated wind speed. This is also accompanied by a slight increase in the blade-root stress. When operating above the rated speed, the stress decreases through the optimal selection of gear combinations.

Asymmetrical Fault Ride Through as Ancillary Service by Constant Power Loads in Grid-Connected Wind Farm

The introduction of distributed generation (DG) into low voltage (LV) systems demands that the generation system remain grid connected during voltage sags to ensure the operational stability. The DG consisting of fixed speed squirrel cage induction generator (SCIG)-based wind turbines is unable to provide reactive power control and needs a dedicated compensating device. Under asymmetrical grid faults the negative sequence flux circulation in the airgap introduces the torque oscillations that lead to the reduction of lifetime of the generation system. This paper proposes the use of distributed constant power loads (CPLs) for asymmetrical fault ride through (FRT) instead of using a centralized STATCOM. It has also been observed that the compensation of negative sequence voltage improves the performance of SCIG by eliminating the torque ripples. The compensation of positive sequence voltage avoids a possible voltage collapse at the LV distribution level and improves the reliability and stability of the wind farm. Centralized compensation of the asymmetrical grid fault by a STATCOM is compared with the distributed compensation by CPLs. The results suggest that each individual CPL injects lower current for maximum FRT enhancement compared to a dedicated STATCOM.

Modeling and Control of Standalone Direct-Driven PMSG WECS for Grid Compatibility at Varying Wind Speeds

Wind energy is one of the most available and exploitable forms of renewable energy. Variable speed PMSG based Wind Energy Conversion System (WECS) offers many advantages compared to the fixed speed squirrel cage induction generators such as improved stator output operation at better power factor, no maintenance cost for gear box (as it is direct-driven) reduction in weight and losses, higher efficiency and ability to run at low speeds. The elimination of the gear box and brushes can enhance the efficiency of wind turbine by 10%. In this paper a Permanent Magnet Synchronous Generator (PMSG) is modeled whose stator is connected to the constant single phase load (in place of grid) through AC/DC thyristors based rectifier followed by capacitor (dc-link) and DC/DC converter control. Overall arrangement provides constant output to connected load if applied with proper controlling techniques. Hence this proposed wind generation system design can be extended for grid connection also via DC/AC inverter control. Results are simulated and verified in MATLAB/Simulink platform at constant rated (12m/s) and varying (stepped) wind speed for smooth and constant output voltage. DOI: http://dx.doi.org/10.11591/telkomnika.v13i3.7097

Voltage stability enhancement using an adaptive hysteresis controlled variable speed wind turbine driven EESG with MPPT

This paper investigates the enhancement in voltage stability achieved while connecting a variable speed wind turbine (VSWT) driven electrically excited synchronous generator (EESG) into power systems. The wind energy conversion system (WECS) uses an AC-DC-AC converter system with an uncontrolled rectifier, maximum power point tracking (MPPT) controlled dc-dc boost converter and adaptive hysteresis controlled voltage source converter (VSC). The MPPT controller senses the rectified voltage (VDC) and traces the maximum power point to effectively maximize the output power. With MPPT and adaptive hysteresis band current control in VSC, the DC link voltage is maintained constant under variable wind speeds and transient grid currents.The effectiveness of the proposed WECS in enhancing voltage stability is analysed on a standard IEEE 5 bus system, which includes examining the voltage magnitude, voltage collapse and reactive power injected by the systems. Simulation results show that the proposed WECS has the potential to improve the long-term voltage stability of the grid by injecting reactive power. The performance of this scheme is compared with a fixed speed squirrel cage induction generator (SCIG), a variable speed doubly-fed induction generator (DFIG) and a variable speed permanent magnet synchronous generator (PMSG).