Hybrid Wind Farm Research Articles

Coordinated control strategy for hybrid wind farms with DFIG-based and PMSG-based wind farms during network unbalance

This paper investigates the coordinated control strategy for a hybrid wind farm with doubly fed induction generator (DFIG)-based and direct-driven permanent-magnet synchronous generator (PMSG)-based wind farms during network unbalance. The negative-sequence current output capabilities of DFIG and PMSG systems under unbalanced grid voltage condition are described. Furthermore, by considering both the negative-sequence current capabilities and requirements of different control targets for each control unit, the controllable operating regions of DFIG and PMSG systems are investigated. According to the controllable operating regions, a targets selection scheme for each control unit is proposed to improve the stability of the hybrid wind farms containing both DFIG-based and PMSG-based wind farms during network unbalance, especially to avoid DFIG-based wind farm tripping from connected power grid under severe grid voltage unbalance conditions. Finally, the proposed coordinated control strategy is validated by the simulation results of a 30-MW-DFIG-based wind farm and a 30-MW-PMSG-based wind farm under different operation conditions and experimental results on a laboratory-scale experimental rig under severe grid voltage unbalance conditions.

Analysis of short circuit characteristic of hybrid wind farm group based on artificial short circuit test

In order to verify the wind farm short circuit current characteristic and its influence to power grid due to large-scale wind farms integration on Rongcheng power station, three-phase and single-phase short circuit tests were carried out. Using the above ‘unit-integrated-wind farm-grid’ modelling methodology, the model can be established in the simulation platform PSASP. Based on the simulation model, the change mechanism of short circuit current is analysed. By comparing the short circuit current characteristics of different type wind turbines with the field test data from the digital fault recorder, the wind turbine's contributions to the system short circuit current are determined detailed with squirrel cage induction generator, doubly fed induction generator, and permanent magnet synchronous generator. In addition, the short circuit current characteristics of wind farm are summarised and deepen understood from the field test data. With the analysis result, Shandong Rongcheng wind farm short circuit field test would have very good reference and directive significance for large-scale wind power centralised integration to the actual power grid.

Evaluation of the Fluid Model Approach for the Sizing of Energy Storage in Wave-Wind Energy Systems

The application of energy storage in offshore renewable generation systems allows managing the intrinsic uncertainty of the resources and improving the utilization factor of the electrical network. Optimal storage design algorithms generally have to evaluate the behavior of the whole system thousands times before converging to the optimal solution and the reliability of the results obviously depends on the quality of input data. On the other hand, the utilization of simplified storage models in the design stage can reduce the simulation time drastically, while still providing useful information. The goal of this paper is to evaluate the applicability of a methodology for sizing the energy storage system in a hybrid wind and wave farm, which is based on fluid models. The description and performance of this modeling approach will be introduced and compared to standard design procedures based on extensive simulations. Advantages and limitations of each approach will be underlined and the impact of input data quality will be discussed.

Minimum number of permanent-magnet synchronous generators for coordinated low-voltage ride-through of induction generators in hybrid wind farms

Minimum number of permanent-magnet synchronous generators for coordinated low-voltage ride-through of induction generators in hybrid wind farms

CONTROL OF SUPERCONDUCTING POWER SUBSTATION TO SMOOTH WIND GENERATION AND IMPROVE SYSTEM FAULT DYNAMICS

Based on comprehensive feasibility analysis, this article proposes to use superconducting magnetic energy storage (SMES) system to suppress the high-frequency power output fluctuations of a hybrid wind farm with doubly fed induction generators (DFIGs) and fixed speed induction generators (FSIGs) so that the primary frequencycontrol of the system can be relieved.

Recycling supercapacitors based on shredding and mild thermal treatment

Supercapacitors are widely used in electric and hybrid vehicles, wind farm and low-power equipment due to their high specific power density and huge number of charge–discharge cycles. Waste supercapacitors should be recycled according to EU directive 2002/96/EC on waste electric and electronic equipment. This paper describes a recycling approach for end-of-life supercapacitors based on shredding and mild thermal treatment.At first, supercapacitors are shredded using a Retsch cutting mill. The shredded mixture is then undergone thermal treatment at 200°C to recycle the organic solvent contained in the activated carbon electrodes. After the thermal treatment, the mixture is roughly separated using a fluidized bed method to remove the aluminium foil particles and paper particles from the activated carbon particles, which is subsequently put into water for a wet shredding into fine particles that can be re-used. The recycled activated carbon has a BET surface area of up to 1200m2/g and the recycled acetonitrile has a high purity.

Optimal Real-Time Scheduling for Hybrid Energy Storage Systems and Wind Farms Based on Model Predictive Control

Energy storage devices are expected to be more frequently implemented in wind farms in near future. In this paper, both pumped hydro and fly wheel storage systems are used to assist a wind farm to smooth the power fluctuations. Due to the significant difference in the response speeds of the two storages types, the wind farm coordination with two types of energy storage is a problem. This paper presents two methods for the coordination problem: a two-level hierarchical model predictive control (MPC) method and a single-level MPC method. In the single-level MPC method, only one MPC controller coordinates the wind farm and the two storage systems to follow the grid scheduling. Alternatively, in the two-level MPC method, two MPC controllers are used to coordinate the wind farm and the two storage systems. The structure of two level MPC consists of outer level and inner level MPC. They run alternatively to perform real-time scheduling and then stop, thus obtaining long-term scheduling results and sending some results to the inner level as input. The single-level MPC method performs both long- and short-term scheduling tasks in each interval. The simulation results show that the methods proposed can improve the utilization of wind power and reduce wind power spillage. In addition, the single-level MPC and the two-level MPC are not interchangeable. The single-level MPC has the advantage of following the grid schedule while the two-level MPC can reduce the optimization time by 60%.

Improving grid integration of wind turbines by using secondary batteries

Abstract Energy storage systems (ESSs) appear as a viable solution to some of the stability and intermittency problems of wind power generation. As a consequence, it is crucial to develop adequate control strategies that allow the coordinate operation of both energy sources. Moreover, in order to minimize the impact of large wind farms on the power system, many countries have set strict grid codes that wind power generators must accomplish. Hence, it is also necessary to pay due attention to the fault ride through capabilities of these hybrid systems. In this paper two different hybrid configurations are modeled in MATLAB/Simulink, consisting on a doubly fed induction generator driven wind turbine and electrochemical batteries as ESS. They are simulated and compared under various operating conditions (i.e. real fluctuating wind speed input with variable active and reactive power grid demand, voltage sags, three-phase and single-phase fault to ground, and overvoltage). A conventional wind turbine without ESS is also considered as a base-case in order to highlight the main benefits of the hybrid schemes. The results show that by implementing one of the presented control strategies, it is possible to enhance the response to faults of the hybrid systems, achieving higher active power injection and helping the recovery to steady-state, thus improving the grid connection capabilities of hybrid wind farms.

An Integrated Topology of Hybrid Marine Farm & Wind Farm

Abstract- Renewable energy has been playing an important role to meet power demand and ‘Green Energy’ market is getting bigger platform all over the world in the last few years. In order to meet the increasing demand of electricity and power, integration of renewable energy is getting highest priorities around the world. Wind is one of the most top growing renewable energy resources and it is the most environmental friendly, cost effective and safe among all renewable energy resources available. Another promising form of renewable energy is ocean energy which covers 70 % of the earth. Offshore Wind farm` (OWF) has already become very popular for large scale wind power integration with the onshore grid. Recently, marine current farm (MCF) is also showing good potential to become mainstream energy sources and already successfully commissioned in United Kingdom. An integration of wind and tidal energy represents a new-trend for large electric energy production using offshore wind generators and marine current generators, respectively. This work first focuses on the modeling of fixed speed IG based marine current farm and variable speed DFIG based wind farm. Detailed modeling and control scheme for the proposed system are demonstrated considering some realistic scenarios. The power system small signal stability analysis is also carried out by eigenvalue analysis for marine current generator topology, wind turbine generator topology and integrated topology. The relation between the modes and state variables are discussed in light of modal and sensitivity analyses. The results of theoretical analyses are verified by MATLAB/SIMULINK.

An analysis of subsynchronous resonance in hybrid marine current and wind farms with squirrel cage induction generator

Subsynchronous resonance (SSR) is a well-known phenomenon in series-compensated systems with synchronous generators. With the rapid growth of renewable energy systems, it is likely that with its integration to series-compensated system for the transmission of bulk power may lead to the problem of SSR. This paper conducts an analysis of SSR phenomena in the squirrel cage induction generator-based hybrid wind farm and marine current farm connected to series-compensated system with power variation due to the addition or removal of small turbine units. A dynamic model has been developed to analyse the induction generator effect and torsional interaction of SSR on the IEEE first bench mark model for SSR studies. The eigenvalue analysis was performed on the developed model with MATLAB and the time domain electro magnetic transient simulation performed on DiGSILENT Power Factory confirms the predicted results by the eigenvalue analysis.

OPERATION OF HYBRID WIND FARM BASED ON SCIG AND DFIG UNDER GUST WIND SPEED

The continuous increasing in the pollution level and in the same timeincreasing in fuel price are factors which lead to the increase in usingrenewable energy sources specially wind energy. Wind energy faces manychallenges, one of the important challenges is that of the rapidly change inwind speed which depends on the weather condition. A change in windspeed affects on the generated power from wind turbine. SCIG and DFIGare famous kinds of wind turbine, Each of them has advantage anddisadvantage, SCIG is cheap but its operation has a great effect on systemstability, especially when it operates without static synchronouscompensator. DFIG keeps the system stable but it is very expensive.Therefore, it's necessary to examine the response of different wind turbinegenerators variation of gust wind speed. This paper investigates the abilityof hybrid wind farm which consists of SCIG and DFIG to operate withoutstatic synchronous compensator under gust wind speed condition. Thegust wind speed is simulated according to the InternationalElectrotechnical Commission IEC 61400.

An Improved Control Strategy for Hybrid Wind Farms

This paper addresses the control requirements of hybrid wind farms, comprising a relatively large number of conventional induction machines (IMs) along with one or very few permanent magnet synchronous machines (PMSMs), capable of compensating the reactive power demanded by the IMs during faulty conditions as well as attenuating the active power variations due to wind gusts. Based on the superposition theorem and the feedback linearization technique, a controller is designed to independently regulate the positive and negative sequence currents of the PMSM voltage source converters (VSCs), overcoming several drawbacks of existing approaches in the presence of unbalanced voltages. In the proposed scheme, the grid-side VSC currents are controlled in order to improve the ride-through capability of IMs, so that the whole wind farm can fulfill demanding grid codes in the absence of extra equipment, such as static compensators. As shown by the test results, combining IM-based wind farms with PMSMs accomplishes several relevant goals: delivering the reactive power consumption of the IMs, increasing the rated active power of the installation, and smoothing mechanical power oscillations.

Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF) is simulated by an equivalent 80-MW induction generator (IG) while an equivalent 60-MW IG is employed to simulate the characteristics of the MCF. A damping controller for the SMES unit is designed by using modal control theory to contribute effective damping characteristics to the studied combined WF and MCF under different operating conditions. A frequency-domain approach based on a linearized system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed control scheme. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective to stabilize the studied combined WF and MCF under various wind speeds. The inherent fluctuations of the injected active power and reactive power of the WF and MCF to the power grid can also be effectively controlled by the proposed control scheme.