Wind Farm Integrated Power System Research Articles

Transient stability analysis of DFIG-based wind farm-integrated power system considering gearbox ratio and reactive power control

Nowadays, integration of large-scale wind farms (WFs) into power systems is experiencing rapid growth. As this rapid integration can affect transient stability significantly, employing doubly fed induction generator (DFIG)-based wind turbines, which have shown better behavior regarding system stability, has attracted much attention. This research contributes to the literature by investigating the transient stability of the power system with increasing penetration of DFIG-based WFs. In the proposed framework, the current-balance form is utilized for the network equations, and in this way, transient stability is performed using time-domain simulation. According to the simulation results, when the rate of wind power generation exceeds 0.7 per-unit, the increasing trend of the critical clearing time (CCT) is reversed and the CCT decreases greatly with the increased wind power penetration. In addition, the reactive power compensation by DFIG, the gearbox ratio, the power system strength, and DFIG parameters are comprehensively investigated as effective parameters on transient stability. Since the rated rotor speed of DFIG significantly impacts the electrical torque and machine currents, the reduction of the rated rotor speed due to the change of the gearbox ratio has been investigated as one of the effective factors to improve the transient stability. The simulation results demonstrate the effectiveness of the proposed approach in improving power system transient stability.

Synchrophasor Data Based Q-V Droop Control of Wind Farm Integrated Power Systems

With increasing scalability of grid-integrated wind farms (WFs), reactive power ancillary service through Q-V droop control of doubly-fed inducton generators (DFIGs) is one of the prime interests of power system operators. However, variable and uncertain availability of wind-resource at the wind turbines creates challenge against allocating reactive power reserve at the WFs for maintaining voltage stability of the grid. This issue can be resolved through online coordination among the WFs. This paper proposes a synchrophasor data based Q-V droop (SQVD) control technique for the WFs integrated to the grid through different point of common couplings (PCCs) in the power system transmission network. The data from the phasor measurement units (PMUs) at the WF-connected PCCs are used to obtain synchronized Q-V droop gain for each WF. Further, distributed coordination among DFIGs within each WF is performed to allocate optimum reactive power share at the converters. The total reserve of each WF is employed by their synchronized droop, in improving voltage stability at both the local PCC and neighboring PCCs. Performance of SQVD is verified at 418-bus practical Indian power system, in different dynamic situations of the grid, and found to be more effective as compared to the constant Q-V droop and variable Q-V droop control methods.

PLL Based Sub-/Super-Synchronous Resonance Damping Controller for D-PMSG Wind Farm Integrated Power Systems

Existing sub-/super-synchronous (SSO) suppression methods for the direct-drive permanent magnet synchronous generators (D-PMSG) integrated power systems are mainly achieved by external devices or sub-synchronous resonance damping controller (SSRDC) at the converters, facing challenges of considerable control costs, complex parameters tuning, or inadaptability to various operating conditions. To address these problems, this paper proposes an adaptive SSRDC based on the phase-locked loop (PLL) for D-PMSG integrated power systems. Firstly, the PLL parameter is found critical to SSO suppression by a comprehensive sensitivity analysis on the dominant poles of the impedance closed-loop transfer function. Motivated by this finding, this paper then designs a PLL-based SSRDC, which features a simple structure, easy parameter tuning, and flexible adaptability to various operating modes. The simplicity in structure is guaranteed by the avoidance of phase compensation. Benefiting from the simple structure, only one key parameter needs to be tuned. Moreover, two principles of parameter tuning are proposed to enhance the efficiency, robustness, and adaptability of the proposed SSRDC. The controller-hardware-in-the-loop (CHIL) tests verify the validity of the proposed SSRDC under various operating conditions. Finally, some concerns about this method such as frequency estimation, computational efficiency and potential impacts on PLL are thoroughly analyzed and clarified.

Investigation on the Electrothermal Performance of a High-Temperature Superconducting Cable in an Offshore Wind Farm Integrated Power System: Fault and Islanding Conditions

The main contribution of this article is to study the electrothermal performance of a 22.9 kV high-temperature superconducting (HTS) AC cable under transients, such as short-circuit faults and islanding operating mode (IOM) of a wind farm. For this purpose, an HTS cable connects a 12 MVA doubly fed induction generator-based wind farm to the load center under two different scenarios of the grid. In the first scenario, the upstream grid is located far from the load center and most of the demanded load is supplied by the wind farm, while in the second scenario, a part of the load is supplied by the wind farm and the rest is supplied by the upstream grid located near the load center. In case of faults and transients in the upstream grid, protection systems isolate the wind farm, and thus, it operates in a specific mode, called IOM. Results indicated that the location of faults and transients, especially IOMs, plays a significant role in the electrothermal performance of HTS cable.

A real-time multi-objective optimization framework for wind farm integrated power systems

Wind energy is a rising industry that is rapidly influencing the global energy environment, leading to pollutant mitigation and ultimately helping to shift the climate change paradigm. The incorporation of wind energy into power grids poses new challenges from the point of view of operating performance for transmission network operators. The inconsistent nature is the most significant issue with wind energy. Wind power differs from time to time and the operator must choose the operation strategy accordingly. In this study, a real-time multiple objective optimal power flow framework is proposed to solve this issue. The related dynamic optimization problem is solved online and the control variables are optimized simultaneously. To guarantee both the feasibility and performance of the proposed method, a multi-objective particle swarm optimization with decomposition is developed. Using modified IEEE 30-bus and IEEE 57-bus test systems, the validation of the proposed approach is described in this research.

Sub-synchronous oscillation in wind farm integrated power system considering static var compensator

Sub-synchronous oscillation in wind farm integrated power system considering static var compensator

Real-time optimal power flow solution for wind farm integrated power system using evolutionary programming algorithm

In order to satisfy the increasing demand for electricity, a huge burden is levied on the conventional coal-fired thermal power generation units, which affects the environment and human health adversely. To tackle this problem, the clean renewable sources of energy have gained more attention. With time, wind power is expected to contribute more significantly and should be used as much as possible. This has provided much focus to the wind farm integrated power system. But, the unsteady behavior of wind energy has made the operation of wind farm integrated power system more complex. Scenario generation methods are used for tackling the unsteady behavior of wind energy. A persistence method of scenario generation is proposed for solving real-time optimal power flow problem in wind farm integrated power system. The proposed persistence method performs better compared to other recent methods in the literature.

Stability Improvement of DFIG-Based Wind Farm Integrated Power System Using ANFIS Controlled STATCOM

The stability of the control grid is a critical prerequisite for a safe and efficient power system service. A thorough knowledge of the effects of the power system volatility is essential for the effective study and control of power systems. This paper presents the simulation outcome of a multimachine power network implemented by a wind farm (WF) utilizing a static synchronous compensator (STATCOM) for better stability control objectives. A similarly aggregated double-fed induction generator (DFIG) powered by a gearbox analogy with an equally aggregated wind turbine (WT) determines the operating output of the wind farm. A proportional–integral–derivative controller (PID)-based damping controller, PID including Fuzzy Logic Controller (FLC), and an adaptive network-based fuzzy inference system (ANFIS) controller of the proposed SATCOM are intended to add sufficient damping properties to the dominating modes of the examined system during diverse working circumstances. To assess the feasibility of the suggested control schemes, a frequency-domain method concentrated on a linearized mathematical structure layout utilizing a time-domain strategy centered on a nonlinear configuration of the device that is subjected to severe fault on the attached bus was carried out consistently. A STATCOM damping controller is configured using the ANFIS method to apply appropriate damping properties to the device’s decisive modes being evaluated under various test conditions. From the findings of the comparative simulation, it can be inferred that the suggested STATCOM along with the planned ANFIS is seen as comparable to STATCOM with PID and STATCOM with PID plus FLC to increase the stability of the studied device.

A Robust Coordinated Expansion Planning Model For Wind Farm-Integrated Power Systems With Flexibility Sources Using Affine Policies

This article presents a two-stage adaptive robust coordinated generation and transmission expansion planning model for a wind farm-integrated power system. Also, dynamic thermal rating (DTR) systems, energy storage systems, and optimal line switching maneuvers are considered as various flexible sources to enhance the flexibility of the power system in response to uncertain variations of net system demand. The proposed approach characterizes the uncertainty of demands, wind power, and DTRs in each representative day by a polyhedral uncertainty set. Additionally, the k-means clustering technique is used to obtain upward/downward variations of correlated uncertain parameters in each representative day and to construct the uncertainty set. The proposed model is inherently intractable as it includes infinite constraints modeling enforced techno-economic limitations for all realizations of uncertain parameters. To resolve this limitation, the proposed intractable model is recast as a tractable mixed-integer linear programming problem using affine policies. The proposed approach is implemented on the Garver 6-bus and IEEE 73-bus test systems. Simulation results illustrate its flexibility, practicality, and tractability.

Transient stability improvement of wind farm integrated power system using STATCOM

The need for Interconnected power system is increasing day by day because of continuous growth of Electrical energy demand and to transmit Electric power to remote places at minimum cost and minimum losses. With the operation of power system in interconnected manner, maintaining the system security is difficult task i.e. whenever a disturbance occurs, the system undergoes stability problems. Even though Conventional energy sources are available, Electrical Engineers prefer Renewable energy sources integration because of Energy crisis and pollution problems related to the former, one such Renewable energy source isWind power.Wind energy has major share in Renewable energy sources because of its abundant availability in the nature. Whenever Wind generators coupled to the power system, the system exhibits drooping voltage characteristics and this situation becomes worse during faults. This condition can be neutralised with FACTS (Flexible AC transmission system) devices, one such FACTS device is STATCOM (static synchronous compensator). STATCOMsupports reactive and real power exchange and also improves Transient stability of the system because of its superior characteristics and quick response. In this paper a 9 bus Wind farm integrated test power system is taken and stability studies are done. Since, Wind farm is integrated with the system whenever a fault occurs, overall system stability is reduced i.e. the conventional synchronous generators can withstand it, whereas the Wind generators can’t. So to enhance the Transient stability of the system, a STATCOM is installed and the system behaviour is observed.

Active Voltage Control for DFIG-Based Wind Farm Integrated Power System by Coordinating Active and Reactive Powers Under Wind Speed Variations

Large-scale wind farms are generally integrated by long-distance transmissions, but power grids cannot sufficiently support the access point voltage of these wind farms. The access point voltage undergoes a stability problem under wind speed variations. However, the reactive power compensation device cannot reconcile the requirements of response speed and compensation capacity. Despite their fast power decoupling control, the reactive power capability of doubly fed induction generators is restricted by active power output. To satisfy the reactive power demand of system under wind speed variations, coordinating the reactive power capability and active power output of wind farm is the key solution, based on which a novel active control idea is proposed. The reactive power capability of wind farm and the reactive power demand of system are both studied, and the controllable conditions of access point voltage are analyzed. Active voltage control strategies, including active adjustment of reactive power reference, active speed control, and active pitch angle intervention according to wind speed ranges, are proposed. In the simulation, the method is verified to adequately consider the reactive power demand, and excavate the wind farm reactive power capability. The method also effectively suppresses the change of grid voltage under wind speed variations.

Enhancing Oscillation Damping in an Interconnected Power System with Integrated Wind Farms Using Unified Power Flow Controller

The well-developed unified power flow controller (UPFC) has demonstrated its capability in providing voltage support and improving power system stability. The objective of this paper is to demonstrate the capability of the UPFC in mitigating oscillations in a wind farm integrated power system by employing eigenvalue analysis and dynamic time-domain simulation approaches. For this purpose, a power oscillation damping controller (PODC) of the UPFC is designed for damping oscillations caused by disturbances in a given interconnected power system, including the change in tie-line power, the changes of wind power outputs, and others. Simulations are carried out for two sample power systems, i.e., a four-machine system and an eight-machine system, for demonstration. Numerous eigenvalue analysis and dynamic time-domain simulation results confirm that the UPFC equipped with the designed PODC can effectively suppress oscillations of power systems under various disturbance scenarios.

Frequency sensitivity analysis of dynamic demand response in wind farm integrated power system

Demand response (DR) has emerged as a very important part of the future smart grid to enhance the power system reliability and frequency stability. This study presents the benefits of DR control and battery energy storage (BES) on frequency regulation in wind farm integrated power system. In this study, a generalised load frequency control model of a hybrid hierarchical DR control mechanism is developed by incorporating the inherent system parameters such as frequency dead-band, aggregated generations/devices and communication time delay and so on. The mathematical formulation for frequency stability and sensitivity analysis are carried out with respect to the frequency change coefficient for switching OFF the DR devices and frequency regulation service shared by conventional supplementary control, DR and BES. The extensive simulation results are presented for system frequency response (SFR) to support the theoretical analysis. It is found that DR has a significant effect to stabilise SFR. The observations drawn from analysis can be helpful for system operators/regional transmission organisation to investigate or plan for deciding the frequency threshold, minimum turn OFF time for individual DR devices, frequency coefficient factor and percentage share of frequency regulation services to restore the frequency quickly.

Robust Transmission and Energy Storage Expansion Planning in Wind Farm-Integrated Power Systems Considering Transmission Switching

This paper presents a new nondeterministic model for joint transmission and energy storage expansion planning along with optimal transmission switching in wind farm-integrated power systems. The proposed approach adopts the underlying idea of robust optimization to characterize the uncertainty sources pertaining to load demands and wind power productions through uncertainty sets. Accordingly, a tractable adaptive min–max–min cost model is introduced to find a robust optimal expansion plan for new lines and storages withstanding the worst-case realization of the uncertain variables. As the adaptive min–max–min cost model cannot be solved directly by the commercial off-the-shelf software packages, a decomposition algorithm using primal cutting planes is introduced to obtain the optimal solution. The proposed approach has been implemented on the IEEE 24-bus and the IEEE 73-bus test systems. Also, the robustness of optimal expansion plans under different circumstances is evaluated through a post-optimization procedure simulating different realizations of the uncertainty sources. Case studies justify the efficiency of the proposed RO-based model.

Frequency Sensitivity Analysis of Load Damping Co-efficient in Wind Farm Integrated Power System

The presence of frequency sensitive loads such as motors has sustainable impact on power system frequency response (SFR). With increasing wind power penetration into the power system, guidelines for frequency regulation need to be revised to ensure system stability and reliability. Frequency regulation becomes more critical with the presence of frequency sensitive loads in wind integrated power system. This paper presents the impact of frequency sensitive loads on system frequency when wind farm is integrated with the conventional power system. A small-signal linearized model of variable speed wind turbine generator is derived. The typical SFR model is developed for wind farm integrated power (WFIP) system. Sensitivity and stability analysis is carried out for linearized model of WFIP system. The observations drawn from the analysis can be useful for the system operators for decision making of appropriate schemes for primary frequency control, demand response, and setting of relays, etc. for secure and stable power system operation. The proposed analysis is validated in IEEE 9-bus system using MATLAB simulation studies.

Fuzzy logic system for frequency stability analysis of wind farm integrated power systems

Fuzzy logic system for frequency stability analysis of wind farm integrated power systems

An economic and low-carbon day-ahead Pareto-optimal scheduling for wind farm integrated power systems with demand response

Demand response (DR) and wind power are beneficial to low-carbon electricity to deal with energy and environmental problems. However, the uncertain wind power generation (WG) which has anti-peaking characteristic would be hard to exert its ability in carbon reduction. This paper introduces DR into traditional unit commitment (UC) strategy and proposes a multi-objective day-ahead optimal scheduling model for wind farm integrated power systems, since incentive-based DR can accommodate excess wind power and can be used as a source of system spinning reserve to alleviate generation side reserve pressure during both peak and valley load periods. Firstly, net load curve is obtained by forecasting load and wind power output. Then, considering the behavior of DR, a day-ahead optimal dispatching scheme is proposed with objectives of minimum generating cost and carbon emission. Non-dominated sorting genetic algorithm-II (NSGA-II) and satisfaction-maximizing method are adopted to solve the multi-objective model with Pareto fronts and eclectic decision obtained. Finally, a case study is carried out to demonstrate that the approach can achieve economic and environmental aims and DR can help to accommodate the wind power.

Probabilistic assessment of oscillatory stability margin of power systems incorporating wind farms

With the increase in penetration of wind power which is essentially intermittent and random, the dynamic performance of the power system will change significantly, and so will the characteristics of the oscillations and their stability margins. This paper provides an attempt to include probabilistic character of wind power into the power system oscillatory stability margin (OSM) analysis. Nataf transformation approach is applied to generate the wind speed samples, which models the correlation between the various wind farms. The mathematical model of OSM for wind farm integrated power system is formulated and is calculated by the integration-based eigenvalue tracing approach. Considering the uncertainties of the wind power, several statistical indices are presented to evaluate OSM. Monte Carlo simulation (MCS) is used to calculate these statistics. The impact of wind power uncertainty on OSM restricted by inter-area mode is investigated in four-machine two-area test system and 16-machine five-area test system, respectively, for different wind farm locations, wind power penetration levels and wind speed correlation (WSC) degrees. Appropriate conclusions are finally drawn.