Inertial Response Identification Algorithm for Development of Dynamic Equivalent Model of DFIG-based Wind Power Plant

As the wind power penetration increases, the frequency stability of the power system is deteriorating. Thus, it is expected that the wind power plants (WPPs) will be required to produce the inertial response during the short-term large-scale frequency disturbances. To study the effects of the inertial response of the WPP, the dynamic equivalent model (DEM) of the WPP should be able to emulate the inertial response of the actual WPP. Otherwise, the simulated system frequency would be different from the actual one. Therefore, the inertial response identification algorithm (IRIA) is proposed in this article. The IRIA is able to identify the gain of the inertial controller and the inertia constants of the WPP according to the actual system frequency and the active power output of the actual WPP. In this article, the actual WPP is represented by the detailed model. In order to prove the effectiveness of the IRIA, three cases with different gains of the inertial controller are studied. The simulation results demonstrate that the proposed IRIA allows the DEM of the WPP to generate similar response of the active power and lead to close response of the system frequency as the actual WPP does in three different scenarios.

As the wind power penetration level increases, the inertial response of a wind power plant (WPP) is important to the grid under load and generation imbalance. In this paper, we present coordinated WPP control for frequency support under wake effects. By de-loading the power from a WPP, the inertial response can be obtained from the kinetic energy of wind turbine rotors. The coordinated WPP control considering wake effects improves the inertial response of WPP by preventing the rotor speed recovery period, which is unfavorable during a frequency drop. The proposed frequency support scheme could prevent large generation reduction right after an inertial response. In addition, more power generation is available when a WPP uses both primary and secondary control. To validate the performance, a WPP with three wind turbines was used as a case study with wake, turbine, and generator models.

The objective of this paper is to analyze and quantify the inertia and frequency responses of wind power plants with different wind turbine technologies (particularly those of fixed speed, variable slip with rotor-resistance controls, and variable speed with vector controls). The fundamental theory, the operating range, and the modifications needed for the wind turbine to contribute to the inertial and primary frequency response during the frequency drop will be presented in this paper. We will demonstrate practical approaches to allow variable slip and speed wind turbines to contribute inertia to the host power system grid. The approaches are based on the inclusion of frequency error and the rate of change of frequency signals in the torque control loop and pitch control actions for wind speeds below and above its rated value. Detailed simulation models in the time domain will be conducted to demonstrate the efficacy of the approaches.

Optimization of wind power generation to minimize operation costs in the daily scheduling of hydrothermal systems

As wind power penetration into power systems increases, it poses a growing challenge to power system operation and stability. This is partly because wind power is highly time variable and cannot inherently contribute to power system frequency regulation. The provision of frequency support from wind turbines under changing wind conditions is examined in this paper. A simplified variable speed wind turbine model is developed. A modified turbine controller to deliver inertial and droop response is proposed. The interaction between inertial and droop response from wind turbines is examined under varying wind.

With the continuous increase in wind power penetration, doubly fed wind turbines can quickly respond to changes in grid frequency, and have particularly important inertia-response characteristics. This article starts with the excitation control principle of a doubly fed induction generator, compares the transient frequency characteristics of the synchronous generator under fault, and proposes that the doubly fed induction generator can control the speed or active power of the generator through excitation. It proves the unique “active power transient frequency characteristics” of doubly fed induction generators. Under different wind speeds, the inertia response capability of the wind turbine is quantified, and the degrees of influence of the inertia time constant and frequency characteristic slope of the doubly fed induction generator on the transient change process are analyzed. Finally, simulation and experiments verify the correctness of the above theory, which provides a basis for significantly improving the transient stability of the power system and realizing the controllability of the transient stability of the power system.

Increasing wind power penetration and the size of Wind Power Plants (WPPs) brings challenges to the operation and control of power systems. Most of WPPs are located far from load centers and the short circuit ratio (SCR) at the Point of Connection (POC) is low, which means that fluctuations of the wind power can cause voltage variations. An optimal voltage control scheme for WPPs with STATCOMs is presented in the paper. It ensures that the voltages within the WPPs and at the high voltage side of the WPPs are within the limits and maximizes the dynamic Var reserve of the WPPs. Case studies were conducted with the simplified Anholt offshore WPP and the case study results demonstrate the efficacy of the proposed optimal voltage control scheme.

During recent years, wind energy has moved from an emerging technology to a nearly competitive technology. This fact, coupled with an increasing global focus on environmental concern and a political desire of a certain level of diversification in the energy supply, ensures wind energy an important role in the future electricity market. For this challenge to be met in a cost-efficient way, a substantial part of new wind turbine installations is foreseen to be erected in big onshore or offshore wind farms. This fact makes the production, loading and reliability of turbines operating under such conditions of particular interest.

Wind power is still the most promising renewable energy source in the year of 2014. Wind power is considered feasible replacement of fossil fuels and energy production using this resource is increasing with the passage of time. Growing wind power production has impacts on the systems synchronized with these wind turbines. As the wind power penetration increases to the main power grids systems, the respective power system operators are more concerned about the reliability and stability of their systems. This increase of wind power penetration in system means that the wind turbines are replacing conventional power plants that usually control and stabilize the system. If this power penetration surpasses a certain level, control tasks for wind turbine system also needs to be considered. If the wind speed increases, much power is produced through turbines. The main problem we are facing in wind power production is that even after generating more than enough power to meet the load demands, surplus energy is being dissipated by dump load, otherwise it can create threat for power system stability as surplus power can have adverse effect on the frequency and voltages. In normal cases, surplus power is dissipated by using dump load. But enough portion of produced power is being wasted this way. In this study, an efficient controller for effectual wind turbine operation by controlling dump load is proposed to keep the system stable and the surplus dumped power is also consumed in productive way through heat generating system which increases the power system overall efficiency.

In several countries, the wind power penetration increased tremendously in recent years. To ensure the proper functioning of the power system, some grid operators already require the capability to provide inertial response or primary control with wind turbines. This paper discusses the emulated inertial response with wind turbines by means of the synthetic inertia and the droop control strategy. The behavior of the synthetic inertia strategy is determined by the inertial and the droop constant, whereas droop control only has a droop constant. When these strategies are used, it is important to tune the control parameters depending on the power system to which the wind turbines are connected. Simulations show that it is possible to enhance but also to deteriorate the frequency response of the system, dependent on these parameters. For different power system compositions, the optimal inertial constant is always close to zero. This way, the synthetic inertia strategy reduces to a fast droop control strategy. This is an important outcome, as it means that no differentiation of the frequency is needed to obtain an optimal inertial response from the wind turbines, which is beneficial in terms of robustness. Consequently, droop control is a viable alternative for the synthetic inertia.

According to the characteristics of double fed asynchronous generator rotor energy flow, research and design based on the DSP control with two-way flow of energy function of Dual PWM converter and discusses the grid side converter control method of Dual PWM converter in particular. The wind turbine simulation model is established by using the electromagnetic transient PSCAD/EMTDC software. The simulation system is used to simulate the P, Q decoupling control and maximum wind energy tracking control of the generator. Wind is a natural phenomenon generated by the solar radiation heat, the earth's surface caused by uneven heating of the atmosphere. It is estimated that only 1% of the wind on the ground will be able to meet the needs of the world's energy. With the continuous improvement of the level of wind power generation technology, the cost of wind power gradually reduced, considering environmental benefits, the cost will be close to the cost of coal-fired power generation. Therefore, great efforts to develop wind energy as the representative of the renewable energy and new energy, to achieve sustainable development, has become the consensus of the whole society, strategic choice to solve the energy crisis and environmental problems. 2.Overview of control technology of doubly fed wind power gener ation Wind power is the kinetic energy contained in the natural wind into electrical energy in the process, the wind turbine wind energy capture and convert it into mechanical energy, driven by rotary generator, and the generator for converting mechanical energy conversion into electrical energy. As countries around the world pay more attention to wind power, wind power has become the world's fastest, most widely studied and applied new energy technology. With the development of wind power technology, wind turbine, wind turbine generator, converter and its control system and the way of the wind turbine, there are different types of. Among them, the doubly fed wind power generation system due to the converter control capacity is small, the speed of operation range wide characteristics become currently the world's most widely used VSCF wind power generation system. Variable speed constant frequency generator in asynchronous generator rotor side applied three-phase low frequency current to realize AC excitation, the output power is constant frequency and constant voltage amplitude, frequency, phase of the exciting current control. At the same time, the active power and reactive power decoupling control of the generator is realized by using the vector control technology. Control active power capable of adjusting the rotation speed of the wind turbine, to capture the maximum wind power tracking control; regulation of reactive power adjustable power factor and improve the dynamic and static stability of the wind turbine and power system operation. In addition, the VSCF wind power generation technology, so to achieve good flexible connection between the generator and power grid system, compared with the traditional constant speed constant frequency generation system easier to achieve grid connected operation and operation

In recent years, wind power and photovoltaic power generation have developed rapidly, and the installed proportion of wind power and photovoltaic power will further increase in the future. Aiming at the strong uncertainty of wind power and photovoltaic power, a scene generation method of wind and solar active power output based on k-medoids clustering and generative adversarial networks is proposed to avoid problems of model convergence and gradient disappearance, meanwhile preserving the diversity of generated results. Using the active power output data of two wind power plants and six photovoltaic power plants in Western China for 365 days a year, the data samples are clustered into ten scenarios by k-mediods method, which are used as training sets under different typical scenarios. The distribution characteristics of active power output data are effectively fitted by the generative adversarial networks, and its generation effect is analyzed. The results show that the scene generation method of wind and solar active power output based on k-medoids clustering and generative adversarial networks has the advantages of fast convergence and high precision.

Future power systems face several challenges; one of them is the use of high power converters that decouple new energy sources from the AC power grid. This decreases the total system inertia affecting its ability to overcome system frequency's disturbances. The wind power industry has created a controller to enable inertial response on wind turbines generators: Artificial, Emulated, Simulated, or Synthetic Inertial. This paper deals with issues related to the synthetic inertia of wind turbines based on full-converters and their effect on the frequency protection/control schemes during the recovery period after system frequency disturbances happen. The main contribution of this paper is to demonstrate (based on simulations) the recovery period of under-frequency transients on future power systems which integrate wind turbines with synthetic inertia capability not completely avoid worse scenarios in terms of under-frequency load shedding. The extra power delivered from a wind turbine during frequency disturbances can substantially reduce the rate of change of frequency providing time for the active governors to respond. However, synthetic inertia might not completely avoid under-frequency load shedding. (6 pages)

Participation of the wind turbine generators (WTGs) in the frequency regulation service is an appealing issue in order to consider the safe increasing of the wind power generation. The droop and virtual inertia control are the most popular approaches that facilitate the WTGs to provide frequency regulation. However, the intermittent nature of the wind complicates the implementation of these methods and has impacts on the wind turbine stability and may cause violation of the allowed power reserve and minimum turbine rotor speed. Therefore, in this paper, a control approach based on the dynamic de-loading technique is proposed, where the wind turbine operating curve is dynamically adjusted in the response of the frequency deviation throughout controlling the turbine tip-speed ratio which helps the turbine provide steady-state power sharing within the reserved power as well as the transient response within its stability criteria. In addition, the inertial response based on a dynamic gain is suggested. The inertial weighting gain has been formulated where it is continuously regulated in the response of rotor speed and reflects the amount of available kinetic energy in the rotating mass. The effectiveness of the proposed control approaches is verified throughout the comparisons of the results with the fixed inertial gain control and the droop control. The simulation results confirm that the combined control of the proposed tip-speed ratio and dynamic inertia control improve the overall system dynamic behavior in terms of frequency response and turbine stability.

The grid connection of large-scale wind power will reduce the equivalent inertia and damping of the system, resulting in a decrease in system frequency stability. The directly-driven permanent magnet synchronous generators (D-PMSG)-based wind turbine (WT) usually uses conventional PD control to support frequency, however, the related controller parameters are difficult to design, reducing economic benefits of WT power generation and slowing speed recovery. To this end, based on the analysis of the dynamic response of D-PMSG grid-tied system, this paper studies the dynamic influence and variation law of controller parameters on system frequency. A WT control strategy based on frequency trajectory planning (FTP) is proposed. The frequency fixed value determined by the power grid regulation is directly taken as the control target to carry out the FTP, and the WT auxiliary power output is controlled according to the planned frequency trajectory. The system frequency is supported quickly in the transient process, ensuring the safe and stable operation of the grid while realizing the economy of WT power generation. The effectiveness and economy of the proposed control strategy is verified by RT-LAB experiment.