Adaptive Settings Of Distance Relay For MOV-Protected Series Compensated Line With Distributed Capacitance Considering Wind Power

Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit, which affects the distance protection. The intermittent wind generation introduces additional complexity to the system performance and distance protection. Wind variation affects the fault current level and equivalent MOV/capacitor impedance during a fault, and hence the distance relay operation. This thesis studies the impact of the intermittent wind power generation on the operation of MOV during faults. For the purpose of simulation, an equivalent wind farm model is proposed to generate a wind generation profile using wind farm generation from California independent system operator (ISO) as a guide for wind power variation to perform the study. The IEEE 12-bus test system is modified to include MOV-protected series capacitor and the equivalent wind farm model. The modified test system is simulated in the MATLAB/Simulink environment. The study has been achieved considering three phase and single line to ground (SLG) faults on the series compensated line to show the effect of wind variation on the MOV operation. This thesis proposes an adaptive setting method for the mho relay distance protection of series compensated line considering effects of wind power variation and MOV operation. The distributed parameters of a transmission line are taken into account to avoid overreaching and underreaching of distance relays. The study shows that variable wind power affects system power flow and fault current in the compensated line during a fault which affects the operation of MOVs for different fault conditions. The equivalent per-phase impedance of the MOV/capacitor circuit has an effect on the system operation and line protection. Distance protection study is also performed with variable wind power, different line compensation levels, and other system conditions. Results show that variable wind power affects apparent impedance calculation of distance relay through the variable equivalent MOV/capacitor impedance. Underreaching and overreaching issues of the distance relay are discussed. Based on the results, a variable distance relay setting is proposed to mitigate the negative impact. Both fixed and variable distance relay settings are presented and compared to each other. The results demonstrate the ability of the proposed adaptive setting method to resetting the distance relays to adapt to various system conditions, including three wind generation and different compensation levels

Validation of multi-machine and single-machine equivalent models for wind farm transient stability studies

Stability study of power system with wind farm is challenging task due to collection of system data, computation burden in case of system order and long simulation time. An aggregated representation of fixed speed wind turbine generator (WTG) is proposed for an actual wind farm which is a part of the Indian utility system. The stability study of actual system and equivalent system are simulated in MATLAB software package. Multi-machine and single-machine equivalent wind farm models are developed based on simple aggregation technique. The transient stability responses of these two equivalent wind farm models that are compared with actual wind farm system at point of common coupling (PCC). The two equivalent wind farm models response provides a satisfactory accuracy with actual system response for the three phase fault and varying wind speed. Also equivalent wind farm model responses are validated with actual system response for different dynamic conditions.Â

Feasibility Study of Raw Material for Hybrid Power Plant in Coastal Cilacap Selatan

Cilacap Regency is a coastal area south of the island of Java. The purpose of this study is to determine the potential of raw materials available in the South Cilacap Coastal area and to determine the potential power that can be generated for the PLTH system through the calculation of the raw material data that has been obtained. This research method begins with direct measurements of wind speed and light intensity. Both devices read data in real time and connect online. The data obtained is processed to determine the wind speed and the average intensity of sunlight. The results of these calculations are entered into the equations to calculate the potential power that can be generated. Based on the calculation, the average wind speed is 3-4 m/s and the light intensity is 54612 watt/m2. The results of the calculation of the potential power that can be generated from the PLTB system in the coastal area of ​​South Cilacap is equivalent to 508 watts/day. The potential power that can be generated from PLTS is 10.8 kW/day. The total potential power that can be generated from the PLTH system on the coast of South Cilacap is equivalent to 273.22 kWh/day.Cilacap Regency is a coastal area south of the island of Java. The purpose of this study is to determine the potential of raw materials available in the South Cilacap Coastal area and to determine the potential power that can be generated for the PLTH system through the calculation of the raw material data that has been obtained. This research method begins with direct measurements of wind speed and light intensity. Both devices read data in real time and connect online. The data obtained is processed to determine the wind speed and the average intensity of sunlight. The results of these calculations are entered into the equations to calculate the potential power that can be generated. Based on the calculation, the average wind speed is 3-4 m/s and the light intensity is 54612 watt/m2. The results of the calculation of the potential power that can be generated from the PLTB system in the coastal area of ​​South Cilacap is equivalent to 508 watts/day. The potential power that can be generated from PLTS is 10.8 kW/day. The total potential power that can be generated from the PLTH system on the coast of South Cilacap is equivalent to 273.22 kWh/day

Dynamic Modeling of Wind Farms with Fixed-Speed Wind Turbine Generators

A wind farm typically consists of a large number of individual wind turbine generators (WTGs) connected by an internal electrical network. To study the impact of wind farms on the dynamics of the power system, an important issue is to develop appropriate wind farm models to represent the dynamics of many individual WTGs. This paper presents various dynamic models, including a detailed model and three reduced-order equivalent models, of wind farms with fixed-speed WTGs. These models are developed and compared by simulation studies in the PSCAD/EMTDC environment under different wind velocity and fluctuation conditions as well as gird fault conditions. Concluding remarks are provided on how to choose an appropriate wind farm model for power system dynamic and transient studies

Wind Development in Minnesota: Policy and Economics

The growth of wind power as an aspect of Minnesota’s portfolio of electricity has been propelled to its current level by policy initiatives at both the federal and state levels. Existing statutes establish requirements for further expansion of wind energy in this state in the years to come. Locally, production economics exert their influence as wind speed and duration are translated to capacity factor, which reveals the amount of power that can be generated at a particular site. After the flow resource is thus quantified, comes the calculus of economic viability. This consists of determining the capital and operating costs and eligibility for loans and grants as well as the negotiations of wind rights, easements, and power purchase agreements. To date, policy initiatives have been directed toward the production, or generation side of this variable flow resource. Entrepreneurs and lawyers have become more skillful at organizing business forms that can effectively bring together partners capable of utilizing the substantial tax benefits available through the federal Production Tax Credit (PTC) as well as attractive state-sponsored incentives and tariffs offered by utilities. The variable nature of electrical power capacity from wind has been problematic for utilities, which try to meet the variable loads required by the summed demand of their customers. In Minnesota, peak power demands occur in summer months when wind power is the lowest. In addition to seasonal demands, daily and weekly patterns must be accommodated by utilities serving the markets for electricity. By developing and using an investment model, it is possible to understand investor motivations driving the growth of wind energy in this state and the country. Net present values (NPV) and internal rates of return (IRR) are calculated over the life of power production projects conforming to various conditions such as wind capacity factor, the federal Production Tax Credit (PTC), state incentive plans for community-based energy providers, federal grant and loan programs, as well as emerging opportunities to sell “green tags” for renewable power generation. The numerous incentives provided for windpower development on the generation side highlight the difficulties of providing sufficient transmission capacity for to carry this power from the often remote areas where generated to load centers. Equivalent incentives deployed with similar imagination are needed to enhance investment in a transmission system capable of carrying increasing volumes of wind and other renewable sources of electricity.Resource /Energy Economics and Policy,

Implications of the North Atlantic Oscillation for a UK–Norway renewable power system

UK wind-power capacity is increasing and new transmission links are proposed with Norway, where hydropower dominates the electricity mix. Weather affects both these renewable resources and the demand for electricity. The dominant large-scale pattern of Euro-Atlantic atmospheric variability is the North Atlantic Oscillation (NAO), associated with positive correlations in wind, temperature and precipitation over northern Europe. The NAO's effect on wind-power and demand in the UK and Norway is examined, focussing on March when Norwegian hydropower reserves are low and the combined power system might be most susceptible to atmospheric variations. The NCEP/NCAR meteorological reanalysis dataset (1948–2010) is used to drive simple models for demand and wind-power, and ‘demand-net-wind’ (DNW) is estimated for positive, neutral and negative NAO states. Cold, calm conditions in NAO− cause increased demand and decreased wind-power compared to other NAO states. Under a 2020 wind-power capacity scenario, the increase in DNW in NAO− relative to NAO neutral is equivalent to nearly 25% of the present-day average rate of March Norwegian hydropower usage. As the NAO varies on long timescales (months to decades), and there is potentially some skill in monthly predictions, we argue that it is important to understand its impact on European power systems

A Wide Area Hierarchical Voltage Control for Systems with High Wind Penetration and an HVDC Overlay

The modern power grid is undergoing a dramatic revolution. On the generation side, renewable resources are replacing fossil fuel in powering the system. On the transmission side, an AC-DC hybrid network has become increasingly popular to help reduce the transportation cost of electricity. Wind power, as one of the environmental friendly renewable resources, has taken a larger and larger share of the generation market. Due to the remote locations of wind plants, an HVDC overlay turns out to be attractive for transporting wind energy due to its superiority in long distance transmission of electricity. While reducing environmental concern, the increasing utilization of wind energy forces the power system to operate under a tighter operating margin. The limited reactive capability of wind turbines is insufficient to provide adequate voltage support under stressed system conditions. Moreover, the volatility of wind further aggravates the problem as it brings uncertainty to the available reactive resources and can cause undesirable voltage behavior in the system. The power electronics of the HVDC overlay may also destabilize the gird under abnormal voltage conditions. Such limitations of wind generation have undermined system security and made the power grid more vulnerable to disturbances. This dissertation proposes a Hierarchical Voltage Control (HVC) methodology to optimize the reactive reserve of a power system with high levels of wind penetration. The proposed control architecture consists of three layers. A tertiary Optimal Power Flow computes references for pilot bus voltages. Secondary voltage scheduling adjusts primary control variables to achieve the desired set points. The three levels of the proposed HVC scheme coordinate to optimize the voltage profile of the system and enhance system security. The proposed HVC is tested on an equivalent Western Electricity Coordinated Council (WECC) system modified by a multi-terminal HVDC overlay. The effectiveness of the proposed HVC is validated under a wide range of operating conditions. The capability to manage a future AC/DC hybrid network is studied to allow even higher levels of wind

Capacity credits of wind and solar generation: The Spanish case

This paper analyses the capacity credits (CCs) of renewable photovoltaic (PV), concentrated solar power (CSP) and wind technologies in the Spanish power system. This system has steadily increased the share of renewables, reaching a penetration level of over 30%. The predictions made by ENTSO-e suggest that this level will increase to 50% by 2030. Therefore, different scenarios are studied in this paper to investigate the evolution of renewable integration and assess the corresponding contributions to reliability. The assessment is performed using a sequential Monte Carlo (SMC) method considering the seasonality of renewable generation and the uncertainties related to renewable sources, failure issues and the maintenance of thermal-based units. The baseline for SMC is provided by historical annual time series of irradiance and wind power data from the Spanish system. In the solar case, these time series are transformed into power time series with models of CSP and PV generation. The former includes different thermal storage strategies. For wind generation, a moving block bootstrap (MBB) technique is used to generate new wind power time series. The CC is assessed based on the equivalent firm capacity (EFC) using standard reliability metrics, namely, the loss of load expectation (LOLE). The results highlight the low contribution of renewables to power system adequacy when the Spanish power system has a high share of renewable generation. In addition, the results are compared with those of similar studies.This work was supported by the University Carlos III of Madrid under project Feasibility of power systems with renewables (2009/00416/002