Load Shedding Program Research Articles

Water-energy nexus in a desalination-based water sector: the impact of electricity load shedding programs

Reliance on water production by desalination as a solution to water scarcity is growing worldwide. High energy demands of seawater desalination raise new challenges for both water and energy management and highlight the importance of understanding the operational dependencies of the water sector on energy supplies. This study provides an in-depth analysis of the impact of the water-energy nexus in a desalination-based water sector, using Israel as a case study. Being large energy consumers, desalination plants are part of the Electricity Load Shedding Program (ELSP), which government energy regulators invoke in times of energy shortage. We focus on the interdependency between the two sectors as manifested at the time of ELSP utilization during an extreme heat wave. We show that energy shedding compensation is 6 to 14 times greater than the economic loss to the desalination plant from no water production, creating an obvious economic incentive to participate in ELSPs. However, this imbalance has a substantial negative impact on the water sector, which may compromise the level of service. Our evaluation concludes that the government authorities regulating water and energy need an official mechanism and policy for joint management strategies that can ensure economic efficiency and reduce the risk of power and water shortages during extreme events.

Design of Protection Relay Coordination Settings and Connecting to PLC Siemens S7-1500 For Load Shadding and HMI Display at PT. Semen Padang

There are some vital loads and must not extinguished on the production activities of PT. Semen Padang cause the operational costs to rerun are very large. To solve this problem, it is necessary to evaluate the coordination settings of protection relays and automatic control systems to supporting the production process of PT. Semen Padang so production efficiency can be maintained. The relay settings to be evaluated are inverse time and instantaneous overcurrent relays by coordinating the main relay, backup relay 1 and backup relay 2 from downstream to upstream load feeder. The designed control system is an automatic load shedding and HMI display that can visualizing the system in realtime using the PLC Siemens S7-1500 with simulating on the PLCSimulator of the TIA Portal 15.1 software. Based on the calculations carried out, there are significant differences in the relay settings from the calculation results with the existing state. the relays installed in the system do not coordinate properly in the existing state, while after the calculation of the coordination relays the relays coordinate well. From the design of the control system, an automatic load shedding program and the display of the HMI system in real time were produced.

Combinational load shedding using load frequency control and voltage stability indicator

This paper proposes a load shedding program for evaluating and distributing the minimum load power to be curtailed required to bring the frequency and voltage, after the system was subjected to a heavy disturbance, to the allowable range for each load bus. The quantity of load shedding was estimated to restore the power system's frequency, taking into account the turbine governor's primary control and the generators' reserve power for secondary control. Calculation and review of the load bus's voltage stability indicator (Li) to prioritize the load shedding quantity at these locations. The lower the voltage stability indicator on the load bus, the less load shedding can occur, and vice versa. The frequency and voltage values are still within allowable ranges with this approach, and a significant amount of load shedding can be prevented, resulting in a reduction in customer service interruption. The proposed method's efficacy was demonstrated when it was checked against the IEEE 30 bus 6 generators power system standard simulated in MATLAB environment and it minimize the power to be shed by around 20% of the conventional load shedding schemes.

Energy Monitoring and Control Using New Linearized Power Flow Technique.(Dept.E)

The paper presents a proposed technique with linearized formula for computing the transmission line power flow in terms of injected power due to any change in power system loading conditions. The formula relates the line power flows to both loads and power generation directly for a transmission network configuration. Being in an integral form, new power flows on the lines can be obtained directly without running a complete load flow programs when the total system generation changes. This formula is a fairly general one as it is suitable for various energy monitoring and control applications such as generation shifts to alleviate the line overloads, the generation redispatch for an incremental change in loading conditions and the on-line load shedding programs as well as the fast contingency analysis.

Alternative operating modes to reduce the load shedding in the power system of El Hierro Island

The activation of the load shedding programs in the six isolated power systems belonging to Canary Archipelago has not been uncommon in last years. These power systems have been increasing the penetration of renewable power generation technologies, which are mainly decoupled from the grid through a power electronic converter and not being able to respond naturally to frequency drops. Common Under Frequency Load Shedding programs are activated when a relevant incident, as the outage of a generation unit, takes place. This work analyses the benefits of alternative control strategies in one of the Canary Islands (El Hierro island) in terms of reducing the need of load shedding activation. These control strategies are the variable speed wind turbines inertial contribution to frequency regulation and the use of Pelton turbines as synchronous condensers. Both strategies do not involve a significant loss in the efficiency or in the available wind energy. Additionally, the participation of variable speed pumps in the frequency regulation, control strategy recently adopted in El Hierro power system, has been included in the analysis. To achieve these objectives, a complete dynamic mathematical model of this power system has been delivered. Representative generation schedules that fulfil several real combinations of wind generation and load were generated and used to carry out the study. The results obtained show the effectiveness of the alternatives control strategies proposed. The amount of load to be shed is reduced or even avoided in many scenarios, but the three alternative control strategies present their own particularities.

Reliability assessment of composite power systems containing sea wave slot‐coned generators

The generated power of the Sea-wave slot-coned generator (SSG), as one of the high capacity wave energy converters, is dependent on the period and height of the waves. The generated power of this energy-converter changes due to the variation in these parameters. Thus, different aspects of the power systems may be affected that must be investigated by increasing the share of these converters for electricity production in the power-systems. In this paper reliability assessment of composite power-systems containing large-scale SSG is performed. The Xie and Beni (XB) index is calculated for obtaining the optimum number of states in the reliability model of the SSG and fuzzy c-means clustering technique is proposed for reducing the number of states of the model. The contingency analysis method is proposed for calculating the reliability indices of the composite power-system incorporating large-scale SSG. DC load-flow method, which considers line capacity, is used to perform load-flow in the composite power-system including generation and transmission networks. In the proposed technique, a load-shedding program with the goal of minimizing the value of lost load is solved using of the linear programming method based on the interior-point-approach for contingency states leading to the load curtailment.

An Adaptive Control Scheme for Variable Speed Wind Turbines Providing Frequency Regulation in Isolated Power Systems with Thermal Generation

The lack of synchronous inertia, associated with the relevant penetration of variable speed wind turbines (VSWTs) into isolated power systems, has increased their vulnerability to strong frequency deviations. In fact, the activation of load shedding schemes is a common practice when an incident occurs, i.e., the outage of a conventional unit. Under this framework, wind power plants should actively contribute to frequency stability and grid reliability. However, the contribution of VSWTs to frequency regulation involves several drawbacks related to their efficiency and equipment wear due to electrical power requirements, rotational speed changes, and subsequently, shaft torque oscillations. As a result, wind energy producers are not usually willing to offer such frequency regulation. In this paper, a new control technique is proposed to optimize the frequency response of wind power plants after a power imbalanced situation. The proposed frequency controller depends on different power system parameters through a linear regression to determine the contribution of wind power plants for each imbalance condition. As a consequence, VSWTs frequency contribution is estimated to minimize their mechanical and electrical efforts, thus reducing their equipment wear. A group of sixty supply-side and imbalance scenarios are simulated and analyzed. Results of the case study are compared to previous proposals. The proposed adaptive control reduces the maximum torque and rotational speed variations while at the same time maintaining similar values of the load shedding program. Extensive results and discussion are included in the paper.

Towards an enhanced power system sustainability: An MILP under-frequency load shedding scheme considering demand response resources

Renewable energy sources (RESs) in the power system have led to the continuation of electricity supply to the consumer and to the sustainable development of the society. Due to the increased penetration of RESs, the uncertainties of electrical energy systems have been intensified, and smart power system operators are thus faced with growing levels of frequency security risks. For preservation of frequency in a power system, a multi-stage automated Under-Frequency Load Shedding (UFLS) program can be utilized to shed the minimum amount of load. In the light of the smart grid paradigm, Demand Response (DR) can be considered as an appropriate strategy to face the adverse effects of the uncertainties of the RESs and increase the balance between generation and consumption. Consequently, it is regarded as a necessity in a smart grid environment to design an innovative UFLS scheme that includes the uncertainties of the RESs and DR programs. This paper addressed a new optimal UFLS intended to minimize load shedding, after accurate tracking of frequency deviations. To resolve the problem of setting UFLS system parameters stochastically, a Mixed-Integer Linear Programming (MILP) formulation is used in an optimization framework. The proposed model is implemented on the IEEE 39-bus test system.

Biomass Power Generation Potential and Utlization in Pakistan

Pakistan is experiencing the worst power shortage since 2007 ranging from 5000 to 7000 MW. This has led to introduction of load shedding program which has caused economic loss @7% to the GDP. The indigenous oil reserves are poor and every year crude oil and petroleum products costing US$ 15.473 billion are imported. The potential of biomass energy is excellent, and Pakistan may generate 38000 GWh electricity annually using 25% crops residue and 50% animal waste. Except for Punjab province survey of crops biomass needs to be conducted to estimate the biomass resource potential in the country. Based upon the data, the size of power plants can be determined, and site of plants can be decided. Very few power plants have been installed by local industry under captive mode and their experience is encouraging. The indigenous capacity building for installation and operation of bio-mass based power plants are required. This paper reviews the power shortage and its implications on economy of Pakistan. It also describes the biomass technologies, resource base and power generation potential along with utilization status in Pakistan. It also discusses possible role of biomass power in mitigating the energy crisis especially in the rural areas. Using only 20-25% of the estimated crops waste of major crops and 50% of animal’s waste Pakistan can generate more than 36,000 GWh equivalent to 45% of the electricity consumption per annum. The crops residue alone can produce 11953 MW (31%) of the power potential with 25% of the available crops residue.

A new load forecasting model considering planned load shedding effect

PurposeLoad forecasting is important to any electrical grid, but for the developing and third-world countries with power shortages, load forecasting is essential. When planed load shedding programs are implemented to face power shortage, a noticeable distortion to the load curves will happen, and this will make the load forecasting more difficult.Design/methodology/approachIn this paper, a new load forecasting model is developed that can detect the effect of planned load shedding on the power consumption and estimate the load curve behavior without the shedding and with different shedding programs. A neuro-Fuzzy technique is used for the model, which is trained and tested with real data taken from one of the 11 KV feeders in Najaf city in Iraq to forecast the load for two days ahead for the four seasons. Load, temperature, time of the day and load shedding schedule for one month before are the input parameters for the training, and the load forecasting data for two days are estimated by the model.FindingsTo verify the model, the load is forecasted without shedding by the proposed model and compared to real data without shedding and the difference is acceptable.Originality/valueThe proposed model provides acceptable forecasting with the load shedding effect available and better than other models. The proposed model provides expected behavior of load with different shedding programs an issue helps to select the appropriate shedding program. The proposed model is useful to estimate the real demands by assuming load shedding hours to be zero and forecast the load. This is important in places suffer from grid problems and cannot supply full loads to calculate the peak demands as the case in Iraq.

Boundary Detection and Enhancement Strategy for Power System Bus Bar Stabilization—Investigation under Fault Conditions for Islanding Operation

Distribution systems can form islands when faults occur. Each island represents a subsection with variable boundaries subject to the location of fault(s) in the system. A subsection with variable boundaries is referred to as an island in this paper. For operation in autonomous mode, it is imperative to detect the island configurations and stabilize these subsections. This paper presents a novel scheme for the detection of island boundaries and stabilizing the system during autonomous operation. In the first stage, a boundary detection method is proposed to detect the configuration of the island. In the second stage, a dynamic voltage sensitivity factor (DVSF) is proposed to assess the dynamic performance of the system. In the third stage, a wide area load shedding program is adopted based on DVSF to shed the load in weak bus-bars and stabilize the system. The proposed scheme is validated and tested on a generic 18-bus system using a combination of EMTDC/PSCAD and MATLAB software’s.

A new demand response algorithm for solar PV intermittency management

This paper presents a new algorithm for managing solar PV intermittency in green buildings using demand response management (DRM) technique. The proposed DRM algorithm utilizes the building air conditioning and mechanical ventilation (ACMV) system to dynamically compensate for the deficit of power generated by solar PV system from its rated capacity. For example, the developed solution will reduce the load demand of the ACMV system equal to the drop of solar generation by controlling the speed of the fan. This will ensure that the amount of power supplied by the grid to the building will remain the same (as before the drop of solar generation) and thus no impact on the grid stability. However, since ACMV system is directly linked to building occupant comfort/health, the proposed solution will also include energy storage management and priority-based load shedding programs to provide support when room temperature (air conditioning) or CO level (ventilation) is above regulatory limit. A thermal model for building temperature variation is developed to test and analyze the proposed algorithm to dynamically manage solar PV fluctuation.

Overcoming Solar PV Intermittency using Demand Response Management in Buildings

Singapore’s National Climate Change Policy is aimed to make energy usage in Singapore more efficient, reduce pollution and expand the nation’s green spaces. Part of the plan is to promote the integration of solar photovoltaics (PVs) on rooftops of high-rise HDB residential and commercial buildings. This initiative contributed to the significant growth in the integration of solar PV systems in the last few years. However, large-scale integration of solar PVs will put at risk the reliability and stability of Singapore’s power system due to its intermittent nature. The intermittency problem of solar PV, typically in the range of minutes, will become very significant in Singapore as the installations of PV systems continue to increase. Conventionally, large energy storage systems are deployed as an energy buffer to compensate for the deficit or surplus of power supplied by solar PV systems. However, the high capital and maintenance costs as well as large space requirement for energy storage systems makes this an unfavorable option for building owners. This paper proposes a solution that utilizes the centrifugal fans in building air conditioning and mechanical ventilation (ACMV) system to dynamically compensate for the deficit or surplus of power supplied by solar PVs. For example, the developed solution will reduce the load demand of fans in the ACMV system equal to the drop of solar generation by controlling the speed of the fan. This will ensure that the amount of power supplied by the grid to the building will remain the same (as before the drop of solar generation) and thus no impact on the grid stability. However, since ACMV system is directly linked to building occupant comfort/health, the proposed solution will also include battery management and priority-based load shedding programs to provide support when room temperature (air conditioning) or CO level (ventilation) is above regulatory limit.

Optimal island partitioning of smart distribution systems to improve system restoration under emergency conditions

In the case of emergency operation, intentional islanding of distributed generations is an interesting solution to maintain the reliable power supply in the smart distribution grid. This paper deals with an optimal systematic strategy to restore the post-contingency distribution grid after the occurrence of severe disturbances causing an outage. Hence, a two-stage solution procedure is developed in this paper. In the first step, the optimal partitioning scheme is addressed through a number of graph-theory related algorithms. By applying these algorithms, the loads are optimally assigned to the distributed generations and optimal load shedding programs are determined and performed if there is a shortage of generation. The second step deals with the adjustments issues. In fact, the preliminarily partitions achieved from the first stage should be checked for feasibility. Also, these partitions should be adjusted if it is necessary in order to satisfy the system related constraints. To this purpose OPF calculation is incorporated and optimal load management measures are taken to mitigate violations considering the voltage constraints, line capacities and controllable loads. Since the proposed method considers the key factors of load priorities, load controllability, power balance, voltage and line capacity constraints, it covers the requirements of practical applications. Numerical results from the PG&E-69 test system are used to verify the effectiveness of the proposed method. The comparison with previous methods demonstrates that the proposed method outperforms other techniques.

AN IMPROVED LOAD SHEDDING SCHEDULING STRATEGY FOR SOLVING POWER SUPPLY DEFISIT

When high electricity demand growth not matched by the growth in generating capacity, energy deficit problem cannot be avoided. Power outages of up to 6 hours per day are part of the power crisis experienced by electricity consumers in Sumatra. The utility has applied load shedding approach to tackle the problem, however, there are weaknesses on the current load shedding program. It is discovered that most of the power outage occurs randomly without any prior notice and sometime lasted for many hours. Load shedding program is not properly scheduled and not fairly distributed among all consumers. A proper scheduling program must have a clear periodic schedule, fixed outage hours, fairly distributed and alternated among consumers and most importantly solve energy deficit problem. This paper presented an improved load shedding scheduling strategy based on Round Robin method. The method is then illustrated and applied on actual daily load profile of Sumatra electrical system.

A Smart Quota System for Rationing Power in African Developing Countries

Electrical energy (electricity) has become an indispensable asset in building sustainable economies and reducing poverty. For such reasons many countries have embarked on various electrification projects, from urban areas to rural areas. However, these projects would not achieve the earlier stated objectives where there is unreliable supply of electric power. Most developing countries especially in Africa are often plagued with power crises. These crises are often as a result of energy constraints and/or generation capacity constraints. Various energy efficiency/demand side management schemes have been implemented to properly ration power. These schemes range from rotational load shedding programs to energy quota systems, with the latter presenting more advantages than the former. Energy quota systems were first known to be only effective in rationing power in energyconstrained environments. However, the advent of smart metering technology has also proved this scheme also effective in capacity-constrained environments. Despite the many advantages of this scheme over rotational load shedding programs, most developing countries in Africa such as Ghana and Nigeria, still use the latter as the only means of rationing power. In this paper, the advantages of energy quota systems over load shedding programs are brought to light, international best practices of this scheme are also discussed and we propose a model energy quota system using smart energy meters. Additionally we propose a design aimed at retrofitting existing (non-smart) meters and converting them into smart meters for developing countries in Africa. The proposed model does not require the replacement of old standalone energy meters.

Load Shedding: A New Proposal

During overloads in the mains, the load curtailment applied to interruptible loads is often the only solution to keep the network in operation. Normally, in contingencies, the difference between the power absorbed and the power produced is very low, often less than 1% of the latter. Therefore if all the loads participated in the load shedding program, the discomfort would be minimal, considering its usually short duration. According to this point of view, we present a new approach to the load shedding program to guarantee the correct electrical system operation by increasing the number of participants. This new load control strategy is named Distributed Interruptible Load Shedding (DILS). Indeed, it is possible to split every user's load into interruptible and uninterruptible parts, and to operate on the interruptible part only. The optimal load reduction request is found by minimizing the expected value of an appropriate cost function, thus taking the uncertainty about the power absorbed by each customer into account. Presently, several users such as hospitals, data centres, supermarkets, universities, industries, etc. might be very interested in typical shedding programs as a way to spare money in their electrical account. However, in the future, when the domotic power plants are likely to be used widely, the distributors could interest the end users in participating in DILS programs for either economic or social reasons. By adopting the DILS program, the distributors can resort to the interruptible loads not only in case of emergency conditions but also during normal and alert operations.

Concepts of undervoltage load shedding for voltage stability

Undervoltage load shedding is an economical solution (or partial solution) to the voltage stability challenges facing electric utilities. Simulations for an equivalent system and for large-scale representation of the Puget Sound (Seattle) area of the Pacific northwest led to several concepts for an undervoltage load-shedding program. Application factors such as undervoltage relay settings and time delay are discussed. Pacific northwest utilities are implementing undervoltage load shedding for the 1991-2 winter operation period. >

Computer Control of Irrigation for Electrical Load Management

ABSTRACT MANY electrical power suppliers have initiated load shedding programs to reduce the operating load on the transmission and delivery system during periods of peak demand. Typically, these programs result in irrigation pump shutoff on a predetermined rotational schedule. A computerized radio telemetry system was developed which automatically determines the soil water status of the field served by each pump based on climatic data, sets priorities for load interruption based on soil water status, and stops pumps upon receipt of a signal from the power supplier. The system also provides for remote control of pumps and monitoring of their operational status.

The Challenge to State Regulation Agencies: The Experience of New York State

The Constitution and the nature of the energy market require the federal government to take the lead in resolving this nation's fuel supply problems; however, there is much that the states can do to help resolve the energy crisis. The New York State Public Service Commission (PSC) has established restrictions on gas use and a load shedding program. New York's recent pioneering legislation for one-stop siting of major power plants and transmission lines should help ensure the construction of needed power facilities which are located and designed for minimum adverse environmental impact. The PSC and other agencies in New York are helping the promotion of energy conserva tion and energy efficiency not only in the conversion of fuels to electric power, but also through improved building design, appliances and transportation. Finally, New York is promoting increased research and development which has been undertaken by the utilities, the federal government and the state, itself. State and federal energy programs will require new interdisciplinary approaches which transcend traditional regulatory processes to achieve the needed balance of our energy, environmental, economic, security and other significant social objectives.