Perform Load Shedding Research Articles

A Data-Driven Method for Power System Emergency Control to Improve Short-Term Voltage Stability

The power system contains a variety of uncertainties of different types of sources and loads, as well as random contingencies. Under these uncertainties and rapidly changing operating conditions, traditional rule-based methods cannot dynamically handle short-term voltage instability. To alleviate this situation, this paper proposes a novel power system emergency control scheme using a data-driven method, which combines edge-conditioned graph convolutional networks and deep reinforcement learning. The edge-conditioned graph convolutional network is utilized to extract the characteristics from not only power system nodes but also transmission lines. Deep reinforcement learning is introduced to perform load shedding actions, so as to guarantee the safety and stability of the electric power system. The IEEE 39-bus network is utilized for simulations to validate the effectiveness of the proposed data-driven method. The outcomes demonstrate the proposed method can generate a superior strategy in a number of the short-term voltage instability(STVI) circumstances.

Smart-UPS with a priority-based load management system

In this paper, a cost-effective Smart-UPS has been developed which will perform load shedding on a priority basis. This smart UPS will include an accessory installed along with the conventional UPS. This paper relates to the field of managing power distribution. In particular, it pertains to a system and method for power distribution among devices, based on priority. The objective of the present disclosure is to efficient supply to distribute power among requirement of devices, to provide cost efficient power management and to enhance output of the devices with limited power back up.The designed project will switch off lower priority loads according to Battery percentage to minimize the load suffered by the battery. The loads connected to supply load are divided into three sections, i.e. high priority (HP), medium priority (MP) and low priority (LP) loads. The project involves the development of a smart UPS system which will automatically switch off/on the high priority (HP) loads, medium priority (MP) and low priority (LP) loads (specified during installation of the UPS as specified by the user).

State-Aware Load Shedding From Input Event Streams in Complex Event Processing

In complex event processing (CEP), load shedding is performed to maintain a given latency bound during overload situations when there is a limitation on resources. However, shedding load implies degradation in the quality of results (QoR). Therefore, it is crucial to perform load shedding in a way that has the lowest impact on QoR. Researchers, in the CEP domain, propose to drop either events or partial matches (PMs) in overload cases. They assign utilities to events or PMs by considering either the importance of events or the importance of PMs but not both together. In this article, we combine these approaches where we propose to assign a utility to an event by considering both the event importance and the importance of PMs. We propose two load shedding approaches for CEP systems. The first approach drops events from PMs, while the second approach drops events from windows. We adopt a probabilistic model that uses the type and position of an event in a window and the state of a PM to assign a utility to an event. We, also, propose an approach to predict a utility threshold that is used to drop the required amount of events to maintain a given latency bound. By extensive evaluations on two real-world datasets and several representative queries, we show that, in the majority of cases, our load shedding approach outperforms state-of-the-art load shedding approaches, w.r.t. QoR.

Smart Distribution Boards (Smart DB), Non-Intrusive Load Monitoring (NILM) for Load Device Appliance Signature Identification and Smart Sockets for Grid Demand Management.

Traditionally, the choices to balance the grid and meet its peaking power needs are by installing more spinning reserves or perform load shedding when it becomes too much. This problem becomes worse as more intermittent renewable energy resources are installed, forming a substantial amount of total capacity. Advancements in Energy Storage System (ESS) provides the utility new ways to balance the grid and to meet its peak demand by storing un-used off peak energy for peak usage. Large sized ESS—mega watt (MW) level—are installed by different utilities at their substations to provide the high speed grid stabilization to balance the grid to avoid installing more capacity or triggering any current load shedding schemes. However, such large sized ESS systems and their required inverters are costly to install, require much space and their efficacy could also be limited due to network fault current limits and impedances. In this paper, we propose a novel approach and trial for 3000+ homes in Singapore of achieving a large capacity of demand management by developing a smart distribution board (DB) in each home with the high speed metering sensors (>6 kHz sampling rate) and non-intrusive load monitoring (NILM) algorithm, that can assist home users to perform the load/appliance profile identification with daily usage patterns and allow targeted load interruption using the smart sockets/plugs provided. By allowing load shedding at device or appliance level, while knowing their usage profile and preferences, this can allow such an approach to become part of a new voluntary interruptible load management system (ILMS) that requires little user intervention, while minimizing disruption to them, allowing ease of mass participation and thus achieving the intended MW demand management capacities for the grid. This allows for a more cost effective way to better balance the grid without the need for generation capacity growth, large ESS investment while improving the way to perform load shedding without disruptions to entire districts. Simply, home users can now know and participate with the grid in interruptible load (IL) schemes to target specific home appliance, such as water heaters or air conditioning, allowing interruptions during certain times of the day, instead of the entire house, albeit with the right incentives. This allows utilities to achieve MW capacity load shedding with millions of appliances with their preferences, and most importantly, with minimal disruptions to their consumers quality of life. In our paper, we will also consider coupling a small sized Home Energy Storage System (HESS) to amplify the demand management capacity. The proposed approach does not require any infrastructure or wiring changes and is highly scalable. Simulation results demonstrate the effectiveness of the NILM algorithm and achieving high capacity grid demand management. This approach of taking user preferences for appliance level load shedding was developed from the results of a survey of 500 households that indicates >95% participation if they were able to control their choices, possibly allowing this design to be the most successful demand management program than any large ESS solution for the utility. The proposed system has the ability to operate in centralized as part of a larger Energy Management System (EMS) Supervisory Control And Data Acquisition (SCADA) that decide what to dispatch as well as in autonomous modes making it simpler to manage than any MW level large ESS setup. With the availability of high-speed sampling at the DB level, it can rely on EMS SCADA dispatch or when disconnected, rely on the decaying of the grid frequency measured at the metering point in the Smart DB. Our simulation results demonstrate the effectiveness of our proposed approach for fast grid balancing.

Two-Stage Load Shedding for Secondary Control in Hierarchical Operation of Islanded Microgrids

A two-stage load shedding scheme is presented to cope with potential power deficits caused by microgrid islanding. Coordinated with the fast response of inverter-based grid-forming distributed energy resources, the proposed approach estimates the load shedding at each stage and the resulting power flow redistribution. The first stage of load shedding will cease any rapid frequency decline in which the locally measured frequency deviation is employed to guide the load shedding level and process. Once a new steady state is reached at the end of first stage, the second stage is activated, which performs load shedding according to load priorities. The effectiveness of the proposed scheme is verified through time-domain simulations in PSCAD/EMTDC based on a scaled-down microgrid system.

Load Shedding Analysis Because of Contingency Damage (N-2) at Transmission Lines 150 kV Subsystem Cirata

Cirata subsystem is part of the 150 kV interconnection system 150 kV West Java which is supplied by two units of IBT 500/150 kV with a power capacity of each IBT is 500 MVA. It has 15 transmission line connecting the substation 13 (GI), while the generation units that exist in the subsystem Cirata is PLTP Patuha with a power of 55 MW and 180 MW hydropower Jatiluhur. The reliability of the power system must be maintained in order to supply power from the generator to the consumer to keep going well. At peak load conditions and contingencies, an electric power system will undergo changes in value, both current and voltage. In this study, which analyzed disorder is a contingency (N-2), a discharge of the two components of transmission line system and generator. The aim is to evaluate and improve the reliability of electric power systems of 150 kV Subsystem Cirata, analyzing the effects of disturbance contingency (N-2) to changes in current and voltage, identify the bus voltage is outside the operating limits, identifying the transmission line that experienced the imposition of critical / exceeds limit operation, and perform load shedding (load sheeding) to overcome the weaknesses of the power system due to disruption contingency N-2. The study was conducted by collecting data required for power flow simulation using Newton-Raphson method in ETAP 12.6.0. The simulation results show the power flow interruption due to voltage profile under the standard contingency SPLN 150 kV + 5% and -10%, and becomes critical channel loading over 50% of the nominal current conductor. While after the release of the load (load sheeding) voltage profile in Subsystem Cirata back normal or standardized SPLN and loading the channel becomes lighter.

Методика выбора параметров противоаварийных команд на отключение потребителей в сетях 0,4 кВ

Conventionally, when accidents entailing active power imbalance occur in a power system, the underfrequency load shedding devices disconnect the necessary and sufficient amount of loads at the 10 kV voltage level. These load shedding operations are carried out without the possibility of taking into account the importance of certain consumers at the 0.4 kV voltage level. What is more, in view of using loads highly sensitive to power supply continuity, recent years have seen more stringent requirements being imposed on the reliability of their power supply. On the other hand, the availability of new computerized facilities opens the possibility of improving the reliability of supplying power to them even in the emergency load limitation mode. Specifically, this can be achieved by integrating the existing relay protection and automatic control systems with the automated electricity consumption monitoring and control system in such a way that consumers at the 0.4 kV level are selectively disconnected by commands of the underfrequency shedding control devices installed at the 10 kV voltage level. The article considers issues concerned with elaborating a procedure for selecting the values of the information parameter specifying the duration of command signals for disconnecting 0.4 kV loads produced by the automatic underfrequency load shedding devices at the 10 kV voltage level. It is proposed to perform load shedding operations by using a new method developed at the Moscow Power Engineering Institute National Research University. According to the proposed method, loads operating at the 0.4 kV voltage level are selectively disconnected through artificially creating a voltage sag (interruption) and using it as the underfrequency shedding command signal for disconnecting less critical loads. The article presents the principle of tuning-out from possible events and phenomena in the power supply network internal and external parts taking into account the existing setpoints of the relay protection and automatic control devices, and the influence of motor loads in generating and transmitting the command signal for short-term interruption of voltage via the 10 and 0.4 kV power network. A procedure for selecting the timing tuning parameters of the emergency control command generating and receiving devices.

A Distributed Control Framework for Integrated Photovoltaic-Battery-Based Islanded Microgrids

This paper proposes a new cooperative control framework for coordination of energy storage units (ESUs), photovoltaic (PV) panels, and controllable load units in single-phase low voltage microgrids (MGs). The control objectives are defined and acted upon using a two level structure; primary and secondary control. Unlike conventional methods, a V–I droop mechanism is utilized in the primary control level. A distributed strategy is introduced for the secondary control level to regulate the MG voltage and manage state of charge (SoC) and power among the ESUs. The distributed secondary controllers are coordinated based on a leader-follower framework, where the leader restores the MG voltage to the rated value and the followers manage the sharing of power between the ESUs so as to balance the SoCs. Once the ESUs reach the minimum charge level, the information state increases above a positive critical value, at which point load control units perform load shedding. Similarly, fair PV curtailment is conducted in case the ESUs reach the maximum charge level. Experimental results are presented to demonstrate the efficacy of the proposed method.

A fuzzy-logic-based control methodology for secure operation of a microgrid in interconnected and isolated modes

Summary Due to the global concerns regarding the climate change, integration of renewable energy sources is considered as a mitigation approach in electric power generation. This requires advanced frequency and voltage control methodologies to overcome the challenges especially in microgrids. This paper presents a 2-step frequency and voltage control methodology for microgrids with high penetration of variable renewable energy sources. An optimized Proportional-Integral controller is designed for a Superconductor Magnetic Energy Storage System to minimize the transient frequency deviations. In cases that the Superconductor Magnetic Energy Storage System cannot stabilize the microgrid frequency in the isolated mode, the microgrid controller activates the next level of the frequency control. In the second level, an intelligent fuzzy-logic frequency controller is designed to adjust controllable loads, controllable generation units as well as perform load shedding. In the interconnected mode, the microgrid controller is able to activate the second level to contribute to the system frequency control. Finally, an intelligent fuzzy-logic voltage controller, realized through distribution static synchronous compensator, is devised to control the voltage magnitude of the main feeders of the microgrid. In this work, a real-time operation algorithm for frequency as well as voltage control is proposed and has been tested by set of simulations on a low voltage benchmark network.

A new technique for islanding operation of distribution network connected with mini hydro

An islanding operation of a distribution network is a topic of interest due to the significant penetration of distributed generation (DG) in a power system network. However, controlling the frequency of an islanded distribution system remains an unresolved issue, especially when the load exceeds the generation. This paper presents a new technique for a successful islanding operation of a distribution network connected with multiple mini hydro based DGs. The proposed technique is based on three main parts. The first part uses an islanding detection technique to detect the islanding event correctly. The second part consists of a power imbalance estimation module (PIEM), which determines the power imbalance between the generation and load demand. The third part consists of a load shedding controller, which receives the power imbalance value and performs load shedding according to load priority. The proposed technique is validated on an 11 kV existing Malaysia distribution network. The simulation results show that the proposed technique is effective in performing a successful islanding operation by shedding a significant number of loads.

A new planning model for assessing the effects of transmission capacity constraints on the reliability of generation supply for large nonequivalenced electric networks

This paper presents a new model for calculating the reliability of large electric power networks with transmission constraints. Generation loss of load probability (LOLP) and expected unserved energy (EUE) are calculated with and without transmission constraints and displayed for the system and for each load area over a wide range of load levels. A two step process first finds the cumulative probabilistic the flow distributions from incremental flows resulting from random generator failures and then performs load shedding as a heuristic process to remove line overloads. Convolution of states allows an extremely large number of generator states to be modeled in a reasonable amount of computation time. Test results for a large network and for the IEEE Reliability Test System (RTS) are discussed in the paper.