Isolated Power System Research Articles

Total power deficit estimation for isolated power system network using H∞ norm method

An isolated electrical network with an independent local distributed generator is very sensitive towards the contingencies between load demand and supply. Although the network system has less complexity in term of structure, its stability condition is crucial due to its stand-alone operating condition. Hence, to monitor the stability of the network, total power deficit is the only variable that can be estimated. This study proposed to utilize the filtering problem to design an estimator that can estimate the total power deficiency. For verification, the design estimator was tested under two cases which are nominal case and parameter uncertainty case. In nominal case, the system parameters are assumed to be known while in parameter uncertainty case the system has contaminated with uncertain parameter where its admissible value is laying in a given polytope. With complying the linear matrix inequality (LMI) constraint, the main objective function of the norm was guaranteed with minimum upper bound. The results show that the dynamical behaviors of designed estimator successfully trace the actual power deficit signal at steady state with minimal estimation error.

Optimization of Equipment Operation in Power Systems Based on the Use in the Design of Frequency-Dependent Models

This article is devoted to the biggest problem of our time: the development of modern and highly efficient equipment for energy systems. We propose improved mathematical models for starting asynchronous motors in isolated power systems. The results of experiments carried out on a model of an isolated network are presented. Both frequency-dependent and frequency-independent models were used. A comparison of various models is given. The advantages of the frequency-dependent model, which provides a more accurate representation of the processes, are shown. The obtained results were discussed, and the possibility of their use for future research was assessed.

Distributed fault-tolerant PI load frequency control for power system under stochastic event-triggered scheme

This article investigates the load frequency control problem of interconnected power systems by proposing a distributed fault-tolerant proportional integral (PI) control strategy. Firstly, a unified actuator fault model is established, and a distributed fault-tolerant PI control strategy is proposed on the basis of the actuator fault model. Then, a stochastic event-triggered scheme (SETS) based on stochastic sampling period is developed to relieve the redundant occupation of network communication resources. Further, an asymptotical stability criterion with H∞ performance is established by means of the Lyapunov method. Finally, illustrative examples are presented from two cases, isolated power system and interconnected power systems, to demonstrate the effectiveness of the designed control approach and the superiority of SETS compared with periodic event-triggered scheme.

Wave Farms Integration in a 100% renewable isolated small power system -frequency stability and grid compliance analysis.

In general terms, the variable penetration of RE in power systems has some inherent drawbacks, such as lack of manageability and resource variability [1]. Medium (in the range of minutes) and short term (in the range of seconds) variability has a negative impact on system reliability, causing a deterioration of system frequency quality in both interconnected and, moreover, isolated systems [1-2]. Specifically, the variability of the wave energy resource is medium- and short-term. Therefore, although wave energy could be very suitable to be integrated in islands due to its location, the variable nature of wave energy could negatively impact the stability of the power grid [3].
 The case study of the work focuses on the island of El Hierro (Canary Islands, Spain). It is an isolated electrical system with a very high penetration of renewable energy sources. The generation of the electrical system is composed of a wind farm, a pumped hydroelectric power plant and conventional generation by means of a diesel power plant.
 In a previous analysis [4], the integration of energy storage systems based on flywheels was analyzed. Based on this previous analysis, the manuscript studies the influence of the integration of the wave energy park in the electrical system of El Hierro.
 On the one hand, a wave farm will be proposed to evaluate the generated power and its associated oscillation [5]. The wave energy resource at different locations along the coast of El Hierro will be taken into account. On the other hand, an aggregated inertial dynamic mode of the electrical power system will be used to evaluate the impact of the generated power on the electrical frequency and the aging/degradation effects of the hydropumping elements. The Spanish Grid Code will be taken into account regarding frequency regulation mechanisms in isolated systems.
 The degradation of the hydraulic pumping systems due to additional frequency regulation stresses and electrical frequency deterioration will be calculated and evaluated in relation to the penetration of wave energy into the system, with and without the flywheel energy storage plant. This will allow quantification of certain technical limits to wave energy penetration in isolated systems and to draw conclusions with reference to the size of such a power system.
 [1] R. S. Kaneshiro et al. “Hawaii Island (Big Island) Wind Impacts” Proc. of Workshop on Active Power Control from Wind Power, Broomfield, CO, USA, 2013.
 [2] H. R. Iswadi et al. “Irish power system primary frequency response metrics during different system non synchronous penetration,” IEEE Eindhoven PowerTech 2015, doi: 10.1109/PTC.2015.7232425.
 [3] Isabel Villalba et al. “Wave farms grid code compliance in isolated small power systems,” IET Renewable Power Generation, 2019, doi: 10.1049/iet-rpg.2018.5351.
 [4] Hilel Garcia-Pereira et al. “Comparison and Influence of Flywheels Energy Storage System Control Schemes in the Frequency Regulation of Isolated Power Systems,” IEEE Access, 2022, doi: 10.1109/ACCESS.2022.3163708.
 [5] M. Blanco et al. “Study of the impact of wave energy generation in the frequency of an island electric grid,” Proc. of the 12th European Wave and Tidal Energy Conference (EWTEC). 2017.

A quantum particle swarm optimization-based optimal LQR-PID controller for load frequency control of an isolated power system

One of the characteristics of a robust power grid is minimal variations in its frequency to load change or loss in generating unit(s). From the perspective of optimal control theory, the issue of load frequency control in the context of the interconnected functioning of power systems is investigated in this work, and a novel load frequency controller is proposed for a single area isolated power network. This novelty incorporates all the primary characteristics of the solutions that are based on a mixture of optimal controller designs by establishing a linear quadratic regulator optimized with quantum particle swarm optimization to design a proportional integral derivative (PID) controller unlike the conventional PID controller designs that are based on a combined Ziegler-Nichols and root locus (ZN-RL) method and manual tuning. The simulation results of the proposed controller using MATLAB show its efficacy in not only ensuring that there is no steady-state error in terms of the system frequency with load changes but also in achieving smoother transients. Following these landmark achievements, a transfer function model of the resulting power grid is constructed. The outcome of the model reveals that the system transients have been improved while keeping the intended steady-state characteristics. Furthermore, it is observed that the proposed load frequency controller has the best performance when compared with the combined ZN-RL method and the manual PID designs. This, therefore, demonstrates the superiority of the proposed design for load frequency control in power systems.

Enhanced energy management system for isolated microgrid with diesel generators, renewable generation, and energy storages

This paper presents an enhanced control and energy management strategy for the remote isolated power system. The presented control method includes the hybrid energy storage system control with a supercapacitor voltage restoration loop. This method improves the transient response and extends the battery lifespan while maintaining the SC voltage at a defined range of operation. To maximize the usage of renewable energy and reduce the diesel generator’s frequent turn-on and off operation, the novel battery state of charge stop control is included in the energy management system. This improves the lifetime of diesel generators and reduces maintenance costs. In the proposed control method, a stabilizing control method is also introduced which helps in a seamless transition from grid-connected mode to islanded operating mode. The effectiveness of the proposed EMS and control method is validated by real-time simulation studies.

Development of Virtual Inertia Control with State-of-Charge Recovery Strategy Using Coordinated Secondary Frequency Control for Optimized Battery Capacity in Isolated Low Inertia Grid

Integrating renewable energy through inverter-based generators has decreased the power system’s inertia. Reduced inertia may lead to frequency instability during power imbalance disturbances, particularly in an isolated power system with limited inertia. The Battery Energy Storage System (BESS) and a virtual inertia (VI) emulation control system have become popular to mitigate this issue. Nonetheless, the BESS utilization for VI emulation is highly dependent on the availability of BESS capacity, which may affect the energy cost. Therefore, developing a VI emulation control strategy that requires less energy and can recover the state of charge (SoC) to a desired level to optimize BESS utilization is required. This paper proposes a VI control with an SoC recovery strategy through coordination with the generators’ secondary frequency control. Instead of relying on the frequency, such as in the conventional approach, the controlled signal of the generators’ secondary frequency control also includes the VI power and BESS SoC. Hence, the generators can contribute to lowering the VI required energy and recovering the BESS SoC. The results show that the proposed method outperforms the conventional method by requiring around 36% lower energy and the ability to maintain the BESS SoC.

An Energy Management Approach for Isolated Power System using Low Load Diesel

Renewable energy sources (RES) are well known sources for providing energy in distant regions. This is the reason that hybrid isolated power system (HIPS) is utilized which integrates solar energy and wind energy. Renewable energy (RE) relies on environmental conditions. The technologies such as batteries or diesel generator (DG) need to be employed to meet the load demand. Battery energy storage system (BESS) can diminish the limitation but this can add expense and intricacy to the system. DG is an excellent choice to meet load demand but it has certain limitations. Due to diesel load set point, excess RE generation is consumed via regulating devices such as dump load or BESS. As a result, systems designed for high RE penetration are now more complex, expensive, and wasteful. This study analyses low load diesel (LLD). It is a method for minimizing surplus generation hence decreasing system intricacy. It also reduces fuel utilization without causing the control architecture to become overly complicated hence reducing the need for BESS. It provides an alternate method for redefining diesel generation's low load capacity. This work provides an economic analysis of LLD including comparisons to traditional BESS applications. This analysis shows low operational cost of the system including LLD than BESS. Hence demonstrating that BESS can be replaced with LLD. The use of LLD also lowers fuel usage. A power system model of HIPS is simulated using MATLAB/Simulink.

Optimization tool for operating isolated diesel-photovoltaic-battery hybrid power systems using day-ahead power forecasts

This paper presents a computational tool based on a genetic algorithm and artificial neural network for optimizing the operation of isolated diesel-photovoltaic-battery hybrid power systems using day-ahead power forecasts obtained with quantile random forests. The optimization tool was conceived to be flexible, i.e., it can be used to operate isolated power systems with multiple configurations of diesel generator sets (DGS), to work with a reduced number of input data, and to be as simple as possible to be used. The optimization relies on combining valley-filling and peak-shaving strategies using battery energy storage systems while considering the combined forecast of demand and photovoltaic (PV) generation. The tool also simulates the behavior of the DGS to define the optimum arrangement of diesel generators considering the variability of both demand and PV generation. The output consists of hourly values of energy storage power dispatch, DGS arrangement, and, if necessary, load shedding and/or PV curtailment. The algorithm that implements the optimization tool, which is currently in the phase of field-test in the isolated diesel-photovoltaic-battery hybrid power system of Fernando de Noronha, Brazil, demonstrated a good performance in computer simulations validated with real measured data.

A novel chaotic chimp sine cosine algorithm part-II: Automatic generation control of complex power system

This is part II of two-paper set deals with the application of the designed algorithm in automatic generation control (AGC) problem of different structures, such as conventional and isolated. The companion paper (i.e., Part I) describes the designed algorithm in detail and shows the validation of the results in support of the proposed algorithm in a systematic manner. The main focus of this study is to apply and validate the algorithm for automatic generation control (AGC) in power systems. Specifically, the algorithm is tested on various AGC models, including a conventional four-area interconnected power system, deregulated power system and an isolated power system model withchange in operating conditions. The employed controller is a proportional-integral-derivative (PID) controller, and its parameters are tuned using the chimp optimization algorithm (CHOA), chaotic chimp optimization algorithm (C-CHOA), and chaotic chimp sine cosine optimization algorithm (C-CHOA-SC).The objective of this study is to assess the effectiveness of the proposed C-CHOA-SC optimization method in tuning the PID controller parameters for AGC in the considered power system models. Through simulations, the study evaluates the performance of the algorithm in terms of AGC efficiency and the ability to maintain dynamic responses within acceptable limits.The simulation results demonstrate that the proposed algorithm outperforms alternative methods in all the tested AGC models. It showcases superior performance while ensuring the desired dynamic response characteristics are maintained.

An Overview of Small Nuclear Power Plants for Clean Energy Production: Comparative Analysis of Distributed Generation Technologies and Future Perspectives

There is a steady trend in the world to increase the share of distributed generation. The volume of self-generated energy commissioning is constantly growing, with projected increases in growth rates in the future. At the same time, demands for efficiency and environmental safety in new power plants are constantly increasing. In this regard, one of the promising areas for the development of distributed energy is the transition to small nuclear power plants (SNPPs). As in the case of wind and solar power plants, SNPP operations are not accompanied by emissions of toxic substances or greenhouse gases into the atmosphere. In addition, SNPPs consume a much smaller volume and mass of fuel compared to conventional small-capacity fossil fuel power plants. This paper describes the characteristics of the main types of distributed generation. The key technical and economic characteristics of existing and prospective small-capacity nuclear fuel facilities are systematized. The results of a comparative analysis of the cost of electricity produced by SNPPs and competing power plants are also presented. In addition, a number of promising regions of the Russian Federation for the introduction of SNPPS have been identified, and a review of the methods of energy storage for SNPPS, which are necessary when working in an isolated power system, has been carried out.

Effectiveness of zero tailpipe vehicles to reduce CO2 emissions in isolated power systems, a realistic perspective: Tenerife Island test case

Effectiveness of zero tailpipe vehicles to reduce CO2 emissions in isolated power systems, a realistic perspective: Tenerife Island test case

Enhance Power Quality through Series Compensation in Power System

Abstract: The power quality requirement is one of the most important issues especially with the introduction of sophisticated device whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence manifested as a non standard voltage, current or frequency that results in failure of end user equipment. One of the major problem deal with sag and harmonics .To solve this problem series compensation is used to improve power quality of an isolated power system is considered. The role of compensator not only mitigates voltage sag but also reduces harmonics due to presence of nonlinear load in the network. In this paper series compensation is proposed and principle of harmonics mitigation is explain and the compensation strategies and control philosophy used in series compensation is explain. The isolated power system model is simulated in matlab Simu link software and simulation result shows the reduce harmonics and thus improve power quality of the isolated power system

An Analysis of the Effects of Renewable Energy Intermittency on the 2030 Korean Electricity Market

Republic of Korea has unique geographical characteristics similar to those of an island, resulting in an isolated power system. For this reason, securing sufficient operating reserves for the system’s stability and reliability in the face of the intermittency of increasing variable renewable energy (VRE) is paramount, and this will pave the way to achieving the nation’s decarbonization target and carbon neutrality. However, the current reserve-operation method in Republic of Korea does not take into account energy-system conditions, such as the intermittency of the VRE. Therefore, this paper presents an analysis of the impact of changes in reserve-operation methods on the electricity market in the future Republic of Korean power system, with the increased levels of VRE that are currently envisioned. Specifically, three reserve-operation methods, including Korea’s current reserve-power-operation standards, were applied to the two power-system plans announced by the Korean government to analyze the annual generator operation and costs. The analysis results show that securing reserves proportional to the VRE would exert negative effects, such as increased power-generation costs and the curtailment of nuclear and VRE generation. These results can contribute to the estimation of operational reserves needed for high levels of VRE and to the design of new the Korean reserve market, to be introduced in 2025.

Impact of powertrain electrification on the overall CO2 emissions of intercity public bus transport: Tenerife Island test case

The adoption of plug-in electric buses are seen as a promising alternative to reduce greenhouse gas (GHG) emissions in the public transport system. Although from an operational point of view this type of vehicles are zero-emissions, the upstream phase contribution can be considerably high in regions with high carbon grid intensities.This paper presents a simulation study to evaluate the energy consumption and the corresponding well-to-wheels (WTW) CO2 emissions of conventional diesel, parallel hybrid and battery electric buses. The test case is the island of Tenerife, an isolated power system highly dependent on fossil-fuels for power generation. Validated models of the aforementioned propulsion architectures were simulated over five representative cycles, covering city and intercity lines with noticeable differences in terms of driving behaviour, distance and gradient. Although battery electric buses present energy consumption reductions of 70% compared to conventional powertrains, the large carbon grid intensity of the island has a negative effect on their potential to reduce WTW CO2 emissions. The results evince that parallel hybrids provide the largest benefit to abate WTW CO2 emissions, reaching a reduction figure of 38% compared to its conventional diesel counterpart.

Event-Trigger-Based Distributed Optimization Approach for Two-Level Optimal Model of Isolated Power System With Switching Topology

Due to the uncertain output of intermittent energy resources and dynamic communication topology, it brings a great challenge for the optimal security control of isolated power system. To address this problem, this article proposes a two-level optimal control strategy with event-triggered switching mechanisms. For ensuring the security of the isolated power system, event-triggered switching mechanisms are proposed in the upper-level model to decrease potential risk of supply security and voltage stability, which can ensure system security as well as a low switching cost. In the lower-level model, a distributed optimization with switching topology is developed to minimize power generation cost under the above switching mechanisms, and the convergence ability of the proposed distributed optimization method is well proved with a uniformly globally exponentially stable condition. The obtained simulation results reveal that the proposed optimization approach can properly deal with the security issue of an isolated power system as well as dynamically minimize the economic cost.

Pulsed Power Load Coordination in Mission- and Time-critical Cyber-physical Systems

Many mission- and time-critical cyber-physical systems deploy an isolated power system for their power supply. Under extreme conditions, the power system must process critical missions by maximizing the Pulsed Power Load (PPL) utility while maintaining the normal loads in the cyber-physical system. Optimal operation requires careful coordination of PPL deployment and power supply processes. In this work, we formulate the coordination problem for maximizing PPL utility under available resources, capacity, and demand constraints. The coordination problem has two scenarios for different use cases, fixed and general normal loads. We develop an exact pseudo-polynomial time dynamic programming algorithm for each scenario with a proven guarantee to produce an optimal coordination schedule. The performance of the algorithms is also experimentally evaluated, and the results agree with our theoretical analysis, showing the practicality of the solutions.

MODIFICATION OF THE MASTER GENERATOR METHOD USED FOR FREQUENCY AND VOLTAGE CONTROL IN ISOLATED POWER SYSTEMS WITH PARALLEL OPERATING AC GENERATORS

Such methods as droop method, curve shifting method and master-slave method were primarily developed for voltage and frequency regulation in isolated power systems with synchronous generators. In modern power systems induction generators, regulated dump loads, energy storage devices with AC/DC and AC/DC/AC power converters, etc. are used in addition to synchronous generators. The investigation of new configurations of power systems is closely tied with further development of control methods for load sharing and regulation of voltage and frequency of the systems. The article reviews simple-to-implement known control methods used for control of isolated power systems with parallel operated synchronous generators and proposes a modification of the master-slave method for control of power systems with parallel operated synchronous and induction generators, static var compensators, dump loads and energy storage devices with interface power converters. The system “Hydroelectric unit with a synchronous generator - dump load - hydroelectric unit with an induction generator - compensating capacitors - transformer – AC local load" is considered and two techniques for regulation of electric frequency and voltage magnitude in the specified system are presented with accordance to the statements of the proposed modified method. The proposed control algorithm of the dump load frequency controller is in agreement with the control algorithm of the speed controller of the master unit. The functions assigned to the electronic PID speed controller of the master unit are to maintain the electric frequency in the system equal to nominal value and regulate the active power sharing. Verification of the proposed control algorithms for isolated electric power systems was carried out. References 23, figures 5, table 1.

Suitability assessment of high-power energy storage technologies for offshore oil and gas platforms: A life cycle cost perspective

This paper presents a technology suitability assessment (TSA) of high-power energy storage (ES) systems for application in isolated power systems, which is demonstrated through the case of offshore oil and gas platforms (OOGPs). OOGPs operate in very harsh environmental conditions (with limited weight and space), and this requires a specific assessment of which ES technologies are suitable for this application. This work presents a TSA procedure to address this problem. ES can be sized to provide many services. In this paper the focus is on primary frequency control, but the proposed approach can be extended to other services. The ES technologies assessed in detail include flywheels, supercapacitors (SCs), superconducting magnetic energy storage (SMES) and lithium-ion (Li-ion) batteries, which are critically selected from a broader pool of alternatives. A life cycle cost perspective is presented using the case study of an OOGP in the North Sea. A weighted TSA score is calculated, which is estimated from five attributes, namely: weight, space, safety, life cycle cost and operational experience. The results of the case study show that SMES has the lowest life cycle cost but has the highest weight and space requirements, thereby giving it the lowest weighted TSA score. Thus, it is unlikely to be a viable solution for the considered application. On the other hand, SCs require the least weight and space and have the second lowest life cycle cost, which gives them the highest weighted TSA score and makes them the most suitable solution for primary frequency control in an OOGP. Note that the results of the case study depends on the inputs (detailed information about the ES technologies) gathered. However, the most important thing is the methodology and the TSA analysis can always be re-run when more accurate inputs are obtained.

電源をPCSのみとする自立系統の事故模擬と事故検知手法検討

The isolated power system (off-grid) using only PCS (Power Conditioning Subsystem) resources is studied. On the other hand, the off-grid of the Japanese general transmission and distribution company using only PCS resources has not been realized. To realize and clarify the safety operation of off-grid, in this paper, fault aspects of off-grid were simulated easily. After the simulation, small experiments of off-grid using only PCS resource were carried out.