Research on dynamic analysis and optimization algorithms for large-scale power systems.

It is expected to install a large amount of generation from renewable energy sources such as wind power generation and photovoltaic generation into power systems. However, a large penetration of such renewable energy sources causes some problems in power systems, e.g. frequency fluctuation. In this paper, a number of Heat Pump Water Heaters (HPWHs), one of the energy efficient-use customers' appliances and Battery Energy Storage System (BESS) are considered as controllable equipment for frequency control. An HPWH is considered as a controllable load because the power consumption can be changed during water heating as long as the heating is finished when the customer would like to use. This paper proposes an effective control of HPWHs installed in the power system with a large penetration of renewable energy sources on the assumption of a two-way communication network. The control period is determined based on the statistical information of the HPWHs.

The significant penetration of renewable energy sources (RES), like wind and solar power plants, into distribution networks has changed their operation considerably and brought new challenges for distributed system operators (DSOs). One of the main problems associated with high penetration of variable RES into distribution networks is voltage rise problem along the radial distribution feeders, with high production variability causing frequent operations of the onload tap changers (OLTC), thereby causing significant deterioration of their operation life expectancy. This paper proposes new method for the Volt Var control in the MV distribution network with the high share of RES relative to the distribution system load. The problem is casted as the mixedinteger nonlinear programming (MINLP) problem associated with the voltage control in the distribution network with the objective to maximize daily RES production and through reactive power control to minimize the daily distribution system losses using the Benders' decomposition method. In order to reduce the number of OLTC switching operations, the time instances in which the change is possible are set a priori. The effectiveness of the proposed method is tested on well-known IEEE 69-bus system.

The penetration of renewable energy sources (RES) has been increased throughout the world. The main characteristic of RESs is that their generating powers are intermittent and unpredictable. This paper presents an interval optimization method to optimally schedule electric vehicles (EV) with considering the uncertainty of RES generation and loads. For this purpose, the RES generation (including photovoltaic and wind power) and loads are considered as interval parameters, and the charging/discharging power of EV is expressed as an interval variable to be optimally computed. The capability of RES inverters to regulate voltages is also considered in the interval optimization model. The objective function is to minimize the network active power losses and total voltage magnitude deviation with considering overall system constraints. The proposed method is tested on a 33-bus distribution system with uncertain RESs and loads, and the optimal day-ahead scheduling of EV is performed. Different case studies are carried out to test the effectiveness of the proposed method. It is demonstrated that the proposed interval optimization method can accurately represent the uncertain problem, and it provides further information compared with the deterministic optimization.

Water scarcity and the dependence on fossil fuels as a primary source of energy are crucial problems for a number of arid countries. The integration of energy and water systems presents a possible solution for both issues. The flexibility of a desalination system can increase the possibility for the penetration of intermittent renewable energy sources and thus provide both fresh water and the potential for the local production of clean energy. Jordan is the fourth most water deprived country in the world and is also highly dependent on energy import. Almost all of its primary energy comes from imported fossil fuels, mostly from natural gas. It is a country rich in wind and solar energy but unfortunately, almost no utilization of that potential. The integration of desalination systems and renewable energy sources is a possible solution both for Jordan’s water and energy supply. The goal of this paper is to demonstrate the desalination module in the H2RES model using Jordan as a case study. H2RES is a flexible energy modelling tool used for the balancing of energy supply and demand on an hourly basis. It is capable of demonstrating the benefits of water and energy integration for the purpose of increasing the penetration of intermittent renewables and the reduction of CO2 emissions. For this purpose, four scenarios have been created. The first one is a business as usual scenario with no desalination, a desalination scenario and two desalination scenarios that utilize the produced brine as energy storage in pump hydro plants. The results will show that the utilization of desalination, especially in the case where desalination is combined with pump storage, can help increase the penetration of renewable energy sources into the electrical grid and thus help decrease the dependence on energy import and reduce the CO2 emissions of the energy system.

Optimization of a wind powered desalination and pumped hydro storage system

The high penetration of inverter-fed renewable energy sources (RESs) in modern energy systems has led to a reduction in the system’s inertial response. This reduction in the rotational inertial response is associated with synchronous generation and might result in a deteriorated frequency response following a power disturbance. This paper investigates the frequency stability of the Kingdom of Saudi Arabia’s (KSA) grid. It includes a description of the changing energy landscape of the KSA’s electricity grid and an investigation of the impact of high penetration levels of inverter-fed RESs on the dynamic behavior of the KSA grid. The impact of RESs has been studied through a simulation of case studies of the future KSA power system using the MATLAB/Simulink simulation software. The frequency stability of the KSA’s power system has been evaluated with various RES levels under peak and base load conditions. The simulation results show that the high penetration levels of RESs dramatically affect the system’s frequency response, especially under off-peak conditions. In addition, the significance of battery energy storage systems (BESSs) for compensating the reduction in the system inertial response has been addressed. The results show the effectiveness of aggregated BESSs for enhancing the system frequency control of the KSA grid.

This paper deals with the problem of stability analysis and controlling a power system in which a synchronous generator and renewable energy sources supply the power to an infinite bus. Firstly the investigation of the existence of the equilibrium points of the system and their stability is presented. For this problem, we derive a sufficient condition on the renewable energy current for the existence of the equilibrium points. In addition, we analyse the stability of the equilibrium points, and show that there is only one equilibrium points which is stable. These results clarify the impact of the penetration of renewable energy sources on the existence of the stable equilibrium points of the system. Secondly, the focus is made on elaborating an output feedback controller, combining a state observer and a nonlinear control law that stabilises the closed loop system whatever the current of renewable energy sources. Numerical simulations are given in order to show the effectiveness of all theoretical results.

Chapter 9 - Integrated Planning of Energy and Water Supply in Islands

We address two infrequently studied problems in scheduling research, i.e. the problems of dynamic scheduling and integration of a job shop and its environment. A dynamic scheduling framework is presented in which dynamic scheduling is carried out through solving a series of static backward scheduling problems. The framework facilitates the integration by establishing the relationship between scheduling, due-date assignment and job release times through backward scheduling. A rolling time window approach is adopted to decompose the scheduling problem in time dimension and accommodate the dynamic conditions in a job shop.

Day-ahead profit-based reconfigurable microgrid scheduling considering uncertain renewable generation and load demand in the presence of energy storage

Thermal power units (TPUs) play a crucial role in accommodating the high penetration of renewable energy sources (RESs) like wind turbines (WTs) and photovoltaics (PVs). This paper proposes an evaluation framework to quantitatively analyze the flexibility potential of retrofitted TPUs in enhancing the accommodate capability of RESs through coupling integration and optimal scheduling. Firstly, the coordination framework for coupling TPUs with RESs is outlined, including a comprehensive analysis of benefits and implementation strategies. Secondly, an annual optimal scheduling model for TPUs and RESs is developed, incorporating deep peak regulation services, ladder-type constraints for retrofitted TPUs, and their operational characteristics before and after the coupling integration. Thirdly, indices to evaluate RES accommodation levels and TPU regulation capacities are proposed to quantify the performance of power sources. Finally, a real-world case study is conducted to demonstrate that integrating retrofitted TPUs with RESs through coupling significantly enhances RES utilization by 3.6% and boosts TPUs’ downward regulation capabilities by 32%.

The operations of electricity and natural gas transmission networks in the U.S. are increasingly interdependent, due to the growing number of installations of gas fired generators and the penetration of renewable energy sources. This development suggests the need for closer communication and coordination between gas and power transmission system operators in order to improve the efficiency and reliability of the combined energy system. In this paper, we present a co-simulation platform for examining the interdependence between natural gas and electricity transmission networks based on a direct current unit-commitment and economic dispatch model for the power system and a transient hydraulic gas model for the gas system. We analyze the value of day-ahead coordination of power and natural gas network operations and show the importance of considering gas system constraints when analyzing power systems operation with high penetration of gas generators and renewable energy sources. Results show that day-ahead coordination contributes to a reduction in curtailed gas during high stress periods (e.g., large gas offtake ramps) and a reduction in energy consumption of gas compressor stations.

The Cyprus power system is undergoing vast changes due to the increasing penetration of renewable energy sources. The isolated nature of the system makes it more vulnerable to large frequency deviations. As a consequence, frequency control becomes challenging especially in the case of large disturbances. To keep the system in admissible frequency limits and avoid brownouts or even system blackout, it is important to have a detailed and accurate model of the system to improve monitoring and control, and enhance the situational awareness of the system operators. One important component of the system to be modelled is the system load. Although this is not a straightforward task, the significance of load modelling can be underlined by the fact that the system response is affected by the type of the system loads. In this sense, the type of the load in combination with the increased penetration of dispersed renewable energy sources can significantly affect the system frequency response to generation loss events. In this paper, the importance of accurate load modelling and the associated effect to the response of the Cyprus power system is examined. The system frequency response to generation loss events for multiple scenarios is investigated. Various load compositions are examined, while PV generation is also considered in order to simulate realistic system conditions. Furthermore, two cases of different plant mix are also examined.

Fast frequency regulation and synthetic inertia in a power system with high penetration of renewable energy sources: Optimal design of the required quantities

Nuclear contribution to the penetration of variable renewable energy sources in a French decarbonised power mix