1 Introduction 1.1 Why Is Flexibility Necessary for the Power System 1.2 Overview of Power System Flexibility 1.2.1 History and Development 1.2.2 Taxonomy-Power System Flexibility Sources 1.2.3 Power System Flexibility Analysis 1.3 Market Solutions 1.4 Summary References 2 Power System Flexibility Modelling 2.1 Introduction 2.2 Power System Flexibility Resource Classification 2.2.1 Demand Side Flexibility Resources 2.2.2 Power Supply Side Flexibility Resources 2.2.3 Grid Side Flexibility Resources 2.3 Flexible Power Supply Resources: Analysis and Modelling 2.3.1 Technical Characteristics of Flexible Power Supply Resources 2.3.2 Economic Characteristics of Power Supply Resources Flexibility 2.4 Demand Side Flexibility Model 2.4.1 Interruptible Load 2.4.2 Adjustable Load 2.4.3 Shiftable Load 2.5 Power Grid Flexible Regulation Technologies 2.5.1 Voltage Source Converter (VSC) Based Multiple-Terminal DC Transmission 2.5.2 AC Grid Flexible Topology Control 2.6 Conclusions References 3 Flexibility-Based Economic Dispatch 3.1 Introduction 3.2 Quantifying Accommodated Domain of Wind Power for Flexible Look-Ahead Unit Commitment 3.2.1 Formulation of ADWP 3.2.2 Flexible Look-Ahead Unit Commitment Models 3.3 Flexibility Based Day-Ahead Generation-Reserve Bilevel Decision Model 3.3.1 Day-Ahead Unit Commitment Model Considering Flexibility Constraint 3.3.2 Flexibility Based Reserve Decision Method 3.4 An Endogenous Approach to Quantifying the Wind Power Reserve 3.4.1 Dynamic S&NCED Model with AARO 3.4.2 Two-Stage Solution Method Based on the Benders Decomposition 3.5 Case Studies 3.5.1 Case Studies of the Flexible Look-Ahead Unit Commitment 3.5.2 Case Studies of the Day-Ahead Generation-Reserve Bilevel Decision Model 3.5.3 Case Studies of the Endogenous Approach to Quantifying the Wind Power Reserve 3.6 Conclusion References 4 Distributed Dispatch Approach in AC/DC Hybrid Systems 4.1 Introduction 4.2 Distributed Dispatch Approach in Bulk AC/DC Hybrid Systems 4.2.1 Distributed Scheduling Framework for Bulk AC/DC Hybrid Transmission Systems 4.2.2 Improved ATC-Based Distributed SCUC for a Bulk AC/DC Hybrid System 4.2.3 Solution Procedure 4.3 Distributed Dispatch Approach in the VSC-MTDC Meshed AC/DC Hybrid Systems 4.3.1 Hierarchy of VSC-MTDC Meshed AC/DC Grid 4.3.2 Hierarchical and Robust Scheduling Formulation 4.3.3 Solution Methodology 4.4 Case Studies 4.4.1 Distributed Dispatch Approach in Bulk AC/DC Hybrid Systems 4.4.2 Distributed Dispatch Approach in VSC-MTDC Meshed AC/DC Hybrid Systems 4.5 Conclusion References 5 Exploring Operational Flexibility of AC/DC Power Grids 5.1 Introduction 5.2 Improving Flexible Operation of MTDC Hybrid Networks by VSC Power Regulation 5.2.1 Problem Description 5.2.2 Flexible Operation Mechanism and Model 5.2.3 Flexible Operation Improvement Mode for VSC Station 5.3 Exploiting the Operational Flexibility of Wind Integrated Hybrid AC/DC Power Systems 5.3.1 SCED Model with TS for Hybrid AC/DC Grid 5.3.2 Two-Stage RO Based on C&CG 5.4 Case Studies 5.4.1 Verify of Power Margin Tracking Droop Regulation (PMT) Mode 5.4.2 Exploring Operational Flexibility of AC/DC Power Networks Using TS 5.5 Conclusion References 6 Demand Side Flexibility 6.1 Introduction 6.2 Residential Load Demand Response Model 6.3 Price-Based Demand Response Model 6.3.1 Energy Management Model of the ITCA 6.3.2 Flexibility of ITCAs 6.3.3 ITCAs' Flexibility Under TOU Power Price 6.3.4 Unit Scheduling Model Considering the Flexibility of ITCAs 6.4 Integrated Energy System Demand Response Model 6.4.1 Typical Topology 6.4.2 Integrated Demand Response Model 6.4.3 Two-Stage Stochastic Chance-Constrained Programming Model 6.5 Case Studies 6.5.1 Residential Load Demand Response 6.5.2 Price-Based Demand Response Model 6.5.3 Integrated Energy System Demand Response 6.6 Conclusion References 7 Large-Scale Distributed Flexible Resources Aggregation 7.1 Introduction 7.2 Large Scale Interruptible and Shiftable Load Aggregation 7.2.1 Equivalent Aggregated Model for Large-Scale Interruptible and Shiftable Loads 7.2.2 Equivalent Model for a Single Group 7.2.3 Scheduling with Equivalent Aggregated Model 7.3 Large Scale EV Aggregation 7.3.1 Market Framework 7.3.2 Aggregate Model of Electric Vehicle Fleets 7.3.3 Model of Optimal Bidding Strategy of Microgrid 7.4 Case Study 7.4.1 Large Scale Interruptible and Shiftable Load Aggregation 7.4.2 Large Scale Distributed Energy Storage Aggregation 7.5 Conclusion References 8 Market Mechanism Design for Enhancing the Flexibility of Power Systems 8.1 Introduction 8.2 The Framework of Balancing Market 8.2.1 The Framework of Balancing Market 8.2.2 Key Design Elements in Imbalance Settlement 8.3 System Model 8.3.1 Balancing Market Clearing Optimization Model Embedded with the Offering Strategy of Wind Power Producers 8.3.2 Offering Strategy of the Wind Power Producer 8.3.3 Objective Function and Constraints 8.3.4 Solution Method 8.3.5 ABM Method 8.3.6 The MCDA Evaluation 8.4 Case Studies 8.4.1 Analysis of Wind Power Supplier's Strategic Offering 8.4.2 Analysis of Strategic Interaction Behavior of Market Players 8.5 Conclusion References