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Über dieses Buch

This book offers a comprehensive reference guide to the important topics of fault analysis and protection system design for DC grids, at various voltage levels and for a range of applications. It bridges a much-needed research gap to enable wide-scale implementation of energy-efficient DC grids. Following an introduction, DC grid architecture is presented, covering the devices, operation and control methods. In turn, analytical methods for DC fault analysis are presented for different types of faults, followed by separate chapters on various DC fault identification methods, using time, frequency and time-frequency domain analyses of the DC current and voltage signals. The unit and non-unit protection strategies are discussed in detail, while a dedicated chapter addresses DC fault isolation devices. Step-by-step guidelines are provided for building hardware-based experimental test setups, as well as methods for validating the various algorithms. The book also features several application-driven case studies.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction to DC Grid

Abstract
This chapter provides the introduction to dc grid. A historical perspective of the dc grid is provided, followed by major installations of the high voltage dc (HVDC) transmission systems. Comparison of ac and dc systems are given in terms of operation, cost. Various applications of dc technologies, for example HVDC transmission, microgrid, transportation sector are discussed. This is followed for introduction to the challenges in protection system design for dc grid.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 2. Components and Architectures of DC Grid for Various Applications

Abstract
This chapter introduces the devices and components, which are the building blocks for dc grid. These include ‘Thyristor’, which is the building block for the line commutated converters (LCC) and Insulated Gate Bipolar Transistors (IGBTs), which is the building block for voltage source converters (VSC). Other emerging converter topologies are introduced. Subsequently, different applications are described, depending on the voltage levels. These include HVDC transmission, utility application like microgrid with energy storage, datacenter with prospective dc power supply and transportation sector like dc shipboard, electric aircraft.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 3. Modeling and Control of Generation System for DC Grid Applications

Abstract
This chapters covers the modeling and control of the ac/dc generation systems which would be implemented in the dc grids. The current and voltage source based ac/dc conversion systems with fixed frequency ac input from the stiff ac grid have been considered for HVDC applications. In addition to the HVDC systems, generation systems for marine and aerospace power systems are also considered. In such applications, the generators are operated at variable speed for improved fuel efficiency. The operation of voltage source converter operated with such variable frequency ac input has also been described in detail.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 4. Faults in DC Networks

Abstract
Understanding of dc fault characteristics is very important for designing robust protection system. This chapters presents the analytical expressions for the different types of dc faults, namely pole-to-pole (PP) and pole-to-ground (PG). Firstly, fault current calculation for current source converter (CSC)-based dc system is presented. This is followed by fault current calculation for voltage source converter (VSC) and modular multilevel converter (MMC)-based dc system. Travelling wave-based fault current calculation is introduced, followed by simulation examples.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 5. Time-Domain Based Fault Detection in DC Grids

Abstract
In this chapter, we will look into the different approach of detecting the dc fault—time-domain methods. There are three different methods to be discussed: overcurrent, rate of change and capacitive discharge. The operation of each method is explained in detail. We obtain the fault signal from the simulation model and apply these methods to evaluate their performance. While they are effective in detecting dc fault, each has their own drawbacks. (1) Overcurrentmethod is only suitable for point-to-point configuration, (2) Rate of change method can be severely affected by signal noise, and (3) Capacitive discharge method requires more signals and computationally extensive.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 6. Frequency-Domain Based Fault Detection: Application of Short-Time Fourier Transform

Abstract
This chapter introduces the frequency-domain based transient analysis of the dc fault currents. Short-Time Fourier Transform (STFT) based fault analysis has been proposed as a frequency domain method for transient state detection in dc networks. This chapter describes in detail the operation of STFT based transient detection with the support of analytical formulations. Application of STFT based transient state detection with sensitivity analysis has been performed for the point-to-point and multi-terminal high-voltage dc transmission system. The results show that STFT method can be effectively be used for fault detection with substantial accuracy.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 7. Time-Frequency Domain Analysis: Wavelet-Transform Based Fault Detection

Abstract
A comprehensive analysis of wavelet-based method detecting and locating fault in HVDC system is detailed in this chapter. We study how wavelet transform can serve as a protection tool to decide right tripping signal. Detailed coefficient is one of the parameters we use to determine the fault occurrence. Using the analytical fault signal, we illustrate how the coefficient changes during pre- and post fault. There are many types of mother wavelets, for instance, Haar, Daubechies, Coiflet and Symlet. The choice of mother wavelet is a topic of interest here. Particularly, we find that Daubechies wavelet is the most optimum for fault detection as far as sensitiveness is concerned. There are some factors that can influence the performance of wavelet transform: fault type, fault resistance, fault location, choice of wavelets and sampling frequency. The simulation results show that the wavelet transform can tolerate these influences reasonably well. We use two types of simulation models: two-terminal and multi-terminal HVDC systems.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 8. Non-unit Protection Strategies for DC Power Systems

Abstract
This chapter introduces the various non-unit protection strategies for dc grid applications. The requirements of the protection coordination strategies are derived and the procedure of implementing the non-unit protection methods is determined by comparison with the existing protocols available for the ac power systems. The parameters and fault detection timing necessary to implement such strategies are identified and derived. Determining the protection settings for the described non-unit protection is also discussed.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 9. Introduction to Directional Protection and Communication Assisted Protection Systems

Abstract
This chapter describes the operation of directional protection and communication assisted unit-protection strategies for dc power systems. The directional analysis of the fault currents has been covered in detail and various combinations of directional protection with comparative studies have been presented. Various communication assisted protection schemes along with the brief comparison with the ac power system is also presented.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 10. Fault Isolation in DC Grids

Abstract
DC fault current breaking devices are important components for enabling robust protection of the dc system. This chapter will present the ongoing developments regarding the dc fault isolation devices. There are two major trends in dc fault isolation, namely based on, dc circuit breaker (DCCB) and converter-based solution. Firstly, the DCCB will be presented with active and passive commutation. This will be followed by hybrid DCCB and converter-based isolation devices. Finally, commercially available DCCBs at high, medium and low voltage levels are presented.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 11. Design of Experiment and Fault Studies

Abstract
Thus far, this book approaches performance validation mainly based on simulation-based fault signal. It is practically infeasible to create the short-circuit in real VSC-HVDC system while it is in operation. To validate the fault detection methods using real fault signal, this chapter lays out the steps to create the VSC-based dc test system in laboratory, from design of converter, sensor components, controller tuning to protection measure. The experimental hardware allows us to create dc fault in a safe manner. The fault current is in good agreement with analytical calculation. Then, we compare the performance of wavelet transform, capacitive discharge and STFT methods using the experimental fault signal.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Chapter 12. Case Studies

Abstract
This chapter introduces protection system design for HVDC system and compact dc distribution applications. In the former case, three fault clearance strategies are investigated and compared based on how fast the system recover from fault. As for latter, we are interested to determine the criteria for selecting the protection methods.
Abhisek Ukil, Yew Ming Yeap, Kuntal Satpathi

Backmatter

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