Dynamic modelling and simulation of electric power systems using the Newton-Raphson method

The research work presented in this thesis is concerned with the development of a dynamic power flow computer algorithm using Newton's method. It addresses both the development of a positive sequence dynamic power flow algorithm for the dynamic study of balanced power systems and a fully-fledged three-phase dynamic power flow algorithm for the dynamic study of power systems exhibiting a significant degree of either structural or operational unbalance. As a prelude to the research work on dynamic power flows, a three-phase Newton-Raphson power flow algorithm in rectangular co-ordinates with conventional HVDC power plant modelling is presented in this thesis, emphasising the representation of converter control modes. The solution approach takes advantage of the strong numerical solutions for combined HVAC-HVDC systems, where power plant and operational imbalances are explicitly taken into account. The dynamic algorithm is particularly suited to carrying out long-term dynamic simulations and voltage stability assessments. Dynamic model representations of the power plants components and the load tap changing transformer are considered, and to widen the study range of dynamic voltage phenomena using this method, extensions have been made to include induction motor and polynomial load modelling features. Besides, reactive power compensators that base their modus operandi on the switching of power electronic valves, such as HVDC-VSC and the STATCOM are taken into account. The dynamic power flow algorithm has primarily been developed making use of the positive sequence and [dq] representations. Extensions are made to developing a three-phase power flows dynamic algorithm. Test cases for the various dynamic elements developed in this research are presented to show the versatility of the models and simulation tool, including a trip cascading event leading up to a wide-area voltage collaps. Comparisons with the output of a conventional transient stability program carried out where appropriate

Smart Demand for Improving Short-term Voltage Control on Distribution Networks

Smart grids must involve active roles from end users in order to be truly smart. The energy consumption has to be done in a flexible and intelligent manner, in accordance with the current conditions of the power system. Moreover, with the advent of dispersed and renewable generation, increasing customer integration to aid power system performance is almost inevitable. This study introduces a new type of smart demand side technology, denoted demand as voltage controlled reserve (DVR), to improve short-term voltage control, where customers are expected to play a more dynamic role to improve voltage control. The technology can be provided by thermostatically controlled loads as well as other types of load. This technology is proven to be effective in case of distribution systems with a large composition of induction motors, where the voltage presents a slow recovery characteristic due to deceleration of the motors during faults. This study presents detailed models, discussion and simulation tests to demonstrate the technical viability and effectiveness of the DVR technology for short-term voltage control.3872473

Real-Time Stability Assessment based on Synchrophasors

peer reviewedIn this paper, an overview is provided of a new method that in real-time provides an early warning for an emerging blackout that are characterized by a slowly increasing angular separation between sub-groups of system generators. Such angular separation between subgroups of generators can eventually cause in very sharp decline in system voltages at intermediate locations between the two groups as the angular separation approaches 180 degree. In order to receive an early warning for the occurrence of such type of blackouts, the boundaries of the system generators aperiodic small-signal stability are suggested to be monitored. For that purpose, method for real-time assessment of aperiodic small-signal rotor angle stability is presented. The approach is based on an element-wise assessment of individual synchronous machines where the aim is to determine the maximum steady state power that each synchronous generator can inject into the system. The limits for maximum injectable power represent the boundary for aperiodic small signal stability. The concept of the proposed method is tested on two different systems. The results show that the method is capable of accurately detecting when a given machine crosses the stability boundary. The method can as well provide in real-time a margin to the machines stability boundary, which can be used as an early warning for an impending system stability problem

Register File Reliability Analysis Through Cycle-Accurate Thermal Emulation

Continuous transistor scaling due to improvements in CMOS devices and manufacturing technologies is increasing processor power densities and temperatures; thus, creating challenges when trying to maintain manufacturing yield rates and devices which will be reliable throughout their lifetime. New microarchitectures require new reliability-aware design methods that can face these challenges without significantly increasing cost and performance. In this paper we present a complete analysis of reliability for the register file architecture of the Leon 3 processor. The analysis conducted is supported by the use of an accurate HW/SW FPGA-based emulation platform that enables a complete design space exploration of thermal and reliability metrics during the execution of an extended set of benchmarks, in a very limited amount of time. The effect of various compiler optimizations and register assignments on the reliability of the register file is then analyzed. Our results quantify the respective effects of these different factors and enable us to design a reliability-aware register file assignment policy that consistently improves the Mean-Time-To-Failure figure (20% on average) for the various types of applications