Distributed Generation Control using Protection Principles

In a distribution system, it is essential to maintain the voltage variation within a specified limit for satisfactory operation of connected customers' equipment. Normally, this goal is achieved by controlling the operation of compensating devices, such as load tap changing transformers, shunt capacitors, series capacitors, shunt reactors, and static VAr compensators. However, technical and regulatory developments are encouraging a greater number of small generator units, known as Distributed Generation (DG), and this has the potential to significantly affect voltage control systems. This paper presents an adaptive voltage control technique which incorporates DG systems into the voltage control system. The control scheme uses On-load Tap Changing Transformer (OLTC) and DG for voltage corrections, both are driven by advanced Line Drop Compensators (LDC). At the substation, the LDC is employed to control step up or step down decisions of the OLTC, while another LDC will be used at DG connection point to set DG parameters. Also, for a more cost-effective system, voltage control action coordination is proposed using magnitude grading and time grading. The control approach is tested on a modified distribution system with load variations that are stochastic in time and location. The results show that the integration of these magnitude grading and time grading, protection principles have considerably reduced the DG energy required to achieve the desired control

A Fuzzy approach for detecting anomalous behaviour in e-mail traffic

This paper investigates the use of fuzzy inference for detection of abnormal changes in email traffic communication behaviour. Several communication behaviour measures and metrics are defined for extracting information on the traffic communication behaviour of email users. The information from these behaviour measures is then combined using a hierarchy of fuzzy inference systems, to provide an abnormality rating for overall changes in communication behaviour of suspect email accounts. The use of fuzzy inference is then demonstrated with a case study investigating the email traffic behaviour of a person’s email accounts from the Enron email corpus

A novel control strategy for a variable speed wind turbine with a permanent magnet synchronous generator

This paper presents a novel control strategy for the operation of a direct drive permanent magnet synchronous generator (PMSG) based stand alone variable speed wind turbine. The control strategy for the generator side converter with maximum power extraction is discussed. The stand alone control is featured with output voltage and frequency controller capable of handling variable load. The potential excess of power is dissipated in the damp resistor with the chopper control and the dc link voltage is maintained. Dynamic representation of dc bus and small signal analysis are presented. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying wind and load conditions. The controller shows very good dynamic and steady state performance

Soft and fast starting induction motors using controllable resistive type fault current limiter

This paper proposes a controllable resistive type fault current limiter for soft and fast starting of induction motors (IMs) based on the primary resistance method. Two methods of constant current and minimized torque pulsations starting for the proposed FCL are presented. A comparison is done and it is shown that method of minimized torque pulsations by the proposed structure leads to a fast and soft starting for IM. Analytical analyses are performed in details and simulation results using PSCAD/EMTDC software are involved to validate the effectiveness of the proposed FCL and its control methods for the soft and fast starting up of IMs

Distributed generation diversity level for optimal investment planning

The task of improving the supply quality and maintaining supply continuity during emergencies has become more feasible for a distribution company (DISCO), owing to new developments in Distributed Generation (DG) technologies. Even though the technical issues regarding DG interconnection to the main grid are of great importance and are being addressed by on-going research, it must be clearly placed in the context of on the financial performance of the utility. In this paper, a general approach to quantify the technical benefits of DG employment is proposed. The power system economic impact is assessed by evaluating supply quality, supply reliability, system power losses and capital investment. Moreover, the rationale for this research also includes the possibility of DG diversity level in contribution to the economical benefits from DG integration. The approach is tested by a system which is developed from a Tasmanian distribution example. Simulation results and discussion are presented to illustrate the effectiveness and usefulness of the method

A Novel Passive Islanding Detection Scheme for Distributed Generations Based on Rate of Change of Positive Sequence Component of Voltage and Current

Islanding operation is one of serious hazards of distributed generation (DG) applications. According to IEEE 1547 standard, its occurrence must be detected within two seconds. This paper presents a novel passive islanding detection method based on rate of change of positive sequence component of voltage (RCPSV) and rate of change of positive sequence component of current (RCPSC) acquired at point of common coupling (PCC) of the targeted DG. Whenever the RCPSC and RCPSV are not equal to zero, their change of magnitudes is continuously compared to predetermined threshold values. If both values of RCPSC and RCPSV exceed the predetermined threshold values, it is concluded that the islanding condition has occurred. Otherwise, it is considered as a non-islanding event. The performance of the proposed method is investigated on a sample network in the presence of doubly fed induction generator (DFIG) based wind turbine and synchronous diesel generator DGs by MATLAB/Simulink software. Different non-islanding case studies are taken into account to evaluate the effectiveness of the proposed approach. The simulation results show that the proposed method has advantage of detecting the islanding rapidly and accurately even with zero non-detection zone (NDZ)