Suresh Chand Verma

Excitation control system design of rotary type frequency converter for performance improvement of power system dynamics

A rotary type frequency converter using two sets of adjustable speed generators/motors is expected to be applied at the interconnections between 50 Hz and 60 Hz power systems in Japan. The rotary type frequency converter can work not only as a power interchanger, but also as a power system stabilizer by effectively utilizing energy stored in rotors. In this paper, we investigate how the rotary type frequency converter affects power system dynamics. Since shaft torsional oscillation and slow response due to mechanical connections are inevitable and may lead to instability in power systems, we also present some countermeasures and control schemes to handle such inherent problems, and to improve the performance of power system dynamics. Control performance and effectiveness is examined for a test model system by digital transient simulation.

Short circuit current estimation using PMU measurements during normal load variation

This paper purposes a short circuit current estimation method using phasor measurement unit (PMU) measurements (synhcrophasors, hereafter called as phasors) of voltages and currents obtained during normal load variation. The method follows the basic concept of representing the source side of power system by an equivalent circuit with a voltage behind back impedance and employs a set of voltage and current phasors measured at substations over a certain period. In order to improve an accuracy of the proposed estimation method, the concept of using a difference between the two consecutive phasors is introduced. Furthermore, to make the method applicable to a real world system, the estimation process is augmented by implementing a reference phasor concept to remove the effects of system wide frequency variations and a filtering process to filter out the outlier phasors. Finally, the validity and effectiveness of the purposed methods were checked and confirmed using field tests.

Study on rotary loop flow controller for futuristic distribution networks

With a rapid increase of environmental friendly Renewable type Dispersed Generation (RDG) like Photovoltaic, Wind Power etc., in Japan and around the world, there are many issues like voltage deviation, reverse power flow and effective management of existing distribution network that are likely to surface on their integration to the network due to the variable output of some RDG. In finding solutions to such issues, loop configuration based futuristic distribution networks are being explored. However, to realize these networks the development of a reliable, efficient and cheaper device like a loop flow controller is imperative. Hence, this paper proposes two types of Rotary Loop Flow Controllers, one is series type and the other is UPFC type. Both of them are based on the induction machine technique with no slip rings and are capable of regulating the power flow by rotating rotors. The proposed controllers are less costly, more efficient, more tolerant to over voltages/currents as compared to self-commutated type controllers. Further, UPFC type rotary loop flow controller has additional advantages like smaller capacity, ability to control reactive power than the series type of rotary loop flow controller. The proper functioning of the proposed controllers is confirmed through simulations and experiments.

Voltage stability constrained risk-based TTC evaluation of a power system with large integration of renewable energy

A future power grid should allow all types of generation including renewable energy, e.g. wind power and photovoltaic (PV). Over recent years, it has been witnessed a fast-growing renewable energy development throughout the world. Japan also pushes toward the renewable energy development setting out a target of 6610 MW wind power and 53 GW PV by 2030. This large penetration of renewable energy could pose negative impacts on the system security due to the uncertain output characteristics. This paper presents a method suitable to examine such impacts of a large penetration of renewable energy on the system Total Transfer Capability (TTC). The uncertainty associated with the renewable energy output and other system parameters is fully taken into account by means of a probabilistic approach, Monte Carlo simulation, and risk-based TTC selection. Besides, this paper considers the steady-state voltage stability to ensure a sufficient margin away from the voltage collapse point. The validity of the proposed method is illustrated through a numerical simulation conducted on the modified IEEE 30-bus test system.

Application of Decision Tree Classification to the Probabilistic TTC Evaluation

AbstractTotal transfer capacity (TTC) is an index used to provide the system operators with key information necessary for the transmission network security and energy trading management. In contrast to deterministic methods, probabilistic methods are justified since they can effectively deal with the uncertainty associated with the system parameters and conditions. In addition, they are also able to cope with wind power generation which has uncertain and fluctuating power output characteristics. In this paper, the TTC is computed using Monte Carlo simulation with transient stability consideration. To alleviate the computational burden due to the addition of the transient stability constraint, decision tree classification is used as a prediction tool for the transient stability assessment during the TTC evaluation. The effectiveness of the proposed method is demonstrated through a numerical example conducted on the modified IEEE 30-bus test system integrated with wind power.

Role of Simulation Technology in Distributed Energy Integration from Japanese Utility Perspective

With a rapid increase of dispersed generation (DG) like wind power etc. in Japan and around the world, there is a growing need for distributed energy integration (DEI) in the power grid as a reliable and a responsible source. In accomplishing this task, a number of underlying technical challenges need to be addressed successfully. In finding solutions to such technical issues, the role of simulation technology is extremely important. In order to appraise the DEI from the Japanese utility perspective, this paper focuses on the simulation studies concerning the modeling aspects of DGs like wind power (WP), etc., validating techniques for the DG systems, as well as the impact of the DGs on protection system or power quality. All these aspects are discussed and described through illustrations.