Operating principle of Soft Open Points for electrical distribution network operation

Soft Open Points (SOPs) are power electronic devices installed in place of normally-open points in electrical power distribution networks. They are able to provide active power flow control, reactive power compensation and voltage regulation under normal network operating conditions, as well as fast fault isolation and supply restoration under abnormal conditions. Two control modes were developed for the operation of an SOP, using back-to-back voltage-source converters (VSCs). A power flow control mode with current control provides independent control of real and reactive power. A supply restoration mode with a voltage controller enables power supply to isolated loads due to network faults. The operating principle of the back-to-back VSCs based SOP was investigated under both normal and abnormal network operating conditions. Studies on a two-feeder medium-voltage distribution network showed the performance of the SOP under different network-operating conditions: normal, during a fault and post-fault supply restoration. During the change of network operating conditions, a mode switch method based on the phase locked loop controller was used to achieve the transitions between the two control modes. Hard transitions by a direct mode switching were noticed unfavourable, but seamless transitions were obtained by deploying a soft cold load pickup and voltage synchronization process

Performance Enhancement of Radial Distribution System via Network Reconfiguration: A Case Study of Urban City in Nepal

Increasing unplanned energy demand increase has led to network congestion, increases power losses and poor voltage profile. To decrease these effects of an unmanaged power system, distribution network reconfiguration provides an effective solution. This paper deals with improving the power losses and poor voltage profile of the Phulchowk Distribution and Consumer Services (DCS) via the implementation of an optimum reconfiguration approach. A Genetic Algorithm (GA) is developed for the optimization. Further, it tries to answer to what extent can we improve the distribution system without overhauling the entire network. The developed simulation algorithm is firstly put into work on the IEEE 33 bus system to better its voltage profile and the poor power losses. The effectiveness of the developed system is validated as it reduced the voltage drop by 5.66% and the power loss by 25.96%. With the solution validated, the algorithm is further implemented in the case of Pulchowk DCS. After reconfiguring the system in different individual cases, optimum network reconfiguration is selected that improved the voltage profile by 3.85%, and the active and reactive power losses by 44.29% and 45.54% respectively from the base case scenario

Spacecraft servicing demonstration plan

A preliminary spacecraft servicing demonstration plan is prepared which leads to a fully verified operational on-orbit servicing system based on the module exchange, refueling, and resupply technologies. The resulting system can be applied at the space station, in low Earth orbit with an orbital maneuvering vehicle (OMV), or be carried with an OMV to geosynchronous orbit by an orbital transfer vehicle. The three phase plan includes ground demonstrations, cargo bay demonstrations, and free flight verifications. The plan emphasizes the exchange of multimission modular spacecraft (MMS) modules which involves space repairable satellites. Three servicer mechanism configurations are the engineering test unit, a protoflight quality unit, and two fully operational units that have been qualified and documented for use in free flight verification activity. The plan balances costs and risks by overlapping study phases, utilizing existing equipment for ground demonstrations, maximizing use of existing MMS equipment, and rental of a spacecraft bus

Handbook of data on selected engine components for solar thermal applications

A data base on developed and commercially available power conversion system components for Rankine and Brayton cycle engines, which have potential application to solar thermal power-generating systems is presented. The status of the Stirling engine is discussed

Planning and Operation of Low Voltage Distribution Networks: A Comprehensive Review

YesThe low voltage (LV) distribution network is the last stage of the power network, which is connected directly to the end user customers and supplies many dispersed small-scale loads. In order to achieve environmental targets and to address the energy shortage issue, governments worldwide increase the renewable energy sources (RES) into the electricity grid. In addition, different types of low carbon technologies (LCTs) such as electric vehicles (EVs) are becoming widely used. A significant portion of RES and LCTs is penetrated into the LV distribution network, which poses a wide range of challenges. In order to address these challenges, there is a persistent need to develop traditional planning and operation frameworks to cope with these new technologies. In this context, this paper provides a comprehensive review about planning, operation, and management of LV distribution networks. The characteristics, types, and topologies of LV distribution networks plus different aspects of operation and planning are investigated. An insightful investigation of the reasons impacts and mitigation of voltage and current unbalanced in LV networks is provided. Moreover, the main three-phase power flow techniques used to analyze the LV networks are analyzed

Bosch CO2 Reduction System Development

Development of a Bosch process CO2 reduction unit was continued, and, by means of hardware modifications, the performance was substantially improved. Benefits of the hardware upgrading were demonstrated by extensive unit operation and data acquisition in the laboratory. This work was accomplished on a cold seal configuration of the Bosch unit

Space programs summary no. 37-29, volume VI FOR the period July 1, 1964 to August 31, 1964. Space exploration programs and space sciences

Summaries covering system development and operations of Ranger VII, Surveyor, and Mariner spacecraft, and engineering development at deep space network facilitie

Demand-Side Load Management Using Single-Phase Residential Static VAR Compensators

Distribution systems are going through a structural transformation from being radially-operated simple systems to becoming more complex networks to operate in the presence of the distributed energy resources (DERs) with significant levels of penetration. It is predicted that the share of electricity generation from DERs will keep increasing as the world is moving away from the power generation involving carbon-emission and towards cleaner energy sources such as solar, wind, and biofuels. However, the unstable behavior of the renewables resources presents challenges to the already existing distribution systems. One such problem is when the distribution feeder experience variable power supply due to the unpredictable behavior of renewable resources. Therefore, it becomes difficult to maintain end-of-line (EOL) voltages within an acceptable range of the ANSI C84.1 Standard. Moreover, electric utility companies consider Conservation by Voltage Reduction (CVR) as a potential solution for managing peak power demand in distribution feeders. Conservation by Voltage Reduction is the implementation of a distribution voltage strategy whereby all distribution voltages are lowered to the minimum allowed by the equipment manufacturer. This strategy is rooted in the fact that many loads consume less power when they are fed with a voltage lower than nominal. Therefore, by implementing CVR, the utility companies can potentially reduce the peak power demand and can delay the up-gradation of the distribution feeder assets. To maximize the benefits from CVR, the whole distribution feeder must participate in regulating power to lower the demand during hours of demand. Hence, there is a need for a local solution that can regulate residential voltage levels from the first customer on the distribution feeder until the EOL of the distribution network. Such a solution will not only provide flexibility to electric utilities for better control over residential voltages but it can also maximize the benefits from CVR. This dissertation presents the concept of a closed-loop Residential Static VAR Compensator (RSVC) that will allow electric utility companies to locally regulate the voltage across the distribution feeder. The proposed RSVC is a novel smart-grid device that can regulate a residential load voltage with a fixed capacitor in shunt with a reactor controlled by two bi-directional switches. The two switches are turned on and off in a complementary manner using a pulse-width modulation (PWM) technique that allows the reactor to function as a continuously-variable inductor. The proposed RSVC has several advantages compared to a conventional thyristor-based Static VAR Compensator (SVC), such as a quasi-sinusoidal inductor current, sub-cycle reactive power controllability, lower footprint for reactive components, and its realization as a single-phase device. The closed-loop RSVC contains two regulation control loops: the primary control loop regulates the customer load voltage to any desired reference voltage within ANSI C84.1 (120 V nominal $\pm$ 5\%) and a secondary loop adjusting the reference voltage to track the point of minimum power consumption by the loads. This approach to CVR has the merit of adapting to the nature of the customer load, which may or may not decrease its energy consumption under a reduced voltage. This local approach to voltage regulation and CVR is a radical departure from current CVR strategies that have been in existence for over 30 years but have not been widely adopted by electric utilities due to high costs and technical challenges