Power control system

Nuvera will design, build, test, and deliver a 15 kilowatt electrical (kWe ) direct current (DC) fuel cell power module that will be specifically designed for stationary power operation using ethanol as a primary fuel. Two PEM fuel cell stacks in parallel will produce 250 amps and 60 volts at rated power. The power module will consist of a fuel processor, carbon monoxide (CO) clean-up, fuel cell, air, fuel, water, and anode exhaust gas management subsystems. A state-of-the-art control system will interface with the power system controller and will control the fuel cell power module under start-up, steady-state, transient, and shutdown operation. Temperature, pressure, and flow sensors will be incorporated in the power module to monitor and control the key system variables under these various operating modes. The power module subsystem will be tested at Nuvera and subsequently be delivered to the Williams Bio-Energy Pekin, Illinois site. 

P. M. Anderson and A. A. Fouad, Power system control and stability. IEEE Press, IEEE, Inc., New York, USA (1994). ISBN 0 780-31029-2... 

The benefits of AFE PWM variable frequency drives coupled to mine hoists indicates that this will be the preferred application for the foreseeable future. When powered by off-grid diesel generation systems, particular attention paid to design specifications of drive transformer or input reactors, generators, load banks, harmonic filter banks, and power system controls can avoid potential power system problems and ensure a successful system implementation. Individual equipment manufacturers need to have an understanding of overall system design... 

Dalvi A and Guay M (2009), Control and real-time optimization of an automotive hybrid fuel cell power system. Control Engineering Practice, 17,924-938. 

Anderson, P.M. and Fouad, A. A. 1977. Power System Control and Stability. Iowa State University Press, lA. Eaton, J.R. and Cohen, E. 1983. Electric Power Transmission Systems. Prentice-HaU, Englewood ChfFs, NJ. IEEE. 1980. IEEE Recommended Practices for Industrial and Commercial Power Systems Analysis. Wiley, New York. 

Russel, B.D. and Council, M.E. 1978. Power System Control and Protection. Academic Press, New York. Stevenson, J.D. 1982. Elements of Power System Analysis. McGraw-Hill, New York. 

There are a number of publications that discuss the reduction of grounding impedances. In recent years it has become common to install digital circuits not only in power system control equipment but also in buildings and home appliances. Thus, it becomes more important to reduce the grounding impedances to guarantee reliable operation of the digital circuits for both steady and transient states as observed in References 47, 48, 49 and 50. From the above, KEPCO carried out a series of field tests to measure the grounding impedances. 

Modern subsea trees, manifolds, (EH), etc., are commonly controlled via a complex Electro-Hydraulic System. Electricity is used to power the control system and to allow for communication or command signalling between surface and subsea. Signals sent back to surface will include, for example, subsea valve status and pressure/ temperature sensor outputs. Hydraulics are used to operate valves on the subsea facilities (e.g. subsea tree and manifold valves). The majority of the subsea valves are operated by hydraulically powered actuator units mounted on the valve bodies. 

The bulk of hydrauhc fluids is specified and purchased on bid. Specifications and approval fists are issued by some manufacturers of hydraulic pumps and system components that require lubrication as well as power for control signal transmission. U.S. government military specifications for hydraulic fluids are fisted ia Table 12, and ASTM tests that are applicable to hydraulic fluids iaclude the foUowiag ... 

J. M. Radovich, Proceedings of Control Power Systems Conference and Exposition, Oklahoma, Mar. 1980, p. 114. 

Field current is an important control element. It controls not only the power factor but also the pullout torque (the load at which the motor pulls out of synchronism). For example, field forcing can prevent pullout on anticipated high transient loads or voltage dips. Loads with known high transient torques are driven freqiiently with 80 percent power-factor synchronous motors. The needed additional field supplies both additional pullout torque and power-factor correc tion for the power system. When high pullout torque is required, the leading power-factor machine is often less expensive than a unity-power-factor motor with the same torque capabihty. 

G) For a generator connected to a power system, abnormal frequency operation may be the result of a severe system disturbance. An isolated unit, however, can operate at a low or high frequency, due to an incorrect speed control adjustment or a malfunctioning of the speed control device. 

This is the most common scheme in normal use for any power system with more than one feeder, connected to a common bus, such as for distribution and sub-distribution power networks, having a number of load points, controlled through a main incoming feeder. In a switchgear assembly, for instance, common protection may be provided at the incoming for a ground fault or combined 0/C and G/F protections as discussed above. In such cases, a restricted G/F protection may not be appropriate or required, as the protection now needed is sy.stem protection, rather than individual equipment proteelion. The incomer must operate whenever a fault occurs at any point on the system. Moreover, for an LT system, where it may not be desirable or possible to provide individual protection to each feeder, such a scheme is adopted extensively. 

For safe operation of power and control equipment and devices operating in such systems it is essential to limit the amplitude of the voltage distortions to a safe value by installing filter circuits based on the system s actual operating conditions. These limits are recommended by leading standards organizations are ... 

IEEE-519 Guide for harmonic control and reactive compensation of static power converters, for harmonic-voltage distortions of general and dedicated power system, as in Table 23.3. 

However, power systems that cater to almost fixed loads at a time and whose variations occur only at specific times of the day may not reejuire it fast response. In such cases, it is possible to provide manual switching methods which will give enough time between two switchings. Manual switching, how ever, has certain shortcomings, due to the human factor such as its accuracy and diligence, as noted above. The recommended practice is therefore to select fast reactive controls as noted below. 

IEEE - Delhi. Section, A Jw/ire Level Course on Reactive Power Control in Electrical Power Systems, December (1984). 

Power reactors are similar to transformers. However, they have only one winding per phase and can be represented as shown in Figure 27.1. They are employed to perform a number of functions, primarily to control and regulate the reactive power of a power system by supplying the inductive and absorbing the capacitive power. Control can be achieved in different ways as noted later. The reactors, depending upon their design and l-(p characteristics, can be classified as follows ... 

Failure of power or controls to the valve (generally related to the seismic capacity of the cable trays, control room, and emergency power). These failure modes are analyzed as failures of separate systems linked to the equipment since they are not related to the specific piece of equipment (i.e., a motor-operated valve) and are common to all active equipment. 

Systems covered include primary, secondary and emergency core cooling systems, control rod, refueling, scram, electrical power, and lube oil, airsupply, battery supplies. 

Simplification of a hydroelectric power plant control system. 

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