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This work focuses on a gain scheduled Model Predictive Controller (MPC) for the dynamic performance enhancement of an excavator boom. The method can be generalized and applied to similar machines with the installation of pressure and boom angle transducers without modifying the hydraulic circuit of the system. In the proposed method, the transient part of pressure signals is isolated and used to counteract the actuator vibrations through a valve-based compensator. A full-scale model of an excavator’s arm has been used for the experimental verification of the proposed approach. The experiments are conducted under various conditions with the proposed controller and compared with the conventional system. Since the stability of these types of machines is extremely important from the safety point of view, a stability analysis has been carried out and closed-loop stability of the system is ensured with the proposed controller. A significant reduction of 58% and 41% have been achieved in the cost function under maximum velocity extension and lowering phase respectively, where maximum boom oscillations are observed. Furthermore, an average vibration reduction of 46 % is obtained using the proposed method. [ABSTRACT FROM AUTHOR]

Underfrequency load shedding is commonly used in the utility systems when AGC (Automatic Generation Control) cannot keep pace with the load demand and the stability of the generators can be jeopardized—undue stresses can be imposed on steam turbine blades. For an industrial system the underfrequency load shedding may have to be resorted to on loss of a source, to restore load-generation balance and prevent Undervoltages in the distribution system. It is documented that as long as the utility source is connected, there may not be any significant change in the frequency. This is because the plant generators, which are relatively small, cannot dictate the system frequency when operating in synchronism. Undervoltage load shedding can be resorted to. In both case the stability and frequency recovery characteristics of the generators must be studied. [ABSTRACT FROM AUTHOR]

Pole amplitude modulation (PAM) motor is a single-winding two speed motor used for induced draft fans. Its cost is much less than that of an adjustable speed drive motor. This paper is prompted by a rigorous study that was undertaken to replace an existing oil filled, leaky, transfer-switch type, two-speed motor starter, with an adjunct of tens of hard wired timers in a utility installation. The paper describes the fundamental operation of a PAM motor, different torque speed and thermal withstand characteristics at two speeds, and design of an alternate starter using conventional vacuum contactors with modern multifunction microprocessor relays to provide effective protection during normal two-speed operation and starting. [ABSTRACT FROM AUTHOR]

The application of STATCOM or STATCON is common in transmission systems—the device has a capability of P-Q control in four quadrants. DSTATCOM (for distribution systems) and dynamic voltage regulator are somewhat synonymous. This paper describes a unique distribution system with three in-plant generators and an interconnection to a weak utility system at 44 kV; the three-phase short-circuit level at the utility source is only 151.7 MVA. So long as the generators are in operation, the power factor at the utility interconnection can be maintained close to unity and the voltage profiles in the system are acceptable—a total of 64 MW of load is served from 3–13.8-kV interconnected bus system. To control the voltage dips on loss of generation, 31 Mvar of capacitor filters (as the distribution system has considerable drive system loads and harmonic analysis study is conducted) are installed, yet the voltage dip can exceed 25%. A STATCOM can restore the voltage in one-half cycle. The STATCOM is also briefly compared with other technologies like TCR and TSC. [ABSTRACT FROM AUTHOR]

Chipper motors in pulp and paper mill environment are of special design—the stability on impact loads is one important consideration. The power factor under normal operation will continuously swing due to varying loads. This paper describes the guesswork-free rigorous calculations of pull-out (out-of-step) power factor based on the parameter of an actual installation. Single phasing is rather a rare occurrence; however, such an event has been experienced in an installation due to overheating and arcing at the fuse clips in a NEMA E2 starter of a chipper motor. Discussions on the single-phase protection of synchronous motors and recommended settings are provided. [ABSTRACT FROM AUTHOR]

This paper describes a selective high-resistance grounding (HRG) system for a large industrial facility with two in-plant generators in cogeneration mode and two utility transformers. In a five-step coordination using sensitive ground fault nondirectional and directional relays, ground faults throughout the distribution system are cleared with a maximum pickup setting of 6 A, and time delay of 0.25 s. A major consideration for HRG systems is that the stray capacitance charging current of the system should be small (10–15 A) to prevent ground fault damage. If the fault is left in place for some duration for a single-line-to-ground fault, insulation stresses occur due to higher line-to-ground voltages on two unfaulted phases. This paper demonstrates that with selective HRG, both these concerns are mitigated. A selective HRG is a bridge between the classical concepts of HRG and low-resistance grounding. The modern advancements in ground sensors and protective relaying can selectively clear low levels of ground fault currents, which make selective HRG a reality. [ABSTRACT FROM AUTHOR]

The design and application of second-order high-pass filters are described for 2-8000-hp ID fan drives, which reduces the voltage harmonic distortion at point of common coupling (PCC) from a high value of 42.41% to 1.32% and also brings the current distortion at PCC within IEEE 519 limits. Failure of the electronic components of the 8000-hp ID fan drives and shutdown of electronic loads downstream of the main 13.8-kV buses were observed, which led to investigation of harmonic problems and their mitigation. The second-order high-pass filters are applied for the first time in industry for such a harmonic distortion problem. [ABSTRACT FROM PUBLISHER]