Sensing bandwidth of electrothermal MEMS transducers in constant voltage and current modes

This paper addresses effects of constant voltage and current biasing methods on sensing bandwidth of electrothermal displacement sensors in micro-electromechanical systems (MEMS). The dynamic response of the sensor is modeled based on first principles. The obtained model successfully captures a variety of nonlinear phenomena. Experiments are conducted to confirm the validity of the model and simulation results

Improving the wind energy conversion system dynamics during fault ride through: UPFC versus STATCOM

There is a continuously growing demand for wind power generation capacity. This situation forces the revision of the grid codes requirements, to remain connected during grid faults, i.e., to ride through the faults, and contribute to system stability during fault condition. In a typical fault condition, the voltage at the Point of Common Coupling (PCC) drops below 80% immediately and the rotor speed of induction generators becomes unstable. In this paper, STATCOM and UPFC are used to improving the low voltage ride- through (LVRT) of wind energy conversion system (WECS) and to damp the rotor speed oscillations of induction generator under fault conditions. Furthermore, the performances of these two equipments are compared with each other. STATCOM can only recover voltage after fault clearing at the terminals of the wind energy conversion system (WECS), while controlling the UPFC as a virtual inductor can lead to increase the voltage at the WECS terminals during the fault clearing. The simulation results show that the UPFC is better than STATCOM in improving the LVRT and rotor stability of the WECS. Also, the simulation results show that UPFC can improve the voltage at the PCC in the fault period, with the voltage at the PCC easily recovering to 1pu, simultaneously. STATCOM can recover the voltage at the PCC only after the fault clearing with a high risk of decreasing the PCC voltage to zero during the fault

Realization of a class of compensators by modulated-demodulated structures with application in tracking of biased sinusoids

We derive conditions under which a modulated-demodulated control system is equivalent to a linear-time-invariant (LTI) transfer function. A design strategy is proposed to realize any LTI compensator with non-repeated complex poles by a modulated-demodulated structure. We also propose two different approaches for tracking of biased sinusoidal reference signals in a modulated-demodulated control system. Tracking and disturbance rejection performances of the proposed methods are evaluated and compared by simulations performed on a non-minimum-phase marginally stable plant

Development of a MEMS position transducer using bulk piezoresistivity of suspensions

This paper addresses a new position transducer for nanopositioners fabricated through a standard micro-electromechanical systems (MEMS) process. The sensor works based on bulk piezoresistivity of a pair of single-crystal silicon beams, which suspend a nanopositioner stage. The beams are deliberately angled to experience opposite axial forces during the motion, yielding opposite piezoresistive changes in their resistances. A Wheatstone bridge and an instrumentation amplifier differentially transform the changes in the beam resistances into the output voltage of the sensor. In comparison with a sensors employing just one monocrystalline or polycrystalline silicon flexible beam as piezoresistor, the proposed design has considerably more linear characteristics, higher resolution and dynamic range, as well as lower noise and drift

Stability of signal transformation method for triangular waveform tracking

This paper is concerned with the mathematical analysis of signal transformation approach to triangular waveform tracking. We provide necessary and almost sufficient conditions for stability and convergence of tracking error for a general class of plants and compensators. Simulation results are presented that reveal the conditions under which the incorporation of signal transformation blocks in a linear feedback loop may introduce control performance improvements

Improvement of transient response in signal transformation approach by proper compensator initialization

In this brief, the transient performance of the signal transformation approach (STA) is considerably enhanced by initializing the state vector of the compensator to appropriate values. For triangular reference tracking, it is shown that the proposed method is identical to the impulsive state multiplication (ISM) approach. Through simulations and experiments, we also show that the proposed method can be equally applied to improve the STA for arbitrarily shaped desired signals, where ISM is not applicable. Tracking efficacy of the proposed method compared with that of an ordinary feedback loop with a similar noise rejection performance is also demonstrated