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Open-loop controller

About: Open-loop controller is a research topic. Over the lifetime, 16148 publications have been published within this topic receiving 224014 citations. The topic is also known as: non-feedback controller & open-loop control law.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a linear time-invariant robust servomechanism controller for islanded (autonomous) operation of a distributed generation (DG) unit and its local load is proposed.
Abstract: A linear time-invariant (LTI) robust servomechanism controller for islanded (autonomous) operation of a distributed generation (DG) unit and its local load is proposed. The DG unit utilizes a voltage-sourced converter (VSC) as the interface medium. The controller design is obtained by introducing a new optimal controller design procedure, in conjunction with a proposed non-conservative robustness constraint. The proposed controller utilizes 1) an internal oscillator for frequency control and 2) a robust servomechanism controller (RSC) to regulate the island voltage. Despite uncertainty of the load parameters, the proposed controller guarantees robust stability and pre-specified performance criteria, e.g., fast transient response and zero steady-state error. The theoretical aspects of the proposed robust servomechanism controller including the existence conditions, design of the controller, and robust stability analysis of the closed-loop system are studied. Moreover, the performance of the robust servomechanism controller based on 1) simulation studies in the MATLAB software environment, and 2) experiments in a laboratory-scale setup, is presented in this paper. In particular, reference signal tracking and robustness of the closed-loop system with respect to the load parameter uncertainty are investigated. Both computer simulation studies and experimental results confirm that the proposed robust controller provides the specified performance characteristics of the closed-loop system.

173 citations

Journal ArticleDOI
TL;DR: A state-variable-based control methodology in the discrete-time domain that ensures the stability and performance of the closed-loop system, even for high-order controllers and large digital signal processor processing delay.
Abstract: This paper presents a current controller based on a stationary reference frame implementation of an integrator in the synchronous reference frame [called here reduced order generalized integrator (ROGI)], suitable for three-phase distributed generation systems. The proposed controller is compared with the traditional second-order generalized integrator (SOGI)-based current controller. It is confirmed that, in normal operation conditions, both controllers have similar performance, requiring the ROGI-based controller much less computational burden than the SOGI counterpart. The proposed controller injects sinusoidal currents synchronized with the grid voltage, without requiring any dedicated synchronization algorithm. Three different current injection strategies are realizable with the same controller structure: balanced current injection, constant instantaneous active power injection, and maximum instantaneous active power injection. A state-variable-based control methodology in the discrete-time domain is presented. It ensures the stability and performance of the closed-loop system, even for high-order controllers and large digital signal processor processing delay. Moreover, it is confirmed that the proposed controller works satisfactorily even on faulty grid conditions.

173 citations

Journal ArticleDOI
TL;DR: In this article, a Two-Degree-of-freedom-Fractional Order PID (2-DOF-FOPID) controller is proposed for automatic generation control (AGC) of power systems.

172 citations

Proceedings ArticleDOI
02 Oct 1993
TL;DR: In this paper, a variable hysteresis band current controller is described, which achieves constant switching frequency without requiring a precise knowledge of the motor parameters and can be readily implemented in hardware.
Abstract: A novel method for implementing a variable hysteresis band current controller is described which achieves constant switching frequency without requiring a precise knowledge of the motor parameters. The controller works by using feedback and feedback variables to create a variable hysteresis band envelope, and then compensating for the interaction between phase back-EMFs that occurs when the neutral of a three-phase motor is left floating. The controller has good dynamic and steady-state response, and its performance is substantially immune to variations in the inverter DC supply voltage and motor parameters. It can be readily implemented in hardware, and only requires a few additional components compared to a conventional hysteresis current controller. Analytical, hardware implementation, simulation, FFT (fast Fourier transform) analysis, and experimental results are presented. >

172 citations

Journal ArticleDOI
TL;DR: In this article, a simple second-order controller that eliminates scan-induced oscillation and provides integral tracking action is demonstrated to improve the tracking bandwidth of an NT-MDT scanning probe microscope from 15 Hz to 490 Hz while simultaneously improving gain margin from 2 to 7 dB.
Abstract: This paper demonstrates a simple second-order controller that eliminates scan-induced oscillation and provides integral tracking action. The controller can be retrofitted to any scanning probe microscope with position sensors by implementing a simple digital controller or operational amplifier circuit. The controller is demonstrated to improve the tracking bandwidth of an NT-MDT scanning probe microscope from 15 Hz (with an integral controller) to 490 Hz while simultaneously improving gain-margin from 2 to 7 dB. The penalty on sensor induced positioning noise is minimal. A unique benefit of the proposed control scheme is the performance and stability robustness with respect to variations in resonance frequency. This is demonstrated experimentally by a change in resonance frequency from 934 to 140 Hz. This change does not compromise stability or significantly degrade performance. For the scanning probe microscope considered in this paper, the noise is marginally increased from 0.30 to 0.39 nm rms. Open and closed-loop experimental images of a calibration standard are reported at speeds of 1, 10, and 31 lines per second (with a scanner resonance frequency of 290 Hz). Compared with traditional integral controllers, the proposed controller provides a bandwidth improvement of greater than 10 times. This allows faster imaging and less tracking lag at low speeds.

172 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202371
2022124
202167
202079
201998
2018155