Closed-loop Operation Research Articles

Closed loop management system algorithms of acquisition operations and maintenance based on alternation early warning

In order to construct the closed-loop management system of abnormal early warning, the decision tree algorithm, survival analysis algorithm and logistic regression algorithm are used synthetically. The improved logistic regression algorithm proposed in this study is used to establish the abnormal e arly warning model, identify the abnormal tendency in advance, and construct the active monitoring and closed-loop operation and maintenance management system to provide the key technical support. The results show that this method improves the real-time processing of data acquisition, reduces the impact on data acquisition, improves the efficiency of operation and maintenance, and carries out timely and accurate early warning. This method proposes active monitoring mechanism based on complex event processing and fast fault location technology based on expert database. From this point of view, testing the key technical indicators of the system proves that the system can effectively promote the improvement of business operation and maintenance efficiency, quality and management level.

Closed-Loop Hierarchical Operation for Optimal Unit Commitment and Dispatch in Microgrids: A Hybrid System Approach

To contribute to a smart grid, the unit commitment and dispatch (UCD) is a very important problem to be revisited in the future microgrid environment. In this paper, the UCD problem is studied by taking account of both traditional thermal units and distributed generation units (DGs) while considering demand response (DR) and carbon emissions trading (CET). Then, the UCD problem is reformulated as the optimal switching problem of a hybrid system. The reformulation allows convenient handling of time-dependent start-up cost for dynamic programming (DP). Afterwards, a closed-loop hierarchical operation (CLHO) algorithm is developed which is capable of producing the optimal schedule in the closed-loop behavior. Theoretical analysis is also presented to show the equivalence of the reformulation and the effectiveness of the CLHO algorithm. Finally, the closed-loop behavior and the effectiveness of the algorithm are further verified by simulation studies. It is also shown that low emission quotas and high emission trading price help reduce the total carbon emissions.

Pid Controller for Thermal Control in Satellites

The paper gives the application of PID controller in satellite launching; it gives out the different technique which involves PID controller. It involves the temperature control (thermistor) in heater which is situated in the satellite. PID controller is implemented with the use of programmable logic controller. Using Ordinary control techniques, it is very difficult for controlling temperature; hence the purpose of proposed research is implementing PID controller design using programmable logic controller (PLC) in order to control the temperature and maintain the output in such a way that there is zero error between process variable and set point/desired output by closed loop operations in the satellite by avoiding the manual monitoring system. A thorough analysis using various PID parameters is presented in terms of system response. Performance of the controller is examined in terms of duty cycle, average current and power dissipation. Finally, a comparative analysis of PID controller for thermal control in satellite is presented

Generalized Likelihood Ratio Test Based Approach for Stator-Fault Detection in a PWM Inverter-Fed Induction Motor Drive

This paper proposes a new approach for the detection of stator faults in inverter-fed induction motor under closed-loop control. These faults, generally, start with interturn short circuit and can evolve to phase-to-phase or phase-to-ground faults, leading to stator currents unbalance. In the considered application, the stator windings are supplied by a static converter for the control of the speed and the rotor flux of the motor. The unbalance fault has been artificially created through additional resistance in series with one phase of the stator windings. The proposed diagnosis approach is based on the computation of the symmetrical components of the stator currents. The supply fundamental frequency and the three-phase phasors are estimated based on the maximum likelihood estimator. Then, the generalized likelihood ratio test is applied for unbalance fault detection. Simulation and experimental results on a 1.5-kW induction motor illustrate the effectiveness of the proposed approach, leading to an effective diagnosis procedure for stator faults in inverter-fed induction motor under steady state and closed-loop operation.

Modelling and simulation of Math function based controller combined with PID for smooth switching between the battery and ultracapacitor

ABSTRACTTo obtain the better performance of Hybrid Electric Vehicles/Electric Vehicles (HEVs/EVs), are implemented with Hybrid Energy Storage System (HESS), in that Battery is main source and UltraCapacitor (UC) is the auxiliary source. The battery is connected to DC Bus through Boost Converter and UC is connected through Buck-Boost Converter. Battery and UC voltage levels are maintained less than the DC bus voltage. The main aim of this research is to design an intelligent controller for a smooth transition between the sources in the HESS. A Math Function Based (MFB) Controller is modeled and implemented to an electric motor for HEVs/EVs application. The MFB controller has to work based on the motor’s speed and this controller creates the closed loop operation of the overall system with smooth operation between the energy sources. Proportional-Integral-Derivative (PID) controller is used here to maintain the constant voltage profile for various loads at the terminals of the electric motor. Combination of PID and MFB controllers have given closed loop operation of the entire model with smooth switching between the sources. HESS with proposed controller has been applied to four different types of loads and another type with consecutive load changes are simulated in MATLAB/Simulink and obtained satisfactory results.

DfRem-Driven Closed-Loop Supply Chain Decision-Making: A Systematic Framework for Modeling Research

With the prevalence of a circular economy, extended producer responsibility, and the maturity of intelligent manufacturing technology, Design for Remanufacture (DfRem) has become a new driving force for the profitability of the modern supply chain. DfRem activities occur at the stage of new product design but have a significant impact on subsequent remanufacturing operations. Based on the closed-loop supply chain operation systems with DfRem, we systematically explored the impact of DfRem on supply chain operation decisions through a case study and modeling analysis and built up a modeling research framework of DfRem-driven closed-loop supply chain (CLSC) operation decision-making. Our research identified DfRem-driven model design elements and discussed the modeling of DfRem-driven investment decision problems, involving different approaches to obtain DfRem investment (i.e., DfRem-driven horizontal or vertical supply chain cooperation) and the ownership of DfRem-level decision-making rights. Moreover, the DfRem-driven two-stage and multi-period modeling processes are elaborated in detail. The aim of this paper is to provide other scholars with a more comprehensive understanding of DfRem research issues, and to establish an integrated DfRem-driven research framework for subsequent scholars to better conduct modeling research on DfRem.

Practical frequency-domain characterization of switching converters under PWM via Floquet theory

This paper presents the application of a frequency-domain characterization approach applicable to modern power systems involving distinct switching converters via Floquet transformation. As main feature, Floquet theory permits to characterize a network involving switching converters in terms of poles location in the complex plane. This feature can be utilized as an auxiliary tool for parameter design and for stability assessment of a switched network, especially in closed-loop operation. The paper shows that Floquet theory is readily applicable to pulse-width modulation schemes employed in modern electrical networks. Two switched networks, i.e., an HVDC system and a grid-tied system of three photovoltaic generators, are presented as case studies to support the statements above.

Sensor-less vector control of induction motor at low-speed operation using modular multilevel converter

ABSTRACTModular Multilevel Converter (MMC) is widely known as one of the most promising topologies for high power medium voltage application. However, MMC is still limited when it comes to Variable Speed Drive (VSD) applications. The reasons behind this is the large fluctuations in the submodules capacitor voltages during low-speed constant torque operation. Thus, the feasibility of sensor-less vector control of MMC based variable speed drive is considered as a difficult task. This paper proposes a novel speed observer for MMC-based VSD suitable for low-speed operation. Speed estimation is carried out by using the stator currents and the input voltages. A discrete model where the rotor parameters do not change during a short sampling time is considered. An extensive simulation is carried out for verifying the closed loop operation of the proposed speed sensor -less MMC-based VSD.

Study on Grid-Connected Strategy of Distribution Network with High Hydropower Penetration Rate in Isolated Operation

As the largest global renewable source, hydropower is a useful supplement to mountainous distribution networks with abundant water resources, and shoulders a large portion of the regulation duty in many power systems. In particular, in the form of decentralized energy sources located to their customers, small hydropower (SHP) improve grid stability by diversifying the electricity system and reducing power loss. The mountainous distribution networks supplied by small hydropower are closed-loop design but open-loop operation, which easily causes the tripping of tie line even further the off-grid operation of small hydropower system. Once the tie line trips, the current countermeasures—such as hydropower shutdown and load shedding—do not fully guarantee the reliability of power supply and the utilization efficiency of hydropower. This paper studies the amplitude-frequency characteristics of SHP off-grid, according to the typical integration of hydropower in South China, a SHP on-grid/off-grid model is established based on the Power Systems Computer Aided Design (PSCAD) platform. It is found that due to the inertia of SHP, the amplitude-frequency characteristics of SHP island system are relatively slow, and the process of non-synchronization with the main grid is gradually expanded. The characteristic of SHP has a certain degree of synchronization with the main grid in the initial island operates stage, which helps to find a novel grid connection method. This paper further proposes the strategy of using fast busbar automatic transfer switch (BATS), which quickly connect the trip-off SHP to the distribution network under the condition of permitting distributed energy grid-connected. The PSCAD simulation results show that proposed strategy has a limited impact on the power grid and prove the effectiveness of the method.

Efficient Modulation and Processing Method for Closed-Loop Fiber Optic Gyroscope with Piezoelectric Modulator.

This paper presents a simple method for compensating the Sagnac phase shift in an interferometric fiber-optic gyroscope (I-FOG) with a piezoelectric modulator. The common advantages of I-FOGs with closed-loop compensation are linearized output characteristics and insensitivity to the light source power, including its time and thermal-induced fluctuations. Whereas closed-loop operation is normally achieved via ramp modulation requiring an electro-optic modulator, all-fiber architectures with a piezoelectric modulator are mostly limited to open loop. Nevertheless, such setups can more conveniently utilize a less expensive single-mode fiber with depolarized light and do not require any custom-made components. The proposed method allows us to combine the advantages of both approaches. Closed-loop compensation is ensured by adding further sinusoidal modulation to the common biasing modulation, such that the Sagnac phase shift is compensated solely at the sampling instants. We describe and experimentally demonstrate the proposed approach, utilizing a test setup to compare our closed-loop solution with open-loop operation. The results denote that the method provides a cost-efficient manner of performance improvement compared to the open-loop I-FOGs based on a piezoelectric modulator.

Torsion balance-based system for high-precision force measurement in horizontal plane: part II. Static and dynamic improvement

In this paper, improved static and dynamic capabilities of the torsion force measurement system (TFMS) are reported based on an earlier development presented in part I (Yan et al 2018 Meas. Sci. Technol. 29 084001) of this work. The force measurements through a closed-loop operation mode are set up, by which the cut-off frequency is improved from 0.002 Hz to 0.1 Hz. Two different actuation and compensation mechanisms are introduced; in the first case the small forces are produced electromagnetically by a commercial voice coil actuator, in the second case electrostatically using a customized capacitive actuator. We apply Newton’s polynomial interpolation to evaluate the measurement results, which reveals that the TFMS is able to resolve forces with approximately 2 nN resolution in the measuring range of ±3 µN.

Design of an Augmented Output-Based Multiloop Self-Tuning PID Control System

Since the control performance of a proportional–integral–derivative (PID) control systems strongly depends on PID gains, lots of schemes for tuning PID gains have been proposed up to now. Recently, data-driven PID tuning schemes whose PID gains are directly determined from the closed-loop operating data attract attention. Lots of controlled objects are multi-input/multi-output systems, though almost data-driven PID tuning schemes target single-input/single-output systems. In this paper, a new design method of a multiloop self-tuning PID controller is proposed. The proposed scheme first employs a postdecoupler to remove the influence of mutual interference. The multiloop self-tuning PID controller is designed for the approximately decoupled system. The effectiveness of the control scheme is evaluated by numerical and experimental examples.

A Novel Closed Loop Current Sensor Based on a Circular Array of Magnetic Field Sensors

During the last years, coreless current sensors based on circular arrays of magnetic field sensors have been investigated. These sensors were limited in bandwidth and accuracy by the magnetic field sensors used to realize the circular arrays. Thus, this paper applied the well-known “closed loop” principle to circular array-based current sensors to overcome these limitations. This paper gives a comparison between circular arrays built from Hall and Fluxgate magnetic field sensors in both the closed loop and open loop operation. If closed loop configuration Fluxgate sensors are used, instead of Hall sensors, the measurement error can be reduced by a factor of two due to their intrinsic characteristics. Moreover, it is shown that the closed loop operation of the circular arrays results in a significant reduction of the temperature drift of the sensitivity for Fluxgate and Hall sensor-based circular arrays. If Hall sensors are used for the circular array, the reduction of the temperature drift of the sensitivity achieved by closed loop operation is about a factor of 10. If Fluxgate sensors are used, a significant reduction of the nonlinearities like hysteresis and a substantial reduction of the temperature drift of the sensitivity was observed.

Design of a Data-Driven Multi-loop Self-Tuning PID Controller

PID controllers have been widely employed in real processes. Since PID gains strongly affect the control performance, lots of schemes for tuning PID gains have been proposed. Recently, data-driven PID tuning schemes which determine PID gains directly from the closed-loop operating data attract attentions. Lots of controlled objects are multi-input and multi-output systems, though almost data-driven PID tuning schemes target single-input and single-output systems. In this paper, a data-driven multi-loop self-tuning PID controller design is proposed. The proposed scheme first employs a post-compensator to remove mutual interference. Multi-loop self-tuning PID controller is designed for the decoupled system. The effectiveness of the control scheme is evaluated by a simulation example.

A Novel Robust Speed Sensor-Less Control of DC Motor

Until now, Physical sensors have been used for estimating the speed of the DC motor for precise speed control. These Physical sensors not only increase the cost but also contribute to the failure of the overall control system. This paper proposes a novel observer for estimating the rotor speed of the DC motor based on the assumption that the speed will not vary during a short sampling period. Speed estimation is carried out by using the armature current and the supply voltage. Initially, a half order observer has been proposed where the speed is the only estimation variable. It has been found out that the half order observer has maintained an accurate speed estimation until a load disturbance has been introduced. In order to overcome this problem, a robust full order observer is proposed where both the speed and current are estimated. The proposed full order observer shows an accurate estimation during both speed step change and load variation. The closed loop operation of the speed sensor-less DC motor is verified through extensive simulation.

Improved Low-Frequency Operation of Hybrid Inverter for Medium-Voltage Induction Motor Drive Under V/f and Vector Control Mode of Operation

In this paper, an improved control method has been proposed for hybrid inverter to drive medium-voltage induction motor. This hybrid inverter consists of high-voltage three-level inverter that is operated in quasi-square-wave mode. Low-voltage high-frequency H-bridge cells are connected in series with the three-level inverter. They eliminate harmonic voltages generated by the high-voltage quasi-square-wave inverter. This paper proposes systemic choice of harmonic voltages that the series cells need to generate. The choice of these harmonic voltages is dynamically modified based on operating frequency of the drive. This method ensures that the quality of motor current remains same at all operating frequency of the drive. The naturally regulated dc bus voltage of the series cells are kept low for the pulsewidth modulation (PWM) operation of the series cells. Several issues of adopting vector control strategy for hybrid drive have been addressed in this paper. Based on this analysis, suitable motor current control strategy has been proposed without speed sensor. Experimental results are produced for open-loop and closed-loop operations of this drive. The results show the satisfactory operation of this hybrid inverter-based induction motor drive operating from 5 to 50 Hz.

Rotation measurements using a resonant fiber optic gyroscope based on Kagome fiber.

We build a resonant fiber optic gyro based on Kagome hollow-core fiber. A semi-bulk cavity architecture based on an 18-m-long Kagome fiber permits achieving a cavity finesse of 23 with a resonance linewidth of 700kHz. An optimized Pound-Drever-Hall servo-locking scheme is used to probe the cavity in reflection. Closed-loop operation of the gyroscope permits reaching an angular random walk as small as 0.004°/h and a bias stability of 0.45°/h over 0.5s of integration time.

Real-Time Validation of a Sliding Mode Controller for Closed-Loop Operation of Reduced Switch Count Multilevel Inverters

The prominence of reduced switch count multilevel inverters is rising owing their merits of decreased number of switches and modular structures. There are topologies that use more than one source; however, utilization of all the sources at all levels is seldom. These topologies will diminish the energy efficiency of the conversion system as all the sources will not deliver the power except at the highest level in the output voltage. These kinds of converters can hamper the penetration of renewable energy into the existing energy mix, as the energy capacity of the renewable source is undermined. In this connection, this paper explores a three-phase multilevel inverter that can extract the power from all the sources at all the levels through series/parallel switchings. Besides, this paper develops a sliding mode based nonlinear controller for closed-loop operation of the multilevel inverter, which is not addressed sufficiently in the literature. The performance of the developed variable gain nonlinear controller is validated against the PI controller for delivering desired powers under different operating conditions/disturbances using simulations and in real-time environment.

Experimental Research on the Bitter-Like HTS Magnet Energized by an Inner Flux Pump

High-temperature superconducting (HTS) 2G conductors have been extensively applied in high magnetic field. This paper presents a novel excitation method of the Bitter-like HTS magnet for a stack of the RE-Ba-Cu-O (RE = rare earth) annular plates. The Bitter-like HTS magnet was energized by a flux pump composed of a copper solenoid coil and a pulsed triangular waveform current source. A single REBCO annular plate's critical current Ic was measured in 77 K (LN2 bath) in self-field, and the structure design of the whole flux pump, the transient process of the induced magnetic field, and the magnetic field attenuation of the Bitter-like HTS magnet under different excitation methods were described and tested in 77 K. Results show that the Bitter-like HTS magnet energized by a flux pump can realize closed-loop operation, and the flux pump with variation pulsed current values has an impact on the induced magnetic field attenuation in the Bitter-like HTS magnet. Furthermore, the flux pump making use of the inner excitation method has a faster excitation speed than the outer excitation method in our previous study.

Fuzzy logic based adaptation mechanism for MRAS based speed estimators

Performance of the controller in adaptation mechanism of speed estimators designed on the basis of model reference adaptive system (MRAS) scheme, plays very vital role. In this paper, a fuzzy logic controller (FLC) is proposed for the adaptation mechanism of speed estimators to be used in induction motor drive. Performance of the proposed FLC is evaluated for two diverse topologies of MRAS speed estimators, namely stator current (SC) type and the rotor flux (RF) type. The drive performance is investigated with speed estimator for closed loop operation on various working conditions.