Proportional Plus Integral Controller Research Articles

Performance assessment of VSC-based HVDC system in asynchronous grid interconnection: Offline and real-time validation of control design with symmetric optimum PI tuning

Asynchronous interconnection is essential for integrating AC networks operating at different frequencies, typically 50 Hz and 60 Hz. This need arises from distributed power generation methods, including offshore renewable sources and diverse regional grid configurations. Advanced strategies are required to overcome these frequency differences and ensure uninterrupted power transfer.High-Voltage Direct Current (HVDC) transmission systems facilitate efficient power exchange, enhancing grid reliability and stability. This study focuses on optimizing the Proportional-plus-Integral (PI) controller parameters within a 20 MVA Voltage Source Converters (VSC)-based HVDC system to enable asynchronous interconnection between offshore and onshore AC networks. The offshore VSC regulates active and reactive power, while the onshore VSC controls DC voltage and reactive power. A vector control approach with symmetric optimum PI tuning is proposed for a comprehensive performance assessment of the VSC-based HVDC transmission system.The effectiveness of the tuned PI controller parameters is evaluated through four test cases using MATLAB/Simulink for offline simulation and Typhoon HIL604 for real-time validation. These cases involve abrupt changes in reference active and reactive power for the offshore VSC; and in reference reactive power and DC voltage for the onshore VSC. Results demonstrate rapid and satisfactory dynamic performance across all test cases, as evidenced by offline simulations and real-time validation.The validation highlights the effectiveness of the proposed control design with symmetric optimum PI tuning, confirming its ability to enhance the overall performance of the HVDC transmission system for efficient asynchronous interconnection.

Design and implementation of digital controller in delta domain for buck converter

This paper presents the design and implementation of a discrete-time controller for a DC-DC Buck converter in the complex delta domain. Whenever any continuous-time system is sampled to get a corresponding discrete-time system with a very high sampling rate, the shift operator parameterized discrete-time system fails to provide meaningful information. There is another discrete-time operator called delta operator. In the delta operator parameterized discrete-time system, the discrete-time results and continuous-time results can be obtained hand to hand, rather than in two special cases at a very high sampling rate. The superior property of the delta operator is capitalized in this paper to design the proposed controller in the discrete domain. The Proportional plus Integral (PI) controller designed in the delta domain is used to maintain the output voltage of the Buck converter at the load end for varying load and varying supply voltage conditions. The controller is designed and implemented using the DS1202 dSPACE board. The output voltage of the Buck converter is scaled to feed to the onboard analogue to digital converter of DS1202. Under the different disturbances, the error between the desired output voltage and the actual output voltage is measured and the delta PI controller is used to manipulate the duty cycle of the converter. The duty cycle of this pulse width modulation (PWM) signal is generated using a DS1202 board and is applied to the gate of the Metal Oxide Semiconductor field-effect transistor (MOSFET) via a suitable driver such that the output voltage of the Buck converter remains at its desired value.

Development of improved sparrow search-based PI controller for power quality enhancement using UPQC integrated with medical devices

Photovoltaic (PV) panel interfaces with the grid create the issues regarding power quality such as voltage distortion, voltage harmonics, etc. To mitigate the harmonics in PV systems, Active Power Filters (APF) are taken. Unified Power Quality Conditioner (UPQC) is utilized for alleviating the problems correlated with voltage dip/swell in source voltage that has regulated the load voltage absolutely. On the other hand, the existing researches do not solve the power quality problems such as Voltage Stability Index (VSI), UPQC cost and power loss. Power quality is taken as the main demanding one in the analyzing the smart grid. Thus, APFs are primarily selected for compensating the problems occurring in power quality as they has some active compensation and are competent of filtering fast. Moreover, power quality constraint with load current must be addressed, which considers the factors like reduced power factor, huge Total Harmonic Distortion (THD) level, and unbalanced power. To reach the ideal efficiency on UPQC, the voltage control of the DC link capacitor is important. Thus, a new power quality enhancement model with UPQC especially for medical devices is focused. The UPQC-connected medical devices are suggested with a new Adaptively Updating-Sparrow Search Algorithm (AU-SSA)-based Proportional plus Integral (PI) controller, which is integrated with renewable energy like wind turbine Squirrel Cage Induction Generator (SCIG) to eliminate the current and harmonics imperfection accurately. This model implements a new power quality enhancement model by formulating a newly derived objective function. Finally, the experimental verification of the proposed scheme is done.

Hybrid adaptive controlled flywheel energy storage units for transient stability improvement of wind farms

This article introduces a novel hybrid adaptation algorithm comprising both continuous mixed p-norm (CMPN) strategy and the block-sparse Bayesian (BSB) technology to online adapt all the proportional plus integral (PI) controller gains of the power converters of flywheel energy storage units (FESUs). The FESU is based on the doubly fed induction machine (DFIM). The principal target is to improve the transient stability of grid-connected wind farms. To obtain a realistic study, the two-drive train model is utilized in the wind farm modeling affecting the transient analyses. The cascaded control scheme is implemented on controlling both the generator side converter and the grid side inverter of the FESU using the proposed adaptive CMPN-BSB PI controller. The FESU is tied to the point of common coupling of the wind farm, which is tied to the standard IEEE 39 bus system. The performance of the proposed technology is tested under subject the system to different severe faults. The validity of adaptive CMPN-BSB PI controlled FESU is tested by comparing the numerical results with that achieved by least mean square adaptive controlled FESU. The numerical results are performed by PSCAD software. The proposed controlled FESUs will help in improving the transient stability of wind farms and their power quality concerns will be enhanced.

Optimum control for dynamic voltage restorer based on particle swarm optimization algorithm

This article <span>addresses a variety of power quality concerns, including voltage sag and swell, surges, harmonics, and so on, utilizing a dynamic voltage restorer (DVR). The proposed controller for DVR is proportional plus integral (PI) controller. Two methods are used for tuning the parameters of PI controller, trial and error and intelligent optimal method. The utilized optimal method is particle swarm optimization (PSO) method. Results depicted that DVR using PI controller tuned by PSO has improved performance than PI controller tuned by trial and error in term of rise time, maximum overshoot and settling time, as well as total harmonic distortion (THD). These improvements are applicable for voltage sag and swell conditions.</span>

Distributed secondary controller to ensure proportional sharing of reactive power in AC microgrid

In an ac microgrid, reactive power sharing accuracy is affected due to unequal values of interconnecting cable impedances. To resolve this issue, secondary controllers are used to compensate the effect of cable impedances. Various types of secondary controllers are suggested in the literature which includes linear proportional plus integral (PI) controllers to minimize the difference in reactive power sharing created by conventional E−Q droop law. The reference value of the PI controller is the average value of reactive powers supplied by the sources. When the PI controller is used to minimize the difference between the actual and reference value of reactive power, the difference between the algebraic sum of reactive powers supplied by the sources and the reactive powers demanded by the loads has a nonzero value. Therefore, the performance of these controllers becomes poor in the case of ac microgrid having sources of unequal ratings. To resolve this issue, a proportional reactive power-sharing (PRPS) controller-based distributed secondary controller is proposed in this paper. The PRPS controller modifies the droop gain of the E−Q droop control loop of each source in such a way that each source supplies reactive power equal to its proportional value of reactive power. The proportional value of reactive power supplied by each source is the power when the equivalent output impedance of all sources as seen by the loads are identical. The key advantage offered by the proposed controller is the accurate reactive power-sharing in the case of ac microgrid having sources of unequal ratings. The proposed controller ensures zero value of the difference between the algebraic sum of reactive powers supplied by the sources and the reactive powers demanded by the loads. This ensures accurate sharing of reactive power among the sources. The validation of the proposed controller is carried out for islanded mode of operation of ac microgrid. Further, the proposed controller requires of low bandwidth communication for its implementation. The effect of the proposed controller on the stability of the system is demonstrated using reduced order small-signal model. The effect of communication delay on the performance of the system is analyzed with the help of roots locus plots. To validate the efficacy of the proposed controller, detailed simulation studies are carried out in Matlab/Simulink.

Model-Predictive Control for the Three-Tank System Utilizing an Industrial Automation System.

A three-tank process has difficulty in controller design because of nonlinear flow and interactions between tanks. This paper addresses the design methodology of the model-predictive controller (MPC) for the three-tank system. The control performance of the proposed MPC controller is compared with the proportional plus integral (PI) controller by both simulations and experiments on the real three-tank pilot with the industrial ABB 800xA automation system. The MPC controller shows a faster response for the two tanks: In the simulation, the settling times are about 120 s for both tanks of the MPC controller. On the other hand, the settling times for the PI controller are about 200 s for the first tank and 150 s for the second tank. The experiments confirm these results.

A Feedback Control Method to Maintain the Amplitude of the RF Signal Applied to Ion Traps

For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed; thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.

LMSRE-Based Adaptive PI Controller for Enhancing the Performance of an Autonomous Operation of Microgrids

Microgrids take a large part in power networks thanks to their operational and economic benefits. This research introduces a novel implementation of an adaptive proportional plus integral (PI) controller to boost the autonomous microgrid operation efficiency. The least mean and square roots of the exponential algorithm are utilized in the adaptive PI control strategy. The multi-objective function for both sunflower optimization (SFO) and particle swarm optimization (PSO) algorithms is obtained by The Response Surface Methodology. The system is evaluated under different environments, which are stated as follows: 1) disconnect the system from the grid (islanding), 2) autonomous system exposure to load variability, and 3) autonomous system exposure to a symmetrical fault. The proposed practicality of the control plan is shown by the data of the simulation, which is extracted from PSCAD/EMTDC software. The strength of the suggested adaptive control is confirmed through matching its results with those obtained using the SFO and PSO based optimal PI controllers.

Influence of Primary Regulation on Frequency Control of an Isolated Microgrid Equipped with Crow Search Algorithm Tuned Classical Controllers

Along with the power demand variations, change in wind speed and irradiance leads to large frequency oscillations especially in case of isolated microgrid integrated with PV and wind power generating units. To minimize such frequency changes, proportional plus integral (PI) and proportional, integral, and derivative (PID) controllers are set up for controllable generating units of isolated microgrid. However, this paper introduced primary regulation concept for diesel generator (DG) along with PI/PID controller mechanism which enhances overall system stability and minimize the frequency oscillations during the initial stages of load/power changes. Also, the choice of PI and PID controllers is introduced in this paper when the DG’s in microgrid equipped with primary regulation loop along secondary control and only secondary control without primary loop as extension of frequency control. The investigations are carried out in regular load change and generation change patterns along with irregular stochastic models. Crow search optimization algorithm (CSOA) provide fine controller parameters in both cases and results carried out in MATLAB-SIMULINK environment

TLBO Algorithm for Multi-Level Inverter-Based Multi-Terminal HVDC System in Grid-Tied Photovoltaic Power Plant

The main objective of this paper is to overcome the problems with conventionally tuned proportional-plus-integral (PI) controller by using TLBO-PI technique, which enhances the dynamic performance. The significant problem is that it is not able to provide optimal parameters, which is overcome by new teaching-learning-based optimization (TLBO) algorithm. This research work develops a new TLBO for multi-level inverter (MLI)-based multi-terminal HVDC (MLI-MT-HVDC) in grid-tied photovoltaic power plants (GTPVPPs). In this, 7-level inverter is replaced by a conventional 3-level, due to its advantage of less number of switching components, less dc source requirement, low total harmonic distortion (THD) and due to main effective reason of application in HVDC transmission. Here two terminals with individual grid integration are interconnected to a common terminal of solar distributed generation (DG). Among those terminals with grid integration, one is faulty and other is healthy terminal, in which the healthy terminal is not affected due to the fault on a faulty terminal. A teacher and students in a class are employed in step-by-step manner to generate an optimal result. The test system is also controlled with a fuzzy logic controller (FLC), adaptive neuro-fuzzy inference system (ANFIS), but due to its simple structure and its application in industries, a PI controller with new optimization method is implemented. Additionally, it is clear that TLBO-PI can reduce the THD to the level as per IEEE 519-2014 standards, improve fault-ride-through (FRT) capability and enhance the dynamic performance better during abnormalities and dynamic load.

Stability enhancement of grid connected PV system using model reference adaptive controller

The power converters which are connected to main grids having various challenges like parametric uncertainty, instability and voltage fluctuations. To solve these issues adaptive control strategies name Model reference adaptive control (MRAC) has been proposed in this paper. The PI( proportional plus integral) is most widely used method for grid connected PV system due to its simplicity. But in PI current controller the gains are fixed and there is issue of steady state error. In order to obtain the zero steady state error and to make the controller gain adaptive an adaptive control scheme called Model reference adaptive control (MRAC) is employed which is used to make PI controller adaptive. The controller parameters are adapted for simultaneous optimization of controller gains at minimum integral square error condition. Analysis and simulation results show the effectiveness of the proposed adaptive control scheme.

Position analysis of brushless direct current motor using robust fixed order H-infinity controller

PurposeThe efficient speed controller is found to be an important requirement to run the motor for the brushless direct current (BLDC) motor. This requirement is considered as superior, as it may increase the operating speed and system efficiency. In the existing methods, proportional plus integral (PI) controller has been included because of its simple architecture. But the PI controller produces load disturbance, control complexity and some parametric (Proportional plus integral) variations. The purpose of this proposed controller is to overcome the problems produced by PI controller in BLDC motor.Design/methodology/approachThe proposed BLDC motor is developed with fixed order H-infinity controller. In this architecture, both the weight functions and transfer functions were included to design the controller. This controller has been included in this BLDC to detect the rotor position. The optimal position of rotor is identified by introducing particle swarm optimization algorithm.FindingsThe torque that obtained in the motor is highly reduced by this proposed controller and also enhances the speed. The BLDC motor is modelled in a MATLAB environment.Practical implicationsThe performance of the torque, speed and back electro-motive force is analysed and compared with the existing controllers such as fuzzy proportional plus integral plus derivative, sensing algorithm and fuzzy proportional plus derivative controller.Originality/valueSimulation results show that the proposed technique gives better results than the other existing controllers.

An auxiliary control aided modified sliding mode control for a PMSG based wind energy conversion system

Purpose This study proposes a modified sliding mode control technique having a proportional plus integral (PI) sliding surface aided by auxiliary control applied to a wind turbine driven permanent magnet synchronous generator. This paper aims to realize real and reactive power control, keeping the voltage under the desired limit during transients. Design/methodology/approach First, a PI sliding surface type sliding mode control (PISMC) is formulated, which is capable of dragging the system to the desired state and stability. Then a saturation function-based auxiliary controller is incorporated with PISMC to enhance its performance during wind speed and system parameter variations. Findings The proposed controller can tackle the problems faced while using a PI controller and the conventional sliding mode controller (CSMC) such as lack of robustness and requirement of unnecessary large control signals to overcome the parametric uncertainties and problem of chattering. Originality/value To justify the superior performance of the proposed controller in terms of robustness, reliability and accuracy a comparative study is done with the CSMC and PI controllers. The simulations are performed using MATLAB.

Comparative Analysis among Single-Stage, Dual-Stage, and Triple-Stage Actuator Systems Applied to a Hard Disk Drive Servo System

In modern times, the design and optimization of different actuator systems for controlling a high-precision position control system represent a popular interdisciplinary research area. Initially, only single-stage actuator systems were used to control most of the motion control applications. Currently, dual-stage actuation systems are widely applied to high-precision position control systems such as hard disk drive (HDD) servo systems. In the dual-stage system, a voice coil motor (VCM) actuator is used as the primary stage and a piezoelectric micro-actuator is applied as the secondary stage. However, a dual-stage control architecture does not show significant performance improvements to achieve the next-generation high-capacity HDD servo system. Research continues on how to fabricate a tertiary actuator for a triple-stage HDD servo system. A thermal positioning controller (TPC) actuator is considered promising as the tertiary stage. The triple-stage system aims to achieve greater bandwidth, track density, and disk speed, with minimum sensitivity and greater error minimization. In this work, these three actuation systems with different combinations of proportional plus integral (PI), proportional plus derivative (PD), and proportional plus integral plus derivative (PID) controller, lag-lead controller, lag filter, and inverse lead plus a PI controller were designed and analyzed through simulation to achieve high-precision positioning. The comparative analyses were done on the MATLAB/Simulink simulation platform.

A novel modified robust load frequency controller scheme

The main target of this study is to allow virtual inertia modern distributed energy resources (DERs) to participate effectively within interconnected power systems via fractional order PI controller. Fractional order proportional plus integral (PI) is a PI whose integral order is a faction rather than integer numbers. The load frequency control (LFC) approach determines the fractional order PI parameters based on an artificial bee colony optimization algorithm. Besides, a per phase linearized model for massless DERs was developed for solving LFC issues. In order to avoid the complexity associated with the power systems, the optimization problem was formulated based on a time domain objective function, which is based on the norm of each area control error vector. The time domain simulated evaluations are compared with the classical PI and integral controllers. Simulated results show that the developed factional order PI outperforms the other controllers in terms of damping the oscillations and many system indices.

Adaptive PI Control Strategy for Microgrid Performance Enhancement

Microgrids attain a significant role in electrical power systems due to their practical and economic benefits. A novel application of an adaptive Proportional plus Integral (PI) controller with the purpose of improving the microgrid performance is presented in this paper. The control strategy of the adaptive PI controller is based on Widrow-Hoff adaptation technique. The efficiency of the suggested controller is proved by comparing its outcomes with that obtained by utilizing Flower Pollination algorithm (FPA) which is used to fine tune the PI controller parameters of the inverter based microgrid. The utilized multi-objective optimization problem used by the FPA is created by the Response Surface Methodology (RSM). Simulation results are carried out using PSCAD/EMTDC environment to check the validity of the proposed control strategy. The simulation results are tested under various operating states such as 1) conversion of the system from grid connected to stand alone mode of operation, 2) subjecting the system to three line to ground fault in the autonomous mode, and 3) exposing the system to the load variability in the islanded mode.

Plug in hybrid vehicle-wind-diesel autonomous hybrid power system: frequency control using FA and CSA optimized controller

Large integration of renewable energy in hybrid power system in isolated mode of operation make frequency control a challenging task. This paper investigates the performance of Cuckoo Search Algorithm (CSA) and Firefly Algorithm (FA) based frequency control strategy of such a hybrid power system, which is a unique work. The generating units of the system are plug in hybrid vehicle (PHEV), wind turbine generators, a diesel engine generator (DEG) and battery energy storage system (BESS). The proportional plus integral (PI)/proportional integral derivative (PID) controllers are employed with PHEV, DEG and BESS to adjust the total active power generation in accordance to the load demand. Addition of PHEV reduces the reliance on the DEG or BESS as a result of variability and uncertainty of wind power. Different disturbance conditions such as step perturbations, random variations of load as well as wind output power, have been considered in the case studies under Matlab simulation to assess the performance of CSA and FA based control strategy. Analysis indicates that CSA based PID controller provides better response compare to GA, PSO and FA based PI/PID controller and CSA based PI controller. Sensitivity analysis has been carried out to check the robustness of FA and CSA optimized PI/PID controller gains.

Control of Third Order Processes Using Optimized Synthesis PI Controller

In closed loop system with PI controller, the most and severe problem is peak overshoot minimization in the closed loop response and tuning the proportional plus integral (PI) controller parameters. This paper deals with the two different tuning methods for obtain the PI controller settings. These methods are used to tune the parameters of PI controller and the closed loop performances of two methods are analyzed for the control of third order processes. From the closed loop responses, the time responses are move to unstable characteristics and the process variables are oscillates due to PI parameters are tuned using Ziegler-Nichols method and direct synthesis method respectively. The control loop performance of the control of third order process is improved with optimized parameters of PI controller. In direct synthesis method, the variable parameter of PI controller is obtained with Genetic algorithm. The controller parameter of PI controller is obtained from optimized variable parameters and results are reveals that the performance of closed loop is enhanced with the elimination of peak overshoot and minimization of oscillation levels in the process variables. Simulation results are confirmation that the proposed design method is better to the Ziegler-Nichols method and direct synthesis method. Furthermore, the proposed method was applied to the control of two different categories of third order processes.

Design and Tuning of Robust Fractional Order Controller for Autonomous Microgrid VSC System

A robust controller design for the voltage control of an autonomous three-phase voltage source converter (VSC) is proposed. As compared with the conventional proportional plus integral (PI) controllers, fractional order controllers make the VSC system robust due to their fractional characteristics. The fractional PI $\lambda$ controller has an additional degree of freedom $\lambda$ along with $k_p$ and $k_i$ gains of the conventional PI controller. Detailed modeling of a VSC is used in the controller design process so as it include inner current control and filter dynamics. The outer fractional voltage controller is designed such that the VSC system satisfies a required phase margin, with improved robustness in the system and capability to attenuate the noise. The overall system stability is analyzed using both bode plot and step response, and these responses are compared with a conventional PI controller. Further, the dynamic performance of the fractional controller is evaluated by simulating the nonlinear system. A hardware prototype is also developed to demonstrate the practical realization of the controller.