Internal Control Loop Research Articles

Improved Performance of the Permanent Magnet Synchronous Motor Sensorless Control System Based on Direct Torque Control Strategy and Sliding Mode Control Using Fractional Order and Fractal Dimension Calculus

This article starts from the premise that one of the global control strategies of the Permanent Magnet Synchronous Motor (PMSM), namely the Direct Torque Control (DTC) control strategy, is characterized by the fact that the internal flux and torque control loop usually uses ON–OFF controllers with hysteresis, which offer easy implementation and very short response times, but the oscillations introduced by them must be cancelled by the external speed loop controller. Typically, this is a PI speed controller, whose performance is good around global operating points and for relatively small variations in external parameters and disturbances, caused in particular by load torque variation. Exploiting the advantages of the DTC strategy, this article presents a way to improve the performance of the sensorless control system (SCS) of the PMSM using the Proportional Integrator (PI), PI Equilibrium Optimizer Algorithm (EOA), Fractional Order (FO) PI, Tilt Integral Derivative (TID) and FO Lead–Lag under constant flux conditions. Sliding Mode Control (SMC) and FOSMC are proposed under conditions where the flux is variable. The performance indicators of the control system are the usual ones: response time, settling time, overshoot, steady-state error and speed ripple, plus another one given by the fractal dimension (FD) of the PMSM rotor speed signal, and the hypothesis that the FD of the controlled signal is higher when the control system performs better is verified. The article also presents the basic equations of the PMSM, based on which the synthesis of integer and fractional controllers, the synthesis of an observer for estimating the PMSM rotor speed, electromagnetic torque and stator flux are presented. The comparison of the performance for the proposed control systems and the demonstration of the parametric robustness are performed by numerical simulations in Matlab/Simulink using Simscape Electrical and Fractional-Order Modelling and Control (FOMCON). Real-time control based on an embedded system using a TMS320F28379D controller demonstrates the good performance of the PMSM-SCS based on the DTC strategy in a complete Hardware-In-the-Loop (HIL) implementation.

DEVELOPMENT OF AN INFORMATION AND LOGIC MODEL FOR PREVENTING EMERGENCIES DUE TO IMPACT ON PROTECTIVE ELEMENTS OF SMALL SHELTER FACILITIES BY SHOCK AND IMPULSE LOAD

The article examines problems of preventing emergencies due to damage to small shelter facilities caused by the impact of unmanned aerial vehicles (UAVs), which, in turn, leads to shock-impulse loading of their upper hemisphere and the following destruction. The development of a civilian protection system against terrorist attacks on civilian infrastructure in the form of an extensive network of small shelter facilities increases the level of individual and collective protection of the population, especially in cities that fall within the area of enemy missile and artillery strikes. Therefore, when designing and building settlements, it is necessary to provide for the possibility of protecting the civilian population from both shrapnel-type damage, which already has a practical implementation in existing projects, and from possible high-precision destruction of the upper hemisphere of small shelter facilities by a UAV warhead of high explosive or thermobaric type. Relevant design solutions should focus on preventing terrorist emergencies due to shock-impulse loading of the upper hemisphere of small shelters, which is formed by considering the information-logic model for preventing local-level emergencies due to shock-impulse loading of small shelter facilities. The information-logic model assumes the existence of two security management loops for a small shelter: external and internal. It is worth noting that the external loop is an integral part of the overall urban (regional) air defence system and includes the block of measures to directly affect the threat (striking UAV) in the form of firearms and electronic warfare. The result of the successful development of management decisions by the external control loop is eliminating the threat of an enemy attack UAV. On the other hand, the experience and individual elements of the UAV are the basis for the formation of initial conditions of the mathematical model for preventing terrorist emergencies due to the shock and impulse load of small shelter facilities. The initial conditions represent the result of the development of two consecutive blocks: a block for collecting UAV characteristics and a block for analysing the shock-impulse load that occurs or is predicted based on the characteristics of the attacking UAV. The basis of the internal control loop is the mitigation design unit, which determines further information exchange within this loop. In particular, it triggers the block for improving the effectiveness of protection, which receives statistical and predictive information on emergencies that have occurred (nature of damage and consequences). It allows for continuous updating of information on the characteristics of construction materials used in the construction of shelter facilities and the effectiveness of design solutions, forming characteristics of a small shelter. The result of the corresponding block is the formation of boundary conditions of the mathematical model for preventing terrorist emergencies due to the shock and impulse loading of small shelters. The basis of the block for forming the coupling equation of the mathematical model for preventing terrorist emergencies due to shock-impulse loading of small shelter facilities is the theoretical and practical achievements of the theory of reliability and its derivative theory of plasticity. An appropriate solution to the problem of preventing terrorist emergencies due to shock and impulse loading of small shelter facilities allows further implementation of management decisions to improve the efficiency of protection. Thus, the study solved an urgent scientific problem, namely, the formation of an information-logical model for the prevention of local-level emergencies due to shock-impulse loading of small shelter facilities, the implementation of which allows to form management decisions to improve the security of small shelters and is the basis for further development of an appropriate mathematical model and methodology. Keywords: information-logic model, shock-impulse load, small shelter facility, emergency.

Control and Intelligent Optimization of a Photovoltaic (PV) Inverter System: A Review

PV power generation is developing fast in both centralized and distributed forms under the background of constructing a new power system with high penetration of renewable sources. However, the control performance and stability of the PV system is seriously affected by the interaction between PV internal control loops and the external power grid. The impact of the PV system on the reliability, stability, and power quality of power systems has restricted them to further participate in power supplies with a large capacity. Traditional control methods have become ineffective at dealing with these problems as the PV system becomes increasingly complex and nonlinear. Intelligent control as a more advanced technology has been integrated into the PV system to improve system control performance and stability. However, intelligent control for the PV system is still in the early stages due to the extensive calculation and intricate implementation of intelligent algorithms. Further investigations should be carried out to effectively combine intelligent control with the PV system to constitute an intelligent PV power system with multiple functions, high stability, and high-performance. This paper provides a systematic classification and detailed introduction of various intelligent optimization methods in a PV inverter system based on the traditional structure and typical control. The future trends and research topics are given to provide a reference for the intelligent optimization control in the PV system.

Control of Quadcopter Based on Adaptive Fast Nonsingular Terminal Sliding Mode

This paper presents a novel approach to address the trajectory tracking control problem for quadcopter systems subjected to multiple disturbances. The proposed method integrates sliding mode control with adaptive control techniques, resulting in an effective adaptive fast nonsingular terminal sliding mode (AFNTSM) controller. The controller structure can be divided into an internal attitude control loop and an external position control loop. In the altitude control loop, a strategy employing AFNTSM is utilized to tackle time-varying external disturbances. In the attitude control loop, given the existence of uncertain system parameters, an attitude controller is designed by combining a PID controller with an extended state observer. The asymptotic stability of the system is verified by using Lyapunov’s theorem. Finally, experimental flights validate the superiority of this control strategy over the traditional PID algorithm.

Trajectory Tracking Outer Loop Regressor-Based Adaptive Controller for a Quadrotor

A high-level control strategy for a quad rotorcraft Unmanned Aircraft System to perform trajectory tracking tasks is presented, which is based on a regressor-based adaptive approach. The high-level control is designed to interact with a low-level (internal) control loop that cannot be modified to suit the needs of academic researchers. Hence, the proposed control framework computes the appropriate high-level inputs for the inner controller, enabling the trajectory tracking task. The controller includes an integral action to overcome steady-state errors that may occur due to parameter estimation errors or constant disturbances. The stability of the equilibrium point is analyzed using Lyapunov theory, which shows that the tracking errors converge to zero and the parameter estimation errors remain bounded. The proposed control framework was tested on a real-time quad rotorcraft platform, and its performance was compared with four different control strategies. The results indicate that the proposed controller exhibits high accuracy and has better performance with respect to the other controllers.

Synchronverters With Fast Current Loops

Virtual synchronous machines (VSM) are inverters that behave towards the power grid like synchronous generators. Hence, they can be used as grid forming inverters and they can support the grid with inertia, droops, fault ride-through and more. Synchronverters are a much studied type of VSM. In this paper we present several improvements and innovations to the synchronverter control algorithm. We offer a complete design procedure for this algorithm. One change is meant to mitigate the fact that earlier designs are very sensitive to grid voltage measurement errors and processing delay, which may cause harmonic distortion and fluctuating amplitude of the grid-side currents. We propose to include a fast current controller as the internal control loop of the inverter. The design of this current controller involves delicate issues of compensating the delays and eliminating the DC components of the currents. The new design enables also a natural way for distortion-less current limitation. We present a smooth start-up procedure. Our simulations and experiments show that the current controller leads to a dramatic reduction of the sensitivity of the VSM to measurement errors, processing delay and grid voltage imbalance.

Active disturbance rejection control of an islanded PV/wind/battery microgrid with power quality enhancement by SAPF

<p><span lang="EN-US">The focus in this study is on an islanded microgrid based on hybrid renewable energy sources and storage systems. This latter is considered as an essential element for all off-grid autonomous systems to offer a reliable and stable operation. The proposed system is composed of a photovoltaic system, a wind power system based on a synchronous generator and a storage system. The proposed control strategy is intended to control, through the load side converter (LSC), the AC bus voltage in terms of amplitude and frequency under different operating conditions, and to obtain, through the bi-directional battery side converter (BSC), a better regulation between the available production and the global load demand. The proposed strategy also contributes to the power quality improvement in the AC bus by controlling the PV inverter to work as a shunt active power filter to provide the required harmonic current component to non-linear loads. A new robust control strategy for internal current and voltage control loops is proposed in this research paper, it’s the active disturbance rejection control (ADRC) and it is based on the extended state observer which allows to estimate all disturbances affecting the control, such as modeling errors and parameter variations.</span></p>

Small-Signal Modeling and Stability Analysis of a Grid-Following Inverter with Inertia Emulation

Power-converter-based energy-harvesting and storage systems are becoming more prevalent in the electrical grid, replacing conventional synchronous generators. Consequently, grid inertia is diminishing, and to address this, inverter-based energy conversion systems are required by grid codes to provide frequency control support to the main grid. This is undertaken to increase the equivalent inertia of the system and reduce frequency variations. This type of control is necessary and designed for handling large system transients. However, it also impacts the small-signal stability of the grid-connected converters. To investigate this issue, this paper addresses the influence of synthetic inertia control on the output admittance of a grid-following inverter and its interaction with the grid equivalent impedance. A synchronous reference frame dynamic model of the grid-following inverter closed-loop system is obtained and linearized at an operating point to analyze the small-signal stability of the low-switching frequency inverter. The models are validated through numerical simulations. The analysis verifies the interactions of the internal control loops, such as the AC current control with voltage feedforward, DC-link voltage control with power-feedforward, phase-locked loop, and AC voltage control with inertial control. Additionally, the interactions between the output admittance of the inverter and the grid impedance are verified using the generalized Nyquist criterion. The stability regions are validated through simulations, and the results show that the system gain margin is reduced for increasing values of synthetic inertia gain and lower grid short-circuit ratios. Furthermore, there is a limit in the voltage and power-feedforward bandwidth to avoid degrading the system stability when utilizing the synthetic inertia control.

Analysis of a Multifunctional Inverter Active-Filtering Function Influence on the Small-Signal Stability of Inverter-Based Islanded AC Microgrids

This paper deals with the small-signal analysis of islanded AC microgrids, considering the coexistence of voltage-controlled converters (VCC) operating under droop control law and current-controlled converters (CCC) operating as multifunctional inverters. Thus, the CCCs can deliver power from a non-dispatchable energy source and, depending on the operation mode, they can perform the active filtering function (AFF), which consists of injecting the harmonic currents associated with the local non-linear loads (NLL) resulting in a microgrid power quality (PQ) improvement. However, the transient characteristics following a local NLL step highly depend on the CCC operation mode. When AFF is disabled, the CCC output is almost not affected by the local NLL step. Instead, the harmonic extraction algorithm dynamics affect the CCC output when AFF is enabled. As a result, the overall system dynamic behavior is significantly affected, since microgrids are low-inertia and small power systems. A generic small-signal model is derived to study these effects, and its accuracy is then validated through simulated and experimental results. It was found through time-domain and frequency-domain sensitivity analyses that the AFF significantly affects the CCC PLL and the dynamic interactions between the microgrid network and the inverter's internal control loops.

Wind farm control and power curve optimization using induction-based wake model

This paper proposes a control strategy to achieve minimum wake-induced power losses in a wind farm. At first, the axial-induction-based wake model is developed to consider the aerodynamic wake interactions among wind turbines. To optimize the generated power of the whole wind farm, the axial induction factor of each wind turbine is calculated by the genetic algorithm. As a supervisory controller, each wind turbine’s optimal axial induction factor calculated by the genetic algorithm is implemented as a setpoint of each wind turbine’s internal controller. In the internal control loop, a comprehensive controller is designed to track the commanded axial induction factor. In the partial load region, the commanded axial induction factor was attained by tuning the generator torque. In the transient and full load regions, the blade pitch angle is tuned to keep the generator speed and torque at the rated values. The performance of the proposed control strategy is investigated through case studies, including three different wind speeds and a time-varying wind speed case in a 3 × 3 wind-farm layout. The simulation results show the satisfactory performance of the proposed approach.

ОЦІНЮВАННЯ ЕФЕКТИВНОСТІ ЗАСТОСУВАННЯ ЗАСОБІВ РАДІОЕЛЕКТРОННОЇ БОРОТЬБИ ДЛЯ ПРОТИДІЇ ВИСОКОТОЧНІЙ ЗБРОЇ ЯК СКЛАДОВОЇ ОПЕРАЦІЇ В ЕЛЕКТРОМАГНІТНОМУ СПЕКТРІ

The presence of a significant number of strike systems of high-precision weapons at the enemy causes an urgent need to create effective systems for the protection of infrastructural and military facilities. One of the elements of such systems can be the forces and means of radio-electronic warfare, which will allow to carry out protective actions in the electromagnetic spectrum. But in the current conditions of resource and time limitations, the involvement of electronic warfare means in such protection systems is a certain scientific and practical problem that needs to be solved, in particular, through the determination of the predicted effectiveness of their functioning in the system of object protection. The article proposes an approach according to which the actions of high-precision weapons in the process of aiming them at objects and the corresponding measures of defense systems used against them are considered antagonistic, since they are performed both with the use of transmitting and receiving radio-electronic means of high-precision weapons, and protection systems. The use of radio-electronic warfare in operations in the electromagnetic spectrum to counter high-precision weapons is being investigated as a component of operations in the electromagnetic spectrum. To conduct the research, a tactical combat episode was considered, in which the accepted assumptions and limitations do not distort the content and physical essence of the processes of radio-electronic warfare with high-precision weapons. It is proposed to evaluate radio-electronic warfare based on the probability indicator of disorganization of the high-precision weapon guidance system. It is shown that, in accordance with the accepted conditions, in the numerical definition, the indicator is limited by the probability of successful guidance, which is provided by an inertial system that does not require the organization of radio communication lines, and data transmission is carried out in the internal control loop. The proposed indicator can characterize the use of electronic warfare forces and means in defense systems against high-precision weapons, since it depends on: from the technical characteristics of samples of high-precision weapons (indirectly determines the immunity of the radio lines of their guidance systems); from the capabilities of the forces and means of radio-electronic warfare with high-precision weapons. Keywords: high-precision weapons; operation in the electromagnetic spectrum; electronic warfare; guidance systems.

Model-based control strategy for the three-phase [formula omitted]-level CHB multilevel converter

This paper presents a control methodology for a three-phase cascaded H-bridge (3ph-CHB) converter in the general case of n-levels (3ph-CHB-nL). The proposed method is used to compensate reactive power and to eliminate the harmonic currents caused by non-linear loads. For this, a generalized modeling process of the CHB-nL converter is first introduced, which includes the effect of the line impedance. The control objectives comprise a current tracking loop, as well as regulation and balance voltage loops for all H-bridges. The proposed controller solution includes an internal control loop to ensure line current tracking towards an extended reference that includes additional degrees of freedom. The current reference has been designed in such a way that, in the steady state, it becomes proportional to the fundamental component of the line voltage. The proposed controller also includes outer voltage loops to guarantee regulation and balance of the involved capacitor voltages. Experimental results have been realized in a three-phase and five-level CHB (3ph-CHB-5L) prototype to assess the performance of the proposed generalized controller.

A Hierarchical Small-Signal Controller Stability Analysis Method for the MMCs

Differing from a two-level voltage source converter (TL-VSC), the internal dynamics of a modular multilevel converter (MMC) are much more complicated. Since the fluctuation of submodule capacitor voltage is unavoidable when transmitting power, the MMCs output voltages cannot track the references perfectly. The interaction between the time-varying capacitor dynamics and controllers may lead to self-instability of the MMCs. In order to address this self-instability issue, this paper first establishes the small-signal closed loop transfer function matrices (TFMs) of the external and internal control loop by the harmonic linearization method. Further, a novel design principle of MMC controllers is proposed. Then, the critical impact factors on the stability of circulating current controller and AC voltage controller are investigated based on the generalized Nyquist criterion(GNC). The proposed models and analysis methods are validated by time-domain simulations in PSCAD/EMTDC.

Analysis of Internal Control Loop Interactions in VSCs: An Individual Design Perspective

This paper addresses the interactions among the control loops of voltage-sourced converters (VSCs) embedded in high-voltage direct current(HVDC) systems and the impact of these interactions on the performance of individual control loops. Furthermore, this paper proposes a method to design the individual control loops, rather than the interconnected control system, such that the overall system stability is ensured in the presence of interactions. This paper addresses three aspects of the impact of control loop interactions on the overall control system of the VSC including stability, transient response, and steady-state response. To illustrate the impact of interactions on the VSC small-signal stability, stability regions of the interconnected control loops are obtained and compared against those of the various individual control loops. Then, a novel formulation of the VSC stability criterion is presented, and the small-gain theorem is utilized to determine a range of stabilizing gains for the interconnected control system. Moreover, new indices using the infinity norm are introduced to evaluate the impact of interactions on the transient response of the VSC. Finally, the DC gain of a certain set of transfer functions is used to assess the impact of control loops interactions on the set-point tracking capability of the VSC

Robust oxygen excess ratio control of PEMFC systems using adaptive dynamic programming

To improve the power generation efficiency and cells lifetime of proton exchange membrane fuel cells, the oxygen excess ratio (OER) control problem is investigated in this paper. With the use of the double-loop cascade control structure, our work reinforces the iteration adaptive dynamic programming (ADP) algorithm and develops a robust OER control strategy drawing upon rich tools and techniques in sliding mode control theory. Our contribution is threefold. First, the proposed OER control policy is insensitive to various dynamics and disturbances by using refined super-twisting sliding mode controller in the external control loop. Second, the ADP-based controller is employed in the internal control loop to approximate the real optimal tracking control policy. The algorithm is computationally efficient and easy to implement in hardware platforms. Third, simulation results show that the proposed OER control strategy has a quick, smooth response, which can be further refined by means of numerous advanced neural network algorithms.

Reduced-Order Model of Distributed Generators With Internal Loops and Virtual Impedance

Reduced-order converter models have attracted attention in microgrid applications for being less computationally expensive and simpler to analyze. However, most of the models already developed in the literature only include basic control loops, while control additions such as virtual impedances and the effect of internal control loops are typically neglected. Also, the frequency range in which these models are applicable has not been thoroughly studied. In this paper, a low-order reduced-order model of a droop-controlled converter that includes internal control loops and virtual impedances is derived. The validity of the assumptions used to reduce the model is analyzed and a criterion for deciding the frequency range in which the model can be used is proposed. Differences between transient and quasi-stationary virtual impedances are highlighted by using the proposed modelling method. In particular, it is analytically shown that quasi-stationary virtual impedances have a larger stability region compared to transient virtual impedances. Simulation and experimental results based on a 60 kVA converter are used to validate the main contributions of this work.

Improving the Power Quality of Island Microgrid With Voltage and Frequency Control Based on a Hybrid Genetic Algorithm and PSO

An efficient power control technique for inverter-based distributed generation (DG) in an islanded microgrid is investigated in this work. The objective is to raise the caliber of the electricity pumped from network-connected DGs. The characteristics that are taken into consideration include voltage and frequency control, dynamic response, and steady-state response, particularly when the microgrid is operating in island mode or when there is a load change. The control method consists of an internal current control loop and an external power control loop based on a synchronous reference frame and a conventional PI controller. The power controller is designed based on voltage-frequency (VF) control. In addition, an intelligent search technique that combines Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) is utilized to automatically modify power controller parameters. The control technique in this research is that the DG modifies its control mode to modify the system voltage and frequency when the microgrid is islanded or load conditions change. The simulation results in MATLAB/SIMULINK software show that the proposed control system has been able to improve the power quality well.

Predictive control strategy on an the ultra-high gain DC/DC converter suitable for photovoltaic energy conversion system

Abstract This paper presents a control scheme based on the predictive control strategy on an ultra-high gain DC/DC converter with two-phase interleaved structure. the proposed converter consists of coupled inductors and a voltage multiplier cell to increase the voltage gain. due to the variations in the input voltage and the load in the photovoltaic system, tracking the input voltage from its reference value and also dividing the current evenly in the interleaved structure are considered as important control objectives. the proposed predictive control scheme is employed to the proposed converter using two internal and external control loops and the use of a second-order luenberger observer. finally, the effectiveness and the desired performance of the proposed predictive control scheme is verified by presenting the simulation results as the real-time validation by MATLAB and ATMEGA16A-PU.

Supporting Simultaneous Air Revitalization and Thermal Control in a Crewed Habitat With Temperate Chlorella vulgaris and Eurythermic Antarctic Chlorophyta.

Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (C. vulgaris, 9–27°C; Chlorophyta-Ant, 4–14°C) and included a constant temperature control (10°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (C. vulgaris; initial: 0.013 mgO2 L–1, final: 3.15 mgO2 L–1 and Chlorophyta-Ant; initial: 0.653 mgO2 L–1, final: 1.03 mgO2 L–1) and culture growth, suggesting environmental acclimation. Antarctic sample conditions exhibited increases or sustainment of oxygen production rates normalized by biomass dry weight, while both C. vulgaris sample conditions decreased oxygen production per biomass. However, even with the temperature-induced reduction, cycled temperature C. vulgaris had a significantly higher normalized oxygen production rate than Antarctic Chlorophyta. Chlorophyll fluorometry measurements showed that the cycled temperature conditions did not overly stress both sample types (FV/FM: 0.6–0.75), but the Antarctic Chlorophyta sample had significantly higher fluorometry readings than its C. vulgaris counterpart (F = 6.26, P < 0.05). The steady state C. vulgaris condition had significantly lower fluorometry readings than all other conditions (FV/FM: 0.34), suggesting a stressed culture. This study compares the results to similar experiments conducted in steady state or diurnally cycled temperature conditions. Recommendations for surface system implementation are based off the presented results. The preliminary findings imply that both C. vulgaris and Antarctic Chlorophyta can withstand the dynamic temperature environment reflective of a thermal control loop and these data can be used for future design models.

Investigation of the Performance of Model Predictive Control for Induction Motor Drives

The current work presents speed, torque and flux control of an induction motor (IM) drive, founded on model predictive control (MPC). Via the MPC techniques, the motor electromagnetic torque and flux linkage are controlled as an internal loop. However, the speed is controlled as the external loop. The internal control loop is founded on finite control set FCS-MPC, and the external control founded on the torque PI controller. The performance of the MPC is tested with various conditions of the drive operation, and the outcomes approve the excellent steady-state and dynamic operation of the system in a wide range of speeds and with torque disturbance.