Current Regulation Loop Research Articles

Practical Energy Management Control of Fuel Cell Hybrid Electric Vehicles Using Artificial-Intelligence-Based Flatness Theory

This paper proposes a practical solution to address the energy management issue in fuel cell hybrid electric vehicles (FCHEVs). This solution revolves around a powertrain system that contains a fuel cell (FC) as the main supply, a photovoltaic cell (PC) as the secondary energy source, and a battery bank (Batt) as backup storage to compensate for the FC’s low response rate. The energy in this hybrid powertrain system alternated between the designated elements and the load via a DC bus, and to maintain a stable output voltage, the DC link was adjusted using a nonlinear approach that is based on the flatness theory and the nonlinear autoregressive moving average (NARMA-L2) neuro-controller. As for the current regulation loops, the sliding mode technique was employed to attain the high dynamic of the reference signals produced by the energy manager loop. To validate the accuracy of the proposed energy management approach (EMA), a test bench was equipped with digital, electronic circuits and a dSPACE DS-1104 unit. This experimental bench contained a fuel cell emulator FC of 1200 W and 46 A, lithium-ion batteries of 24 V, and a solar source capable of 400 W. The obtained results, indeed, attested to the validity of the approach used, yielding a notable performance during multiple charge variations. This ultimately demonstrated that the management approach enhanced the efficiency of the hybrid powertrain.

Adaptive generalized super twisting sliding mode control for PMSMs with filtered high-gain observer

This paper proposes a novel adaptive-gain generalized super twisting algorithm for permanent magnet synchronous motors. The stability of this algorithm is strict proof using the Lyapunov method. Both controllers of the speed-tracking loop and the current regulation loop are designed according to the proposed adaptive-gain generalized super twisting algorithm. Dynamically adjusted gains in the controllers can improve the transient performance and system’s robustness while reducing chattering. A filtered high-gain observer is applied in the speed-tracking loop to estimate the lumped disturbances, including parameter uncertainties and external load torque disturbances. The estimates feeding forward to the controller further improve the robustness of the system. Meanwhile, the linear filtering subsystem reduces the sensitivity of the observer to the measurement noise. Finally, experiments are constructed using the adaptive gain generalized super twisting sliding mode algorithm and the fixed gain one, showing the effectiveness and advantages of the proposed control scheme.

Cooperative Control to Suppress Unbalanced and Harmonic Distortion in the Distribution Network With Inverter-Based Distributed Generators

In the contemporary distribution network, unbalanced and harmonic distortions have been considered some major power quality problems, which have escalated especially due to the high penetration of unbalanced and nonlinear loads. This study first analyzes the dispute around the distortion restraint and grid-connected unbalanced/harmonic current suppression quantitatively and proposes a distributed control strategy that facilitates an effective suppression of output voltage and grid-connected current, with accurate unbalanced/harmonic power sharing. Compared with the majority of existing studies only addressing the voltage-controlled mode (VCM) inverters, our scheme can also be applied to current-controlled mode (CCM) inverters without adding additional current regulation loops. The proposed control strategy is independent of line parameters and robust to load changes. The corresponding small-signal dynamic model is constructed to analyze the system stability and the controller hardware-in-the-loop simulations aid in determining the outcome of the proposed strategy.

Robust soft computing control algorithm for sustainable enhancement of renewable energy sources based microgrid: A hybrid Garra rufa fish optimization – Isolation forest approach

A novel hybrid Garra rufa Fish optimization (GRFO) – isolation Forest (iForest) soft computing approach is proposed in this paper for optimizing the controller parameters in an isolated test microgrid. The test microgrid comprises of two PV units and one wind generator synchronized via Voltage Source Converters (VSC) in the ac side. Each VSC is regulated based on power generation in individual micro sources. The operation of VSC is the key factor maintaining the stability of the micro grid. Each VSC is controlled by outer power loop and inner current regulation loop employing PI controllers. The performance of the VSC is enhanced using the proposed hybrid GRFO – iForest algorithm for tuning the PI controller gains. The performance of the proposed approach is then compared with conventional tuning PI controller and optimization techniques like Ant Lion Optimization (ALO) and Modified Ant Lion optimization based Artificial Neural Network (MALANN). The gain parameter of the proposed controller is optimally tuned and the controller provides reliable sustainable microgrid system operation. The proposed approach is simulated in MATLAB/Simulink and validated using OP-4500 Real Time Simulator environment. Based on the results, the performance of the GRFO-iForest approach is superior during steady-state and transient operation. It enhances the sustainability of the microgrid by restoring normal operating conditions after a small physical disturbance and the microgrid remains stable with the optimized regulator. The stability of the overall system is proved with the mathematical model.

Analytical Modeling and Control of Dual Active Bridge Converter Considering All Phase-Shifts

In the field of power electronics-based electrical power conversion, the Dual Active Bridge (DAB) topology has become very popular in recent years due to its characteristics (e.g., bidirectional operation and galvanic isolation), which are particularly suitable to applications such as interface to renewable energy sources, battery storage systems and in smart grids. Although this converter type has been extensively investigated, its analysis and control still pose many challenges, due to the multiple control variables that affect the complex behavior of the converter. This paper presents a theoretical model of the single-phase DAB converter. The proposed model is very general, i.e., it can consider any modulation technique and operating condition. In particular, the converter is seen as composed by four legs, each capable of generating voltage on the inductor, and by the two output legs, which can steer the resulting inductor current to the load. Three variables are considered as the control inputs, i.e., the phase-shifts with respect to one leg. This approach results in a very simple yet accurate closed-form algorithm for obtaining the inductor current waveform. Moreover, a novel analytical model is proposed for calculating the average output current, based on the phase-shift values, independently of the output voltage. It is also shown that average output current can be varied cycle-by-cycle, with no further dynamics. In fact, average output current is not affected by the initial value of inductor current or by DC offset (which may arise during transients). The proposed models can be exploited at several stages of development of a DAB: during the design stage, for fast iteration, when selecting its operating points and when designing the control. In fact, based on the analytical results, a novel control loop is proposed, which adopts a “fictitious” (i.e., open-loop) inner current regulation loop, which can be applied to any modulation scheme (e.g., Single Phase-Shift, Triple Phase-Shift, etc.). The main advantage of this control scheme is that the simple dynamics of the output voltage versus the average output current can be decoupled from the complicated relationship between the phase-shifts and the output current. Moreover, a Finite Control Set (FCS) method is proposed, which selects the optimal operating points for each operating condition and control request, ensuring full Zero-Voltage Switching (ZVS) in all cases. The analytical results obtained and control methods proposed are verified through simulations and extensive experimental tests.

Differential Input Current Regulation in Parallel Output Connected Battery Power Modules

Parallel output connected converters have been widely investigated with a focus on equal current and power sharing. However, parallel output connected battery power modules (BPMs) require unequal currents to enable state-of-charge (SOC) control in active battery management systems (BMS.) This article presents simple differential input current regulation for SOC control. Compared with equal current sharing, differential current regulation is more critical on the system stability due to the cross-coupling between the paralleled BPMs. The article proposes design guidelines that enable differential current control while considering the cross-coupling between the paralleled BPMs. The small-signal model of a battery brick consisting of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> parallel output connected BPMs that operate in boost mode is presented. This article shows the effect of paralleling and differential currents on the individual input current regulation loops. Simulations and experiments verify the analysis. Experimental validation using a 300-W prototype consisting of three parallel output connected battery modules in an active BMS is presented.

An enhanced implementation of SRF and DDSRF-PLL for three-phase converters in weak grid

Abstract Renewable energy generation systems connected to utility grid require perfect synchronization to grid which is one of the most important issues that needs to be taken into consideration. This paper proposed a hardware-accelerated implementation for the decoupled double synchronous reference frame phase-locked loop (DDSFR-PLL) for grid synchronization in grid-connected converters in weak grid that suffers from phase voltage-unbalance, variable phase and frequency conditions. Since the transformations and filtering of this method is computationally intensive and needs to be executed as fast as possible by the microcontroller unit (MCU) and Due to the presence of other current and voltage regulation loops in the same interrupt service routine (ISR) with high frequency rate, a hardware-based acceleration using the STM32G4x4 MCU built-in filter, filter math accelerator (FMAC) and coordinate rotation digital computer (CORDIC) is used to speed the execution time. This study addresses the description, derivation and implementation of the both DQ-PLL and DDSRF-PLL algorithms. The performance of both pure-software and accelerated implementation is demonstrated, compared and run on a three-level active neutral point clamped (ANPC) converter board. In proposed method, CPU load dropped from 80.5% by using the conventional software implementation to 23.6% (70% load reduction).This reduction in CPU load enables the addition of more features and more advanced current and voltage control algorithms.

БЕЗДАВАЧЕВЕ КЕРУВАННЯ ДВИГУНОМ ПОСТІЙНОГО СТРУМУ

In this paper, a new speed control algorithm for a permanent magnet DC motor which does not require implementation of the angular speed sensor is presented. Three steps are performed to develop the control system: design of speed tracking control algorithm assuming the speed measurement; design of speed observer; design of sensorless speed control algorithm based on the principle of separation. Information about speed is taken from the speed observer using the motor current value. The stability of the composite system dynamics consisting of three subsystems (the speed regulation loop, current regulation loop, and speed observer) is analyzed. The feedback gains tuning procedure for decoupling of three subsystems is given. The simulation results show that the dynamic performance of the designed system is similar to the performance of the system with angular speed measurement. The resulting closed-loop system has structural robustness properties with respect to parametric and coordinate disturbances. References 12, figures 2.

Стійкість двоконтурних систем керування напругою DC-DC перетворювача

The paper is devoted to research and development of the cascaded DC-link voltage control systems for DC-DC boost converters whose mathematical model is highly nonlinear and non-minimum phase. The relevance of the analysis method for classic control systems for DC-DC boost converters is substantiated, which are similar to vector-controlled electric drives systems if the speed controller is replaced by DC-link voltage controller. It is shown that the reduced-order solution of initial nonlinear system dynamics can be obtained giving the time-scale separation between the input current and the DC-link voltage control processes based on the singular perturbation systems theory. In its turn, it is concluded that the reduced-order system dynamics is locally (asymptotically) stable if cascaded control algorithm is applied. The similarity of the time-scale separation conditions for the cascaded control systems with proportional and proportional-integral DC-link voltage controller is shown. The time-scale separation of the control processes is achieved if inner current regulation loop is much faster than the outer voltage regulation loop. The simulation study demonstrates that if the time-scale separation conditions between the input current and the DC-link voltage regulation are met then the full-order system dynamics of the DC-link voltage regulation of DC-DC boost converters is close to the reduced-order system dynamics. The control algorithm has a typical structure of the modern controlled converters applied in hybrid energy storage systems for electric vehicles. From the results of the simulation study, it follows that the influence of the inner resistance of the input inductance on the system stability and quality indicators of the DC-link voltage control process is insignificant for the investigated DC-DC boost converter.

Fuzzy Logic Control Contribution to the Rotor Speed Control of the Doubly Fed Induction Generator

This paper presents the control of the wind energy system (WES), based on the doubly fed induction machine in generating mode (DFIG) using Artificial Intelligence (AI) technique based on fuzzy logic control. The performances of the conventional Integral Proportional (PI) and Fuzzy-PI controllers are compared with respect to the speed variation of the generator. The objective of the control strategy based on Fuzzy-PI controller is to ensure perfect tracking of the rotor speed and control the current regulation loops. The performances of the fuzzy-PI controller are studied via simulation on the Matlab/Simulink. We obtained perfect results that show the value of using a fuzzy PI controller.

Simplified Speed Control of Permanent Magnet Synchronous Motors Using Genetic Algorithms

In this paper, a simplified control scheme is introduced for permanent magnet synchronous motors (PMSMs). The control strategy consists of a direct voltage controller that capitalizes on the motor's model to achieve accurate speed tracking. As such, no explicit currents loop regulation is needed which simplifies the control structure and unlike other control strategies, no motor's parameter knowledge, voltage or current transducer is required. But, the absence of current regulation loops yields higher energy consumption, which limits the motor's range of operation. Therefore, a genetic algorithm is presented to determine control gains with optimal current consumption ensuring operation at the full range of the machine. Simulation and experimental results for different situations highlight the performance of the proposed controller in transient, steady-state, and standstill conditions. Furthermore, the simplicity of the control scheme makes it a good candidate for a low-cost implementation of real-time PMSM drives.

Sliding-Mode Flux-Weakening Control With Only Single Current Regulator for Permanent Magnet Synchronous Motor

A sliding-mode scheme using only a single current regulator for both speed and flux-weakening control has been proposed for permanent magnet synchronous motor. The scheme is simple and can effectively resolve problems faced by conventional flux-weakening control with dual current regulation loops. However, with only a single current regulator, the scheme still needs an additional mechanism for either maximizing electromagnetic torque or optimizing efficiency. As for reinforcing its immunity and robustness towards changing operating conditions, sliding-mode speed control complemented by an equivalent load-torque observer during flux-weakening has been proposed and designed accordingly. Effectiveness of the eventual scheme, in terms of widening load capacity or improving light-load efficiency of the motor, has been verified in simulations and experiments.

Virtual Flux Based Direct Power Control on Vienna Rectifier

This paper proposes the virtual flux based direct power control for Vienna rectifier. No need for the input voltage sensors, the current regulation loop and PWM voltage modulation block along with the active and reactive power decoupling are some of the salient advantages of this method that make it suitable for controlling the conventional active rectifiers. However, due to the three-level nature of the Vienna configuration, balancing the output capacitors voltages is inevitable leading to a modified virtual flux based technique. Applying this modification, a separate switching table has been jammed into the proposed technique in order to control the capacitors voltages. Simulation results show the superiority of the virtual flux technique over the conventional Vienna control techniques from point of the mentioned advantages.

An Efficiency Comparison of Fuel-Cell Hybrid Systems Based on the Versatile Buck–Boost Converter

This paper extends the use of the versatile buck–boost converter to power manage a parallel hybrid system topology as an alternative to the well-known serial hybrid (SH) topology and the most recent series–parallel hybrid (SPH) topology. These systems utilize a proton exchange membrane fuel cell as the primary source in combination with an auxiliary storage device (ASD), and the selected converter is in charge of the power management between the sources (fuel cell or ASD) and the load. Therefore, the converter has a very important role in the system since it is responsible of ensuring a dc-bus voltage regulation with a safe and reliable operation of the entire system while also guarantee a high power conversion efficiency. Hence, this is the third topology, where the coupled-inductor dc–dc buck–boost converter is studied to demonstrate and exploit its advantages such as noninverting voltage step-up and step-down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. In order to determine which topology (SH, PH, or SPH) exhibits the highest power conversion efficiency under a certain load profile, it is important to ensure a fair efficiency comparison that will only reflect the properties of the topology and not its individual components. Therefore, the same design criteria, the same control, and the same components were used for all the studied topologies. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.

Robust sliding-mode control of wind energy conversion systems for optimal power extraction via nonlinear perturbation observers

This paper designs a novel robust sliding-mode control using nonlinear perturbation observers for wind energy conversion systems (WECS), in which a doubly-fed induction generator (DFIG) is employed to achieve an optimal power extraction with an improved fault ride-through (FRT) capability. The strong nonlinearities originated from the aerodynamics of the wind turbine, together with the generator parameter uncertainties and wind speed randomness, are aggregated into a perturbation that is estimated online by a sliding-mode state and perturbation observer (SMSPO). Then, the perturbation estimate is fully compensated by a robust sliding-mode controller so as to provide a considerable robustness against various modelling uncertainties and to achieve a consistent control performance under stochastic wind speed variations. Moreover, the proposed approach has an integrated structure thus only the measurement of rotor speed and reactive power is required, while the classical auxiliary dq-axis current regulation loops can be completely eliminated. Four case studies are carried out which verify that a more optimal wind power extraction and an enhanced FRT capability can be realized in comparison with that of conventional vector control (VC), feedback linearization control (FLC), and sliding-mode control (SMC).

Multi-Objective Optimized Controller for Torque Ripple Minimization of Switched Reluctance Motor Drive System

Background/Objectives: In this paper, BC based optimized PID controller is developed for torque ripple minimization of SRM drive system. The proposed control algorithm comprised two optimized PID controllers for speed error and current error regulation loops of the SRMD control system. The proposed control algorithm is also optimizes the commutation angles for reducing the high torque ripples. Methods/Statistical Analysis: A new control algorithm for Torque Ripple Minimization of Switched Reluctance Motor (SRM) Drive system is proposed. The proposed control algorithm comprised two optimized Proportional, Integral and Derivative (PID) controllers for speed error and current error regulation loops of the SRMD control system. The proposed control algorithm is also optimizes the commutation angles for reducing the high torque ripples. In the proposed optimized controller, Artificial Bees Colony algorithm (ABC) is the optimization algorithm implemented to tune the gains of both PID controllers and commutation angles of the converter circuit. For tuning the accurate gains and angles, the multi objective functions are developed. The effectiveness of the proposed BC algorithm is implemented in the MATLAB/SIMULINK platform. Findings: The proposed control algorithm is based on the optimized PID controller for the speed and the current loops of the SRM drive system. The proposed control algorithm was used to optimize the gain parameters of the PID controller along with the commutation angles of the inverter. Here, the minimization of the error values of speed and torque serves as the objective functions. The advantages of the proposed method are robust performance as well as the increased level of reliability and flexibility in solving more complex problems. Applications/Improvements: The results obtained include superior performance with degradation in torque ripple and settling time. These merits are produced with elitism and a high-speed global search methodology, thus enhancing the dynamic performance of the SRM drives.

Energy Management of a Fuel-Cell Serial–Parallel Hybrid System

In this paper, a serial-parallel hybrid (SPH) power system formed by a fuel cell (FC), an auxiliary storage device (ASD), and the current-controlled dc-dc converters responsible for the power management are realized by using the digital signal controller (DSC) TMS32F28335. The main energy management goal is to transfer energy from the sources (FC or ASD) to the load while ensuring dc bus voltage regulation and high power conversion efficiency. In addition, a safe and reliable operation of the system has to be achieved. The selected converter and its controller features are noninverting voltage step up and step down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. All these features allow it to be positioned in different FC system localizations and simplify the design of the master control. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.

Robust proportional resonant regulator for grid-connected voltage source inverter (VSI) using direct pole placement design method

Based on the introduction of a dual-loop current control strategy for a grid-connected inverter, an averaged switching model of a grid-connected inverter with an LCL-filter in discrete domain is built under a stationary frame and a proportional resonant (PR) regulator is adopted in the current loop to track the given fundamental sinusoidal current. The impacts of PR parameters, LCL parameters and digital delay on the root locus are studied, respectively. The parameters of the LCL-filter and the PR current regulator loop are designed to assure system stability and dynamic response during a wide power range by using the pole placements method. Finally, a 10 kW prototype of a grid-connected inverter with an LCL-filter is set up to verify the effectiveness, the practicality and robustness of the proposed PR current design method.

Sensorless Position Control of Permanent-Magnet Motors With Pulsating Current Injection and Compensation of Motor End Effects

The sensorless position control of permanent-magnet motors is successfully implemented by superimposing a high-frequency voltage signal on the voltage reference or adding a high-frequency current signal to the current reference. The former approach is usually preferred because of its simplicity, although the latter one may allow better performance. This paper presents a new algorithm for the sensorless control of low-saliency permanent-magnet synchronous motors based on high-frequency sinusoidal current signal injection into the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis. Different from the related literature, the position information is derived by analyzing the measured high-frequency currents. The amplitude of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis voltage reference is also exploited to improve performance. A proportional-integral (PI) controller plus a resonant term (PI-RES) is adopted to ensure the accurate tracking of both the dc and high-frequency components of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current reference. The main advantages of the proposed approach are the increased accuracy and sensitivity with respect to the approach based on voltage injection, the insensitiveness to inverter nonlinearities that are compensated by the current regulation loop, the actual control on the injected current value, and the practical absence of acoustic noise. Experiments on a linear tubular permanent-magnet synchronous motor prototype have been carried out to verify the aforementioned advantages. This paper also presents a discussion of the parameters of the PI-RES.

Modified Current Control Schemes for High-Performance Permanent-Magnet AC Drives With Low Sampling to Operating Frequency Ratio

These days, high-frequency permanent-magnet synchronous motors (PMSMs) are used in industry; their maximum synchronous frequency is higher than 1 kHz. However, the sampling and switching frequencies of the digital inverter that consists of the digital controller and pulsewidth-modulation voltage source inverters are limited due to the cost and efficiency reasons. As a result, the current regulation loop has some problems when the high-frequency PMSM runs around its maximum speed and the ratio of the sampling frequency over the synchronous frequency, F ratio = (f samp/fr), is small. In this paper, the problems of the current regulation loop caused by small F ratio in the high-frequency PMSM drive are carefully investigated. Two problems are discussed in this paper: the stability problem and the sampling error. In addition, solutions for the problems are developed; a complex proportional and integral controller with predicted active damping terms is developed to stabilize the current regulation loop, and a model-based error estimator is offered to compensate the sampling error. The developed solutions are verified by simulations and experiments.