Hysteresis Current Regulator Research Articles

Exploring The Potentials and Drawbacks of Hysteresis Current Controller For SRM: A Case Study Of Wind Energy Conversion System

Switched Reluctance Machines (SRMs) have drawn interest in renewable energy systems because of their special qualities and applicability. This study examines the idea of hysteresis current regulation in a wind energy conversion system with a Switched Reluctance Generator (SRG). The system is modeled in MATLAB/SIMULINK. The model is simulated and analyzed to ascertain the system’s benefits and shortcomings, focusing on reducing torque ripples in SRG. Considering most classical controllers are complicated to construct, the hysteresis current control is straightforward and effective. However, this controller's two primary shortcomings are that it produces a variable switching frequency and increases current ripples at a steady state, both enhancing acoustic noise in SRM. Lastly, the report suggests that improving controller performance should be the primary emphasis of future research in this field.

An Adaptive Control of A Stepper Motor Drive Using a Hysteresis Current Control Approach

Stepper motors are widely used in industrial and consumer applications due to their low cost, great dependability, and capability for open-loop control. Open-loop has a straightforward design, but it has a low step objective, a big torque wave, and low energy productivity. A new sensorless speed control structure based on hysteresis current regulator is proposed in order to work on the exhibition without increasing equipment costs. It does not convert currents between a-b and d-q coordinates using Park and inverse Park transformations, in contrast to the traditional sensorless speed control. The dynamic performance of the hysteresis current controller is excellent. It has been extensively studied and used in inverter fed drives and voltage source inverters. This approach provides quick dynamic performance and incorporates the virtual rectifier stage's line modulation methodology into the overall modulation. The outcomes of the simulation and experiment show that the suggested plan is efficient and workable. Through experimentation and evaluation of the suggested controller's speed and position tracking capabilities, MATLAB/Simulink simulation (R2020a) is used to confirm its efficacy.

Multilevel Parallel Active Power Filter Based on ANFIS Controller for Harmonic Alleviation

This paper implements a parallel active power filter (APF) with a three-level inverter and an adaptive neuro-fuzzy inference system (ANFIS)-based controller for voltage regulation. The limitations with nonlinear industrial loads are that they have high power rating and conventional two-level parallel APF cannot be used for mitigating harmonics in such applications. Hence, here a multilevel inverter-based parallel APF that meets the requirement of high-voltage high-power application is proposed. A three-level hysteresis current regulator generates gating pulses for the switches in parallel APF. The modified version of instantaneous real and reactive power (p–q) theory is applied for obtaining reference current with ease. Simulations are done to verify the performance of ANFIS controller in MATLAB with dynamic load changes and distorted supply condition. The outcome of simulation with ANFIS controller is compared with that of fuzzy logic controller (FLC), and its performance is found to be relatively better than FLC with respect to reduction in total harmonic distortion and regulation of inverter DC side capacitor voltage.

A New Application of Vector Based Current Regulator for STATCOM to Improve Dynamic Performance of DFIG

Abstract. Wind turbine generator (WTG) installation has been rapidly growing globally in the last few years. In the year of 2017, the WTG installation has reached a global cumulative installation of about 539 GW. Among several types of WTG, the doubly fed induction generator (DFIG) has been taking a large portion of the overall WTG installation since 2004. This popularity is due to the DFIG several advantages that include more extracted energy when compared with the fixed speed type and low cost due to the one-third size of the used converters when compared to the full converter type. However, the DFIG is vulnerable to grid faults. In this paper, a new application of Vector Based Hysteresis Current Regulator (VBHCR) of STATCOM is introduced to enhance the dynamic performance of DFIG-based wind turbine farm. The system under study is investigated using Matlab. Robustness of the proposed VBHCR is investigated through exploring the system performance under various levels of voltage sags. Simulation results show that for certain level of voltage sags at the point of common coupling (PCC), VBHCR-STATCOM can effectively improve the performance of the DFIG. As a result, voltage profile at the PCC can comply with the fault ride through codes of Spain to avoid the disconnection of the DFIGs from the grid.

Braking Torque Closed-Loop Control of Switched Reluctance Machines for Electric Vehicles

In order to promote the application of switched reluctance machines (SRM) in electric vehicles (EVs), the braking torque closed-loop control of a SRM is proposed. A hysteresis current regulator with the soft chopping mode is employed to reduce the switching frequency and switching loss. A torque estimator is designed to estimate the braking torque online and to achieve braking torque feedback. A feed-forward plus saturation compensation torque regulator is designed to decrease the dynamic response time and to improve the steady-state accuracy of the braking torque. The turn-on and turn-off angles are optimized by a genetic algorithm (GA) to reduce the braking torque ripple and to improve the braking energy feedback efficiency. Finally, a simulation model and an experimental platform are built. The simulation and experimental results demonstrate the correctness of the proposed control strategy.

A Novel Three-Level Hysteresis Current Regulation Strategy for Three-Phase Three-Level Inverters

This paper presents a new hysteresis current regulation strategy for the neutral point clamped and flying capacitor (FC) three-level inverters. The strategy uses the measured average of the switched phase leg output voltage to adjust the controller hysteresis band as the load back EMF varies to maintain a near constant phase leg switching frequency. The phase leg switchings are then fine tuned to a fixed frequency clock to further improve frequency regulation. Next, the zero-crossings of the measured phase leg average voltages are used to select between positive and negative switched output voltage levels, so that only one hysteresis current regulator is required for the full inverter switched output voltage range. For the FC inverter, a state machine is then added to select between redundant switching states to maintain balanced capacitor voltages. Finally, the controller is extended to a three-phase system by subtracting the common mode interacting current from the total phase leg current error before making any switching decision. The resulting controller achieves a line-to-line harmonic performance that is very close to open-loop phase disposition pulse width modulation, while retaining all of the dynamic benefits of hysteresis current regulation.

An Improved Three-Phase Variable-Band Hysteresis Current Regulator

This paper presents an improved variable-band hysteresis current controller for a two-level three-phase voltage source inverter (VSI). The controller takes the average voltages of the phase-leg switched outputs as an approximation to the load back-EMF voltages, and uses these results to vary the hysteresis bands so as to maintain constant phase-leg switching frequencies. The switching frequency control process is then further refined by fine tuning the hysteresis band variations to synchronize the zero crossings of the phase-leg current errors with a fixed reference clock so as to achieve a nearest space vector switching sequence, which further ensures that the switched output spectrum has been optimized. Finally, a technique is proposed to replace the third phase-leg current regulator with a fixed-frequency open-loop pulse-width modulator, where its commanded reference is generated from the average switched output voltages of the other two phase legs. This avoids the hazard of the three independent hysteresis current regulators adversely interacting with each other in a conventional system, resulting from an overconstrained control problem with only two degrees of freedom. Additionally, this approach allows the linear modulation range to be increased by adding a common-mode third-harmonic component to the third phase-leg reference command signal.

고효율 스위칭을 위한 개선된 히스테리시스 전류제어기

Hysteresis current regulator has been used widely because of its simple principle and structure. However, when the current band width is too narrow or the applied voltage is relatively too high, the switching frequency may increase abruptly and it generates a large amount of heat. Thus, this study will suggest a better and simple method to reduce the switching frequency. For single phase current control, the proposed hysteresis current control is executed by adding 0 mode state and comparing the slope of the current reference. This simple method decreases the generated switching frequency and significantly reduces the generated heat. This proposed method was proved with simulations and experiments comparing with the classical hysteresis current control method.

Improving dynamic performance of wind energy conversion systems using fuzzy-based hysteresis current-controlled superconducting magnetic energy storage

Application of distributed wind energy conversion systems (WECS) in modern power systems and smart grids has significantly increased during the last decade. In particular, wind turbines equipped with doubly fed induction generator (DFIG) have dominated the market since 2004 as they represented about 55% of the worldwide total wind capacity during this year. This study investigates the application of superconducting magnetic energy storage (SMES) units to improve the dynamic performance of DFIG-based WECS during small and large disturbances in the grid side. A new control approach for the SMES unit using hysteresis current regulator and fuzzy logic is introduced. Detailed simulation results show that the proposed SMES controller is very effective in improving the dynamic performance of the WECS and is able to maintain its parameters within the safety margins of various grid codes during disturbance events considered in this study.

Improvement of Power Factor and Harmonic Elimination in Distribution Line using PI with Hysteresis Current Controller

Power quality improvement is a major research area in current context. Though much work has been done by many researchers still scope is there to work on this area. In this paper an attempt is made to eliminate the harmonics as well as for the improvement of power factor. Here distribution static synchronous compensator (DSTATCOM) is used to improve power factor in distribution line & mitigate harmonics with an optional feature of voltage regulation. Further the frequency analysis of the distribution line is analyzed both before & after compensation. A relay based hysteresis current regulator is used for DSTATCOM controller in indirect current control technique. Simulation is carried out in standard MATLAB environment. Results of simulations are presented for linear & nonlinear load.

Using equidistant vector-based hysteresis current regulators in DFIG wind generation systems

This paper proposes a novel equidistant vector-based hysteresis current regulator (VBHCR) in the rotor-side converter (RSC) of DFIG-based wind generation systems. The Γ-form equivalent circuit is used for the machine modelling, with the discrete formulation of the RSC output voltage. The overall vector control scheme is then explored and the control structure of the proposed equidistant VBHCR is presented. When compared to the commonly used PI current regulators, the proposed VBHCR exhibits several advantages such as very fast transient response, simple hardware implementation, satisfactory steady-state performance, and intrinsic robustness to machine parameters variations. Moreover, fixed hysteresis bands are replaced with equidistant bands in order to limit the instantaneous variations of the switching frequency and reduce the maximum switching frequency of the RSC. Detailed simulation studies are carried out for a 1.5 MW DFIG-based wind generator to examine the operation of the proposed current regulator under various operating conditions and demonstrate its superiority over the standard PI current regulator.

Enhanced Vector Control of Doubly-Fed Induction Generator Based Wind Turbines to Comply with the Australian Grid Code Requirements

Recent regulatory requirements outlined in the Australian Grid Code dictates fault ride-through and voltage support requirements for wind energy conversion systems. This paper introduces an enhanced vector control scheme for doubly-fed induction generator (DFIG) based wind turbines to comply with these requirements. A unified three-phase signal processor (UTSP) is implemented to readily extract the synchronisation signal from the three-phase grid voltage. The proposed UTSP is also used for the on-line calculation of the grid voltage amplitude, which is needed to provide the reactive power support according to the Australian regulations. The standard proportional-integral current regulators in the rotor-side and grid-side converters are replaced with vector-based hysteresis current regulators to increase the voltage sag/swell ride-through capacity of DFIG. The main advantages of the proposed current regulator are its very fast transient response and simple control structure. Simulation results show the effectiveness of the proposed vector controller to comply with the Australian Grid Code requirements under various grid disturbances.

A Novel Vector-Based Hysteresis Current Regulator for Doubly-Fed Induction Generator Wind Turbines Under Non-Ideal Supply Conditions

This paper proposes a novel vector-based hysteresis current regulator (VBHCR) in the rotor-side converter of doubly-fed induction generator (DFIG) based wind turbine to enhance its operation under non-ideal supply voltage conditions. First, the induction generator is modelled using the “Γ-form” equivalent circuit and the stator-voltage-oriented vector control of DFIG is introduced. Then, the principle and practical implementation of the proposed VBHCR in the rotor-side converter of DFIG is presented. This current regulator employs two sets of hysteresis comparators working in three-phase and rotor reference frames, integrated with a switching table. Compared to the commonly-used proportional-integral current regulators, it reveals very fast transient response with a simple control structure. Simulation results, obtained for a 1.5 MW DFIG, show the validity of the proposed control scheme under normal operation conditions, as well as its desirable steady-state performance. Furthermore, the advantages of the proposed current regulator under non-ideal supply voltage conditions (including unbalance and harmonic distortions) are illustrated.

Enhanced Hysteresis-Based Current Regulators in Vector Control of DFIG Wind Turbines

This paper proposes enhanced hysteresis-based current regulators in the field-oriented vector control of doubly fed induction generator (DFIG) wind turbines. The proposed control scheme is synchronized with the virtual grid-flux space vector, readily extractable by a quadrature phase-locked loop (QPLL) system. Identical equidistant-band vector-based hysteresis current regulators (VBHCRs) are then used to control the output currents of the rotor-side and grid-side converters. The proposed hysteresis-based technique has excellent steady-state performance and reveals several advantages in comparison with the commonly used proportional-integral (PI) current regulator, including very fast transient response, simple control structure, and intrinsic robustness to the machine parameters variations. Moreover, the fixed hysteresis bands in VBHCRs are replaced with equidistant bands to limit the instantaneous variations of the switching frequency and reduce the maximum switching frequencies experienced in the converters. Extensive simulation studies are carried out for a 1.5 MW DFIG-based wind turbine to examine the operation of the proposed vector control scheme under changing wind speed and compare its transient and steady-state performances with the conventional PI current regulators.

스위칭 손실 저감을 위한 기준전류 기울기를 이용한 단상 히스테리시스 전류 제어에 관한 연구

히스테리시스 전류 제어방식은 원리와 구조가 간단하여 널리 사용되었으나, 전류 오차 허용 밴드폭이 너무 작거나, 전원 전압이 상대적으로 너무 큰 경우 등에는 스위칭 주파수가 급격히 증가하여 많은 열을 발생할 수 있는 등의 단점이 있었다. 이에 본 연구에서는 단상 전류제어에서 0 모드를 추가하고, 기준 전류의 기울기를 비교하여 히스테리시스 전류 제어를 수행함으로써 대폭적인 스위칭 주파수 감소와 안정적인 전류제어가 가능하게 하였다. 또한 이를 컴퓨터 시뮬레이션을 통해 그 타당성을 확인하였다.

Improved Multilevel Hysteresis Current Regulation and Capacitor Voltage Balancing Schemes for Flying Capacitor Multilevel Inverter

This paper focuses on the development of multilevel hysteresis current regulation strategies. Two such strategies have been discussed and some modifications in their control tasks have been proposed to achieve more reliable and improved performance. In general, the multiband concept has been used while making the proposals. The hysteresis band size considerations have also been presented by taking into account the desired and existing system conditions. The proposed modulation schemes have been applied to a five-level flying-capacitor inverter, whose operation under hysteresis current control mode is much less established. A new method of flying-capacitor voltage balancing is proposed which ensures balanced flying-capacitor voltages and, at the same time, maintains the desired current profile. It uses a time-based approach for controlling the capacitor voltages and achieves appreciable voltage spectrum under wide range of load power factor conditions. The performance of the proposed strategies is confirmed through both simulation and experimental investigations.

A Robust Multilevel Hybrid Compensation System for 25-kV Electrified Railway Applications

On many electrified railway systems with single-phase 25-kV industrial frequency supply, the power quality can be particularly poor when conventional thyristor based locomotives are operating, and this constrains the amount of power that can be delivered to the locomotives. This paper presents a hybrid shunt compensation system consisting of alternatively a cascaded or a reduced topology multilevel active power filter, and a low rating passive damping filter. The active power filter is controlled by a novel hysteresis current regulation strategy, and both mitigates low-order voltage harmonic distortion along the feeder and provides root mean squared voltage support. The passive filter damps harmonic resonances that are typical in such 25-kV traction systems. The results show that the filter system can significantly increase traction system power transfer capacity with only a relatively small capital investment, allowing older thyristor based locomotives and increased traffic levels to be supported without necessarily requiring a complete system upgrade. Simulation and experimental results are included showing the performance of the filter for both steady state and transient conditions.

A Reduced Common Mode Hysteresis Current Regulation Strategy for Multilevel Inverters

This paper presents a new hysteresis current regulation technique with reduced common mode switching for three-phase multilevel inverters. The proposed technique uses three independent multilevel hysteresis current regulators to generate three sets of complementary gating signals through the comparison of the measured current errors with implemented hysteresis limits. These gating signals are then distributed to each complementary switch pair of the multilevel inverter structure to switch with reduced common mode voltage. Additionally, by intelligently compensating for transition delays during dead-times, common mode voltage can essentially be eliminated completely. Two versions of the common mode regulation technique are derived by using either the line currents or differences between the line currents, known as delta currents, as the control variables. A detailed investigation is presented to determine that the delta currents are the optimal control variables. The performance of the proposed strategy is confirmed through both simulation and experimental investigations.

A time-based double-band hysteresis current regulation strategy for single-phase multilevel inverters

Most multilevel inverter hysteresis current regulators use either multiple hysteresis bands, or a time-based switching logic that forces the current error back to zero by recursively stepping through successive voltage levels. Of these two alternatives, the time-based approach has the merit of only requiring simple analog circuitry and digital logic to implement the voltage level selection process for inverters of any number of voltage levels. However, the approach can be less stable and has a poorer dynamic response than a multiple hysteresis band system. This paper presents a double-band regulator that uses the slope of the current error to help determine the appropriate steady state voltage level to keep this error within the inner hysteresis band, while still allowing switching to the extreme inverter states during transient conditions to reduce the current error as rapidly as possible. The regulator achieves better stability and dynamic performance than previously reported schemes. The paper also presents an adaptation of the system to control a hybrid seven-level inverter. Theory, simulation, and experimental results are presented.

Bi-directional single-phase half-bridge rectifier for power quality compensation

A single-phase half-bridge rectifier with a capacitor clamped scheme is proposed. Four power switches and one flying capacitor are employed in the proposed rectifier. Bipolar and unipolar PWM control schemes are used to perform power factor correction and achieve low total harmonic distortion of line current. A neutral point voltage balance compensator, hysteresis current controller and DC link voltage regulator are used to balance neutral point voltage, to track line current command, and to maintain the constant DC bus voltage. The proposed control scheme and the circuit configuration can also perform a shunt active power filter operation to eliminate the harmonic currents and compensate the reactive power generated from the nonlinear load. Analytical and experimental results are presented to illustrate the validity and effectiveness of the proposed control scheme.