Hysteresis Current Control Scheme Research Articles

VOT and VFT-Based hybrid digital hysteresis control for UPS inverter

When the digital hysteresis current control (DHCC) strategy is applied to control the uninterruptible power supply (UPS) inverter, here are some issues such as large hysteresis tracking error caused by sampling interval and severe switching frequency swing caused by rapid change rate of inductor current. To address these issues, this paper presents a digital control strategy based on the hybrid digital hysteresis current control (HDHCC) of variable opening time (VOT) and variable falling time (VFT) for UPS inverter. Firstly, the HDHCC structure is established and the working principle of the inverter system is described in detail. Then, the tracking error and switching frequency error of the DHCC are derived. Based on the performance requirement of quasi-constant frequency control of UPS inverter, VOT and VFT control criteria without the dependency of circuit parameters are given. The experimental results demonstrate that the hybrid digital hysteresis control strategy based on VOT and VFT has the advantages of high current tracking accuracy, accurate switching frequency control, small output voltage waveform distortion, and simple implementation.

A Current Amplifier Circuit and Control Strategy Based on FPGA

With the extensive application of electric vehicles, energy storage systems and other power electronic equipment, the research on large capacity controllable current source will be an important direction in the future. This paper proposes controllable current source controlled by a full digitally hysteresis current based on field programmable gate array(FPGA), in which the single phase full bridge topology is adopted as the main circuit of current source. The two levels and three levels hysteresis current control strategies are analyzed and compared with the platform of PSCAD/EMTDC. The user defined component was adopted to realize the two difference control strategies with fortran language program. The simulation results verified that the two levels hysteresis current control strategy is much more fit for the controllable current source. Finally, a prototype is designed and fulfilled and it is controlled by the digitally controller with FPGA. The hysteresis current control is realized by FPGA controller with VHDL programming. The experimental results show that the researched hysteresis current control technology is effective for the current amplifier

Genetic Algorithm Based PI Control with 12-Band Hysteresis Current Control of an Asymmetrical 13-Level Inverter

In this paper, a twelve-band hysteresis control is applied to a recent thirteen-level asymmetrical inverter topology by employing a robust proportional-integral (PI) controller whose parameters are decided online by genetic algorithm (GA). The asymmetrical inverter topology can generate thirteen levels of output voltage incorporating only ten switches and exhibits boosting capability. A 12-band hysteresis current control strategy is applied to ensure the satisfactory operation of the inverter. It is designed to provide a sinusoidal line current at the unity power factor. The tuning of the PI controller is achieved by a nature inspired GA. Comparative analysis of the results obtained after application of the GA and the conventional Ziegler–Nichols method is also performed. The efficacy of the proposed control on WE topology is substantiated in the MATLAB Simulink environment and was further validated through experimental/real-time implementation using DSC TMS320F28379D and Typhoon HIL real-time emulator (Typhoon-HIL-402).

Modified hysteresis current control of multilevel converter for grid connected battery storage system

Due to active power demand in the distributed power system, the large voltage deviation appears in the grid network. The battery energy storage system is optimal solution to support the active power when it is needed, which improves the voltage stability. To maintain the accuracy in the active power injection, the modified hysteresis current control of multilevel converter for grid connected battery storage system is proposed in this paper. It supplies accurate active power by estimating the exact reference current from the grid voltage at every sampling period. This novel control mechanism ensures that there will not be any mismatch in the active power requirement and supply; thereby it enhances the quality of grid under nay situation. The detailed control block diagram is addressed to generate the required PWM signals. And also, the detailed operating waveforms are discussed in this paper. The equivalent circuit of power transfer to grid is also reported in this paper. Mathematically it gives that the proposed approach can inject the actual active power needed by the system. To validate the proposed modified hysteresis current control scheme of multi-level converter, the entire simulation study has been developed and carried out in PSCAD/EMDTC software. The measured results observed and presented in this paper and also it confirms that the proposed has practical feasibilities to implement in the real system.

An improved hysteresis current control scheme during grid voltage zero‐crossing for grid‐connected three‐level inverters

AbstractFor three‐level inverters, hysteresis current control (HCC) has been widely used in applications such as active power filters due to its fast‐dynamic response, and it does not need to control each frequency separately with multiple controllers, which makes it simpler. However, the large fluctuation range of switching frequency is a serious disadvantage of hysteresis current control. Especially, the switching frequency decreases significantly during grid voltage zero‐crossing. This frequency fluctuation will cause low‐frequency harmonics. The purpose of this paper is to propose a sampling compensation scheme, which can solve the problem of switching frequency fluctuation near the zero‐crossing of grid voltage. Based on the variable hysteresis band strategy, the virtual sampling and switching time prediction algorithm is designed, which does not need to increase the sampling frequency or add additional controller. Therefore, nearly fixed switching frequency can be achieved while maintaining the control performance. Both simulation and experimental tests have verified the efficacy of the proposed scheme.

Neutral Point Clamped Transformer-Less Multilevel Converter for Grid-Connected Photovoltaic System

Transformer-less (TL) inverter topologies have elicited further special treatment in photo-voltaic (PV) power system as they provide high efficiency and low cost. Neutral point clamped (NPC) multilevel-inverter (MLI) topologies-based transformer-less are being immensely used in grid-connected medium-voltage high-power claims. Unfortunately, these topologies such as NPC-MLI, full-bridge inverter with DC bypass (FB-DCBP) suffer from the shoot-through problem on the bridge legs, which affect the reliability of the implementation. Based on the previous above credits, a T type neutral point clamped (TNP)—MLI (TNP-MLI) with transformer-less topology called TL-TNP-MLI is presented to be an alternate which can be suitable in the grid-connected PV power generation systems. The suggested TL-TNP-MLI topologies free from inverter bridge legs shoot-through burden, switching frequency common-mode current (CMC), and leakage current. The control system of the grid interface with hysteresis current control (HCC) strategy is proposed. The effectiveness of the proposed PV connected transformer-less TNP-MLI topology with different grid and PV scenario has been verified through the MATLAB/Simulink simulation model and field-programmable gate area (FPGA)-based experimental results for a 1.5 kW system.

A robust high-speed sliding mode control of permanent magnet synchronous motor based on simplified hysteresis current comparison

A robust high-speed sliding mode control (SMC) of three phase permanent magnet synchronous motor (PMSM) is presented. The SMC served for inner speed control while a simplified hysteresis current control (HCC) scheme was used in the outer current control to generate gating signals for the inverter switches. The present research leverages on the ability of SMC to directly access system speed error which it attempts driving to zero by cancelling modelling uncertainties and disturbances. Performance comparison was done for the SMC model and an existing model having classical PI controller. With the initial positive speed command of 200 rpm at 5 Nm constant loading, rotor speed with SMC neatly settled to the reference speed at 0.085 seconds without overshoot while the rotor speed of the model with PI controller settled at 0.217 seconds after overshoot. This translates to 155.3% speed enhancement. Similar superior speed performance of the SMC was also observed during recovering from sudden speed reversal. While the SMC model recovered and settled to the reference speed of -200 rpm at 0.369 seconds, the model with PI controller settled at 0.482 seconds. From the results, it can be seen that SMC demonstared superiority over the conventioanl PI controller for complex drives systems.

Performance analysis of shunt active filter for harmonic compensation under various non-linear loads

Abstract This paper shows the motivation towards the development of a dq-Proportional Resonant (PR) control strategy in shunt active power filter design for eliminations of distortions in source currents for different loading conditions. The switching signals for the inverter of shunt active power filter (APF) have been generated by the hysteresis current control scheme. The controller performance has been verified by using different types of loads such as non-linear balanced, unbalanced and variable etc., with the system in MATLAB/Simulink environment. An experimental prototype has also been developed in the laboratory and results are analyzed to validate the efficacy of the proposed controller.

An instantaneous symmetrical component active power theory with finite control state based model predictive control strategy for distribution STATCOM

AbstractIn this paper, a novel Instantaneous Symmetrical Component Active Power theory with Finite Control State based Model Predictive Control (ISCAP‐FCS‐MPC) strategy is proposed for Distribution‐Static‐Compensator (DSTATCOM) to enhance the power quality in distribution system. Unlike conventional control schemes, the proposed method does not necessitate modulators for switching pulse creation and the discrete implementation of the system is offered to assess the forthcoming actions of the source currents for each of the eight achievable switching actions. These switching actions are generated with regard to turbulences raised in load as well as source sides. The proposed methodology is justified via MATLAB/Simulink environment and a relative analysis is realized through conventional Proportional Integral based Hysteresis Current Control (PI‐HCC) strategy. Further, an experimental investigation is accomplished with consideration of Real‐Time Digital Simulator (RTDS) incorporated with front end processor Xilinx spartan‐3 XC3S5000.

Novel Hysteresis Regulation Strategy for a Two-level Inverter Fed Induction Motor Drive to Achieve Nearly Constant Switching Frequency

Constant switching frequency (CSF) is an important objective to be achieved by any control strategy deployed on a Voltage Source Inverter (VSI) so that the filter design will be easier. Though the invent of Multi-Level Inverters (MLI’s), the Two-Level Inverters (TLI’s) are widely used when it comes to current control strategies. In this paper, a new hysteresis current control strategy is proposed for a TLI in order to achieve nearly CSF. In this method, the constant switching frequency is achieved by creating a Variable Band (VB), which varies according to the switching frequency average of the pole voltage. The proposed control strategy creates VB’s such that it mimics the Continuous Space Vector Pulse Width Modulation (CSVPWM) and also the Bus-Clamping Pulse Width Modulation – 60° and 30° (BCPWM60 – BCPWM30). The paper also analyses the proposed control strategy under different criteria such as current THD, dynamic performance and parameter variation. This performance of the proposed strategy is simulated using MATLAB Simulink platform and experimentally validated on a 2.2 kW, three phase, Induction Motor (IM) using dSPACE-1103 kit.

Hysteresis Current Control for Multilevel Converter in Parallel-Form Switch-Linear Hybrid Envelope Tracking Power Supply

Parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply is constituted by a linear amplifier and a switched-mode converter connected in parallel. The switched-mode converter is usually implemented by a buck converter with hysteresis current control. However, the slew rates of the load current and the inductor current of the buck converter cannot match well when the slew rate of the load current has a wide variation range. The unmatched slew rates will lead to a high switching frequency of the buck converter or a large loss of the linear amplifier, which degrades the overall efficiency. In this paper, a multilevel converter is adopted to replace the buck converter in the parallel-form SLH ET power supply, and the hysteresis current control scheme is proposed for the multilevel converter to dynamically adjust its inductor current slew rate to approach that of the load current to improve the overall efficiency. The optimal design for the efficiency-related parameters including the inductor, the current hysteresis, and the number and values of the voltage levels in the multilevel converter is given. A prototype of the parallel-form SLH ET power supply with hysteresis current controlled multilevel converter is fabricated and tested in the lab. The measured overall efficiency is 79.4% when tracking the envelope of wideband code division multiple access signal with 5 MHz bandwidth and outputs 18 W average power, and a 3.8% efficiency improvement is achieved over that with the hysteresis current controlled buck converter.

Hybrid hysteresis current control and low‐frequency current harmonics mitigation based on proportional resonant in dc/ac inverter

In the two-stage photovoltaic (PV) micro-inverters, the bipolar hysteresis current control with soft switching for dc/ac inverter can achieve fast dynamic response, robust current regulation and high efficiency even with higher switching frequency. To further reduce the switching losses, unipolar hysteresis current control is desirable. However, it suffers from zero-crossing distortions and low frequency harmonics in the grid current. To solve those problems, this paper proposes a combined proportional resonant (PR) and hybrid hysteresis current control strategy. By investigating the reasons for zero-crossing distortions, hybrid hysteresis current control is applied to enable bipolar modulation around the zero-crossing zone and unipolar modulation in all other zones of the line period. At the same time, due to the wide hysteresis bands for soft switching, low output inductance and non-negligible sampling intervals from the digital controller, there will be many low frequency harmonics in the spectrum of output inductor current which deteriorates the quality of power absorbed by the grid. Therefore, the PR control may be used as well to mitigate the low frequency harmonics. The theoretical analysis of the proposed solutions are explained in this paper. Detailed simulation and experimental results are presented to verify the feasibility of the proposed control strategy.

Smoothly Transitive Fixed Frequency Hysteresis Current Control Based on Optimal Voltage Space Vector

This paper proposes a smoothly transitive fixed frequency hysteresis current control (ST-FHCC) scheme applied to an active power filter (APF). First of all, a switching fixed frequency hysteresis current control (S-FHCC) is introduced, which is based on phase-to-phase decoupling and switching the control strategies under mode 0 or mode 1, and its weakness is described in detail. To enhance it, an improved approach of regulating the hysteresis bandwidth is presented to fix the switching frequency with switch phases being regulated, based on the optimal voltage space vector (OVSV). Furthermore, a flexible division of the voltage-space-vectors diagram is developed to divide the original voltage-space-vectors diagram into six sub-regions, upon which the control strategies under mode 0 and mode 1 can be switched alternately in order to obtain a smooth transition. As a consequence, ST-FHCC can thoroughly avoid the inherent weakness of S-FHCC of switching that is not smooth as a result of the low control accuracy of current errors. Case studies are carried out through power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) while simulation results verify the effectiveness and superiority of ST-FHCC compared to S-FHCC.

Simultaneous active and reactive power compensation using STATCOM with supercapacitor energy storage system

STATCOM is taking challenges skilfully in the field of power system to maintain the AC bus voltage constant and to compensate for reactive power. When the STATCOM is integrated with energy storage device through DC/DC buck-boost converter, it compensates the active power also. In this paper, the regulation of DC link voltage to its rated value has been done to compensate simultaneous active and reactive power demanded by the load. The circuit model, mathematical expressions and MATLAB/Simulation model based on the mathematical model has been analysed. The hysteresis current control (HCC) strategy is used to generate the pulses for the 6-pulse 2-level voltage source converter (VSC). The conventional PI controller is used to generate the reference current direct and quadrature axis components. The PI controller is also used to generate the modes, whether it works in buck mode or boost mode. These modes decide the charging and discharging of supercapacitor. Here total reactive power is taken by STATCOM and the grid reactive power is near to zero and hence the burden on the grid is drastically reduced.

Simultaneous active and reactive power compensation using STATCOM with supercapacitor energy storage system

STATCOM is taking challenges skilfully in the field of power system to maintain the AC bus voltage constant and to compensate for reactive power. When the STATCOM is integrated with energy storage device through DC/DC buck-boost converter, it compensates the active power also. In this paper, the regulation of DC link voltage to its rated value has been done to compensate simultaneous active and reactive power demanded by the load. The circuit model, mathematical expressions and MATLAB/Simulation model based on the mathematical model has been analysed. The hysteresis current control (HCC) strategy is used to generate the pulses for the 6-pulse 2-level voltage source converter (VSC). The conventional PI controller is used to generate the reference current direct and quadrature axis components. The PI controller is also used to generate the modes, whether it works in buck mode or boost mode. These modes decide the charging and discharging of supercapacitor. Here total reactive power is taken by STATCOM and the grid reactive power is near to zero and hence the burden on the grid is drastically reduced.

Active Power Sharing and Reactive Power Compensation in a Grid-tied Photovoltaic System

In the present scenario of energy crisis, researches on non-conventional energy sources have grown appreciably. The electrical energy derived from the PV panel is considered as the most useful natural resources. This paper deals with the operation and control of a grid interfaced PV system. Inverter control is achieved by using adaptive hysteresis current control scheme. The proposed inverter control technique interfaces renewable energy source and the AC bus of micro grid. It provides the possibility of injecting power from the renewable sources and favours reactive power compensation. The resulting controller is simulated in MATLAB/SIMULINK and results are analyzed.

Research and Simulation of Two-Phase Interleaving Boost Converter

本文介绍了交错并联技术的基本原理及其优点，详细分析两相交错并联Boost变换器基本原理，分别采用PI控制和数字电流滞环控制方法，简单叙述了两种控制方法的原理并进行优缺点的分析与对比。使用MATLAB仿真，结果显示采用交错并联技术能在很大程度上减小流过开关管的电流，降低开关损耗和输出电压、输出电流纹波；相对于PI控制，采用数字电流滞环的控制方法使得整个电路的性能得到提升。 This paper introduces the basic principle and unique advantages of interleaving technology, and analyzes the efficacy of the two-phase interleaved boost converter in detail. In the control part of the circuit, a PI control strategy and digital hysteresis current control strategy are respectively adopted for the sake of comparison. Via MATLAB simulation, interleaving technology is shown to possess a number of important advantages compared to other methods, such as high frequency output voltage ripple with lower switching frequency, reducing current flowing through the switch tube, reducing switching loss, decreasing output voltage ripple, and output current ripple. Compared to the PI control method, the digital hysteresis current control method makes the performance of whole circuit is improved.

Three‐level hysteresis current control strategy for three‐phase four‐switch shunt active filters

In this study, a three-level hysteresis current-control (HCC) strategy is proposed for three-phase four-switch shunt active power filters. The four-switch topology which utilises four switching devices together with two series connected capacitors is able to reduce the cost, switching losses and improve the reliability of system. In this topology, when the current control of phases A and B is achieved successfully, the current control of phase C which is connected to the midpoint of the series connected capacitors is achieved automatically. The current control is achieved by using a three-level HCC strategy. An important consequence of using this control strategy is that it enables access to the zero level of the input voltage of active filter so that a switching device is only switched when the current error is negative, while it remains off when the current error is positive. Furthermore, the imbalance in the capacitor voltages is eliminated by adding a feedback term (the difference in the capacitor voltages multiplied by a suitable gain) to the current control. The proposed control strategy offers a reduced switching frequency, losses and cost. The steady-state and dynamic performance of the proposed control strategy is verified through simulations and experimental studies.

Vector selection approach‐based hexagonal hysteresis space vector current controller for a three phase diode clamped MLI with capacitor voltage balancing

The purpose of this study is to provide a broad idea about current control scheme and equilibrating voltages in DC-link capacitors of the neutral-point clamped multilevel inverter (NPC-MLI), using an innovative hexagonal space vector hysteresis current control (SVHCC) scheme. The main ideology is to force the literal current vector to reach the reference current vector through an appropriate voltage vector selection sequence. This proposed scheme defines two hexagonal hysteresis bands encompassing the error vector, as a first step. With respect to the error vector location, the selection of the adjacent vector is acted to minimise the error vector. In addition to the error vector selection, the capacitor voltage is also equilibrated by controlling the degree of freedom available in selecting the switching vectors. The SVHCC scheme is intelligent in performing modulation depth dependent selection of switching vectors between the groups namely closest three vector and preferred three vector (PTV). This scheme balances the DC-link capacitors’ voltages within a tolerance limit for any value of modulation index. The proposed scheme is asserted through MATLAB/Simulink software. The superiority of the proposed technique is validated through the 2 kW NPC-MLI supported with SPARTAN III 3AN –XC3S400 field programmable gate array.

Double-band hysteresis current-controlled single-phase shunt active filter for switching frequency mitigation

This paper proposes a double-band hysteresis current-control (DBHCC) scheme for single-phase shunt active filters. The idea behind this scheme is to enable access to the zero level of the active filter’s input voltage so that a switching device is only switched during a half-cycle, while it remains either on or off during the other cycle. Average switching frequency expressions of the conventional single-band hysteresis current-control (SBHCC) and DBHCC schemes have been derived. It is shown that the DBHCC results in a much lower average switching frequency than that of SBHCC scheme leading to reduced switching losses for the same parameter values. It is also worth to note that the DBHCC scheme offers a smaller total harmonic distortion (THD) of the source current for small hysteresis band values. The steady-state and transient performance of the proposed control scheme has been tested through simulations under a diode bridge rectifier load, a diode bridge rectifier with RL load and a triac-controlled resistive load.