Pulse Width Modulation Current Control Research Articles

A maximum power point tracking of a photovoltaic system connected to a three-phase grid using a variable step size perturb and observe algorithm

Purpose. The production of electricity from solar energy is necessary because of the global consumption of this energy. This article’s study is based on increased energy extraction by improving maximum power point tracking (MPPT). From different MPPT techniques proposed, the perturb and observe (P&O) technique is developed because of its low implementation cost and ease of implementation. Methods. A modified variable step-size P&O MPPT algorithm is investigated which uses fuzzy logic to automatically adjust step-size to better track maximum power point, compared with the conventional fixed step-size method. The variable step P&O improves the speed and the tracking accuracy. This controller is implemented on a boost DC-DC power converter to track the maximum power point. The suggested controlled solar energy system includes a boost converter, a voltage-source inverter, and a grid filter. The control scheme of a three-phase current-controlled pulse-width modulation inverter in rotating synchronous coordinate d-q with the proposed MPPT algorithm and feed-forward compensation is studied. Results. The photovoltaic grid-connected system controller employs multi-loop control with the filter inductor current of the inverter in the inner loop to achieve a fast dynamic response and the outer loop to control bus voltage for MPPT, the modeling, and control of three phase grid connected to photovoltaic generator is implemented in the MATLAB/Simulink environment and validated by simulation results.

A review on technological aspects of different PWM techniques and its comparison based on different performance parameters

AbstractUse of Pulse Width Modulation (PWM) techniques has enabled the converters to be used in low‐frequency high‐power applications. The main objectives of PWM are to reduce the line current harmonic, switching energy loss, and torque pulsation and motor acoustic noise (for motor drive applications). This paper mainly deals with selective harmonic elimination PWM (SHEPWM), Hysteresis current controlled PWM (HCPWM), space vector PWM (SVPWM), bus‐clamping PWM (BCPWM), and the most advanced wavelet PWM technique (WPWM). Different conventional as well as advanced soft computing techniques have been discussed for SHEPWM in order to solve the complex non‐linear transcendental equations and obtain the optimized switching angles. The paper also deals with different conventional and advanced bus clamping sequences that have shown superior result in mitigating the switching loss. In order to judge the true performance of SHEPWM and CSVPWM in terms of accuracy of obtaining the switching angles, convergence rate, THD, torque ripple, switching energy loss, etc., a common experimental test bench consisting of three‐phase, two‐level, six switch inverter coupled with a 2 hp, 50 Hz, three‐phase induction machine has been formed. The selected BIA‐based SHEPWM and CSVPWM have been implemented in the MATLAB simulation software, and the same has also been applied to the experimental test bench through dSPACE 1104 DAC card. Performance of HCPWM and different BC‐PWM sequences has also been verified using the same experimental test bench. This manuscript will help the researches and practitioners working in this field, to gain a clear idea about the type of PWM to be used for their specific application in order to achieve superior performance.

Investigations on variable and constant switching frequency hysteresis controller for VSI fed IM drive

In various current controlled-pulse width modulated (CC-PWM) techniques which are extensively employed in high performance drives, hysteresis current control (HCC) offer significant simple implementation and good dynamic response. However, conventional HCC have drawbacks, such as, limit cycle oscillations, overshoot in current error, generation of sub-harmonic components in the current, and non-optimum switching of inverter voltage vectors which can create variable switching frequency. This work proposes a new constant switching current error space phasor (CESP)-based hysteresis controller with a simple online computation of the boundary and phase voltage harmonic spectrum similar to voltage controlled bus clamping PWM (VC-BCPWM)-based VSI fed induction motor drive. The error boundary computed using voltage and current errors in the present sampling interval is used for identifying next vector to be switched. The current controller using CESP approach is simulated using MATLAB Simulink and experimentally verified on 2.2 kW IM drive.

A Hysteresis Current Controller PWM Scheme Applied to 3-Level NPC Inverter for Distributed Generation Interface

In this article, a novel pulsewidth modulation (PWM) technique is proposed for an existing space vector hysteresis current controller (SVHCC) scheme. A three-level neutral-point-clamped (NPC) inverter is used for dual purpose of shunt active power filtering and solar photovoltaic (PV) power integration to a distribution grid. This dual-purpose NPC inverter utilizes the proposed PWM technique for solving the neutral-point voltage-balancing issue in a unique way. Due to the inherent advantages of the SVHCC, the current control is characterized by fast action and optimal switching. A single reference current required for both filtering and maximum PV power integration is generated using instantaneous power theory, where a diode bridge rectifier load is considered to demonstrate the controller performance while compensating nonlinear current components. Thus, not only a unique space-vector-based PWM technique is adopted for fast-tracking of currents, but also a sliding current error boundary is used for the first time. This sliding technique tackles the dc-link balance issue of the NPC inverter while controlling the output currents simultaneously. The simulation and hardware results prove the aforementioned performance and demonstrate the efficacy of the proposed PWM current controller.

Design, Producing and Testing of 12-Step Three-Phase Voltage Source Inverter with Flexible Independent PWM Current Control for Brushless Direct Current Motor

Brushless motors are used in wide areas in the industrial and domestic applications owing to their superior advantages over other type electric motors such as induction and brushed direct current motors. Owing to fact that the brushless direct current motors and their drivers are cheaper and easier to design than drives of permanent magnet synchronous motors, brushless direct current motors are preferred a large application areas. But BLDC motor drivers are still run classical three-phase six-step inverter. Because of that the BLDC motors are run classical three-phase six-step inverter, the BLDC motor does not show its real dynamic performance. If BLDC motor is run via 12-step inverter, it gives a better dynamic performance than that of six-step inverter. The aim of this study, to manufacture 12-step inverter which controls phase currents using pulse width modulation (PWM) technique and to analyze the dynamic performance of BLDC motor running under purposed 12-step inverter. In the 12-step inverter, two or three transistors are on conduction mode at each time interval alternatively and in order to keep switching losses minimum only one transistor runs PWM mode in this study. The experimental results show that purposed flexible independent PWM 12-step inverter works perfectly and this proposed inverter provides the BLDC motor generating high dynamic performance than that of six-step one.

Improving the dynamic performance of grid connected wind farms using modern UPFC

Reliable power from Wind energy is one of the promising non-conventional energy sources for the future. But the fluctuating nature of wind introduces power quality problems affects the stability of the entire grid. Another issue is that power system grid is non-linear dynamic system which needs plenty of real and reactive power to provide its load and power loss is unreliable. Nowadays Flexible AC Transmission Systems (FACTS) controllers are handling a transmission line power surges which magnify the entire grid operation. This manuscript aims at reducing the power quality issues using Unified Power Flow Controller (UPFC) which is interconnected at the Point of Common Coupling (PCC) to improves the transmission ability of the system and enhance the dynamic response of ac grids. The distortions in the waveform are reduced by the proper switching of the semiconductor devices of the UPFC. The switching is controlled using a PI controller with current controlled Pulse Width Modulation (PWM). The gains of the PI controller are tuned using Modified Particle Swarm Optimization Technique (MPSO). The power quality is then analyzed with Total Harmonics Distortion (THD) and the performance is simulated in SIMULINK/MATLAB. These results are acquired by means of modified Particle Swarm Optimization (MPSO), to demonstrate the superiority of the proposed method, the simulation conceded out on grid connected wind power system with Proportional Integral Controller, Fuzzy Logic Controller, Artificial Bee Colony Algorithm and Modified Particle swarm Optimization.

Modelling and comparative dynamic analysis due to demagnetization of a torque controlled permanent magnet synchronous motor drive for energy-efficient electric vehicle

In this paper modelling and comparative dynamic analysis of a field oriented controlled permanent magnet synchronous motor (PMSM) torque drive employing a hysteresis current controller and a PWM (Pulse Width Modulation) operated current controller is presented. To illustrate the proposed concept in this torque controlled drive, torque and mutual flux linkages are applied as external inputs and speed of the machine is kept fixed. Moreover the magnitude of torque angle as well as stator current reference is controlled through the proposed machine dynamics. In fact a computation based on demagnetization of direct axis current to achieve the flux weakening in this proposed drive for current compensation is also introduced. To achieve the faster computation and accuracy Euler’s integration technique is used to solve the proposed complex dynamics of the permanent magnet synchronous machine. In a hysteresis current, controllers with a large hysteresis band current ripple and the torque pulsations are prominent at higher carrier frequency of the inverter. Additionally, a relationship with the magnitude of torque pulsations, PWM carrier frequency and the hysteresis window size is also achieved through various case-studies. Furthermore, the presence of current ripple and the pulsations generate some noise as well as vibration in a typical electric propulsion system. Afterwards a PWM current controller with identical operating conditions is proposed for such reduction of torque pulsation as well as ripples in the current waveform. Finally various feasible results are presented through MATLAB simulation and necessary hardware implementation to justify the comparative assessment of the proposed controllers for dynamic performance analysis in energy-efficient electric vehicles.

Development and Operation Control of a Switched-Reluctance Motor Driven Flywheel

This paper presents the development of a switched-reluctance machine (SRM) driven flywheel system, its charging/discharging controls, and performance evaluations. By properly setting and tuning the winding commutation instant, the same SRM can be operated as a motor and a generator in the SRM-driven flywheel system with satisfactory performances. Moreover, the hysteresis current controlled pulsewidth modulation scheme with hard freewheeling and the commutation angle dynamic shift controller are proposed to enhance the flywheel discharging generating performance. For interfacing the flywheel system to the dc microgrid, a half-bridge bidirectional dc-dc interface converter is developed. It is operated in a buck mode under flywheel charging and in a boost mode under flywheel discharging. The dynamic modeling and controller design are conducted to yield well-regulated dc output voltage under varying flywheel-driven switched-reluctance generator (SRG) speed. Finally, the measured results are given to verify the performances of the established flywheel and its interconnected operation to a wind SRG-based dc microgrid.

Modified Synchronous Reference Frame Based Shunt Active Power Filter with Fuzzy Logic Control Pulse Width Modulation Inverter

Harmonic distortion in power networks has greatly reduced power quality and this affects system stability. In order to mitigate this power quality issue, the shunt active power filter (SAPF) has been widely applied and it is proven to be the best solution to current harmonics. This paper evaluates the performance of the modified synchronous reference frame extraction (MSRF) algorithm with fuzzy logic controller (FLC) based current control pulse width modulation (PWM) inverter of three-phase three-wire SAPF to mitigate current harmonics. The proposed FLC is designed with a reduced amount of membership functions (MFs) and rules, and thus significantly reduces the computational time and memory size. Modeling and simulations of SAPF are carried out using MATLAB/Simulink R2012a with the power system toolbox under steady-state condition, and this is followed with hardware implementation using a TMS320F28335 digital signal processor (DSP), Specrum Digital Inc., Stafford, TX, USA. The results obtained demonstrate a good and satisfactory response to mitigate the harmonics in the system. The total harmonic distortion (THD) for the system has been reduced from 25.60% to 0.92% and 1.41% in the simulation study with and without FLC, respectively. Similarly for the experimental study, the SAPF can compensate for the three-phase load current by reducing THD to 5.07% and 7.4% with and without FLC, respectively.

Design and operation of a multifunction photovoltaic power system with shunt active filtering using a single-stage three-phase multilevel inverter

In this paper, the control of a multifunction grid-connected photovoltaic (PV) system with a three-phase three-level (3L) neutral point clamped (NPC) inverter is proposed, which can perform shunt active filtering. Normally, the shunt active filtering is achieved by detecting the harmonic and reactive currents of the nonlinear load and then injecting the compensating current into the grid. Therefore, the proposed system can inject PV power to a grid with power factor correction and current harmonic filtering features simultaneously. In addition, a single-stage compact and efficient transformerless power conversion topology is used in this paper for the grid-connected solar PV system with maximum power point tracking capability. In order to control the multilevel inverter-based combined system, a synchronous reference frame control technique and hysteresis current control pulse width modulation method have been applied. The system configuration and control strategy are verified and validated by simulations based on MATLAB/Simulink and implemented in real-time using the dSPACE DS1103 controller board. The simulation with experimental results indicates that the injected currents are sinusoidal and current total harmonic distortion is about 3.9%, lower than the IEEE 519 harmonic limit.

Power Quality Improvement of PMSG-Based DG Set Feeding Three-Phase Loads

This paper presents power quality improvement of a permanent-magnet-synchronous-generator-based diesel generator (DG) set feeding three-phase loads using a static compensator (STATCOM). A three-leg voltage-source converter (VSC) with a capacitor on the dc link is used as a STATCOM. The reference source currents for the system are estimated using an Adaline-based control algorithm. A pulsewidth modulation current controller is used for generation of gating pulses of insulated-gate bipolar transistors of the three-leg VSC of the STATCOM. The STATCOM is able to provide voltage control, harmonics elimination, power factor improvement, load balancing, and load compensation. The performance of the system is experimentally tested on various types of loads under steady-state and dynamic conditions. A three-phase induction motor with variable-frequency drive is used as a prototype of diesel engine with the speed regulation. Therefore, the DG set is run at constant speed so that the frequency of supply remains constant irrespective of loading condition.

A Switched-Reluctance Generator With Interleaved Interface DC–DC Converter

This paper presents the development of a wind switched-reluctance generator (SRG) with interleaved interface dc-dc converter. First, the power circuit and control scheme of the SRG are properly designed. The hysteresis current-controlled pulse width modulation (PWM) scheme is designed to achieve good winding current tracking control, and the robust voltage control scheme is developed to yield well-regulated dc output voltage under varying prime mover driving speed and load conditions. Moreover, the voltage regulation and the developed power performances of SRG are further enhanced using the proposed commutation shift approach. Next, an interleaved current-fed push-pull interface dc-dc converter with two modules is developed to establish the boosted common dc bus voltage of a dc microgrid from the SRG output having fault-tolerant capability. The rating analysis and circuit component design are conducted in detail. Similarly, well-regulated voltage with lower ripples is also yielded via the properly designed schematic and control scheme.

Three-level NPC inverter based new DSTATCOM topologies and their performance evaluation for load compensation

Now-a-days for effective load compensation, a conventional three-level neutral point clamped (CNPC) inverter topology is more preferably used. This compensator, however, faces the problems of additional clamping diodes, which reduces the redundant switching states and improves the problem of capacitor voltage imbalance; further increasing the inverter cost. In this paper, a detailed analysis of conventional NPC voltage source inverter (VSI) based Distribution Static Compensator (DSTATCOM) is given for shunt applications and to overcome its limitations, Conergy NPC and Active NPC VSI based new DSTATCOM topologies are proposed, exclusively for the load compensation. To demonstrate the effectiveness of the aforementioned topologies for shunt compensation, a three phase four wire system has been taken into consideration. Instantaneous symmetrical component theory (ISCT) is used for reference current generation, while, the hysteresis current control pulse width modulation (PWM) is used to generate the switching sequence for all the NPC configurations. A detailed simulation study has been carried out in MATLAB environment and the comparative evaluation of all the above DSTATCOM topologies is being provided.

PMSM-driven satellite reaction wheel system with adjustable DC-link voltage

This paper presents a digital signal processor-based permanent magnet synchronous motor (PMSM)-driven satellite reaction wheel with DC-link voltage adjustable according to speed and photovoltaic voltage. After the PMSM-driven reaction wheel is established, an improved current-controlled pulse-width modulation scheme is designed to yield precise sinusoidal winding current command tracking, and a simple, robust, model-following control scheme is designed to yield good dynamic speed response. To provide an adjustable and well-regulated DC-link voltage, DC/DC boost and DC/DC buck-boost front-end converters are established and compared. The stable chopping-controlled dynamic braking mechanism is also established.

Current Controlled PWM for Multilevel Voltage-Source Inverters with Variable and Constant Switching Frequency Regulation Techniques: A Review

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

Unified Three-Terminal Switch Model for Current Mode Controls

Current mode controls have been widely used in many power converters with various topologies. Small signal equivalent circuit model is an effective tool for controller design. However, no unified equivalent circuit model applicable to various converters is available. This paper proposes a unified three-terminal switch model for current mode controls with constant frequency and variable frequency modulations operating in continuous conduction mode, providing an accurate and simple equivalent circuit for various converters using current mode control schemes. By identifying the invariant three-terminal structure in current mode control pulsewidth modulation (PWM) converters, which consists of active switch, passive switch, inductor, and closed current loop, the terminal current and voltage relationships are studied and represented by a small signal equivalent circuit. A small signal model for a current mode control PWM converter can be obtained by point-by-point substitution of the PWM switch with its equivalent circuit. The proposed model is verified by simulation and experimental results of various converters, and compared with other models to demonstrate its accuracy. The proposed model is accurate up to half of switching frequency.

On the Switched-Reluctance Motor Drive With Three-Phase Single-Switch Switch-Mode Rectifier Front-End

This paper presents a switched reluctance motor (SRM) drive powered by a three-phase single-switch (3P1SW) switch-mode rectifier (SMR). The digital controls of both power stages are realized in a common DSP. In the front-end SMR, a robust current harmonic cancellation scheme and a robust voltage control scheme are developed. The undesired line current and output voltage ripples are regarded as disturbances and they are reduced via the proposed robust controls. In voltage control, a feedback controller is augmented with a simple robust error canceller. The robust cancellation weighting factor is automatically tuned according to load level to yield compromised voltage and power quality control performances. The chaotic phenomena can be automatically avoided and better SMR operating performance is obtained simultaneously. With boostable and regulated dc-link voltage, the current and speed dynamic responses of the followed SRM drive are enhanced, and the vibration and speed ripple are also lessened. As to the SRM drive, a random-band hysteresis current-controlled pulsewidth modulation (CCPWM) scheme (RB-HCCPWM) with harmonic spectrum shaping is developed and applied for its winding excitation control. The winding current harmonic spectrum is more dispersedly distributed to yield reduced stator vibration and speed ripple. Moreover, the commutation advanced shift is applied to yield further performance improvement of SRM drive.

Design and Control for a Charge-Regulated Flyback Switch-Mode Rectifier

This paper presents the design and control of a single-stage charge-regulated varying-frequency flyback switch-mode rectifier (SMR). First, the ratings of key constituted circuit components are derived, and accordingly, the power circuit is designed and implemented. Then, a novel charge-regulated, varying-frequency, current-controlled pulsewidth modulation (CCPWM) switching scheme is developed. In the proposed control scheme, the switch turn-on time is fixed, and the turn-off time interval is determined by the comparison result between the low-pass filtered switch current and its current command. The proposed switching scheme possesses the features of without slope compensation, having more dispersedly distributed harmonic spectrum, robust current tracking control, and ease of implementation using off-the-shelf integrated circuits. Finally, the quantitative and robust voltage regulation controls considering nonlinear behavior are made. Good dc output voltage regulation and ac input power quality control performances under wide load range are obtained. Some simulated and measured results are provided to demonstrate the performance of the developed SMR.

On Acoustic-Noise-Reduction Control Using Random Switching Technique for Switch-Mode Rectifiers in PMSM Drive

This paper presents an acoustic-noise-reduction control using a random switching technique for front-end switch-mode rectifiers (SMRs) of a permanent-magnet synchronous-motor (PMSM) drive. First, the PMSM drive and its front-end ac-switch-based SMR are established. The proper controls are conducted to let the motor drive possess good driving characteristics. In the acoustic-noise-reduction control for a low-frequency SMR under a voltage closed-loop control, the important audible vibration modes of the SMR inductor are first identified from the measurements. Then, the controls for eliminating one specific vibration mode and two vibration modes simultaneously via deterministic and stochastic approaches are studied. Specifically, a novel random three-stage excitation scheme is devised. As to the high-frequency SMRs, the random switching frequency ramp-comparison current-controlled pulse-width modulation (CCPWM) scheme and the randomly varying band hysteresis CCPWM scheme are developed. Theoretical bases of all the proposed control approaches are derived, and their comparative performances are evaluated experimentally.

Single-Switch Single-Phase Switch-Mode Voltage-Tripler Rectifier

A single-phase voltage-tripler rectifier operating in the switch-mode is studied. This is based on a diode pump circuit, in which the voltage across the boost capacitor adds to the supply to pump twice the peak supply voltage onto the output capacitor. An only active power switching device also provides the necessary control over the current. The experimental prototype using an insulated-gate bipolar transistor is implemented to investigate the operation under the current-controlled pulse-width modulation. The experimental results confirm that the input current can almost be waveshaped sinusoidally with a near-unity power factor.