Pulse Width Modulation Control Research Articles

New backstepping controllers with enhanced stability for neutral point clamped converters interfacing photovoltaics and AC microgrids

This work presents a new approach to obtain pulse width modulation (PWM) backstepping controllers with enhanced stability for neutral point clamped (NPC) multilevel converters to deliver energy from photovoltaic (PV) panels into AC microgrids. Stability enhanced backstepping non-linear controllers are obtained from the equations of the dq frame converter model to regulate the PV voltage to track the power point, and to balance the capacitor voltages through DC biasing of the PWM carriers, using a novel dynamic equation of the capacitors incremental unbalance voltage, while controlling the grid injected AC currents. Besides, the proposed controllers can change the PV panels operating point to curtail inject power for AC voltage / frequency regulation. The NPC converter and AC microgrid are simulated in MATLAB / Simulink and implemented in the laboratory to evaluate the performance of the PV energy conversion using the new stability enhanced backstepping PWM control. Simulation and experimental results show that, regarding predictive controllers, the novel stability enhanced backstepping requires lower microprocessor power than predictive controllers while presenting a similar behavior in PV voltage and power point tracking regulation, or for voltage / frequency regulation of the microgrid. AC injected currents show low levels of total harmonic distortion similar to predictive controllers and can operate at near unity power factor.

Hybrid Switching Control-Based DC to AC Inverter for Microgrid Using Renewable Energy Sources

Hybrid switching control-based direct current (DC) to alternating current (AC) inverter is a method of controlling the flow of power from DC sources such as solar panels or wind turbines to AC loads in a microgrid. In a microgrid, renewable energy sources are often used to supplement traditional sources of energy and improve overall energy efficiency. To simulate micro-grid systems, an effective three-legged IGBT inverter has been developed using Matlab R2016a/Simulink. The inverter switches are controlled by a pulse controller, which creates the switching gate pulses. This work models the output voltage and current waveforms of the three-phase 180° voltage source inverter that supplies nonlinear loads. To lower the total harmonic distortion (THD) of the current and voltage outputs of the three-phase voltage source converter (VSC), a filter circuit and a two-level pulse width modulation (PWM) generator have been presented. This pulse-width modulation generator compares the modulating signal and a high-frequency triangular carrier wave. Sinusoidal pulse width modulation (SPWM) is used for PWM control. Moreover, the hybrid switching control-based DC-to-AC inverter utilizes a combination of pulse width modulation (PWM) and hysteresis current control techniques to maintain a constant AC output voltage and frequency. PWM control is used to regulate the voltage, while hysteresis current control is used to regulate the current. Additionally, an inductor-capacitor-inductor (LCL) filter is used to improve the stability of the power converter by providing a damping effect on the system. Overall, the LCL filter is a versatile and effective tool for improving the performance of power inverters, especially in applications where high efficiency and low harmonic distortion are important. IUBAT Review—A Multidisciplinary Academic Journal, 6 (1): 25-46

Modeling and Performance Analysis of a Grid-Connected Photovoltaic System with Advanced Controller considering Varying Environmental Conditions

This paper presents a mathematical model of 255 kW grid-connected solar photovoltaic (SPV) system. To study the performance characteristics of the grid-connected SPV system, a new hybrid adaptive grasshopper optimization algorithm with the recurrent neural network (AGO-RNN) control technique was implemented. Furthermore, the power quality at the point of common coupling (PCC) has been studied using the conventional (PSO) and proposed AGO-RNN controllers. The characteristics of the PV system were analyzed under varying environmental (variable irradiance and temperature) conditions considering 3 different cases such as (i) standard test conditions (STC), (ii) variable radiation with constant temperature, and (iii) variable radiation with variable temperature. For each case, the total harmonic distortion (THD) has been calculated using the proposed AGO-RNN control technique, and the results were compared with particle swarm optimization (PSO) technique. The 255 kW PV model is initially developed and connected to a three-level NPC inverter, an MPPT-based perturbation and observation algorithm. Later, the PV model is controlled by an AGO-RNN pulse width modulation (PWM) controller and is then integrated to the main grid at PCC. The main advantage of this technique is exploiting the separate DC-DC converter between the SPV module and the inverter. Finally, the proposed grid-connected SPV system was simulated on MATLAB for analyzing the performance of the system based on its I-V and P-V characteristics, inverter voltage, grid power, gird voltage, grid current, power factor, and THD under different environmental conditions. The simulation results demonstrate that the current magnitude and THD of the SPVGC system are improved with the cutting-edge AGO-RNN controller compared to PSO in all three different scenarios, and this value is less than 1.6%, which is within the permitted limits of IEC 61727 standards.

A single-phase direct buck-boost AC–AC converter with minimum number of components

In this paper, a single-phase direct pulse width modulation (PWM) buck-boost AC–AC converter is proposed. The proposed converter utilizes a minimum number of semiconductor switches and passive components that decreases the converter power losses and offers high efficiency. It can be operated with simple PWM control and doesn’t require soft-commutation strategies. It does not suffer from input source shoot-through and commutation problems. Moreover, it supplies both continuous input and output currents. The common sharing ground of the input and output gives the proposed converter the feature that it can be utilized for voltage sag and swell compensation. A comparison of the proposed converter performance with similar existing converters is presented. Also, detailed circuit analysis, component design guidelines, and simulation results using the MATLAB/Simulink environment are demonstrated. A laboratory prototype has been built and tested to validate the converter performance and confirm the results obtained by computer simulation.

Experimental Investigation of Decoupled Discontinuous PWM Strategies in Open-End Winding Induction Motor Supplied by a Common DC-Link

Currently open-end winding induction motors fed by a dual inverter (OEWIM-DI) present an innovative approach to enhance the performance of modern electric drive systems; such as electrical vehicles and electric aircraft applications. However, the dual inverter topology requires a proper switching control strategy to enable the OEWIM drive to fully achieve its performance. This work aims to investigate experimentally the impact of different Decoupled Discontinuous Pulse Width Modulation (DDPWM) control strategies on the performance of the OEWIM-DI supplied by a common DC-link. The criteria performance adopted in this study are: (i) the Total Harmonic Distortion (THD) of the current and voltage, (ii) the Zero Sequence Voltage (ZSV), (iii) the Common Mode Voltage (CMV), and (iv) the dual inverters losses. The various DDPWM control schemes for the 1.5 kW OEWIM-DI motor drive are implemented on a dSPACE 1104 board and the results are compared with the popular and widely used Space-Vector PWM (SVPWM) strategy. From the results, it can be concluded that the optimised DDPWM technique gives the best performance. This technique has reduced the CMV by one level and reduce the losses by 50% while having the same THD and ZSV obtained with the SVPWM technique.

Averaged Behavior Model of Current-Mode Buck Converters for Transient Power Noise Analysis

Accurate evaluation and simulation of power noise is critical in the development of modern electronic devices. However, the widely used target impedance fails to predict the low-frequency noise generated in a device due to the existence of the dc–dc converter, whose output impedance can change under different loading conditions. A physical circuit model is then desired to replicate the behavior of a voltage regulator module, and the average technique is an efficient method to estimate the noise of a pulsewidth-modulated (PWM) converter. With the emergence of converters with adaptive on-time (AOT) controllers, more complex averaging methods are required, but none of them supports transient simulation. A general, efficient, and accurate modeling technique is presented in this article, whose framework supports both current-mode PWM and AOT controllers. In addition, a novel two-step parameter extraction method is proposed, which can be used to evaluate the equivalent values of internal feedback parameters of an encrypted simulation model or from measurement. The modeling method is validated by both simulation and measurement.

A Variable Switching Frequency Space Vector Pulse Width Modulation Control Strategy of Induction Motor Drive System With Torque Ripple Prediction

The constant switching frequency space vector pulse width modulation (CSFSVPWM) generates high-frequency harmonics with integer multiples of the switching frequency, making it fail to fully exploit the potential of pulse width modulation (PWM) technique. In this paper, a variable switching frequency space vector pulse width modulation technique with the function of torque ripple prediction is proposed for induction motor drive system, which could optimize the high-frequency harmonic current distribution and torque ripple. The mathematical correlation between inverter average voltage and instantaneous voltage under the space vector pulse width modulation (SVPWM) is first analyzed, followed by the analysis of current ripple in a switching cycle using the typical seven-segment SVPWM, thus the torque ripple of induction motor during this period can be predicted. The switching period is dynamically adjusted according to the magnitude of predicted torque ripple, and the average switching frequency is maintained to be the same with that of CSFSVPWM. The effectiveness of the proposed method in suppressing high-frequency current harmonics and torque ripple is fully verified by experimenting on a 2.2 kW induction motor drive system, and a comprehensive comparison with CSFSVPWM and random PWM modulation is implemented.

Single‐phase five‐level common‐ground transformerless inverter using switched capacitors for photovoltaic application

AbstractTransformerless inverters (TLIs) are extensively used in the photovoltaic (PV) grid‐connected system. TLI with a common ground structure exhibits multiple excellent features that improve the efficiency of the inverter, eliminating leakage current and boosting the voltage. The use of TLI eliminates the electrical isolation required between PV and the grid, resulting in a leakage current (LC) issue. The LC affects the power quality of the inverter and creates a safety‐related issue. This paper presents a new TLI topology based on the common ground (CG) structure. This topology uses eight switches and two self‐balanced switched capacitors. Phase disposition pulse width modulation (PD‐PWM) control scheme is used to create a five‐level output voltage. Further, adequate analysis for component selection and loss analysis is carried out to evaluate the efficiency. Its CG configuration certifies that there is minimal LC and common mode voltage (CMV). It also supports the active and reactive power of the grid. Its dual gain makes it suitable for photovoltaic (PV) applications. This topology is simulated for leading, lagging, unity power factor (UPF), and changes in input voltage and load conditions. Later, a corresponding experimental test is carried out on a laboratory prototype (1 kW). An equitable comparison is carried out for the component, stresses, and features like CG, and LC, along with efficiency.

Design of a Power Converter for Solar Energy Storage System

This paper presents a single-stage three-port isolated power converter that enables energy conversion among a renewable energy port, a battery energy storage port, and a DC grid port. The proposed converter integrates an interleaved synchronous rectifier boost circuit and a bidirectional full-bridge circuit into a single-stage architecture, which features four power conversion modes, allowing energy adjustment for both the renewable energy and the battery storage energy ports when power is supplied by the renewable energy port. It also features bidirectional functionality that allows the battery storage energy port to provide energy storage through the DC grid port, thereby providing uninterrupted power supply functionality. The converter uses four power switches and two inductors to boost and convert energy from the renewable energy port to the battery storage energy port or to the DC grid port through the bidirectional full-bridge circuit. The converter is also capable of 1 kW power energy conversion by utilizing an adjustable duty cycle with a fixed frequency of 100 kHz and phase-shift control through a built-in pulse width modulation control module of a TMS320F28 series digital signal processor. According to the experimental results, the converter developed in this study can achieve a conversion efficiency of up to 94%.

Research on internal model control and hybrid modulation strategy of a MW-level direct-drive PMSM for traction drives in electric locomotive

Aiming at the problem of motor control performance degradation caused by the cross-coupling and low switching frequency condition in the high-power direct-drive permanent magnet synchronous motor (PMSM) control system, a robust current control of PMSM based on internal model control (IMC) and hybrid pulse width modulation (PWM) is proposed and applied to the control of a MW-level direct-drive PMSM in electric locomotive traction system. Firstly, combined with the characteristics of the low switching frequency of the electric locomotive inverter, a hybrid PWM strategy is adopted. Secondly, the IMC of PMSM is designed, and the IMC is adopted to solve the problems of more control parameters and cross-coupling of direct-drive PMSM in the d-q axis under low switching frequency, which improves the robustness of the whole locomotive system. Finally, the experiments have been carried out on a 1.2 MW direct-drive PMSM for traction system in electric locomotive, the correctness and effectiveness of IMC and hybrid PWM strategy are verified.

Improvement of Power Quality in Primary Distribution Systems Based on Static-Var Compensators

A flexible AC Transmission Systems (FACTS) is a new technology offers a fast and reliable control over the transmission and distribution parameters like voltage and phase angle between the sending end voltage and receiving end voltage. Distribution static synchronous compensator (DSTATCOM) is a second generation member of the (FACTS) controllers. Reactive power compensation is an important aspect in the control of distribution systems. Reactive current in addition to increasing the distribution system losses, introduces voltage drop at lead point and finally it causes poor power quality in power systems. Primary radial distribution feeders have high resistance to reactance ratio, which causes voltage drop and high power loss in radial distribution systems. providing high demanding power to entire load while maintaining voltage magnitude at acceptable range is one of the major system constraints, using of capacitor banks to improve the reactive power have not quite enough at high reactive power feeder, because it have more slow in step by step response and have not capable to generate continuously variable reactive power. In some primary distribution feeders at the state of Khartoum, it is observed that there are some appropriate drops in voltage and quality service at high reactive power loads although some individual capacitor banks have been connected at these feeders, from here we researched for a new technology to overcome this problem. A steady-state model of (DSTATCOM) is proposed and developed to compensate the reactive power by using a Voltage Source Converter (VSC) with Pulse Width Modulation (PWM) and cascade control of four direct proportional integral controllers (PI) in synchronous reference frame. The detailed modeling and control design of (DSTATCOM) with specific typical radial primary distribution feeders (industrial, commercial, residential) are presented and implemented along necessary mathematical model equations in the Matlab software. Simulation schemes of (DSTATCOM) are done with help of control block diagrams and stability analysis. Load flow is an important method for analysis, operation and planning studies of any power system in a steady-state condition. In this research backward forward sweeps load flow method (Kirchhoff’s Laws) has been proposed rather than Newton-Raphson and Fast decoupled methods because the distribution feeders have a high R/X ratio which make the systems are ill-conditioned iterations analysis. (DSTATCOM) was installed on specific typical radial feeders at the (DSTATCOM) which using for distribution lines and load compensation has been the subject of considerable interest beside it is a new technology for a good power quality solution. Keywords: Power System, Flexible AC Transmission Systems (FACTS) Devices, STATCOM, PI Controller DOI: 10.7176/ISDE/13-1-05 Publication date: May 31 st 2023

Boundary-Based PWM Control Scheme for a DC-DC Buck Converter Operating in CCM

This paper presents a control scheme for DC-DC buck converters operating in Continuous Conduction Mode (CCM) that achieves fast and accurate regulation of the output voltage while reducing the computational burden on the control system. The study investigates the boundary-based control scheme for a buck converter and models the converter circuit as a Switched Dynamical System (SDS) using hybrid automaton due to its continuous and discrete states. The boundaries of these states are determined to enable the implementation of a fixed-frequency Pulse-Width Modulation (PWM) control scheme. The proposed control scheme was evaluated through simulation with variations in input voltage, load, and reference voltage. It was further analyzed for model mismatch due to parametric variations and parasitic parameters, which demonstrated its effectiveness and robustness under various operating conditions. The SDS approach for controlling the buck converter is simple, requires minimal mathematical calculations, and is free from modeling errors. The output voltage was stable under regulatory and servo problems, as well as sinusoidal input testing. The proposed scheme was compared with other conventional schemes and found superior in terms of steady-state and dynamic response. Additionally, integral compensation was introduced to counter parasitic parameters, which was found to be effective.

Transient modelling and simulation of a switched reluctance machine in different operating modes

An appropriate numerical computational method and simplest model captures the performance of Switched Reluctance Machines (SRMs). Several papers and computer software-based simulation models are reported in the literature. Each model has its own merits and demerits. This paper proposes a mathematical model, based on a combination of voltage and mechanical equations, suitable for the transient running of a switched reluctance machine. The simulation results of current, torque and speed profile of SRM are produced under current chopping control and voltage pulse width modulation control. The proposed work has used experimental data of flux linkage and static torque in the mathematical model for best performance and control of the machine. The obtained simulation results are verified with experimental results. This model can be extended to a range of rotor position where the machine can be switched at decreased and increased inductance region which gives motoring and generating operation mode.

A Multimode Control Scheme for Output Regulation and Voltage Balancing in a Stacked-Switch Resonant Converter With Extended High Efficiency for Wide Gain Range Applications

In this article, a new hybrid comprehensive multimode control system is proposed for a stacked-switch bidirectional CLLC resonant converter for wide voltage gain applications. By configuring the presented leg with different switching patterns, the presented leg in the converter can operate in different modes: full-wave (FW), half-wave (HW), or voltage-doubler (VD) through the converter’s built-in circuit redundancy. The proposed hybrid control scheme consists of different control modes: variable frequency modulation, pulse-width modulation (PWM), and asymmetric PWM (APWM) control. Correspondingly, four voltage gain curves are derived from the proposed converter. With the proposed approach, the converter is able to achieve constant voltage regulation while constraining the range of switching frequency, allowing very high efficiencies to be realized for a wide range of input voltages. Soft-switching is achieved for all the semiconductor devices for the entire operating range. The steady-state and dynamic performances of the proposed hybrid comprehensive control system are verified through a proof-of-concept 400-V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim ~1$ </tex-math></inline-formula> -kV/ 700-V, 1-kW laboratory prototype. Results confirmed that the efficiency is maintained between 95.03% and 96.97% throughout the specified input voltage range.

Fixed-Frequency PWM Control and Stability of Series-Stacked Buffer for 2ω-Power Decoupling

Active second-harmonic ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> ) filters have become an integral technology for single-phase power converters in high-power density designs. The series-stacked buffer (SSB) has emerged as an attractive topology among the existing solutions due to its low power, high efficiency, and compact design. However, one of the challenges in adopting SSB lies in its control, where hysteresis current control has been adopted conventionally. This results in a wide variation in the switching frequency, making the digital control implementation and filter design complex. On the other hand, fixed-frequency pulsewidth modulation (PWM) control necessitates developing a model for the systematic controller design to ensure stability and desired filtering performance. The assumption of SSB modeled as a second-harmonic current source, independent of the dc bus circuit components, fails to capture the dc bus loading effect on the SSB. In this work, a dynamic model of SSB is developed where the main dc bus and its passive elements are considered. The derived model enables a systematic approach for the controller design while ensuring the desired <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> filtering. The stability limits and parameter sensitivities of the model are studied analytically and in simulations. The analytical model is validated, and the proposed controller performance and stability limit are verified experimentally on a hardware prototype. A video demonstrating the transition from stable to unstable operation is provided.

Boundary-Based Hybrid Control Algorithm for Switched Boost Converter Operating in CCM and DCM

It is essential to have enhanced efficiency for the DC-DC converters operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). This requires a hybrid controller designed using pulse width modulation (PWM) and pulse frequency modulation (PFM) schemes. This paper fixates on a boundary-based hybrid control algorithm for the second-order DC-DC converter - the switched boost converter. The proposed algorithm works in PWM control scheme for CCM operation, whereas DCM operation uses PFM control scheme. The boundary conditions are defined by the load current, output voltage, and switching frequency. Here, an attempt is carried out to have the advantages of both the control schemes. The boost converter is represented by the switched system operating in three modes. Violating transition guards condition orchestrates the switching among these modes. A supervisor detects the CCM and DCM operations, and subsequently switches between PWM and PFM control scheme. Extensive circuit-level simulations are carried out in MATLAB to show the efficacy of the suggested algorithm under the fluctuating line, load, and set-point.

Design and Implementation of Hybrid Controller for Dynamic Power Management in a DC Microgrid

Nowadays more and more devices and appliances are operated with electricity, thus the electrical crisis is increasing exponentially day by day. In order to avoid the occurrence of electricity crisis, various power generation resources are used at the utility side to enhance the power generation to meet the consumers’ demand for electricity. Hence, a suitable control scheme has to be implemented at the microgrid to reduce the electrical fluctuation, power loss and manage the power quality. The Adaptive Proportional Integral Voltage Controller (APIVC) and hysteresis current controller (HCC) are integrated to enhance the quality of power generated. The electrical fluctuation is reduced by the proposed efficient hybrid parallel source controller model for DC Microgrid. The proposed model exerts decentralized control, which is an advanced droop control where communication is not required. The outer voltage control loop and inner current control loop provide faster control to maintain the grid voltage constant. The grid voltage is set as the reference value and the actual value is sensed to generate error value, which sets the reference value of current. The error signal is processed to provide switching signals for the converters. The performance analysis and simulation results show that the proposed mechanism performed better than the conventional methods such as Hysteresis Band Current Controller (HBCC) with Pulse Width Modulation (PWM) and Proportional Integral Voltage Controller (PIVC) with Hysteresis Current Controller (HCC), in terms of the electrical fluctuation, power loss and manage the power quality in the microgrid.

Cyber–physical system for fast prototyping of power electronic converters in EMI shaping context

Dynamic development of power systems, which utilize power electronic converters as interfaces between the renewable energy sources, as well as complex control and measuring arrangements, forces the cooperation of specialists representing various fields to assure electromagnetic compatibility (EMC) of the so-called smart industrial systems. Low voltage DC grid applications involving multiple power electronics devices may turn the grid susceptible to noise injection and impair the signal integrity and power quality due to the electromagnetic interference (EMI) emission and due to devices and grid interactions. The EMI propagation leads to misreading measurements and faulty conditions of equipments and in ICT (Information and Communications Technology) systems within the conducted emission frequency range, which impacts the hosting capacity of the grid. This paper proposes a cyber–physical system based on the NI-PXI platform for fast-prototyping and EMC assessment as pre-compliance tool of low-voltage DC grid in smart industrial systems. Thus, the LabVIEW-based design as well as the EMC-testbench system validation were performed with a DC/DC converter through the pulse-width modulation control algorithms. In addition, a case study has been investigated to evaluate the interferences between the converter and Power Line Communication. Hence, the theoretical control algorithms, hardware and software details, and experimental results are discussed, highlighting the paradigms of one flexible and collaborative cyber–physical system from the area of smart industrial systems.

Series APF based on Five and Seven-Level NPC Inverters using modified PQ Method

This paper presents the performance analysis of Series Active Power Filter (Series APF) based on five and seven-level neutral point clamped (npc) using modified instantaneous reactive power control strategy to use for harmonic and all voltage disturbances compensation. The conventional configuration based on standard voltage source inverter (VSI) with hysteresis controller presents several drawbacks such us uneven switching frequency and limited power applications. Multi-level inverters such us Five and seven-level are currently being investigated and used in various industrial applications; their advantages include the capability to reduce the harmonic content and decrease the voltage or current ratings of the semiconductors with low switching losses, low electromagnetic interference, and low acoustic noise. Fuzzy controllers are successfully employed in various industrial applications and are found more robust than conventional controllers; they represent a good alternative to classic control systems. To benefit of all these advantages two configuration of Series APF are presented in this paper adopting the same control scheme based on Phase Disposition-Sinusoidal Pulse Width Modulation (PD-SPWM) and fuzzy logic control (FLC). The proposed two series APF are evaluated using MATLAB-Simulink software and SimPowerSystem Toolbox for harmonic compensation and in case of all voltage disturbances compensation. The simulation results show the performance and the efficiency of the proposed Series APF based on seven-lever (npc) inverter in the improvement of the power quality.

Single-Inductor, Multiple-Input, Multiple-Output, DC-DC Converter Based on a New Software Zero-Current Switching (ZCS) Technique

A single-inductor multiple-input multiple-output converter is proposed in this paper that can be used in low-power systems due to low output current and voltage. This converter is implemented discretely, and only one microcontroller is employed to control the system. The unique zero-current switching (ZCS) technique considered in this paper is such that only by reading the inductor’s left-side voltage the optimal value of the inductor discharge duty cycle is determined. This method can be generalized to low-power and high-power converters, whether implemented and designed as discrete or integrated. This converter works in discontinuous conduction mode. It uses pulse width modulation control and the time-multiplexing control method, which makes the system have high efficiency and makes the cross-regulation problem between the converter’s outputs tiny. The control algorithm considered in this converter is digital, which determines the optimal charge and discharge duty cycles. Also, the switching frequency of this converter is constant, relatively low, and equal to 5[Formula: see text]kHz. The efficiency of this converter has reached 91.6% by using the ZCS technique and other mentioned control methods.