Single-phase Pulse Width Modulation Inverter Research Articles

Performance investigations of five-level reduced switches count Η-bridge multilevel inverter

Introduction. This research paper describes a simple five-level single-phase pulse-width modulated inverter topology for photovoltaic grid applications. Multilevel inverters, as opposed to conventional two-level inverters, include more than two levels of voltage while using multiple power switches and lower-level DC voltage levels as input to produce high power, easier, and less modified oscillating voltage. The H-bridge multilevel inverter seems to have a relatively simple circuit design, needs minimal power switching elements, and provides higher efficiency among various types of topologies for multi-level inverters that are presently accessible. Nevertheless, using more than one DC source for more than three voltage levels and switching and conduction losses, which primarily arise in major power switches, continue to be a barrier. The novelty of the proposed work consists of compact modular inverter configuration to connect a photovoltaic system to the grid with fewer switches. Purpose. The proposed system aims to decrease the number of switches, overall harmonic distortions, and power loss. By producing distortion-free sinusoidal output voltage as the level count rises while lowering power losses, the constituted optimizes power quality without the need for passive filters. Methods. The proposed topology is implemented in MATLAB/Simulink with gating pulses and various pulse width modulation technique. Results. With conventional topology, total harmonic distortion, power switches, output voltage, current, power losses, and the number of DC sources are investigated. Practical value. The proposed topology has proven to be extremely useful for deploying photovoltaic-based stand-alone multilevel inverters in grid applications.

Analysis and Mitigation of Dead-Time Harmonics in the Single-Phase Full-Bridge PWM Converter With Repetitive Controllers

In order to prevent the power switching devices (e.g., an insulated-gate bipolar transistor, IGBT) from shoot-through in voltage-source converters during a switching period, the dead time is added either in the hardware driver circuits of the IGBTs or implemented in software in pulse width modulation (PWM) schemes. Both solutions will contribute to a degradation of the injected current quality. As a consequence, the harmonics induced by the dead time (referred to as “dead-time harmonics” hereafter) have to be compensated in order to achieve a satisfactory current quality, as required by standards. In this paper, the emission mechanism of dead-time harmonics in single-phase PWM inverters is, thus, presented considering the modulation schemes in detail. More importantly, a repetitive controller has been adopted to eliminate the dead-time effect in single-phase grid-connected PWM converters. The repetitive controller has been plugged into a proportional-resonant-based fundamental-frequency current controller so as to mitigate the dead-time harmonics and also to maintain the control of the fundamental-frequency grid current in terms of dynamics. Simulations and experiments are provided, which confirm that the repetitive controller can effectively compensate the dead-time harmonics and other low-order distortions, and also, it is a simple method without hardware modifications.

Influence Rate of Semiconductor ON-Voltage in Inverter Circuit on Iron Loss Inside a Non-Oriented Electrical Steel Sheet

We calculate an iron loss attributed to semiconductors ON-voltages in an inverter circuit and reveal influence rate of the ON-voltages on whole iron loss. In our previous work, it has been revealed by inverter excitation that the ON-voltages make minor loops in magnetic hysteresis of magnetic material and the loops affect iron loss characteristics. In this paper, it is investigated by a factor analysis how much the on-voltage has an influence on iron loss, quantitatively. We separate whole iron loss caused in a non-oriented electrical steel sheet into three losses: loss by the ON-voltage, loss by fundamental component, and loss by inverter carrier. The rates of these losses are evaluated under several conditions of single-phase pulse width modulation inverter excitation, and the results show that the proportion of loss by ON-voltages is up to around 10% depending on inverter excitation parameter: fundamental frequency, carrier frequency, modulation index, and magnetic flux density.

Simple Time Averaging Current Quality Evaluation of a Single-Phase Multilevel PWM Inverter

This paper addresses theoretical calculation of a single-phase multilevel pulsewidth modulation (PWM) inverter current total harmonic distortion (THD). Analytical approach introduced in late 1980s for a two-level inverter is generalized for an arbitrary level count for a single-phase inverter. Although the obtained closed-form piecewise analytical solutions assume (infinitely) large ratio of switching and fundamental frequencies and pure inductive load, they are practically very accurate for the ratios of (apparent) switching and fundamental frequencies larger than 25–30 and inductance-dominated loads. Along with strict mathematical solutions, simple accurate Bessel function approximation and hyperbolic average trend one are suggested. The formulas clearly reveal a single-phase PWM inverter current THD dependence on modulation index for an arbitrary voltage level count and are easily modified to cover grid-connected cases.

Parallel Structure Fractional Repetitive Control for PWM Inverters

In this paper, a parallel structure fractional repetitive control (RC) scheme is proposed to improve the performance of pulsewidth-modulation (PWM) inverters in fractional cases where the sampling rate of the digital control system is not an integral multiple of the fundamental frequency. By introducing a correction factor, the new control scheme increases the control gains for all harmonics and locates poles accurately at targeted harmonic frequencies. As a result, the proposed control scheme achieves better tracking and rejection performance than conventional RC. Moreover, the parallel structure fractional repetitive controller requires less data memory. Dynamic response is also improved. The stability and convergence of this method are proved. Experimental results on a single-phase PWM inverter illustrate the advantages of this control scheme.

A Generic Digital $nk \pm m$-Order Harmonic Repetitive Control Scheme for PWM Converters

In this paper, a generic digital nk ± m-order harmonic repetitive control ( nk ± m RC) scheme is presented for constant-voltage constant-frequency pulsewidth-modulation (PWM) converters to track/remove any nk ± m-order harmonic frequencies efficiently, e.g., 4k ± 1-order harmonics for single-phase converters or 6k ± 1-order harmonics for three-phase converters. Compared with conventional RC, the proposed nk ± m RC occupies less data memory and can achieve zero-error tracking or perfect disturbance rejection of nk ± m-order harmonics at much faster error convergence rate. What is more, the proposed RC provides a unified formula for various RC schemes. Application examples of 6k ± 1-RC-controlled three-phase PWM inverter and 4k ± 1-RC-controlled single-phase PWM inverter demonstrate the effectiveness and advantages of the proposed RC scheme.

On an Auxiliary Power Unit With Emergency AC Power Output and Its Robust Controls

The development of an auxiliary power unit (APU) with 110 V/60 Hz output from conventional battery, laptop computer battery pack, or other available dc sources and its robust controls are presented in this paper. First, a front-end current-fed push-pull dc/dc converter is designed and implemented. It is used to establish the boosted and well-regulated dc-link voltage for the followed inverter. The quantitative designed feedback controller is augmented with a novel robust tracking error cancellation scheme (RECC) to achieve the desired regulation performance. Then, a full-bridge single-phase pulse-width modulated inverter is established to yield 110 V/60 Hz source for emergency use. In treating the inverter waveform control, the causes of waveform distortion under nonlinear loads are explored. Then a novel robust model following control scheme is proposed accordingly. In the proposed control scheme, the simple model following controller is augmented with a RECC. Theoretic bases of all the proposed control schemes are derived thoroughly. The simulation and experimental evaluations indicate that the developed APU possesses good output voltage waveform under unknown and nonlinear loads.

A State Equation Model of a Single-Phase Grid-Connected Inverter Using a Droop Control Scheme With Extra Phase Shift Control Action

This paper presents a state equation model of a single-phase pulsewidth modulation inverter connected to the grid, using frequency-active power and voltage-reactive power droops, including an extra phase shift loop. The influence of the control parameters on the system's behavior can be studied using the proposed state equation model, which was obtained from the small-signal analysis. The model's results are compared with numerical simulations of the nonlinear system to verify their accuracy. Comparisons are also made with experimental data reported in the literature.

On Zero Steady-State Error Voltage Control of Single-Phase PWM Inverters With Different Load Types

This paper comprehensively investigates and compares different multiloop linear control schemes for single-phase pulsewidth modulation inverters, both in stationary and synchronous (d -q) frames, by focusing on their steady-state error under different loading conditions. Specifically, it is shown how proportional plus resonant (P + R) control and load current feedback (LCF) control can, respectively, improve the steady-state and transient performance of the inverter, leading to the proposal of a PID + R + LCF control scheme. Furthermore, the LCF control and capacitive current feedback control schemes are shown to be subject to stability issues under second and higher order filter loads. Additionally, the equivalence between the stationary frame and d -q frame controllers is discussed depending on the orthogonal term generation method, and a d-q frame voltage control strategy is proposed eliminating the need for the generation of this orthogonal component. This is achieved while retaining all the advantages of operating in the synchronous d-q frame, i.e., zero steady-state error and ease of implementation. All theoretical findings are validated experimentally using a 1.5 kW laboratory prototype.

Output Current Ripple-Free PWM Inverters

In this brief, a simple modular passive ripple mirror circuit (PRMC) is proposed for eliminating the inherent high-frequency current ripple of pulsewidth modulation (PWM) inverters. The proposed passive circuit is robust in the sense of without containing either any power semiconductor switch or any extra control. Only the reflected high-frequency ripples are automatically induced and processed for proper cancellation with the original ripples. It turns out that not only the output power quality can be enhanced but also the inductance of the main power circuit can be reduced greatly. As an example, a single-phase PWM inverter is chosen for illustrating the effectiveness of the proposed PRMC. Experimental results show that the proposed PRMC can, indeed, achieve the desired performance.

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

This paper proposes the use of a three-phase high-frequency semicontrolled rectifier for wind energy conversion systems based on permanent magnet generators. The main advantages of the topology are: simplicity, since all active switches are connected to a common point, robustness, as short-circuit through a leg is not possible, and high efficiency due to reduced number of elements. As a disadvantage, higher but acceptable total harmonic distortion of the generator currents results. The complete operation of the converter and theoretical analysis are presented. Additionally, a single-phase pulsewidth modulation inverter is also employed in the grid connection. Experimental results on 5-kW prototype are presented and discussed.

Ripple Current Reduction of a Fuel Cell for a Single-Phase Isolated Converter Using a DC Active Filter With a Center Tap

A ripple current reduction method is proposed that does not require additional switching devices. A current ripple that has twice the frequency component of the power supply is generated in the dc part when a single-phase pulsewidth-modulated inverter is used for a grid connection. The current ripple causes shortening of the lifetime of electrolytic capacitors, batteries, and fuel cells. The proposed circuit realizes a dc active filter function without increasing the number of switching devices, because the energy buffer capacitor is connected to the center tap of the isolation transformer. In addition, the buffer capacitor voltage is controlled by the common-mode voltage of the inverter. The features of the proposed circuit, control strategy, and experimental results are described, including the result of ripple reduction, to approximately 20% that of the conventional circuit.

Plug-In Dual-Mode-Structure Repetitive Controller for CVCF PWM Inverters

Repetitive control (RC) is found to be a high-performance control scheme for constant-voltage constant-frequency (CVCF) pulsewidth-modulated (PWM) converters to eliminate output total harmonic distortion. In this paper, a dual-mode-structure RC (DMRC) is proposed to further improve the control performance of RC. The proposed DMRC controller comprises of two paralleled periodic signal generators: an odd-harmonic one and an even-harmonic one. Without additional complexity and loss of tracking accuracy, DMRC can achieve a faster error convergence rate than the conventional RC does. Moreover, the tracking accuracy of DMRC is higher than that of odd-harmonic RC. In the presence of nonlinear load disturbances and parameter uncertainties, an application example of a DMRC-controlled single-phase PWM inverter is provided to evaluate the proposed DMRC scheme. Systematical experimental results show the effectiveness and superior advantages of the DMRC approach.

AN H∞ ROBUST CONTROLLER FOR SINGLE-PHASE PWM INVERTERS

A robust controller for a single-phase Pulse-Width Modulation (PWM) inverter is designed. The single-phase PWM inverter generates an AC sinusoidal output from a DC link voltage. Robustness of the output waveform against load variations and minimum Total Harmonic Distortion (THD) are the main goals in this design. The importance of this design methodology results from the changes in the inverter's transfer function as affected by load variations. So it is necessary to use a robust controller such as H∞.

A novel current-tracking method for active filters based on a sinusoidal internal model [for PWM invertors

A new current control method based on the internal model principle in control theory is proposed. It introduces a sinusoidal internal model into the control system. It does not use any coordinate transformations. The method can be used for tracking an arbitrary number of harmonics: a DC component or fundamental frequency component signal. It is applied to a single-phase pulsewidth modulation inverter and active filter. The validity is confirmed by simulation and experimental results.

Modulation strategy for single phase PWM inverters

A novel pulse width modulation (PWM) strategy that closely approximates the harmonic performance of the off-line harmonic minimised PWM technique for single phase PWM inverters is presented. The proposed on-line PWM technique digitally reproduces the characteristics of hysteresis band modulation for which the switching frequency is directly controlled by adapting the width of the hysteresis band. The software implementation is achieved using the conventional equations for regular-sampled PWM, combined with the pulse-position modulation (PPM) function characteristic of hysteresis band modulation.

A digital control technique for a single-phase PWM inverter

This paper describes the closed-loop control of a single-phase pulsewidth modulated (PWM) inverter using the generalized predictive control (GPC) algorithm. This approach determines the desired switching signals by minimizing a cost function that reduces the tracking error and the control signals. Experimental results have demonstrated that the prototype system performs well.

Zero-voltage-switching PWM inverter for high-frequency DC-AC power conversion

A zero-voltage-switching (ZVS) three-phase pulse width modulated (PWM) inverter which uses a parallel-resonant DC-link (PRDCL) circuit proposed by J. He and N. Mohan (1989) is examined. The PRDCL circuit is aimed at both providing zero-DC link voltage periods for PWM inverter switchings and imposing minimum DC bus voltage stress to PWM inverters. A simple circuit control scheme and the design formulas are offered. To confirm the circuit theoretical analyses and results, a 50 W ZVS single-phase PWM inverter experimental prototype using the proposed PRDCL circuit was fabricated and tested. The test results have proved the proposed circuit and concept. Power device selections and device stress evaluations are described. A detailed comparison of the proposed PRDCL ZVS inverter system with conventional voltage source PWM inverters is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Deadbeat controlled PWM inverter with parameter estimation using only voltage sensor

A technique based on deadbeat control theory is proposed to obtain a nearly sinusoidal PWM (pulsewidth-modulated) inverter output voltage using only a voltage sensor. The closed loop sampled-data feedback scheme inherently results in very fast response to load disturbance and nonlinear load, producing low total harmonic distortion. Parameter estimation of the plant provides a type of self-tuning of the proposed controller. A theoretical analysis, simulation, and experimental results are presented for a single-phase PWM inverter controlled by an Intel 8086 microprocessor.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Study on the compensation of source and load non-linearities in a PWM inverter

The authors propose a study on the analysis of the operation of a single-phase PWM (pulse width modulation) inverter structure-taking into account non-linearities such as an impedant supply or nonlinear loads (triacs, rectifiers). They analyze the control action in order to optimize the load voltage harmonic spectrum. Two principal considerations for the study are first, to avoid unduly increasing the switching frequency, and second, to optimize the power to weight ratio of the converter. Numerical simulations and experimental results are obtained to validate the proposed method.