Carrier-based PWM Research Articles

Hybrid Modulation Technique With DC-Bus Voltage Control for Multiphase NPC Converters

The article presents a novel carrier-based pulsewidth modulation technique for multiphase neutral point clamped converters. The technique is aimed to actively control the neutral point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole common mode voltage injection or on the sole multistep switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index, and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms.

Implementation of LDN to MLI and RSC-MLI configurations with a simple carrier-based modulation

The design of multilevel inverters (MLI) and reduced switch count (RSC) MLIs majorly depend on the requirements of desired output voltage levels, number of dc sources switching devices, and their ratings. With regard to these requirements ‘Level Doubling Network (LDN)’ configuration is introduced. LDN has the ability to double the output voltage levels of any MLI or RSC-MLI, preserving inverter modularity. However, the implementation of LDN to MLI or RSC-MLI is not unified and varies with switching operations. Thus, this work presents the implementation of LDN to popular MLI and RSC-MLI configurations and further presents a brief comparison on theswitch count, number of levels, and harmonic performance for both LDN and non-LDN cases. Further, a generalized carrier-based PWM scheme is presented to implement the LDN for any MLI and RSC-MLI configurations irrespective of voltage levels, dc-voltage ratios, and topological configuration. The performance of the inverter and the proposed modulation scheme are validated on MATLAB/Simulink environment.

Uniform carrier‐based PWM method for three‐phase three‐level three‐wire and four‐wire converter system with neutral‐point balancing

In this study, a simple carrier-based pulse-width modulation (CBPWM) method is proposed for a three-phase three-level neutral-point-clamped converter with neutral-point (NP) balancing, which can be applied to three-phase three-wire (TPTW) and three-phase four-wire (TPFW) converter systems simultaneously. First, the effect of each switching state for the NP potential in TPTW and TPFW systems is analysed in detail, and a newly NP control strategy by reconstructing the switching state and adjusting the corresponding duration time is deduced for all operation conditions, it only needs to add the offset voltage to the modulation reference voltage to guarantee the NP balance and is easy to implement. Then, under all operating conditions, the mathematical model of NP current is derived and analysed to evaluate the low-frequency voltage oscillation in the NP. Finally, the effectiveness and feasibility of the proposed CBPWM strategy are verified by the experimental results based on a 12 kVA laboratory prototype.

A Review of Modular Multilevel Converters for Stationary Applications

A modular multilevel converter (MMC) is an advanced voltage source converter applicable to a wide range of medium and high-voltage applications. It has competitive advantages such as quality output performance, high modularity, simple scalability, and low voltage and current rating demand for the power switches. Remarkable studies have been carried out regarding its topology, control, and operation. The main purpose of this review is to present the current state of the art of the MMC technology and to offer a better understanding of its operation and control for stationary applications. In this study, the MMC configuration is presented regarding its conventional and advanced submodule (SM) and overall topologies. The mathematical modeling, output voltage, and current control under different grid conditions, submodule balancing control, circulating current control, and modulation methods are discussed to provide the state of the MMC technology. The challenges linked to the MMC are associated with submodule balancing control, circulating current control, control complexity, and transient performance. Advanced nonlinear and predictable control strategies are expected to improve the MMC control and performance in comparison with conventional control methods. Finally, the power losses associated with the advanced wide bandgap (WBG) power devices (such as SiC, GaN) are explored by using different modulation schemes and switching frequencies. The results indicate that although the phase-shifted carrier-based pulse width modulation (PSC-PWM) has higher power losses, it outputs a better quality voltage with lower total harmonic distortion (THD) in comparison with phase-disposition pulse width modulation (PD-PWM) and sampled average modulation pulse width modulation (SAM-PWM). In addition, WBG switches such as silicon carbide (SiC) and gallium nitride (GaN) devices have lower power losses and higher efficiency, especially at high switching frequency in the MMC applications.

Vector-Splitting Method to Reduce Common-Mode Voltages in Two-Level Inverters for Grid Connection

This article proposes a new pulsewidth modulation (PWM) strategy to reduce common-mode voltages (CMVs) in grid-connected two-level inverters. Reduction of CMVs is an important issue in the field of distributed energy resources (DERs) because CMVs at a high switching frequency cause ground leakage currents that lead to safety issues in the applications of DERs. In the proposed PWM strategy, each reference vector is split into two vectors during the PWM period. The peak-to-peak magnitude of CMV is reduced by one-third as the split vectors are synthesized without using zero vectors. The influence of the dead-time and its compensation in the proposed method are also described. Our proposed method can be easily implemented with carrier-based PWM. Simulation and experimental results are presented to verify the performance of the proposed strategy.

A Novel Three-Phase Dual-Output Neutral-Point-Clamped Three-Level Inverter

A novel topology of a three-phase dual-output neutral-point-clamped three-level inverter (DO-NPC-TLI) is proposed. DO-NPC-TLI can achieve two groups of ac voltage outputs with adjustable frequency and amplitude. We describe the topology in detail. The proposed topology is based on a neutral-point-clamped three-level inverter (NPC-TLI). A total of eight switches and six clamping diodes are added to the NPC-TLI to form the new topology, and then analyze the working principle of the circuit. With the consideration of neutral point voltage balance, a modulation strategy combining the time-sharing modulation idea and virtual space vector pulsewidth modulation (VSVPWM) is proposed. In order to simplify the complicated calculation process of VSVPWM, a carrier-based PWM based on VSVPWM is proposed. All of the duty ratios are used to calculate the modulation waves of DO-NPC-TLI. The driving signals of switches are generated by comparing the modulation waves with a carrier. The modulation strategy mentioned above is verified by the experiment. The correctness of the experimental results illustrates the effectiveness of the modulation strategy and the feasibility of the proposed topology.

PWM Investigation of a Field-Oriented Controlled Five-Phase PMSM Under Two-Phase Open Faults

The decoupled model of Five-Phase Permanent Magnet Synchronous Motors (5Ph PMSMs) under a two-phase open circuit has been developed recently, yet the corresponding PWM has not been fully exploited. The Pulse Width Modulation (PWM), which is straightforward for a balanced system, can be problematic to fit a 5Ph PMSM under faulty conditions. During the open faults, the neutral voltage is drifting over the mid-point of DC bus, thus, the PWM typically designed for a balanced system always fails. In this article, an affine transformation is first presented to offset the drifting neutral effect, and only then PWMs can be effective. A quasi-sinusoidal PWM, a Space Vector PWM, and a min-max Carrier-based PWM are presented and compared experimentally. Each method has its own merits and demerits, and their effectiveness or rather the proposed affine transformation is validated by the experimental results.

Performance Evaluation of Cascaded and Reduced Switch Multilevel Inverter Using Modified Carrier Based PWM Technique

This paper proposes an improved harmonic distorted modified triangular carrier-based multicarrier pulse width modulation for generating the switching pulses of a multilevel inverter. This modified triangular wave consists of a triangular wave bearing a close resemblance to an ‘M’ shaped wave. The design of this carrier signal has been optimized to maintain a low level of total harmonic distortion (THD), while increasing the fundamental o/p voltage to ensure the effective DC voltage utilization. Moreover, this optimization reduces the switching losses and improve the efficiency of the power inverter. With the help of this carrier signal, High-frequency alternative phase opposition disposition pulse width modulation (APODPWM) is generated. This new control scheme has been applied to seven levels of conventional cascaded H-bridge with reduced switch multilevel inverter. The output is compared with conventional carrier-based APODPWM. The comparison is made in terms of THD, fundamental output voltages and inverter losses. To ensure quality performance, conventional carrier and modified carrier-based multicarrier PWM topologies are used for the Cascaded seven-level inverter with reduced switch seven-level inverter having a carrier frequency of 2 kHz and modulation index of 0.8-1.30. According to the simulation results, by using the proposed modulation scheme the THD and the switching loss were reduced by 9.64[%] and 4.2[%] respectively. Besides, the proposed modulation technique increases the fundamental output voltages. The total simulation process is done in MATLAB Simulink environment.
 GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 6(1), Dec 2019 P 12-19

Dual-Electric-Port Bidirectional Flux-Modulated Switched Reluctance Machine Drive With Multiple Charging Functions for Electric Vehicle Applications

This article proposes a simplified dual-electric-port drive for a flux-modulated switched reluctance machine (SRM) with flexible charging capability for electric vehicle applications. In the driving mode, the developed flux modulation control can be achieved by directly employing the modular three-leg converter compared to the conventional open-winding topology. The zero-sequence current excitation can be flexibly controlled between the dual port and the number of power switches is also significantly reduced. The corresponding carrier-based pulsewidth modulation method and harmonic current suppression strategy are both developed to improve the machine performance. In the standstill condition, flexible battery charging can be easily achieved by the drive circuit, including both the dc and ac charging, without using any additional passive components and power devices. Then, the current distribution control scheme and power factor correction strategy are further developed for the dc and ac charging, respectively. Compared with existing drive topologies, advanced flux-modulated control and flexible energy control both can be achieved with machine performance improvement and drive cost reduction. Experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategies.

Generalized PWM Method for Series-End Winding Motor Drive

Series-end winding motor drive (SWMD) is a novel motor drive with both high dc voltage utilization and zero-axis current control capability, which can replace the role of open-end winding motor drive in different types of ac machines. Three-phase SWMD has advantages of wide speed range, low-cost, high-density, and is easy for multiphase expansion. However, due to the complex vector selection process, the corresponding SVPWM method is computationally complex, especially for the multiphase application. Therefore, the main aim of this article is to propose a generalized carrier-based pulse width modulation method, which serves as the foundation for multiphase expansion of SWMD. By finding a general expression between the leg voltage and the phase voltage in the synchronous rotating framework, the proposed method can generate any desired phase voltage in a multiphase SWMD, whether it is sinusoidal or nonsinusoidal. The feasibility of the proposed drive and method has been verified by three kinds of electrical machines in experiments.

Analysis and Design of Modular Multilevel Converter (MMC) Based on Full Bridge Switching Modules (FBSM) for Harmonic Elimination using POD PWM Control Method

Modular Multilevel Converter (MMC) in HVDC for transmitting the power in longer distance because of high in transmission efficiency rate and cost-effective compared to AC system in many industries. The control of voltage and power is earlier and superior method is modular multilevel converter for HVDC transmission. The use of MMC has reduced the filter size and low frequency. Staircase, carrier-based PWM, space vector and selective harmonic elimination are the method using in MMC system control. Unbalanced networks are studied, and strategies are introduced such that in these circumstances MMC contributes to improving the grid efficiency. It involves the key applications in the transmission of high voltage direct current (HVDC) along with other applications of Medium Voltage (MV) and Low Voltage (LV). The MMC with POD-PWM is built using the MATLAB / Simulink method and concludes the advantages and improvements of converter modulation to reduce the voltage ripple and increase the voltage levels.

Band-Limited Three-Level Modulation for Balancing Capacitor Voltages in Neutral-Point-Clamped Converters

In this article, a band-limited three-level modulation scheme is proposed for a three-phase neutral-point-clamped (NPC) converter with an aim to balance the average capacitor voltages under all operating conditions. When conventional carrier-based pulsewidth modulation is applied, the amplitude of neutral point (NP)-voltage ripple tends to increase under linear imbalances, while the NP voltage can shift, leading to instability in the presence of nonlinear loads. A previously proposed three-level modulation scheme was able to eliminate all low-frequency capacitor voltage ripple by switching a phase between three levels in each switching period. This approach significantly increased the switching loss. The proposed modulation scheme limits the increase in switching loss by employing two operational bands, one fixed band applied to the capacitor voltages and another variable band applied to the phase currents. If the instantaneous capacitor voltages exceed the voltage band, then an appropriate phase-leg is switched in three levels to guarantee that the capacitor voltages cannot diverge further. If the instantaneous capacitor voltages reside within the voltage band, a variable current band is used to regulate switching in three voltage levels in order to obtain lower switching losses as compared to the conventional three-level modulation scheme. Therefore, the proposed modulation scheme presents a tradeoff between switching losses and capacitor voltage ripple. The experimental results are obtained under different loading conditions for validating the performance of the proposed modulation scheme.

A new approach to extract reference currents for multilevel shunt active filter in three phase systems

<span lang="EN-US">In this article, we present a new study of technique to extract reference currents for three-level shunt active filter controlling by fuzzy logic. The APFs is realized using three phase voltage and the carrier-based PWM strategy. A new technique for identifying reference currents will be developed. It is based on concordia method using multi-variable filter, and makes the total or selective extraction harmonic currents of references, and by consequence making their compensations, total or selective. The results of digital simulation in the Matlab-Simulink environment of a system of power to thyristor outputs on an inductive load show well the effectiveness of this new technique of extraction of the harmonics of reference.</span><p> </p>

A New Carrier-Based Pulse Width Modulation Scheme with Reduced Output Voltage Total Harmonic Distortion for Multi-Level Inverters

This paper proposes a novel Pulse Width Modulation (PWM) switching technique based on Optimized Carrier Peaks-PWM (OCP-PWM) which can be used to control both single phase and three-phase multilevel inverters. The proposed PWM scheme is designed according to multi-peak selection on carriers a way to define the optimum values for carrier peaks and then minimizing the output voltage Total Harmonic Distortion (), switching frequency (f s), and also switching losses, in comparing with the other carrier-based PWM methods. To examine the performance of the presented PWM scheme, a five-level converter has been employed including six power MOSFETs to produce five level in the output. In comparison with typical PWM switching methods for single-phase inverters, the presented PWM scheme produces low harmonic components in the output voltage. To investigate the reliability of the presented PWM scheme for single-phase five-level converters a 2.5kVA/400 V prototype is carried out by applying a TMS320F28335 digital signal processor.

A modified carrier-based PWM technique for minimization of leakage current in transformer less single-phase grid-tied PV system

This paper discusses the impact of leakage current and its dependency on common mode voltage in transformer less single-phase grid connected photovoltaic (PV) system. Further a new carrier-based PWM method is derived for H bridge single-phase grid-tied PV inverter to minimize leakage current. The proposed modulation strategy is compared with conventional techniques through simulation in MATLAB R2018a. The superiority of the proposed technique is validated in laboratory prototype of a 500 W single-phase grid-tied PV system. The hardware results validate the theoretical findings in appropriate.

Discontinuous Space Vector Modulation Schemes for Modular Multilevel Converters

In this article, a new, simple, and generalized discontinuous pulse width modulation (PWM)-based submodule capacitor voltage balancing approach is proposed and generated within the carrier-based PWM for modular multilevel converters (MMCs). In this scheme, different variants of zero-sequence voltage (ZSV) component is injected into the pulse width modulator so that each arm of the MMC is virtually clamped to positive or negative dc bus during a specific interval to achieve discontinuous modulation. A simple approach based on the location of the voltage vector mapping to a two-level space-vector diagram is presented to determine various ZSV components. The effectiveness of the proposed scheme with a voltage balancing algorithm is demonstrated through PLECS simulations and experimentally verified using a hardware-in-the-loop-based system. The performance of MMC with different ZSV injections is holistically evaluated to determine the best possible sequence over a wide range of modulation index.

A Simple Zero-Sequence Voltage Injection Method for Carrier-Based Pulsewidth Modulation of the Three-Level NPC Inverter

This article proposes a simple zero-sequence voltagei injection method for the carrier-based pulsewidth modulation (CBPWM) of the three-level neutral-point-clamped (NPC) inverter. The injected zero-sequence voltage signal is simply determined by comparing the three reference voltage signals and the dc-link capacitor voltages, respectively. Theoretical analyses show that the CBPWM with the proposed method can balance the dc-link capacitor voltages and eliminate/reduce the ripples of the dc-link capacitor voltages of the NPC inverter. Compared with other CBPWM schemes, the CBPWM with the proposed method has lower computation cost, does not need the information of the three-phase currents, and can reduce the switching loss of the NPC inverter. The CBPWM with the proposed zero-sequence voltage injection method and its superiority is validated experimentally in comparison with existing CBPWM schemes. The proposed method works in both inverter and rectifier modes, which is validated by simulation results.

Speed Control Strategy for Three Phase Induction Machine Fed Inverter Base on Carrier Base Pulse Width Modulation (CBPWM)

Abstract— An induction motors (IM) in many industries is used because it has several advantages, such as a very simple and strong construction, the price is relatively cheap, has good efficiency, power factor is quite good, and maintenance is easier. Besides the advantages of induction motors also have disadvantages, one disadvantage of induction motors is not being able to maintain a constant speed when there is a change in load. If the load changes, the speed of the induction motor will decrease. One method of regulating the speed of an induction motor presented in this study is the regulation of an induction motor using a carrier based PWM (CBPWM) inverter with the field oriented control (FOC) technique. The estimation of rotor rotation, torque and flux is done by carrier- based PWM technique which is given input voltage and stator current. To achieve the desired flux and torque, estimation is used as feedback in the control system. In this study, it will be simulated the induction motor speed regulation with a carrier base-based inverter using Matlab. The results obtained through simulation show the length of time to reach the reference speed for speeds of 1500 rpm and 1450 rpm is around 0.45 seconds. And THD average 2,675%.

Research on the Equivalent Virtual Space Vector Modulation Output of Diode Clamped N-level Converter under Multi-Modulation Carrier Modulation

Diode-clamped multi-level converters have DC-side capacitors in series, which will lead to the unbalance of DC-side capacitor voltage, the distortion of the output waveform, the increase of total harmonic distortion (THD), and even the damage of switching devices, which will make the system inoperable. The proposal of virtual space vector pulse-width modulation (VSVPWM) realizes the balanced control of the capacitor voltage, but when the output level of converter increases, the implementation of VSVPWM becomes very complicated, and the amount of calculation also increases greatly, thus hindering its application in the multi-level circuit. Compared with VSVPWM, the carrier-based pulse-width modulation (CBPWM) is simple to operate and easy to implement. If the equivalent relationship between CBPWM and VSVPWM can be found, the application of VSVPWM can be generalized to any level, and the advantages of VSVPWM can be fully utilized. This paper aims to study the inner relationship of VSVPWM and the multi-modulation carrier CBPWM (MCBPWM). After strict theoretical analysis, the equivalent relationship of VSVPWM and MCBPWM in the three-level and four-level and converter is realized by injecting the zero-sequence component into the modulation waves. Furthermore, the equivalent relationship between VSVPWM and MCBPWM is deduced to the N-level converter. Finally, the correctness of the relevant theoretical analysis is verified by the experiment.

A Novel 2$N$ + 1 Carrier-Based Pulse Width Modulation Scheme for Modular Multilevel Converters With Reduced Control Complexity

This article presents a simple pulse width modulator to achieve both N + 1 and 2N + 1 modulation in a modular multilevel converter. The proposed implementation needs a single triangular waveform to control a modular multilevel converter with a large number of submodules. Hence, the proposed approach significantly reduces the required triangular carrier count and solves the practical implementation issues associated with the carrier-based pulse width modulation schemes in the digital control platforms. The performance of the proposed approach is validated with detailed experimental studies. The results show that the proposed strategy effectively generates a multilevel voltage waveform at the load terminals. Furthermore, the performance of the proposed approach is compared with the traditional phase-shifted carrier pulse width modulation schemes. In addition, it can be easily applied to the n-level modular multilevel converter with any type of submodule configuration.