Phase Shifted Carrier PWM Research Articles

Design of the power supply system for the plasma current modulation on J-TEXT tokamak

In order to further study the influence of current modulation parameters on suppressing tearing instability, the plasma current should be modulated in a wider range. So a modification scheme is designed to improve the performance of ohmic heating power supply system on J-TEXT tokamak. A multilevel cascade circuit with carrier phase-shifted PWM technique has been proposed. Coupled inductors are connected in the form of cyclic symmetry to restrain the circulating current caused by multiple paralleled branches. The simulation proves this proposed current modulation power supply system matches output requirement and achieves good current sharing effect. Finally, a prototype is designed, and the experiment results can verify the correctness of the simulation model well.

Simplified model and submodule capacitor voltage balancing of single‐phase AC/AC modular multilevel converter for railway traction purpose

A single-phase AC/AC modular multilevel converter (MMC) can interact directly with 25 kV railway grid without a bulky 50 Hz step-down transformer. This brings in great savings in size and cost. Submodule (SM) voltage balancing of this kind of MMCs remains a major technique issue. This study proposes a voltage-balancing solution for this scenario which consists of intra- and inter-arm voltage balancing methods. The former combines the advantages of carrier phase-shifted pulse-width modulation (PWM) and phase disposition PWM based voltage-balancing methods. It only uses two proportional regulators, easing the control system significantly. The latter is based on a power channel between the upper and lower arms. It avoids interferences with input/output voltage and current, and gets rid of common mode current component which would be injected into the grid with conventional inter-arm balancing methods. By assuming perfect voltage-balancing, a simplified mathematical model is also developed, which reveals more clearly the power conversion relationship. Simulations and experiments verify the proposed voltage-balancing methods and the mathematical model.

An Improved Phase-Shifted Carrier Pulse Width Modulation Based on the Artificial Bee Colony Algorithm for Cascaded H-Bridge Multilevel Inverters

Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.

New Scheme of Phase-Shifted Carrier PWM for Modular Multilevel Converter With Redundancy Submodules

This letter proposes a new scheme of phase-shifted carrier pulse-width modulation for the modular multilevel converter with redundancy submodules (SMs). The proposed scheme can offer a smooth transition for the redundancy SM from the standby state to the startup operation when normally operating down. The operational feasibility of the proposed scheme was first verified through simulations with PSCAD/EMTDC, and then hardware-in-the-loop system tests with the real-time digital simulator.

Modulation, Harmonic Analysis, and Balancing Control for a New Modular Multilevel Converter

The modular multilevel converter (MMC) has been receiving increased attentions in recent years. The new modular multilevel converter is a derivative topology from the traditional MMC in which the number of sub-modules (SMs) necessitated by each phase can be reduced by one. This paper presents a phase-shifted carrier pulse-width modulation (PSC-PWM) for the new MMC with an optimal phase-shifted angle to suppress the harmonics of the output voltage. Further, the harmonic features when the capacitor voltage of the middle SM is selected as two different values are also investigated. Moreover, in order to avoid introducing an unnecessary dc offset current at the ac terminals of the new MMC, a novel capacitor voltage balancing scheme is proposed by adjusting the amplitude of the reference signals rather than the offset. Finally, the validity and effectiveness of the proposed modulation and balancing schemes have been verified by experimental results based on a three-phase prototype of the new MMC.

The Harmonic Analysis of RMP Coil Power Supply in EAST TOKAMAK

In EAST TOKAMAK, resonant magnetic perturbation (RMP) coils, which are powered by RMP coil power supply (PS), are set to research edge localized mode, resistive wall mode and error field correction. In order to meet the requirements of fast response and output voltage ripple proposed by physical experimenters, the structure of multiple modules using cascaded carrier phase-shifted PWM H-bridges is adopted, which enhances the equal switch-frequency of the PS and improves the quality of output voltage. In the paper, theoretical calculation applying Fourier analysis is given to analyze its harmonics. Both simulation results on Matlab and test results of output voltage ripple show that the RMP coil PS can meet the requirements.

A Novel Modulation Scheme and Voltage Balancing Algorithm for Modular Multilevel Converter

The control complexity of modular multilevel converter (MMC) increases with the number of submodules per arm. In particular, the implementation of a pulsewidth modulation (PWM) scheme and a voltage balancing approach for MMC is a major challenge. This paper proposes a generalized low-cost less computational decoupled sampled average PWM scheme for MMC. In this approach, the reference output voltage is generated by averaging the two nearest voltage levels from the top and bottom arms in each sampling interval. In addition, a simplified voltage balancing approach is proposed for MMC. The proposed approach does not require a sorting technique to select the submodules. Instead, the relative comparison logic is presented. The effectiveness of the proposed modulation scheme and voltage balancing approach is evaluated on a single-phase MMC system with three-level flying capacitor submodules. The proposed approach is extended to a three-phase system, which results in dynamic balancing of the zero-sequence voltage. Hence, the zero-sequence current is minimized. The performance of the proposed three-phase approach is compared with that of the conventional phase-shifted carrier PWM scheme. The simulation and experimental studies show successful voltage balancing among submodule capacitor voltage, low harmonic distortion, and less ripple in output current.

基于CPS-SPWM调制的级联H桥有源电力滤波器研究

本文介绍了载波相移脉宽调制适用于大功率场合的理论依据，讨论了级联H桥多电平变流器较其他形式变流器的优势，采取了载波相移脉宽调制在级联H桥变流器的实现方法，采用基于CPS-SPWM调制级联型多电平变流器的并联电力有源滤波器的拓扑结构，探讨了三相瞬时无功功率理论在检测层面的应用，并对其进行仿真和分析。仿真结果表明，在较低的开关频率下，基于CPS-SPWM调制级联H桥并联型APF可以对负载谐波和无功功率进行准确、有效的补偿。 The theory basis that fits for large capacity power electronic equipment of CPS-SPWM is introduced. The advantages over other modulation strategies of CPS-SPWM are discussed. The implementation method of carrier phase-shift pulse-width modulation in the cascade H-bridge converter is adopted. The topology based on shunt active power filter of CPS-SPWM modulation cascade multi-level converter is used. The three-phase instantaneous reactive power theory in the detection level is discussed and its simulation and analysis is presented. The results of simulation and experiment indicate that the shunt active power filter with CPS-SPWM based cascade H-bridge multilevel converters can compensate load harmonics and passive power precisely and efficiently at lower switch frequency.

A Low-THD Class-D Audio Amplifier With Dual-Level Dual-Phase Carrier Pulsewidth Modulation

In this paper, a class-D audio amplifier which combines the advantages of the phase-shifted carrier pulsewidth modulation (PWM) and the multiple-level carrier PWM is proposed with a dual-level dual-phase carrier (DLDPC) PWM. The proposed closed-loop amplifier includes a second-order integrator and a DLDPC triangular wave generator. Two sets of 180° out-of-phase triangular waves are used as carriers, and each set has its respective offset voltage level with nonoverlapping amplitude. By performing the double Fourier analysis, it can be found that the linearity can be enhanced and the distortion can be reduced with the proposed modulation. Experimental results show that the proposed fully differential DLDPC PWM class-D audio amplifier features a total harmonic distortion lower than 0.01% with an output voltage swing of $\pm$ 5 V.

Phase-Shifted Carrier Pulse Width Modulation Based on Particle Swarm Optimization for Cascaded H-bridge Multilevel Inverters with Unequal DC Voltages

High-voltage cascaded H-bridge multilevel (CHBML) inverters usually include many isolated dc voltage sources. Some dc source faults result in a drop in the dc voltage, thereby leading to unequal cell dc voltages. On the other hand, the differences in cell dc source parameters result in unequal dc voltages too. At present, riding through the faults of dc sources and operating under the condition of unequal dc voltages are required to improve the reliability of CHBML inverters. Unfortunately, the conventional phase-shifted carrier pulse width modulation (PSCPWM), which is widely used for CHBML inverters, cannot eliminate low-frequency sideband harmonics when cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM based on the particle swarm optimization algorithm. This modulation technique eliminates low-frequency sideband harmonics by calculating and regulating the carrier phases according to different cell dc voltages. The proposed PSCPWM enhances the reliability of the CHBML inverter and extends the range of its application. Simulation and experimental results obtained from the prototype of the CHBML inverter verify the theoretical analysis and the achievements made in this paper.

Application of Cascaded Multilevel Inverter for High Voltage Grid-Connected PV System

The cascaded multilevel inverter may be the best topology to satisfy continuously increasing capacity and scale of grid-connected photovoltaic generation system due to its modularized circuit layout and sufficiently high operating voltage without devices in series. The operating principle of the cascaded multilevel inverter is presented. The control strategy of carrier phase shift PWM is proposed and discussed in detail. A grid-connected photovoltaic (PV) generation system based on a seven level cascaded inverter is provided. Simulation model of a seven level cascaded inverter with phase shifted PWM is built in Simulink environment and simulation results verify that the cascaded multilevel inverter can output high level voltage without devices in series, reduce harmonics, and output high quality waveforms.

New Hexagonal Three-Phase Voltage-Source Converter Topology for High-Power Applications

This paper presents a voltage-source converter (VSC) topology for high-power applications. This topology combines three three-phase converters with isolated dc buses. The proposed topology can be implemented by using two-level or multilevel three-phase converters. In this paper, three three-level neutral-point-clamped (3L-NPC) converters have been combined. Two zero-sequence blocking transformers (ZSBTs) are used to interconnect the three converters. In order to validate the good performance of the proposed VSC topology, two modulation techniques are implemented: phase-shifted carrier pulsewidth modulation (PSCPWM) and selective harmonic elimination (SHE) modulation. The VSC topology has been simulated in the simulation tool Saber, and the results have been validated experimentally in a test bench of 60 kVA.

Multilevel Inverter Scheme for Performance Improvement of Pole Phase Modulated Multiphase Induction Motor Drive

Pole-phase modulation (PPM) is one of the effective speed and torque control techniques for multiphase induction motor (MIM) drives. Performance of the drive in low-pole high-speed mode for steady run is good even with two-level voltage excitation due to the inherent advantages of high phase number. The drive operation under high-pole high-torque starting mode suffers degradation in performance due to reduction in phase number in a way to increase number of poles. Extending conventional multilevel converter topologies for performance improvement of MIMs increases the device count and control complexity considerably. In this paper, a simple technique to generate multilevel voltage across the phase of a pole-phase-modulated induction motor (PPM IM), for improving the performance of the drive under high-pole operation is presented. The technique requires least changes in the control scheme and no additional switches for the power circuit. Exploiting the advantages of equal voltage profile coils (EVPCs) for carrier phase-shifted PWM control is the main focus of this paper. In addition, generalization of PPM is revisited in this paper to add a small constraint on the pole ratio to avoid unequal pole width for some pole-phase combinations. The effectiveness of the proposed scheme is shown through simulation with finite-element method (FEM) model of nine-phase squirrel cage induction motor and two-level nine-phase inverter cosimulated in Ansys Maxwell two-dimensional (2-D) and Simplorer environment. Experimental validation is also done on 5 hp nine-phase two-level induction motor drive controlled using Spartan6 FPGA board.

Carrier Phase-Shift PWM to Reduce Common-Mode Voltage for Three-Level T-Type NPC Inverters

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

Novel carrier‐based hybrid pulse width modulation method for cascaded capacitor‐clamp multilevel inverter

This study presents a new carrier-based hybrid pulse width modulation (PWM) Method for the cascaded capacitor-clamp multilevel inverter (CCCMLI), which combines the benefits of a new alternative level-shifted carrier PWM and a phase-shifted carrier PWM. For modulating the CCCMLI, the phase disposition sub-harmonic PWM was first proposed, but does not show good performances in an even load sharing between inverter cells connected in series, flying-capacitor voltage balancing and output waveform quality. On the other hand, a proposed PWM method enables to achieve a balanced load sharing between cascaded cells even at low amplitude modulation indices as well as the excellent voltage balancing control of the flying-capacitors with a much smaller voltage ripple and the good harmonic characteristics in output waveforms. The proposed modulation is verified through both simulation and field-programmable gate array (FPGA) based experimental results.

Circulating Harmonic Current Elimination of a CPS-PWM-Based Modular Multilevel Converter With a Plug-In Repetitive Controller

An improved circulating current control method by applying a digital plug-in repetitive controller is discussed for harmonic elimination of a carrier-phase-shift pulse-width-modulation (CPS-PWM)-based modular multilevel converter (MMC) in this paper. The performance of the controller is analyzed in detail based on an improved circulating current control model with the consideration of the submodule voltage disturbance. It is shown that the proposed control method has the merits of simplicity, versatility, and better performance of circulating harmonic current elimination than the traditional proportional integral controller. The stability analysis of the proposed method are also discussed in the paper as well as the design principles. Finally, the experimental results including the steady-state performance and the transient response are given, which validates the feasibility and excellent performance of the proposed control scheme.

Reduced DC voltage source flying capacitor multicell multilevel inverter: analysis and implementation

Voltage source multicell multilevel converters (VSMMCs) have been extensively exploited in medium-voltage high-power fed industrial applications. One of the typical breeds of the VSMMCs is flying-capacitor multicell converter (FCMC). This study presents an improved configuration for FCMCs, accompanied by its analysis, modelling and implementation. The main advantage of the proposed converter, in comparison with the conventional one, is that the number and voltage rating of the required dc voltage sources are halved in the improved topology which results in reducing the cost, size, installation area and weight of the FCMCs effectively. This amelioration is attained by adding four power switches to the conventional topology of an FCMC without making any amendments to the number and voltage rating of high-frequency power-switches and flying capacitors (FCs). The proposed switching and control methodology for the adopted FCMC is based on the phase-shifted carrier pulse width modulation technique with applying some amendments; therefore the natural balancing phenomenon of the FC voltages, one of the critical advantages of the FCMCs, is preserved in the proposed VSMMC. Experimental measurements taken from the 3-cell-four-level and 4-cell-five-level laboratory prototype systems of the proposed converter are presented in order to validate and corroborate the effectiveness and advantages of the proposed topology, its switching and suggested control strategy. Furthermore, experimental studies are accomplished on an 8-cell-nine-level prototype system of the proposed FCMC to peruse its feasibility and viability for higher number of cells and voltage levels. In addition, comparison of the proposed converter with the other types of multilevel converters is carried out to underline the advantages of the proposed structure profoundly.

A New Selective Loop Bias Mapping Phase Disposition PWM With Dynamic Voltage Balance Capability for Modular Multilevel Converter

This paper presents an improved phase disposition pulsewidth modulation (PWM) (PDPWM) for the modular multilevel converter (MMC) which is based on the selective loop bias mapping (SLBM) method. Its main idea is to change the bias of the PDPWM carrier wave cycling according to the balance situation of the system. This new modulation method can operate at symmetric condition to generate an output voltage with as many as 2N + 1 levels, and by SLBM, the voltages of the upper/lower arm capacitors can be well balanced. Compared to carrier phase-shifted PWM, this method is more easily to be realized and has much stronger dynamic regulation ability. Specially, this method has no issues of sorting, which makes it suitable for MMC with a large number of submodules in one leg. With simulation and experiments, the validity of the proposed method has been shown.

Triphase Symmetrical Cascaded Multilevel Inverter (5L) for PV Systems Controlled by Various Multicarrier PWM Strategies

This paper presents a comparative study in the Matlab/Simulink environment among six multicarrier pulse width modulation strategies (MCPWM), of triphase symmetrical cascaded H-bridge multilevel inverter (five level). We will consider the Phase Disposition PWM, the Phase Opposition Disposition PWM, the Alternate Phase Opposition Disposition PWM, the Carrier Overlapping PWM, the Variable frequency PWM and the Phase Shifted Carrier PWM. Each type of these MCSPWM controls the same inverter. The symmetric voltage sources, supplying inverters cells are simulated using a DC voltage representing photovoltaic arrays (PV). Comparison of these MCPWMs is based on the spectral quality and magnitude of the output compound and simple voltages. The different strategies are carried out in Matlab/Simulink software environment with simulation results

Analysis and Operation of Modular Multilevel Converters With Phase-Shifted Carrier PWM

Many publications have been presented on the modulation and control of the modular multilevel converter, some of which are based on phase-shifted carrier modulation. This paper presents an analysis of how the switching frequency affects the capacitor voltages, circulating currents, and alternating voltages using phase-shifted carrier modulation. It is found that switching frequencies that are integer multiples of the fundamental frequency should be avoided as they can cause the capacitor voltages to diverge. Suitable switching frequencies are derived for which the arm and line quantities will be periodic with symmetric operating conditions in the upper and lower arms. Thus, the practical outcome of this paper is a detailed description of how the switching frequency should be chosen in order to achieve advantageous operating conditions. The theoretical results from the analysis are validated by both simulations and experimental results.