Phase-shifted Carrier Research Articles

Parallel two-step spatial carrier polarized phase-shifting common-path digital holography

A zero-order term causes bad effect on the phase reconstruction of off-axis holography, which can be solved by two-step carrier phase-shifting. Therefore, a common-path digital holography is proposed by using parallel two-step spatial carrier polarized phase-shifting in a 4f optical system for quantitative phase imaging. This holography is established based on a 4f optical system by inserting a 45° tilted cube polarized beamsplitter to split the horizontal and vertical polarization components in one beam. Via intentional polarization modulation, two off-axis holograms with π/2 phase-shift can be captured in one shot, so the subtraction between two holograms would cancel out the zero-order term. The phase distribution of a thin specimen can be retrieved with enhanced quality. There are two apertures at the input plane of the 4f optical system, one for object and the other for nothing, while only one polarized cube beamsplitter is inserted into a 4f optical system. Thus, this system is common-path with strong anti-noise ability and high stability, while it also has simple optical configuration and easy optical alignment. Several experimental results would be presented to demonstrate the validity of the proposed holography.

Topology, Analysis, and Modulation Strategy of a Fully Controlled Modular Reconfigurable DC Battery Pack With Interconnected Output Ports for Electric Vehicles

Modular battery-integrated converters or so-called dynamically reconfigurable battery packs are expanding into emerging applications. Although they offer many degrees of freedom (DoF), the state of the art focuses on single-output systems and neglects the potential of such systems to generate multiple outputs with minimum added components. This paper investigates the feasibility of a multiport system for various independent loads. The proposed techniques can achieve higher functionality and reduce power conversion stages. Interleaved ports with shared modules can also increase modules’ utilization, avoid redundant power electronics, and reach a better cost-weight trade-off. However, using conventional modulation techniques in particular phase-shifted carrier modulation can be challenging with shared modules among multiple ports, and different control objectives can adversely impact the overall performance. Therefore, this paper analyzes the inherent dynamics of modular batteries and proposes a strategy to decouple the control of multiple ports to simplify power electronics’ complexity and size while improving performance. In addition to the distinct advantages of modular reconfigurable batteries, the proposed concept would not require additional active switches, can operate with a wide range of output voltages, can reduce the size of the filters and transformers, and is extendable to larger setups. Simulation and experiments verify the developed concept.

High-Frequency Current Harmonic Analysis and Suppression in Dual Three-Phase PMSMs With Advanced Carrier Phase-Shift PWM

High-Frequency Current Harmonic Analysis and Suppression in Dual Three-Phase PMSMs With Advanced Carrier Phase-Shift PWM

Improved carrier phase shift modulation and voltage equalization control strategy in modular multilevel converter

Improved carrier phase shift modulation and voltage equalization control strategy in modular multilevel converter

Circuit simulation-based comparison of power electronics devices in a five-level converter for UAV applications

<p>In this paper, the performance of a 5-level cascaded H-bridge inverter in unmanned aerial vehicle (UAV) applications is analized to identify, at the converter design stage, the better device choice depending on different UAV operation scenarios. Considering that regardless of the specific application there are some typical operations, such as take-off, climb, land, cruise, and potential recurring climbs and descents, the results can support the choice by considering the typical working conditions of the specific application where the UAV would be used. The results have been obtained by simulating the H-bridge inverter considering the circuit models of insulated-gate bipolar transistors (IGBTs), GaN high-electron-mobility transistors (HEMTs), and Si and SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) provided by manufacturers. The study has highlighted that the choice of the device depends on the UAV usage, switching frequency, and load conditions. More specifically, considering the typical devices and systems costs in the case of a selective harmonic elimination procedure operating at the fundamental switching frequency, the Si devices should be used. Moreover, the preference for using IGBTs or Si MOSFETs depends on the typical working conditions of the UAV application. In the case of phase-shift carrier modulation technique, at 4 kHz the MOSFET is the best device and the choice between Si and SiC devices depends on the UAV application's main operation scenarios. At 20 kHz the SiC MOSFET is the best device, while at higher frequencies the GaN HEMT cost should be faced to take advantage of its best performance.</p>

Velocity Estimation Using Time-Differenced Carrier Phase and Doppler Shift with Different Grades of Devices: From Smartphones to Professional Receivers

Velocity estimation has a key role in several applications; for instance, velocity estimation in navigation or in mobile mapping systems and GNSSs is currently a common way to achieve reliable and accurate velocity. Two approaches are mainly used to obtain velocity based on GNSS measurements, i.e., Doppler observations and carrier phases differenced in time (that is, TDCP). In a benign environment, Doppler-based velocity can be estimated accurately to within a few cm/s, while TDCP-based velocity can be estimated accurately to within a few mm/s. On the other hand, the TDCP technique is more prone to availability shortage and the presence of blunders. In this work, the two mentioned approaches are tested, using three devices of different grades: a high-grade geodetic receiver, a high-sensitivity receiver, and a GNSS chip mounted on a smartphone. The measurements of geodetic receivers are inherently cleaner, providing an accurate solution, while the remaining two receivers provide worse results. The case of smartphone GNSS chips can be particularly critical owing to the equipped antenna, which makes the measurements noisy and largely affected by blunders. The GNSSs are considered separately in order to assess the performance of the single systems. The analysis carried out in this research confirms the previous considerations about receiver grades and processing techniques. Additionally, the obtained results highlight the necessity of adopting a diagnostic approach to the measurements, such as RAIM-FDE, especially for low-grade receivers.

Variable Carrier Phase-Shift Method for Integrated Contactless Field Excitation System of Electrically Excited Synchronous Motors

Variable Carrier Phase-Shift Method for Integrated Contactless Field Excitation System of Electrically Excited Synchronous Motors

Carrier Phase Shift Method of SPWM for Concurrent Wired and Wireless Power Transfer Systems

This paper presents an approach for concurrent power transfer to wired and wireless systems using just a single inverter. The approach utilizes a novel carrier phase-shift (CPS) method that independently controls the inverter output voltages at the fundamental and switching frequencies. This proposed method can be a cost-effective solution to wireless power transfer (WPT) systems used in contactless slip rings (CSR), which transfer power to auxiliary loads such as sensors, radars, and IoT devices. There are two separate converters in conventional CSR systems: one is for the motor drive, and the other is for the WPT system. It is proposed that the switching harmonics of the motor drive can also be utilized to excite the WPT system while the low-frequency component can still be used to drive the motor. In order to control these independently, the CPS method is introduced. The proposed method is investigated analytically for sinusoidal-PWM (SPWM). Then, an experimental setup consisting of a 3-phase 3-wire GaN-based inverter and a 3-phase motor is built. Experimental results show that the WPT and motor systems are operated concurrently, and their powers are controlled independently by the proposed method.

A Novel Carrier Based Precharging Technique for Single-Phase Odd-Level Flying Capacitor Multilevel Converters (FCMCs)

Flying Capacitor Multilevel Converter(FCMC) needs all its flying-capacitors charged to the appropriate voltage levels during stat-up. This paper presents a novel carrier based precharging technique for single-phase odd-level FCMCs. A new set of modified phase-shifted carrier signals are derived for precharging. These carrier signals when compared to zero modulation signal, ensure the synthesisation of sufficient number of zero output voltage switching modes (zero-modes) of the converter. The proposed precharging technique is detailed using a five-level FCMC and then generalized to higher odd-level FCMCs. State-space averaging models are derived to validate the proposed technique mathematically. Extensive simulation and experimental results are provided to validate the functionality of the proposed technique.

Fault detection and localization method for modular multilevel converters in offshore DC wind turbines

The offshore DC wind turbine, consisting of direct-drive permanent magnet synchronous generator (PMSG) and modular multilevel converter (MMC), has become a promising candidate for the large-capacity wind energy conversion system. Submodule (SM) failure detection and localization are crucial for reliable operation of the MMC. However, existing techniques mainly focus on the rated operation condition, which may not be suitable for the MMC in wind turbine due to varying wind speed. Moreover, proper injection of second-order harmonic circulating current (SHCC) is desirable to reduce capacitor voltage ripple and power loss, which may also affect the accuracy of fault detection. This paper proposes a fault-tolerant strategy immune to variable operation conditions, as well as SHCC injection, for the MMC with phase-shifted carrier modulation. Firstly, the inherent switching harmonics of circulating current with SM failure are analyzed, based on which the fault detection method is developed. Then, the localization approach is presented by measuring the difference of SM capacitor voltages. Compared with existing techniques, the proposed strategy requires neither estimator nor additional sensor, which is robust, simple, and economical. Finally, both simulation and experimental results demonstrate the effectiveness of the proposed method, which is not influenced by SHCC and varying wind speed.

A New Model-Based Dead-Time Compensation Strategy for Cascaded H-Bridge Converters

Cascaded H-bridge multilevel converter can generate high-voltage and high-power output with low harmonics. However, the error voltage caused by dead time effect will distort the output waveform, which depends on the phase current polarity. Since the normal dead time compensation method based on current sampling is often disturbed by sampling error and transmission delay, a novel current prediction method is proposed for dead time compensation of cascaded H-bridge converter in this paper. This method, based on phase shift carrier pulse width modulation, reconstructs the switch pattern, and combined with the system model, can easily predict the phase currents. Excellent compensation performance can be obtained by dead time compensation according to the predicted current. Simulation and experiments are built to validate the excellent performance of the proposed method applied to cascaded H-bridge converters.

Discrete-Time Sliding Mode Current Control for a Seven-Level Cascade H-Bridge Converter

This paper deals with the implementation and performance analysis of discrete-time sliding mode (DTSM) current control applied to a seven-level cascade H-bridge converter to track three-phase reference currents for a reactive load. The converter output voltages are synthesized using a modulation scheme based on phase-shifted carrier modulation. Simulation and experimental tests have been added to demonstrate the performance of the proposed controller. At the same time, the effectiveness of the DTSM is verified under transient and steady-state conditions, respectively, by measuring the total harmonic distortion and the mean square error.

A Method Based on Phase-shifting Carrier for Reducing DC-link Current Harmonics in Dual Three-phase PMSM Drive under Open-phase Conditions

The All-Electric of modern military equipment has become an important trend, in the field of aircraft the traditional servo control focus on the exact control of the motor. With the development of power electronics technology, a high-power motor has expanded into a multiphase kind which cast off the limitation of traditional three-phase motors. The multiphase motor has more control resources and fault-tolerant control ability under the fault condition, which has practical meaning for high safety and high-reliability applications in an airborne environment. The multiphase motor can be controlled by a series of phase-shift carriers, which can reduce DC current ripple more effectively than the traditional carrier-based pulse width modulation, but it needs to find the optimal phase shift angle. In this paper, the optimal carrier phase shift angle is analyzed mathematically which can be used for both under health and single open-phase fault of a dual three-phase motor, and the simulation result illustrates that the carrier phase shift method used in this paper has the DC current ripple optimization effect.

Common DC-Link Capacitor Harmonic Current Minimization for Cascaded Converters by Optimized Phase-Shift Modulation

This paper investigates the influence of a constant carrier phase shift on the DC-link capacitor harmonic current of cascaded converters used in fuel-cell and mild-hybrid electric vehicles. In these applications, a DC-DC converter can be adopted between the battery and the motor drive inverter in a cascaded structure, where the two converters share the same DC-link. Since the DC-link capacitor of such a system represents a critical component, the optimization of the converter operation to limit the current stress and extend the lifetime of the capacitor is an primary objective. This paper proposes the use of a carrier phase shift between the modulations of the two converters in order to minimize the harmonic current of the DC-link capacitor. By harmonic analysis, an optimal carrier phase shift can be derived depending on the converter configuration. Analytical results are presented and validated by hardware-in-the-loop experiments. The findings show that the pulse width modulation carrier phase shift between the interleaved boost converter and the voltage source motor drive inverter has a significant influence on the DC-link capacitor current and thus on its lifetime. A case study with two-cell and three-cell interleaved boost converters shows a possible DC-link capacitor lifetime extension of up to 390%.

A Robust Capacitor Voltage Balancing Method for CPS-PWM-Based Modular Multilevel Converters Accommodating Wide Power Range

Capacitor voltage balancing is one of the most important issues for the safe, reliable, and economical operation of the modular multilevel converter (MMC). This article proposes a modified individual capacitor voltage balancing method for MMCs with phase-shifted carrier pulsewidth modulation (PWM) (CPS-PWM) to solve the problem of the poor dynamic performance that the conventional individual voltage balancing methods suffer at low output power. In the proposed method, the information of arm current is incorporated into the balancing algorithm to cancel out the coupling effect of the output power on balancing control. Compared with conventional balancing methods, the proposed method shows better robustness against varying output power and maintains a good dynamic performance in a wider power range. The complete modeling process and parameter design are presented and considered for system stability. The effectiveness of the proposed method is verified with both MATLAB/Simulink simulation and experimental results.

Brain Tumor Detection from MRI Images Using MATLAB Code

Cascaded H-bridge topology has been used in grid tied converters for battery energy storage system due to its modular structure. To fully utilize the converter’s modularity, this paper proposes a hierarchical distributed control architecture that consists of primary control, secondary control and battery state of charge (SOC) balancing control. Primary control ensures accurate current tracking while a distributed secondary control based on consensus algorithm is presented to regulate power sharing among modules and is proved to be stable theoretically. A distributed SOC balancing control is further introduced to improve energy efficiency of battery energy storage system. Finally, the hierarchical distributed control strategy is implemented using hardware controllers and a software platform. Besides, a carrier phase shift control is also implemented to achieve multilevel output voltage and harmonic reduction. The experimental results demonstrate the performance of the proposed control scheme effectively. Keywords—: Battery SOC balancing, cascaded H-bridge, consensus algorithm, distributed control.

A New Carrier Phase-Shift Modulation Based on Switching the Displacement Angle

In this paper, a new carrier phase-shift (CPS) modulation method based on switching the displacement angle (SDA) is proposed to compromise the harmonic content of the output voltage and the circulating current. It can be used in medium- and low-voltage applications where the AC-side voltage and DC-side current of the modular multilevel converter (MMC) are required to have low harmonic content simultaneously. In this proposed SDA-based CPS modulation, the carrier displacement angle of the MMC with N submodules in each arm is periodically switched between the values of 0 and π/N degrees, so that the harmonic content of the output voltage and the harmonic content of the circulating current will not be in extreme conditions, which occurs when the displacement angle is set to 0 or π/N degrees. The effectiveness of this method has been verified by simulation and experimental results.

Improved CPS-PWM Approach for Over-Modulation Operations of Hybrid Modular Multilevel Converter

The over-modulation capability of the hybrid modular multilevel converter (MMC), mixed by half-bridge and full-bridge submodules (SMs), has acquired widespread attention recently, which can significantly increase the design freedom of the hybrid MMC. When the hybrid MMC is applied in the medium-voltage occasions, an improved carrier phase shift pulsewidth modulation (CPS-PWM) approach is put forward in this article for its over-modulation operation under the nominal and variable dc conditions. It is featured with high flexibility, adjustability, and simple implementation. A new standard voltage is introduced to normalize the modulation wave, by which there is always a sufficient margin between the peaks of the normalized modulation wave and carrier waves under any modulation indexes. Also, it can perform well when the nominal dc voltage of the hybrid MMC is not the integer multiple of SM voltage. Moreover, the carrier wave arrangements are decoupled with the number of SMs, dc voltage, and ac voltage, so the variable dc operation of the hybrid MMC can be achieved without rearranging the carrier waves. Finally, the simulations and experiments are carried out to confirm the effectiveness of the proposed CPS-PWM approach for over-modulation operations under the steady-state and variable dc conditions.

A Three-Level Output Modulation Strategy for Conventional 3 × N Direct Matrix Converters

To utilize the full potential of the direct matrix converter (DMC) and improve the output waveform quality, a three-level output strategy for conventional 3N (N3) DMCs is presented, where three-level output voltages are achieved without any changes in the topology. In this developed strategy, the DMC is treated as a two-stage converter that consists of a fictitious rectifier and a neutral-point clamped (NPC) three-level inverter. By applying a phase-shifted carrier modulation strategy to the rectifier and a modified carrier-based double-signal pulse width modulation strategy to the NPC inverter, sinusoidal input and output, reduced switching losses, and controllable input power factors are achieved in conventional 3N DMCs. The developed three-level output strategy improves output waveform quality while sacrificing input performance to some extent. Finally, the effectiveness of the developed strategy is verified by both simulations and experimental results.

Precise Mathematical Model of PSCM Class-D Amplifiers

A mathematical analysis of four-level (three-phase) phase-shifted carrier modulation class-D amplifiers with analog feedback is proposed. The nonlinear difference equations are extracted and solved using the perturbation theorem. In this way, a closed-form function describes the low-frequency part of the output for an arbitrary input signal. The results are generalized for an arbitrary number of levels by analogy, well matched with the previous model of two-, three-, and the proposed four-level ones. The analytical results confirm that, apart from switching frequency, the multilevel class-D amplifiers converge to linear amplifiers as the number of output levels increases. An analytical equation expresses the harmonic distortion of practically interesting five-level amplifiers with bridge-tied load. The model is verified by system-level simulations and circuit-level implementation. In this way, a prototype fully differential five-level circuit is implemented on the printed circuit board to confirm the model.