Output Phase Voltage Research Articles

Modeling of Six Switch Single Phase to Three Phase Matrix Converters

The Matrix Converter (MC) chosen in this work is capable of providing a variable three phase output voltage from a fixed single phase input using single stage phase conversion principle. This MC effectively provides three phase power to three phase variable speed drives. The implementation of MC requires solid state bidirectional switches. A new pulse generation scheme is developed to produce three phase voltage at the output. The performance of the Matrix Converter is evaluated using MATLAB/SIMULINK for different frequencies. Simulation results for three phase resistive and inductive loads are presented. The simulation results validate the developed conversion strategy.

Common-Mode Voltage Elimination in a Three-to-Five-Phase Dual Matrix Converter Feeding a Five-Phase Open-End Drive Using Space-Vector Modulation Technique

This paper proposes a space-vector modulation (SVM) algorithm for a five-phase open-end winding motor drive system, fed by a dual nonsquare matrix converter (MC). The input to each of the MCs (MC-1 and MC-2) is a three-phase utility grid, and the output is a five-phase with variable voltage, variable frequency capability. The major contribution of this paper is the elimination of the detrimental common-mode voltage (CMV) that appears across the motor winding. In addition, the proposed SVM allows for a unity power factor at the input side, while boosting the output phase voltage by up to 150% of input. This paper presents a comprehensive analysis, to obtain the expression for the SVM modulating signals that are used to generate the switching pulses for the MC. To verify the idea, a modular, reconfigurable 5-kW MC prototype, feeding a five-phase induction motor is built. The control algorithm is implemented on a dSPACE-1006 platform. The test shows that the CMV is successfully eliminated from the motor winding. Other results (i.e., current and voltage waveforms) are also found to be in very close agreement with the theoretical prediction and MATLAB simulation.

Three-Phase AC–AC Hexagonal Chopper System With Heterodyne Modulation for Power Flow Control Enhancement

This paper proposes a three-phase ac chopper system for the interconnection of various distributed generation (DG) farms or main utilities to enhance the active and reactive power flow control. The absence of large energy storage component in direct ac–ac converter makes the system footprint small and reliable. As the interface for different ac sources, the presented converter can be configured as star or delta. However, delta connection is preferred as it can trap the potential zero-sequence current and reduce the current rating of the switching devices. In this way, the proposed converter resembles the hexagonal chopper, and it offers an inherent degree of freedom for output voltage phase shifting. Considering the scalability in high-voltage applications, a new version of the hexagonal chopper with half-bridge cell modular multilevel structure is developed. The modular multilevel ac hexagonal chopper (M2AHC) is operated in quasi-two-level mode to suppress the electromagnetic interference (EMI) caused by high-voltage switching. Quasi-two-level operation divides the voltage level transition into multisteps, diminishing the voltage rising and falling rates ( dv / dt ) in high-voltage condition. Then, heterodyne modulation is adopted for the presented chopper system, supplying a new degree of freedom to decouple the phase and amplitude regulation. Based on this idea, system control strategy is developed in synchronous reference frame (SRF). Simulations and experimentations have confirmed the validity of the proposed approaches.

Three-Phase AC–AC Converter With Controllable Phase and Amplitude

Based on single-phase ac–ac converter with controllable phase and amplitude (ACCPA), a three-phase ACCPA without third harmonic trap was proposed for power transmission control in grid by adopting a symmetrical relationship of three phase. The three-phase ACCPA is comprised of two parts, which are used to adjust the phase and amplitude of three-phase output voltage, respectively, and continuously. Its front part is made up of three buck-type ac converters, and the back part is a three-phase boost-type ac converter. The operation principle of three-phase ACCPA, the adjustable ranges of the phase and amplitude of the front part, and the calculation formulas of control parameters under ideal conditions were studied and deduced in detail. Furthermore, the control accuracy of the phase angle was discussed for the three-phase ACCPA with digital control, and then, the method to select close-loop control parameters was obtained. The control strategy of three-phase ACCPA was presented and a prototype was fabricated. The experimental waveforms and testing results verified the correctness of the theoretical analysis and the feasibility of the control strategy.

Modular-Cell Inverter Employing Reduced Flying Capacitors With Hybrid Phase-Shifted Carrier Phase-Disposition PWM

This paper proposes a new approach of modular-cell inverter with a reduced number of flying capacitors (RFCI) using hybrid carrier-based pulsewidth modulation (PWM) named as phase-shifted carrier phase-disposition PWM (PSC-PD-PWM). The novel multilevel inverter topology is designed by clamping a series of modular cell onto a low-operational-frequency cell. The proposed transformerless RFCI reduces significantly the component counts, cost, and size of the converter. The overall performances of RFCI are greatly enhanced as compared with the classical multilevel flying capacitor inverter (MFCI). Hence, a comparative analysis of the proposed RFCI is made against the classical MFCI in this paper based on seven-level output phase voltages. The feasibility of the RFCI with PSC-PD-PWM is validated through experimental results under dynamic operating conditions.

Use of Three-Level Power Converters in Wind-Driven Permanent-Magnet Synchronous Generators with Unbalanced Loads

This paper describes the design and implementation of three-level power converters for wind-driven permanent-magnet synchronous generators with unbalanced loads. To increase voltage stress and reduce current harmonics in the electrical power generated by a wind generator, a three-phase, three-level rectifier is used. Because a synchronous rotating frame is used on the AC-input side, the use of a neutral-point-clamped controller is proposed to increase the power factor to unity and reduce current harmonics. Furthermore, a novel six-leg inverter is proposed for transferring energy from the DC voltage to a three-phase, four-wire AC source with a constant voltage and a constant frequency. The power converters also contain output transformers and filters for power buffering and filtering, respectively. All three output phase voltages are fed back to control the inverter output during load variations. A digital signal processor is used as the core control device for implementing a 1.5 kV, 75 kW drive system. Experimental data show that the power factor is successfully increased to unity and the total current harmonic distortion is 3.2% on the AC-input side. The entire system can attain an efficiency of 91%, and the voltage error between the upper and lower capacitors is approximately zero. Experimental results that confirm the high performance of the proposed system are presented.

Three-phase AC/AC converter for voltage sag/swell compensator and phase shifter based on Ćuk B2 matrix-reactance chopper

This paper proposes a new topology for an AC/AC converter without DC energy storage to compensate deep voltage sags and swells and to control the output voltage phase shift. The analyzed topology is based on an AC/AC ĆukB2 bipolar matrix-reactance chopper. The proposed solution is intended to protect sensitive loads and energy flow control in the AC power grid. The main advantage of the proposed solution is the combination of the properties of a series AC voltage compensator and phase shifters without DC energy storage. The presented AC/AC voltage converter is able to compensate single phase voltage interrupts, three-phase up to 50% voltage sags and swells, and change the phase of output voltage simultaneously and independently in relation to the input voltage. The paper presents an operational description, theoretical analysis and the experimental test results from a 1kVA laboratory model using a PWM control strategy with open feedback loop.

Sub-module Short Circuit Fault Diagnosis in Modular Multilevel Converter Based on Wavelet Transform and Adaptive Neuro Fuzzy Inference System

As the modular multi-level converter is now developing rapidly, especially in high power applications, and the large amount of sub-modules in the modular multi-level converter will increase the probability of failures, fault detection and diagnosis of the sub-modules are of importance for continuous operation and post-fault maintenance. In this article, a fault diagnosis technique is proposed for the short circuit fault in a modular multi-level converter sub-module using the wavelet transform and adaptive neuro fuzzy inference system. The fault features are extracted from output phase voltage by employing wavelet transform under different fault conditions. Then the fuzzy logic rules are automatically trained based on the fuzzified fault features to diagnose the different faults. Neither additional sensor nor the capacitor voltages are needed in the proposed method. The high accuracy, good generalization, as well as the time-saving characteristic is verified by conducting a comparison with the neural network method.

New MCPWM Strategy for a CHBMLI with Induction Motor Load

The paper attempts to develop a new pulse width modulation (PWM) strategy suitable for the cascaded H-Bridge multilevel inverter (CHBMLI) with a view to improve the performance of the Induction motor connected to it. The philosophy endeavors to arbitrate on the appropriate use of the reference sine wave in the generation of switching pulses for the power switches in the MLI. It dwells on the choice of the portions that essay an effective change of the modulation index to bring about a variation in the output voltage. The inherent poignant features of the phase disposition (PD) modulation technique intertwine with the reformulated philosophy to trace a nearly sinusoidal output voltage. The etiquette framework orchestrates to dispense with the higher frequency components and furnish an improved output voltage spectrum. The relatively lower total harmonic distortion (THD) indices for both output phase and line voltages allow the 60 degree PWM to claim an enhanced performance for the CHBMLI and in turn the induction motor. The delicacies of the field programmable gate array (FPGA) augur to realize the pulses and the experimental results from a suitable prototype adequately validate the simulated performance. The emphasis entices for opening up the portals of the traditional topology to a new dimension and ensures its use in practical applications.

Discontinuous SVPWM Techniques of Three-Leg VSI-Fed Balanced Two-Phase Loads for Reduced Switching Losses and Current Ripple

In this paper, various types of discontinuous space vector pulse-width modulation techniques for a three-leg voltage source inverter supplying balanced two-phase loads are proposed. The main objectives of the paper are to analyze switching loss characteristics associated with semiconductor devices and to reduce output current ripple by dealing with various types of zero space vector time in each switching sequence. Capabilities of reductions in switching losses and current ripple for both balanced and unbalanced output phase voltages at high modulation index and load power factor angle of 30° lagging are focused. The validity of the proposed techniques is verified by simulation and experimental results in terms of voltage spectrum, current waveforms, reductions in switching losses, and output current ripple at high modulation index when compared to a continuous space vector pulse-width modulation technique.

Improved three‐phase, five‐level pulse‐width modulation switched voltage source inverter

This study presents an improved three-phase, five-level pulse-width modulation (PWM) switched voltage source inverter. The single-carrier, multilevel PWM scheme is employed to generate the gating signals for the power switches. Operational principles with switching functions are given. By controlling the amplitude modulation index, three- and five-level output phase voltage waveforms can be achieved. For modulation indices of 0.45, and 0.9, the proposed inverter topology was subjected to an R–L load and the respective number of output voltage level were synthesised. For a step change in the modulation index, the response of the proposed multilevel inverter circuit topology is demonstrated. Fast Fourier transform analyses of the output line voltage waveforms, at the indicated depth of modulation, were carried out and the corresponding total harmonic distortion values were obtained. Comparison of the proposed inverter configuration and the classical 3-ϕ topologies is given based on the power circuit component count. Moreover, analysis of the conduction power losses in the power semiconductor switches of the proposed inverter topology is given. To verify the performance of the proposed inverter architecture, simulations and experiments are carried out on a 3.46 kW rated prototype of the proposed inverter for an R–L load; and adequate results are presented.

Векторная ШИМ для двухсекционного преобразователя частоты

The paper deals with analysis of operating modes of two-section frequency converter (TSFC) based on two series-connected voltage inverters. The author considers implementation of the vector pulse-width modulation for analyzed converter. The schemes of converter powering and the vector diagram of the output voltage states are presented. It is shown that the vector state diagram corresponds to the diagram of the traditional three-level converter. The proposed algorithm of vector PWM provides a doubled frequency of phase voltage switching with respect to the switching frequency of the power switches. The presented algorithm of the vector PWM eliminates the necessity to compensate the 2nd and 4th harmonics that occur when using a traditional sinusoidal PWM with asymmetric reference signal. Also this technique slightly improves harmonic composition of the output voltage of the convertor. However additional switching of the zero vector increases the load on the power switches. To implement the presented algorithm it is useful to apply FPGA module. The paper presents the plot of the phase output voltage of the converter and its spectral composition.

Performance Comparison of PWM Schemes of Dual-inverter FED Five-phase Motor Drives

The dual-inverter fed open-end winding configuration can be categorized as a new breed of multilevel converters. The structure is simple and offers a lot of advantages. However, the development of suitable PWM schemes is more complicated, due to the availability of a large number of switching states and existence of the multiple two-dimensional planes. An overview of attempts to develop suitable modulation techniques for the dual-inverter fed five-phase machine drives recognizes that progress has been made over the past few years. This paper presents a performance comparison of three PWM schemes of the dual-inverter fed five-phase, open-end winding motor drives. The quality of the phase output voltages are compared and the adequate analyses are provided. The simulation results show that the Carrier Based Phase Disposition (PD) PWM scheme enables generation of the most excellent output voltage among the three PWM schemes. The Total Harmonics Distortion (THD) of the output voltages generated by the carrier based PWM scheme reduces by 65% and 15% on average compared to the THD of the output voltages produced by the URS PWM scheme and the decomposition PWM scheme respectively.

Power flow control of TET system for a novel artificial anal sphincter system

This paper presents an adaptive transcutaneous energy transfer system (TETS) integrated with a novel elastic scaling artificial anal sphincter system (ES-AASS) for treating severe faecal incontinence (FI). The ES-AASS is based on a novel executive mechanism that uses a spring scalable structure to clamp the rectum. To deliver the correct amount of power (i.e. to match the load demand under variable coupling conditions or different operation stages of the implanted device) for internal battery charging and ensure safety for the human body, theoretical analysis was conducted as a control rule with respect to the relationship between the phase of driver signals and output voltage. An easy regulating procedure to stabilize output voltage with a phase shift controller is also presented. To validate the phase control rules, a prototype of the TETS was constructed and its performance was validated across the whole coupling coefficient range (0.09 ∼ 0.29) as well as load resistance (50 ∼ 120 Ω). The results show that the output voltage of the secondary side can be maintained at a constant 7 V with a phase regulation range of 78.7–178.2° and the proposed controller has reached a maximal end-to-end power efficiency of 74.2% at 1 W.

A Fast and Generalized Space Vector Modulation Scheme for Multilevel Inverters

This paper presents a fast and generalized space vector pulse width modulation (SVPWM) scheme for any multilevel inverter. The SVPWM scheme generates all the available switching states and switching sequences based on two simple and general mappings, and calculates the duty cycles simply as if for a two-level SVPWM, thus independent of the level number of the inverter. Because the switching states, duty cycles, and switching sequences are all obtained by simple calculation in the proposed SVPWM scheme, no lookup table is needed and the scheme is computationally fast. The generalized method of generating the switching states (first mapping), calculating the duty cycles, and determining the switching sequence (second mapping) is described in this paper. The scheme is suitable for any reference vector with any modulation index, and can be conveniently extended to meet specific requirements, such as symmetric switching sequences. Compared with prior methods, the SVPWM scheme proposed in this paper provides two more degrees of freedom, i.e., the adjustable switching sequences and duty cycles, thus offering significant flexibility for optimizing the performance of multilevel inverters. The influence of redundant switching sequences in the output phase voltage of inverters is demonstrated for a nine-level inverter. This paper also thoroughly compares the proposed SVPWM scheme with prior methods. Both simulation and experimental results are given.

Robust Nonlinear Adaptive Control of a “Boost” Converter via Algebraic Parameter Identification

This paper presents the design of a robust nonlinear adaptive controller for trajectory tracking maneuvers of the nonminimum phase output voltage on a dc-to-dc “boost” power converter with uncertain time-varying parameters. The unknown parameter variations concern both the resistive load and the input voltage supply value. A generalized proportional-integral (GPI) indirect control, exploiting the flatness property of the system, performs fast adaptations on the feedback controller and on the desired output reference trajectory owing to a fast online algebraic parameter identification procedure. The required updating of the algebraic parameter identification process is periodically triggered to cope with the time variations of the unknown plant parameters. The proposed control scheme is shown to be quite effective for handling the significant plant uncertainties when tested through experiments on a laboratory prototype. An adaptive linear quadratic regulator optimal control based on feedback linearization was designed in order to compare its performance against that of the proposed GPI adaptive scheme. An integral square error index was used for the evaluation.

Comprehensive Mathematical Description and Harmonic Analysis of Hybrid Two-Dimensional–Three-Dimensional Space Vector Modulation

This paper presents the mathematical and harmonic analyses of output phase voltages of three-phase voltage source inverters which employ a hybrid two-dimensional-three-dimensional (2-D-3-D) space vector modulation (SVM) voltage control algorithm. The explicit time-domain representation of the harmonic components in addition to the total harmonic distortion (THD) of the output phase voltages is given in terms of system and control parameters. This paper also investigates the harmonic characteristics and THD performance against the linearity of the modulation region which helps in the harmonic performance and design studies of such inverters employing the hybrid 2-D-3-D SVM. The fundamental component of the output voltages follows the reference with lower THD in the linear modulation region rather than the overmodulation region. Experimental results are used to validate these analyses as well as the effectiveness of the hybrid 2-D-3-D SVM algorithm for generating balanced and low THD phase voltages.

Wavelet Modulus Maxima for Single Switch Open Fault in Multi-level Inverter

The multi-level inverter is widely used in high-power and high-voltage applications. Multi-level inverters use a large number of switches for high power conversion, resulting in increased system's fault probability. To ensure stable operation of the system, several fault diagnosis methods have been carried out by researchers. In this article, a fault diagnostic system in a multi-level inverter using wavelet modulus maxima is developed. The working situation of the power devices of a five-level diode-clamped multi-level inverter drive system under an open-circuit fault is analyzed through MATLAB (The MathWorks, Natick, Massachusetts, USA) simulation. The wavelet modulus maxima of output phase voltages are used to detect faulty phase (leg), and wavelet modulus maxima of DC bus currents are used to detect fault type and fault switch. Wavelet analysis is used for feature extraction, which can be used as input to the expert system to develop a fault identifier. The open-circuit fault on the five-level diode-clamped multi-level inverter of power devices is carried out experimentally. The experimental prototype is developed to validate the fault analysis with simulation results.

Novel Carrier-Based PWM Strategy of a Three-Level NPC Voltage Source Converter without Low-Frequency Voltage Oscillation in the Neutral Point

A novel carrier-based PWM (CBPWM) strategy of a three-level NPC converter is proposed in this paper. The novel strategy can eliminate the low-frequency neutral point (NP) voltage oscillation under the entire modulation index and full power factor. The basic principle of the novel strategy is introduced. The internal modulation wave relationship between the novel CBPWM strategy and traditional SPWM strategy is also studied. All 64 modulation wave solutions of the CBPWM strategy are derived. Furthermore, the proposed CBPWM strategy is compared with traditional SPWM strategy regarding the output phase voltage THD characteristics, DC voltage utilization ratio, and device switching losses. Comparison results show that the proposed strategy does not cause NP voltage oscillation. As a result, no low-frequency harmonics occur on output line-to-line voltage and phase current. The novel strategy also has higher DC voltage utilization ratio (15.47% higher than that of SPWM strategy), whereas it causes larger device switching losses (4/3 times of SPWM strategy). The effectiveness of the proposed modulation strategy is verified by simulation and experiment results.

Study on Generating Characteristics of Free-Piston Engine Generator

In order to increasing the energy efficiency of Free-piston engine generator (FPEG), an experiment was taken on to study the generating characteristics for it is one of the most impressive factors. The results show that: The aptitude of phase voltage is related with velocity of piston and flux of linear generator, phase difference is 120 degree; the piston is not moving in uniform motion; the velocity around TDC and BTD has obviously different; with the work frequency increase, the output phase voltage is increasing; when the external resistor is equal to interal resistor, the output power reaches it maximum.