Conventional Three-phase Inverter Research Articles

Power router based on conventional three-phase bridge inverter and DC–DC converter

As the generation capacity increases and clean energy cost reduces, the current power grid and energy management system cannot meet optimal allocation and auxiliary function of clean energy power generation. High-end manufacturing is very important to a country's economic development, and for high-end manufacturing particular with high energy consumption, energy cost reduction and power reliability improvement are of critical importance. The power router is an effective power device which cannot only realise the power control of each power supply, but also can optimise allocation of electrical energy by strong communication equipment. Meanwhile, it can improve electricity quality and support the manufacturing load as power supply when the power grid is fault. The current power router based on high-frequency transformer, however, is so complicated and expensive that it is difficult to be used by manufacturing. A different type power router which is more suitable for high-end manufacture is proposed. The conventional transformer, three-phase bridge inverter and DC–DC converter are used. By DC bus topology, power electronic device is convenient to be integrated, and power can be interacted among different converters.

A Hybrid Nine-level Inverter Topology for an Open-end Stator Winding Induction Motor

In this article, a new hybrid nine-level inverter topology for an induction motor with an open-end stator winding is proposed. In the proposed topology, one end of the open-end winding is fed by a three-phase five-level inverter, and the other end is connected to a conventional three-phase two-level inverter. The three-phase five-level structure is realized by cascading a three-level flying capacitor inverter with capacitor-fed H-bridge in each phase. In the proposed topology, a total of 17,576 space vector combinations are available; hence, the capacitor voltages can be maintained at desired levels using switching redundancies. As compared to conventional topologies that require 48 switches, the proposed topology requires only 30 switches and completely eliminates the requirement of clamping diodes, which are required in a neutral point clamped inverter. Also, it requires only two capacitors per phase, whereas the nine-level flying capacitor inverter requires 28 capacitors per phase. In case of fault in any H-bridge, the system can be operated as a five-level inverter at its full power rating and improves the reliability of the inverter. The performance of the proposed system has been experimentally investigated on a 1.5-kW open-end stator winding induction motor, and results are presented.

Highly efficient three-phase three-level multilevel inverter employing different commutation strategies

This paper introduces a new three-phase three-level voltage source inverter. The proposed topology consti- tutes the conventional three-phase two-level inverter with three bidirectional switches. For purpose of generating the appropriate switching gate signals, two different commutation strategies are suggested and analyzed. A comparison between both strategies in terms of power losses and efficiency are presented. To ensure the feasibility of the proposed conguration with its suggested commutation strategies, the prototype of the proposed inverter was manufactured and the experimental results are given.

Dynamic Voltage Restorer Based on Three-Phase Inverters Cascaded Through an Open-End Winding Transformer

This paper investigates a dynamic voltage restorer (DVR) composed of two conventional three-phase inverters series cascaded through an open-end winding (OEW) transformer, denominated here DVR-OEW. The DVR-OEW operating with either equal or different dc-link voltages is examined. The proposed topology aims to regulate the voltage at the load side in the case of voltage sags/swells, distortion, or unbalance at the grid voltage. A suitable control strategy is developed, including space-vector analysis, level-shifted PWM and its equivalent optimized single-carrier PWM, as well as the operating principles and characteristics of the DVR. Comparisons among the DVR-OEW and conventional configurations, including a neutral-point clamped converter-based DVR, are furnished. The main advantages of the DVR-OEW compared to the conventional topologies lie on: 1) reduced harmonic distortion, 2) reduced converter losses, and 3) reduced voltage rating of the power switches. Simulated and experimental results are presented to validate the theoretical studies.

A generalized scalar pulse-width modulation for nine-switch inverters: An approach for non-sinusoidal modulating waveforms

Abstract The nine-switch inverter has been proposed recently and, since then, a large number of applications have been investigated, specially as a substitute to the dual-bridge (back-to-back) converter. The main advantage of the nine-switch inverter is its lesser number of switches (nine instead of twelve of the back-to-back converter), which has as a tradeoff some restrictions in the total attainable amplitude at its outputs, dependent on the phase shift between its two terminal sets. Thus, when migrating modulation techniques from the conventional three-phase inverter to the nine-switch inverter, more concerns have to be addressed. This paper deals with pulse-width modulation strategies that can be easily implemented by using the concept of generalized scalar modulation in this type of inverter. In fact, such concept leads to a systematic and straight approach to the generation of any continuous or discontinuous pulse-width modulation strategy. Aiming the reduction of switching losses, the generalized modulation is applied with a specific distribution parameter that reduces the number of switchings of the three-phase nine-switch inverter. Experimental results confirm the validity of the proposed method.

Three‐phase hybrid multilevel inverter with less power electronic components using space vector modulation

This study presents a new design and implementation of a three-phase hybrid multilevel inverter (MLI) using space vector modulation. The proposed MLI consists of a reduced number of dc sources and switches to minimise the control complexity. The developed topology consists of two stages: main stage and auxiliary stage. The main stage is a conventional three-phase inverter with one high-voltage input dc source and six switches. The auxiliary stages contain three individual cells. Each cell consists of two switches and one low-voltage input dc source. This topology is a modular type and without changing the previous connection it can be extended for more number of output voltage levels by adding certain number of auxiliary stages. A space vector modulation control technique has been utilised in order to generate different switching sequences. The special feature of the proposed system is its capability to maximise the number of voltage levels using a reduced number of isolated dc voltage sources and electronic switches. A prototype has been developed and tested for various modulation indexes to verify the control technique and performance of the topology. Experimental results validate the simulation results and the experimental results show a good similarity with the simulation results.

Total Harmonic Distortion Analysis of a Four Switch 3-Phase Inverter Fed Speed Sensorless Control of IM Drives

This paper investigates the performance of a Model reference adaptive system (MRAS) based cost-effective drive system of an induction motor (IM) for low-cost applications - high performance industrial drive systems . In this paper, the MRAS is used as a speed estimator and the motor is fed from a four-switch three-phase (FSTP) inverter instead of a conventional six-switch three-phase (SSTP) inverter. This configuration reduces the cost of the inverter, the switching losses, and the complexity of the control algorithms and interface circuits, the proposed control approach reduces the computation for real-time implementation.. The robustness of the proposed MRAS-based FSTP inverter fed IM drive is verified by Experimental results at different operating conditions using digital signal processor (DSP1103) for a 1.1 Kw motor. A performance comparison of the proposed FSTP inverter fed IM drive with a conventional SSTP inverter system is also made in terms of speed response and total harmonic distortion (THD) of the stator current. The proposed FSTP inverter fed IM drive is found quite acceptable considering its performance, cost reduction and other advantages features. DOI: http://dx.doi.org/10.11591/ijpeds.v4i1.5036

On-line compensation of dead-time and inverter nonlinearity with disturbance voltage observer

This paper discusses and analyses a simple on-line compensation scheme for dead-time and inverter nonlinearity in the pulse width modulated (PWM) voltage source inverter (VSI). Dead-time effect and voltage drop in switching devices cause nonlinearity between reference and output voltage. In a conventional three-phase six-switch inverter, this nonideal condition adds extraneous harmonics that badly disturb voltage characteristics. In its turn, voltage disturbance causes distortion of the current waveform and degrades performance. In this paper, an on-line dead-time compensation method based on inverse dynamics control is proposed, and it is much simpler than conventional full/reduced order observation methods adopted in dead-time compensation. Disturbance voltages are observed on-line with no additional circuitry or off-line measurements. The observed disturbance voltages are fed back to the voltage reference for compensation. Stability problem of the proposed observer arisen from inverter delay and parameter mismatch was analysed. The proposed method is applied to a surface-mounted permanent-magnet synchronous motor (SPMSM) drive. The effectiveness of the proposed scheme is validated by the experimental results.

Low-Cost Direct Torque Control Algorithm for Induction Motor Without AC Phase Current Sensors

This paper presents a novel low-cost and simple phase-current reconstruction algorithm for three-phase induction motor (IM) under direct torque control (DTC) using the information obtained from only one shunt resistor (in series with low-side switches in a conventional three-phase inverter). The aim is to develop a low-cost high-performance IM drive. The proposed algorithm is robust and very simple. It uses the dc current to reconstruct the stator currents needed to estimate the motor flux and the electromagnetic torque. A theoretical concept is developed, the modified look-up table is presented, and current-access tables are designed and used in the phase-current reconstruction. The limitations are also studied and presented.

Single-phase induction motor drive system using z-source inverter

Employing conventional three-phase inverter in variable speed single-phase drive suffers from limited maximum output voltage applied to motor or voltage utility factor (VUF). In this study, a z-source inverter (ZSI) has been used to drive a single-phase induction motor (SPIM). By the proposed topology, VUF and consequently torque speed characteristic of the single-phase motor is improved. The equations for employing ZSI in SPIM drive and modulation method are described. Results of two simulations using conventional inverter and ZSI are presented. The results show that using ZSI leads to an increase in motor electromagnetic torque compared to conventional three-phase inverter due to improved VUF. The experimental results confirm the theory and simulation.

Distributed Generation System using Parallel Inverters Supplied by Unstable DC Source

This study presents the analysis and design of distributed generation system. The system consists of a full-bridge DC-DC converter, two units of three-phase inverters connected in parallel and a controller. Two units of conventional three-phase DC-AC inverters connected in parallel with series resistors were added to the inverter output to maintain the same current in each inverter and to minimize the circulating current in the parallel inverters. High frequency third harmonic injection PWM (THIPWM) was employed to reduce the total harmonic distortion and to make maximum use of the DC bus voltage. The generation of control algorithm for three-phase inverter is implemented in Digital Signal Processing (DSP) boards. The THIPWM have been done such that the inverter output voltage is synchronized with the grid voltage thus making the inverter suitable for grid connection. The three-phase inverter operates with a total harmonic distortion of less than 2 on output voltage and current signals. Experimental results are shown validate the proposed system. A full distributed generation system has been implemented and tested, the testing of the system proves that the system operates with minimum circulating current on the parallel connected inverter and minimum harmonic distortion on the inverter output voltage and current.

Three-Phase Power Quality Compensator Under the Unbalanced Sources and Nonlinear Loads

A three-phase voltage-source inverter for a power quality compensator under the unbalanced mains and nonlinear loads is proposed to provide balanced three-phase source current and improve input power factor. The proposed converter is based on the conventional three-phase voltage-source inverter with three additional ac power switches to achieve three-level pulsewidth modulation. The voltage stress of three ac power switches is clamped to half the dc-link voltage. The balanced reference mains currents are estimated using the dc-bus voltage and load currents. A proportional-integral voltage controller is used in the outer loop to compensate the switching losses of the voltage-source inverter. To perform the integrated power quality compensation, a hysteresis current control scheme is adopted to track the balanced line current command in phase with mains voltage. Three voltage levels are generated on the ac terminal of the proposed inverter. Computer simulation and experimental results are provided to verify the effectiveness of the proposed control scheme.

Two-dimensional motion motor with circular core and plural divided windings supplied separately

We have proposed a circular shape of induction type two-dimensional motion motor called the surface induction motor in which the winding is controlled at each coil. For a simpler drive using conventional three-phase inverters, a surface induction motor with divided windings is proposed, in which one inverter is used for supplying power to one group of windings. Continuously change of thrust direction is verified by using a test machine. The experimental and theoretical results give that the six-division type with three three-phase inverters or eight-division type surface motor supplied by four three-phase inverters is best.

Two-dimensional drive characteristics by circular-shaped motor

An induction-type motor with a toroidal core, called a surface induction motor (SIM), is proposed for any directional motion in a two-dimensional plane. In the case of small size, the SIM has large thrust compared with a linear induction motor (LIM) because the slots in the SIM can be used effectively. For practical use, a conventional double-layer winding and ordinary three-phase inverters are used. However, the winding is divided into four or eight sections in the direction of the circumference of the core. The eight-division-type SIM supplied by four inverters can change the direction of linear motion continuously with constant thrust by increasing the main winding current by only about 11%.