3-phase PWM Inverter Research Articles

Closed-Loop Harmonic Suppression for Grid Connected 3-Phase PWM Inverters

Closed-Loop Harmonic Suppression for Grid Connected 3-Phase PWM Inverters

Design and Analysis of PWM Inverter for 100KVA Solid State Transformer in a Distribution System

Conventional Magnetic Transformers are key components in a distribution system as it performs several functions like voltage transformation and isolation. However due to increase in penetration of renewable energies into distribution system, existing conventional transformers are expected to be replaced by a solid-state transformer (SST) which offers several advantages as reported in literature. SST can also be used to connect AC or DC grids because it can be operated at a much higher frequency and voltage which results in reduction in the size of conventional transformers as size of transformer is inversely proportional to frequency. In this paper, design and analysis of a 3-phase PWM Inverter using half - bridge topology for 11kV/381V, 100kVA solid-state transformer (SST) is presented for power distribution system application. The mathematical model of SST is developed using analytical calculations and then implemented in MATLAB simulation program. Finally it is implemented in hardware in a laboratory for a half-bridge topology. The main system has been virtually created in order to actualize the conversion from DC to AC.

Low Order Harmonic Analysis of 3-Phase SPWM and SV-PWM Inverter Systems Driving an Unbalanced 3-Phase Induction Motor Load

The Variable Frequency Drives (VFD) are a common type of controlling the speed of 3-phase induction motors which are based on two control modulation techniques of Voltage Source Inverter: Sinusoidal Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SV-PWM). The SPWM control technique is known as an easier implementation, but the SV-PWM control technique can be distinguished by an easier digital realization and a better utilization of DC bus. All 3-phase PWM inverters produce a total harmonic distortion (THD) on its output, which causes electromechanical and thermal stresses. The aim of this paper is comparing the low order current harmonics while driving an unbalanced 3-phase induction motor (the case of deterioration of the insulation as a result of inter-turn short circuits between few turns of the same phase) using SPWM and SV-PWM two-level 3-phase Voltage Source Inverters (VSI). For this type of unbalanced 3-phase induction motor, the SVPWM and SV-PWM schemes are modeled and simulated using Matlab/Simulink software. A detailed comparative analysis of THD-phase currents is made for both modulation strategies at different switching frequencies while keeping the constant amplitude modulation index.

An Optimal Current Distribution Method of Dual-Rotor BLDC Machines

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

추가적인 센서가 필요 없는 3상 PWM 인버터의 LCL 필터 능동댐핑

In this paper, a new active damping method of LCL filter without capacitor voltage sensors is proposed for 3 phase PWM Inverter. Normally, L filter or LCL filter is used as an output filter of grid connected PWM inverter. An LCL filter has more excellent performance than L filter to reduce harmonic current, so the small inductance value can be used. However, the resonance problem in LCL filter is happen due to the zero impedance by the addition of LC branch. To solve the resonance problem, the various active damping method has been proposed so far. Generally, the virtual resistor active damping methods is required to additional hardware sensors for measurement of capacitor voltage and current. In this paper, the new active damping method is proposed without any capacitor voltage or current sensors. In the proposed method, the resonance component of the capacitor voltage of LCL filter can be observed by a simple MRAS(Model Reference Adaptive System) observer without additional hardware sensors, and this component is suppressed by feedforward compensation. The validity of the proposed method is proven by simulation and experiment on the 3-phase PWM inverter system.

양방향 스위치를 이용한 H-bridge 구조의 새로운 멀티레벨 인버터

Recently, Switching devices become cheaper, depending on the multi-level inverters are considered as the power-conversion systems for high-power and power-quality demanding applications. The multi-level inverters can reduce the THD(Total Harmonic Distortion) as the output which is similar sinusoidal waveform by synthesizing several capacitor DC voltages. However it has some disadvantages such as increased number of components, complex PWM control method. Therefore, this paper is proposed the new multi-level inverter topology using an new H-bridge output stage with a bidirectional auxiliary switch. The proposed topology is the 4-level 3-phase PWM inverter with less switching part than conventional multi-level inverters and reactive power control possible. In order to understand the new multi-level inverter, topology analysis and switching patterns and modes according to the current loop are described in this paper. The proposed multi-level inverter topology is validated through PSIM simulation and the experimental results are provided from a prototype.

Development of High-Efficiency Low-Cost Drive System of Small-Size Electric Vehicles

Abstract –This paper designs the high-efficiency and the low-cost drive system of the small-size electric vehicles (EVs). The power circuit for driving the dc motor is designed by considering both the cost and efficiency. In order to reduce the conduction loss of MOTFET and diode for controlling an armature voltage, some MOSFETs and diodes at the armature are in parallel connection. An operating sequence for both the field current and the armature voltage according to the accelerator pedal angle is suggested for changing smoothly the rotating direction of dc motor. Through the simulation studies, the performances of the proposed methods are verified. Keywords: Electric vehicle, conduction loss, buck converter, switching loss, DC motor 1. Introduction Recently, because environmental pollution and the energy crisis are rising globally, electric vehicles (EVs) are promising instead of traditional gasoline vehicles. As the EVs are driven by electricity stored in a battery, they still suffer from the main problem as short driving range due to the low energy content of the batteries. As how to use the battery’s energy efficiently is a hot issue for developing EVs, it is important to design the drive system of a traction motor with high efficiency. Selection of traction motors for propulsion system is very important step that requires special attention. In fact, the choice of electric-propulsion systems for EVs mostly depends on three factors: efficiency, cost, and reliability. In an industrial point of view, the major types of electric motors adapted or under serious consideration for EVs include the dc motor, an induction motor (IM), and brushless DC (BLDC) motor. The BLDC motor has been widely used in the EVs, because it provides high power density, and has higher efficiency than induction motor [1]-[3]. By the way, in order to drive the BLDC motor, the 3-phase PWM inverter and complex control system are required [4]. Recently, the price of PM has been dramatically raised. They cause the increase of the manufacturing cost of the EVs. The small-size EVs such as the golf car and scooters require the simple propulsion system in order to reduce the manufacturing cost. Although a brushed dc motor has some problems such as requirement of maintaining both the brush and commutation, it has some advantages like a simple drive system and high starting torque. Thus, the dc motor as the traction motor is more suitable at the low cost small-size EVs [5]. In this paper, the power circuit for driving the dc motors is designed by considering both the cost and efficiency. In order to reduce the conduction loss of MOTFET and diode for controlling an armature voltage, some MOSFETs and diodes at the armature are in parallel connection. An algorithm to change smoothly the rotating direction of the motor is suggested. In order to verify the performances of proposed methods, some simulation studies are carried out.

High-Efficiency Grid-Tied Power Conditioning System for Fuel Cell Power Generation

This paper proposes a grid-tied power conditioning system for the fuel cell power generation, which consists of a 2-stage DC-DC converter and a 3-phase PWM inverter. The 2-stage DC-DC converter boosts the fuel cell stack voltage of 26-48V up to 400V, using a hard-switching boost converter and a high-frequency unregulated LLC resonant converter. The operation of the proposed power conditioning system was verified through simulations with PSCAD/EMTDC software. Based on the simulation results, a laboratory experimental set-up was built with a 1.2kW PEM fuel-cell stack to verify the feasibility of hardware implementation. The developed power conditioning system shows a high efficiency of 91%, which is a very positive result for the commercialization.

Battery Operated Wheelchairs, Using 3-Phase Cage Rotor Induction Machines and PWM Inverters

Battery Operated Wheelchairs, Using 3-Phase Cage Rotor Induction Machines and PWM Inverters

Computer-aided design of PWM inverter systems

The increasing availability of digital computers now makes the computer-aided design of powerelectronic systems an attractive and cost-effective development tool. The paper describes the detailed development of an extremely versatile PWM computer modelling package which can be used as a `stand-alone′ package for harmonic analysis, or alternatively as a `building-block′ for developing more complex systems. The capabilities of the package are demonstrated, using a number of examples of single-phase and 3-phase PWM inverters, which serve to highlight a number of important operational characteristics of PWM inverters. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter-drive system.