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This paper deals with a 3kW multilevel inverter used for PV applications. A comparison has been made based on simulations using IGBTs and SiC MOSFETs to see how much efficiency can be gained when SiC diodes are used. A prototype with the same IGBTs and SiC MOSFETs has been built but using regular soft-recovery Si diodes instead of SiC diodes. Efficiencies and switching transitions for different switching...
It is an ideal to perform a combined test of an inverter and a motor for a smooth start-up at the site. There is a method to carry out a full load test without driving a machine. It is called “Back-to-back test”. It is possible to obtain 25MW output of testing facility in our company. In this paper, it is introduced the performance evaluation of the test results such as, torque ripple analysis of...
This paper proposes a novel three-phase PWM ac-ac converters, presents detailed circuit operation and operating principle. The proposed converters employs the basic switching cell structure and coupled inductor to solve commutation problem without sensing input voltage polarity. The commutation scheme allows that the proposed converters can be short and open circuited without generating high switch...
The explanations of the PWM strategies of a direct matrix converter are classified into “Direct AC/AC converter”, “Virtual AC/DC/AC Conversion” and “Instantaneous Space Vector Diagram”. Since the PWM strategies of matrix converters are complex, it may be difficult to understand the same PWM strategies under the different explanations. This paper presents the visualization of the PWM waveforms of the...
This paper proposes the new LLC converter with unique control method. Generally, LLC resonant converter, which is controlled by PFM, has the drawback of (1) difficulty of PWM controllability, (2) difficulty of constant current limitation, and (3) narrow input voltage range limitation. These difficulties come from the resonant operation. In order to overcome those drawbacks, a hybrid control of PFM...
This paper deals with the measurement of the magnetic properties of electrical steel under the influence of pulse width modulation (PWM) in comparison to an ideal sinusoidal waveform. At first the theory and practice of measuring the magnetic properties with the ring core method are described. Next the measurement setup and results are depicted. The results show the well-known fact that a sinusoidal...
An iron loss characteristic with three ring specimens connected in a star type and in a delta type on three phase inverter excitation is investigated. It is indicated that iron loss obtained from star-connection is about 14 % larger than that obtained from delta-connection. This difference is caused by potential of neutral point having the third harmonics on star-connection. Therefore, although the...
Wind energy is one of the renewable energy been developing in recent years. Wind turbines are generally connected to the utility grid as the generation resources. In local application, the wind generator can be implemented in the DC or AC micro-grid. In the DC micro-grid, the output AC/DC converter of wind generator should accomplish the AC/DC power conversion and maximum power tracking. This paper...
This paper examines the control performance of a permanent magnet synchronous motor drive system based on direct torque control (DTC) using a SiC-MOSFET inverter (SiC inverter). The dead-time of the inverter affects the performance of the motor control. In high-speed drives, the dead-time effect increases because the control period becomes shorter. By using a SiC inverter for which the switching speed...
Open-end winding machine configuration provides better fault tolerance and flexibility for control compared with a conventional three-phase neutral connected electric motor. In this paper, three types of pulse width modulation (PWM) schemes - sinusoidal PWM, space vector PWM, and symmetrical sinusoidal PWM for open-end winding induction motor drives are being examined. The three PWM schemes are simulated...
An energy storage system is integrated into a power-grid to compensate for the power fluctuation from renewable energy systems. This paper proposes a high-efficiency and low-cost energy storage system for the power-grid. The proposed system combines multi-energy storage devices such as a LaB and an EDLC for reducing the cost incurred by the system for the complete operation period. This paper also...
A transformerless single-phase PV inverter has been tested with latest generation 650V/ 20A SiC MOSFETs from ROHM. Test results show that the inverter can be operated with high efficiency at high switching frequencies due to high switching and conduction performance of the devices. Results also show that reduction in output filter size, reduced harmonic distortion and increase in power density are...
A high efficiency 3-phase hybrid 7-level inverter is presented in this paper. Compared with traditional hybrid 7-level converters, the proposed topology and its T-type cell have lower power loss and simple configuration. It can be easily implemented and applied in renewable energy areas. In the paper, power loss of proposed T-type cell is analyzed, by which conduction loss of T-type cell is proved...
Multi-port converters (MPCs) are the prospective alternative in the hybrid power system, which can simplify the system structure and reduce the cost. In some operation conditions, one port may quit from the system, leaving this idling port at zero power. Under the exclusive operation, different control strategies can be used. Based on the analysis of the soft-switching ranges and the conduction losses,...
The I type 3L-NPC (Three-level Neutral-Point-Clamped) converter is the most popular multilevel converter used in the renewable energy system for its low switching loss, reduced devices voltage stress. However, it suffers from problems of high conduction losses. The T type 3L-NPC is researched in the literatures to overcome the drawbacks of I type inverter. But, the high side and low side power devices...
A novel carrier-based modulation strategy of NPC three-level converter which achieves neutral point voltage balance under the whole modulation index and power factor is proposed in this paper. It divides the traditional single modulation wave of each phase in SPWM strategy into two modulation waves, which are compared respectively with the carrier to decide the output switch state of the converter...
This paper proposes a CLC filter design of a flyback-inverter for photovoltaic systems. This applied system is small power system; therefore, the capacity and size of the entire system are critical factor. The proposed CLC filter consists of a conventional CL filter and an additional capacitor. The CLC filter, which guarantees the same performance about the current ripple reduction as that of the...
Power amplifier suitable for booster of small-size nonlinear power source such as photovoltaic (PV) cells is presented. The amplifier is developed to simulate large size of nonlinear power source and is utilized to examine various PV power systems. The amplifier is simple and compact to carry. Principle of PV cell booster with the amplifier is described. Prototype of the amplifier utilized as PV cell...
This paper proposes a current sensorless maximum power point tracking (MPPT) control strategy for a dual-mode photovoltaic (PV) module-type interleaved flyback inverter (ILFI). A flyback inverter, which is one of many transformer topologies, is generally used because of its simplicity and low cost. The topology used in this paper is the interleaved topology; therefore, the secondary ripple current...
This paper proposes a novel method of suppressing inrush currents of squirrel-cage induction machines using matrix converter in wind power generation systems. In the proposed method, the series-connected side of the matrix converter behaves as a resistor for the induction machine current. Digital computer simulation is implemented to confirm the validity and practicability of the proposed method using...
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