FRT Operation for Single-Phase Grid-Tied Inverter with Active Power Decoupling Capability

Jun-ichi Itoh,Satoshi Nakamura,Satoshi Nagai,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes a Fault Ride-Through (FRT) operation for a single-phase grid-tied inverter with an active power decoupling capability. The power decoupling circuit achieves the double-line-frequency power pulsation compensation with a small capacitance; consequently, a transient response with a sudden load change becomes worsen because a large energy buffer, i.e. bulky electrolytic capacitors, does not apply. In particular, high overshoot voltages occur in a DC-link voltage when the grid voltage sag of the single-phase grid occurs, resulting in the interrupt of the FRT operation due to the over voltage protection. In order to solve this problem, the buffer capacitance is designed in the consideration of the overshoot amount of the DC-link voltage. The theoretical value of the overshoot amount is verified with a 1-kW prototype. As an experimental result, The error between the experimental and the calculation value is within 10%. Furthermore, the proposed control achieved both the FRT operation and the active power decoupling capability.

Reduction of a Boost Inductance using a Switched Capacitor DC-DC Converter

Jun-ichi Itoh,Koichi Matsuura,Koji Orikawa 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The loss analysis of a switched capacitor converter (SCC) with a boost reactor is discussed in this paper. The proposed SCC can deliver an output voltage independent from the circuit structure comparing to other voltage control methods. The main feature of this circuit is that most of the energy for the boost up function is transferred from a flying capacitor which results the inductance of the input reactor can be reduced. The reactor size of the proposed SCC is smaller than that of the conventional boost converters. A 1000 W 3-level SCC prototype has been built and tested. The efficiency of 97.8% is achieved at 1000 W when the boost up ratio is three times. Moreover, the loss analysis shows the main loss of the proposed SCC is the diode conduction loss.

Voltage Unbalance Compensation Method with Zero Voltage Switching for Series Connected Switching Devices

Jun-ichi Itoh,Ryosuke Iso,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes a voltage unbalance compensation method of series-connected switching devices for high voltage application such as DC distribution systems. In the series connection, a turn-off voltage unbalance occurs in switching devices due to a parasitic parameter mismatch and a switching timing mismatch among switching devices. In this paper, a capacitor snubber and Zero Voltage Switching (ZVS) operation are utilized to reduce voltage unbalance. In particular, the proposed method reduces the parasitic capacitor (collector-emitter capacitance) mismatch among series-connected devices by a capacitor snubber circuit, whereas the switching losses are effectively reduced by ZVS. As the simulation results, it is confirmed that the collector-emitter voltage unbalance is reduced by 88% by the proposed method in comparison with a snubber-less configuration. Finally, in order to confirm the effectiveness of the proposed method, experiments with a test circuit applied with the proposed method are conducted. According to the experimental results, the voltage unbalance is reduced by 86.0% due to the application of the proposed method.

Minimum Neutral Clamp Capacitor Design Considering Voltage Saturation for a Three-Level Inverter

Jun-ichi Itoh,Takaaki Tanaka 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

A neutral point clamped inverter has a voltage fluctuation problem at the neutral point capacitor. This paper discusses the minimum value of the neutral point capacitor considering the voltage command saturation with the voltage fluctuation suppression control method. This paper clearly demonstrates the stable relationships among the input voltage, the output voltage and the capacitance value. In addition, the minimization design procedure of the capacitance value basis on this analysis is demonstrated. The validity of the design method is confirmed by experimental results.

Voltage Control Method in Non-linear Dead-time Effect Region for Dual Active Bridge DC-DC Converter

Jun-ichi Itoh,Kengo Kawauchi,Hayato Higa,Hiroki Watanabe,Keisuke Kusaka 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes a voltage control method for a Dual Active Bridge (DAB) converter with three-level operation in the dead-time effect region. The non-linear transmission power error is reduced by controlling the zero current phase to the dead-time or more because the nonlinear error of the transmission power occurs when the inductor current reaches zero during the dead-time. In addition, the voltage control is operated under the linear region which is decided from the output current and the zerovoltage period. The validation of the proposed method is confirmed by a 2.3-kW prototype. In the experiments, the non-linear error in the transmission power is reduced by 76.3%. The linearity between a control variable and an output current is confirmed. In addition, a load step between two modes of three-level operation is achieved without the dc offset in the inductor current. Moreover, the RMS value of the inductor current is reduced by 50.2% compared with the conventional triangular modulation.

Design of Flux-Axis Angular Speed Estimation using Induced Voltage in Speed Sensor-less Field Oriented Control for Induction Motor

Jun-ichi Itoh,Kazuya Kawai,Koroku Nishizawa,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes a design method of the flux-axis angular speed estimation using induced voltage in a speed sensor-less field oriented control for induction motor (IM) drive systems. In this method, the d-axis induced voltage is regulated to zero by a feedback control to estimate the fluxaxis angular speed. A low pass filter (LPF) is necessary in this estimation to avoid the recursive calculation. In this paper, the design method of compensation gain kpem and the cut-off angular frequency of LPF ωlpf are considered. As a result, the relation between kpem, ωlpf, convergence time of the d-axis induced voltage have a match to the equation and designed model in this paper. Furthermore, the maximum error between the simulation and estimated results of the time constant of the flux-axis angular speed introduced due to LPF is 3.7% when ωlpf is 200 rad/s. As the experimental results, when a torque step of 100% is applied to the induction motor, the convergence time of the motor speed is 1.6 s as the worst case with kpem set as 2.0 p.u. and the cut-off angular frequency set as 1000 rad/s. However, if kpem is set as 2.0 p.u. and ωlpf is set as 400 rad/s, the convergence time of the motor speed is 0.43 s as the best case, which is reduced by 73.1% compared to the worst case. As the result, kpem should decide by the target steady-state error, lpf should bigger than the cut-off angular frequency of the PI controller ωASR. Where, if the ωlpf is high, the convergence time of the motor speed is high.

Capacitor volume evaluation based on ripple current in Modular Multilevel Converter

Toshiki Nakanishi,Jun-ichi Itoh 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

This paper discusses the overall volume evaluation of capacitors in Modular Multilevel Converter (MMC). First, a theoretical formula of the ripple voltage on each cell capacitor in the MMC is clarified. Second, a formula of the total electrostatic energy is clarified. As a result, it is difficult to evaluate the overall volume of the capacitors because the total electrostatic energy is constant even the number of cells changes. Against the problem, the overall volume of the capacitors is designed by using the database of commonly-marketed electrolytic capacitors which are generally implemented into many products. In conclusion, the parallel connection of the capacitor with the small ripple current is better than using one capacitor with the large ripple current in order to achieve the size reduction of capacitors. Finally, it is necessary to close the ratio of the charge voltage to the withstand voltage to 1.0 in order to achieve the volume minimization.

Parameter design of a Five-Level Inverter for PV systems

Yugo. Kashihara,Jun-ichi. Itoh 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper discusses the parameter design method for an active neutral-point-clamped (ANPC) multilevel inverter. The power losses of the ANPC inverter are calculated by mathematical expressions and the mathematical results are confirmed well agreed with the experimental results. Furthermore, this paper also discusses on the optimization of the switching frequency, in order to improve the efficiency and to downsizing the capacitor volume.

<i>PLASTOCHRON3/GOLIATH</i> encodes a glutamate carboxypeptidase required for proper development in rice

Kawakatsu, Taiji,Taramino, Graziana,Itoh, Jun-Ichi,Allen, Justin,Sato, Yutaka,Hong, Soon-Kwan,Yule, Ryan,Nagasawa, Nobuhiro,Kojima, Mikiko,Kusaba, Makoto,Sakakibara, Hitoshi,Sakai, Hajime,Nagato, Yasu Blackwell Publishing Ltd 2009 The Plant journal Vol.58 No.6

<P>Summary</P><P>Most aerial parts of the plant body are products of the continuous activity of the shoot apical meristem (SAM). Leaves are the major component of the aerial plant body, and their temporal and spatial distribution mainly determines shoot architecture. Here we report the identification of the rice gene <I>PLASTOCHRON3</I> (<I>PLA3</I>)/<I>GOLIATH</I> (<I>GO</I>) that regulates various developmental processes including the rate of leaf initiation (the plastochron). <I>PLA3</I>/<I>GO</I> encodes a glutamate carboxypeptidase, which is thought to catabolize small acidic peptides and produce small signaling molecules. <I>pla3</I> exhibits similar phenotypes to <I>pla1</I> and <I>pla2</I>– a shortened plastochron, precocious leaf maturation and rachis branch-to-shoot conversion in the reproductive phase. However, in contrast to <I>pla1</I> and <I>pla2</I>, <I>pla3</I> showed pleiotropic phenotypes including enlarged embryo, seed vivipary, defects in SAM maintenance and aberrant leaf morphology. Consistent with these pleiotropic phenotypes, <I>PLA3</I> is expressed in the whole plant body, and is involved in plant hormone homeostasis. Double mutant analysis revealed that <I>PLA1</I>, <I>PLA2</I> and <I>PLA3</I> are regulated independently but function redundantly. Our results suggest that PLA3 modulates various signaling pathways associated with a number of developmental processes.</P>

Minimum Flying Capacitor for N-level Capacitor DC/DC Boost Converter

Asmarashid Ponniran,Koji Orikawa,Jun-ichi Itoh 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

This paper proposes a Flying Capacitor DC/DC Boost Converter (FCBC) with a small capacitance of the flying capacitor. As a result the size and weight of the proposed converter can be reduced. The capacitance of the flying capacitor is designed based on switching device voltage rating and regardless of the output voltage ripple influences. Moreover, the achieved maximum efficiency of the designed 3-level FCBC is 98.5% at the output power of 1kW. Finally, the effectiveness of small capacitances of the flying capacitor in the 3-level and 5-level FCBCs are investigated. The characteristics of the distorted voltage across an input voltage source and an input inductor and the distorted current to the output side which is an output capacitor and a load are investigated with several capacitances of the flying capacitors for 3-level and 5-level FCBCs. As a result, it is experimentally confirmed that the distortion of the voltage across the input voltage source and the input inductor is drastically reduced by increasing the number of level. On the other hand, the distortion of the current to the output side which is the output capacitor and the load is almost same even the number of level is increased. Therefore, the experimental results show that small capacitance of the flying capacitor can be used in the n-level FCBC.