Novel DC Switch and DC Socket for High Voltage DC Power Feeding Systems

Hirofumi MATSUO*, Shinji MATSUMOTO*, Masayuki SUETOMI*, Shuji FUJINO*,

Koosuke HARADA**, Wengzong LIN*** and Yue SUI***

*Graduate School of Science & Technology, Nagasaki University, Nagasaki 852-8521, Japan **Research Institute of Energy Electronics, Sojo University, Kumamoto 860-8691, Japan

***Faculty of Engineering of Minjiang University, Fuzhou 350108, China

h-matsuo@nagasaki-u.ac.jp Abstract- This paper presents a novel and reliable DC switch

and DC socket for high voltage DC power feeding system, in which the arc does not occur when the are turned on/off and inserted/removed, respectively. The novel prototype DC switch and DC socket have been made. Both are almost same circuit configuration and operation principle and then composed of two mechanical relays and a single MOSFET.

It has been tested for the proposed DC switch to protect not only the arc but also thermal problem. As a result, it is confirmed that the arc thermal problem do not occur when the MOSFET and relays are turned on/off and relays are on in steady state, respectively, and that they have the excellent performance characteristics using simple semiconductor snubbers with the overvoltage clamp function.

I. INTRODUCTION Nowadays, a great interest in the dispersed source using

green electrical energy has been taken from the view point of the environmental problem of glob al warming due to the carbon dioxide in which the solar cell, fuel cell, wind turbine and so on are employed [1-11]. Conventionally, the AC power feeding systems with the voltage of 100 ~400 V have been used generally in the communication building, green home and so forth. In such systems, it seems that there exists the zero-cross point in the AC current. Therefore, there is no need to develop specially the new AC switch, plug and socket apparatuses. Recently, the DC power feeding systems with the high voltage of 300 ~ 400 V have been developed and employed widely in the data center, communication building and so forth. In these systems, it is required strongly that the reliable DC switch, plug and socket apparatus should be developed to protect a fire, electrical shock and stress [12-15].

This paper presents a novel and reliable DC switch, and

DC socket, in which the arc and rush currents and surge voltage do not occur when they are turned-on / off and inserted / removed. The novel prototype DC switch and DC socket have been made, both are almost same circuit configuration and operation principle and composed of two

mechanical relays and a single MOSFET. It has been tested in the proposed DC switch and to protect not only the surge voltage but also thermal problem caused by the arc and rush currents. As a result, it is confirmed that the surge voltage and thermal problem do not occur when the MOSFET and two relays are turned on / off and on in steady state, and the DC switch and DC socket have the excellent steady state and dynamic characteristics.

II. CIRCUIT CONFIGURATION AND OPERATION

2.1 Circuit Configuration Fig. 1 shows the proposed DC switch apparatus composed

of the micro-switch, a single MOSFET Q1 (R6046ANZ) and two mechanical relays RY2 and RY3 (ALFG2PF24). The internal resistance of Q1, RY2 and RY3 are 0.065 Ω, 0.050 Ω, 0.050 Ω, respectively, which are measured values. Ed and Z are the DC high voltage source and load impedance, respectively. The DC current I is the current through the DC switch apparatus. The micro-switch is the controller and generates the basic signals to control Q1, RY2 and RY3.

2.2 Circuit Operation Fig. 2 shows the timing waveforms to drive the DC switch

apparatus. In this figure, SQ1, SRY2 and SRY3 are driving signals for the MOSFET Q1, mechanical switch RY2 and RY3, respectively. The operation of the semiconductor switch is divided into 5 states of State 1 through State 5 shown in Table 1. In this case, each state is determined by the combination of the element conditions, in which Q1, RY2 and RY3 are ON and / or OFF. Table 2 shows the operation modes, in which Mode I and Mode II are the turn-on and turn-off modes of the DC switch, respectively. In this table, the mode means the sequence of several states.

MOSFET Q1 and mechanical relay RY2 are ON in State 4,

and then the DC current I flows through Q1 and RY2. The power loss in Q1 is smaller than that in RY2. As shown in Fig. 2, the time intervals when the current I flow through only Q1 in State 3 in Mode I and II are T2-T1 and T5-T4,

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respectively. As a result it is expected that the energy loss in Q1 can be made small by shortening T2-T1 and T5-T4 and that the heat-sink of Q1 can be removed. In Q1 of this DC switch, the power loss is 6.5 W in State 3 and 1.23 W in State 4, respectively.

III. EXPERIMENTAL RESULT Fig. 3 shows the voltage and current waveforms of the

mechanical relay and MOSFET, in which is turned-on. The waveforms, in which only the mechanical relay and proposed DC switch are used, are shown in Fig. 3(a) and Fig. 3(b), respectively. In this experiment, Ed = 300 V and I = 10A in Fig. 1, in which Z = R // C, R = 30 Ω and C = 47 uF. It is seen in these figures that there exists the surge current caused by the capacitive load when only the mechanical relay is used and turned-on and that the surge current is not large when the DC MOSFET switch is done. Fig. 4 shows the current and voltage waveforms of the mechanical relay which is turned-off. The relay has been welded and broken after its on and off operation for about tenth times. The prototype DC switch and DC socket using this proposed DC switch have been made and tested. As a result, it is confirmed that the MOSFET in the prototype switch can be used without the heat-sink as shown in Fig. 5 and that the socket can be made small in size of 90 mm × 45 mm × 30 mm as shown in Fig. 6.

Further, the final full paper presents in detail with the

simulation and experimental results about not only the turn-on waveforms of the voltages across and currents through the mechanical relay and proposed DC semiconductor switch but also turn-off ones, considering the parasitic inductance of the DC feeding cables. Also, the time interval T1, T2, T3, T4 and T5 are determined adequately to solve the thermal problem of the DC MOSFET switch.

IV. CONCLUSION A novel DC switch and DC socket have been proposed and

the prototypes of DC switch and DC socket have been made and tested. As a result it has been confirmed that thermal problem due to the arc and rush currents and surge voltage does not occur in the high voltage DC feeding system and that their performance characteristics are excellent using simple semiconductor snubbers with the high voltage clamp function.

This work was supported by the foundation of NEDO

(New Energy Development Organization) of Japan Government in 2009 and 2010.

Fig.1. Basic circuit of the proposed semiconductor switch

Fig.2. Timing waveforms to drive the semiconductor switch

Z

Table 1. States in the proposed DC switch

Table 2. Operation modes

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Current

Voltage

Current

Voltage

REFERENCE

［ 1］ H. Matsuo, et al: “New Solar Cell Power Supply System Using a Boost Type Bidirectional DC-DC Converter”, IEEE Transactions on Industrial Electronics, Vol. IE-31, No. 1, pp.51-55, Feb. 1984

［ 2］ H. Matsuo, et al: “New Maximum Power Tracker of the Solar Cell Power Supply System”, Proceedings of the 1st IEEE International Photovoltaic Science and Engineering Conference, pp.609-612, Nov. 1984

［ 3］ H. Matsuo, et al: “New Solar Cell Power Supply System Using a Bidirectional PWM Inverter with Energy Storage Transformer”, Proceedings of the 1st IEEE International Photovoltaic Science and Engineering Conference, pp.327-330, Nov. 1984

［ 4］ K. Kobayashi, H. Matsuo and Y. Sekine, “Novel Solar-Cell Power Supply System Using a Multiple-Input DC-DC Converter”, IEEE Transactions onIndustrial Electronics, Vol. 53, No. 1, pp.281-286, Nov. 2005

Current

Voltage

(a) Only mechanical relay

Fig.4. Current and voltage waveforms of the mechanical relay which is turned-off, welded and broken.

Fig. 6. Prototype DC socket (300 V, 30 A)

(a) Top view (b) Bottom view

(b) MOSFET is the proposed DC semiconductor switch

Fig.3. Current and voltage waveforms of the mechanical relay and MOSFET which are turned-on

I :50A/div V:50V/div H:25us/div

GND

I :50A/div V:50V/div H:25us/div

GND

I :50A/div V:50V/div H:25us/div

GND

Fig.5. Prototype DC switch (300V, 30A)

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[5] H. Matsuo and K. Kobayashi: “DC power distribution system”, Japanese Patent No. 4084316, Application date: February 13, 2004, 2004-2

［ 6］ S. Meenakshi, K. Rajambal, C. Chellamuthu, and S.Elangovan, “Intelligent controller for a stand-alonehybrid generation system”, in Proc. IEEE Power India Conf., 2006.

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［ 9］ K. Kobayashi, H. Matsuo, Y. Sekine, “Novel solar-cell power supply system using a multiple-input dc-dc converter”, IEEE Trans. Ind. Electron., Vol. 53, No. 1, pp.281-286, Feb. 2006.

［ 10］ K. Kobayashi, H. Matsuo, Y. Sekine, “An excellent operating point tracker of the solar-cell power supply system”, IEEE Trans. Ind. Electron., Vol. 53, No. 2, pp.495-499, Apr. 2006.

［ 11］ S. K. Kim, J. H. Jeon, C. H. Cho, J. B. Ahn, S. H. Kwon, “Dynamic modeling and control of a grid-connected hybrid generation system with versatile power transfer”, IEEE Trans. Ind. Electron., Vol. 55, No. 4, pp.1677-1688, Apr. 2008.

[12] H. Matsuo and K. Kobayashi: “DC Switch”, Japanese Patent No. 4473029, Application date: March 31, 2004, 2004-3

[13 ] H. Matsuo and K. Kobayashi: “DC Socket”, Japanese Patent No. 430865, Application date: March 31, 2004, 2004-3

[14 ] H. Matsuo and K. Kobayashi: “DC Plug”, Japanese Patent No. 430864, Application date: March 31, 2004, 2004-3

[15] S. Matsumoto and H. Matsuo et al: “ Novel DC Switch and Socket for High Voltage DC Power Feeding Systems”, IEICEJ Technical Report, 5 pages, No. 9, September, 2011, 2011-9

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