Category SOLAR CELLS – RESEARCH AND APPLICATION PERSPECTIVES

DC to AC inverter for AC buss system

When the distance between renewable energy clusters of solar cells, batteries and electrical loads is relatively far (can be hundred kms) and the electrical loads mostly are AC electrical loads, then it is necessary to consider to use AC buss system, which supported by DC to AC

inverters. By utilizing AC buss system, for long distance electrical transmission, the increase of AC voltage can be conducted by using passive transformator, which is common to be used. However, the integration process of several renewable energy autonomy systems is relatively more complex than integration in DC buss system. The problems in AC buss inte­gration are due to more parameters that must be synchronized, such as voltage, frequency and phase...

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Discontinuous Conduction Mode (DCM)

At this mode, the inductor current will drop to zero before finishing one switching period, as shown on Fig 5. As the CCM analysis, the voltage inductor integral during one period is zero.

 

ViDTs + (Vi – Vo)D1Ts = 0

 

(11)

 

Then

 

Vo Dj + D

V = D1

 

(12)

 

and

 

10 = Dj

11 Dj + D

 

(13)

 

Lb vL(t)

 

Lb h(t)

 

Lb

 

image215

image319

a. Mode 1(0 < t < ton);

b. Подпись: c.Mode 2(ton < t < (D+Dj)Ts); Mode 3(D + D1)Ts< t < Ts

From Fig 5.c, the average input current is equal to the inductor current,

v.

Ii =2L7DTS(D + D1) (14)

By using equation (13),

io=( tlt; )DD1 (15)

In practice, duty cycle D should change to respone the Vt change, such that obtaining con­stant Vo...

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Continuous Conduction Mode (CCM)

Mode 1 (0 < t < tn),

Mode 1 starts, when switch S (MOSFET) switched on at t = 0 until t = ton. The equivalent cir­cuit for Mode 1 is shown on the following Fig 4a. By assuming that the serial resistance val­ue DC voltage source is relatively low, there will be an inductor current transient iL(t) larger than zero and increase linearly at the beginning of transient. Inductor voltage is VL= Vi.

Mode 2 (tn< t < Ts ),

Mode 2 starts, when switch S (MOSFET) switched off at t = ton until t = Ts. The equivalent circuit for Mode 2 is shown on Fig 4b. Inductor voltage, VL in this period is Vt – Vo. In this case V< Vo, it means in Mode 2, VLis in opposite direction to VL in Mode 1.

In steady state operation, the signal formed due to switching is repeated over all the time...

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Boost converter for DC buss system

Boost converter is an electronic circuit for DC to DC converting. It functions to increase volt­age VDC higher, i. e. by controlling the signal driver duty cycle. Boost Converter base circuit requires only 4 fundamental components, which are: inductor, electronic switch, diode and output capacitor, shown on Fig 3. The converter circuit can be operated in 2 modes, which depends on the energy storage capacities and the relative length of the switching period [3]. Those 2 methods are CCM (Continuous Conduction Mode) and DCM (Discontinuous Coduction Mode), where CCM is for efficient power conversion and DCM is for low power conver – sion[3].

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Buss system

Solar cell produces DC electric energy. For solar cell system, where the solar cell array has radius not more than 100-m to batteries and electrical loads, it is effective and cost efficient to be connected by DC buss system. By using DC buss system, in order to transfer electrical energy from solar cells to batteries and loads, the parameter needs to be considered is volt­age. The DC buss is the most efficient and cost effective, since it does not require electrical conversion from DC to AC. DC buss can be extended for more than 100-m, even can be more than several kms...

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Solar cell and eficiency

The main characteristic of solar cell is I-V curve. It has several derivative parameters such asIsc (short circuit current), Voc (open circuit voltage) and the maximum possible delivered energy Pmp = Vmp ■ Imp, as shown on the following Fig 2.

image307 Подпись: (2)

The main parameter that determines the solar cell efficiency is the maximum square area (power) as form of multiplication I-V (Pmp = Vm? ■ I ), which is a maximum square formed inside I-V curve as shown on Fig 2 above. The next derivative parameter is fill factor FF that represents the ratio PMP to the product VOC and ISC. This parameter gives an insight abou – thow "square" is the output characteristic.

Подпись: h image310 Подпись: (3)

In the case of solar cell with sufficient efficiency, in general, it has FF between 0.7 and 0.85...

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Electric energy management in an autonomy unit of solar cell system

A perspective

There are at least 2 strategic ways to implement renewable energy resources especially solar cell systems to fulfill the national electrical energy needs. The first strategy is to encourage the people to fulfill their own basic residential electric energy need by building private solar cell system. The second strategy is to let the Government as the regulator to drive a consorti­um of companies to build large plants of solar cell system to fulfill the regional or national electric energy need. Of course, the consortium will require a large amount of financial in­vestment at the starting point, however along with the time, the long term electric cost will be getting lower and more cost effective, since solar cell system requires very minimum maintenance cost and free of sola...

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Electric Energy Management and Engineering in Solar Cell System

Purnomo Sidi Priambodo, Didik Sukoco, Wahyudi Purnomo, Harry Sudibyo and Djoko Hartanto

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/52572

1. Introduction

Solar cell system has many competitive advantages in comparisson to other renewable ener­gy resources. For instance, wind-turbin is very dependable to geographical location and has very high noise pollution if applied in residential area. Other example is micro-hydro, which depends on altitude and available in very limited locations. Furthermore, nuclear energy should be forgotten since its high radioactive risk...

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