Category SOLAR CELLS – RESEARCH AND APPLICATION PERSPECTIVES

Batteray charging model

Charging process can be approximated by capacitance circuit model that is illustrated on Fig 17 below. Capacitance C models and illustrates the capacity of the battery, while Resistance R(V, i) models and illustrates the speed of battery charging and charging dissipation. For the sake of simplification, we assume that R is always constant. The lower R, then the faster bat­tery charging process, at the same time it has lower dissipation. The main point, the good battery should has lower R.

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Figure 17. Batteray charging model [8].

Current equation for charging model based on the capacitance circuit is:

i = C*v + G(V, T, i)V (27)

Battery charging cycle on this model, has characteristic graph, which is shown on Fig 18, below.

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Figure 18. Charging Process [8]

When the battery is n...

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Batteray analysis

Electric energy storage is used to store the received energy from solar cells (at noon), in or­der to be utilized at the time when there is no available electrical energy supply from the solar cell (at night). In general, electric energy storage can be realized in the form of wet and dry batteries, super capacitors and even carrier energy storage in the form of hydrogen gas storage. Priambodo et al [7], have shown that electrical energy received from solar cell array can be stored by converting it into energy carrier in the form of H2 gas by using electrolysis method. Furthermore, the stored H2 gas can be used when there is no available supply elec­tric energy from solar cells, by using fuel cell system. In this chapter, we will limit discus­sion to battery storage only.

Solar cell syst...

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Energy management: Energy flow-in, flow-out and monitoring energy in the baterrays

The keyword for energy management in solar cell system is sustainability. The main rule, if the total electrical energy supply from solar cells to the batteries is less than the total used energy, then to maintain the sustainabilty, there must be energy supply from the external energy resource(s). Moreover, if the total electrical energy supply from solar cells to the bat­teries is more than the total used energy, then the collected energy from the solar cells must be stored to the batteries, if full, then must be delivered to the external AC buss. This pur­pose is that the excess of supply energy can be utilized by other outside consumers that con­nected to common external AC buss...

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3-Level PWM realization

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2-level PWM, which is illustrated on Fig 11, is successful to suppress the higher order har­monics, such that improving inverter efficiency close to 80%. In order to suppress more on higher order harmonics, it is proposed to use 3-level PWM. To realize the 3-level PWM con­cept, it is required a circuit that can control the synchronization of switch pairs: S: with S4 and S2 with S3, which are represented by H-bridge on Fig 7. The circuit that realizes 3-level PWM is shown on Fig 12. It is the development of basic concept of 2-level as shown on Fig 11. The 3-level PWM requires 2 equal inputs of sine wave references with 1800 phase differ­ent. The resulting 3-level PWM signal is shown on Fig. 12 below.

Подпись:Подпись:Comparisson between 2 sine reference signals dan triangle carrier signal Pulse fo...

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Sinusoidal pulse wave modulation

The basic principal in forming PWM sine wave is by comparing two waves i. e. sinus wave as the reference and triangle wave as the carrier in real time. The sine wave has frequency fr, which will be the inverter output frequency, i. e. 50 Hz or 60 Hz. The carrier signal has fre­quency fc, which becomes switching frequency in inverter circuit. The ratio between fc and fris called frequency modulation ratio, m, which is defined as:

Подпись: (21)fc ftri mf fr fsin

The typical switching frequency is between 2 kHz – 15 kHz, and sufficient for power system applications. The higher carrier frequency, the easier conducting filtering that is separating fundamental frequency output from the carrier frequency and its higher harmonics. Howev-

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er, the higher the switching or triangle frequency, it will incre...

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Full-bridge Inverter

Fig 7 shows the circuit configuration of full-bridge inverter 1-phase. The circuit consists of 4 switching elements: Si, S2 S3, and S4. The circuit operation consists of 2 conditions:

1. At S1 and S4 ON, S2 and S3 OFF, in the first half period, then the output voltage will drop on the load with value of Vdc.

2. While at S2 and S3 ON, S1 and S4 OFF, in the second half periode, then the output volt­age will drop on the load with value of – Vdc.

Подпись: Figure 7. The circuit configuration of full-bridge inverterand example of output signal. image219 Подпись: t

As explained in half-bridge inverter, to avoid short condition on VDC, the switching process should be designed such that at S1and S4ON, S2and S3must be OFF and vice versa. For the sake of this purpose, gate driver should use dead time mechanism.

From Fig 6 and Fig 7, it can be concluded that the peak-to-peak output voltage of half-bridg...

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Half-bridge inverter

Подпись: Figure 6. The circuit configuration of half-bridge inverterand example of output signal image217 Подпись: t

The following Fig 6 shows the circuit configuration of half bridge inverter. The circuit con­sists of 2 switching elements, S2 dan S2. Each element has one anti parallel diode. The switch­ing element can be transistor, MOSFET, or IGBT.

The basic operation of half-bridge inverter circuit consists of 2 conditions:

1. At S1ON during 0 – T/2 period, the output voltage will drop on the load with value of VJ2;

2. At S2On during T/2 – T period, the output voltage will drop on the load with value of – Vdc/2.

The switching process for S2and S2 must be designed such that both are not in "ON" condi­tion at the same time. If this happens, it will happen short connection input Vdc, which will cause damage on the switching elements.

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Full bridge inverter

DC-AC inverter is a vital component in the solar cell system in order to support AC buss system for AC load. DC to AC inverter technology has been developed since the beginning of electronics technology era. At the beginning, DC-to-AC inverter was developed based on sinusoidal oscillator, which is amplified by push-pull amplifier of B class that has maximum efficiency of 50%. The 50% power loss is due to instantaneous drop-voltage at the final tran­sistors on the push-pull amplifier. The fact of the 50% power loss is due to the sinusoidal form of the current and voltage running through the final transistor in DC to AC inverter circuit.

By realizing that push-pull final has maximum 50% efficiency, then full-bridge inverter tech­nology was developed to increase the efficiency of DC to AC in...

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