Modeling and Simulation of an off Grid PV system for with Battery Backup for Remote and Rural Area Network

Modeling and Simulation of an off Grid PV system for with Battery Backup for Remote and Rural Area Network

Ashish Dhanowa M.tech-EE Dept., UIET, KUK

Vijay Kumar Garg Asst. Prof., EE-Dept., UIET, KUK

Abstract – Solar PV systems are now popular everywhere in world. These systems generates electricity to meet the demands along with conventional resources but also electrifying the rural areas where grid facility not available. In this paper an off grid PV system for a domestic load (a house load) modelled and simulated in matlab.

1. INTRODUCTION

   Solar off grid PV system so called because there is no grid connection available and PV system work independently. For a house load an off grid PV system have components like modules, battery (if battery backup), controller converter and inverter (as most of appliances are running on AC). For whole system design it is necessary to estimate the load and then each component is selected as per ratings.

2. Load Estimation

   In a house following appliances are common and table 1 shows appliances with their rating and load estimations.

   Table 1 Load estimations

   LOAD	W AT TS	Q U A N T I T Y	HO UR /D AY	TOTAL WATTS	TOTAL WATTS- HOUR/DAY
   TV	15 0	1	6	150	900
   CFL	20	4	10	80	800
   REFRIG ERATO R	50 0	1	12	500	6000
   FAN	40	3	8	120	720
   COMPU TER	15 0	1	2	150	300
   TOTAL				960 1000	8720 8800

   So a house load is = 1 kW or 8800 Wh/day

   For 1 kW load following PV components are required as shown in table 2.

   Table 2 PV Components and their ratings

   COMPONENT	DESCRIPTION	RESULT
   Load	Estimated	1 kW
   PV array	Size	2.5 kW
   	Total panels	10
   	In series	2
   	In parallel	5
   	Panel power	295 Wp
   Charge controller	Capacity	52
   	Number of controller	3
   Inverter	Size	1.25 kVA

   The PV panel or module has following specifications:

   Table 3 PV module specifications

   Parameter	Value
   Peak power	295 watts
   Module Efficiency	14.7%
   Peak power voltage	36.51 volts
   Peak power current	8.08 amps
   Open circuit voltage	44.78 volts
   Short circuit current	8.30 amps
   Number of cells	72 cells
   Max. System voltage	1000 volts DC

3. PV ARRAY MODELING

   PV array in matlab Simulink is a mathematical model which uses the equations of equivalent circuit model of solar cell. This PV array configure according to requirement of model. Figure shows a PV array:

   Figure 1 PV array subsystem

4. BUCK CONVERTER MODELING

   A buck converter with fixed duty cycle is modeled to give constant output DC of 48V. The circuit and Simulink model of buck converter shown in figure below:

   Figure 2 Buck converter subsystem

   Figure 3 Buck converter model

   Here values of inductor (L), capacitor (C), duty cycle (D) and PWM switching frequency () are:

   > 0.0056 = 1.567

   D = 0.42 and = 10000

5. INVERTER MODELING

   Here all the appliances need AC power for their working so the inverter is necessary in the system which gives AC output with desired level (120V/230V). Inverter in this model build by using PWM technique. Sine wave and triangular wave is compared to generate PWM which used to switching on/off semiconductor switches and DC input is converted in to AC. A transformer for step up of converted AC is used to get desire AC voltage level (230V here). Below figure shows inverter model in matlab.

   Figure 4 Inverter subsystem

   Figure 5 Inverter model

6. OFF GRID PV SYSTEM MODEL WITH NO LOAD The models of PV array, Buck converter and Inverter is connected to make an off grid PV system model. Figure below shows the PV system in Matlab Simulink without load.

   Figure 6 PV system Simulink model without load

   At no load and standard operating conditions (1kW/2 irradiance and 25 operating temperature) following results are obtained.

   Figure 7 Output Power & Voltage of PV array

   Figure 8 PV array current & Buck converter output

   Figure 9 Inverter Output

7. OFF GRID PV SYSTEM WITH LOAD

   Now model is connected to 1 kW load which is estimated in table 1. Figure shows the model with load and results obtained from simulation. These results are taken at standard operating conditions (1 kW/2 Irradiance and 25 operating temperature of array).

   Figure 10 PV system with load

   Figure 11 Output Power, Voltage & current of PV array

   Figure 12 Buck converter & inverter (across load) output

   8 BATTERY OPERATION

   Battery in the off-grid system is for supplying load when there is no sun irradiance on the solar panels. Battery charged from array when load is less and excess power is generated by array and battery discharge through load when there is no power from the array. To prevent the under discharging of battery state of charge is monitored and when it less than 25% battery disconnected form the load by breaker. Below figure shows the battery in the PV system simulation.

   1. CONCLUSION

      This study presents a simple but efficient off-grid photovoltaic system for a domestic load that can meet the daily load demands. The results show that the average daily load requirement of a house of 8800 Wh/day. In order to meet this load demand, an array of 10 solar panels required. Modeling and simulation of system shows the results for load and no load conditions at standard operating conditions.

   2. REFERENCES

1. Design of an off grid photovoltaic system: A case study of government technical collage, wudil, kano state by Ishaq M, Ibrahim U Haruna and Abubakar Harnua from Bayero University, Kano, Nigeria. IJSTR volume 2, issue 12, dec- 2013.

2. Appliance ratings from website – http://www.absak.com/library/power-consumption-table

3. Simulation of grid connected photovoltaic system by Jingzhe Song (js4153).

4. Circuit Simulation for Solar Power Maximum Power Point Tracking with Different Buck-Boost Converter Topologies by Jaw-Kuen Shiau *, Min-Yi Lee , Yu-Chen Wei, and Bo- Chih hen, Department of Aerospace Engineering, Tamkang University, Tamsui, New Taipei City, 25137, Taiwan.

5. A PDF of Design Calculations for Buck-Boost Converters Application Report SLVA535A August 2012 Revised September 2012, by Texas Instruments.

6. Inverter explanation and techniques https://www.wpi.edu/Pubs/E-project/Available/E-project- 042711-190851/unrestricted/PWM_Techniques_final.pdf

7. Solar Panel Mathematical Modeling Using Simulink by Chandani Sharma (Research Scholar) Anamika Jain (HOD), Electronics & Communication Engg. Graphic Era University, Dehradun Uttrakhand, India published in Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.67-72.

8. Using small-scale solar power plant to supply rural homes with electricity in the Ngan-ha locality (Cameroon) by Thang Dieudonné (Global Village Cameoon, Cameroon) and Fongnzossie Evariste (University of Douala, Advanced School for Technical Teachers Training, Douala).

9. Website – www.pveducation.com

10. Website –

http://www.openelectrical.org/wiki/index.php?title=Solar_Sy stem_Sizing