Chapter 3: PV-ARRAY CONFIGURATIONS3.1 IntroductionThe various PV array configurations are employed such as Series, Parallel, TCT, SP to meet certain voltage and power specifications. The various simulink models of the above configurations are studied under full irradiance and under partial shading condition to determine the best suitable configuration. In our study a 3×3 PV array is studied and its P-V and I-V curves are plotted using simulation models.
Various cases which include specific patterns in which given sequence of PV cells are shaded are taken to study the effect of partial shading. The shading patterns considered in the study is shown in Figure 3.1. The case where no shading occurs is also studiedleft61087000FIGURE 3.1Our main objective is to identify if different configurations of the PV Arrays would result in lower losses due to partial shading effects.
This is done by setting up different configurations in MATLAB and simulating partial shading by changing the insolation levels. Here the insolation level without any partial shading is taken as to be 1000W/m2 however under partial shading the insolation level is taken as 500W/m23.2 PV Array Configurations3.2.1 Total Cross Tied Configuration (TCT)TCT configuration which stands for Total Cross Tied is composed of serially connected paralleled PV panels.
It is seen that in the TCT configuration the V-P curve exhibits two peaks. TCT scheme is widely used to remove the impact of partial shading. It performs better than other configurations due to the presence of cross ties under partially shaded conditionAccording to a study assessing the manufacturing cost of TCT-connected modules, TCT-connected modules do not cost more than the SP-connected modules during mass level productionAccording to a study assessing the manufacturing cost of TCT-connected modules, TCT-connected modules do not cost more than the SP-connected modules during mass level productiThe basic Simulink model of a TCT configuration without any partial shading along with the P-V and I-V graph is plotted shown is shown in figure 3.2a2540-4445FIGURE 3.
2a3.2.2 Series Parallel Configuration (SP)SP configuration stands for Series Parallel configuration which consists of parallelly connected series strings of PV panels.
3.2.3 Parallel ConfigurationParallel configuration consists of parallelly connected string of PV panel. In a parallel configuration during shading there is no current limitations as the total string current will be the sum of individual panel current and the variation in voltage is also very less. Thus in parallel connection operation panels operate at their maximum power points and hence ensuring maximum power extraction . 3.
2.4 Series ConfigurationSeries configuration consists of serially connected PV panel so that a single current flows through the array. Series configuration generally impose current limitations as when during shading , the shaded panel is operating at its optimal power and the bypass diode connected across is inactive then the non shaded panels will be operating at points far away from their maximum power points . This increases with increase in shade intensity 3.3 Partial Shading Of PV Array ConfigurationsAll cases of partial shading are studied by changing the irradiation levels of certain PV modules.
For better understanding refer to fig 3.3 which represents the shading patterns. Also P-V and I-V curves under no shading are studied. This given section will cover three cases of shading for each configuration. 443103013970Case 300Case 3243141513970Case2020000Case237401513970Case100Case1Note: Case 4 is also studied where in no partial shading is considered3.3.1 TCT ShadingCase 1As explained above TCT configuration is shaded as per the figure showing case 1 and P-V and I-V curves are plotted