Since solar energy generation is getting more and more important worldwide PV systems and solar parks are becoming larger consisting of an increasing number of solar panels being serially interconnected. As a consequence panels are frequently exposed to high relative potentials towards ground causing High Voltage Stress (HVS). The effect of HVS on long term stability of solar panels depending on the leakage current between solar cells and ground has been first addressed by NREL in 2005 [1). This potential degradation mechanism is not monitored by the typical PV tests listed in lEG 61215 [2). Depending on the technology different types of Potential Induced Degradation (PIO) occur. This paper is focusing on PIO of wafer based standard p-type silicon technology aiming on increasing life times for solar panels once exposed to external potentials in the field. A test setup is presented for simulation of the PIO in the lab and the influence of cell properties on PIO is demonstrated in order to reveal the cell being the precondition for the PIO. However, PIO can also be stopped or minimized on panel and system level as shown in the paper. BACKGROUND

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The Couple Tank (CT) system remains as a benchmark to investigate and test new emerging control schemes in the process industry since its dynamic emulates many factual system in the field of process control. In this paper, we examine the performance evaluation of two control algorithms, proportional derivative controller (PD) and proportional-integral-derivative controller (PID). The dynamics of the CT system is experimentally derived by system identification method and validated with a mathematical model that depicts the dynamic behaviour of the coupled tank system. Furthermore, the control schemes are expanded on the model obtained through system identification method. The simulation results showed that the PD controller did not meet all the specified control objectives. To improve the response an integral controller was incorporated to the PD controller and the response was compared to that of the PID controller and uncompensated system. The results revealed that the PID controller satisfied all the control goals. However, the PD controller was more satisfactory in terms of time response criteria.

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