Efficient Voltage Regulation for Stand Alone Photovoltaic Cell using PI Controller for AC Voltage Application
Abstract— This paper focuses on the renewable energy system PV (Photo Voltaic) Cell in stand alone model. The system consisting of solar PV cell, DC-DC Boost converter, and inverter coupled to the load system. An 18V photovoltaic cell and a DC-DC boost converter is designed for the purpose of boosting the PV cell output voltage. The advantage of using the proposed DC-DC converters are only one sensor is required, high power density, more efficient with reduced complexity of control. An inverter is used to convert DC to AC for application purposes. A control technique is adopted for controlling the entire converter system. The PI controller is designed for DC-DC boost converter and inverter using standard Ziegler-Nicholz technique. The performance of the system is analyzed under both variation in temperature of PV cell and load parameter for the feasibility of controller.
Theoretical analysis and simulation results are provided to verify its performance.
Keywords: PV Cell, DC-DC Converter, DC-AC Converter, PI Controller, Pulse Width Modulation, Boost Converter.
I. INTRODUCTION
One of the major issues confronting users and designers of [1] solar energy system is the random, fluctuating nature of the energy sources. This makes them unpredictable’ are even ‘unreliable’ in the eyes of some compared to traditional supplies of electric energy. In reality, the load on electric network supplied is itself random, being subject to seasonal and environmental influences such as the weather. All plant, whether, renewable or not, suffers from occasional breakdown, which also impacts on supply availability. This gives a basis of designing renewable energy system – not on the basis of an unachievable 100% reliability but to a reliability (are more strictly ‘availability’) approaching that of a traditional sub urban grid supply. The solar distributions were used to obtain a net system availability using convolution processes. This paper presents a different approach one based on designing of PV cell, modeling of DC-DC boost converter and Inverter. An PI controller is designed to ensure regulation of system ,under supply and load disturbances. Finally the system is analyzed using MATLAB Semolina tool box to verify the performance.
II. A STAND ALONE PV SYSTEM
Figure 1 shows the block diagram of PI controller for a standalone PV system. The power from Photovoltaic Cell
is given to the DC-DC boost converter where the input
voltage is boosted up to the required DC voltage.
Then given to the DC-AC converter and later this arrangement is controlled through a controller. The actual Parameter, which has to be controlled, is compared with the reference parameter and this error is fed as an input to the controller. The controller takes the error as input and generates a corresponding control signal. This is investigated in this thesis for better control algorithm.
II. a.. PV CELL
Solar cells have many applications [2]-[3]. They have long been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth-orbiting satellites and space probes, consumer systems, e.g. handheld calculators or wrist watches, remote radiotelephones and water pumping applications. More recently, they are starting to be used in assemblies of solar modules (photovoltaic arrays) connected to the electricity grid through an inverter, often in combination with a net metering arrangement. Solar cells are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from the elements (rain, hail, etc.).
Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak dc voltage and current. The power output of a solar array is measured in watts or kilowatts. In order to calculate the typical energy needs of the application, a measurement in watt-hours, kilowatt-hours or kilowatt-hours per day is often used. A rule of thumb commonly used is that peak power time’s 20% gives average power, equating to one kW peak producing 4.8 kWh per day.

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