PID Controller Case Study

Fig.4.1 shows the general block diagram of the PID controller. The main advantages of this controller are oscillation free, higher stability and fast response. The united operation of proportional, integral and derivative control gives the control strategy for process control. It continuously calculates an error value e(t) as the variation between a preferred set point and a calculated variable and applies a rectification based on proportional, integral and derivative terms. In this controller has much attention required for selecting finest values of proportional, integral and derivative gains. The gain of the PID controller can be obtained by trial and error method. The control diagram for DC-DC boost converter is illustrated in Fig 4.2.

The deviated output of the comparator is the input of the voltage control loop (Gv). The output of the voltage controller (Iboost_ref) is then compared with the DC-DC converter output current (Iboost) feedback in the current control loop (Gi). The controller output decides the amount of duty cycle to be instructed to the PWM so as to regulate the input voltage indirectly. The panel current and voltage are filtered to remove any noise on the panel current and voltage sensing that may confuse the MPPT algorithm. To prevent the output voltage from rising higher than the rating of the components, the voltage feedback is mapped to the internal comparators, which can trip of the PWM in case the output voltage of the boost converter exceed the maximum voltage which is shown in fig.4.2. This process is repeated till the system reaches MPP. This is illustrated in the following Fig 4.4 To evaluate the performance of the Perturb & Observe and Incremental Conductance methods the solar explorer kit ‘TMDSSOLAR (P/C) EXPKIT’ is used. The TMDSSOLARPEXPKIT ships with the F28035 MCU control card is a part of a Piccolo family in the C2000 MCU

These devices are heterogeneous dual core devices which control the power stage of the device. The photograph of the hardware set up is shown in Fig. 5.1. The PV panel is commonly called as DC source with a non-linear V-I characteristics. The various techniques are used to condition the power from the PV source and it can be used in variety of applications such as to charge the batteries and feed the power to the grid. There are different power stages like 20V, 2A DC power supply and 50W solar panel can be connected to the board. On the other hand, the immediate demonstration of the power processing from the solar panel, a PV emulator power stage is integrated on the board. It consists of light sensor, control card socket, AC/DC power adapter and DC-DC buck-boost converter and so on. The buck-boost converter accepts the DC power typically 20V which generates the DC output based on the light sensor. The sensed output voltage and current makes the V-I characteristics of the PV panel emulator. The DIMM 100 control card is used to control the DC-DC boost converter stage. The boost stage is used to enhance the voltage from the panel and track the