Week 1

• The aim of Week 1

In the first week, the basic circuit model and theoretic information were determined. Several tests were conducted which indicated that the method to realize power factor correction needed to reconsidered and improved. 

• Background theory

Power factor is defined as the ratio of real power to the apparent power which is utilized to measure the efficiency of the power system. An triangle could be used to demonstrate the relationship between these parameters in the figure 1. 

Figure 1. Triangle relationship of Power

The value of power factor will tend to 1 if the efficiency of the system is high enough. Therefore, in order to improve the operating efficiency, the reactive power ought to be reduced to minimize the theta in the triangle. 

• Testing and Results

The most straightest way to increase PF is to add capacitors to reduce Q. In this project, capacitor banks controlled by BJT were utilized to compensate the negative reactive power. 

In order to decide the value of added capacitor, the value of PF ought to be determined. In this project, zero crossing detector will be applied to output the phase pulse of the voltage and current of the load. The basic simulation is shown below.

Figure 2. Simulation Circuit in Proteus

However, the actual circuit was not built successfully and there existed problems in the simulation. These problems need to be fixed in the second week. 

The output pulses of load voltage and current will be input into ARM, where the input time will be recorded and the differences will be calculated. Then the time difference will be converted into phase angle and capacitors could be added.