Proceedings- Books 3 125 Design of Discrete PID Controller to Improve Performance of Power Factor Correction (PFC) Circuit Abstract – Recently, an adjustable speed drive (ASD) is widely used on many industries. A power factor is one of important aspect to be considered, since it can drawback reactive power to supply side during its operating condition. This paper presents a discrete PID algorithm which applied by inner and outer loops controller circuit. This makes a better control action on power factor correction (PFC) circuit based on buck topology. Three phase IGBT inverter loaded by 10 hp 220/380 V 50 Hz squirrel cage induction motor is used as a PFC load to meet real implementation on industries. This proposed system is designed and simulated by PSIM software. From the simulation result, a control circuit achieve its best performance. A power factor increase significantly. Keywords: discrete PID controller, PID algorithm, power factor, PFC circuit, adjustable speed drive. 1 Introduction ASD (also called VSD or VFD) is widely used on many industries. AC adjustable-speed drives (ASD) are growing in popularity, mainly because ac motors are simpler than dc motors. Moreover, recent advances in inverter and microprocessor technology have reduced controller cost and improved its performance and reliability [1]. Figure 1. Generic block diagram of ASD AC ASD can be thought of as electrical control devices that change the operating speed of a motor. ASD’s are able to vary the operating speed of the motor by changing the electrical frequency input to the motor. The basic steps for this process are shown in the block diagram of Figure 1, and the circuit is known as a DC link converter. The first step is to convert AC power into DC power. The second step is to convert this DC power back into AC at the desired frequency [ 1],[2]. Although they can improve displacement power factor (DPF), modern ASDs also create harmonics, which reduce real power factor. (Real power factor includes harmonics and DPF.) For instance, while a ASD can improve DPF to close to 1.0, the harmonics generated by the ASD can cause the real power factor to decline to between 0.75 and 0.80. These harmonic currents (most often the fifth and seventh harmonics) tend to exacerbate resistance losses and can even negate the transformer capacity benefits of improved DPF [4], [5],[6]. A power factor is one of important aspect to be considered, since it can drawback reactive power to supply side during its operating condition. To increase power factor is to make the input to a power supply (rectifier) look like a simple resistor. An active power factor corrector does here by programming the input current in response to the input voltage [6]. Power factor (p.f) is defined as the ratio of the real power (P in Watt) to the apparent power (S in VA), i.e., S P f p = . [1] or, it can be written as, VI P f p = . [2] where P is the input real power, V is the root-mean- square (rms) input voltage and I is the rms input current. There are two factors affect the power factor. First, if the input voltage and current are not in phase, P will be less than the product of V and I, leading to a low power factor. The worst case corresponds to a 90 o phase shift between V and I. Second, if the current contains a high harmonic content, I becomes large, again leading to a low power factor. Mathematically we can express the power factor as the product of a displacement factor (DPF) and a distortion factor, i.e., .... 1 1 cos . 2 1 3 2 1 2 +       +       + • = I I I I f p ϕ [3] Aripriharta, Lecturer State Universty of Malang (UM) & Member of IAENG, aripriharta@um.ac.id Setiadi Cahyono Putro, Senior Lecturer State Universty of Malang (UM), scp0324@yahoo.com Displacement factor Distortion factor