Compensators
- 1. compensators Types of compensators S-Plane representation of compensator Comparision of Compensators Prepared By Mr.K.Jawahar, M.E., Assistant Professor Department of EEE Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 2. Compensator • The control system are designed to perform specific tasks. The requirement of a control system are usually specified as performance specifications. • The specifications related to accuracy, relative stability and speed of the response. The design problem may be stated as follows: • When a set of specifications are given for a system, then a suitable compensator should be designed so that the overall system will meet the given specification. • The compensation schemes used for feedback control system is either series compensation or parallel feedback compensation. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 3. The choice between series and parallel compensation depends on: 1. Nature of signals in the system 2. Power levels at various points 3. Components available 4. Designer’s experience 5. Economic considerations and so on. The different types of electrical or electronics compensators used are Lag compensator Lead compensator Lag-lead compensator Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 4. In control systems, compensation is required in the following situations, • When the system is absolutely unstable, then compensation is required to stabilize the system and also to meet the desired performance. • When the system is stable, compensation is provided to obtain the desired performance. The systems with type number 2 and above are usually absolutely unstable systems. Hence for systems with type number 2 and above, lead compensation is required, because the lead compensator increases the margin of stability. In the systems with type number 1 or 0, stability is achieved by adjusting the gain. In such cases any of the three compensators may be used to obtain the desired performance. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 5. S-plane representation of LAG compensator: • The lag compensator has a pole at s=-1/ßT and a zero at s=-1/T. • Here ß>1, so the zero is located to the left of the pole on the negative real axis. where T >0 and ß >1 S-plane representation of LEAD compensator: • The lead compensator has a zero at s=-1/T and a pole at s=-1/αT. • Here α<1, so the zero is closer to the origin than the pole. where T >0 and α <1 Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 6. S-plane representation of LAG-LEAD compensator: • The lag selection has one real pole and one real zero with pole to the right of zero. • The lead selection also has one real pole and one real zero but the zero is to the right of the pole. Where ß > 1 and 0<α<1 Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 7. Realization of lag compensator using electrical network: Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 8. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 9. Realization of lead compensator using electrical network: Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 10. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 11. S. No Lag Compensator LeadCompensator Lag-Leadcompensator 1 A compensator having the characteristics of a lag network is called lag compensator. A compensator having the characteristics of a lead network is called lead compensator. A compensator having the characteristics of a lag-lead network is called lag-lead compensator. 2 If a sinusoidal signal is applied, then in steady state the output will have a phase lag with respect to the input. If a sinusoidal signal is applied, then in steady state the output will have a phase lead with respect to the input. If a sinusoidal signal is applied, then in steady state both phase lag and lead occurs in the output, but in different frequency region. 3 Lag compensation results in a large improvement in steady state performance but results in slower response due to reduced bandwidth. The lead compensation increases the bandwidth, which improves the speed of the response and also reduces the amount of overshoot. A lag-lead compensation combines the advantages of lag and lead compensations. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE
- 12. Reference: • A.Nagoor Kani, “ Control Systems”, RBA Publications, June 2012. Compensators Kongunadunadu College of Engineering and Technology Depar tment of EEE