Presentation no. 2 Control of Biomass plant Close loop control for biomass plant

PRESENTATION NO.2

Control of Biomass plant

Close loop control for biomass plant

Introduction

• The gas turbine is one of the most commonly used sources of power generation in our world today.
• The biogas fuels from the biomass generation operation can be conditioned to be used as fuels for the turbine.
• Heavy duty gas turbines (HDGT) are widely used for power generation because of its long life and fuel flexibility etc.
• We can classify HDGT in to single shaft and twin shaft.
• Speedtronic governor and Woodward governor respectively are used for speed control.

Modelling of Gas Turbine

• The transfer function of the gas turbine model includes various limiters: Fuel system, compressor and turbine system
• The HDGT model has three limiters such as: speed limiter, temperature limiter and acceleration limiter.
• All the above is connected to low value select unit (LVS) which select the minimum amount of fuel for limiters.
• Fuel system dynamics includes fuel system actuator and valve positioner. 
• The gas turbine dynamics includes the combustor delay and torque function

Functional block diagram of Single shaft HDGT

The Speed Governor

• The error signal represent the different between two speeds the first is the refrence speed Nr and the actual speed N which drives the speed governor.
• The speed governor is characterized by either droop or isochronous governor control.
• The transfer function for the speed governor is given by the following equation:

The Gas-turbine Fuel System

• Based on the demand signal Wd the gas-turbine fuel system generate produce the fuel signal Wf. 
• Mainly the gas-turbine system consist of two components :
• First: valve positioner, represented by the following equation:
• Second: fuel system actuator, represented by the equation: 

The Torque

• The torque characteristics depends on many different elements like: fuel supply (Wf) and turbine speed (N).
• Also The lower limit of fuel flow (Wfl) and the rated speed of the turbine (Nrated) are also responsible for the torque, F2.
• The torque equation as follow:

The Acceleration limiter

• The acutual speed of the turbine change due to the consept of acceleration.
• The acceleration controller control the speed of the gas turbine by adjusting the fuel flow in the startup stage.
• The transfer function model of the acceleration control loop is shown:

The Temperature Controller

• The exhaust temperature(Tx) is mainly depended on two parameters,the fuel suuply signal and the actual speed of gas the turbine.this realtion could be represented by the following equation:
• Where:
• Tr:refrence temp
• Wf:the fuel supply signal
• N:the speed of the gas turbine

The Temperature Controller

• In the temp controller could be measurerd by:
• Thermocouple:represented by the TF
• Radition shield:represented by the TF 

The temperature controller only will be active when Tx value exceeds the set point value given by the refrence temoerature.the TF for the temperature controller as follow 

The Temperature limiter

• Combinig all the mentioned above from the thermocouple,radination shield to the temp controller,we can represent the transfer function model of temperature limiter loop as follow:

HDGT Plant 

HDGT parameters

Transfer Function Model for HDGT

• The LTFM of HDGT model has been obtained by superposition of the transfer function between the input signals and output signal from. Reference speed, Fuel flow rate under no load condition, Load torque and fuel flow lower limit and rated speed signal from turbine torque function are considered as the input signals for linearization. The LTFM is obtained from the algebraic sum of these transfer function and expressed in Equation .

Transfer Function Model for HDGT

Step response by MATLAB

Step response by MATLAB