Reference no: EM132418338

EN0711 - Wind Energy Conversion Systems - Northumbria University

Computer Aided Assignment

Assignment Brief:

Wind turbine induction generator for stand-alone applications

1. Requirements

• Write a report (a text of maximum 1000 words, excluding diagrams, contents, references etc.) to include responses to the tasks from Section 3. You can use technical publications, books or any other usual University Library resources, but you must not make verbatim extracts from these. Sources of information should be acknowledged and appropriately referenced in your report.

• Submit the report to the Student Central no later than 19th Dec 2019. You must complete the Assignment Submission Form you'll find there. A copy of this form will be returned to you as a receipt, which you should keep as proof of the assignment submission.

• Academic Integrity Statement: You must adhere to the University Regulations on academic conduct. Formal inquiry proceedings will be instigated if there is any suspicion of plagiarism or any other form of misconduct in your work. Refer to the University's Assessment Regulations for Northumbria Awards if you are unclear as to the meaning of these terms. The latest copy is available on the University website.

• Failure to submit: The University requires all students to submit assessed coursework by the deadline stated above.

2. Case Study

The main objective of the assignment is to simulate dynamic performance of a typical fixed-speed autonomous wind-diesel energy conversion system (WECS) for remote geographical areas isolated from a conventional utility grid. A structural block diagram (Fig. 1) and details of such a system are presented in the Appendix. The 3- phase WECS considered consists of a classical wound-rotor diesel synchronous generator, a wind turbine driving a cage induction generator, a Y-connected customer load, and a variable secondary load. The power system is initially operated in steady state supplying the main load only, and an additional load is switched on at 0.3 s time instant by closing the circuit breaker. You are expected to analyse the system transient response to this step load change by computer simulations and make the relevant conclusions/observations from the results obtained.

The Wind Turbine block uses a 2-D Lookup Table to compute the turbine torque output (Tm) as a function of wind speed (w_Wind) and turbine speed (w_Turb) according to the wind turbine characteristic shown in Fig. 2.

The Secondary Load block is represented by eight sets of 3-phase resistors in series with GTO thyristor switches, which can be assumed ideal for convenience of analysis. The nominal power of each set follows a binary progression so that the load can be varied from 0 to 446.25 kW in 1.75 kW steps.

3. Tasks

(1) How are the voltage and frequency control achieved in the WECS of Fig. 1 at low (say, 5 m/s or 6 m/s) and high (e.g. 11 m/s) wind speeds? Identify the respective operating modes of the synchronous machine under these two wind conditions? Explain your answers.

(2) Study the classical d-q theory of 3-phase synchronous generators and 3-phase induction generators, and write the respective dynamic model equations in a rotor reference frame defining the meanings of ALL the parameters used. Ignore iron losses and magnetic saturation.

(3) Show a structural diagram and explain the main function(s) of the Discrete Frequency Regulator block in Fig. 1.

(4) Implement the block diagram of Fig. 1 in Matlab/Simulink environment and run the simulations for 5 s (with a sudden load change occurring at 0.3 s) at a wind speed of 11 m/s using the ode23tb numerical integration routine. Assume a linear magnetic circuit of the machines i.e. do not simulate saturation effects. Present and discuss the generated waveforms for the following performance indicators in your report: voltages [pu], currents [pu] and real powers [kW] (for: consumer load, induction generator and secondary load), reactive power of the synchronous machine [kVAr], induction machine speed [pu], and system line frequency [Hz].

(5) Using the above results and the information provided in Fig. 2, estimate the power factor of the induction generator in steady-state after connecting the additional 50 kW load. Compare the numerical (i.e. from your computer simulations) and analytical (i.e. model predictions using an approximate equivalent circuit and ignoring magnetising reactance) solutions for the induction generator electrical power under these operating conditions.

Attachment:- Wind Energy Conversion Systems.rar