Renewable Energy Integration Assessment

ELEC 7313 – Renewable Energy Integration Assignment 2022

Read the provided files for this assignment on UQ Blackboard, and based on the data given (PSSE .sav file, .dyr file, .sld file, and .py automation files), answer the following questions. The cases provided in the assignment are Case 1 (all power generators are synchronous generators- SGs), case 2 (one SG at Bus 102 is replaced by one inverter-based renewable energy source-IBR), and case 3 (2 SGs are replaced by two IBRs at Buses 102 and 206). You are encouraged to use the Python automation files as a base to create your case specific Python automations files for your assignment. You need to submit your assignment reports and your Python automation files to Blackboard for marking purposes. (24 marks in total)

1. Activity one: system frquency dynamic analysis (13 marks)

a) Calculate the total system inertia (in MVAs) of power generators for all three cases provided in the assignment. Then, tabulate the results of the three cases and comment on the trend of system inertia through the three cases.

Note that inertia constant is the stored energy at the rated speed divided by generator MVA rating(2 marks)

12

1 2 3 4 5 6

--

101
102
206
211
3011
3018

-- --

Total (MVAs)

b) Based on the three PSSE case studies provided, trip the synchronous generator SG connected at Bus 101 at two second and monitor the system frequency response of all three cases. Plot all the frequency responses (in Hz from 0s to 50s) in the same figure for comparison purposes. (2 marks)

c) Explain the impact of the generator tripping at Bus 101 on the system frequency nadir (???? ) values in all three cases. Plot the frequency response curves again in a time

duration, which can indicate the rate of change of frequency (RoCoF) of the system during the tripping event. And also comment on the results. (2 marks)

d)  Considering the governor droop 5% in the .dyr files for all synchronous machines, use a theoretical approach to calculate the frequency in steady-state conditions after the SG tripping at Bus 101 for all three cases. Hint: use the rating of the generators existing in the .sav file for the calculation. Also, the extra mechanical power provided by the

TGOV1 governer model is ????? ? (1/R) ? ???????????????????????? , while in the case of HYGOV model, the extra power is ????? ? (1.215/R) ? ???????????????????????? as hydro governors are a bit different from other governors (detailed reasons of the differences are beyond the scope of this course). (2 marks)

e)  Monitor and plot the real power outputs (P_elec in MW, 0s – 50s) of all the generators (including the tripping generator at Bus 101 at 2s) in the cases 1-3 and comment on the power provided by inverter-based renewable generators (IBRs) during the frequency disturbance. Hint: plot the output power of all generators of each case in one plot for each case. (3 marks)

f)  Change the droop coefficients of all synchronous generators from 5% to 3%, and plot the curves of frequency response (in Hz) of all three cases by tripping the same SG connected at Bus 101 as in activity 1 sub-questions b)-e). Write down the conclusion based on the plotted curves and the theory learned in the lecture. Hint, the location of the droop coefficient values of each SG governor in .dyr file can be obtained by checking the model library section in PSSE documentation. (2 marks)

2. Activity Two: system strength analysis (11 Marks)

a) Complete the Tables 1-3 below by calculating the steady-state short circuit currents Isc, system’s MVAsc and short circuit ratio (SCR) at the buses specified in the tables (refer to Blackboard assignment additional help file for more details on how to apply fault in PSS/E in steady-state conditions). Moreover, write down your conclusion based on the theory learned in the lecture.     (4 marks)

Table 1: Case 1 with all SGs

Case 1
Bus VLL (kV)

152 500 102 21.6 206 18

Isc (A)

MVAsc

Rating (MVA)

--

900 1000

SCR (MVAsc/Rating) --

SCR (MVAsc/Rating) --

SCR (MVAsc/Rating) -

Table 2: Case 2 by replacing one SG with one IBR

Case 2
Bus VLL (kV)

152 500 102 21.6 206 18

Isc (A)

MVAsc

Rating (MVA)

--

900 1000

Table 3: Case 3 by replacing two SGs with two IBRs

Case 3
Bus VLL (kV)

152 500 102 21.6 206 18

Isc (A)

MVAsc

Rating (MVA)

--

900 1000

b)  Plot the voltage curves (in pu from 0s to 5s) at Bus 152 for case 1 and case 3 by applying a solid L-L-G fault (zero fault impedance) at two second at Bus 152 for 100ms in a dynamic simulation. Comment on the plotted curves based on the theory learned in the lecture. (2 marks)

c)  Following the fault introduced in activity 2, sub-question b), plot the voltage curves (in pu) for the nearby buses of Bus 152 (they are Buses 151, 153, 202, and 3004) in case 1 & case 3 and comment on the plotted curves results based on the theory learned in the lecture. (3 marks)

d)  Following activity 2, sub-questions b) & c), Monitor and plot the reactive power response (in MVAr) for both case 1 and case 3 at Buses 102 and 206. Compare the reactive power response during the fault event between the IBR (under the LVRT) and the SG (under exciter control). (2 marks)