## Recent Update

## About the test cases library

This website provides a power system oscillation test cases library generated by simulation to test algorithms for identifying the source of poorly damped or forced oscillation. All cases were created by simulation on a WECC 179-bus power system model (click to see description on the WECC 179-bus system base case model). With each test case of the library, we provide a case description, simulation results (to mimic PMU measurements with oscillation), and the simulation model in in the PSS/E V30 format.

The development of this test cases library was led by Dr. Slava Maslennikov (ISO-NE). The website is maintained by Mr. Bin Wang (UTK) and Dr. Kai Sun (UTK). Related simulation models and Matlab codes were prepared by Mr. Bin Wang. There are totally 27 oscillation cases including 9 cases on poorly damped natural electromechanical oscillations and 18 cases on forced oscillations. More cases will be added on an as-needed basis.

S. Maslennikov, B. Wang, Q. Zhang, F. Ma, X. Luo, K. Sun, E. Litvinov, "A Test Cases Library for Methods Locating the Sources of Sustained Oscillations," IEEE PES General Meeting, Boston, MA, July 17-21, 2016.

## Motivation and objective

## Test cases

### ➤Power system model

The power flow and dynamic files of all cases can be downloaded as one package using the link below. For forced oscillation cases, the dynamic files for modelling the external forces and their block diagrams are also included in the package. With the model, users can easily modify the parameters of their interests and design their own cases.

[DOWNLOAD]All Models (676KB)Instructions:

- For all natural oscillation cases, users can directly run the time-domain simulation in any program that accepts models in PSS/E V30 format.
- For all forced oscillation cases, users can run the time-domain simulation in either of the two ways below: (i) Install DSATools by Powertech Lab and run the simulation in TSAT.

(ii) Design the model for the external force according to the block diagram included in the above package and run the simulation using the users' own program.

### ➤Simulated PMU measurements

The simulated data from all cases can be downloaded from the links below. With these measurement data, users can directly load them into their program and run their location algorithm without dealing with models or simulations.

[DOWNLOAD] All in one (168MB) or Cases 1ND to 3ND (18MB) Cases 4ND to 6ND (18MB) Cases 7ND to 9ND (18MB) Cases 1F to 3F (18MB) Cases 4F1 to 4F3 (18MB) Cases 5F1 to 5F3 (18MB) Cases 6F1 to 6F3 (18MB) Cases 7F1 to 7F2 (12MB) Cases 1FM to 7FM1 (25MB)Instructions:

- In each txt-file, the first column is time and the rest of the columns are measurement data.
- A Matlab m-file for loading these data into the workspace is provided. [DOWNLOAD]LoadData2Matlab (2KB)

### ➤Approach for generation of test cases

### ➤Summary of natural oscillation cases (Click case # for details)

Case # | D | Frequency/Hz | Damping | Source location | Fault location | Description |
---|---|---|---|---|---|---|

ND_1 | D45=-2 D159=1 |
1.41 | 0.01% | 45 | 159 | Single source - single local mode |

ND_2 | D35=0.5 D65=-1.5 |
0.37 | 0.02% | 65 | 79 | Single source - single inter-area mode |

ND_3 | D6=2 D11=-6 |
0.46 0.70 1.63 |
2.22% 1.15% -0.54% |
11 | 30 | Single source - one unstable local mode and two poorly damped inter-area modes |

ND_4 | D6=5 D11=-9 |
0.46 0.70 1.63 |
0.68% -0.58% 0.54% |
11 | 6 | Single source - one unstable inter-area mode and two poorly damped local and inter-area modes |

ND_5 | D6=3 D11=-8 |
0.46 0.70 1.63 |
0.69% -0.19% -0.48% |
11 | 30 | Single source - two unstable local and inter-area modes, and one poorly damped inter-area mode |

ND_6 | D45=-2 D159=-0.5 |
1.41 | -0.93% | 45&159 | 159 | Two sources with comparable contribution into a single unstable local mode |

ND_7 | D45=-0.5 D159=-0.5 |
1.41 | -0.40% | 45&159 | 159 | Two sources with different contributions into a single unstable local mode |

ND_8 | D45=-2.5 D159=1 D36=-1 |
1.27 1.41 |
-1.06% -0.22% |
45&36 | 159 | Two sources - two unstable local modes |

ND_9 | D11=-10 | 0.46 0.69 1.63 |
-0.86% -1.81% -0.40% |
11 | 79 | Single source - three unstable modes |

The default value of damping coefficient D for all generators is 4. In each case, any deviations from the default values are shown in the second column of the above table. The source of oscillations is the generator with negative D value.

Eigenanalysis results for the above cases are here (Eigenanalysis ND.xls).

As an example, here are the details of the cases ND_1, ND_4, and ND_6 and ND_7.

### ➤Summary of forced oscillation cases (Click case # for details)

**Forced signal is injected into the excitation system of a generator**

Case # | Type of injected signal | Frequency of first harmonic/Hz | Source location | Description |
---|---|---|---|---|

F_1 | Sinusoidal | 0.86 | 4 | Resonance with local 0.86Hz mode |

F_2 | Sinusoidal | 0.86 | 79 | Resonance with local 0.86Hz mode |

F_3 | Sinusoidal | 0.37 | 77 | Resonance with inter-area 0.37Hz mode |

F_4_1 | Sinusoidal | 0.81 | 79 | Forcing frequency is below natural 0.84Hz mode |

F_4_2 | Sinusoidal | 0.85 | 79 | Forcing frequency is between natural 0.84Hz and 0.86Hz modes |

F_4_3 | Sinusoidal | 0.89 | 79 | Forcing frequency is higher than natural 0.86Hz mode |

F_5_1 | Sinusoidal | 0.42 | 79 | Forcing frequency is below natural 0.44Hz inter-area mode |

F_5_2 | Sinusoidal | 0.46 | 79 | Forcing frequency is between natural 0.44Hz and 0.47Hz inter-area modes |

F_5_3 | Sinusoidal | 0.50 | 79 | Forcing frequency is higher than natural 0.47Hz inter-area mode |

F_6_1 | Periodic, rectangular | 0.1 | 79 | Spectra of forced harmonics consist of 0.1Hz, 0.3Hz, 0.5Hz, 0.7Hz, etc modes |

F_6_2 | Periodic, rectangular | 0.2 | 79 | Spectra of forced harmonics consist of 0.2Hz, 0.6Hz, 1Hz, 1.4Hz, etc modes |

F_6_3 | Periodic, rectangular | 0.4 | 79 | Spectra of forced harmonics consist of 0.4Hz, 1.2Hz, 2Hz, etc modes |

F_7_1 | Sinusoidal | 0.65 0.43 |
79 118 |
Two sources of forced signals creating resonance with two different modes, respectively |

F_7_2 | Sinusoidal | 0.43 | 70 118 |
Two sources of forced signals creating resonance with the same mode |

Each case of forced oscillations has only one generator with periodic signal injected into its excitation system. The presence of the excitation system to one generator only slightly changes the parameters of oscillations (Eigenanalysis Forced.xls) comparing to the base case (Eigenanalysis base case.xls).

Spectra of injected rectangular-wave disturbances in cases F_6_n (n = 1, 2, or 3) consist of only odd harmonics and the frequency of the first harmonic is shown in third column of the above table.

As an example, here are the details of the cases F_5_2, F_6_2.

**Forced signal is injected into the governor of a generator**

Case # | Type of injected signal | Frequency of first harmonic/Hz | Source location | Description |
---|---|---|---|---|

FM_1 | Sinusoidal | 0.86 | 4 | Resonance with local 0.86Hz mode |

FM_3 | Sinusoidal | 0.37 | 77 | Resonance with inter-area 0.37Hz mode |

FM_6_2 | Periodic, rectangular | 0.2 | 79 | Spectra of forced harmonics consist of 0.2Hz, 0.6Hz, 1Hz, 1.4Hz, etc modes |

FM_7_1 | Sinusoidal | 0.65 0.43 |
79 118 |
Two sources of forced signals creating resonance with two different modes, respectively |

Each case of forced oscillations from the above table has only one generator with periodic signal injected into its governor. The model of each generator remains classical.

The forced signal for each case is modeled by individual User Defined Model (UDM) implemented in TSAT software. The structure and parameters of each UDM can be found in corresponding block-diagram. Common element for each UDM is the block BLK, Steam turbine. That is the ''Governor End Block Type T4'' in TSAT with the following parameters: T4=0.5; T5=T6=T7=0; Pmax=1.0; K2=1; K2=K3=K4=K6=K7=K8=K9=0; LPBUS=0.

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