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Location

This example model can be found in the HYPERSIM under the category "How To" with the file name "PSSE_Import_118_Bus.ecf". The PSS®E reference model is provided with this example in folder PSSE_ref_model, and the folder structure of this example is as follows:

Description

The example utilizes a modified edition of the original IEEE118 bus model mentioned in [2]. The IEEE 118-bus test case is an approximate representation of the American Electric Power system in the U.S. Midwest as it existed in December 1962. The system consists of 19 generators, 35 synchronous condensers, 177 lines, 9 transformers, and 91 loads [2]. All gen units except for gen_69 and gen_89 are identical and each consists of a GENROU, EXST1, TGOV1, and PSS1A. The gen unit of gen_69 which is on the slack bus has only a GENROU. Finally, the gen unit of gen_89 consists of a GENROU and a TGOV1.

The original benchmark network is a model implemented in PSS®E v32.1.0. Then, the PSS®E reference model is imported to HYPERSIM via the Unified Database. The successful import of the PSS®E model and accurate mapping of all components with their respective parameters in HYPERSIM are demonstrated in this example. All the necessary components required to complete the IEEE-118 bus benchmark model in HYPERSIM are available in the Unified Database.

Import the PSS®E model

The goal of the PSS®E import tool is to save time by automatically importing models from PSS®E to HYPERSIM, as well as to avoid potential errors caused by manual importing. The PSS®E import tool comprises a parser, mapper, and exporter. The parser analyzes and interprets PSS®E model components and parameters, converting the PSS®E file into a list of objects. The mapper establishes mappings between PSS®E and Unified Database (UDB) components and parameters. Finally, the exporter creates the HYPERSIM model after successful database import.

1. Create a new HYPERSIM model

2. Follow the steps in PSS®E Network Import to import the model.

   • The folder named PSSE_ref_model contains three files: IEEE_118_bus.raw, IEEE_118_bus.dyr, and IEEE_118_bus.gps. The first two files (IEEE_118_bus.raw and IEEE_118_bus.dyr) are required, while the third file (IEEE_118_bus.gps) is optional. It is essential that all three files have the same name, and in this case, they do.

3. Wait until the end of the import process. A message “Import successful” in the Import Panel interface indicates that the import is completed.

Analysis and adjustment of model

Once the import process of the ieee118 case is finished, it is necessary to analyze the generated model to identify and address any potential errors before initiating the simulation.

To conduct an initial analysis of the model, simply select the Analyze button found within the Network section of the HYPERSIM tab.

As illustrated in below, an error would occur when the analysis is performed.

This error occurs when a combination of a CP transmission line model and a PI transmission line model are connected in parallel. The CP model allows the network to be decoupled into two independent cores, while the PI model does not possess this capability, leading to the occurrence of this error. In order to address this issue, the user must replace the two CP lines specified in the error (line_35_to_37_1 and line_54_to_55_1) with two PI lines. The parameters for the PI lines being substituted should be set according to the illustrations provided below.

To configure the parameters line_35_to_37_1, set the parameters in the following manner:

To configure the parameters line_54_to_55_1, set the parameters in the following manner:

After replacing the two problematic CP lines with their corresponding PI lines, if we reanalyze the system as mentioned earlier, it becomes evident that the error has been resolved and in the output box below the schematic, you will receive this message.

Network analysis of [PSSE_Import_118_Bus.exe] done in 1.1317 sec.

Simulation and Results

Load flow test

Usually, before validating models dynamically, load flow validation is carried out. To compare HYPERSIM and PSS®E, two sets of variables are compared after running load flow on the ieee118 case in both software:

1. Voltage and phase angle of each bus.

2. Active and reactive power generation from each machine.

Before discussing the steps for performing load flow, it's important to mention that HYPERSIM has a Load Flow tool within the Network section of the HYPERSIM ribbon. This tool allows users to define power flow criteria and provides detailed power flow results. Additionally, load flow results can be obtained using the Netlist tool which is also within the Network section of the HYPERSIM ribbon.

In order to compare the results of HYPERSIM with PSSE, the same criteria used in PSSE have been defined for HYPERSIM as well. To do so, begin by checking the box labeled "Use Qmin and Qmax limits," and then configure the following parameters: Frequency (Hz): 60.0, Power base (MVA): 100.0, PQ tolerance (WA): 0.001, and Max iterations: 60. Also to display the results in the Reports section, select the checkbox labeled “Display voltage in PU“.

Once the criteria are set, the load flow analysis is executed. As the analysis finished, it was observed that the load flow converged successfully. Finally, the comprehensive results of the analysis were displayed in the log window.

To compare HYPERSIM with PSS®E two groups of parameters have been compared:
1- Voltage and angle of each bus
2- Active and reactive power generation from each machine

The figures below illustrate the absolute errors between the HYPERSIM and PSS®E results for bus angles and bus voltages. It has been observed that the maximum error between PSS®E and HYPERSIM for bus voltage is approximately 0.00102 per unit (pu), while the maximum error for bus angle is approximately 0.131 degrees. In terms of the active and reactive power generated by machines, the maximum absolute error for active power is 0.01178 pu and the maximum absolute error for reactive power is 0.0139 pu. These errors are deemed acceptable, indicating a close match between the results obtained from HYPERSIM and PSS®E.

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Bus voltage load flow error

Dynamic test

In this section, the validation of the imported model is analyzed for a short-circuit case which is a dynamic scenario. Both PSS®E and HYPERSIM implement the short circuit, which involves a 3-phase ground fault happening at bus 1 at t = 3 seconds and it is cleared at t = 3.1 seconds by tripping the transmission lines connected to bus 1.

In PSS®E, fault information is not included in the raw file (.raw) or the dyr file (.dyr). Consequently, automatic importing of fault information from PSS®E to HYPERSIM is not feasible. To replicate the faults from PSS®E in HYPERSIM, the user needs to intervene manually and implement the faults manually.

Adapting the model to conduct the short circuit test

This section provides a step-by-step explanation of the manual process for replicating three-phase faults from PSS®E in HYPERSIM.

• Add a 3-phase fault from the Network Switches and Breakers library, and link it to bus 1.

• Set up the fault:

  • Activate the General operation in the Timing tab.

  • In the General tab, modify the Control type to External (input pins).

  • Input the following values for the parameters in the Timing tab:

• Use a Constant (1), a Pulse Delay (Td=3s, and Ton=1e9s), and a Gain (15, which is 1111 in binary to operate all 3 phases and ground) to trigger the fault at 3s.

The fault will be cleared by disconnecting bus 1 at 3.1s. To disconnect bus 1, both line_1_to_2 and line_1_to_3 must be disconnected from bus 1.

• In order to disconnect them, place two circuit breakers (CB) at the terminals of both lines that connect them to bus 1.

• For the CBs, enable Generation operation and configure the Control type to be External.

• Similar to the fault trigger logic, use a Constant (1), a Pulse Delay (Td=3.1s, and Ton=1e9s), a Gain (7, which is 111 in binary to operate all 3 phases), and a Not logic to build the trigger circuit to open the breakers. Connect the control signals to both breakers.

After configuring the fault settings, it's essential to initialize the HYPERSIM model before starting the simulation. To do this, select the checkbox titled "Perform load flow and set initial conditions at simulation start" in the general tab of the simulation settings.

Record HYPERSIM results with Datalogger

In HYPERSIM, the model time step is set to 5 µs to align with the PSS®E simulation settings. The https://opal-rt.atlassian.net/wiki/spaces/HDI/pages/3548177 is employed to record the desired sensor measurements from t = 0 s to t = 15 s, with a decimation factor of 1 applied. Additionally, for the chosen signal groups, the number of frames to record is set to 1, the frame length is adjusted to 15 seconds, and the output file autonaming checkbox is deselected. Apart from the predetermined sensors provided in the given example, users have the option to follow the instructions in Sensor Management to record additional sensors.

The provided ScopeView template, PSSE_Import_118_Bus.svt, facilitates the comparison of simulation recordings between PSS®E and HYPERSIM. It is noted that the source files need to be replaced before playing the recorded data. The results from the PSS®E analysis for this case study have been included in the Reports_SC_PSSe.csv file, and this file can be integrated into ScopeView. However, if the user wishes to conduct a new case study, such as analyzing a different short circuit at another bus, they should replace the existing PSS®E results in the template with the new results obtained from the new case study. To replace the HYPERSIM results, the .oprec file can be found in the Recordings folder at PSSE_Import_118_Bus_hyp after running the imported model.

Results

After the implementation of the model in HYPERSIM, the results are obtained. In order to demonstrate the consistency between HYPERSIM and PSS®E results, only a subset of parameters are compared. However, users have the option to observe additional parameters in both PSS®E and HYPERSIM if desired. The provided figure displays the voltage per unit measurements at buses 1, 2, and 3, where it can be observed that the HYPERSIM results align well with the results obtained from PSS®E.

The provided figures highlight two specific examples of generators and transmission lines, but it is important to note that similar behavior was observed for other cases as well. These examples serve as representative instances to demonstrate the ability of HYPERSIM to replicate the results obtained from PSS®E. The figures showcase the active and reactive power flowing through three transmission lines (line_2_to_12, line_3_to_5, and line_3_to_12) and the active and reactive power generated by two specific generators (connected to buses 10 and 12), which are indicative of the overall consistency observed across other similar cases.

It is important to add that there are some small differences during the transient events, which is considered normal. These differences can be attributed to four main factors:

1. Electromagnetic transient simulation in HYPERSIM provides more accurate results during transients, including the DC component of the fault current, which is not accounted for in the phasor simulation of PSS®E.

2. The modeling approach for synchronous machine saturation differs between HYPERSIM and PSS®E. PSS®E employs a quadratic curve, whereas HYPERSIM uses a linear interpolation method.

3. HYPERSIM calculates positive sequence voltage and power based on instantaneous voltages and currents using a moving window of one power cycle. As a result, there might be a slight delay in measurements.

4. The behavior of circuit breakers in HYPERSIM is different as they open only at the zero crossing of the current, potentially leading to slightly different timing of clearing and opening of breaker poles.

References

[1] ePHASORsim example model phasor06_IEEE118, “Islanding of power grid in presence of large disturbances”.

[2] http://publish.illinois.edu/smartergrid/ieee-118-bus-system/

[3] PSS®E 35.1.0 Program Application Guide Volume 2.