EQUIPMENT MODELING
The selection of the equipment to be modeled by FINIST and the fidelity of such modeling is dictated by the concerns of the operational personnel training. The equipment model has to be adequate in the variety of the behaviors that FINIST has to represent during training sessions.
GENERATION
FINIST has a sophisticated generator model. It uses Park's synchronous generator equations. Generator reactive power capability curve is taken into account. FINIST uses a generalized excitation system model and automatic voltage regulator model to provide proportional integration differential (PID)-regulation of bus voltage. Field voltage, current channels, frequency regulation, reactive armature power and power factor regulation are also modeled. Individual generator automatic regulator as well as plant-wide regulation is modeled.
FINIST models the following power plant types:
Fossil-fuel power plants
FINIST has separate models for condenser-type and cogeneration-type power plants. FINIST models the fossil-fuel power plants in great detail. The simulator models throttle pressure control loops, fuel supply control, valve opening, steam flow rate, frequency droop. Either the turbine or the steam generator may lead. FINIST explicitly models feedwater heater as well as reheater and superheater.
Hydroelectric
FINIST uses non-linear hydro-turbine model with PID-governor. FINIST also incorporates the ability to model outside generation control systems and unequal load distribution between several machines of the same hydro power plant. FINIST has different models for high- and medium to small-head power plants as different turbine types are used in those plants. FINIST models power plant reservoir and the dependency of static water pressure on head size. This dependency is significant for medium and small head power plants which have limited reservoir size, for sequences of hydro-plants and for pumped-storage plants. FINIST assumes that water column and penstock are non-elastic (rigid) and there are no hydraulic interactions between machines in multi-machine power plant.
Pumped-storage
The pumped-storage hydro power plant model allows FINIST to implement the main operating states and state changes of operational concern: the dynamics of control in generation mode and power consumption in the pump mode. In FINIST, the static water pressure calculation in pumped-storage plant is similar to those of ordinary hydroelectric plants with limited reservoir size. FINIST models the changing operation from generation to pumping by introducing appropriate time delays. For example, switching to pumping is modeled by decreasing generated power to zero, pausing for pumping preparation procedures and changing the unit to active power consumption with fixed water flow from lower to upper reservoir.
Nuclear
FINIST models nuclear power plants in a somewhat simplified manner. It is assumed that the plants are run in base load mode and do not participate in frequency or generation control. Primary and secondary coolant dynamics are not considered. Core neutron control and heat transfer are modeled with second-order differential equations.
Every modeled generator unit can be monitored and controlled by the operator either as a single unit or as a part of a generation group. FINIST offers rather sophisticated generator models with a large number of parameters and controls.
Transformers
FINIST represents transformers using equivalent-Y circuit. The equivalent circuit accounts for a number of transformer parameters including winding resistance loss, leakage flux and magnetizing current. The transformation coefficient can be either real or complex. A transformer may have an on-load or off-load tap-changer and provide regulation of either voltage or phase or both. FINIST correctly models both automatic and external regulation.
Transmission lines
FINIST models a transmission line with a P-equivalent circuit. However, non-linear corona losses may be modeled as particular load with appropriate sensitivity function. Effective use of the variety of reactive power sources to control the power system is an essential skill of an operator. Hence, FINIST has to faithfully model the sources of reactive power. Specifically, FINIST models shunt and series capacitor and reactor banks as well as synchronous compensators. The capacitor and reactor banks can be switched or thyristor controlled.
FINIST models series reactor or capacitor banks as fixed admittance devices whose admittance changes in increments. The shunt reactors and capacitors are modeled as variable or fixed impedance devices. Thyristor controlled or switched devices are modeled, although thyristor control transients are not considered.
Load
Adequate load modeling in an electric power system simulator is challenging as the aggregate load data for system objects are not provided or even measured in real systems as the telemetered data is usually insufficient to adequately reconstruct the necessary load properties. This is especially true for the transient and dynamic properties of the load that are necessary to properly model system behavior during disturbances and outages. At the transmission level, the load is composed of transmission level customers as well as transformers to the distribution networks. The latter represent integral demand of the lower-voltage end customers.
FINIST implements several standard load components. Individual load components have customizable frequency and voltage sensitivity functions as well as a variety of other parameters. The most important operational load characteristics can be represented by adding a composition of such components to the appropriate modeled system buses. The load model can be further tuned by adjusting the parameters of these components. FINIST can also use Zipf model to bring further realism to the load representation. FINIST has a separate model for power plant auxiliary needs power circuits. FINIST can model gradual load change well as cold load pickup. In case of load change, the transition is linear; in case of cold (just connected) load, its pickup is exponential.
Control systems and protection relays
FINIST models protection relays as well as special protection schemes of arbitrary complexity. FINIST implements a generic controls model that is used adequately model of all such systems. This model has: a multi-stage trigger, an actuator and a reloader. There is an actuator for each stage of the trigger. There is an activation time delay for each trigger. That is, the actuator is executed if the trigger condition is continuously true during this time delay. The actuator may change various state parameters. The reloader's activation conditions are programmed similar to the trigger's. Using this generic model, FINIST implements most widely used standard relays. Triggers model over and under-voltage, overcurrent, underfrequency, out-of-step relaying and similar conditions over the system objects such as generators, transformers or power lines.
MODEL EXTENSION AND DEVELOPMENT
FINIST power system models incorporates many years of experience of Monitor Electric engineers, researchers and authorities in the field. However, the model is designed to be easily extensible. Monitor Electric engineers continue to perfect the model and regularly release model updates. Moreover, FINIST APIs are open and well-documented. This allows third-party developers to add components and functionality to the model as needed.
