Case Studies

I maintain a blog where I have posted about the code development. You can find it here. I will continue that blog, but this page contains case studies in a more organized manner. Each case presents a particular system and besides being reference material also helps to test the simulator for bugs as the systems get more complex.



Single-phase transformer with generalized magnetic circuit

Abstract: This test case is of a single-phase transformer fed by an inverter. The secondary of the transformer feeds a resistor load through an LC filter. The simulation shows how this model can be used for switched converter circuits without instability problems.

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Using storage to relieve overloading of a UPS

Abstract: In this case, the operation of an online UPS is demonstrated where the UPS operates in current control mode under normal operation and switches to voltage control mode when the main supply fails to ensure continuous supply of power to the load.

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Online Uninterrupted Power Supply (UPS)

Abstract: In this case, the operation of an online UPS is demonstrated where the UPS operates in current control mode under normal operation and switches to voltage control mode when the main supply fails to ensure continuous supply of power to the load.

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Four inverter microgrid with two voltage sources and two current sources

Abstract: In this case a microgrid is formed from two three-phase inverters controlled in the voltage control mode but sharing load in a decentralized manner through droop control laws. The remaining two inverters are in current control mode. One of the inverters is a modeled as a load and draws a controlled amount of active and reactive power from the grid. The other inverter is a source and can supply active and reactive power. The results show how such a microgrid operates and how power is shared.

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Two current controlled inverters interfaced to a three-phase grid

Abstract: In this case, two of the inverters with LCL filters in the previous case are considered here. These inverters can be controlled in any manner and in this report are controlled such that one of the inverters supplies the reactive power demanded by the load while the other inverter supplies the active power demanded by the load.

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Reactive power compensator with higher order filter

Abstract: This case presents a reactive power compensator achieved using a three-phase Voltage Source Inverter. This is the first case presented with the circuit schematic in multiple spreadsheets. The simulation is broken into two parts with the first part achieving the compensator with controllable voltage sources with the focus on the current controller tuning. The second case considers the inverter with the pulse width modulator.

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Reactive power compensator

Abstract: This case presents a reactive power compensator achieved using a three-phase Voltage Source Inverter. This is the first case presented with the circuit schematic in multiple spreadsheets. The simulation is broken into two parts with the first part achieving the compensator with controllable voltage sources with the focus on the current controller tuning. The second case considers the inverter with the pulse width modulator.

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Single-phase three winding transformer

Abstract: This case considers a single-phase three winding transformer. This transformer is fed by two voltage sources at different voltages from different windings and supplies a load bank in the third winding. The transformer is modeled as a set of controllable voltage sources but is considered as an ideal transformer without the magnetization characteristics.

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Microgrid with two controllable voltage sources with droop control

Abstract: This case considers two three-phase voltage sources feeding a load. In order to share the load,the sources are controlled to emulate synchronous generators with frequency-active power and voltage-reactive powerdroops. This simulation is a preliminary to the case of two three-phase inverters forming a microgrid.

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Three-phase three-level inverter in closed loop current control mode while connected to a three-phase grid

Abstract: This is an extension of the previous case and presents a three-phase three-level diode clamped inverter. The inverter is run in closed loop current control mode while connected to a three-phase grid. The simulation results show the advantages of three level switching by comparing the results with a similar two level inverter with an identical current control loop.

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Single-phase three-level inverter in open loop

Abstract: This case is a three-level diode clamped inverter. The inverter is run in open loop with varying modulation signals to show the multilevel switching operation.

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Three phase inverter in current control mode interfaced to a three phase inverter in voltage control mode

Abstract: This case has two converters connected together. One of the voltage source converters has an LC filter at its output and is controlled in voltage controlled mode. Another three phase inverter with an inductor filter at its output is connected to the first converter and controlled in current control mode. The control on both converters is implemented independently as a combination of the case studies below.

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Three Phase Inverter with LC Filter

Abstract: A three phase Voltage Source Converter has an LC filter at its output. The converter is controlled in voltage control mode with the voltages across the capacitors being regulated to be balanced three-phase sinusoids. The controller implemented is a nested PI control in synchronous rotating reference frame with an outer voltage loop and an inner current loop.

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Three Phase Grid Connected Inverter with L Filter

Abstract: A three phase Voltage Source Converter is operated in current control mode. The controller implemented is a simple PI control in synchronous rotating reference frame. Such an inverter does not have much application but the main purpose of this test case is to describe how to use control functions with the simulator.

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Three Phase Standalone Inverter with L Filter

Abstract: A three phase Voltage Source Converter is operated in current control mode. The controller implemented is a simple PI control in synchronous rotating reference frame. Such an inverter does not have much application but the main purpose of this test case is to describe how to use control functions with the simulator.

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