Conference Agenda

Detailed Equivalent Models (DEMs) of Modular Multilevel Converters (MMCs) are generally developed based on Thevenin equivalent circuits with a time-varying resistor. This approach may become computationally inefficient, specifically for the simulation of large power systems with many nodes, where the network admittance matrix needs to be frequently re-inverted every time a switching event occurs. This paper proposes a novel strategy to eliminate admittance matrix re-inversions during the converter's normal operation and restrict it only to when the converter undergoes blocking. The proposed DEM thus yields marked reductions in the simulation time of MMC circuits, and is particularly useful in studies wherein repetitive simulations are necessary. Models are implemented for MMCs with half-bridge (HBSM) and full-bridge (FBSM) sub-modules in the PSCAD/EMTDC simulator, and their accuracy is thoroughly validated for normal and blocked operating conditions. It is shown that the developed models are 30% and 60% more computationally efficient, respectively, for HBSM and FBSM MMCs in comparison to existing DEMs.

This work analyses a voltage source back-to-back converter interfacing two alternating current systems from a multivariable perspective. Since the plant is not functionally controllable, frequency-dependent relative gain array analysis is carried out to aid in the choice of the most suitable variables to be controlled in a specific frequency range. This analysis is crucial to choose the low- and high-frequency controllers. A systematic approach is developed to tune a centralized optimal control. Validation of theoretical analysis and proposed multiple-input multiple-output (MIMO) control law is performed through experimental results.

This paper presents an equivalent time-domaingrid-following inverter-based generator model, which can be usedin Electromagnetic Transients Programs (EMTP). It is developedin the Alternative Transients Program (ATP) using the ATPDrawgraphical interface. A complete benchmark photovoltaic modelavailable in ATP/ATPDraw environment is taken as referenceto evaluate the proposed model under steady-state and faultscenarios. The obtained results showed that the proposedmodel is simpler and less time-consuming than the completemodel, being capable of easily consider the implementation ofdifferent components/controls of Inverter-Based Resources (IBR)in EMTP. The settings used in the implemented control schemesproved to be effective, resulting in an average error of about2.33% during fault conditions. Also, a reduction of about 70 % inthe execution time was achieved when compared to the analyzedbenchmark one, attesting its usefulness for power system studieswith high presence of grid-following IBRs

Recently, many high voltage direct current (HVdc) transmission lines are being constructed with the intention of becoming “backbones” of future power grids. Grid-Forming (GFM) controlled Voltage Source Converters (VSCs) are anticipated to provide significant stability advantages compared with Grid-Following (GFL) VSCs in HVdc converters connected to weak ac grids or to grids with high penetration of renewable inverter-based resources (IBRs). This paper proposes an adaptive fault ride through controller for Virtual Synchronous Machine (VSM) GFM control, which has significantly improved fault ride through capability over the more conventional GFM with cascaded or switchable current limiting. The performance of the proposed adaptive control is investigated using Electromagnetic Transient (EMT) simulation. The results show that the proposed adaptive control has superior post disturbance recovery from ac faults as well as phase angle shifts, and overcomes the instability reported in GFMs connected to strong ac networks.

This paper proposes a method for detecting,classifying and locating incident faults on transmission line (TL)of a bipolar HVDC system. This method is based on the travelingwaves theory and uses the redundant discrete wavelet transformto filter voltage signals monitored at only one system terminal.The model represents the Brazilian HVDC system of the MadeiraRiver, which is simulated in the Alternative Transient Program(ATP). Different fault scenarios are analyzed, being generatedby varying type, resistance and fault location. Moreover, inorder to make the simulation more realistic, the TL is modeledbased on frequency dependent parameters. Thereby, the impactsof line parameter uncertainties and transient attenuation onthe proposed method are analyzed. From the obtained results,it is concluded that the method correctly detects all faulttypes through the use of a self-adaptive detection threshold.Furthermore, it is verified that the self-adaptive threshold detectsthe fault times instants with an efficiency superior to the fixedthreshold. In the classification step, all faults were correctlyclassified through rules elaborated based on the voltage variationlevel. Finally, the total average errors of fault location representsonly 0.047% of the TL extension. Moreover, it is verified thatfault location errors for pole:pole faults were inferior to thoseobtained for pole:ground faults, being the efficiency of the methodinversely proportional to the fault resistance.

This paper focuses on a specific issue of bipolar HVDC lines with a dedicated metallic return (DMR). DMR is insulated to a lower level than the pole and its insulators are shorter. One event, for example, pole-to-groundfault will cause a fault on both the pole insulation and the DMR insulation simultaneously because the DMR insulation fault will be supported by the DC current and will turn into a DC arc. To ensure independent pole operation, these types of events should be avoided or, if the DMR does flashover, to extinguish the fault as soon as possible. This is studied through the paper and different solutions are tested to protect the DMR.