This paper proposes a unified Control-Performance-Index (CPI) framework for screening modernization alternatives in multi-infeed HVDC (MIDC) system. Electromagnetic-transient (EMT) simulations generate a station-by-fault CPI matrix which is then hierarchically aggregated into event (EvtCPI) and station (StnCPI) indices to rank contingency severity and converter performance, respectively. A reference-score composition integrates the voltage and frequency domains into a single alternative ranking (SysRefScore). The framework is validated on a three-Bipoles system representative of Manitoba Hydro’s prospective upgrades. Results show that the CPI approach yields quantitative rankings across control modes, ratings, and topologies–including mixed LCC-rectifier/VSC-inverter and all-VSC configurations. Among the studied options, the combination of an all-VSC topology, higher rating, and inverter ac-voltage control delivers the most robust post-fault performance under the fault set considered. StnCPI identifies vulnerable converters within the MIDC, while EvtCPI ranks fault severity. A Python automation workflow streamlines the process of CPI framework, enabling reproducible, decision-ready screening for planners.

Earlier research has identified that the phenomenon of cascaded commutation failure (CF) in multi-infeed LCC-HVdc systems connected into weak ac grids is not caused merely by ac voltage reduction, but also significantly by the presence of low order voltage harmonics. Traditional CF mitigation strategies, such as controller optimization have limited effect in reducing such cascaded CFs. In this paper, we propose a novel approach involving the addition of shunt ac filters tuned to the 2nd and 3rd harmonics to mitigate cascaded CF by inhibiting inter-inverter harmonic propagation. These filters significantly reduce the equivalent impedance magnitudes at the relevant harmonics as seen from the local inverter ac bus to the common receiving end grid. As a result, the current harmonics generated by CF in the local inverter are less likely to propagate to remote inverters via the connecting tie-lines. Electromagnetic transient simulations demonstrate that the proposed scheme substantially reduces the probability of cascaded CF under various fault conditions. Furthermore, it is shown that installing only the 2nd or 3rd harmonic-tuned filter, as done in some previous studies, may inadvertently increase the risk of cascaded CF, underscoring the importance of the proposed filtering scheme which targets multiple low order harmonics.

The saturation of magnetizing paths in synchronous machines significantly impacts machine performance, including loading capability. In electromagnetic transient (EMT) programs, magnetic saturation is traditionally modeled by adjusting the d-axis or q-axis magnetizing inductances (or flux linkages) [1-4]. A similar approach is applied in phasor-domain programs [5]. While these methods account for d- and q-axis saturation simultaneously, they overlook the rotor's inherent structure and the angular displacement of the MMF wave in the airgap.This paper presents the development and validation of an EMT synchronous machine model that incorporates cross-magnetizing effects into the saturation algorithm. The proposed method evaluates saturation based on the magnitude and angle of the MMF. Additionally, the paper examines the impact of various simplifications on the loading capability of synchronous generators.

This work demonstrates how a Battery Energy Storage System (BESS) interfaced with a Unified Grid Forming–Following (UGFF) controller can be operated in a stable and dynamically satisfactory manner across a comprehensive range of operating conditions. The UGFF controller leverages a recently proposed control strategy that seamlessly integrates Grid-Following (GFL) and Grid-Forming (GFM) control approaches. The analysis employs a 33rd-order linearized state-space (SS) model of the BESS. This state-space model is validated through comparison with an Electromagnetic Transients (EMT) model implemented on a real-time digital simulator. The EMT model also enables the investigation of large-signal dynamics, which are beyond the capabilities of the linearized SS model. Based on these analyses, key parameters of the ac system and the UGFF controller are appropriately tuned to ensure both small-signal stability and satisfactory large-disturbance performance, providing a comprehensive understanding of their impact on system dynamics. The results demonstrate that the tuned UGFF controller exhibits strong adaptability across a wide range of system conditions, including varying Short-Circuit Ratio (SCR) levels and post-fault recovery scenarios. In addition, the EMT studies show that online adjustment of the controller parameters via upstream controls enables the system to regain stability following diverging oscillation or large disturbances. The performance of the UGFF-equipped BESS is also compared with that of similar approaches in a modified IEEE 14-bus system to assess its behavior under practical conditions.

Modular Multi-level Converters (MMC) are becoming a popular choice for replacing conventional synchronous generators (SG) with renewable energy sources. These devices can also be operated using grid-forming control strategies such as Virtual Synchronous Generator (VSG) to emulate the inertia support provided by SG. Prior literature has reported that the internal current controller in conventional grid-forming inverters can cause unstable interactions with strong ac networks. An alternative approach is directly controlling the MMC currents using the hysteresis control approach, eliminating the need for a current limiter loop. The behaviour of such current-controlled MMC (CC-MMC) emulating VSG characteristics has been reported for single generator systems only. This paper examines the operation of systems involving multiple CC-MMCs emulating SG characteristics. Similar to SG-based systems, such CC-MMCs also exhibit low-frequency interactions. The critical modes and their damping are obtained using the traditional small-signal analysis, where the CC-MMCs are represented using transient stability models of SGs. This allows for the design of supplementary damping controllers as in the case of traditional SG-based systems. The performance of the damping controller is verified using detailed EMT simulations of the overall system with multiple CC-MMCs.

Multi-rate Electromagnetic Transient (EMT) simulations use smaller time-steps for parts of the network requiring greater accuracy, and larger time-steps for the rest of the network. This paper presents an analytical approach for evaluating the stability of multi-rate EMT simulations of linear time-invariant (LTI) networks. It is shown that their resulting discrete time system is inherently time-periodic. Leveraging this characteristic, a sampled-data time-invariant representation of the simulated network is derived. The overall simulation's numerical stability can then be assessed through eigenvalue analysis. The paper shows that contrary to popular belief, a multi-rate EMT simulation may become unstable even if the well-known A-stable trapezoidal rule is used. The proposed approach is validated with example simulations.

This paper presents a novel acceleration slope-based hysteresis current control strategy for modular multilevel converters (MMCs). This approach enables the MMC to function as a high-bandwidth, high-precision current source while still retaining the low inherent harmonic generation and low losses of the MMC. Unlike traditional hysteresis current control in two-level voltage-source converters (VSCs), which toggle between two output voltage levels, the MMC’s multiple voltage levels offer more flexible current slope control with fewer switching actions. The proposed control is compared to other voltage generation techniques, such as nearest-level control, showing that the resulting losses are similar to those of traditional voltage-controlled MMCs. The paper also demonstrates the application of this strategy in a STATCOM with active filtering, highlighting faster response times. Additionally, a current source type Grid Forming Converters (GFMs), e.g., Virtual Synchronous Generator (VSG), is presented, illustrating how the proposed control enhances stability in both weak and strong ac grids. The effectiveness of the proposed method and two applications are validated through electromagnetic transient (EMT) simulations and hardware-in-loop (HIL) simulation.

Voltage and frequency regulation in weak ac systems connected to Line Commutated Converter (LCC)-based High Voltage Direct Current (HVdc) transmission systems presents significant challenges. Synchronous condensers (SCs) are commonly utilized to provide reactive power and inertia support. Although SCs effectively mitigate frequency deviations, their kinetic energy exchange is constrained to maintain synchronism, and excessive inertia may delay frequency restoration. Furthermore, SCs regulate voltage more slowly than power electronic devices such as STATCOMs. This paper investigates a proposed hybrid topology that combines a back-to-back (BtB) medium voltage DC (MVdc) system with an SC. By interfacing the SC to the ac network via a reconfigurable pair of voltage source converters (VSCs), the equivalent inertia and voltage regulation capabilities of the SC can be dynamically adjusted. This approach not only improves the short circuit current and allows fast voltage regulation through the STATCOM configuration, but also allows the SC frequency to deviate significantly from the frequency of the ac network. Consequently, the hybrid BtB-SC system emulates an SC with a substantially higher inertia rating than a directly connected SC. The performance of this hybrid system is evaluated and compared to a conventional SC system using Electromagnetic Transient (EMT) simulations.

Modular Multilevel Converters (MMC) have found extensive application in connecting Renewable Energy Sources to the power grid. Recently, MMCs operated in the Grid Forming (GFM) mode have garnered significant interest due to their superior performance in weak AC networks. The Virtual Synchronous Generator (VSG) is a GFM technology designed to emulate the behavior of a real synchronous generator (SG). There is flexibility in selecting the VSG’s parameters as they are not constrained by the physical attributes of an actual SG. This paper proposes employing the Genetic Algorithm (GA) to select these parameters, underscoring its simplicity and effectiveness in meeting diverse constraints and objectives. Small Signal (SS) models are constructed at potential operational points, with GA leveraging the SS model’s eigenvalues to select parameter values that enhance dynamic performance, ensuring resilience across a wide range of operating conditions. The effectiveness of these designed parameters is validated through Electromagnetic Transients (EMT) simulations.

Modeling Dual-Active-Bridge (DAB) topologies in a real time simulator presents challenge due to the high switching frequency and the substantial number of submodules. This requires both the firing pulses’ precision and high-speed matrix computation. In this paper, an aggregated model is proposed for a typical Dual-Active-Bridge (DAB) circuit using the state-space circuit approach. It accurately implements the duty cycle of the firing pulses and consequently enhances accuracy. The two H- bridge converters and the ac transformer with the blocking capacitors are consolidated into a single-unit. To address scenarios involving multi-level cascaded DAB units with input series output parallel (ISOP), the multiple single-unit blocks are further packed into an aggregated model. Compared to using single-unit models for the cascaded topology, our developed aggregated model not only conserves electrical nodes, but also the calculation time for history terms, resulting in reduced hardware resources. The simulation timestep can be efficiently reduced, resulting in an outcome of better precise and the capability to model much higher switching frequencies. The proposed aggregated model can be widely applied in the real-time simulation of cascaded DAB topologies, accommodating switching frequency up to 100kHz.

This paper explores the potential for additional renewable energy options in the Canadian province of Manitoba, which already produces nearly 100% of its electrical energy using hydro power.It considers the perspectives of the national and provincial governments with regard to the future of electric transportation.It also consolidates available data collected in the province.Finally, it explores the possibilities of future applications of the concept of smart grid in the context of how this may assist the optimal energy source mix for this province.There are reasons other than economics which could drive Manitobans to invest in renewable energy sources different from hydro power.The electric vehicle (EV) is a prime example of a load that should be supplied by new renewable energy.The reduction in the consumption of petrol, the reduction of pollution, and the education in energy efficiency justify the use of renewable energies in EVs.

One fault that has hitherto not widely been investigated is the open circuiting of an HVdc conductor, as its occurrence is relatively rare. Using electromagnetic transient (EMT) simulation, this paper addresses the void in HVdc fault analysis by giving useful insight into the impact of HVdc open conductor faults on current and voltage transients. In order to simulate the resulting series arc between falling HVdc conductors, the Schavemaker model, a well-known empirical model, is adapted by introducing the dynamics of varying arc length. The modified Schavemaker arc model is implemented in PSCAD/ EMTDC. This study analyzes the impact of each parameter of the Schavemaker arc model on the arc conductance variation during an open conductor fault. This study shows that the arc time constant is the most influential parameter on the arc conductance variation while the time-varying reference arc voltage and arc cooling power introduces the effect of variable arc lengths to the Schawmaker model.

This paper will investigate the effect of resonance on the power electronic devices. As a case study, a capacitive-ladder-based electronic voltage regulator has been chosen for the study and experimental test. Firstly, an extensive simulation has been performed in PSCAD software to check the capability of the electronic voltage regulator during different faults and transients originating from the inductive load side. The simulation proved that the system would not fail for the short circuit fault and the voltage regulator could perform its tasks. For the experimental side of the results, an extensive theoretical analysis has been performed to make sure that there will be no resonance in the selected rating for the test, and therefore capacitor value has been chosen to be far away from the resonance region. For the experiment test, the voltage regulator is in series with a main supply transformer with a rating of 168kV-13.8kV, and the voltage regulator provides 10% of the LV side voltage to maintain the load voltage in an acceptable range. To isolate the electronic voltage regulator from HV side, the voltage regulator has been connected through a series transformer. When connecting the electronic voltage regulator to a standalone transformer and increasing the voltage gradually to perform some tests to verify lack of the resonance, a flashover happened to the thyristors in the voltage regulator and some capacitors became faulty, resulting in a loss in the capacitance value of more than 50%. Further investigation has been done, and it proved that at a specific voltage level, a resonance will be amplified between the capacitor and the regulated transformer which causes the system to experience a massive transient voltage. This led us to the conclusion that the parasitic capacitances and internal circuit of the transformer could push the system to the resonance region, even for a short period of time, and it is proven that the power electronic device such as thyristors cannot handle the surge current claimed in their datasheet. The paper will include simulation results and electric stress evaluation.

In earlier work, cascaded commutation failure (CF) in multiple LCC-HVdc inverters of the multi-infeed system has been attributed to inverter side ac grid faults. However, this paper discusses a phenomenon where the cascaded CF is caused by rectifier side ac faults. The risk of this phenomenon is evaluated considering various fault inception instants, types, durations, and severities by electromagnetic transient simulations. The underlying mechanism of the phenomenon is identified by calculating the area under the commutating voltage curve. It is found that the commutating voltage waveform distortion arising from asymmetrical operation of the primary inverter after the fault clearance causes the initial CF. This CF subsequently introduces significant low-order harmonics into common inverter side ac grid, which propagate to the remote inverter ac bus and consequently induce the cascaded CF. It is also shown that if the tie-line impedance between inverter ac buses limits the propagation of low-order harmonics, the cascaded CF can be avoided. The dependency of the phenomenon on ac grid parameters is further quantified using the CF immunity index (CFII). It is inferred that the phenomenon is alleviated with the increased rectifier and inverter side ac grid strength as well as tie-line impedance magnitude at fundamental frequency.

This paper presents the application of a numerical approach known as proper generalized decomposition (PGD) to calculate the per-unit length (PUL) ac resistance of rectangular conductors. PGD has been successfully used in areas such as fluid mechanics and biomedical applications. It solves a partial differential equation (PDE) by decomposing the answer into a set of unknown one-dimensional (1D) functions in an iterative approach until it reaches a predetermined convergence. In this paper, a frequency-dependent meshing scheme is employed in the PGD technique at each frequency to properly take skin and proximity effects into account. One of the main advantages of PGD over traditional numerical approaches such as finite element or finite difference methods is that it confines the answers within a set of one-dimensional functions, which require fewer computational resources. Different examples of single and multiple rectangular conductors are considered to study skin and proximity effects. The PGD results are compared with those obtained using a commercial finite element method (FEM) software to verify the accuracy of the model. This approach can be used in applications such as white box modeling of transformers, EMC analysis, hairpin winding design used in electric vehicles, and busbar simulation.

This paper investigates commutation failure (CF) in line commutated HVdc converters within multi-infeed HVDC systems and thereby provides valuable insights for the operation and design of HVdc systems. CF susceptibility across various operational scenarios, fault types, and ac system representations at different frequencies is explored. An Electromagnetic Transients (EMT) model is constructed and parameter changes are applied using Monte-Carlo Simulation. The process is fully automated with the use of a controlling program written in Python, which varies parameter values and facilitates result retrieval and post-simulation analysis. A typical analysis results in several hundred thousands of simulation runs, requiring the procedure to be implemented on a parallel computing platform. The results show that two-phase faults are the most critical CF triggers, an aspect often overlooked in previous literature focused on three-phase or single-phase-to-ground faults. Furthermore, the frequency dependent characteristics of the ac network can result in very different CF susceptibilities.

This article proposes a frequency domain technique to quantify the accuracy of multi-rate electro-magnetic transient simulation. Frequency domain transfer relationships are introduced to mathematically represent the up- and down-sampling processes required for interfacing the large and small time-step subnetworks. These are then used to derive the frequency domain equations for the boundary node voltages. By comparing these with the theoretical ones for the original real-world network, a "simulation accuracy spectrum" is developed to quantify the accuracy of multi-rate simulation. The procedure is demonstrated with the example of multi-rate simulation of the IEEE 39-BUS system connected with a VSC-HVdc converter.

Power system controllers are typically designed using continuous time realizations and are then implemented in a digital platform using discrete equations. The performance of the controller is then evaluated with Hardware-in-loop EMT simulation in which the controller is interfaced with a real-time simulation model of the power network. In order to assess the performance of this simulation setup, the paper investigates how the time-step selection and interfacing delays of the digital controller implementation affect the dynamic behaviour of the overall simulation. The paper formulates an analytical approach using the well-known lifting technique, from which a shift-invariant model is derived for the overall system. An eigenvalue based small-signal stability assessment and parametric sensitivity analysis is conducted with the resulting model which is further validated through time-domain EMT simulations.

Adverse controller interactions involving IBRs are a major concern for power system engineers. IBR controllers are not standardized and are proprietary, making it difficult to study and mitigate these interactions. In this scenario, having a supplementary damping controller that modulates an available set point of the existing controller could be a pragmatic solution. There is a vast and positive experience in designing stabilizers for conventional synchronous generators using standardized control structures like washout and lead-lag blocks. The aim is to have similar, straightforward, and easily implementable damping controllers for the emerging IBR based networks. This paper presents an investigation into this issue using a three-IBR system example. For certain controller parameters, the system exhibits poorly damped low frequency oscillations between the IBRs. A simple supplementary damping controller structure using a local feedback signal is found to be feasible for mitigating the IBR oscillations. The frequency scanning approach which is well-suited for black-box system identification is found to be an effective tool for supplementary damping controller design.

This paper introduces a grid forming (GFM) control method - detailed synchronous machine emulation virtual synchronous generator (VSG). The proposed method makes a voltage source converter exactly emulate a synchronous generator (SG), using a current source interface. The precise emulation of an SG gives tighter control over overcurrent and improved transient damping. Electromagnetic Transients (EMT) simulation is used to demonstrate the operation, and small signal model is used to assess the stability performance. Small signal analysis shows that the resulting VSG operates stably, and oscillatory modes can be damped by appropriate optimization of the virtual damping windings resistances.