Average-value Model Research Articles

The Relationship Between Climate Change and Indonesia's Malaria Burden

ABSTRACTMalaria has been with humans for thousands of years. It is caused by parasites of the genus Plasmodium that are transmitted by female Anopheles mosquitoes. The variation of global malaria distribution has recently been associated with changing climatic conditions, such as temperature, precipitation, windspeed, and humidity. One country where malaria transmission remains high in select subnational areas is Indonesia. Founded upon previous findings on the relationship between climate change and malaria, this research delves into the same equation for the case of Indonesia through a structural model which overcomes the variable co‐interaction between temperature, precipitation, windspeed, and humidity. This study follows an ecological study design with yearly longitudinal data (t = 20, n = 432). The method of analysis employed is a structural equation modelling approach for panel datasets with an output of factor loading values to determine association levels. The independent variable is a climate change construct of maximum, minimum, and average values from temperature, windspeed, relative humidity and precipitation as observables taken from the NASA Langley Research Center (LaRC) POWER Project. Meanwhile, the dependent variable is yearly malaria incidence rates at the city and regency level extracted from the Malaria Atlas Project dataset. All variables are standardized to account for unit differences. The SEM results indicate a standardized relationship between a latent climate variable with malaria incidence in a statistically significant manner. However, differences in coefficient directions between the three models indicate that the relationship remains elusive. In the maximum value model, a standard deviation increase in the climate change construct from its mean is associated with a 0.04 standard deviation increase in malaria incidence from its own mean (p < 0.001). On the other hand, in the minimum and average value models, a standard deviation increase in limate change construct from its mean is associated with a 0.12 and 0.09 standard deviation decrease of malaria incidence from its own mean respectively (p < 0.001). Although statistical significance was established across all models which indicated relatively good fit across select indices, the standardized coefficient values presented in this study suggest that any associations between long term climatic variations (measured by yearly data) and malarial incidences are modest at best. The results of the structural equation models also indicate that other factors are at play when it comes to malaria case variations—as explained by the residual terms across all models.

An accelerated modelling method of full-bridge modular multilevel converter considering dead-time

To avoid short-circuits of the same side switching of power converters, the dead time is of significance in the pulse trigger gating signal for full bridge modular multilevel converter (FB-MMC). However, the previous equivalent models use the binary resistance switching model to equivalent the switching state which is impossible to simulate the switching with dead time, and the detailed model (DM) with higher levels is time-consuming and inefficient in electromagnetic transient (EMT) simulation. To address this problem, based on the state-space averaging method, a speed-up average value model (AVM) of FB-MMC considering dead time is proposed. Firstly, the working state of FB-MMC is obtained through analysing the switching states with dead time and is classified into three cases according to the capacitor. Secondly, derived from state-space equation, the three cases are integrated into a unified model by introducing the duty cycle, and then the equivalent controlled source is used as the interface circuit between the external grid and capacitor. Finally, a 49-level two-terminal MMC-HVDC system consisting of FB-MMC is constructed in PSCAD / EMTDC simulations, showing that the proposed AVM compared with DM has high accuracy and operation efficiency.

A current injection method for converter power loss representation in electromagnetic transient simulation

The power-electronics converters are increasingly applied in modern power system, which contains various sub-systems, such as renewable energy power plants and high voltage direct current transmission systems, etc. The electromagnetic transient simulation has been one of the important tools for the study of complex system containing large numbers of power converters. The coordination control of the power converters and corresponding power generation and load units is one of the challenges ensuring stability and obtaining optimal efficiency. However, the detailed modeling of the power converters considering the conduction and switching losses can cost a great number of computation resources, which makes it difficult to simulate a large system. This work proposed a current injection method for converter power loss representation, which can accurately consider the conduction and switching losses of the power-electronics switches with low computation complexity. A look-up table (LUT) of the power loss ratio is calculated before the simulation, and a current source representing the power loss is connected in parallel with the converter to track the reference loss generated by the look-up table. The proposed method can be combined with multiple converter modeling schemes, such as the two-resistance model, the switching-function model, and the average value model, etc. The topologies of the two-level converter and the modular multi-level converter (MMC) were used in the case studies to demonstrate the effectiveness of the proposed method. Compared to the device-level model, the simulation power loss deviation is 0.64% and 4.13% applying the current injection method model in the case studies of the two-level converter and the MMC.

Improved Dynamic Performance of Average-Value Modelled Active Front-End Rectifiers

Active front-end (AFE) rectifiers have become widely employed in power systems to achieve unity power factor and harmonic mitigations. The typical modeling approaches applied for AFE rectifiers in the literature mostly relied on two baselines: the detailed model and the time-average model. The former approach deals with the switching element model (SEM), which leads to significant harmonics in currents with distorted waveforms. The latter approach uses the average-value model (AVM) to overcome the currents’ harmonics as well as provide fast responses. However, even the AVM baseline has shown problems during the starting stage (lack of control signals) and over the dead-time periods, which causes serious issues in the implementation process. This paper presents an improved dynamic AVM for AFE rectifiers by precisely considering the issues mentioned above, along with the practical starting procedure and desirable initialization. The studied AFE rectifier is developed using the voltage-oriented control (VOC) technique based on the different modeling methodologies, including SEM, Conventional AVM, and the proposed AVM. The performance of all models is analyzed and compared using simulation results with MATLAB/Simulink R2023a Function blocks for all the algorithm parts and SimScape elements for the electrical circuit model. The simulation results illustrate that the performance of the proposed AVM approach can closely resemble the behavior of the SEM baseline with low harmonic distortion. To evaluate the performance of the proposed model, several case studies are investigated to verify the AFE rectifier operation, regarding mostly the total harmonic distortion (THD) wherein the THD percentages are improved to 4.78 and 2.5 from 5.14 and 2.78 for low- and high-power loads, respectively.

Numerically Efficient Average-Value Model for Voltage-Source Converters in Nodal-Based Programs

Numerically Efficient Average-Value Model for Voltage-Source Converters in Nodal-Based Programs

Average-Value Model for Voltage-Source Converters With Direct Interfacing in EMTP-Type Solution

Average-value models (AVMs) of high-frequency switching voltage-source converters (VSCs) are indispensable for fast/efficient simulation of VSC-based power systems. However, in EMT/EMTP-type programs large simulation time-steps cannot be utilized with conventional non-iterative interfacings of AVMs due to numerical inaccuracy/instability as a result of a one-time-step interfacing delay. In this letter, a directly-interfaced AVM has been developed for the VSCs which eliminates the interfacing delay and allows large time-steps. This is achieved by formulating the AVM in the nodal form that is solved simultaneously with the overall network nodal equations. The new proposed model is demonstrated to outperform the existing AVMs of VSCs in terms of accuracy at fairly large time steps.

Compensation-Voltage-Injection-Based Neutral-Point Voltage Fluctuation Suppression Method for NPC Converters

Three-level neutral-point clamped (NPC) inverters are widely used in the new energy power generation, motor drive, and many other occasions. However, the neutral-point voltage imbalance of an NPC inverter will affect the output of the inverter system, and the control of the neutral point voltage has become a popular research topic. In this paper, a compensation-voltage-injection-based neutral-point voltage balancing method is proposed. During the switching cycle, the average value model of the neutral-point current under different voltage vectors is applied to calculate the value of the compensation voltage that needs to be injected. The self-balance of the neutral-point voltage based on a switching cycle is realized, and the influence of modulation ratio and power factor on equalization ability is discussed. A MATLAB/Simulink simulation model and a small power prototype are established to verify the effectiveness of the method, and the simulation and experimental results show that the proposed method can effectively suppress the neutral-point voltage fluctuation in a wide range of modulation ratios and power factors.

Variable Multiple Interleaved Bi-Directional DC/DC Converter with Current Ripple Optimization

In order to reduce the current ripple and improve the power density of the system, the multiple structure design is generally adopted by the traditional bidirectional DC/DC converter. However, the fixed multiplicity design can’t make the DC/DC power converter always output the smallest current ripple under different duty ratios. Through this research, it is found that the current ripple is related to duty cycle and parallel multiplicity, and then a variable multiplicity bidirectional DC/DC power converter is proposed. Firstly, the relationship between the current ripple and parallel multiplicity and duty cycle is deduced, and the basic topology of variable multiplicity bidirectional DC/DC power converter is determined; Secondly, the average value model and AC small signal model of the system are established based on the topological structure, and then the state equation is obtained. Thirdly, the current compensation control method is designed based on the state equation. Finally, the experimental platform of variable multiplicity bidirectional DC/DC power converter is built.

A Resilient Prosumer Model for Microgrid Communities with High PV Penetration

Worldwide energy shortages and the green energy revolution have triggered an increase in the penetration of standalone microgrids. However, they have limited generation capacity and are wasteful when excess generated energy is curtailed. This presents an opportunity for the coordinated operation of multiple prosumer microgrids that absorb this waste to enhance their resiliency and reliability. This paper proposes a reliable prosumer model with an inbuilt energy management system (EMS) simulator that considers the mentioned deficiencies for constructing resilient interconnected prosumer microgrids. The EMS simulator operates in a real-time dynamic environment to coordinate the prosumer components and performs flexible switching for (1) prioritizing critical load by shedding the non-critical load and (2) meeting load demand locally or from other interconnected prosumers. The EMS simulator maintains energy balance by setting limits for the battery energy storage system (BESS) to preserve energy during low generation and performs real-time monitoring. The novelty of this model lies in its simplicity and flexibility, which allows interconnected prosumer microgrids to operate in cooperation without the need for communication. The proposed model is evaluated in a post-disaster off-grid scenario using a single-phase average value model that considers reasonable computation time. The simulation results of the proposed system indicate the preservation of stored energy while maintaining critical resources beyond three days of poor weather conditions.

New energy vehicle engine speed control method based on vehicle networking technology

In view of the current new energy vehicles only implement torque control on the drive motor, resulting in the engine speed fluctuation, affecting the vehicle running stability and reducing the engine efficiency and energy saving effect, a new energy vehicle engine speed control method based on Internet of vehicles technology is proposed. The battery and operation data are obtained through the sensor of the new energy vehicle Internet of vehicles, and the data are controlled and transmitted by the controller area network. The overall external dynamic characteristics of the engine are analyzed by using the average value model. According to the principle of engine dynamic system, the throttle intake manifold model, combustion torque model and power output sub model are constructed respectively. The speed is controlled by double working points According to the variable parameter PID control of the engine, the load prediction is introduced to optimize the speed control, and the internal pressure value of the accumulator is obtained through the SOP value to realize the speed control of the new energy vehicle engine. The experimental results show that the engine speed control method can effectively improve the energy-saving effect and efficiency of the engine, reduce the engine speed fluctuation, and improve the vehicle running stability under the condition of meeting the driver’s torque demand.

Direct Interfacing of Parametric Average-Value Models of AC–DC Converters for Nodal Analysis-Based Solution

AC–DC converters are widely used in many power-electronic-based systems. There is an increasing need to simulate such systems using larger time-steps in offline and/or real-time electromagnetic transient (EMT or EMTP) simulators. The so-called parametric average-value models (PAVMs) have been developed to allow larger time-steps and provide fast simulations. However, the application of PAVMs in nodal-analysis-based EMTP programs typically requires a one-time-step delay between the interfacing sources and the network solution (i.e., indirect interfacing), causing inaccuracy and numerical instability at medium-to-large time-steps. This paper presents a direct interfacing method for PAVMs of line-commutated rectifiers (LCRs). The proposed method linearizes the PAVM interfacing equations and incorporates the respective sub-matrices and history terms into the network nodal equations, which eliminates the need for a time-step delay. Simulation studies verify the effectiveness of the proposed method in EMTP-type solution wherein very good accuracy and numerical stability is achieved at fairly large time-steps, which has not been previously possible with conventional methods.

Strategy to reduce transient current of inverter-side on an average value model high voltage direct current using adaptive neuro-fuzzy inference system controller

Growing-up of high voltage direct current (HVDC) penetration into modern power systems (PS) makes difficulty on the PS operation. The HVDC produces high and slow transient current (TC) at start-time, especially for higher up-ramp rate (Urr>20 pu/s). Its condition makes the HVDC cannot be linked and synchronized into the PS rapidly. A strategy to reduce the TC is proposed by an adaptive network based fuzzy inference system (ANFIS) control on inverter HVDC-link to cope up this problem. The ANFIS control is tuned with the help of conventional control in various train-data by using offline mode. Response of ANFIS scheme is improved by suppressing TC at the values of 3.75% for the both phases (A and C), and 3.95% for phase B, for the Urr=30 pu/s. While the conventional control achieved at 9.1% for the both phases (A and B), and 9.2% for the phase C. The ANFIS control gives shorter settling time (0.553 s) than the conventional control (0.584 s) for all phases. The proposed control is more effective than the conventional control at all the scenario.

Average-Value Modeling of Line-Commutated Inverter Systems With Commutation Failure

Line-commutated converters are extensively used as the interface between ac grids and classic HVDC systems. At the inverter side, commutation failure of switches is one of the most common faults that can pose threats to the system operation. Practical and reliable study of such phenomena relies on accurate and efficient converter models for simulations. Recently, a parametric average-value model (PAVM) has been presented for ac–dc rectifiers, which considers the internal faults of the converter. In this paper, the PAVM methodology is extended to the dc–ac inverter systems, including the commutation failure of switches. The proposed PAVM also augments an automatic fault detection technique to determine the faulty switches. Using comprehensive simulation studies, the developed model is verified to accurately predict the commutation failure of switches and reconstruct the waveforms consistent with the detailed switching models of inverters while being computationally more efficient. The proposed PAVM is envisioned to be an efficient and accurate asset for simulation of HVDC systems and inevitable when faults of switches need to be considered.

Full Simulation Modeling of All-Electric Ship with Medium Voltage DC Power System

This paper proposes the full simulation model for the electrical analysis of all-electric ship (AES) based on a medium voltage DC power system. The AES has become popular both in the commercial and the military areas due to a low emission, a high fuel consumption efficiency, and a wide applicability. In spite of many advantages, it is complex and difficult to construct the whole system with many mechanical and electrical components onboard. Full electrical analysis is essentially required to simplify the design of the AES, a control and optimization of a ship electric system. The proposed full simulation model of the AES includes the mechanical and the electrical elements by using the MATLAB/Simulink. The mechanical elements are comprised of a steam turbine and a hydrodynamic model of a ship which is adopted by an average value model that is based on the characteristic equation of the mechanical system. The electrical elements are developed by full detailed models which consist of generators, a propulsion motor, a battery, and a power electronics system. In order to design the distribution of the ship, the presented simulation model combined the mechanical and the electrical systems. The consistency of the developed individual models and the integrated AES was verified through the results of the presence or absence of the energy storage system for the speed acceleration and deceleration, loss of prime mover, and full propulsion load rejection.

Modified average‐value model for high‐performance fault transient simulation of AC‐DC hybrid power networks

Due to the complicated transients and the possibility of transition from a minor fault in AC subsystems to a severe blocking event of a high-voltage direct–current (HVDC) transmission line, the study of AC-DC hybrid power systems requires both efficient and accurate electromagnetic transient (EMT) simulation. However, the computational efficiency of such simulations is restrained by the switching events when detailed models of line-commutated converters (LCCs) are used. Recently the average-value modelling technique has been developed for accelerating the simulation while still accurately capturing the transient characteristics of line-commutated AC–DC converters. This study presents the application of the average-value model in the modelling of the LCC-HVDC system and gives a further discussion about the deficiency of the model. A modified interface and the corresponding soft-switching technique are proposed for enhancing the simulation performance of the LCC-HVDC model in the transition between normal and faulty operation. The model is tested on a series of LCC-based systems including a hybrid power system with four LCC-HVDC lines to verify its efficiency and accuracy. The results indicate that the developed model can accurately predict the transients of the system both in symmetrical and asymmetrical operation while being computationally efficient.

Average-Value Modeling of Direct-Driven PMSG-Based Wind Energy Conversion Systems

Control design and stability analysis of direct-driven permanent magnet synchronous generator (PMSG)-based wind energy conversion systems (WECSs) typically involve extensive time-domain simulations and frequency-domain analyses. Those studies rely on accurate and computationally efficient models of WECSs. Detailed switching models can accurately describe the transients of power-electronic converters, but they suffer from low computational efficiency due to the repeated switching events. In this paper, a numerically efficient model is developed for a direct-driven PMSG-based WECS. Analytical and parametric average-value modeling techniques are applied to its switching subsystems, including a 12-pulse diode rectifier, a three-phase-interleaved boost converter, a dual three-phase voltage source inverter (VSI), and a crowbar circuit. The average-value models (AVMs) improve the simulation efficiency by representing the terminal characteristics of switching subsystems with a set of algebraic equations. In addition, numerical linearization techniques can be directly employed for them to obtain frequency-domain characteristics. The proposed model is verified against the detailed switching model and existing AVM in MATLAB/Simulink. It is shown to have excellent accuracy in both time-domain and frequency-domain studies while maintaining high computational efficiency.

Super-Twisting Algorithm Second-Order Sliding Mode Control of a Bidirectional DC-to-DC Converter Supplying a Constant Power Load.

The Super-Twisting Algorithm is employed to control the voltage of a Bidirectional DC-to-DC Converter of an on-board propulsion system in presence of large load variations. The Bidirectional DC-to-DC Converter is modeled using average value modeling, and it is shown by an alternative approach that the zero dynamics for the converter topology supplying a Constant Power Load are unstable with the DC bus voltage as output, and stable for the inductor current as output. Here, a derivation of the controller gains is presented based on the average model of the system. The gains are described with respect to the inductor current and its bounded perturbations. The performance of the proposed controller is compared to a conventional cascaded PI controller, and exhibits strong robustness with respect to external system variations.

Improved Average-Value and Detailed Equivalent Models for Modular Multilevel Converters with Embedded Storage

The paper develops two computationally efficient models, namely a detailed equivalent model and an average-value model, with provisions for representation of the critical state of converter blocking, for modular multilevel converters with embedded storage. These models are indispensable in the simulation of dc faults. The developed detailed equivalent model provides accuracy that matches electromagnetic transient (EMT) simulations, with much reduced computational burden; the developed average-value model represents the averaged behavior of the converter by neglecting switching transients. Both models are extensively evaluated in the context of an HVDC system against benchmark results form a detailed switching model developed in PSCAD/EMTDC. The results confirm the validity and accuracy of the models for steady state, transient, and faulted operating conditions including when the converter is blocked in response to a dc fault.

Average-Value Modeling of Line-Commutated AC–DC Converters With Unbalanced AC Network

AC–DC line-commutated converters (LCCs) are widely utilized in existing and emerging ac–dc power systems. Analysis of such systems under balanced and unbalanced conditions is often carried out using electromagnetic transient (EMT) simulation programs. Therein, the detailed switching models of LCCs are often the computational bottlenecks for system-level studies. Recently, the parametric average-value models (PAVMs) have been developed to achieve fast and efficient simulations of switching converters. In this paper, the PAVM methodology is extended to consider operation of LCCs under unbalanced conditions in the ac network. This is done in the extended PAVM by formulating the ac-side harmonics in positive and negative sequences as well as the dc-side harmonics (i.e., ripples) with respect to the ac network imbalance. The new PAVM is validated experimentally and by simulations, and is demonstrated to be accurate in reconstructing the ac and dc waveforms under unbalanced conditions in the ac network. Meanwhile, the proposed PAVM is computationally much faster than its detailed switching model counterpart.

Medium voltage DC distribution system simulation based on average-value model

Transient simulations with of DC distribution system based on switch model (SM) are computationally expensive because of a large number of switching events in power electronics converters. As an alternative, average-value model (AVM) replaces the switch with controlled source, which can effectively improve the simulation efficiency. This paper takes a typical double-ended DC distribution system as an example and introduces the key equipment selected in the system. Then AVMs of corresponding equipment are given. The DC distribution system based on AVM and SM is built respectively in the PLECS software. The simulation result shows that simulation based on AVM can effectively reflect the steady-state and dynamic characteristics of the system and greatly improve the simulation speed, which can provide an effective and fast reference for the stable operation of DC distribution system in different working modes.