Demand Distortion Research Articles

A novel design of fourth-order harmonic passive filters for total demand distortion minimization using crow spiral-based search algorithm

Mathematical design of a new fourth-order harmonic passive filter is presented and its optimal strategy is proposed with regards to various design scenarios. The considered objective function is total demand distortion minimization of the supply current. The crow spiral-based search algorithm (CSSA) is applied to solve the design problem formulated. This CSSA relies on a spiral search mechanism that improves the convergence and balances the exploration and exploitation abilities of the conventional crow search algorithm. Various power quality indices are taken into consideration like the individual and total harmonic voltage distortion values, individual and total current harmonic distortion values, active power loss, actual and displacement power factor percentages, and resonance damping capabilities. These indices were handled as non-linear constraints in the design. Additionally, a comparative investigation of the different damped filters is presented to assess the planned filter performance. The results obtained confirm the success of the filter design proposed in this paper.

Market Share Contracts in B2B Procurement Settings with Heterogeneous User Preferences

Market share contracts, a form of loyalty discounts, where the discount is contingent on the buyer meeting or exceeding a target share of total procurement, are used in many business to business (B2B) settings. We study the impact of such contracts on demand allocation, prices, and welfare in a setting where a single central B2B buyer procures multiple units of a product on behalf of a set of users with heterogeneous preferences. We find that linear pricing creates a demand distortion, which goes away with the use of market share contracts. These contracts serve as strategic tools for vendors whose products are strongly preferred by a substantial fraction of the users in the buying organization to shift the locus of competition and extract away rents from weaker rivals, and sometimes from buyers. The impact of such contracts on the welfare of the buyers is therefore ambiguous, but when these contracts are used, the overall surplus goes up as disutility from demand distortion is avoided. While both quantity threshold contracts and two‐part tariffs can replicate the efficiency properties of market share contracts when demand is deterministic, they cannot guarantee the avoidance of demand distortion when buyer demand is uncertain.

Automated Controller Design for the PMSM Using Dynamic Mode Decomposition

This work presents a method to automatically generate a high performance controller for the permanent magnet synchronous motor (PMSM). The method consists of two components, a nominal system identification and a harmonic component identification. Both identification methods are based on dynamic mode decomposition (DMD). The nominal system identification is used to assign the feedback gaines by matching the desired closed-loop eigenvalues and eigenvectors. The harmonic system identification is used to generate vectors that are multiplied by a delay embedding of the current to predict harmonic components at the next time-step. The method is applied to two experimental test setups, one interior permanent magnet (IPM) and one surface mount permanent magnet (SPM) motor. It is shown that the automatically generated feedback controller is able to achieve a more precise transient response than the traditional rule-based PI controller. It is also shown the harmonic compensation method is able to reduce total demand distortion (TDD) on phase currents better than a traditional adaptive filter approach without the need for gain tuning. This work shows a novel approach to using DMD for the complete system identification of the PMSM, and lays the foundation for using DMD with delay embeddings to analyze and manipulate harmonic signals in a predictive way.

Power Quality and Performance Analysis of Grid-Connected Solar PV System Based on Recent Grid Integration Requirements

The electrical energy demand is steadily growing, and hence, the integration of photovoltaic system to the distribution networks is also dramatically increasing though it has a significant effect on the network’s power quality. The purpose of this paper is to analyze the impact of solar PV integration on the power quality of distribution networks. The study is conducted using ETAP software, taking one of the radial distribution networks available in Bahir Dar city during the peak of connected loads which has the least voltage profile. Furthermore, the optimal location of the PV in the network is done using particle swarm optimization. Accordingly, the appropriate location of the PV system is determined to be the farthest end bus (bus 34). Also, the impact in terms of voltage and current harmonic distortion on the distribution feeder network is comparatively discussed by comparing the distribution system parameters with different penetration levels of solar PV system. The simulation results obtained demonstrate that high harmonic distortion level is injected correspondingly as the penetration capacity of PV system increased which indicates that the solar PV system should be integrating only up to a maximum possible capacity the network can carry. The integration of the PV system beyond this maximum penetration level causes production of high harmonic distortion which adversely affects the system performance. At the maximum penetration level which allows the acceptable harmonic distortion limit, the total voltage harmonic distortion and current demand distortion are found to be 4.97% and 14.98%, respectively.

High power quality maximum power point tracking-based islanding detection method for grid-connected photovoltaic systems

Islanding is a condition when distributed generators (DGs) are disconnected electrically from the upstream network. This unwanted situation should be detected effectively to ensure the safety of the maintenance staffs and power quality (PQ) requirements. This paper presents a new high PQ maximum power point tracking (MPPT)-based methodology for detecting the islanding operating mode of grid-connected photovoltaic systems (GCPVSs). In the recommended two-level scheme, a disturbance is injected into the MPPT algorithm under suspicious conditions, recognized by a passive criterion. This disturbance declines the DG active power output remarkably, drifting the output voltage beyond the minimum standard set in islanding state while its impact is negligible at the network presence. The effectiveness of the proposed technique has been evaluated through several hardware-in-the-loop simulations for a case study system, containing two power plant GCPVSs equipped with a pair of multi-functional relays. The results highlight precise islanding classification within 137 ms with the small non-detection zone. Moreover, the results of PQ analyses indicate acceptable total demand distortion and harmonic spectra of the output current in compliance with the existing standards under various DG power penetrations. Since the presented scheme diminishes the active power output in case of suspicious islanding events, its influence on GCPVS efficiency has been studied as well. The outputs underline that the efficiency drops by 0.52% whilst the disturbance is stimulated every minute of the time. It is finally concluded that the proposed technique provides a reliable islanding classification as well as insignificant degradation of PQ and efficiency.

AC Current Ripple Harmonic Pollution in Three-Phase Four-Leg Active Front-End AC/DC Converter for On-Board EV Chargers

Three-phase four-leg voltage-source converters have been considered for some recent projects in smart grids and in the automotive industry, projects such as on-board electric vehicles (EVs) chargers, thanks to their built-in ability to handle unbalanced AC currents through the 4th wire (neutral). Although conventional carrier-based modulations (CBMs) and space vector modulations (SVMs) have been commonly applied and extensively studied for three-phase four-leg voltage-source converters, very little has been reported concerning their pollution impact on AC grid in terms of switching ripple currents. This paper introduces a thorough analytical derivation of peak-to-peak and RMS values of the AC current ripple under balanced and unbalanced working conditions, in the case of three-phase four-leg converters with uncoupled AC-link inductors. The proposed mathematical approach covers both phase and neutral currents. All analytical findings have been applied to two industry recognized CBM methods, namely sinusoidal pulse-width modulation (PWM) and centered PWM (equivalent to SVM). The derived equations are effective, simple, and ready-to-use for accurate AC current ripple calculations. At the same time, the proposed equations and diagrams can be successfully adopted to design the conversion system basing on the grid codes in terms of current ripple (or total harmonic distortion (THD)/total demand distortion (TDD)) restrictions, enabling the sizing of AC-link inductors and the determination of the proper switching frequency for the given operating conditions. The analytical developments have been thoroughly verified by numerical simulations in MATLAB/Simulink and by extensive experimental tests.

Optimal Design of Passive Power Filter Using Multi-Objective Pareto-Based Firefly Algorithm and Analysis Under Background and Load-Side’s Nonlinearity

In this paper, the optimal designing of passive power filter (PPF) is formulated as a multi-objective optimization (MOO) problem under several constraints of system's performance indices (PIs) such as individual as well as total harmonic distortion (THD) in the line current and the point of common coupling's (PCC) voltage, distribution line's ampacity under harmonic currents overloading, steady-state voltage profile, load power factor (PF) and a few associated with the filter itself. The optimal design parameters of a third-order damped filter are simultaneously determined for achieving maximum PF at the PCC while keeping system's other indices such as total demand distortion (TDD) in the line current, total voltage harmonic distortion (TVHD) at the PCC and total filter cost (FC) incurred at a minimum by obtaining a best-compromised solution using the newly proposed multi-objective Pareto-based firefly algorithm (pb-MOFA). A novel MOO approach inspired by the modified firefly algorithm and Pareto front is established in order to deal with PPF design problems. The extension of MOFA is considered for producing the Pareto optimal front and various conclusions are drawn by analysing the trade-offs among the objectives. The efficiency and accuracy of the proposed pb-MOFA, in solving the concerned MOO problem, is validated by comparing an obtained solution and three computed PIs viz. convergence metric (CM), generational distance (GD) and diversity metric (DM) with those obtained from popular multi-objective Pareto-based PSO (pb-MOPSO), non-dominated sorting genetic algorithm (NSGA-II) and recently introduced multi-objective slime mould algorithm (MOSMA). The need for true Pareto front (TPF) is served by the one obtained by Monte Carlo method. At last, the impacts of different background voltage distortion (BVD) levels and load-side's nonlinearity levels (NLLs) on filter performance are analysed.

HIL-Assessed Fast and Accurate Single-Phase Power Calculation Algorithm for Voltage Source Inverters Supplying to High Total Demand Distortion Nonlinear Loads

The dynamic performance of the local control of single-phase voltage source inverters (VSIs) can be degraded when supplying to nonlinear loads (NLLs) in microgrids. When this control is based on the droop principles, a proper calculation of the active and reactive averaged powers (P–Q) is essential for a proficient dynamic response against abrupt NLL changes. In this work, a VSI supplying to an NLL was studied, focusing the attention on the P–Q calculation stage. This stage first generated the direct and in-quadrature signals from the measured load current through a second-order generalized integrator (SOGI). Then, the instantaneous power quantities were obtained by multiplying each filtered current by the output voltage, and filtered later by utilizing a SOGI to acquire the averaged P–Q parameters. The proposed algorithm was compared with previous proposals, while keeping the active power steady-state ripple constant, which resulted in a faster calculation of the averaged active power. In this case, the steady-state averaged reactive power presented less ripple than the best proposal to which it was compared. When reducing the velocity of the proposed algorithm for the active power, it also showed a reduction in its steady-state ripple. Simulations, hardware-in-the-loop, and experimental tests were carried out to verify the effectiveness of the proposal.

Implementing a demand side management strategy for harmonics mitigation in a smart home using real measurements of household appliances

Significant developments on semiconductor technology have captured the electronic industry and paved the way for dominating household appliances market. Typical loads in this market generally have nonlinear voltage-current characteristics. Therefore, highly-integrated power-electronic based electrical equipment in the demand side has caused harmonic pollution, which is one of the most important power quality problems in distribution system operation. To address this issue, there have been significantly great attempts to keep total harmonic distortion (THD) and total demand distortion (TDD) levels within International standard limits defined by IEEE 519 and IEC 61000. On the other hand, load shifting has recently drawn special attention of power grid planners to improve system performance substantially in the smart grid paradigm. In this study, the real harmonic measurements of residential appliances (both linear and nonlinear) are carried out in the Smart Home Laboratory in Yildiz Technical University, Istanbul, Turkey. Different load profiles are then created with a high accuracy based on the measured voltage and current, active, reactive and apparent power. Also, three case studies are considered to investigate the impacts of load shifting strategies on power quality requirements in terms of satisfying the relevant standards. As a result, it is shown that the TDD value decreases below nearly 8% limitation by mitigating the harmonic distortion and the TDD index, which indicates the harmonic distortion effect on the system regarding the desired standard limits of IEEE.

Analysis of Electrical Power Disturbances in Distribution and Industrial Systems

The objective of this study is to clearly analyse by identifying and providing specifications on each disturbance. The main targets are the study of faults that suddenly happen on wires which supply loads, and the survey of detrimental effect coming from the load especially common loads used in industries. Simulation results were presented to illustrate analysis of these disturbances on a Distribution Line network. For signle-phase earthing fault model, the results show the duration of the voltage sag of 90 ms with the magnitudes of 0 kV, 30.97 kV and 30.98 kV respectively for Va, Vb and Vc. For phase to phase fault model, the duration is around 85 ms with Va = 21.3 kV and Vb=Vc= 0kV. When using non-linear loads, the obtained THD varies from 32.10 % to 44.32 % and the total demand distortion (TDD) from 91.42% to 95.21 %.

Effects of mixed electronic loads on the electrical energy systems considering different loading conditions with focus on power quality and billing issues

•The conditions under which electronic loads cause power quality issues are presented.•Total demand distortion has been calculated considering different variables.•Different variables considered: short-circuit and voltage levels, transformers, and cables.•The conditions which cause violation of the limits set by IEEE 519 have been presented.•The billing proposals under nonsinusoidal conditions are reviewed and discussed.

Study of Dual Active Bridge With Modified Modulation Techniques for Reduced Link Current Peak Stress and Harmonics Losses in Magnetics

High-frequency-link power-conversion is gaining popularity in recent days due to reduction of the size and weight of the converters for various applications. The performance of the dual active bridge heavily depends on the nature of modulation strategy used and on the loading conditions. Look-up table (LUT) based output power and output voltage dependent modulation strategies to investigate the peak current stress and harmonics in high-frequency link current is proposed in this article. The modulator is, thus, simple to implement. The peak stress, the harmonics (total demand distortion) in link current, and associated losses due to the proposed techniques are compared in four main cases, namely, first, single-phase shift, second, dual-phase shift, third, triple phase shift, and, fourth, modified phase shift (MPS)-I, -II, and -III. In MPS-I, weighted aggregate of harmonic currents minimization including fundamental component is carried out to achieve the minimum conduction losses in the magnetic elements. The same method is extended for minimizing the peak-to-peak ripple in the link current as MPS-II. In MPS-III, the desired total demand distortion in the ac-link current is enforced. The variation of voltage transfer ratio between input and output is taken into consideration using two-dimensional (2-D) LUT. Moreover, the requirement of 2-D LUTs are eliminated by using suitable curve-fitting exercise for the output load voltage variation and 1-D LUTs of coefficients. A detailed simulation study, associated mathematical analysis of the methods adopted and experimental verification are presented from 1 kW prototype.

Adaptive current harmonic estimation under fault conditions for smart grid systems

This paper presents an adaptive harmonic disturbances detection under fault conditions in a smart grid (SG) system. Monitoring and controlling SG networks require real-time measuring. This measuring demands high-speed, fully integrated, and two-way communication technologies.On a fault condition, the online accurate monitoring becomes difficult due to the transient current occurrences requiring adaptive methods to achieve SG requirements. In this work an adaptive technique to reliable monitoring harmonic distortion in the power network has been proposed. Harmonic estimation is implemented by utilizing the least square (LS), Kalman filter (KF), Maximum Likelihood estimation (MLE), and Goertzel Algorithm to obtain the amplitude of the harmonics in the network and its variation under dynamic fault conditions. The tested smart micro-grid (SmG) includes wind turbines (WT) and photovoltaic (PV) panels with time-variable loads at a medium voltage level. Consequently, the total demand distortion (TDD) estimations using the filtering estimators are also compared with the predictions obtained by the conservative power theory (Tenti) accordingly. Finally, a performance-complexity tradeoff analysis demonstrated the (dis)advantages of each filtering method.

The Cost of Legal Restrictions on Experience Rating

We investigate the cost of legal restrictions on experience rating in auto and home insurance. The cost is an opportunity cost as experience rating can mitigate the problems associated with unobserved heterogeneity in claim risk, including mispriced coverage and resulting demand distortions. We assess this cost through a counterfactual analysis in which we explore how risk predictions, premiums, and demand in home insurance and two lines of auto insurance would respond to unrestricted multiline experience rating. Using claims data from a large sample of households, we first estimate the variance‐covariance matrix of unobserved heterogeneity in claim risk. We then show that conditioning on claims experience leads to material refinements of predicted claim rates. Last, we assess how households’ demand for coverage would respond to multiline experience rating. We find that the demand response would be large.

All SiC PWM rectifier‐based off‐board ultrafast charger for heavy electric vehicles

本研究涉及用于重型电动汽车钛酸锂电池的基于全碳化硅脉宽调制 (SiC PWM) 整流器的非车载超快充电器 (UFC) 的设计、实现和实验性能。根据标称电池电压（400–1000 V DC）和充电容量，建议使用不同的 UFC 配置。评估了UFC在单位功率因数和超前功率因数下的工作原理和控制，并讨论了PWM整流器的相应工作模式。在进行的所有分析中都考虑了 SiC 功率金属氧化物半导体场效应晶体管 (MOSFET) 和内置 SiC 肖特基二极管的反向传导特性的组合效应。开发的 UFC 的工作性能，例如 SiC 功率 MOSFET 模块的开关特性、效率、输入电流总需求失真 (ITDD) 和 SiC PWM 整流器的热限制已经针对各种充电电压和充电容量进行了评估，两者都通过计算机模拟和实验室测试。本研究还给出了建议系统的电源电路布局考虑因素。开发的 200 kW UFC 在 10 kHz 开关频率下获得了出色的性能结果，在高达电池容量五倍的所有充电率下运行效率高于 98.5%，并且在整个运行范围内 ITDDs <2.2%。

Market Share Contracts in B2B Procurement Settings with Heterogeneous User Preferences

Market share contracts, a form of loyalty discounts, where the discount is contingent on the buyer meeting or exceeding a target share of total procurement, are common in many B2B settings. We study the impact of such contracts on demand allocation, prices, and welfare in a setting where a single central B2B buyer procures multiple units of a product on behalf of a set of users with heterogeneous preferences. We find that regular (linear) pricing creates a demand distortion, which goes away with the use of market share contracts. These contracts serve as strategic tools for vendors with preferred products to shift the locus of competition and extract away rents from weaker rivals, and sometimes from buyers. The impact of such contracts on the welfare of the buyers is therefore ambiguous, but when these contracts are used, the overall surplus goes up as disutility from demand distortion is avoided. While similar in many respects, quantity threshold contracts cannot guarantee the avoidance of demand distortion when buyer demand is uncertain.

A Hybrid Phase Shift-Pulsewidth Modulation and Asymmetric Selective Harmonic Current Mitigation-Pulsewidth Modulation Technique to Reduce Harmonics and Inductance of Single-Phase Grid-Tied Cascaded Multilevel Converters

In this article, a low-frequency hybrid modulation technique which is composed of a phase shift-pulsewidth modulation (PS-PWM) and an asymmetric selective harmonic current mitigation-PWM (ASHCM-PWM) are proposed for cascaded multilevel converters to meet the harmonic limit of IEEE 519 2014. In the proposed technique, the harmonics within the concerned frequency range due to PS-PWM are reduced by the ASHCM-PWM so that the cascaded H-bridge (CHB) converter can meet IEEE 519 harmonic limit. The equation set which helps a grid-tied CHB converter meet both harmonic limit and total demand distortion, is developed. The design technique for critical parameters, such as the inductance and the switching frequency of the proposed hybrid modulation technique, is developed. Simulation and experiments are conducted on a single-phase 3-cell 7-level grid-tied CHB converter to validate the proposed technique.

Harmonic failure in the filter of Static Var Compensator

The Static Var Compensator (SVC) is an important transmission component for the stability of the power system, it has 3 main components: Thyristor- controlled reactor (TCR), Thyristor-switched capacitor (TSC) and filters. The filters are the weakness part in this power system. In this kind of equipment, the worst problem associated with a filter failure is the harmonic damage in the power system, the currently international standards doesńt have enough information about the damage in the power system with high harmonic influence caused by SVC with the filter failure.In this research the main scope is to provide a new assessment procedure for energy and industrial companies for the application of equipment on the utility system, it will illustrate the harmonic assessment levels, at the point of common coupling (PCC).A real failure analysis is made for a better comprehension of the concepts of the PCC, it is very important to know the way of harmonic current flow and other parameters as: Average maximum demand load current, the short circuit ratio (SCR), the total demand distortion (TDD) and total harmonic distortion (THD). I will provide a better understanding and recommendation for the IEEE Standard 519, the dimension should address the time variations and the statistical characteristics of the harmonic levels. The harmonic is important due to levels, control on the utility system. This engineering failure analysis of the filter applications and interface with other energy companies.

Disturbance Frequency 9 – 150 kHz Characteristics towards Total Demand Distortion on On-Grid Solar Panel System in the Electrical System of Kuningan Gas Station

To use solar energy into electricity, a solar panel system is needed which of course uses solar panels. As we know, a solar panel system has quite a lot of non-linear equipment, for example is an inverter. The use of this inverter will affect the power quality of the output of solar panels, one of which is disturbance. At a frequency range of 9 – 150 kHz, electrical equipment with an inverter will produce a disturbance in the system. So, in this paper, the study was conducted to observe the characteristics of the disturbance frequency of 9 – 150 kHz towards total demand distortion on on-grid solar system in the electrical system at the gas station so that it can be used as a guide for future disturbance and solar energy research.

Assessment of an Improved Finite Control Set Model Predictive Current Controller for Automotive Propulsion Applications

This paper presents an investigation on finite control set model predictive current control, validated experimentally with a rear axle electrical drive unit used in automotive applications. An improved problem formulation is suggested which lowers the computational turnaround time of the solver with approximately $\text{40}\%$ for an horizon length of $N=4$ . Apart from the computational requirement aspects, the assessment focuses on inverter efficiency, phase current total demand distortion, and acoustic performance. The proposed solution is evaluated against a standard double proportional and integrator (PI) field-oriented current controller with pulsewidth modulation. It is shown that the proposed solution is feasible, the associated optimization problem at hand can be solved in real time, while exploiting the attractiveness of the proposed improvements. In summary, it is concluded that the inverter efficiency can be improved without deteriorating neither the phase current harmonics nor the acoustic performance.