Simulation-Based Study of Harmonic Distortion from EV Chargers in Low-Voltage Distribution Networks

A comparative assessment of SARIMA, LSTM RNN and Fb Prophet models to forecast total and peak monthly energy demand for India

Harmonics generated by power converters have become a serious problem for the AC mains as they can only be removed by using bulky passive filters. Besides, harmonic compensation by shunt passive or active filters causes undesirable interference such as resonance with the AC mains. To solve this problem, the authors have proposed a combined system of a shunt passive and series active filter. This system is self-adaptable and only a small power active filter is needed to compensate the harmonics generated by large converters. The control algorithm of the active filter is based on instantaneous active and reactive power calculations. A combined system is used to minimise harmonic currents and voltage in the AC systems. Here, the authors demonstrate that the study of a three phase system can be realized by using a single phase equivalent circuit when the line currents are balanced. The series active filter plays the role of an active impedance. This means that it presents a negligible impedance for the fundamental frequency and a pure resistance for the harmonics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The continual growth of renewables in the distribution scale is converting the conventional arrangement of power grid into a modern arrangement in which the Distribution Generation (DG) units are included within the distribution section of any power system. These renewable units include power electronics-based converters in their construction and the advent of these new technologies deteriorates the Power Quality (PQ) and introduces serious issues of harmonic distortion in both voltage and current waveforms. This research attempts to alleviate the problem of harmonic distortion in low voltage distribution networks containing solar PV modules through the proper sizing of adaptive Passive Harmonic Filters (PHFs). For this purpose, a real distribution network is simulated by ETAP environment, and the harmonic's load flow study is performed to specify the harmonic content at various busbars in the network. Hence PHF models based on the frequency scan performed are proposed to minimize the Total Harmonic Distortion (THD) in the network. The results of the simulations performed have shown that this approach reduces the THD significantly to comply with the permissible limits specified by the international standards IEEE STD 519 and IEC STD 61,000–3–6.

Shunt passive filters, which are connected in parallel to harmonic-producing loads, have been widely used for harmonics suppression in power systems because of low costs and high efficiency, although they have inherent problems such as series and parallel resonance. On the other hand, shunt active filters, which are also placed in parallel, have such an inherent problem as initial and running costs are high, compared with those of shunt passive filters. To solve these inherent problems in shunt passive and shunt active filters, the authors have proposed a combined system of a shunt passive filter and a small rated series active filter.The purpose of this paper is to reduce the required rating of the series active filter, considering a practical application of the combined power filter to harmonic compensation for large capacity thyristor converters. The points are summarized as follows:(1) The required rating of the series active filter can be reduced less than one-tenth by connecting a series resonant circuit in parallel to the secondary of current transformer.(2) It is clarified theoretically and verified experimentally that compensation characteristics of the new combined system are equivalent to those of the already proposed system with no series resonant circuit.

Since the beginning of operation of China's /spl plusmn/500 kV Gezhouba-Nanqiao (GZB-NQ) HVDC link, the smoothing reactor and the capacitors of its DC filters have faulted many times due to reasons of design, construction and others. In order to solve these problems, a method of harmonics suppression and passive filter regulation is presented using an active DC filter on the DC-side of the GZB power converter substation. The active DC filter is connected at the bottom of one existing passive DC filter at the GZB converter station. The construction and control strategies of the active DC filter, as well as the principle of regulating passive filter load are presented. Digital simulation results show that the practical feasibility of the control technique and load regulation scheme for passive filters proposed in this paper.

With the rapid development of social economy, electric energy plays an indispensable role in social life and has become an important symbol of the country’s comprehensive national strength. However, with the rapid development of power electronic technology, many nonlinear loads appear in the power system, which has become the most important harmonic source in the power system. Harmonics will not only affect the normal operation of various electrical equipment, but also damage the peripheral communication system and equipment of public power grid. Therefore, we must control the harmonics in the power grid. The traditional treatment scheme is to use LC passive filter (PF), but it can only filter out harmonics of a specific number of times. In addition,it is sensitive to power grid parameters, may produce resonance, so that the harmonics are amplified, and the volume of the filter device is huge. In order to overcome the above problems, active power filter (APF) appears, which can dynamically compensate harmonics according to harmonic frequency and size, and has excellent flexibility and practicability. However, in terms of cost, the cost of APF with the same capacity is much higher than that of PF. Therefore, based on the respective characteristics of PF and APF, this paper makes an in-depth research and design of hybrid active power filter (HAPF). In this system, the passive filter completes the main harmonic compensation and reactive power improvement, while the active filter is used to help the passive filter overcome the disadvantage of easy resonance.

The dc–ac conversion in microgrids leads to second-order oscillations in the dc side voltages and source currents. These oscillations are mitigated using either active or passive filters. Active filters are preferred, as they mitigate oscillations with lesser component size than passive filters. The active filters are regulated to absorb the harmonic ripples at the ripple frequency, and do not provide any voltage support during dc bus voltage fluctuations due to load changes. In this article, a robust integral sliding mode control (RISMC) is proposed to regulate bidirectional converter (BDC)-based dc active filters to facilitate voltage conditioning along with reduction of second-order harmonics which are caused due to dc–ac conversions. The proposed RISMC enhances capability of the BDC active filters to provide dc bus voltage conditioning in case of transience during load variations and uncertain voltage fluctuations. The proposed control consists of a nominal dual-loop PI control which regulates the voltage of the storage capacitor of BDC and a nonlinear integral sliding mode control which regulates dc bus voltage. The proposed control mitigates voltage and current ripples hence preventing them to propagate toward the sources while providing additional voltage support functionality. The proposed control is verified through simulations and experimentation.

Along the last years, the practical use of active&#13;\nfilters to mitigate harmonics has been extended in electric power&#13;\nsystems. Different configurations of series active filters versus&#13;\nshunt active filters have been proposed, among them, hybrid&#13;\ntopologies which combine active and passive filters.&#13;\nNevertheless, there is not any clear accordance about the most&#13;\nsuitable configuration for each type of harmonic sources. In this&#13;\npaper, four different topologies of active power filters to&#13;\neliminate harmonics have been analyzed. An experimental&#13;\nprototype has been implemented to each configuration and have&#13;\nbeen submitted to different performance tests. With this&#13;\nobjective, a test bank has been developed, which includes&#13;\nnonlinear loads kind harmonic current source, ahrmonic voltage&#13;\nsource, and other whose behavior is between they both. The&#13;\nanalysis of experimental results obtained allows the most&#13;\nsuitable active filter power topology to be determined for each&#13;\ntype of load.

This paper discusses a technique of reducing harmonics in electric power grids using Shunt Hybrid Active Power Filter. The filter is controlled by a Model-Predictive Control technique. It can predict the output current magnitude based on its predictive model by noticing the constructed grid topology. Then, this current prediction has been compared to reference currents in order to get an optimal switching pattern concerning a cost function while the optimization has been conducted in order to figure out the maximum condition for the switching pattern. In addition, the Shunt Hybrid Active Power Filter has been compared by combining passive and active filters, which has been expected to be able to reduce harmonics optimally. The use of an LC filter in a single tuned has been also targetted in order to reduce the harmonics in the fifth-order, while the active filter would reduce harmonics due to their resonances. The constructed model has been tested in the simulation in order to evaluate how much harmonic reduction could be performed by the model, and how this model has coped with an unbalanced load, and later affecting the electric power quality. The simulation shows that Shunt Hybrid Active Power Filter along with the Model-Predictive Control method tested by non-linear loads, in terms of balanced and unbalanced loads, can reduce Total Harmonic Distortion of current loads to under 1%. As for unbalanced loads, the phase angle on source voltage does not encounter displacement. Therefore, the Model-Predictive Control on Shunt Hybrid Active Power Filter can effectively be used to reduce harmonics in the grid, during both balanced and unbalanced loading condition.

There are some restricted features of AC filters installed in LCC HVDC, which is no longer suited to the new power system. There's an urgent need to improve the filtering design in LCC HVDC and active filter is the most promising technology. In the research we designed a new type hybrid filter, which is simply combined by passive filter and an IGBT valve. We chose the reasonable passive filter capacity and passive filter topology. We designed two control strategies and combined used them according to the passive filter property. We designed the starting capacitor and the clamping arrester, furthermore we raised starting strategies and fault protection strategies. We calculated the filter performance in Harmonic Numerical Calculation Progress, compared it with traditional passive filter and found that an active filter can replace all passive filters. We simulated the filtering performance in EMTDC program and validated the dynamic performance. Finally, we calculated the cost and occupation of active filter scheme.

Silicon carbide (SiC) based inverters are widely used due to their fast switching and ability to withstand high temperatures and Voltage. This helps to increase efficiency and reduces switching losses compared to the silicon-based inverter. However, this fast-switching device causes an increase in the Voltage at the junction of the cable and motor due to the reflected wave. The main causes of overvoltage are cable/motor impedance mismatch, fast-switching inverter devices (IGBT), and inverter-motor separation. To extend the induction motor lifespan, overvoltage reduction is necessary. Passive and active filters solve the problem, but passive filters are bulky and have high power loss. This paper presents a shunt active filter approach for an inverter-fed induction motor to reduce overvoltage. To show the effectiveness of the proposed approach, the findings were compared to the topology of the clamp-type active filter already in use. The shunt active filter used Proportional Integral (PI) and fuzzy controllers to generate reference current according to the Synchronous Reference Frame (SRF) theory. Harmonics in the power system were removed using the SRF theory. The unique aspect of this work is how the reference current is produced in the shunt active filter using the SRF theory. The proposed shunt active filter with a fuzzy controller was added to the hardware implementation to achieve better results than previous active filters.

Over the last decade governments in Australia and around the globe have heavily promoted the installation of rooftop solar photovoltaics (PV) in residential low voltage (LV) distribution networks. While distributed solar PV offers a range of benefits, they have not significantly reduced distribution network demand during critical periods due to the incongruity between the residential load profile and the solar PV generation curve. The residential load profile has load demand in the morning, moderate demand during mid-morning, low demand during the middle of the day and peak demand in the evenings. In winter the mid-morning demand is greater than in summer leading to instances where there are two peak demand periods during the day. Solar PV generation is low during the morning and steadily increases until the middle of the day and then decreases until the evening. Peak solar PV generation typically occurs when demand in the network is low. This entails that solar PV resources are poorly utilised and high concentrations of solar PV generation in LV distribution networks can often lead to the degradation of power quality through overvoltage and instances of reverse power flow. Moreover, the addition of solar PV to existing LV networks with unbalanced phases can often exacerbate existing power quality issues in a particular overloaded phase. Corrective measures to address power quality issues may require costly augmentations to the electricity network.

We present in this paper a control method of a novel hybrid parallel active power filter (HPAPF) used for harmonic currents elimination and reactive power compensation in the power system for three-phase variable frequency drives (VFDs). The HPAPF configuration is built from two filter components including harmonics tuned passive filter and active power electronics filter. The active power electronics filter of the proposed HPAPF system is controlled by a novel control algorithm that makes use of Fourier analysis to facilitate accurate selective harmonics targeting allowing the cooperation between passive and active components. In the proposed topology, a coupling of the passive filter component and the active filter allows significant reduction in current rating of the active filter component. This rating reduction scheme implies a great economic advantage of the proposed HPAPF compared to the methods which are based only on traditional pure active power electronics filters. The hardware design and the control algorithm of the proposed HPAPF are verified by MATLAB/Simulink software.

The estimation of low and high-pass active filter parameters with opposite charged system search algorithm

Harmonic contamination is a serious problem in Low Tension power distribution systems employing several types of non-linear loads e.g. diode/thyristor rectifiers, cyclo-converters, IGBT/MOSFET based inverters, adjustable speed drives, Switched Mode Power Supply, etc. Each of these load, overheat the distribution transformers and hamper the power quality. Hence, it is necessary to limit the harmonics to meet IEEE: 519-2014 harmonic standard. To reduce the harmonic currents, the simplest method is to utilize the passive filters generally known as Harmonic Traps. However, passive filters alone cannot eliminate all harmonic components. Besides, there are limitations on the use of passive filtering. Hence, hybrid filtering technique incorporating passive and active filters is the solution for the present power electronic systems. The active filters may be connected either in series or parallel with the mains. Hybrid harmonic filter considered in this paper is an effective solution for harmonic mitigation and its effective implementation. The detail design and simulation of a innovative hybrid filter for harmonic elimination in low tension power distribution systems is presented in this paper. The percentage total harmonic distribution of the compensated load voltage has been considered as a measure of performance.