Interharmonic Generation Research Articles

Impact of Solar Radiation on Luminaires and Energy Efficiency in Isolated Residential Photovoltaic Systems

This research centers on the implementation of photovoltaic systems in residential applications, coupled with battery-based energy storage, and evaluates their efficiency in generating energy, specifically for lighting in buildings. The methodology hinges on detecting interharmonic signals to characterize potentially disruptive frequencies and identify the origins of various failures. Multiple case studies are presented to validate the method’s efficacy, including one involving fluorescent lamp circuits and another examining variations in solar radiation during the summer season. Real-world experiments are conducted in a residential setting, and the results are thoroughly analyzed. Various types of interharmonic generation behaviors are demonstrated, which are influenced by fluctuations in solar radiation and the appropriate installation of solar panels. The findings reveal that the absence of solar radiation below 300 W/m2 in a photovoltaic system relying on energy storage adversely affects interharmonics in luminaires installed within a residential space.

Analysis of Interharmonics Generation in Induction Motors Driven by Variable Frequency Drives and AC Choppers

In modern power systems, interharmonics have emerged as noninteger frequency components that appear in current or voltage signals. Double-stage AC-DC-AC converters have been identified as a primary source of interharmonics. Previous studies have highlighted modulation techniques, filters, passive components, unbalanced conditions and DC link effects as relevant factors. However, the interaction between these factors and the inertial properties of induction motors has not been explored. This study assesses various types of AC drives, including variable frequency drives (VFDs) and soft starters (AC choppers), to investigate their interaction with machine inertial properties in interharmonic generation. The employed technique for time-frequency spectral analysis is the wavelet synchrosqueezed transform combined with a clustering method. This paper demonstrates that the interaction of the inertial properties of low-power induction motors with the variations of the switching frequencies of the VFDs, the filters used in the DC link and a soft start indirectly contribute to harmonic generation and potentially to interharmonics in the electrical grid and the outputs of the inverter.

Inter-harmonics Mitigation for PV-based Converters Using INHARE MPPT Algorithm

The need for environmentally-friendly energy generation and massive exploitation of fossil fuels are leading to the increased demand for renewable energy sources like photovoltaic (PV) and wind energy, etc. The fluctuating behaviour of PV causes various disadvantages, of which the generation of Inter-harmonics is the major problem. The production of Inter-harmonics by the load-interfacing inverters is primarily due to the Maximum Power Point Tracking (MPPT) techniques employed in PV system. The requirement of multiple perturbations in tracking peak points is the primary cause behind the inter-harmonic generation. Since solar irradiation varies throughout a specific period, there can be situations, where the operating irradiance changes abruptly from one state to the other. These abrupt changes generate enormous fluctuations in the MPPT power output, resulting in an inter-harmonics generation. This paper proposes an evolved INter-HARmonic-Elimination (INHARE) algorithm for minimizing the PV fluctuating behaviour, leading to lower voltage ripple and settling time. The proposed INHARE algorithm is examined for a 0.52 kW PV system, where the Inter-harmonics content is reduced considerably in load current for the case of varying irradiances at a constant temperature.

A hybrid random parameters modification to MPPT algorithm to mitigate interharmonics from single-phase grid-connected PV systems

As the on-grid photovoltaic (PV) system’s penetration level increases, the utility grid power quality (PQ) becomes a vital emerging issue to spot the lights on. The recent studies confirmed that one source of interharmonics emission from PV inverters is the maximum power point tracking (MPPT) algorithms. Following this issue, a strong relationship has been found between the interharmonics generating characteristics and the MPPT parameters, such as the sampling rate and perturbation step size. Utilizing a big step size and fast sampling rate will enhance the tracking performance but will raise the level of interharmonics injected into the grid and lower the overall efficiency. Therefore, there is a trade-off between MPPT parameters, efficiency, and interharmonics characteristics in PV systems. To alleviate mentioned issue, this paper investigates the mechanism of interharmonics generation and emission under different power operating conditions. Accordingly, a new mitigation technique is presented for interharmonics generation in grid-connected PV systems. The proposed method is based on modifying the MPPT algorithm in a way that maintains its performance characteristic while effectively minimizing the generated interharmonics by a random selection of big or small perturbation step sizes and fast or slow sampling rate, respectively. Thereby, the frequency spectrum distribution is modified, and interharmonics peaks are reduced in the output injected current to the grid by 27 % compared to the other conventional and modified perturb and observe (P&O) MPPT algorithms found in the literature. The effectiveness of the proposed method is verified by simulation studies on a single-phase grid-connected PV system.

Assessing the Impact of Harmonics and Interharmonics of Top and Mudpump Variable Frequency Drives in Drilling Rigs

Declining extraction costs and process efficiencies have incented the revival of the oil and gas sector postrecession. The application of drilling rigs has been done more efficiently. These loads are very large, temporary in nature, and mobile. The drilling of each well can be done as quickly as a few hours and typically not more than a few days. These massive loads are complex to own, maintain, and operate, as a result few specialized drillers share the market. Because of the requirements for variable speed and control, drilling rigs are driven by variable frequency drives (VFDs), which are in their clear majority of older technologies such as six-pulse thyristor bridge or SCR-driven motors. These technologies are known to impose steep ramp rates (up and down) as well as rich harmonic content and variable, typically low, power factor. Furthermore, the locations of drilling rigs are typically remote, where distribution systems, if present, are weak, which lead to large background voltage distortions when such loads are present. This paper presents measurements, simulations, and analytical assessments of the characteristics and effects of harmonics and interharmonics (IHs) generated by top-drive and mud-pump VFDs in a large drilling rig operated in Alberta, Canada. Measurement results reveal very high harmonic and IH generation. To further refine the impact assessment of these harmonic emissions, the harmonic attenuation effect of the VFDs is quantified to avoid overestimating the harmonic generation of the loads. The thermal impact of the current harmonics on the coupling transformer is also quantified.

The spectral correlation theory application of random processes for estimation of power losses involving higher harmonic and intergarmonic

One of the negative consequences of non-sinusoidal regimes is the occurrence of additional power losses in the elements of electrical networks. Traditionally, in this case, additional losses caused by higher harmonics of the current are determined. A significant spectrum of interharmonics appears along with higher harmonics in the currents in case of a number of rapid varying loads, as well as loads receiving power from frequency converters.Thus, the problem of estimating the additional power losses at the frequencies of the interharmonics arises. Today, the estimating the additional power losses associated with the generation of interharmonics is insufficient studied due to the complexity of the mathematical apparatus that take into account the presence of interharmonics.The researches conducted have shown that application of the spectrally-correlation theory of random processes allows solving the engineering problem of estimating additional power losses in power supply systems. The advantage of this approach is the possibility of estimating additional power losses both at the operational stage and at the design stage.

Characterization of Input Current Interharmonics in Adjustable Speed Drives

This paper investigates the interharmonic generation process in the input current of double-stage adjustable speed drives (ASDs) based on voltage-source inverters and front-end diode rectifiers. The effects of the inverter output-side low order harmonics, caused by implementing the double-edge symmetrical regularly sampled space vector modulation technique, on the input current interharmonic components are presented and discussed. Particular attention is also given to the influence of the asymmetrical regularly sampled modulation technique on the drive input current interharmonics. The developed theoretical analysis predicts the drive interharmonic frequency locations with respect to the selected sampling strategies. Simulation and experimental results on a 2.5 kW ASD system verify the effectiveness of the theoretical analysis.

Interharmonic Source Model for Current-Source Inverter-Fed Variable Frequency Drive

This paper presents a concise frequency-domain interharmonic model for the current-source inverter-fed (CSI-fed) variable frequency drives (VFDs). This model is in the form of a Thevenin equivalent circuit. The equivalent voltage source is determined only by the VFD operating point, while the equivalent impedance is influenced by the system impedance, the dc-link impedance, and motor parameters. This model, verified by simulations and measurements, can be used to predict the interharmonic propagation in a system supplying CSI-fed VFDs. The model also reveals the interharmonic generation characteristics of the VFDs, which will help the proper selection of mitigation options. Based on the model, the analysis of the nature of the interharmonic source of CSI-fed VFD has been conducted. Some applications are demonstrated as well.

Modeling, Limits and Baseline of Voltage Interharmonics Generation in Andean Wind Farms

The following study focuses on the analysis of voltage interharmonics based on power quality experimental data of Villonaco's Wind Farm. This park is located on the Villonaco hill, province of Loja at 2720 meters above sea level in the Andes of Ecuador. The study arises due to the problem that there are no standards to define the limits of interharmonics generation for power plants. This work consists of two aspects: the statistical modeling of voltage interharmonics and the generation of the baselines. The general proposed methodology, the application for Villonaco's wind farm and the results and conclusions obtained are detailed. In addition, taking advantage that the wind farm meets the power quality standards, the voltage interharmonics characterization is done, in order to provide the first interharmonics baseline in wind farms built on the Andean region.

Multiple-Period Repetitive Controller for Selective Harmonic Compensation with Three-Phase Shunt Active Power Filter

This paper presents a shunt active power filter (SAPF) for compensating inter-harmonics and harmonics when inter-harmonics content is evident in the grid. The principle of inter-harmonics generation in the grid was analyzed, and the inter-harmonics effect on repetitive controllers was discussed in terms of control performance. Traditional repetitive controllers are not applicable in inter-harmonic compensation. Moreover, the effect of an ideal controller on harmonics signals was analyzed on the basis of the internal model principle. The repetitive controller was improved in the form of a basis function according to theoretical analysis. The finite-dimensional repetitive controller, which is also called the multiple-period repetitive controller, was designed for the control of multiple periodic signals. A selective harmonic compensation system was developed with SAPF. This system can be used to compensate harmonics and inter-harmonics in the grid. Finally, system control performance was verified by simulation and experimental results.

On the Interharmonic Components Generated by Adjustable Speed Drives

The interharmonic generation process is addressed with reference to high power adjustable speed drives based on double stage conversion systems using line commutated or pulse width modulated inverters. Reference is made to ideal supply conditions. Formulas to forecast the interharmonic frequencies due to the interaction between the rectifier and the inverter are developed and a proper symbolism is proposed to recognize the interharmonic origins. Comprehensive analyses are performed for both the considered adjustable speed drives in a wide range of output frequencies and with reference to supply system side, output side, and dc link.

Evaluation of current interharmonics from AC drives

Distortion levels on power systems have been continuously increasing due to the increasing presence of power converters. The distortion currents injected by some converters can include interharmonics as well as harmonics. The generation of interharmonics in AC-DC-AC power converters is discussed, and a method to predict levels of current interharmonics is developed. The results show that very low interharmonic levels can be expected for a well designed PWM inverter operating with linear modulation and balanced load. Interharmonics can be expected in cases when the inverter is in overmodulation or when the inverter load is unbalanced. The paper also discusses the relative effects of DC link inductance and source inductance on interharmonic propagation.

Adaptive frequency-selection method for a Newton solution of harmonics and interharmonics

To reduce the excessive computation time required to model the generation of interharmonics with Newton-based iterative harmonic analysis, this paper presents an adaptive harmonic domain solution which exploits the inherent sparsity that exists in the harmonic and interharmonic arrays. It is shown that the proposed method produces identical results to the full solution in a fraction of the time.