Voltage Harmonic Components Research Articles

Distorting Electrical Power of the Alternating Current in the Simplest Circuit with a Diode

The development of electric power industry is accompanied by an increase in the number of consumers subjected to loads with nonlinear characteristics. The arising problem of the distortion of electrical energy that takes place when the mentioned consumers are in operation is partially solved by using means of improving the quality of electrical energy. The increase in the share of small generating plants that are placed in the nodes of consumers exacerbates the interaction of non-linear loads, forming additional parallel streams of electrical energy. Distorted electrical power is not an indication to account. Existing views on distorting power are amenable to criticism. In the well-known works, the proposals for the assessment of power using the quadratic norm and the quadratic norms of its components have been grounded. For the analysis of processes of formation the components of electrical power, a diagram of the simplest circuit containing a series-connected source of electromotive force, resistors and a diode is considered; also, the circuit was conditionally separated into a source and a consumer. The analysis of the power formation of each circuit element is performed with the use of the expression of current and voltage, as periodic functions represented by the trigonometric form of Fourier series. The power components are separated with the use of the known interaction of harmonic components of current and voltage of different orders. For the circuit elements, the power components formed by current and voltage harmonics of the same order are selected as well as power components formed by current and voltage harmonics of different orders, in which, in their turn, the power components are selected that have the same order as the first ones. The power formed by the action of the latter group is proposed to be attributed to the distorting power and to account its action by the corresponding quadratic norm. A numerical calculation has been performed with a use of the specified power component distribution. Time diagrams illustrate the process of interaction of the power components, which–in the case of the diode–leads to no change in power over time.

Realisation and Approbation of Conditionally Constant Coefficients Method for Loss Counter Measuring Tools

To date, electrical power in a form of higher-order current harmonics and voltage are reported to be worsening substantially in power lines of industrial and non-commercial consumers. This fact relates to the change of power consumer types to use different household and industrial power receivers. Higher-order harmonic current components cause extra losses in transformers. As a consequence, electrical power delivery is less efficient and losses increase. Therefore, it is necessary to measure harmonic components of current and voltage in distribution networks. The paper presents a measuring tool of loss counter developed on the base of constant coefficients method. Performance and relative accuracy were studied experimentally using a variable-speed drive with the results reported in the paper. The developed measuring tool meets the standards of admitted relative accuracy and is applicable to implement conditionally constant coefficients method in order to calculate excessive losses to be caused by non-sinusoidal loads in transformers of distribution networks.

Adaptive Command Current Observation Algorithm of UPQC on Experimental Microgrid

The experimental microgrid is developed to test the feasibility of different source-network-load matching microgrid structures. The different combinations of distributed energy and loads put forward higher requirements for the accuracy and adaptive ability of power quality management. In this paper, the unified power quality regulator (UPQC) was used to control the power quality and a control strategy with adaptive ability to disturbance of the microgrid models was proposed. On the one hand, the adaptive observer was designed to detect the compensation current signal, which reduced the influence of voltage harmonic components on the compensation current detection accuracy while reducing the amount of observation calculation. On the other hand, aimed at the slow response of traditional PID to DC voltage fluctuation of inverters and thus affecting the accuracy of current observation, the nonlinear variable domain fuzzy controller, which can modify the fuzzy expansion factor online, was adopted to improve the real-time performance of the control. The algorithm was simulated in MATLAB platform, and the results verified the effectiveness of the control strategy.

Multi-objective coordination control of distributed power flow controller

In this paper, distributed power flow controller (DPFC) constraints are analyzed. The energy balance relationship between fundamental wave and third harmonic in series and shunt-side converter is deduced. A proportional integral (PI) controller of the DPFC is constructed. The PI controller uses the voltage amplitude and phase angle injected into the system in the series side, along with the modulation ratio of the three-phase converter on the shunt side as the control variables. A multiobjective coordinated control equation is proposed, which factors the constraints of the energy balance between series and shunt side, device capacity limit, safe operation limit, fundamental component, as well as third harmonic component of the injection voltage at the series side. The equation minimizes the variance between the actual value of the control target and its given value to ensure that the DC capacitor voltage, both in the series and shunt side, is stable at target value. Simulations are conducted to verify correctness and effectiveness of the proposed control method.

A proposal to power quality improvement based on SHAPF with P-SSI controller parameters optimized by multi-objective optimization and applied through gain scheduling technique

The voltage and current harmonic components occurs in the electric grid mainly due to the utilization of non-linear devices. Once their harmful effects are known, the maintenance of a low THD (total harmonic distortion) level in the grid increases the system reliability. In this context, the shunt active power filters (SHAPF) offers good operational performance for harmonic compensation when compared to traditional passive filters. However, the tuning of the controllers parameters is an important issue, once a SHAPF has two control loops implemented in a cascade configuration. Such loops influence the behavior of two important variables for the SHAPF operation, i.e. the voltage error in the DC Link and the THD in the source current. Since both variables should be minimized and considering that they work in a trade-off condition, a multi-objective optimization algorithm is used in this work, in order to obtain a set of solutions that minimize both variables. In the sequence, only the solution with the lowest THD associated with an overshoot lower than 10% in the load commutation is chosen and used by a gain scheduling algorithm during 5s simulation with loads different from those used in the optimization process. The results show a reduction of the harmonics from 18.09% in the load to 0.9% in the source. This is a reduction of 95% of the THD level propagated to the source. In addition, the 0.9% THD level propagated to the current source is much lower than the recommended by the IEEE 519 that is of 5%.

An SVM Approach for Five-Phase Current Source Converters Output Current Harmonics and Common-Mode Voltage Mitigation

In this article, an enhanced five-segment space vector modulation (SVM) approach is proposed for a five-phase current source converter (CSC) to simultaneously reduce its output current harmonics and common-mode voltage (CMV). To realize proper output current harmonics mitigation, the reference current vector is synthesized by adjacent four large vectors and one zero vector in the fundamental plane. At the same time, the dwell times of four adjacent large vectors are calculated to actively control the corresponding current projection in the third sequence plane. In addition, the zero vector is selected according to the ranking of the instantaneous filter capacitor voltage absolute value to reduce the peak CMV. Comparing to voltage source converter (VSC) counterparts where the CMV is not affected by the ac output voltage and current harmonic components, it is interesting to find that the CMV enveloping of the CSC has a strong connection with its third harmonic output current. Then, a sequence arrangement for the five-segment SVM approach is proposed to ensure only one switch action during vector states transition. Finally, a transformerlike loss model is established to evaluate the loss performance of the CSC with a different modulation approach and a vector sequence selection method.

Optimized Parameters Design and Adaptive Duty-Cycle Adjustment for Class E DC–DC Converter With on‐off Control

The Class E dc–dc converter, with a simple topology and zero-voltage-switching (ZVS) for the power switch, can operate at a switching frequency of up to megahertz. In this paper, an optimized ZVS operation condition for minimizing the switch voltage stress, switch rms current, and switch voltage harmonic components is derived for the on ‐ off controlled Class E dc–dc converter by optimizing the time instant at which the switch voltage resonates back to zero. Based on this result, a step-by-step parameter design approach is proposed for a Class E dc–dc converter with a large input inductor, which avoids time-consuming simulations or complex numerical calculations. Then, a capacitance compensation approach is further proposed to extend the design results to a Class E dc–dc converter with a resonant input inductor. Furthermore, an adaptive duty-cycle adjustment scheme is proposed for reducing the reverse conduction loss of the power switch, thereby improving the conversion efficiency over the entire input voltage range. Finally, a prototype of a 20-MHz 10-W Class E dc–dc converter is built and tested in the laboratory, and experimental results are presented to verify the effectiveness of the proposed optimized parameter design approach and the adaptive duty-cycle adjustment scheme.

A DDS-Based Wait-Free Phase-Continuous Carrier Frequency Modulation Strategy for EMI Reduction in FPGA-Based Motor Drive

In ac motor drives, the fixed-frequency harmonic components of output voltage and current from the inverter with fixed-frequency pulsewidth modulation usually lead to electromagnetic interference (EMI). The spread spectrum clock generation (SSCG) is a widely used solution for this problem. Adjusting the switching frequency to reduce EMI is one kind of practicable scheme among SSCG methods. How to design an optimal or suitable modulation profile is a research emphasis of scholars and has been discussed in depth in many literatures. However, apart from the modulation profile, the mode and quality of carrier are also important and can be improved. In most frequency modulation methods, due to the limitation of the conventional carrier generation mode, the implementation of the new frequency instruction has to wait for the termination of the last switching period. In order to eliminate the waiting state and design a simpler algorithm, this paper has proposed a wait-free phase-continuous carrier frequency modulation (WPCFM) strategy by combining the direct digital frequency synthesizer theory and proper temporal planning of control interruptions. Besides, a theoretical analysis of WPCFM, including quantization error, frequency jitter, phase delay, and voltage distortion, has been finished. Moreover, compared with conventional methods, a more convenient, feasible, and simpler field-programmable gate array based algorithm implementation method and the control structure of WPCFM are also introduced. The analysis shows that, although WPCFM causes a slight increase of the current ripple, it can solve the partial frequency nonuniform distribution problem of the conventional method, and it has a potential value of applications in the wide band gap motor drive systems. The effectiveness of the WPCFM is verified by several sets of EMI reduction experiments where classical periodic carrier frequency modulations are applied.

A Method of Estimating Mutual Inductance and Load Resistance Using Harmonic Components in Wireless Power Transfer System

In general, for the WPT (Wireless Power Transfer) system, as the mutual inductance and load resistance are calculated according to the measured data of both the transmitter and receiver, the wireless communication modules are needed to share data. A method for estimating mutual inductance and load resistance without wireless communication is proposed, based on the fundamental and third harmonic components. The circuit is decomposed with respect to the frequencies, by which the mathematic model is established. The fundamental and harmonic components of the output voltage and current of a high-frequency inverter are found by FFT (Fast Fourier Transform). The experimental WPT system with a SiC power MOSFET is designed, and the effectiveness of the proposed method is verified by the simulation and experiment results. Additional hardware and frequency scanning operation are not needed because of the use of the harmonic components.

REDUCING ELECTRIC POWER LOSSES IN THE SYSTEM OF POWER SUPPLY DUE TO COMPENSATION OF HIGHER HARMONICS OF CURRENTS: ECONOMIC AND ENERGY EFFICIENCY OUTCOMES

The issue of increasing energy efficiency and energy saving is of great importance for the countries with high energy intensity of the gross domestic product, including Russia and the rest of the Commonwealth of Independent States. The measures adopted in Russia on the federal and regional level as part of the State Program on Energy Efficiency and Energy Development are focused on reducing the energy intensity of Russia’s gross domestic product and introduce sustainable practices on energy saving in Russia’s commercial and budget sectors. This paper presents a case study describing the way to reduce electric power losses in a system of power supply (SPS) of an industrial enterprise. In particular, the case study determines the level of the higher harmonic components of current and voltage at the existing enterprise for the production of reinforced concrete products. The results of the experiment were reproduced using a simulation model of the power supply system in the Matlab/Simulink package. A comparative analysis of using a passive and hybrid filter compensating device to reduce the level of the higher harmonics of current and voltage was carried out by means of modeling. The active losses in the SPS from non-sinusoidal mode are calculated. In addition, the economic effect of using the proposed method is estimated.

Modelling of Dynamic Compensation for Isolated Neutral Power Network

The paper deal with causes and consequences of the negative influence of harmonic components of currents and voltages in medium voltage distribution networks. The dynamic compensation benefits for filtering harmonic components of currents and voltages and eliminating current and voltage distortion from the power system are considered. In the paper the model of isolated neutral power network with the dynamic compensation device is created by simulation in the Matlab Simulink software. In the model a three-phase network was simulated by blocks from the SimPowerSystem database and the non-sinusoidal load was simulated by a three-phase bridge diode rectifier. The dynamic compensation filtering device is simulated by an inverter on IGBT-transistors and consisted of shunt reverse diodes, smoothing filters and capacitive storage. The simulation results show the reduction of the voltage distortion limits to the normalized values, thus we can eliminate the non-sinusoidal form of the voltage curve and make it sinusoidal by dynamic compensation in the distribution network. The dynamic compensation device operates correctly in the created model and is suitable for high-nonlinear, inductive, fast-changing and harmonic-generating loads, as it effectively fights against the violation of the quality of electrical energy.

A Study of Over-modulation Impact on the MSI Series Micro-Grid Output Voltage

In order to analyse the over-modulation technique impact on the micro-source inverter (MSI) series micro grids (SMGs) output voltage, firstly Double Fourier method applied to derive the single inverter output voltage characteristics under over-modulation condition; Secondly, based on the characteristics of the MSI series micro-grids, a new formula of the system output voltage is derived. Thirdly, the impact on the system output voltage fundamental component and harmonic component is analysed in detail, the results show that the output voltage fundamental component increases with the increasing modulation while keeps constant after a certain over-modulation depth. Finally, a simulation was carried out and the simulation verified the theoretical analysis.

IPT system for tail‐free household appliances in the smart home system

Inductive power transfer (IPT) is a new power supply technology for household appliances to eliminate the effects of sparks and wires. Besides, the smart home is a popular intelligent system to connect the facilities in the home. To combine the advantages of IPT technology and smart home system perfectly, the transmission of the control signal is as important as the transmission of power for IPT system. This work proposes a method that makes the power and control signal transmission synchronously from the supply side to receiving end to achieve the wireless power supply and the intelligent control for household appliances such as televisions, air conditioners, air purifiers etc. In the proposed method, the fundamental and harmonic components of the inverter output voltage are used as the power carrier and the signal carrier, respectively. One is to supply power to household appliances and the other is to transmit a control signal to them. On the basis of this method, the features of harmonics such as low energy and high frequency are well used, which enable both stable power transmission and high-speed signal transmission. The effectiveness of the proposed method is verified by an experimental platform of kW level.

A Coupled Virtual Impedance for Parallel AC/DC Converter Based Power Electronics System

In this paper, a coordinated control method is proposed for three-phase ac/dc hybrid microgrid power electronic interlinking unit with dual converters sharing both dc and ac links. Unlike the conventional dual converters-based system where the same control strategy is applied to both converters, converter1 in this proposed system is controlled by a closed-loop current regulation algorithm while converter2 employs voltage controller with coupled adaptive virtual impedance. With the flexible control of the coupled virtual impedance, the system performance is enhanced in the following three aspects. First, in grid-tied operation mode, the output power difference between dual converters is used as an input to tune the coupled virtual impedance of converter2 for a rapid dynamic power response. Second, the proposed coordinated control with inherent voltage support is able to achieve a seamless transfer without additional efforts. Third, during system islanded operation, a generalized power sharing and an active PCC voltage harmonic and unbalanced components mitigation are achieved via the adjustment of the coupled virtual impedance. Finally, the scalability of the proposed method in a system with more converters is briefly discussed and verified.

Harmonic Suppression Strategy in Single-phase SPWM Based on Mixed Integer Nonlinear Programming

In single-phase bipolar SPWM inverter circuit, the output voltage contains high content of harmonic components. To solve this problem, we build a model of output voltage in single-phase SPWM bipolar inverter based on SPWM theory and Fourier series theory. Through theoretical analysis, calculation and plotting, we work out the distribution of harmonic in output voltage, investigate the relationship between amplitude modulation (AM) depth and harmonic components and finally determine a proper amplitude modulation depth to efficiently reduce harmonic components. To further reduce harmonic components of output voltage, we use LC low-pass filter. Then, based on the mathematical model of the filter and the distribution law of harmonics, we establish a mixed integer nonlinear programming to fully suppress harmonics and reduce switching losses. After searching for two times based on genetic algorithm, we work out the best frequency-modulation ratio and LC low-pass filter parameter. Finally in simulation, total harmonic distortion is reduced from 213.47 percent to 0.16 percent after harmonic suppression strategy implemented. The result has proved the effectiveness of the harmonic suppression strategy we applied, which can be used as a reference for output voltage harmonic elimination in single-phase SPWM inverter.

Model Predictive Control of Electric Spring for Voltage Regulation and Harmonics Suppression

This paper presents a model predictive control (MPC) strategy for electric spring (ES) to address the power quality problems, especially voltage regulation and harmonic suppression, which are more acute for a growing proportion of renewable energy generation to the grid. A Kalman filter is used to estimate the random variation of the supply voltage and extract the fundamental and harmonic components of the supply voltage, respectively. In this way, the supply voltage, which is treated as an external disturbance for the plant, can be established in the state-space model form. Such processing brings great convenience to the application of MPC and also lays a foundation for MPC to achieve an ideal control effect. Based on an integrated state-space model of the supply voltage and the ES, an MPC controller is designed for power quality improvement. Simulation studies are carried out and the simulation results are presented to verify the effectiveness and accuracy of the control strategy.

Effect of high frequency harmonic voltage on the performance of line start permanent magnet synchronous motor

PurposeA large number of high-frequency harmonic voltages exist in the output voltage of the inverter, which will affect the performance of the motor. The purpose of this paper is to obtain the influence of high frequency harmonic voltage on the performance of the line start permanent magnet synchronous motor (LSPMSM) and reveal the mechanism of influence. The research results can provide help for the design of LSPMSM driven by inverter drives.Design/methodology/approachFirst, the actual output voltage data of the inverter is collected, and then the fundamental voltage and high frequency harmonic voltage data can be obtained by performing the fast Fourier transformation method on the voltage data. Second, the finite element model is established. During the finite element calculation, the obtained fundamental voltage and the main harmonic voltage components are used as the voltage source. To research the effect of high frequency harmonic voltage on the performance of motor, a reference group without high frequency harmonic voltage is set up, which is used to compare and analyze the effect of high-frequency harmonics on the performance of the motor. To verify the correctness of the model, a prototype based on the model parameters is manufactured, and then the back EMF experiment and load experiment are performed. The test data and calculation results are compared and analyzed.FindingsThe coupling relationship between high frequency time harmonic magnetic field and low frequency space harmonic magnetic field is obtained. The stator copper loss and rotor eddy-current loss are calculated and analyzed under normal supply voltage and abnormal supply voltage, and the influence mechanism is revealedOriginality/valueThe coupling relationship between high frequency time harmonic magnetic field and low frequency space harmonic magnetic field is obtained. The sensitivity of the high frequency harmonic voltage to the stator copper loss and rotor eddy-current loss is obtained, and the mechanism of losses change is revealed.

A laboratory application for teaching the effect of harmonics on transformer core saturation

Harmonics in supply voltage or load current in a transformer have undesirable effects on the core and windings. As the harmonic content increases, higher core loss and eddy current loss in the windings results in higher operating temperatures. It causes magnetic flux density in the core to increase and shifts the operating point through the saturated region. This phenomenon is mostly taught in undergraduate education as theoretical information. However, as a difficult concept to understand, harmonics phenomenon might be taught by using experiments for active learning, visualizing the effects in a laboratory setting, and making the connection between theoretical and practical applications for deeper and meaningful learning. In this study, a teaching method for effects of harmonics is proposed and phase shift between the fundamental and harmonic component of the supply voltage on the transformer B–H characteristic in a laboratory application is introduced by an experimental work performed on toroidal transformers. Feedback from students shows that the proposed method is very efficient and useful for students to better understand the effects of harmonics on the transformer cores.

On Harmonic Injection Anti-Islanding Techniques Under the Operation of Multiple DER-Inverters

This paper studies the significant impact of distributed-energy-resource (DER) inverters (which are connected to the same node) on anti-islanding protection of DER-installations. As it concerns the harmonic injection-based schemes, the induced harmonic voltage component that is provoked by each inverter is compromised, as synchronous injection (injection at the same time intervals) among the inverters cannot be reassured. Therefore, harmonic injection-based anti-islanding schemes will fail if the harmonic voltage component falls below a certain level. In this framework, a novel metric (i.e., the upgrade factor, UF ) is introduced, indicating the supplementary power (of DERs) that can be installed in the same point of common coupling without compromising the effectiveness of the harmonic injection scheme. As this metric enables the evaluation of harmonic injection schemes prior to the future integration of DERs, it could be a substantial addendum into the relevant standards that evaluates the anti-islanding features of grid-tied DER-inverters. Finally, this paper proposes a technique (implemented in the software level), which maximizes UF and reassures the effectiveness of the harmonic injection schemes under the power variations of installed inverters. Extensive simulations and experimental tests have been conducted that verify the effectiveness of the proposed strategy under various penetration-levels and islanding-network conditions.

Flux Observer Model for Sensorless Control of PM BLDC Motor With a Damper Cage

Sensorless control methods are commonly employed to derive the rotor position and speed information indirectly in permanent magnet (PM) brushless motor drives. Thereinto, the simple yet effective flux observer method is extensively applied in a wide range of applications. However, damper cage is sometimes employed in the rotor of certain PM brushless motor. Normally, high-order current harmonic components occur in such damper cage during operations. The introduction of these extra current contents can significantly hinder the performance of the conventional flux observer. By applying Park transformation, the fundamental harmonic components of stator phase currents, flux linkages, and voltages during steady-state operation, become constants under rotor synchronous reference frame, while the currents in the rotor damper cage are still alternating. In this paper, an improved flux observer method is proposed to filter the harmonic contents under the rotor synchronous reference frame for PM brushless motor with rotor damper cage. The validity and performance of the proposed flux observer are verified by both numerical analysis and experimental results.