Harmonic Suppression Strategy Research Articles

A Harmonic Suppression Strategy Based on Adaptive Synchronous Rotating Frame Transformation for Improving the Estimation Accuracy of Sensorless Drivers With Small Capacitors

A Harmonic Suppression Strategy Based on Adaptive Synchronous Rotating Frame Transformation for Improving the Estimation Accuracy of Sensorless Drivers With Small Capacitors

Input and Output Harmonic Suppression Strategy of Single-Phase AC–DC–AC Converter

Input and Output Harmonic Suppression Strategy of Single-Phase AC–DC–AC Converter

Current harmonic suppression strategy for permanent magnet synchronous motor based on small phase angle resonant controller

AbstractIn this study, a small phase angle resonant controller (SPARC) is designed to suppress the current harmonics in a permanent magnet synchronous motor (PMSM). First, the analytical model of the PMSM is established. Second, a SPARC is designed to improve the problem of the overly large phase angle of the resonant controller at the resonant frequency. Third, the frequency error caused by the SPARC discretisation is compensated online. Finally, an experimental platform is built for the PMSM harmonic suppression, and the effectiveness and feasibility of the proposed method are verified through a comparison with the method of motor control using quasi‐resonant controller.

High-Frequency Harmonic Suppression Strategy and Modified Notch Filter-Based Active Damping for Low-Inductance HPMSM

The voltage inverters have the high-frequency switching characteristic, which will generate massive high-frequency harmonics in the motors. Especially, the inductance of the high-speed permanent magnet synchronous motor (HPMSM) is designed to be small, and the high-frequency harmonic content will be higher than that of ordinary motors, which adversely affects the system. To overcome this problem, this paper proposed a harmonic suppression method based on the LC filter and the adaptive notch filter for HPMSMs. The LC filter is connected between the inverter and the HPMSM to filter out high-frequency harmonics, however, at the cost of the system resonance. Therefore, the adaptive notch filter with the frequency tracking capability is designed to offset specific resonant peaks by constructing an antiresonant peak. The least mean square adaptive algorithm automatically adjusts the filter parameters according to the variation of the input signal to ensure accurate filtering in complex cases. Simulation and experiment results prove the practicability and effectiveness of the proposed scheme. The harmonic contents of HPMSM are significantly reduced, and the dynamic response performance of the control system is improved.

A Novel Current Harmonic Suppression Method for HSPMSG Based on the Hybrid Rectifier

This paper presents a novel current harmonic suppression scheme for the high-speed permanent magnet synchronous generator (HSPMSG). Aiming to effectively reduce current harmonics for the HSPMSG, this paper focuses on two areas: improving the rectifier power topology and developing a current loop controller. Firstly, a hybrid rectifier based on Silicon-Carbide/Silicon (SiC/Si) is designed to equivalently increase the switching frequency of the HSPMSG to address the problem of low carrier frequency ratio. In addition, an improved space-vector-modulation (ISVM) strategy based on the hybrid rectifier is proposed. However, the harmonic distortion caused by rectifier nonlinearity will deteriorate as the switching frequency is increased. For further suppressing harmonic disturbances caused by rectifier nonlinearity, a resonant-super-twisting (R-STW) controller is designed by combining the resonant controller and the super-twisting (STW) controller in this paper. The stability of the STW is demonstrated by Lyapunov stability theory and the resonant controller is discretized. Finally, a number of simulations and experiments based on a high-speed permanent magnet synchronous generator are carried out to verify the effectiveness of the control method proposed in this paper.

An Adaptive Virtual Impedance Method for Grid-Connected Current Quality Improvement of a Single-Phase Virtual Synchronous Generator under Distorted Grid Voltage.

The proportion of distributed generation systems in power grids is increasing, leading to the gradual emergence of weak grid characteristics. Moreover, using voltage-sourced grid-connected inverters can enhance the stability of a weak grid. However, due to the presence of background harmonics in weak grids, the grid voltage can cause significant distortions in the grid-connected current, which adversely affects the quality of the grid-connected current. This paper begins by briefly introducing the principle of the virtual synchronous generator (VSG). Then, the output current of the voltage source inverter is analyzed to elucidate the mechanism of harmonic current generation. Considering the distortion in the grid-connected current of the voltage source grid-connected inverter caused by background harmonics in the grid voltage, a harmonic current suppression strategy based on an adaptive virtual harmonic resistor is proposed. The proposed strategy employs a signal separation module based on multiple second-order generalized integrators connected through a cross-feedback network. This module effectively separates the fundamental and harmonic currents from the grid-connected current, extracts the amplitudes of the fundamental and harmonic currents through coordinate transformation, and adaptively adjusts the virtual harmonic resistance magnitude through the negative feedback control of the harmonic content (the ratio of the harmonic current amplitude to the fundamental current amplitude). These measures are used to enhance the quality of the grid-connected current. Additionally, the stability of the system is analyzed using the root locus of the open-loop transfer function. Finally, the effectiveness of the proposed method is validated through a combination of MATLAB/Simulink simulations and experimental results.

Active disturbance rejection controller design for harmonic suppression in MPC optimal control based on harmonic state space modeling

SummaryThis paper proposes a harmonic suppression strategy for photovoltaic‐voltage source converters (PV‐VSC). The proposed method utilizes a harmonic state space (HSS) model‐combine model predictive control (MPC) algorithm, which provides a comprehensive representation of the global characteristics of AC/DC harmonic coupling impedance in photovoltaic systems. The HSS‐based converter model operates as a linear time‐varying periodic system, which allows for the implementation of MPC to optimize the HSS equation. This optimization yields voltage increments across various harmonic orders, providing feedforward compensation for the current controller. By incorporating feedback signals into the current control, harmonic compensation is achieved, resulting in improved power quality. Furthermore, a decoupled proportional resonance‐linear adaptive disturbance rejection control (PR‐LADRC) is employed to effectively mitigate steady‐state errors and decrease total harmonic distortion in the presence of DC‐side disturbances. This is accomplished by decoupling the disturbance observer from the controller and integrating the increment feedback signal derived from the MPC‐HSS. Finally, the efficacy of the proposed method and the analysis results are corroborated through numerical simulations.

Grid-Side Current Harmonic Suppression and Power Factor Improvement Using q – Axis Damping Current Injection for PMSM Drives Without Electrolytic Capacitor

The dc-link film capacitor with low-capacitance in permanent magnet synchronous motor (PMSM) drives without electrolytic capacitor will not only reduce the system stability, but also generate LC resonance with the grid-side filter inductor, which is the important reason for high grid side harmonic current and low power factor. In this paper, a grid side current harmonic suppression strategy using q-axis damping current injection is proposed to address these issues of PMSM drives without electrolytic capacitor. The analysis of the transfer function based on the simplified circuit of the drive shows the instability and LC resonance of the system. The feedforward modification method based on the difference between the quasi-dc-link voltage and the dc-link voltage is applied to improve the system performance. Meanwhile, the specific implementation of the proposed method by injecting damping current into the q-axis is introduced. In addition, a phase disturbance angle is introduced in the proposed control strategy to adjust the phase of quasi-dc-link voltage. By properly adjusting the phase disturbance angle, the conduction angle of the single-phase uncontrolled rectifier bridge can be effectively expanded, and the grid side power factor can be further improved. Experiments on a PMSM drive with the low-capacitance of dc-link film capacitor are carried out to verify the effectiveness of the proposed method.

Inverter Harmonic Suppression for Permanent Magnet Synchronous Machine Drives Based on Discontinuous SVPWM With Variable Switching Frequency

Since one phase of discontinuous space vector pulse-width modulation (DSVPWM) is always clamped, the inverter nonlinearity induces obvious 3rd and 6th harmonics in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis currents and voltages. Besides, there are non-negligible spiky switching harmonics in permanent magnet synchronous machine (PMSM) drives of PWM-controlled with fixed switching frequency. To solve these issues, an inverter harmonic suppression strategy for DSVPWM with variable switching frequency is proposed in this paper. Firstly, an inverter nonlinearity model including dead time, switching delay, and device voltage drops under DSVPWM is proposed, and a standstill test is presented for the estimation of distorted voltage terms due to inverter nonlinearity. Then the spiky switching harmonics are dispersed by the proposed chaotic-DSVPWM based on Tent map. Finally, the effectiveness of the proposed method is demonstrated on a PMSM platform, which shows quite good performance in the suppression of both low- and high-frequency harmonics. The paper reveals that the inverter harmonics under DSVPWM can be easily reduced by distorted voltage compensation and variable switching frequency.

Harmonic Suppression Strategy of LCL Grid-Connected PV Inverter Based on Adaptive QPR_PC Control

To reduce the influence of voltage harmonics on the grid current, a control strategy based on adaptive quasi-proportional phase compensated resonance (QPR_PC) is proposed. Firstly, the LCL grid-connected photovoltaic inverter system model is established, and the stability performance of the three-level inverter system under double closed-loop control is analyzed using the output impedance model of the inverter. Then, a QPR regulator for the zero steady-state error tracking of AC signals is studied. To solve the problem that the system has poor robustness against frequency changes when the traditional QPR regulator is used in the static coordinate system, this paper improves the traditional QPR regulator to optimize the response characteristics of the closed-loop system. Based on the QPR regulator, a phase margin compensation structure is introduced to form QPR_PC control. Then adaptive frequency design is added to ensure good control even when the power grid frequency drifts, which is the control strategy proposed in this paper. Verification shows that the proposed method improves the phase margin of output impedance at a specific frequency, restrains the interference of the 3rd, 5th, and 7th harmonics of grid voltage, and improves the dynamic performance of the system and the quality of grid-connected current. Finally, the simulation results show that the total harmonic distortion rate of grid-connected current is reduced by 1.03% after adopting this strategy, which verifies the effectiveness and correctness of the proposed method.

Harmonic Resonance Suppression Strategy of the Front-End Vienna Rectifier in EV Charging Piles

Owing to the distributed installation position, the electric vehicle (EV) charging pile is usually connected to the grid via transmission cables of different lengths. The resonance of parasitic inductance and parasitic capacitance on the transmission cables might amplify the background harmonics, which result in a serious distortion of the grid-connected current of the front-end Vienna rectifier of EV charging piles. To overcome the resonance issue, this article proposes a harmonic resonance suppression strategy of the Vienna rectifier, which reshapes the closed-loop input harmonic impedance of the Vienna rectifier to be close to the characteristic impedance of the transmission cable by optimizing the traditional dual closed-loop control strategy of the Vienna rectifier based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> coordinate frame. The proposed suppression strategy can not only ensure the low ripple output voltage of the Vienna rectifier, but also suppress the background harmonic resonance amplification; thus, the power quality of the Vienna rectifier grid-connected current and the voltage at the point of common coupling will be improved effectively. Both the simulation and experimental results verify the effectiveness and correctness of the proposed strategy.

An Adaptive-Frequency Harmonic Suppression Strategy Based on Vector Reconstruction for Current Measurement Error of PMSM Drives

The errors of gain and offset caused by the current sensor measurement can lead to the first and second harmonics in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis currents of the permanent magnet synchronous motor (PMSM) drives. An adaptive-frequency harmonic suppression strategy based on the vector reconstruction for current measurement error is proposed. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis current vector is recoordinate transformed using the division-frequency position as the transformation matrix angle. Thus, the frequency of the fundamental component can be decoupled from that of the harmonics in the current vector. In this way, the single-frequency harmonic suppressor can be established in the reconstructed coordinate frame. The current vector error is converged by adaptively adjusting the filtering weight and frequency so as to eliminate the harmonics. In view of the change of fundamental frequency, the variable step of the convergence is used to obtain the ideal filtering effect at different speeds and reduce the negative impact of current sensor measurement errors. The effectiveness of the proposed method is verified on the 11.7-kW PMSM drive platform.

Multiple Synchronous Rotating Frame Transformation-Based 12th Current Harmonic Suppression Method for an IPMSM

In order to solve the problem that the three-phase current of the interior permanent magnet synchronous motor (IPMSM) contains the 11th and 13th current harmonics, a multiple synchronous rotating frame transformation (MSRFT)-based current harmonic suppression method is established. Firstly, the influencing factors of current harmonics in IPMSM vector control are analyzed, and the influence mechanism of the inverter’s dead-time effect and the permanent magnet flux linkage harmonics on the current harmonics is described. Secondly, a simple current harmonic extraction method is proposed by optimizing the traditional current harmonic extraction method based on MSRFTs. The proposed method achieves the accurate extraction of the current harmonic components. Thirdly, a harmonic voltage generation method is established and is combined with the proposed current harmonic extraction method to form a current harmonic suppression strategy. Finally, the feasibility and effectiveness of the proposed method are verified via MATLAB/Simulink simulations and experiments. The simulation and experimental results show that the proposed current harmonic extraction method can extract the current harmonic components accurately, and the proposed current harmonic suppression strategy can suppress the 11th and 13th current harmonics effectively.

A Harmonic Suppression SVPWM Strategy for the Asymmetric Six-Phase Motor Fed by Two-Level Six-Phase VSI Operating in the Overmodulation Region

For the asymmetric six-phase motor fed by a two-level six-phase voltage source inverter (VSI), when the modulation index is less than 0.5774, the motor operates in the linear region, and the harmonics in the Z1 − Z2 subspace can be suppressed to zero. When the modulation index is beyond 0.5774 and less than 0.6221, the motor operates in overmodulation regions, and the harmonics in the Z1 − Z2 subspace cannot be suppressed to zero. To minimize the harmonics in the Z1 − Z2 subspace for these regions, a harmonic suppression strategy, namely, harmonic suppression overmodulation strategy (HSOS), is proposed in this paper. The lower-order harmonics of the Z1 − Z2 subspace, namely, the 5th, 7th, 17th and 19th, are considered. Compared with the traditional four-vector overmodulation strategy (TFOS), the content of the 5th harmonic is reduced by about 20%, and the total harmonic distortion (THDZ1Z2) of these four kinds of harmonics is reduced by about 21% in the proposed HSOS. Finally, the simulation and experiment are carried out to verify the effectiveness of the proposed strategy.

Investigation of an Output Voltage Harmonic Suppression Strategy of a Power Quality Control Device for the High-End Manufacturing Industry.

Due to the influence of nonlinear loads, power quality control devices under the traditional double closed-loop control strategy suffer from a large output voltage harmonic distortion rate and a slow harmonic suppression response and cannot meet the high-quality power supply requirements of high-end manufacturing. A compound control strategy based on voltage feedback and current feed-forward is proposed to solve the voltage quality problem under a nonlinear load. Firstly, based on the mathematical model of power quality control device, the working principle and voltage current coupling relationship are analyzed. Then, an output voltage compound control strategy based on feed-forward and feedback is proposed, and the harmonic suppression mechanisms are deduced and analyzed. Finally, simulation and experimental results are presented to show that, compared with the traditional double closed-loop control strategy, the harmonic suppression effect of the composite control strategy proposed in this paper can be increased by 2.2%, and the response time is decreased to 100 ms.

A harmonic suppression strategy for grid-connected inverters based on quadrature sinewave extractor

Grid-connected inverters need to reduce current harmonics as much as possible. After introducing the input signal’s fundamental and main harmonic quadrature components, a discrete state model is created, and the discrete observer design method is used to propose a harmonic extraction algorithm called quadrature sinewave extractor (QSE). The QSE is a stable recursive operator with the advantages of no phase displacement and the ability to eliminate mutual influence between harmonic components. Compared to the widely used proportional multi-resonant controller, QSE can reduce current harmonics and improve system stable performance by using it in the current control of grid-connected inverters. Finally, comparative experiments on a three-phase grid-connected inverter are used to verify the proposed method’s effectiveness.

Third-order current harmonic suppression and neutral-point voltage balance control strategy for single-phase three-level NPC inverter

The imbalance of capacitor voltage on the DC side of the inverter will cause the third-order current harmonics and the device will be damaged greatly with the increase of voltage stress. The mechanism of imbalance capacitors voltage and the third-order current harmonics generated by the double frequency fluctuation are analyzed. This paper presents a feedforward capacitor differential pressure control strategy based on PR controller, which is aimed at the single-phase three-level NPC inverter and considers the cause of double modulation wave. The PR controller is used in the current loop to suppress the third-order harmonic by static-free tracking of the AC signal, and the voltage balance is realized by the feedforward DC-link capacitor voltage difference to offset the DC component of the output side. The simulation model and 1kW prototype driven by the control strategy have been established to demonstrate that the capacitor voltage of the inverter is balanced and the third-order harmonic is suppressed efficiently.

Frequency coordination and harmonic suppression strategy based on composite virtual impedance in hybrid energy storage system

Under the traditional droop control, hybrid energy storage system cannot take advantage of the respective merits of battery and supercapacitor for frequency coordination, which shortens system life. Because of the single-phase inverter load, the second harmonic current is generated in the front-stage converter when the output power pulsates at twice the output voltage frequency. This paper proposes a strategy for frequency coordination and second harmonic current suppression based on composite virtual impedance. Under this strategy, the system equivalent output impedance exhibits resistance and inductance in low-frequency part, dominated by the battery side. The battery reacts slowly to absorb the low-frequency power fluctuations and provide the energy required by load at steady state. It is capacitive in the high-frequency range, with the supercapacitor side dominating. The supercapacitor quickly absorbs the high-frequency part of power fluctuation to suppress the impact of load mutation on DC bus and improve system dynamics. Meanwhile, the strategy realises that the inductor branch impedance is significantly larger than the capacitor branch impedance at double frequency, suppressing the second harmonic current and increasing the system efficiency. Experimentation confirms the effectiveness of the control strategy.

Improved Deadbeat Predictive Control Based Current Harmonic Suppression Strategy for IPMSM

When the interior permanent magnet synchronous motor (IPMSM) is running, there are abundant harmonics in the stator current. In order to achieve the suppression of current harmonics, the current harmonic extraction method and current harmonic controller are studied in this paper. Firstly, a simple and accurate method for extracting current harmonics is proposed by means of multiple synchronous rotating frame transformation (MSRFT). Secondly, an improved deadbeat predictive control (IDPC) based current harmonic controller is designed after analyzing the advantages and disadvantages of traditional current harmonic controllers. Thirdly, IDPC-based current harmonic suppression strategy is proposed by combining the proposed current harmonic extraction method and the proposed current harmonic controller. The proposed strategy can still effectively achieve current harmonic suppression when the motor runs at low speed, medium speed and high speed and the controller parameters are mismatched with the motor parameters. Finally, the feasibility and effectiveness of the proposed strategy are verified by simulation and experiments.

Impedance Characteristics and Harmonic Analysis of LCL-Type Grid-Connected Converter Cluster

This study addresses the output impedance model of the LCL-type grid-connected converter considering the dead-time effects and the digital control delay. The model shows that the digital control delay will affect the accuracy of the output impedance of the grid-connected converter, and the dead-time effects are only equivalent to superimposing a disturbance voltage on the original output impedance model. The derived output impedance model is verified by comparing it with the switching model in the PSIM simulation environment. The harmonic interaction between converter cluster and utility grid is modeled and analyzed based on the output impedance model. A combined harmonic suppression strategy is incorporated into every converter control scheme to suppress the harmonic interaction. Simulation results are presented to demonstrate the correctness of harmonic interaction analysis and the effectiveness of the proposed suppression strategy.