Harmonic Current Suppression Research Articles

Decoupling Control Optimization Based on Analysis and Compensation of Back EMF Disturbance in High Precision Current Converter

In high performance applications, LC filter usually is added to power converter for optimizing the output current ripple characteristics of the system. However, the LCL link composed of LC filter and resistor-inductance load causes the resonance, which leads to the traditional closed-loop not appropriate to be applied directly. Consequently, the active damping compensation method based on harmonic current is considered to suppress the resonance, and the suppression effects of different damping parameters on the resonant peak are compared and analyzed. Moreover, back EMF treated as a nonlinear disturbance affects the accuracy of current. Therefore, the current harmonic suppression method based on feedforward control for resonant pole-based dual buck soft-switching converter (RPDBSC) is presented, and the current suppression method of feedforward control is analyzed by the decoupling control model of bias current. This paper focuses on the improvement of the closed-loop control strategy for high precision current converters, and the effectiveness of the proposed method is verified by simulation and experiment.

Current harmonics suppression of the large aperture telescope based on segmented arc PMSM

Current harmonics suppression of the large aperture telescope based on segmented arc PMSM

Current harmonic suppression for permanent magnet synchronous motor based on phase compensation resonant controller

Permanent magnet synchronous motor always suffers from air gap field distortion and inverter nonlinearity, which lead to the harmonic components in motor currents. A resonant controller is a remarkable control method to eliminate periodic disturbance, whereas the conventional resonant controller is limited by narrow bandwidth and phase lag. This article presents a novel resonant controller with a precise phase compensation method for a permanent magnet synchronous motor to suppress the current harmonics. Based on the analysis of the current harmonic characteristics, the proposed resonant controller for rejecting a set of selected current harmonic components is plugged in the current loop, and it is parallel to the traditional proportional–integral controller. Furthermore, the stability analysis of the proposed resonant controller is investigated, and the parameters are tuned to get a satisfactory performance. Compared with the conventional resonant controller, the proposed resonant controller can achieve good steady-state performance, dynamic performance, and frequency adaptivity performance, simultaneously. Finally, the experimental results demonstrate the effectiveness of the proposed suppression scheme.

Direct current control strategy of LCL‐type converter for harmonic suppression under distorted grid condition

The grid voltage distortion represents a significant cause of the grid quality degradation when a renewable energy system is incorporated into the traditional grid. In this paper, a direct harmonic current control strategy is proposed for an LCL converter under distorted grid conditions. The proposed strategy improves the power quality and enhances the converter robustness under the non-ideal grid conditions. Traditionally, in the harmonic suppression strategy, the capacitor current is commonly used as a harmonic information source to control and suppress harmonics, which not only realises active damping, but also provides harmonic current suppression. Unlike the existing technologies, the proposed strategy realises the closed-loop control and harmonic current suppression by sampling the converter-side current. The proposed strategy can achieve a more efficient harmonic suppression than the traditional methods without requiring additional sensors and hidden danger of resonance. The impedance characteristics of multi loops are analysed when a distorted voltage is applied to the LCL converter. Then, the corresponding control strategy is proposed. The similarities and differences in harmonic suppression and stability between the proposed strategy and the traditional strategies are presented and discussed. Finally, the effectiveness and feasibility of the proposed strategy are verified by the simulation and experimental results.

Harmonic current suppression method with adaptive filter for permanent magnet synchronous motor

ABSTRACT Due to the distortion of air gap magnetic field and the inherent non-linear characteristics of the inverter, the stator current of permanent magnet synchronous motor (PMSM) contains a large number of high order harmonic components, which distorts the current waveform and generates torque ripple, limiting the application of the PMSM in high speed and precision situations. To solve this problem, a harmonic current suppression method is proposed based on synchronous rotating coordinate transformation theory and adaptive filtering algorithm. The PMSM harmonic mathematical model is established and the coordinate transformation method is used to extract the 5th and 7th harmonic currents. On the basis of the original double closed-loop control system, the harmonic current loop is added, and the harmonic components are suppressed by injecting harmonic voltages. In order to improve the filtering effect and reduce the harmonic content, an adaptive filter is designed to replace the conventional low pass filter in the process of harmonic current extraction. According to the results of coordinate transformation, the adaptive filter continuously adjusts the parameters online through the least mean square (LMS) algorithm to extract the harmonic current. The simulation and experimental results proved the correctness and effectiveness of the proposed method.

Dual-Electric-Port Bidirectional Flux-Modulated Switched Reluctance Machine Drive With Multiple Charging Functions for Electric Vehicle Applications

This article proposes a simplified dual-electric-port drive for a flux-modulated switched reluctance machine (SRM) with flexible charging capability for electric vehicle applications. In the driving mode, the developed flux modulation control can be achieved by directly employing the modular three-leg converter compared to the conventional open-winding topology. The zero-sequence current excitation can be flexibly controlled between the dual port and the number of power switches is also significantly reduced. The corresponding carrier-based pulsewidth modulation method and harmonic current suppression strategy are both developed to improve the machine performance. In the standstill condition, flexible battery charging can be easily achieved by the drive circuit, including both the dc and ac charging, without using any additional passive components and power devices. Then, the current distribution control scheme and power factor correction strategy are further developed for the dc and ac charging, respectively. Compared with existing drive topologies, advanced flux-modulated control and flexible energy control both can be achieved with machine performance improvement and drive cost reduction. Experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategies.

MMLSTOGI based control for suppression of current harmonics in PV‐tied grid

In a photovoltaic array (PVA) tied grid system, PVA and the grid are connected at AC bus (ACB) to feed the power to the grid and the load connected locally at the ACB. The photovoltaic energy conversion system (PVECS) requires an improved dynamic controller to control the grid voltage harmonics under variable solar power and nonlinear unbalanced load conditions. The conventional filtering controllers are unable to remove the sub-harmonics and DC-offset in the input signal. Moreover, their attenuation for the dominant lower order harmonics is unsatisfactory for unbalanced loading conditions and highly nonlinear loads. A MMLSTOGI (mixed multi-level second and third order generalized integrator) based control is used in this work. It effectively mitigates the dominant lower-order harmonics and the DC-offset of load currents and extracts their in-phase and quadrature-phase fundamental components (FCs). The PVA is connected at ACB through interfacing voltage source converter (VSC). The DC-link voltage is ascertained by generating its reference value using an incremental conductance (InC) based maximum power point tracking. The PVA power is feed-forwarded in the control to enhance the dynamics of the system. The control is validated on a developed model in MATLAB SIMULINK background, and using a developed prototype.

DC-Biased Sinusoidal Current Excited Switched Reluctance Motor Drives Based on Flux Modulation Principle

This article proposes a novel current control technique for three-phase switched reluctance motor (SRM) drives with harmonic current suppression, based on developed flux modulation principle. For conventional SRM control systems, the unsmooth and discontinuous stator current cause serious torque ripple, vibration, and noise, due to the doubly salient motor structure. In order to overcome shortcomings in conventional drives, the developed flux modulation principle is employed for the SRM in this article, where the working principle is investigated in detail, including the excitation magnetic field, flux modulator, and armature magnetic field. Then, a new control strategy is presented to generate the dc-biased sinusoidal current, by employing the modular open-winding converter. Furthermore, a harmonic current suppression strategy is put forward for the new drive to improve the motor performance, by employing a developed vector proportional integral control scheme. Compared to existing SRM drives, the torque ripple and motor vibration can be both significantly reduced, the motor structure and winding arrangement do not need to be changed, and the robustness of the motor system is improved. Finally, experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategy.

Pseudo affine projection assisted multitasking approach for power quality improvement in grid‐interactive photovoltaic (PV) system

The electronically interfaced photovoltaic (PV) system and its control approach form an intrinsic part of the distributed generation (DG) system. This study proposes pseudo affine projection (PAP)-assisted multitasking control scheme for grid-integrated DG inverter under input grid voltage disturbances. The PAP approach is based on the convergence of active weighted values and is independent of the input signal property, which manifests a discrete characteristic. Additionally, it exhibits a unique capability of updating weight based on multiple, delayed input signal vectors. The fundamental distinguishing feature of the proposed PAP is its intrinsic learning behaviour and therefore it provides an optimal solution to the ingrained paradox between steady-state misadjustment and convergence speed compared to its conventional counterpart affine projection. The PAP-assisted algorithm practically enables DG inverter to perform multiple tasks including suppression of source current harmonics, unbalancing, and neutral current. It also provides load reactive current support with unity power factor operation while transferring the maximum active power into the utility grid. The practicality of the proposed PAP algorithm is investigated through MATLAB/Simulink software. Finally, the experimental results recorded with the dSPACE-1104 based real-time control platform show good to excellent agreement with simulations in the steady-state, as well as transient phenomena.

Suppression Method of Current Harmonic for Three-Phase PWM Rectifier in EV Charging System

Under the unbalanced condition of grid voltages, the second-order harmonic voltage ripple will <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">appear on</b> the DC bus of the three-phase PWM rectifier due to the existence of the negative sequence voltages. In addition, the total harmonic distortion (THD) of the grid currents will increase correspondingly. In this paper, the coupling mechanism between the DC bus voltage ripple and the grid harmonic currents is revealed. Based on the situation above, a grid harmonic current suppression method is proposed. Compared with existing methods, the proposed method has the advantages in the following three aspects. Firstly, the proposed method does not require either the extraction of positive/negative sequence or the positive/negative sequence current control, which can highly reduce the complexity of the system. Secondly, the grid current harmonics can be reduced by an improved proportional quasi resonant (IPQR) controller. Thirdly, the IPQR controller has little effect on the parameter design of the control system, which facilitates the control design. Finally, the experiments show the accuracy of the theoretical analysis and the effectiveness of the proposed method.

Current Harmonic Suppression for Permanent-Magnet Synchronous Motor Based on Chebyshev Filter and PI Controller

In permanent-magnet synchronous motor (PMSM), the winding current consists of different orders of harmonics due to the manufacture error, deadtime, and disturbances. This article proposes a winding current harmonic suppression method for PMSM by reducing the dominant fifth- and seventh-order current ripples. First, with reference frame transformation, the fifth- and seventh-order current ripples convert to sixth-order ripples in the synchronous reference frame (SRF). Then, with further transformation, these sixth-order ripples turn to dc signals. Next, the type-II Chebyshev filter is designed to extract these dc signals. Also, the proportional-integral (PI) controller is adopted to generate the current harmonic control voltage, which is setting the dc current harmonic signals reference to be zero. Finally, the current harmonic control voltage is compensated to the voltage reference in the SRF. Both the simulation and experimental results are presented to verify the effectiveness of the proposed method.

Photovoltaic system operation as DSTATCOM for power quality improvement employing active current control

This paper presents photovoltaic (PV) system control as distributed static compensator (DSTATCOM), termed as PV-DSTATCOM, operated with active current control (ACC) and feed-forward control loop (FFCL). Besides active power injection into the utility grid, the proposed PV system autonomously transforms into a DSTATCOM to provide various ancillary services including source current harmonic suppression, load reactive current compensation, zero sequences component mitigation, and power factor correction. Since PV-DSTATCOM operates with ACC, it precisely extracts the fundamental in-phase and quadrature components of current. It introduces high-gain at the third-order harmonic and thereby alleviates stationary errors in the current control loop of PV inverter. The proposed ACC+FFCL structure is computationally efficient and unconditionally stable. Practically, FFCL addresses the challenges emerged due to nonlinearity introduced by the PV unit and ensure a rapid power balance between the PV unit and electric grid. Further, a simplified perturb and observe based maximum power point tracker has been employed to evacuate the maximum power from the PV array. The proficiency of the developed ACC+FFCL structure is investigated through a comprehensive set of transient studies using MATLAB/Simulink software. Finally, a laboratory setup has been developed using the dSPACE-1104 platform and experimental results are recorded with detailed comparative evaluation.

Harmonic Current and Inrush Fault Current Coordinated Suppression Method for VSG Under Non-ideal Grid Condition

For the virtual synchronous generator, the voltage-controlled harmonic suppression method will seriously deteriorate the magnitude of inrush fault current in the moment of grid symmetrical fault, because the suppression effects of harmonic current and inrush fault current are mutually constrained from the perspective of its output impedance. For this issue, a harmonic current and inrush fault current coordinated suppression method is proposed to achieve both good results of harmonic current suppression in normal grid and inrush fault current limitation in fault grid, which mainly includes a passive branch, an active branch and an improved virtual synchronous generator (VSG) control. The passive branch is installed between the PCC and grid to introduce an additional voltage variable. Meanwhile, with the proper feed-forward of the PCC voltage and additional voltage, the active branch is used to increase the mid/high frequency impedance viewed from the grid fault point to VSG, and also decrease the harmonic impedance viewed from the PCC to VSG. Then, not only the transient inrush fault current is limited, but also the harmonic current introduced from the nonlinear load is mostly absorbed. Moreover, the improved VSG control is used to limit the steady-state fundamental frequency fault current. Therefore, the contradictory between harmonic current and inrush fault current suppression for VSG is well solved. Finally, the experiment results validate the proposed control method.

The Method of Joint Compensation of Reactive Power, Load Balancing and Filtering Harmonics Currents of an Asymmetric Nonlinear Load Connected in a Triangle

This article explores the method of joint suppression of harmonic currents, balancing currents and partial compensation of the reactive power of a non-linear asymmetric load connected in a triangle using a device installed on the low voltage side of a power transformer

Improved super‐twisting sliding mode control of a stand‐alone DFIG‐DC system with harmonic current suppression

This study presents an improved super-twisting sliding mode (SSM) approach to a stand-alone doubly fed induction generator (DFIG) for direct current (DC) generation system. By taking the uncertainties into consideration, an improved SSM regulator based on an extended state observer (ESO) is proposed to enhance the robustness of DC-voltage regulation. Moreover, a novel sinusoidal rotor current calculation method is proposed to generate sinusoidal reference of rotor current. A resonant-based ESO (R-ESO) SSM approach is proposed to regulate rotor current. By applying the R-ESO to estimate the model-related part of DFIG, the tracking performance with respect to a sinusoidal reference is improved. Then, the suppression ability to fifth and seventh harmonic currents are enhanced. Finally, both simulations and experiments on a 6-kW DFIG-DC system are provided to show the effectiveness of DC-voltage regulation and harmonic current suppression of the proposed approach.

Current Harmonic Suppression in Dual Three-Phase Permanent Magnet Synchronous Machine With Extended State Observer

Dual three-phase (DTP) permanent magnet synchronous machines (PMSM) have been utilized in many applications due to their outstanding performance. However, large stator current harmonics limit the further application of the DTP-PMSM due to the low impedance in the harmonic subspace. To solve this problem, this article proposes a current harmonic suppression strategy based on an extended state observer (ESO). A detailed analysis is carried out to demonstrate the disturbance rejection ability and robustness of the proposed method. The theoretical analysis also shows that the ESO strategy outstands the conventional proportional-integral controller and advanced proportional resonance (PR) controller in terms of harmonic reduction. The advantages are verified by simulation and experimental results under different operating conditions. The proposed strategy still works well when considering other factors that may cause harmonic distortion, such as magnetic circuit saturation, saliency ratio, over-modulation of the inverter, the voltage drop caused by electric devices, and dead time. Meanwhile, some limitations are also pointed out. The proposed strategy can also be easily applied to other multiphase PMSM types.

Modeling, analysis and suppression of current harmonics of Langevin-type ultrasonic motors under high voltage

For achieving high speed and large thrust, Langevin-type ultrasonic motors (LTUM) are generally operated under high voltage. However, high voltage causes the current harmonics of piezoelectric material nonlinear phenomena, which will decrease the efficiency, the output force, and the accuracy of LTUMs. In this study, the nonlinearity of current harmonics of LTUM are described and analyzed by a novel nonlinear equivalent circuit model using Lagrange equations. Thereafter, based on a nonlinear tuning method, a specific driver circuit is suggested to suppress the current harmonics. Experimental results validate that the time response of the current is consistent with that of the model and furtherly demonstrate that the total harmonic current distortion decreases by 68% utilizing the proposed nonlinear tuning method under 500 Vpp.

Circulating Harmonic Currents Suppression of Level-Increased NLM Based Modular Multilevel Converter With Deadbeat Control

This article first analyzes the effect of the level-increased nearest level modulation (NLM) to the circulating current of the modular multilevel converter (MMC). The total inserted submodule (SM) number in one phase-leg of the MMC is variable using the level-increased NLM, which can significantly increase the peak-to-peak value of the circulating harmonic currents. Then, a circulating harmonic currents suppression method is proposed by applying deadbeat control for the MMC with level-increased NLM. Compared with the existing direct circulating current control approaches for the MMC, the proposed method presents specific extension and adjustment principle of the total inserted SM number. Therefore, the proposed method can improve the dynamic control performance and handle large circulating harmonic currents at steady state. And it can well coordinate the modulation and circulating harmonic currents suppression stages to avoid disturbing the ac-side output voltage while regulating the circulating current. The effectiveness of the proposed method is evaluated by a single-phase industrial-level simulated MMC system and a laboratory experimental platform.

Multiobjective Coordinated Control Strategy for Grid-Connected Inverter under Unbalanced Voltage Conditions

AbstractTo improve grid-connected inverter operation performance, a power oscillation and current harmonic suppression coordinate control strategy that considers the problem of overcurrent is propo...

Current Harmonic Suppression Algorithm for Asymmetric Dual Three-Phase PMSM

Based on the vector space decomposition (VSD) transformation, the currents of an asymmetric dual three-phase permanent magnet synchronous motor (ADT-PMSM) with isolated neutral points are decoupled into the torque, producing α-ß components in the fundamental subspace and the loss-producing x-y components in the harmonic subspace. In order to suppress the current harmonics, a feedforward voltage compensation that is calculated according to the dead time, turn on/off time, and the voltage drop is added to the reference voltage of the control algorithm. Due to the limitations of the feedforward voltage compensation method, a feedback current control loop is set up in the x-y subspace, where an improved resonant controller is adopted to generate the compensation voltage. The improved resonant controller can achieve a high gain at a specific frequency. The experimental results verify the effectiveness of the proposed method.