Harmonic Injection Method Research Articles

Active vibration suppression for integrated electric drive systems based on the CNN-LSTM considering dead zone

To address the problems that the torque ripple and vibration of integrated electric drive system caused by dead-zone, which leads to the decrease of electric drive system reliability and vehicle comfort, this paper establishes a current harmonic model and nonlinear integrated electric drive system model considering the dead-zone. A predictive model for harmonic compensation voltage is constructed based on the conventional current harmonic injection method. Subsequently, an active vibration suppression method based on CNN-LSTM is proposed. The method reduces the vibration of the electric drive system by suppressing the current harmonics and suppresses the torque ripple at the same time. Simulation and experimental results show that the method effectively suppresses the vibration of the electric drive system, reduces current harmonics and control parameters, improves the system response speed, and decreases the torque ripple at high speed.

Speed harmonic suppression of PMSM and its application in ball screw vibration suppression

Abstract The speed ripple of surface-mounted permanent magnet synchronous motor (SPMSM) causes vibration of the ball screw, which degrades the accuracy and stability of the ball screw system.The harmonic injection method can suppress the speed ripple by decreasing the speed harmonic of SPMSM. When the speed ripple is suppressed, the vibration of the ball screw is also reduced.
However, large amount of calculation, complex parameter adjustment, and long suppression time limit its performance in suppressing vibration of ball screw. Therefore, in this paper, we propose a speed harmonic suppression method based on the online measurement of the transfer function from inject voltage harmonic to speed harmonic. In the proposed method, the transfer function is measured after the motor reaches a stable operating condition. And then, the designed speed harmonic controller parameters are set according to the measurement results. Compared with the existing method, the method based on online measurement has less calculation, simple parameter adjustment, fast suppression speed, and good performance in suppressing the vibration of ball screw. Experimental verifications are carried out in the forward and backward condition of the ball screw.

Torque Ripple Suppression in the 6/4 Variable Flux Reluctance Machine with Open Winding Configuration by Using Harmonic Injection

High torque ripple can be observed with a 6/4 variable flux reluctance machine (VFRM). In order to minimize the torque ripple in VFRMs, this paper presents a harmonic injection method for 6/4 VFRMs with an open-winding configuration. By analyzing the impact of harmonics on VFRMs, the method involves detecting the third harmonic using a first-order low-pass filter (FLPF). Subsequently, the extracted harmonics are controlled and shifted to counteract the voltage harmonics in both inverters without inducing phase imbalance or overvoltage. With the proposed method, the torque ripple can be significantly reduced by about 50% under load conditions. The effectiveness of the harmonic injection method is validated through a prototype VFRM.

A suggestion for space harmonic injection into motor current to reduce propeller vibration

Propellers produce fluctuating thrust and torque as they rotate in a non-uniform wake field. They contribute most of the vibration and noise generated by the propeller and can lead to mechanical damage to shafts and bearings. Recently, the demand for electric propulsion ships has increased. As the torque and speed fluctuations are generated in marine propellers, harmonic components in the current and voltage of the propulsion motor occur and lead to increased losses, device degradation, and torque pulsations. In this study, a harmonic injection method is proposed to reduce the impact of motor and mechanical vibration caused by the fluctuating load torque of the propeller. A harmonic component is applied to the current of the motor to generate a motor torque with a different phase of the same magnitude as the variation of the load torque of the motor. In this study, a computational fluid dynamics simulation was performed to obtain the torque of the target vessel, medium range tanker, and a MATLAB Simulink was used to model the motor simulation. It was found that the harmonic injection method can reduce the mechanical torque fluctuation of the motor by 87%.

Harmonic Injection Control of Permanent Magnet Synchronous Motor Based on Fading Memory Kalman Filtering

In order to reduce the harm of harmonic disturbances of the permanent magnet synchronous motor (PMSM) control system to the drive and improve the accuracy of the control system, a harmonic injection control method based on asymptotic fading memory Kalman filtering is proposed. Compared with the traditional harmonic injection method, this method reduces the torque pulsation of the PMSM, converges faster, and realizes fast stabilization of the control system. In order to improve the control accuracy of the system, extended Kalman filtering is used to estimate the mechanical angular velocity and optimize the harmonic extraction process to reduce the interference of noise signals in the extraction process. At the same time, a fading memory factor is introduced to replace the fixed gain in the Kalman filter, which can correct the system error and effectively prevent the filtering dispersion, thus enhancing the system’s stability. Finally, the system is simulated and experimentally analyzed, and the results show that the method can improve the dynamic response speed, stability, and control accuracy of the system compared with the traditional harmonic injection method.

Low order speed harmonic suppression in FOC-PMSM based on the closed-loop transfer mechanism of injected voltage

In the field oriented control (FOC) permanent magnet synchronous motor (PMSM) servo system, torque ripple impairs motor performance. Harmonic injection methods can suppress torque ripple by injecting additional voltage harmonic to offset the existing speed harmonic. However, since FOC is a closed-loop motion control strategy, the transfer path from injected voltage harmonic to speed harmonic is affected by FOC, especially in very low frequency. Due to the influence of FOC on the transfer function, the relation between the injected voltage harmonic and speed harmonic varies with operating conditions and motor control parameters. It causes the existing harmonic injection methods ineffective to suppress low order speed harmonics. To solve the problem, in this paper, the closed-loop transfer mechanism of injected voltage harmonics is analyzed and the closed-loop transfer function is derived. Based on the derived closed-loop transfer function, a low order speed harmonic suppression method is proposed. With the derived transfer function, the proposed method can adapt to the variations of the relation between low order injected voltage harmonic and speed harmonic under different operation conditions. Finally, the accuracy of the derived closed-loop transfer function and the effectiveness of the proposed low order speed harmonic suppression method are evaluated by experiment.

An Optimized Active Power Backflow Suppression Strategy for Cascaded H-Bridge PV Grid-Connected Inverter During Inter-Phase Short-Circuit Fault

Active power backflow is a unique problem of three-phase isolated cascaded H-bridge (CHB) PV inverter during asymmetric grid voltage fault, resulting in the continuous rise of H-bridge dc-bus voltages and that the inverter will be eventually shut down and off-grid due to voltage out of control. The existing methods are able to completely suppress the active power backflow during single-phase short-circuit fault and two-phase short-circuit fault, but fails in a large operating zone when inter-phase short-circuit fault occurs. For this issue, this paper proposes a novel multiple specific harmonic voltages injection method based on the existing fundamental-frequency zero-sequence voltage compensation strategy, which calculates and injects the optimal third, fifth, seventh and ninth harmonic voltage according to the fault type, drop depth and the normalized power, for minimizing the amplitude of three-phase modulation voltages and then significantly shrinking active power backflow zone of three-phase isolated CHB PV inverter. Then, the area of the active power backflow zones for different control methods is quantitatively calculated and compared by adopting the polynomial fitting to show the advantages of the proposed method. Finally, experimental results are achieved by a low voltage and low power experimental prototype to verify its effectiveness and feasibility.

Amplitude-Phase Based Optimal Voltage Harmonic Injection for Speed Harmonic Minimization in SPMSM

Low torque ripple level is the prerequisite for surface-mounted permanent magnet synchronous machines (SPMSM) to maintain control accuracy and speed stability. Since the speed harmonic's amplitude is proportional to the torque harmonic's amplitude, torque ripple can be reduced by speed harmonic minimization. Harmonic injection method is a practical speed harmonic minimization method. But current harmonic regulation and complex theoretical derivation are required in existing methods. What's more, the effectiveness of many methods will deteriorate when the parameters of PMSM and PI controllers vary. In order to avoid the influence of parameter variations and complex algorithms, an amplitude-phase based optimal voltage harmonic injection method is proposed for speed harmonic minimization in this paper. The influence of the injected voltage harmonic's amplitude and phase on the speed harmonic's amplitude is firstly analyzed. And then a simple speed harmonic controller based on the optimization of injection voltage harmonic's amplitude and phase is designed. The proposed method does not rely on the motor parameters. Moreover, the proposed method is easy to implement. It does not need to regulate current harmonics. The proposed method is simulated and experimentally evaluated under both steady-state and transient conditions.

Torque Ripple Reduction of PMSM Based on Modified DBN-DNN Surrogate Model

Due to the nonlinearity and dead time of the inverter, a great number of harmonic components is introduced into the motor input current, causing the torque ripple of the motor. The paper aims to suppress the torque ripple of a low-speed and high-torque permanent magnet synchronous motor (PMSM) with a two-step stator voltage optimization method, including a high precision harmonic voltage injection (HPHVC) method and a deep belief network (DBN)-deep neural network (DNN) voltage prediction model. Firstly, a closed-loop harmonic current detection system with Type-II Chebyshev filter is adopted to enhance the harmonic current extraction accuracy. Secondly, a harmonic voltage algorithm is designed considering the dq-axis current coupling relationship, which improves the accuracy of harmonic voltage calculation. Thirdly, a dq-axis voltage prediction model is constructed using DBN-DNN algorithm as the surrogate model, which further reduces the current harmonic components caused by the harmonic injection structure and the PI control algorithm, reduces the torque pulsation of the motor, and boosts the dynamic performance of the motor. Finally, the experimental platform is constructed by embedding the proposed strategy into the field oriented control system for reducing the torque pulsation. The experimental results verify the proposed strategy.

A new series‐connected 36‐pulse rectifier with hybrid DC‐reinjection method for high power output

AbstractIn this study, a new 36‐pulse rectifier with a hybrid DC‐reinjection circuit is proposed. It multiplies the AC‐side input voltage steps from 12 to 36 using a hybrid auxiliary circuit for voltage and current modulation. Both the AC and DC side harmonics of the rectifier system are efficiently suppressed when combined with filter capacitors at DC side. Only 2 more diodes and an IGBT are used in the proposed approach for constituting the injection circuit. The cascaded structure of rectifier bridges allows for significant voltage gain, making it appropriate for high power output rectification applications. The proposed 12‐pulse rectifier's phase shifting structure and 36‐pulse rectifier's operational theory are introduced. The injection transformer's turn ratio and the IGBT's conduction angle are both designed to have the lowest possible harmonic distortion of the voltage at AC side. Analyses are done on the rectifier's impedance matching feature and energy loss of IGBT. The operating performance of the rectifier is assessed when the active switch fails. With the help of a 1.8 kW prototype and a HIL system based on Starsim, the theoretical portion is confirmed. The results of the simulation and experiments support the effectiveness of the hybrid voltage harmonic injection method studied.

A novel power balance control scheme for cascaded H-bridge multilevel converters with battery energy storage

Battery energy stored quasi-Z source cascaded H-bridge based photovoltaic power generation system combines advantages of quasi-z-source inverter, cascaded H-bridge, and battery energy storage system. However, the battery state of charge imbalance between the cascaded H-bridge inverter modules would reduce the system's performance and efficiency and potentially cause the system to fail. An integrated control technique of adaptive state of charge balancing based on gain scheduling and three-phase power balance of third harmonic injection based on fundamental frequency whole zero sequences is suggested for the quasi-Z source cascaded H-bridge battery storage system. Based on the mathematical relationship between the instantaneous state of charge of battery energy stored quasi-z-source cascaded H-bridge and the voltage reference value, this method updates the proportional controller gain in each sampling period. It combines the third harmonic injection method based on the fundamental frequency zero sequence to select the optimal modulation ratio Mn. Rapid state of charge balancing is accomplished without overmodulation while increasing the power balance range and decreasing DC link voltage swings. The simulation results validate the method's usefulness. The simulation results validate the proposed control method for ensuring power distribution between each phase and achieving a balanced state of charge of the battery energy stored quasi-Z source cascaded H-bridge photovoltaic system's battery energy storage.

A Three-stage AC side startup strategy for hybrid MMC

When a hybrid modular multilevel converter (MMC) starts from the AC side, the capacitor voltages of full-bridge submodules (FBSMs) will be twice those of half-bridge submodules (HBSMs) in the uncontrolled charging stage due to their structural differences, making it difficult to further charge the SMs in the ensuing controlled charging stage. To solve this problem, a three-stage AC-side startup strategy for hybrid MMCs is proposed. Compared with conventional closed-loop startup strategies, it charges HBSMs and FBSMs simultaneously with the third harmonic injection method, which eliminates the inrush current. And then the HBSMs are charged separately by orthogonal decomposition of the arm voltage after FBSMs are fully charged, which avoids overcharging the FBSMs. Thus, hybrid MMCs can start from the AC side quickly without inrush current, and the unbalance between different SMs is eliminated. The necessity and feasibility of the proposed strategy are discussed in detail. Aiming at possible errors in arm voltage orthogonal decomposition and current phase tracking, control loops for HBSMs and FBSMs are derived and analyzed. Finally, the complete three-stage startup strategy is designed. Simulation results and experimental results are provided to support the theoretical analysis and validate the proposed strategy.

A Harmonic Injection Method Equivalent to the Resonant Controller for Speed Ripple Reduction of PMSM

This article proposes a straightforward and effective control strategy to reduce the periodic speed ripple of the permanent-magnet synchronous motor. The control strategy can be described as injecting current harmonics whose amplitude and phase can be adjusted automatically to compensate for periodic speed ripple. Compared with the resonant controller with the Tustin transform, the method proposed in the article can track speed ripple frequency without frequency displacement, realizing no steady-state error. Besides, the system stability is analyzed, and the phase compensation scheme is proposed to increase the phase stability. Moreover, the equivalence between the harmonic injection module and the resonant controller has been analyzed, which provides a simple way to understand the phase compensation of the resonant controller. The theoretical analysis and experimental results are presented to verify the feasibility of the proposed harmonic injection method.

Online Control Strategy for Radial Vibration Suppression of PMSM by Multiharmonic Current Injection Method

In the radial vibration suppression of the motor, the current harmonic injection method is an effective method. The radial force model of surface permanent magnet synchronous machine (SPMSM) is analyzed, and the relationship of the frequency, amplitude and phase between harmonic current and radial vibration harmonic is obtained. A current harmonic injection method is derived by using the current closed-loop transfer function in vector control, which can adjust the frequency, amplitude and phase of current harmonics to realize the change in the amplitude of radial vibration harmonics. one current harmonic is selected to suppress one even-order radial vibration harmonic, and the gradient descent method is adopted to online calculate the frequency amplitude and phase of the current harmonics injected at the minimum amplitude of radial vibration harmonics. In order to avoid the influence of the single current harmonic on the high radial vibration harmonics, a sequential vibration suppression method is proposed to realize the comprehensive suppression of every low-even-order vibration harmonics. Finally, an on-line control system for the radial vibration suppression of SPMSM with multi-current harmonics injection is designed. The prototype is a 750W SPMSM, the amplitude of all low-even radial vibration harmonics are suppressed significantly by this method, which verifies the correctness and effectiveness of this method.

Optimal third harmonic injection based nearest level control of large‐scale solar photovoltaic multilevel converter

This paper presents a new control approach with an optimal third harmonic injection-based nearest level modulation (OTHI-NLM) technique for a large-scale solar photovoltaic (SPV) system. This system uses a single-source multilevel converter to feed solar power into the grid. The merits of the optimal third harmonic injection (OTHI) and nearest level modulation (NLM) are considered for switching the SPV converter. A unique analysis to have an adaptive optimal injection with varying solar irradiance is conducted and compared with the well-known carrier-based high-frequency switching technique. The variations of harmonics for OTHI-NLM, an optimal third harmonic pulse width modulation (OTHI-PWM), and a constant third harmonic injection method are analysed at different irradiance levels. This optimal injection provides benefits such as enhanced DC bus utilization (DBU), better harmonics performance at different solar irradiance levels. The detailed methodology of the OTHI algorithm, nearest level modulation (NLM) technique with an optimal quotient calculation, and an instantaneous optimal third harmonic injection (THI) in closed-loop are presented. The comparative analysis shows the effectiveness of the SPV grid-tied structure over well-known ones. The power quality of the renewable energy system is investigated in dynamic solar irradiations. Moreover, simulation results are presented and validated in a real-time test bench.

Transfer Mechanism Analysis of Injected Voltage Harmonic and its Effect on Current Harmonic Regulation in FOC PMSM

Harmonic injection method is widely used in the suppression of current harmonic and torque ripple in field-oriented control (FOC) permanent magnet synchronous motor (PMSM) servo system. However, under some working conditions of FOC PMSM, the harmonic injection method fails to suppress the current harmonics and causes oscillation. To analyze the cause of oscillation, the transfer mechanism of injected voltage harmonic is analyzed in this article, and the relation between injected voltage harmonic and current harmonic is derived. The theoretical analysis results show that the relation between harmonics will change with motor speed and parameters of FOC PMSM. When the relation between harmonics is reversed, the existing harmonic injection method will fail and cause harmonic oscillation. To solve this problem, a simple improvement of the harmonic injection method is proposed in this article based on the proposed close-loop model. The correctness of the mathematical derivation and the effectiveness of the proposed method is evaluated by experiment and simulation.

Flexible Nonsinusoidal Zero Sequence Voltage Injection Method to Extend Negative Sequence Current Compensation Range for Star-Connected CHB STATCOM

DC voltage balance based on zero sequence voltage is commonly used for star-connected cascaded H-Bridge (SCHB) STATCOM to compensate negative sequence current. However, zero sequence voltage injection brings about side-effect of increasing STATCOM output voltage and thus the Negative sequence Current Compensation Range (NCCR) is significantly limited to avoid overmodulation. To extend the NCCR, improving the dc voltage utilization by injecting third harmonic component is a typical method. Compared with third harmonic injection (THI), square wave features lower peak-to-average ratio. Unfortunately, the capability of square wave injection (SWI) for the NCCR extension has not been well explored. In this article, to further extend NCCR, not only the SWI is employed for SCHB STATCOM, but also it is compared with THI in term of NCCR by establishing the relationship between the maximum STATCOM voltage and negative sequence current. The comparison results reveal that the THI and SWI both have their own strengths and weaknesses in NCCR, which highly depends on the amplitudes and phases of positive and negative sequence currents. Furthermore, the criteria associated with the amplitudes and phases of the positive and negative sequence currents are derived to determine the harmonic injection method with larger NCCR by using symbolic-graphic combination method and MATLAB tools. As a result, a new harmonic injection method is proposed by selecting the THI or SWI with larger NCCR flexibly according to the amplitudes and phases of positive and negative sequence currents. Finally, the proposed method is verified by experimental results on a 400 V/7.5 kVar SCHB STATCOM prototype.

Coupling Harmonic Voltages Considered Harmonic Currents Injection Method for Torque Ripple Reduction

Coupling Harmonic Voltages Considered Harmonic Currents Injection Method for Torque Ripple Reduction

A harmonic injection method for improving NVH performance of permanent magnet synchronous motor

A harmonic injection method is proposed for reduce permanent magnet synchronous motor torque ripple and noise, which is based on harmonic model of PMSM. The effectiveness of the method is verified by simulation and experiment. It is proved that this method can significantly improve NVH performance of the motor.

Model Predictive Control for Torque Ripple Suppression Caused by Misalignment of the Gearbox

This paper presents a model predictive control (MPC) based harmonic current injection method (HCIM) to suppress the torque ripple caused by misalignment in gearbox. As it is inefficient to determine the amplitude and phase of harmonic currents manually, the MPC is used to search the appropriate harmonic currents to implement HCIM efficiently. A cost function for MPC is designed to minimize a resultant torque ripple which is calculated by summing the misalignment torque ripple and compensation torque. The compensation torque is an input variable of the predictive model. In order to predict the resultant torque ripple accurately, an estimation method of the misalignment torque ripple with torque sensor is also proposed. The calculated compensation torque is converted into harmonic currents and the harmonic currents can be injected into a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current. As a result, the misalignment torque ripple can be suppressed. Experimental results demonstrate verification for estimation method of misalignment torque ripple, and effectiveness of the HCIM. In addition, the proposed MPC-HCIM is also verified by experiments, and the misalignment torque ripple is effectively suppressed by using the proposed method. By using the proposed method, high degree of precision in torque control can be achieved with low quality gearbox which has misalignment.