Optimal Pulse Width Modulation Research Articles

Synchronous Optimal Pulsewidth Modulation for High-Power AC Motor Drives: A Review

Synchronous Optimal Pulsewidth Modulation for High-Power AC Motor Drives: A Review

Optimal Pulse Width Modulation of Three-Level Converters With Reduced Common-Mode Voltage

Optimal Pulse Width Modulation of Three-Level Converters With Reduced Common-Mode Voltage

Comparative Study of Advanced Modulation and Control Schemes for Dual Three-Phase PMSM Drives With Low Switching Frequencies

In this paper, multiple advanced low-switching-frequency modulation and control schemes are investigated for dual three-phase permanent-magnet synchronous motor (PMSM) drives. The modulation schemes under investigation include multisampling space vector modulation (MS-SVM), selective harmonic elimination pulse width modulation (SHEPWM) and synchronous optimal pulse width modulation (SOPWM) while the control schemes include complex vector control, model predictive control (MPC) and flux trajectory control-based model predictive pulse pattern control (MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C). The difference between three-phase and dual three-phase PMSM drives at low switching frequencies is analyzed. Moreover, an optimal pulse width modulation (PWM)-based MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C scheme is proposed for the dual three-phase PMSM, where the optimal PWM modulation and MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C control are combined such that the optimal steady-state and dynamic control performance is achieved among the modulation and control schemes investigated. Experimental results are given to compare and validate the proposed control scheme.

Permanent magnet synchronous motor stator flux trajectory tracking control based on switching time correction

In this paper, aiming at the problems that the existing stator flux trajectory tracking control method often needs to design complex fundamental wave component observers and the switching time correction based on steady-state solution lacks accurate theoretical calculation equations, a permanent magnet synchronous motor stator flux trajectory tracking control method using optimal PWM (Pulse Width Modulation) is proposed. The outer loop is the speed regulator, whose output is combined with the flux linkage of the permanent magnet of the motor as the reference vector of the stator flux linkage. And the motor speed with the rotor position is combined to calculate the amplitude and phase angle of the reference stator voltage vector, which is used to optimize PWM pulse mode and to determine switching action. Meanwhile, the switching time of optimal PWM is corrected in real time through the stator flux deviation to eliminate the deviation between the stator flux reference value and the actual value. This method does not need to estimate the fundamental component of voltage, current or flux linkage. And unlike the traditional vector method, there is no current inner loop, which can significantly improve the dynamic response speed while simplifying the control structure. Simulation and experiments also fully verify the effectiveness of the proposed control method.

Synchronous Optimal PWM With Continuous Switching-to-Fundamental Frequency Ratio

In high-power applications, the synchronous optimal pulse width modulation (SOPWM) serves as a vital modulation method that achieves an excellent tradeoff between the switching losses and the current harmonic. However, the optimized pulse patterns of SOPWM are constrained due to the discrete pulse numbers, which leads to the underutilization of the allowable maximum switching frequency. Therefore, the corresponding current harmonic could not be reduced as low as possible. In response to this issue, the SOPWM with a continuous switching-to-fundamental frequency ratio is proposed in this article. First, the deduction of the traditional pulse patterns is introduced based on the symmetry of the voltage pulse waveform. Then, the principle of the proposed strategy is illustrated in detail, and an overall comparison with traditional SOPWM is given theoretically. With the proposed strategy, a considerable reduction of the current THD is achieved over almost the whole high-speed range, and the losses and efficiency of the system are analyzed by the finite element method (FEM). Finally, theoretical results are verified by simulation and experimental tests.

Cooling and preheating behavior of compact power Lithium-ion battery thermal management system

A novel honeycomb battery thermal management system with a combination of liquid-cooling and composite phase change material has been proposed for the cylindrical power lithium-ion battery to improve the cooling effect under harsh discharge conditions and the capacity reduction in low-temperature environment. The cooling and preheating performance have been compared at a discharge rate of 4C for three different monomer battery systems without any heat dissipation elements, with passive composite phase change material, or with hybrid cooling elements. The effects of the thickness of composite phase changed material, the size of micro-channel, the channel level number, the flow velocity of inlet liquid and the heating strategy on the cooling behaviour of the monomer battery are studied and examined. Furthermore, the impacts of inlet/outlet arrangement mode and inlet liquid flow velocity on the thermal behaviour of the cell module are analysed. When the environment temperature is 40 °C, the optimal parameters on thermal performance are decided, which reliably control the highest temperature, cell–cell temperature difference and the mass fraction of liquid phase of composite phase change material within an allowable range, and save the space of the module as much as possible. At the discharge rate of 4C and the coolant inlet flow velocity of 0.06 m/s, the highest temperature and cell–cell temperature difference of the module can be controlled at 46.21 °C and 3.5 °C, respectively, and keep the mass fraction of the liquid phase of composite phase change material at around 55% after battery discharge. When the battery module is heated from −15 °C to 10 °C, there are different optimal pulse width modulation heating strategies for 20 W and 10 W heating belts and the battery module can be rapidly heated in about 6 min.

Guest Editorial Special Issue on Emerging Converter Topology, Operation, and Design Technologies

Power electronics play a key role in the transition to carbon neutrality. To enhance the performances of power electronics systems, new theories and methods are entering the field of power converter research, leading to increasing diversity of the knowledge database regarding converter design and operation methods. In addition to the conventional case-bycase design methodology, new automated and generalized converter design philosophies integrating topology derivation and synthesis methods, optimal pulse-width modulation (PWM), and advanced control strategies are gaining attention in both academia and industry. By implementing these methods, the converter design process can be greatly improved while the potentials of various power converters can be fully explored, leading to elevated converter performances.

Superfast and large-depth-range sinusoidal fringe generation for multi-dimensional information sensing

Among many multi-dimensional information sensing methods such as structured-light and single-pixel imaging technologies, sinusoidal fringe generation is general and crucial. Current methods of sinusoidal fringe generation force concessions in either the speed or the depth range. To mitigate this trade-off, we have simultaneously achieved both speed breakthrough and depth range enhancement by improving both the optical projection system and binary coding algorithm based on an off-the-shelf projector. Specifically, we propose a multifocal projection system and oblique projection method, which essentially eliminates the existence of a single focal plane in the conventional axisymmetric system and utilizes its anisotropy characteristics to achieve a superior filtering effect. Furthermore, the optimal pulse width modulation technique is introduced to modulate the square binary pattern for eliminating specific harmonics. To the best of our knowledge, the proposed method, for the first time, simultaneously achieved superfast (9524 frames per second) and large-depth-range (560 mm, about three times that of the conventional method) sinusoidal fringe generation with consistently high accuracy. Experimental results demonstrate the superior performance of the proposed method in multi-dimensional information sensing such as 3D, 4D, and [ x , y , z , t ; s (strain)].

Highly Efficient Sensorless Multicontrol Mode Compressor IPMSM Drive With Seamless Transitions

Motor drives with interior permanent magnet synchronous motors are typically used with vector or rectangular control (RC). Both of these control methods have well-known pros and cons; therefore, the most appropriate control mode is selected at the stage of drive design. Then, at the experimental verification of the drive prototype, the optimal pulse-width modulation (PWM) frequency is detected and the operation of motor drive is adjusted to this frequency and the corresponding sampling time. The systems constructed according to this algorithm have efficiency with one peak, which is typically selected to be at the rated mode motor drive. As a result, motor drives operate in other modes with lower efficiency, which is subject to further improvements. This article proposes the usage of multicontrol mode, which combines the benefits from each control method. The author suggests usage of the RC at lower speeds and vector control at higher speeds. Furthermore, the PWM frequency of motor drives is also changed, depending on the operating speed, which improves drive performance. This combination of control methods results in efficiency, which has several maximums and increases overall drive efficiency.

Optimal pulse width modulation for permanent magnet synchronous motor drive with improved torque and thermal losses using pulse numbers

This paper utilises the concept of pulse numbers to provide a new optimal pulse width modulation strategy for permanent magnet synchronous motor operation. The benefits of traditional modulation systems are preserved, as is an improvement in torque and thermal loss reduction. The continuous modulation approaches' performance limitations are solved by separating the performance constraints based on the drives surface area. The rotating component, which is regulated through odd and even pulse numbers, is used to mimic torque and thermal losses. With increases to 20 rpm and 30 rpm speeds, the suggested methods boost the 6% to 8% line current. Thermal losses are reduced by 21° C to 23° C, and torque is improved by 2 to 4 Nm. The proposed system is implemented by creating a MATLAB model that ensures the theoretic concept.

DC-Link Capacitor and Inverter Current Ripples in Anisotropic Synchronous Motor Drives Produced by Synchronous Optimal PWM

An accurate approximation of the dc-link capacitor current is crucial for the design of the dc-link capacitor as the capacitor current ripple affects lifetime, size, weight, and cost of the voltage source inverter (VSI). In this article, analytical expressions for the dc-link capacitor current and the inverter current are derived for two-level VSIs feeding anisotropic interior permanent magnet synchronous machines (IPMSMs) controlled by synchronous optimal pulsewidth modulation (SOPWM). The magnetic anisotropic properties of the IPMSM are considered and half-wave symmetric SOPWM signals are utilized. Experimental results evaluate the effect of various pulse patterns on the produced inverter current and dc-link capacitor current ripples and validate the correctness of the derived expressions.

Model Prediction and Pulse Optimal Modulation of Electrically Excited Synchronous Motor at Low Switching Frequency

In this paper, in order to improve the control performance of a high-power electrically excited synchronous motor (EESM) under low switching frequency, and to improve the poor dynamic response of the traditional selective harmonic elimination pulse width modulation (SHEPWM) strategy, an optimized pulse width modulation (PWM) pulse mode with specific harmonic elimination and good dynamic performance is studied. Based on the fast response characteristics of predictive control, it combines the rolling time domain optimization theory with SHEPWM strategy. Firstly, the stator flux linkage of EESM is taken as the tracking target, and the real-time tracking error value of flux linkage is transformed into a voltage-second product; then, the predictive rolling time domain is established, the above error voltage-second product value is optimized in this time domain and the switching angle of SHEPWM is dynamically adjusted to minimize the stator tracking error so as to realize the dynamic adjustment of EESM at low switching frequency. Through MATLAB simulation and a 50 kW experimental platform, the optimized modulation strategy proposed in this paper has been verified to have good dynamic regulation performance at low switching frequency (≈500 Hz).

An Optimized Pulsewidth Modulation for Dual Three-Phase PMSM Under Low Carrier Ratio

In a high-power traction system, the stator current of the dual three-phase permanent magnet synchronous motor (DTP-PMSM) suffers from a large number of current harmonics due to the limitation of the switching frequency of the inverter. Thus, this article proposes a novel current harmonic distortion minimization pulsewidth modulation (PWM) method under a low carrier ratio to suppress current harmonics for the DTP-PMSM, which takes the salient pole ratio, the leakage inductance, and the load angle of DTP-PMSM into consideration. The mathematical model of current harmonics of DTP-PMSM using synchronous PWM is established under a low carrier ratio. The established model demonstrates that the current harmonics of the DTP-PMSM are not only affected by the inverter output voltage but also affected by the salient pole ratio, the leakage inductance, and the load angle of DTP-PMSM. To achieve better control performance on harmonics suppression of the DTP-PMSM, an optimization problem considered characteristics of the DTP-PMSM is formulated to minimize the current harmonics by regulating the switching angles of each phase. The total harmonic distortion of stator current can be reduced effectively by solving the optimization problem. The effectiveness and robustness of the proposed method are verified and compared with three other methods under the same switching frequency.

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.

Influence of Hydraulics on Electric Drive Operational Characteristics in Pump-Controlled Actuators

Transitioning from a valve- to pump-controlled system has been observed in working hydraulics to reduce energy consumption and accelerate the response to decarbonization requirements in Non-road Mobile Machinery (NRMM). The utilization of an electric motor as a prime mover significantly enhances the chances of completing this task. While the concept of combining hydraulics with an electric motor is not new, the functionality of electro-hydraulics can be improved due to multidisciplinary domains, the impact of the electric drive and its control is usually underestimated. Thus, this study aims to evaluate the influence of hydraulics on electric drive operational characteristics in pump-controlled actuators. It utilizes an electro-hydraulic model and simulation study under various conditions, a stability analysis, and a Pulse Width Modulation (PWM) of the frequency converter (FC) evaluation on a selected variable speed pump-controlled actuator to demonstrate the influence of hydraulics on an electric drive. Experimental validation of the model demonstrated an acceptable accuracy of 5%. Moreover, the stability analysis indicated a rise time of about 0.051 s, an overshoot of 0.53%, a transient process time of 0.13 s, and a steady-state value difference of 0.16%; all of which guarantees stable operation of the electric drive with a hydraulic load. In addition, an optimal PWM of an FC frequency of 5 kHz was selected to guarantee accurate speed control with minimum overshoot.

A Novel Predictive Direct Torque Control Using an Optimized PWM Approach

This article presents a novel predictive direct torque control (DTC) scheme using an optimized pulsewidth modulation (PWM) and a dead-time compensation. In the proposed method, two effective voltage vectors are selected according to the predicted torque and flux errors based on zero-voltage vector. The back electromotive force and flux-torque coupling are also taken into consideration. The torque and flux variations per sampling period are predicted by the zero-voltage vector and the two effective voltage vectors. The switching period of the three voltage vectors (zero, first effective, and second effective) are determined by the torque and flux errors along with the predicted torque and flux variations that have been calculated in the previous step. To improve the prediction result, a dead-time compensation algorithm and a modified PWM switching scheme are adopted to reduce dead-time effect. The detailed implementation of the proposed control scheme is presented. The effectiveness of the proposed predictive DTC-PWM is verified by both simulation and experiments. The results are also compared with the conventional method.

A Developed H-Bridge Cascaded Multilevel Inverter with Reduced Switch Count

Multilevel Inverter integrates several Direct Current (DC) sources to produce a single-phase Alternating Current (AC) waveform that can be used to meet the domestic and commercial power demand. This article introduces a novel Multi Source Cascaded Multilevel Inverter with a reduced number of switches for the efficient use of DC voltage sources. The conversion efficiency can be increased by the presented topology which is simple in design to overcome the significant switching losses in the power electronics devices. Optimal Firing Angle and Phase Opposition Disposition Pulse width Modulation Techniques were used to reduce the harmonics at the desired output of the inverter and also to improve the power quality of the presented topology. This article also proposes two Asymmetric Multilevel Inverter Topologies. A comparison has been made, on the number of switches required and the efficiency of the inverters to differentiate the presented Topologies from other topologies of the multilevel inverter. Finally, the performance characteristics of the presented topologies have been designed and investigated using MATLAB Simulation. Simulation results were validated using an experimental setup.

Optimal Simultaneous PWM Control for Three- Phase Dual-Active-Bridge Converters to Minimize Current Stress in the Whole Load Range

In order to reduce the current stress and improve the efficiency of three-phase dual-active-bridge (3p-DAB) converters in the whole load range, in this article, a simplified derivation based on a segmented analytical method is proposed to obtain an optimal simultaneous pulsewidth-modulation (PWM) control scheme. First, the average transferred power and the current stress of the 3p-DAB at different modes can be calculated based on the segmented analytical method. Second, in the light of the expressions of current stress and average transferred power of the 3p-DAB, the current stress minimization problem can be transferred into inequality constraints’ issues for different modes. The optimization process is derived step by step and the closed-form analytic expression of the optimal control strategy is presented. Then, a simple table of the global optimal control scheme that minimizes the current stress under buck or boost operating scenarios can be obtained. Furthermore, a closed-loop control structure is designed to implement the optimal simultaneous PWM control in practice. Finally, experimental comparison with existing modulation schemes has been implemented on a laboratory prototype to verify the theoretical analysis and the outstanding performance of the proposed strategy.

Si/SiC hybrid 5-level active NPC inverter for electric aircraft propulsion drive applications

Medium voltage DC(MVDC) system is considered as a promising technology to improve the efficiency and power density of electric aircraft propulsion(EAP) drives. To adapt to the MVDC voltage level and achieve high drive performance, a five-level active neutral point clamped(5L-ANPC) inverter consisting of three-level ANPC and flying capacitor circuits is investigated, which possesses higher voltage capability, lower output harmonics, as well as mitigated dv/dt and common-mode voltage. To fulfill the requirements of high-speed operation and pursue further enhanced efficiency and power density of the inverter for the next-generation EAP drives, Silicon Carbide(SiC) semiconductor devices are considered for implementing the 5L-ANPC inverter. However, the large commutation loops associated with certain switching states of the inverter lessen the benefits of configuring all the switches as SiC devices. As a result, a hybrid Si/SiC 5L-ANPC inverter is developed with a synchronous optimal pulse(SOP) width modulation strategy for controlling the switches in cell 2 and finite-control-set model predictive controller(FCS-MPC) for those in cell 3 of the inverter. Consequently, in the proposed topology, the SiC devices are merely used for the high-frequency switches in cell 3 and the rest of the low-frequency switches are configured with Si IGBTs. This Si/SiC hybrid ANPC inverter concurrently provides high efficiency and low implementation cost at high-speed operation mode. Simulation and experimental results are provided to verify the effectiveness of the proposed hybrid inverter.

Expansion of Operating Speed Range of High-Speed BLDC Motor Using Hybrid PWM Switching Method Considering Dead Time

In vehicle electrical systems with limited battery power, the output torque and speed of high-speed brushless DC (BLDC) motors can decrease due to unstable and reduced supply voltage or manufacturing errors in the motor back electromotive force (EMF). This paper presents a method that can guarantee the output performance of an inverter through a control algorithm without a separate power supply system and DC-link voltage increase. The proposed control algorithm can increase the output torque and speed of a high-speed BLDC motor by using appropriate selection and change of the inverter’s pulse width modulation (PWM) control method. In this paper, the operation and electrical characteristics of various PWM methods of BLDC motors are analyzed, and the optimal PWM method for improving the control performance of high-speed BLDC motors is presented. In addition, the relationship between the switching frequency, dead time, and voltage utilization was mathematically analyzed. Based on the results of this analysis, the proposed control algorithm automatically changes the PWM switching mode at the point where the output torque and speed need to be extended. The effectiveness and feasibility of the control method proposed in this paper is verified through the experimental results on the designed and manufactured high-speed BLDC motor system for vehicles.