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This paper introduces an advanced space vector modulation technique for three-level neutral-point-clamped (3L-NPC) converters. The studied 3L-NPC converters within aircraft electric starter generator (ESG) systems normally operate at high modulation index, low pulse ratio and full power factor range for most of the operation time. Conventional modulation techniques exhibit large neutral point voltage ripple and possible voltage imbalance under such conditions. The increase of neutral point voltage ripple implies significant increase in converter capacitor size and decrease in capacitor reliability. The modulation technique introduced in this paper achieves improved neutral point voltage balancing within each switching period through enhanced applications of small vectors and restriction on medium vectors. The advanced implementation of small vectors is achieved using a sharing factor aided by a robust incremental current prediction procedure. With the predicted machine currents, the proposed method enables the optimum application of small vectors to balance the neutral point voltages. Simulation results based on a PLECS/Simulink model and experimental results obtained from a 45kVA, 32krpm aircraft electric starter generator prototype platform validate the reduction of the neutral point voltage ripple.

Pulse width modulation in voltage source inverters with an arbitrary number of phases is analyzed in this paper. The problem is treated as purely algebraic, without any use of space vectors. Regardless of avoiding space vectors, the same results are achieved. It is shown that the problem of determining duty ratio values does not have a unique solution, and that there is one degree of freedom to choose one duty ratio, but within a limited range. Limits of the range are derived. Feasibility constraints for the required set of line voltages are derived, reducing to the requirement that the highest of the line voltages should be lower than the DC bus voltage. The analysis is illustrated in cases varying from two to five phases, and experimentally verified in the case of three phases. The method is simple and could be applied to any number of phases, even for the voltages that are not sinusoidal.

Integration of the impacts of time and space harmonics simultaneously during the design stages of inverter-fed induction machines (IMs) is crucial for the accurate calculation of electromagnetic (EM) torque and ripples. Traditional magnetic field-based models offer an analytical approach for determining the EM torque in IMs by calculating inductances. However, by assuming infinite core permeabilities, these models neglect the impact of the core magnetomotive force (MMF) drops due to the difficulties in accurately calculating these drops and the impracticality of isolating the contribution from each phase, which is essential for inductances calculations. These factors contribute to deficiencies in this modeling approach, which become more noticeable when the combined impacts of time and space harmonics on MMF drop calculations are also disregarded. Therefore, this paper introduces a novel magnetic-field-based model to predict the torque and torque ripples of inverter-fed induction motors by addressing the above limitations. This involves modifying the turns and winding function, and calculating the core MMF drops based on the timely variation of non-sinusoidal core flux densities, considering their major and minor flux-density loop effects. Consequently, the associated energy is used to calculate the net available energy, thereby enhancing torque calculations. Compared to the experimental results obtained from an 11kW prototyped induction motor, the proposed model exhibits notable enhancements, achieving average accuracies of 96.4% for average torque and 94.51% for torque ripples, in contrast to the respective traditional model accuracies, 81.1% and 45.1%.

This paper proposes a novel virtual vector space vector pulse width modulation (SVPWM) method called Average Zero common mode voltage (AZCMV) PWM to mitigate low-frequency CMV in four-level neutral point clamped (4L-NPC) inverters. Due to the absence of zero CMV vectors in the space vector diagram (SVD) of 4L inverter, the proposed SVPWM method introduces virtual average zero CMV vectors, which are the combination of active vectors, and have an average CMV of zero. The SVPWM scheme is simply implemented in the transformed two-level (2L) SVD by the aid of base vectors. Then, three types of 2L SVD are presented. Effective and hybrid 2L-SVPWM control strategy based on four nearest vectors SVPWM, symmetrical and asymmetrical SVPWM is proposed to optimize output harmonic and switching losses. With the proposed SVPWM method, the peak-to-peak value of CMV can be reduced to one ninth of the total DC link voltage, which is lower up to five times as compared to the sinusoidal PWM (SPWM). Furthermore, the average value of CMV is zero in a switching sequence. The effectiveness of the proposed method has been verified by simulation and experimental results.

V-source inverter can obtain a high output voltage by using a small shoot-through duty ratio and especially applies to the occasions of large range input voltage, such as photovoltaic (PV) power generation, and so on. However, traditional V-source needs to use a low-frequency transformer to ensure galvanic isolation between the grid and PV system. In order to combine the advantages of both V-source inverter and transformerless PV inverter, this paper proposes a modified single-phase V-source PV grid-connected inverter and a corresponding modulation strategy. By directly connecting negative terminal of PV array to the neutral line of the grid, the proposed topology can eliminate the leakage current completely. In this paper, the operation principle and modulation strategy of the modified transformerless V-source inverter are illustrated. Finally, a 200W laboratory prototype is built to verify the performance of the proposed topology.

Air-conditioners are now widely being used in offices and domestic homes due to the rising global temperatures. Inverter-driven air-conditioners offer superior cooling performance, enhanced control, and a more compact design than non-inverter-driven air-conditioners. Further, inverter-driven air conditioners are more efficient and also cost-effective within a pay-back period. Nowadays, efficient motor drives that meet international efficiency (IE) standards are the need of the hour. Permanent magnet-assisted reluctance motor (PMa-SyRM) drives are one such feasible solution for air conditioner applications, where very less magnet volume is used thereby improving the efficiency whilst minimizing the overall cost. This paper presents a variable-speed rare-earth-free ferrite Al-Ni-Co hybrid PMa-SyRM drive for an air conditioner application. Hall-sensors are used for detection of the rotor position and a simple current advance angle based control is implemented to extract both the magnetic and reluctance torque components from the hybrid PMa-SyRM. Later, simulation studies are carried-out and the cost and the efficacy of the proposed control is compared with that of the conventional maximum torque per ampere (MTPA) control. Finally, a prototype drive is fabricated and experimental validation under various load conditions is carried-out and the results are presented.

The integration of solar photovoltaic (PV) arrays for induction motor drives (IMDs) has attained a lot of research interest due to the versatile applications of IMD including water pumping, cement industries, electric vehicles, and rolling mills etc. Multilevel inverters (MLIs) are a prominent solution for driving medium voltage induction motors (IMs) due to their superior performances over two-level voltage source inverters (VSIs). However, the power quality performance of MLI fed IMDs greatly depends on the pulse width modulation (PWM) strategy employed. Traditional PWM strategies for MLIs suffer from power quality problem such as lower order harmonics, high THD, unbalanced power loss distribution, high switching power loss, thermal instability and electromagnetic interference (EMI) problems. In this paper, a modified PWM strategy is proposed for a solar PV fed 3-level neutral point clamped (NPC) inverter driven IMD. The proposed PWM strategy introduces a new modulating signal with level shifted triangular carriers. The proposed modulating signal is formed by utilizing a $13^{\mathrm {th}}$ harmonic signal and saturated balanced 3-phase sinusoidal signals. The proposed PWM technique is named as $13^{\mathrm {th}}$ harmonic injected 60°-PWM (THISDPWM). The THISDPWM reduces the lower order harmonics contents, overall THD, and switching power losses of the NPC inverter compared to different existing PWM strategies. Apart from that, a robust artificial neutral network (ANN) based incremental conductance maximum power point tracking (MPPT) algorithm is also introduced to control the dc-link voltage of the PV fed NPC inverter driven IMD system. The presented ANN based dc-link controlled technique ensures stable dc-link voltage against wide range of PV parameters variation. All the simulation works are carried out in MATLAB/Simulink environment and a reduced scale laboratory prototype of the IMD is built and tested to validate the performance of the proposed THISDPWM technique.

A data center is a major hub of different converters ensuring continuous power to the server loads. The pulse width modulation switching techniques with frequency emission from 2 to 150 kHz (i.e., supraharmonics) in these converters call for a study of the magnitude and propagation of this emission within data centers where UPS is one of the main contributors of supraharmonics. The paper shows, with measurements and model, the change in magnitude and propagation of supraharmonics with the change in the operating mode of the UPS. The magnitude of supraharmonics shows a non-linear dependency on the power consumed in the online mode. In bypass mode, the magnitude of supraharmonics shows a dependency on the type of load connected. The filter connected between PE-N at the input side of the UPS can cause resonance in the phase conductors. The results show that to study the emission, immunity, and electromagnetic compatibility of supraharmonics for UPS, the factors such as operating mode, the type of load connected, and the input and output impedance need to be considered.

Due to the rapid advancement of power semiconductor devices, the use of voltage source inverters (VSIs) has gained widespread acceptance. As a consequence, the performance of the voltage source inverter has emerged as a critical aspect that is highly reliant on the modulation strategy. The pulse width modulation (PWM) technique is the most widely utilized method of controlling power semiconductor switches of VSI. Power quality is always considered as an industrial concern for VSI-based power system such as grid-connected renewable energy systems and industrial motor drives which largely depends on the PWM technique used for switching. However, the existing PWM schemes for VSIs suffer from high total harmonic distortion (THD) and power loss problems. To mitigate the THD and power loss of VSI, a hybrid PWM technique has been proposed in this paper. The proposed hybrid PWM technique introduces a modified modulating signal along with newly shaped carrier signal. A two-level VSI is used to evaluate the performance of the proposed hybrid PWM technique both for with and without filter conditions against RL load. The proposed hybrid PWM technique offers 0.89% filtered voltage THD and 0.69% filtered current THD which are lower than that of existing PWM techniques. On the contrary, at without filter condition, the proposed hybrid PWM technique shows THDs of 45.77% and 12.50% for inverter output voltage and current, respectively which are also lower than those of existing PWM techniques. Apart from these, the proposed hybrid PWM technique reduces the switching and conduction power losses of the VSI as compared to existing PWM techniques. The simulation works are carried out in MATLAB/Simulink environment and a reduced scale experiment is conducted in laboratory to evaluate the performance of the proposed hybrid PWM technique.

Adaptive front-lighting systems (AFSs) have been widely adopted to automotive industries for providing higher driver’s safety. As their light sources, multi-string light-emitting diodes (LED) arrays have been widely adopted because of their simpler driver controls. Recently, micro-structured AFSs ( $\mu $ AFSs) with a micro-LED ( $\mu $ LED) array are highly demanded for their controllability of individual LEDs. However, the integration of a $\mu $ LED array and its high-power active-matrix driver are not available on the market. Moreover, a high-power driver causes not only a significant variation in driving current, but also a higher power density requiring over-temperature protection (OTP). In this paper, the average current through each $\mu $ LED is adaptively controlled with pulse width modulation (PWM) in conjunction with an additional PWM control for temperature calibration. Experimental results with a 16 $\times 16\,\,\mu $ LED array placed on top of the proposed driver show that a 5-bit PWM signal controls the average current through each $\mu $ LED cell up to 11 mA. The maximum current error of 4.11% at 100 °C is reduced to 0.23%. When OTP is enabled, the amount of average pixel current reduction depends on the given temperature. The maximum power efficiency of the proposed $\mu $ AFSs driver is as high as 92.3%.

PV systems efficiency highly depends on the MPPT strategy to be implemented in the PV converter. Many MPPT methods on the literature are focused on improving the steady state and transient system performance extracting the maximum energy from the sun. In this paper, the impact of the MPPT methods in the PV converter is analyzed focusing the study on the capacitor across the PV array lifespan. The obtained results demonstrate that the low frequency PV voltage oscillations that are present in many MPPT methods have a large negative impact on this capacitor lifespan. Experimental and simulation results are presented in order to show that advanced MPPT methods, which avoid these low frequency oscillations, achieve higher capacitor lifespan values compared with the values obtained by applying well-known MPPT methods such as the perturb and observe or incremental conductance strategies.

This paper aims to evaluate a Type-II insulated wire (i.e., Glass fibre insulated wire) as a function of thermal ageing time based on partial discharges (PD) activity. Partial discharge inception voltage (PDIV), partial discharge extinction voltage (PDEV), and repetitive partial discharge inception voltage (RPDIV) measurements have been performed on both unaged and thermally aged specimens. Each specimen modelled the turn-to-turn insulation; hence it was made by a pair of Glass fibre wires wrapped in PTFE tape for a mechanical purpose. The PD tests have been carried out under positive and negative unipolar square waveform excitations using different rise times: 80, 400 and 800 ns. The trend of PD quantities vs exposure time demonstrates that the effect of space charge accumulation under unipolar excitation must be taken into account when unaged and thermally aged specimens are compared. Results revealed that although sometimes thermally aged samples might show a temporary superiority in the short run, unaged ones always present a better performance after space charge accumulation, as expected. Following the statistic postprocessing of the collected data, shape/slope parameters of the Weibull distribution relevant to PDIV can be used as an ageing indicator for Glass fibre insulated wire. Finally, the permittivity evaluation vs thermal and electrical stresses have been performed, relying on the measured capacitance of each specimen just after every PD test. Such analysis revealed that thermal ageing increases permittivity in the long run. However, electrical stress has different impacts on permittivity depending on the rise time, polarity, and magnitude of the applied voltage.

The paper analyzes the influence of the number of rotor bars on the stator current spectral content in a three-phase cage induction motor fed by a pulse-width modulated (PWM) inverter. It is shown that each of the higher-order time harmonics in the supply voltage produces space harmonics in a rotating magnetic flux density wave, which results in induced rotor slot harmonics (RSHs) in the stator current spectrum. The conditions for the existence of these space harmonics are identical to those applying to a mains-fed motor. In other words, the number of rotor bars of a mains-fed motor yielding an RSH-free stator current spectrum produces the same stator current spectrum even in case the motor is inverter-fed. Additionally, to minimize the adverse effects of RSHs in the stator current spectrum, one must consider not only the number of rotor bars, but also its relationship with the frequency modulation ratio of the PWM inverter. Analytical predictions are presented to illustrate these results supported both by numerical simulations of the induction motor modelled through the winding function theory and experimentally taking the case a two-pole cage induction machine as a case study.

This paper proposes a three-level dual-buck inverter (DBI) that reduces reverse recovery current and compensates reactive power. To reduce the reverse recovery problem of main switching diodes in the DBI, the auxiliary circuit consisting of diodes and coupled inductors is adapted. The auxiliary circuit enables zero-current turn-off of the diodes. The coupled inductor design is also conducted considering not only for unity power factor (PF) but also non-unity PF operations. By utilizing the auxiliary circuit, the reverse recovery and the shoot-through problems in silicon devices can be significantly mitigated so that the efficiency and the reliability of the DBI are much improved. Meanwhile, the pulse-width modulation scheme is also proposed to supply reactive power with the DBI which is a unidirectional inverter. In the proposed modulation method, the duty offset is simply added according to the required PF and the operating region of the DBI. By doing so, traditional current control concepts for bidirectional inverters can be directly applied to the DBI without any modification. By utilizing the proposed techniques, the reliability, efficiency, and utilization of the DBI can be significantly improved. The experimental results with a 3 kVA DBI prototype demonstrate the effectiveness of the proposed DBI.

In this paper, a novel communications protocol, based on pulse width is presented, which is able to transmit data frames with bytes encoded in ASCII using a single transmission line. It is possible to transmit data between different embedded systems in the same electronic board or in different electronic boards. The computational cost is low and permits to transmit information in lengths up to 30 m. The protocol was tested in a system for measuring physichochemical parameters of water, composed of a floating body, a submerged probe to measure variables at different depths and a graphical user interface to receive and save data in a server. The floating body and the submerged probe are two independent embedded systems, interconnected with the proposed protocol; the system was implemented in a small water body, to cope with a relevant environment. The results show a good performance of the protocol in the transmission of data frames with high robustness, since in a period of 37 h the data were transmitted and received regularly, with a sample time of 5 minutes. The complexity of the algorithm was compared with other well-known protocols, resulting in fewer machine cycles, implemented in an eight-bit microcontroller.

Common-mode voltage (CMV) in electric drives causes leakage current causing consequently EMI problems, loss and reduction of their components’ lifetime. Several solutions have been proposed which usually lead to higher cost because additional components are used. This paper is focused on the mitigation of the resulting CMV produced by the operation of the VSD by means of a specifically designed PWM method. The proposal is based on the analysis of the CMV harmonic spectrum using the Fourier analysis. The CMV mitigation is achieved by modifying the time-shift displacement of the carriers each sampling time considering a multi-carrier PWM technique. The resulting method has been evaluated in a down scaled experimental setup and it is easily implementable on mostly off-the-shelf mid-range micro-controller control platforms.

Electric variable speed drives (VSDs) based on two VSDs connected to a multiphase machine are an attractive solution to replace high-power mechanic and hydraulic systems in many sectors of industry and transportation because they present high performance with reduced cost, volume and weight. Among the causes which affect the reliability of dual VSDs, the common-mode current flowing through the machine bearing is an important issue. This paper faces the mitigation of the common-mode current by reducing the common-mode voltage (CMV) generated by the operation of a dual VSD. The CMV reduction is carried out without introducing any extra device and/or passive filtering method. This CMV reduction is performed by applying a specific phase-displacement between the modulation strategies of each single inverter drive. The proposed technique has been evaluated in a down scaled experimental setup in order to test its effectiveness.

Pulse width modulation (PWM) control for power converters have been vastly investigated and used in many industrial application. For medium voltage and high power applications, low switching frequency PWM techniques are preferred over high switching frequency-based PWM techniques. The preprogrammed low switching frequency-based PWM technique known as selective harmonics elimination (SHE) gives the better quality waveform at a lower switching frequency. The main difficulty in applying SHE PWM is in solving of non-linear transcendental equations for obtaining switching angles. Several methods have been proposed for computation of switching angles that include numerical techniques, optimization techniques, and algebraic techniques. However, the computation of switching angles is still a challenging task in the application of SHE PWM. In this paper, a novel fast convergent homotopy perturbation method (HPM) is proposed to compute switching angles for a multilevel inverter at a faster rate. The solutions obtained by the proposed technique is as accurate as obtained by the algebraic methods with no dependency on the initial guess. The proposed technique can compute the higher number of switching angles with multiple solutions in some modulation index range. A prototype is developed and the computed switching angles have been verified using field-programmable gate arrays (FPGA) controller to validate the results for practical applications.

Information obtained about magnetic anisotropy via neutral point voltage measurements can be used to estimate the position of synchronous and induction machines at all speeds including standstill. Due to its usually high signal-to-noise ratio, this estimation method can be an attractive alternative to approaches that acquire anisotropy information via current measurements. The position estimation method looked at in this paper relies on anisotropy information in the form of position-dependent inductance ratios. These are obtained through measurement of the voltage between the machine’s neutral point and an artificial neutral point during the application of different voltage vectors via a two-level switching inverter. We analyze the conditions placed on and the consequences of implementing necessary modifications to a standard space vector modulation. Five different modified modulation strategies are compared and investigated, including two newly proposed strategies which use only a minimal set of active and zero voltage vectors for measurement of the inductance ratios and therefore allow high utilization of available voltage and a high update rate of the estimated position. Experimental results for three low-power three-phase permanent magnet synchronous machines are presented which suggest that modulation strategies that use active measurement vectors in all three instead of only two axes of the machine are less susceptible to systematic deviations in the position estimation that presumably result from nonlinear machine properties. As part of the machine model, a normalizing inductance variation ratio is introduced, which simplifies expressions and supports the comparison of motors.

This paper discusses the problem of the Takagi-Sugeno (T-S) filter design form for a three level inverter drive system. A traditional filter always defines the noise in the infinite frequency domain, which results in low filtering accuracy. When the frequency of ranges of noises is known in advance, we can design the fuzzy filter in the finite-frequency domain where the fuzzy filter can estimate the rotor flux. The proposed fuzzy filter can get a better noise-attenuation performance. A three-level inverter drive system is designed and modulated by the space vector pulse width modulation (SVPWM) method. Noise sources with different frequencies are injected into the model to verify the effectiveness of the proposed method and then compared to simulations and experiment.

The paper presents a novel approach to the Pulse Width Modulation (PWM) duty cycle computing for complex or irregular voltage vector arrangements in the two (2D) and three-dimensional (3D) Cartesian coordinate systems. The given vectors arrangement can be built using at least three vectors or collections with variable number of involved vectors (i.e. virtual vectors). Graphically, these vectors form a convex figure, in particular, a triangle or a tetrahedron. The reference voltage vector position inside that figure can be expressed by the barycentric coordinates, which are calculated using the second (2D case) or the third-degree determinant (3D case) - without trigonometry and angles. Thus, the speed of the PWM duty cycle computation rises significantly. The use of the triangle area or the tetrahedron volume, instead of the standard vector projection also permits for a well-defined and universal approach to identifying the reference vector position, especially for converters with complex and/or deformed space-vector diagrams (i.e. floating DC-link, multisource DC-link). The proposed computation scheme is based on simple instructions without trigonometry thereby, the DSP processor, or digital solution for field-programmable gate array, can fast-perform this operation using atomic operations. The aim of the presented considerations is not a novel PWM modulation, but a computable idea of a general calculation scheme for cases in which the distribution of vectors is non-trivial. A detailed algebraic and geometric analysis, as well as mathematical proofs on the total consistency of the results with the standard projection method, are also included. Subsequently, the Three-Dimensional Space Vector Modulation (3D-SVM), is considered as a special background to present a novel approach.

One of the disadvantages of the charging systems and voltage regulation systems in alternative energy systems is that when the direct current (DC)/alternative current (AC) or AC/DC conversion is made from the energy source, the energy flow at 2w frequency between the direct current side and the alternative current side causes ripples in the DC, inductors, and capacitors. The ripples that occur in 2w frequency increase the harmonic distortion and reduce the efficiency in the photovoltaic energy system. For addressing this problem, different control methods are evaluated in this paper for the elimination of ripples that occur at 2w frequency, both on the perspective of DC control side and AC control side with a thorough comparative analysis with existing results in the literature. In the present study, the model of Single-Phase Quasi-Z Source (QZS) inverter and closed-loop control methods of the inverter are examined and compared with pulse width modulation (PWM) methods. In addition, the control methods are used to eliminate the ripples at 2w frequency in the use of inverters, and the advantages and disadvantages of these methods are presented.

A novel hybrid resonant zero-current- switching (ZCS) three-level DC-DC converter based on a dual transformer with two output filter capacitors is proposed in this paper, which is suitable for application in distributed photovoltaic power generation at medium voltage integrated with a DC distribution network. The proposed converter adds an auxiliary circuit to the traditional neutral point clamped (NPC) three-level (TL) circuit, which contains the basic NPC three-level circuit. Pulse width modulation (PWM) is adopted in the auxiliary circuit portion to realize the power and voltage regulation of the whole converter, and enable the main switches to operate with a fixed duty cycle. This has the advantages of simplified control. By reasonable design of the turn's ratio of the main transformer, the main three-level circuit can deliver most of the power and achieve ZCS within the under full load range that significantly reduced the switching losses. Therefore, the turns ratio of the auxiliary transformer can be optimized to reduce the loss of the converter further and improve the conversion efficiency as discussed in detail, while the parameters' design principles are put forward. Finally, a prototype of 300V-1.5kV/1.5 kW is built to verify the performance of the proposed converter.

This paper studies the acoustic noise of induction motor with low switching frequency model predictive control and compares its noise performance with the traditional pulse width modulation with proportional-integral controllers. First, the relationship among the air-gap magnetic field, the electromagnetic force, and the acoustic noise is modeled to describe the influence of control algorithm on the noise characteristics of motors. As the counterpart with the traditional pulse width modulation control, a finite control set model predictive control strategy with low switching frequency is proposed. The steady-state performance and switching frequency constraint ability of the proposed model predictive control strategy are verified on the experimental platform. Second, the noise spectrums of these two control strategies are sampled and compared in different operating conditions, and the influence of the weighting factor on the noise spectrum is also discussed. It is proved by the experimental results that model predictive control has better noise performance than the traditional sinusoidal pulse width modulation under the same switching frequency and the total harmonic distortion of stator current.

Brushless dc motors (BLDCMs) exhibit relatively large torque ripple due to the current pulsation during the commutation process. In this paper, first, the production mechanism of the commutation torque ripple is analyzed in detail, where the diode freewheeling in the inactive phase winding and the non-commutation torque ripple under the existing PWM modulation modes are compared for a three-phase six-switch inverter-fed BLDCM drive. The torque ripple expression of each PWM mode is derived analytically. Thereafter, a new region-refinement PWM method is proposed, in which a normal operation region of 60° is refined into two 30° sub-regions, and PWM-ON and ON-PWM modulation method is suitable to be employed, respectively, in the former and latter 30° regions. To verify the effectiveness of reducing the non-commutation torque ripple, both simulations and experiments are conducted on a three-phase prototyped BLDCM. The results demonstrate that the torque ripple under the proposed PWM mode can be reduced significantly.

In this paper, a new control strategy for an induction motor (IM) drive system fed from three-phase pulse width modulation (PWM) ac chopper is proposed. The main objective of the proposed control scheme is to achieve input power factor correction (PFC) of the IM drive system under different operating conditions. PFC is achieved by continuously forcing the actual three-phase supply currents with the corresponding reference currents, which are generated in phase with the supply voltages, using hysteresis band current control (HBCC) technique. The proposed control strategy has two loops: the inner loop and outer loop. The output of the outer loop is the magnitude of the supply reference current resulting from either speed controller or startup controller, whereas the output of the inner loop is PWM signals of the ac chopper. The proposed ac chopper features a smaller number of active semiconductor switches, four IGBTs, with only two PWM gate signals. As a result, the proposed system is simple, reliable, highly efficient, and cost effective. Mathematical analysis of the drive system is presented. Components of the input LC filter are designed using frequency response. The IM drive system is modeled using MATLAB/SIMULINK, and a laboratory prototype was built and tested. The simulation and experimental results confirm the validity and robustness of the proposed control strategy.

Hybrid pulse width modulation schemes are widely used in high-power traction converters with a limited switching frequency. During the transition between modulation modes, sudden changes in the voltage harmonics cause the induction motor to enter a transient process, and ultimately lead to torque impacts, current shocks and other adverse effects. To improve the existing solution for such effects, theoretical support is provided in this paper by using an equivalent circuit model and a dynamic model of an induction motor, and a specific implementation scheme for a smooth transition is given considering the third-harmonic frequency component that appears in the phase voltage during the transition. The feasibility and correctness of the scheme are proven by a simulation and an experiment.

This paper analyzes the unique nonlinear characteristics of a high-speed drive circuit for proportional solenoid, i.e., the inverse discharging drive circuit (IDDC), which has a faster discharging speed than a traditional drive circuit. The experimental results clearly show the piecewise nonlinear relationship between the current and the pulse-width modulation (PWM) duty ratio of the control signal of the IDDC. The mathematical model of the IDDC working processes in one PWM period is constructed in detail to analyze the IDDC nonlinear characteristics. The computational equations of the significant nonlinear features, including the critical PWM duty ratio, the steady-state current, the amplitude of the current oscillation, and the response time of the circuit, are deduced through algebraic analyses, which are verified by a comparison between the experimental and calculated results. These analyses aid the design and control of a solenoid drive circuit for a hydraulic proportional valve. Finally, a modified PI controller that considers the nonlinear characteristics of the IDDC is designed, and the experimental results show that the designed controller significantly improves the response speed of the solenoid current.

Total harmonic distortion, produced with the existing PWM techniques for a Z-source inverter topology, is higher due to the unsymmetrical shoot-through, if separate controls of ac and dc sides are required. This paper proposes the concept of symmetrical shoot-through-based modulation and compares the performance with the case of the popular simple boost control. The proposed modulation method achieves a sinusoidal and symmetrical distribution of shoot-through states. This ensures an improved current and voltage profile at the output, along with the capability of decoupled control for the shoot-through and the modulation index control. The effectiveness of the proposed method has been demonstrated and validated through analysis, simulation, and experimentation. This concept can be applied to all the variants of Z-source-based power conversions.