Device Voltage Drop Research Articles

Differential-Mode Circulating Current Suppression for Paralleled Inverters Fed PMSM Drives Considering Dead Time Compensation

Paralleled inverters are widely employed in permanent magnet synchronous machine (PMSM) drives to increase system capacity and reliability. Due to the discrepancy of paralleled inverters, the differential-mode circulating current (DMCC) is a major concern in paralleled inverters fed PMSM drives. The DMCC would result in current unbalance and efficiency reduction. To address this issue, a low-frequency DMCC suppression considering dead time compensation is proposed in this paper, which can be effective in the suppression of both DMCC and zero-sequence circulating current. In detail, the DMCC due to the discrepancy of control settings such as dead time and switching period, is eliminated by a proposed dead time compensation. Besides, the DMCC owing to the hardware differences including device voltage drops, device turn-on/off delays and filter inductances etc., is suppressed by a proposed regulation of phase conduction time, being free of disturbing the command voltage of drive system. Finally, the effectiveness of the proposed method is experimentally validated under both two-level and three-level space vector modulations.

Electrothermal Coupling Model With Distributed Heat Sources for Junction Temperature Calculation During Surges

High junction temperature is usually the main factor leading to device failures in high-power working conditions, such as surges or avalanches. It is of great significance to obtain the junction temperature quickly and accurately. Direct measurement of junction temperature is inconvenient, and usually indirect electrical measurement combined with model calculation is used. An electrothermal coupling junction temperature calculation model with distributed heat sources is proposed in this article. This model can accurately and quickly predict the device behavior during the surge process, as well as the voltage drop and temperature changes of each part of the device, without actually performing surge tests. This article describes the theoretical basis and calculation principles of the model. By taking a commercial SiC merged PiN Schottky diode as an example, this article also explains the details of the establishment of the electrical and thermal characteristic models of the device, as well as the calculation steps of the junction temperature by the thermal coupling model. The calculated device voltage drop curve of the device is in good agreement with the measured ones, and the calculated junction temperature curve is more consistent with the device failure mechanism than the one by the traditional RC thermal circuit model.

Ultrahigh Linearity of the Magnetic-Flux-to-Voltage Response of Proximity-Based Mesoscopic Bi-SQUIDs

Superconducting double-loop interferometers (bi-SQUIDs) have been introduced to produce magnetic flux sensors specifically designed to exhibit ultra-highly linear voltage response as a function of the magnetic flux. These devices are very important for the quantum sensing and for signal processing of signals oscillating at the radio-frequencies range of the electromagnetic spectrum. Here, we report an Al double-loop bi-SQUIDs based on proximitized mesoscopic Cu Josephson junctions. Such a scheme provides an alternative fabrication approach to conventional tunnel junction-based interferometers, where the junction characteristics and, consequently, the magnetic flux-to-voltage and magnetic flux-to-critical current device response can be largely and easily tailored by the geometry of the metallic weak-links. We discuss the performance of such sensors by showing a full characterization of the device switching current and voltage drop \textit{vs.} magnetic flux for temperatures of operation ranging from 30 mK to $\sim 1$ K. The figure of merit of the transfer function and of the total harmonic distortion are also discussed. The latter provides an estimate of the linearity of the flux-to-voltage device response, which obtained values as large as 45 dB. Such a result let us foresee a performance already on pair with that achieved in conventional tunnel junction-based bi-SQUIDs arrays composed of hundreds of interferometers.

1.2-kV 4H-SiC Merged PiN Schottky Diode With Improved Surge Current Capability

This paper presents the design and experimental analysis of 1200-V 4H-silicon carbide (SiC) merged PiN Schottky (MPS) diodes. Design considerations and device performances of the MPS diodes are compared with those of the junction barrier Schottky (JBS) diodes via numerical simulation and experiments. Due to the limited P+ width/ratio in JBS diodes, p-n junction is not turned on until very high current/voltage bias is applied. This increases the device voltage drop and energy dissipation in high current stress conditions. Thanks to the wide P+ region design and the ohmic contact on the P +regions, the p-n junction turn-on voltage in MPS diodes is substantially decreased, and the surge current capability is improved accordingly. Furthermore, the surge capability of two layouts of the MPS diodes are compared. Layout A with ~60% high P+ ratio can improve the surge current capability by 10% and 20% compared with layout B design (with ~50% P+ ratio) and pure JBS diode (with ~40% P+ ratio), respectively. The reliability of the MPS diodes is studied by repetitive pulse surge current tests. No obvious degradation appears after 5500 test cycles under a surge current stress 20 times the device nominal current rating.

A Practical Approach for Core Loss Estimation of a High-Current Gapped Inductor in PWM Converters With a User-Friendly Loss Map

Core loss estimation of filter inductors is increasingly important for modeling and optimizing high-frequency, high-efficiency, and high-density pulsewidth modulation (PWM) power electronic converters. However, data provided by inductor core manufacturers are insufficient for core loss estimation in PWM converters, particularly in the case of customized gapped inductors. This paper presents a whole process of characterizing and estimating the core loss of a customized high-current gapped inductor for PWM converters. To excite the inductor for the B–H loop measurement, a test circuit formed by a half-bridge structure is proposed, which has the ability to compensate the asymmetric rectangular voltage on the inductor caused by the device voltage drops. To overcome the other challenges raised by a high excitation current, a refined discontinuous test procedure, triple pulse test, is proposed to reduce the requirements of the high-current test setup (thermal stress, current–time stress for current probes, capacity of dc sources, etc.). For practical purposes, a user-friendly loss map approach is proposed involving only time-domain and electrical variables to replace magnetic variables to enable the straightforward loss mapping process and core loss calculations. Presented experimental results show consistency between the estimated inductor loss and measured values. Overall, the proposed testing approach can be easily implemented on the user's side to develop a loss map of a given inductor. The established core loss map enables the users to accurately and rapidly estimate the core loss of a tested inductor for given PWM waveforms.

Operating modes and practical power flow analysis of bidirectional isolated power interface for distributed power systems

Due to the intermittent nature of the renewable energy sources including photovoltaic and wind energy, the energy storage systems are essential to stabilize dc bus voltage. Considering the discharge depth of super-capacitors and energy-storage batteries, the bidirectional isolated power interface will operate for a wide range of voltage and power. This study focuses on in-depth analysis of the dual-active-bridge dc–dc converter that is controlled by the dual-phase-shift scheme to improve the conversion efficiency in distributed power system. The power flow of each operating mode with dual-phase-shift control is characterized based on a detailed analysis of the effects of “minor parameters”, including the deadtime and power device voltage drops. The complete output power plane of the dual-active-bridge converter with dual-phase-shift control is obtained and compared with experimental results. The optimal operating mode is determined according to the practical output power range and the power flow characteristics. Experimental evaluation shows the effectiveness of the proposed power flow model with dual-phase-shift control and significant efficiency improvement using the optimal mode of dual-phase-shift compared with the conventional phase shift control.

Nonactive Power Loss Minimization in a Bidirectional Isolated DC–DC Converter for Distributed Power Systems

Originated from analyzing nonactive power loss, a novel optimization method and modulation solution for bidirectional isolated dual-active-bridge (DAB) dc-dc converters are proposed in order to achieve high efficiency in a wide operating range. A comprehensive nonactive power loss model is developed, including both the nonactive components delivered back to the source and from the load. This paper points out that when the minimum nonactive power loss is achieved, zero-voltage soft switching can be naturally fulfilled. The optimal phase-shift pair obtained by the proposed method can keep low values of both root mean square (RMS) current and circulating power. Rather than using ideal power flow analysis, the nonactive power loss model directly embodies practical nonideal factors, including device voltage drops. Based on the analysis, an extended dual phase shift is proposed, and different operation cases are analyzed with comparison of performance indices. Experimental tests verify the theoretical analysis and show effectiveness of the proposed approach to achieve nonactive power loss minimization and efficiency improvement.

Harmonic Distortion Optimization of Cascaded H-Bridge Inverters Considering Device Voltage Drops and Noninteger DC Voltage Ratios

This paper considers achieving the minimum total harmonic distortion (THD) or frequency-weighted THD (WTHD) of the staircase-modulated output voltage of single-phase multilevel inverters, with or without elimination of the lowest order harmonics. The minimal THD values, together with the corresponding step angles and dc voltage source ratios, have been obtained for the 5-, 7-, 9-, 11-, and 13-level cases; accounting for the device voltage drops when the load is resistive or is moderately inductive is described. Similarly, the minimal WTHD values, together with the corresponding step angles and dc source voltage ratios, have been obtained for the five-, seven-, and nine-level waveform cases. The results show that requiring harmonic elimination leads to larger W/THD than the minimum W/THD that can be achieved without this requirement. Furthermore, a 13-level waveform is needed to attain a voltage THD less than 5%, and a nine-level waveform is needed to attain a WTHD less than 0.5%. Experimental measurements are presented as verification of the analytical results.

Compensation of Nonlinearities in Diode-Clamped Multilevel Converters

The application of multilevel converters for exciting permanent-magnet machines with low-phase inductance to dc-link voltage ratios facilitates a reduction in high-frequency switching harmonics. However, converter nonlinearities and, in-particular, on-state device voltage drops, create additional low-frequency harmonics. This paper therefore proposes a generic compensation scheme to accommodate the effects of such converter nonlinearities and, in doing so, improve the harmonic quality of the machine phase currents. Experimental results gathered from a prototype five-level diode-clamped converter validate the benefits of the proposed scheme by showing quantitative reductions in low-frequency harmonics.

Disturbance Observer‐Based Simple Nonlinearity Compensation for Matrix Converter Drives

This paper presents a new method to compensate the nonlinearity for matrix converter drives using disturbance observer. The nonlinearity of matrix converter drives such as commutation delay, turn‐on and turn‐off time of switching device, and on‐state switching device voltage drop is modeled by disturbance observer and compensated. The proposed method does not need any additional hardware and offline experimental measurements. The proposed compensation method is applied for high‐performance induction motor drives using a 3 kW matrix converter system without a speed sensor. Simulation and experimental results show that the proposed method using disturbance observer provides good compensating characteristics.

Simple Power Control for Sensorless Induction Motor Drives Fed by a Matrix Converter

This paper presents a new and simple method for sensorless control of matrix converter drives using a power flowing to the motor. The proposed control algorithm is based on controlling the instantaneous real and imaginary powers into the induction motor. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-ON and turn-OFF times of switching devices, and on-state switching device voltage drop are modeled using a PQ power transformation and compensated using a reference power control scheme. The proposed sensorless control method is applied for the induction motor drive using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.

Speed-Sensorless DTC-SVM for Matrix Converter Drives With Simple Nonlinearity Compensation

This paper presents a new method to improve the sensorless performance of matrix converter drives using a parameter estimation scheme. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-on and turn-off times of switching devices, and ON-state switching device voltage drop is modeled using p-q-r transformation and compensated using a reference current control scheme. To eliminate the input current distortion due to the input voltage unbalance, a simple method using p-q-r transformation is also presented. The proposed compensation method is applied for high performance induction motor drives using a 3-kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy.

Performance improvement of sensorless vector control for matrix converter drives using PQR power theory

This paper presents a new method to improve sensorless performance of matrix converter drives using PQR power transformation. The non-linearity of matrix converter drives such as commutation delay, turn-on and turn-off time of switching device, and on-state switching device voltage drop is modelled using PQR transformation and compensated using a reference current control scheme. To eliminate the input current distortion due to the input voltage unbalance, a simple method using PQR transformation is also proposed. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy.

The properties of aluminum, platinum silicide and copper based contacts for silicon high-power devices

Electrical, thermo-electrical and thermo-mechanical properties were compared for PtSi, aluminum (Al, PtSi–Al, PtSi–AlCuSi, PtSi–TiW–AlCuSi), and copper based contacts (TiW–Ni–Cu, TiW–Ni–Cu–Ni–Au, PtSi–TiW–Ni–Cu, PtSi–TiW–Ni–Cu–Ni–Au). High-power 2.5kV/150A P-i-N diode with both lapped and etched anode surface was used to characterize the performance of the contacts in the conditions of free floating silicon in pressed package. The devices with PtSi contacts have the lowest forward voltage drop, but do not survive the operation in pressed package under thermal cycling. The copper based contacts with PtSi layer give lower voltage drop and better thermo-mechanical ruggedness compared to that of aluminum. These features are conserved even with passivation against corrosion using Ni–Au. The contacts without the PtSi layer have high voltage drop and fail under thermal cycling. The composition of the contact layer is shown to influence the thermal behavior of device voltage drop. The crossing point current is found to decrease with increasing contact layer thickness. The lowest magnitude gives the aluminum contact.

A Nonlinearity Compensation Method for a Matrix Converter Drive

This paper presents a new method to compensate the nonlinearities for matrix converter drives. The nonlinearities of matrix converter drives such as commutation delay, turn-on and turn-off time of the switching devices, and on-state switching device voltage drop is corrected by a new matrix converter model using the direction of current. The proposed method does not need any additional hardware or complicated software and it is easy to realize by applying the algorithm to the conventional vector control. The proposed compensation method is applied for high-performance induction motor drives using a 3-kW matrix converter system without a speed sensor. Experimental results show the proposed method provides good compensating characteristics.