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1500-V photovoltaic (PV) configuration is the standard design in the solar PV industry. Extending the maximum dc voltage from 1000 to 1500 V can reduce the installation cost of the entire power plant. However, it may affect the reliability of the corresponding 1500-V PV inverters, due to the increased loading stresses, i.e., voltage stress and thermal loading of power devices. In this context, this article proposes a solution to the reliability enhancement of silicon carbide-mosfet-based 1500-V PV inverters with variable gate resistance. This solution offers a possibility to adaptively adjust the switching speed to make a compromise between the switching power loss and voltage overshoot during commutation, thus enhancing the reliability. The evaluation results based on the mission profile of a 125-kW 1500-V PV system installed in Denmark indicate that the PV inverter with the proposed design, i.e., variable gate resistance, can improve reliability performance compared to the fixed gate resistance solution while ensuring a safer operating voltage margin. [ABSTRACT FROM AUTHOR]

Objective. To observe the efficacy and safety of transurethral columnar balloon dilation of the prostate (TUCBDP) for benign prostatic hyperplasia (BPH) in a multicenter trial. Method. This multicenter study included 2050 patients with BPH who underwent TUCBDP from 11 cities of Zhejiang Province, from September 2015 to June 2021. Clinical assessment included recording and measurement of preoperative and postoperative data including prostate volume, serum prostate-specific antigen (PSA) levels, IPSS score, quality of life (QoL), maximum urinary flow rate (Qmax), postvoid residual urine (PVR), International Index of Erectile Function (IIEF-5), and Male Sexual Health Questionnaire-Ejaculatory Dysfunction Short Form (MSHQ-EjD-SF). Additionally, the correlation of the indicators was analyzed using linear regression and early postoperative complications were also recorded. Results. One month after surgery, the patients' IPSS score, QoL, and PVR were significantly decreased, while the Qmax, IIEF-5, and MSHQ-EjD-SF scores were increased considerably, compared with preoperative data. After surgery, the patient's IPSS score, QoL, and Qmax were improved year by year, while PVR gradually decreased. Three months after TUCBDP, IIEF-5 and MSHQ-EjD-SF levels reached the climax. Linear regression analysis showed that the serum PSA level was significantly positively correlated with Qmax at 3 months after TUCBDP, while at 6 months after surgery, it was negatively related to IPSS and QoL. Early postoperative complications appeared in 384 cases during follow-up. Conclusion. Collectively, TUCBDP may effectively improve the urinary and sexual function of BPH patients, with fewer postoperative complications, and its efficacy is not limited by age and prostate volume. It can be considered a better treatment option for BPH. [ABSTRACT FROM AUTHOR]

There is an increasing demand in integrating energy storage with photovoltaic (PV) systems to provide more smoothed power and enhance the grid-friendliness of solar PV systems. To integrate battery energy storage systems (BESS) to an utility-scale 1500 V PV system, one of the key design considerations is the basic architecture selection between DC- and AC-coupling. Hence, it is necessary to assess the reliability of the power conversion units, which are not only the key system components, but also represent the most reliability-critical parts, in order to ensure an efficient and reliable 1500 V PV-battery system. Thus, this paper investigates the BESS solutions of DC- and AC-coupled configurations for 1500 V PV systems with a comparative reliability analysis. The reliability analysis is carried out through a case study on a 160 kW/1500 V PV-system integrated DC- or AC-coupled BESS for PV power smoothing and ramp-rate regulation. In the analysis, all of the DC-DC and DC-AC power interfacing converters are taken into consideration along with component-, converter-, and system-level reliability evaluation. The results reveal that the reliability of the 1500 V PV inverter can be enhanced with the DC-coupled BESS, while seen from the system-level reliability (i.e., a PV-battery system), both of the DC- and AC-coupled BESSs will affect the overall system reliability, especially for the DC-coupled case. The findings can be added into the design phase of 1500 V PV systems in a way to further lower the cost of energy. [ABSTRACT FROM AUTHOR]

The dead-time elimination pulsewidth modulation (PWM) enables the drive pulses of the upper and the lower switching devices to alternate according to the current polarity, thus abandoning the dead time and essentially avoiding the dead-time effect in power converters. However, the current zero crossing will be distorted by the current jump generated by the drive-pulse alternation, and the current zero-crossing distortion will be further intensified if errors exist in the detected current polarity. Thanks to the noise-attenuation and frequency-adaptability characteristics of the double second-order generalized integrator frequency-locked loop (DSOGI-FLL), it can obtain accurate current polarities even in harmonic and unbalanced conditions. A DSOGI-FLL-based dead-time elimination PWM is, therefore, proposed in this paper, and several improvements are made to minimize the current zero-crossing distortion. An underlap period is added when alternating the upper and lower drive pulses to smooth the current jump at zero crossing, and a delay compensation term is inserted in the DSOGI-FLL to compensate both the current measurement delay and the control delay. The effectiveness of the proposed DSOGI-FLL-based dead-time elimination PWM has been validated by experiments, respectively, in the unbalanced-current, power-change, and frequency-variation conditions with an RL load, as well as in a grid-connected converter. [ABSTRACT FROM AUTHOR]