A status review of photovoltaic power conversion equipment reliability, safety, and quality assurance protocols

Wang

IEEE Trans. Power Electron.

et al. 2019

The photovoltaic (PV) output voltage varies over a wide range depending on operating conditions. Thus, the PVconnected converters should be capable of handling a wide input voltage range while maintaining high efficiencies. This paper proposes a new series resonant dc-dc converter for PV microinverter applications. Compared with the conventional series resonant converter (SRC), a dual-mode rectifier (DMR) is configured on the secondary side, which enables a twofold voltage gain range for the proposed converter with a fixed-frequency phase-shift modulation scheme. The zero-voltage switching (ZVS) turn-on and zero-current switching (ZCS) turn-off can be achieved for active switches and diodes, thereby minimizing the switching losses. Moreover, a variable dc-link voltage control scheme is introduced to the proposed converter, leading to a further efficiency improvement and input-voltage-range extension. The operation principle and essential characteristics (e.g., voltage gain, soft-switching, and root-mean-square current) of the proposed converter are detailed in this paper, and the power loss modeling and design optimization of components are also presented. A 1-MHz 250-W converter prototype with an input voltage range of 17 V-43 V is built and tested to verify the feasibility of the proposed converter. Index terms-PV microinverter, dc-dc converter, series resonant converter, wide input voltage range, 1-MHz frequency.

Section: Soft-switchingmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

A 1-MHz Series Resonant DC–DC Converter With a Dual-Mode Rectifier for PV Microinverters

Wang

IEEE Trans. Power Electron.

et al. 2019

IEEE Trans. on Ind. Applicat.

“…Among those, enhancing the reliability and lifetime of PV inverters has high potential for a significant cost reduction [5]. The field experience has shown that the PV inverter failure contributes to a large portion of the unexpected operating and maintenance cost [6]- [8]. This gives a negative impact to the overall cost of energy in addition to the energy production loss during the inverter down-time periods.…”

Section: Introductionmentioning

confidence: 99%

Mission Profile-Oriented Control for Reliability and Lifetime of Photovoltaic Inverters

Sangwongwanich

Yang

Séra

et al. 2020

With the aim to increase the competitiveness of solar energy, the high reliability of Photovoltaic (PV) inverters is demanded. For PV applications, the inverter reliability and lifetime are strongly affected by the operating condition that is referred to as the mission profile (i.e., solar irradiance and ambient temperature). Since the mission profile of PV systems is location-dependent, the inverter reliability performance and lifetime expectation can vary accordingly. That is, from the reliability perspective, PV inverters with the same design metrics (e.g., component selection) may be over-or under-designed under different mission profiles. This will increase the overall system cost, e.g., initial cost for over-designed cases and maintenance cost for under-designed cases, which should be avoided. This paper thus explores the possibility to adapt the control strategies of PV inverters to the corresponding mission profiles. With this, similar reliability targets (e.g., component lifetime) can be achieved even under different mission profiles. Case studies have been carried out on PV systems installed in Denmark and Arizona, where the lifetime and the energy yield are evaluated. The results reveal that the inverter reliability can be improved by selecting a proper control strategy according to the mission profile.

“…The lifetime/warranty of PV modules is about 25 years, but the inverters have to be replaced every 5 to 10 years [8]; this implies that the lifetime of the MIs needs to be extended to match that of the PV modules. Therefore, reliability evaluation and reliability-oriented design of PV MIs under a harsh environment is paramount [9]- [10].…”

Section: Introductionmentioning

confidence: 99%

Wear-Out Failure Analysis of an Impedance-Source PV Microinverter Based on System-Level Electrothermal Modeling

IEEE Trans. Ind. Electron.

Chub

Wang

et al. 2019

The wear-out performance of an impedancesource photovoltaic (PV) microinverter (MI) is evaluated and improved based on two different mission profiles. The operating principle and hardware implementation of the MI are firstly described. With the experimental measurements on a 300-W MI prototype and system-level finite element method (FEM) simulations, the electro-thermal models are built for the most reliability-critical components, i.e., power semiconductor devices and capacitors. The dependence of the power loss on the junction/hotspot temperature is considered, the enclosure temperature is taken into account, and the thermal cross-coupling effect between components is modeled. Then the long-term junction/ hotspot temperature profiles are derived and further translated into components' annual damages with the lifetime and damage accumulation models. After that, the Monte Carlo simulation and Weibull analysis are conducted to obtain the system wear-out failure probability over time. It reveals that both the mission profile and the thermal cross-coupling effect have a significant impact on the prediction of system wear-out failure, and the dc-link electrolytic capacitor is the bottleneck of long-term reliability. Finally, the multi-mode control with a variable dclink voltage is proposed, and a more reliable dc-link electrolytic capacitor is employed, which results in a remarkable reliability improvement for the studied PV MI.