This paper presents a novel virtual prototyping routine for power electronic converter systems. The approach facilitates a comprehensive and systematic benchmarking of different converter concepts based on a multiobjective optimization regarding the efficiency, power density, and costs. The underlying modeling framework is based on detailed and experimentally verified models. In particular, novel cost data as well as unpublished switching loss and core loss measurements are incorporated. The proposed virtual prototyping routine is employed to carry out a comparative study of the potential of Si and SiC semiconductors in a 10-kW residential three-phase photovoltaic inverter application. For this purpose, a state-of-the-art hard-switched three-level Si insulated-gate bipolar transistor (IGBT) system is compared to a hard-switched and to a soft-switched two-level SiC MOSFET system. The candidate systems for each concept are selected among the $\boldsymbol {\eta}$ - $\boldsymbol {\rho}$ - $\boldsymbol {\sigma}$ Pareto-optimized designs based on the life cycle costs. The hard-switched two-level SiC candidate system is found to be the most attractive solution featuring the lowest life cycle costs. When compared to the Si-based candidate system, not only a better power density and efficiency result. At the same time, besides the lower life cycle costs ( $-$ 22%), lower component costs ( $-$ 5%) can also be attained. The attractiveness of the found SiC solution is underlined by the simple control and the lowest component count among all concepts.

Comparative Life Cycle Cost Analysis of Si and SiC PV Converter Systems Based on Advanced $\eta$- $\rho$-$\sigma$ Multiobjective Optimization Techniques

The rapid development of renewable energy systems (RES), especially photovoltaic (PV) energy and wind energy, poses increasing requirements for highpower, low-loss, fast-switching, and reliable semiconductor devices to improve system power capacity, efficiency, power density and reliability. The recent commercialization of wide bandgap (WBG) devices, specifically Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, provides very promising opportunities for meeting such requirements with their attractive features of high voltage blocking capability, ultra-low switching losses, fast switching speed, and high allowable operating temperatures. This paper analyzed the performance benefits and application challenges of using SiC or GaN devices in both PV and wind energy conversion systems. Solutions to these challenges of using WBG devices in various RES were reviewed and proposed, and the benefits of using such emerging devices were confirmed in simulation based on a 250 kW commercial-scale PV inverter and a 250 kW doubly fed induction generator wind turbine system.

Application of wide bandgap devices in renewable energy systems — Benefits and challenges

Wide bandgap (WBG) power electronics is a very small segment of power electronics market (1%) and about 0.05% of the total semiconductor market today. The U.S. has a strong foothold in both the silicon carbide (SiC) and gallium nitride (GaN) markets today, but there exists an increasing competition from Europe, Japan, and China. This work presents market, value chain and energy savings potential analyses for several major application areas: data centers (uninterruptable power supplies (UPS) and server power supply units (PSU), renewable power generation (Photovoltaic (PV)-solar and wind), motor drives, rail traction, and hybrid/electric vehicles. These application areas hold great opportunities for WBG, stemming from increased government efficiency standards and promoting of alternative energy generation and an existing strong supply chain. Major threats to U.S. WBG integration stem from the loss of government assistance, alternative energy saving technologies, and an increasing threat of foreign manufacturers.

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Wide bandgap semiconductor opportunities in power electronics

As a result of the ongoing improvements in the area of power electronics, the penetration of power electronic converter systems into numerous traditional and modern applications has continuously been increasing. A prominent example is the developments in today’s electric power systems towards smart grids featuring high shares of new renewable energy sources such as solar and wind. Another example is the growing utilization of electric propulsion in automobiles and aircraft. Both examples are driven by the increased environmental awareness and the demand for higher functionality of the modern society. Based on the observed trends in state-of-the-art applications, it can be expected that the need for enhanced power electronic converter systems with a higher efficiency, reliability and functionality at concurrently lower costs, weight, volume and development time will further increase in the near future. The analysis of the relevant literature shows that the dimensioning and optimization of converter systems is often carried out with a limited scope and focusing on only one or a few performance criteria. This is often a consequence of a missing systematic approach which enables a comprehensive consideration of the inherent trade-offs between different performance measures (e.g. converter volume vs. losses). Furthermore, the employment of such an approach is often prohibited due to incomplete modeling frameworks to quantitatively assess the respective performance measures. Notably, suitable cost models to assess the costs of the typical components in converter systems are rare to find in literature. As a result of these deficits, it is unlikely that the optimal solution (topology, modulation scheme and component dimensioning) for a given application can be found by such limited approaches. The main focus of this thesis is thus set on the derivation of a suitable methodology which enables a systematic multi-objective optimization and comprehensive comparison of power electronic converter systems regarding achievable efficiency, volume, weight and costs. Thereby, a modeling framework is established which allows for the assessment of typical converter components such as semiconductors, inductors, capacitors, cooling systems and printed circuit boards regarding the selected performance measures. In addition to the component models, further models are developed which describe the converter behavior and the resulting current and voltage waveforms in the system depending on the employed modulation scheme and operating point. The models and their parameters are derived based on analytical calculations, simula-

Advanced Modeling and Multi-Objective Optimization of Power Electronic Converter Systems

Return on investment (ROI) analyses of solar photovoltaic (PV) systems used for residential usage have typically shown that at least 10 to 12 years is needed to break even, with this amount varying based on tax credits and reliability. This paper discusses the challenges with the reliability of current solar photovoltaic systems and the key reliability bottlenecks, with a focus on the ROI. The problem stems primarily from reliability issues of currently available power electronics hardware. This paper’s analysis of failure data shows that the short warranties and reliability concerns associated with solar PV inverters reduce the long-term ROI of residential solar PV systems by up to 10%. This paper, therefore, provides key insights for accurate ROI calculations for solar PV investments. Furthermore, methods to improve the reliability of PV inverters, such as selection of capacitors, inverter topology, and incorporating wide-bandgap semiconductor devices, are presented.

The Effect of Inverter Failures on the Return on Investment of Solar Photovoltaic Systems

The recent developments in wide band-gap devices based GaN and SiC is showing a high impact on the PV-inverter technology, which is strongly influenced by efficiency, power density and cost. Besides the high efficiency of PV inverters, also the mechanical size, the compactness and simple structure have an important role in the cost reduction. To increase the efficiency of PV systems, most of solutions for PV inverters have moved to three-level (3L) structures reaching typical efficiencies of 98% due to low switching losses of 600V Si IGBT or MOSFET and reduced core losses in the filter. With the appearance of SiC 1200V MOSFETs, it becomes possible to return to more simple two-level (2L) structure with comparable efficiency but high potential to reduce the overall cost. This paper deals with a comparison study between a Si-based 3L-Diode Neutral Point Clamped (DNPC) and a SiC-based 2L-Full Bridge (FB) three-phase PV-inverter topologies in terms of efficiency, thermal loading distribution and costs. Moreover the above mentioned PV-inverters are built and tested in laboratory in order to validate the obtained results.

Wide-band gap devices in PV systems - opportunities and challenges

High penetration of wind energy into the grid may introduce stability and power quality problems due to the fluctuating nature of the wind and the increasing complexity of the power system. By implementing advanced functionalities in power converters, it is possible to improve the performance of the wind farm and also to provide grid support, as it is required by the grid codes. One of the main compliance difficulties that can be found in such power plants are related to reactive power compensation and to keep the harmonics content between the allowed limits, even if the power of the WPP converters is increasing. This paper deals with an advanced control strategy design of a three-level converter performing STATCOM and Active Filter functionalities. The proposed system is called Smart-STATCOM since it has the capability of self-controlling reactive power and harmonic voltages at the same time. Therefore, deciding the amount of non-active currents (fundamental, 5th and 7th harmonics) to be injected depending on the PCC voltage quality. Experimental results of the proposed control strategy are analyzed in order to validate the performance of the entire system.

Smart — STATCOM control strategy implementation in wind power plants

This paper presents a control design and implementation analysis of a three level grid connected converter to be deployed in large scale wind turbine applications, which main purpose is to obtain enhanced grid interaction by limiting its harmonic injection capability. The implementation of advanced power converter control in high power converters allows the proposed wind turbine system to provide active and reactive power supply while performing active filter functionalities for the 5th and 7th harmonic current components. Finally, the performance of the system is verified under several practical study cases by performing a laboratory analysis of the obtained results.

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C. Sintamarean

Papers

Wide-band gap devices in PV systems - opportunities and challenges

Smart — STATCOM control strategy implementation in wind power plants

Control of an active filter based three level grid connected converter for wind turbine applications