This chapter summarizes the application of power electronics converters and systems in PV energy system. The chapter is organized with introduction given in Section 13.1 to cover the broad view of the PV generation in the context of power system environment. Section 13.2 is dedicated to the power electronic technologies used in PV generation with topics from the state of the art of technologies and the reliability aspects of the PV inverter. In Section 13.3, the system integration is presented to cover integration of the PV inverter with the power system grid and to understand the type of controls and control actions relevant to power system operation, reliability, and stability. In Section 13.4, the standard commonly adopted for PV generation covering different aspects of acceptable grid integration including protection, islanding, power quality, and ancillary services. Finally, in Section 13.5, the field measurement for PV generation is covered.

A novel modular Transformerless, Self-balanced, Static Synchronous Series Compensator (TSB-SSSC) capable of delivering ultra-high current, with the objective of dynamically balancing the impedance of the transmission power grid, is proposed. Balancing transmission lines is crucial in power optimization and delivery because it increases the power transfer capability without building new power lines. The transformerless SSSC needs to support and control the line current from a few hundred to several thousand amperes. This paper presents how the ultra-high current architecture of the TSB-SSSC is achieved by operating multiple converters with self-balancing capabilities in parallel. The mechanism of self-balancing is based on the intrinsic physics of the capacitor and is enabled by a passive network of capacitor equalizers that keep the capacitor voltage equal during switching disconnection. The second self-balancing system consists of an inductive component that balances possible differences among delay switching caused by the aging of the multiple IGBTs from the different converters that form the SSSC. This work presents the analytical set of equations that describes the system and a complete set of simulations where the effectiveness of self-balancing paralleling topology is shown.

In the near future, the massive production and deployment of electric vehicles (EVs) will need to be matched by the availability of an equivalently large number of dc fast-charging capabilities. This article explores the possibilities that public dc fast-charging systems will not be enough to satisfy the demand for a convenient network of EV-charging stations, creating the need for a residential dc fast charger that has the potential to become the enabling block for dc residential systems. DC residential systems also present a natural solution for the integration of solar panels and battery storage. DC fast chargers can efficiently and easily integrate solar energy produced and currently stored on the ac power grid, forming the backbone for a dc residential grid. Furthermore, the infrastructure needed for EV dc fast chargers can easily accept a future migration of other natural dc systems, such as modern air conditioning (A/C), heat pumps, refrigeration, lighting, and, ultimately, the other remaining appliances.

Several decades ago, the prevalent concept of the community was that there were fundamentally different approaches to diagnosing and maintaining mechanical versus electrical/electronic devices. For mechanical devices, the approaches were more concentrated on wear and tear, based on life-based model estimation; for electrical/electronic devices, the approaches were concentrated only on probabilistic and random phenomena. In other words, electronic approaches were mainly confined to statistics, assigning a probabilistic value of failure to each of the components to determine the overall reliability of the equipment. With some few exceptions, while the statistical approach is extremely valuable, we can do more in understanding reliability because the process of electromagnetic energy conversion of a device requires matter. More specifically, matter is the enabler of the process, channeling and regulating the conversion of one form of energy to another, usually from electric to magnetic or vice versa. The fact that the converters require matter as “the enabler” exposes the fundamental principle: that aging governs electrical elements in the same fashion as do the mechanical parts. Consequently, solid-state materials such as conductors, insulators, or semiconductors transfer energy from molecule to molecule, atom to atom, degrading during the process, which is modified by the level of temperature, electromagnetic fields, humidity, and other factors. Therefore, small cracks that appear due to impurities or “hot collisions” progress over time and are manifested as aging in the material, which usually shows as a loss of elasticity or an increase in the losses associated with energy transfer. This process creates a degradation “marker” that can be identified in many cases at the early stages of the degradation process. The understanding, identification, and progression of these degradation markers are the focal point of this chapter.

This chapter focuses on lithium-ion batteries. It also covers relevant aspects of this technology, focusing on the impedance measurement as a diagnostic tool mechanism for detecting aging on this type of batteries. Furthermore, we divide such mechanisms into online and offline methods based on their means of operation during the service time of the battery.

The reliability of a power converter depends mainly on the endurance of its main component, the power semiconductor. Therefore, particular attention is paid in this chapter to understand the models that allow the identification of features and early indicators of problems that establish the groundwork for early fault diagnosis in inverters. The two major switch technologies that control the market are field-effect transistors (FETs) and insulated gate bipolar transistors (IGBTs), which are bipolar devices integrating concepts from bipolar junction transistors (BJTs; IGBTs) which are bipolar devices integrating concepts from BJTs and FETs. From the beginning of power electronics, silicon-based semiconductors have been the undisputed king, but modern silicon-based power semiconductors are being challenged by silicon carbide (SiC) and more recently by gallium nitride (GaN). Regardless of the semiconductor material, early diagnostics in semiconductors are based not only on the understanding of the failure mechanisms but also on the “parasitic structures” that are intrinsically associated with the fabrication of the device. The identification and characterization of these “parasitic or associated structures” allow for the development of unified models with general characteristics across different materials and structures of power semiconductors. The aging effects are, in general, reflected in the parasitic structures early in the process of degradation, creating an ideal approach for understanding failure propagation. Fortunately, semiconductor devices share a similar structure, and a standard model across all power semiconductors is used in this chapter to understand aging and to enable early diagnostics.

This work compares variable speed controllers applied to single phase unbalanced induction motors. The single phase machine feeds from three phase inverters or double H bridges with scalar and vector control. For comparing the machine's performance the controller uses first a classical table based DTC and predictive based DTC for the vector controller, and later a standard V/f for the scalar controller. The simulations use a voltage behind reactance model of the single phase machine implemented in Simulink®, and experimental tests confirm the validity of the simulations. Also, the results show the feasibility of using different controllers, vector or scalar, to obtain low start-up currents, speed regulation and high electric torque, when compared with a direct start-up using capacitors in the auxiliary winding.

The switching frequency of inductive power transfer (IPT) is sensitive to the air gap between the primary and secondary coils. The mutual inductance might change significantly for different air gaps, resulting in a shift for the switching frequency. The mutual inductance is usually acquired through experimental measurement, finite element analysis, or frequency tracking control. In this paper, Neumann's formula is simplified to compute the mutual inductance of two coils. A frequency-gap model is presented to offer a simple way to calculate the unity-gain frequency for a symmetrical series-series (SS) IPT. Finite element simulation and experiment were conducted to verify the model. The experimental results show that the unity-gain frequency can be output within an average computational time of 9.8ms, and the gain fluctuates from 0.95 to 1.05 when the air gap changes from 7.5cm to 25cm.

There has recently been a significant interest directed towards residential battery storage systems mainly motivated by high penetration of renewables, the low cost and high efficiency of power electronic devices, and the advancements in the safety and energy density of the batteries, especially Lithium-Ion (Li-Ion) batteries. Furthermore, the possibility for the end user to become a utility-independent entity with the capacity to overcome power outages and tariff rises is even further propelling this fast growing industry. Lithium iron phosphate (LiFePO 4 ) battery is one of those technologies chosen to take the lead in residential battery storage due to its intrinsic safe performance, good energy density and price. This paper describes an online method for estimating the impedance of LiFePO 4 batteries when they are used in residential single phase energy storage systems. Single phase power systems have the intrinsic characteristics of delivering power at twice the frequency of the grid; by energy conservation principle, this pulsating characteristics is transferred directly to the current in the DC stage of the battery storage system. The proposed method takes advantage of this phenomenon and, without interrupting the energy conversion process or adding any external perturbation to the system, is able to characterize, in situ, the AC impedance behavior of the battery. Experimental results are provided to validate the proposed method and simulations show the potential applicability of this method in the assessment of the actual battery aging state.

The use of a second phase in household electric wiring is a requirement for feeding heavy loads in those countries using 100 ~ 127 Vrms as the standard voltage. One problem of this wiring is the unbalance between phase currents since single-and two-phase loads coexist. A back-to-back topology is proposed for an active power filter to add it the ability of active power compensation. The presented topology uses the same number of hardware components of others proposed topologies that just are able of reactive power compensation. The system is tested implementing a predictive direct current control when is connected to two different two-phase systems: those obtained by taking two phases of a three-phase system (120° between phases) and for two phases obtained from a split-phase transformer secondary (180° between phases).

This paper evaluates the use of a Photo Voltaic (PV) parameter estimation method based on implicit optimization algorithms and its use in power controller strategies by explicit model representation obtained with First and Second Order Approximation Models (FOAM, SOAM). An explicit function linking voltage, current and power of PV) cells is presented using the parameters obtained during the implicit estimation. The proposed method gives direct analytical solutions, resulting from a truncated Taylor series for the single diode PV-model. The analytical equations are easier to put into practical use and give solutions with an equivalent precision similar to the numerical method (Newton-Raphson Method) for the PV's cell voltage produced under particular conditions of temperature and solar radiance. The main benefit of this set of equations, useful also for optimal voltage estimation, is that offer an accurate and simple determination of the voltage profile using the manufacturer's data-sheet and PV plant's location for an specific design. The verification of the proposed method uses information from the manufacturer's datasheets of 12 different PV cells. The comparison of the results, for the analytical expressions versus the Newton-Raphson solution, validates the proposed method.

Wireless power transfer (WPT) via magnetic resonance coupling is considered a promising outlet for electric vehicle (EV) charging due to the noncontact method. Unlike a traditional transformer, with WPT, the relative spacing and lateral distance between the primary and secondary coils are highly variable, which can affect the wireless power delivery and lower the efficiency. A magnetic positioning approach that shares the wireless charging structure is proposed to solve the misalignment issue associated with wireless EV charging. The proposed alignment sensing system employs multiple auxiliary minor coils on the secondary side to position the charging pad. The positioning principle and equivalent circuit were analyzed. The 108 samples were tested and they were distributed throughout the detection range of 70 cm. The experimental results demonstrate that >92% of those samples have positioning errors of <2 cm and 98% of them have positioning errors of <3 cm.

Wireless power transfer is a promising alternative option for electric vehicle charging due to its non-contact operation. However, the magnetic coupling variation caused by misaligned coils limits its practical application. The output voltage can significantly drop due to the coupling change, lowering the power transfer capability. A uniform-gain frequency tracking control is proposed to keep the output voltage stable within a large misalignment. The uniform-gain control is achieved through voltage gain and impedance analysis across the frequency domain. Experimental results demonstrate that the voltage variation of uniform gain control is within 3.3% across the misalignment range of 200mm, while it is 57.2% for the same misalignment range under fixed frequency control.

A bidirectional inverter is proposed based on a two phase Neutral Point Clamping type 2 (NPC2) topology combined with a grounded buck boost inverter. The proposed system can work without the need of a transformer thanks to the combination of the topology, switching pattern and inductive filter that prevents the discharge of parasitic stray capacitance to ground. The inverter has the ability to operate as a back-up system as well as a grid-tied system. The structure of the NPC2 supports independent loads in each phase, enabling transformerless operation in split phase power systems such as 240V/120V, the default residential system in the US.

In order to consistently provide efficient EV wireless charging, changes in efficiency caused by coil misalignment should be investigated. This body of work uses a vector network analyzer to record the power transmission coefficients then calculate the efficiency and coupling factors. An automated 3-axis platform was built for coil motion control. The test result shows that the efficiency can remain at 90% as long as the misalignment ratio is within 0.5 and the air gap ratio is from 0 to 0.25.

A low-cost and high-efficiency hybrid semi-adiabatic enclosure is proposed. The principle behind it consists in extracting generated heat using natural convection or forced air when the ambient temperature allows it. Outside of this range, for low ambient temperatures, a reduced heat exchange to the minimum optimal temperature is achieved by transforming the enclosure into a highly adiabatic system by closing the isolated air vents. When the heat generated from the batteries is not enough for the initial starting conditions, passive heating is available for temperature increase. When the outdoor temperature exceeds the upper range, a thermo-electrical cooling system is implemented. In this paper, simulation results in PSIM are shown, as well as some experimental results, validating the feasibility of the implementation.

The switching frequency of inductive power transfer may change along with the air gap between two coils due to mutual inductance variation. The mutual inductance is conventionally estimated through experimental measurement or finite element analysis. To simplify this process, a frequency-gap model for series–series compensated inductive power transfer is proposed to calculate the unity-gain frequency based on known air gap and coil geometric parameters. Neumann's formula is applied to compute the mutual inductance of the primary and secondary coils. The experimental results show that the unity-gain frequency can be predicted with varying loads and air gaps (75–250 mm), and a demonstrated unity-gain error of <6%.

This paper presents a direct and approximate model of PV cell that considers variations in surrounding temperature and solar irradiation. The method uses the one diode model approximation and PV parameters from the manufacturer's data, together with a selective (first or second order) Taylor series. In this paper, a recursive solution for the PV cell's complete implicit model equations supplies data supporting the proposed approximate method results. The proposed model allows adjustment of the MPPT algorithm to simplify in real time the inverter control algorithm. It also provides a way to find the temperature and solar irradiation or errors produced by nonuniform irradiation on the solar panels.