Abstract-To study the stability of a nominal cyclic steady state in power electronic converters, it is necessary to obtain a linearization around the periodic orbit. In many past studies, this was achieved by explicitly deriving the Poincaré map that describes the evolution of the state from one clock instant to the next and then locally linearizing the map at the fixed point. However, in many converters, the map cannot be derived in closed form, and therefore this approach cannot directly be applied. Alternatively, the orbital stability can be worked out by studying the evolution of perturbations about a nominal periodic orbit, and some studies along this line have also been reported. In this paper, we show that Filippov's method-which has commonly been applied to mechanical switching systems-can be used fruitfully in power electronic circuits to achieve the same end by describing the behavior of the system during the switchings. By combining this and the Floquet theory, it is possible to describe the stability of power electronic converters. We demonstrate the method using the example of a voltage-mode-controlled buck converter operating in continuous conduction mode. We find that the stability of a converter is strongly dependent upon the so-called saltation matrix-the state transition matrix relating the state just after the switching to that just before. We show that the Filippov approach, especially the structure of the saltation matrix, offers some additional insights on issues related to the stability of the orbit, like the recent observation that coupling with spurious signals coming from the environment causes intermittent subharmonic windows. Based on this approach, we also propose a new controller that can significantly extend the parameter range for nominal period-1 operation.

Newcastle University ePrints -eprint.ncl.ac.uk Wu X, Hu X, Moura S, Yin X, Pickert V. Stochastic control of smart home energy management with plug-in electric vehicle battery energy storage and photovoltaic array. AbstractEnergy management strategies are instrumental in the performance and economy of smart homes integrating renewable energy and energy storage. This article focuses on stochastic energy management of a smart home with PEV (plug-in electric vehicle) energy storage and photovoltaic (PV) array. It is motivated by the challenges associated with sustainable energy supplies and the local energy storage opportunity provided by vehicle electrification. This paper seeks to minimize a consumer's energy charges under a time-of-use tariff, while satisfying home power demand and PEV charging requirements, and accommodating the variability of solar power. First, the randomvariable models are developed, including Markov Chain model of PEV mobility, as well as predictive models of home power demand and PV power supply. Second, a stochastic optimal control problem is mathematically formulated for managing the power flow among energy sources in the smart home. Finally, based on time-varying electricity price, we systematically examine the performance of the proposed control strategy. As a result, the electric cost is 493.6% less for a Tesla Model S with optimal stochastic dynamic programming (SDP) control relative to the no optimal control case, and it is by 175.89% for a Nissan Leaf.

Abstract-ThisHowever, IGBTs are known to be prone to failure [12]-[19], and the situation would only get worse when operating in the harsh environment beneath the bonnet of an electric vehicle. ) have received much attention by the industry. Nonetheless, when the bonding using these new technologies fails, the entire device will be damaged with catastrophic consequences.Without a doubt, the detection of an IGBT fault prior to (prognosis) or even after (diagnosis) its occurrence is of critical importance to the healthy operation of the system. Conventional vehicles are equipped with an on-board diagnostic (OBD) system which can detect a "happened" fault and flag it up to the driver of the vehicle. In the event of an IGBT failure, the detection must be quick enough (ideally, less than 10 μs) to prevent a fault from propagating, which places a limit on the hardware setup

SUMMARYWe propose a method of estimating the fast-scale stability margin of dc-dc converters based on Filippov's theory-originally developed for mechanical systems with impacts and stick-slip motion. In this method one calculates the state transition matrix over a complete clock cycle, and the eigenvalues of this matrix indicate the stability margin. Important components of this matrix are the state transition matrices across the switching events, called saltation matrices. We applied this method to estimate the stability margins of a few commonly used converter and control schemes. Finally, we show that the form of the saltation matrix suggests new control strategies to increase the stability margin, which we experimentally demonstrate using a voltage-mode-controlled buck converter.

Abstract-This paper presents a novel real-time power device temperature estimation method which monitors the power MOSFET's junction temperature shift arising from thermal aging effects and incorporates the updated electrothermal models of power modules into digital controllers. Currently, the real-time estimator is emerging as an important tool for active control of device junction temperature as well as on-line health monitoring for power electronic systems but its thermal model fails to address the device's ongoing degradation. Because of a mismatch of coefficients of thermal expansion between layers of power devices, repetitive thermal cycling will cause cracks, voids and even delamination within the device components, especially in the solder and thermal grease layers. Consequently, the thermal resistance of power devices will increase, making it possible to use thermal resistance (and junction temperature) as key indicators for condition monitoring and control purposes. In this paper, the predicted device temperature via threshold voltage measurements is compared with the real-time estimated ones and the difference is attributed to the aging of the device. The thermal models in digital controllers are frequently updated to correct the shift caused by thermal aging effects. Experimental results on three power MOSFETs confirm that the proposed methodologies are effective to incorporate the thermal aging effects in the power device temperature estimator with good accuracy. The developed adaptive technologies can be applied to other power devices such as IGBTs and SiC MOSFETs, and have significant economic implications.

Maximum power point tracking (MPPT) controllers play an important role in photovoltaic systems. They maximize the output power of a PV array for a given set of conditions. This paper presents an overview of the different MPPT techniques. Each technique is evaluated on its ability to detect multiple maxima, convergence speed, ease of implementation, efficiency over a wide output power range, and cost of implementation. The perturbation and observation (P & O), and incremental conductance (IC) algorithms are widely used techniques, with many variants and optimization techniques reported. For this reason, this paper evaluates the performance of these two common approaches from a dynamic and steady state perspective. Keywords Photovoltaic (PV) System, Boost Converter, Maximum Power Point Tracking (MPPT)S. E. Babaa et al. 60as shown in Figure 1. Therefore, for maximum efficiency, it is necessary to use a maximum power point tracking (MPPT) algorithm to deliver optimal available PV output power at different operating points to the load. With this in mind, many maximum power point tracking algorithms have been developed, and much research has been carried out to optimize the various techniques [4]- [6].This paper provides an overview of the most common MPPT approaches. From this, it is found that the perturbation and observation (P & O) and incremental conductance (IC) algorithms are particularly popular approaches [5]. For this reason, this paper presents a simulation study comparing the relative performance of these two techniques with respect to dynamic and steady state performance, and hence overall system efficiency.

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Abstract-This brief proposes a novel controller which greatly enhances the performance of a power-factor correction converter. This controller is optimally tuned to place the eigenvalues of the system well inside the unit circle and hence it guarantees stable operation over a wide range of input voltages. The design of the controller is based on the stability analysis of the system using the state transition matrix over a clock cycle. It is shown that the transition matrix across the switching manifold greatly influences the system's performance, allowing the system to be stabilized by periodically altering the manifold. The results are validated by analytical and numerical studies.