The energy internet concept has been considered as a new development stage of the Smart Grid, which aims to increase the energy transmission efficiency and optimise the energy dispatching in time and space. Energy router is a core device in the energy internet and it connects all the devices together into a net structure and manages power flows among them. The research work presented in this paper described the energy router's structure and function expectations from the network perspective, and improved the existing energy router design. Open-shortest-path first (OSPF) protocol and virtual circuit switching mode are referenced from the Internet in the energy local area network (e-LAN) design. This paper proposed a design of an energy routing algorithm based on graph theory in an e-LAN. A lowest-cost routing selection algorithm is designed according to the features of power transmission, and a source selection and routing design algorithm is proposed for very heavy load conditions. Both algorithms have been verified by case analyses.

Switched mode power supplies (SMPSs) are essential components in many applications, and electromagnetic interference is an important consideration in the SMPS design. Spread spectrum based PWM strategies have been used in SMPS designs to reduce the switching harmonics. This paper proposes a novel method to integrate a communication function into spread spectrum based PWM strategy without extra hardware costs. Direct sequence spread spectrum (DSSS) and phase shift keying (PSK) data modulation are employed to the PWM of the SMPS, so that it has reduced switching harmonics and the input and output power line voltage ripples contain data. A data demodulation algorithm has been developed for receivers, and code division multiple access (CDMA) concept is employed as communication method for a system with multiple SMPSs. The proposed method has been implemented in both Buck and Boost converters. The experimental results validated the proposed DSSS based PWM strategy for both harmonic reduction and communication.

I. INTRODUCTIONHOTOVOLTAIC (PV) generation has been one of the most popular renewable energy technologies in the world. Conventionally, dozens of panels are series-connected to increase the output voltage, and then feeds to a grid-tied inverter. The output currents of all panels are equal due to the series connection. However, the current generation of PV panel is dependent on solar intensity and its condition. If some panels generate less current than the string current due to partial shading, the unshaded panels have to lower their output current to match with the shaded ones. Consequently, the unshaded panels will not work at their maximum power point (MPP), which leads to a waste of power [1]. Such problem can also be Manuscript received February 4, 2018; revised April 24, 2018; accepted May 4, 2018. This work is sponsored by the National Nature Science Foundation of China under Grants 51577170, National Key Technologies R&D Program of China No. 2017YFE0112400, and the European Union's Horizon 2020 research and innovation programme under grant agreement No. 734796.Y. Zhu, J. Wu, R. Wang and X. He are with the College of Electrical Engineering, Zhejiang University, Hangzhou; 310027, China. (e-mail: y_zhu@foxmail.com; eewjd@zju.edu.cn; rui_chi@163.com;hxn@zju.edu.cn).Z. Lin is with the Department of Electrical, Electronic and Power Engineering, Aston University, Birmingham, B4 7ET, U.K. (email: z.lin@ieee.org).induced by manufacture difference, nonuniform aging, etc.To mitigate the aforementioned problem, dc-dc power optimizer (DCPO), which is a dc-dc converter with input connected to the PV panel and output connected to other DCPOs in series, has been proposed and widely studied [1]- [9]. By equipping each PV panel with a DCPO, the panel can work independently at its MPP, thus distributed maximum power point tracking can be achieved.In [1]-[4], different topologies of DCPO have been compared and analyzed. Buck, boost, buck-boost, etc., are candidate topologies for DCPO. Buck and boost converters are the most efficient and low-cost topologies [2][3], while buck is only suited for long string and boost is for short strings. Buck-boost, cuk and sepic converters are flexible in voltage ranges but always at an efficiency and alternatively cost shortcoming [1][2] [4]. In [5]- [7], modeling of a single DCPO and of a PV string equipped with DCPOs have been studied in detail, which is very helpful for system designing. In [8], a novel maximum power point tracking (MPPT) technique based on DCPO is proposed, which shows the effectiveness of DCPO in panel MPPT. [9] proposes an intelligent PV module concept based on DCPO and PLC, and it shows great potentials of DCPO in intelligent PV system development.In a PV system equipped with DCPOs, PV status monitoring, intelligent control algorithm, and outage management can be implemented only if communication links among DCPOs are provided. Due to the cost-sensitive characteristic of PV system, low-cost communication method is preferred. For conventional PV status monitoring s...

Power electronics and communication electronics are both based on electromagnetic theory, but they are usually regarded as two distinct subfields in electrical engineering. In fact, however, electric power is the most common matter-based carrier of messages; thus, power electronics and communications can be jointly considered. Here we study the essential nature of dc-dc power converters and characterize the similarity of their operation principle to that of communication systems. Based on this similarity and the double modulation methods used in power electronics and communication, a double modulation strategy for both power and data is presented and applied in dc-dc power converters to achieve what we call 'talkative power'. A modulation strategy called frequency hopping-differential phase shift keying (FH-DPSK) is also presented to overcome the crosstalk between chosen transmission systems. The proposed talkative power strategy sheds new light on and provides inspiration for the further development of power electronics and communication.

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