Aiming to distinguish sources and loads for the rapid scaling of renewable power sources, a novel power packet dispatching system has been proposed with a structure similar to those of communication systems. Accurate clock synchronization is necessary to achieve the exchange of information attached in a power packet. At the same time, the clock synchronization is an interesting topic for developing power packet dispatching between multi-sender and a receiver. This work outlines the implementation of second-order autonomously controlled clock synchronization into the power packet dispatching system. At first, we derive the second-order controlled model of a digital clock synchronization method and analyze the stability of the developed model. Secondly, through experiments, it is shown that the information of power packets can be recognized correctly and the power can be distributed to directed loads. This paper demonstrates the validity of the asynchronous power packet dispatching based on our derived model. k ð Þ NCO denotes the clock period of NCO. In Eq. (1), k indicates the serial number of reference clock cycle, and Δ(k) represents the phase difference between the two clock signals. We define Δ(k) > 0 if REF leads NCO, Δ(k) < 0 if REF lags NCO, and Δ(k) = 0 when REF and NCO are synchronized. t k indicates the start time of the k-th reference clock cycle. Here, the clock synchronization between REF and NCO means T k ð Þ NCO ¼ T REF , and thus, from Eq. (1), it is clear that the achievement of clock SECOND-ORDER CLOCK SYNCHRONIZATION 731 a 2 is also a constant parameter, which is taken to be positive. By substituting Eqs. (A3) and (A4) into Eq. (A2), the second-order controlled model can be obtained, SECOND-ORDER CLOCK SYNCHRONIZATION 741

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This paper investigates and proposes one advantageous function of a power packet dispatching system, which has been proposed by authors' group with being apart from the conventional power distribution system. Here is focused on the feature on safety of power packet dispatching which covers two aspects: information safety (protect the information of packet from attackers) and power safety (keep loads safe regarding supplied power from packet). For the purpose of achieving the information safety and the power safety, we introduce simple modulations of power packets before sending them. In particular, in order to protect the information of packets, partial packet modulation is proposed first, i.e., modulating partial information tags of packets. Modulation scheme based on chaotic signal is one possibility for this purpose and we adopt the differential chaos shift keying (DCSK) scheme in this paper. Next, the power safety can be achieved by applying pulse width modulation (PWM) to the payload of packets. Meanwhile, considering the effect of the noise on the packet dispatching, further modulation of the payload using the DCSK scheme is proposed, which can spread the spectrum of the noise. Consequently, we introduce the concept of whole packet modulation, in which PWM is applied to the payload of packets first, and then modulation using the DCSK scheme is applied throughout the whole packet. In this manner, both the information safety and the power safety can be achieved and the spectrum of noise is spread as well. Additionally, it is worth mentioning that the rigorous examination of the modulation method is not the target in this moment.

This paper investigates and confirms one advantageous function of a power packet dispatching system, which has been proposed by authors' group with being apart from the conventional power distribution system. Here is focused on the function to establish the security of power packet dispatching for prohibiting not only information but also power of power packet from being stolen by attackers. For the purpose of protecting power packets, we introduce a simple encryption of power packets before sending them. Encryption scheme based on chaotic signal is one possibility for this purpose. This paper adopts the Differential Chaos Shift Keying (DCSK) scheme for the encryption, those are partial power packet encryption and whole power packet encryption.