  Energy storage units (ESUs) including EVs and home batteries enable several
attractive features of the modern smart grids such as effective demand response
and reduced electric bills. However, uncoordinated charging of ESUs stresses
the power system. In this paper, we propose privacy-preserving and
collusion-resistant charging coordination centralized and decentralized schemes
for the smart grid. The centralized scheme is used in case of robust
communication infrastructure that connects the ESUs to the utility, while the
decentralized scheme is useful in case of infrastructure not available or
costly. In the centralized scheme, each energy storage unit should acquire
anonymous tokens from a charging controller (CC) to send multiple charging
requests to the CC via the aggregator. CC can use the charging requests to
enough data to run the charging coordination scheme, but it cannot link the
data to particular ESUs or reveal any private information. Our centralized
scheme uses a modified knapsack problem formulation technique to maximize the
amount of power delivered to the ESUs before the charging requests expire
without exceeding the available maximum charging capacity. In the decentralized
scheme, several ESUs run the scheme in a distributed way with no need to
aggregator or CC. One ESU is selected as a head node that should decrypt the
ciphertext of the aggregated messages of the ESUs' messages and broadcast it to
the community while not revealing the ESUs' individual charging demands. Then,
ESUs can coordinate charging requests based on the aggregated charging demand
while not exceeding the maximum charging capacity. Extensive experiments and
simulations are conducted to demonstrate that our schemes are efficient and
secure against various attacks, and can preserve ESU owner's privacy.
