**6.2 Power quality issues**

*Wind Solar Hybrid Renewable Energy System*

*6.1.2 Distributed control*

sion neural network (GRNN).

battery charge controller.

*6.1.3 Hybrid control*

compensates voltage.

*6.1.4 Control communication*

maximize the utilization of the hybrid system. Centralized control requires fast communication and supercomputing to handle a large amount of data in a short time. This is less reliable due to single point attack risk. A new topology of WPVHPS is proposed by Singaravel et al. [52]. In this topology, the sources are connected

It is very suitable for grid-integrated renewable sources. Alagoz et al. [53] describe that DERs are gradually increasing count with each consumer turning into a prosumer. This can take the best out of it if there is a bidirectional interaction between DERs. A service-oriented infrastructure can be formed by a tree-like usermode network (UMN). In [54] the coordination control of a WPVHPS and a proton exchange membrane fuel cell (PEMFC) is studied. A grid-connected WPVHPS is proposed in [55]. The pitch control of the wind turbine uses radial basis function network-sliding mode (RBFNSM), and the MPPT of PV system uses general regres-

For control of the voltage and frequency at the point of common coupling firefly algorithm (FA) based proportional integral (PI), and PID controllers [56] are used. In [57] authors have shown that the modified adaptive accelerated particle swarm optimization (MAAPSO) proves better than PSO for PID and fractional order PID

This type is regarded as a combination of centralized and distributed control and is more versatile. Qi et al. [58] reviewed supervisory model predictive control (MPC) and developed it in distributed architecture taking two spatially distributed wind and PV subsystems each with storage, in a DC power grid, with a local load connected. For a WPVHPS with fuel cell, [59] a direct control scheme in a hybrid AC/DC structure is developed that deploys a harmonic virtual impedance loop and

Dynamic interaction between transmission and distribution systems caused due

For the energy control in a distributed manner, energy routers can serve dynamically the energy distribution in the grid, where the whole structure can be termed as energy Internet [62]. Cao et al. [63] discuss in detail energy internet called as version 2.0 of smart grids that has the two-way flow of information and power. More openness and peer-to-peer communication are introduced. This network can balance power with more interaction and options. Anticipatory or predictive control is possible based on information to anticipate future states and appropriate

to transformations in power systems make control vulnerable. This is also happening in case of integration of renewable power plants to grid. Vision for perfect grid management can never undermine the importance of control communication. If the output of a renewable energy power plant is greater than 10% of the line capacity, temporary unavailability [60] can adversely affect power grid stability, so demands a communication. It is important to develop an intelligent, self-adaptive, dynamic and open system. So, a multi agent system (MAS) is proposed [61] to handle the energy management of the hybrid PV-wind generation system in which

each agent with a RES reacts intelligently to changes.

decision-making for timely action.

together to the grid via only a single boost converter—inverter setup.

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The power quality is also an issue with the WPVHPS integrated. This section briefly indicates the power quality problems in grid integration. A well-written review has been brought by [65] for problems and solutions so far concerned with such system in grid-connected condition. Voltage and frequency fluctuation and harmonics are major power quality issues with a severe effect on the weak grid. Appropriate design and advanced fast control can solve it. Filters, control of PWM inverter, and droop control can be a solution to it. Kabalci et al. [66] discuss a threephase inverter control scheme to limit total harmonic distortion within standards.
