Renewable Penetration Controller

Figure F.1. The complete wind penetration controller architecture

LN- Load Index

GN- Generator index

Xn- Load increase multiplier

Yn-PV generation displacement multiplier

SSSA- Small signal stability analysis

TSA - Transient stability analysis

OPF- Optimal power flow

Pw- Maximum real power output from all the wind farms

Nf – Number of wind farms

The architecture of the complete wind penetration controller is given in Figure. The controller is integrated with the existing SCADA system of the central load dispatch Centre. Two pipelines have been separately shown for the data and control transfer. The controller functionary is divided into three clusters. Each cluster is also functionally independent.

a) Control algorithm cluster

b) Optimization cluster

c) Stability cluster

The input – output interface is available for the generation, load and grid control. The expected working of each group is explained in subsequent sections. The red color indicates the modules in the controller that need to be implemented; whereas, the green color indicates the modules which has already been implemented.

F.1 Control algorithm cluster

The control algorithm group consists of various algorithms for maximization of wind penetration along with the storage calculator and contingency analyzer. Initially the basic power flow routine is executed and the suitable method is selected based on the user (grid) requirements. In most of the cases, the combined approach is idealistic.

For efficient grid integration, and to overcome the intermittency, the storage has to be increased for maximizing the penetration. More over a suitable generation mix makes the grid healthier and can reduce the storage. The amount of storage required is analyzed by the power flow analysis routine. Fuel cell, Air compression storage etc. can be used to increase the grid storage requirements. The amount of storage required and switched depends on the transient load with stand capability of the grid, which in turn depends on the moment of inertia of the rotating machines of the grid. A transient fault analysis program is required to access the with stand capability and to the judge the degree of storage required. Storage requirement calculator need to be integrated with the transient stability module of the controller. For those grid where, adequate fuel mix is available storage can be reduced or can be eliminated. More over pumped storage power plants, fast

acting thermal power plants, more spinning reserve etc. can be used as a substitute for storage. The feasibility analysis of the additional penetration cost saving to the storage investment is a financial optimization problem and is integrated to the controller by market analyzer cum OPF module. Similarly contingency analysis module works out the alternate restoration strategy to meet the unpredicted contingencies in course of attaining maximum penetration.

F.2 Optimization cluster

The optimization cluster contains modules such as market analyzer and planner, optimal power flow, and FACTS controller optimizer with the aid of various single objective and multi objective algorithms. The cluster optimizes the maximum wind penetration subject to conditions such as minimization of losses, optimal placement of FACTS controllers, optimal power flow etc.

by using algorithms such as NSGA-II and NSPSO etc. Moreover, since controller is materialized through PSAT module, add on PSAT feature of GAMS interface can also be exploited with or without the OPF module.

Maximum wind penetration to the grid can be increased to very higher levels, but the question is at what cost. Often the wind energy is also traded in deregulated market. The controller even though works on real time, can be made more deterministic and tuned to market by adding historic information so that it can partially address the market issues of hour ahead and day ahead market. In that case, wind historic data can be used for training the neural network in the particle swarm optimization algorithm. For day ahead market capacity credit based analysis can be taken into account for accurate predictions.

F.3 Stability cluster

The stability cluster has modules for voltage stability analysis, small signal stability analysis and transient stability analysis. Transient stability module also takes care of fault ride through with stand capability of the wind farms in case of transient faults. To identify the maximum penetration strategy, transient stability and fault ride through capacity has to be analyzed after allocating a suitable storage margin.

F.4 Hardware realization

The architecture of the complete controller shown in the Figure F.1 can be embedded into a FPGA chip or PLC or microcomputer with a suitable interface from RTUs, SCADA etc. For better and user friendly approach and control. A small one can be realized as a laboratory model for a miniature energy park with mini micro power stations with DGs.