Distributed Load-Frequency Control in Power Systems

Optimum frequency response with decentralized drivers in power system

“…The proposed method is based on the measurement and control of the internal rotor angle of selected generators and its main contributions are: ‐Determination of the optimal parameters for the D_LFC controllers. ‐Optimum design of the frequency response of the system with the capacity to adequately control its maximum drop and its response recovery caused by unbalances between load and generation. ‐Optimum PMU placement problem has also been solved for tackling the dynamic problem of D_LFC. Not all generators on the system require a PMU. ‐Generalization of the proposal introduced in [21], surpassing limitations related to the consideration of a specific GOV type. …”

“…By doing this, it is possible to control the speed of the rotor, allowing the return of the frequency to its nominal value of operation after the occurrence of a load change event or the output of a generator. Figure 4 shows a control diagram for each generating unit, including the measurement of its internal rotor angle [21].…”

“…Here: $$k_{pi}$$ is the regulation constant of the rotor angle variations and $$k_{fi}$$ is the regulation constant of the generator speed variations. The minimum and maximum values for these constants are obtained through a steady‐state and transient stability analysis process [21]. $$P_{ref_i}$$ is the power reference given by the dispatch center.…”

“…In this way, these generators do not require a PMU that can measure the internal rotor angle. On the other hand, for generators to be assigned to full load‐frequency control, their controller constants $$k_{fi}$$ and $$k_{pi}$$ need to be different from zero within their adequate range [21].…”

“…Although that, mathematically, this equation is very similar to Equation (8), it is pertinent to indicate that there are certain differences between them, such as: (i) the proposed control scheme respects the static characteristic of the machine, and its regulation properties, while in isochronous mode, the generators tend to compete since they do not have this characteristic, (ii) another important point to compare is that the proposed scheme contemplates a setpoint of the internal rotor angle $$\delta _{ref}$$ for each generator, which allows the local controller to make decisions regarding the deviation of its angle reference, which will influence the transferred power due to their mutual relationship [21], which cannot be done by isochronous mode. In the proposed control, the power required by each of the generators can be controlled, in addition to the fact that in interconnected systems it is possible to regulate the programmed power exchange.…”