Investigation of the minimal reactive power support of generators

With the emergence of competitive electricity power markets, reactive power ancillary services or reactive power markets have attracted more and more attention from researchers and system operators all over the world. Reactive power is an important system support service for the secure and reliable operation of power systems. Improper management of reactive power can also hinder the operational efficiency of other power markets. It has recently been recognized that the reactive power of a generator has several roles, namely, supplying reactive demand, maintaining system security and supporting its real power transmission. It is rational that the minimal reactive power used to support its real power transmission should not receive financial compensation in power markets. Hence this component of reactive power can be regarded as the minimal reactive power support of a generator. An optimal power flow (OPF) based method is proposed to study quantitatively basic components of a generator's reactive power. A simple 5-bus system is used to illustrate the proposed concept. The test results verify the rationality of the model and demonstrate the existence of minimal reactive power support of generators. The operational constraints that influence the generator's minimal reactive power support are also discussed.