The power system control and complexity increases further when GT driven generators are also coupled with an exhaust heat recovery system. Most heat recovery systems are largely de-coupled from the electrical power system, even though the amount of GT waste heat recovered is proportional to the electrical load. This de-coupling is achieved by accepting the variable heat input from the GT exhaust and supplementing it with inbuilt auxiliary-fired burners. Alternatively separately fired boilers or local heating systems may be provided. Time constants associated with steam system disturbances tend to be much longer than those associated with electrical power system disturbances, hence the heat recovery control management system has time to respond and initiate secondary heat sources. However, some exhaust heat recovery systems, such as HRSG's require a minimum GT exhaust heat and mass flow for stable operation. Thus some form of PMS controlled secondary governor regulation may also be required to ensure the GT's are loaded above a minimum load, as well as the other requirements for load sharing, frequency control and GT DLN operating limits.