How does a power plant increase load?
The question should be 'How does a power plant handle an increase in load?'
So do power plants that generate electricity increase voltage or do they increase amps to increase watts?
An increase in load is met by an increase in prime mover input power in order to maintain the constant generator RPM required tospeed that would satisfy the constant voltage and frequency requirements of the consumer.
The result is increased current at constant voltage and frequency.