A complete new insight into why excitation-governor control with power system stabilizers (PSSs) has been so successful for the control of turbogenerators connected to an infinite bus is provided by the small-signal multivariable analysis framework, individual channel analysis and design (ICAD). The multivariable analysis justifies treating the turbogenerator system as a pseudo-single-input single-output (SISO) system where the governor loop is first closed and the exciter loop is treated as a SISO system for the prime purpose of rejecting voltage disturbances. The function of the PSS is identified as that of overcoming an awkward switch-back frequency-domain characteristic of the excitation channel so as to permit high-performance excitation channel bandwidths up to 10 rad s(-1) that otherwise could not be obtained. Thus, in addition to the control requirements of set point regulation of the terminal voltage and shaft speed, the PSS provides for a second control requirement of strong voltage disturbance rejection over the important frequency range 0-10 rad s(-1). The PSS control option is also assessed against other control options. Several other results concerning stability robustness to system uncertainties in different system configurations follow from the analysis in a transparent and immediate way.