document: A nonlinear modulation strategy for hybrid AC/DC power systems A nonlinear control strategy to improve transient stability of a multi-machine AC power system with several DC links terminated in the presence of large disturbances is presented . The approach proposed in this paper is based on differential geometric theory , and the HVDC systems are taken as a variable admittance connected at the inverter or rectifier AC bus . After deriving the analytical description of the relationship between the variable admittance and active power flows of each generator , the traditional generator dynamic equations can thus be expressed with the variable admittance of HVDC systems as an additional state variable and changed to an affine form , which is suitable for global linearization method being used to determine its control variable . An important feature of the proposed method is that , the modulated DC power is an adaptive and non-linear function of AC system states , and it can be realized by local feedback and less transmitted data from , adjacent generators . The design procedure is tested on a dual-infeed hybrid AC/DC system
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