In this paper, the rotor position estimation accuracy of rotating carrier signal injection utilizing zero-sequence carrier voltage method for dual three-phase (DTP) permanent-magnet synchronous machines (PMSMs) is investigated. When utilizing the zero-sequence carrier voltage, the system bandwidth and rotor position estimation accuracy can be significantly enhanced. However, undesirable sixth harmonic estimation error occurs for single three-phase PMSM with rotating signal injection due to multiple saliency components in the zero-sequence carrier voltage. To solve such a problem, the existing methods require time-consuming offline measurements and complex structures. Fortunately, for the case of DTP-PMSM drives, thanks to the existence of additional degrees of freedom, two high-frequency signals can be injected independently for two winding sets. Therefore, by applying the optimum phase shift angle between the injected signals, a modified rotating carrier signal injection using zero-sequence voltage-based sensorless control strategy is proposed to suppress the sixth harmonic position errors. In addition, a new simple measurement method of zero-sequence carrier voltage is proposed where one voltage sensor is placed between the two isolated neutral points. The proposed method can achieve improved rotor position estimation accuracy with low computational burden. The experimental results verify the effectiveness of the proposed strategy.