| 摘要 |
A method of determining a rotational state of a three-phase alternating supply voltage is connected to a mains side converter, having an intermediate voltage circuit (Udc+, Udc-) and comprises phase-specific upper and lower controllable switches (S11,S21,S31,S12,S22,S32), which are connected in series between the intermediate voltage circuit, free-wheeling diodes (D11,D21,D31,D12,D22,D32) connected in parallel with each of the controllable switches, and resistive circuits (R11,R12;R21,R22;R31,R32) connected in parallel with the lower controllable switches. The method comprises the steps of selecting a voltage limit (Vref), comparing the voltages of the three-phase alternating supply in the resistive circuits (R11,R12;R21,R22;R31,R32) with the voltage limit (Vref), determining a first time instant (T1) and a second time instant (T2) when a first and a second of the voltages of the resistive circuits (R11,R12;R21,R22;R31,R32) cross the voltage limit (Vref), determining the phase sequence of the three-phase alternating supply voltage (U1,U2,U3) from the first and second voltage, determining the frequency of the three-phase alternating supply voltage from the determined time instants (T1,T2).
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