A smart converter for a synchronous motor comprising:
- two inputs to be connected to a DC source,
- at least N phase lines to be connected to a phase of the synchronous motor, N being at least equal to or greater than 3,
- a rectifier inverter block comprising an arm of transistors per phase line, each connected between both inputs and comprising an output connected to a corresponding phase line to convert the direct current at the inputs into alternating current on the corresponding phase line,
- a measurement block comprising one current sensor per phase line each to measure a current in the corresponding phase line, and each to produce an overall current signal representative of the current in the phase lines measured by the current sensors,
- a smart control unit comprising:
- a control block connected to a control member of each transistor of the rectifier inverter block in order to control them, the control block being configured to transmit a control signal to each transistor to form, on each line, an overall alternating voltage signal the overall alternating voltage signals being phase shifted from one another by 360°/N, each overall alternating voltage signal each comprising the superimposition:
- 1. of an alternating power voltage signal having a first amplitude value according to a first frequency between a first and a second value,
- 2. with a measurement signal having a second amplitude less than the first amplitude and a second frequency at least 20 times greater than the second value of the first frequency,
- 3. such that the measurement signals are phase shifted from each other by 360°/N,
- a calculation block for estimating the angular position of the rotor comprising a first demodulator block and a second demodulator block, connected to the measurement block to receive the overall current signals representative of the currents in the phase lines by the measurements of the current sensors, the calculation block for estimating the angular position of the rotor being configured to:
- 1. receive an overall signal representative of the current of a line by each corresponding current sensor,
- 2. demodulate each overall current signal by the first demodulator block at the second frequency, to extract a demodulated measurement signal at a time instant t, and to identify a current value of each demodulated measurement signal, and to identify two possible angular positions of the rotor as a function of the values of each demodulated measurement signal at time instant t,
- 3. simultaneously demodulate each overall signal by the second demodulator at a value of twice the second frequency to extract at a time instant t a sign of an order-2 harmonic of the current of each measurement signal, and
- 4. estimate the angular position of the rotor as a function of the sign of the harmonic identified from both possible rotor angular positions identified.