DEVICE AND PROCEDURE FOR TESTING A POWER MODULE COMPRISING A MULTICHANNEL POWER CONVERTER AND A SYNCHRONOUS MULTIPHASE AND MULTICHANNEL     ELECTRICAL MACHINE

A device for testing a power module comprising a multichannel power converter and a synchronous multiphase and multichannel electrical machine intended to be supplied by the converter, whereby the synchronous multiphase and multichannel electrical machine has phases connected to one another by groups of three phases. The power converter comprises as many voltage inverters as there are groups of three phases connected to said converter, whereby each inverter is connected to a group of three phases.

FIELD OF INVENTION

The disclosure relates to a device and a procedure for testing an electrical power module, and more particularly a procedure for testing a synchronous multiphase and multichannel electrical machine and its associated multichannel power converter.

BACKGROUND OF THE INVENTION

Before delivering an electrical power module to a customer, the manufacturer aims to verify the correct operation of the module. This module comprises a power converter and an electrical machine powered by said power converter. The manufacturer aims to verify the electrical and mechanical characteristics of the module. It also aims to verify the operation of the control and acquisition chains comprising sensors, interfacing modules, and actuators. It aims to optimize the costs of the testing operations, and to reduce the investments related to the manufacturing of the test bench.

In addition, the power module customer also wishes to test the power module.

The usual procedure for testing an electrical power module includes a test bench specific to the tests conducted, known as a “back-to-back test bench”. This test procedure requires that the assembly being tested, comprising the electrical machine and its associated power converter, be mounted on the test bench. The test bench is a large and very heavy device. For example, a test bench for of a generator suitable for a wind turbine weighs around 140 tons.FIG. 1shows a back-to-back test bench specific to these tests, as known from the standard technique.

The test bench comprises two electrical power modules1and2. A first electrical power module1comprises a power converter3which supplies an electrical machine4operating in motor mode. The shaft of the motor5of this first electrical power module is mechanically connected to the shaft of the second power module2. The second power module2, which is the object of the test procedure, comprises an electrical machine6associated with a power converter7. The second power module2operates in generator mode. The first power module1is supplied by a three-phase electrical network R. It drives the second power module2connected to a three-phase network R′. The electrical and mechanical characteristics of the second power module recorded during the test procedure are analyzed, and allow it to be concluded whether the tested power module2conforms or not.

A second test is performed on the integration line of the module in its environment before shipping, such as in the case of a wind turbine, when the power module is mounted in the nacelle of the wind turbine. This is a functional test. The power module is supplied by an external source. It is checked that the axle of the electrical machine starts to move.

However, the usual test procedures have several disadvantages.

The module being tested must be mounted on a test bench, which implies that the assembly cannot be tested in its working environment, and customers that are not equipped with such a test bench cannot test their power module easily.

For example, in the case of a power module operating in generator mode and equipping an offshore wind turbine, the power module cannot be tested when it is integrated into the nacelle of the wind turbine and connected to all of the auxiliary components. The interfaces connecting the power unit to the other components cannot be tested either.

In addition, the test procedure performed prior to shipping the module is brief. It involves ensuring that the powertrain is able to drive the shaft of the electrical machine. No diagnosis can be made regarding the quality of the devices comprising the power module, such as the sensors included in the nacelle which perform the acquisition of the characteristics of the electrical machine.

The global acquisition and control chains linked between the power converters and the nacelle cannot be tested under real operating conditions.

BRIEF SUMMARY

An objective of in an embodiment therefore to eliminate these disadvantages.

In view of this, the disclosure proposes a device for testing a power module comprising a multichannel power converter and a synchronous multiphase and multichannel electrical machine intended to be supplied by the converter, whereby the synchronous multiphase and multichannel electrical machine has phases connected to one another by groups of three phases.

One characteristic of the device according to in an embodiment that the power converter comprises as many voltage inverters as there are groups of three phases connected to said converter, whereby each inverter is connected to a group of three phases.

Another characteristic of in an embodiment that the three phases of a group are connected in a star or delta configuration or by any other coupling.

In an embodiment, the stator of the synchronous multiphase and multichannel electrical machine comprises a plurality of groups of three phases with a magnetic coupling level to make it possible to control each channel separately.

In an embodiment, the synchronous multiphase and multichannel electrical machine operates in motor or generator mode.

Another characteristic of the device is that the shaft of the synchronous multiphase and multichannel electrical machine is free.

The disclosure also relates to a procedure for testing a power module comprising a multichannel power converter and a synchronous multiphase and multichannel electrical machine intended to be supplied by the converter, whereby the synchronous multiphase and multichannel electrical machine comprises a stator comprising phases connected to one another by groups of three phases, the groups of phases are magnetically decoupled from each other and are each connected to the multichannel power converter, and a transformer connected to a three-phase electrical network supplies the multichannel power converter.

Another characteristic of the procedure according to in an embodiment that it comprises at least one step whereby a group of three phases drives the rotor of the electrical machine at a predetermined rotational speed, and one or more other groups of three phases that form the object of the test procedure operate in generator mode and apply electromagnetic torque to the rotor of the synchronous multiphase and multichannel electrical machine.

In an embodiment, the three phases of a group are connected in a star or delta configuration or by any other coupling.

Another characteristic of the procedure according to in an embodiment that the transformer supplies the multichannel power converter with a power value equal to the value of the power lost during the various energy conversion steps.

In an embodiment, during the different test steps, only active powers are exchanged between the multichannel power converter, the synchronous multiphase and multichannel electrical machine and the transformer.

DETAILED DESCRIPTION

Reference is made toFIG. 2, which shows an electrical power diagram of an electrical power module comprising a multiphase and multichannel electrical machine and a multichannel power converter. For example, in a non-limiting application, the power module is intended to be integrated into the nacelle of a wind turbine.

The power circuit of the power module comprises a multichannel three-phase power converter11and a synchronous multiphase and multichannel electrical machine10supplied by the converter. The same-phase inputs of the power converter11are connected to one another and to the corresponding output of a three-phase transformer12. The transformer12is supplied by a three-phase electrical network R. The entire device comprising the power converter11and the multiphase and multichannel electrical machine10is controlled by a control device (not shown).

The synchronous multiphase and multichannel electrical machine10comprises a stator and a rotor. The stator includes a plurality of phases that are multiples of three. The phases are connected to one another by groups of three phases. By way of a non-limiting example hereunder, the three phases of a group are connected in a star configuration. Of course, there is no departure from the disclosure when the phases are connected in any configuration whatsoever, in particular but not exclusively in a delta configuration. The stars have a strong magnetic decoupling between them. As a result, the magnetic fluxes generated by one star do not disturb another star. The magnetic decoupling level allows each channel to be controlled separately.

InFIG. 2, the machine10comprises, for example, nine phases grouped into three groups of triple phases13,14,15connected in a star configuration.

The power converter11has a plurality of identically formed channels. Each output of a channel is connected to a group of triple phases in the star configuration of the electrical machine10. Therefore, the number of channels of the power converter11is equal to the number of triple-phase groups in the star configuration of the machine10. The inputs of the same-phase channels are connected to one another and to the corresponding output of the transformer12.

InFIG. 2, the electrical machine comprises three groups of triple phases in a star configuration13,14and15. Therefore, the power converter11comprises three channels16,17,18.

Reference is made toFIG. 3, which shows the formation of the channel16of the multichannel power converter11. All channels are formed identically.

Channel16comprises a harmonic filtering device20whose inputs are intended to be connected to the transformer12and to the other channel inputs of the power converter11. The outputs of the filter20are connected to the inputs of a controlled and reversible bridge rectifier21. The outputs of the bridge rectifier21are connected to a capacitor bank22. The DC voltage filtering assembly22comprises two groups of series-connected capacitors whose ends are connected to the rectifier bridge21, to a brake chopper23and to the inputs of a reversible voltage inverter25, and whose midpoint between the two capacitors is connected to the brake chopper. A second capacitor bank24formed identically to capacitor bank22is connected to the inputs of the reversible voltage inverter25. The midpoint between the two capacitors of the capacitor bank24is connected to the reversible voltage inverter25. The outputs of the voltage inverter25are connected to a dV/dT filter26. The outputs of the filter26are connected to a group of triple phases in the star configuration of the electrical machine10.

The filtering device20, the controlled and reversible bridge rectifier21, the brake chopper23, the reversible voltage inverter25and the dV/dT filter26are not discussed in detail here, since these elements are known to skilled technicians.

Reference is made toFIG. 4, which shows the power exchange fluxes during the test procedure of a star assembly and an associated voltage inverter. The test procedure is repeated for each group of triple phases or for a plurality of groups of triple phases in the star configuration of the electrical machine10and the associated channel(s) of the power converter11being tested.

The test procedure is shown, for example, in the assembly27, which comprises the triple-phase group in a star configuration15and the channel18of the power converter11.

The rotor of the electrical machine10is set in motion by the assembly28, which comprises the triple-phase groups in a star configuration13and14supplied by the channels16and17of the power converter11. The assembly27is initially supplied by the transformer12. The triple-phase groups in a star configuration13and14are called motor groups.

The number of triple-phase motor groups in a star configuration is chosen such that the total rated power output delivered by the stars is at least equal to the rated power of the tested assembly.

The electrical machine10is controlled in terms of its speed.

When the rotor of the electrical machine10reaches the connection speed, and after the synchronization of the assembly27, the assembly27being tested is controlled such that it operates in power generation mode.

The connection speed corresponds to the rotational speed from which the electrical machine and the power converter assembly would produce sufficient power to supply an electrical network if they were operating in generator mode. In the case of a wind turbine, for example, the connection speed is 3.7 rpm.

The assembly27controls the electrical machine10in terms of its torque.

The electrical power Pgengenerated by the assembly27is transferred to the motor assembly28. The motor powers Pmot1and Pmot2consumed by the assembly27are equal to the sum of the power Pgenand the power lost during the various energy conversion steps Ploss.

The transformer12compensates for the losses generated by the electrical machine10and the power converter11. The electrical network R now only provides the power lost during the energy conversion steps Ploss.

The dimensions of the transformer are reduced, for example for an electrical machine10with a rated power of 6 MW, i.e. a power of 2 MW per group of triple phases in a star configuration, if two groups of triple phases in a star configuration are motor groups. A transformer with a power of a few dozen KW is therefore sufficient to conduct the test procedure.

In an embodiment, only active power flows are exchanged between the transformer12, the multichannel three-phase power converter11and the synchronous multiphase and multichannel electrical machine10.

The resistive electromagnetic torque generated by the assembly27comprising a group of triple phases in a star configuration15and the channel18of the associated power converter11applied to the rotor of the electrical machine10is increased gradually. As a result, the rotational speed of the rotor decreases. The control system increases the motor power delivered by the assembly28until the rotational speed setpoint is reached. The resistive torque can thus be increased until the power generated by the resistive torque is equal to the motor power generated by the assembly28. The power generated by the assembly27is compared to the expected values in order to validate the operation of the assembly27.

This test procedure has the advantage of testing the power module over its entire range of use by using the acquisition, control and power chains of the module in its environment, such as in the case of a wind turbine, when the power module is mounted in the nacelle of the wind turbine. In an embodiment , the test device has an architecture that makes it possible to perform power exchanges within the power module without a mechanical interface5with another test module in rotation. The power modules11can thus be tested functionally (in terms of their control and power) prior to shipping the machine10.