MULTI-MOTOR INVERTER FOR A PLURALITY OF MOTORS AND DETECTION METHODS FOR DETECTING SHIFTS IN THE SPEEDS OF THE MOTORS

Abstract

The invention relates to a control system (1) comprising a multi-motor inverter (PWR) for the controlled parallel operation of a number of n EC motors (M1, . . . , Mn) whose respective rotor position is detected sensorlessly and controlled by the common inverter.

Claims

1. A control system (1) comprising a multi-motor inverter (PWR) for the controlled parallel operation of a number of n EC motors (M1, . . . , Mn), where n2, comprising a. a stabilization system comprising a stabilization controller (R.sub.S), b. a dq-current controller, to which at least the target current value I.sub.d,target is inputted as a controlled variable from the stabilization controller (R.sub.S) arranged on the input side in space vector representation, on the basis of which the dq-current controller determines the voltage control variable U.sub.d, c. wherein at least one or more current detection circuits are provided to measure the phase current of one or more of the n EC motors (M1, . . . , Mn) in order to detect current oscillations and/or oscillations on the basis of the detected information about the current and to regulate the multi-motor system into a stable state via the target current variable I.sub.d,target by means of the stabilization controller (R.sub.S).

2. The control system (1) according to claim 1, characterized in that a speed controller (RD) is provided on the input side of the current controller in order to provide at least the target speed.

3. The control system (1) according to claim 1, characterized in that the stabilization system has a transformer in order to determine the target current value I.sub.d,target from at least two detected phase currents (I.sub.M1,u, I.sub.M2,v, . . . ) and the rotor position by means of a Clarke-Park transformation.

4. The control system (1) according to claim 1, characterized in that the alternating component of the current signal is recorded in order to determine the oscillations and specified to the current controller, preferably by means of appropriate fundamental wave detection or filtering and amplification, as the setpoint I.sub.d,target in order to impart a greater torque to the lagging motor and a reduced torque to the leading motor in order to thereby reduce the determined oscillation.

5. A method for operating n EC motors, where n2, in parallel operation on a common multi-motor inverter (PWR) with a control system (1) according to claim 3, with at least the following steps: d. specifying a target rotation frequency by a fixed speed setpoint .sub.target, e. setting a target q-current I.sub.q_target based on the difference between speed setpoint .sub.target and the speed of the sensorless rotor position determination .sub.U, a voltage control variable U.sub.q being generated by the dq-current controller from the target q-current I.sub.q_target, f. detecting at least one, preferably a plurality of phase currents (I.sub.M1,u, I.sub.M2,v, . . . ) with a separate current detection device, the stabilization system determining the target current value I.sub.d,target by means of Clarke-Park transformation from at least two detected phase currents (I.sub.M1,u, I.sub.M2,v, . . . ) and the rotor position, g. determining the voltage control variable U.sub.d based on the d-target current value I.sub.d_target in order to transform them using Clarke-Park transformation and then to send them via a PWM modulator as switching commands to the multi-motor inverter (PWR) for the controlled parallel operation of the EC motors (M1, . . . , Mn).

6. A method for operating n EC motors, where n2, in parallel operation on a common multi-motor inverter (PWR) with a control system (1) according to claim 4, with at least the following steps: h. simultaneous or nearly simultaneous, rotor-position-dependent measurement of the phase currents at the multi-motor inverter (PWR) or at the motor(s) is carried out at certain mechanical and/or electrical angles of the estimated rotor position of the multi-motor system; i. determining whether there is oscillation of the motors in the multi-motor system by analyzing the current signals for their AC component, and if so, j. stabilizing the motors by issuing appropriate switching commands to the multi-motor inverter (PWR) or setting the output voltages to the motors in order to counteract or eliminate the oscillation.

7. The method according to claim 6, wherein in the event of a load jump during operation of the plurality of motors, an extracted oscillation frequency is used to compensate for the oscillation and to stabilize the system.

8. The method according to claim 1, wherein the current detection provides at least one measurement on the motor phase of a motor and, additionally, either a residual current measurement or a further current measurement on another motor.

9. The method according to claim 1, wherein the current detection is performed directly on the motors.

10. The method according to claim 1, wherein a shutdown can occur upon detection of a phase failure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a block diagram of a known method for controlling a multi-motor controller, but supplemented with a modified stabilization controller;

[0036] FIG. 2 is a block diagram of a stabilization controller for use in the multi-motor controller that has been modified according to the invention; and

[0037] FIG. 3 is a block diagram of an alternative stabilization controller for use with the multi-motor controller that has been modified according to the invention.

[0038] The invention will be explained in greater detail below on the basis of the embodiments with reference to FIGS. 1 to 3, with same reference symbols in the figures indicating same structural and/or functional features.

[0039] FIG. 1 shows a control system 1 comprising a multi-motor inverter PWR for the controlled parallel operation of a number of two EC motors M1 (motor 1), M2, (motor 2).

[0040] For this purpose, a detection device RLU is provided for determining at least the rotor position and speed of a fictitious motor at the inverter output using the previously measured phase currents or the residual current I.sub.u,v,w and the terminal voltage U.sub.u,v,w of the two EC motors. The detection device RLU is thus particularly designed to obtain the rotor position .sub.U, the residual current I.sub.uvw being used as an input variable and the terminal voltage U.sub.uvw also being used to determine the variables of rotor position .sub.U and speed .sub.U.

[0041] In both embodiments, a control device is provided downstream of the control and transformation device, to which the voltage variables U.sub.d, U.sub.q and current variables I.sub.d,q_actual outputted by the transformation device are fed in order to generate switching commands SZB for the multi-motor inverter PWR in order to operate the two motors.

[0042] The control and transformation device has a Clarke-Park transformer TP for transforming the rotor position .sub.U and residual current I.sub.uvw into a dq current value I.sub.d,q_actual in space vector representation for the control device.

[0043] The two embodiments can be represented equally by FIG. 1, since the difference lies in the stabilization controller R.sub.S (see FIGS. 2 and 3).

[0044] FIG. 2 shows a block diagram of a first embodiment of a stabilization system with a stabilization controller RS for use with the multi-motor controller PWR that has been modified according to the invention.

[0045] After the transformation of the input variables shown, including the phase currents used for the two motors M1, M2, these are fed to the fundamental wave detection F and further processed (using conventional mathematical algorithms and methods, which will therefore not be described in further detail). The stabilization controller R.sub.S makes the current variable I.sub.d_target available.

[0046] FIG. 3 shows an alternative stabilization solution which determines the delta between the measured motor phases and, on that basis, determines the target value of the d-current. The sample & hold blocks sample the current values and then calculate the difference. This difference is then passed directly to the stabilization controller R.sub.S. In addition, the oscillation frequency of the motors is filtered out by the fundamental wave detection (TP) and made available to the stabilization controller R.sub.S.

[0047] Here too, the stabilization controller R.sub.S makes the current variable I.sub.d_target available. However, current sampling takes place here. The processing is shown in the block diagram.

[0048] In the variant currently being presented, the number of observers required has been reduced to just one observer. This is possible because only the information on the vibration of the mechanical subcomponents needs to be known in order to stabilize the system. The implementation now being presented determines this information directly from the current without requiring multiple measuring points and observers.

[0049] In order to implement the first design variant, only measuring points on the residual current and on a total of two different phases of the two motors are required. An observer for the inverter KOS can be implemented based on the residual current measurement. Based on the other two measurements in combination with the residual current measurement, the vibration component of the motors can be determined on the basis of a simple Clarke-Park transformation. This serves as basic information for the setpoint of the d-current controller.

[0050] The second design variant utilizes the difference in current between two identical motor phases to determine the oscillation term. This means that no Clarke-Park transformation is necessary, but a current measurement in two identical motor phases is required. Please note that measurements do not necessarily have to be taken in the same phases. In the case of different phases, however, mathematical processing of the data (e.g., buffering, synchronization) must be used to ensure that, for example, the max./min. or the signals of a phase offset by 60/120 are always compared.

[0051] The invention is not limited in its execution to the abovementioned preferred exemplary embodiments. Rather, a number of variants are conceivable which make use of the illustrated solution even in the form of fundamentally different embodiments.