JP2005535276A - Generator / motor system and method of operating the system - Google Patents

Abstract

The present invention relates to a generator / motor system and a method for operating the system. This system and method reduces the flow in the filter. The generator / motor system includes an induction motor (DM) in addition to a pulse control converter and filter capacitors (C1, C2). In the embodiment of the present invention, the pulse control converter is constituted by two identical pulse control converters (PWR1, PWR2) each having half of the rated power. During operation, according to the required rotational speed, the system is connected between a star circuit in which only the first pulse controlled rectifier is in operation and a single phase circuit in which both pulse controlled rectifiers are in operation. Rectify. Even when only one of the pulse-controlled rectifiers is used, the induction motor approximately doubles the number of stator turns in order to obtain the same degree of torque as in the prior art.

Description

  The invention relates to a generator / motor system as described in the preamble of claim 1 and to a method for operating this generator / motor system.

  At present, in an automobile having an internal combustion engine, an attempt is made to form a single electric machine by combining a starter and a generator.

  However, during these attempts, there is a problem that two completely contradictory requirements must be met even in the general design phase.

  On the other hand, in order to start and accelerate the internal combustion engine, it is necessary to give a very high rotational torque. This torque depends on the size of the engine or the number of cylinders of the internal combustion engine and may be greater than 240 Nm. Furthermore, the electric motor must have the necessary torque to accelerate the internal combustion engine to the starting speed.

  On the other hand, after the internal combustion engine has been successfully started, the electric motor, which is designed as a starter / generator, should be operated primarily as a generator in order to power the car's in-vehicle power system. In this connection, a constant power output must be maintained with as high an efficiency as possible over a very wide range of rotational speeds predetermined by the internal combustion engine, ie in the range of 600 to 6000 rpm. There is.

  Both requirements are met by a standard drive consisting of a three-phase rotating field machine 30 and a voltage application pulse control inverter (PRW) 31 in a rotating field bridge circuit with a filter capacitor C, as shown in FIG. Is economically impossible to satisfy.

  In this context, a problem that needs to be overcome is the miniaturization and complete integration of power electronics that are indispensable. The required filter capacitor is an obstacle to integration. In particular, for a relatively low in-vehicle power system voltage, i.e. 42V, a phase current of approximately 1200 A in an asynchronous machine is currently under consideration to generate the required starting torque. In this connection, for example, an intermediate circuit capacitor C, as shown in FIG. 3a, which shows the design of a conventional drive system having a rotating field machine 30, a pulse control inverter 31, and an intermediate circuit capacitor C, Are expected, and these dimensions prevent integration.

  Also, measurements in the absorption space immediately reveal that no compromise can be made here. Filtering is necessary to meet stringent EMC requirements in automobiles. It is necessary to reduce the machine current, and thus the filter current, while maintaining other characteristics of the drive as well.

  The configuration of a drive system having a rotating magnetic field machine and a pulse control inverter is as described below with reference to FIG.

  FIG. 3b shows the conventional rotational speed / torque characteristics. The solid line in FIG. 3b shows what can be achieved with the specific configuration of the rotating field machine and the power of the associated pulse-controlled inverter.

  For example, in the case of increasing the starting torque while maintaining the pulse power inverter's (apparent) power while maintaining the standard pulse control inverter form, ie one pulse control inverter in a 6 pulse bridge circuit, rotating magnetic field The machine windings must be changed accordingly. In the simplest case, thin the wire and increase the number of turns. As a result, the characteristic curve indicated by the broken line in FIG. 3b is obtained. This measure can increase the starting torque without changing the power of the pulse-controlled inverter, but it is clear that this can only be achieved at the expense of generator power at relatively high rotational speeds. . The shape point drops accordingly. Due to the relatively high number of turns, the rotating field machine can reach the depletion mode of its magnetic field, ie the modulation limit of the pulse-controlled inverter, at an early stage and then output less power during the generator mode.

  In particular, the cost of pulse controlled inverters also plays a decisive role in automotive applications, specifically in starter / generator devices. The cost of a pulse-controlled inverter is today determined primarily by the current intensity that must be rectified in the form of the pulse-controlled inverter, rather than mainly by the current intensity that the pulse-controlled inverter must bear. This characteristic variable determines the cost of the filter that must be specially prepared in the automotive industry, especially in the sensitive field of EMC. Furthermore, the filter hinders miniaturization and has a problem of reliability particularly at high temperatures. For this reason, in particular, an attempt to configure the power electronics in the drive circuit as efficiently as possible is necessary to reduce the current to be rectified.

  Non-Patent Document 1 describes a rotating field machine having switchable poles, two winding systems and two individual pulse-controlled inverters. However, with certain combinations of these winding systems, the optimum winding factor cannot be obtained, and as a result, the rotating field machine can provide the maximum possible pulse controlled inverter current for a pulse controlled inverter of a given outer dimension. It cannot be converted into torque in an optimal form. Dynamic behavior when the rotating field machine is switched cannot occur without the occurrence of a corresponding torque transient effect. This creates significant problems in the drive phase and can adversely affect user comfort. The long-known Dahlander circuit has a similar problem.

  In US Pat. No. 6,057,049, a so-called diode-clamped dual / three-level converter, which is known per se, is operated in such a way that a parallel / series switching of two winding systems takes place by means of a novel pulse method. At the same time, the pole number of the rotating field machine can be maintained during switching. Since the switching is done by different presettings of the voltage vector, this switching takes place with little noise and no torque transient effects. Furthermore, the winding system can be “pivoted” within their phase, thus further reducing the filtered intermediate circuit current. While this system is the most technologically advanced, it is extremely complex and expensive.

  For this reason, a system having a power converter for power supply and a mechanical power converter, which can be called a genuine converter, can achieve a high degree of flexibility and can be most suitable. Such a genuine converter is described in Non-Patent Document 2, for example. In said document, a significant reduction in pulsating current can be achieved by synchronizing the pulse pattern. If the pulsating current can be reduced, the efficiency of the system can be increased at the same time. This is because the relatively large amount of energy in the capacitor in the power converter for power supply is conventionally converted to dissipated energy.

German Patent Application Publication No. 199 31 010A1 M.M. M. Osama, T. A. TA Lipo: “Modeling and analysis of a wide-range of speed-range induction motor based on electrical pole,” IEEE Transactions on Industry Application (September / October 1997, Vol. 33, No. 5) L. L. Sack: “Reduction of loss in the DC-link capacitor of two-stage self-commutated converters”, Proceedings of EPE 1999, Rhone. Switzerland

  For this reason, the object of the present invention is to provide a generator / motor system and a motor / generator which can significantly reduce the current to be rectified in a pulse-controlled inverter, simply and cost-effectively. It is to configure a method for operating the system.

  This object is achieved according to the invention by a generator / motor system having the features of claim 1 and a method for operating this generator / motor system having the features of claim 8. .

  By dividing the pulse-controlled inverter into two identical pulse-controlled inverters each having half of the rated power, the generator / motor system is operated in both a star circuit and a single-phase circuit, resulting in a filter It is particularly advantageous to be able to obtain a uniform current load over a wide range. As a result, in the star circuit, only about half of the conventional phase current needs to be rectified, so both peak current during start-up and setting the filter to this peak load is avoided.

  This and other objects, advantages and features of the present invention will become apparent from the following description of preferred exemplary embodiments, taken in conjunction with the drawings.

  FIG. 1 shows a circuit diagram of a generator / motor system according to the present invention. The generator / motor system according to the invention comprises a three-phase rotating field machine DM, the individual generator phase windings or machine phases a, b, and c of this rotating field machine DM having first and second pulses. The control inverters PWR1 and PWR2 are connected. The first and second pulse control inverters PWR1 and PWR2 have the same design and the same rated power. Each of the pulse control inverters PWR1 and PWR2 is six electronic branch switches S1 to S6, which are formed of, for example, MOS transistors or IGBTs (Integrated Gate Bipolar Transistors) and arranged symmetrically and in series to form three branch pairs. Electronic branch switches S1 to S6, and filter capacitors C1 and C2 connected in parallel with the pulse control inverter. As a result of the division into the first and second pulse control inverters PWR1 and PWR2, a significantly smaller capacitor can be selected for these filter capacitors C1 and C2, which has a favorable effect on the overall size and power loss.

  Between the two pulse control inverters PWR1 and PWR2, an electronic switch S7 is formed in parallel with the mechanical phases a, b and c, and via this electronic switch S7, the positive bus bar of the first pulse control inverter PWR1 is It can be connected to the positive bus bar of the second pulse control inverter PWR2 and can then be disconnected. This electronic switch S7 is not required but can be bidirectional. A power MOS transistor having a parasitic reverse bias diode can be used for switch S7 as a non-bidirectional switch.

  Hereinafter, a method of operating a generator / motor system according to the present invention will be described with reference to FIG.

  The generator / motor system according to the present invention is capable of two different modes of operation.

1. Operation in a star circuit In the star circuit, branch switches S1, S2 and S3 are closed, branch switches S4, S5 and S6 and electronic switch S7 are opened. Thus, the pulse control inverter PWR1 forms a star point for the three machine phases a, b and c shown. In the voltage application pulse control inverters PWR1 and PWR2 in the 6-pulse bridge circuit, the potential of the star point is abrupt between 1/3 and 2/3 of the voltage of the intermediate circuit as a function of the switched-on voltage vector. Go down. If these switches are made of MOS, the reverse biased diode need not be activated.

  Compared to the prior art, only half of the pulse control inverter, specifically, the pulse control inverter PWR1, is used to conduct the current. As a compensation for this, the rotating field machine DM has a stator with a large number of turns. Is provided. The flux linkage that determines the torque is thus maintained. As a result, the characteristic curve branch 1 in FIG. 2 is obtained. An equivalently large torque is introduced, but only half of the circuit, specifically the pulse-controlled inverter PWR1, is involved in converting energy, so that only about half of the original phase current is rectified. If the same ripple is allowed with respect to the voltage of the intermediate circuit, the consumption of the filter will be almost halved.

2. Operation with a single-phase circuit ("V-connection") Of course, the number of turns of the stator of the rotating field machine DM is almost doubled, so the modulation limit of the pulse control inverter PWR1 is compared with the standard solution Is already half the rotational speed. Here, the star point formed by the pulse control inverter PWR1 is eliminated and the generator / motor system is operated with a single phase circuit. For this purpose, the electronic switch 7 is closed and the pulse control inverter PWR1 is connected so that each phase receives its own half-bridge, ie the branch switches of the first and second pulse control inverters PWR1 and PWR2 are Operates as all closed. By reducing the terminal voltage by approximately half, the modulation limit of the generator / motor system according to the present invention is further shifted to the higher rotational speed side. The same design point is obtained. Thus, the characteristic curve branch 2 of the generator / motor characteristic curve according to the invention substantially overlaps the characteristic curve of one standard circuit.

  Consequently, the object is achieved by using the switchable generator / motor system according to the invention. By switching the motor / generator system, the current load of the filter is made uniform over a wide range. Accordingly, setting of the filter in accordance with the peak current during start-up and this peak load is avoided.

  Switching from one operating mode to another is performed according to the invention so as to be optimized with respect to efficiency. Only the maximum characteristics are shown in FIG. In the case of partial loads, the control unit, which can be implemented as a software module, determines the switching point depending on the exact characteristic diagram so that it is optimized for efficiency. Since the switching is performed without causing an impact, it is theoretically possible to perform the switching as frequently as possible.

  Furthermore, an advantage of using the circuit according to the invention is that a part of the quiescent current of the capacitor can be cut off using the switch S7.

  In addition, even if a fault (e.g., a short circuit or break) occurs in an electronic switch in the generator / motor system, the single phase circuit operates with an asynchronous machine, in this case somewhat limited operation. Can increase reliability. As a result, it is always possible to form a rotating magnetic field. This is not possible with a standard three-phase bridge circuit.

  Further, the reduction in pulsating current not only reduces the overall size of the filter, but also reduces the consumption of the filter, thus increasing efficiency.

1 is a circuit diagram of a generator / motor system according to the present invention. FIG. The torque / rotational speed characteristics of a conventional generator / motor system and the corresponding torque / rotational speed characteristics of the generator / motor system according to the present invention. The figure which shows the structure of the conventional drive system. The figure which shows the conventional rotational speed / torque characteristic.

Claims (9)

In an in-vehicle power system generator and an electric generator / motor system as a starter applied to mobile units, automobiles, ships, etc.
A rotating magnetic field machine (DM) having a generator three-phase winding (a, b, c), and a power generating three-phase winding (a, b, an electrical generator / motor system having a pulse controlled inverter connected to c),
The pulse control inverter is divided into first and second pulse control inverters (PWR1, PWR2) that are the same and have half the maximum power, and the first and second pulse control inverters (PWR1, PWR2) are respectively Each of the three branch pairs (S1, S4; S2, S5; S3, S6) has three branch pairs (S1, S4; S2, S5; S3, S6). Consisting of at least two symmetrically arranged electronic branch switches (S1 to S6) connected to the relevant windings of the line (a, b, c) and arranged in series in the same direction, said branch pair ( S1, S4; S2, S5; S3, S6) are connected to a DC voltage source via the branch switches (S1 to S6), and the generator phase windings (a, b, c) are connected to the DC voltage. Source pole and said Connected between the center points of the successive branch pairs (S1, S4; S2, S5; S3, S6), and in any case, the filter capacitors (C1, C2) are connected to the first and second pulse control inverters. (PWR1, PWR2) are connected in parallel to the branch pair (S1, S4; S2, S5; S3, S6), and an electronic switch (S7) includes the first pulse control inverter (PWR1) and the second pulse control. Formed by a positive bus bar that connects an inverter (PWR2) to the positive electrode of the DC voltage source, and via the electronic switch (7), the positive bus bars of the pulse control inverters (PWR1, PWR2) are connected to or disconnected from each other. An electrical generator / motor system characterized in that it is obtained.   The electrical generator / motor system of claim 1, wherein the electronic switch (S7) is unidirectional.   2. The electrical generator / motor system according to claim 1, wherein the electronic switch (S7) is a power MOS transistor having a parasitic reverse bias diode.   2. The electric generator / motor system according to claim 1, wherein the electronic switch (S7) is a bidirectional switch.   The electric generator / motor system according to any one of claims 1 to 4, wherein the branch switches (S1 to S6) are power MOS transistors having parasitic reverse bias diodes.   When only one pulse control inverter (PWR2) is connected in the circuit, the rotating magnetic field machine (DM) has all of the pulse control inverters, that is, the first and second pulse control inverters (PWR1, PWR2). However, the number of turns of the stator is increased so that the flux linkage corresponding to the flux linkage when connected in the circuit can be generated without increasing the number of turns of the stator. The electric generator / motor system according to any one of claims 1 to 5.   A control unit is further provided, characterized in that the control unit shifts the switching point depending on the characteristic diagram from the star circuit operation mode to a single-phase circuit so as to be optimized with respect to efficiency at partial loads. The electric generator / motor system according to any one of claims 1 to 6. A method for operating a generator / motor system according to any one of the preceding claims,
The branch switch (S1 to S3) disposed on the positive electrode side of the DC voltage source of the first pulse control inverter (PWR1) is closed and maintained, and is disposed on the negative electrode side of the DC voltage source. The generator / motor system by opening and maintaining both the branch switches (S4 to S6) and the electronic switch (S7) and all the branch switches of the second pulse control inverter (PWR2). Operating with a star circuit,
Detecting a rotational speed of the rotating magnetic field machine (DM) and determining a switching point depending on a characteristic diagram;
At the determined switching point, the control unit is used to close the electronic switch S7, the first pulse control inverter, each generator phase winding (a, b, c) is its own H By operating the generator / motor system to receive a bridge, i.e., all of the branch switches of the first and second pulse control inverters (PWR1, PWR2) are closed. Switching to operation in a phase circuit. 9. The method of claim 8, wherein the switch point is determined to be optimal with respect to efficiency.

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