CN1835351A - Synchrous dynamo exciter of rotatable power electronic converter - Google Patents

Abstract

The excitation unit includes rotating transformer, electronic power and control circuit, and rotation diode rectification circuit. The electronic power and control circuit connected to primary winding and primary magnetic core of the rotating transformer is fixed on end plate of stator on synchro motor together. Secondary winding and secondary magnetic core of the rotating transformer are connected to the rotation diode rectification circuit. The rotation diode rectification circuit outputs exciting current to excitation coil of rotor in synchro motor. Secondary winding and secondary magnetic core and rotation diode rectification circuit are fixed on the rotor. There is air gap between primary magnetic core and secondary magnetic core, which are rotated relatively. The disclosed excitation unit of rotatable electronic converter supplies stable adjustable dc excitation for synchro motor, promoting competitive power of speed control system of synchro motor.

Description

Rotatable Power Electronic Converter Synchronous Motor Excitation Device

1. Technical field

The invention relates to an excitation device of a synchronous motor, in particular to a device for exciting a synchronous motor by using a power electronic converter.

2. Background technology

Synchronous motor power generation operation (that is, synchronous generator) is the first choice for most power generation occasions. It is widely used from large generators with 100 megawatts to rectifier generators with more than 100 watts. In aviation, almost all modern aircraft power generators use synchronous generators. The excitation method of ordinary synchronous generators is: the winding is installed on the rotating rotor, the collector ring is installed on the rotating shaft, and the excitation DC is introduced through the brush. Because there is no back electromotive force in the excitation winding, the excitation capacity is small; compared with , AC excited motors (such as induction motors) require a larger excitation capacity. However, the existence of the brush slip ring will reduce the operational reliability of the motor and increase the workload of maintenance.

In order to solve the problem of low reliability of the excitation circuit of the synchronous motor, people have devoted a lot of effort over the years to find a brushless excitation scheme for the synchronous motor. These brushless excitation schemes mainly include: (1) A permanent magnet motor that realizes a brushless excitation, and a permanent magnet material is installed on the rotor to provide the excitation magnetic potential required by the motor, thereby realizing brushless. However, the permanent magnet motor has the following disadvantages: ① the demagnetization protection cannot be realized when the power generation operation fails; ② the output voltage cannot be adjusted by adjusting the excitation method, and other measures must be taken to stabilize the voltage, so it cannot be widely used; ③ permanent magnet motor Because of its high efficiency and energy-saving features, it is widely used in electric vehicles, energy-saving home appliances, etc.; it is often used as a servo drive in industrial applications. From zero speed to base speed, permanent magnet brushless servo motors can work well, but In the range of constant power speed regulation with weak magnetic field above the base frequency, its performance is still unsatisfactory. Due to the large reluctance of the magnetic circuit of ordinary surface-mounted permanent magnet motors, weakening the magnetic field requires the stator to provide a large demagnetization current , occupies the effective capacity of the winding; even if the specially designed permanent magnet motor can successfully achieve a wide range of field-weakening speed-up, if the inverter is out of control or power-off, the permanent magnet motor will output high voltage when the speed is too high , may damage the inverter or cause other hazards; ④Rare earth permanent magnet materials are more expensive, so the manufacturing cost of permanent magnet motors is higher; (2) A brushless synchronous generator using a rotating rectifier, this generator actually It uses a rotating armature generator as the exciter of the main generator. The output of the exciter provides DC excitation for the main generator through a three-phase rotating rectifier, eliminating the brush slip ring and greatly improving the reliability. However, this This rotary rectifier brushless alternator has several obvious disadvantages: ① the exciter part is increased, the axial space is increased, and the power density is reduced; ② the output of the voltage regulator needs to pass through the excitation winding of the exciter, the excitation motor Only the pivot winding and rotating rectifier can work on the excitation winding of the main generator. The transformation process is complicated, which greatly affects the dynamic performance of the system; Output or insufficient output; (3) T.F.Chen proposed a brushless, exciterless synchronous generator structure in 1997 (see Chan, T.F; Lie-Tong Yan's "Brushless and Exciterless Alternator Performance Analysis ", contained in "IEEE Energy Conversion" Volume 12, No.1, March 1997 Edition, pages 32-37), the stator winding adopts two sets of parallel three-phase windings (split by pole phase group), in The two sets of center points are connected to the adjustable DC power supply, forming a DC current in the two sets of windings, and forming a static DC magnetic field between the air gaps; the rotor winding cuts this magnetic field to form an induced potential, and the rotor winding coil is short-circuited by a diode, then the rotor winding A DC current in one direction flows through the center, and a rotating excitation magnetic field is formed, and a three-phase voltage is output in the armature winding. Obviously, because the rotor excitation current of this motor is intermittent, the output waveform of the generator is poor, and the utilization rate of the iron core is reduced. It is also not suitable for motor speed regulation operation; (4) Fukuo Shibata proposed a novel scheme of brushless and non-exciter (see Shibata, F.; Naoe, N "Brushless and non-exciter self-excitation synchronous Generator characteristics", contained in "Proceedings of the 1990 IEEE Industrial Application Society Annual Conference", p. 293-300, volume 1.1, October 1990 edition), two sets of three-phase stator windings with 6 terminals connected to the ws of the transformer 6 terminals, the center tap is the voltage output of the three-phase winding, the excitation current and the load current flow through the winding at the same time, the excitation current and the load current circuit are different. The number of poles of the formed winding is 2 times or 1/2 relationship; the DC excitation current and the induced AC current flow through the rotor coil at the same time, and the number of poles formed by the two currents of induction and excitation is 2 or 1/2 relationship, JK The magnetic field currents corresponding to different numbers of poles flow through the terminal and M1M2 terminals respectively. The output waveform of this form of brushless generator is improved, but the disadvantage is that the transformer is added, and the volume and weight increase; (5) Sakutaro Nonaka proposed a A brushless scheme for synchronous motors using power electronics and its control technology (see Nonaka, S.; Kawaguchi, T. "A New Type of Variable-speed Alternator System Using Brushless Self-exciting Synchronous Generators" , in "Proceedings of the 1990 IEEE Industrial Application Society Annual Meeting", pp. 691-696, Volume 1.1, October 1990 Edition; Nonaka, S.; Kawaguchi, T. "Brushless Self-exciting Three-phase Synchronous Motor Excitation Scheme", contained in "IEEE Industrial Application Magazine", Volume 28, No.6, Page 1322-1329, 1992 Edition; Nonaka, S.; Kawaguchi, T. "A new type of brushless self-excitation Type synchronous generator variable speed AC power generation system", contained in "IEEE Industrial Applications Magazine", Vol. A new type of brushless synchronous generator system with a good combination of power electronic devices. The magnetic field used to generate excitation is superimposed in the rotating magnetic field of the stator. The magnetic field is generated by the converter according to a suitable modulation strategy, so that an induced potential is generated in the rotor winding , due to the rectification effect of the diode, the required unidirectional DC excitation current is generated, but obviously the output waveform of the generator contains a large number of harmonics, which cannot be directly used; (6) Jun Oyama proposed a rotor for the brushless synchronous motor with AC excitation Directional control scheme (see Oyama, J.; Higuchi, T., "Characteristics of AC Excited Brushless Synchronous Motors Under Vector Control", in Proceedings of the 19th Annual Meeting of IEEE Power Electronics Experts Meeting, Vol. 1.1 , pp. 423-430, 1988 edition), this scheme does not require an exciter, the rotor excitation winding is a single-phase short-circuit winding, and the three-phase AC current supplied by the inverter to the stator winding forms a rotating pulse vibration in the air gap of the motor magnetic field. The excitation current component and torque component are determined by detecting the position of the rotor. The pulsating rotating magnetic field formed by the torque component is located on the d-axis, and the alternating excitation component is located on the q-axis to ensure a constant direction of torque. Obviously, the torque is a large pulsation Yes, resulting in the application of this scheme is limited.

In summary, these brushless and exciterless synchronous motor solutions have the following defects: (1) Additional windings or additional devices are added, which increases the complexity of the motor structure, resulting in an increase in the volume and weight of the motor and a decrease in power density ; (2) The excitation current is not constant; (3) There is no excitation at zero speed and low speed; (4) The output voltage waveform deviates from sinusoidal; (5) The excitation adjustment is inconvenient; (6) Torque ripple; (7) The efficiency is low.

3. Contents of the invention

1. Purpose of the invention: The purpose of the invention is to provide a synchronous motor excitation device for a power electronic converter with stable excitation current and small volume for the operation of a synchronous motor.

2. Technical solution: In order to achieve the purpose of the above invention, the rotatable power electronic converter synchronous motor excitation device of the present invention includes a rotary transformer, a power electronic power and control circuit and a rotary diode rectifier circuit, wherein the power electronic power and control circuit and the rotary The primary winding and primary magnetic core of the transformer are connected and fixed together on the stator end cover of the synchronous motor; the secondary winding and secondary magnetic core of the resolver are connected to the rotating diode rectifier circuit, and the rotating diode rectifying circuit excites the rotor of the synchronous motor The coil outputs excitation current, and the secondary winding, secondary magnetic core and rotating diode rectifier circuit are fixed on the rotor together; there is an air gap between the primary magnetic core and the secondary magnetic core, and they rotate relatively.

In this technical solution, the rotary transformer can be divided into dynamic and static parts. The static part is the primary winding and the primary magnetic core, which are installed together with the stator of the synchronous motor. The moving part is the secondary winding and the secondary magnetic core. The rotor is installed together and rotates with the rotor; the dynamic and static parts are separated by an air gap. Ensure that the area of the magnetic circuit coupling surface of the dynamic and static parts remains unchanged during relative rotation, does not affect the coupling magnetic flux of the transformer, and can still maintain the transmission of magnetic field energy, and can transmit electromagnetic energy between relatively rotating magnetic cores to achieve a rotatable state Next power transfer transformation. Common topologies of existing isolated DC-DC converters, such as flyback, forward, push-pull, bridge, etc., can all be adopted for the rotatable power electronic converter of the present invention. Regardless of the topology, to design a rotatable power electronic converter, the resolver needs to be designed into two parts, dynamic and static, and inserted into the air gap to form a rotatable transformer. In practical application, the transmitted excitation power adopts the flyback and forward modes when the excitation power is tens of watts, and the bridge conversion form is used for the excitation conversion power above hundreds of watts. When the actual synchronous motor is running, whether it is electric or power generation, it needs to be adjusted according to the operating parameters such as load size and speed to achieve high operating performance. The circuit of the rotatable power electronic converter of the present invention is actually a synchronous motor excitation regulation circuit, which adjusts the duty cycle of the switching conversion circuit according to the excitation current control command (excitation current given value, given by other control units), and changes the output excitation current size.

In the present invention, the rotary transformer can adopt a high-frequency pulse transformer, and through magnetic coupling, the electric energy of the primary side and the secondary side can be converted and transferred to realize input and output isolation; the primary magnetic core and secondary magnetic core of the rotary transformer are designed to be ring-shaped, and surround the synchronous The shaft of the motor transmits electrical energy through electromagnetic coupling.

The working principle of the present invention is as follows: input direct current for power supply, through the power electronic power circuit and control circuit available in the prior art, obtain a voltage pulse with variable duty ratio, apply it to the primary side of the resolver, and pass through the electromagnetic pulse of the resolver Coupling, the non-contact inductive transfer of energy from the stationary part of the transducer to the rotating part of the transducer. Through the rotating diode rectification circuit available in the prior art, a stable direct current is generated to supply power to the excitation winding of the motor. After the motor generates electricity, it takes samples from the AC output and feeds back to the power electronic power circuit and control circuit for control. By adjusting the duty cycle of the power switch, the purpose of adjusting the excitation current of the motor is achieved.

3. Beneficial effects: the advantage of the present invention is that it can provide a stable and adjustable DC excitation for the synchronous motor in the range from zero speed to any operating speed, which can greatly improve the competitiveness of the synchronous motor speed control system, especially when the power is several In the speed control system above kilowatts, compared with the expensive permanent magnet motor, the synchronous motor adopting the new brushless excitation method proposed by the application will be more competitive; the generator adopting the new brushless excitation method of the application invention will be Effectively improving the quality of the power supply of my country's new aircraft and chariots has great practical significance for national defense construction, and has great application and promotion value in civilian power generation and servo drive.

4. Description of drawings

Fig. 1 is a working principle diagram of the present invention;

Fig. 2 is a schematic diagram of the radial air gap structure of the rotary transformer of the present invention;

Fig. 3 is a schematic diagram of the axial air gap structure of the rotary transformer of the present invention;

Figure 4 is a schematic diagram of the position of the rotary high-frequency transformer in the motor.

5. Specific implementation

The present invention will be further described below in conjunction with accompanying drawing:

As shown in the figure, the rotatable power electronic converter synchronous motor excitation device includes a rotary high-frequency transformer 1, a power electronic power and control circuit 2 and a rotary diode rectifier circuit 3, wherein the power electronic power and control circuit 2 and the rotary transformer 1 The primary winding 7 and the primary magnetic core 8 are connected and fixed together on the stator end cover of the synchronous motor. The secondary winding 9 of the rotary transformer 1, the rotary diode rectifier circuit 3 and the rotor excitation winding 4 form a circuit. The secondary magnetic core 10 and The rotary diode rectifier circuit 3 is fixed on the rotor of the synchronous motor; the rotary transformer 1 adopts a high-frequency pulse transformer; the primary magnetic core 8 and the secondary magnetic core 10 of the high-frequency pulse transformer are designed as rings, surrounding the shaft of the synchronous motor. When the device is working, the DC power 5 is input to supply power, through the power electronic power circuit and the control circuit 2, a voltage pulse with a variable duty ratio is obtained, which is applied to the primary side of the resolver 1, and the energy is transferred from the resolver through the electromagnetic coupling of the resolver. The non-contact induction of the static part of the converter is transmitted to the rotating part of the converter; through the rectification circuit 3, a stable DC current is generated to supply power to the excitation winding 4 of the motor; after the motor generates electricity, it is sampled from the AC output and fed back to the power electronics The power circuit and the control circuit 2 implement control; by adjusting the duty cycle of the power switch, the purpose of adjusting the excitation current of the motor is achieved.

As shown in Figure 2, when the air gap of the resolver 1 is radial, its magnetic core is an annular shape similar to a pot, and the transformer winding is placed in the middle, the secondary magnetic core 10 is fixed on the rotating shaft 6, and the stationary primary The magnetic core 8 is fixed on the stator end cover, and its center hole should make the rotating shaft 6 protrude freely;

As shown in Figure 3, when the air gap of the resolver 1 is in the axial direction, its magnetic core is a cylindrical annular structure protruding on both sides, the secondary magnetic core 10 is installed on the rotating shaft 6 of the motor, and the stationary primary magnetic core 8 is installed on the on the motor frame.

As shown in Figure 4, the primary winding 7 of the resolver is embedded in the primary magnetic core 8 and fixed with the stator end cover of the synchronous motor, and the secondary winding 9 is embedded in the secondary magnetic core 10 and fixed together with the rotary diode rectifier circuit 3 On the rotor 11, it rotates with the rotor 11; when designing and assembling, it is necessary to ensure the length of the minimum required air gap where the dynamic and static parts do not rub against each other, and to ensure that the area of the magnetic circuit coupling surface remains unchanged during relative rotation, without affecting The coupled magnetic flux of the transformer.

Claims (3)

1, a kind of synchrous dynamo exciter of rotatable power electronic converter, it is characterized in that this device comprises resolver (1), electric and electronic power and control circuit (2) and rotating diode rectification circuit (3), wherein, the elementary winding (7) of electric and electronic power and control circuit (2) and resolver (1), elementary magnetic core (8) connects the stator terminal that also together is fixed on synchronous machine and covers, the secondary winding (9) of resolver (1), secondary magnetic core (10) is connected with rotating diode rectification circuit (3), rotating diode rectification circuit (3) is to rotor excitation coil (4) the output exciting current of synchronous machine, secondary winding (9), secondary magnetic core (10) and rotating diode rectification circuit (3) together are fixed on the rotor; Air gap separation and relative rotation are arranged between elementary magnetic core (8) and the secondary magnetic core (10).

2, synchrous dynamo exciter of rotatable power electronic converter as claimed in claim 1 is characterized in that resolver (1) is a high-frequency pulse transformer.

3, synchrous dynamo exciter of rotatable power electronic converter as claimed in claim 1 is characterized in that, the elementary magnetic core (8) of resolver (1) and secondary magnetic core (10) are annular, around the rotating shaft of synchronous machine.

Images