RU2484576C1 - Stabilised electric machine power supply source - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: device contains a synchronous generator with stator and excitation windings, a rectifier connected to the stator winding, a voltage sensor connected to the rectifier output pins, a voltage setting device, a control circuit and a device for rigid negative feedback; included in the control circuit are additional connected element: a comparison unit, a regulating device, a key element, a reverse diode; additionally introduced are a sensor of excitation current in the excitation winding circuit, a device for isodromic (flexible) negative feedback; functionally. The device is intended for transmission of excitation current oscillations as may occur from the excitation current sensor output to the third input of the comparison unit without phase shift.

EFFECT: damping excitation current self-oscillations and fast quench of the generator output voltage LF modulation.

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Description

Technical field

The invention relates to electrical engineering and can be used to create stabilized electrical machine power sources based on synchronous generators.

When using pulsed and continuous systems to control the voltage of a synchronous generator (operating in a wide range of changes in speed and load - from idle to nominal value), the problem of ensuring their stability as automatic control systems arises. To improve the quality of the generated electricity, a reduction (exclusion) of low-frequency modulation of the voltage of the synchronous generator is required.

A known source of stabilized power supply based on a synchronous generator (Meshchaninov P.A. Automation of ship electric power systems. L .: Sudostroenie, 1970, p. 63, Fig. 3.5), in which the excitation current of the generator is generated by the automatic excitation control unit according to the generator voltage signals and load current.

A variation of such a power source is known (“Electrical equipment of armored vehicles.” Military Publishing House of the USSR Ministry of Defense, 1971, p. 49, Fig. 2.4), in which a transistor operating in the key mode and used as a regulating element included in the generator field winding circuit controlled by a control unit connected by an input to the output terminals of the generator and generating a signal as a function of the voltage deviation of the generator.

The disadvantage of both analogues is the lack of stability of the output voltage of the synchronous generator when changing the speed and load in a wide range of values.

The closest technical solution adopted for the prototype is described in the book "Theory, design and calculation of automotive electrical equipment." M .: Engineering, 1979, pp. 165-166, Fig. 102. A power supply based on a synchronous generator with stator and field windings contains: an unregulated rectifier connected to the stator winding, a field circuit power supply circuit, a voltage regulator based on a zener diode, a two-input comparison unit, a regulating device made on a transistor, a key element made according to a composite circuit a transistor, a voltage sensor in the form of a resistive divider connected to the output of the rectifier. A reverse diode is included in the collector circuit of one of the transistors of the composite transistor, and an excitation winding is included in the collector circuit of the second transistor. The device is designed to stabilize the voltage of a synchronous generator using a pulse controller when changing the speed of the generator and its load. The presence of rigid collector feedback accelerates the process of switching transistors.

The disadvantage of the prototype is that with certain combinations of speed and load of the synchronous generator (especially for those that use longitudinal damper windings), a partial loss of stability of the voltage stabilization system may occur (due to the appearance of secondary harmonics from frequency mismatch), which leads to low-frequency modulation of the output voltage of the generator and, as a consequence, to a deterioration in the quality of the generated electricity.

The aim of the invention is to create, on the basis of a synchronous generator, a stabilized electrical machine power source, which will be a stable automatic control system that generates high-quality electric energy by suppressing the emerging low-frequency modulation of the output voltage of the synchronous generator during its operation in a wide range of rotation speed and load magnitude.

Disclosure of invention

The essence of the invention consists in introducing into the electrical circuit of an electric machine power supply a number of essential features that provide stabilization of the output voltage for any disturbances that occur when the speed and load are changed. These include: a generator excitation current sensor and an isodromic negative feedback device (in brief, IOOS devices). Isodromic (flexible) feedback eliminates low-frequency modulated oscillations of the output voltage of the power source.

According to the invention, the stabilized electrical machine power supply includes a synchronous generator with stator and field windings, a rectifier connected to the stator winding, a voltage sensor that monitors the output voltage value, connected in parallel with the rectifier output, and a hard feedback device. To control this power source are: voltage regulator, a comparison node, a regulating device, a key element, a reverse diode. The voltage regulator is connected to one of the inputs of the comparison node. The output of the voltage sensor is connected through a hard feedback device to the second input of the comparison node. And the third input of the comparison node is connected to the output of the IOOS device, the input of which is connected to the output of the excitation current sensor. The output of the comparison node is connected through the control device to the input of the key element, one output of which is connected to the negative pole of the rectifier, and the other through a resistor to the anode of the reverse diode. A field current sensor is connected there, which is installed in series with the field coil, which is connected via a free terminal to the cathode of the reverse diode and the positive terminal of the rectifier. Thus, the comparison node compares three signals: the target value of the output voltage, the actual value of the output voltage and the scaled value of the magnitude of the oscillation of the excitation current caused by the loss of stability of stabilization of the synchronous generator.

The used IOOS device serves to transmit the emerging oscillations of the excitation current from the output of the excitation current sensor to the third input of the comparison unit without a phase shift. In a specific implementation, the IOOS device consists of a scaling operational amplifier, a capacitor, and several resistors. The output of the excitation current sensor through a capacitor and resistor is connected to one input of the scaling operational amplifier, and through resistors to another input of this amplifier. The fluctuations of the excitation current are measured by the excitation current sensor, fed to the input of the IOOS device, scaled by the operational amplifier and fed to the third input of the comparison unit. This leads to damping of self-oscillations of the excitation current and the elimination of low-frequency modulation of the generator voltage. The time constant of the RC circuit is chosen so as not to introduce a phase shift in the transmitted signal from the output of the excitation current sensor to the third input of the comparison unit, that is, the regulation begins to act almost immediately after the appearance of self-oscillations.

Graphic illustrations:

The figure of the graphic image shows a functional diagram of a stabilized electrical machine power source.

The implementation of the invention

A specific model of the proposed stabilized electrical machine power source based on a synchronous generator 1 contains stator windings 2 and an excitation winding 3, an unregulated rectifier 4 connected to stator windings 2. The positive pole of the rectifier 4 is connected to the junction point of the first output of the excitation winding 3 and the cathode of the reverse diode 5. The key element 6 with the first output is connected to the resistor 7, accelerating the decrease in the excitation current when the key element is turned off, and the second output is connected to the negative terminal of the rectifier Itel 4. Comparison node 8 with the first input connected to the output of the voltage regulator 9. A voltage sensor 10 is connected in parallel with the output of the rectifier 4, the output of which is connected via the hard negative feedback device 11 to the second input of the comparison unit 8. The output of the comparison unit 8 is connected to the input of the regulating device 12, the output of which is connected to the input of the key element 6. The excitation current sensor 12 is located between the first output of the key element 6 connected to the resistor 7 and the second output of the excitation winding 3. Sensor output the excitation current 13 is connected to the IOOS device 14, which includes: a scaling operational amplifier (hereinafter referred to as the amplifier) 15, a capacitor 16, and resistors 17-22. The input of the IOOS device 14 is the connection point of one plate of the capacitor 16 and the terminal of the resistor 17, the other terminal of which is combined with the terminals of the resistors 18 and 19. Another terminal of the resistor 18 is connected through the resistor 20 to the second plate of the capacitor 16 and the first input of the amplifier 15. Another terminal of the resistor 19 connected to the second input of the amplifier 15 and through the resistor 21 to the output of the amplifier 15, which is connected through the resistor 22 to the third input of the comparison unit 8.

The following may be selected as specific elements of the described flowchart:

- synchronous generator 1 with stator and field windings, with damper longitudinal circuits with a power of 1 kW at 24000 rpm;

- unregulated rectifier 4 - three-phase rectifier module type M6D-63-400, 63 A, 400 V;

- reverse diode 5 - diode type 2D206V;

- key element 6 - transistor type 2T8174A, 40 A, 600 V;

- resistor 7 - resistor type C5-47, 40 W, 24 Ohms;

- the comparison node 8 may be the inputs of the operational amplifier on which the regulating device 12 is made;

- voltage adjuster 9 - Zener diode type D818I;

- generator voltage sensor 10 - voltage divider on resistors of type C2-33H;

- the device negative feedback 11 can be made in the form of an RC low-pass filter;

- control device 12 - operational amplifier type 140UD7;

- excitation current sensor 13 - type LA25 - NP / SP44;

- scaling operational amplifier 15 - operational amplifier type 140UD7;

- capacitor 16 - capacitor type K10-47a, 50 V, 0.47 uF;

- resistors 17-22 - resistors of type C2-33H.

The device operates as follows. Upon receipt of the signal to set the level of the output voltage of the generator from the setter 9 to the first input of the comparison unit 8, the regulating device 12 opens the key element 6, and the current created by the voltage of the generator 1 from the residual magnetic flux flows through the excitation winding 3 of the generator 1. While the negative feedback voltage supplied to the second input of the comparison unit 8 from the output of the generator voltage sensor 10 through the hard negative feedback device 11 is less than the signal for setting the voltage of the generator from the voltage generator 9 to the first input of the comparison unit 8, the excitation current and the generator voltage 1 will grow like an avalanche until the equality of the negative feedback signal to the generator voltage reference signal. Since the regulating device 12 is a relay element, the voltage stabilization of the generator will occur in a pulsed manner by changing the ratio between the on and off states of the key element 6 (pulse-width regulation method).

When low-frequency self-oscillations of the generator 1 occur due to a partial loss of stability of the voltage stabilization of the generator 1 with certain combinations of the rotational speed and load of the generator, the low-frequency modulation of the voltage of the generator 1 occurs and, therefore, the quality of the generated voltage deteriorates. These oscillations of the excitation current are measured by the excitation current sensor 13 and fed to the input of the IOOS 14 from its output, scaled by the operational amplifier 15 and fed from the output of the IOOS 14 to the third input of the comparison unit 8. This signal damps the self-oscillations of the excitation current and eliminates low-frequency modulation generator voltage. Moreover, the time constant of the RC circuit of the IOOS device 14, determined by the values of the capacitor 16 and resistor 20, is selected in such a way that the phase shift of the transmitted signal from the output of the excitation current sensor 13 to the third input of the comparison unit 8 is excluded. At the first time, the signal is proportional to the measured deviation, and then it gradually decreases in accordance with a decrease in the amplitude of self-oscillations in the field winding.

Such a technical solution for stabilizing the voltage of a synchronous generator makes it possible to present an electric machine power source as an automatic control system, that is, it allows automatic elimination of the low-frequency modulation of the output voltage that suddenly arises (with certain combinations of the generator speed and load value).

Claims (2)

1. A stabilized electrical machine power supply comprising a synchronous generator with stator and field windings, a rectifier connected to the stator winding, a voltage sensor connected in parallel with the output terminals of the rectifier, a voltage regulator, a control circuit, and a hard negative feedback device, the control circuit including series-connected elements - a comparison node, a regulating device, a key element, a reverse diode, while the first input of the comparison node is connected voltage regulator, its second input is with the output of the voltage sensor through a negative negative feedback device, one output of the key element is connected through a resistor to the anode of the reverse diode, its other output is connected to the negative terminal of the rectifier, and the cathode of the reverse diode is connected to the field winding and positive terminal a rectifier, characterized in that it contains a field current sensor and an isodromic negative feedback device, the field current sensor being included in the field winding circuit, and the output of this sensor ka is connected to the input of the isodromic negative feedback device, the output of which is connected to the third input of the comparison node. 2. The stabilized electrical machine power supply according to claim 1, characterized in that the isodromic negative feedback device includes a scaling operational amplifier and a capacitor with a group of resistors, the nominal values of which determine the parameters of the RC circuit, which eliminates the phase shift of the feedback signal from the sensor field current.