RU2687049C1 - Method of driving electric aggregate with asynchronous generator - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to electrical engineering and power engineering and can be used in electrical units with asynchronous generators that operate autonomously (without being connected to the electrical network). In the method of controlling an electrical unit with asynchronous generator, pre-charging of exciter forcing capacitors and selection of the moment of connecting required number of capacitors to the generator are carried out.EFFECT: technical result is an increase in dynamic stability when switching on large loads, increasing voltage stability, reducing duration of transients, eliminating system self-oscillations and improving power quality.1 cl, 4 dwg

Description

The technical field to which the invention relates.

The invention relates to electrical engineering, in particular, to a method of controlling an electrical unit with an asynchronous generator, can be used in autonomous and stationary electrical units and power plants with asynchronous generators using capacitor excitation.

The level of technology

A device for regulating and stabilizing the voltage of an autonomous asynchronous generator, in which there is a three-phase group of non-switched capacitors and several groups (in this case, three) switched capacitors, is known. Groups of switched capacitors are connected to the stator windings of the generator when the generator voltage drops due to increasing load connection. The voltage drop of the generator is estimated by the sensor in the form of a three-phase rectifier, loaded on the measuring resistance, from which part the voltage is measured. Three-phase electronic switches in the form of three-phase optoelectronic alternating current relays are used as switching devices. The device implements a method of controlling an asynchronous generator by connecting additional three-phase capacitors to the generator windings depending on the average value of the three-phase generator voltage with additional control of the generator voltage phase to turn on the capacitors at the moment the phase voltage passes through zero. The three-phase electronic switch connects additional phase excitation capacitors, initially in a discharged state and in subsequent modes in various degrees of charge. (see US Pat. of the Russian Federation No. 237639, MPK ⁸ Н02Р 9/46, “Device for regulating and stabilizing the voltage of an autonomous generator” / Bogatyrev, NI, etc. // Bul. 2009 No. 32).

The disadvantages of the method implemented in the device:

- measured and reference voltage voltage monitoring devices have a ripple, which reduces the accuracy of voltage maintenance;

- low voltage stability;

- switching off the capacitors by optoelectronic three-phase relays occurs at the moment of the current passing through "zero", while a charge remains on the capacitor, which, when the voltage is switched on again in the "zero" phase, leads to the shock current of the capacitors;

- when connecting uncharged capacitors in the "zero" phase voltage, the generator charges the capacitors for 1/4 of the period;

- the generator, in addition to the connected load, is additionally loaded, charging the discharged, additionally connected capacitors, the power balance in the "generator - excitation capacitors - load" system is disturbed, due to the lack of reactive and active power of the generator, this may disrupt the stability of both the generator and drive motor;

- at uneven loading of phases, voltage unbalance of phases is possible, which is not monitored by the sensor, which measures the average value of three-phase voltage only by linear voltages;

- the inclusion of all capacitors only in delta excludes the possibility of correction of phase voltage unbalance:

- in the claimed device in Fig. 1, 2 there are no device elements that provide control of voltage transition through the "zero";

- the device does not have a mandatory output of the star windings of the generator, which is a neutral wire.

A device for regulating and stabilizing the voltage of an autonomous multifunctional asynchronous generator is known, in which the generator contains a low-voltage stator winding that is connected to a zero point and, on the other hand, has first output terminals for a low-voltage load to which a rectifier is connected to supply the load. direct current; a high-voltage winding is also connected to the low-voltage terminals; a battery of non-switched self-excitation capacitors is connected to the phases of the battery, and a battery of switched excitation capacitors, a high-voltage winding voltage control device and high-voltage terminals are connected via a three-phase electronic key. The voltage control device evaluates the voltage level by the magnitude of the three-phase rectified voltage and provides one common signal to the three-phase electronic key. A three-phase electronic switch, made in the form of an optoelectronic three-phase relay, simultaneously connects additional excitation capacitors. This device implements a control method similar to that described in the previous analogue, namely: a method of controlling an asynchronous generator by connecting to the generator windings additional discharged batteries of three-phase capacitors depending on the average value of the three-phase generator voltage with additional control of the generator voltage phase, for switching on capacitors at the time of transition phase voltage through the "zero".

The three-phase electronic switch connects additional phase excitation capacitors, initially in a discharged state and in subsequent modes in various degrees of charge. (see Pat. RF №2457612, IPC ⁸ H02R 9/46, "A device for regulating and stabilizing the voltage of an autonomous multifunctional asynchronous generator" / Bogatyrev NI, etc. // Bul. 2012 No. 21).

The disadvantages of the method implemented in the device:

- measured and reference voltage voltage monitoring devices have a ripple, which reduces the accuracy of voltage maintenance;

- switching off the capacitors by optoelectronic three-phase relays occurs at the moment of current transition through "zero", while a charge remains on the capacitor, which, when the voltage is switched on again in the "zero" phase, leads to the shock current of the capacitor discharge;

- when connecting uncharged capacitors in the "zero" phase voltage, the generator charges the capacitors for 1/4 of the period;

- the generator, in addition to the connected load, is additionally loaded, charging the discharged, additionally connected capacitors, the power balance in the "generator - excitation capacitors - load" system is disturbed due to the lack of reactive and active power of the generator, this can disrupt the stability of both the generator and drive motor;

- at non-uniform loading of phases, voltage unbalance of phases is possible, which is not monitored by the sensor measuring the average value of three-phase voltage only by linear voltages;

- the inclusion of all capacitors only in a triangle excludes the possibility of correction of phase voltage unbalance;

- in the claimed device in Fig. 1, 2 there are no elements of the device that provide control of voltage transition through the "zero".

There are a number of ways to control hypertension:

- magnetic bias stator;

- change in capacitor capacitance;

- connecting inductive or active resistances;

- the use of nonlinear capacitors (variconds).

(See p. 39 Asynchronous generators for autonomous electric power plants. M. NTF "Energoprogress" 88 p. 2004).

The disadvantages of these methods are:

- low voltage stability;

- the complexity of the device;

- increased energy loss,

- the lack of variconds with significant capacity;

- low speed dynamic processes in the system "asynchronous generator - excitation capacitors - load" when the load is turned on.

Known devices power generating systems firms "EISMANN, GEKO" with asynchronous generators. In these power plants, for example, 2801 Е-А / МНВА, 9001 ЕЕ - AA / SEBA, Н-9000Е, etc., asynchronous generators with a capacity from 2.5 to 9.0 kW are used. The devices contain one group of permanently connected capacitors to the generator and the second, connected with increasing load. The control method implemented in these devices is based on the connection of additional capacitors by a contactor when the generator voltage drops. A further increase in the power of the aggregates is constrained by the limited possibilities of the applied control method (see the catalogs of the EISMANN and GEKO firms, www.metallwarenfabik.com).

The disadvantages of the control method implemented in the devices of these companies are identical to those described in the above descriptions of analogues, and this is due to the limited power range of the produced electrical units.

The closest to the technical essence and the achieved effect, taken by the authors as a prototype, is the method of a discrete control system for an asynchronous generator complex with a digital voltage regulator operating at a constant frequency of rotation of the drive motor. The method implements stepwise control of the capacitance value of the excitation capacitors connected to the asynchronous generator when the voltage of one of the phases changes, caused by the change in the load value.

An asynchronous generator contains one non-switched three-phase block of self-excitation capacitors, and several (five) switched blocks of excitation capacitors, and two control systems. The first control system controls the voltage value of only one of the phases and, depending on its size, turns on and off the three-phase optothyristor switches connecting the excitation capacitors to the phase windings of the generator. The second system controls the starting device for asynchronous electric motors from an autonomous asynchronous generator. This system limits the starting current of the connected electric motor and thereby reduces the voltage drop of the generator. The executive part of the second control system also consists of a three-phase optothyristor switch (it is not disclosed in the description that the start-up motor with start-up current limitation is supposedly controlled by phase regulation of the current). Each block of three-phase field capacitors is connected to a star without a connection to the neutral of the asynchronous generator. Phase capacitors in series with the current-limiting resistor are connected to the phase windings of the generator by means of pairs of oppositely connected optothyristors. Additionally, instead of optothyristors, capacitors can be manually connected with a switch (see Vishnevsky, LV, Pass AE. Control systems for asynchronous generator complexes, Kiev, Lybid, 1990, 167 p. Section 3.5, Figure 3.8, 3.9).

The disadvantages of this method are:

- the impossibility of obtaining a stable frequency of the generator at variable load, since the rotational speed of the driving motor is unchanged, and the transforming magnetic field has a slip;

- unstable output frequency of the generator, depending on the magnitude of the load, since the rotational speed of the drive motor is constant;

- control of the voltage value is carried out only in one phase;

- there is no measurement of current values;

- there is no separate control of the values of load and excitation currents;

- voltage distortion when overcharging capacitors;

- at uneven loading of phases, violation of symmetry of phase voltages is possible;

- the use of three-pole shunt switches that are manually activated, leads to unacceptable inrush current charging capacitors;

- additional energy loss and inefficient use of excitation capacitors due to the series-connected current-limiting resistors;

- the impossibility of an independent, phase-wise capacitors;

- the success of the motor start is not monitored;

- there is no connection of capacitors to the generator neutral, which excludes the possibility of balancing the system of phase voltages;

- the motor is started at a non-sinusoidal current, which adversely affects the operation of both the engine and the whole asynchronous generator system;

- there is no relationship between the two control transfer management systems.

Summarizing the known methods, we can conclude that all known methods implement a change in the value of the capacitors connected to an asynchronous generator when the load is connected.

DISCLOSURE OF INVENTION

The objective of the proposed invention is to develop a method of controlling an electrical unit with an asynchronous generator, which has:

- increased dynamic stability with the inclusion of large loads;

- increased voltage stability;

- reduced duration of transient processes;

- lack of system self-oscillations due to the surge of switching current;

- increased quality of electricity (voltage and frequency deviations);

- reduced voltage asymmetry with unbalanced phase load;

- reduced heating of the windings due to excessive capacitive field current.

The technical result, which can be obtained using the present invention, is to increase the dynamic stability when turning on large loads, increase voltage stability, reduce the duration of transient processes, eliminate system self-oscillations due to a surge of switching current, improving power quality (voltage and frequency deviations) , reducing the voltage unbalance with asymmetrical loading of the phases, reducing the heating of the windings due to excessive capacitive field current.

The technical result is achieved due to the fact that the capacitors of the phase blocks forcing the excitation are alternately precharged to the amplitude value of the voltage of the generator phases by the pulse-step method using two-way alternating current keys, and in two phases the capacitors are charged with the same polarity, and in the third phase they are charged with the opposite polarity; when the load is switched on, the phase charged capacitors of the excitation forcing are connected to the corresponding phase of the generator at the time point when the amplitude value of the voltage of this phase reaches the same polarity with the voltage of the capacitor, and the priority of connecting the capacitors is determined by the phase with the nearest voltage maximum; when the load is disconnected, the excitation forcing capacitors are disconnected in compliance with the alternation of attaining voltage maxima of the phases at the times of reaching the maximum voltage of the corresponding phase; The required capacitance value of the connected capacitor phase blocks is chosen according to the power value determined by the controller of the control system according to the measurement of the generator voltage, load current and phase angles.

Brief Description of the Drawings

FIG. 1 shows a method for controlling an electrical unit with an asynchronous generator. The electrical circuit of the power unit with asynchronous generator.

FIG. 2 - the same, the process of charging the capacitors forcing the excitation.

FIG. 3 - the same, the process of switching on the phase capacitors forcing the excitation.

FIG. 4 is the same block diagram of the control system.

The implementation of the invention

The control method of an electrical unit with an asynchronous generator is implemented, for example, by a device containing a power unit (see Fig. 1) and a control system (see Fig. 4). The power part contains the prime mover 1 which is connected by a shaft to the rotor 2 located in the stator 4. On the rotor 2 there is a short-circuited winding 3, and on the stator 4 there are three phase windings 5 connected in a star with the derived common point of the star (neutral). To the phase windings 5 are connected capacitors 6 of the initial self-excitation of the asynchronous generator, having a small capacity. The phase windings 5 are connected blocks of phase capacitances 7 providing additional speeding up the excitation of the generator. The connection of blocks of phase capacitances 7 is carried out with electronic keys 8. Electronic AC keys 8 are made of two parallel-connected branches. One branch conducts a positive half current wave, and the second negative one. Each branch of the controlled electronic key 8 contains in series according to the included transistor 9 and the diode 10. The phase capacitors 11 of the additional forcing of the excitation are controlled by the controlled electronic keys 8 of the alternating current to the phase windings 5 of the generator. The use of the transistor 9 provides on and off capacitors 11 at the desired time. In the known control methods for switching use thyristors, which turn off the circuit only at the moment of current transition through “zero”. In electric units with asynchronous generators, for the smoothness of voltage regulation, several blocks of phase capacitances 7 are used two or more, in this case the second 12. The electronic switch 8 with one branch provides a small pulse current for a smooth step charge of the capacitors 11 forcing the excitation with voltage of the required polarity. In the operating mode of the load, both branches of the electronic key 8 work. The electric unit prepared for operation is automatically turned on by the contactor 13. A load 14 is connected to the output terminals of the contactor 13. If a load with a large initial current is connected before the contactor 13 of the resistance 15 is turned on, the load current 14 is preliminarily limited.

The control system of an electrical unit with an asynchronous generator is implemented, for example, by a device whose block diagram is shown in FIG. 4. The device contains a current sensor 16 in the phase windings 5 of the generator, a current sensor 17 of the magnitude of the reactive current of the field capacitors, a current sensor 18 of the magnitude of the load current. The measuring device 19 values of voltage, frequency and current generator. Converters matching information voltage 20, current 21 and frequency 22 of the generator.

Differentiation device 23, which determines the rate of change of the load current (dI _n / dt). The speed sensor 24 of the rotor 2 (n). Microprocessor unit 25 control unit. The primary engine control actuator 26 1. The electronic key control channels 27 and the actuator control channel 28 26.

The method works as follows.

When starting the primary motor 1 of the electrical unit (see Fig. 1), the rotor 2 of the asynchronous generator rotates with a given rotational speed (n). Due to the residual magnetization of the rotor magnetic core 2 in the windings 5 of the stator 4 of the generator, a small electromotive force is induced. The winding 5 of the stator 4 and the short-circuited winding 3 of the rotor 2 have inductance. Due to the capacitors 6 connected to the windings 5 of the stator, an oscillating circuit of self-excitation is formed, in which the total inductance of the windings 3 of the rotor 2 and the windings 5 of the stator 4 vary periodically due to the rotation of the rotor 2. Variable inductance of the circuit and the presence of electromotive force in the windings 5 of the stator 4 lead to the excitation of forced oscillations in the circuit and intensive self-excitation of the asynchronous generator, including elements 2, 3, 4, 5. The energy for the forced oscillations in the circuit comes from the primary motor 1. In the phase windings 5 of the stator 4, a smooth increase in voltage occurs.

The voltage reaches the value of the idling voltage on the windings 5 of the generator, determined by the parameters of inductance and capacitance of the capacitors 6 in the self-excitation circuit.

In stand-alone asynchronous generators, additional phase blocks 7, 12 with capacitors 11, connected with electronic switches 8 when the load 14 is turned on, are used to force generator excitation. Additional blocks 7, 12 of capacitors 11 forcing the excitation (usually not 2, as in the description of the application, but several) are not initially connected to the windings 5 of the stator 4 of the generator. In the known methods and devices, the capacitors 11 are discharged. In the proposed method, the capacitors 11 are pre-charged. The charge of additional capacitors 11 forcing the excitation is carried out by one of the branches of the electronic key 8 AC.

FIG. 2 shows the process of charging the capacitor 11, for example, connected to the phase U of the generator. The capacitor 11 is completely discharged and the voltage on it is zero. The capacitor is connected by the transistor 9 at the time T ₀ , and the voltage at the phase U is also zero. As the voltage U increases, the current and voltage of the capacitor 11 increase. At time T ₁ , the capacitor 11 is switched off by the transistor 9, and the capacitor is charged to the voltage U ₁ . At the next positive half-wave at time T _2, when the voltages of the capacitor 11 and the phase U are equal, the next capacitor connection is made. In this case, the charge current is zero. The charge of the capacitor continues, at the moment of time T _{3 the} shutdown is performed. The voltage on the capacitor increased to U ₂ . Similarly, in the time interval T ₄ - T ₅ , the charge level of the capacitor is reached up to the amplitude value U _m . A smoothly increasing voltage on the capacitors 11 is provided by small pulses of charge current, which does not disturb the operation of the generator. This method of charging capacitors 11 eliminates switching losses of switching on transistors 9 and diodes 10. The capacitors 11 phases of blocks 7, 12 are alternately charged from the windings 5 of the excited generator.

The disconnection of fully charged capacitors 11 to the amplitude voltage of the windings 5 is made at the moment of reaching the amplitude value of the voltage of the corresponding phase winding 5 of the generator. After charging the capacitors 11 of all blocks 7, 10, they remain in the disconnected position with electronic keys 8 from the windings 5 of the generator. The electrical unit with an asynchronous generator is prepared for operation and the generator contactor 13 is turned on. The load 14 is connected to the electrical unit with its switching devices.

With a long absence of load and a slight decrease in voltage on the capacitors 11 due to self-discharge, they are compensated by short-time switching on of the electronic switches 8 to the voltage of the corresponding phase at a moment close to the amplitude value, and turning off after passing through the maximum voltage of the corresponding phase of the generator.

It is possible to implement the control method according to two variants of the charging algorithm of the phase capacitors 11 in the unit and their connection to the windings 5 of the generator.

The first variant of the algorithm (see Fig. 3) is based on the charging of the phase capacitors 11 of the block to an amplitude voltage of different polarity. Two phases of the same polarity are used and the third is opposite, for example, capacitors 11 at the U phase are charged positively U _cu and at the V phase they are charged positively U _cv , and at the W phase they are charged negatively - U _cw . The length of time between the extreme controlled amplitudes of the voltages of the phases of the windings 5 in this variant is 33 ms. The time interval between the connections of the charged phase capacitors 11 to the corresponding phases of the windings 5 is 16.5 ms. After connecting the load 14 at an arbitrary time, for example t ₀ (see Fig. 3), after an interval t _{in, the} phase capacitor 11 is switched on with the nearest voltage maximum, in this case the phase U at time t ₁ . Further, the next phase capacitor 11 is switched on after it - W at the moment t ₂ . And further, the third capacitor 11 of phase V at the moment of time 13. The maximum duration of the pause between connecting the load and connecting the first charged capacitor 11 does not exceed 16.5 ms.

The second possible variant of the connection algorithm (see Fig. 3) is based on pre-charging all three phase capacitors 11 of the phase unit to an amplitude voltage of one polarity, for example, U phase is charged positively with U _cu and phase V is charged positively with U _cv , and phase W also charges positively U _cw . Similarly, all capacitors 11 can be charged negatively.

The length of time between the extreme controlled positive amplitudes of the voltages of the phases of the windings 5 in the second embodiment is 66 ms. The time interval between the connections of the charged phase capacitors 11 to the corresponding phases of the windings 5 is 33 ms.

After connecting the load 14 at an arbitrary time, for example, t ₀ (see Fig. 3), after an interval t _in at time t _{1, the} phase capacitor 11 is turned on with the nearest voltage maximum, in this case, U, then the next phase V capacitor is turned on at time t ₃ and further - the third phase capacitor W at time t ₄ . The maximum duration of the pause between connecting the load 14 and the first charged capacitor 11 does not exceed 33 ms.

Obviously, the first variant of the algorithm will provide the best dynamic characteristics of the transient process when the load is switched on due to the minimal connection time of the capacitors 11 forcing the excitation.

Simultaneous connection to the windings 5 of the generator uncharged capacitors 11 (which is performed in the known methods) significantly complicates and degrades the dynamic characteristics of the transient process when the load is turned on 14. This is due to the fact that the connected capacitors 11 need to be charged to the voltage level of each phase at a given time. This additionally loads the generator and may lead to its overload. In this case, the capacitors 11 are an additional load that reduces the stability of the excitation of the generator.

периода, то требуется дополнительная мощность генератора (источника) 3 кВт. На три фазы суммарная дополнительная нагрузка составит 9 кВт. Таким образом, к генератору помимо основной нагрузки 5 кВт добавляется еще кратковременная зарядная 9 кВт. Следовательно, генератор потеряет возбуждение, и нарушится работа электроагрегата. Вторая проблема состоит в том, что разряженный конденсатор 11, включаемый в момент амплитудного напряжения, создает бросок тока заряда конденсатора и может достигать 200 I_n. В данном случае это составит 2.2 кА. Естественно, асинхронный генератор таких ударных нагрузок не может принять, и нарушается его устойчивость возбуждения. Асинхронный генератор не имеет существенного запаса по перегрузке в отличие от синхронного.Let's give an example. To a three-phase asynchronous generator it is necessary to add capacitors with a capacity of 100 microfarads per phase. This is necessary when connecting the load to the generator about 5 kW. To charge the capacitor at the current voltage of 380 V, an energy of 15.1 J is needed. Since the charge will occur in time

period, the additional power of the generator (source) of 3 kW is required. Three phases total additional load will be 9 kW. Thus, in addition to the basic load of 5 kW, a short-term charging 9 kW is added to the generator. Consequently, the generator will lose the excitation, and the work of the electrical unit will be disrupted. The second problem is that a discharged capacitor 11, turned on at the time of the amplitude voltage, creates a surge in the charge current of the capacitor and can reach 200 I _n . In this case, it will be 2.2 kA. Naturally, an asynchronous generator of such shock loads cannot accept, and its excitation stability is disturbed. An asynchronous generator does not have a significant overload margin, in contrast to a synchronous one.

The application of the proposed control method eliminates these problems. The system should provide a balance of active and reactive power at the moment of switching on load 14 and capacitors 11. If the balance is disturbed, the system goes from a steady state and the generator goes into a mode of excitation failure, and the voltage becomes zero. Known methods and devices, in particular, firms "EISMANN" and "GEKO", based on the use of pre-exaggerated parameters of capacitance capacitors. However, this method leads to excessive heating of the generator windings 5 with capacitive current and a specific underestimated limit of the connected load. This is due to the limiting low value of power (up to 9 kW) of electrical units with asynchronous generators of these companies. In the proposed method, the capacitors are pre-charged, so the additional power from the generator is not consumed and the shock currents of charge of the capacitors 11 are eliminated completely. In addition, charged capacitors 11 are an additional source of reactive power for load 14 and improve the dynamics of making large loads 14 by an asynchronous generator.

Consider how the control of the electrical unit with the proposed method (see Fig. 4). The control is performed by a microcontroller on a multi-loop system. The first circuit, consisting of elements 1-24-25-28-26-1, monitors and regulates the speed of rotation of the prime mover 1 and the associated rotor 2 of the asynchronous generator. The second circuit, consisting of elements 16-19-20-21-22-25-27-8, monitors and regulates the total current, voltage and frequency of the generator. The third circuit (17-25-27-8-9) monitors and regulates the total current of capacitors 11, the voltage of charged capacitors 11. The fourth circuit (18-23-25-27-8) controls the magnitude of the load current 14 and its derivative, determines the required capacitance of capacitors 11 for a given load 14.

At idle of the electrical unit, before connecting the load 14, control is exercised along the internal circuit. The frequency of rotation of the prime mover 1 is measured by the sensor 24 and transmitted to the microcontroller control system 25. By feedback 28, the control system 25 commands the actuator 26 for the amount of fuel supplied to the prime mover 1 to stabilize the rotational speed.

When the load of the electrical unit measuring device 17 evaluates the amount of current in the windings 5 of the generator, the voltage and frequency. The current value is measured by the current transformer 16 and transmitted to the measuring device 19. The measuring device 19 converted by the magnitude of the voltage, current and frequency via communication channels 20, 21, 22 transmits information to the control device 25. When the load 14 is connected, the sensors 18 measure 23 values of the load current 14 and the rate of its rise, the voltage of the phases and the angle of the phase shift between the current and voltage. This data enters the microcontroller 25. The microcontroller 25 determines the active and reactive components of the connected load 14 and determines the required additional capacity of the capacitor unit 7, 12 for connection. It is determined in which phase the voltage maximum is reached earlier. To the winding of this phase is connected according to the charged capacitor 11 at the time of reaching the maximum voltage of this phase. Then the capacitors 11 of the other phases are connected in the same way. When this happens, the reactive power is added to the “generator-load” system and the required voltage level and reactive power of the excitation boost in the generator are maintained. This is necessary because when the load is connected, there is a sharp increase in the consumption of reactive and active power and a decrease in voltage. If in the “generator-load” system there is a shortage of generated power, the generator will be excited and the voltage will drop to zero. Connecting the pre-charged capacitors 11 is equivalent to connecting additional generating capacity, providing a balance of active and reactive power in the generator-load system. With the traditional well-known method of connecting capacitors 11 without pre-charging, the connected capacitor 11 itself becomes an additional load for the generator due to the need to charge it and overloads the generator, which leads to a breakdown of the excitation.

When connecting the load 14 increase the active and reactive power consumed from the generator. At the same time, the slip of the magnetic field of the asynchronous generator increases and the voltage frequency decreases. At a constant frequency of rotation of the drive motor 1, the frequency of the generator voltage decreases. To maintain a stable generator frequency, an increase in the rotational speed of the primary engine 1 is necessary. Feedback on the generator frequency affects the actuator 26, which controls the supply of additional fuel and corrects the rotation frequency of the primary engine 1. The speed of the process of increasing power consumption is high, therefore, the connection of additional charged capacitors should be made minimum time. In order to accelerate the obtaining of information about the load, not only the magnitude of the current, but also the speed (dI _n / dt) of the rise of the current (load) is determined.

Since the next highest voltage peaks of the generator phases have different polarity, therefore, according to the first control variant, capacitors 11 also have the corresponding charge polarity. The inclusion angle of the extreme phases is 120 degrees or 33.3 ms. Such a short turn-on time of charged capacitors 11 ensures the dynamic stability of the generator even when an extremely large load is connected 14 of a different nature, including an asynchronous electric motor.

On the same control system, software implementation of the simplified second control algorithm is possible with a longer connection time for capacitors 11, when the capacitors of the 11 phases are charged with a voltage of the same polarity. In this variant of the control algorithm, the switching time of the capacitors 11 will be 240 degrees or 66.6 ms, that is, it is slightly inferior to the previous one.

When a motor of comparable power is connected to the electric plant, the generator contactor 13 is pre-disconnected, and the limited starting current of the electric motor passes through the resistance shunt contactor 13 15. As the motor speed increases, the starting current decreases. The Executive unit at the command of the microcontroller control system 25 turns on the generator contactor 13, excluding the shunting resistances 15 from the motor power supply circuit.

When disconnecting the load 14, the process of disconnecting the capacitors 11 is carried out in the reverse order. At the nearest maximum of the phase voltage, the capacitor 11 of one phase is disconnected, then in turn, similarly, in other phases. This ensures a smooth reduction of excess reactive power and prevents surges in the generator voltage when the load is reset (disconnected). The disconnection of the capacitors 11 occurs at zero current in the circuit, that is, without switching losses in the transistor 9 and the diode 10. In this case, the capacitors 11 are again prepared for operation.

Reducing the slip of the magnetic field of the generator due to reduced load increases the frequency of the generator. The sensor frequency generator 22 feedback frequency generator through a microcontroller control system 25 acts on the actuator 26 and reduces the fuel supply and the frequency of rotation of the primary engine.

Known methods and devices control only the magnitude of the voltage without assessing the nature of the load 14 (active, reactive component) and its growth rate, which does not allow an accurate determination of the capacitor 11 capacity required for connecting. This affects the dynamics of the electrical unit.

In the proposed method, the nature and rate of increase of load 14 are evaluated, which allows to improve the dynamics of the electrical unit and increase the stability of the generator voltage.

Similarly, the proposed method of controlling an electrical unit with a single-phase asynchronous generator.

The proposed invention in comparison with the prototype and other known solutions has the following advantages:

- increased dynamic stability when turning on large loads;

- increased voltage stability;

- increased quality of electricity (voltage and frequency deviations);

- reduced heating of the windings due to excessive capacitive field current, etc.

Claims (1)

The control unit with an asynchronous generator by initial self-excitation due to the permanently connected capacitors and forcing the generator excitation when the load is connected to additional connected capacitor blocks to the generator phase windings, characterized in that the capacitors of the phase forcing the excitation unit are alternately precharged to the amplitude value of the generator phase voltage with a pulse step method bidirectional keys of alternating current, and in two f Ah, the capacitors are charged with voltage of one polarity, and in the third phase they are charged with voltage of opposite polarity. When the load is switched on, the phase charged capacitors forcing the excitation are connected to the corresponding phase of the generator at the time of reaching the amplitude value of the voltage of this phase, which also coincides in polarity with the voltage of the capacitor, and the connection priority capacitors is determined by the phase with the nearest voltage maximum; when the load is disconnected, the forcing capacitors Ia excitation disable achieve compliance with the alternation of phases of voltage maxima at timings of reaching the maximum of the corresponding phase voltage, the required value of capacitance of capacitors connectable phase block is selected by the power value determined by the controller according to the control system of the generator voltage detecting load current and phase angles.

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