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INVENTION
Patent of the Russian Federation RU2084077
DEVICE FOR FREQUENCY REGULATION OF N-PHASE ELECTRIC UNITS
The name of the inventor: Klimov BP; Stryutskov V.K.
The name of the patent holder: Russian Joint Stock Company of Energy and Electrification "UES of Russia"; Joint Stock Company "Scientific-Research Institute of electric power"
Address for correspondence:
Date of commencement of the patent: 1995.08.17
Use: in autonomous wind and hydroelectric power plants. Essence: the frequency control device of the n-phase power units contains a phase frequency voltage sensor, the first ballast groups of m-parallel-connected controllable resistors, control units. The device includes second ballast groups with one controlled resistance in each group, which are connected in parallel to the corresponding ballast groups. The controllable resistance of the corresponding second ballast group is connected to the (m + 1) th output of the control unit. This makes it possible to simplify the design of the device and increase its manufacturability by reducing the number m of controllable resistances of one standard.
DESCRIPTION OF THE INVENTION
The device relates to electrical engineering and is designed to stabilize the frequency of alternating current generators with autoballast load, mainly for autonomous wind and hydroelectric power stations of relatively low power (up to 500 kW).
There are known devices in which the autoballast load, connected in parallel with the useful electric load, ensures the invariability of the operating mode of the turbine-generator-load system in the presence of compensating influences both from the side of the turbine and from the electric load of the generator [1; 2]
In [1], the system of frequency stabilization of micro hydroelectric power stations (electrohydroaggregate) with autoballast load is described, realizing, so-called, phase control method. This system comprises a primary engine (turbine), a three-phase alternator, three groups of ballast resistors with thyristor switches, block phase (angle) adjustment and electrical components and payload.
When the payload changes from zero to the nominal value from signals from the current sensors, the thyristors are phase controlled to maintain the constancy of the total active power dissipated in the payload and ballast loads of the generator, which in fact ensures the stability of the frequency of its output voltage.
However, the device [1] due to the phase adjusting ballast resistors are connected to different sections of a sinusoidal curve, resulting in significant distortion of the output voltage of the generator form.
This disadvantage is eliminated in the device [2] which is the closest in technical essence to the proposed device.
The structure of the prototype device [2] includes: three groups of ballast resistors with thyristor keys, a control unit, a phase frequency voltage sensor.
The difference between the prototype and the analogue [1] consists in increasing the number of thyristor-resistor ballast sections in each group and using so-called non-current thyristor switching at the moments of the transition of the corresponding phase voltages through zero values. The thyristor keys are controlled discretely in binary code as a function of the generator voltage frequency. Number tsifroupravlyaemyh ballast sections (m) is determined by the permissible degree of quantization ballast load conditions to ensure the specified quality of frequency regulation. The smaller the sections the "coarser" the regulation and the greater the amplitude of the oscillations of the frequency of the output generator.
Since high quality of frequency regulation is achieved only with a large number of m ballast sections, the device [2] is complicated.
Moreover, in the prototype, the current thyristor load is proportional to the binary code and the use of one type of thyristors is inexpedient for technical and economic reasons, and the use of several typologies significantly reduces the processability of the device.
Another drawback of the prototype [2] as well as other known devices is the absence of channels for separate regulation of the phases of the load, which is necessary with its asymmetry of the consumer.
It is an object of the present invention to provide an apparatus characterized by sufficient constructive simplicity and improved processability, as well as the ability to balance the phase currents of the generator with an asymmetric load of the consumer.
The subject of the invention is a frequency control device for n-phase power units, comprising a phase voltage frequency sensor, n-first ballast groups of m-parallel-connected controllable resistances in each group, n-control units, wherein the first inputs of the control units are combined and connected to the output of a frequency sensor Phase inputs, the m-outputs of each control unit are connected to the inputs of the controlled resistances of the corresponding first ballast group, the inputs of the phase-frequency voltage sensor, the sinus input of each control unit and the first power output of each first ballast group are intended for connection to the respective phase buses of the electric power unit and the second power terminals The first ballast groups are intended to be connected to the zero bus of the electric generating set, and n-second ballast groups with one controlled resistance in each group are inserted which are connected in parallel to the corresponding first ballast groups, and each control unit is equipped with (m + 1) th output which is connected To the input of the controlled resistance of the corresponding second ballast group.
This makes it possible to simplify the design and improve the processability of the device providing a low level of distortion of the voltage phase curve by an optimal combination of "coarse" discrete regulation using a binary code and "precise" control by discrete phase control.
The invention has the development that the device comprises n-sensors of active components of the phase currents and each control unit is provided with a second input, wherein the first input terminal of each active phase current sensor is connected to the first power terminal of the corresponding ballast group, the second input terminal Each sensor of the active component of the phase current is designed to connect to the circuit of the corresponding electrical load, and the output of each sensor of the active component of the phase current is connected to the second input of the corresponding control unit.
This gives an additional effect, since it makes it possible, if necessary, to equalize the loads of the phases of the generator under the asymmetric load of the consumer.
Another development of the proposed solution is the internal execution of each control unit in the form of a differential amplifier, an analog-to-digital and a digital-to-analog converter, a multichannel and one-channel pulse former equipped with sync inputs that are a sync path of the control unit, wherein the inputs of the differential amplifier are the first and second inputs of the unit The output of the differential amplifier is connected to the input of the analog-to-digital converter, whose high-order discharges are connected to the corresponding inputs of the multichannel pulse former, and the low-order outputs are connected via a digital-to-analog converter to the input of the single-channel pulse former, the outputs of the multichannel pulse former form the m- And the output of the single-channel pulse former is the (m + 1) th output of the control unit.
This is the most preferred implementation of the combination of "rough" and "precise" ballast load control.
The essence of the invention is explained in the drawing, which shows the block diagram of the device for case n 3 with the internal execution of the control unit.
The device comprises a first phase frequency sensor 1, three first ballast groups 2 of m-parallel-connected controllable resistances in each group made, for example, in the form of ballast resistors 3 with triac keys 4, three control units 5, three second ballast groups 6 with one controlled resistance 3, 4 in each group, three sensors 7 active components of the phase currents. The first inputs of the blocks 5 are combined and connected to the output of the sensor 1, the m-outputs of each block 5 are connected to the inputs of the controlled resistances 3,4 of the corresponding ballast group 2. The sensor inputs 1, the sinus outflow of each block 5 and the first power output of each ballast group 2 and its parallel Groups 6 are combined and output to terminals 8, 9, 10. The second power terminals of group 2 and 6 are output to terminal 11. Each control unit 5 is provided with a (m + 1) th input that is connected to the input of the controlled resistance of the corresponding ballast group 6.
The first input terminal of each sensor 7 is connected to the first power terminal of the corresponding ballast group 2, the second input terminals of the sensors 7 are output to the terminals 12, 13, 14, and the output of each sensor 7 is connected to the second input of the corresponding unit 5.
The control unit 5 is implemented as a differential amplifier 15, an analog-to-digital converter 16, a digital-to-analog converter 17, a multi-channel pulse former 18 and a single-channel pulse former 19. The shapers 18 and 19 are provided with synchroprocesses, which are a synchro flow of the control unit 5. The inputs of the differential amplifier 15 are the first and second inputs of the unit 5, the output of the amplifier 15 is connected to the input of the converter 16, the high-order outputs of which are connected to the inputs of the driver 18, and the low-order outputs are connected via the converter 17 to the input of the driver 19. The outputs of the driver 18 form the m- Outputs of the control unit 5, and the output of the driver 19 is the (m + 1) th output of the unit 5.
The primary motor (turbine) 20, an alternating current generator 21 with a three-phase stator winding system constituting the electric unit, a payload 22 and switches 23 to which the terminals 12, 13, 14, phase lines 24, 25, 26 must be connected Terminals 8, 9, 10 are connected, and the zero bus 27 to which terminal 11 is to be connected is not included in the device and is shown in the figure to explain the principle of operation.
The device works as follows. Voltage regulation comprises two components: the signal from the sensor 1, the generating voltage proportional to the frequency and the signal from the sensor 7, the load is proportional to the phase generator.
On the basis of the signal of the phase voltage sensor 1 and the signals from the sensors 7 of the active components of the phase currents, the differential amplifier 15 of each unit 5 generates a signal which is input to the input of the analog-digital converter 16, its outputs generate discrete signals in binary code proportional to the frequency of the generator's phase voltages. In this case, the output of the transistor 16 with the help of the multichannel driver 18 produces the pulses for controlling the triacs 4 of the ballast group 2 at the moments of the transition of the corresponding phase voltage through zero, which ensures the so-called "rough" frequency control.
The low-order code of the analog-to-digital converter 16 is converted into a step-shaped DC signal which is input to the single-channel input of the 19 phase control pulses by the digital-to-analog converter 17, which opens the triac 4 of the corresponding group 6, providing "fine" frequency control .
It is the combination of "coarse" and "precise" regulation that allows to reduce the total number of ballast sections, sufficient to provide a given quality of frequency regulation, and thus, accordingly, simplify the design of the device and increase its manufacturability.
With the asymmetric payload 22, due to the introduction and the FIG. 1, the connection of the sensors 7, the phases of the generator 21, which are loaded more, are loaded with a ballast load to a lesser degree than the underloaded phases and vice versa, and in fact an additional effect is achieved that is equalization of the phase currents of the generator 21.
Sensors 7 can be made, for example, using current transformers and phase detectors [3] As the controllable resistors, in addition to triacs, counter-parallelly connected thyristors can be used.
The phase-to-phase voltage sensor 1 is a frequency discriminator with an output filter. [4] A single-channel phase lock pulse former 19 can be performed using a sawtooth or sinusoidal reference signal [5] A multi-channel pulse former 18 can be performed, for example, as in [6]
Industrial applicability. Referring to Fig. 1, a pilot production lot of the device samples was manufactured.
The conducted batches of manufactured samples at the small hydro power plant stand at the Scientific Research Institute of Power Structures (NIIES) showed that the control system ensures a high quality of the control process (frequency variation within ± 0.5 HZ and higher harmonic content in the generator output voltage of not more than 5 %). In this case, the dimensions of the device in comparison with its technical implementation according to the prototype scheme were reduced by 20% (by reducing the number of resistor-symmetric sections from 8 to 5).
CLAIM
1. Frequency control device for n-phase power units, comprising a phase-frequency voltage sensor, n first ballast groups of m parallel-connected controllable resistances in each group, n control units, the first inputs of the control units being combined and connected to the output of the phase-frequency voltage sensor, m Outputs of each control unit are connected to the outputs of the controlled resistances of the corresponding first ballast group, the inputs of the phase frequency voltage sensor, the sinus input of each control unit and the first power output of each first ballast group are intended for connection to the respective phase buses of the electric power unit and the second power outputs of the first ballast groups are for Connection to the zero bus of the electric generating set, characterized in that n second ballast groups with one controlled resistance in each group are inserted which are connected in parallel with the corresponding first ballast groups and each control unit is provided with an (m + 1) th output which is connected to an input of a controlled Resistance of the corresponding second ballast group.
2. The device according to claim 1, characterized in that it comprises n sensors of active components of the phase currents, and each control unit is provided with a second input, wherein the first input terminal of each active phase current sensor is connected to the first power terminal of the corresponding first ballast group, the second The input terminal of each active phase current sensor is designed to connect to the corresponding electrical load circuit, and the output of the active phase current sensor is connected to the second input of the corresponding control unit.
3. The device according to claim 2, characterized in that each control unit is made as a differential amplifier, analog-digital and digital-to-analog converters, multi-channel and single-channel pulse former equipped with sync inputs, which are the sync path of the control unit, with the inputs of the differential amplifier being the first And the second inputs of the control unit, the output of the differential amplifier is connected to the input of the analog-to-digital converter, whose high-order discharges are connected to the corresponding inputs of the multichannel pulse former, and the low-order outputs are connected through the digital-to-analog converter to the input of the single-channel pulse former, the outputs of the multichannel pulse former form m outputs And the output of the single-channel pulse former is the (m + 1) th output of the control unit.
print version
Date of publication 02.04.2007gg
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