CN105871291A - Bumpless transfer method used for frequency converter and common frequency power network - Google Patents

Bumpless transfer method used for frequency converter and common frequency power network Download PDF

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Publication number
CN105871291A
CN105871291A CN201610224083.1A CN201610224083A CN105871291A CN 105871291 A CN105871291 A CN 105871291A CN 201610224083 A CN201610224083 A CN 201610224083A CN 105871291 A CN105871291 A CN 105871291A
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China
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power
converter
frequency
control
motor
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CN201610224083.1A
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Chinese (zh)
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CN105871291B (en
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熊成林
葛兴来
宋文胜
王青元
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西南交通大学
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P1/00Arrangements for starting electric motors or dynamo-electric converters
    • H02P1/16Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters
    • H02P1/26Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual polyphase induction motor
    • H02P1/28Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual polyphase induction motor by progressive increase of voltage applied to primary circuit of motor
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P3/00Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
    • H02P3/06Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
    • H02P3/18Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor

Abstract

The invention discloses a bumpless transfer method used for a frequency converter and a power frequency power network. The real-time power of a motor under a pre-grid-connected working condition is measured in real time by additionally installing two frequency converter output current sensors on the frequency converter which can realize motor soft starting and can realize synchronization with a power grid, then the frequency converter is converted into direct power control and a set value for the direct power control is set to be the real-time power of the motor, then the frequency converter is connected with a power frequency power grid in parallel, the power set value of the frequency converter is gradually reduced until zero after the parallel connection is completed, and then the frequency converter is removed to realize power supply of the power frequency power grid of the motor. The soft stop process of the motor is on the contrary. According to the bumpless transfer method, the control method for the frequency converter is switched between a control manner such as constant voltage frequency ratio control and a direct power control mode according to requirements, so that bumpless transfer between the power frequency power grid and the frequency converter under the motor and load soft starting and soft stop working condition thereof is realized, currentless breaking and closing of a target power supply are achieved, the transient process existing in a traditional method is avoided, and the reliability of the whole system is improved.

Description

A kind of converter and common frequency power network of being used for is without impact changing method
Technical field
The present invention relates to power electronic equipment, especially converter loaded starting switch to the application of common frequency power network.
Background technology
Rush of current produced by AC asynchronous motor across-the-line starting and torque shock ends bring adverse effect can to electric power system and dragging system, variable frequency soft start scheme is typically used for needs loaded starting occasion, i.e. start to start from zero-speed with converter drive motor, gradually boost raising speed, until it reaches its rated speed.The methods such as variable frequency soft start uses voltage/frequency to control in proportion, senseless control, will not produce overcurrent;Starting torque equal to nominal torque can be provided, be suitable for needing heavy duty or the equipment of full load starting.
If converter only undertakes the task of soft start, not making speed governing operation, then, after converter drive motor reaches rated speed, motor is switched to the direct powered operation of common frequency power network, converter can remove to start other motor again.Such as, piping-main scheme many pumps constant pressure water supply system is exactly a typical example.When hydraulic pressure is too high need termination of pumping time, in order to avoid " water hammer effect ", do not allow to sudden shut off pump power, and require that being gradually lowered rotating speed slowly stops.At this moment motor will be switched to converter again drag, it is achieved ramp to stop.The most inevitably carry out the mutual handover operation between electrical network and converter.
Use and switch between variable-frequency power sources and power frequency supply, mainly have the advantage that 1) dash current in switching, torque can be reduced, the service life of extension device;2) there is preferable energy-saving effect;3) capacity of supply transformer can be greatly reduced.
It is converted to the changing method of power frequency and mainly has a following four:
1) directly switch.Refer on the premise of ensureing that converter is consistent with electric network source phase sequence, direct back brake switching power frequency supply and variable-frequency power sources, directly do not detect the amplitude of voltage, frequency and phase place during switching.This mode requires system and protects fluctuation when can allow switching and impact, thus is rarely employed.
2) asynchronised handover.Refer to detect the amplitude of voltage and frequency and do not detect the switching of voltage-phase.When situation the most serious during asynchronised handover occurs in the phase contrast 180 ° of frequency converter output voltage and line voltage, can cause the biggest surge voltage and electric current, dash current maximum is up to about 30 times of rated current.This mode requires that impact when system can allow switching and torque change, and is normally only used for small-power low-voltage variable frequency system.
3) synchronism switching.Refer to the detection amplitude of voltage, frequency and the switching of phase place.Using synchronism switching technology can make 2.5 times less than Rated motor electric current of switching electric current, during synchronism switching, rotating speed changes minimum before and after power frequency supply throws people.
4) soft handover.Refer to after the detection amplitude of voltage, frequency and phase place, the voltage that the same frequency of control converter output, homophase, amplitude are controlled, it is achieved " unperturbed " switches.Soft handover has first to be thrown rear cutout and first cuts and throw two kinds of situations afterwards.During power frequency supply is switched to variable-frequency power sources, variable-frequency power sources is made to keep consistent with motor side residual voltage phase place first with phase-detection with phase-locked control, on the basis of the V/F of converter keeps being basically unchanged, select optimum high voltage converter switchover operation point, adjust output voltage and the frequency of converter.So, motor basic non-impact current when putting into high voltage converter, the torque of motor is held essentially constant.During variable-frequency power sources is switched to power frequency, by the phase and frequency of phase lock loop locks power frequency supply, controls high voltage converter and make motor switch over when slightly higher than rated voltage and frequency.This way it is possible to realize the soft handover between high-voltage variable frequency power source and power frequency supply.
From above-mentioned introduction it can be seen that the switching of existing variable-frequency power sources and power frequency supply there is problems in that 1) power rush.Either switch to power frequency supply in variable-frequency power sources or switch to variable-frequency power sources from power frequency supply, all there is the operation of full-loading condition deenergization or locking pulse, therefore electrical network or variable-frequency power sources are all existed power rush.2) transient process is produced.Motor load is inductive load, and in a perceptual loop, unexpected disconnecting circuit, will necessarily produce cut-off overvoltage, and corresponding component is produced impact.3) motor load all exists for electrocuting district.Being all to excise current power supply due to existing method, then put into another one power supply, therefore motor certainly exists power supply dead band.
Summary of the invention
Above deficiency in view of prior art, it is an object of the invention to provide a kind of for converter with common frequency power network without impact changing method, when needs carry out variable-frequency power sources with the load switching of power frequency supply band, bearing power can be controlled in power frequency supply and the controlled switching of variable-frequency power sources, thus realize excision or disconnected without flow point or without stream Guan Bi time closed pair answers target power.
It is an object of the invention to by following means realization: a kind of converter and common frequency power network of being used for is without impact changing method, by converter, two frequency converter output voltage sensor TV1 and TV2, two output current of frequency converter sensor TA1 and TA2, two common frequency power network voltage sensor TV3 and TV4 and the switch K1 of control converter switching, control in the system of power frequency supply switching K2 composition, measure the realtime power of motor under pre-grid-connected operating mode in real time, as required the control method of converter is switched between the soft-start methods such as constant voltage constant frequency control and direct Power Control pattern, realize switching without impact between common frequency power network and converter under motor and load soft start thereof and soft stop operating mode, processing procedure including following:
A. motor and load thereof are switched to power frequency supply process by variable-frequency power sources:
1) Guan Bi switch K2 converter uses conventional constant voltage constant frequency control mode to start, start after accelerating to normal speed, utilize inverter output terminal voltage sensor TV1 and TV2, power frequency supply voltage sensor TV3 and TV4 to realize pre-grid-connected, make inverter output terminal voltage completely the same with power frequency supply voltage-phase, amplitude, frequency and phase sequence;
2) after motor is stable, frequency converter output voltage sensor TV1 and TV2, output current of frequency converter sensor TA1 and TA2 is utilized to calculate the real-time active power of motor under conditions present and reactive power and as active power reference P*, reactive power reference Q* under direct Power Control pattern;
3) converter transfers direct Power Control to, voltage magnitude signal required in direct Power Control, power reference needed for phase signal is power frequency supply voltage signal, direct Power Control are given as P*, Q*;
4) Guan Bi switch K1, converter and power frequency supply parallel running;
5) power reducing converter gives to zero, and motor load power shifts to power frequency supply according to certain speed;After the output of converter reduces to zero completely, disconnect K2, it is achieved the excision of converter;
B, motor and load thereof are switched to converter soft stop process by power frequency supply:
1) starting converter use direct Power Control, the power reference needed for voltage magnitude signal required in direct Power Control, phase signal are power frequency supply voltage signal, direct Power Control given is zero;
2) Guan Bi switch K2, by converter and power frequency supply parallel running;
3) by given for the power of converter motor actual power P*, the Q* of being revised as, and the real output of converter is made to increase according to certain speed, until the actual power of converter reaches set-point;
4) open switch K1, excise power frequency supply;
5) control strategy of converter is transferred constant voltage constant frequency control to, and realize the soft stop of motor.
Described one is used for converter with common frequency power network without impact changing method, is transformed into direct Power Control and realizes when being switched over by converter.Its direct Power Control algorithm can use traditional switch list direct Power Control, power feedforward direct Power Control, prediction direct Power Control etc..
Method disclosed by the invention, during by variable-frequency power sources is switched with power frequency supply, by the control mode switching of converter to direct Power Control and control as requested converter power output, realize the parallel connection of target power no-load to excise with no-load, thus realize the nothing impact switching of variable-frequency power sources and power frequency supply, thoroughly eliminate when existing variable-frequency power sources switches with power frequency supply and there is transient process, it is to avoid the adverse effect that system is produced by transient process, improve the reliability of system.
Accompanying drawing explanation
Fig. 1 is that variable-frequency power sources switches schematic diagram with power frequency supply.
Fig. 2 is that the present invention uses frequency converter control system structure chart.
Fig. 3 is the control figure of a kind of power feedforward that the present invention uses, and mainly includes that loading the links such as realtime power calculating, phaselocked loop, feed-forward power control, modulation is constituted.
Fig. 4 is that the power of the present invention controls schematic diagram, and (a) is the adjustment schematic diagram of active power, and (b) is the adjustment schematic diagram of reactive power, as a example by motor load power is switched to common frequency power network by converter.
Detailed description of the invention
The invention will be further described with embodiment below in conjunction with the accompanying drawings.
A kind of converter and common frequency power network of being used for is without impact changing method, by converter, two frequency converter output voltage sensor TV1 and TV2, two output current of frequency converter sensor TA1 and TA2, two common frequency power network voltage sensor TV3 and TV4 and control the switch K1 of converter switching, in system that control power frequency supply switching K2 forms, it is characterized in that this system can motor completed by converter soft start and with synchronized after switch to common frequency power network power time, it is possible to realize converter and the grid-connected without impact of electrical network and converter without stream excision.The switching schematic diagram of converter and power frequency supply is as shown in Figure 1.The present invention use frequency converter control system structure as shown in Figure 2, in figureu abu bcFor inverter output terminal line voltage,i ai bFor converter output current phase, after inverter output terminal voltage and current signal are processed by frequency converter control system, obtain the phase place of inverter output terminal voltage, amplitude and the active-power P of converter output, reactive power Q;u ABu BCFor power frequency electric netting twine voltage, after converter processes, obtain amplitude and the phase place of common frequency power network voltage;Control system uses different control modes in different stage, and generates the switching device of the pulsed drive inverter that sets out, thus forms the output voltage of inverter.
A kind of power feedforward direct Power Control that the present invention uses is as shown in Figure 3.
Power disclosed by the invention controls schematic diagram as shown in Figure 4, and its detailed description of the invention is as follows:
1, motor and load thereof are switched to power frequency supply by variable-frequency power sources:
1) Guan Bi switch K2 converter uses the soft starting modes such as conventional constant voltage constant frequency control to start, start after accelerating to normal speed, inverter output terminal voltage sensor TV1 and TV2, power frequency supply voltage sensor TV3 and TV4 is utilized to realize pre-grid-connected, even if inverter output terminal voltage is completely the same with power frequency supply voltage-phase, amplitude, frequency and phase sequence;
2) after motor is stable, frequency converter output voltage sensor TV1 and TV2, output current of frequency converter sensor TA1 and TA2 is utilized to calculate the real-time active power of motor under conditions present and reactive power and as active power reference P under direct Power Control pattern*, reactive power reference Q*
3) converter transfers direct Power Control to, voltage magnitude signal required in direct Power Control, power reference needed for phase signal is power frequency supply voltage signal, direct Power Control are given as P*、Q*
4) Guan Bi switch K1, converter and power frequency supply parallel running, but power frequency supply does not now have power to export;
5) power reducing converter gives to zero, and motor load power shifts to power frequency supply according to certain speed;After the output of converter reduces to zero completely, disconnect K2, it is achieved the excision of converter.
2, motor and load thereof are switched to converter soft stop by power frequency supply:
1) starting converter use direct Power Control, the power reference needed for voltage magnitude signal required in direct Power Control, phase signal are power frequency supply voltage signal, direct Power Control given is zero;
2) Guan Bi switch K2, by converter and power frequency supply parallel running;
3) it is revised as motor actual power P by given for the power of converter*、Q*, and make the real output of converter increase according to certain speed, until the actual power of converter reaches set-point;
4) open switch K1, excise power frequency supply;
5) control strategy of converter is transferred the soft starting modes such as constant voltage constant frequency control to, and realize the soft stop of motor.
So, by the control to converter, can be achieved with motor and bearing power thereof switching without impact between variable-frequency power sources and power frequency supply, thus avoid corresponding transient process.
The present invention is used for converter with common frequency power network without impact changing method, soft of motor can be realized and can realize on the converter with synchronized, by installing two output current of frequency converter sensors additional, measure the realtime power of motor under pre-grid-connected operating mode in real time, then converter is transferred to direct Power Control and the set-point of direct Power Control is set as the realtime power of motor, subsequently converter is together in parallel with common frequency power network, after parallel connection completes, it is gradually reduced the power set-point of converter to zero, it is then sliced out converter, it is achieved motor common frequency power network is powered.The soft stop process of motor is in contrast.The control method of converter is switched between the two with direct Power Control by the present invention as required at soft starting modes such as constant voltage constant frequency controls; achieve and switch without impact between common frequency power network and converter under motor and load soft start thereof and soft stop operating mode; the no current breaking and closing of target power are reached; avoid the transient process that traditional method exists, improve the reliability of whole system.
Without departing from the spirit and scope of the present invention; those skilled in the art, in the case of without departing from scope and spirit of the present invention, all should fall within the scope and spirit of the invention about form and all obvious amendment of details or change what it was carried out.

Claims (4)

1. one kind is used for converter with common frequency power network without impact changing method, by converter, two frequency converter output voltage sensor TV1 and TV2, two output current of frequency converter sensor TA1 and TA2, two common frequency power network voltage sensor TV3 and TV4 and the switch K1 of control converter switching, control in the system of power frequency supply switching K2 composition, measure the realtime power of motor under pre-grid-connected operating mode in real time, as required the control method of converter is switched with direct Power Control between the two at constant voltage constant frequency control soft-start method, realize switching without impact between common frequency power network and converter under motor and load soft start thereof and soft stop operating mode, processing procedure including following:
A, motor and load thereof are switched to power frequency supply process by variable-frequency power sources:
1) Guan Bi switch K2 converter uses conventional soft starting mode to start, start after accelerating to normal speed, utilize inverter output terminal voltage sensor TV1 and TV2, power frequency supply voltage sensor TV3 and TV4 to realize pre-grid-connected, make inverter output terminal voltage completely the same with power frequency supply voltage-phase, amplitude, frequency and phase sequence;
2) after motor is stable, frequency converter output voltage sensor TV1 and TV2, output current of frequency converter sensor TA1 and TA2 is utilized to calculate the real-time active power of motor under conditions present and reactive power and as active power reference P*, reactive power reference Q* under direct Power Control pattern;
3) converter transfers direct Power Control to, voltage magnitude signal required in direct Power Control, power reference needed for phase signal is power frequency supply voltage signal, direct Power Control are given as P*, Q*;
4) Guan Bi switch K1, converter and power frequency supply parallel running;
5) power reducing converter gives to zero, and motor load power shifts to power frequency supply according to certain speed;After the output of converter reduces to zero completely, disconnect K2, it is achieved the excision of converter;
B, motor and load thereof are switched to converter soft stop process by power frequency supply:
1) starting converter use direct Power Control, the power reference needed for voltage magnitude signal required in direct Power Control, phase signal are power frequency supply voltage signal, direct Power Control given is zero;
2) Guan Bi switch K2, by converter and power frequency supply parallel running;
3) by given for the power of converter motor actual power P*, the Q* of being revised as, and the real output of converter is made to increase according to certain speed, until the actual power of converter reaches set-point;
4) open switch K1, excise power frequency supply;
5) control strategy of converter is transferred constant voltage constant frequency control control mode to, and realize the soft stop of motor.
The most according to claim 1 for converter and common frequency power network without impact changing method, it is characterized in that, and the converter grid-connected without impact of converter and electrical network without stream excision be by converter soft start complete and realize with synchronized after, current transformer is switched to direct Power Control and realizes;Described direct Power Control method can use switch list direct Power Control, power feedforward direct Power Control, prediction direct Power Control method.
The most according to claim 2 for converter and common frequency power network without impact changing method, it is characterized in that, the power setting of described converter direct Power Control low-converter, time in parallel with electrical network, the power of converter is given as converter when running on pre-and net state, the numerical value obtained by sensor voltage transducer TV1 and TV2, the real-time survey calculation of current sensor TA1 and TA2, namely motor gives the realtime power under operating mode;When converter is excised by needs, converter Direct Power set-point is reduced to zero by Rated motor operating mode set-point, excises converter the most again.
The most according to claim 2 for converter and common frequency power network without impact changing method, it is characterized in that, the speed that transducer power set-point reduces to zero from the realtime power of Rated motor operating mode is the rated power according to motor, the setting of converter mute time.
CN201610224083.1A 2016-04-11 2016-04-11 One kind is used for frequency converter with common frequency power network without impact switching method Active CN105871291B (en)

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CN109245661A (en) * 2018-09-29 2019-01-18 苏州英威腾电力电子有限公司 Work frequency conversion switching circuit, control method, system, device and readable storage medium storing program for executing

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