CN204068262U - Active Power Filter-APF containing power cell - Google Patents
Active Power Filter-APF containing power cell Download PDFInfo
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- CN204068262U CN204068262U CN201420534837.XU CN201420534837U CN204068262U CN 204068262 U CN204068262 U CN 204068262U CN 201420534837 U CN201420534837 U CN 201420534837U CN 204068262 U CN204068262 U CN 204068262U
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Abstract
The utility model relates to the Active Power Filter-APF containing power cell.Power cell comprises H-bridge inverter circuit, the DC link electric capacity be connected with inverter circuit DC bus and the control circuit controlling power cell work, described power cell also comprises a copped wave power circuitry, and a small amount of active power being combined with active power filter absorption realizes the control of power cell DC bus-bar voltage.Active Power Filter-APF comprises: the inverter be often made up of at least one power cell, voltage detecting circuit, current detection circuit, central control system, filter circuit, pre-charge circuit, service entrance switch, interface and telecommunication circuit, cooling device etc.
Description
Technical field
The utility model relates to the Active Power Filter-APF containing power cell.
Background technology
Due to various non-linear electric loading, as the increase of frequency converter, rectifying device, arc furnace, high voltage direct current transmission current transformer etc., the problem such as harmonic pollution, power factor decline, asymmetrical voltage, power failure, voltage fluctuation and flicker of electrical network is more and more outstanding.
China Machine Press of China " harmonics restraint and reactive power compensation " (ISBN7-111-06298-1/TM.728) the 7th chapter describes the Active Power Filter-APF for low-voltage power supply electrical network.Active Power Filter-APF is a kind of novel electric power electric device for dynamic harmonic wave, compensating reactive power, and the harmonic wave that all can change size and frequency and the idle of change compensate fast.Utilize power electronic equipment to produce corresponding harmonic current injection power supply grid to offset the harmonic current of nonlinear load generation, thus stop harmonic current to flow into electrical network, avoid line voltage to distort.As required, Active Power Filter-APF can also realize no-power compensation function.Low-voltage active electric power filter is widely applied, but due to the restriction of power electronic device voltage withstand class, low-voltage active electric power filter generally can only be used for the lower electrical network of electric pressure (as 380V or following).As line voltage higher grade (as 6KV), low-voltage active electric power filter is usually adopted to add transformer-coupled mode.
US Patent No. 6075350 proposes a kind of Active Power Filter-APF adopting multiple power unit cascade, as shown in Figure 1.Its principle adopts the mode of multiple power unit cascade to realize high voltage active electric filtering function.Its power cell composition structure as shown in Figure 2.Can find out, the power cell of composition inverter is single-phase H bridge construction, is made up of 4 power electronic device (comprising inverse parallel fly-wheel diode) and DC link electric capacity and interlock circuit.
When this active power filter normally works, all power cell DC bus-bar voltage must control in a suitable value.The control of power cell DC bus-bar voltage is the difficult point that this Active Power Filter-APF realizes.The method that this patent proposes is: get wherein a certain power cell DC bus-bar voltage and, as feedback signal, compare with set-point, forms closed-loop control, realizes control and the balance of power cell DC bus-bar voltage in conjunction with the method for pulse rotation simultaneously.
The subject matter that the Active Power Filter-APF that this patent proposes exists has:
1. direct current bus voltage control method only carries out closed-loop adjustment by being sent to central control system after the detection of the DC bus-bar voltage of a certain particular power cell, can only realize the control of this particular power cell DC bus-bar voltage in principle.Between power cell characteristic and operating mode variant time, even if having employed the method for pulse rotation, because the DC bus-bar voltage of other power cell does not form closed-loop control, the DC bus-bar voltage that still there will be other power cell departs from set-point.
2. the output of inverter is directly connected to electrical network after device after filtering, and when Active Power Filter-APF powers on for the first time, the impulse current caused due to power cell internal capacitor charging may cause Active Power Filter-APF to damage.
3., when in inverter during any one power cell fault, whole Active Power Filter-APF just quits work, and does not have power unit redundancy function.
Chinese patent 200310115393.2 proposes a kind of dc-voltage balance circuit of the reactive generating device based on chain inverter, as shown in Figure 3.Its principle is the minimum value utilizing minimum capacity voltage to ask for device to obtain in all power cell DC bus-bar voltage, then using this value as reference voltage, the DC bus-bar voltage of power cell is carried out regulating error with it, output pulse width modulation signal, after amplifier, regulating power unit DC bus-bar voltage, realizes the balance of different capacity unit DC bus-bar voltage.
This utility model can realize the balance of different capacity unit DC bus-bar voltage, but can not by the DC voltage control of power cell in a certain set point.In addition, in this utility model, discharge resistance two end does not arrange fly-wheel diode, and when resistance endoparasitism inductance is larger, the surge voltage produced in DC bus adjustment IGBT turn off process may cause IGBT excessive pressure damages.
Utility model content
Technical problem to be solved in the utility model is: provide a kind of and overcome above-mentioned deficiency, can realize the Active Power Filter-APF containing power cell that each power cell DC bus-bar voltage controls and control method thereof.
An Active Power Filter-APF containing power cell, comprises the inverter, voltage detecting circuit, current detection circuit and the central control system that are often made up of at least one power cell; Described power cell comprises H-bridge inverter circuit, the DC link electric capacity be connected with H-bridge inverter circuit DC bus and the control circuit controlling power cell work, and described inverter is connected with electrical network by filter circuit, pre-charge circuit, service entrance switch successively;
Described power cell also comprises copped wave power circuitry, realizes the control to each power cell DC bus-bar voltage; In described copped wave power circuitry, discharge resistance is attempted by described H-bridge inverter circuit DC bus two ends after connecting with power electronic device, the input of voltage detecting circuit is connected with the DC bus of described H-bridge inverter circuit, the output of voltage setting circuit and the error of the output of voltage detecting circuit after are relatively input to voltage control circuit, the output of voltage control circuit is connected to the input of Drive Protecting Circuit, and the output of Drive Protecting Circuit is connected to the gate pole of power electronic device;
Described filter circuit is reactor or LC filter, for preventing described electrical network and described inverter two voltage source direct-coupling, utilizes the voltage difference of this two voltage source to produce offset current after described reactor effect simultaneously;
Described pre-charge circuit, is made up of the current-limiting resistance of parallel connection and contactor; When being connected to electrical network for the first time, the impulse current produced during for limiting DC link capacitor charging in described power cell;
Be provided with in described central control system and order by optical fiber to described power cell transmission and accept the fiber optic interface circuits from described power cell feedback information.
Conditioning in described central control system and A/D change-over circuit respectively with for detection of grid voltage voltage detecting circuit, for detect described input current of inverter current detection circuit, be connected for the current detection circuit detecting load current.
Described inverter is three-phase inverter, and three-phase forms star connection.
Described inverter is three-phase inverter, and the described central point of inverter star connection is connected with the central point of three phase network.
Described inverter is three-phase inverter, and three-phase forms delta connection.
Described inverter is single-phase inverter, for single-phase electrical network.
Between described power cell two output, be provided with bypass circuit, for the power cell auto by pass by fault, remaining power cell works on.
Also comprise that be connected with described central control system, for dispelling the heat cooling device.
Also comprise the interface and telecommunication circuit that are connected with described central control system, for realizing the interface in described Active Power Filter-APF and ox portion and communicating.
The charge-discharge circuit and accumulator of connecting successively is provided with between described H-bridge inverter circuit DC bus two ends.
The technical solution of the utility model three is:
A control method for Active Power Filter-APF, comprises the steps:
1) all ripple offset current calculates: according to load current 1L, calculates link through harmonic compensation current, obtains the required harmonic current ih absorbed of Active Power Filter-APF;
2) active current is given: the phase place of active current ip and line voltage V
shomophase, its size obtains in proportion according to the capacity of Active Power Filter-APF, and ensures the discharge power balance of each power cell meritorious absorption value and copped wave power circuitry only;
3) reactive power compensation Current calculation: the target power factor reached according to the idle component of load current and needing after compensating, calculates the reactive current iq that Active Power Filter-APF needs to provide;
4) the set-point if=ih+ip+iq of input current of inverter, detect the actual input current 1 of inverter as value of feedback, obtain the trigger impulse of each power cell through Current adjustment and many level PWMs link, make the actual value tracing preset value of input current of inverter.
Described reactive current iq is zero, and harmonic current ih is non-vanishing, and Active Power Filter-APF only realizes harmonic restraining function.
Described harmonic current ih is zero, and reactive current iq is non-vanishing, and Active Power Filter-APF only realizes no-power compensation function, and now Active Power Filter-APF is equivalent to static reacance generator.
Beneficial effect
The beneficial effects of the utility model are:
The utility model is parallel with copped wave power circuitry due to DC bus two end of each power cell, solves power cell DC bus-bar voltage control problem, and the independence achieving each power cell DC bus-bar voltage controls.When Active Power Filter-APF powers on for the first time, line voltage can be charged to the electric capacity of power cell DC link by pre-charge circuit, solves impulse current problem when powering on for the first time, major loop device is selected more reasonable, reduce costs, reduce the impact to electrical network simultaneously.Due to the difference of power cell characteristic, the DC bus-bar voltage of each power cell is not necessarily equal in charging process, the DC bus-bar voltage of individual power unit may be higher, at this moment copped wave power circuitry just can work, guarantee that the DC bus-bar voltage of power cell can not exceed set point, the safety of electric capacity and power electronic device in guaranteed output unit; Now copped wave power circuitry serves the dynamic equalization function of DC bus-bar voltage between the power cell that is cascaded in pre-charge process.After being equipped with power unit by-pass circuit, can realize power unit redundancy function, the continuation realizing Active Power Filter-APF in power cell fault situation runs.
The Active Power Filter-APF that the utility model relates to can be applied to the fields such as power transmission and transformation, metallurgy, railway, is especially suitable for high-voltage fence (more than 380V, below 800KV), realizes the function such as harmonics restraint and dynamic passive compensation.
Accompanying drawing explanation
Fig. 1 is US Patent No. 6075350 power unit cascade formula active power filter structure;
Fig. 2 is the power cell of US Patent No. 6075350;
Fig. 3 is the dc-voltage balance circuit of Chinese patent 200310115393.2;
Fig. 4 is the power cell of band copped wave power circuitry of the present utility model;
Fig. 5 is the power unit cascade formula active power filter structure of band copped wave power circuitry of the present utility model;
Fig. 6 is the scheme forming LC filter after reactor increases filter capacitor;
Fig. 7 is Active Power Filter-APF control principle drawing;
Each branch current waveform when Fig. 8 is Active Power Filter-APF work;
Fig. 9 is the method that employing two controllable silicons carry out bypass;
Figure 10 is the power unit cascade formula Active Power Filter-APF for three-phase four-wire system electrical network band zero line;
Figure 11 is the power unit cascade formula Active Power Filter-APF for single-phase electrical network;
Figure 12 is the power cell after increasing energy storage link and charge-discharge control circuit.
Embodiment
Below in conjunction with drawings and Examples, the utility model is described in further detail.
Fig. 4 is the power cell of the utility model for the band copped wave power circuitry of Active Power Filter-APF.Power cell forms H-bridge inverter circuit by four power devices, and DC link adopts capacitor to carry out filtering and energy storage, and DC bus two end of power cell is parallel with copped wave power circuitry, realizes the control of power cell DC bus-bar voltage.
Power electronic device Q1 ~ the Q4 of power cell can adopt the devices such as IGBT, MOSFET, IGCT, IEGT, illustrates for IGBT.Utilize the modes such as pulse width modulation (PWM) to realize direct current and become the reversals exchanged, the alternating voltage needed for output.Four power electronic device Q1 ~ Q4 respectively with four sustained diode 1 ~ D4 inverse parallel of inversion, as shown in Figure 4.As a rule, existing commercialization IGBT module is encapsulated in fly-wheel diode and igbt chip in same module.As required, each device shown in figure can adopt the parallel connection of multiple device and/or series connection to realize, to expand capacity.Each power cell, except above-mentioned main circuit, also must be completed the function such as other protection of the driving of power electronic device Q1 ~ Q4, protection and power cell by setting unit control circuit, and be communicated with central control system by optical fiber.The driving of power electronic device, protection and surge absorbing circuit and connection in series-parallel technology etc. are that those skilled in the art is known, repeat no more.
Capacitor banks C is connected in parallel on DC bus two end, provides High frequency filter and energy storage function.Capacitor can adopt electrochemical capacitor or thin-film capacitor, can be made up of as required multiple electric capacity connection in series-parallel, is equipped with grading resistor during series connection.
Copped wave power circuitry 401 is made up of voltage setting circuit, voltage detecting circuit, voltage control circuit, Drive Protecting Circuit, power electronic device Q5, discharge resistance Rb, sustained diode 5.
Voltage setting circuit is used for the desired value that setting power unit DC bus-bar voltage controls.Set point is generally a fixed value, also by central control system setting, suitably adjusts according to different operating states.
Voltage detecting circuit is used for the DC bus-bar voltage of detection power unit, and the common methods such as usual available Hall voltage transducer or electric resistance partial pressure realize.
Voltage control circuit be used for the actual detected value Vdc of power cell DC bus-bar voltage and power cell DC bus-bar voltage set point Vdc* is compared, its deviation through hysteresis comparator or other related circuit, output pulse width modulation signal.Its objective is that controlling DC bus-bar voltage is stabilized in set point.
Drive Protecting Circuit is connected to the gate pole of power electronic device after amplifying for the pulse-width signal exported by voltage control circuit, thus drives power electronic device.Drive Protecting Circuit is protected power electronic device simultaneously.Such as, when power electronic device overcurrent being detected, close trigger impulse.
Power electronic device Q5 is used for the work of controlled discharge resistance Rb, thus controls DC bus-bar voltage.Power electronic device Q5 can adopt the power electronic device such as IGBT.
Power cell DC bus two end is connected in parallel on after discharge resistance Rb and power electronic device Q5 series connection.When power electronic device Q5 conducting, the energy that Capacitor banks C stores is discharged by discharge resistance Rb, makes the instantaneous decline of DC bus-bar voltage.
Sustained diode 5 and discharge resistance Rb parallel connection.Main Function provides continuous current circuit when power electronic device Q5 turns off to the electric current that the entozoic stray inductance of discharge resistance Rb flows through.When discharge resistance Rb adopts noninductive resistance, sustained diode 5 also can not be arranged.
The position of power electronic device Q5, discharge resistance Rb and inverse parallel sustained diode 5 can exchange up and down.
Inverter needs to draw a small amount of active power to maintain the DC bus-bar voltage of each power cell Capacitor banks two end from electrical network in the course of the work.Power definition after Active Power Filter-APF deducts reactor, H bridge inversion link, the loss equal loss of DC link capacitor group own from the active power that electrical network is drawn is the clean meritorious absorption value of Active Power Filter-APF.When the clean meritorious absorption value of power cell is greater than zero, power cell DC link electric capacity is charged, DC bus-bar voltage rises, then copped wave electric discharge is carried out by copped wave power circuitry, the average discharge power of each power cell copped wave power circuitry and the clean meritorious absorption value of each power cell realize balance, and DC bus-bar voltage is controlled at required numerical value.The active power drawn from electrical network due to Active Power Filter-APF is very little, ' as 1 ~ 2% of Active Power Filter-APF rated capacity, thus in copped wave power circuitry the electric current of power electronic device and the average power of discharge resistance also very little.But the instantaneous power of discharge resistance must be greater than power cell meritorious absorption value only, when guaranteeing power electronic device Q5 conducting, DC bus-bar voltage can instantaneous decline.Because each power cell characteristic and operating mode can be variant, what cause different capacity unit to be drawn is clean meritorious inconsistent, but owing to taking independently copped wave power circuitry in each power cell, so the consistent of each power cell DC bus-bar voltage still can be ensured.
Realize example below using hysteresis comparator as voltage control circuit, the operation principle of copped wave power circuitry is described.Actual detected value Vdc and the power cell DC bus-bar voltage set point Vdc* of each power cell DC bus-bar voltage compare, and its deviation, through having the comparator of stagnant ring, controls conducting or the shutoff of power electronic device Q5.The hysteresis band of hysteresis comparator is set as 2 Δ Vdc, and wherein Δ Vdc is power cell DC bus-bar voltage permissible variation.As actual detected value Vdc > Vd*c ten Δ Vdc; hysteresis comparator exports high level; after Drive Protecting Circuit, make power electronic device Q5 conducting, the energy that DC link electric capacity stores is discharged by discharge resistance Rb, impels actual detected value Vdc to decline.As Vdc < Vdc*-Δ Vdc, hysteresis comparator output low level, makes power electronic device Q5 turn off after Drive Protecting Circuit, stops electric discharge, and clean the gaining merit simultaneously utilizing power cell to draw impels DC bus-bar voltage to rise.And as Vdcc*+Vdc > Vdc > Vdc*-Δ Vdc, hysteresis comparator exports constant.This is break-make repeatedly, forces DC bus-bar voltage tracking fixed valure, and only zigzag fuctuation within a narrow range in the error range 2 Δ Vdc allowed, reaches the object that DC bus-bar voltage controls.Also need of course simultaneously to limit the highest switching frequency of power electronic device Q5.
Voltage control circuit, except with except hysteresis comparator, also can adopt periodic sampling to control the mode such as comparison circuit, Switching Power Supply integrated circuit and realize.
Power cell DC bus-bar voltage set point Vdc* and power cell DC bus-bar voltage permissible variation Δ Vdc is set to a fixed value usually, also by central control system setting, suitably adjusts according to different operating states.
Power cell DC bus-bar voltage set point Vdo* setting principle is: before running after pre-charge process and precharge terminate, because power electronic device Q1 ~ Q4 in now power cell is in off state, be equivalent to line voltage and charged to the electric capacity of each power cell by the sustained diode 1 ~ D4 in each power cell of being cascaded.Power cell DC bus-bar voltage set point Vdc* guarantees to be higher than the DC bus-bar voltage that Series power cell-average bears.The copped wave power circuitry of major part power cell is not done, and only has individual power unit owing to being adjusted by copped wave power circuitry when property difference causes DC bus-bar voltage too high.If the set point of power cell DC bus-bar voltage set point Vdc* is too low, the DC bus-bar voltage of all power cells can be caused always higher than set point, and the situation of power electronic device Q5 conducting always, must avoid.When active electric filter device normally works, following requirement should be met: after power unit cascade, the maximum output voltage of inverter enough supports the pressure drop on line voltage and reactor L; Consider the normal fluctuation of line voltage; The harmonic voltage component superposed in inverter output voltage during consideration harmonic compensation.
According to mentioned above principle, DC bus-bar voltage set point Vdc* can be selected with reference to following formula
Vdc*≥KUlnp/n
Wherein Ulnp is electrical network phase voltage peak value, and n is the power cell number that is often in series, and K is the coefficient after comprehensive voltage ripple of power network, reactor pressure drop and inverter output voltage harmonic component, usually gets more than 1.2.
The Active Power Filter-APF of the power grid application being 3KV for line voltage effective value, supposes often to be formed by 3 power unit cascades, selects K=1.2, can obtain Vdc* >=1.2* (3000*1.414/1.732)/3=980V.Desirable power cell DC bus-bar voltage set point Vdc* is 1000V.Main circuit can select the withstand voltage IGBT device for 1700V, and selection rated voltage is the electrochemical capacitor 3 groups series connection of 450V.
Fig. 5 is the structure of the power unit cascade formula Active Power Filter-APF of band copped wave power circuitry of the present utility model.Comprise inverter, filter circuit, pre-charge circuit, service entrance switch, voltage detecting circuit and current detection circuit, central control system, optical fiber, interface and telecommunication circuit, the cooling device etc. of being often with the power cell of copped wave power circuitry to form by least one to form.
Inverter 510 is often in series successively by the individual power cell with the band copped wave power circuitry of independent direct current link of n (n is more than or equal to 1).Three-phase forms star connection, and the high-voltage output end 506,507,508 after series connection is by being connected to the three-phase of electrical network separately after filter circuit, pre-charge circuit and service entrance switch.It is 3 level that each power cell exports, and is respectively positive DC bus-bar voltage, negative DC bus-bar voltage and zero level, and after n power unit cascade, inverter exports phase voltage is 2n+1 level.Typically, as shown in Figure 5, in inverter, the power cell of three-phase series forms star connection.Under specific circumstances, also three-phase can be connected according to delta connection.
Filter circuit adopts reactor L as filter element usually.The effect of reactor L prevents electrical network Vs and inverter from exporting V
fthe direct-coupling of these two voltage sources, the voltage difference both simultaneously utilizing produces the electric current needing to compensate after reactor effect.Reactor also plays inhibitory action to the high-frequency harmonic electric current that power electronic device switching process produces simultaneously.In order to improve high-frequency harmonic inhibition, reducing the EMI (electromagnetic interference) of Active Power Filter-APF, except reactor L, also can increase high-frequency filter capacitor C.Composition LC filter circuit, as shown in Figure 6.Filter circuit can also take other various known structure.Reactor can adopt three single-phase reactors as shown in Figure 5, also can adopt a three-phase reactor.Reactor can adopt the material such as silicon steel sheet or non-crystaline amorphous metal as the reactor of iron core or air core reactor.
The effect of pre-charge circuit is impulse current when playing capacitor charging in power-limiting unit when Active Power Filter-APF is connected to electrical network for the first time.If there is no pre-charge circuit, when Active Power Filter-APF accesses electrical network for the first time, electric capacity in power cell has a charging process, line voltage charges to the electric capacity of each power cell by the sustained diode 1 in power cell, D2, D3 and D4, and now four fly-wheel diodes are equivalent to constitute a single-phase full bridge rectification circuit.When electric capacity is uncharged, electric capacity two end is almost equivalent to short circuit.Because the impedance of the reactor L connected between inverter and electrical network is limited, very large charging current can be caused, damage is caused to the device such as fly-wheel diode, electric capacity.
In Fig. 5, pre-charge circuit is composed in parallel by current-limiting resistance R and contactor M, current-limiting resistance R also can replace with reactor, pre-charge circuit plays metering function when Active Power Filter-APF powers on, in constant power unit, capacitance voltage reaches a certain numerical value, as power cell DC bus-bar voltage set point Vdc* 70% time, by central control system adhesive contactor M, by current-limiting resistance bypass, complete pre-charge process.Also a certain set point is dropped to by detecting charging current, or the foundation that the time delay regular hour terminates as charging.Because the current-limiting resistance operating time is very short, become short time duty so can design.Contactor uses three-phase ac contactor usually, also can replace with contactless electronic beam switch such as controllable silicons.When three-phase three-wire system is applied, in order to cost-saving, also only pre-charge circuit can be set in two-phase wherein.After pre-charge process terminates, Active Power Filter-APF enters operation standby condition, accepts operating instruction at any time, and inverter exports corresponding voltage and carries out harmonics restraint and reactive power compensation.
Service entrance switch VCB can adopt vacuum circuit-breaker, as shown in Figure 5, fuse also can be adopted to add the schemes such as contactor, when not working for Active Power Filter-APF and the isolation of electrical network and cutting off the electricity supply when Active Power Filter-APF specific fault, realizes necessary protection.Physically, service entrance switch accessible site is inner at Active Power Filter-APF, also can be arranged on separately Active Power Filter-APF outside.
Active Power Filter-APF needs the input current of detection of grid voltage, load current and inverter as feedback signal usually.Voltage check device can adopt the methods such as voltage transformer, Hall voltage transducer, high-tension resistive dividing potential drop.Can phase voltage Vsa be detected, Vsb and Vsc, or detection line voltage Vsab, Vsbc and Vsca.Current sensing means adopts Hall current sensor or other high-performance electric flow sensor usually, for three-phase three-wire system electrical network, often overlap employing two current sensors, if current sensor CT1 and CT2 in Fig. 5 is for detecting load current, current sensor CT3 and CT4 is for detecting input current of inverter.For three line four-wire system electrical networks, load current detection at least needs three current sensors.
Also the detection of load current il can be replaced by the method detecting total current is, i.e. il=ie-if.Like this, also can be realized the control of Active Power Filter-APF as feedback signal by detection of grid voltage, total current and input current of inverter.
Central control system 509 completes the core controlling functions of Active Power Filter-APF, comprising: the compositions such as conditioning and A/D change-over circuit, processor, field programmable gate array, fiber optic interface circuits, interface circuit.The feedback signal of voltage and current testing circuit converts digital signal to through A/D after modulate circuit process, is gathered by processor.Processor can adopt the high speed digital signal processors such as DSP, carries out harmonic current and the reactive current calculating of load according to the voltage and current of sampling; Then according to the target that harmonics restraint and reactive power compensation will reach, in conjunction with meritorious given value of current value, the electric current that inverter needs input is calculated; Carry out closed-loop current control, the voltage instruction needed for output inverter.Field Programmable Gate Array can adopt the devices such as FPGA, mainly realizes many level PWMs; Fiber optic interface circuits is ordered by optical fiber to power cell transmission and accepts the feedback information from power cell, and the signal of Optical Fiber Transmission comprises the switch command of power electronic device in power cell, the state feedback of power cell, guard signal etc.Usual each power cell needs 1 pair of optical fiber, and every platform three phase active electric power filter needs 3n to optical fiber altogether.Central control system goes back connecting interface telecommunication circuit simultaneously, realize and outside interface, man-machine interface, the function such as communicate.Central control system also realizes various defencive function; Cooperation control pre-charge circuit, cooling circuit and service entrance switch etc.
Fig. 7 is the control principle drawing of active electric filter device, and the variable in figure does not specialize A, B, C three-phase, represents and is suitable for wherein any phase.Control algolithm is realized in conjunction with software computing by hardware circuit usually.
Harmonic compensation current calculates link operation principle: according to the load current il detected, utilize trapper by the fundametal compoment ilf filtering in load current, obtain the harmonic component ilb=il-ilf in load current.Then the harmonic compensation effect reached as required, obtains the required harmonic current lh* absorbed of Active Power Filter-APF.When needs compensate whole harmonic wave, ih*=-ilh.As required, also can compensate targetedly for the harmonic wave of specific times specially.
The given active current ZP of the given link of active current carrys out guaranteed output unit and absorbs a small amount of active power, independently controls each power cell DC bus-bar voltage in conjunction with the copped wave power circuitry in each power cell.The phase place of active current ZP and line voltage Vs homophase, its size, usually according to the capacity of Active Power Filter-APF, then obtains according to certain ratio, is such as set as 1 ~ 2% of rated current.Active current ip* can be set as a fixed value, also suitably can be adjusted according to operating condition by central control system.The principle that active current ZP* is arranged guarantees the average discharge power balance of each power cell meritorious absorption value and copped wave power circuitry only, realizes the control of DC bus-bar voltage.
Need the occasion of carrying out reactive power compensation at the same time, target compensation electric current has also superposed the fundamental reactive current iq* for reactive power compensation.Reactive power compensation Current calculation link operation principle is: utilize the phase difference between the available load fundamental current of the technology such as phase-locked loop and line voltage, and the amplitude in conjunction with load fundamental current just can obtain the idle component of load current.Then according to the target power factor needing after compensation to reach, the reactive current iq* that Active Power Filter-APF needs to provide is calculated.Reactive current iq* and line voltage Vs differs 90 degree, and when reactive current iq* delayed line voltage Vs phase angle is 90 degree, it is idle that Active Power Filter-APF absorbs perception; When reactive current iq* advanced line voltage Vs phase angle is 90 degree, it is idle that Active Power Filter-APF sends perception.
In sum, the target compensation electric current that Active Power Filter-APF absorbs can comprise three parts: for offsetting the corresponding harmonic current 1h* of load current harmonic component; For a small amount of active current iP* of holding power unit DC bus-bar voltage; For the corresponding reactive current iq* that compensating load is idle.The set-point if-*=ih}*+iPtl*+iq* of input current of inverter.When reactive current iq* is 0, when harmonic current ih* is not 0, Active Power Filter-APF only realizes harmonic restraining function; When harmonic current ih* is 0, when reactive current lq* is not 0, Active Power Filter-APF only realizes no-power compensation function, and now Active Power Filter-APF is equivalent to static reacance generator (SVG or STATCOM); When reactive current iq* and harmonic wave electric current I n* is not all 0, Active Power Filter-APF realizes harmonics restraint and no-power compensation function simultaneously.
The current i f detecting the actual input of inverter, as value of feedback, obtains the trigger impulse of corresponding each power cell, by Optical Fiber Transmission to each power cell after Current adjustment and many level PWMs link.The usual adoption rate integral controller of Current adjustment, proportional controller or other current control method, in order to accelerate dynamic response, can set up feedforward link.Many level PWMs link, except phase-shifting carrier wave formula multilevel PWM methods, can also take square wave to superpose the method such as fitting process, space voltage vector control method.When unit control circuit performance is enough, also by optical fiber directly by inverter output voltage instruction Vf, power cell can be sent to, completes PWM controlling functions by power cell self, obtain the trigger impulse of work GBT.Final purpose makes the quick tracing preset value if* of input current of inverter actual value if.
For harmonic component in load current and idle component detection in addition to the method as described above, the real-time detection method based on instantaneous reactive power theory and the method based on fourier transform can also be adopted.
The current waveform of each branch road when Fig. 8 is Active Power Filter-APF work, for A phase, the reference direction of electric current is according in Fig. 5 shown in arrow.Wherein ila is the load current waveform of A phase, can find out because load is Nonlinear Integer current load, cause load current waveform Severe distortion, containing larger harmonic component.When Active Power Filter-APF works, its A phase input current waveform is as shown in ifa.The total current 1sa=1la+1fa that electrical network A phase exports.Can find out, due to the effect of Active Power Filter-APF, draw the electric current contrary with harmonic component in load current, or can be regarded as and have issued the electric current equivalent with harmonic component in load current, cause in total power network current substantially not containing harmonic wave, waveform close to sinusoidal wave, thus ensure that grid voltage waveform does not produce distortion.The effect of interface and telecommunication circuit is the interface and the communication function that realize Active Power Filter-APF and outside, includes but not limited to man-machine interface, as display screen, and indicator light, button etc.; External control and state terminal, as the input and output and fieldbus etc. of various switching value, analog quantity.
The effect of cooling device is dispelled the heat to IGBT or other element.Usually heater element can be arranged on fin or heat pipe and dispel the heat, coolant can adopt natural air cooling, forced ventilation cooling or water-cooled etc.Final purpose ensures that the temperature of device is operated in allowed band.
In order to improve the reliability of device further, power unit by-pass can be adopted to realize power unit redundancy function as option.When power cell fault, automatically by the power unit by-pass of fault, remaining power cell works on.When inverter output voltage has rich, namely, when the output voltage of inverter enough and line voltage mates after remaining power unit cascade after every phase bypass power cell, Active Power Filter-APF can be realized by the power cell of bypass fault and continue to run.When power cell output voltage does not reach above-mentioned requirements, standby power units can be increased on the original basis, i.e. the method for n+1.During normal work, n+1 power cell of every phase all works or selects wherein n work, after having power cell fault to be bypassed, guarantees that a remaining n power cell can provide enough output voltages.
Power cell with bypass functionality as shown in Figure 9.By increasing bypass circuit 901 and the realization of required control circuit on existing power cell basis.When power cell is normal, controllable silicon SCR 1 and SCR2 are in off state, when power cell fault, block power electronic device Q1 ~ Q4, then trigger controlled silicon conducting, realize the short circuit that power cell exports T1 and T2, complete bypass functionality.Usually also need to arrange fuse F, when preventing power electronic device Q1 ~ Q4 fault from cannot turn off, remaining DC bus-bar voltage causes bypass circuit to damage by bypass circuit short circuit.Except adopting controllable silicon as except by-pass switch, other power electronic device or contactor also can be adopted as by-pass switch.
Generally speaking, after the bypass of a certain phase power cell fault, other two corresponding power cells also should bypass, to ensure the symmetry of inverter three-phase voltage.Also can adopt central point offset power unit by-pass technology, i.e. the power cell of a bypass fault, by conjunction with the phase adjusted between three-phase voltage, mutual deviation time normal 120 degree is adjusted to other angle, realize the balance of output line voltage.
Active Power Filter-APF can be used for the supply network that frequency is 50HZ, 60HZ, 400HZ or other frequency.Can be used for the electrical network of three-phase triangle, star connection (band zero line or not with zero line), or for single-phase electrical network and polyphase electrical system (number of phases of Active Power Filter-APF corresponding to the electrical network number of phases).Also can be used for direct current network, as the harmonics restraint of high voltage direct current transmission electrical network DC side.
Active Power Filter-APF can also realize the correction of threephase load current imbalance, reduces the asymmetric degree flowing through the three-phase current of electrical network.
In three-phase four-wire system electrical network, if the central point of inverter is connected with the central point of load, Active Power Filter-APF can also provide zero-sequence current to reduce the electric current flowing through electrical network zero line.Corresponding main circuit as shown in Figure 10.Now, load current detection and input current of inverter detect each needs three current sensors.
For single-phase electrical network power unit cascade formula Active Power Filter-APF main circuit as shown in figure 11.
If after making the capacitor of power cell DC link into ultracapacitor by traditional electrochemical capacitor or thin-film capacitor, when electrical network momentary power failure, utilize the energy that ultracapacitor stores, Active Power Filter-APF can solve that line voltage is instantaneous falls problem.
As Figure 12, the accumulator such as batteries or superconducting coil and charge-discharge circuit is equipped with in power cell DC bus link, and in conjunction with active power controller, Active Power Filter-APF can be powered to load continuous when grid cut-off, realizes the function of Dynamic Voltage Regulator (DVR), battery energy storage system (BESS) or superconductive energy storage system (SMES).Time normal, Active Power Filter-APF draws corresponding active power from electrical network, accumulators group or superconducting coil charging, and when grid cut-off or when falling, batteries or superconducting coil electric discharge, Active Power Filter-APF exports corresponding active power to electrical network.Charge-discharge circuit can adopt conventional accumulator charging/discharging circuit or chopped mode superconducting coil energy steering circuit.
Power cell is except two level H-bridge inverter circuit structures shown in Fig. 4, and inverter bridge also can adopt three level (central point clamping type) or many level block.When actual product realizes, in order to reduce costs, reduce volume, can consider physically two or more power cells to be done together, become a big unit.Typically, the power cell specification in an Active Power Filter-APF is identical, can exchange.Under special circumstances, the power cell mixing series connection of different voltage specification can also be adopted.
Existing low-voltage active electric power filter is the three-phase PWM circuit of two level or three-level structure due to what adopt, and in order to reach desirable harmonic effect, the switching frequency of power electronic device needs higher, as 10KHZ usually.In power unit cascade formula Active Power Filter-APF, in each power cell, the switching frequency of power electronic device can be relatively low, as about 1KHZ, the advantage brought like this is that the switching loss of power electronic device is greatly lower, and the electromagnetic interference that Active Power Filter-APF produces simultaneously also reduces greatly.Owing to have employed cells cascaded multilevel structure, the switching frequency of inverter output voltage equivalence is still very high, and the level number exporting phase voltage is 2n+1, can realize good harmonic suppression effect.
Active Power Filter-APF usually and nonlinear load use in parallel, as required, also can use by being connected between power supply and nonlinear load after transformer coupled.When individual capacity is inadequate, multiple stage Active Power Filter-APF can in parallelly use to expand capacity.Active Power Filter-APF also can carry out used in combination with passive power filter, comprises the various modes such as series hybrid uses and parallel connection is used in combination.As required, also transformer-coupled method can be adopted, the side of transformer (as 6KV) is received Active Power Filter-APF, opposite side receives more high-tension electrical network (as 110KV), make Active Power Filter-APF can be used for more high-tension electrical network, the quantity of Series power unit is unlikely to again too many simultaneously.When adopting transformer coupled, when the leakage inductance of transformer is enough large, reactor L can not be arranged, and is replaced by transformer leakage inductance.
The utility model is described above with reference to embodiment of the present utility model; but those of ordinary skill in the art obviously can make various amendment, changes and improvements to embodiment, but these amendments, changes and improvements all should belong to protection range of the present utility model.
Claims (8)
1. the Active Power Filter-APF containing power cell, every inverter, voltage detecting circuit, current detection circuit and central control system be made up of at least one power cell forms, described power cell comprises H-bridge inverter circuit, the DC link electric capacity be connected with H-bridge inverter circuit DC bus and the control circuit controlling power cell work, is characterized in that; Described inverter is connected with electrical network by filter circuit, pre-charge circuit, service entrance switch successively;
Described power cell also comprises copped wave power circuitry, realizes the control to each power cell DC bus-bar voltage; In described copped wave power circuitry, discharge resistance is attempted by described H-bridge inverter circuit DC bus two ends after connecting with power electronic device, the input of voltage detecting circuit is connected with the DC bus of described H-bridge inverter circuit, the output of voltage setting circuit and the error of the output of voltage detecting circuit after are relatively input to voltage control circuit, the output of voltage control circuit is connected to the input of Drive Protecting Circuit, and the output of Drive Protecting Circuit is connected to the gate pole of power electronic device;
Described filter circuit is reactor, for preventing described electrical network and described inverter two voltage source direct-coupling, utilizes the voltage difference of this two voltage source to produce offset current after described reactor effect simultaneously;
Described pre-charge circuit, is made up of the current-limiting resistance of parallel connection and contactor; When being connected to electrical network for the first time, the impulse current produced during for limiting DC link capacitor charging in described power cell;
Be provided with in described central control system and order by optical fiber to described power cell transmission and accept the fiber optic interface circuits from described power cell feedback information; Conditioning in described central control system and A/D change-over circuit respectively with for detection of grid voltage voltage detecting circuit, for detect described input current of inverter current detection circuit, be connected for the current detection circuit detecting load current.
2. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: described inverter is three-phase inverter, and three-phase forms star connection; The described central point of inverter star connection is connected with the central point of three phase network.
3. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: described inverter is three-phase inverter, and three-phase forms delta connection.
4. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: described inverter is single-phase inverter, for single-phase electrical network.
5. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: between described power cell two output, be provided with bypass circuit, for the power cell auto by pass by fault, remaining power cell works on.
6. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: also comprise that be connected with described central control system, for dispelling the heat cooling device.
7. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: also comprise the interface and telecommunication circuit that are connected with described central control system, for realizing the interface of described Active Power Filter-APF and outside and communicating.
8. the Active Power Filter-APF containing power cell according to claim 1, is characterized in that: between described H-bridge inverter circuit DC bus two ends, be provided with the charge-discharge circuit and accumulator of connecting successively.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US9935491B2 (en) | 2015-10-13 | 2018-04-03 | Industrial Technology Research Institute | Polyphase power dispatching system and method |
| CN110571824A (en) * | 2019-08-30 | 2019-12-13 | 北京星航机电装备有限公司 | iron core magnetization experimental equipment and direct voltage adjustable SVG control method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9935491B2 (en) | 2015-10-13 | 2018-04-03 | Industrial Technology Research Institute | Polyphase power dispatching system and method |
| CN110571824A (en) * | 2019-08-30 | 2019-12-13 | 北京星航机电装备有限公司 | iron core magnetization experimental equipment and direct voltage adjustable SVG control method thereof |
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