CN105071403B - Reactive power compensator and control method based on dual H-bridge modular multilevel topology - Google Patents
Reactive power compensator and control method based on dual H-bridge modular multilevel topology Download PDFInfo
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- CN105071403B CN105071403B CN201510474771.9A CN201510474771A CN105071403B CN 105071403 B CN105071403 B CN 105071403B CN 201510474771 A CN201510474771 A CN 201510474771A CN 105071403 B CN105071403 B CN 105071403B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
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Abstract
Reactive power compensator and its control method based on dual H-bridge modular multilevel topology, it is related to a kind of high-power, many level reactive power compensators and its control method.The problem of the invention aims to solve low prior art transverter output level number and bad loop current suppression effect.The present invention includes three-phase alternating-current supply, load, MMC transverters, signal acquisition circuit, control circuit and drive circuit, the MMC transverters include the identical bridge arm being connected in parallel of three structures, each bridge arm is included on point symmetry in bridge arm and the upper bridge arm being connected in series and lower bridge arm, the upper bridge arm includes reactor, the first H-bridge unit, the second H-bridge unit and some half-bridge cells being serially connected, the reactor of the reactor of upper bridge arm and lower bridge arm is connected in series, and the midpoint of three bridge arms of transverter is connected between three-phase alternating-current supply and load by conductor in parallel.The present invention realizes the reactive-load compensation in high-power field.
Description
Technical field
The present invention relates to a kind of new reactive power compensator and its control method, and in particular to based on dual H-bridge modularization
The reactive power compensator and its control method of many level topologys, belong to high-power, many level reactive power compensation technology fields.
Background technology
With continuing to develop for power system scale, the capacity and voltage class of reactive power compensator are proposed new
It is required that, it is constantly developed to high-power field, many level topological structures arise at the historic moment.
The basic thought of multilevel converter is to approach Sine Modulated waveform with multiple output level numbers.More typical is more
Level topological structure has three kinds：Diode clamp bit-type, striding capacitance type and H bridge cascade connection types.Diode clamp bit-type is with winged across electricity
Appearance type structure, with the increase of level number, required switching device and clamp capacitor quantity is greatly increased, and is unfavorable for realization higher
The translation circuit of level, and capacitance voltage is difficult equilibrium, and popularization and application are restricted.H bridge cascade structures, are exported when three-phase
During current-unbalance, active energy can not be transmitted between bridge arm, it is difficult to realize the capacitor voltage balance between three-phase module.
The content of the invention
The invention aims to solve, prior art transverter output level number is low and loop current suppression effect is bad
Problem.
The technical scheme is that：Based on the reactive power compensator of dual H-bridge modular multilevel topology, including three intersecting
Power supply, load, MMC transverters, signal deteching circuit, DSP module and drive circuit are flowed, the transverter includes three structure phases
With the bridge arm being connected in parallel, each bridge arm is included on point symmetry in bridge arm and the upper bridge arm being connected in series and lower bridge arm, described
Upper bridge arm includes resistance, reactor, the first H-bridge unit, the second H-bridge unit and some half-bridge cells being serially connected, upper bridge arm
The reactor of reactor and lower bridge arm be connected in series, the midpoint of three bridge arms of transverter is connected on three-phase alternating current by conductor in parallel
Between power supply and load, the input of signal deteching circuit connect respectively the output end of three AC powers, the input of load,
The output end of transverter, three bridge arms of transverter, the first H-bridge unit, the second H-bridge unit and each half-bridge cells, signal detection
The output end of circuit connects the input of DSP module, and the output end of DSP module is set up by drive circuit with transverter to be connected.
The DSP module includes the first control unit and the second control unit, the output end of the first control unit and second
The output end of control unit is set up with drive circuit be connected respectively, and first control unit includes first comparator, the second ratio
Compared with device, the 3rd comparator, the 4th comparator, the 5th comparator, the first PI controllers, the 2nd PI controllers, the 3rd PI controllers,
First coordinate converter, the second coordinate converter, the first reactor, the second reactor, the first modulating unit and capacitance voltage row
Sequence unit, after first comparator, the first PI controllers, the second comparator, the 2nd PI controllers and the 3rd comparator are sequentially connected in series
The first coordinate converter is accessed, the 4th comparator, the 3rd PI controllers and the 5th comparator access the first coordinate after being sequentially connected in series
Converter, the output end of the first coordinate converter connects the first modulating unit, the output end connection electric capacity electricity of the first modulating unit
Sequencing unit is pressed, the output end connection drive circuit of capacitance voltage sequencing unit, the output end connection second of the transverter is sat
Converter is marked, the first output end of the second coordinate converter connects the second comparator and the second reactor, the second reactor respectively
Output end connect the 3rd comparator, another output end of the second coordinate converter connects the 4th comparator and the first reactance respectively
Device, the output end of the first reactor connects the 5th comparator.
Second control unit includes the 6th comparator, the 7th comparator, the 8th comparator, the 9th comparator, the first ratio
Controller, the second proportional controller, the 4th PI controllers, the 5th PI controllers, function module and the second modulating unit, the 6th ratio
The 9th is accessed after being sequentially connected in series compared with device, the first proportional controller, the 7th comparator, the 4th PI controllers and the second proportional controller
Comparator, the 8th comparator, the 5th PI controllers and function module access the 9th comparator after being sequentially connected in series, the 9th comparator
Output end connects the second modulating unit, the output end connection drive circuit of the second modulating unit.
The reactive power compensator based on dual H-bridge modular multilevel topology includes voltage zero-crossing detection circuit, described
Voltage zero-crossing detection circuit includes voltage sensor, comparison circuit and phase inverter, and the input connection three of voltage sensor is intersected
Flow the output end of power supply, the output end of voltage sensor connects the input of comparison circuit, the output end of comparison circuit passes through anti-
Phase device circuit accesses DSP module.Although the voltage of general power network is power frequency 50Hz, can also there are the phenomenon fluctuated up and down, institute
With, it is necessary to be tracked using voltage zero-crossing detection circuit to mains frequency, the electric voltage frequency and power network for producing SVG ACs
Frequency is consistent.
The reactive power compensator based on dual H-bridge modular multilevel topology includes current detecting and modulate circuit, institute
Stating current detecting and modulate circuit includes current sensor, optical isolation amplifier and biasing circuit, the output of current sensor
End connection optical isolation amplifier, the output end connection biasing circuit of optical isolation amplifier, biasing circuit output end is electric current
Detection and the output end of modulate circuit, anti-interference energy that is delayed caused by sampling element and improving detection signal can be reduced as far as possible
Power.
The reactive power compensator based on dual H-bridge modular multilevel topology includes current foldback circuit, overcurrent protection
Circuit includes comparator and catching diode circuit, and the inverting input of comparator and the output end of signal acquisition circuit, which are set up, to be connected
Connect, midpoint of the output end through clamp circuit of comparator is set up with DSP module to be connected, and passes through TMS320F2812 power drive
Protection interrupts PDPINTA to realize current protection process.
The control method of the reactive power compensator based on dual H-bridge modular multilevel topology, including using based on wink
When reactive power theory ip-iqElectric current testing is detected to electric current；To half-bridge cells, the first H-bridge unit and the 2nd H bridges
Unit is controlled respectively；
The control to half-bridge cells includes the compensation to System Reactive Power and maintains the steady of half-bridge cells capacitance voltage
It is fixed, modulated signal is generated according to the voltage, current double closed-loop control method that are decoupled based on closed loop, using the electricity based on phase-shifting carrier wave
Holding voltage ranking method makes the capacitance voltage of half-bridge cells stable；
The control to the first H-bridge unit increases level number using the first H-bridge unit, and maintains the first H bridge lists
The stabilization of first capacitance voltage；
The control to the second H-bridge unit includes the balanced and whole reactive power compensator of the second H-bridge unit capacitance voltage
The suppression of circulation.
Capacitance voltage ranking method based on phase-shifting carrier wave includes：
(1) determination of level number need to be put into
First, the shifting of modulating wave and each bridge arm that feed forward decoupling control is obtained will be passed through using shifting modulation technology
Phase triangular carrier is compared, and the level number N needed, the phase shift triangular carrier is produced by the first modulating unit；
Then, judge obtaining level number N, obtain new level number k；Further according to each bridge arm half-bridge cells electric capacity
The flow direction of voltage levels ordering scenario and bridge arm current selects corresponding k half-bridge cells input；
(2) the step of half-bridge cells capacitance voltage ranking method
According to bridge arm current iarmDirection carry out judge as follows：
Work as iarm>When 0, then k minimum half-bridge list of capacitance voltage is put into according to half-bridge cells capacitance voltage ranking results
Member；
Work as iarm<When 0, then capacitance voltage k half-bridge list of highest is put into according to half-bridge cells capacitance voltage ranking results
Member.
The method for increasing level number using the first H-bridge unit includes：
Modulated signal is approached using phase-shifting carrier wave technology, level number N is obtained, is then judged；
If level number N is original 2n+1 level, the first H-bridge unit need not put into operation, and half-bridge cells need
Level number k=N, the control signal of half-bridge cells is obtained according to level number k；
If level number is 2n new level, the first H-bridge unit puts into operation, and controls mould by the first H-bridge unit
Block obtains the control signal of the first H-bridge unit, while determining new level number k, then passes through half-bridge list according to new level number k
First control module obtains the control signal of half-bridge cells unit.
Because the input of the first H-bridge unit and excision will coordinate input and the excision of the half-bridge cells of series connection, to the first H bridges
The control process of unit includes：The electric current and DC capacitor voltage that bridge arm is crossed in first convection current detected, according to the sense of current and
The size of the DC capacitor voltage of current first H-bridge unit obtains charging and discharging state needed for the first H-bridge unit, further according to charge and discharge
Electricity condition and the sense of current obtain output voltage state, and then obtain the drive signal of the first H-bridge unit.
The second H-bridge unit capacitance voltage balancing procedure includes：Each the second H-bridge unit of mutually upper and lower bridge arm electric capacity electricity
The set-point V of pressureH,refIt is compared with the actual capacitance voltage of the second H-bridge unit, through PI controllers, the bridge arm is multiplied by its output
After the sign function of electric current, by the second H-bridge unit voltage signal V of generationr,refPWM ripples are obtained after being compared with triangular carrier, are driven
Corresponding power switch pipe in dynamic second H-bridge unit, carries out charge and discharge control to the electric capacity of the second H-bridge unit, realizes the 2nd H bridges
The equilibrium of cell capacitance voltage, wherein, r=P, N.
The loop current suppression process includes：Reference value by each phase circulation respectively with circulation is compared, now circulation
Reference value icir,ref=idc/ 3, idcFor three-phase MMC DC bus currents, obtained result is formed by a proportional controller
The voltage reference value of one the second H-bridge unit, 2 parts are divided into by this voltage reference value, respectively with the mutually upper and lower bridge arm
The voltage signal of two H-bridge units is added.
The present invention has the following effects that compared with prior art：High-power can be applied to the invention provides one kind
The reactive power compensator in field, advantage is that the topological structure of MMC transverters has common DC bus, and three alternate energy can
Mutually flowing, also can normally run, therefore, the STATCOM based on MMC transverters can be realized during system imbalance of three-phase voltage
Reactive power, harmonic wave and unbalanced comprehensive compensation.It is each in every mutually upper and lower bridge arm on the basis of former MMC systems to add 2
H-bridge unit, wherein half-bridge cells are used to control the fundamental wave load current in bridge arm, and the first H-bridge unit can be realized to output electricity
Flat several is multiplied to 4n+1, and the second H-bridge unit is used to suppress circulation as voltage correction module.The new MMC of the present invention
The loop current suppression device control program of topological structure is simple, without carrying out the negative phase-sequence coordinate transform of two frequencys multiplication, the software resource of occupancy
Comparatively it is fewer, and load current and circulation is controlled by half-bridge cells and H-bridge unit respectively, is independent of each other；It is described
A kind of capacitance voltage ranking method based on phase-shifting carrier wave, it is simple and be easily achieved, half-bridge cells capacitance voltage is kept steady
It is fixed.And the switching that half-bridge cells can be avoided unnecessary, reduces the on-off times of power tube, reduces switching loss.
Brief description of the drawings
Fig. 1, system entire block diagram；
Fig. 2, tradition MMC topological structure schematic diagrames；
Fig. 3, new MMC topological structures schematic diagram；
Fig. 4, the determination flow chart that level number need to be put into；
Fig. 5, the first H-bridge unit control block diagram；
Fig. 6, half-bridge cells working state schematic representation；
Fig. 7, H-bridge unit structural representation；
Fig. 8, ip-iqDetection method schematic diagram；
Fig. 9, active and reactive current control block diagram；
Figure 10, feedforward decoupling equivalent control block diagram；
The control block diagram of Figure 11, STATCOM voltage and current double closed-loop；
Figure 12, STATCOM system main-control block diagram；
Figure 13, capacitance voltage ranking method flow chart；
Figure 14, novel topological structure modulation strategy block diagram；
Figure 15, Three phase MMC topological structures equivalent model schematic diagram；
Figure 16, the second control unit fundamental diagram；
Figure 17, voltage zero-crossing detection circuit schematic diagram；
Figure 18, current detecting and its modulate circuit circuit diagram；
Figure 19, current foldback circuit circuit diagram；
A phase voltages, current waveform figure before Figure 20, compensation；
A phase voltages, current waveform figure after Figure 21, compensation；
Figure 22, half-bridge cells capacitance voltage oscillogram；
Figure 23, conventional topologies a phases export phase voltage waveform figure；
Figure 24, New Topological a phases export phase voltage waveform figure；
Three phase circulation oscillograms before and after Figure 25, suppression；
A phases bridge arm current oscillogram before and after Figure 26, loop current suppression；
The capacitance voltage oscillogram of the H-bridge unit of Figure 27, a phase second.
Embodiment
The embodiment of the present invention is described with reference to the drawings, the reactive-load compensation based on dual H-bridge modular multilevel topology
Device, including three-phase alternating-current supply, load, transverter, signal acquisition circuit, DSP module and drive circuit, the transverter bag
Include the identical bridge arm being connected in parallel of three structures, each bridge arm include on point symmetry in bridge arm and the upper bridge arm being connected in series and
Lower bridge arm, the upper bridge arm includes resistance, reactor, the first H-bridge unit, the second H-bridge unit and some half-bridges being serially connected
The resistance that resistance on unit, first bridge arm is respectively on R11 and R12, the second bridge arm is respectively R21 and R22, the 3rd bridge
Resistance on arm is respectively R31 and R32, and the reactor of the reactor of upper bridge arm and lower bridge arm is connected in series, three bridges of transverter
The midpoint of arm is connected between three-phase alternating-current supply and load by conductor in parallel, and the input of signal acquisition circuit connects three respectively
The output end of AC power, the input of load, the output end of transverter, three bridge arms of transverter, the first H-bridge unit, the
Two H-bridge units and each half-bridge cells, the output end of signal acquisition circuit connect the input of DSP module, the output of DSP module
End is set up with transverter by drive circuit and is connected.Signal acquisition circuit detection power network three-phase voltage, load-side three-phase current,
The bridge arm current of three phase feedback currents, the capacitance voltage of each half-bridge cells and H-bridge unit DC side and three-phase that MMC is exported；
Then, the feedback quantity of detection is subjected to computing and regulation in a control unit, obtains pwm control signal；Finally, by control signal
Carry out power amplifier to drive power switch pipe in MMC half-bridge cells and H-bridge unit, make the corresponding compensation electric current of transverter output, it is real
Existing reactive-load compensation.
The topological structures of the new MMC modularization multi-level converters of present embodiment is as shown in figure 3, with public straight
Bus is flowed, three alternate energy can mutually flow, in the case where power network distorts, reactive power, harmonic wave and not can be realized
The comprehensive compensation of balance, high modularization, it is easy to Redundancy Design, and many level are output as, close to sine wave, harmonic content
It is small.Traditional MMC is per each n half-bridge cells of mutually upper and lower bridge arm, its structure as shown in Fig. 2 it is 2n that it, which exports phase voltage level number,
+ 1, the present invention, which carries novel topological structure, to bring up to 4n+1 by level number.
SM is half-bridge cells, and as shown in Figure 2, each half-bridge cells carry reverse fly-wheel diode to its structure by two
IGBT and 1 storage capacitor C composition, bridge arm current is ism, the output voltage of each half-bridge cells is usm, each half-bridge cells
Capacitance voltage is Vd。
Each half-bridge cells can only export 0 and VdTwo kinds of voltage status, use S1And S2T is represented respectively1And T2On off state,
DC capacitor voltage is Vd.The different on off state correspondence half-bridge cells of switching tube different output voltage and capacitor charge and discharge
State, as shown in table 1.
The half-bridge cells of table 1 difference on off state corresponding states table
MMC half-bridge cells working condition is as shown in fig. 6, arrow shows the flow direction of electric current in figure.Half-bridge cells have three
Plant working condition：
1)T1(D1) open, T2(D2) turn off as input state, such as Fig. 6 a)；
2)T1(D1) shut-off, T2(D2) open as excision state, such as Fig. 6 b)；
3)T1And T2It is turned off as blocking, such as Fig. 6 c)；
If siFor the switch function of MMC half-bridge cells, it is represented by
The then equivalent output voltage u of each half-bridge cellsoIt is represented by
uo=siVd (2)
The HB1 units of H-bridge unit are referred to as the first H-bridge unit, the HB2 units of H-bridge unit are referred to as the second H-bridge unit.The
One H-bridge unit and the second H-bridge unit have 3 kinds of on off states, sj∈ { -1,0,1 }, sj value determine H-bridge unit output electricity
The polarity of pressure.First H-bridge unit and the second H-bridge unit are all H-bridge unit, and its structure chart is as shown in fig. 7, wherein uhFor H bridge lists
First output voltage；Use S1、S2、S3And S44 switch transistor Ts are represented respectively1、T2、T3And T4On off state, DC capacitor voltage
For VH.The different output voltage of the different on off state correspondence H-bridge unit of 4 switching tubes and capacitor charge and discharge state, such as the institute of table 2
Show.
Table 2H bridges unit difference on off state corresponding states table
The DSP module includes the first control unit and the second control unit, the output end of the first control unit and second
The output end of control unit is set up with drive circuit be connected respectively, and first control unit compares including first comparator 1, second
Compared with device 3, the 3rd comparator 5, the 4th comparator 7, the 5th comparator 9, the first PI controllers 2, the 2nd PI controllers 4, the 3rd PI
Controller 8, the first coordinate converter 6, the second coordinate converter 12, the first reactor 10, the modulation of the second reactor 11, first are single
Member 30 and capacitance voltage sequencing unit 32, first comparator 1, the first PI controllers 2, the second comparator 3, the 2nd PI controllers 4
The first coordinate converter is accessed after being sequentially connected in series with the 3rd comparator 5, the 4th comparator 7, the 3rd PI controllers 8 and the 5th compare
Device 9 accesses the first coordinate converter 6 after being sequentially connected in series, the output end of the first coordinate converter 6 connects the first modulating unit 30, the
The output end connection capacitance voltage sequencing unit 32 of one modulating unit 30, the output end connection driving of capacitance voltage sequencing unit 32
Circuit, the output end of the MMC transverters connects the second coordinate converter, and the first output end of the second coordinate converter connects respectively
The second comparator 3 and the second reactor 11 are connect, the output end of the second reactor 11 connects the 3rd comparator 5, the second coordinate transform
Another output end of device connects the 4th comparator 7 and the first reactor 10, the output end connection the 5th of the first reactor 10 respectively
Comparator 9.
Second control unit include the 6th comparator 13, the 7th comparator 15, the 8th comparator 18, the 9th comparator 21,
First proportional controller 14, the second proportional controller 17, the 4th PI controllers 16, the 5th PI controllers 19, the and of function module 20
Second modulating unit 31, the 6th comparator 13, the first proportional controller 14, the 7th comparator 15, the 4th PI controllers 16 and
Two proportional controllers 17 access the 9th comparator 21, the 8th comparator 18, the 5th PI controllers 19 and Function Modules after being sequentially connected in series
Block 20 accesses the 9th comparator 21 after being sequentially connected in series, the output end of the 9th comparator 21 connects second modulating unit 31, the
The output end connection drive circuit of two modulating units 31.
The DSP control module of present embodiment realizes adopting for voltage x current using the TMS320F2812 of TI companies as core
The functions such as collection, the generation of CPS-SPWM ripples, capacitance voltage sequence, auxiliary circuit is by groups such as the protection circuits of Switching Power Supply and periphery
Into.
The reactive power compensator based on dual H-bridge modular multilevel topology includes voltage zero-crossing detection circuit, such as schemes
Shown in 17, the voltage zero-crossing detection circuit includes voltage sensor 22, comparison circuit 23 and phase inverter 24, voltage sensor 22
Input connect the output end of three-phase alternating-current supply, the output end of voltage sensor 22 connects the input of comparison circuit 23,
The output end of comparison circuit 23 connects DSP module by phase inverter 24, and the line voltage of sine wave is detected by voltage zero-cross
Circuit produces rising edge and overlapped with positive voltage zero-crossing point of power grid, and with the square-wave signal of power network same frequency, then pass through and survey
Measure the cycle that the time interval between two neighboring rising edge can obtain line voltage.
The reactive power compensator based on dual H-bridge modular multilevel topology includes current detecting and modulate circuit, such as
Shown in Figure 18, the current detecting and modulate circuit include current sensor 25, optical isolation amplifier 26 and biasing circuit 27,
The output end connection optical isolation amplifier 26 of current sensor 25, the output end connection biasing circuit of optical isolation amplifier 26
27, the output end of biasing circuit 27 is current detecting and the output end of modulate circuit, input and load and the change of current of current detecting
Device output is connected, and output end is sent to DSP and carries out signal transacting, and the present invention is real using the current Hall module CHB-25NP of high speed
Existing three-phase current detection, and isolated using optical isolation amplifier 26, the optical isolation amplifier that present embodiment is used
Model HCPL7840.
The reactive power compensator based on dual H-bridge modular multilevel topology includes current foldback circuit, such as Figure 19 institutes
Show, the current foldback circuit includes comparator 28 and clamp circuit 29, the midpoint of clamp circuit 29 is set up with DSP module to be connected
Connect, in the case of electric current is normal, the comparator LM393 output high level of present embodiment, but when the electric current in circuit is excessive,
Comparator LM393 output level is changed into low level, and triggering error protection is interrupted, so that DSP blocks all pwm pulse signals
Output, to protect whole SVG systems.
The control method of reactive power compensator based on dual H-bridge modular multilevel topology, is specifically included：Using based on wink
When reactive power theory ip-iqElectric current testing is detected to electric current；Current detecting schematic diagram is as shown in Figure 8, it is necessary first to
Calculate instantaneous active electric current ipWith instantaneous reactive current iq：
Wherein：
The i that formula (3) is calculatedp、iqAfter low pass filter, DC component is obtainedObtained again by inverse transformation
Three-phase fundamental current iaf、ibfAnd icf：
Use three-phase current ia、ib、icSubtract corresponding three-phase fundamental wave component iaf、ibf、icf, you can obtain the humorous of three-phase current
Ripple and idle composition sum iah、ibh、ich。
The control method of reactive power compensator based on dual H-bridge modular multilevel topology is included to half-bridge cells, the first H
Bridge unit and the second H-bridge unit are controlled respectively；
The control to half-bridge cells includes the compensation to System Reactive Power and maintains the steady of half-bridge cells capacitance voltage
It is fixed, modulated signal is generated according to the voltage based on Feedforward Decoupling, current double closed-loop control method, using the electricity based on phase-shifting carrier wave
Holding voltage ranking method makes the capacitance voltage of half-bridge cells stable；
The Feedforward Decoupling process includes：
The dq components v of line voltage and STATCOM output voltages is obtained by coordinate transformsd, vsq, vcd, vcqIt is as follows：
Wherein：δ is the phase difference of STATCOM output voltages and line voltage, and M is modulation ratio, and Us is line voltage, udc
For DC capacitor voltage.
By component V of the STATCOM output voltage under dq coordinate systemscdAnd VcqAs controlled quentity controlled variable, then by formulaAs can be seen that by controlling vcdAnd vcqSize with regard to can adjust STATCOM with
The exchange of electric network active and reactive power, so as to reach the purpose of reactive-load compensation.
Inverter output voltage vcdAnd vcqExpression formula be
Active and reactive current control block diagram is obtained according to formula (6) as shown in Figure 9.In order to realize to dq decoupler shafts, the present invention
Take feed forward decoupling control strategy.Wherein, the loss of whole current transformer is equivalent to fixed resistance R, linked reactor and circuit
Inductance is equivalent to inductance L.
Introduce x in the middle of variable1, x2：
Obtained by formula (6), (7)
By x1, x2Pi controller is designed to, can be obtained
Feedforward decoupling equivalent control block diagram is then can obtain as shown in Figure 10, by the given electric current under dq coordinate systems and feedback electricity
It is poor that stream is made, and 2 intermediate variable x are exported through 2 PI controllers1、x2, so as to realize decoupling under dq coordinate systems, finally give such as figure
K in the two close cycles STATCOM system architecture diagrams based on Feedforward Decoupling shown in 10, formula (9)1、k2For proportionality coefficient, T1, T2
For the time of integration.
As seen from Figure 11, STATCOM systems are made up of outer voltage and the part of current inner loop 2, Voltage loop be in order to
DC capacitor voltage is adjusted, its result is used as given value of current value id*；Electric current loop process includes that the idle of load-side need to be measured
Electric current, is set to specified rate iq*, inverter send electric current through dq conversion draw current feedback amount again with id*、iq* compare, then
PI regulations are carried out, the voltage v that STATCOM wants output is finally obtainedcd、vcq；
The control to the first H-bridge unit increases level number using the first H-bridge unit, and maintains the first H bridge lists
The stabilization of first capacitance voltage；
By the Double closed-loop of voltage and current strategy based on Feedforward Decoupling, based on phase-shifting carrier wave voltage sequence control methods with
And the control method of the first H-bridge unit of increase level number is combined, and constitutes STATCOM idle compensating controls, referred to as first
Control unit；The H-bridge unit of loop current suppression second is referred to as the second control to the control of selfcapacity voltage and suppression system circulation
Unit.Then the STSTCOM system main-control strategies based on New Topological can be obtained as shown in figure 12.
For traditional MMC, in the case where the half-bridge cells number of every mutually upper and lower bridge arm is respectively n, while coordinating carrier wave to move
Phase modulation technique, the output voltage maximum level number of its AC is 2n+1.
In new MMC, first H-bridge unit is respectively added in each bridge arm, its DC capacitor voltage is half-bridge
The half of unit DC capacitor voltage, is Vd/ 2, so its output level number is just 3, is respectively+Vd/ 2,0 and-Vd/
2, coordinating the half-bridge cells of each bridge arm series connection can be widened output level number, i.e., in original 2n+1 level number
Between insert 2n new level number, level number has been reached 4n+1.
Each bridge arm can cascade multiple half-bridge cells, but the direct current of each half-bridge cells in modular multilevel topology
It is separate to hold voltage, in practice due to capacitance fluctuations differential loss, switching loss difference and drive signal difference
Deng can cause the imbalance between the DC capacitor voltage of half-bridge cells, influence the output voltage of modular multilevel structure.
In order to maintain the equilibrium of half-bridge cells capacitance voltage, the present invention is using the half-bridge cells capacitance voltage sequence control based on CPS-SPWM
System strategy, so that half-bridge cells capacitance voltage keeps stable.
Half-bridge cells capacitance voltage sequence control strategy based on CPS-SPWM is by CPS-SPWM modulation techniques and half-bridge
Cell capacitance voltage ranking method is effectively combined, and its process includes：
(1) determination of level number need to be put into, its process is as shown in Figure 4
First, the shifting of modulating wave and each bridge arm that feed forward decoupling control is obtained will be passed through using shifting modulation technology
Phase triangular carrier is compared, and the level number N needed, the phase shift triangular carrier is produced by capacitance voltage sequencing unit；
Then, judge obtaining level number N, obtain new level number k；Further according to each bridge arm half-bridge cells electric capacity
The flow direction of voltage levels ordering scenario and bridge arm current selects corresponding k half-bridge cells input；
(2) half-bridge cells capacitance voltage ranking method, flow chart is as shown in figure 13：
According to each bridge arm current iarmDirection judged, be specially：
Work as iarm>When 0, i.e., bridge arm current charges to half-bridge cell capacitance, then according to half-bridge cells capacitance voltage ranking results
Putting into k minimum half-bridge cells of capacitance voltage, i.e. bridge arm current raises its voltage this k half-bridge cells electric capacity charging.
Work as iarm<When 0, i.e., bridge arm current is discharged half-bridge cell capacitance, then according to half-bridge cells capacitance voltage ranking results
Input capacitance voltage k half-bridge cells of highest, i.e. bridge arm current makes the reduction of its voltage to this k half-bridge cells electric capacity electric discharge.
So it is achieved that the balance of half-bridge cells capacitance voltage.
The control strategy block diagram for adding the new MMC of the first H-bridge unit is as shown in figure 14：
(1) modulated signal is approached first with phase-shifting carrier wave technology, obtains level number N, then level number is entered
Row judges.
If level number N is original 2n+1 level, the first H-bridge unit need not put into operation, and half-bridge cells need
Level number k=N, the control signal of half-bridge cells is obtained according to level number k；
If level number is 2n new level, the first H-bridge unit puts into operation, and controls mould by the first H-bridge unit
Block obtains the control signal of the first H-bridge unit, while determining new level number k=N-sign (uh), it is then logical according to level number k
Cross the control signal that half-bridge cells control module obtains cascading half-bridge cells.
(2) because the input of the first H-bridge unit and excision will coordinate input and the excision of the half-bridge cells of series connection, so the
The control method flow chart of one H-bridge unit is as shown in Figure 5：The electric current and DC capacitor voltage that bridge arm is crossed in first convection current are examined
Survey, the charging and discharging state according to needed for the size of the sense of current and the DC capacitor voltage of current first H-bridge unit obtains module,
Output voltage state is obtained further according to charging and discharging state and the sense of current, and then obtains the drive signal of the first H-bridge unit.Table 3
For the first H-bridge unit output voltage state decision table.
The H-bridge unit output voltage state decision table of table 3 first
The control to the second H-bridge unit includes the balanced and whole reactive power compensator of the second H-bridge unit capacitance voltage
Circulation suppression control, be specially：
The equivalent model of Three phase MMC power topologies is as shown in figure 15, wherein, DC bus current is idc, three
Bridge arm current is respectively i in phaseaP、ibP、icP, bridge arm current is respectively i under three-phaseaN、ibN、icN, three-phase output current is respectively
ia、ib、ic。
Below by taking a phases as an example, the operation principle to new MMC topological structures is analyzed, can according to KCL Circuit theories
Know, a phase output currents are represented by
ia=iaP-iaN (10)
If the circulation of a phase bridge arms is icir,a, because the circuit structure of upper and lower bridge arm is identical, then have
Formula (11) is added with (12), obtained
The electric current i of three-phase MMC dc busdcFor the phase circulation sum of a, b, c tri-, i.e.,
idc=icir,a+icir,b+icir,c (14)
Due to three-phase symmetrical, three phase circulations are represented by
In formula, izj *Two frequency multiplication negative phase-sequence of acs in circulation, wherein, j=a, b, c, convolution (11), (12) with
(15) it can obtain：
Composite type (16) and (17), the two frequency multiplication negative phase-sequence alternating components that can obtain a phase circulations are
The power model of MMC systems can be equivalent to controllable voltage source VjrWherein, j=a, b, c；R=P, N, then bridge in a phases
Output voltage VaPWith the output voltage V of lower bridge armaNIt is represented by：
In Figure 15 equivalent model, the output voltage of the first H-bridge unit and the second H-bridge unit is respectively VH1,jrWith
VH2,jr, using the midpoint of DC bus-bar voltage as reference, the three-phase voltage of MMC systems output is Vj, the resistance of each bridge arm is
Re, according to KVL Circuit theories, can be obtained
Formula (21) is added with (22), in conjunction with formula (11) to (13), can be obtained：
It can be seen from formula (23) can by control two the second H-bridge units output voltage sum (VH2,aP+
VH2,aN) size and voltage difference (Ud-VaP-VaN) the equal purpose so as to reach elimination circulation.
Formula (22) is subtracted into formula (21), can be obtained
From formula (24), the second H-bridge unit has little to no effect to MMC output voltage, and reason has two：First,
The output voltage grade of two H-bridge units is very little for the output voltage of MMC systems；Secondly, the 2nd H bridge lists are controlled
The voltage of each mutually upper and lower bridge arm of member insertion is equal, therefore (V in formula (24)H2,aN-VH2,aP) this can approximately be regarded as
0, have no effect on the output voltage of system.From formula (24), by using rational control strategy, the second H-bridge unit is controlled
Output voltage can just suppress circulation.
Figure 16 is the schematic diagram of new MMC systems a phases the second H-bridge unit controller, is realized while circulation is suppressed
To the Balance route of H-bridge unit capacitance voltage.
As seen from Figure 16, by each phase circulation and circulation reference value icir,ref=idc/ 3 are compared, obtained knot
Fruit passing ratio adjusts the voltage reference value to form the second H-bridge unit, and this reference value is divided into 2 parts, this is added in respectively
The Voltage Reference of the mutually upper and lower H-bridge unit of bridge arm second, it is so, also that the second H-bridge unit is defeated to MMC while circulation is eliminated
The influence for going out voltage is preferably minimized.
Second control unit will also maintain the equilibrium of the second H-bridge unit capacitance voltage while circulation is suppressed.Each phase
The set-point V of upper and lower the second H-bridge unit of bridge arm capacitance voltageH, refIt is compared with the actual capacitance voltage of the second H-bridge unit,
Through PI controllers, it exports the sign function for being multiplied by the bridge arm current, if bridge arm current is more than 0, then symbol function is+1；If bridge
Arm electric current is less than 0, and then symbol function is -1.Finally, by the voltage signal V of generationR, refPWM is obtained after being compared with triangular carrier
Ripple, wherein r=P, N；Corresponding power switch pipe in the second H-bridge unit is driven, discharge and recharge is carried out to the electric capacity of the second H-bridge unit
Control, to realize the balance of capacitance voltage.
Second H-bridge unit switching frequency of control circulation is higher than the switching frequency of power model, so, circulation controller
Namely the bandwidth of the second control unit is higher than the first control unit, so as to restrained effectively the negative phase-sequence ring of predominantly two frequencys multiplication
Stream.Because the capacitance voltage rated value of the second H-bridge unit in the second control unit is relatively low, its switching loss is in higher switch frequency
Also will not be very big under rate.
To System Reactive Power compensation effect, simulating, verifying is carried out, a phase voltages, current waveform before Figure 20 is power network compensation.
It can be seen that electric current substantially lags behind voltage before compensation, Figure 21 is a phase voltages and current waveform after compensation, mutually electricity
Pressure, the phase of electric current are consistent.It can be seen that the present invention has good compensation effect to idle.
Half-bridge cell capacitance electric voltage equalization effect is analyzed, Figure 22 is the electric capacity of half-bridge cells in the upper and lower bridge arm of a phases
Voltage, it can be seen that half-bridge cells capacitance voltage is stablized in 1000V or so, fluctuates in 10V or so, illustrates CPS-SPWM's
Half-bridge cells capacitance voltage ranking method has the equal pressure energy power of preferable half-bridge cells to STATCOM systems.
Simulation analysis are carried out to system output voltage, when the half-bridge cells number that each bridge arm is connected is 2, opened up based on tradition
The STATCOM output a phase voltages for flutterring structure MMC are as shown in figure 24, are 5 level；And based on novel topological structure MMC's
STATCOM a phases output voltage is 9 level, as shown in figure 24.Therefore, one electric capacity electricity of series connection in conventional topologies structure MMC
Press as the first H-bridge unit of half-bridge cells voltage half, obtained new MMC structures realize the increasing of output-voltage levels number
Plus, verify the correctness and feasibility of novel topological structure.
Loop current suppression ability to system carries out simulation analysis, in the MMC of New Topological, adds the second H-bridge unit and enters
Row loop current suppression, Figure 25 gives three phase circulation waveforms before and after the second H-bridge unit of addition, wherein：Figure 25 (a) is not add second
Three phase circulation waveforms before H-bridge unit, it can be seen that three phase circulations are about 15A.After Figure 25 (b) is the second H-bridge unit of addition
Three phase circulation waveforms, it can be seen that three phase circulations have obtained effective suppression, are reduced within 2A.Therefore set forth herein add second
H-bridge unit topology MMC, which has, preferably suppresses circulation ability.
Simulation analysis are carried out to bridge arm current, before and after loop current suppression the contrast of a phase bridge arm current waveforms as shown in figure 26, figure
26 (a) is the electric current of the upper and lower bridge arm of a phases before loop current suppression, the as we can see from the figure upper and lower bridge arm of a phases before loop current suppression
There are substantial amounts of harmonic components in electric current, its amplitude reaches 30A；Figure 26 (b) is the electric current of the upper and lower bridge arm of a phases after loop current suppression
Waveform, is frequency and fundamental wave identical sinusoidal waveform, and amplitude is reduced to 10A.
Capacitance voltage stabilizing ability to the second H-bridge unit carries out simulation analysis, and Figure 27 is the H bridges of a phases the 2nd in New Topological
The capacitance voltage of unit, it can be seen that the capacitance voltage value stabilization of the second H-bridge unit is in reference value 20V, it was demonstrated that the 2nd H bridge lists
Member also maintains the balance of itself H-bridge unit capacitance voltage while circulation is suppressed.
Claims (1)
1. a kind of control method of the reactive power compensator based on dual H-bridge modular multilevel topology, it is characterized in that described base
Include three-phase alternating-current supply, load, MMC transverters, signal detection in the reactive power compensator of dual H-bridge modular multilevel topology
Circuit, DSP module and drive circuit, the transverter include the identical bridge arm being connected in parallel of three structures, and each bridge arm includes
On point symmetry in bridge arm and the upper bridge arm being connected in series and lower bridge arm, the upper bridge arm includes resistance, the reactance being serially connected
Device, the first H-bridge unit, the second H-bridge unit and some half-bridge cells, the reactor of upper bridge arm are connected company with the reactor of lower bridge arm
Connect, the midpoint of three bridge arms of transverter is connected between three-phase alternating-current supply and load by conductor in parallel, signal deteching circuit
Input connect respectively three AC powers output end, load input, the output end of transverter, three bridges of transverter
Arm, the first H-bridge unit, the second H-bridge unit and each half-bridge cells, the output end of signal deteching circuit connect the defeated of DSP module
Enter end, the output end of DSP module is set up by drive circuit with transverter to be connected；
The DSP module includes the first control unit and the second control unit, the output end of the first control unit and the second control
The output end of unit is set up with drive circuit be connected respectively, and first control unit includes first comparator（1）, second compare
Device（3）, the 3rd comparator（5）, the 4th comparator（7）, the 5th comparator（9）, the first PI controllers（2）, the 2nd PI controllers
（4）, the 3rd PI controllers（8）, the first coordinate converter（6）, the second coordinate converter（12）, the first reactor（10）, second
Reactor（11）, the first modulating unit（30）With capacitance voltage sequencing unit（32）, first comparator（1）, the first PI controllers
（2）, the second comparator（3）, the 2nd PI controllers（4）With the 3rd comparator（5）The first coordinate converter is accessed after being sequentially connected in series,
4th comparator（7）, the 3rd PI controllers（8）With the 5th comparator（9）The first coordinate converter is accessed after being sequentially connected in series（6）,
First coordinate converter（6）Output end connect the first modulating unit（30）, the first modulating unit（30）Output end connection electricity
Hold voltage sequencing unit（32）, capacitance voltage sequencing unit（32）Output end connection drive circuit, the MMC transverters it is defeated
Go out the second coordinate converter of end connection, the first output end of the second coordinate converter connects the second comparator respectively（3）With second
Reactor（11）, the second reactor（11）Output end connect the 3rd comparator（5）, another output end of the second coordinate converter
The 4th comparator is connected respectively（7）With the first reactor（10）, the first reactor（10）Output end connect the 5th comparator
（9）；
Second control unit includes the 6th comparator（13）, the 7th comparator（15）, the 8th comparator（18）, the 9th comparator
（21）, the first proportional controller（14）, the second proportional controller（17）, the 4th PI controllers（16）, the 5th PI controllers（19）、
Function module（20）With the second modulating unit（31）, the 6th comparator（13）, the first proportional controller（14）, the 7th comparator
（15）, the 4th PI controllers（16）With the second proportional controller（17）The 9th comparator is accessed after being sequentially connected in series（21）, the 8th ratio
Compared with device（18）, the 5th PI controllers（19）And function module（20）The 9th comparator is accessed after being sequentially connected in series（21）, the 9th compares
Device（21）Output end connect second modulating unit（31）, the second modulating unit（31）Output end connection drive circuit；
The reactive power compensator based on dual H-bridge modular multilevel topology includes voltage zero-crossing detection circuit, the voltage
Zero cross detection circuit includes voltage sensor（22）, comparison circuit（23）And phase inverter（24）, voltage sensor（22）Input
The output end of end connection three-phase alternating-current supply, voltage sensor（22）Output end connection comparison circuit（23）Input, than
Compared with circuit（23）Output end pass through phase inverter（24）Connect DSP module；
The reactive power compensator based on dual H-bridge modular multilevel topology includes current detecting and modulate circuit, the electricity
Stream detection and modulate circuit include current sensor（25）, optical isolation amplifier（26）And biasing circuit（27）, current sense
Device（25）Output end connection optical isolation amplifier（26）, optical isolation amplifier（26）Output end connection biasing circuit
（27）, biasing circuit（27）Output end is current detecting and the output end of modulate circuit；
This control method is included using based on instantaneous reactive power theoryElectric current testing is detected to electric current；Half-and-half
Bridge unit, the first H-bridge unit and the second H-bridge unit are controlled respectively；
The control to half-bridge cells includes the compensation to System Reactive Power and maintains the stabilization of half-bridge cells capacitance voltage, root
According to voltage, current double closed-loop control method the generation modulated signal decoupled based on closed loop, using the electric capacity electricity based on phase-shifting carrier wave
Pressure ranking method makes the capacitance voltage of half-bridge cells stable；
The control to the first H-bridge unit increases level number using the first H-bridge unit, and maintains the first H-bridge unit electricity
Hold the stabilization of voltage；
The control to the second H-bridge unit includes the balanced and whole reactive power compensator circulation of the second H-bridge unit capacitance voltage
Suppression；
Capacitance voltage ranking method based on phase-shifting carrier wave includes：
It is determined that needing the level number put into：
First, the phase shift three of modulating wave and each bridge arm that feed forward decoupling control is obtained will be passed through using shifting modulation technology
Angle carrier wave is compared, the level number neededN, the phase shift triangular carrier produces by the first modulating unit；
Then, to obtaining level numberNJudged, obtain new level numberk；Further according to each bridge arm half-bridge cells capacitance voltage
The flow direction selection of height ordering scenario and bridge arm current is correspondingkIndividual half-bridge cells input；
The half-bridge cells voltage ranking method is specifically included：
According to bridge arm currentDirection carry out judge as follows：
When>When 0, then capacitance voltage is put into according to half-bridge cells capacitance voltage ranking results minimumKIndividual half-bridge cells；
When<When 0, then capacitance voltage highest is put into according to half-bridge cells capacitance voltage ranking resultsKIndividual half-bridge cells；
The method for increasing level number using the first H-bridge unit includes：
Modulated signal is approached using phase-shifting carrier wave technology, level number is obtainedN, then judged；
If level numberNFor original 2n+ 1 level, then the first H-bridge unit need not put into operation, half-bridge cells need electricity
Flat numberk=N, according to level numberkObtain the control signal of half-bridge cells；
If level number is new 2nIndividual level, then the first H-bridge unit puts into operation, and is obtained by the first H-bridge unit control module
To the control signal of the first H-bridge unit, while determining new level numberk, then according to new level numberkPass through half-bridge cells control
Molding block obtains the control signal of half-bridge cells unit；
Control process to the first H-bridge unit is specifically included：The electric current and DC capacitor voltage that bridge arm is crossed in first convection current are examined
Survey, the charge and discharge according to needed for the size of the sense of current and the DC capacitor voltage of current first H-bridge unit obtains the first H-bridge unit
Electricity condition, obtains output voltage state, and then obtain the driving letter of the first H-bridge unit further according to charging and discharging state and the sense of current
Number；
The set-point of each the second H-bridge unit of mutually upper and lower bridge arm capacitance voltageWith the actual capacitance electricity of the second H-bridge unit
Pressure is compared, through PI controllers, and its output is multiplied by after the sign function of the bridge arm current, by the second H-bridge unit electricity of generation
Press signalCorresponding power switch pipe in PWM ripples, the second H-bridge unit of driving is obtained after being compared with triangular carrier, to second
The electric capacity of H-bridge unit carries out charge and discharge control, realizes the equilibrium of the second H-bridge unit capacitance voltage, wherein,r=P,N；
The loop current suppression process includes：Reference value by each phase circulation respectively with circulation is compared, now the ginseng of circulation
Examine value=i dc/ 3, obtained result forms the voltage reference value of second H-bridge unit by a proportional controller,
This voltage reference value is divided into 2 parts, the voltage signal with the mutually upper and lower H-bridge unit of bridge arm second is added respectively, whereini dcFor three-phase MMC DC bus currents.
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| CN105576671A (en) * | 2016-03-04 | 2016-05-11 | 国网黑龙江省电力有限公司哈尔滨供电公司 | Reactive compensation device and reactive compensation method based on modular multilevel converter |
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| CN106787929A (en) * | 2016-12-13 | 2017-05-31 | 苏州富艾姆工业设备有限公司 | A kind of fast control power-supply system and control method |
| CN108233747B (en) | 2016-12-16 | 2020-12-04 | 台达电子企业管理（上海）有限公司 | Modular power supply system |
| CN106684919B (en) * | 2017-03-13 | 2019-08-09 | 合肥工业大学 | Improved Cascade-type photovoltaic grid-connected inverter method for controlling power balance |
| CN107294412B (en) * | 2017-06-26 | 2019-10-11 | 西安交通大学 | Improve the modulator approach of semi-bridge type Modular multilevel converter output level number |
| CN107517007A (en) * | 2017-10-18 | 2017-12-26 | 西安交通大学 | A kind of nearly square-wave frequency modulation method of MMC type HVDC converter |
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