CN106099990A - High permeability distributed photovoltaic quality of voltage improves device and control system thereof - Google Patents

Abstract

The invention discloses a kind of high permeability distributed photovoltaic quality of voltage and improve device and control system thereof, quality of voltage improves device and uses the series and parallel type current transformer of three-phase four-arm structure, wherein, tandem type current transformer connects power distribution network power supply, parallel connection type current transformer connects load, tandem type current transformer exports after LC wave filter, power distribution network is sealed in by series transformer, parallel connection type current transformer is incorporated to power distribution network through inductance, after bidirectional thyristor series connection current-limiting inductance, in parallel with series transformer again, constitute bypass loop；Electrochemical capacitor is parallel to DC side, stable DC voltage, and fast energy storage element uses super capacitor cabinet, is carried out exchange and the buffering of energy by DC/DC changer and DC side.The quality of voltage of the present invention improves device and solves and have magnetic saturation characteristic and be supported on series compensation device and put into or the magnetic saturation that causes when logging off and magnetic bias problem, it is to avoid the damaging influence that dash current brings, and realizes safely and effectively compensating.

Description

High permeability distributed photovoltaic quality of voltage improves device and control system thereof

Technical field

The present invention relates to a kind of high permeability distributed photovoltaic quality of voltage and improve device and control system thereof, belong to distributed Technical field of power generation.

Background technology

In the low and medium voltage distribution network of Thief zone distributed power generation, the energy stream fluctuation that distributed generation system brings can cause Quality of voltage problem；Power distribution network self can cause quality of voltage problem due to reasons such as the system failures: the most non-linear Load, uncompensated load etc. can cause the problem such as current harmonics, imbalance, thus also have influence on quality of voltage.Employing electric power becomes Stream device/inverter type DG constitutes quality of voltage and improves device, can solve all kinds of quality of voltage problems in power distribution network.

For the control problem of the distribution network voltage quality of band distributed power generation, domestic and international solution is typically based on two kinds Method: EMS EMS (Energy Management System) and custom power technology CPT (Custom Power Technology)。

(1) EMS scheme

EMS, by each distributed power generation in reasonable distribution management region, is implemented in combination with stablizing of voltage with power distribution network； In the occasion of high permeability DG, typically carrying out partition management, the most each interregional chopper by band coincidence performance separates, microcomputer The each district of protection coordination；Also can distribute multiple distributed power generation rationally according to actual field needs, reduce and produce quality of voltage problem Probability.

(2) CPT scheme

CPT power application electronic technology improves quality of voltage problem, by power electronic equipment or claim static (Gu static/ State) controller, for mesolow electrical power trans mission/distribution system, make the electric power of offer reach the reliability level needed for user and quality of voltage Level.DFACTS technology in CPT, as the frontier of power system research, is flexible transmission technology FACTS (FlexibleAC Transmission Systems) extension in power distribution network；DFACTS technology is by Power Electronic Technique, letter Breath technology, control technology etc. combine, and are absorbed in control motility and the quality of power supply of user side (distribution system), for the modern times Power system provides a kind of resolution policy brand-new, comprehensive.DFACTS device mainly has: active filter APF (Active Power Filter), distribution static synchronous compensator DSTATCOM (Distribution STATCOM), pay no attention to power-off source UPS (Uninterruptible Power Supply), dynamic electric voltage recovery device DVR (Dynamic Voltage Restorer), system One quality of power supply improve device UPQC (Unified Power Quality Conditioner), APF therein, DSTATCOM, DVR actual application prospect is wide, and UPQC is considered as then the method that function is the most comprehensive, ideal.

Distribution network voltage Quality Control Technology scheme under distributed power generation, line voltage occurs to drop temporarily, rise sharply or during harmonic wave, Series converter injecting compensating voltage does not changes with the voltage waveform of holding critical load.Series transformer can effectively every From series converter and the electrical connection of electrical network, but once series transformer generation supersaturation, the voltage of injection can produce greatly Exiting pour current, threaten transformator and the safe operation of series converter, and the possibility that protective relaying maloperation is made can be greatly increased Property, reduce power supply reliability.Designed by the structure of transformator, reduce the peakflux density of transformer core, increase ferrum Heart cross section, can reduce the rated operation point of transformer core, increase saturated nargin, even if to ensure to occur D.C. magnetic biasing unshakable in one's determination Also will not supersaturation；Although method is simply direct, but the core section effective material of consumption excessive, very big can be caused, increase fortune The series of problems such as iron loss, economy decline, manufacturing cost height, volume and weight is huge, inconvenient transport during row.Triple-frequency harmonics Injection method, DC injection method and exchange injection method etc. can be used to maintain balance of flux, it is to avoid magnetic saturation, and effect is obvious, but control Method processed is complex.

Summary of the invention

The technical problem to be solved is the defect overcoming prior art, it is provided that a kind of distributed light of high permeability Volt quality of voltage improves device and control system thereof.

For solving above-mentioned technical problem, the present invention provides a kind of high permeability distributed photovoltaic quality of voltage to improve device, electricity Pressure quality is improved device and is used tandem type current transformer and the parallel connection type current transformer of three-phase four-arm structure, wherein, tandem type current transformer Four ports connect power distribution network power supplys, four ports of parallel connection type current transformer connect load；The three-phase of tandem type current transformer is defeated After going out the LC wave filter through being made up of inductance Ls and electric capacity Cs, seal in power distribution network by series transformer；Parallel connection type current transformer Three-phase output be incorporated to power distribution network through inductance Lp, inductance Lp is also in series with pre-charge resistance R1 and catalyst KMpl, KMp2；Double After IGCT SCRA, SCRB, SCRC connect current-limiting inductance LA, LB, LC respectively, more respectively with series transformer TsA, TsB, TsC is in parallel, constitutes bypass loop；After electrochemical capacitor Cdcl, Cdc2 series connection, it is parallel to DC side, stable DC voltage；Quickly storage Super capacitor cabinet can be used by element, be carried out exchange and the buffering of energy by DC/DC changer and DC side；Described quality of voltage Improve device and also include bleeder resistance R2 and boost inductance Lb.

Aforesaid series transformer selects booster transformer.

Aforesaid super capacitor cabinet selects 200 ultracapacitors to be used in series.

Aforesaid quality of voltage improves device and achieves flux regulator strategy, and flux regulator method is as follows: set series-transformer The threshold value of device primary current, when tandem type current transformer puts into operation, detects primary current by current transformer, when this electric current reaches To when setting threshold value, it is believed that magnetic flux is saturated, now stop the output of tandem type current transformer, to maintain magnetic flux not to be further added by；Work as benefit After repaying voltage zero-cross, tandem type current transformer continues to put out, and for the saturated magnetic bias caused of magnetic flux in elimination upper half, this half cycle exports Voltage reaches the former calculating output valve of 120%, normally exports in the time after this half cycle.

Aforesaid quality of voltage improves device and achieves switching control strategy, and quality of voltage improves device access power distribution network and carries out work After work, DC bus-bar voltage is now the voltage of super capacitor cabinet, controls Guan Bi catalyst KMp1 and KMp2, exchanges 380V power supply Charged to DC side by pre-charge resistance R1, parallel connection type current transformer, after charging complete, Guan Bi catalyst KMp1, disconnection contact Device KMp2；DC/DC changer is started working, adjustment DC voltage to setting value 690V, detection line voltage and load current, Load-side is uneven or harmonic content is beyond when requiring, parallel connection type current transformer puts into operation；There is voltage dip, rapid in line voltage During up voltage quality problems, tandem type current transformer puts into operation, and output compensates change in voltage, after quality of voltage problem eliminates, and string Connection type current transformer is deactivated, by the bypass of bidirectional thyristor SCRA, SCRB, SCRC.

High permeability distributed photovoltaic quality of voltage improves the control system of device, including power supply, AD conversion unit, DSP and isolation drive unit；Described power supply supply AD conversion unit, DSP Digital Signal Processing DC source needed for device and isolation drive unit；The analogue signal of voltage sample and current sample is become by AD conversion unit DSP is sent into after digital quantity；DSP carries out signal processing, number to the digital quantity of input Student movement calculation, logical judgment, require output desired signal according to control strategy；DSP output signal includes PWM Signal, SCR signal and KM signal, the pwm signal in DSP output signal is exported extremely by isolation drive unit Quality of voltage improves the tandem type current transformer of device, parallel connection type current transformer and DC/DC changer, exports SCR signal to voltage matter Amount improves the bidirectional thyristor of device, the output of KM signal improves the catalyst of device to quality of voltage, it is achieved be distributed high permeability Formula photovoltaic voltage quality improves the control of device.

System protection signal is exported to DSP by aforesaid isolation drive unit.

Aforesaid voltage sample use electric resistance partial pressure sampling, after voltage sample by isolation operational amplifier HCPL7800 with And impedance op-amps CA3140 enters AD conversion unit；Described current sample uses LEM current sensor, current sample After, output signal is directly entered AD conversion unit.

Aforesaid AD conversion unit uses MAXl25 chip, and selects driving buffering tri-state gate circuit 74F245 chip Realize the level match with DSP and speeds match.

The beneficial effect that the present invention is reached:

The high permeability distributed photovoltaic quality of voltage of the present invention improves device, based on balance of flux principle, it is provided that a kind of magnetic Saturated suppression strategy, by control series compensation device output voltage, solve have magnetic saturation characteristic be supported on series connection mend Repay device to put into or the magnetic saturation that causes when logging off and magnetic bias problem, it is to avoid the destructive shadow that dash current brings Ring, and realize safely and effectively compensating.

The present invention passes through series converter output reactive power, and series and parallel current transformer jointly completes no-power compensation function, carries The high utilization rate of series converter.

Accompanying drawing explanation

Fig. 1 is that the quality of voltage flown across dc-link capacitance midpoint improves device topological structure；

Fig. 2 is that the quality of voltage of three-phase three brachium pontis band isolating transformer improves device topological structure；

Fig. 3 is that the quality of voltage of three-phase four-arm improves device topological structure；

Fig. 4 is that quality of voltage improves device series connection access power distribution network schematic diagram；

Fig. 5 is series connection control principle drawing；

Fig. 6 is that the quality of voltage of the present invention improves device main circuit structure figure；

Fig. 7 is that the quality of voltage of the present invention improves device main circuit parameter equivalent circuit diagram；

Fig. 8 is the control system block diagram that quality of voltage improves device；

Fig. 9 is voltage x current sampling conditioning and analog digital conversion FB(flow block)；

Figure 10 is three-phase software phase-lock loop control flow chart.

Detailed description of the invention

The invention will be further described below in conjunction with the accompanying drawings.Following example are only used for clearly illustrating the present invention Technical scheme, and can not limit the scope of the invention with this.

Quality of voltage improves device and has merged tandem type compensation device and the performance of parallel connection type compensation device, and with fast energy storage Based on constitute DC link, it is provided that compensate the energy stream between required energy and equalizing and buffering series and parallel current transformer.At height In the low and medium voltage distribution network of osmotic formula generating, quality of voltage improves device and solves the electricity that the fluctuation of distributed power generation power stream brings While pressure quality problems, also can solve all kinds of quality of voltage problems that power distribution network self brings.

Quality of voltage improves the topological structure numerous types of device, in the actual application of three-phase system, flies with three-phase four-wire system Across dc-link capacitance midpoint, three-phase three brachium pontis band isolating transformer structure, three-phase four-arm structure three types the most conventional.

It is illustrated in figure 1 three-phase four-wire system and flies across dc-link capacitance midpoint configuration, utilize two dc-link capacitance midpoints Midpoint as system output voltage constitutes center line, improves device topology with three-phase three brachium pontis composition three-phase four-wire system quality of voltage Structure.This circuit power device is less, and cost is relatively low；But DC voltage utilization rate is on the low side, the peak value of output phase voltage is less than The half of DC bus-bar voltage, midpoint need to balance control, and the capacity of required dc-link capacitance is bigger.

The quality of voltage being illustrated in figure 2 three-phase three brachium pontis band isolating transformer improves device topological structure.Three-phase three bridge Accessing △ IV transformator between arm current transformer and load, primary connects around group selection △ shape, can make uneven generation Zero-sequence current is at Three-Phase Transformer primary coil internal circulation flow；Transformer secondary output is around group selection Y connection, it is possible to provide uneven Current in middle wire path during load.Owing to transformator is operated in fundamental frequency, volume, weight are relatively big, relatively costly.

A brachium pontis, i.e. three-phase four-arm shown in pie graph 3 is increased on the basis of conventional three-phase bridge-type inverter Quality of voltage improves device topological structure.Power device increases so that controller design and debugs relative complex, but this structure can Directly to control neutral point voltage, not only can realize three-phase work but also can single-phase work, degree of freedom is high, and applicable situation is wide；Three is phased System processed can separate control, and control method is versatile and flexible, can well solve imbalance of three-phase voltage and injustice The problem that weighing apparatus load brings.

The present invention selects the quality of voltage of three-phase four-arm to improve device topological structure.As it is shown on figure 3, U_dFor Equivalent DC Power supply, the energy-storage units can being made up of for core ultracapacitor, accumulator etc. is powered, it is possible to by electrical network when normally working Power supply；After three-phase four-bridge arm converter filters via resistance sense, A, B, C, N-port and power distribution network serial or parallel connection can be passed through.

When loading asymmetric in power distribution network, owing to circuit has certain impedance, each phase voltage of load necessarily leads to not Balance；During the fluctuation of power distribution network generation power stream, will also result in load voltage ripple, all can produce corresponding quality of voltage problem. Improving quality of voltage, the voltage on critical loads to be ensured keeps the sine voltage of three-phase symmetrical.Represented by Fig. 3 Variable, founding mathematical models, obtain the relation between each variable, use symmetrical component method to extract the positive sequence of output voltage, negative phase-sequence And each order components of zero sequence, it is respectively controlled to realize improving the purpose of quality of voltage.

C is filter capacitor, R, L, R_n、L_nFor filtering resistance sense, (quality of voltage of four bridge legs changes a, b, c, m, n, g representative graph 3 Kind device topological structure) middle each node indicated, u_anRepresent voltage, i between node a, n_LaRepresent and flow through inductance in a phase Current value, other is similar to, and can obtain following relation according to circuit theory:

$\left[\begin{array}{c}{u}_{an}\\ u_{bn}\\ u_{cn}\end{array}\right]=(R+L_s)\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]+\left[\begin{array}{c}{u}_{ao}\\ u_{bo}\\ u_{co}\end{array}\right]+\left[\begin{array}{c}{u}_{gn}\\ u_{bo}\\ u_{co}\end{array}\right]---\left(1\right)$

$\left\{\begin{array}{c}{u}_{mn}=(R_n+L_{n}s)i_g+u_{gn}\\ -i_g=i_{La}+i_{Lb}+i_{Lc}\end{array}\right.---\left(2\right)$

$\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]=C_s\left[\begin{array}{c}{u}_{ao}\\ u_{bo}\\ u_{co}\end{array}\right]+\left[\begin{array}{c}{i}_{ao}\\ i_{bo}\\ i_{co}\end{array}\right]---\left(3\right)$

$\left\{\begin{array}{c}{u}_{ao}=u_{ao\_p}+u_{ao\_n}+u_{ao\_0}\\ u_{bo}=u_{bo\_p}+u_{bo\_n}+u_{bo\_0}\\ u_{co}=u_{co\_p}+u_{co\_n}+u_{co\_0}\end{array}\right.---\left(4\right)$

$\left\{\begin{array}{c}{u}_{an}=u_{an\_p}+u_{an\_n}+({\tilde{u}}_{{\mathrm{an}}_0}+\frac{U_d}{2})\\ u_{bn}=u_{bn\_p}+u_{bn\_n}+({\tilde{u}}_{bn\_0}+\frac{U_d}{2})\\ u_{cn}=u_{cn\_p}+u_{cn\_n}+({\tilde{u}}_{cn\_0}+\frac{U_d}{2})\end{array}\right.---\left(5\right)$

Can be obtained by formula (1):

$\left[\begin{array}{c}{u}_{an\_p}\\ u_{bn\_p}\\ u_{cn\_p}\end{array}\right]=(R+L_s)\left[\begin{array}{c}{i}_{La\_p}\\ i_{Lb\_p}\\ i_{Lc\_p}\end{array}\right]+\left[\begin{array}{c}{u}_{ao\_p}\\ u_{bo\_p}\\ u_{co\_p}\end{array}\right]---\left(6\right)$

$\left[\begin{array}{c}{u}_{an\_n}\\ u_{bn\_n}\\ u_{cn\_n}\end{array}\right]=(R+L_s)\left[\begin{array}{c}{i}_{La\_n}\\ i_{Lb\_n}\\ i_{Lc\_n}\end{array}\right]+\left[\begin{array}{c}{u}_{ao\_n}\\ u_{bo\_n}\\ u_{co\_n}\end{array}\right]---\left(7\right)$

$\left[\begin{array}{c}{i}_{La\_p}\\ i_{Lb\_p}\\ i_{Lc\_p}\end{array}\right]=C_s\left[\begin{array}{c}{u}_{ao\_p}\\ u_{bo\_p}\\ u_{co\_p}\end{array}\right]+\left[\begin{array}{c}{i}_{ao\_p}\\ i_{bo\_p}\\ i_{co\_p}\end{array}\right]---\left(8\right)$

$\left[\begin{array}{c}{i}_{La\_n}\\ i_{Lb\_n}\\ i_{Lc\_n}\end{array}\right]=C_s\left[\begin{array}{c}{u}_{ao\_n}\\ u_{bo\_n}\\ u_{co\_n}\end{array}\right]+\left[\begin{array}{c}{i}_{ao\_n}\\ i_{bo\_n}\\ i_{co\_n}\end{array}\right]---\left(9\right)$

Understanding according to formula (6)～(9), the positive sequence of output voltage and negative sequence component can independently control, and do not divided by zero sequence The impact of amount.In view of positive sequence is consistent with negative sequence component mathematical model, can be uniformly controlled them.

$\left[\begin{array}{c}{u}_{an\_p}+u_{an\_n}\\ u_{bn\_p}+u_{bn\_n}\\ u_{cn\_p}+u_{cn\_n}\end{array}\right]=(R+L_s)\left[\begin{array}{c}{i}_{La\_p}+i_{La\_n}\\ i_{Lb\_p}+i_{Lb\_n}\\ i_{Lc\_p}+i_{Lc\_n}\end{array}\right]+\left[\begin{array}{c}{u}_{ao\_p}+u_{ao\_n}\\ u_{bo\_p}+u_{bo\_n}\\ u_{co\_p}+u_{co\_n}\end{array}\right]---\left(10\right)$

$\left[\begin{array}{c}{i}_{La\_p}+i_{La\_n}\\ i_{Lb\_p}+i_{Lb\_n}\\ i_{Lc\_p}+i_{Lc\_n}\end{array}\right]=C_s\left[\begin{array}{c}{u}_{ao\_p}+u_{ao\_n}\\ u_{bo\_p}+u_{bo\_n}\\ u_{co\_p}+u_{co\_n}\end{array}\right]+\left[\begin{array}{c}{i}_{ao\_p}+i_{ao\_n}\\ i_{bo\_p}+i_{bo\_n}\\ i_{co\_p}+i_{co\_n}\end{array}\right]---\left(11\right)$

$\frac{1}{3}(u_{an}+u_{bn}+u_{cn})=\frac{1}{3}(R+L_s)(i_{La}+i_{Lb}+i_{Lc})+\frac{1}{3}(u_{ao}+u_{bo}+u_{co})+u_{gn}---\left(12\right)$

$\frac{1}{3}(i_{La}+i_{Lb}+i_{Lc})=\frac{1}{3}{C}_s(u_{ao}+u_{bo}+u_{co})+\frac{1}{3}(i_{ao}+i_{bo}+i_{co})---\left(13\right)$

$u_{gn}=\frac{U_d}{2}+{\tilde{u}}_{mn}-(R_n+L_{n}s)i_g---\left(14\right)$

$i_{La\_0}=-\frac{1}{3}{i}_g---\left(15\right)$

${\tilde{u}}_{an\_0}+\frac{U_d}{2}=(R+L_s)i_{La\_0}+u_{ao\_0}+u_{gn}---\left(16\right)$

${\tilde{u}}_{an\_0}=-\[(\frac{R}{3}+R_n)+(\frac{L}{3}+L_n)s\]i_g+u_{ao\_0}+{\tilde{u}}_{mn}---\left(17\right)$

${\tilde{u}}_{an\_0}=\[1+(R+3R_n)Cs+(L+3L_n){\mathrm{Cs}}^2\]u_{ao\_0}+\[R+3R_n+(L+3L_n)s\]i_{ao\_0}+{\tilde{u}}_{mn}---\left(18\right)$

From formula (18) it can be seen that the zero-sequence component of output voltage can be by three-phase voltage reference signal or four bridge legs reference The control of signal realizes.Generally, three-phase voltage reference signal is for controlling the positive and negative sequence of three-phase output voltage flexibly Component, relatively independent with four bridge legs, so using four bridge legs reference signal to control the zero-sequence component of output voltage.By three Phase four bridge legs structure realizes the control of each component of voltage positive sequence, negative phase-sequence and zero sequence, i.e. can get the standard sine output of voltage.

The quality of voltage of the present invention improves device and uses series system to access power distribution network, and quality of voltage improves device series connection access and joins During electrical network, general by transformator access electrical network, as shown in Figure 4, A1 Yu A2, B1 Yu B2, C1 Yu C2 seal in three-phase loop respectively. It is easy analysis, it is assumed that have employed the ideal transformer that no-load voltage ratio is 1:l herein.Fig. 5 show single-phase series control principle drawing, electricity Pressure upgrader is regarded a voltage source as and is expanded；U_GRepresent distribution network voltage；U_sRepresent voltage source and expand voltage；Z represents and includes electricity Source internal resistance is in interior line impedance, and I is the electric current flowing through this impedance；U_LFor load voltage.

When distribution network system is properly functioning, voltage source is great need not play a role, and when quality of voltage occurs in distribution network system During problem, it is necessary to be controlled the quality of voltage with proof load, occur that fall and system band are not temporarily with distribution network voltage below Balance the load and respectively series connection control is carried out power characteristic analysis under two kinds of standalone case.

From Fig. 5 circuit relationships,

U_L=U_G-IZ+U_s (19)

When distribution network system is normal, U_s=0, i.e. U_L=U_G-IZ.Certain moment U_GFall as U_sagTime, to maintain load electricity Pressure value is constant, needs to compensate the power distribution network drop-off voltage during dropping temporarily.As long as output is so that electric current maintains original numerical value, Load voltage values will maintain original value, can obtain according to formula (19),

$I=\frac{U_{sag}+U_s-U_L}{Z}---\left(20\right)$

Make U_s=U_G-U_sag, requirement can be met, now voltage source expands U_sApparent energy S of output_sFormula (21) can be passed through near Seemingly try to achieve.

S_s=I U_s=I (U_G-U_sag) (21)

During distribution network system band unbalanced load, use series connection control and compensation；From formula (19), U_GConstant situation Under, each phase current is uneven, then the pressure drop causing impedance Z is uneven so that U_LUneven.Utilize voltage source U_sTo go to compensate resistance The change in pressure drop of anti-Z, can keep the threephase load balance of voltage.Assume that the electric current after change is I_x, three-phase equilibrium electric current is I, then U_s It is represented by,

U_s=(I_x-I)·Z (22)

But, in many cases and inapplicable, such as system phase open circuit or system band three-phase are or not this compensation way The situation of the constant-current type load of balance.

In sum, the present invention devises a kind of high permeability distributed photovoltaic quality of voltage and improves device, as shown in Figure 6, The quality of voltage of the present invention improves device main circuit structure figure, and quality of voltage improves tandem type current transformer and the parallel connection type current transformer of device Being three-phase four-arm structure, wherein, A1, B1, C1, N1 are four ports of tandem type current transformer, connect power distribution network power supply, A2, B2, C2, N2 are four ports of parallel connection type current transformer, connect load.The three-phase output of tandem type current transformer is through by inductance Power distribution network is sealed in after the LC wave filter of Ls and electric capacity Cs composition and series transformer TsA, TsB, TsC, parallel connection type current transformer Three-phase output is incorporated to power distribution network through inductance Lp, and inductance Lp is also in series with pre-charge resistance R1 and catalyst KMpl, KMp2, preliminary filling Electricity resistance R1, limits charging current.Bidirectional thyristor SCRA～SCRC connects after current-limiting inductance LA～LC respectively, then with change of connecting Depressor TsA～TsC is in parallel, constitutes bypass loop.DC side, stable DC electricity it is parallel to after electrochemical capacitor Cdcl and Cdc2 series connection Pressure.Super capacitor cabinet, as fast energy storage, carries out exchange and the buffering of energy by DC/DC changer and DC side.R2 is for letting out Electric discharge resistance, it is provided that letting out when DC bus-bar voltage is too high can loop；Lb is boost inductance.

The quality of voltage of the present invention improves device design capacity 100kVA (series and parallel current transformer is each according to 50kVA), controls Power supply is powered as AC220V, input and output voltage grade AC380V, converter switches frequency fs=7.2kHz.Series and parallel unsteady flow Device output-current rating virtual value is 50000/3/220=75.8A.

The design of each device parameters is as follows:

(1) DC side electric capacity of voltage regulation Cdcl, Cdc2

DC voltage is required to support current transformer output AC 380V voltage, and the compensation electric current required for producing, I.e. there are enough energy snubber abilities.Under SPWM pattern, DC bus-bar voltage U_ocCan approximate and be calculated by following formula.

$U_{oc}=\frac{2\sqrt{2}{U}_{AC}}{m}$

Wherein, " U_AC=220V, m are the index of modulation, take l herein, then can try to achieve U_oc=622V.Further, since in reality Dutycycle amplitude limit, magnetically saturated control strategy, the impact of the condition such as dividing potential drop of current transformer output filter, actual take dc bus Voltage U_dcFor 690V, experiment sampled value is 687V.The most desirable the pressure of electric capacity Cdc1, Cdc2 is 450V.

When dc bus has out-of-balance current to fluctuate, electric capacity Cdc1, Cdc2 absorb buffering energy, cause unidirectional current to emboss Ripple, bus capacitor value can be obtained by the peak value of current imbalance (owing to DC energy storage link can reduce the fluctuation of electric current, herein Ask for extreme value, put aside the regulation effect of DC energy storage).

(2) the inductance Ls in LC wave filter and electric capacity Cs

The corner frequency fn of the output LC wave filter of tandem type current transformer is far below switching frequency fs, to switching frequency and The harmonic wave of neighbouring frequency band has obvious inhibitory action.Switching frequency fs=7.2kHz, the corner frequency taking wave filter is switch The 1/10 of frequency, i.e. fn=720Hz.Ls=1.27mH, owing to tandem type current transformer requires the pressure drop on filter inductance as far as possible It is little, so compromise takes Ls=1mH, Cs=50uF.Ls rated current virtual value is 75.8A.

(3) parallel filtering inductance Lp

Parallel filtering inductance Lp value is the biggest, and the ripple of electric current is the least, and current changing rate is the least simultaneously, parallel converters Dynamic responding speed is the slowest, should take into account both effects during selection.Owing to parallel connection type wave filter mainly realizes harmonics restraint and idle The function compensated, the surge requirements scope of harmonic wave is less, typically takes the 5%-10% of first-harmonic rated current.Parallel filtering electricity The span of sense Lp is about at 1.27mH-3.18mH, and compromise consideration takes Lp=3mH, and rated current virtual value is 75.8A.

(4) current-limiting inductance LA, LB, LC

Current-limiting inductance LA, LB, LC connect with bidirectional thyristor SCRA, SCRB, SCRC respectively, limit the electric current in branch road. Actual according to engineering, current-limiting inductance impedance generally takes about the 1% of rated load impedance, therefore takes LA=LB=LC=0.09mH, Rated current virtual value is 75.8A.

(5) boost inductance Lb

According in DC/DC translation circuit, the relationship between expression of stable state and electric current consecutive hours inductance and voltage:

$L_b\frac{\mathrm{\Δ}I}{\mathrm{\Δ}t}=U$

In formula, U is DC/DC changer DC input voitage, the i.e. DC voltage of ultracapacitor, counts according to 400V herein Calculate；Δ I calculates according to the 15%-20% of rated current；Δ t is the ON time in each switch periods of power device, switch Frequency is that 7.2kHz, DC/DC changer is output as VQC DC bus-bar voltage U_dc(690V) Δ t=(1-400/ can, be calculated 690)/7200.The problems such as the fluctuation of consideration ultracapacitor DC voltage, boost inductance leaves allowance, rated current virtual value It is 1 00kVA/400V=250A.

(6) transformator TsA, TsB, TsC

The output of tandem type current transformer, after LC wave filter, seals in electrical network loop by series transformer, series connection Transformator has played isolation tandem type current transformer and the effect of electrical network, and coordinates the structure of three-phase four-arm to form three-phase independence Control.Transformator selects booster transformer, can reduce the current requirements to tandem type converter switches device；Direct current is female simultaneously Line voltage maintains higher (690V), it is also possible to reduce the requirement of current transformer output filter.

Transformator TsA, TsB, TsB basic parameter: rated capacity 50kVA/3=17kVA, no-load voltage ratio is 1:2, input voltage (grid side) AC110V, output voltage (current transformer side) AC220V, voltage reaches core sataration during 300V；Input current 152A； Output electric current 75.8A；Saturation magnetic induction 1.98T unshakable in one's determination.Series transformer can produce magnetic saturation phenomenon when putting into operation.

(7) bleeder resistance R2

Bleeder resistance need to meet long-term work requirement, and power generally takes about the 10% of power system capacity, then can obtain and release The power P r2=10% 100=10kW of resistance R2, bleeder resistance R2 are 50 Ω/10kW.

(8) pre-charge resistance R1

At the system work initial stage, DC bus-bar voltage needs charging to reach certain level, and otherwise impact high pressure is in electric capacity both sides, Heavy current impact can be caused.After putting into pre-charge resistance R1, charge circuit can be constituted with DC side electric capacity of voltage regulation Cdcl, Cdc2, Generally in ls-3s, the DC voltage being reached 90% by RC charging can meet requirement.R1=is taken according to circuit theory 100fl, considers according to the mean power of pre-charge resistance, and pre-charge resistance R1 is 100 Ω/1kW.

(9) power device

Select the parameter of power device according to each loop voltage, current requirements, bidirectional thyristor SCRA, SCRB, SCRC select Select 600V/300A；IGBT2 in super capacitor cabinet selects 1 700V/1 00A, and IGBT3, IGBT4 select 1700V/400A；Its Remaining IGBT all selects 1 700V/300A.

(10) bank of super capacitors

Ultracapacitor is in the aspect function admirable such as power density and efficiency for charge-discharge so that it is suitable as energy Buffer uses.But the terminal voltage of ultracapacitor is the lowest, the terminal voltage of the most single ultracapacitor is about 3V, single Energy storage capacity the most relatively small (the Maxwell ultracapacitor herein applied, capacity 3000F, the terminal voltage of ultracapacitor 2.7V), it is not suitable for real system.

Many ultracapacitor connection in series-parallel generally are got up to form bank of super capacitors, in order to provide energy by actual application Or carry out power buffering, and it is generally used for mesolow occasion.DC voltage maximum Umax=NU1=210*2.5= 525V, DC voltage minima Umin=NU2=210*1=210V, it is desirable to DC voltage about 400V, consider Determine that 200 ultracapacitors of selection are used in series eventually, and control single capacitance voltage and maintain about 2V.

(11) main circuit parameter analysis

Fig. 7 show the equivalent circuit of main circuit parameter, according to the aforementioned circuit parameter solved, Ls=1mH, Cs= 50uF, Lp=3mH, Cp=3.3uF, n=2, Rn=0.387, jwLn=j*0.0069, ignore transformer primary secondary impedance, electricity Source Us impedance and Rc resistance.

The quality of voltage of the present invention improves device and achieves flux regulator, by detecting the electric current on the former limit of series transformer, and control The output of tandem type current transformer processed, while eliminating series transformer magnetic saturation problem, it is achieved effective, simple, practical voltage Compensate function.

Flux regulator method is as follows: set the threshold value of series transformer primary current, when tandem type current transformer puts into operation, Primary current is detected, when this electric current reaches to set threshold value, it is believed that magnetic flux is saturated, now stops tandem type by current transformer The output of current transformer, to maintain magnetic flux not to be further added by；After compensating voltage zero-cross, tandem type current transformer continues to put out, for eliminating The saturated magnetic bias being likely to result in of magnetic flux in upper half, this half cycle output voltage reaches 120%, and (design of series transformer is generally stayed Have the saturated nargin of 120%) left and right former calculating output valve, normally export in the time after this half cycle.

The quality of voltage of the present invention improves device and achieves switching control strategy, and quality of voltage improves device access power distribution network and carries out After work, DC bus-bar voltage is now the voltage of bank of super capacitors, controls Guan Bi catalyst KMp1 and KMp2, exchanges 380V Power supply is charged (being equivalent to uncontrollable rectifier) to DC side by pre-charge resistance, parallel connection type current transformer, and after charging complete, Guan Bi connects Tentaculum KMp1, disconnection catalyst KMp2；DC/DC changer is started working, and adjusts DC voltage to setting value 690V.Detection electricity Net voltage and load current, load-side is uneven or harmonic content is beyond when requiring, parallel connection type current transformer puts into operation；Electrical network electricity When extruding existing voltage dip, the quality of voltage problem such as rise sharply, tandem type current transformer puts into operation, and output compensates change in voltage, electricity After pressure quality problems eliminate, tandem type current transformer is deactivated, by the bypass of bidirectional thyristor SCRA, SCRB, SCRC.

Being selected primarily based upon movement time and allow the current capacity two indices that passes through to determine of switchgear.Two-way IGCT SCR constitutes switchgear and realizes the break-make of circuit, and A.C. contactor or AC circuit breaker speed of action can be overcome slow And the problem that full-control type semiconductor power device proof voltage rush of current ability is relatively weak, it is possible to meet simultaneously rapidity and Shock proof performance requirement.IGCT SCR electric current of make-and-break ability is strong, impact resistance and cheap, can be as preferably switch Equipment, but it is as half control type device, and its gate pole triggers signal can only control break-over of device, it is impossible to control to turn off.According to VQC The influence research that SCR is turned off by the characteristic of middle load, the size of load and the output voltage amplitude of series converter and direction, Establishment is forced shutdown principle.Naturally turn off the lag compensation problem brought for SCR, in proposition VQC, SCR's is forced shutdown control Strategy, it is achieved the function of the timely and effective input of VQC series converter/exit electrical network.

Improve device design control system for above-mentioned quality of voltage, be used for controlling quality of voltage and improve device.With digital signal Processor TMS320F28335 is core, constitutes control system in conjunction with peripheral control circuits.Control system mainly includes power supply electricity Source, combined-voltage sampling (using electric resistance partial pressure sampling), current sample (using LEM current sensor), analog digital conversion, isolation The unit such as driver element and digital quantity input and output.

As shown in Figure 8, needed for control system supplying the unit such as analog digital conversion, DSP, isolation drive DC source；Digital quantity is sent into DSP by analog digital conversion by voltage sample and current sample；DSP numeral Signal processor carries out signal processing, mathematical operation, logical judgment etc. to the digital quantity of input, requires output according to control strategy Desired signal；(tandem type current transformer, parallel connection type current transformer, DC/DC become to export corresponding pwm signal by isolation drive unit Parallel operation is applied), the SCR signal state of the bidirectional thyristor (switching), KM signal (on-off control of catalyst)；PDP signal is for being Blanket insurance protects signal.

The analogue signal of each electricity, need to could send into DSP after becoming digital quantity by analog digital conversion. Voltage signal through electric resistance partial pressure sample after, by have high common mode inhibition capacity isolation operational amplifier HCPL7800 and High input impedance operational amplifier CA3140 enters analog digital conversion: after current signal is sampled by LEM current sensor, output letter Number it is directly entered analog digital conversion.TMS320F28335 carries 12 analog-digital converters, can only receive the unipolarity letter of 0～3.3V Number, conversion accuracy is difficult to meet the requirement of high performance system.The present invention uses 14 A/D converter MAXl25 of Maxim company Chip realizes high-precision analog digital conversion.The input of MAXl25 voltage and output level are+5V, select and drive buffering tri-state gate circuit 74F245 chip completes the level match with DSP and speeds match, simultaneously MAXl25 and DSP digital signal Processor concurrent working can alleviate the work load of DSP.

If Fig. 9 is voltage, the sampling conditioning process of electric current and the flow chart of analog digital conversion.

Quality of voltage improves in device work process, needs to detect the phase information of line voltage.Ask when there is quality of voltage During topic, when particularly line voltage occurs to drop phase shift or voltage distortion temporarily, detect that the phase place of line voltage is outstanding the most in real time For important.The present invention uses software phase-lock loop based on Instantaneous Power Theory, and the method for application synchronous rotating angle, by three Phase abc rest frame converts to biphase rest frame, is then passed through being obtained d, q axle component by rotating coordinate transformation, logical Cross the component to q axle and carry out PI regulation composition closed loop, thus obtain corresponding phase information.The control flow of software phase-lock loop is such as Shown in Figure 10, wherein, 1/S is voltage controlled oscillator, ω₀=100 π rad/s, for electrical network rated frequency；u_sa、u_sb、u_scFor three-phase electricity Net voltage；T_abc-αβTransformation matrix for three phase static coordinate to biphase static coordinate；T_αβ-dqFor biphase static coordinate to biphase rotation Turn transformation of coordinates matrix.

$T_{abc-\mathrm{\α}\mathrm{\β}}=\sqrt{\frac{2}{3}}\left|\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right|$

$T_{\mathrm{\α}\mathrm{\β}-dq}=\left|\begin{array}{cc}cos\mathrm{\θ}& sin\mathrm{\θ}\\ -sin\mathrm{\θ}& cos\mathrm{\θ}\end{array}\right|.$

The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For Yuan, on the premise of without departing from the technology of the present invention principle, it is also possible to make some improvement and deformation, these improve and deformation Also should be regarded as protection scope of the present invention.

Claims (9)

1. high permeability distributed photovoltaic quality of voltage improves device, it is characterised in that quality of voltage improves device and uses three-phase four bridge The tandem type current transformer of arm configuration and parallel connection type current transformer, wherein, four ports of tandem type current transformer connect power distribution network power supply, Four ports of parallel connection type current transformer connect load；The three-phase output of tandem type current transformer is through being made up of inductance Ls and electric capacity Cs LC wave filter after, seal in power distribution network by series transformer；The three-phase output of parallel connection type current transformer is incorporated to join through inductance Lp Electrical network, inductance Lp is also in series with pre-charge resistance R1 and catalyst KMpl, KMp2；Bidirectional thyristor SCRA, SCRB, SCRC are respectively After series connection current-limiting inductance LA, LB, LC more in parallel with series transformer TsA, TsB, TsC respectively, constitute bypass loop；Electrolysis electricity After holding Cdcl, Cdc2 series connection, it is parallel to DC side, stable DC voltage；Fast energy storage element uses super capacitor cabinet, passes through DC/DC changer and DC side carry out exchange and the buffering of energy；Described quality of voltage improve device also include bleeder resistance R2 and Boost inductance Lb.

High permeability distributed photovoltaic quality of voltage the most according to claim 1 improves device, it is characterised in that described series connection Transformator selects booster transformer.

High permeability distributed photovoltaic quality of voltage the most according to claim 1 improves device, it is characterised in that described super Capacitor box selects 200 ultracapacitors to be used in series.

High permeability distributed photovoltaic quality of voltage the most according to claim 1 improves device, it is characterised in that described voltage Quality is improved device and is achieved flux regulator strategy, and flux regulator method is as follows: set the threshold value of series transformer primary current, string When connection type current transformer puts into operation, detect primary current by current transformer, when this electric current reaches to set threshold value, it is believed that magnetic Logical saturated, now stop the output of tandem type current transformer, to maintain magnetic flux not to be further added by；After compensating voltage zero-cross, tandem type Current transformer continues to put out, and for the saturated magnetic bias caused of magnetic flux in elimination upper half, this half cycle output voltage reaches the former meter of 120% Calculate output valve, normally export in the time after this half cycle.

High permeability distributed photovoltaic quality of voltage the most according to claim 1 improves device, it is characterised in that described voltage Quality is improved device and is achieved switching control strategy, and quality of voltage improves device and accesses after power distribution network is operated, DC bus-bar voltage Be now the voltage of super capacitor cabinet, control Guan Bi catalyst KMp1 and KMp2, exchange 380V power supply by pre-charge resistance R1, Parallel connection type current transformer charges to DC side, after charging complete, and Guan Bi catalyst KMp1, disconnection catalyst KMp2；DC/DC changer Start working, adjust DC voltage to setting value 690V, detection line voltage and load current, load-side imbalance or harmonic wave Content is beyond when requiring, parallel connection type current transformer puts into operation；When there is voltage dip, the quality of voltage problem that rises sharply in line voltage, Tandem type current transformer puts into operation, and output compensates change in voltage, and after quality of voltage problem eliminates, tandem type current transformer exits work Make, by the bypass of bidirectional thyristor SCRA, SCRB, SCRC.

6. the high permeability distributed photovoltaic quality of voltage described in claim 1 to 5 any one improves the control system of device, its It is characterised by, including power supply, AD conversion unit, DSP and isolation drive unit；Described power supply electricity DC source needed for source supply AD conversion unit, DSP and isolation drive unit；Voltage sample and electric current The analogue signal of sampling sends into DSP after becoming digital quantity by AD conversion unit；At DSP digital signal Reason device carries out signal processing, mathematical operation, logical judgment to the digital quantity of input, requires the required letter of output according to control strategy Number；DSP output signal includes pwm signal, SCR signal and KM signal, and isolation drive unit is by DSP numeral Pwm signal output in signal processor output signal improves the tandem type current transformer of device, parallel connection type current transformer to quality of voltage With DC/DC changer, the output of SCR signal is improved to quality of voltage the bidirectional thyristor of device, KM signal is exported to voltage matter Amount improves the catalyst of device, it is achieved high permeability distributed photovoltaic quality of voltage improves the control of device.

Control system the most according to claim 6, it is characterised in that described isolation drive unit is by defeated for system protection signal Go out to DSP.

Control system the most according to claim 6, it is characterised in that described voltage sample uses electric resistance partial pressure sampling, electricity AD conversion unit is entered by isolation operational amplifier HCPL7800 and impedance op-amps CA3140 after pressure sampling；Institute Stating current sample and use LEM current sensor, after current sample, output signal is directly entered AD conversion unit.

Control system the most according to claim 8, it is characterised in that described AD conversion unit uses MAXl25 chip, And select and drive buffering tri-state gate circuit 74F245 chip to realize the level match with DSP and speed Join.