CN104764965A - Voltage sag generating device based on magnetic controllable reactor (MCR) - Google Patents

Abstract

The invention discloses a voltage sag generating device based on a magnetic controllable reactor (MCR). The device comprises a fixed reactor, the magnetic controllable reactor, a photovoltaic power station and a control system; the magnetic controllable reactor is connected with the photovoltaic power station in parallel, and then the fixed reactor is connected to a generatrix with a known voltage level power source; a voltage with a known voltage level power source is marked as UN; one end of the control system is connected to the line inlet of the photovoltaic power station, and the other end of the control system is connected with the magnetic controllable reactor. According to the device, a voltage value of the line inlet of the photovoltaic power station is detected by the magnetic controllable reactor in real time, a reactance value of the magnetic controllable reactor is controlled, so that the wire inlet voltage value of the photovoltaic power station changes from 10% to 90%, a network voltage sag when a network is broken is stimulated, and the grid-connected low voltage ride through capacity of the photovoltaic power station is detected; in addition, based on the achievement of the magnetic controllable reactor, an inductance value can be continuous, stepless and adjustable, and the grid-connected low voltage ride through capacity of the photovoltaic power station can be accurately detected.

Description

A kind of voltage dip generating means based on magnet controlled reactor (MCR)

Technical field

What the present invention relates to is a kind of voltage dip test unit of new forms of energy distributed power generation interconnection technology field, particularly a kind of voltage dip generating means based on magnet controlled reactor (MCR).

Background technology

Current photovoltaic generation has become the important form that solar energy resources develops, the wherein access in large-sized photovoltaic power station, profound influence is produced by the safe and stable operation of electrical network, particularly when electric network fault, the unexpected off-grid of photovoltaic plant can worsen operation of power networks state further, brings more serious consequence.

In the end of the year 2010, " photovoltaic plant access electric power network technique regulation " that State Grid Corporation of China puts into effect explicitly points out, " photovoltaic plant should possess the ability of certain withstand voltage exception, avoids departing from when line voltage is abnormal, causes the loss of electric network source ".

Therefore, under the situation of electric network fault, in order to photovoltaic plant can not off-grid suddenly, worsen the running status of electrical network further, need a kind of device that can test out its low voltage ride-through capability; But, research approach also not relevant in prior art.

Summary of the invention

The object of this invention is to provide a kind of line voltage based on MCR and fall generating means temporarily, can simulating grid fault time the line voltage state of falling temporarily, test out low voltage ride-through capability during photovoltaic electric station grid connection accurately.

The object of the invention is to be achieved through the following technical solutions:

Line voltage based on MCR falls a generating means temporarily, and this device comprises: constant reactance device, magnet controlled reactor MRC, photovoltaic plant and control system;

Wherein, described magnet controlled reactor accesses the bus of the level power supplies such as known voltage with connecting with described constant reactance device after described photovoltaic plant parallel connection; The voltage of the level power supplies such as described known voltage is designated as U _n;

One end of described control system is connected to photovoltaic plant incoming line place, and the other end is connected with described magnet controlled reactor; It is for detecting the magnitude of voltage at photovoltaic plant incoming line place in real time, and makes the primary voltage value of photovoltaic plant at described U with this reactance value controlling described magnet controlled reactor _n10% ~ 90% between change, when carrying out simulating grid fault, line voltage falls temporarily, tests the low voltage ride-through capability of photovoltaic electric station grid connection with this.

Further, the rated voltage of described constant reactance device is identical with the voltage of the level power supplies such as described known voltage, and its inductance value is L, then the rated current flowing through the every phase of described constant reactance device is:

$I_L=\frac{U_N}{\sqrt{3}\×2\mathrm{\πfL}};$

Wherein, f is system frequency.

Further, the rated voltage of described magnet controlled reactor is identical with the voltage of the level power supplies such as described known voltage, and its inductance value is the maximum allowed current then flowing through the every phase of described magnet controlled reactor is:

$I_{\mathrm{MCR}}=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}\left(\frac{1}{9}L\right)};$

Wherein, L is the inductance value of constant reactance device;

When magnet controlled reactor is time, the electric current now flowing through magnet controlled reactor is maximum, is expressed as:

$I_{\max }=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}(L_S+L+\frac{1}{9}L)};$

Wherein, L _sfor system impedance, its computing formula is: s _dfor the capacity of short circuit of this bus.

Further, described magnet controlled reactor comprises interconnective reactor winding and rectification circuit;

Described reactor winding comprises two iron cores, each iron core is equipped with upper and lower two groups of coils, and the two groups of coils up and down in one of them iron core are designated as coil L _awith coil L _c, the two groups of coils up and down in another iron core are designated as coil L _bwith coil L _d; Wherein, coil L _aleading-out terminal and coil L _dend of incoming cables be connected, coil L _bleading-out terminal and coil L _cend of incoming cables be connected, same iron core be also provided with thyristor VT1, VT2 between two coils up and down; After two coil cross connections up and down of different iron core, across being provided with fly-wheel diode on it intersects end points.

Further, control system detects the magnitude of voltage at photovoltaic plant incoming line place in real time, and makes the primary voltage value of photovoltaic plant at described U with this reactance value controlling described magnet controlled reactor _n10% ~ 90% between change and comprise:

Control system detects the magnitude of voltage at photovoltaic plant incoming line place in real time, then the result of detection is compared with the magnitude of voltage of setting, controls magnet controlled reactor according to comparative result, until the magnitude of voltage at photovoltaic plant incoming line place is equal with the magnitude of voltage of setting;

Wherein, if the magnitude of voltage detected is less than the magnitude of voltage of setting, then the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor is increased by control system; Trigger Angle increases, then VT1, VT2 conduction angle reduces, and causes coil DC current to reduce, and core sataration degree reduces, and the reactance value of magnet controlled reactor increases;

If the magnitude of voltage detected is larger than the magnitude of voltage of setting, then control system reduces the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor; Trigger Angle reduces, then the conduction angle of VT1, VT2 increases, and causes coil DC current to increase, and core sataration degree increases, and the reactance value of magnet controlled reactor reduces.

Further, the minimum capacity of short circuit of described grid-connected point is:

$S_{d,\min }=\frac{{U_N}^2}{2\mathrm{\πf}\left({L+L}_S\right)}$

Wherein, L is the inductance value of constant reactance device, L _sfor system impedance;

The minimum capacity of short circuit of the grid-connected point of described photovoltaic plant volume ratio is little more than 10 times.

As seen from the above technical solution provided by the invention, primary voltage is detected in real time by utilizing control system, then the reactance value controlling described magnet controlled reactor makes the primary voltage value of photovoltaic plant change between 10% ~ 90% of nominal voltage of a system, and when carrying out simulating grid fault, line voltage falls temporarily; The program realizes based on magnet controlled reactor, and therefore the inductance value of reactor can accomplish that continuous stepless is adjustable, can test out the low voltage ride-through capability of photovoltaic electric station grid connection more accurately.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawings can also be obtained according to these accompanying drawings.

Fig. 1 falls the structural representation of generating means temporarily for a kind of line voltage based on MCR that the embodiment of the present invention provides;

The structural representation of the magnet controlled reactor that Fig. 2 provides for the embodiment of the present invention;

Fig. 3 falls reactor parameter in generating means temporarily for determination line voltage that the embodiment of the present invention provides and carries out the process flow diagram of electric network fault simulation.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on embodiments of the invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to protection scope of the present invention.

Fig. 1 falls the structural representation of generating means temporarily for a kind of line voltage based on MCR that the embodiment of the present invention provides.As shown in Figure 1, this device mainly comprises: constant reactance device L1, magnet controlled reactor (MCR) L2, photovoltaic plant and control system.

Wherein, described magnet controlled reactor accesses the bus of the level power supplies such as known voltage with connecting with described constant reactance device after described photovoltaic plant parallel connection; The voltage of the level power supplies such as described known voltage is designated as U _n; One end of described control system is connected to photovoltaic plant incoming line place, and the other end is connected with described magnet controlled reactor.

Can also comprise three isolating switchs K1, K2, K3 in this device, before power supply is not powered, isolating switch K1, K2, K3 are all in gate-dividing state, and after this Power supply, K2 closes, K1 and K3 disconnects, and is photovoltaic plant bypass power supply.

In the embodiment of the present invention, in order to test low-voltage crossing ability during photovoltaic electric station grid connection, thus closed by isolating switch K1 and K3, K2 disconnects.Now, detected the magnitude of voltage of photovoltaic plant incoming line (test point as in Fig. 1) in real time by control system, and make the primary voltage value of photovoltaic plant at described U with this reactance value controlling described magnet controlled reactor _n10% ~ 90% between change, when carrying out simulating grid fault, line voltage falls temporarily, tests the low voltage ride-through capability of photovoltaic electric station grid connection with this accurately.

Due to constant reactance device in this device the highest to bear 90% rated voltage, so the shunt reactor that rated voltage is higher should be selected, the essential characteristic of shunt reactor and the visible GB of parameter " reactor " (GB 10229).In the present embodiment, the rated voltage of described constant reactance device is identical with the voltage of the level power supplies such as described known voltage, and its inductance value is preset as L, then the rated current flowing through the every phase of described constant reactance device is:

$I_L=\frac{U_N}{\sqrt{3}\×2\mathrm{\πfL}};$

Wherein, f is system frequency.

In order to make the primary voltage of photovoltaic plant change between 10% ~ 90% of rated voltage, then the voltage that magnet controlled reactor is got should be able to change between 10% ~ 90%, so the inductance value of magnet controlled reactor should be between; Meanwhile, if the rated voltage of described magnet controlled reactor is identical with the voltage of the level power supplies such as described known voltage, then the maximum allowed current flowing through the every phase of described magnet controlled reactor is:

$I_{\mathrm{MCR}}=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}\left(\frac{1}{9}L\right)};$

Wherein, L is the inductance value of constant reactance device;

When magnet controlled reactor is time, the electric current now flowing through magnet controlled reactor is maximum, is expressed as:

$I_{\max }=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}(L_S+L+\frac{1}{9}L)};$

Wherein, L _sfor system impedance, its computing formula is: s _dfor the capacity of short circuit of this bus.

In the embodiment of the present invention, the rated current of constant reactance device and the maximum allowed current of magnetic control reactance all should be greater than I _maxif the rated current of any one reactor is less than this maximum current, then should reset the inductance value L of constant reactance device.

When determining the parameter of constant reactance device and magnet controlled reactor, the minimum capacity of short circuit of grid-connected point (the grid-connected point as in Fig. 1) can be calculated, is expressed as:

$S_{d,\min }=\frac{{U_N}^2}{2\mathrm{\πf}\left({L+L}_S\right)};$

Wherein, L is the inductance value of constant reactance device, L _sfor system impedance;

Due to primary voltage value can be caused during photovoltaic electric station grid connection unstable, therefore, the minimum capacity of short circuit of the grid-connected point of photovoltaic plant volume ratio is little more than 10 times, to reduce photovoltaic electric station grid connection to the impact of primary voltage as far as possible.

In addition, the such scheme of the embodiment of the present invention realizes based on magnet controlled reactor, and magnet controlled reactor wiring is simple, and reactance value can accomplish that continuous stepless is adjustable.Therefore the low voltage ride-through capability of photovoltaic electric station grid connection can be tested out more accurately.Its structural representation as shown in Figure 2, mainly comprises: interconnective reactor winding and rectification circuit;

Described reactor winding comprises two iron cores, each iron core is equipped with upper and lower two groups of coils, and the two groups of coils up and down in one of them iron core are designated as coil L _awith coil L _c, the two groups of coils up and down in another iron core are designated as coil L _bwith coil L _d; Wherein, coil L _aleading-out terminal and coil L _dend of incoming cables be connected, coil L _bleading-out terminal and coil L _cend of incoming cables be connected, same iron core be also provided with thyristor VT1, VT2 between two coils up and down; After two coil cross connections up and down of different iron core, across being provided with fly-wheel diode on it intersects end points.

When power supply is in positive half cycle, thyristor VT1 bears forward voltage, and VT2 bears reverse voltage.The conducting if VT1 is triggered, power supply provides direct-current control voltage and electric current to circuit.In like manner, the conducting if VT2 is triggered when power-half cycle, also will produce direct-current control voltage and electric current, and it is consistent with during VT1 conducting to control sense of current.In a power frequency period of power supply, the conducting in turn of thyristor VT1, VT2 plays the effect of full-wave rectification, and fly-wheel diode plays afterflow effect.The Trigger Angle changing VT1, VT2 just can change the size controlling electric current, thus changes the saturation degree of iron core of electric reactor, smoothly regulates the reactance value of reactor continuously.

The magnetic permeability L-μ corresponding relation of the iron circuit of magnet controlled reactor calculates according to the following formula:

wherein $R_0=\frac{l_0}{{\mathrm{\μ\μ}}_0{S}_0}$

In formula: ψ, -magnetic linkage, unit is magnetic flux (weber); I is DC excitation electric current; W is the number of turn; μ is relative permeability; μ ₀for gas magnetic permeability, 0.4 π 10 ^-8prosperous/centimetre; l ₀for the length of magnetic path (centimetre); S ₀for magnetic circuit xsect (square centimeter); R ₀-magnetic resistance.

Be more than the main composition structure of device provided by the present invention, do detailed introduction below in conjunction with accompanying drawing 3 for its course of work.

As shown in Figure 3, first, need rated voltage and the inductance of determining constant reactance device and magnet controlled reactor, then judge whether the maximum current flowing through these two reactors is less than its rated current (this two step is described in detail above, therefore repeats no more); If so, then next step can be continued; Otherwise, also need the rated voltage and the inductance that redefine constant reactance device and magnet controlled reactor.

Then, the magnitude of voltage of setting photovoltaic plant incoming line place (test point as Fig. 1 place), the magnitude of voltage of photovoltaic plant incoming line is detected in real time by control system, again the result of detection is compared with the magnitude of voltage of setting, according to comparative result, magnet controlled reactor is controlled, until the magnitude of voltage at photovoltaic plant incoming line place is equal with the magnitude of voltage of setting.

Wherein, if the magnitude of voltage detected is less than the magnitude of voltage of setting, then the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor is increased by control system; Trigger Angle increases, then VT1, VT2 conduction angle reduces, and causes coil DC current to reduce, and core sataration degree reduces, and the reactance value of magnet controlled reactor increases;

If the magnitude of voltage detected is larger than the magnitude of voltage of setting, then control system reduces the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor; Trigger Angle reduces, then the conduction angle of VT1, VT2 increases, and causes coil DC current to increase, and core sataration degree increases, and the reactance value of magnet controlled reactor reduces.

In the process of above-mentioned adjustment thyristor, by the inductance value of magnet controlled reactor, DC excitation electric current I corresponding with it can be calculated, be calculated the Trigger Angle α of thyristor by DC excitation electric current I, thus adjusted.

For the ease of understanding, be described below in conjunction with a concrete example; It should be noted that, the numerical value adopted in following example is only citing, and user can do corresponding change according to the demand of reality.

In this example, supply voltage U _nbe set to 35kV, the capacity of short circuit S of bus _dfor 600MVA, then system impedance L _sfor:

$X_S=\frac{U_N^2}{S_d}=\frac{{35}^2}{600}\mathrm{\Ω}=2.04\mathrm{\Ω},L_S=\frac{X_S}{2\mathrm{\πf}}=\frac{2.04}{314}H=6.5\mathrm{mH};$

The rated voltage choosing constant reactance device is nominal voltage of a system 35kV, inductance value L is 300mH, so the rated current flowing through this reactor one phase is:

$I_L=\frac{35000}{\sqrt{3}\×2\mathrm{\π}\×50\×0.3}A=214.4A$

The voltage got to make magnet controlled reactor can change between 10% ~ 90%, and the inductance value of magnet controlled reactor need be between.The rated voltage choosing magnet controlled reactor is electrical network nominal voltage 35kV, so the maximum allowed current flowing through the every phase of magnet controlled reactor is:

$I_{\mathrm{MCR}}=\frac{35000}{\sqrt{3}\×2\mathrm{\π}\×50\×0.033}A=1949.2A$

When the inductance value of magnet controlled reactor is 33.3mH, the electric current of circuit is maximum, and electric current is now:

$I_{\max }=\frac{35000}{\sqrt{3}\×2\mathrm{\π}\×50\×0.3398}A=189.3A$

The rated current of above-mentioned constant reactance device and the maximum allowed current of magnet controlled reactor are all greater than the maximum current flowing through circuit, so the type selecting success of reactor.Now, the minimum capacity of short circuit of grid-connected point is:

$S_{d,\min }=\frac{{35}^2}{2\mathrm{\π}\×50\×0.3065}=12.72\mathrm{MVA}$

Due to primary voltage value can be caused during photovoltaic electric station grid connection unstable, therefore, the minimum capacity of short circuit of the grid-connected point of photovoltaic plant volume ratio is little more than 10 times, to reduce photovoltaic electric station grid connection to the impact of primary voltage as far as possible, therefore, in this example the capacity of selectable photovoltaic plant at about 1MVA.

Afterwards, can according to the low-voltage crossing ability of mode test light overhead utility as shown in Figure 3.

The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (6)

1. the line voltage based on MCR falls a generating means temporarily, it is characterized in that, this device comprises: constant reactance device, magnet controlled reactor MRC, photovoltaic plant and control system;

Wherein, described magnet controlled reactor accesses the bus of the level power supplies such as known voltage with connecting with described constant reactance device after described photovoltaic plant parallel connection; The voltage of the level power supplies such as described known voltage is designated as U _n;

One end of described control system is connected to photovoltaic plant incoming line place, and the other end is connected with described magnet controlled reactor; It is for detecting the magnitude of voltage at photovoltaic plant incoming line place in real time, and makes the primary voltage value of photovoltaic plant at described U with this reactance value controlling described magnet controlled reactor _n10% ~ 90% between change, when carrying out simulating grid fault, line voltage falls temporarily, tests the low voltage ride-through capability of photovoltaic electric station grid connection with this.

2. device according to claim 1, is characterized in that, the rated voltage of described constant reactance device is identical with the voltage of the level power supplies such as described known voltage, and its inductance value is L, then the rated current flowing through the every phase of described constant reactance device is:

$I_L=\frac{U_N}{\sqrt{3}\×2\mathrm{\πfL}};$

Wherein, f is system frequency.

3. device according to claim 1, is characterized in that, the rated voltage of described magnet controlled reactor is identical with the voltage of the level power supplies such as described known voltage, and its inductance value is the maximum allowed current then flowing through the every phase of described magnet controlled reactor is:

$I_{\mathrm{MCR}}=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}\left(\frac{1}{9}L\right)};$

Wherein, L is the inductance value of constant reactance device;

When magnet controlled reactor is time, the electric current now flowing through magnet controlled reactor is maximum, is expressed as:

$I_{\max }=\frac{U_N}{\sqrt{3}\×2\mathrm{\πf}(L_S+L+\frac{1}{9}L)};$

Wherein, L _sfor system impedance, its computing formula is: s _dfor the capacity of short circuit of this bus.

4. the device according to claim 1 or 3, is characterized in that, described magnet controlled reactor comprises interconnective reactor winding and rectification circuit;

Described reactor winding comprises two iron cores, each iron core is equipped with upper and lower two groups of coils, and the two groups of coils up and down in one of them iron core are designated as coil L _awith coil L _c, the two groups of coils up and down in another iron core are designated as coil L _bwith coil L _d; Wherein, coil L _aleading-out terminal and coil L _dend of incoming cables be connected, coil L _bleading-out terminal and coil L _cend of incoming cables be connected, same iron core be also provided with thyristor VT1, VT2 between two coils up and down; After two coil cross connections up and down of different iron core, across being provided with fly-wheel diode on it intersects end points.

5. device according to claim 1, is characterized in that, control system detects the magnitude of voltage at photovoltaic plant incoming line place in real time, and makes the primary voltage value of photovoltaic plant at described U with this reactance value controlling described magnet controlled reactor _n10% ~ 90% between change and comprise:

Control system detects the magnitude of voltage at photovoltaic plant incoming line place in real time, then the result of detection is compared with the magnitude of voltage of setting, controls magnet controlled reactor according to comparative result, until the magnitude of voltage at photovoltaic plant incoming line place is equal with the magnitude of voltage of setting;

Wherein, if the magnitude of voltage detected is less than the magnitude of voltage of setting, then the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor is increased by control system; Trigger Angle increases, then VT1, VT2 conduction angle reduces, and causes coil DC current to reduce, and core sataration degree reduces, and the reactance value of magnet controlled reactor increases;

If the magnitude of voltage detected is larger than the magnitude of voltage of setting, then control system reduces the Trigger Angle of thyristor VT1, VT2 in magnet controlled reactor; Trigger Angle reduces, then the conduction angle of VT1, VT2 increases, and causes coil DC current to increase, and core sataration degree increases, and the reactance value of magnet controlled reactor reduces.

6. device according to claim 1, is characterized in that, the minimum capacity of short circuit of described grid-connected point is:

$S_{d,\min }=\frac{{U_N}^2}{2\mathrm{\πf}(L+L_S)}$

Wherein, L is the inductance value of constant reactance device, L _sfor system impedance;

The minimum capacity of short circuit of the grid-connected point of described photovoltaic plant volume ratio is little more than 10 times.