CN106208146A - A kind of based on the control method improving controllable transformer photovoltaic generation voltage stability containing bidirectional power pipe - Google Patents

Abstract

The invention discloses a kind of control method improving photovoltaic generation voltage stability based on the controllable transformer containing bidirectional power pipe, this controller is made up of with control module controllable transformer, voltage, current sensor and measurement.This control method is to utilize controllable transformer to turn on rapidly, the electronic power switch turned off, control conducting and the shutoff of controllable transformer outlet side (secondary), increase by four groups of bidirectional power pipes simultaneously and change intersection phase winding conducting direction, thus maximum magnitude changes the phase place of controllable transformer output voltage, amplitude, passing ratio integral controller follows setting voltage and active power, realize the real-time regulation having output voltage amplitude and phase place, when voltage on line side has larger fluctuation, photovoltaic DC field is carried out reactive-load compensation, improve photovoltaic DC field voltage stability, and have with low cost, the feature that reliability is high.

Description

A kind of based on the raising controllable transformer photovoltaic generation voltage stabilization containing bidirectional power pipe The control method of property

Technical field

The present invention relates to photovoltaic power generation grid-connecting technical field, a kind of raising photovoltaic generation based on controllable transformer The control method of voltage stability.

Background technology

In recent years, a large amount of along with new forms of energy such as photovoltaic generations access and constantly infiltration, large-scale power network the most mutually Even, power system is increasingly sophisticated, and operation of power networks encounters unprecedented opportunities and challenge.The motility of operation of power networks, trend Controllability and grid stability seem and become more and more important, and building intelligent grid has become the inexorable trend of power network development.At one In the electrical network that structure is day by day complicated, it is possible to dynamic route control road trend becomes the important guarantee of Power System Reliability.Meanwhile, by In long period and the high cost of power system investment, existing equipment is the most preferably utilized to seem extremely important.Along with power load Contradiction between electricity needs is increased by being continuously increased of lotus, supply of electric power breach and people constantly increases, generation of electricity by new energy The most grid-connected basic configuration being future electrical energy and supplying, is also the basic demand of intelligent grid, how to improve existing power system To the receiving ability of new forms of energy and after how ensureing to access the reliability and stability of system become current much-talked-about topic.

Along with being continuously increased of photovoltaic system installed capacity, photovoltaic generation has become as the important generating side of a lot of country Formula.And photovoltaic generation is due to higher to the dependency of meteorological condition, daylight abundance can with normal power generation, and to during night by Being in stopped status in lacking light note, among one day, illumination variation also can be bigger, and photovoltaic system output can ripple therewith Dynamic.When net side system breaks down and has bigger Voltage Drop, photovoltaic system may off line and bring huge to power system Large impact, whether photovoltaic power generation equipment has voltage stability seems and becomes more and more important.

Usually, in order to make photovoltaic system have voltage stability, inverter algorithm can be improved, work as voltage on line side When falling, limiting meritorious current reference value, stable DC busbar voltage, support system normally works.But inverter can be made Algorithm complex is greatly increased, and can increase program erroneous judgement risk.

Summary of the invention

For the problems referred to above, it is an object of the invention to provide a kind of based on the controllable transformer raising light containing bidirectional power pipe The control method of volt generating voltage stability, when system network side Voltage Drop, records photovoltaic DC field PCC by sensor grid-connected Point voltage, electric current, according to electrical network and photovoltaic DC field running status, utilize controllable transformer, by quick electronic power switch Load tap changer output voltage amplitude and phase angle are dynamically controlled, thus regulates the active power of its output and idle merit Rate, carries out reactive-load compensation to photovoltaic DC field, stablizes the grid-connected point voltage of PCC, improves its voltage stability.

The present invention adopts the following technical scheme that

A kind of control method improving photovoltaic generation voltage stability based on the controllable transformer containing bidirectional power pipe, it is special Point is that the method includes following concrete steps:

Step 1., measure with control module to control initialize, receive host computer give voltage set-point V₀With The set-point P of active power₀；

Controllable transformer tap no-load voltage ratio N；

ω 0 is the angular frequency corresponding to 50 or 60Hz；

Oneth PI control module control coefrficient k_p1And k_i1, 1≤k_p1≤100,1≤k_i1≤ 100, just set value and be 10, by grasping Work person presses photovoltaic DC field operation conditions and sets, and reactive compensation power is the biggest, and coefficient value is the biggest, takes its maximum during rated power 100；

2nd PI control module control coefrficient k_p2And k_i2, 1≤k_p2≤100,1≤k_i2≤ 100, just set value and be 10, by grasping Work person presses photovoltaic DC field operation conditions and sets, and active power is the biggest, and coefficient value is the biggest, takes its maximum 100 during rated power；

Step 2., measure with control module receive input voltage transformer, output voltage transformer and output Current Mutual Inductance The input voltage V that device inputs respectively_in, output voltage V_out, output electric current I_out, output voltage is β with the angle of output electric current, if Input voltage V_inAmplitude be | V_in|, output voltage V_outAmplitude be | V_out|, export electric current I_outAmplitude be | I_out|, defeated The initial magnitude going out voltage fundamental is V¹ _out, transmission line of electricity reactance value L, distant place line voltage V_{Electrical network 2}Amplitude be V₂, phase angle is α；

Active-power P by following equation calculating actual measurement:

$P=\frac{1}{\sqrt{2}}{V}_{out}{I}_{out}cos\mathrm{\β}$

According to active-power P₀, calculate the initial phase angle theta of output voltage of controllable transformer₀

$P_0=\frac{V_2{V}_{out}}{{\mathrm{\ω}}_{0}L}sin(\mathrm{\α}-{\mathrm{\θ}}_0)$

According to photovoltaic DC field operation conditions, carry out active power regulation；

By changing the modulated signal of controllable transformer tap switch, regulate amplitude and the phase place of its output voltage

Step 3., according to active-power P₀And actual measurement active-power P, calculate controllable transformer output voltage phase according to following formula Angle θ:

Step 31. is calculated as follows input value μ of a PI control module by the first comparison module_S1:

μ_S1=P₀-P, wherein P is the active power value of the first comparison module input；

Step 32. the oneth PI control module is controlled computing after the output receiving described first comparison module, defeated Go out corresponding controlled quentity controlled variable μ_C1, computing formula is as follows: μ_C1=k_p1μ_S1+k_i1∫μ_S1Dt,

Wherein, k_p1And k_i1It it is the control coefrficient of a PI control module；

Step 33. calculates the phase angle theta of controllable transformer fundamental voltage output of voltage as follows by the first addition module:

θ=θ₀+μ_C1；

Step 4., according to voltage set-point V₀And actual measurement output voltage V_out, according to following formula, calculate the defeated of controllable transformer Go out voltage magnitude V_out1:

Step 41. is calculated as follows input value μ of the 2nd PI control module by the second comparison module_S2:

μ_S2=V₀-V_out, wherein V_outIt is the voltage of the first comparison module input；

Step 42. the 2nd PI control module is controlled computing after the output receiving described second comparison module, defeated Go out corresponding controlled quentity controlled variable μ_C2, computing formula is as follows:

μ_C2=k_p2μ_S2+k_i2∫μ_S2Dt,

Wherein, kp2 and ki2 is the control coefrficient of the 2nd PI control module；

Step 43. calculates the amplitude of controllable transformer fundamental voltage output of voltage as follows by the second addition module V_out1,

$V_{out1}=V_{out}^1+{\mathrm{\μ}}_{C2}$

Step 5., be calculated the index of modulation by formula:

By phase angle theta and amplitude V of above-mentioned calculated controllable transformer fundamental voltage output of voltage_out1Substitute into following formula, Try to achieve V_outrefAnd controllable transformer control parameter:

$\begin{array}{c}{V}_{outref}=V_{out1}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\θ})\\ =(V_{in}*\sqrt{{\[(1+N)D_1+(1-N)(1-D_1)-\frac{N}{2}\]}^2+{\left(\sqrt{3}{\mathrm{ND}}_2\right)}^2})*\sin ({\mathrm{\ω}}_{0}t-\mathrm{\θ})\\ \mathrm{\θ}=\arctan \left(\frac{\±\sqrt{3}{\mathrm{ND}}_2}{\[(1+N)D_1+(1-N)(1-D_1)\]}\right)\end{array}$

If K1 is bidirectional power pipe Sa1 and Sa3 switching signal, K2 is bidirectional power pipe Sa2 and Sa4 switching signal, this control Signal processed has two kinds of duties:

(1) when voltage phase angle θ take "+" time, K1=1, K2=0, bidirectional power pipe Sa1 and Sa3 turn on, bidirectional power pipe Sa2 and Sa4 turns off, two phase winding forward conductions；

(2) when voltage phase angle θ takes "-", K1=0, K2=1, bidirectional power pipe Sa1 and Sa3 turns off, bidirectional power pipe Sa2 and Sa4 turns on, two phase winding reverse-conductings；

Then can get power cell 9 duty cycle control signal in the pulse-width signal of insulated gate bipolar transistor D1 and power cell 10 duty cycle control signal D2；

Step 6., according to pulse width modulation duty D1 and D2, control to insulated gate bipolar transistor pulse-width signal The conducting of insulated gate bipolar transistor；

To step 6. 2. 7. step repeat step, according to pulse width modulation duty D1 obtained and D2, by controlling absolutely The conducting of edge grid bipolar transistor realizes voltage magnitude grid-connected to photovoltaic DC field and phase adjusted, and then improves its voltage stabilization Property.

Compared with prior art, beneficial effects of the present invention is as follows:

1) utilize the existing element of power system, utilize ULTC to install small-power power electronic devices additional and constitute, Cost is relatively low；

2) network re-active power and reactive power can be carried out discrete control, and there is bigger range of accommodation；

3) method flexibility ratio is big, it is achieved simple, low to hardware requirement；

4) having quick instantaneous regulatory function, response time is short, can improve photovoltaic system voltage stability.

Accompanying drawing explanation

Fig. 1 photovoltaic DC field based on controllable transformer improves the schematic diagram of voltage stability；

The Fig. 2 controllable transformer phase structure figure containing bidirectional power pipe；

Fig. 3 photovoltaic DC field based on controllable transformer improves the control law figure of voltage stability method；

Fig. 4 photovoltaic DC field based on controllable transformer improves the control flow chart of voltage stability method.

Detailed description of the invention

The present invention will be further described with embodiment below in conjunction with the accompanying drawings, but should not limit the protection model of the present invention with this Enclose.

Fig. 1 is the systematic schematic diagram improving photovoltaic generation voltage stability based on controllable transformer, and it includes electrical network 1, Input and output voltage sensor 2 and 3, export current sensor 4, controllable transformer 5, photovoltaic DC field 6 and measurement and control mould Block 7.

Described electrical network 1 is distant place electrical network, is connected with controllable transformer 5 secondary.

The limit former with controllable transformer 5, side of described input voltage transformer 2 is connected, and voltage signal output end is with described Measurement be connected with the voltage signal inputs mouth of control module 7；

The side of described output voltage transformer 3 is connected with controllable transformer 5 secondary, and voltage signal output end is with described Measurement be connected with the voltage signal inputs mouth of control module 7；

The side of described output current transformer 4 is connected with controllable transformer 5 secondary, and current signal output end is with described Measurement be connected with the voltage signal inputs mouth of control module 7；

Described controllable transformer 5, by many transformators 8 separately, power cell 9 and 10, intersects and seals in module 11 mutually, filtering Electric capacity 12 and 13 is constituted.

The secondary of described many parted hairs transformator 8 comprises major joint " 1 " and plus tapping head " 1+N " minus tapping head " 1-N "；

Described power cell 9 is by the first group power (S₁), the second group power (S₂), filter inductance (L_f1) and filtering Electric capacity (C_f1) composition, this first group power (S described in power cell 9₁) and the second group power (S₂) by 2 insulated gates Bipolar transistor is reversely connected in series to form, the first described group power (S₁) one end and described many parted hairs transformator 8 secondary The plus tapping head " 1+N " on limit is connected, the second group power (S₂) the minus tapping of one end and described many parted hairs transformator 8 secondary Head " 1-N " is connected, the first described group power (S₁) and the second group power (S₂) the other end and described filter inductance (L_f1) input be connected, this filter inductance (L_f1) the other end input that seals in module 11 mutually with described intersecting be connected, Described filter capacitor (C_f1) be connected on the plus tapping head " 1+N " of described many parted hairs transformator 8 secondary and minus tapping head " 1-N " it Between, the first described group power (S₁) and the second group power (S₂) the phase controlling end and described measurement Yu control module 7 End should be controlled be connected；

Described power cell 10 is by the 3rd group power (S₃), the 4th group power (S₄), filter inductance (L_f2) and filter Ripple electric capacity (C_f2) composition, this 3rd group power (S described in power cell 10₃) and the 4th group power (S₄) by 2 absolutely Edge grid bipolar transistor is reversely connected in series to form, the 3rd described group power (S₃) one end seal in mould mutually with described intersecting Outfan one end of block 11 is connected, the 4th group power (S₄) one end another with the outfan that described intersecting seals in module 11 mutually One end is connected, the 3rd described group power (S₃) and the 4th group power (S₄) the other end and described filter inductance (L_f2) One end be connected, this filter inductance (L_f2) the other end be connected with the outfan of described many parted hairs transformator 8, described filtering Electric capacity (C_f2) be connected between the outfan that described intersection seals in module 11 mutually, the 3rd described group power (S₃) and the 4th group Power tube (S₄) control end be connected with the corresponding controling end of described measurement with control module 7；

Described intersection seals in the module 11 secondary by the other biphase the most transformators 8 separately of described intersection phase winding mutually The winding of plus tapping head 14, minus tapping head 15 composition and and four groups of bidirectional power pipe compositions；

As a example by A phase, the NVbin that described intersection seals in NVcin winding that module 11 seals in by C phase mutually, B phase seals in around Group and four bidirectional power pipe compositions, the bidirectional power pipe (S of this intersection phase transformation module 11_a1) one end and described filter inductance (L_f1) the other end be connected, the other end and described C phase NV_cinWinding minus tapping head 15 is connected, C phase NV_cinWinding plus tapping head With described B phase NV_binWinding minus tapping head is connected, B phase NV_binWinding plus tapping head and described bidirectional power pipe (S_a3) one End is connected, described bidirectional power pipe (S_a3) the power tube S of the other end and power cell 10₃Corresponding input is connected；Institute Bidirectional power pipe (the S stated_a2) one end and described bidirectional power pipe (S_a1) one end is connected, the other end and described two-way merit Rate pipe (S_a3) one end be connected；Described bidirectional power pipe (S_a4) one end and described bidirectional power pipe (S_a1) other end phase Even, the other end and described bidirectional power pipe (S_a3) the other end be connected；

Described filter capacitor 12 one end and the secondary of described many parted hairs transformator 8 comprise major joint " 1 " and connect, another End and described filter inductance (L_f1) connect；

Described filter capacitor 13 one end and described filter inductance (L_f1) connect, the other end and described filter inductance (L_f2) connect；

The secondary of described controllable transformer 5 is connected with described distant place electrical network 1；

Described photovoltaic DC field 6 port of export is connected with the former limit of described controllable transformer 5.

Described measurement and control module 7 are digital signal processor, single-chip microcomputer or computer.Measure and control module 7 Control signal outfan outfan with described voltage sensor 2,3 and current sensor 4 respectively be connected, this measurement and control The input of molding block is connected with host computer.The control signal of the power switch pipe of described controllable transformer 5 is by measuring and controlling Molding block 7 provides.

A kind of control method improving photovoltaic generation voltage stability based on the controllable transformer containing bidirectional power pipe, including Following concrete steps:

Step 1., measure and control mould 7 pieces to controlling to initialize, receive the voltage set-point V that host computer is given₀With The set-point P of active power₀；

Controllable transformer tap no-load voltage ratio N；

ω 0 is the angular frequency corresponding to 50 or 60Hz；

Oneth PI control module control coefrficient k_p1And k_i1, 1≤k_p1≤100,1≤k_i1≤ 100, just set value and be 10, by grasping Work person presses photovoltaic DC field operation conditions and sets, and reactive compensation power is the biggest, and coefficient value is the biggest, takes its maximum during rated power 100；

2nd PI control module control coefrficient k_p2And k_i2, 1≤k_p2≤100,1≤k_i2≤ 100, just set value and be 10, by grasping Work person presses photovoltaic DC field operation conditions and sets, and active power is the biggest, and coefficient value is the biggest, takes its maximum 100 during rated power；

Step 2., measure with control module 7 receive input voltage transformer, output voltage transformer and output Current Mutual Inductance The input voltage V that device inputs respectively_in, output voltage V_out, output electric current I_out, output voltage is β with the angle of output electric current, if Input voltage V_inAmplitude be | V_in|, output voltage V_outAmplitude be | V_out|, export electric current I_outAmplitude be | I_out|, defeated The initial magnitude going out voltage fundamental is V¹ _out, transmission line of electricity reactance value L, line voltage V_{Electrical network 2}Amplitude be V₂, phase angle is α；

Active-power P by following equation calculating actual measurement:

$P=\frac{1}{\sqrt{2}}{V}_{out}{I}_{out}cos\mathrm{\β}$

According to active-power P₀, calculate the initial phase angle theta of output voltage of controllable transformer₀

$P_0=\frac{V_2{V}_{out}}{{\mathrm{\ω}}_{0}L}sin(\mathrm{\α}-{\mathrm{\θ}}_0)$

According to photovoltaic DC field operation conditions, carry out active power regulation；

By changing the modulated signal of controllable transformer tap switch, regulate amplitude and the phase place of its output voltage；

Step 3., according to active-power P₀And actual measurement active-power P, calculate controllable transformer output voltage phase according to following formula Angle θ:

Step 31. is calculated as follows the input value μ S1 of a PI control module by the first comparison module:

μ_S1=P₀-P, wherein P is the active power value of the first comparison module input；

Step 32. the oneth PI control module is controlled computing after the output receiving described first comparison module, defeated Go out corresponding controlled quentity controlled variable μ_C1, computing formula is as follows: μ_C1=k_p1μ_S1+k_i1∫μ_S1Dt,

Wherein, k_p1And k_i1It it is the control coefrficient of a PI control module；

Step 33. calculates the phase angle theta of controllable transformer fundamental voltage output of voltage as follows by the first addition module:

θ=θ₀+μ_C1；

Step 4., according to voltage set-point V₀And actual measurement output voltage V_out, according to following formula, calculate the defeated of controllable transformer Go out voltage magnitude V_out1:

Step 41. is calculated as follows input value μ of the 2nd PI control module by the second comparison module_S2:

μ_S2=V₀-V_out, wherein V_outIt is the voltage of the first comparison module input；

Step 42. the 2nd PI control module is controlled computing after the output receiving described second comparison module, defeated Go out corresponding controlled quentity controlled variable μ_C2, computing formula is as follows:

μ_C2=k_p2μ_S2+k_i2∫μ_S2Dt,

Wherein, k_p2And k_i2It it is the control coefrficient of the 2nd PI control module；

Step 43. calculates the amplitude of controllable transformer fundamental voltage output of voltage as follows by the second addition module V_out1,

$V_{out1}=V_{out}^1+{\mathrm{\μ}}_{C2}$

Step 5., be calculated the index of modulation by formula:

By phase angle theta and amplitude V of above-mentioned calculated controllable transformer fundamental voltage output of voltage_out1Substitute into following formula, Try to achieve V_outrefAnd controllable transformer control parameter:

$\begin{array}{c}{V}_{outref}=V_{out1}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\θ})\\ =(V_{in}*\sqrt{{\[(1+N)D_1+(1-N)(1-D_1)-\frac{N}{2}\]}^2+{\left(\sqrt{3}{\mathrm{ND}}_2\right)}^2})*\sin ({\mathrm{\ω}}_{0}t-\mathrm{\θ})\\ \mathrm{\θ}=\arctan \left(\frac{\±\sqrt{3}{\mathrm{ND}}_2}{\[(1+N)D_1+(1-N)(1-D_1)\]}\right)\end{array}$

If K1 is bidirectional power pipe Sa1 and Sa3 switching signal, K2 is bidirectional power pipe Sa2 and Sa4 switching signal, this control Signal processed has two kinds of duties:

(1) when voltage phase angle θ take "+" time, K1=1, K2=0, bidirectional power pipe Sa1 and Sa3 turn on, bidirectional power pipe Sa2 and Sa4 turns off, two phase winding forward conductions；

(2) when voltage phase angle θ takes "-", K1=0, K2=1, bidirectional power pipe Sa1 and Sa3 turns off, bidirectional power pipe Sa2 and Sa4 turns on, two phase winding reverse-conductings；

Then can get power cell 9 duty cycle control signal in the pulse-width signal of insulated gate bipolar transistor D1 and power cell 10 duty cycle control signal D2；

Step 6., according to pulse width modulation duty D1 and D2, control to insulated gate bipolar transistor pulse-width signal The conducting of insulated gate bipolar transistor；

To step 6. 2. 7. step repeat step, according to pulse width modulation duty D1 obtained and D2, by controlling absolutely The conducting of edge grid bipolar transistor realizes voltage magnitude grid-connected to photovoltaic DC field and phase adjusted, and then improves its voltage stabilization Property.

Claims (2)

1. based on the control method improving controllable transformer photovoltaic generation voltage stability containing bidirectional power pipe, its feature Being, the method comprises the following steps:

Step 1., measure with control module to control initialize, receive host computer give voltage set-point V₀And wattful power The set-point P of rate₀；

Controllable transformer tap no-load voltage ratio N；

ω 0 is the angular frequency corresponding to 50 or 60Hz；

Oneth PI control module control coefrficient k_p1And k_i1, 1≤k_p1≤100,1≤k_i1≤ 100, just set value and be 10, by operator Setting by photovoltaic DC field operation conditions, reactive compensation power is the biggest, and coefficient value is the biggest, takes its maximum 100 during rated power；

2nd PI control module control coefrficient k_p2And k_i2, 1≤k_p2≤100,1≤k_i2≤ 100, just set value and be 10, by operator Setting by photovoltaic DC field operation conditions, active power is the biggest, and coefficient value is the biggest, takes its maximum 100 during rated power；

Step 2., measure and divide with control module reception input voltage transformer, output voltage transformer and output current transformer The input voltage V not inputted_in, output voltage V_out, output electric current I_out, output voltage is β with the angle of output electric current, if input Voltage V_inAmplitude be | V_in|, output voltage V_outAmplitude be | V_out|, export electric current I_outAmplitude be | I_out|, output electricity The initial magnitude of pressure first-harmonic is V¹ _out, remote transmission line of electricity reactance value L, distant place line voltage V_{Electrical network 2}Amplitude be V₂, phase angle is α；

Active-power P by following equation calculating actual measurement:

$P=\frac{1}{\sqrt{2}}{V}_{out}{I}_{out}cos\mathrm{\β}$

According to active-power P₀, calculate the initial phase angle theta of output voltage of controllable transformer₀

$P_0=\frac{V_2{V}_{out}}{{\mathrm{\ω}}_{0}L}sin(\mathrm{\α}-{\mathrm{\θ}}_0)$

According to photovoltaic DC field operation conditions, carry out active power regulation；

By changing the modulated signal of controllable transformer tap switch, regulate amplitude and the phase place of its output voltage；

Step 3., according to active-power P₀And actual measurement active-power P, according to following formula calculating controllable transformer output voltage phase angle theta:

Step 31. is calculated as follows input value μ of a PI control module by the first comparison module_S1:

μ_S1=P₀-P, wherein P is the active power value of the first comparison module input；

Step 32. the oneth PI control module is controlled computing after the output receiving described first comparison module, exports phase Controlled quentity controlled variable μ answered_C1, computing formula is as follows: μ_C1=k_p1μ_S1+k_i1∫μ_S1Dt,

Wherein, k_p1And k_i1It it is the control coefrficient of a PI control module；

Step 33. calculates the phase angle theta of controllable transformer fundamental voltage output of voltage as follows by the first addition module:

θ=θ₀+μ_C1；

Step 4., according to voltage set-point V₀And actual measurement output voltage V_out, according to following formula, calculate the output voltage of controllable transformer Amplitude V_out1:

Step 41. is calculated as follows input value μ of the 2nd PI control module by the second comparison module_S2:

μ_S2=V₀-V_out, wherein V_outIt is the voltage of the first comparison module input；

Step 42. the 2nd PI control module is controlled computing after the output receiving described second comparison module, exports phase Controlled quentity controlled variable μ answered_C2, computing formula is as follows:

μ_C2=k_p2μ_S2+k_i2∫μ_S2Dt,

Wherein, k_p2And k_i2It it is the control coefrficient of the 2nd PI control module；

Step 43. calculates amplitude V of controllable transformer fundamental voltage output of voltage as follows by the second addition module_out1,

$V_{out1}=V_{out}^1+{\mathrm{\μ}}_{C2}$

Step 5., be calculated the index of modulation by formula:

By phase angle theta and amplitude V of above-mentioned calculated controllable transformer fundamental voltage output of voltage_out1Substitute into following formula, try to achieve V_outrefAnd controllable transformer control parameter:

$\begin{array}{c}{V}_{outref}=V_{out1}sin({\mathrm{\ω}}_{0}t-\mathrm{\θ})\\ =(V_{in}*\sqrt{{\[(1+N)D_1+(1-N)(1-D_1)-\frac{N}{2}\]}^2+{\left(\sqrt{3}{\mathrm{ND}}_2\right)}^2})*sin({\mathrm{\ω}}_{0}t-\mathrm{\θ})\end{array}$

$\mathrm{\θ}=arctan\left(\frac{\±\sqrt{3}{\mathrm{ND}}_2}{\[(1+N)D_1+(1-N)(1-D_1)\]}\right)$

If K1 is bidirectional power pipe Sa1 and Sa3 switching signal, K2 is bidirectional power pipe Sa2 and Sa4 switching signal, and this controls letter Number there are two kinds of duties:

(1) when voltage phase angle θ take "+" time, K1=1, K2=0, bidirectional power pipe Sa1 and Sa3 turn on, bidirectional power pipe Sa2 and Sa4 turns off, two phase winding forward conductions；

(2) when voltage phase angle θ takes "-", K1=0, K2=1, bidirectional power pipe Sa1 and Sa3 turn off, bidirectional power pipe Sa2 and Sa4 turns on, two phase winding reverse-conductings；

Then can get power cell 9 duty cycle control signal D1 in the pulse-width signal of insulated gate bipolar transistor and Power cell 10 duty cycle control signal D2；

Step 6., according to pulse width modulation duty D1 and D2, control insulation to insulated gate bipolar transistor pulse-width signal The conducting of grid bipolar transistor；

To step 6. 2. 7. step repeat step, according to pulse width modulation duty D1 obtained and D2, by controlling insulated gate The conducting of bipolar transistor realizes voltage magnitude grid-connected to photovoltaic DC field and phase adjusted, and then improves its voltage stability.

The most according to claim 1 based on the controllable transformer raising photovoltaic DC field voltage stability containing bidirectional power pipe Control method, it is characterised in that the control law of a described PI control module and described 2nd PI control module is that ratio is amassed Divide control mode.