CN104518525B - The Protection control system of alternating current-direct current mixing grid power current transformer and control method thereof - Google Patents

Abstract

A kind of protection controller being suitable for AC network unbalanced alternating current-direct current mixing grid power current transformer aims to solve the problem that the output behavior of networking current transformer time breaking down in AC network side.Owing to during AC network fault, the existence of electrical network negative sequence component can cause system three-phase current unbalance or the problem such as non-sine, DC side existence bigger voltage ripple, power swing, jeopardize current transformer safety, shorten the current transformer life-span, it is necessary to the impact on system of the conservative control electrical network negative sequence component.Flexible positive sequence and negative phase-sequence control strategy under the d q synchronous coordinate system that the present invention uses; by the regulation of parameter; the positive-negative sequence content of Reasonable adjustment alternating current net side current reference; make network side current waveform quality and system instantaneous active power, instantaneous reactive power obtain conservative control, thus realize the protection to current transformer and control.

Description

The Protection control system of alternating current-direct current mixing grid power current transformer and control method thereof

Technical field

A kind of Protection control system being suitable for AC network unbalanced alternating current-direct current mixing grid power current transformer and controlling party thereof Method, belongs to current transformer in alternating current-direct current mixing electrical network and controls technical field.

Background technology

The application of alternating current-direct current electrical network, expands the electric electronic current change technology application in electric power system power distribution field, but existing control Method processed is premised on ac grid voltage three-phase symmetrical, and three phase network fault is inevitable.In new-energy grid-connected If three phase network breaks down, rules and regulations now current transformer can not off-network immediately, possess low-voltage in certain time scope domestic demand Ride-through capability；In alternating current-direct current hybrid power transmission and distribution are applied, during electric network fault, the existence due to electrical network negative sequence component can cause system Three-phase current unbalance or the problem such as non-sine, DC side existence bigger voltage ripple, power swing, jeopardize current transformer and electrical network Equipment also makes it shorten the life-span.If three-phase current non-sine, this can produce serious harm to utility network, as made electric network element produce Raw additional harmonic loss, makes the overheated even breaking out of fire of circuit, causes the misoperation of relay protection and automaton, makes electrically Measuring instruments metering is inaccurate, and neighbouring communication system is produced interference；If DC side exists bigger ripple, also it is extremely harmful , as reduced system effectiveness, the logical relation of interference digital circuit, electrical equipment produces harmonic wave, produces surge voltage or electric current； If the reactive power fluctuation of system can not conservative control, the power factor of system can be had a strong impact on, utility network is brought unfavorable shadow Ring, as caused electric current to increase and place capacity increase, make the loss of equipment and circuit increase.Due to a large amount of electronic power convertors Apply in alternating current-direct current electrical network, conservative control DC voltage ripple, system can be reached by the break-make controlling power electronic devices Oscillation of power and the purpose of injection power network current waveform quality, the ability that raising system runs without interruption in case of a fault, prolong In the service life of long current transformer, reduce the harm to public electric wire net.

Mostly existing control algolithm is to control active power ripple, and reactive power ripple and network side current waveform quality are single Controlling target, and need many-sided control in the actual application of nowadays novel alternating current-direct current mixing electrical network, this just requires multiple Control target carries out conservative control.

Summary of the invention

It is an object of the invention to provide a kind of Protection control system being suitable for AC network unbalanced alternating current-direct current mixing grid power current transformer and Its control method, by introducing regulation parameter, dynamically adjusts the positive-negative sequence component in current reference, can Controling network side current wave flexibly Form quality amount and system power fluctuation, both can to a certain degree eliminate two double-frequency oscillations of system instantaneous active power, take into account again system The control of instantaneous reactive power.

It is a feature of the present invention that:

A kind of protection controller being suitable for AC network unbalanced alternating current-direct current mixing grid power current transformer, it is characterised in that With alternating current-direct current electrical network as application target, in active power ripple, reactive power ripple and the multiple control of network side current waveform quality The optimization control scheme of goal seeking suitable system.Described method contains AC network top-cross DC converter (1) and controller (2).

AC network top-cross DC converter (1), the DC terminal of described AC network top-cross DC converter (1) and DC load (when 1 is used as AC-to DC conversion) connected, or the DC terminal of AC network top-cross DC converter (1) be connected with direct voltage source (when 1 is used as direct current to exchange conversion)；The exchange end of described AC network top-cross DC converter (1) is connected with electrical network；

Controller (2), is a kind of digital control circuit, uses any one of digital signal processor, single-chip microcomputer, computer； The control end of the alternating current net side AC-DC converter of described controller (2) control end corresponding with alternating current net side AC-DC converter is connected, This controller realizes the network side current waveform quality to AC-DC converter and system instantaneous active power, instantaneous reactive according to the following steps Power realizes controlling.Concrete regulating step is as follows:

Step 1. initializes, and i.e. sets following parameter in this protection controller, and all electric currents and voltage parameter all use per unit value:

If phaselocked loop q axle reference value v of protection controller⁺ _qref=0, phaselocked loop d axle reference value V_{d_ref}=1；

The steady-state value of the phaselocked loop angular velocity of protection controller is ω₀, operator set by operation of power networks situation；

The Bus Voltage loop set-point V of protection controller_busref；

The forward-order current d axle set-point i of protection controller⁺ _dref；

The forward-order current q axle set-point of protection controller

The negative-sequence current d axle set-point i of protection controller^- _dref；

The negative-sequence current q axle set-point of protection controller

Oneth PI controller control coefrficient k_p1And k_i1, 0 < k_p1<1000,0<k_i1< 1000, operator set by operation of power networks situation；

2nd PI controller control coefrficient k_p2And k_i2, 0 < k_p2<1000,0<k_i2< 1000, by operator by operation of power networks situation Set；

3rd PI controller control coefrficient k_p3And k_i3, 0 < k_p3<1000,0<k_i3< 1000, by operator by operation of power networks situation Set；

4th PI controller control coefrficient k_p4And k_i4, 0 < k_p4<1000,0<k_i4< 1000, by operator by operation of power networks situation Set；

5th PI controller control coefrficient k_p5And k_i5, 0 < k_p5<1000,0<k_i5< 1000, by operator by operation of power networks situation Set；

6th PI controller control coefrficient k_p6And k_i6, 0 < k_p6<1000,0<k_i6< 1000, by operator by operation of power networks situation Set；

Protection control parameter k ,-1 < k < 1, operator set by operation of power networks situation；

Given reference power P₀, operator press DC side busbar voltage and control loop requirements set；

Step 2. line voltage positive-negative sequence separates to separate with current on line side positive-negative sequence and performs according to the following steps:

Step 21. positive-negative sequence separates and uses the double synchronized algorithm of decoupling, and d-q axle draws according to turning clockwise and rotating counterclockwise respectively Line voltage positive sequence d-q component and negative phase-sequence d-q component.

Step 22. positive sequence and negative phase-sequence decoupling, eliminate the vibration in the d-q component obtained in step 21, obtain line voltage d axle Positive-sequence component v_d ⁺, d axle negative sequence component v_d ^-, q axle positive-sequence component v_q ⁺, d axle negative sequence component v_q ^-；

Step 23. current on line side positive-negative sequence separates and uses the double synchronized algorithm of decoupling, and d-q axle is respectively according to turning clockwise and inverse Hour hands rotate and draw current on line side positive sequence d-q component and negative phase-sequence d-q component；

Step 24, positive sequence and negative phase-sequence decoupling, eliminate the vibration in the d-q component obtained in step 23, obtains netting side electricity Stream d axle positive-sequence component i_d ⁺, d axle negative sequence component i_d ^-, q axle positive-sequence component i_q ⁺, d axle negative sequence component i_q ^-；

Step 3. phaselocked loop calculates and performs according to the following steps:

Step 31. is by the input value of the first comparator calculating the oneth PI controller:For three-phase voltage positive sequence q axle Component, is drawn by according to step 2, and unit is per unit value；v_qrefForSet-point；

Step 32. the oneth PI controller is controlled computing after the output receiving described first comparator, and output is corresponding Controlled quentity controlled variable is:Wherein, k_p1And k_i1It it is the control coefrficient of a PI controller；

Step 33. by first adder calculate as follows phaselocked loop to voltage on line side phase-locked after output phase angle: $\mathrm{\&theta;}=\&Integral;$ $((k_{p1}{v}_q^{*}+k_{i1}\&Integral;v_q^{+}\mathrm{dt})+{\mathrm{\&omega;}}_0);$

In above formula, θ is the phase angle of alternating current net side voltage.

The regulation of step 4. DC B us Voltage loop performs according to the following steps:

Step 41. calculates the input value of the 2nd PI controller: V by the second comparator_busref-V_bus,V_busFor DC bus-bar voltage, Unit is per unit value；V_busrefFor V_busSet-point；

Step 42. the 2nd PI controller is controlled computing after the output receiving described second comparator, and output is corresponding Controlled quentity controlled variable is k_p2(V_busref-V_bus)+k_i2∫(V_busref-V_bus) dt, wherein k_p2And k_i2It it is the control system of the 2nd PI controller Number；

Step 43. multiplier calculates the output of Bus Voltage loop as follows:

P₀=V_bus*(k_p2(V_busref-V_bus)+k_i2∫(V_busref-V_bus)dt)；

In above formula, P₀Active power reference value is given for AC-DC converter.

Step 5. protects controller design to perform according to the following steps:

According to equation below calculating d-q axle current on line side reference value:

$\left[\begin{array}{c}{i}_{\mathrm{dref}}^{+}\\ i_{\mathrm{qref}}^{+}\\ i_{\mathrm{dref}}^{-}\\ i_{\mathrm{qref}}^{-}\end{array}\right]=\frac{2}{3}\frac{P_0}{(v_d^{+2}+v_q^{+2}+k(v_d^{-2}+v_q^{-2}))}\left[\begin{array}{c}{v}_d^{*}\\ v_q^{+}\\ {\mathrm{kv}}_d^{-}\\ {\mathrm{kv}}_q^{-}\end{array}\right]$

P is calculated by step 4₀,Being drawn by step 2, k is drawn by step 1.

The regulation of step 6. positive sequence d shaft current ring performs according to the following steps:

Step 61. calculates the input value of the 3rd PI controller: i by the 3rd comparator⁺ _dref-i⁺ _d,i⁺ _dFor forward-order current d axle amount, by Step 2 obtains, and unit is per unit value；i⁺ _drefFor i⁺ _dSet-point；

Step 62. the 3rd PI controller is controlled computing after the output receiving described 3rd comparator, and output is corresponding Controlled quentity controlled variable is: ${u^{+}}_d=k_{p3}(i_{\mathrm{dref}}^{+}-i_d^{+})+k_{i3}\&Integral;(i_{\mathrm{dref}}^{+}-i_d^{+})\mathrm{dt};$

In above formula, wherein k_p3And k_i3It it is the control coefrficient of the 3rd PI controller；u⁺ _dFor positive sequence d axle modulation waveform；

The regulation of step 7. negative phase-sequence d shaft current ring performs according to the following steps:

Step 71. calculates the input value of the 4th PI controller: i by the 4th comparator^- _dref-i^- _d,i^- _dFor negative-sequence current d axle amount, by Step 2 obtains, and unit is per unit value；i^- _drefFor i^- _dSet-point；

Step 72. the 4th PI controller is controlled computing after the output receiving described 4th comparator, and output is corresponding Controlled quentity controlled variable is: ${u^{-}}_d=k_{p4}(i_{\mathrm{dref}}^{-}-i_d^{-})+k_{i4}\&Integral;(i_{\mathrm{dref}}^{-}-i_d^{-})\mathrm{dt};$

In above formula, wherein k_p4And k_i4It it is the control coefrficient of the 4th PI controller；u^- _dFor negative phase-sequence d axle modulation waveform；

The regulation of step 8. positive sequence q shaft current ring performs according to the following steps:

Step 81. calculates the input value of the 5th PI controller: i by the 5th comparator⁺ _qref-i⁺ _q,i⁺ _qFor forward-order current q axle amount, by Step 2 obtains, and unit is per unit value；i⁺ _qrefFor i⁺ _qSet-point；

Step 82. the 4th PI controller is controlled computing after the output receiving described 4th comparator, and output is corresponding Controlled quentity controlled variable is: ${u^{+}}_q=k_{p5}(i_{\mathrm{qref}}^{+}-i_q^{+})+k_{i5}\&Integral;(i_{\mathrm{qref}}^{+}-i_q^{+})\mathrm{dt};$

In above formula, wherein k_p5And k_i5It it is the control coefrficient of the 5th PI controller；u⁺ _qFor positive sequence q axle modulation waveform；

The regulation of step 9. negative phase-sequence q shaft current ring performs according to the following steps:

Step 91. calculates the input value of the 6th PI controller: i by the 6th comparator^- _qref-i^- _q,i^- _qFor negative-sequence current q axle amount, by

Step 2 obtains, and unit is per unit value；i^- _qrefFor i^- _qSet-point；

Step 92. the 6th PI controller is controlled computing after the output receiving described 6th comparator, and output is corresponding Controlled quentity controlled variable is: ${u^{-}}_q=k_{p6}(i_{\mathrm{qref}}^{-}-i_q^{-})+k_{i6}\&Integral;(i_{\mathrm{qref}}^{-}-i_q^{-})\mathrm{dt};$

In above formula, wherein k_p6And k_i6It it is the control coefrficient of the 6th PI controller；u^- _qFor negative phase-sequence q axle modulation waveform；

Step 10. controller output:

Controller described in step 101. passes through above-mentioned voltage u⁺ _d、u⁺ _q、u^- _dAnd u^- _qControl alternating current net side changer, it is achieved changer The control of instantaneous active power, reactive power and DC voltage, unit is per unit value；

The u that controller will obtain⁺ _d、u⁺ _q、u^- _dAnd u^- _qFirst pass through the coordinate transform of positive-negative sequence dq-abc, obtain u_a、u_bAnd u_c Three amounts, coordinate transform formula is as follows, and wherein θ is the synchro angle of net side alternating voltage, by step 3 gained:

$\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\frac{\sqrt{2}}{\sqrt{3}}\left(\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \cos (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})\\ \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})\end{array}\right)\left[\begin{array}{c}{u}_d^{+}\\ u_q^{+}\end{array}\right]+\frac{\sqrt{2}}{\sqrt{3}}\left(\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \cos (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})\\ \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})\end{array}\right)\left[\begin{array}{c}{u}_d^{-}\\ u_q^{-}\end{array}\right]$

By u_a、u_bAnd u_cThree amounts are as control signal with carrier wave ratio relatively, it is thus achieved that the driving letter of net top-cross DC converter (1) Number, then driving signal is delivered to the control end of three brachium pontis of (1) so that net top-cross DC converter (1) output is corresponding Voltage vector, control current on line side, thus regulate output.

What the present invention proposed uses the flexible positive sequence under d-q coordinate and the control system of negative phase-sequence control method, logical in this controller Cross introducing regulation parameter, dynamically adjust the positive-negative sequence component in current reference, network side current waveform quality and system can be controlled flexibly Power swing, uses this controller both can to a certain degree eliminate two double-frequency oscillations of system instantaneous active power, takes into account again system The control of instantaneous reactive power.This controller has unified several conventional Control Method by a variable, and by adjusting variable Size, conservative control power ripple, DC voltage ripple and network side current waveform quality, feature is as follows:

1. adjust the positive-negative sequence component in current reference by introducing regulation dynamic state of parameters, instantaneous to active power instantaneous value, reactive power Value and network side current waveform quality are controlled；

2., on the premise of dynamic calculation electric current positive-negative sequence component, under d-q coordinate system, design controller, it is achieved d axle and q decoupler shaft, Do not increase any cost.

Accompanying drawing explanation

Fig. 1 is the hardware elementary diagram of net top-cross DC converter.

Fig. 2 is the controller system figure of net top-cross DC converter.

Fig. 3 is the control law figure of net top-cross DC converter.

Fig. 4 is the control flow chart of net top-cross DC converter.

Fig. 5 is to use different adjustment parameter current on line side and the idle simulation result figure of system instantaneous active.Wherein 1a, 1b, 1c Current on line side when parameter k is-1, system instantaneous active power and the oscillogram of instantaneous reactive power is controlled for protection；2a, 2b, 2c is that protection controls current on line side when parameter k is 0, system instantaneous active power and the oscillogram of instantaneous reactive power；3a, 3b, 3c be protection control parameter k be 1 side electric current, system instantaneous active power and the oscillogram of instantaneous reactive power.

Detailed description of the invention

Fig. 1 is that AC/DC convertor is applied to grid-connected schematic diagram, and it is made up of net top-cross DC converter 1, controller 2, with Under each ingredient be discussed in detail:

Net top-cross DC converter 1 carries out handing over straight conversion, it is achieved the electric energy mutual conversion between direct current and exchange；

Controller 2 is responsible for data sampling, is processed, calculates and control etc., is controlled net top-cross DC converter, it is achieved right Changer is in instantaneous active, instantaneous reactive and the control of network side current waveform quality.

Fig. 2 is controller system figure, and Fig. 3 is control law figure, and Fig. 4 is control flow chart, Fig. 3 be separately contained in Fig. 2 and In Fig. 4.Controller 2, by signals collecting, carries out calculating, processing, and end product passes through the direct Controling network top-cross of controller 2 DC converter 1, it can be proportional integral (PI) as shown in Figure 3, it is also possible to be PID (PID) control mode Or other control mode；Control parameter k and can carry out flexible according to controlling requirement, thus the instantaneous of Controling network side converter has Merit, instantaneous reactive and network side current waveform quality.

Fig. 5 is to be tested by different k value, it is assumed that single-phase falling occurs in A phase, and falling the degree of depth is 0.3, arranges parameter k respectively For-1,0,1.The working effect of power converter protection controller during stream mixing electrical network AC network imbalance, obtains instantaneous having Merit power, instantaneous reactive power, three-phase current on line side respond.Found out by experimental result, during k=0, just can obtain the net side of symmetry Electric current, when k=1 and-1, the asymmetric degree of electric current is the most serious.The change of k also can affect system instantaneous active power and nothing The fluctuation of merit power.The instantaneous active power fluctuation minimum of system, system instantaneous reactive power fluctuation maximum as k=-1.Along with K value increases to 1 from-1, and the instantaneous active power fluctuation of system is gradually increased, and the instantaneous reactive power fluctuation of system is gradually reduced. The instantaneous reactive power fluctuation minimum of system as k=1.Fig. 5 simulation result shows, the alternating current-direct current mixing electrical network exchange of the present invention During unbalanced power supply, power converter protection controller can the instantaneous reactive power to changer of efficient, flexible, instantaneous active merit Rate and three-phase current on line side are controlled protection.

The present invention is according to concrete control requirement, Reasonable adjustment variable k as can be seen here.Mix at flexible DC power transmission and alternating current-direct current electrical network Under its development of connection, under three phase network failure condition, the control realizing different purpose according to the protection controller of the present invention is adjusted Joint, thus realize electrical network and power converter are controlled the purpose of protection.It is pointed out that the scheme carried herein is to difference In the case of electric network fault the most applicable.

Claims (1)

1. a control method for the Protection control system of alternating current-direct current mixing grid power current transformer, this Protection control system includes AC network top-cross DC converter (1) and controller (2)；The DC terminal of described AC network top-cross DC converter (1) and direct current Load or direct voltage source are connected, and the exchange end of this AC network top-cross DC converter (1) is connected with electrical network；Described controller (2) control end is connected with the control end of AC network top-cross DC converter (1), the input of this controller (2) and electrical network It is connected；It is characterized in that, this control method comprises the steps:

Step 1. initializes, and i.e. sets following parameter, and all electric currents and voltage parameter all use per unit value:

Phaselocked loop q axle reference value v⁺ _qrefIt is set to 0, phaselocked loop d axle reference value V_{d_ref}It is set to 1；

The steady-state value of phaselocked loop angular velocity is set to ω₀, set by grid operating conditions；

Bus Voltage loop set-point is set to V_busref；

Forward-order current d axle set-point i⁺ _dref；Forward-order current q axle set-point

Negative-sequence current d axle set-point i^- _dref；Negative-sequence current q axle set-point

Oneth PI controller control coefrficient k_p1And k_i1, 0 < k_p1<1000,0<k_i1< 1000, operator set by operation of power networks situation；

2nd PI controller control coefrficient k_p2And k_i2, 0 < k_p2<1000,0<k_i2< 1000, by operator by operation of power networks situation Set；

3rd PI controller control coefrficient k_p3And k_i3, 0 < k_p3<1000,0<k_i3< 1000, by operator by operation of power networks situation Set；

4th PI controller control coefrficient k_p4And k_i4, 0 < k_p4<1000,0<k_i4< 1000, by operator by operation of power networks situation Set；

5th PI controller control coefrficient k_p5And k_i5, 0 < k_p5<1000,0<k_i5< 1000, by operator by operation of power networks situation Set；

6th PI controller control coefrficient k_p6And k_i6, 0 < k_p6<1000,0<k_i6< 1000, by operator by operation of power networks situation Set；

Protection control parameter k ,-1 < k < 1, operator set by operation of power networks situation；

Variable P₀For AC-DC converter active power of output reference value, in AC network top-cross DC converter, this variable is by directly Stream side bus voltage controls what loop determined, and occurrence is pressed system requirements by operator and set；

Step 2. line voltage positive-negative sequence separates to separate with current on line side positive-negative sequence and performs according to the following steps:

Step 21. line voltage positive-negative sequence separates and uses the double synchronized algorithm of decoupling, and d-q axle is respectively according to turning clockwise and counterclockwise Rotation draws line voltage positive sequence d-q component and negative phase-sequence d-q component；

Step 22. positive sequence and negative phase-sequence decoupling, eliminate the vibration in the d-q component obtained in step 21, obtain line voltage d axle Positive-sequence component v_d ⁺, d axle negative sequence component v_d ^-, q axle positive-sequence component v_q ⁺, d axle negative sequence component v_q ^-；

Step 23. current on line side positive-negative sequence separates and uses the double synchronized algorithm of decoupling, and d-q axle is respectively according to turning clockwise and inverse Hour hands rotate and draw current on line side positive sequence d-q component and negative phase-sequence d-q component；

Step 24, positive sequence and negative phase-sequence decoupling, eliminate the vibration in the d-q component obtained in step 23, obtains netting side electricity Stream d axle positive-sequence component i_d ⁺, d axle negative sequence component i_d ^-, q axle positive-sequence component i_q ⁺, d axle negative sequence component i_q ^-；

Step 3. phaselocked loop calculates and performs according to the following steps:

It is v that step 31. first comparator calculates the input value of a PI controller⁺ _qref-v⁺ _q,；Wherein, phaselocked loop q axle reference value v⁺ _qrefFor line voltage q axle positive-sequence componentSet-point；

Step 32. the oneth PI controller is controlled computing after the output receiving described first comparator, and output is corresponding Controlled quentity controlled variable isWherein, k_p1And k_i1It it is the control coefrficient of a PI controller；

Step 33. first adder calculates the phaselocked loop phase angle θ to the alternating current net side voltage that voltage on line side exports after phase-locked, public Formula is as follows:

$\mathrm{\&theta;}=\&Integral;\left(\right(k_{p1}{v}_q^{+}+k_{i1}\&Integral;v_q^{+}dt)+{\mathrm{\&omega;}}_0);$

The regulation of step 4. DC B us Voltage loop performs according to the following steps:

It is V that step 41. second comparator calculates the input value of the 2nd PI controller_busref-V_bus, wherein, V_busFor DC bus-bar voltage, Unit is per unit value；V_busrefFor V_busSet-point；

Step 42. the 2nd PI controller is controlled computing after the output receiving described second comparator, and output is corresponding Controlled quentity controlled variable is k_p2(V_busref-V_bus)+k_i2∫(V_busref-V_bus) dt, wherein k_p2And k_i2It it is the control system of the 2nd PI controller Number；

Step 43. multiplier calculates the output of Bus Voltage loop as follows:

P₀=V_bus*(k_p2(V_busref-V_bus)+k_i2∫(V_busref-V_bus)dt)；

In formula, P₀For AC-DC converter active power of output reference value；

Step 5. calculates d-q axle current on line side reference value, and formula is as follows:

$\left[\begin{array}{c}{i}_{dref}^{+}\\ i_{qref}^{+}\\ i_{dref}^{-}\\ i_{qref}^{-}\end{array}\right]=\frac{2}{3}\frac{P_0}{(v_d^{+2}+v_q^{+2}+k(v_d^{-2}+v_q^{-2}\left)\right)}\left[\begin{array}{c}{v}_d^{+}\\ v_q^{+}\\ {\mathrm{kv}}_d^{-}\\ {\mathrm{kv}}_q^{-}\end{array}\right]$

The regulation of step 6. positive sequence d shaft current ring performs according to the following steps:

Step 61. the 3rd comparator calculates the input value of the 3rd PI controller: i⁺ _dref-i⁺ _d, wherein, i⁺ _drefFor current on line side d axle just Order components i⁺ _dSet-point；

Step 62. the 3rd PI controller is controlled computing after the output receiving described 3rd comparator, and output is corresponding Controlled quentity controlled variable is:

In formula, k_p3And k_i3It it is the control coefrficient of the 3rd PI controller；u⁺ _dFor positive sequence d axle modulation waveform；

The regulation of step 7. negative phase-sequence d shaft current ring performs according to the following steps:

Step 71. the 4th comparator calculates the input value of the 4th PI controller: i^- _dref-i^- _d, wherein, i^- _dFor current on line side d axle negative phase-sequence Component, unit is per unit value；i^- _drefFor i^- _dSet-point；

Step 72. the 4th PI controller is controlled computing after the output receiving described 4th comparator, and output is corresponding Controlled quentity controlled variable is:

In formula, k_p4And k_i4It it is the control coefrficient of the 4th PI controller；u^- _dFor negative phase-sequence d axle modulation waveform；

The regulation of step 8. positive sequence q shaft current ring performs according to the following steps:

Step 81. calculates the input value of the 5th PI controller: i by the 5th comparator⁺ _qref-i⁺ _q, wherein, i⁺ _qFor current on line side q Axle positive-sequence component, is obtained by step 2, and unit is per unit value；i⁺ _qrefFor i⁺ _qSet-point；

Step 82. the 4th PI controller is controlled computing after the output receiving described 4th comparator, and output is corresponding Controlled quentity controlled variable is:

In formula, k_p5And k_i5It it is the control coefrficient of the 5th PI controller；u⁺ _qFor positive sequence q axle modulation waveform；

The regulation of step 9. negative phase-sequence q shaft current ring performs according to the following steps:

Step 91. the 6th comparator calculates the input value of the 6th PI controller: i^- _qref-i^- _q, wherein, i^- _qDivide for current on line side q axle negative phase-sequence Amount, is obtained by step 2, and unit is per unit value；i^- _qrefFor i^- _qSet-point；

Step 92. the 6th PI controller is controlled computing after the output receiving described 6th comparator, and output is corresponding Controlled quentity controlled variable is:

In formula, k_p6And k_i6It it is the control coefrficient of the 6th PI controller；u^- _qFor negative phase-sequence q axle modulation waveform；

Step 10. controller output:

Controller described in step 101. passes through above-mentioned voltage u⁺ _d、u⁺ _q、u^- _dAnd u^- _qControl AC network top-cross DC converter, it is achieved The control of instantaneous active power, reactive power and the DC voltage of AC network top-cross DC converter, unit is per unit value；

The u that controller will obtain⁺ _d、u⁺ _q、u^- _dAnd u^- _qFirst pass through the coordinate transform of positive-negative sequence dq-abc, obtain u_a、u_bAnd u_c Three amounts, coordinate transform formula is as follows:

$\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\frac{\sqrt{2}}{\sqrt{3}}\left(\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \cos (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})\\ \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})\end{array}\right)\left[\begin{array}{c}{u}_d^{+}\\ u_q^{+}\end{array}\right]+\frac{\sqrt{2}}{\sqrt{3}}\left(\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \cos (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;})\\ \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})& -\sin (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;})\end{array}\right)\left[\begin{array}{c}{u}_d^{-}\\ u_q^{-}\end{array}\right]$

By u_a、u_bAnd u_cThree amounts are as control signal with carrier wave ratio relatively, it is thus achieved that the driving signal of AC network top-cross DC converter, then Driving signal is delivered to the control end of three brachium pontis of AC network top-cross DC converter so that AC network top-cross DC converter is defeated Go out corresponding voltage vector, control current on line side, thus regulate output.