CN105790253A - Double-loop control method - Google Patents

Abstract

The invention discloses a double-loop control method and belongs to the current voltage control technology field. The method comprises steps that S1, a non-linear interference observer adaptive to a voltage balancer is set; S2, an observation value of an output current of the voltage balancer is acquired through employing the non-linear interference observer for observation; and S3, the observation value is taken as a current feedforward of a bipolar DC micro power grid so as to realize current inner-loop control of current voltage double-loop control on the bipolar DC micro power grid. Through the method, without extra current sensors, current voltage double-loop control on the bipolar DC micro power grid voltage balancer is realized, and dynamic response and stability of double-loop control are improved.

Description

A kind of double loop control

Technical field

The present invention relates to current/voltage and control technical field, particularly relate to a kind of double loop control.

Background technology

Micro-capacitance sensor is the system that one group of micro battery, load, energy-storage system and control device are constituted.Micro-capacitance sensor is conducive to concentrating the distributed power source of low capacity, and operational mode is flexible, it is possible to transfer islet operation at electric network fault or the electrical network quality of power supply to when being reduced to a certain degree；Again can also be incorporated into the power networks after electric network fault releases or the quality of power supply meets.

Relative to exchange micro-capacitance sensor, direct-current grid has a lot of outstanding feature.Most of distributed power sources and power consumer terminator are all direct currents, are connected to direct-current grid and can reduce the number of times of energy conversion, reduce loss and fault rate.Simultaneously because without kelvin effect, direct current supply line provides higher load capacity.Direct-current grid is also better than the anti-interference of exchange micro-capacitance sensor, and direct-current grid is also much lower than exchange micro-capacitance sensor in the investment of infrastructure.And, the problem that exchange micro-capacitance sensor self there is also some complexity, dash current, reactive power flowing, harmonic current and the three-phase imbalance etc. that such as synchronization between distributed power source, transformator cause so that controlling of exchange micro-capacitance sensor is more much more complex than the control of direct-current grid.In sum, compared to exchange micro-capacitance sensor, direct-current grid have energy-efficient, cost is more, controls is simple and reliability height etc. advantage.

In prior art, for simple DC micro power grid system, in this system, distributed power source, energy-storage units and AC and DC power load access unipolarity dc bus usually by corresponding power electronic equipment.Power motility for improving direct-current grid, meeting the different Distributed Renewable Energy Power System of electric pressure, energy-storage units and alternating current-direct current load to access, DC power-supply system can adopt bipolarity three-wire system topology (being commonly referred to positive pole, negative pole and center line).Outlet form according to direct-current grid center line, bipolarity three-wire system topology mainly includes following several: 1) adopt bi-directional DC-DC or the series connection of DC-AC current transformer of two identical capacity, both are center line altogether, then positive and negative electrode bus is generated respectively, actually direct-current grid has been internally formed two individually controllable current supply circuits, although reliability is higher, but need two set total power electronic power conversion devices, more costly.2) by dividing dc-link capacitance, draw a pole from which as direct-current grid center line, when positive and negative interpolar distributed power source or load unbalanced, if adopting three level neutral point clamped multi DC-AC current transformer (the i.e. NeutralPointClampedConverter with neutral-point potential balance function, it is called for short NPC), then can ensure that the direct current positive and negative busbar balance of voltage, but for conventional two level DC-AC or independent direct current micro-capacitance sensor, then cannot realize direct current both positive and negative polarity busbar voltage balance and control.

In prior art, usually by balance of voltage device, the dc bus of direct-current grid is carried out voltage balancing control.But a large amount of distributed renewable energy power generation unit, load etc. have obvious stochastic volatility in direct-current grid, this kind of fluctuating power especially short-time rating impacts and is impacted by the voltage being likely to align negative DC bus.In the voltage balancing control strategy of traditional balance of voltage device, generally adopt voltage/current double-loop control algorithm to realize control, but have the disadvantage that cannot the dynamic responding speed of Guarantee control system and stability margin simultaneously for this algorithm.

Summary of the invention

According to the above-mentioned problems in the prior art, the technical scheme of a kind of double loop control is now provided, when being intended to not use extra current sensor, it is achieved the voltage x current double-loop control of bipolarity direct-current grid balance of voltage device, and improve dynamic response and the stability of double-loop control.

Technique scheme specifically includes:

A kind of double loop control, it is adaptable to bipolarity direct-current grid；Wherein, described bipolarity direct-current grid connects a balance of voltage device；

Described balance of voltage device includes:

It is series at the first switch between positive pole and a primary nodal point of the input voltage of described bipolarity direct-current grid, and is series at the second switch between the negative pole of described input voltage and described primary nodal point；

It is series at the first electric capacity between the positive pole of described input voltage and a secondary nodal point, and is series at the second electric capacity between the negative pole of described input voltage and described secondary nodal point；And

It is series at the inductance between described primary nodal point and described secondary nodal point；

Described DC voltage control method includes:

Step S1, sets the Nonlinear Disturbance Observer being adapted to described balance of voltage device；

Step S2, obtains the observation of described balance of voltage device output electric current according to the observation of described Nonlinear Disturbance Observer；

Step S3, using the described observation current feed-forward as described bipolarity direct-current grid, controls so that described bipolarity direct-current grid to carry out the current inner loop in current/voltage double-loop control.

Preferably, this double loop control, wherein, described first switch includes:

It is series at the full-controlled switch pipe between positive pole and the described primary nodal point of the input voltage of described bipolarity direct-current grid；And

It is parallel to the fly-wheel diode at described full-controlled switch pipe two ends.

Preferably, this double loop control, wherein, described second switch includes:

It is series at the full-controlled switch pipe between the negative pole of described input voltage and described primary nodal point；And

It is parallel to the fly-wheel diode at described full-controlled switch pipe two ends.

Preferably, this double loop control, wherein, described full-controlled switch pipe is insulated gate bipolar transistor.

Preferably, this double loop control, wherein, described first electric capacity is equal with the capacitance of described second electric capacity；

In described step S1, set up designing a model of described Nonlinear Disturbance Observer according to following formula:

$\left\{\begin{array}{c}\frac{dz}{dt}=-\frac{l_1}{2C_0}z-\frac{{l_1}^2{u}_{dc1}}{2C_0}+\frac{1}{2C_0}{l}_1{i}_L\\ \widetilde{i_0}=z+l_1{u}_{dc1}\end{array}\right.;$

Wherein,

u_dc1For representing the positive pole output voltage of described balance of voltage device；

C₀For representing described first electric capacity and the capacitance of described second electric capacity；

i_LFor representing the electric current flowing through described inductance；

l₁For representing the observation gain of described Nonlinear Disturbance Observer, l₁∈[1,10]；

Z is for representing the middle output state variable of described Nonlinear Disturbance Observer；

For representing the described observation in described step S2.

Preferably, this double loop control, wherein, in described step S3, according to following formula, process, according to the described observation as described current feed-forward, the electric current loop reference value obtaining described balance of voltage device:

$i_{Lref}=\widetilde{i_0}+(u_{dc1}-u_{dc2})(k_{pu}+k_{iu}/s);$

Wherein,

i_LrefFor representing the described electric current loop reference value in described balance of voltage device；

For representing the described observation in described step S2；

u_dc1For representing the positive pole output voltage of described balance of voltage device；

u_dc2For representing the negative pole output voltage of described balance of voltage device；

k_puRatio for representing the controller of the outer voltage in described current/voltage double-loop control controls parameter；

k_iuFor representing the integration control parameter of the controller of the outer voltage in described current/voltage double-loop control；

k_iu/ s represents k_iuTime is integrated computing.

Preferably, this double loop control, wherein, described first switch turns on described second switch complementation；

In described step S3, according to following formula, described current inner loop is controlled:

d₂=(i_Lref-i_L)(k_pi+k_ii/s)；

Wherein,

d₂For representing the dutycycle of described second switch；

i_LrefFor representing the described electric current loop reference value in described balance of voltage device；

i_LFor representing the electric current flowing through described inductance；

k_piRatio for representing the controller of the current inner loop in described current/voltage double-loop control controls parameter；

k_iiFor representing the integration control parameter of the controller of the current inner loop in described current/voltage double-loop control；

k_ii/ s represents k_iiTime is integrated computing.

Preferably, this double loop control, wherein, set up designing a model of described balance of voltage device according to following formula:

$\left\{\begin{array}{c}\frac{{\mathrm{du}}_{dc1}}{dt}=-\frac{i_L}{2C_0}+\frac{i_0}{2C_0}\\ \frac{{\mathrm{di}}_L}{dt}=\frac{(d_1-1)u_{dc}}{L_{dc}}+\frac{u_{dc1}}{L_{dc}}\end{array}\right.;$

Wherein,

u_dc1For representing the positive pole output voltage of described balance of voltage device；

C₀For representing described first electric capacity and the capacitance of described second electric capacity；

i_LFor representing the electric current flowing through described inductance；

i₀For representing the output electric current of described balance of voltage device；

d₁For representing the dutycycle of described first switch；

u_dcFor representing the both positive and negative polarity voltage of described bipolarity direct-current grid；

L_dcFor representing the inductance value of described inductance.

Technique scheme provides the benefit that: provide a kind of double loop control, can when not using extra current sensor, realize the voltage x current double-loop control of bipolarity direct-current grid balance of voltage device, and improve dynamic response and the stability of double-loop control.

Accompanying drawing explanation

Fig. 1 is in the preferred embodiment of the present invention, it is adaptable to the electrical block diagram of the balance of voltage device of bipolarity direct-current grid；

Fig. 2 is in the preferred embodiment of the present invention, the overall procedure schematic diagram of a kind of double loop control；

Fig. 3 is in the preferred embodiment of the present invention, it is adaptable to the electrical block diagram of the balance of voltage device of test；

Fig. 4-7 is the effect comparison schematic diagram between double loop control and traditional voltage/current double loop control of application technical solution of the present invention.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under the premise not making creative work, broadly fall into the scope of protection of the invention.

It should be noted that when not conflicting, the embodiment in the present invention and the feature in embodiment can be mutually combined.

Below in conjunction with the drawings and specific embodiments, the invention will be further described, but not as limiting to the invention.

In the preferred embodiment of the present invention, based on the above-mentioned problems in the prior art, a kind of double loop control of existing offer, the method is applicable to bipolarity direct-current grid.So-called bipolarity direct-current grid, it is entirely different with unipolar direct-current grid on circuit structure.A balance of voltage device is connected on the net at this bipolarity DC micro-electric.The circuit structure of this balance of voltage device is concrete as it is shown in figure 1, include:

It is series at the positive pole u of the input voltage of bipolarity direct-current grid_dc+ and a primary nodal point A between the first switch, and be series at the negative pole u of input voltage_dc-and primary nodal point A between second switch；

It is series at the positive pole u of input voltage_dc+ and a secondary nodal point B between the first electric capacity C₁, and it is series at the negative pole u of input voltage_dc-and secondary nodal point B between the second electric capacity C₂；And

It is series at the inductance L between primary nodal point A and secondary nodal point B；

Then in the preferred embodiment of the present invention, according to the circuit structure shown in above-mentioned Fig. 1, above-mentioned double loop control specifically includes:

Step S1, sets the Nonlinear Disturbance Observer being adapted to balance of voltage device；

Step S2, obtains the observation of balance of voltage device output electric current according to Nonlinear Disturbance Observer observation；

Step S3, using the observation current feed-forward as bipolarity direct-current grid, controls so that bipolarity direct-current grid to carry out the current inner loop in current/voltage double-loop control.

In a specific embodiment, first the designing a model of setting voltage static organ, this model is following formula such as:

$\left\{\begin{array}{c}\frac{{\mathrm{du}}_{dc1}}{dt}=-\frac{i_L}{2C_0}+\frac{i_0}{2C_0}\\ \frac{{\mathrm{di}}_L}{dt}=\frac{(d_1-1)u_{dc}}{L_{dc}}+\frac{u_{dc1}}{L_{dc}}\end{array}\right.;---\left(1\right)$

Wherein,

u_dc1For representing the positive pole output voltage of balance of voltage device；

C₀For representing the first electric capacity C₁With the second electric capacity C₂Capacitance, i.e. C₁=C₂=C₀；

i_LFor representing the electric current flowing through inductance L；

i₀For representing the output electric current of balance of voltage device；

d₁For representing the dutycycle of the first switch；

u_dcFor representing the both positive and negative polarity voltage of bipolarity direct-current grid, i.e. cathode voltage u_dc+ and cathode voltage u_dc-between magnitude of voltage；

L_dcFor representing the inductance value of inductance L.

In this balance of voltage device, above-mentioned first switch and second switch are complementary conductings.In other words, by the dutycycle d of the first switch₁The dutycycle d of second switch can be obtained₂, vice versa.

In this embodiment, design designing a model of Nonlinear Disturbance Observer further according to above-mentioned balance of voltage device, particularly as follows:

$\left\{\begin{array}{c}\frac{dz}{dt}=-\frac{l_1}{2C_0}z-\frac{{l_1}^2{u}_{dc1}}{2C_0}+\frac{1}{2C_0}{l}_1{i}_L\\ \widetilde{i_0}=z+l_1{u}_{dc1}\end{array}\right.;---\left(2\right)$

Wherein,

l₁For representing the observation gain of Nonlinear Disturbance Observer.In practice, the realization difficulty brought in order to avoid observation gain values is excessive, such as saturation effect or noise aggravation etc., generally by the response speed that ensures Nonlinear Disturbance Observer than feedback control system response speed faster for the purpose of, observation gain is set to l₁∈[1,10]；

Z is for representing the middle output state variable of Nonlinear Disturbance Observer；

For representing the observation in above-mentioned steps S2.

Then in this embodiment, this observation the most at lastAs the current feed-forward of this bipolarity direct-current grid, and according to this current feed-forward, the balance of voltage device in this bipolarity direct-current grid is carried out current/voltage double-loop control.Specifically, according to above-mentioned current feed-forward, the current inner loop of balance of voltage device is controlled.And in technical solution of the present invention, the control mode for outer voltage still adopts traditional control mode to realize.

In the preferred embodiment of the present invention, still as it is shown in figure 1, above-mentioned first switch includes:

It is series at the positive pole u of the input voltage of bipolarity direct-current grid_dc+ and primary nodal point A between full-controlled switch pipe S₁；And

It is parallel to the sustained diode at full-controlled switch pipe two ends₁。

Correspondingly, above-mentioned second switch includes equally:

It is series at the negative pole u of the input voltage of above-mentioned bipolarity direct-current grid_dc-and primary nodal point A between full-controlled switch pipe S₂；And

It is parallel to the sustained diode at full-controlled switch pipe two ends₂。

Specifically, in the preferred embodiment of the present invention, above-mentioned full-controlled switch pipe S₁And S₂It is usually IGBT (InsulatedGateBipolarTransistor, insulated gate bipolar transistor).

Then in the preferred embodiment of the present invention, the dutycycle of above-mentioned first switch is exactly full-controlled switch pipe S₁Dutycycle.Similarly, the dutycycle of above-mentioned second switch is exactly full-controlled switch pipe S₂Dutycycle.

In the preferred embodiment of the present invention, in above-mentioned steps S2, the observation of Nonlinear Disturbance Observer can be obtained according to above-mentioned formula (2)And in above-mentioned steps S3, can process, according to the observation as current feed-forward, the electric current loop reference value obtaining balance of voltage device according to following formula:

$i_{Lref}=\widetilde{i_0}+(u_{dc1}-u_{dc2})(k_{pu}+k_{iu}/s);---\left(3\right)$

Wherein,

i_LrefFor representing the electric current loop reference value in balance of voltage device；

For representing the observation in step S2；

u_dc1For representing the positive pole output voltage of balance of voltage device；

u_dc2For representing the negative pole output voltage of balance of voltage device；

k_puRatio for representing the controller of the outer voltage in current/voltage double-loop control controls parameter；

k_iuFor representing the integration control parameter of the controller of the outer voltage in current/voltage double-loop control；

k_iu/ s represents k_iuTime is integrated computing.

Specifically, in the preferred embodiment of the present invention, above-mentioned k_puAnd k_iuThe selection of parameter needs to consider dynamic response and the stability margin of voltage/current double-loop control, such as need the open-loop phase angle nargin ensureing the double loop control in technical solution of the present invention at about 45 ° (such as 45 ° to 60 °), and ensure that the regulating time of double-loop control is not more than 0.25s.

In the preferred embodiment of the present invention, the process through above-mentioned formula (3) finally gives above-mentioned electric current loop reference value i_Lref.Subsequently, in above-mentioned steps S3, it is possible to according to above-mentioned electric current loop reference value, according to following formula, current inner loop is controlled:

d₂=(i_Lref-i_L)(k_pi+k_ii/s)；(4)

Wherein,

k_piRatio for representing the controller of the current inner loop in current/voltage double-loop control controls parameter；

k_iiFor representing the integration control parameter of the controller of the current inner loop in current/voltage double-loop control；

k_ii/ s represents k_iiTime is integrated computing.

Similarly, in the preferred embodiment of the present invention, above-mentioned k_piAnd k_iiParameter select need also exist for determining according to practical situation.Such as needing to consider the major loop parameter of real system, to ensure that in dicyclo, the overshoot of current inner loop is less than 10%, and regulating time is not more than 0.05s.

In the preferred embodiment of the present invention, calculate the dutycycle d obtaining above-mentioned second switch₂After, owing to the first switch and second switch are complementary conductings, therefore can be easy to calculate the dutycycle d obtaining the first switch₁, thus finally giving design a model (above-mentioned formula (1)) of above-mentioned balance of voltage device, and it is controlled according to the current inner loop in this formula (1) double-loop control to balance of voltage device.

In sum, in technical solution of the present invention, Nonlinear Disturbance Observer can realize the quick tracking of the output electric current to balance of voltage device when increasing extra current sensor, the current value of the balance of voltage device output then observed by Nonlinear Disturbance Observer is as the input quantity of the current perturbation feedforward of current inner loop in voltage/current double-loop control, and effectively suppresses the fluctuation of transient state both positive and negative polarity DC bus-bar voltage by the feedforward and impact.

In one preferred embodiment of the present invention, design circuit structure as shown in Figure 3, i.e. the cathode voltage u of test voltage static organ on the circuit structure shown in Fig. 2_dc1And the resistance between secondary nodal point B, and the cathode voltage u of balance of voltage device_dc2And the resistance between secondary nodal point B.

Then in this embodiment it is possible to by k_puIt is set to 0.05, k_iuIt is set to 5, k_piIt is set to 0.05, k_iiIt is set to 2, above-mentioned observation gain l₁It is set to 4.Then in circuit structure as shown in Figure 3, it is respectively adopted current/voltage Double-loop Control Technology of the prior art and adopts the current/voltage Double-loop Control Technology in technical solution of the present invention that this circuit structure is carried out double-loop control.It controls result as shown in figures 4 to 7, wherein:

Fig. 4 applies the voltage pulsation schematic diagram that current/voltage Double-loop Control Technology of the prior art obtains；

Fig. 5 is the voltage pulsation schematic diagram that the current/voltage Double-loop Control Technology in application technical solution of the present invention obtains；

Fig. 6 applies the current fluctuation schematic diagram that current/voltage Double-loop Control Technology of the prior art obtains；

Fig. 7 is the voltage pulsation schematic diagram that the current/voltage Double-loop Control Technology in application technical solution of the present invention obtains.

Major loop parameter selects as follows as shown in Figure 1: the both positive and negative polarity voltage udc of bipolarity direct-current grid is 500V, and dc-link capacitance C is 2200 μ F, filter inductance Ldc is 2mH, filter capacitor C₀Being 2200 μ F, negative pole and middle line-to-line load are resistance 25 Ω.Transient operating mode is carry out the change of positive and negative interpolar uncompensated load in analog DC micro-capacitance sensor by the resistance variations between simulation positive pole and center line, is specially transient operating mode 1: the resistance between positive pole and center line sports 10 Ω from 100 Ω；Transient operating mode 2: it is 100 Ω that the resistance between positive pole and center line suddenlys change back from 10 Ω.

As shown in Figure 4, when applying current/voltage Double-loop Control Technology of the prior art, when transient operating mode 1, from steady-state value 250V sudden change, to about 277V, (Sudden Changing Rate is about 27V to cathode voltage Udc1, reach 10.8%), cathode voltage Udc2 is from steady-state value 250V sudden change to about 223V (Sudden Changing Rate is about 27V, reaches 10.8%).

As shown in Figure 5, under same operating mode, after current/voltage Double-loop Control Technology in application technical solution of the present invention, cathode voltage Udc1 is only changed to about 254V from steady-state value 250V, and (Sudden Changing Rate is about 4V, reach 1.6%), cathode voltage Udc2 is from steady-state value 250V sudden change to about 246V (Sudden Changing Rate is about 4V, reaches 1.6%).

By contrasting it is found that apply technical solution of the present invention, positive and negative electrode DC voltage change amount can be effectively suppressed.

Fig. 6 show and applies the current waveform that current/voltage Double-loop Control Technology of the prior art obtains, in its partial enlarged drawing such as Fig. 6 shown in right half part.The inductive current of balance of voltage device is output as ripple current, its meansigma methods is 7.5A, ripple peak-to-peak value respectively 10A and 5A, frequency is 100 delicate, (peak-to-peak value is relevant to the major loop parameter of balance of voltage device, system running state and switching frequency with switching frequency).

Then Fig. 7 applies the current waveform that the current/voltage Double-loop Control Technology in technical solution of the present invention obtains, and is contrasted with Fig. 6.

The foregoing is only preferred embodiment of the present invention; not thereby restriction embodiments of the present invention and protection domain; to those skilled in the art; the equivalent replacement done by all utilizations description of the present invention and diagramatic content and the obtained scheme of apparent change should be can appreciate that, all should be included in protection scope of the present invention.

Claims (8)

1. a double loop control, it is adaptable to bipolarity direct-current grid；It is characterized in that, described bipolarity direct-current grid connects a balance of voltage device；

Described balance of voltage device includes:

It is series at the first switch between positive pole and a primary nodal point of the input voltage of described bipolarity direct-current grid, and is series at the second switch between the negative pole of described input voltage and described primary nodal point；

It is series at the first electric capacity between the positive pole of described input voltage and a secondary nodal point, and is series at the second electric capacity between the negative pole of described input voltage and described secondary nodal point；And

It is series at the inductance between described primary nodal point and described secondary nodal point；Described DC voltage control method includes:

Step S1, sets the Nonlinear Disturbance Observer being adapted to described balance of voltage device；

Step S2, obtains the observation of described balance of voltage device output electric current according to the observation of described Nonlinear Disturbance Observer；

Step S3, using the described observation current feed-forward as described bipolarity direct-current grid, controls so that described bipolarity direct-current grid to carry out the current inner loop in current/voltage double-loop control.

2. double loop control as claimed in claim 1, it is characterised in that described first switch includes:

It is series at the full-controlled switch pipe between positive pole and the described primary nodal point of the input voltage of described bipolarity direct-current grid；And

It is parallel to the fly-wheel diode at described full-controlled switch pipe two ends.

3. double loop control as claimed in claim 1, it is characterised in that described second switch includes:

It is series at the full-controlled switch pipe between the negative pole of described input voltage and described primary nodal point；And

It is parallel to the fly-wheel diode at described full-controlled switch pipe two ends.

4. double loop control as claimed in claim 2 or claim 3, it is characterised in that described full-controlled switch pipe is insulated gate bipolar transistor.

5. double loop control as claimed in claim 1, it is characterised in that described first electric capacity is equal with the capacitance of described second electric capacity；

In described step S1, set up designing a model of described Nonlinear Disturbance Observer according to following formula:

$\left\{\begin{array}{c}\frac{dz}{dt}=-\frac{l_1}{2C_0}z-\frac{{l_1}^2{u}_{dc1}}{2C_0}+\frac{1}{2C_0}{l}_1{i}_L\\ {\tilde{i}}_0=z+l_1{u}_{dc1}\end{array}\right.;$

Wherein,

u_dc1For representing the positive pole output voltage of described balance of voltage device；

C₀For representing described first electric capacity and the capacitance of described second electric capacity；

i_LFor representing the electric current flowing through described inductance；

l₁For representing the observation gain of described Nonlinear Disturbance Observer, l₁∈[1,10]；

Z is for representing the middle output state variable of described Nonlinear Disturbance Observer；

For representing the described observation in described step S2.

6. double loop control as claimed in claim 1, it is characterised in that in described step S3, according to following formula, processes, according to the described observation as described current feed-forward, the electric current loop reference value obtaining described balance of voltage device:

$i_{Lref}={\tilde{i}}_0+(u_{dc1}-u_{dc2})(k_{pu}+k_{iu}/s);$

Wherein,

i_LrefFor representing the described electric current loop reference value in described balance of voltage device；

For representing the described observation in described step S2；

u_dc1For representing the positive pole output voltage of described balance of voltage device；

u_dc2For representing the negative pole output voltage of described balance of voltage device；

k_puRatio for representing the controller of the outer voltage in described current/voltage double-loop control controls parameter；

k_iuFor representing the integration control parameter of the controller of the outer voltage in described current/voltage double-loop control；

k_iu/ s represents k_iuTime is integrated computing.

7. double loop control as claimed in claim 1, it is characterised in that described first switch and described second switch complementation conducting；

In described step S3, according to following formula, described current inner loop is controlled:

d₂=(i_Lref-i_L)(k_pi+k_ii/s)；

Wherein,

d₂For representing the dutycycle of described second switch；

i_LrefFor representing the described electric current loop reference value in described balance of voltage device；

i_LFor representing the electric current flowing through described inductance；

k_piRatio for representing the controller of the current inner loop in described current/voltage double-loop control controls parameter；

k_iiFor representing the integration control parameter of the controller of the current inner loop in described current/voltage double-loop control；

k_ii/ s represents k_iiTime is integrated computing.

8. double loop control as claimed in claim 7, it is characterised in that set up designing a model of described balance of voltage device according to following formula:

$\left\{\begin{array}{c}\frac{{\mathrm{du}}_{dc1}}{dt}=-\frac{i_L}{2C_0}+\frac{i_0}{2C_0}\\ \frac{{\mathrm{di}}_L}{dt}=\frac{\left(d_1-1\right)u_{dc}}{L_{dc}}+\frac{u_{dc1}}{L_{dc}}\end{array}\right.;$

Wherein,

u_dc1For representing the positive pole output voltage of described balance of voltage device；

C₀For representing described first electric capacity and the capacitance of described second electric capacity；

i_LFor representing the electric current flowing through described inductance；

i₀For representing the output electric current of described balance of voltage device；

d₁For representing the dutycycle of described first switch；

u_dcFor representing the both positive and negative polarity voltage of described bipolarity direct-current grid；

L_dcFor representing the inductance value of described inductance.