CN105048508A - Method and system for controlling T-type three-level single-phase grid-connected inverter - Google Patents

Abstract

The invention discloses a method and a system for controlling a T-type three-level single-phase grid-connected inverter. The method comprises the following steps: acquiring the grid voltage, the output current of an inverter and the direct-current bus voltage at the current moment; calculating the reference output voltage of the inverter at the current moment; and calculating the function value of a default control objective function in each switching state, taking the minimum objective function value among the obtained nine objective function values as the optimal objective function value, and determining the optimal direct-current bus voltage at next moment according to the optimal objective function value. According to the invention, on the basis of contracting the default control objective function, predictive control on the direct-current bus voltage at next moment is realized through finite switching state models. Therefore, inverter active power, reactive power and neutral point voltage balance control can be realized without complex PWM control or current inner-loop closing, and the T-type tri-level single-phase grid-connected inverter control process is simplified.

Description

A kind of control method of T-shaped three level single-phase grid-connected inverter and system

Technical field

The present invention relates to combining inverter control technology field, particularly a kind of control method of T-shaped three level single-phase grid-connected inverter and system.

Background technology

In recent years, along with energy resource consumption increases year by year, conventional energy resource is day by day exhausted, and the regenerative resource such as solar energy and wind energy is developed rapidly.The bridge that combining inverter is connected with electrical network as distributed generation system is the core of distributed generation system.Wherein, T-shaped three level single-phase grid-connected inverter is a kind of important combining inverter, and it has less power switch pipe and inverter efficiency advantages of higher.

Prior art is mainly controlled T-shaped three level single-phase grid-connected inverter by control methods such as the PI control methods under dq rotating coordinate system or the quasi-resonance control methods under rest frame.But these control methods all relate to PWM (PulseWidthModulation, pulse width modulation) control and electric current closes inner ring, and cause its control procedure comparatively complicated, flexibility is poor.

Can find out in sum how to simplify the control procedure of T-shaped three level single-phase grid-connected inverter, thus raising control flexibility ratio is current problem demanding prompt solution.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of control method and system of T-shaped three level single-phase grid-connected inverter, simplify the control procedure of T-shaped three level single-phase grid-connected inverter, thus improve control flexibility ratio.Its concrete scheme is as follows:

A kind of control method of T-shaped three level single-phase grid-connected inverter, be applied to T-shaped three level single-phase grid-connected inverter, described inverter comprises power switch pipe collection, described power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, and each power switch pipe group includes four power switch pipes; Wherein, described power switch pipe collection can form nine kinds of on off states; Described method comprises:

Obtain the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, described inverter output current is the output current of described a phase brachium pontis or described b phase brachium pontis, and described DC bus-bar voltage comprises positive bus-bar voltage and negative busbar voltage;

Utilize described line voltage and described inverter output current, the reference output voltage of described inverter under calculating current time;

Utilize the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Described default control target function is the predetermined function for calculating neutral point voltage departure degree;

Using minimum for numerical value in a described nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

Preferably, describedly utilize described line voltage and described inverter output current, the process calculating the reference output voltage of described inverter under current time specifically comprises:

Utilize linear interpolation method, to current time and under the historical juncture reference output current of described inverter carry out interpolation arithmetic, obtain the reference output current of inverter described in subsequent time, wherein, the reference output current of described inverter is the reference output current of described a phase brachium pontis or described b phase brachium pontis;

Utilize the reference output current of inverter described in described line voltage, described inverter output current and subsequent time, calculate described reference output voltage.

Preferably, describedly utilize the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, the process obtaining nine target function values accordingly comprises:

Utilize the DC bus-bar voltage of current time and described nine kinds of on off states, the output voltage respectively under calculating current time corresponding to each on off state of described inverter, correspondingly obtains nine output voltage values;

Utilize the DC bus-bar voltage of described inverter output current, current time and described nine kinds of on off states, calculate the DC bus-bar voltage described in subsequent time corresponding to each on off state of inverter respectively, correspondingly obtain nine groups of d-c bus voltage value, wherein, one group of d-c bus voltage value comprises a positive bus-bar magnitude of voltage and a negative busbar magnitude of voltage;

Utilize described reference output voltage, described nine output voltage values and described nine groups of d-c bus voltage value, the functional value of described default control target function under calculating each on off state respectively, obtain described nine target function values accordingly; Wherein said nine target function values and described nine groups of d-c bus voltage value one_to_one corresponding.

Preferably, described according to this optimal objective function value, determine that the process of the DC bus-bar voltage of subsequent time optimum comprises:

The magnitude of voltage of the DC bus-bar voltage of subsequent time optimum is defined as by with one group of d-c bus voltage value corresponding to this optimal objective function value.

Preferably, described default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for described reference output voltage, u _abk () represents described output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.

Preferably, λ _vvalue be 0.3.

The invention also discloses a kind of control system of T-shaped three level single-phase grid-connected inverter, be applied to T-shaped three level single-phase grid-connected inverter, described inverter comprises power switch pipe collection, described power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, and each power switch pipe group includes four power switch pipes; Wherein, described power switch pipe collection can form nine kinds of on off states; Described system comprises:

Data acquisition module, for obtaining the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, described inverter output current is the output current of described a phase brachium pontis or described b phase brachium pontis;

First computing module, for utilizing described line voltage and described inverter output current, the reference output voltage of described inverter under calculating current time;

Second computing module, for utilizing the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Described default control target function is the predetermined function for calculating neutral point voltage departure degree;

Voltage determination module, for using minimum for numerical value in a described nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

Preferably, described first computing module comprises:

First computing unit, for utilizing linear interpolation method, to current time and under the historical juncture reference output current of described inverter carry out interpolation arithmetic, obtain the reference output current of inverter described in subsequent time, wherein, the reference output current of described inverter is the reference output current of described a phase brachium pontis or described b phase brachium pontis;

Second computing unit, for utilizing the reference output current of inverter described in described line voltage, described inverter output current and subsequent time, calculates described reference output voltage.

Preferably, described second computing module comprises:

3rd computing unit, for utilizing the DC bus-bar voltage of current time and described nine kinds of on off states, the output voltage respectively under calculating current time corresponding to each on off state of described inverter, correspondingly obtains nine output voltage values;

4th computing unit, for utilizing the DC bus-bar voltage of described inverter output current, current time and described nine kinds of on off states, calculate the DC bus-bar voltage described in subsequent time corresponding to each on off state of inverter respectively, correspondingly obtain nine groups of d-c bus voltage value;

5th computing unit, for utilizing described reference output voltage, described nine output voltage values and described nine groups of d-c bus voltage value, the functional value of described default control target function under calculating each on off state respectively, obtains described nine target function values accordingly; Wherein said nine target function values and described nine groups of d-c bus voltage value one_to_one corresponding.

Preferably, described default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for described reference output voltage, u _abk () represents described output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.

In the present invention, the control method of T-shaped three level single-phase grid-connected inverter comprises: obtain the line voltage of current time, inverter output current and DC bus-bar voltage; Then line voltage and inverter output current is utilized, the reference output voltage of inverter under calculating current time; Then DC bus-bar voltage and nine kinds of on off states of reference output voltage, inverter output current, current time are utilized, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly, wherein, default control target function is the predetermined function for calculating neutral point voltage departure degree; Finally using minimum for numerical value in a nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.Therefore, the present invention utilizes the default control target function for calculating neutral point voltage departure degree, determine the target function value corresponding to each on off state in inverter nine kinds of on off states, then the DC bus-bar voltage of subsequent time optimum is determined according to the target function value that numerical value in nine target function values is minimum, also be, the present invention is on the basis constructing default control target function, by limited on off state model, and then the PREDICTIVE CONTROL achieved subsequent time DC bus-bar voltage, just can realize inverter active power thus, reactive power and neutral voltage balancing control, and without using complexity PWM control and electric current close inner ring, the visible control procedure that this invention simplifies T-shaped three level single-phase grid-connected inverter, thus improve control flexibility ratio.

Accompanying drawing explanation

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

Fig. 1 is the topological structure schematic diagram of T-shaped three level single-phase grid-connected inverter;

The control method flow chart of Fig. 2 a kind of T-shaped three level single-phase grid-connected inverter disclosed in the embodiment of the present invention;

The control method flow chart of Fig. 3 a kind of T-shaped three level single-phase grid-connected inverter specifically disclosed in the embodiment of the present invention;

The Control system architecture schematic diagram of Fig. 4 a kind of T-shaped three level single-phase grid-connected inverter disclosed in the embodiment of the present invention.

Embodiment

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

The embodiment of the invention discloses a kind of control method of T-shaped three level single-phase grid-connected inverter, be applied to T-shaped three level single-phase grid-connected inverter, Fig. 1 is the topological structure schematic diagram of T-shaped three level single-phase grid-connected inverter, T-shaped three level single-phase grid-connected inverter comprises power switch pipe collection, power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, wherein, the first power switch pipe group comprises power switch tube S a1, power switch tube S a2, power switch tube S a3 and power switch tube S a4; Second power switch pipe group comprises power switch tube S b1, power switch tube S b2, power switch tube S b3 and power switch tube S b4.It should be noted that, the drive singal of power switch tube S a1 and the drive singal of power switch tube S a3 are complementary signal, the drive singal of power switch tube S a2 and the drive singal of power switch tube S a4 are complementary signal, the drive singal of power switch tube S b1 and the drive singal of power switch tube S b3 are complementary signal, and the drive singal of power switch tube S b2 and the drive singal of power switch tube S b4 are complementary signal.

Wherein, power switch pipe collection can form nine kinds of on off states, and above-mentioned nine kinds of on off states have been shown in table 1.

Table 1

j	Sa1 Sa2 Sa3 Sa4	Sa	Sb1 Sb2 Sb3 Sb4	Sb
					0	1 1 0 0	1	0 0 1 1	-1
1	1 1 0 0	1	0 1 1 0	0
					2	0 1 1 0	0	0 0 1 1	-1
3	0 1 1 0	0	0 1 1 0	0
					4	1 1 0 0	1	1 1 0 0	1
5	0 0 1 1	-1	0 0 1 1	-1
					6	0 1 1 0	0	1 1 0 0	1
7	0 0 1 1	-1	0 1 1 0	0
					8	0 0 1 1	-1	1 1 0 0	1

Sa in table 1 represents the on off state of a phase, and Sb represents the on off state of b phase; According to power switch tube S a1 ~ Sa4 nine kinds on a phase brachium pontis different cut-off state, correspondingly can determine the on off state Sa of a phase; According to power switch tube S b1 ~ Sb4 nine kinds on b phase brachium pontis different cut-off state, correspondingly can determine the on off state Sb of a phase, corresponding numeral 1 when each power switch pipe is opened in table 1, corresponding numeral 0 during shutoff.When Sa or Sb is 1 time, represent that output is connected with busbar voltage positive pole P point; When Sa or Sb is 0 time, represent that output is connected with busbar voltage neutral point O point; When Sa or Sb is-1 time, represent that output is connected with busbar voltage negative pole N point.As can be seen from Table 1, the on off state that in T-shaped three level single-phase grid-connected inverter, power switch pipe collection is formed can be expressed as:

S _j＝[SaSb] ^T；

Wherein, j=0 ..., 8; Visible, the on off state that in T-shaped three level single-phase grid-connected inverter, power switch pipe collection is formed has nine kinds.

Fig. 2 shows the control method of T-shaped three level single-phase grid-connected inverter disclosed in the embodiment of the present invention, and the method comprises:

Step S11: obtain the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, inverter output current is the output current of a phase brachium pontis or b phase brachium pontis, and DC bus-bar voltage comprises positive bus-bar voltage and negative busbar voltage;

Step S12: utilize line voltage and inverter output current, the reference output voltage of inverter under calculating current time;

Step S13: the DC bus-bar voltage and the nine kinds of on off states that utilize reference output voltage, inverter output current, current time, calculates the functional value of default control target function under each on off state respectively, obtains nine target function values accordingly; Default control target function is the predetermined function for calculating neutral point voltage departure degree;

Step S14: using minimum for numerical value in a nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

In the embodiment of the present invention, the control method of T-shaped three level single-phase grid-connected inverter comprises: obtain the line voltage of current time, inverter output current and DC bus-bar voltage; Then line voltage and inverter output current is utilized, the reference output voltage of inverter under calculating current time; Then DC bus-bar voltage and nine kinds of on off states of reference output voltage, inverter output current, current time are utilized, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly, wherein, default control target function is the predetermined function for calculating neutral point voltage departure degree; Finally using minimum for numerical value in a nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

Therefore, the embodiment of the present invention utilizes the default control target function for calculating neutral point voltage departure degree, determine the target function value corresponding to each on off state in inverter nine kinds of on off states, then the DC bus-bar voltage of subsequent time optimum is determined according to the target function value that numerical value in nine target function values is minimum, also be, the embodiment of the present invention is on the basis constructing default control target function, by limited on off state model, and then the PREDICTIVE CONTROL achieved subsequent time DC bus-bar voltage, just can realize inverter active power thus, reactive power and neutral voltage balancing control, and without using complexity PWM control and electric current close inner ring, the visible embodiment of the present invention simplifies the control procedure of T-shaped three level single-phase grid-connected inverter, thus improve control flexibility ratio.

The embodiment of the invention discloses a kind of control method of T-shaped three level single-phase grid-connected inverter specifically, shown in Figure 3, relative to a upper embodiment, the present embodiment expands further instruction and optimization to technical scheme.Specific as follows:

A upper embodiment step S12 specifically can comprise:

Step S121: utilize linear interpolation method, to current time and under the historical juncture reference output current of inverter carry out interpolation arithmetic, obtain the reference output current of subsequent time inverter, wherein, the reference output current of inverter is the reference output current of a phase brachium pontis or b phase brachium pontis;

Step S122: the reference output current utilizing line voltage, inverter output current and subsequent time inverter, calculates reference output voltage.

Further, a upper embodiment step S13 specifically can comprise:

Step S131: the DC bus-bar voltage and the nine kinds of on off states that utilize current time, the output voltage respectively under calculating current time corresponding to each on off state of inverter, correspondingly obtains nine output voltage values;

Step S132: the DC bus-bar voltage and the nine kinds of on off states that utilize inverter output current, current time, calculate the DC bus-bar voltage corresponding to each on off state of subsequent time inverter respectively, correspondingly obtain nine groups of d-c bus voltage value, wherein, one group of d-c bus voltage value comprises a positive bus-bar magnitude of voltage and a negative busbar magnitude of voltage;

Step S133: utilize reference output voltage, nine output voltage values and nine groups of d-c bus voltage value, calculates the functional value of default control target function under each on off state respectively, obtains nine target function values accordingly; Wherein nine target function values and nine groups of d-c bus voltage value one_to_one corresponding.

Further, a upper embodiment step S14 specifically can comprise:

Step S141: using minimum for numerical value in a nine target function values target function value as optimal objective function value;

Step S142: be defined as the magnitude of voltage of the DC bus-bar voltage of subsequent time optimum by with one group of d-c bus voltage value corresponding to this optimal objective function value.

The embodiment of the invention discloses the control method of another concrete T-shaped three level single-phase grid-connected inverter, relative to a upper embodiment, the present embodiment expands further instruction and optimization to technical scheme.Specific as follows:

Obtain the line voltage e of current time _g(k), inverter output current i _a(k) (being herein the output current of a phase brachium pontis), positive bus-bar voltage V _p(k) and negative busbar voltage V _n(k).

Utilize linear interpolation method, interpolation arithmetic is carried out to the reference output current of current time (i.e. k moment) inverter, the reference output current of (k-1) moment inverter and the reference output current of (k-2) moment inverter, obtain the reference output current in subsequent time (i.e. k+1 moment), concrete formula is:

$i_a^{*}(k+1)=i_a^{*}\left(k\right)-i_a^{*}(k-1)+i_a^{*}(k-2)---\left(1\right)$

Wherein, the reference output current of above-mentioned inverter refers to the reference output current of a phase brachium pontis.

Utilize line voltage e _g(k), inverter output current i _athe reference output current of (k) and subsequent time inverter calculate reference output voltage concrete formula is:

$u_{ab}^{*}\left(k\right)=\frac{L}{T_s}\[i_a^{*}(k+1)-i_a\left(k\right)\]+e_g\left(k\right)+{\mathrm{Ri}}_a\left(k\right)---\left(2\right)$

Wherein, L represents inductance, T _srepresent the sampling period;

Utilize positive bus-bar voltage V _p(k), negative busbar voltage V _nk () and nine kinds of on off states, the output voltage respectively under calculating current time corresponding to each on off state of inverter, correspondingly obtains nine output voltage values u _ab(k), concrete formula is:

u _ab(k)＝V _p(k)(Sa1-Sb1)+V _n(k)(Sa2-Sb2)(3)

Utilize inverter output current i _a(k), positive bus-bar voltage V _p(k), negative busbar voltage V _nk () and nine kinds of on off states, calculate the DC bus-bar voltage corresponding to each on off state of subsequent time inverter respectively, correspondingly obtain nine groups of d-c bus voltage value and (comprise positive bus-bar magnitude of voltage V _pand negative busbar magnitude of voltage V (k+1) _n(k+1)), concrete computing formula is:

$\left\{\begin{array}{c}{i}_{C1}\left(k\right)=-\left(\right(Sa==1)\·i_a(k)-(Sb==1)\·i_a(k\left)\right)-\left(\right(Sa==0)\·i_a(k)-(Sb==0)\·i_a(k\left)\right)\\ i_{C2}\left(k\right)=-\left(\right(Sa=1)\·i_a(k)-(Sb==1)\·i_a(k\left)\right)\end{array}\right.---\left(4\right)$

$\{\begin{array}{c}{V}_p(k+1)=V_p\left(k\right)+\frac{T_s}{C_2}{i}_{C2}\left(k\right)\\ V_n(k+1)=V_n\left(k\right)+\frac{T_s}{C_1}{i}_{C1}\left(k\right)\end{array}---\left(5\right)$

Wherein, C ₁and C ₂represent bus capacitor; i _c1(k) and i _c2k () is bus capacitor electric current, (Sa==1) represents as Sa=1, exports 1, as Sa=0, exports 0; And the situation of (Sa==0), (Sb==1) and (Sb==0) and (Sa==1) is similar, repeat in this inconvenience.Can know according to above-mentioned formula, the present invention passes through nine kinds of on off states and the inverter output current i of the power switch pipe collection of T-shaped three level single-phase grid-connected inverter _a(k), just measurable go out d-c bus voltage value corresponding to each on off state of subsequent time inverter, and without using the bus capacitor current i of instrument and equipment to inverter _c1(k) and i _c2k () measures, thus to control without using the PWM of complexity for the present invention and electric current closes inner ring and just can realize laying important foundation to the control of inverter.

The derivation of above-mentioned formula (4) is as follows:

Can derive from Fig. 1, the bus capacitor current i of T-shaped three level single-phase grid-connected inverter _c1(k) and i _c2k () can be expressed as:

$\left\{\begin{array}{c}{i}_{C2}\left(k\right)=i_{dc}\left(k\right)-i_p\left(k\right)\\ i_{C1}\left(k\right)=i_{C2}\left(k\right)-i_o\left(k\right)=i_{dc}\left(k\right)-i_p\left(k\right)-i_o\left(k\right)\end{array}\right.---(4-1)$

Consider that the object that inverter neutral point balance controls is for realizing bus capacitor energy balance, now DC bus current i _dcvalue be 0, then have:

$\left\{\begin{array}{c}{i}_{C2}\left(k\right)=-i_p\left(k\right)\\ i_{C1}\left(k\right)=i_{C2}\left(k\right)-i_o\left(k\right)=-i_p\left(k\right)-i_o\left(k\right)\end{array}\right.---(4-2)$

In addition, according to nine kinds of on off states and the inverter output current i of power switch pipe collection in T-shaped three level single-phase grid-connected inverter _a(k) and i _bk (), can obtain the neutral point current of inverter:

$\left\{\begin{array}{c}{i}_p\left(k\right)=\left(\right(Sa==1)\·i_a(k)+(Sb==1)\·i_b(k\left)\right)\\ i_o\left(k\right)=\left(\right(Sa==0)\·i_a(k)+\left(Sb==0\right)\·i_b\left(k\right))\end{array}\right.---(4-3)$

Consider for T-shaped three level single-phase grid-connected inverter, have i _a(k)=-i _b(k) (4-4)

According to formula (4-3) and formula (4-4), formula (4) can be obtained.

On the basis of above-mentioned steps, and then utilize reference output voltage nine output voltage values u _abk () and nine groups of d-c bus voltage value, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Wherein, default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for reference output voltage, u _abk () represents output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.Consider λ _vlarger, neutral voltage balancing performance is better, when being then deteriorated to the tracking performance of electric current, therefore in the present embodiment, preferentially by λ _vvalue be set to 0.3.Nine target function values utilizing formula to obtain respectively with nine groups of d-c bus voltage value one_to_one corresponding.

Using minimum for numerical value in a nine target function values target function value as optimal objective function value; Then be defined as the magnitude of voltage of the DC bus-bar voltage of subsequent time optimum by with one group of d-c bus voltage value corresponding to this optimal objective function value, thereby simplify the control procedure of T-shaped three level single-phase grid-connected inverter, thus improve control flexibility ratio.

The embodiment of the invention also discloses a kind of control system of T-shaped three level single-phase grid-connected inverter, be applied to T-shaped three level single-phase grid-connected inverter, inverter comprises power switch pipe collection, power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, and each power switch pipe group includes four power switch pipes; Wherein, power switch pipe collection can form nine kinds of on off states; Shown in Figure 4, the system in the present embodiment comprises:

Data acquisition module 11, for obtaining the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, inverter output current is the output current of a phase brachium pontis or b phase brachium pontis;

First computing module 12, for utilizing line voltage and inverter output current, the reference output voltage of inverter under calculating current time;

Second computing module 13, for utilizing DC bus-bar voltage and nine kinds of on off states of reference output voltage, inverter output current, current time, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Default control target function is the predetermined function for calculating neutral point voltage departure degree;

Voltage determination module 14, for using minimum for numerical value in a nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

Concrete, above-mentioned first computing module 12 can comprise the first computing unit and the second computing unit: wherein,

First computing unit can be used for utilizing linear interpolation method, to current time and under the historical juncture reference output current of inverter carry out interpolation arithmetic, obtain the reference output current of subsequent time inverter, wherein, the reference output current of inverter is the reference output current of a phase brachium pontis or described b phase brachium pontis;

Second computing unit can be used for the reference output current utilizing line voltage, inverter output current and subsequent time inverter, calculates reference output voltage.

Further, in the present embodiment, the second computing module 13 specifically can comprise the 3rd computing unit and the 4th computing unit: wherein,

3rd computing unit can be used for the DC bus-bar voltage and the nine kinds of on off states that utilize current time, and the output voltage respectively under calculating current time corresponding to each on off state of inverter, correspondingly obtains nine output voltage values;

4th computing unit can be used for the DC bus-bar voltage and the nine kinds of on off states that utilize inverter output current, current time, calculate the DC bus-bar voltage corresponding to each on off state of subsequent time inverter respectively, correspondingly obtain nine groups of d-c bus voltage value;

5th computing unit can be used for utilizing reference output voltage, nine output voltage values and nine groups of d-c bus voltage value, calculates the functional value of default control target function under each on off state respectively, obtains nine target function values accordingly; Wherein nine target function values and nine groups of d-c bus voltage value one_to_one corresponding.

In the present embodiment, default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for reference output voltage, u _abk () represents output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.

About the function more specifically of computing unit each in the present embodiment, with reference to correlation method disclosed in a upper embodiment, can not repeat them here.

In the embodiment of the present invention, the control system of T-shaped three level single-phase grid-connected inverter comprises: data acquisition module, for obtaining the line voltage of current time, inverter output current and DC bus-bar voltage; First computing module, for utilizing line voltage and inverter output current, the reference output voltage of inverter under calculating current time; Second computing module, for utilizing DC bus-bar voltage and nine kinds of on off states of reference output voltage, inverter output current, current time, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly, wherein, default control target function is the predetermined function for calculating neutral point voltage departure degree; Finally by voltage determination module, using minimum for numerical value in a nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

Therefore, the embodiment of the present invention utilizes the default control target function for calculating neutral point voltage departure degree, determine the target function value corresponding to each on off state in inverter nine kinds of on off states, then the DC bus-bar voltage of subsequent time optimum is determined according to the target function value that numerical value in nine target function values is minimum, also be, the embodiment of the present invention is on the basis constructing default control target function, by limited on off state model, and then the PREDICTIVE CONTROL achieved subsequent time DC bus-bar voltage, just can realize inverter active power thus, reactive power and neutral voltage balancing control, and without using complexity PWM control and electric current close inner ring, the visible embodiment of the present invention simplifies the control procedure of T-shaped three level single-phase grid-connected inverter, thus improve control flexibility ratio.

Finally, also it should be noted that, in this article, the such as relational terms of first and second grades and so on is only used for an entity or operation to separate with another entity or operating space, and not necessarily requires or imply the relation that there is any this reality between these entities or operation or sequentially.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or equipment and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or equipment.When not more restrictions, the key element limited by statement " comprising ... ", and be not precluded within process, method, article or the equipment comprising described key element and also there is other identical element.

Above the control method of a kind of T-shaped three level single-phase grid-connected inverter provided by the present invention and system are described in detail, apply specific case herein to set forth principle of the present invention and execution mode, the explanation of above embodiment just understands method of the present invention and core concept thereof for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (10)

1. the control method of a T-shaped three level single-phase grid-connected inverter, it is characterized in that, be applied to T-shaped three level single-phase grid-connected inverter, described inverter comprises power switch pipe collection, described power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, and each power switch pipe group includes four power switch pipes; Wherein, described power switch pipe collection can form nine kinds of on off states; Described method comprises:

Obtain the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, described inverter output current is the output current of described a phase brachium pontis or described b phase brachium pontis, and described DC bus-bar voltage comprises positive bus-bar voltage and negative busbar voltage;

Utilize described line voltage and described inverter output current, the reference output voltage of described inverter under calculating current time;

Utilize the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Described default control target function is the predetermined function for calculating neutral point voltage departure degree;

Using minimum for numerical value in a described nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

2. the control method of T-shaped three level single-phase grid-connected inverter according to claim 1, it is characterized in that, describedly utilize described line voltage and described inverter output current, the process calculating the reference output voltage of described inverter under current time specifically comprises:

Utilize linear interpolation method, to current time and under the historical juncture reference output current of described inverter carry out interpolation arithmetic, obtain the reference output current of inverter described in subsequent time, wherein, the reference output current of described inverter is the reference output current of described a phase brachium pontis or described b phase brachium pontis;

Utilize the reference output current of inverter described in described line voltage, described inverter output current and subsequent time, calculate described reference output voltage.

3. the control method of T-shaped three level single-phase grid-connected inverter according to claim 2, it is characterized in that, describedly utilize the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, the process obtaining nine target function values accordingly comprises:

Utilize the DC bus-bar voltage of current time and described nine kinds of on off states, the output voltage respectively under calculating current time corresponding to each on off state of described inverter, correspondingly obtains nine output voltage values;

Utilize the DC bus-bar voltage of described inverter output current, current time and described nine kinds of on off states, calculate the DC bus-bar voltage described in subsequent time corresponding to each on off state of inverter respectively, correspondingly obtain nine groups of d-c bus voltage value, wherein, one group of d-c bus voltage value comprises a positive bus-bar magnitude of voltage and a negative busbar magnitude of voltage;

Utilize described reference output voltage, described nine output voltage values and described nine groups of d-c bus voltage value, the functional value of described default control target function under calculating each on off state respectively, obtain described nine target function values accordingly; Wherein said nine target function values and described nine groups of d-c bus voltage value one_to_one corresponding.

4. the control method of T-shaped three level single-phase grid-connected inverter according to claim 3, is characterized in that, described according to this optimal objective function value, determines that the process of the DC bus-bar voltage of subsequent time optimum comprises:

The magnitude of voltage of the DC bus-bar voltage of subsequent time optimum is defined as by with one group of d-c bus voltage value corresponding to this optimal objective function value.

5. the control method of the T-shaped three level single-phase grid-connected inverter according to any one of Claims 1-4, is characterized in that, described default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for described reference output voltage, u _abk () represents described output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.

6. the control method of T-shaped three level single-phase grid-connected inverter according to claim 5, is characterized in that, λ _vvalue be 0.3.

7. the control system of a T-shaped three level single-phase grid-connected inverter, it is characterized in that, be applied to T-shaped three level single-phase grid-connected inverter, described inverter comprises power switch pipe collection, described power switch pipe collection comprises the first power switch pipe group being positioned at a phase brachium pontis and the second power switch pipe group being positioned at b phase brachium pontis, and each power switch pipe group includes four power switch pipes; Wherein, described power switch pipe collection can form nine kinds of on off states; Described system comprises:

Data acquisition module, for obtaining the line voltage of current time, inverter output current and DC bus-bar voltage, wherein, described inverter output current is the output current of described a phase brachium pontis or described b phase brachium pontis;

First computing module, for utilizing described line voltage and described inverter output current, the reference output voltage of described inverter under calculating current time;

Second computing module, for utilizing the DC bus-bar voltage of described reference output voltage, described inverter output current, current time and described nine kinds of on off states, calculate the functional value of default control target function under each on off state respectively, obtain nine target function values accordingly; Described default control target function is the predetermined function for calculating neutral point voltage departure degree;

Voltage determination module, for using minimum for numerical value in a described nine target function values target function value as optimal objective function value, and according to this optimal objective function value, determine the DC bus-bar voltage of subsequent time optimum.

8. the control system of T-shaped three level single-phase grid-connected inverter according to claim 7, is characterized in that, described first computing module comprises:

First computing unit, for utilizing linear interpolation method, to current time and under the historical juncture reference output current of described inverter carry out interpolation arithmetic, obtain the reference output current of inverter described in subsequent time, wherein, the reference output current of described inverter is the reference output current of described a phase brachium pontis or described b phase brachium pontis;

Second computing unit, for utilizing the reference output current of inverter described in described line voltage, described inverter output current and subsequent time, calculates described reference output voltage.

9. the control system of T-shaped three level single-phase grid-connected inverter according to claim 8, is characterized in that, described second computing module comprises:

3rd computing unit, for utilizing the DC bus-bar voltage of current time and described nine kinds of on off states, the output voltage respectively under calculating current time corresponding to each on off state of described inverter, correspondingly obtains nine output voltage values;

4th computing unit, for utilizing the DC bus-bar voltage of described inverter output current, current time and described nine kinds of on off states, calculate the DC bus-bar voltage described in subsequent time corresponding to each on off state of inverter respectively, correspondingly obtain nine groups of d-c bus voltage value;

5th computing unit, for utilizing described reference output voltage, described nine output voltage values and described nine groups of d-c bus voltage value, the functional value of described default control target function under calculating each on off state respectively, obtains described nine target function values accordingly; Wherein said nine target function values and described nine groups of d-c bus voltage value one_to_one corresponding.

10. the control system of the T-shaped three level single-phase grid-connected inverter according to any one of claim 7 to 9, is characterized in that, described default control target function is:

$g\left(k\right)=\left(\right|u_{ab}^{*}\left(k\right)-u_{ab}\left(k\right)\left|\right)+{\mathrm{\λ}}_v\left(\right|V_p\left(k+1\right)-V_n\left(k+1\right)\left|\right);$

Wherein, for described reference output voltage, u _abk () represents described output voltage values, V _p(k+1) the positive bus-bar magnitude of voltage of subsequent time is represented, V _n(k+1) the negative busbar magnitude of voltage of subsequent time is represented, λ _vfor neutral voltage balancing weight coefficient.