CN102832644B - System and method for controlling three-phase grid-connected inverter - Google Patents

Abstract

The invention provides a system for controlling a three-phase grid-connected inverter. The system comprises a voltage collecting unit, a current collecting unit, a first computing unit, a k value storage unit, a k value obtaining unit, a second computing unit and a PWM (Pulse Width Modulation) wave generator, wherein the first computing unit is used for computing a three-phase bridge arm reference voltage and an output current amplitude according to the sampled three-phase network voltage instantaneous value and an output current instantaneous value of an inverter three-phase bridge arm; the k value obtaining unit is used for inquiring a k value table and obtaining the k value; the second computing unit is used for computing a zero-sequence component according to the k value; and the PWM wave generator is used for injecting the zero-sequence component into the three-phase bridge arm reference voltage to generate a PWM switch signal of the three-phase bridge arm. The invention also provides a corresponding control method. According to the system and the method for controlling the three-phase grid-connected inverter, the switching loss is reduced, the complex power-factor angle calculation is avoided, and the efficiency is increased.

Description

Three-phase grid-connected inverter control system and method

Technical field

The present invention relates to three-phase grid-connected inverter, more particularly, relate to a kind of three-phase grid-connected inverter and power device control method.

Background technology

The regenerative resource such as solar energy, wind energy is not only contained abundant, and environmental protection, will be the best alternative energy source of fossil energy, and more and more cause the great attention of national governments at present.Usually, these regenerative resources must convert electric energy easy to use to by solar-energy photo-voltaic cell, wind-driven generator etc., and this electric energy is transported to three-phase utility network by three-phase grid-connected inverter, thus realize the grid-connected use of the regenerative resource such as solar energy, wind energy.

The efficiency being converted into electric energy due to solar energy, wind energy etc. is lower, therefore while guarantee MPPT maximum power point tracking, the conversion efficiency of three-phase grid-connected inverter is extremely important: the efficiency often improving one percentage point, mean a lot of photovoltaic cell of few installation or wind-driven generator, this will be conducive to reducing system cost.Therefore, how to improve the conversion efficiency of three-phase grid-connected inverter, reduce inverter losses, become the study hotspot of new energy grid-connected power technology.

The main circuit of three-phase grid-connected inverter is generally made up of two power level voltage source type three-phase full-bridge inverting circuit, alternating current filter and transformer (when having electrical isolation to require).Existing two power level voltage source type three-phase grid inverter circuits adopt three phase full bridge circuit realiration, and it is made up of three brachium pontis, and each brachium pontis is connected by 2 power devices, and intermediate connections is as a phase voltage output.By controlling opening and turning off the moment of 6 power devices, the real-time control to three-phase output current can be realized.

Control at present to power device, usual employing space voltage vector modulation (being called for short SVPWM) scheme, the program controls each power device and once opens and a turn off process in a switch periods, all can produce certain switching loss turning on and off in process at every turn.In order to make three-phase grid inverter circuit output current harmonics content less, generally take the way improving switching frequency, but this can cause larger power device switching loss, thus causing three-phase grid-connected inverter conversion efficiency to reduce.

In addition, unitized discontinuous modula tion technology (being called for short GDPWM) can also be adopted to reduce the switching loss of three-phase two-level inverter.GDPWM adopts on fundamental sine wave reference voltage basis, inject different zero-sequence component realizations, the be failure to actuate total interval of power switch within a primitive period of each brachium pontis is 120 °, need the power-factor angle calculating inverter leg side in real time to determine the zero-sequence component injected, thus make switching loss minimum.But the power-factor angle that the program must calculate brachium pontis side in real time obtains the zero-sequence component injected, computational process is complicated, efficiency is lower.

Summary of the invention

The technical problem to be solved in the present invention is, for above-mentioned three-phase grid-connected inverter switching loss and zero-sequence component calculation of complex, inefficient problem, provides a kind of three-phase grid-connected inverter control system and method.

The technical scheme that the present invention solves the problems of the technologies described above is, a kind of three-phase grid-connected inverter control system is provided, comprise voltage sampling unit, current sampling unit, the first computing unit, k value table memory cell, k value acquiring unit, the second computing unit and PWM wave producer, wherein:

Described voltage sampling unit, obtains three-phase power grid voltage instantaneous value for sampling;

Described current sampling unit, for the output current instantaneous value obtaining inverter three-phase brachium pontis of sampling;

Described first computing unit, calculates inverter three-phase brachium pontis reference voltage and output current amplitude for the output current instantaneous value according to described three-phase power grid voltage instantaneous value, inverter three-phase brachium pontis;

Described k value table memory cell, for storing k value table, described k value table comprises the k value corresponding to output current instantaneous value of different inverter three-phase brachium pontis output current amplitudes, three-phase brachium pontis reference voltage, inverter three-phase brachium pontis, and described k value is 0 or 1;

Described k value acquiring unit, obtains k value for the output current instantaneous value inquiry k value table according to described output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis;

Described second computing unit, for calculating zero-sequence component according to described k value;

Described PWM wave producer, for injecting three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis by described zero-sequence component.

In three-phase grid-connected inverter control system of the present invention, described second computing unit is by following formulae discovery zero-sequence component v _z ^*:

v _z ^*＝-kv _max ^*-(1-k)v _min ^*+(2k-1)，

Wherein v _max ^*=max{v _a ^*, v _b ^*, v _c ^*, v _min ^*=min{v _a ^*, v _b ^*, v _c ^*, v _a ^*, v _b ^*, v _c ^*for inverter three-phase brachium pontis reference voltage.

In three-phase grid-connected inverter control system of the present invention, in described k value table, when described output current amplitude is between 0 to the first setting current amplitude, described k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When described output current amplitude sets between current amplitude at the first setting current amplitude to the second, described k value puts in order relevant to the size of inverter each phase brachium pontis reference voltage; When described output current amplitude is greater than the second setting current amplitude, described k value is relevant to the size of each value in three-phase brachium pontis reference voltage.

In three-phase grid-connected inverter control system of the present invention, described first setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 30 degree; Described second setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 75 degree.

The present invention also provides a kind of three-phase grid-connected inverter control method, comprises the following steps:

A () sampling obtains the output current instantaneous value of three-phase power grid voltage instantaneous value and sampling acquisition inverter three-phase brachium pontis;

B () calculates inverter three-phase brachium pontis reference voltage and output current amplitude according to the output current instantaneous value of described three-phase power grid voltage instantaneous value, inverter three-phase brachium pontis;

C () obtains k value according to the output current instantaneous value inquiry k value table of described output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis, and calculate zero-sequence component according to described k value, and described k value is 0 or 1;

D described zero-sequence component is injected three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis by ().

In three-phase grid-connected inverter control method of the present invention, in described step (c), by following formulae discovery zero-sequence component v _z ^*:

v _z ^*＝-kv _max ^*-(1-k)v _min ^*+(2k-1)，

Wherein v _max ^*=max{v _a ^*, v _b ^*, v _c ^*, v _min ^*=min{v _a ^*, v _b ^*, v _c ^*, v _a ^*, v _b ^*, v _c ^*for inverter three-phase brachium pontis reference voltage.

In three-phase grid-connected inverter control method of the present invention, in described k value table, when described output current amplitude is between 0 to the first setting current amplitude, described k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When described output current amplitude sets between current amplitude at the first setting current amplitude to the second, described k value puts in order relevant to the size of inverter each phase brachium pontis reference voltage; When described output current amplitude is greater than the second setting current amplitude, described k value is relevant to the size of each value in three-phase brachium pontis reference voltage.

In three-phase grid-connected inverter control method of the present invention, described first setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 30 degree; Described second setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 75 degree.

In three-phase grid-connected inverter control method of the present invention, described step (b) comprising:

(b1) the three-phase power grid voltage instantaneous value obtained sampling, after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtains d, q axle component e of three-phase power grid voltage _d, e _q; And by the output current instantaneous value of the inverter three-phase brachium pontis obtained of sampling after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtain d, q axle component i of three-phase output current _d, i _q;

(b2) according to d, q axle component e of three-phase power grid voltage _d, e _q, d, q axle component i of three-phase output current _d, i _q, the given i of reactive current _d ^*and the given i of active current _q ^*, after the uneoupled control of idle/active power, obtain d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _q;

(b3) by d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _qafter the inverse transformation that two-phase rotational coordinates is tied to three-phase static coordinate system, obtain inverter three-phase brachium pontis reference voltage v _a ^*, v _b ^*, v _c ^*.

In three-phase grid-connected inverter control method of the present invention, d, q axle component v of the reference voltage of inverter three-phase brachium pontis described in described step (b2) _d, v _qobtained by following formulae discovery:

$\left\{\begin{array}{c}{v}_d=\frac{L}{T_c}(i_d^{*}-i_d)-\mathrm{\ω}{\mathrm{Li}}_q+{\mathrm{Ri}}_d+e_d\\ v_q=\frac{L}{T_c}(i_q^{*}-i_q)+\mathrm{\ω}{\mathrm{Li}}_d+{\mathrm{Ri}}_q+e_q\end{array}\right.,$ Wherein R is line equivalent resistance, L is filter inductance, ω is electrical network angular frequency, T _cfor switch periods.

Three-phase grid-connected inverter control system of the present invention and method, by the instantaneous value magnitude relationship of multilevel iudge inverter three-phase brachium pontis reference voltage, or the instantaneous value magnitude relationship of multilevel iudge inverter three-phase output current, calculate the zero-sequence component injecting three-phase brachium pontis reference voltage, thus realize unitized discontinuous modula tion, while reduction switching loss, avoid complicated power-factor angle and calculate, improve efficiency.

Accompanying drawing explanation

Fig. 1 is the applied environment schematic diagram of three-phase grid-connected inverter control system of the present invention.

Fig. 2 is the schematic diagram of three-phase grid-connected inverter control system embodiment of the present invention.

Fig. 3 is the schematic flow sheet of three-phase grid-connected inverter control method embodiment of the present invention.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

As shown in Figure 1, be the applied environment schematic diagram of three-phase grid-connected inverter control system of the present invention.The converting direct-current voltage into alternating-current voltage that solar-energy photo-voltaic cell, wind-driven generator etc. export is connected to the grid by power electronic equipment.First power switch pipe Q1 forms first brachium pontis (A phase brachium pontis) as upper pipe and the second power switch pipe Q2 as lower pipe, 3rd power switch pipe Q3 forms second brachium pontis (B phase brachium pontis) as upper pipe and the 4th power switch pipe Q4 as lower pipe, 5th power switch pipe Q5 forms the 3rd brachium pontis (C phase brachium pontis) as upper pipe and the 6th power switch pipe Q6 as lower pipe, and above-mentioned three-phase bridge knee-joint is in the two ends of direct voltage.

The points of common connection of the first power switch pipe Q1 and the second power switch pipe Q2 exports as A phase brachium pontis, and connect one end of first line equivalent resistance R1, the other end of R1 is connected with one end of the first filter inductance L1, and the other end of L1 connects a phase line voltage; The points of common connection of the 3rd power switch pipe Q3 and the 4th power switch pipe Q4 exports as B phase brachium pontis, and connect one end of the second line equivalent resistance R2, the other end of R2 is connected with one end of the second filter inductance L2, and the other end of L2 connects b phase line voltage; The points of common connection of the 5th power switch pipe Q5 and the 6th power switch pipe Q6 exports as C phase brachium pontis, and connect one end of tertiary circuit equivalent resistance R3, the other end of R3 is connected with one end of the 3rd filter inductance L3, and the other end of L3 connects c phase line voltage.One end of first filter capacitor C1 is connected with c phase line voltage, and one end of the second filter capacitor C2 is connected with b phase line voltage, and one end of the 3rd filter capacitor C3 is connected with a phase line voltage; The other end of the first filter capacitor C1, the second filter capacitor C2 and the 3rd filter capacitor C3 links together.

As shown in Figure 2, be the schematic diagram of three-phase grid-connected inverter control system embodiment of the present invention.In the present embodiment, three-phase grid-connected inverter control system comprises voltage sampling unit 22, current sampling unit 21, first computing unit 23, k value table memory cell, k value acquiring unit 24, second computing unit 25 and PWM wave producer 26.Above-mentioned voltage sampling unit 22, current sampling unit 21, first computing unit 23, k value table memory cell, k value acquiring unit 24, second computing unit 25 and PWM wave producer 26 can be made up of multiple different hardware, also can be made up of the software based on same hardware.

Voltage sampling unit 22 obtains three-phase power grid voltage instantaneous value e for sampling _a, e _b, e _c, and phase relation is e _aadvanced e _b, e _badvanced e _c.Current sampling unit 21 obtains the output current instantaneous value i of inverter three-phase brachium pontis for sampling _a, i _b, i _c.

First computing unit 23 is for the three-phase power grid voltage instantaneous value e obtained that samples according to above-mentioned voltage sampling unit 22 _a, e _b, e _c, current sampling unit 21 samples the output current instantaneous value i of inverter three-phase brachium pontis obtained _a, i _b, i _ccalculate inverter three-phase brachium pontis reference voltage and output current amplitude.

Particularly, the three-phase power grid voltage instantaneous value that first this first computing unit 23 uses formula (1) to obtain sampling, after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtains d, q axle component e of three-phase power grid voltage _d, e _q; And the output current instantaneous value of the inverter three-phase brachium pontis using formula (2) sampling to be obtained is after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtains d, q axle component i of three-phase output current _d, i _q.

$\left[\begin{array}{c}{e}_d\\ e_q\end{array}\right]=\frac{2}{3}\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\·\left[\begin{array}{ccc}1& -1/2& -1/2\\ 0& \sqrt{3}/2& -\sqrt{3}/2\end{array}\right]\·\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right]---\left(1\right)$

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\frac{2}{3}\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\·\left[\begin{array}{ccc}1& -1/2& -1/2\\ 0& \sqrt{3}/2& -\sqrt{3}/2\end{array}\right]\·\left[\begin{array}{c}{i}_A\\ i_B\\ i_C\end{array}\right]---\left(2\right)$

Wherein θ is the synchronous rotary angle based on grid voltage orientation.

Then, the first computing unit 23 is according to d, q axle component e of three-phase power grid voltage _d, e _q, d, q axle component i of three-phase output current _d, i _q, the given i of reactive current _d ^*and the given i of active current _q ^*, through formula (3) idle/uneoupled control of active power after, obtain d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _q.

$\left\{\begin{array}{c}{v}_d=\frac{L}{T_c}(i_d^{*}-i_d)-\mathrm{\ω}{\mathrm{Li}}_q+{\mathrm{Ri}}_d+e_d\\ v_q=\frac{L}{T_c}(i_q^{*}-i_q)+\mathrm{\ω}{\mathrm{Li}}_d+{\mathrm{Ri}}_q+e_q\end{array}\right.---\left(3\right)$

Wherein R is line equivalent resistance, L is filter inductance, ω is electrical network angular frequency.

Finally, the first computing unit 23 is by d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _qafter the two-phase rotational coordinates of formula (4) is tied to the inverse transformation of three-phase static coordinate system, obtain the three-phase brachium pontis reference voltage v of inverter _a ^*, v _b ^*, v _c ^*.

$\left[\begin{array}{c}{v_A}^{*}\\ {v_B}^{*}\\ {v_C}^{*}\end{array}\right]=\frac{2}{3}\left[\begin{array}{cc}1& 0\\ -1/2& \sqrt{3}/2\\ -1/2& -\sqrt{3}/2\end{array}\right]\·\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\·\left[\begin{array}{c}{v}_d\\ v_q\end{array}\right]---\left(\text{4}\right)$

First computing unit 23 is also according to the output current instantaneous value i of the inverter three-phase brachium pontis of current sampling unit 21 sampling acquisition _a, i _b, i _ccalculate output current amplitude I _s.

K value table memory cell is for storing k value table, and this k value table comprises the k value corresponding to output current instantaneous value of different output current amplitude, three-phase brachium pontis reference voltage, inverter three-phase brachium pontis, and wherein k value is 0 or 1.K value acquiring unit 24 obtains k value according to the output current instantaneous value inquiry k value table of output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis.When specific implementation, above-mentioned k value table memory cell can be arranged in k value acquiring unit 24.

The k value that second computing unit 25 obtains for tabling look-up according to k value acquiring unit 24 calculates zero-sequence component.Particularly, this second computing unit 25 calculates zero-sequence component v by formula (5) _z ^*, wherein v _max ^*for any time v _a ^*, v _b ^*, v _c ^*maximum, v _min ^*for any time v _a ^*, v _b ^*, v _c ^*minimum value.

v _z ^*＝-kv _max ^*-(1-k)v _min ^*+(2k-1) (5)

Wherein v _max ^*=max{v _a ^*, v _b ^*, v _c ^*, v _min ^*=min{v _a ^*, v _b ^*, v _c ^*.

PWM wave producer 26 is for injecting three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis by zero-sequence component.Particularly, the zero-sequence component v that first will calculate of PWM wave producer 26 _z ^*respectively with inverter three-phase brachium pontis reference voltage v _a ^*, v _b ^*, v _c ^*be added, try to achieve the reference voltage v of unitized discontinuous modula tion _a ^*, v _b ^*, v _c ^*, as shown in formula (6); Then by the reference voltage v of unitized discontinuous modula tion _a ^*, v _b ^*, v _c ^*crossingly with bipolarity triangle carrier signal respectively namely obtain pwm switching signal corresponding to three-phase inverter three brachium pontis.

$\left\{\begin{array}{c}{v_A}^{**}={v_A}^{*}+{v_z}^{*}\\ {v_B}^{**}={v_B}^{*}+{v_z}^{*}\\ {v_C}^{**}={v_C}^{*}+{v_z}^{*}\end{array}\right.---\left(6\right)$

In above-mentioned three-phase grid-connected inverter control system, in k value table, when described output current amplitude is between 0 to the first setting current amplitude, k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When output current amplitude sets between current amplitude at the first setting current amplitude to the second, the magnitude relationship between k value to three-phase brachium pontis reference voltage is relevant; When output current amplitude is greater than between the second setting current amplitude, k value is relevant to the size of each value in three-phase brachium pontis reference voltage.As shown in table 1, be an example of k value table.

Table 1 k value is shown

In above-mentioned table 1, the first setting current amplitude is the inverter output current amplitude that inverter leg side power-factor angle is corresponding when equaling 30 degree; Second setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 75 degree.Particularly, the first setting current amplitude and the second setting current amplitude calculate by following formula (7) and obtain inverter leg side power-factor angle inverter output current amplitude I corresponding when equaling 30 degree, 75 degree respectively _s30, I _s75:

Wherein E _sfor known grid voltage amplitude, R be line equivalent resistance, L is filter inductance, ω is electrical network angular frequency.

As shown in Figure 3, be the schematic diagram of three-phase grid-connected inverter control method embodiment of the present invention, the method comprises the following steps:

Step S31: sampling obtains the output current instantaneous value of three-phase power grid voltage instantaneous value and sampling acquisition inverter three-phase brachium pontis.

Step S32: the output current instantaneous value according to described three-phase power grid voltage instantaneous value, inverter three-phase brachium pontis calculates three-phase brachium pontis reference voltage and output current amplitude.

This step calculates except output current amplitude except comprising according to the output current instantaneous value of inverter three-phase brachium pontis, specifically also can comprise: the three-phase power grid voltage instantaneous value first obtained sampling, after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtains d, q axle component e of three-phase power grid voltage _d, e _q; And by the output current instantaneous value of the inverter three-phase brachium pontis obtained of sampling after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtain d, q axle component i of three-phase output current _d, i _q; Secondly according to d, q axle component e of three-phase power grid voltage _d, e _q, d, q axle component i of three-phase output current _d, i _q, the given i of reactive current _d ^*and the given i of active current _q ^*, through formula (3) idle/uneoupled control of active power after, obtain d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _q; Then by d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _qafter the inverse transformation that two-phase rotational coordinates is tied to three-phase static coordinate system, obtain the three-phase brachium pontis reference voltage v of inverter _a ^*, v _b ^*, v _c ^*.

Step S33: the output current instantaneous value inquiry k value table according to described output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis obtains k value, and this k value is 0 or 1.

In above-mentioned k value table, when output current amplitude is between 0 to the first setting current amplitude, k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When output current amplitude sets between current amplitude at the first setting current amplitude to the second, the magnitude relationship between k value to three-phase brachium pontis reference voltage is relevant; When output current amplitude is greater than between the second setting current amplitude, k value is relevant to the size of each value in three-phase brachium pontis reference voltage.Particularly, above-mentioned first setting current amplitude can be inverter output current amplitude corresponding when inverter leg side power-factor angle equals 30 degree; Second setting current amplitude can be inverter output current amplitude corresponding when inverter leg side power-factor angle equals 75 degree.

Step S34: and calculate zero-sequence component according to k value.Particularly, in this step, zero-sequence component vz is calculated by above-mentioned formula (5) ^*.

Step S35: zero-sequence component is injected three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis.Particularly, the zero-sequence component v first will calculated _z ^*respectively with inverter three-phase brachium pontis reference voltage v _a ^*, v _b ^*, v _c ^*be added, try to achieve the reference voltage v of unitized discontinuous modula tion _a ^*, v _b ^*, v _c ^*, as shown in formula (6); Then by the reference voltage v of unitized discontinuous modula tion _a ^*, v _b ^*, v _c ^*crossingly with bipolarity triangle carrier signal respectively namely obtain pwm switching signal corresponding to three-phase inverter three brachium pontis.

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

Claims (10)

1. a three-phase grid-connected inverter control system, is characterized in that: comprise voltage sampling unit, current sampling unit, the first computing unit, k value table memory cell, k value acquiring unit, the second computing unit and PWM wave producer, wherein:

Described voltage sampling unit, obtains three-phase power grid voltage instantaneous value for sampling;

Described current sampling unit, for the output current instantaneous value obtaining inverter three-phase brachium pontis of sampling;

Described first computing unit, calculates inverter three-phase brachium pontis reference voltage and output current amplitude for the output current instantaneous value according to described three-phase power grid voltage instantaneous value, inverter three-phase brachium pontis;

Described k value table memory cell, for storing k value table, described k value table comprises the k value corresponding to output current instantaneous value of different inverter three-phase brachium pontis output current amplitudes, three-phase brachium pontis reference voltage, inverter three-phase brachium pontis, and described k value is 0 or 1;

Described k value acquiring unit, obtains k value for the output current instantaneous value inquiry k value table according to described output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis;

Described second computing unit, for calculating zero-sequence component according to described k value;

Described PWM wave producer, for injecting three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis by described zero-sequence component.

2. three-phase grid-connected inverter control system according to claim 1, is characterized in that: described second computing unit is by following formulae discovery zero-sequence component v _z ^*:

v _z ^*＝-kv _max ^*-(1-k)v _min ^*+(2k-1)，

Wherein v _max ^*=max{v _a ^*, v _b ^*, v _c ^*, v _min ^*=min{v _a ^*, v _b ^*, v _c ^*, v _a ^*, v _b ^*, v _c ^*for inverter three-phase brachium pontis reference voltage.

3. three-phase grid-connected inverter control system according to claim 1 and 2, it is characterized in that: in described k value table, when described output current amplitude is between 0 to the first setting current amplitude, described k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When described output current amplitude sets between current amplitude at the first setting current amplitude to the second, described k value puts in order relevant to the size of inverter each phase brachium pontis reference voltage; When described output current amplitude is greater than the second setting current amplitude, described k value is relevant to the size of each value in three-phase brachium pontis reference voltage.

4. three-phase grid-connected inverter control system according to claim 3, is characterized in that: described first setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 30 degree; Described second setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 75 degree.

5. a three-phase grid-connected inverter control method, is characterized in that: comprise the following steps:

A () sampling obtains the output current instantaneous value of three-phase power grid voltage instantaneous value and sampling acquisition inverter three-phase brachium pontis;

B () calculates inverter three-phase brachium pontis reference voltage and output current amplitude according to the output current instantaneous value of described three-phase power grid voltage instantaneous value, inverter three-phase brachium pontis;

C () obtains k value according to the output current instantaneous value inquiry k value table of described output current amplitude and three-phase brachium pontis reference voltage or output current amplitude and inverter three-phase brachium pontis, and calculate zero-sequence component according to described k value, and described k value is 0 or 1;

D described zero-sequence component is injected three-phase brachium pontis reference voltage to generate the pwm switching signal of three-phase brachium pontis by ().

6. three-phase grid-connected inverter control method according to claim 5, is characterized in that: in described step (c), by following formulae discovery zero-sequence component v _z ^*:

v _z ^*＝-kv _max ^*-(1-k)v _min ^*+(2k-1)，

Wherein v _max ^*=max{v _a ^*, v _b ^*, v _c ^*, v _min ^*=min{v _a ^*, v _b ^*, v _c ^*, v _a ^*, v _b ^*, v _c ^*for inverter three-phase brachium pontis reference voltage.

7. three-phase grid-connected inverter control method according to claim 5, it is characterized in that: in described k value table, when described output current amplitude is between 0 to the first setting current amplitude, described k value is relevant to the size of each value in the output current instantaneous value of inverter three-phase brachium pontis; When described output current amplitude sets between current amplitude at the first setting current amplitude to the second, described k value puts in order relevant to the size of inverter each phase brachium pontis reference voltage; When described output current amplitude is greater than the second setting current amplitude, described k value is relevant to the size of each value in three-phase brachium pontis reference voltage.

8. three-phase grid-connected inverter control method according to claim 7, is characterized in that: described first setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 30 degree; Described second setting current amplitude is the inverter output current amplitude that described inverter leg side power-factor angle is corresponding when equaling 75 degree.

9. the three-phase grid-connected inverter control method according to any one of claim 5-8, is characterized in that: described step (b) comprising:

(b1) the three-phase power grid voltage instantaneous value obtained sampling, after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtains d, q axle component e of three-phase power grid voltage _d, e _q; And by the output current instantaneous value of the inverter three-phase brachium pontis obtained of sampling after three-phase static coordinate system to the linear transformation of two-phase rotating coordinate system, obtain d, q axle component i of three-phase output current _d, i _q;

(b2) according to d, q axle component e of three-phase power grid voltage _d, e _q, d, q axle component i of three-phase output current _d, i _q, the given i of reactive current _d ^*and the given i of active current _q ^*, after the uneoupled control of idle/active power, obtain d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _q;

(b3) by d, q axle component v of inverter three-phase brachium pontis reference voltage _d, v _qafter the inverse transformation that two-phase rotational coordinates is tied to three-phase static coordinate system, obtain inverter three-phase brachium pontis reference voltage v _a ^*, v _b ^*, v _c ^*.

10. three-phase grid-connected inverter control method according to claim 6, is characterized in that: d, q axle component v of the reference voltage of inverter three-phase brachium pontis described in described step (b2) _d, v _qobtained by following formulae discovery:

$\left\{\begin{array}{c}{v}_d=\frac{L}{T_c}(i_d^{*}-i_d)-\mathrm{\ω}{\mathrm{Li}}_q+{\mathrm{Ri}}_d+e_d\\ v_q=\frac{L}{T_c}(i_q^{*}-i_q)+\mathrm{\ω}{\mathrm{Li}}_d+{\mathrm{Ri}}_q+e_q\end{array}\right.,$ Wherein R is line equivalent resistance, L is filter inductance, ω is electrical network angular frequency, T _cfor switch periods.