CN104158222A - Grid-connected inverter direct power control method with voltage compensation - Google Patents

Abstract

The invention discloses a grid-connected inverter direct power control method with voltage compensation. According to the method, in combination with a state observer, the defects that parameter changes of the characteristic matrix of a traditional state observer are not considered, and influences on an observation result by the input deviation of the traditional state observer are not considered are overcome. A state observer based on an inner model is adopted for obtaining an accurate observation state quantity, a controlled object is transformed through state feedback, and then the network access current of a grid-connected inverter is controlled; meanwhile, by the adoption of the direct power control method, network side power can be controlled in real time; on the premise that the cost is not increased, the fluctuation magnitude of bus capacitor voltage is decreased, and circuit stability is improved.

Description

A kind of combining inverter direct Power Control method of compensation with voltage

Technical field

The invention belongs to grid converter control technology, be specifically related to a kind of combining inverter direct Power Control method of compensation with voltage.

Background technology

Along with the continuous application of the renewable resources such as photovoltaic generation, wind power generation, seawave power generation, distributed generation system becomes the emphasis of Recent study, is subject to extensive concern.Combining inverter is as the key components of renewable energy system, and its control performance directly affects and network electric energy quality and grid connection efficiency.

In order to realize sine-converter, DC bus-bar voltage need keep relative stability in a rational level.The too high withstand voltage properties to device (bus capacitor, inverse switch pipe etc.) of DC bus-bar voltage requires just high, and cost increases greatly; DC bus-bar voltage is too low, may cause SPWM modulation ratio to be greater than 1, can not realize sine-converter.For parallel networking type photovoltaic inverter, the stable balance that depends on DC source input electric energy and inversion output electric energy of DC bus-bar voltage, accomplish that actual DC source input electric energy is greater than inversion output electric energy, and busbar voltage raises, otherwise busbar voltage reduces.But, accomplish that actual DC source input power is very difficult with the complete equipilibrium that exchanges power output, this be because: 1, DC source input current is periodically pulsing direct current, processor sampling instant difference, the electric current obtaining is also different, and the DC source input power calculating according to this sample rate current is also different; 2, when inverter is worked, owing to there being multiple power electronic devices, for example insulated gate bipolar transistor or mos field effect transistor, more than being operated in thousands of hertz frequencies, measuring circuit is easily subject to the interference of switching noise, and the measurement result of DC source input voltage or current signal easily produces error; 3, in circuit, device for power switching can produce loss, and this loss is not definite value, is difficult to determine.So in fact parallel networking type photovoltaic inverter DC source input electric energy and inversion output electric energy are difficult to guarantee rigorous equilibrium, in this case, DC bus-bar voltage just has fluctuation.In existing control strategy for inverter, there is scholar to propose to utilize the method for its networking electric current of inverter leg Current Indirect Control, the method has been improved the stability of system, but can not ensure the current waveform quality that networks.Subsequently, a lot of scholars begin one's study and adopt two closed loop control methods of direct networking Current Control, and outer shroud adopts networking current closed-loop, and interior ring adopts respectively the Damping Schemes such as capacitor current feedback, capacitance voltage feedback, brachium pontis current closed-loop.Above-mentioned pair of close-loop control scheme, suppresses system oscillation by interior ring, improves the stability of a system; But in each scheme there is coupling in inner and outer ring design, affects system control performance; And these schemes need to increase extra transducer, increase system hardware cost.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides a kind of combining inverter direct Power Control method of compensation with voltage, do not increasing under the prerequisite of extra cost, reducing the amplitude of bus capacitor voltage fluctuation, improving the stability of circuit.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

A kind of combining inverter direct Power Control method of compensation with voltage, the combining inverter control structure relating to comprises connected successively DC power supply, booster circuit, inverter bridge, filter and electrical network, between booster circuit and inverter bridge, be connected with bus capacitor, bus capacitor is connected across between two outputs of the circuit boosting; It is characterized in that: the method comprises the steps:

(1) utilize current sensor to detect current on line side i _l2, utilize voltage sensor senses electrical network electromotive force e _{a, b, c}, calculate phase angle theta by phase-locked loop pll;

(2) based on current on line side i _l2with electrical network electromotive force e _{a, b, c}, obtain observation state amount by the state observer based on inner membrance, comprising: observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

(3) according to observation bridge arm voltage with observation brachium pontis electric current calculate instantaneous active power p and instantaneous reactive power q;

(4) based on observation DC bus-bar voltage given with DC bus-bar voltage obtain the given p of active power by generatrix voltage compensation ^*;

(5) to instantaneous active power p and the given p of active power ^*make the poor active power error signal e that obtains _p=p ^*-p, to instantaneous reactive power q and the given q of reactive power ^*make the poor reactive power error signal e that obtains _q=q ^*-q;

(6) by pi regulator to active power error signal e _pwith reactive power error signal e _qcarry out closed-loop process, then convert and obtain voltage control signal in conjunction with phase angle theta through dq/ α β with

(7) pass through voltage control signal with obtain the control signal U of the SVPWM of inverter bridge _i.

Concrete, the course of work of the state observer based on inner membrance in described step (2) comprises the steps:

(21) select DC bus-bar voltage U _dc, electrical network electromotive force e _{a, b, c}with current on line side i _l2as quantity of state, by electrical network electromotive force e _{a, b, c}with current on line side i _l2as input variable, utilize formula (1) to obtain grid-connected inverter system discrete state space equation:

$\left\{\begin{array}{c}x(k+1)=A_{d}x\left(k\right)+B_{d}u\left(k\right)\\ y\left(k\right)=C_{d1}x\left(k\right)+D_{d}u\left(k\right)\end{array}\right.---\left(1\right)$

Wherein: A _dfor grid-connected inverter system eigenmatrix, B _dfor grid-connected inverter system input matrix, C _d1for grid-connected inverter system output matrix, D _dfor grid-connected inverter system directly transmits matrix;

X (k) represents quantity of state, comprises DC bus-bar voltage U _dc, electrical network electromotive force e _{a, b, c}with current on line side i _l2;

X (k+1) is the quantity of state through a bat time delay;

U (k) is grid-connected inverter system input variable, comprises electrical network electromotive force e _{a, b, c}with current on line side i _l2;

Y (k) is grid-connected inverter system output variable, comprises observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

(22), according to grid-connected inverter system discrete state space equation, consider respectively grid-connected inverter system eigenmatrix variable quantity △ A _dwith grid-connected inverter system input variable deviation △ u (k), by the principle of duality, through type (2) obtains the state observer state space equation based on inner membrance:

$\left\{\begin{array}{c}\hat{x}(k+1)={\hat{A}}_d\hat{x}\left(k\right)+{\hat{B}}_d{u}^{\′}\left(k\right)+G(1+{\mathrm{\φ}}_e^{-1}\left(z\right))[y\left(k\right)-\hat{y}\left(k\right)]\\ \hat{y}\left(k\right)={\hat{C}}_{d1}\hat{x}\left(k\right)+{\hat{D}}_{d}u\left(k\right)\end{array}\right.---\left(2\right)$

Wherein: for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for state observer directly transmits matrix;

represent observer state amount, comprise observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

for the observer state amount through a bat time delay;

U'(k) be state observer input variable, comprise electrical network electromotive force e _{a, b, c}with current on line side i _l2;

G is the feedback matrix of state observer;

for state observer output variable, comprise observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

for state observer output error;

for internal mold item.

Concrete, when state observer eigenmatrix when parameter changes, through type (1) and formula (2) obtain observation error △ x ₁for:

Wherein: for considering state observer eigenmatrix the internal mold item arranging when parameter changes; (a) part in formula (3) reaches 0 value by expected pole assignment method, and formula (3) is by (b) part setting, make (b) part and (c) part the two and reach 0 value, finally make error △ x ₁reach 0 value.

Further, in described formula (3) according to state observer output error be set to First-order Integral link or ratio resonance link.

Concrete, as state observer input variable u'(k) while there is deviation, through type (1) and formula (2) obtain observation error △ x ₂for:

Wherein: for state observer input variable u'(k) the internal mold item that arranges while there is deviation; (d) part in formula (4) reaches 0 value by expected pole assignment method, and formula (4) is by (e) part setting, make (e) part and (f) part the two and reach 0 value, finally make error △ x ₂reach 0 value.

Further, in described formula (4) according to state observer output error be set to First-order Integral link or ratio resonance link.

Concrete, in described step (3), the computational methods of instantaneous active power p and instantaneous reactive power q are as follows:

P＝P _a+P _b+P _c＝U _ai _L1acosθ _a+U _bi _L1bcosθ _b+U _ci _L1ccosθ _c

P＝Q _a+Q _b+Q _c＝U _ai _L1asinθ _a+U _bi _L1bsinθ _b+U _ci _L1csinθ _c

Wherein: U _a, U _b, U _cfor the effective value of each phase phase voltage; i _l1a, i _l1b, i _l1cfor the effective value of each phase phase current; θ _a, θ _b, θ _cfor each phase phase voltage phase angle more leading than phase current, the i.e. impedance angle of each phase load.

Concrete, the given p of active power in described step (4) ^*obtain by following method: will with after comparing, be added and obtain with the DC source input power of the zero hour in inversion cycle; Wherein: U _dcfor bus capacitor voltage, C is bus capacitor.

Beneficial effect: the combining inverter direct Power Control method of compensation with voltage provided by the invention, bonding state observer, overcome traditional state observer and do not considered that state observer eigenmatrix parameter changes and the deficiency of the impact of state observer input deviation on observation effect, adopt a kind of state observer based on inner membrance to obtain observer state amount accurately, transform controlled device by state feedback, and then carry out combining inverter networking Current Control; Meanwhile, the present invention adopts direct Power Control method, can realize net side power is controlled in real time; The present invention is not increasing under the prerequisite of extra cost, has reduced the amplitude of bus capacitor voltage fluctuation, has improved the stability of circuit.

Brief description of the drawings

Fig. 1 is the control structure figure of combining inverter of the present invention;

Fig. 2 is the state observer structure chart based on inner membrance;

Fig. 3 is the hardware configuration schematic diagram of combining inverter.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

Be a kind of combining inverter direct Power Control method of compensation with voltage as shown in Figure 1, Figure 2 and Figure 3, the combining inverter control structure relating to comprises connected successively DC power supply, booster circuit, inverter bridge, filter and electrical network, between booster circuit and inverter bridge, be connected with bus capacitor, bus capacitor is connected across between two outputs of the circuit boosting; It is characterized in that: the method comprises the steps:

(1) utilize current sensor to detect current on line side i _l2, utilize voltage sensor senses electrical network electromotive force e _{a, b, c}, calculate phase angle theta by phase-locked loop pll;

(2) based on current on line side i _l2with electrical network electromotive force e _{a, b, c}, obtain observation state amount by the state observer based on inner membrance, comprising: observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

(3) according to observation bridge arm voltage with observation brachium pontis electric current calculate instantaneous active power p and instantaneous reactive power q;

(4) based on observation DC bus-bar voltage given with DC bus-bar voltage obtain the given p of active power by generatrix voltage compensation ^*;

(5) to instantaneous active power p and the given p of active power ^*make the poor active power error signal e that obtains _p=p ^*-p, to instantaneous reactive power q and the given q of reactive power ^*make the poor reactive power error signal e that obtains _q=q ^*-q;

(6) by pi regulator to active power error signal e _pwith reactive power error signal e _qcarry out closed-loop process, then convert and obtain voltage control signal in conjunction with phase angle theta through dq/ α β with

(7) pass through voltage control signal with obtain the control signal U of the SVPWM of inverter bridge _i.

Be illustrated with regard to specific embodiment of the invention process below.

The course of work of the state observer based on inner membrance in step (2) is described as follows.

Choose quantity of state, comprise DC bus-bar voltage U _dc, electrical network electromotive force e _{a, b, c}with current on line side i _l2, note x=[i _l1u _dcu _{a, b, c}] ^t; Choose input variable, comprise electrical network electromotive force e _{a, b, c}with current on line side i _l2, note u=[i _l2e _{a, b, c}] ^t; Setting up grid-connected inverter system state-space model is:

$\left\{\begin{array}{c}x=\mathrm{Ax}+\mathrm{Bu}\\ y=\mathrm{Cx}+\mathrm{Du}\end{array}\right.$

Wherein: A is grid-connected inverter system eigenmatrix, B is grid-connected inverter system input matrix, and C is grid-connected inverter system output matrix, and D is that grid-connected inverter system directly transmits matrix.

For the ease of digital control, rotation proportion f _s=10kHz, utilizes the discretization method of zero-order holder, by continuous state equation discretization, obtains combining inverter discrete state space equation and is:

$\left\{\begin{array}{c}x(k+1)=A_{d}x\left(k\right)+B_{d}u\left(k\right)\\ y\left(k\right)=C_{d1}x\left(k\right)+D_{d}u\left(k\right)\end{array}\right.---\left(1\right)$

Wherein: A _dfor grid-connected inverter system eigenmatrix, B _dfor grid-connected inverter system input matrix, C _d1for grid-connected inverter system output matrix, D _dfor grid-connected inverter system directly transmits matrix; X (k) is discretization quantity of state, and x (k)=[i _l1(k) U _dc(k) U _{a, b, c}(k)] ^t, i _l1(k) be discrete domain brachium pontis electric current, U _dc(k) be discrete domain DC bus-bar voltage, U _{a, b, c}(k) be discrete domain bridge arm voltage; X (k+1) is the quantity of state through a bat time delay; U (k)=[i _l2(k) e _{a, b, c}(k)] ^t, i _l2(k) be discrete domain current on line side, e _{a, b, c}(k) be discrete domain electrical network electromotive force; Y (k) is grid-connected inverter system output variable.

According to grid-connected inverter system discrete state space equation, consider respectively grid-connected inverter system eigenmatrix variable quantity △ A _dwith grid-connected inverter system input variable deviation △ u (k), by the principle of duality, obtain the state observer state space equation based on inner membrance:

$\left\{\begin{array}{c}\hat{x}(k+1)={\hat{A}}_d\hat{x}\left(k\right)+{\hat{B}}_d{u}^{\′}\left(k\right)+G(1+{\mathrm{\φ}}_e^{-1}\left(z\right))[y\left(k\right)-\hat{y}\left(k\right)]\\ \hat{y}\left(k\right)={\hat{C}}_{d1}\hat{x}\left(k\right)+{\hat{D}}_{d}u\left(k\right)\end{array}\right.---\left(2\right)$

Wherein: for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for state observer directly transmits matrix; represent observer state amount, comprise observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage for the observer state amount through a bat time delay; U'(k) be state observer input variable, the feedback matrix that G is state observer; for state observer output variable, for state observer output error; for internal mold item.

When state observer eigenmatrix when parameter changes, through type (1) and formula (2) obtain observation error △ x ₁for:

Wherein: for considering state observer eigenmatrix the internal mold item arranging when parameter changes; (a) part in formula (3) reaches 0 value by expected pole assignment method, and formula (3) is by (b) part setting, make (b) part and (c) part the two and reach 0 value, finally make error △ x ₁reach 0 value.In formula (3) according to state observer output error be set to First-order Integral link or ratio resonance link.

As state observer input variable u'(k) while there is deviation, through type (1) and formula (2) obtain observation error △ x ₂for:

Wherein: for state observer input variable u'(k) the internal mold item that arranges while there is deviation; (d) part in formula (4) reaches 0 value by expected pole assignment method, and formula (4) is by (e) part setting, make (e) part and (f) part the two and reach 0 value, finally make error △ x ₂reach 0 value.In formula (4) according to state observer output error be set to First-order Integral link or ratio resonance link.

In step (3), the computational methods of instantaneous active power p and instantaneous reactive power q are as follows:

P＝P _a+P _b+P _c＝U _ai _L1acosθ _a+U _bi _L1bcosθ _b+U _ci _L1ccosθ _c

P＝Q _a+Q _b+Q _c＝U _ai _L1asinθ _a+U _bi _L1bsinθ _b+U _ci _L1csinθ _c

Wherein: U _a, U _b, U _cfor the effective value of each phase phase voltage; i _l1a, i _l1b, i _l1cfor the effective value of each phase phase current; θ _a, θ _b, θ _cfor each phase phase voltage phase angle more leading than phase current, the i.e. impedance angle of each phase load.

The given p of active power in step (4) ^*obtain by following method: will with after comparing, be added and obtain with the DC source input power of the zero hour in inversion cycle; Wherein: U _dcfor bus capacitor voltage, C is bus capacitor.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (8)

1. the combining inverter direct Power Control method of a compensation with voltage, the combining inverter control structure relating to comprises connected successively DC power supply, booster circuit, inverter bridge, filter and electrical network, between booster circuit and inverter bridge, be connected with bus capacitor, bus capacitor is connected across between two outputs of the circuit boosting; It is characterized in that: the method comprises the steps:

(1) utilize current sensor to detect current on line side i _l2, utilize voltage sensor senses electrical network electromotive force e _{a, b, c}, calculate phase angle theta by phase-locked loop pll;

(2) based on current on line side i _l2with electrical network electromotive force e _{a, b, c}, obtain observation state amount by the state observer based on inner membrance, comprising: observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

(3) according to observation bridge arm voltage with observation brachium pontis electric current calculate instantaneous active power p and instantaneous reactive power q;

(4) based on observation DC bus-bar voltage given with DC bus-bar voltage obtain the given p of active power by generatrix voltage compensation ^*;

(5) to instantaneous active power p and the given p of active power ^*make the poor active power error signal e that obtains _p=p ^*-p, to instantaneous reactive power q and the given q of reactive power ^*make the poor reactive power error signal e that obtains _q=q ^*-q;

(6) by pi regulator to active power error signal e _pwith reactive power error signal e _qcarry out closed-loop process, then convert and obtain voltage control signal in conjunction with phase angle theta through dq/ α β with

(7) pass through voltage control signal with obtain the control signal U of the SVPWM of inverter bridge _i.

2. the combining inverter direct Power Control method of compensation with voltage according to claim 1, is characterized in that: the course of work of the state observer based on inner membrance in described step (2) comprises the steps:

(21) select DC bus-bar voltage U _dc, electrical network electromotive force e _{a, b, c}with current on line side i _l2as quantity of state, by electrical network electromotive force e _{a, b, c}with current on line side i _l2as input variable, utilize formula (1) to obtain grid-connected inverter system discrete state space equation:

$\left\{\begin{array}{c}x(k+1)=A_{d}x\left(k\right)+B_{d}u\left(k\right)\\ y\left(k\right)=C_{d1}x\left(k\right)+D_{d}u\left(k\right)\end{array}\right.---\left(1\right)$

Wherein: A _dfor grid-connected inverter system eigenmatrix, B _dfor grid-connected inverter system input matrix, C _d1for grid-connected inverter system output matrix, D _dfor grid-connected inverter system directly transmits matrix;

X (k) represents quantity of state, comprises DC bus-bar voltage U _dc, electrical network electromotive force e _{a, b, c}with current on line side i _l2;

X (k+1) is the quantity of state through a bat time delay;

U (k) is grid-connected inverter system input variable, comprises electrical network electromotive force e _{a, b, c}with current on line side i _l2;

Y (k) is grid-connected inverter system output variable, comprises observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

(22), according to grid-connected inverter system discrete state space equation, consider respectively grid-connected inverter system eigenmatrix variable quantity △ A _dwith grid-connected inverter system input variable deviation △ u (k), by the principle of duality, through type (2) obtains the state observer state space equation based on inner membrance:

$\left\{\begin{array}{c}\hat{x}(k+1)={\hat{A}}_d\hat{x}\left(k\right)+{\hat{B}}_d{u}^{\′}\left(k\right)+G(1+{\mathrm{\φ}}_e^{-1}\left(z\right))[y\left(k\right)-\hat{y}\left(k\right)]\\ \hat{y}\left(k\right)={\hat{C}}_{d1}\hat{x}\left(k\right)+{\hat{D}}_{d}u\left(k\right)\end{array}\right.---\left(2\right)$

Wherein: for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for state observer directly transmits matrix;

represent observer state amount, comprise observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

for the observer state amount through a bat time delay;

U'(k) be state observer input variable, comprise electrical network electromotive force e _{a, b, c}with current on line side i _l2;

G is the feedback matrix of state observer;

for state observer output variable, comprise observation brachium pontis electric current observation DC bus-bar voltage with observation bridge arm voltage

for state observer output error;

for internal mold item.

3. the combining inverter direct Power Control method of compensation with voltage according to claim 2, is characterized in that: when state observer eigenmatrix when parameter changes, through type (1) and formula (2) obtain observation error △ x ₁for:

Wherein: for considering state observer eigenmatrix the internal mold item arranging when parameter changes; (a) part in formula (3) reaches 0 value by expected pole assignment method, and formula (3) is by (b) part setting, make (b) part and (c) part the two and reach 0 value, finally make error △ x ₁reach 0 value.

4. the combining inverter direct Power Control method of compensation with voltage according to claim 3, is characterized in that: in described formula (3) according to state observer output error be set to First-order Integral link or ratio resonance link.

5. the combining inverter direct Power Control method of compensation with voltage according to claim 2, it is characterized in that: as state observer input variable u'(k) while there is deviation, through type (1) and formula (2) obtain observation error △ x ₂for:

Wherein: for state observer input variable u'(k) the internal mold item that arranges while there is deviation; (d) part in formula (4) reaches 0 value by expected pole assignment method, and formula (4) is by (e) part setting, make (e) part and (f) part the two and reach 0 value, finally make error △ x ₂reach 0 value.

6. the combining inverter direct Power Control method of compensation with voltage according to claim 5, is characterized in that: in described formula (4) according to state observer output error be set to First-order Integral link or ratio resonance link.

7. the combining inverter direct Power Control method of compensation with voltage according to claim 1, is characterized in that: in described step (3), the computational methods of instantaneous active power p and instantaneous reactive power q are as follows:

P＝P _a+P _b+P _c＝U _ai _L1acosθ _a+U _bi _L1bcosθ _b+U _ci _L1ccosθ _c

P＝Q _a+Q _b+Q _c＝U _ai _L1asinθ _a+U _bi _L1bsinθ _b+U _ci _L1csinθ _c

Wherein: U _a, U _b, U _cfor the effective value of each phase phase voltage; i _l1a, i _l1b, i _l1cfor the effective value of each phase phase current; θ _a, θ _b, θ _cfor each phase phase voltage phase angle more leading than phase current, the i.e. impedance angle of each phase load.

8. the combining inverter direct Power Control method of compensation with voltage according to claim 1, is characterized in that: the given p of active power in described step (4) ^*obtain by following method: will with after comparing, be added and obtain with the DC source input power of the zero hour in inversion cycle; Wherein: U _dcfor bus capacitor voltage, C is bus capacitor.