CN103401459B - Triangularly connected chain H bridge suspended type inverter interphase DC side voltage balancing control method - Google Patents

Abstract

The invention discloses a triangularly connected chain H bridge suspended type inverter interphase DC side voltage balancing control method. The method is based on combination of zero sequence current injection and split phase control and comprises overall DC side voltage control, interphase DC side balancing control and phase DC side balancing control. Each phase modulating voltage output by the overall DC side voltage control is corrected via each phase modulating wave correction required by interphase balance output by the interphase DC side voltage balancing control, as a result, output voltage modulating wave of each phase is obtained, then the output voltage modulating wave of each unit is obtained via the phase DC side balancing control, and finally, pulse signals of each switch component are generated via a wave carrier phase-shifting PWM (Pulse-width Modulation) module. According to the method, three phases are comprehensively considered, the DC side balancing control is performed by adopting different methods under different conditions, and the method has great significance in application of large-scale network connection and large-scale energy storage of a triangularly connected chain H bridge network connecting inverter and matched renewable resources.

Description

The alternate dc-voltage balance control method of chain H bridge direct hanging type inverter that a kind of triangle connects

Technical field

The invention belongs to the applied technical field of high-voltage and high-power power electronic technology in electric power system, relate to the chain H bridge direct hanging type DC side voltage of converter balance control method be connected with the triangle of zero-sequence current injection method based on individual-phase control method.

Background technology

In recent years, along with the development of new forms of energy, H bridge cascade structure becomes the focus of research in fields such as parallel network reverse, energy storage, electric power electric transformers, it has great importance for cooperation regenerative resource large-scale grid connection, extensive energy storage and enhancing stability of power system.

The combining inverter of this type can access high-voltage fence by transformer-free, structure is easy to modular implementation, and there is comparatively low switching losses and harmonic wave, but there is parallel connection type loss and mixed type differential loss and pulse delay difference in each H bridge DC side separate in its structure, there is the factors such as Voltage unbalance in the electrical network connected, this just causes the unbalanced problem of DC voltage.Compared to cascade connection type STATCOM (STATCOM) occasion that engineer applied is comparatively ripe, cascade connection type combining inverter equivalence can become the device of heavy load or current source owing to existing in DC side, self may cause larger uneven difference, this causes very large impact by the output performance of device and reliability.

The dc-voltage balance of chain H bridge inverter controls to be achieved by the method increasing additional hardware circuit and control, but the method is at increase cost with while strengthening system complexity, also reduces the reliability of device.In software approach, alternate DC side balance for star structure controls, document is had to propose the method injecting residual voltage, negative sequence voltage, negative-sequence current, but the characteristic of triple line current coupling is different from triangular structure in star structure, thus these methods are not suitable for triangular structure.Have the research having carried out individual-phase control method for STATCOM, but be different from STATCOM, what combining inverter mainly exported is active current, and the method can cause serious three-phase phase current uneven, thus pollutes electrical network.Also the control method proposed for the injection zero-sequence current of triangular form structure is had, the energy exchange between each single-phase chain inverter can be realized when keeping three-phase phase current balance, thus reach the object of alternate DC side balance, but the method regulating power is limited, and reckon without the unbalanced impact of grid side.

Summary of the invention

Goal of the invention: for above-mentioned Problems existing, the object of the invention is to propose a kind of chain H bridge direct hanging type DC side voltage of converter balance control method be connected with the triangle of zero-sequence current injection method based on individual-phase control method, the method can select different balance control methods according to different situations, improves the output performance of device and alternate power adjustments ability.

Technical scheme: the alternate dc-voltage balance control method of chain H bridge direct hanging type inverter that a kind of triangle connects, comprises the steps:

1) overall DC voltage control:

1.1) gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate the mean value that in three-phase, all H-bridge unit DC voltages are total

1.2) by described average voltage and instruction average voltage after comparing, through proportional integral computing, obtain instruction active current value

1.3) positive sequence component decomposited in the line voltage of the electric power system be connected with inverter and line current is converted through abc-dq phase coordinates obtain

1.4) to described and described instruction active current value adopt forward-order current decoupling control method, obtain each phase modulation voltage

2) alternate DC side balance controls:

2.1) gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate each phase H-bridge unit DC voltage mean value by described average voltage respectively with step 1.1) described in average voltage through proportional integral computing after comparing, obtain each active power Δ P needing to adjust mutually _aB, Δ P _bC, Δ P _cA;

2.2) by described Δ P _aB, Δ P _bC, Δ P _cAcarry out abc-α β to convert, obtain Δ P _α, Δ P _β;

2.3) to described Δ P _α, Δ P _βrevise, offset the power that electrical network negative sequence voltage produces, obtain revised Δ P ' _α, Δ P ' _β;

2.4) positive and negative zero sequence decomposition is carried out, the line voltage obtained according to described decomposition and line current dq axle component to the line voltage of the electric power system be connected with inverter and line current with described Δ P ' _α, Δ P ' _β, the command value calculating individual-phase control method is respectively zero-sequence current I ₀, θ ₀with negative-sequence current I _n, θ _n, the command value of zero-sequence current injection method is zero-sequence current I ' ₀, θ ' ₀;

2.5) command value under negative phase-sequence dq0 coordinate is calculated adopt zero-sequence current injection method to calculate negative phase-sequence dq0 coordinate to give an order value cause ovennodulation according to described zero-sequence current injection method, then adopt individual-phase control method to calculate described command value detailed process is as follows:

By step 2.4) the described zero-sequence current command value I ' that obtains ₀, θ ' ₀with actual line electric current negative sequence component through switching discriminant computing output logic amount, export as " 1 " choice for use zero-sequence current injection method according to described amount of logic, amount of logic exports as " 0 " choice for use individual-phase control method; Described switching discriminant is:

$|\stackrel{\&RightArrow;}{e}-\mathrm{j\&omega;L}({\stackrel{\&RightArrow;}{i}}^P+{\stackrel{\&RightArrow;}{i}}_0^{\&prime;})|<U_{\mathrm{DC}}^{\max }$

Wherein, for line voltage vector, for line current positive sequence vector, for the zero-sequence current vector that zero-sequence current injection method generates, for the maximum voltage amplitude that single-phase chain link can export, L is the inductance between each phase chain link of DC-to-AC converter and electric power system;

2.6) command value under described negative phase-sequence dq0 coordinate is utilized and the line voltage of electric power system and line current are carried out positive and negative zero sequence and are decomposed the dq axle component obtained carry out negative-sequence current uneoupled control, and obtain each phase modulating wave correction needed for alternate balance through dq0-abc coordinate transform

2.7) described each phase modulating wave correction is utilized to described step 1) in each phase modulation voltage of obtaining compare correction, obtain the output voltage modulating wave of final each phase

3) interior DC side balance controls mutually:

3.1) according to the output voltage modulating wave of described each phase draw every mutually in the output voltage modulating wave u of each H bridge inverter unit _abi, u _bci, u _cai;

3.2) by described voltage modulated ripple u _abi, u _bci, u _caiby the pulse signal of each switching device of phase-shifting carrier wave PWM CMOS macro cell.

Beneficial effect: (1) this method mainly relies on software simulating, can conveniently realize, without the need to configuring hardware power and the voltage balancing circuit of additional complexity;

(2) this method adopts individual-phase control method and zero-sequence current injection method to combine, the differentiation switching of two kinds of methods ensure that the output of device does not occur ovennodulation, prevent and occur the problems such as harmonic wave is excessive, output performance and the regulating power of device are taken into account, not only there is stronger regulating power to DC voltage, and ensure that there is not larger pollution to electrical network and affects the compensation performance of device;

(3) algorithm adopts dq rotating coordinate system, and the realization of algorithm, can the fine astatic control that must realize current on line side than more fast simple and convenient under rest frame;

(4) this method is power system voltage, all includes negative sequence component and zero-sequence component in the model set up of electric current, has taken into full account the unbalanced factor from grid side, has added the control to electrical network negative-sequence current and zero-sequence current.

Accompanying drawing explanation

Fig. 1 is the cascade combining inverter structure chart that triangle connects;

Fig. 2 is master control block diagram;

Fig. 3 is overall DC voltage control block diagram;

Fig. 4 is alternate DC side balance control block diagram, and wherein (a) is alternate balancing instructions value generation block diagram, and (b) is negative phase-sequence and zero-sequence current control block diagram;

Fig. 5 is changing method realization figure.

Embodiment

Below in conjunction with accompanying drawing the present invention done and further explain.

The present invention is used for the chain H bridge direct hanging type DC side voltage of converter balance that triangle connects and controls, and Fig. 1 is the cascade combining inverter structure chart that triangle connects, and to be wherein respectively single-phasely in series by N number of H-bridge unit respectively, adopts triangle to connect between three-phase.

As shown in Figure 2, each phase modulation voltage of overall DC side voltage control module output each phase modulating wave correction needed for the alternate balance exported by alternate dc-voltage balance control module revise, thus obtain the output voltage modulating wave of each phase the output voltage modulating wave u of unit is drawn again by DC side balance control module in mutually _abi, u _bci, u _cai, finally by the pulse signal of each switching device of phase-shifting carrier wave PWM CMOS macro cell.

The alternate dc-voltage balance control method of chain H bridge direct hanging type inverter that triangle connects, the method comprises the steps:

1) overall DC voltage control:

1.1) gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate the mean value that in three-phase, all H-bridge unit DC voltages are total

1.2) as described in Figure 3, by described average voltage and instruction average voltage after comparing, through proportional integral computing, obtain instruction active current value

1.3) positive sequence component decomposited in system line voltage and line current is obtained through the conversion of abc-dq phase coordinates wherein, system line voltage and line current, not containing zero-sequence component, with voltage positive sequence component for reference, are defined as follows by the line voltage of electric power system:

$\left\{\begin{array}{c}{i}_{\mathrm{AB}}=\sqrt{2}{I}_p\sin \left(\mathrm{\&omega;t}\right)+\sqrt{2}{I}_n\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_n)+\\ \sqrt{2}{I}_0\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_o)\\ i_{\mathrm{BC}}=\sqrt{2}{I}_p\sin (\mathrm{\&omega;t}-\frac{2}{3}\mathrm{\&pi;})+\sqrt{2}{I}_n\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_n+\frac{2}{3}\mathrm{\&pi;})+\\ \sqrt{2}{I}_o\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_o)\\ i_{\mathrm{CA}}=\sqrt{2}{I}_p\sin (\mathrm{\&omega;t}+\frac{2}{3}\mathrm{\&pi;}+)+\sqrt{2}{I}_n\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_n-\frac{2}{3}\mathrm{\&pi;})+\\ \sqrt{2}{I}_0\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_o)\end{array}\right.---\left(2\right)$

Wherein: e _pfor line voltage positive sequence component, e _nfor line voltage negative order components, ω is 2 π * 50, for the phase angle of negative sequence voltage, I _pfor line current positive sequence component, I _nfor line current negative sequence component, I _ofor line current zero-sequence component, θ _n, θ _obe respectively the phase angle of negative phase-sequence and zero sequence line current;

1.4) to described and described instruction active current value adopt forward-order current decoupling control method, obtain each phase modulation voltage

2) alternate DC side balance controls:

2.1) as shown in Fig. 4 (a), gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate each phase H-bridge unit DC voltage mean value by described average voltage respectively with step 1.1) described in average voltage through proportional integral computing after comparing, obtain each active power Δ P needing to adjust mutually _aB, Δ P _bC, Δ P _cA;

Suppose for each mutually in identical real component, for the real component that negative sequence voltage produces, for the real component that zero-sequence current produces, for the real component that negative-sequence current produces, then each phase active power $P=\stackrel{\&OverBar;}{P}+{\mathrm{\&Delta;P}}_n^e+{\mathrm{\&Delta;P}}_n^I+{\mathrm{\&Delta;P}}_0^I,$ After active power three be each mutually variable active power Δ P, be expressed as:

Wherein: e _pfor line voltage positive sequence component, e _nfor line voltage negative order components, ω is 2 π * 50, for the phase angle of negative sequence voltage, I _pfor line current positive sequence component, i _nfor line current negative sequence component, I _ofor line current zero-sequence component, θ _n, θ _obe respectively the phase angle of negative phase-sequence and zero sequence line current;

Three-phase variable active power Δ P _aB, Δ P _bC, Δ P _cAsum is zero, the imbalance of illustrative system voltage and inject active power that zero sequence and negative-sequence current produce and can not have an impact to total meritorious of three-phase, and can by adjustment I _n, I ₀, θ _n, θ ₀size each single-phase active power is regulated, thus reach the object of DC voltage between equilibrium phase;

2.2) by variable for described three-phase active power Δ P _aB, Δ P _bC, Δ P _cAcarry out abc-α β to convert, obtain Δ P _α, Δ P _β;

2.3) to described Δ P _α, Δ P _βrevise the power of offsetting electrical network negative sequence voltage and producing, obtain revised Δ P ' _α, Δ P ' _β;

2.4) as shown in Fig. 4 (b), positive and negative zero sequence decomposition is carried out, the line voltage obtained according to described decomposition and line current dq axle component to the line voltage of electric power system and line current with described Δ P ' _α, Δ P ' _β, the command value calculating individual-phase control method is respectively zero-sequence current I ₀, θ ₀with negative-sequence current I _n, θ _n, the command value of zero-sequence current injection method is zero-sequence current I ' ₀, θ ' ₀;

Wherein, in individual-phase control method, each regulated quantity computational methods are:

$\left\{\begin{array}{c}{I}_n=I_o\\ {\mathrm{\&theta;}}_n=-{\mathrm{\&theta;}}_o\end{array}\right.---\left(6\right)$

$I_o=\frac{\sqrt{X^2+Y^2}}{{4e}_p^2-e_n^2}---\left(7\right)$

${\mathrm{\&theta;}}_o=\left\{\begin{array}{cc}{\tan }^{-1}\frac{Y}{X}+g(-X)& X\&NotEqual;0\\ -\frac{\mathrm{\&pi;}}{2}\mathrm{sign}\left(Y\right)& X=0\end{array}\right.---\left(8\right)$

Wherein:

$g\left(x\right)=\left\{\begin{array}{cc}0& x>0\\ \mathrm{\&pi;}& x<0\end{array}\right.---\left(9\right)$

Wherein, in zero-sequence current injection method, each regulated quantity computational methods are:

$I_o^{\&prime;}=\frac{\sqrt{X^{\&prime;2}+Y^{\&prime;2}}}{e_p^2-e_n^2}---\left(12\right)$

${\mathrm{\&theta;}}_o^{\&prime;}=\left\{\begin{array}{cc}{\tan }^{-1}\frac{Y^{\&prime;}}{X^{\&prime;}}+g(-X^{\&prime;})& X^{\&prime;}\&NotEqual;0\\ -\frac{\mathrm{\&pi;}}{2}\mathrm{sign}\left(Y^{\&prime;}\right)& X^{\&prime;}=0\end{array}\right.---\left(13\right)$

Wherein:

2.5) command value under negative phase-sequence dq0 coordinate is calculated adopt zero-sequence current injection method to calculate negative phase-sequence dq0 coordinate to give an order value cause ovennodulation according to described zero-sequence current injection method, then adopt individual-phase control method to calculate described command value detailed process is as follows:

By step 2.4) the zero-sequence current command value I ' that obtains ₀, θ ' ₀with actual line electric current negative sequence component through switching discriminant (16) computing output logic amount, export as " 1 " choice for use zero-sequence current injection method according to amount of logic, amount of logic exports as " 0 " choice for use individual-phase control method; Switch discriminant whether causes ovennodulation according to zero-sequence current injection method, this switching discriminant is:

$|\stackrel{\&RightArrow;}{e}-\mathrm{j\&omega;L}({\stackrel{\&RightArrow;}{i}}^P+{\stackrel{\&RightArrow;}{i}}_0^{\&prime;})|<U_{\mathrm{DC}}^{\max }---\left(16\right)$

As shown in Figure 5, if discriminant is set up, discriminant link output logic amount is 1, is 0 after inverter, the amount namely exported and if discriminant is false, discriminant link output logic amount is 0, then $I_d^{n*}=I_n\cos {\mathrm{\&theta;}}_n,$ $I_q^{n*}=-I_n\sin {\mathrm{\&theta;}}_n,$ $i_o^{*}=i_o=I_o\sin (\mathrm{\&omega;t}+{\mathrm{\&theta;}}_o);$

Wherein, for line voltage vector, for line current positive sequence vector, for the zero-sequence current vector that zero-sequence current injection method generates, for the maximum voltage amplitude that single-phase chain link can export, L is the inductance between each phase chain link of DC-to-AC converter and electric power system;

2.6) command value under described negative phase-sequence dq0 coordinate is utilized and the line voltage of electric power system and line current are carried out positive and negative zero sequence and are decomposed the dq axle component obtained carry out negative-sequence current uneoupled control, and obtain each phase modulating wave correction needed for alternate balance through dq0-abc coordinate transform

2.7) described each phase modulating wave correction is utilized to described step 1) in each phase modulation voltage of obtaining compare correction, obtain the output voltage modulating wave of final each phase

3) interior DC side balance controls mutually:

3.1) according to the output voltage modulating wave of described each phase draw the output voltage modulating wave u of unit _abi, u _bci, u _cai;

3.2) by described voltage modulated ripple u _abi, u _bci, u _caiby the pulse signal of each switching device of phase-shifting carrier wave PWM CMOS macro cell.

The above is only the preferred embodiment of the present invention; it should be pointed out 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 (1)

1. the alternate dc-voltage balance control method of chain H bridge direct hanging type inverter of triangle connection, it is characterized in that, the method comprises the steps:

1) overall DC voltage control:

1.1) gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate the mean value that in three-phase, all H-bridge unit DC voltages are total

1.2) by mean value total for described DC voltage and instruction average voltage after comparing, through proportional integral computing, obtain instruction active current value

1.3) positive sequence component decomposited in the line voltage of the electric power system be connected with inverter and line current is converted through abc-dq phase coordinates obtain

1.4) to described and described instruction active current value adopt forward-order current decoupling control method, obtain each phase modulation voltage

2) alternate DC side balance controls:

2.1) gather each phase chain H bridge direct hanging type inverter direct-flow side total voltage, calculate each phase H-bridge unit DC voltage mean value by described average voltage respectively with step 1.1) described in the total mean value of DC voltage through proportional integral computing after comparing, obtain each active power △ P needing to adjust mutually _aB, △ P _bC, △ P _cA;

2.2) by described △ P _aB, △ P _bC, △ P _cAcarry out abc-ab conversion, obtain △ P _a, △ P _b;

2.3) to described △ P _a, △ P _brevise, offset the power that electrical network negative sequence voltage produces, obtain revised △ P ' _a, △ P ' _b;

2.4) positive and negative zero sequence decomposition is carried out, the line voltage obtained according to described decomposition and line current dq axle component to the line voltage of the electric power system be connected with inverter and line current with described △ P ' _a, △ P ' _b, the command value calculating individual-phase control method is respectively zero-sequence current I ₀, θ ₀with negative-sequence current I _n, θ _n, the command value of zero-sequence current injection method is zero-sequence current I ' ₀, θ ' ₀; Wherein, θ ₀, θ _n, θ ' ₀be current phase angle;

2.5) command value under negative phase-sequence dq0 coordinate is calculated adopt zero-sequence current injection method to calculate negative phase-sequence dq0 coordinate to give an order value cause ovennodulation according to described zero-sequence current injection method, then adopt individual-phase control method to calculate described command value detailed process is as follows:

By step 2.4) the described zero-sequence current command value I ' that obtains ₀, θ ' ₀with actual line electric current negative sequence component through switching discriminant computing output logic amount, export as " 1 " choice for use zero-sequence current injection method according to described amount of logic, amount of logic exports as " 0 " choice for use individual-phase control method; Described switching discriminant is:

$|\stackrel{\&RightArrow;}{e}-\mathrm{j\&omega;L}({\stackrel{\&RightArrow;}{i}}^P+{\stackrel{\&RightArrow;}{i}}_0^{\&prime;})|<U_{\mathrm{DC}}^{\max }$

Wherein, for line voltage vector, for line current positive sequence vector, for the zero-sequence current vector that zero-sequence current injection method generates, for the maximum voltage amplitude that single-phase chain link can export, L is the inductance between each phase chain link of DC-to-AC converter and electric power system;

2.6) command value under described negative phase-sequence dq0 coordinate is utilized and the line voltage of electric power system and line current are carried out positive and negative zero sequence and are decomposed the dq axle component obtained carry out negative-sequence current uneoupled control, and obtain each phase modulating wave correction needed for alternate balance through dq0-abc coordinate transform

2.7) described each phase modulating wave correction is utilized to described step 1) in each phase modulation voltage of obtaining compare correction, obtain the output voltage modulating wave of final each phase

3) interior DC side balance controls mutually:

3.1) according to the output voltage modulating wave of described each phase draw every mutually in the output voltage modulating wave u of each H bridge inverter unit _abi, u _bci, u _cai;

3.2) by described voltage modulated ripple u _abi, u _bci, u _caiby the pulse signal of each switching device of phase-shifting carrier wave PWM CMOS macro cell.