CN101055994A - Integrated control method for the combined network power generation and grid power active filtering - Google Patents

Abstract

Translated fromChinese

一种并网发电和电网电力有源滤波的统一控制方法，采用Park变换将逆变器输出三相电流i_a，i_b，i_c转换到以电网角频率同步旋转的dq坐标系中，该三相电流i_a，i_b，i_c变换为完全解耦的d轴瞬时有功电流i_d和q轴瞬时无功电流i_q。通过独立控制有功电流i_d及无功电流i_q的大小和方向，实现对电网的有功输出和无功补偿。同时对并网逆变器接入点后的三相负荷电流i_La，i_Lb，i_Lc进行Park变换得到i_Ld，i_Lq，检测其所含的d轴谐波电流分量

和q轴谐波电流分量

，把d轴谐波电流分量

和有功电流i_d相加得到d轴总的指令电流i_dref，把q轴谐波电流分量

和无功电流i_q相加得到q轴总的指令电流i_qref，控制该dq轴指令电流i_dref，i_qref可实现对电网的有功输出、无功补偿和谐波抑制。本发明可充分发挥分布式发电的优越性，并大大提高了电网质量。

A unified control method for grid-connected power generation and grid power active filtering, using Park transformation to convert the inverter output three-phase current i_a , i_b , i_c into a dq coordinate system that rotates synchronously with the angular frequency of the grid. The three-phase currents_ia ,_ib ,_ic are transformed into completely decoupled d-axis instantaneous active current_id and q-axis instantaneous reactive current i_q . By independently controlling the size and direction of the active current id and reactive current i_q , the_active output and reactive power compensation to the grid are realized. At the same time, perform Park transformation on the three-phase load currents i_La , i_Lb , and i_Lc behind the grid-connected inverter access point to obtain i_Ld , i_Lq , and detect the d-axis harmonic current components contained in them

and q-axis harmonic current components

, put the d-axis harmonic current component

Add the active current_id to get the total command current_idref of the d-axis, and the harmonic current component of the q-axis

The total command current i_qref of the q-axis is obtained by adding the reactive current i_q , and controlling the command current_idref of the dq-axis, i_qref can realize active power output, reactive power compensation and harmonic suppression to the power grid. The invention can give full play to the advantages of distributed power generation, and greatly improves the quality of the power grid.

Description

Generate electricity by way of merging two or more grid systems and the unified control method of grid power active power filtering

Technical field

The present invention relates to a kind of generating electricity by way of merging two or more grid systems and the control method of grid power active power filtering, particularly the distributed power generation power supply is realized generating electricity by way of merging two or more grid systems and the unified control method of grid power active power filtering.

Background technology

Energy shortage is the significant problem that the world today faces, and it is significant to research and develop high performance distributed power generation power supply.(Distributed Generation DG) refers at user side or near the electricity generation system than low capacity (being generally thousands of watts to tens megawatts) of electricity consumption situ configuration distributed power generation.It has varying duty adjusting function flexibly, can save the power transmission and transformation investment, supports the economical operation of existing power distribution network, is extensive use of characteristics such as regenerative resource.Distributed power generation utilizes generatings such as solar energy, wind-force, miniature gas turbine and fuel cell usually.Combining inverter is the crucial power electronic equipment of distributed power source energy back to electrical network.

Chinese patent 03150908.8 " realize simultaneously generating electricity by way of merging two or more grid systems and electric network reactive compensation integral method ", the solar power plant utilance that influenced by Changes in weather to be caused at parallel network power generation is not high, and frequent arranged side by side and off-the-line action causes system's control difficulty, the shortcoming that the equipment component loss increases and shortens useful life, proposed a kind ofly to realize simultaneously generating electricity by way of merging two or more grid systems and the integral method of electric network reactive compensation, it can be become the direct current of photovoltaic array output delivers on the three-phase 380V AC network by inverter, simultaneously can also realize a certain amount of reactive power compensation, improve the electrical network quality of power supply other reactive load on the local power grid.This control method is significantly improved than the grid-connected control algolithm of common only active power of output, but it does not consider the harmonic wave in the electrical network only to idle compensation the in the electrical network.

Have a large amount of nonlinear-loads in the actual electrical network, they are injected into electrical network with a large amount of harmonic waves.The harm of harmonic wave is very big in the electrical network, it can make the supply power voltage waveform distortion occur and power supply quality is descended, the energy consumption of electric power system increases, the power supply unit lost of life, also can cause electromagnetic interference to power electronic equipment on every side with time-harmonic wave, therefore the harmonic problem of administering in the electrical network seems urgent day by day.(Active Power Filter is to carry out harmonic wave to suppress advanced method APF) and based on the active power filter of electronic power inverter.The basic principle of APF is a detection load electric current at first in real time, calculates the harmonic component that it contained then, and then control inverter sends offset current, offsetting the harmonic component that is contained in the load current, thereby can improve line voltage electric current quality.

Summary of the invention

The present invention seeks at the deficiency in the above-mentioned background technology, proposed to generate electricity by way of merging two or more grid systems and the unified control method of grid power active power filtering, it can be delivered to distributed power source primary side energy on the electrical network by electronic power inverter, can also carry out reactive power compensation and harmonic wave inhibition to the nonlinear-load on the electrical network simultaneously, make line voltage, the electric current at distributed power source access point place all keep sinusoidal, improved grid supply quality greatly.

The present invention adopts instantaneous reactive power theory, using the Park conversion that inverter is exported three-phase current is transformed in the dq coordinate system that rotates synchronously with the electrical network angular frequency, this three-phase current is transformed to full decoupled instantaneous active current of d axle and q axle instantaneous reactive current, just can realize meritorious output and reactive power compensation to electrical network by independent control size and Orientation meritorious, reactive current.Simultaneously the three-phase load electric current behind the combining inverter access point is carried out the Park conversion, detect its contained dq axle harmonic current components then, this harmonic component adds that respectively first-harmonic is gained merit and idle component promptly obtains total dq axle instruction current, just can realize simultaneously that by controlling this instruction current meritorious output, reactive power compensation and harmonic wave to electrical network suppress.

Specific as follows:

(1) usefulness voltage sensor real-time sampling three phase network voltage or wherein a phase line voltage utilize phase-locked loop to obtain the phase place of line voltage, as the phase reference of Current Control, obtain the set-point of active current and reactive current according to instantaneous reactive power;

(2) with the three-phase load electric current behind the current sensor real-time sampling combining inverter access point, detect its contained harmonic component according to harmonic current detecting method, this harmonic current components is added to respectively on the fundamental active current and fundamental reactive current that obtains according to (1), and then obtains total active current command value and referenced reactive current value;

(3) use the three-phase current of current sensor real-time sampling combining inverter output as feedback, this value of feedback and the command value that obtains according to (2) are carried out closed-loop control after relatively, adopt the Direct Current Control method to obtain the required pwm pulse of inverter switching device pipe, make the good trace command electric current of feedback current.

After adopting distributed power source of the present invention to receive electrical network, the system that distributed power source and subsequent transmission line, load are formed presents the linear impedance characteristic to electrical network, when all idle and harmonic wave is all compensated, the line voltage electric current is sine wave and same-phase, present resistance characteristic, thoroughly improved grid supply quality.When the capacity of distributed power source is enough big, the line voltage electric current can be anti-phase, present negative resistance property, distributed power source is described except the needed whole active power of its back loading, reactive power and harmonic power are provided, unnecessary active power feeds back to electrical network.Adopt distributed power source of the present invention to have the advantage of combining inverter and active power filter simultaneously, both can give full play to the superiority of distributed power generation, improved power grid quality again greatly, reduce power transmission and distribution and set up the required sky high cost of active power filter separately, effectively supported the economic and reliable operation of distribution.

The present invention is not only applicable to distributed power source, also is applicable to all by the electric energy that inverter is incorporated into the power networks, and comprises the electric energy that obtains from electrical network.The present invention is equally applicable to all combining inverter topological structures.

Description of drawings

Fig. 1 distributed power generation power supply schematic diagram that is incorporated into the power networks;

Fig. 2 harmonic current detects schematic diagram;

Fig. 3 generates electricity by way of merging two or more grid systems and electrical network APF unifies the control method schematic diagram;

Fig. 4 electrical network A phase voltage current simulations waveform;

Fig. 5 hookup electrical connecting wires figure;

Electrical network A phase voltage current waveform during Fig. 6 DG no-output;

Fig. 7 DG only injects electrical network A phase voltage electric current, the inverter output current when gaining merit;

Fig. 8 DG only carries out the electrical network A phase voltage electric current behind the APF;

Fig. 9 DG carries out APF and the electrical network A phase voltage electric current that injects after gaining merit simultaneously.

Embodiment

Fig. 1 is the distributed power generation power supply schematic diagram that is incorporated into the power networks, prime mover Prime Mover represents the resulting DC power supply of distributed power generation among the figure, both can be the directly direct current of output of photovoltaic cell, fuel cell, also can be the alternating current that internal combustion engine, miniature gas turbine, the diesel engine of rectification sends.Voltage source inverter VSI is connected with electrical network by filter inductance L.LOAD is the load that inserts on the three phase line.e_a, e_b, e_cRepresent three phase network voltage, i_Sa, i_Sb, i_ScRepresent the three phase network output current, v_a, v_b, v_cRepresent the line voltage at distributed power source access point place, i_a, i_b, i_cRepresent the three-phase current of combining inverter output, i_La, i_Lb, i_LcRepresent the three-phase load electric current.

The present invention adopts instantaneous reactive power theory, uses the Park conversion that inverter is exported three-phase current i_a, i_b, i_cBe transformed in the dq coordinate system with the rotation synchronously of electrical network angular frequency this three-phase current i_a, i_b, i_cBe transformed to the full decoupled instantaneous active current i of d axle_dWith q axle instantaneous reactive current i_q, by independent control active current i_dAnd reactive current i_qSize and Orientation, realize meritorious output and reactive power compensation to electrical network.And simultaneously to the three-phase load current i behind the combining inverter access point_La, i_Lb, i_LcCarry out the Park conversion, detect its contained dq axle harmonic current components then

This harmonic component

Add the meritorious and idle component i of first-harmonic respectively_d, i_qPromptly obtain total dq axle instruction current i_Dref, i_Qref, by controlling this instruction current i_Dref, i_QrefJust can realize simultaneously that meritorious output, reactive power compensation and harmonic wave to electrical network suppress.

The instantaneous reactive power theory of three-phase circuit is at first proposed by the safe literary composition of the red wood of Japan in nineteen eighty-three, after this should theory through constantly research is perfect gradually, on a lot of textbooks and document, argumentation is being arranged all.Suppose that the instantaneous voltage electric current in the three-phase symmetrical circuit is respectively e under the abc rest frame_a, e_b, e_cAnd i_a, i_b, i_c, they are transformed in the dq coordinate system that rotates synchronously with the electrical network angular frequency, be respectively:

$\left[\begin{array}{c}{e}_d\\ e_q\end{array}\right]=C\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right]---\left(1\right)$

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]---\left(2\right)$

C is called the Park transformation matrix in the formula, that is:

$C=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})& \sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})\\ -\cos \mathrm{\ωt}& -\cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})& -\cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})\\ \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}\end{array}\right]$

In the dq coordinate system, the instantaneous active power of three-phase circuit and instantaneous reactive power are:

$\left\{\begin{array}{c}p=\frac{3}{2}(e_d{i}_d+e_q{i}_q)\\ q=\frac{3}{2}(e_d{i}_q-e_q{i}_d)\end{array}\right.---\left(3\right)$

Owing to simultaneously electrical network has been carried out active power filtering, so think that line voltage is desirable sine wave.In circuit shown in Figure 1, have following formula to set up:

$\left\{\begin{array}{c}{v}_a=e_a=E\·\sin \left(\mathrm{\ωt}\right)\\ v_b=v_b=E\·\sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})\\ v_c=e_c=E\·\sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})\end{array}\right.---\left(4\right)$

E is the amplitude of electrical network phase voltage in the formula, and it is carried out the Park conversion can get:

$\left\{\begin{array}{c}{e}_d=E\\ e_q=0\end{array}\right.---\left(5\right)$

Wushu (5) substitution formula (3) can get:

$\left\{\begin{array}{c}p=\frac{3}{2}(e_d{i}_d+e_q{i}_q)=\frac{3}{2}{\mathrm{Ei}}_d\\ q=\frac{3}{2}(e_d{i}_q-e_q{i}_d)=\frac{3}{2}{\mathrm{Ei}}_q\end{array}\right.---\left(6\right)$

Formula (6) shows that under the distortionless prerequisite of three phase network voltage, the d shaft current determines the instantaneous active power of three-phase circuit, i_dBe called instantaneous active current component; The instantaneous reactive power of q shaft current decision three-phase circuit, i_qBe referred to as the instantaneous reactive current component, the decoupling zero of realized being incorporated into the power networks active current and reactive current.By independent control i_d, i_qSize and Orientation just can realize meritorious output and reactive power compensation to electrical network.

For the three-phase load current i_La, i_Lb, i_Lc, utilize the Park conversion that it is transformed in the dq coordinate system equally, can get:

$\left[\begin{array}{c}{i}_{\mathrm{Ld}}\\ i_{\mathrm{Lq}}\end{array}\right]=\left[\begin{array}{c}{\stackrel{\‾}{i}}_{\mathrm{Ld}}+{\tilde{i}}_{\mathrm{Ld}}\\ {\stackrel{\‾}{i}}_{\mathrm{Lq}}+{\tilde{i}}_{\mathrm{Lq}}\end{array}\right]=C\begin{array}{c}\left[\begin{array}{c}{i}_{\mathrm{La}}\\ i_{\mathrm{Lb}}\\ i_{\mathrm{Lc}}\end{array}\right]\end{array}\begin{array}{}\end{array}---\left(7\right)$

I in the formula_Ld, i_LqBe DC quantity, represent fundamental active current component and reactive current component in the load current respectively,Be of ac, represent harmonic current components, can realize the detection of harmonic current by method shown in Figure 2.

At first utilize phase-locked loop pll to obtain and electrical network A phase voltage e among Fig. 2_aThe cosine and sine signal sinwt of homophase ,-coswt is then to the three-phase load current i_La, i_Lb, i_LcCarry out the Park conversion to obtain the instantaneous real component i under the dq axle_LdWith instantaneous reactive component i_Lq, after the LPF low-pass filtering, obtain the DC component i that it contains_LdAnd i_Lq, then the instantaneous real component i on the d axle_LdWith DC component i_LdSubtract each other and obtain d axle harmonic current components

Instantaneous reactive component i on the q axle_LqWith DC component i_LqSubtract each other and obtain q axle harmonic current components

Control principle of the present invention at first utilizes phase-locked loop pll to obtain and electrical network A phase voltage e as shown in Figure 3_aThe cosine and sine signal sinwt of homophase ,-coswt, this signal is as Park and Park in the The whole control algorithm^-1The time base of conversion.Obtaining harmonic current components according to the described method of Fig. 2

After, more respectively with the fundamental active current component i that obtains according to formula (6)_dWith fundamental reactive current component i_qAddition so just obtains total dq axle instruction current signal i_Dref, i_QrefObtaining total dq axle instruction current signal i_Dref, i_QrefAfter, can adopt the Direct Current Control method: as stagnating chain rate, triangular wave relatively waits, and obtains pwm pulse, drives VSI and makes feedback current trace command electric current.

The present invention has carried out emulation and test in the laboratory:

1, Matlab emulation

In Matlab/Simulink, utilize Power System Blockset to set up distributed power source grid-connected system model, system parameters is: three-phase 380V AC power, lag behind and trigger thyristor rectifier bridge, rectification load is 10 Ω resistance and the series connection of 10mH inductance, and the combining inverter output inductor is 4mH, internal resistance 0.2 Ω, 630V DC power supply Equivalent Distributed formula power supply, PWM switching frequency 10kHz.Before electrical network A phase voltage that shown in Figure 4 is, current simulations waveform: the 0.06s during phase control rectifier power network current seriously distort and phase lag; 0.06s and carried out APF between the 0.14s, current waveform becomes sine, phase place still lags behind; 0.14s and between the 0.2s when carrying out APF, it is meritorious and 10kVar is idle to have injected 5kW again, electric current and voltage homophase, and amplitude reduces greatly; 0.2s and same when carrying out APF between the 0.24s, it is meritorious and 10kVar is idle, electric current and voltage inversion, the unnecessary meritorious electrical network that feeds back to have injected 20kW.

2, test

Utilize TMS320LF2407ADSP to carry out total digitalization test as processor, the hookup electrical connection diagram as shown in Figure 5, wherein the inverter output inductor is 4mH, internal resistance 0.2 Ω.At three phase network voltage 380V, busbar voltage is stabilized in and does following test under the condition of 630V:

Test one: the electrical network A phase voltage that records during the output of distributed power source no current, current waveform are as shown in Figure 6, and be visible because distortion has to a certain degree also appearred in the non-linear line voltage that caused of electric current.

Test two: distributed power source only has the combining inverter function, the electrical network A phase voltage, electric current and the inverter output current wave that record during output 10kW active power are as shown in Figure 7, as seen the inverter output current has good sine, electrical network is not polluted, but to mains by harmonics without any improvement.Because distributed power source provides part active power, so power network current reduces, has alleviated the burden of electrical network.

Test three: when distributed power source only has the APF function, the electrical network A phase voltage that records, electric current as shown in Figure 8, visible line voltage electric current is sine wave and same-phase, grid supply quality obviously improves.

Test four: distributed power source is except having the APF function, measured electrical network A phase voltage, current waveform were as shown in Figure 9 when 22.4kW active power was provided again, as seen the line voltage electric current is sinusoidal wave and anti-phase, power factor is-1, distributed power source is described except load required active power and harmonic wave are provided, unnecessary active power feeds back to electrical network.

Claims (2)

1, a kind of generating electricity by way of merging two or more grid systems and the unified control method of grid power active power filtering adopts the Park conversion that inverter is exported three-phase current i_a, i_b, i_cBe transformed in the dq coordinate system with the rotation synchronously of electrical network angular frequency this three-phase current i_a, i_b, i_cBe transformed to the full decoupled instantaneous active current i of d axle_dWith q axle instantaneous reactive current i_q, by independent control active current i_dAnd reactive current i_qSize and Orientation, realize meritorious output and reactive power compensation to electrical network, it is characterized in that electrical network gain merit and export and reactive power compensation the time, the three-phase load current i behind the combining inverter access point_La, i_Lb, i_LcCarry out the Park conversion and obtain i_Ld, i_Lq, detect its contained d axle harmonic current components then

With q axle harmonic current components

Then d axle harmonic current componentsWith active current i_dAddition obtains the total instruction current i of d axle_Dref, q axle harmonic current components

With reactive current i_qAddition obtains the total instruction current i of q axle_Qref, control this dq axle instruction current i_Dref, i_QrefCan realize that meritorious output, reactive power compensation and harmonic wave to electrical network suppress.

2, according to claim 1 generating electricity by way of merging two or more grid systems and the unified control method of grid power active power filtering is characterized in that utilizing phase-locked loop pll to obtain and electrical network A phase voltage e_aThe cosine and sine signal sinwt of homophase ,-coswt is as Park and Park in the The whole control algorithm^-1The time base of conversion is to the three-phase load current i_La, i_Lb, i_LcCarry out the Park conversion, obtain the instantaneous real component i under the dq axle_LdWith instantaneous reactive component i_Lq, after the LPF low-pass filtering, obtain the DC component i that it contains_LdAnd i_Lq, then the instantaneous real component i on the d axle_LdWith DC component i_LdSubtract each other and obtain d axle harmonic current components

Instantaneous reactive component i on the q axle_LqWith DC component i_LqSubtract each other and obtain q axle harmonic current componentsD axle harmonic current components

With active current i_dAddition obtains the total instruction current i of d axle_Dref, q axle harmonic current components

With reactive current i_qAddition obtains the total instruction current i of q axle_Qref, adopt the Direct Current Control method to make feedback current trace command electric current then, can realize that meritorious output, reactive power compensation and the harmonic wave to electrical network suppresses.

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