CN100514831C - Grid-connected inverter current control method employing inductance current weighted average value to feed back - Google Patents

Abstract

The invention discloses an interconnected de-to-ac converter current controlling means, which comprises the following steps: using two current transducer to check inversion side series inductance and current of net side seies inductance; using weighted average of two-phase current as feedback signal controlled by inversion outgoing current; comparing with the given signal controlled by live wire entanglement current; inputting the proportional-inte-gral controller into error signal; using outcoming signal adjusted by the proportion integral for antecedence switch operated pulse duration modulation signal; controlling outgoing current waveform and amplitude of interconnected de-to-ac converter, wherein the weight value of two inductance currents in feedback signal is the ratio of inductance value and two inductance whole inductance value. The invention can improve the resistance of electrified wire netting aberration and harmonic disturbance, which inhibits electrified wire netting current waveform distortion factor and harmonic content.

Description

Adopt the parallel inverter current control method of inductive current weighted average feedback

Technical field

The present invention relates to the combining inverter control method, especially adopt the parallel inverter current control method of inductive current weighted average feedback.

Background technology

Inverter with the operation function that generates electricity by way of merging two or more grid systems, its circuit such as Fig. 1 (a), (b) shown in, generally include the single-phase or three-phase inverter of PWM (pulse width modulation) control based on HF switch, be used for the LCL low pass filter that inversion grid connection connects operation, the current transducer that is used for current detecting, be used for the current regulator and the switch driving circuit that contain current error calculating and error signal proportional and integral controller that inverter is incorporated into the power networks, inverter is output current control when being incorporated into the power networks, and is the sinusoidal wave of strictness and has higher generated output factor to guarantee electric current.Traditional current control method is a feedback signal with the inversion side inductive current (being inverter output current) or the grid side inductive current (power network current) of LCL low pass filter mostly, and modes such as employing proportional integral do to regulate the also operation of control inverter to error signal.Because it is third-order system that the filter of LCL structure makes controlling object, near the filter corner frequency, there is very big gain spike, for guaranteeing system stability, the gain of proportional and integral controller is restricted, value is less, thereby make system less, limited the inhibition ability of system output current steady-state error and harmonic wave in the open-loop gain of low-frequency range.This method also is subject to the influence of line voltage distortion and Harmonic Interference.

Summary of the invention

The purpose of this invention is to provide a kind of stable state amplitude and phase error that under the control of satisfying system stability requires, reduces output current, enhancing is to the resistivity of electrical network distortion and Harmonic Interference, the parallel inverter current control method that the employing filter intermediate current of restriction power network current waveform distortion and harmonic content feeds back.

The parallel inverter current control method of employing inductive current weighted average feedback of the present invention, it is characterized in that at the single-phase or three-phase inverter of pulse width modulation control that comprises based on HF switch, be used for the LCL type low pass filter that inversion grid connection connects operation, the current transducer that is used for current detecting, be used for that inverter is incorporated into the power networks to contain electric current weighting average, in the combining inverter circuit of the current regulator of Error Calculation and error signal proportional and integral controller and switch driving circuit, adopt two current transducers to detect respectively to flow through the electric current of inversion side series inductance and net side series inductance, and with the weighted average of these two electric currents feedback signal as inverter output current control, compare with the given signal of the control of power network current, relatively the error signal of back output is imported proportional and integral controller, with the pulse width modulating signal of the output signal after the proportional integral adjusting as the inverse switch operation, the output current wave and the amplitude of control combining inverter, wherein the weights of two inductive currents in feedback signal are the ratio of inductance value and two inductance total inductance amounts separately.

The present invention adopts the parallel inverter current control method of inductive current weighted average feedback to realize the stable output of combining inverter, and make controlling object transform first-order system as by third-order system originally approx, can realize the high performance control of power-supply system output current.Test shows that in the power-supply system of 5kW power, the line voltage distortion factor surpasses under 5% service conditions, and the distortion factor of the output current that is incorporated into the power networks is less than 3%, and power factor is greater than 0.99.

Control method simple possible of the present invention, than traditional control method, only need to increase a current transducer and detect electric current, is that weights are weighted average computation with inversion outlet side inductive current and two signals of grid side inductive current with the ratio of each self-inductance in total inductance, promptly obtains new Current Control feedback signal.When control ring designs, still adopt traditional proportional integral (PI) to regulate, but because the present invention is to the transformation of system's Control current feedback signal, make the characteristic of controlling object of current regulator be similar to the first-order system of single inductor filter, can design and adopt proportional plus integral control easily, when guaranteeing system stability, can select for use than direct inverter output current feedback or the directly bigger proportional gain of control mode of power network current feedback, thereby obtain stable output, less steady-state error and better dynamic response characteristic.Adopt this technology can make the output current waveform distortion degree of grid-connected system lower, harmonic content is little, phase accuracy is higher, and line voltage distortion and background harmonics disturbed have stronger resistivity, the distortion of inhibition power network current.Finally make grid-connected system obtain higher power factor and good output current wave.

The present invention is applicable to that with semiconductor device such as MOSFET, IGBT be power switch, adopts the three-phase or the single-phase grid-connected operation inverter of various forms PWM control, is used for the various power-supply systems that are incorporated into the power networks such as solar energy, wind-force, fuel cell power generation.

Description of drawings

Fig. 1 (a) is that traditional employing inverter output current is the combining inverter circuit diagram of feedback control signal;

Fig. 1 (b) is that traditional employing power network current is the combining inverter circuit diagram of feedback control signal;

Fig. 2 is a kind of physical circuit legend that adopts the combining inverter of the inventive method;

Fig. 3 is the characteristic comparison diagram that adopts the inventive method and conventional method control grid-connected system; Wherein figure (a) is the gain characteristic curve of parallel network reverse power-supply system; Figure (b) is the system circuit gain curve that has comprised the proportional integral conditioning controller.

Embodiment

Shown in Figure 2 is the combining inverter circuit that adopts the inventive method, it comprises that pulse width modulation (PWM) control single-phase inverter 1 based on HF switch is (in the legend, single-phase inverter is the voltage-source type semibridge system, employing IGBT is a power switch), be used for the low pass filter 2 that inversion grid connection connects operation, be used for two current transducers 3 that inversion side inductive current detects and the grid side inductive current detects, be used for current regulator 4 and switch driving circuit 5 that inverter is incorporated into the power networks, wherein current regulator 4 contains the electric current weighting average computation, Error Calculation, circuit takes place in error signal proportional and integral controller and PWM.

Parallel inverter current control method of the present invention is: the electric current that adopts two current transducers to detect respectively to flow through inversion side series inductance L1 and net side series inductance L2, it is the electric current of two series inductances of LCL filter, and with the weighted average of these two electric currents feedback signal as current regulator, relatively obtain error signal with given current signal, by proportional integral (PI) adjuster error signal is done to obtain the PWM modulation signal after proportional integral is regulated, circuit and the operation of switch driving circuit control inverter take place by PWM in the PWM modulation signal, realize the output current wave of inversion grid connection electricity generation system and the closed-loop control of amplitude.Wherein the weights of two inductive currents in feedback signal are the ratio of inductance value and two inductance total inductance amounts separately.

Inverter adopts Current Control PWM mode to move among the present invention, the HF switch frequency component of output current is suppressed under the effect of LCL filter effectively, and the stability of output fundametal compoment and the inhibition of steady-state error and low-frequency harmonics then are decided by the closed-loop control of output current.By the change of filter and feedback signal, make the control characteristic of power-supply system change, the parameter of pi regulator also correspondingly can be improved, and reaches better closed-loop control characteristic.

Adopt the power-supply system characteristic contrast of the inventive method and conventional method control:

With a 5kW power-supply system is example, for the inverter output current feedback, referring to Fig. 1 (a), feedback current (i ₁) with respect to inverter output voltage V _iGain can be expressed as:

$\frac{I_1\left(s\right)}{V_i\left(s\right)}=\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+1}{s(L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}$

Its amplitude and phase characteristic are shown in Fig. 3 (a) curve 1.

For the power network current feedback, referring to Fig. 1 (b), feedback current (i ₂) with respect to inverter output voltage V _iGain can be expressed as:

$\frac{I_2\left(s\right)}{V_i\left(s\right)}=\frac{1}{s(L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}$

Its amplitude and phase characteristic are shown in Fig. 3 (a) curve 2.

Curve 1 and curve 2 show that there is very big gain spike in the system gain when adopting traditional inverter output current feedback and current on line side FEEDBACK CONTROL between 1kHz and 2kHz;

The inventive method adopts the weighted average of LCL two inductive currents as feedback signal, referring to Fig. 2, and feedback current (i _f) with respect to inversion out-put supply V _iGain can be expressed as:

$\frac{I_f\left(s\right)}{V_i\left(s\right)}=\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+1}{s(L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">W</figure-callout>}}_1+\frac{1}{s(L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">W</figure-callout>}}_2$

If the electric current weighting value is chosen as the ratio of each self-inductance and total inductance amount, i.e. W ₁=L ₁/ (L ₁+ L ₂), W ₂=L ₂/ (L ₁+ L ₂), then following formula can be converted into:

$\frac{I_f\left(s\right)}{V_i\left(s\right)}=\frac{({\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+1){\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2}{s(L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="2"\; label="Cs"\; filenames="C200610050624E00082.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}$

After the simplification

$\frac{I_f\left(x\right)}{V_i\left(s\right)}=\frac{1}{s({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610050624E00071.png,C200610050624E00082.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}$

Therefore adopt the system gain characteristic curve of parallel network reverse power supply of the present invention will become straight line, shown in Fig. 3 (a) curve 3, the gain spike no longer occurs.

When the design proportion integral controller, at first should satisfy the requirement of system stability, promptly the phase deviation of cross-over frequency place should be less than 180 degree on the 0dB line for loop gain.Next is that the low-frequency range loop gain should be big as far as possible, and corner frequency is higher, with the stable state accuracy and the dynamic response characteristic of raising system output.Fig. 3 (b) is for having comprised the current closed-loop control system loop gain characteristic Bode diagram of proportional and integral controller, wherein curve 1 is the traditional inverter output current feedback loop gain characteristic shown in Fig. 1 (a), curve 2 is the traditional power network current feedback loop gain characteristic shown in Fig. 1 (b), and curve 3 is a LCL filter inductance electric current weighting mean value feedback loop gain characteristic of the present invention.Because there is not spike in feedback control system loop gain of the present invention, under the requirement of guaranteeing system's control stabilization, can select bigger proportional and integral controller gain, system is obviously improved in the gain of low-frequency range, thereby strengthened the current error inhibition ability of (comprising fundamental voltage amplitude error, phase error and low-frequency harmonics component) during closed-loop control.

Claims (1)

1. adopt the parallel inverter current control method of inductive current weighted average feedback, it is characterized in that the combining inverter circuit comprises the single-phase or three-phase inverter of pulse width modulation control based on HF switch, be used for the LCL type low pass filter that inversion grid connection connects operation, the current transducer that is used for current detecting, be used for current regulator and switch driving circuit that inverter is incorporated into the power networks, wherein, being used for current regulator that inverter is incorporated into the power networks, to contain electric current weighting average, Error Calculation and error signal proportional and integral controller, in above-mentioned combining inverter circuit, adopt two current transducers to detect respectively to flow through the electric current of inversion side series inductance (L1) and net side series inductance (L2), and with the weighted average of these two electric currents feedback signal as inverter output current control, compare with the given signal of the control of power network current, relatively the error signal of back output is imported proportional and integral controller, with the pulse width modulating signal of the output signal after the proportional integral adjusting as the inverse switch operation, the output current wave and the amplitude of control combining inverter, wherein the weights of two inductive currents in feedback signal are the ratio of inductance value and two inductance total inductance amounts separately.

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