CN103023360B - Single-phase alternating current (AC)/ direct current (DC) converter with secondary fluctuating power decoupling and control method thereof - Google Patents

Abstract

The invention discloses a single-phase alternating current (AC)/ direct current (DC) converter with secondary fluctuating power decoupling and a control method thereof. The converter comprises a network side transformer, a network side filter, an H-bridge circuit and a power decoupling circuit. The network side filter comprises a filter inductor L2 and a filter capacitor C2; and the power decoupling circuit comprises an energy-storing inductor L1, a switch device S5 and a follow-current diode D1. Two terminals P and N are arranged on the direct current side of the single-phase AC/DC converter, and a capacitor C1 is connected between the two terminals in bridging mode. A middle point B of a second bridge arm for connecting a switch device S3 and a switch device S4 in the H-bridge circuit is connected with an emitting pole of the switch device S5 and the cathode of the follow-current diode D1 through the energy-storing inductor L1. The direct current side of the converter only needs to install the capacitor C1 with small capacitance, so that large-capacitance electrolytic capacitors large in size and short in service life in the prior art can be saved. The converter adopts a double closed-loop control method of a direct-side voltage ring and a corresponding current ring, so that the direct current side voltage of the AC/DC converter has fast and accurate tracking capability.

Description

A kind of single-phase AC/DC converter and control method thereof with the decoupling zero of secondary wave kinetic power

Technical field

The present invention relates to a kind of single-phase AC/DC converter and control method thereof with the decoupling zero of secondary wave kinetic power.

Background technology

Single-phase AC/DC converter in electric power system, as single-phase photovoltaic DC-to-AC converter, single-phase uninterrupted power supply etc., if ensure the current sinusoidal of its AC network side, will inevitably there is the low frequency power fluctuation of secondary line voltage frequency in the DC side of converter so.If this intrinsic secondary wave kinetic power in single phase system is not carried out to filtering, this secondary wave kinetic power can cause the low-frequency fluctuation of DC voltage, this fluctuation in many application scenarios by the harm causing in various degree, for example greatly reduce photovoltaic battery panel generating efficiency, reduce the useful life of DC side storage battery, or cause input current to have triple-frequency harmonics.

And in order to eliminate the intrinsic secondary wave kinetic power of single phase system, a simple way configures jumbo electrochemical capacitor exactly, this has not only increased system bulk, and the life-span of electrochemical capacitor under higher temperature can greatly shorten, this will cause useful life of whole device shorten.Certainly, also can replace electrochemical capacitor with thin-film capacitor, but large capacity thin-film capacitor cost is too high, so this scheme is also unsatisfactory.

Normally the secondary wave kinetic power of single phase system AC is absorbed by storage capacitor or inductance for the solution of this problem at present.The CPS-PAF topological structure that main topological project has Greece scholar Kyritsis to propose, this topology has increased an inductance, electric capacity and a switch brachium pontis, and adopts DC side Active Power Filter Technology, reaches the object of the fluctuation that suppresses middle dc voltage.Japanese scholars Shimizu etc. has proposed the single-phase invertor topology that three switch brachium pontis add energy storage inductor, the secondary wave kinetic power of this topology in also can decoupling zero single phase system.But the passive or switching device that these topological structures increase is many, and cost is relatively high, and useful life is shorter.

Summary of the invention

The object of the invention is to for the deficiencies in the prior art, propose a kind of single-phase AC/DC converter and control method thereof with secondary wave kinetic power decoupling ability, it is simple in structure, with low cost.

A single-phase AC/DC converter with secondary wave kinetic power decoupling zero function, comprises successively connected net side transformer 1, net side filter 2, H bridge circuit 3 and power decoupling circuit 4;

Net side transformer 1 is connected with electrical network, and power decoupling circuit 4 is connected with DC load;

Described net side filter 2 comprises filter inductance L ₂with filter capacitor C ₂; Filter capacitor C ₂in parallel with the former limit of net side transformer 1;

Described power decoupling circuit 4 comprises an energy storage inductor L ₁, switching device S5 and afterflow diode D1; The collector electrode of switching device S5 connects the positive pole of DC load, and the emitter of switching device S5 is connected with the negative electrode of sustained diode 1, energy storage inductor L ₁first end connect the negative electrode of sustained diode 1; The anode of sustained diode 1 connects the negative pole of DC load;

The DC side parallel of this single-phase AC/DC converter has capacitor C ₁;

Described H bridge circuit is made up of switching device S1, switching device S2, switching device S3 and switching device S4, the emitter of switching device S1 is connected with the collector electrode of switching device S2 and forms the first brachium pontis, the emitter of switching device S3 is connected with the collector electrode of switching device S4 and forms the second brachium pontis, the first brachium pontis and the second brachium pontis are all in parallel with DC load, be that switching device S3 is connected with the collector electrode of switching device S1 and is connected to the positive pole of DC load, the emitter of switching device S4 and switching device S2 is extremely connected and is connected to the negative pole of DC load; The emitter B point of switching device S3 meets energy storage inductor L ₁the second end; The one end on the emitter connection network side transformer 1 former limit of switching device S3, the emitter of switching device S1 is through described filter inductance L ₂connect the other end on net side transformer 1 former limit.

A kind of control method of the single-phase AC/DC converter with secondary wave kinetic power decoupling zero function, adopt the above-mentioned single-phase AC/DC converter with secondary wave kinetic power decoupling zero function, and according to following steps, the DC voltage of described single-phase AC/DC converter controlled:

Step 1: signals collecting, gathers AC input voltage u _gwith AC input current i _g, DC voltage u _dcand energy storage inductor current i _lc, the signal of collection is input to dsp processor after analog-to-digital conversion process;

Step 2: the 3 road signals that gather are judged, if the signal value overrate of arbitrary road signal is implemented pwm signal and blocked, otherwise proceeds to step 3; Described pwm signal blocks the switching signal that refers to all switching tubes to 0, makes all switching tubes in off state;

Wherein, described 3 road signals are AC input current i _g, DC voltage u _dcand energy storage inductor current i _lc; AC input current i _gwith inductance L ₂or the load current value of switching tube compares, DC voltage u _dcwith capacitor C ₁load voltage value compare, energy storage inductor current i _lcwith inductance L ₁load current value compare;

Step 3: adopt line voltage phase-lock-loop algorithm, using AC input voltage as input variable, pass through a 100Hz trapper after multiplying each other with the sine value of upper one the AC input voltage phase of obtaining interrupt cycle, with filtering quadratic component wherein; Filtered result is by a pi regulator, the phase signal of regulator output voltage; One of input parameter that this phase signal calculates as energy storage inductor instruction current in current interrupt cycle;

Step 4: calculate energy storage inductor instruction current, according to the energy storage inductor instruction current and the AC input current that draw, electric current loop is carried out to closed-loop control, wherein energy storage inductor instruction references electric current and AC input reference current are set-point, and energy storage inductor instruction current and AC input current are value of feedback; Utilize direct current pressure ring PI controller to carry out closed-loop control to DC voltage, wherein, DC side reference voltage is set-point, and DC voltage is value of feedback;

Step 5: the duty ratio of utilizing dsp processor compute switch signal, switching signal is transferred to drive circuit, and produce by carrier modulating method and PWM the break-make that circuit formation pwm signal removes control switch pipe, control the DC voltage value trace voltage given value of single-phase AC/DC converter.

Specifically comprising the steps: of described step 4

Steps A: calculate energy storage inductor instruction current the amplitude I of energy storage inductor instruction current _lcbe respectively with phase theta:

Wherein, I _gfor AC input current amplitude, V _gfor AC input voltage amplitude, ω is line voltage angular frequency, L _gfor the inductance value of filter inductance, L _cfor the inductance value of energy storage inductor, angle expression formula as follows:

$j={\tan }^{-1}\left(\frac{L_g{\mathrm{wI}}_g}{V_g}\right)$

Step B: direct current pressure ring PI control procedure;

By the reference value and the DC voltage value u that samples and obtain of DC voltage _dcdifference be input to pi controller (PI), pi controller is output as the amplitude of the reference current of AC input, the cosine value of the AC input voltage phase of this amplitude and phase-locked loop multiplies each other as the reference current of AC input current controller, i.e. AC input reference current;

By the closed-loop control of electric current loop in step C, the actual input current of AC can be followed the tracks of AC input reference current, make converter AC input power P _acsize changes, by formula

$\mathrm{\ΔP}=P_{\mathrm{ac}}-P_{\mathrm{dc}}=C_{\mathrm{dc}}\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}$

Learn: if DC side flows out power P _dcconstant, converter AC input power P _acflow out power P with DC side _dcif difference power Δ P non-vanishing, the size of DC voltage will change, thus the variation of the actual input current size of AC makes DC voltage u _dcchange, whole process has formed voltage close loop control;

Wherein, the size of the reference value of described DC voltage is rear class load required voltage;

Step C: electric current loop closed-loop control, make energy storage inductor current tracking energy storage inductor instruction current, AC input current is followed the tracks of AC input reference current; Two output valve process duty ratio calculating that current controller is respectively AC input current controller and energy storage inductor current controller, the size of each duty cycle of switching is changed, the variation of duty ratio acts on change the size of the average voltage at energy storage inductor and AC input inductance two ends, thereby change inductive current, forms the closed-loop control to energy storage inductor electric current and AC input current;

AC is inputted to reference current and the AC input current i that samples and obtain _gdifference input AC side input current controller, controller is by ratio resonant controller (PR) and feedforward term u _gbe added composition, its form is as follows:

$u_{\mathrm{ab}}^{*}=u_g+L^{-1}\left\{(k_{p1}+\frac{k_r}{s})e_i\right\}$

Wherein k _p1for proportional control factor, k _rfor resonance control coefrficient, error e _ifor current reference signal i with energy storage inductor current sampling signal _gpoor, controller is output as node A, Node B two ends reference voltage using one of input parameter calculating as switching signal duty ratio;

By the command value of energy storage inductor electric current the energy storage inductor current i obtaining with sampling _lcdifference be input in energy storage inductor current controller, the current controller of energy storage inductor is output as the reference voltage at energy storage inductor two ends described energy storage inductor current controller is by pi controller PI and resonant controller R and corresponding feedforward term composition, its form is as follows:

$u_l^{*}=L_c{I}_{\mathrm{Lc}}\frac{d\left|\cos (\mathrm{wt}+q)\right|}{\mathrm{dt}}+L^{-1}\left\{(k_p+\frac{k_{i1}}{s}+\frac{k_{i2}s}{s^2+4w^2}+\frac{k_{i4}s}{s^2+16w^2})e_i\right\}$

Wherein, k _pfor proportional control factor, k _i1for integral control coefficient, k _i2for secondary resonance control coefrficient, k _i4be four resonance control coefrficients; Error e _ifor current reference signal i with energy storage inductor current sampling signal _lcpoor, L ^-1for anti-Laplacian, for the command voltage at energy storage inductor two ends, the input parameter calculating as switching signal duty ratio.

The duty ratio of the switching signal in described step 5 refers to, the duty ratio of switching device S1, switching device S3, switching device S5 is respectively dx, dh, du, the duty cycle signals of switching device S2, switching device S4 is respectively dy=1-dx, dl=1-dh, and wherein dx, dh, du, dy, dl are respectively switching device S1, switching device S3, switching device S5, switching device S2 and the service time of switching device S4 in one-period;

<math> <mrow> <mi>max</mi> <mrow> <mo>(</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> <mtext>&lt;du&lt;min</mtext> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> </mrow></math>

Max, min are respectively maximizing, the function of minimizing; for energy storage inductor two ends command voltage; for node A, Node B two ends reference voltage; After du is solved out, dl, dx press energy storage inductor command voltage computing formula and node A, Node B two ends reference voltage computing formula calculates.

The value of described du is shown below:

$\mathrm{du}=\frac{\max (u_l^{*},u_{\mathrm{ab}}^{*}+u_l^{*})+\min (1+u_l^{*},1+u_l^{*}+u_{\mathrm{ab}}^{*})}{2}$

Wherein, for energy storage inductor two ends command voltage; for node A, Node B two ends reference voltage.

Beneficial effect

The present invention proposes a kind of single-phase AC/DC converter and control method thereof with the decoupling zero of secondary wave kinetic power, this New single-phase AC/DC converter is only made up of net side transformer, net side filter, H bridge circuit and power decoupling circuit, simple in structure, with low cost, intrinsic secondary wave kinetic power in the single-phase AC/DC system of energy decoupling zero, only exchanging mobile in input side and decoupling zero circuit, DC side is arrived in non-conducting to make secondary wave kinetic power, thereby significantly reduce the low-frequency fluctuation of DC voltage, pressed for the load of rear class provides galvanic current.Adopt after this scheme, the rear class of converter only need to be installed the direct current capacitor compared with low capacity, thereby has saved bulky and the shorter big capacity electrolyte capacitor of life-span that in traditional scheme, must install.Control method based on this converter makes electric current loop and Voltage loop have quick follow-up control.

Brief description of the drawings

Fig. 1 is the structured flowchart of converter of the present invention;

Fig. 2 is control system DSP control block diagram of the present invention;

Fig. 3 is the control algolithm block diagram of control system of the present invention;

Fig. 4 is control algolithm flow chart of the present invention;

Fig. 5 is the middle dc voltage comparing result of conventional topologies structure and converter topology structure of the present invention

Fig. 6 is control system switching signal schematic diagram of the present invention;

Fig. 7 is input voltage and AC input current waveform in the present invention;

Fig. 8 be in the present invention energy storage inductor current waveform and with AC input current waveform;

Fig. 9 is energy storage inductor actual current tracing energy-storage inductance instruction current effect waveform in the present invention;

Figure 10 is that in the present invention, AC input actual current is followed the tracks of AC input reference current waveform;

Figure 11 is line voltage phase-lock-loop algorithm schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, that the present invention is described in detail is as follows:

As shown in Figure 1, a kind of single-phase AC/DC converter with secondary wave kinetic power decoupling zero function, comprises successively connected net side transformer 1, net side filter 2, H bridge circuit 3 and power decoupling circuit 4;

Net side transformer 1 is connected with electrical network, and power decoupling circuit 4 is connected with DC load;

Described net side filter 2 comprises filter inductance L ₂with filter capacitor C ₂; Filter capacitor C ₂in parallel with the former limit of net side transformer 1;

Described power decoupling circuit 4 comprises an energy storage inductor L ₁, switching device S5 and afterflow diode D1; The collector electrode of switching device S5 connects the positive pole of DC load, and the emitter of switching device S5 is connected with the negative electrode of sustained diode 1, energy storage inductor L ₁first end connect the negative electrode of sustained diode 1; The anode of sustained diode 1 connects the negative pole of DC load;

The DC side parallel of this single-phase AC/DC converter has capacitor C ₁;

Described H bridge circuit is made up of switching device S1, switching device S2, switching device S3 and switching device S4, the emitter of switching device S1 is connected with the collector electrode of switching device S2 and forms the first brachium pontis, the emitter of switching device S3 is connected with the collector electrode of switching device S4 and forms the second brachium pontis, the first brachium pontis and the second brachium pontis are all in parallel with DC load, be that switching device S3 is connected with the collector electrode of switching device S1 and is connected to the positive pole of DC load, the emitter of switching device S4 and switching device S2 is extremely connected and is connected to the negative pole of DC load; The emitter B point of switching device S3 meets energy storage inductor L ₁the second end; The emitter of switching device S3 also connects the one end on net side transformer 1 former limit, and the emitter of switching device S1 is through described filter inductance L ₂connect the other end on net side transformer 1 former limit.

Fig. 2 is control system DSP control block diagram of the present invention, and in Fig. 2, main circuit comprises the single-phase AC/DC converter with secondary power decoupling zero of the present invention, and control circuit comprises controller 7, drive circuit 8 and the modulate circuit 6 of sampling accordingly.The right-hand member of net side filter 2 is connected with net side transformer 1, finally accesses in 220V AC network.

Switching tube S5 and sustained diode 1 and energy storage inductor L ₁l in the decoupling zero circuit 4 of composition ₁be connected with the B point of the second brachium pontis of H bridge, the emitter-base bandgap grading of switching tube S5 is connected with the negative electrode of diode D1, and the collector electrode of switching tube S5 is connected with DC bus and E point, and E is power decoupled point, and the power fluctuation on the DC bus on the Decoupling Point E left side is inhibited.In the capacitor C of the DC bus two ends cross-over connection low capacity on the Decoupling Point E left side ₁, capacitor C ₁load is below connected between P, N point, and P point connects the positive pole of rear class DC load, and N point connects the negative pole of rear class DC load.

The right-hand component sample circuit of sample circuit 6 is responsible for sampling and the conditioning of transformer 1 auxiliary direction voltage and current on line side, and the left-hand component sample circuit of sample circuit 6 is responsible for the energy storage inductor L in DC voltage and decoupling zero circuit ₁sampling and the conditioning of electric current.Controller 7 is responsible for the important process such as calculating and modulation, and each pwm switching signal is passed to drive circuit 8, thereby reaches the object of controlling each switch.

In the present invention, the topological modulator approach of converter and the modulation strategy of conventional H bridge circuit are different, need to consider the job requirement of decoupling zero circuit and H bridge circuit simultaneously.Net side filter is second order LC low pass filter, object is the switching harmonics electric current that filtering switching device produces on the one hand, be to stop to a certain extent the impact on converter such as voltage harmonic from electrical network on the other hand, be illustrated in figure 3 the control algolithm block diagram of control system of the present invention.

Suppose AC input voltage u _gfor:

u _g＝V _gcos(ωt) (1)

Wherein ω is line voltage angular frequency, V _gfor the amplitude of AC input voltage.

If ensure system input current and voltage same-phase, AC input current i _gexpression formula should be:

i _g＝I _gcos(ωt) (2)

I in formula _gfor current amplitude size.Now converter AC input power P _acto be formed by two parts: the input power P of electrical network _acwith filter inductance L ₂the reactive power absorbing:

$P_{\mathrm{ac}}=V_g{I}_g{\cos }^2\left(\mathrm{\&omega;t}\right)-L_2\mathrm{\&omega;}{I}_g^2\cos \left(\mathrm{\&omega;t}\right)\cos (\mathrm{\&omega;t}+\frac{\mathrm{\&pi;}}{2})---\left(3\right)$

DC side power is made up of two parts, and a part is the power of load absorption (or power supply sends), and another part is the power that energy storage inductor absorbs.Suppose energy storage inductor L ₁on instruction current be dC side power can be expressed as so

$P_{\mathrm{dc}}=u_{\mathrm{dc}}{i}_{\mathrm{dc}}+I_{\mathrm{Lc}}\cos (\mathrm{\&omega;t}+\mathrm{\&theta;})U_{\mathrm{Lc}}\cos (\mathrm{\&omega;t}+\mathrm{\&theta;}+\frac{\mathrm{\&pi;}}{2})---\left(4\right)$

Wherein u _dcfor DC voltage, i _dcfor the electric current of DC load, I _lcfor the amplitude of energy storage inductor instruction current, U _lcfor the amplitude of energy storage inductor both end voltage.

If ignore switching loss, according to input-output power conservation, so:

P _ac＝P _dc (5)

The direct current power part of formula (5) the right and left and AC power part correspondent equal, have for direct current component so:

u _dci _dc＝0.5V _gI _g (6)

Have for AC portion:

$V_g{I}_g\cos \left(2\mathrm{\&omega;t}\right)+L_g\mathrm{\&omega;}{I}_g^2\sin \left(2\mathrm{\&omega;t}\right)=I_{\mathrm{Lc}}{U}_{\mathrm{Lc}}\cos (2\mathrm{\&omega;t}+2\mathrm{\&theta;}+\frac{\mathrm{\&pi;}}{2})---\left(7\right)$

Abbreviation above formula obtains:

In above formula can obtain energy storage inductor L by formula (8) ₁the amplitude I of instruction current _lcbe respectively with phase theta:

It should be noted that because the electric current in the energy storage inductor in this topological decoupling zero circuit can not be reverse, therefore, adopt I _lcthe absolute value of cos (ω t+ θ) | I _lccos (ω t+ θ) | the current-order as energy storage inductor is because the energy that inductance stores only and the size of electric current and and sense of current irrelevant, so this watt level that does not affect energy storage inductor absorption and send.

Right | I _lccos (ω t+ θ) | carry out Fourier analysis, electric current can be write as:

$i_{\mathrm{Lc}}^{*}=I_d\{1-2\underset{n=\mathrm{2,4,6}}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{\cos \left(\mathrm{n\&omega;t}\right)}{n^2-1}\}---\left(10\right)$

I in above formula _dfor current i _lcdC component, can find out in 2,4 even-order harmonics mainly containing, and the harmonic components after 4 times is very low, in engineering, can ignore, therefore can add 2 by adoption rate integration (PI), 4 resonant controller (R) are as the current controller of power decoupling circuit, in order to improve the tracking effect of energy storage inductor current controller, energy storage inductor current controller is designed to as follows:

$u_l^{*}=L_c{I}_{\mathrm{Lc}}\frac{d\left|\cos (\mathrm{\&omega;t}+\mathrm{\&theta;})\right|}{\mathrm{dt}}+L^{-1}\left\{(k_p+\frac{k_{i1}}{s}+\frac{k_{i2}s}{s^2+4{\mathrm{\&omega;}}^2}+\frac{k_{i4}s}{s^2+16{\mathrm{\&omega;}}^2})e_i\right\}---\left(11\right)$

Its detailed control block diagram as shown in the first half of accompanying drawing 3, wherein, for the command voltage at energy storage inductor two ends, k _pfor proportional control constant, k _ifor integral control constant, k _i2be 2 resonant controller constants, k _i4be 4 resonant controller constants, the Section 1 on formula (11) the right is feedforward term.

As shown in Figure 4, be control algolithm flow chart of the present invention, input line voltage is 220V/50Hz, transformer primary pair side no-load voltage ratio is 4:1, input filter capacitor C ₂capacitance be 5uF, input filter reactance L ₂inductance value L _gfor 3mH, decoupling zero inductance L ₁inductance value be L _c=10mH, DC capacitor C on DC bus ₁capacitance be 100uF, load resistance is 75 Ω, DC voltage reference value size is 120V, sample frequency and switching frequency are 10kHz, as follows to the control method step of converter in the present invention:

The first step, gathers voltage u _g, u _dcand current i _g, i _lc, and extract AC input voltage u by single-phase phase-locked loop _gphase information;

Second step, utilizes u _gphase information ω t, the amplitude I of AC input current _gand AC input voltage amplitude V _g, according to formula (9), try to achieve energy storage inductor L ₁current reference waveform | I _lccos (ω t+ θ) |;

The 3rd step, adopts line voltage phase-lock-loop algorithm, using AC input voltage as input variable, passes through a 100Hz trapper, with filtering quadratic component wherein with the sine value of upper one the AC input voltage phase of obtaining interrupt cycle after multiplying each other; Filtered result is by a pi regulator, the phase signal of regulator output voltage; One of input parameter that this phase signal calculates as energy storage inductor instruction current in current interrupt cycle, line voltage phase-lock-loop algorithm is as shown in figure 11;

To DC bus-bar voltage u _dcprocess, make it by the trapper of 100Hz, after filtering, assignment is to DC voltage controller, and subtract each other with direct voltage reference value, its poor input as Voltage loop PI controller, (ω t) multiplies each other, and its result, as the reference of the input current of AC input current controller, is AC input reference current with the cosine cos of AC input voltage phase again in the output of this PI controller;

The 4th step, the current reference signal of energy storage inductor | I _lccos (ω t+ θ) | with the current i of the energy storage inductor of sampling _lcsubtract each other its poor input as energy storage inductor current controller, the output of this current loop controller and feed-forward signal be added one of input of calculating as duty cycle of switching, the input signal of another AC input current controller and the input current i of sampling _gafter subtracting each other, through AC input current controller, exchange the output valve of input current controller as an input signal of duty cycle of switching calculating;

The 5th step, utilize the duty ratio of dsp processor compute switch signal, switching signal is transferred to drive circuit, and produces by carrier modulating method and PWM the break-make that circuit formation pwm signal removes control switch pipe, control the DC voltage value trace voltage given value of single-phase AC/DC converter.

In new topology, the numbering of each switching tube numbering and respective nodes is illustrated in fig. 2 shown below, and the duty ratio of switching tube S5 is distributed and be coordinated with the duty ratio of switching tube S1 and switching tube S2, to control direct voltage and energy storage inductor L ₁in electric current.

Decoupling zero circuit has four kinds of mode of operations: the first mode of operation switching tube S5 and switching tube S4 closure, switching tube S3 opens, now inductance L ₁upper voltage is u _dc, the inductive current switching tube S5 that flows through, switching tube S2 and inductance L ₁; Switching tube S4 closure in the second mode of operation, switching tube S5, switching tube S3 open, inductance L ₁by diode D1 and switching tube S4 afterflow.In the third mode of operation, switching tube S5 and switching tube S3 closure, switching tube S4 opens, inductance L ₁by switching tube S3 and switching tube S4 afterflow.Second and the third pattern in, inductance L ₁both end voltage is all approximately 0.In the 4th kind of mode of operation, switching tube S3 closure, switching tube S5 and switching tube S4 open, inductance L ₁by the inverse parallel diode afterflow of diode D1 and switching tube S3, now inductance both end voltage is-u _dc.

If the duty ratio of switching tube S1, switching tube S3, switching tube S5 is respectively dx, dh, du, for preventing leading directly to, the switching signal complementation of switching tube on same brachium pontis, so the duty cycle signals of switching tube S2, switching tube S4 is respectively dy=1-dx, dl=1-dh.Suppose that switching frequency is enough high, application switch cycle average theory, considers action time of above four kinds of patterns in a switch periods, energy storage inductor two ends command voltage for:

$u_l^{*}\left(t\right)=(\mathrm{du}+\mathrm{dl}-1)\&CenterDot;u_{\mathrm{dc}}---\left(12\right)$

Node A, Node B two ends reference voltage for:

$u_{\mathrm{ab}}^{*}\left(t\right)=(1-\mathrm{dl}-\mathrm{dx})\&CenterDot;u_{\mathrm{dc}}---\left(13\right)$

Can find out that by above formula (12) and formula (13) these two equations have three control freedom degrees, be respectively du, dl, dx.Due to decoupling zero circuit and the shared brachium pontis of H bridge, first ensure the normal work of H bridge portion, therefore duty ratio dl, dx should meet:

$\left\{\begin{array}{c}0<\mathrm{dl}=1+u_l^{*}-\mathrm{du}<1\\ 0<\mathrm{dx}=\mathrm{du}-u_l^{*}-u_{\mathrm{ab}}^{*}<1\end{array}\right.---\left(14\right)$

The restrictive condition that solves thus duty ratio du is:

$\left\{\begin{array}{c}{u}_l^{*}<\mathrm{du}<1+u_l^{*}\\ u_l^{*}+u_{\mathrm{ab}}^{*}<\mathrm{du}<{1+u}_l^{*}+u_{\mathrm{ab}}^{*}\end{array}\right.---\left(15\right)$

Above-mentioned two inequality of simultaneous can obtain:

<math> <mrow> <mi>max</mi> <mrow> <mo>(</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> <mtext>&lt;du&lt;min</mtext> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>16</mn> <mo>)</mo> </mrow> </mrow></math>

For the sake of simplicity, du of the present invention gets the mean value between maximin:

$\mathrm{du}=\frac{\max (u_l^{*},u_{\mathrm{ab}}^{*}+u_l^{*})+\min (1+u_l^{*},1+u_l^{*}+u_{\mathrm{ab}}^{*})}{2}---\left(17\right)$

After du is solved out, dl, dx can calculate by formula (12) and formula (13), and finally produce the input of circuit as PWM.

Under MATLAB/Simulink environment, system has been carried out to emulation, Fig. 5 is traditional H bridge topological sum topology of the present invention DC voltage u while adopting same main circuit parameter _dcfluctuation situation simulation result, can find out that the present invention can obviously reduce the fluctuation of single-phase AC/DC converter DC voltage.Fig. 6 is that each switching signal produces schematic diagram; Fig. 7 is AC input voltage u _gwith input current i _gwaveform, can find out input current and voltage same-phase and substantially sinusoidal; Fig. 8 is the current i of energy storage inductor _lcwaveform and AC input current i _gwaveform, both phase relation cotypes (9) match.Fig. 9 is energy storage inductor actual current i _lctracing energy-storage inductance instruction current schematic diagram, Figure 10 is AC input actual current i _gfollow the tracks of AC input reference current schematic diagram, energy storage inductor actual current waveform and AC input actual current waveform is substantially identical with respect to given value of current value, has shown the tracking performance that current controller is good.

Claims (4)

1. one kind has the control method of the single-phase AC/DC converter of secondary wave kinetic power decoupling zero function, it is characterized in that, adopt a kind of single-phase AC/DC converter with secondary wave kinetic power decoupling zero function, this converter comprises successively connected net side transformer (1), net side filter (2), H bridge circuit (3) and power decoupling circuit (4);

Net side transformer (1) is connected with electrical network, and power decoupling circuit (4) is connected with DC load;

Described net side filter (2) comprises filter inductance L ₂with filter capacitor C ₂; Filter capacitor C ₂in parallel with the former limit of net side transformer (1);

Described power decoupling circuit (4) comprises an energy storage inductor L ₁, switching device S5 and afterflow diode D1; The collector electrode of switching device S5 connects the positive pole of DC load, and the emitter of switching device S5 is connected with the negative electrode of sustained diode 1, energy storage inductor L ₁first end connect the negative electrode of sustained diode 1; The anode of sustained diode 1 connects the negative pole of DC load;

The DC side parallel of this single-phase AC/DC converter has capacitor C ₁;

Described H bridge circuit is made up of switching device S1, switching device S2, switching device S3 and switching device S4, the emitter of switching device S1 is connected with the collector electrode of switching device S2 and forms the first brachium pontis, the emitter of switching device S3 is connected with the collector electrode of switching device S4 and forms the second brachium pontis, the first brachium pontis and the second brachium pontis are all in parallel with DC load, be that switching device S3 is connected with the collector electrode of switching device S1 and is connected to the positive pole of DC load, the emitter of switching device S4 and switching device S2 is extremely connected and is connected to the negative pole of DC load; The emitter B point of switching device S3 meets energy storage inductor L ₁the second end; The one end on the former limit of emitter connection network side transformer (1) of switching device S3, the emitter of switching device S1 is through described filter inductance L ₂connect the other end on the former limit of net side transformer (1);

And according to following steps, the DC voltage of described single-phase AC/DC converter is controlled:

Step 1: signals collecting, gathers AC input voltage u _gwith AC input current i _g, DC voltage u _dcand energy storage inductor current i _lc, the signal of collection is input to dsp processor after analog-to-digital conversion process;

Step 2: the 3 road signals that gather are judged, if the signal value overrate of arbitrary road signal is implemented pwm signal and blocked, otherwise proceeds to step 3; Described pwm signal blocks the switching signal that refers to all switching tubes to 0, makes all switching tubes in off state;

Wherein, described 3 road signals are AC input current i _g, DC voltage u _dcand energy storage inductor current i _lc; AC input current i _gwith inductance L ₂or the load current value of switching tube compares, DC voltage u _dcwith capacitor C ₁load voltage value compare, energy storage inductor current i _lcwith inductance L ₁load current value compare;

Step 3: adopt line voltage phase-lock-loop algorithm, using AC input voltage as input variable, after multiplying each other with the sine value of upper one the AC input voltage phase of obtaining interrupt cycle, pass through a 100Hz trapper, with filtering quadratic component wherein, filtered result is by a pi regulator, the phase signal of regulator output voltage; One of input parameter that this phase signal calculates as energy storage inductor instruction current in current interrupt cycle;

Step 4: calculate energy storage inductor instruction current, according to the energy storage inductor instruction current and the AC input current that draw, electric current loop is carried out to closed-loop control, wherein energy storage inductor instruction references electric current and AC input reference current are set-point, and energy storage inductor instruction current and AC input current are value of feedback; Utilize direct current pressure ring PI controller to carry out closed-loop control to DC voltage, wherein, DC side reference voltage is set-point, and DC voltage is value of feedback;

Step 5: the duty ratio of utilizing dsp processor compute switch signal, switching signal is transferred to drive circuit, and produce by carrier modulating method and PWM the break-make that circuit formation pwm signal removes control switch pipe, control the DC voltage floating voltage side reference voltage set-point of single-phase AC/DC converter.

2. the control method of the single-phase AC/DC converter with secondary wave kinetic power decoupling zero function according to claim 1, is characterized in that, described step 4 specifically comprises the steps:

Steps A: calculate energy storage inductor instruction current the amplitude I of energy storage inductor instruction current _lcbe respectively with phase theta:

Wherein, I _gfor AC input current amplitude, V _gfor AC input voltage amplitude, ω is line voltage angular frequency, L _gfor the inductance value of filter inductance, L _cfor the inductance value of energy storage inductor, angle expression formula as follows:

$j={\tan }^{-1}\left(\frac{L_g{\mathrm{wI}}_g}{V_g}\right)$

Step B: direct current pressure ring PI control procedure;

By the reference value and the DC voltage value u that samples and obtain of DC voltage _dcdifference be input to pi controller (PI), pi controller is output as the amplitude of AC input reference current, the cosine value of the AC input voltage phase of this amplitude and phase-locked loop multiplies each other as the reference current of AC input current controller, i.e. AC input reference current;

By the closed-loop control of electric current loop in step C, the actual input current of AC can be followed the tracks of AC input reference current, make converter AC input power P _acsize changes, by following formula

$\mathrm{\&Delta;P}=P_{\mathrm{ac}}-P_{\mathrm{dc}}=C_{\mathrm{dc}}\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}$

Learn: if DC side flows out power P _dcconstant, converter AC input power P _acflow out power P with DC side _dcdifference power Δ P non-vanishing, the size of DC voltage will change, thus the variation of the actual input current of AC makes DC voltage u _dcchange, whole process forms voltage close loop control;

Wherein, the size of the reference value of described DC voltage is rear class load required voltage;

Step C: electric current loop closed-loop control, make energy storage inductor current tracking energy storage inductor instruction current, AC input current is followed the tracks of AC input reference current; Two current controllers are respectively AC input current controller and energy storage inductor current controller, the output valve of described two current controllers is calculated through duty ratio, the size of each duty cycle of switching is changed, the variation of duty ratio is by the size of the average voltage at change energy storage inductor and AC input inductance two ends, thereby change inductive current, forms the closed-loop control to energy storage inductor electric current and AC input current;

AC is inputted to reference current and the AC input current i that samples and obtain _gdifference input AC side input current controller, controller is by ratio resonant controller (PR) and feedforward term u _gbe added composition, its form is as follows:

$u_{\mathrm{ab}}^{*}=u_g+L^{-1}\left\{(k_{p1}+\frac{k_r}{s})e_i\right\}$

Wherein k _p1for proportional control factor, k _rfor resonance control coefrficient, error e _ifor current reference signal i with energy storage inductor current sampling signal _gpoor, controller is output as node A, Node B two ends reference voltage using one of input parameter calculating as switching signal duty ratio;

By the command value of energy storage inductor electric current the energy storage inductor current i obtaining with sampling _lcdifference be input in energy storage inductor current controller, the current controller of energy storage inductor is output as the reference voltage at energy storage inductor two ends described energy storage inductor current controller is by pi controller (PI) and resonant controller (R) and corresponding feedforward term composition, its form is as follows:

$u_l^{*}=L_c{I}_{\mathrm{Lc}}\frac{d\left|\cos (\mathrm{\&omega;t}+\mathrm{\&theta;})\right|}{\mathrm{dt}}+L^{-1}\left\{(k_p+\frac{k_{i1}}{s}+\frac{k_{i2}s}{s^2+4{\mathrm{\&omega;}}^2}+\frac{k_{i4}s}{s^2+16{\mathrm{\&omega;}}^2})e_i\right\}$

Wherein, k _pfor proportional control factor, k _i1for integral control coefficient, k _i2for secondary resonance control coefrficient, k _i4be four resonance control coefrficients; Error e _ifor current reference signal i with energy storage inductor current sampling signal _lcpoor, L ^-1for anti-Laplacian, for the command voltage at energy storage inductor two ends, the input parameter calculating as switching signal duty ratio.

3. the control method of the single-phase AC/DC converter with secondary wave kinetic power decoupling zero function according to claim 1, it is characterized in that, the duty ratio of the switching signal in described step 5 refers to, switching device S1, switching device S3, the duty ratio of switching device S5 is respectively dx, dh, du, switching device S2, the duty cycle signals of switching device S4 is respectively dy=1-dx, dl=1-dh, wherein dx, dh, du, dy, dl is respectively switching device S1, switching device S3, switching device S5, switching device S2 and the service time of switching device S4 in one-period,

<math> <mrow> <mi>max</mi> <mrow> <mo>(</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> <mtext>&lt;du&lt;min</mtext> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>,</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>u</mi> <mi>l</mi> <mo>*</mo> </msubsup> <mo>+</mo> <msubsup> <mi>u</mi> <mi>ab</mi> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> </mrow></math>

Max, min are respectively maximizing, the function of minimizing; for energy storage inductor two ends command voltage; for node A, Node B two ends reference voltage; After du is solved out, dl, dx press energy storage inductor two ends command voltage computing formula and node A, Node B two ends reference voltage computing formula calculates.

4. the control method of the single-phase AC/DC converter with secondary wave kinetic power decoupling zero function according to claim 3, is characterized in that, the value of du is shown below:

$\mathrm{du}=\frac{\max (u_l^{*},u_{\mathrm{ab}}^{*}+u_l^{*})+\min (1+u_l^{*},1+u_l^{*}+u_{\mathrm{ab}}^{*})}{2}$

Wherein, for energy storage inductor two ends command voltage; for node A, Node B two ends reference voltage.