CN104065103A - Double closed loop control method for photovoltaic Boost convertor of photovoltaic energy storage system - Google Patents

Abstract

The invention discloses a double closed loop control method for a photovoltaic Boost convertor of a photovoltaic energy storage system. When the photovoltaic Boost convertor is in the working state of constant current power supply, the output end of the photovoltaic Boost convertor collects a current signal and a voltage signal and feeds the signals back to a current loop PI adjuster of the photovoltaic Boost convertor. According to the control method, an outer ring is a Boost circuit output voltage ring, so that wave form of output voltage is changed, and stability precision and anti-interference performance are improved; an inner ring is a Boost circuit inductive current ring, so that the dynamic property of the system is improved. By means of the whole control method, stable direct current bus voltage can be obtained. Compared with an MPPT control strategy of an existing photovoltaic side Boost convertor, the whole photovoltaic energy storage system can be stably controlled, and control complexity of the whole system is reduced at the same time.

Description

A kind of two closed loop control methods of photovoltaic Boost converter of photovoltaic energy storage system

Technical field

The present invention relates to photovoltaic energy storage field, relate in particular to the double-loop control strategy of photovoltaic side BOOST converter in photovoltaic energy storage system.

Background technology

Traditional photovoltaic system, photovoltaic Boost convertor controls strategy mostly adopts MPPT maximum power point tracking (Maximum Power Point Tracking, MPPT) pattern, can obtain maximum generating efficiency, and obtain optimum benefit.

In photovoltaic energy storage system, power inverter comprises photovoltaic side Boost converter, battery side Buck-Boost converter and load-side full-bridge inverter.Three converters all jump on common DC bus, thereby form a direct current microgrid.Wherein the MPPT control strategy of photovoltaic side Boost converter can not obtain stable DC bus-bar voltage, is unfavorable for the stable control of whole photovoltaic energy storage system, and the algorithm of the whole system simultaneously also increasing is controlled complexity.

Summary of the invention

Technical problem to be solved by this invention is to realize a kind of Double closed-loop of voltage and current strategy that can obtain stable DC bus-bar voltage.

To achieve these goals, the technical solution used in the present invention is: a kind of two closed loop control methods of photovoltaic Boost converter of photovoltaic energy storage system, described photovoltaic energy storage system comprises photovoltaic module, lithium ion battery, public electric wire net, local load and power inverter, described power inverter comprises photovoltaic side Boost converter, battery side Buck-Boost converter and load-side full-bridge inverter, described lithium ion battery connects load-side full-bridge inverter through battery side Buck-Boost converter, described photovoltaic module connects load-side full-bridge inverter through photovoltaic side Boost converter, described converter connects load-side full-bridge inverter and connects local load,

When photovoltaic Boost converter is under photovoltaic power supply operating state, photovoltaic Boost converter output terminal gathers electric current and voltage signal and feeds back to electric current loop and the Voltage loop pi regulator of photovoltaic Boost converter.

By the cross-over frequency f of compensation after-current ring _icbe arranged on 1/15 place of switching frequency fs, and by the corner frequency f of electric current loop pi regulator _inbe arranged between concussion link corner frequency and compensation after-current ring cross-over frequency

The inductance parameters of described photovoltaic Boost converter is got L=2mH, dc-link capacitance parameter is got C=2000uF, DC bus-bar voltage is 480V, duty ratio gets 0.5, load is taken as R=46.08 Ω according to photovoltaic peak power output 5kW design, described pi regulator comprises Voltage loop pi regulator and electric current loop pi regulator, and wherein the parameter of electric current loop pi regulator is $\left\{\begin{array}{c}{K}_{\mathrm{ip}}=0.015\\ K_{\mathrm{ii}}=15\end{array}\right.,$ The parameter of Voltage loop pi regulator is $\left\{\begin{array}{c}{K}_{\mathrm{vp}}=2\\ K_{\mathrm{vi}}=500\end{array}\right..$

The break angular frequency of described concussion link is: wherein D is switching tube S1 duty ratio, D '=1-D, and C is dc-link capacitance.

Control method outer shroud of the present invention is Boost circuit output voltage ring, can improve output voltage waveforms, improves stable state accuracy and Immunity Performance; Interior ring is Boost circuit inductance electric current loop, can improve the dynamic property of system.Whole control method can obtain stable DC bus-bar voltage, compare with the MPPT control strategy of existing photovoltaic side Boost converter, can be so that the stable control of whole photovoltaic energy storage system, and the control complexity of the whole system also having reduced simultaneously.

Accompanying drawing explanation

Below the content that in specification of the present invention, every width accompanying drawing is expressed is briefly described:

Fig. 1 photovoltaic energy storage system topological figure;

Fig. 2 Boost equivalent schematic diagram;

Fig. 3 Boost converter is operated in the control block diagram under CV pattern;

Fig. 4 Boost converter is operated in the rear open loop amplitude-frequency performance plot of electric current loop compensation under CV pattern;

Fig. 5 Boost circuit working Voltage loop control block diagram under CV pattern;

The Voltage loop control block diagram that Fig. 6 simplifies;

Fig. 7 Boost circuit working is the rear open loop amplitude-frequency performance plot of Voltage loop compensation under CV pattern.

Embodiment

Known referring to Fig. 1, a kind of photovoltaic energy storage system comprises photovoltaic module, lithium ion battery, public electric wire net, local load and power inverter, wherein power inverter comprises photovoltaic side Boost converter, battery side Buck-Boost converter and load-side full-bridge inverter, this lithium ion battery connects load-side full-bridge inverter through battery side Buck-Boost converter, this photovoltaic module connects load-side full-bridge inverter through photovoltaic side Boost converter, this converter connects load-side full-bridge inverter and connects local load, above-mentioned three converters all jump on common DC bus, thereby form a direct current microgrid.

Known referring to Fig. 2, when system (CV-Constant Voltage) pattern under constant current-supplying state, control DC bus-bar voltage constant, its control strategy adopts the two closed-loop controls shown in Fig. 3, G _idand G (S) _vi(s) be that Boost circuit is based upon the transfer function under small-signal alternate model, its expression is as follows:

$\left\{\begin{array}{c}{G}_{\mathrm{id}}\left(s\right)=\frac{{\hat{i}}_L\left(s\right)}{\hat{d}\left(s\right)}=\frac{V_{\mathrm{PV}}(\mathrm{RCS}+2)}{({\mathrm{LCS}}^2+\frac{L}{R}S+D^{\′2})D^{\′}R}\\ G_{\mathrm{vi}}\left(s\right)=\frac{{\hat{v}}_o\left(s\right)}{{\hat{i}}_L\left(s\right)}=\frac{D^{\′2}R-\mathrm{SL}}{(\mathrm{RCS}+2)D^{\′}}\end{array}\right.---\left(1\right)$

Wherein: C is dc-link capacitance, R is the load of Boost circuit equivalent, and D is switching tube S1 duty ratio, D '=1-D.

According to formula (1), the open-loop transfer function of electric current loop before compensation is:

$G_i\left(s\right)=\frac{K_{\mathrm{PWM}}\·V_{\mathrm{PV}}\·(\mathrm{RCS}+2)}{({\mathrm{LCS}}^2+\frac{L}{R}S+D^{\′2})D^{\′}R}---\left(2\right)$

Wherein: K _pWMfor modulator is input to the transfer function that duty ratio is exported, its value is 1.

By actual parameter substitution formula (2), known, in formula, denominator does not have real root, therefore controlled device contains a second order concussion link:

$G\left(s\right)=\frac{V_{\mathrm{PV}}}{({\mathrm{LCS}}^2+\frac{L}{R}S+D^{\′2})D^{\′}R}=\frac{\frac{V_{\mathrm{dc}}}{\mathrm{LCR}}}{S^2+\frac{1}{\mathrm{RC}}S+\frac{D^{\′2}}{\mathrm{LC}}}---\left(3\right)$

The break angular frequency of this concussion link is:

${\mathrm{\ω}}_c=\frac{D^{\′}}{\sqrt{\mathrm{LC}}}---\left(4\right)$

By the cross-over frequency f of compensation after-current ring _icbe arranged on switching frequency f _s(15kHz) 1/15 place.The corner frequency fin of electric current loop pi regulator is arranged between concussion link corner frequency and compensation after-current ring cross-over frequency, to guarantee to compensate after-current ring amplitude-versus-frequency curve, with the slope of-20dB/dec, passes zero point, be taken as 1000rad/sec, have:

$\left\{\begin{array}{c}{f}_{\mathrm{in}}=\frac{1000}{2\mathrm{\π}}\\ f_{\mathrm{ic}}=\frac{f_s}{15}\end{array}\right.---\left(5\right)$

If electric current loop pi regulator parameter is:

$C_i\left(s\right)=\frac{K_{\mathrm{ip}}S+K_{\mathrm{ii}}}{S}---\left(6\right)$

By following equation group, can solve and obtain current loop controller parameter:

$\left\{\begin{array}{c}\frac{K_{\mathrm{ii}}}{K_{\mathrm{ip}}}=1000\\ {|\frac{K_{\mathrm{ip}}S+K_{\mathrm{ii}}}{S}\·\frac{K_{\mathrm{PWM}}{V}_{\mathrm{PV}}(\mathrm{RCS}+2)}{({\mathrm{LCS}}^2+\frac{L}{R}S+D^{\′2})D^{\′}R}|}_{s=j2\mathrm{\π}{f}_{\mathrm{ic}}}=1\end{array}\right.---\left(7\right)$

Photovoltaic side inductance parameters is got L=2mH, and dc-link capacitance parameter is got C=2000uF, and DC bus-bar voltage is 480V, and duty ratio gets 0.5, and load is taken as R=46.08 Ω according to photovoltaic peak power output 5kW design.Above parameter substitution formula (7) can be solved to electric current loop pi regulator parameter.Finally getting parameter is:

$\left\{\begin{array}{c}{K}_{\mathrm{ip}}=0.015\\ K_{\mathrm{ii}}=15\end{array}\right.---\left(8\right)$

Before and after compensating referring to Fig. 4, the Bert figure of electric current loop open-loop transfer function is known, compensation after-current ring open-loop transfer function amplitude-versus-frequency curve with the slope of-20dB/dec through zero point.System cross-over frequency is 2.6e+3rad/sec, and Phase margin is 68.7deg, can obtain good dynamic characteristic and steady-state characteristic.

As shown in Figure 5, the part using electric current loop closed loop transfer function, as controlled device.Because electric current loop bandwidth is far above Voltage loop, thus the proportional component that the closed loop transfer function, Available Gain of electric current loop is 1 replacement, therefore the Voltage loop structure being simplified is as shown in Figure 6.

According to formula (1), above-mentioned Voltage loop controlled device contains two corner frequencies.The cross-over frequency fvc of Voltage loop after compensation is arranged on to 1/5 of electric current loop cross-over frequency fic.The corner frequency fvn of Voltage loop pi regulator is arranged on after the less corner frequency of controlled device and compensation between Voltage loop cross-over frequency, to guarantee to compensate rear Voltage loop amplitude-versus-frequency curve, with the slope of-20dB/dec, through zero point, is taken as 250rad/sec.Have:

$\left\{\begin{array}{c}{f}_{\mathrm{vn}}=\frac{250}{2\mathrm{\π}}\\ f_{\mathrm{vc}}=\frac{f_{\mathrm{ic}}}{5}\end{array}\right.---\left(9\right)$

If Voltage loop pi regulator parameter is:

$C_v\left(s\right)=\frac{K_{\mathrm{vp}}S+K_{\mathrm{vi}}}{S}---\left(10\right)$

By following equation group, can solve and obtain Voltage loop controller parameter:

$\left\{\begin{array}{c}\frac{K_{\mathrm{vi}}}{K_{\mathrm{vp}}}=250\\ {|\frac{K_{\mathrm{vp}}S+K_{\mathrm{vi}}}{S}\·\frac{D^{\′2}R-\mathrm{SL}}{(\mathrm{RCS}+2)D^{\′}}|}_{s=j2\mathrm{\π}{f}_{\mathrm{vc}}}=1\end{array}\right.---\left(11\right)$

By relevant parameter substitution above formula, can try to achieve Voltage loop pi regulator parameter.Finally getting parameter is:

$\left\{\begin{array}{c}{K}_{\mathrm{vp}}=2\\ K_{\mathrm{vi}}=500\end{array}\right.---\left(12\right)$

The Bert figure of Voltage loop open-loop transfer function before and after compensating as shown in Figure 7.After compensation Voltage loop open-loop transfer function amplitude-versus-frequency curve with the slope of-20dB/dec through zero point.System cross-over frequency is 536rad/sec, and magnitude margin is 21.2dB, and Phase margin is 66.5deg, can obtain good dynamic characteristic and steady-state characteristic.

By reference to the accompanying drawings the present invention is exemplarily described above; obviously specific implementation of the present invention is not subject to the restrictions described above; as long as adopted the improvement of the various unsubstantialities that method of the present invention design and technical scheme carry out; or without improving, design of the present invention and technical scheme are directly applied to other occasion, all within protection scope of the present invention.

Claims (4)

1. two closed loop control methods of the photovoltaic Boost converter of a photovoltaic energy storage system, it is characterized in that: described photovoltaic energy storage system comprises photovoltaic module, lithium ion battery, public electric wire net, local load and power inverter, described power inverter comprises photovoltaic side Boost converter, battery side Buck-Boost converter and load-side full-bridge inverter, described lithium ion battery connects load-side full-bridge inverter through battery side Buck-Boost converter, described photovoltaic module connects load-side full-bridge inverter through photovoltaic side Boost converter, described converter connects load-side full-bridge inverter and connects local load,

When photovoltaic Boost converter is under photovoltaic power supply operating state, photovoltaic Boost converter output terminal gathers electric current and voltage signal and feeds back to electric current loop and the Voltage loop pi regulator of photovoltaic Boost converter.

2. two closed loop control methods of the photovoltaic Boost converter of photovoltaic energy storage system according to claim 1, it is characterized in that: the cross-over frequency fic of compensation after-current ring is arranged on to 1/15 place of switching frequency fs, and the corner frequency fin of electric current loop pi regulator is arranged between concussion link corner frequency and compensation after-current ring cross-over frequency.

3. two closed loop control methods of the photovoltaic Boost converter of photovoltaic energy storage system according to claim 1 and 2, it is characterized in that: the inductance parameters of described photovoltaic Boost converter is got L=2mH, dc-link capacitance parameter is got C=2000uF, DC bus-bar voltage is 480V, duty ratio gets 0.5, load is taken as R=46.08 Ω according to photovoltaic peak power output 5kW design, and described pi regulator comprises Voltage loop pi regulator and electric current loop pi regulator, and wherein the parameter of electric current loop pi regulator is the parameter of Voltage loop pi regulator is

4. two closed loop control methods of the photovoltaic Boost converter of photovoltaic energy storage system according to claim 2, is characterized in that: the break angular frequency of described concussion link is: wherein D is switching tube S1 duty ratio, D '=1-D, and C is dc-link capacitance.