CN102510218A - Direct current to direct current (DC-DC) power converter with high boost ratio - Google Patents

Abstract

A high step-up ratio DC-DC power converter, which relates to the technical field of voltage conversion, is to solve the problems of conventional boost converters with small step-up transformation ratio and large voltage stress of switching devices. It includes a DC At the input end, the input power can be a photovoltaic cell or a fuel cell (Vin), or a general DC power supply, including two boost inductors (L1, L2), two power switch tubes (T1, T2), two unidirectional Composed of rectifier diodes (D1, D2) and two capacitors (C1, C2). Compared with the conventional BOOST or two-phase interleaved parallel BOOST boost converter, the high boost ratio DC-DC power converter of the present invention has a larger boost transformation ratio under the same duty cycle, and the switching tube The voltage stress is low, which is beneficial to reduce the ripple of the input current, and the control is convenient and flexible. It is very suitable for the grid-connected power generation system of renewable energy such as photovoltaic/fuel cells in the future, and has a good application and promotion prospect.

Description

A High Step-Up Ratio DC-DC Power Converter

technical field

The invention relates to a high step-up ratio DC-DC power converter, which belongs to the technical field of power electronics.

technical background

At present, the world is facing prominent problems such as energy shortage, environmental pollution and greenhouse effect, while solar energy or fuel cell is a renewable clean energy with great room for development. In recent years, the power generation technologies related to these renewable energy sources have developed rapidly, and the use of photovoltaic cells or fuel cells for grid-connected power generation has attracted more and more attention. Due to the influence of environment, temperature and other factors, the output voltage of photovoltaic/fuel cells usually fluctuates greatly, and the voltage level of single battery panels or fuel cells is low, so the current grid-connected power generation devices of solar photovoltaic cells or fuel cells generally A two-stage structure is adopted, that is, the front stage is a DC-DC boost circuit, and the latter stage is an inverter. The pre-stage DC-DC boost circuit usually adopts BOOST or two-phase interleaved parallel BOOST circuit to boost the voltage. The boost ratio of the converters of these two structures is equal. When the input voltage is low, in order to achieve a higher output voltage, The switch conduction duty cycle will be very high, which will reduce the efficiency of the converter on the one hand, and at the same time the switching frequency will not be easy to further increase. In addition, in order to prolong the service life of photovoltaic cells and fuel cells, the input current ripple of the front-end DC-DC power converter should be as small as possible, so research on new high-performance converters with larger boost ratio and smaller input current ripple It has important theoretical significance and application value to meet the needs of the subsequent grid-connected inverter by using a DC-DC power converter.

Invention content:

The purpose of the present invention is to propose a high-performance high-boost ratio DC-DC power converter and its control method. This power converter can increase the boost ratio and effectively reduce the switching voltage stress of the converter. At the same time, the ripple of the input current can be reduced, which is beneficial to prolonging the service life of the battery and effectively improving the performance of the converter. The converter is not only suitable for the application range of conventional DC-DC converters, but also suitable for new energy power generation systems such as solar photovoltaic, fuel cell power generation and wind power generation.

The high step-up ratio DC-DC power converter of the present invention is shown in Figure 1, and its specific features are as follows:

1. A DC-DC power converter with a high step-up ratio, suitable for photovoltaic/fuel cell power generation systems. It is characterized in that it includes a DC input power supply (Vin) which can be a photovoltaic cell or a fuel cell, a first boost inductor (L1), a second boost inductor (L2), two power switch tubes (T1, T2), two It consists of a unidirectional rectifier diode (D1, D2) and two output capacitors (C1, C2); the specific connection method is: one end of the first boost inductor (L1) and one end of the second boost inductor (L2) are simultaneously connected to The positive pole of the input power supply (Vin) is connected, the other end of the first boost inductor (L1) is respectively connected to the drain of the power switch tube (T1) and the anode of the diode (D1), and the other end of the inductor (L2) is connected to the power switch The drain of the tube (T2) is connected, the negative pole of the input power supply (Vin) is connected to the source of the power switch tube (T1) and the power switch tube (T2), and is connected to the cathode of the diode (D2), and the output capacitor (C1) One end of the output capacitor (C1) is connected to the cathode of the diode (D1), the other end of the output capacitor (C1) is connected to the drain of the power switch tube (T2), and one end of the output capacitor (C2) is connected to the drain of the power switch tube (T2), The other end of the output capacitor (C2) is connected to the anode of the diode (D2), and the two ends of the load are respectively connected to the cathode of the diode (D1) and the anode of the diode (D2).

2. The high step-up ratio DC-DC power converter according to claim 1, characterized in that one end of the output capacitor (C1) is respectively connected to the cathode of the diode (D1) and to the positive pole of the output terminal, and the output capacitor (C1 ) are respectively connected to the drain of the power switch tube (T2) and to one end of the output capacitor (C2), and the other end of the output capacitor (C2) is connected to the anode of the diode (D2) and the cathode of the output terminal.

3. The high step-up ratio DC-DC power converter according to claims 1 and 2, characterized in that the drain of the power switch tube (T1) is respectively connected to one end of the first inductor and the anode of the diode (D1), The source of the power switch tube (T1) is respectively connected to the cathode of the input power supply (Vin) and the cathode of the diode (D2), and the drain of the power switch tube (T2) is connected to one end of the first inductor, and then connected to the output capacitor ( The junction of C1) and (C2).

4. The control method of the converter of the present invention is: the drive signals of (T1) and (T2) are phase-shifted by a phase angle of π, that is, assuming that the periods of the drive signals of (T1) and (T2) are both T, their conduction takes up The duty ratios are all D, if the driving signal of (T1) starts at time zero, then the driving signal of (T2) starts at time T/2.

Of course, a complementary control method can also be used to control the on and off of the two switches.

The converter of the present invention can not only realize the output voltage with a higher transformation ratio, but also effectively reduce the voltage stress of the switch tube and effectively reduce the ripple of the input current. The converter has excellent performance and is very suitable for photovoltaic power generation in the future. It is used in occasions such as fuel cell power generation, and has good application and promotion prospects.

Technical solutions

The present invention is achieved through the following technical solutions:

5. Accompanying drawing 1 shows the topological structure of the high step-up ratio DC-DC power converter of the present invention, including a DC input power supply (Vin), which can be a photovoltaic cell or a fuel cell, or a general DC power supply, the first A boost inductor (L1), a second boost inductor (L2), two power switch tubes (T1, T2), two unidirectional rectifier diodes (D1, D2), and two output capacitors (C1, C2) ; The specific connection method is: one end of the first boost inductor (L1) and one end of the second boost inductor (L2) are connected to the positive pole of the input power supply (Vin) at the same time, and the other end of the first boost inductor (L1) is respectively It is connected to the drain of the power switch tube (T1) and the anode of the diode (D1), the other end of the inductor (L2) is connected to the drain of the power switch tube (T2), and the negative pole of the input power supply (Vin) is connected to the power switch tube ( T1) is connected to the source of the power switch tube (T2) and at the same time connected to the cathode of the diode (D2), one end of the output capacitor (C1) is connected to the cathode of the diode (D1), and the other end of the output capacitor (C1) is connected to The drain of the power switch tube (T2), one end of the output capacitor (C2) is connected to the drain of the power switch tube (T2), the other end of the output capacitor (C2) is connected to the anode of the diode (D2), and the two ends of the load are respectively Connect between the cathode of diode (D1) and the anode of diode (D2).

In the present invention, when the input inductor (L1), (L2) current works in a continuous state or a critical continuous state, two control methods can be adopted:

(a) Complementary control

When the complementary control method is adopted, the circuit has two working modes as shown in Figure 2, 2(a) is the power switch tube (T1) is turned on, and the power switch tube (T2) is turned off mode, 2(b) The power switch tube (T1) is turned off and the power switch tube (T2) is turned on.

(b) Phase shift control

When the phase-shift π phase angle control is adopted, the circuit has two working modes with a duty cycle less than 0.5 and a duty cycle greater than or equal to 0.5.

When the duty cycle is less than 0.5, there are three working modes, as shown in Figure 2(a), 2(b), 2(c), 2(a) represents the power switch tube (T1), conduction, power switch tube (T2) off mode; 2(b) means the power switch tube (T1) is off and the power switch tube (T2) is on mode; 2(c) means the power switch tubes (T1) and (T2) are off at the same time broken mode;

When the duty cycle is greater than or equal to 0.5, the converter operates in the following three modes: the power switch (T1) and (T2) conduct simultaneously, as shown in Figure 2(d); the power switch (T1) conduction, the power switch tube (T2) is in the off mode, as shown in Figure 2(a); the power switch tube (T1) is off, and the power switch tube (T2) is in the conduction mode, as shown in Figure 2(b) Show;

Beneficial effect:

Compared with the existing BOOST or two-phase interleaved parallel BOOST power converter, the present invention has the following beneficial effects: in the case of the same duty cycle, the DC-DC power converter of the present invention has a higher step-up transformation ratio , the voltage stress of the switching tube is low, and the input current ripple can be effectively reduced at the same time, and the implementation method of the control circuit is simple and flexible, especially suitable for independent power generation or grid-connected power generation systems of solar photovoltaic cells and fuel cells.

Description of drawings

Fig. 1 is a topological structure diagram of a high boost ratio DC-DC power converter of the present invention.

Fig. 2 is an equivalent circuit diagram of each switching mode of the high step-up ratio DC-DC power converter of the present invention.

Fig. 3 is the emulation experiment waveform figure when adopting the cross-phase-shifting control method of the present invention's high step-up ratio DC-DC power converter steady-state operation, wherein the conduction duty ratio of T1 and T2 is 0.6, and the abscissa The unit is seconds, iL1 and iL2 are the currents flowing through the inductors L1 and L2, and the unit is ampere; VT1, VT2 respectively correspond to the voltage stress of the switching tubes T1 and T2, and the unit is volts; Vin and Vo correspond to the input voltage and output voltage, The unit is volts.

Detailed ways

The present invention is described in further detail below in conjunction with accompanying drawing and specific embodiment: present embodiment is carried out under the premise of technical solution of the present invention, has provided embodiment and operation process, but protection scope of the present invention is not limited to following Example.

1. Complementary control:

The input inductances (L1) and (L2) of this embodiment work under continuous or critical state of current. When using complementary control, the converter of the present invention has two working modes. The two working modes of this embodiment will be described in detail below. Analysis, and further deduce the transformation ratio of the output and input voltage of the converter of the present invention.

In the following description, T _S is the switching period of the switching tube (T1) and (T2), Ton is the conduction time of the switching tube (T1) in each switching cycle, and T _off is the switching period of the switching tube (T1) in each switching cycle. The turn-off time in the switching cycle, D is the conduction duty cycle of the power switch tube (T1), and (T2) and (T1) are completely complementary, then the converter works in the following two modes at this time.

Working mode 1: This mode is shown in Figure 2(a), that is, when the switching tube (T1) is turned on and the switching tube (T2) is turned off in each switching cycle, its dynamic characteristic equation is:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Working mode 2: This mode is shown in Figure 2(b), that is, when the switching tube (T1) is turned off and the switching tube (T2) is turned on in each switching cycle, its dynamic characteristic equation is:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

From the volt-second balance principle of the inductor, it can be deduced that the relationship between the output voltage and the input voltage of the converter of the present invention when using complementary control is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In this control method, the voltages on the two capacitors are:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V\; C"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">V</figure-callout></span><figure-callout\; id="1"\; label="V\; C"\; filenames="HSA00000605671000011.png,HSA00000605671000031.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{{\mathrm{<span\; class="notranslate">\; </span>}}_{}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; DV</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

2. Phase shift control

The input inductances (L1) and (L2) of the present embodiment work under continuous current or critical state, and D is the conduction duty ratio of each switching tube. When phase-shift control is adopted, the converter of the present invention has four kinds of operations mode, and its equivalent circuit is shown in Fig. 2. Utilizing the volt-second balance principle of the inductor current, it can be deduced that the relationship between the output and the input voltage of the converter of the present invention is:

When 0<d<0.5

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

When 0.5≤d<1

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

In the embodiment of the present invention, the input voltage Vin=48V, the inductance L1=L2==0.1mH, C1=C2=47uF/400V, the switching frequency fs=40KHz, the accompanying drawing 3 shows that the duty cycle d= In the case of 0.6, the simulation experiment waveform of this embodiment.

The simulation experiment result is completely consistent with the theoretical analysis, which illustrates the feasibility and effectiveness of the high boost ratio DC-DC power converter of the present invention and its control scheme. The high boost ratio DC-DC power converter of the present invention has The higher step-up ratio can effectively reduce the voltage stress of the switch tube and reduce the ripple of the input current. It is a DC-DC power converter with superior performance.

Claims (4)

1. A high step-up ratio DC-DC power converter, suitable for photovoltaic/fuel cell power generation systems. It is characterized in that it includes a DC input power supply (Vin) which can be a photovoltaic cell or a fuel cell, a first boost inductor (L1), a second boost inductor (L2), two power switch tubes (T1, T2), two It consists of a unidirectional rectifier diode (D1, D2) and two output capacitors (C1, C2); the specific connection method is: one end of the first boost inductor (L1) and one end of the second boost inductor (L2) are simultaneously connected to The positive pole of the input power supply (Vin) is connected, the other end of the first boost inductor (L1) is respectively connected to the drain of the power switch tube (T1) and the anode of the diode (D1), and the other end of the inductor (L2) is connected to the power switch The drain of the tube (T2) is connected, the negative pole of the input power supply (Vin) is connected to the source of the power switch tube (T1) and the power switch tube (T2), and is connected to the cathode of the diode (D2), and the output capacitor (C1) One end of the output capacitor (C1) is connected to the cathode of the diode (D1), the other end of the output capacitor (C1) is connected to the drain of the power switch tube (T2), and one end of the output capacitor (C2) is connected to the drain of the power switch tube (T2), The other end of the output capacitor (C2) is connected to the anode of the diode (D2), and the two ends of the load are respectively connected to the cathode of the diode (D1) and the anode of the diode (D2). 2. The high step-up ratio DC-DC power converter according to claim 1, characterized in that one end of the output capacitor (C1) is respectively connected to the cathode of the diode (D1) and connected to the positive pole of the output terminal, and the output capacitor (C1 ) are respectively connected to the drain of the power switch tube (T2) and to one end of the output capacitor (C2), and the other end of the output capacitor (C2) is connected to the anode of the diode (D2) and the cathode of the output terminal. 3. The high step-up ratio DC-DC power converter according to claim 1, 2, characterized in that the drain of the power switch tube (T1) is respectively connected to one end of the first inductor and the anode of the diode (D1), The source of the power switch tube (T1) is respectively connected to the cathode of the input power supply (Vin) and the cathode of the diode (D2), and the drain of the power switch tube (T2) is connected to one end of the first inductor, and then connected to the output capacitor ( The junction of C1) and (C2). 4. The converter according to claims 1, 2, and 3, characterized in that: when the two switch tubes are controlled by a cross-phase shift of 180° and when the duty cycle is greater than or equal to 0.5, the voltage gain is:

And 0.5≤D<1; when the duty cycle is less than 0.5, the voltage gain is:

And 0<D≤0.5, D is the conduction duty cycle of the switch tube (S1), and the conduction duty cycle of the switch tube (S2) is also D.

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