CN204465345U - Lossless clamped three-winding full-bridge converter for photovoltaic power generation - Google Patents

Abstract

The utility model discloses a kind of harmless clamper three winding full-bridge converter being applicable to photovoltaic generation, relate to photovoltaic generation micro-capacitance sensor field, this device comprises photovoltaic array, Boost, DC side storage capacitor, full-bridge inverter, harmless clamper three winding full-bridge converter, LC filter circuit.Wherein photovoltaic array, Boost, DC side storage capacitor, full-bridge inverter, harmless clamper three winding full-bridge converter, LC filter circuit are connected successively, power to local DC load; Harmless clamper three winding full-bridge converter adopts the full-bridge converter of cascaded structure and harmless clamp circuit to form by three groups of secondary sides, and harmless clamp circuit is made up of three clamp diodes and two high-frequency filter capacitors.The utility model has the following advantages: Width funtion inputs, and high voltage exports, and system reliability is high, loss is little, efficiency is high, and the voltage stress of rectifier diode is little.

Description

Lossless clamped three-winding full-bridge converter for photovoltaic power generation

technical field

The utility model relates to the field of solar photovoltaic power generation, in particular to a non-destructive clamped three-winding full-bridge converter based on photovoltaic power generation.

Background technique

The use of solar energy is an important way to alleviate the global energy shortage and environmental pollution problems. Photovoltaic power generation is one of the research hotspots in recent years. To supply power to loads with high DC voltage, the battery voltage is generally low, which cannot meet its power supply needs. The current mature power electronic conversion technology can convert solar energy into electrical energy, and then realize voltage conversion and power control.

In the process of energy conversion, in order to achieve maximum power tracking, the output terminal voltage of the full-bridge inverter will vary in a wide range, and the output voltage of the full-bridge converter is clamped, which requires the input voltage of the full-bridge converter The range of variation is wide, often more than double the range of variation. In response to this, corresponding research has been carried out at home and abroad: a full-bridge converter suitable for high-voltage and high-power applications is used, but due to the existence of transformer leakage inductance and rectifier diode junction capacitance, the converter rectifier diode will be in the initial stage of cut-off. Withstand high oscillating overvoltage, which puts forward high requirements on the withstand voltage level of rectifier diodes, resulting in greater device loss and EMI problems, including transformers, switch tubes and rectifier diodes.

Weakening the voltage stress of the rectifier diode becomes a difficult problem of the device. The traditional method uses capacitors, resistors, and diodes to form an RCD clamp circuit, but the resistance loss is large, which reduces the efficiency of the system; the use of a clamp circuit can suppress the oscillating voltage, but reduces the reliability of the system.

The utility model proposes a non-destructive clamping three-winding full-bridge converter suitable for photovoltaic power generation. The energy of the photovoltaic array is delivered to the full-bridge converter through the Boost boost circuit and the full-bridge inverter. The lossless clamp full-bridge converter is composed of a series-structured full-bridge converter and a lossless clamp circuit. The lossless clamp circuit consists of It consists of three clamping diodes and two high frequency filter capacitors. By optimizing the turn ratio of the secondary side winding, the duty cycle range is wider, and the minimum duty cycle reaches 0.382. The full-bridge converter can work in the occasion where the input voltage variation range is greater than twice the output voltage. At the same time, the circuit topology makes The rectifier diode voltage stress remains below the output voltage.

Contents of the invention

The technical problem to be solved by the utility model is to provide a non-destructive clamped three-winding full-bridge converter suitable for photovoltaic power generation in view of the deficiencies in the prior art. It is composed of a lossless clamping circuit, and the lossless clamping circuit is composed of three clamping diodes and two high-frequency filter capacitors. By optimizing the turn ratio of the secondary side winding, the duty cycle range is wider, and the converter can work where the input voltage variation range is greater than twice the output voltage, and the voltage stress of the rectifier diode is kept below the output voltage.

The technical solution of the utility model is: the converter device includes a photovoltaic array, a Boost converter, a DC side energy storage capacitor, a full-bridge inverter, and a lossless clamp three-winding full-bridge converter. Among them, the photovoltaic array, Boost converter, DC side energy storage capacitor, full-bridge inverter, and lossless clamped three-winding full-bridge converter are connected in sequence to supply power to the local DC load. The lossless clamped three-winding full-bridge converter consists of three groups The secondary side is composed of a series-structured full-bridge converter and a non-destructive clamping circuit. The non-destructive clamping circuit is composed of three clamping diodes and two high-frequency filter capacitors.

Optimizing the design of the turn ratios of the three windings on the secondary side of the full-bridge converter can broaden the working range of the full-bridge inverter's duty cycle.

The voltage stress of the rectifier diodes in the full bridge converter is kept below the output voltage.

The minimum duty cycle of the full bridge inverter reaches 0.382.

Compared with the prior art, the utility model has the following advantages: optimize the design of the turn ratio of the three windings on the secondary side of the converter, broaden the duty ratio working range of the converter, and have wide voltage input and high voltage output performance; The circuit has no switch tube, and the system reliability is high; the lossless clamping circuit is adopted, the system loss is small, and the system efficiency is high; the voltage stress of the rectifier diode is small.

Description of drawings

Figure 1 is a topology diagram of a lossless clamped three-winding full-bridge converter suitable for photovoltaic power generation.

Among them: u _g - grid voltage; C ₀ - photovoltaic side energy storage capacitor; L ₀ -Boost boost inductor; C ₁ , C ₂ - DC side voltage divider energy storage capacitor; S ₀ -Boost boost circuit switch tube; S ₁ -S ₄ -single-phase full-bridge inverter switching tube; i _pv -photovoltaic side DC current; L _s1 -L _s2 -converted to transformer secondary leakage inductance; V _{inv -full} -bridge inverter output voltage; D ₁ -D ₁₂ - rectifier diode of full bridge converter; C _D1 -C _D12 - equivalent junction capacitance of rectifier diode of full bridge converter; L _b1 -L _b3 - inductance value of output filter inductor; C _b1 -C _b3 - output filter The capacitance value of the capacitor; V ₁ -V ₃ -the output voltage of the rectifier circuit; V _o -the output voltage of the full-bridge converter.

Detailed ways

As shown in Figure 1, an embodiment of the utility model includes a photovoltaic array, a Boost converter, a DC side energy storage capacitor, a full-bridge inverter, a lossless clamped three-winding full-bridge converter, and an LC filter circuit. Among them, the photovoltaic array, Boost converter, DC side energy storage capacitor, full-bridge inverter, lossless clamping three-winding full-bridge converter, and LC filter circuit are connected in sequence to supply power to the local DC load. Among them, the lossless clamping three-winding full-bridge The converter device consists of three sets of full-bridge converters with a series structure on the secondary side and a lossless clamping circuit. The lossless clamping circuit consists of three clamping diodes D _c1 -D _c3 and two high-frequency filter capacitors C _c1 , C _c2 constitutes. The switching tube _S0 of the single-phase full-bridge inverter _S1 - _S4 is composed of an IPM module, and the model of the IPM module is PM50B5LA060.

Among them: the Boost boost circuit realizes maximum power tracking; the full-bridge inverter realizes DC/AC conversion; the full-bridge converter clamps the output voltage to provide high output voltage to the load. Boost circuit and single-phase full-bridge inverter are the existing topological structures, and the working mode will not be elaborated. The working principle of the lossless clamped three-winding full-bridge converter will be explained in detail.

The first group of uncontrolled rectifier bridges (D ₁ -D ₄ ): when D ₁ and D ₄ (or D ₂ and D ₃ ) are turned on and the output voltage V ₁ reaches the voltage V _Cb2 of capacitor C _b2 =V _o , D _C1 turns on, so the rectifier diodes D ₁ -D ₄ voltage stress is clamped at V _o . The energy generated by the oscillating circuit is transferred to C _b2 through _DC1 , and when the oscillation process ends, the energy of C _b2 is transferred to the load.

The second group of uncontrollable rectifier bridges (D ₅ -D ₈ ): when D ₅ and D ₈ (or D ₆ and D ₇ ) are turned on, the rectified output voltage V ₂ reaches the voltage of capacitor C _b1 V _Cb1 = V _Cb1 + When V _Cb2 , D _C2 conducts, the diode voltage D ₅ -D ₈ stress is clamped at the voltage V _Cb1 +V _Cb2 , the energy generated by the oscillation circuit is transferred to C _b1 through D _C2 , when the oscillation process ends, C The energy of _b1 is transferred to the load.

The third group of uncontrollable rectifier bridges (D ₉ -D ₁₂ ): the clamping process of the rectifier diodes D ₉ -D ₁₂ is similar to that of the first group of rectifier diodes D ₁ -D ₄ . The diode voltage stress is clamped by D _C3 and C _b2 such that the voltage stress is clamped at V _o .

If the turn ratios of the three sets of windings are the same, the converter cannot work when d<0.5, where d is the duty cycle of the uncontrollable rectifier bridge. The analysis is as follows: Assuming that the turn ratio of the three windings on the primary and secondary sides of the high-frequency transformer is 1:n:n:n, then V ₁ =V ₂ =V ₃ , V _o =(V ₁ +V ₂ +V ₃ )d .

In order to prevent the clamping diode of the clamping circuit from being continuously turned on during energy transfer and causing a short circuit in the filter inductor, the following conditions must be met:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Cb</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Cb</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Thus, d>0.5 is obtained. Therefore, the minimum duty cycle allowed by the full-bridge converter is 0.5, which cannot achieve a wider input voltage range.

In order to realize a wider input voltage range of the full-bridge converter, it is necessary to redesign the three-winding structure with different turn ratios, and make the turn ratio of the transformer 1:n:kn:n, so

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; inv</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k\; n</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; inv</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dn</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; inv</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Similarly, the formula must satisfy formula (1), and we can get:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

At this time d _min /(2+k)≈0.382

Theoretical analysis shows that when the turn ratio of the transformer is 1:n:0.618n:n, the minimum duty cycle of the circuit can reach 0.382, which can make the working range of the input voltage wider than the previous minimum duty cycle of 0.5.

Claims (3)

1. be applicable to the harmless clamper three winding full-bridge converter of photovoltaic generation, comprise photovoltaic array, Boost, DC side storage capacitor, full-bridge inverter, harmless clamper three winding full-bridge converter, LC filter circuit, it is characterized in that photovoltaic array, Boost, DC side storage capacitor, full-bridge inverter, harmless clamper three winding full-bridge converter, LC filter circuit are connected successively, power to local DC load; Harmless clamper three winding full-bridge converter adopts the full-bridge converter of cascaded structure and harmless clamp circuit to form by three groups of secondary sides, and harmless clamp circuit is made up of three clamp diodes and two high-frequency filter capacitors.

2. the harmless clamper three winding full-bridge converter being applicable to photovoltaic generation according to claim 1, it is characterized in that, the rectifier diode voltage stress in full-bridge converter remains on below output voltage.

3. the harmless clamper three winding full-bridge converter being applicable to photovoltaic generation according to claim 1, it is characterized in that, the lowest duty cycle of full-bridge inverter reaches 0.382.