阅读说明：本技术 一种三电平llc变换器及其控制方法 (Three-level LL C converter and control method thereof ) 是由 何艳凯 张运刚 张学武 薛玉山 郭小强 于 2020-04-18 设计创作，主要内容包括：本发明公开了一种三电平LLC变换器及其控制方法,所述三电平LLC变换器包含四个直流输入滤波电容,四个开关器件,一个钳位电容,两个滤波器,两个变压器,两个二极管以及一个输出稳压电容；所述控制方法包含输出电压分数阶控制调节以及驱动信号产生环节。所述三电平LLC变换器拓扑开关应力小,为直流母线电压的一半,开关损耗小,提高系统效率,最后所述三电平LLC变换器能够实现电路输入电容电压自平衡,无需增加大量电压传感器和复杂电压均衡控制算法,其系统控制结构简单,具备优良的抗扰性,稳态和动态性能,具有工程应用价值。(The invention discloses a three-level LL C converter and a control method thereof, wherein the three-level LL C converter comprises four direct current input filter capacitors, four switching devices, a clamping capacitor, two filters, two transformers, two diodes and an output voltage stabilizing capacitor, and the control method comprises an output voltage fractional order control regulation and driving signal generation link, the three-level LL C converter is small in topological switch stress and half of direct current bus voltage, small in switch loss and capable of improving system efficiency, and finally the three-level LL C converter can achieve circuit input capacitor voltage self-balancing without adding a large number of voltage sensors and complex voltage balance control algorithms.)

1. A three-level LL C converter comprises a switch unit, a transformer and an output rectifying unit, wherein the switch unit is electrically connected with the output rectifying unit by the transformer, and the switch unit is formed as the input end of the converter and is connected with a power supply V_inThe output rectifying unit is formed as a converter output end V_oThe switch unit comprises switch devices S1, S2, S3 and S4, and is characterized in that:

the switching devices S1, S2, S3 and S4 are connected in series at the open/close sides thereof to a power supply V_inBetween the positive and negative electrodes of (1);

the electric switch unit is connected with a capacitor loop in parallel, and the capacitor loop comprises a power supply V_inCapacitors C1, C2, C3 and C4 which are connected in series sequentially from the positive electrode to the negative electrode;

the transformer comprises a first transformer and a second transformer;

the series connection point of the switching device S1 and the switching device S2 is connected with the primary side anode of the first transformer through an inductor L1, and the primary side cathode of the first transformer is electrically connected with the series connection point of a capacitor C1 and a capacitor C2 of the capacitor loop;

the series connection point of the switching device S3 and the switching device S4 is connected with the primary side anode of the second transformer through an inductor L2, and the primary side cathode of the second transformer is electrically connected with the series connection point of a capacitor C3 and a capacitor C4 of the capacitor loop;

the series point of the switching device S2 and the switching device S3 is electrically connected with the series point of the capacitor C2 and the capacitor C3.

2. The three-level LL C converter according to claim 1, wherein a clamping capacitor C5 is connected in parallel between the switching device S2 and the switching device S3.

3. The tri-level LL C inverter as claimed in claim 1, wherein said output rectifying unit includes diodes D1 and D2, and the anodes of the secondary sides of said first and second transformers are respectively connected in series with diodes D1 and D2 and then electrically connected to form a transformer output terminal V_oThe secondary sides of the first and second transformers are connected to form a transformer output end V_oThe negative electrode of (1).

4. The three-level LL C converter as claimed in claim 3, wherein the transformer output V_oA filter capacitor C6 is connected in series between the anode and the cathode.

5. A control method based on the three-level LL C converter of claim 1, wherein the control method comprises

Step 1, fractional order control and regulation of output voltage:

the error of the output voltage is △ u₀＝V_o ^*-V_oWherein △ u₀As an output voltage error magnitude, V_o ^*For output voltage reference, V_oIs output voltage feedback;

the output voltage error is controlled by fractional order to adjust the transfer function of 1 toThe output voltage feedback has a transfer function of fractional order control regulation 2

k1, k2, k3 are control variables, λ a, λ b are fractions,

subtracting the two results to obtain the reference frequency f^*；

Step 2, a driving signal generation link:

the reference frequency f obtained in the step 1^*And sending the signals to a three-level PFM driving signal generating module to generate driving signals for controlling the four switching devices S1, S2, S3 and S4.

Technical Field

The invention relates to the technical field of converters, in particular to a three-level LL C converter and a control method thereof.

Background

With the rapid development of the power electronic industry, LL C converters are widely applied, such as military power supplies, electric vehicle Charging piles, new energy power generation systems, uninterruptible power supplies, smart grids and the like, LL C converters can achieve soft switching technology, further eliminate switching loss, reduce electromagnetic interference, improve conversion efficiency of electric energy, achieve high efficiency and high power density of the system, however, voltage regulation of the conventional LL C Converter and the control method thereof has great dependence on load conditions, so that the output voltage Range of the conventional LL C Converter is limited, in order to solve the problem, Wanghao et al provides a PWM LL C Type Converter based on pulse width 865 Converter adapter applied to IEEE Transaction on Power Electronics, compared with the conventional LL C topology, the design of the PWM LL C Converter is optimized, the wide voltage Range of the load condition is achieved, the PWM LL C Converter based on PEV changing Applications is provided, compared with the conventional strategy, the three-phase voltage level Converter has a wide voltage output gain Range, the three-phase voltage level control algorithm is not required by a high-voltage balance control algorithm, and a high-voltage level control algorithm is required by a broadband voltage balance Converter equivalent to achieve a wide-voltage output voltage Range of a broadband voltage output voltage balance control algorithm equivalent to achieve a broadband voltage balance of a broadband load voltage regulator equivalent, a broadband voltage output voltage regulator equivalent, and a broadband voltage balance control algorithm with a broadband voltage equivalent to achieve a broadband voltage balance of a broadband voltage equivalent to a broadband voltage equivalent to achieve a broadband voltage equivalent to a broadband voltage equivalent load equivalent voltage equivalent to a broadband voltage equivalent load equivalent of a broadband voltage equivalent to a broadband voltage equivalent load equivalent to a broadband voltage equivalent of a broadband voltage equivalent to a.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a three-level LL C converter and a control method thereof, which have the advantages of small switching stress, small switching loss, high system efficiency and the like, can realize circuit capacitance self-balance without adding a large number of voltage sensors and complex voltage balance control algorithms, and have excellent interference resistance, steady state and dynamic performance.

The invention adopts the specific technical scheme that:

a three-level LL C converter comprises a switch unit, a transformer and an output rectifying unit, wherein the switch unit is electrically connected with the output rectifying unit by the transformer, and the switch unit is formed as the input end of the converter and is connected with a power supply V_inThe output rectifying unit is formed as a converter output end V_oThe switching unit includes switching devices S1, S2, S3 and S4,

the switching devices S1, S2, S3 and S4 are connected in series at the open/close sides thereof to a power supply V_inBetween the positive and negative electrodes of (1);

the electric switch unit is connected with a capacitor loop in parallel, and the capacitor loop comprises a power supply V_inCapacitors C1, C2, C3 and C4 which are connected in series sequentially from the positive electrode to the negative electrode;

the transformer comprises a first transformer and a second transformer;

the series connection point of the switching device S1 and the switching device S2 is connected with the primary side anode of the first transformer through an inductor L1, and the primary side cathode of the first transformer is electrically connected with the series connection point of a capacitor C1 and a capacitor C2 of the capacitor loop;

the series connection point of the switching device S3 and the switching device S4 is connected with the primary side anode of the second transformer through an inductor L2, and the primary side cathode of the second transformer is electrically connected with the series connection point of a capacitor C3 and a capacitor C4 of the capacitor loop;

the series point of the switching device S2 and the switching device S3 is formed as a point N, the series point of the capacitor C2 and the capacitor C3 is formed as a point O, and the point N is electrically connected with the point O.

The capacitors C1, C2, C3 and C4 are DC input filter capacitors,

and a clamping capacitor C5 is connected in parallel between the switching device S2 and the switching device S3.

Said outputThe rectifying unit comprises diodes D1 and D2, and the secondary anodes of the first and second transformers are respectively connected with diodes D1 and D2 in series and then electrically connected to form a transformer output end V_oThe secondary sides of the first and second transformers are connected to form a transformer output end V_oThe negative electrode of (1).

The output end V of the transformer_oA filter capacitor C6 is connected in series between the anode and the cathode.

A control method based on a three-level LL C converter comprises the following steps

Step 1, fractional order control and regulation of output voltage:

the error of the output voltage is △ u₀＝V_o ^*-V_oWherein △ u₀As an output voltage error magnitude, V_o ^*For output voltage reference, V_oIs output voltage feedback;

the output voltage error is controlled by fractional order to adjust the transfer function of 1 toThe output voltage feedback has a transfer function of fractional order control regulation 2(k1, k2, k3 are control variables, λ a, λ b are fractions), and the two results are subtracted to obtain the reference frequency f^*；

Step 2, a driving signal generation link:

the reference frequency f obtained in the step 1^*And sending the signals to a three-level PFM driving signal generating module to generate driving signals for controlling the four switching devices S1, S2, S3 and S4.

The invention has the beneficial effects that:

the three-level LL C converter and the control method thereof provided by the invention have the advantages of small switching stress, small switching loss, high system efficiency and the like, can realize circuit capacitance self-balancing without adding a large number of voltage sensors and a complex voltage balance control algorithm, have excellent interference resistance, steady state and dynamic performance, and improve the system performance of the LL C converter.

Drawings

FIG. 1 is a circuit diagram of a three-level LL C converter provided by the present invention;

fig. 2 shows an embodiment of a method for controlling a three-level LL C converter according to the present invention.

Detailed Description

The invention will be further described with reference to the following drawings and specific embodiments: