CN111277160A - A six-switch power decoupling circuit and its control method - Google Patents

Abstract

The invention discloses a six-switch power decoupling circuit and a control method thereof, wherein the six-switch power decoupling circuit comprises the following steps: six switch tubes S₁‑S₆Six diodes D₁‑D₆Two capacitors C_d1、C_d2And an inductance L_d；S₁‑S₆Are each independently of D₁‑D₆Antiparallel, S₁Emitter and S₂Forming a first branch, S₃Emitter and S₄Are connected in series with C_d1Form a second branch, S₅Emitter and S₆Are connected in parallel and in series with C_d2A third branch is formed, and the three branches are connected in parallel at the same time; inductor L_dAnd S₁The collector of (a) is connected to the micro-inverter ac output side. The invention is based on the micro-inversionThe alternating current output side of the transformer is connected with a power decoupling circuit, so that energy buffering is born, the coupling capacitance value is greatly reduced, the secondary disturbance power is reduced, and the performance and the service life of the micro inverter are improved. The six-switch power coupling circuit is controlled by adopting a pulse modulation technology PEM, and the six-switch power coupling circuit has the characteristics of simple structure and convenience in control.

Description

A six-switch power decoupling circuit and its control method

technical field

The invention relates to the technical field of micro-inverters, in particular to a six-switch power decoupling circuit and a control method thereof.

Background technique

Micro-inverters have many advantages, such as high power generation, easy expansion, low cost, hot-swap and modular design, which make them gradually become the mainstream of distributed power generation systems. However, in a distributed generation system, under the control of Maximum Power Point Tracking (Maximum PowerPoint Tracking, MPPT), the input power generated by the photovoltaic modules is constant, but the power entering the grid is the power pulse of twice the power frequency. The instantaneous values of are inconsistent. Therefore, in traditional micro-inverters, electrolytic capacitors are used to balance the instantaneous input and output power, but this also causes the life of electrolytic capacitors to be much shorter than other components in the circuit. Therefore, the study of electrolytic capacitor-free micro-inverters has become a way to improve the performance and life of micro-inverters, and scholars at home and abroad have carried out researches one after another.

The electrolytic capacitor-free micro-inverter technology realizes energy buffering by connecting a power decoupling circuit in parallel in the micro-inverter, and the power decoupling circuit is composed of a power switch and passive devices. There are three types of power decoupling circuits classified by access point: DC input side type, DC-link (DC support capacitor) intermediate side type, and AC output side type.

Among them, the DC input side power coupling circuit is usually suitable for single-stage grid-connected micro-inverters. A flyback single-stage micro-inverter proposed by Professor Shimizu of Tokyo Metropolitan University in Japan. After using the power decoupling circuit, the 100W micro-inverter only needs 40uF film capacitors, but the conversion efficiency is very low, only 70%. Professor B.J. Pierquet from the University of Washington proposed a two-stage micro-inverter structure, in which a power decoupling circuit is connected in series between the photovoltaic array and the micro-inverter to control energy storage and voltage fluctuations, avoiding the use of electrolytic capacitors, and at the same time Micro-inverter reactive power transmission is maintained. However, although this type of circuit has a simple structure, the power decoupling control of the system is relatively complex, and the MPPT and islanding detection operations are also difficult, which reduces the system efficiency, the system boost ratio is low, the photovoltaic DC output voltage is high, and the decoupling capacitance value still larger.

In the multi-level micro-inverter, due to the high voltage of the intermediate DC side, the power decoupling technology of the DC-link intermediate side type is adopted. G.A.J.Amaratunga et al. of the University of Cambridge, UK, proposed a three-level structure micro-photovoltaic grid-connected micro-inverter. The micro-inverter consists of a phase-shifted full-bridge circuit, a Buck circuit and a full-bridge micro-inverter. Among them, the phase-shift full-bridge circuit realizes the boost and MPPT functions, the Buck circuit generates a sinusoidal half-wave current, and the last stage circuit generates a sinusoidal injection current. At this time, in order to reduce the decoupling capacitor value, the DC side voltage fluctuates greatly and still produces considerable secondary power disturbance.

It can be seen that the existing electrolytic capacitor-free micro-inverter technology generally has the problems of complex structure, inconvenient control, large decoupling capacitance value, and large secondary power disturbance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a six-switch power decoupling circuit and a control method thereof, so as to solve the ubiquitous complex structure, inconvenient control, large decoupling capacitance value and two The problem of large secondary power disturbance.

For achieving the above object, the present invention provides the following scheme:

A six-switch power decoupling circuit, comprising: a first switch S ₁ , a second switch S ₂ , a third switch S ₃ , a fourth switch S ₄ , a fifth switch S ₅ , and a sixth switch S ₆ , first diode D ₁ , second diode D ₂ , third diode D ₃ , fourth diode D ₄ , fifth diode D ₅ , sixth diode D ₆ , the first capacitor C _d1 , the second capacitor C _d2 and the inductance L _d ;

The collector of the _first switch S1, the collector of the _third switch S3 and the collector of the _fifth switch S5 are all connected to one end of the AC output side of the micro-inverter;

The emitter of the _first switch S1 is connected to the emitter of the _second switch S2; the _first switch S1 is connected to the _first diode D1 in antiparallel; The two switch tubes S ₂ are connected in reverse parallel with the second diode D ₂ ;

The emitter of the _third switch S3 is connected to the emitter of the _fourth switch S4 _; the collector of the fourth switch S4 is connected to one end of the first capacitor _Cd1 ; the The _third switch S3 is connected in antiparallel with the third diode _D3 ; the _fourth switch S4 is connected in reverse parallel with the _fourth diode D4;

The emitter of the _fifth switch S5 is connected to the emitter of the six switches; the collector of the six switches is connected to one end of the second capacitor _Cd2 ; the _fifth switch S5 is connected to the The _fifth diode D5 is connected in antiparallel; the sixth switch tube _S6 is connected in antiparallel with the _sixth diode D6;

The collector of the second switch tube S ₂ , the other end of the first capacitor C _d1 and the other end of the second capacitor C _d2 are all connected to one end of the inductor L _{d ;} The other end is connected to the other end of the AC output side of the micro-inverter.

Optionally, the inverse parallel connection is that the emitter of the switch tube is connected to the anode of the diode, and the collector of the switch tube is connected to the cathode of the diode.

Optionally, the other end of the inductor L _d is connected to the common ground terminal of the AC output side of the micro-inverter and the grid voltage.

Optionally, the first capacitor Cd1 and the second capacitor Cd2 are both decoupling capacitors.

A control method of a six-switch power decoupling circuit, wherein the six-switch power decoupling circuit comprises: a first switch tube S ₁ , a second switch tube S ₂ , a third switch tube S ₃ , a fourth switch tube S ₄ , The fifth switch S ₅ , the sixth switch S ₆ , the first diode D ₁ , the second diode D ₂ , the third diode D ₃ , the fourth diode D ₄ , the fifth diode tube D ₅ , sixth diode D ₆ , first capacitor C _d1 , second capacitor C _d2 and inductor L _d ; the collector of the _first switch S1 and the collector of the _third switch S3 The electrode and the collector of the _fifth switch S5 are both connected to one end of the AC output side of the micro-inverter; the emitter of the _first switch S1 is connected to the emitter of the _second switch S2; The first switch S ₁ is connected in anti-parallel with the first diode D ₁ ; the second switch S ₂ is connected in anti-parallel with the second diode D ₂ ; the third switch S ₃ The emitter of the _fourth switch S4 is connected to the emitter of the fourth switch S4 _; the collector of the fourth switch S4 is connected to one end of the first capacitor _Cd1 ; the _third switch S3 is connected to the The third diode _D3 is in antiparallel; the _fourth switch S4 is antiparallel to the _fourth diode D4; the emitter of the _fifth switch S5 is connected to the six switches The emitter of the six-switch tube is connected to one end of the second capacitor C _d2 ; the fifth switch tube S ₅ is connected to the fifth diode D ₅ in anti-parallel; _Six switches S6 are connected in antiparallel with the _sixth diode D6; the collector of the _second switch S2, the other end of the first capacitor C _d1 , and the second capacitor C _d2 The other end is connected to one end of the inductor L _d ; the other end of the inductor L _d is connected to the other end of the AC output side of the micro-inverter;

The control method includes:

obtaining the output voltage of the AC output side of the micro-inverter and the decoupling current of the six-switch power decoupling circuit;

Judging whether the output voltage of the AC output side of the micro-inverter is greater than 0, and obtaining a first judgment result;

If the first determination result is that the output voltage at the AC output side of the micro-inverter is greater than 0, determine whether the decoupling current is in the same direction as the output voltage, and obtain a second determination result;

If the second judgment result is that the decoupling current is in the same direction as the output voltage, controlling the six-switch power decoupling circuit to operate in the first operating mode to absorb energy;

If the second judgment result is that the decoupling current and the output voltage are in opposite directions, controlling the six-switch power decoupling circuit to work in the second working mode to release energy;

If the first judgment result is that the output voltage at the AC output side of the micro-inverter is less than 0, judge whether the decoupling current is in the same direction as the output voltage, and obtain a third judgment result;

If the third judgment result is that the decoupling current and the output voltage are in the same direction, controlling the six-switch power decoupling circuit to operate in a third operating mode to absorb energy;

If the third determination result is that the decoupling current and the output voltage are in opposite directions, the six-switch power decoupling circuit is controlled to work in a fourth working mode to release energy.

Optionally, the controlling the six-switch power decoupling circuit to work in the first working mode to absorb energy specifically includes:

Control the second switch tube S ₂ , the fourth switch tube S ₄ , the fifth switch tube S ₅ and the sixth switch tube S ₆ to be off, and the third switch tube S ₃ to be turned on , the first switch tube S ₁ is controlled by the pulse energy modulation PEM signal as the main control switch; at this time, the first capacitor C _d1 absorbs energy.

Optionally, the controlling the six-switch power decoupling circuit to work in the second working mode to absorb energy specifically includes:

Control the first switch S ₁ , the third switch S ₃ , the fifth switch S ₅ and the sixth switch S ₆ to be off, and the second switch S ₂ to be turned on , the fourth switch tube S ₄ is controlled by the PEM signal as a main control switch; at this time, the first capacitor C _d1 releases energy.

Optionally, the controlling the six-switch power decoupling circuit to work in a third working mode to absorb energy specifically includes: the first switch S ₁ , the third switch S ₃ , and the fourth switch _The tube S4 and the _fifth switch tube S5 are both turned off, the sixth switch tube _S6 is turned on, and the _second switch tube S2 is controlled by the PEM signal as the main control switch; at this time, the second capacitor C _d2 absorbs energy.

Optionally, the controlling the six-switch power decoupling circuit to work in a fourth working mode to absorb energy specifically includes: the second switch S ₂ , the third switch S ₃ , and the fourth switch Both the tube S4 and the sixth switch tube _S6 are turned off, the _first switch tube S1 is turned _on , and the _fifth switch tube S5 is controlled by the PEM signal as the main control switch; at this time, the second capacitor C _d2 releases energy.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The invention discloses a six-switch power decoupling circuit and a control method thereof, comprising: six switch tubes S ₁ -S ₆ , six diodes D ₁ -D ₆ , two capacitors C _d1 , C _d2 and an inductance L _d ; S ₁ -S ₆ are inversely parallel with D ₁ -D ₆ respectively, the emitter of S ₁ is connected with the emitter of S ₂ to form the first branch, the emitter of S ₃ is connected with the emitter of S ₄ and is connected in series C _d1 constitutes the second branch, the emitter of S ₅ is connected to the emitter of S ₆ and is connected in series with C _d2 to form the third branch, and the three branches are connected in parallel at the same time; the inductance L _d is connected to the collector of S ₁ in a micro-reverse The AC output side of the inverter. By connecting the power decoupling circuit on the AC output side of the micro-inverter, the invention undertakes energy buffering, greatly reduces the coupling capacitance value, reduces the secondary disturbance power, and improves the performance and life of the micro-inverter. In addition, the invention adopts the pulse modulation technology PEM to control the six-switch power coupling circuit, and has the characteristics of simple structure and convenient control.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a schematic diagram of a topology structure of a six-switch power decoupling circuit provided by the present invention;

2 is a schematic diagram of the structure and power relationship of a six-switch power decoupling circuit without electrolytic capacitor micro-inverter provided by the present invention;

3 is a schematic diagram of the relationship between the input power (P _I ), the output power (P _o ) and the decoupling power (P _c ) in the micro-inverter provided by the present invention;

4 is a schematic diagram of the working mode sequence of a coupling circuit in a power grid cycle provided by the present invention;

5 is a schematic diagram of four working modes of the power decoupling circuit provided by the present invention; FIG. 5(A) is a schematic diagram of a first working mode of the power decoupling circuit, and FIG. 5(B) is a second working mode of the power decoupling circuit Schematic diagram; FIG. 5(C) is a schematic diagram of the third working mode of the power decoupling circuit, and FIG. 5(D) is a schematic diagram of the fourth working mode of the power decoupling circuit;

6 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention working in the first working mode; A schematic diagram of the equivalent circuit of the coupling circuit working in the first working mode;

7 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention working in the second working mode; The schematic diagram of the equivalent circuit of the coupling circuit working in the second working mode;

8 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention operating in a third working mode; Schematic diagram of the equivalent circuit of the coupling circuit working in the third working mode;

FIG. 9 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention operating in a fourth working mode; FIG. 9(a) is a schematic diagram of the main control switch on-off control and current flow path, and FIG. 9(b) is a six-switch power decoupling circuit. Schematic diagram of the equivalent circuit of the coupling circuit working in the fourth working mode;

10 is a schematic diagram of the MATLAB simulation model of the control circuit of the six switch tubes provided by the present invention; wherein NOT is a NOT gate, AND is an AND gate, OR is an OR gate, boolean is a Matlab function that converts numerical values into Boolean values, T1- T6 is the driving signal of six corresponding switch tubes;

Fig. 11 is the MATLAB simulation schematic diagram of the PEM signal generation circuit provided by the present invention;

12 is a MATLAB simulation diagram of a power decoupling circuit composed of six switches provided by the present invention;

Figure 13 is a schematic diagram of the driving signal of the switch tube of the six-switch decoupling circuit provided by the present invention; Figure 13 (a) is the driving signal of the decoupling circuit S ₁ S ₂ , (b) is the driving signal of the decoupling circuit S ₃ S ₄ , ( c) Drive signal for decoupling circuit S ₅ S ₆ .

14 is a schematic diagram of the relevant waveforms when the micro-inverter provided by the present invention is not connected to the six-switch power decoupling circuit;

FIG. 15 is a schematic diagram of relevant waveforms when the micro-inverter provided by the present invention is connected to a six-switch power decoupling circuit;

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a six-switch power decoupling circuit and a control method thereof, so as to solve the ubiquitous complex structure, inconvenient control, large decoupling capacitance value and two The problem of large secondary power disturbance.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a schematic diagram of a topology structure of a six-switch power decoupling circuit provided by the present invention. As shown in FIG. 1 , the six-switch power decoupling circuit includes: a first switch S ₁ , a second switch S ₂ , a third switch S ₃ , a fourth switch S ₄ , and a fifth switch S ₅ , the sixth switch _S6 , the _first diode D1, the _second diode D2, the third diode _D3 , the _fourth diode D4, the _fifth diode D5, the sixth diode The diode D ₆ , the first capacitor C _d1 , the second capacitor C _d2 and the inductor L _d . Among them, S ₁ -S ₆ are respectively connected in reverse parallel with D ₁ -D ₆ , the emitter of switch _S1 is connected with the emitter of switch S2 to form the _first branch, and the emitter _of switch S3 is connected to the switch S2. _The emitter of S4 is connected in series with C _d1 to form the second branch, the emitter of switch _S5 is connected with the emitter of switch _S6 and connected in series with C _d2 to form the third branch, and the three branches are connected in parallel at the same time. One end of the inductor L _d is connected to the common ground terminal of the AC output side of the micro-inverter and the grid voltage, the other end of the inductor L _d is connected to the collector of the switch S2, and the collector _of the switch S1 is connected to the AC output side of the micro _- inverter one end. The inverse parallel connection is that the emitter of the switch tube is connected to the anode of the corresponding diode, and the collector of the switch tube is connected to the cathode of the corresponding diode.

Specifically, as shown in FIG. ₁ , the collector of the first switch S1, the collector of the _third switch S3 and the collector of the _fifth switch S5 are all connected to the micro-inverter One end of the AC output side; the emitter of the _first switch S1 is connected to the emitter of the _second switch S2; the _first switch S1 is opposite to the _first diode D1 The second switch tube S ₂ is connected in reverse parallel with the second diode D ₂ ; the emitter of the third switch tube S ₃ is connected to the emitter of the fourth switch tube S ₄ ; the The collector of the _fourth switch S4 is connected to one end of the first capacitor _Cd1 ; the _third switch S3 is connected to the third diode _D3 in antiparallel; the fourth switch S ₄ is connected in reverse parallel with the _fourth diode D4; the emitter of the _fifth switch S5 is connected to the emitter of the six-switch; the collector of the six-switch is connected to the second one end of the capacitor C _d2 ; the fifth switch tube S ₅ and the fifth diode D ₅ are in anti-parallel; the sixth switch tube S ₆ and the sixth diode D ₆ are anti-parallel; The collector of the second switch tube S ₂ , the other end of the first capacitor C _d1 and the other end of the second capacitor C _d2 are all connected to one end of the inductor L _{d ;} The other end is connected to the other end of the AC output side of the micro-inverter.

The other end of the inductor L _d is connected to the common ground terminal of the AC output side of the micro-inverter and the grid voltage.

The first capacitor Cd1 and the second capacitor Cd2 are both decoupling capacitors.

Only when the two switches of the same branch are disconnected at the same time, the branch is completely disconnected. By controlling the on-off of the switch tube, the working mode of the circuit is changed to realize energy buffering.

FIG. 2 is a schematic diagram of the structure and power relationship of a six-switch power decoupling circuit (referred to as a power decoupling circuit) micro-inverter provided by the present invention. As shown in Figure 2, the micro-inverter and the power decoupling circuit constitute a micro-inverter, the micro-inverter adopts a common structure, and the power decoupling circuit part adopts the six-switch power decoupling circuit provided by the present invention. The AC output side is connected to the power decoupling circuit in parallel, and the inductor L and the capacitor C constitute a filtering device. where V _dc is the DC side voltage, I _dc is the DC side current, U _inv is the AC output side voltage of the micro-inverter, v _grid is the grid voltage, i _grid is the injection current of the micro-inverter to the grid, and P _I is the DC side side input power, P _o is the output power of the micro-inverter, and P _c is the decoupling power of the power decoupling circuit.

Due to the inconsistency between the DC side input power and the instantaneous output power of the micro-inverter, the traditional method uses electrolytic capacitors to balance the two, but the life of the micro-inverter is greatly shortened. Using the three-phase six-switch power decoupling circuit in the present invention to replace the electrolytic capacitor can greatly improve the stability and life of the micro-inverter.

Figure 3 shows the relationship between input power (P _I ), output power (P _o ), and decoupling power (P _c ) in a microinverter. As shown in Figure 3, in the microinverter, the power decoupling circuit balances the input power and the instantaneous output power. Specifically, when P _I <P _o , P _c >0, the power decoupling circuit supplements the input power; when P _I >P _o , P _c <0, the power decoupling circuit absorbs excess input power. DC side input power P _I , instantaneous output power P _o .

As shown in Figure 2, the output voltage U _inv of the micro-inverter is positive and negative, so the input voltage of the power decoupling circuit is also positive and negative, and the decoupling current is also positive and negative, so the power decoupling circuit has four working modes :

Mode 1 (that is, the first working mode): when U _inv >0, the decoupling current is in the same direction as the voltage, and the power decoupling circuit absorbs energy;

Mode 2 (ie the second operating mode): when U _inv >0, the decoupling current and voltage are in opposite directions, and the power decoupling circuit releases energy;

Mode 3 (that is, the third working mode): when U _inv < 0, the decoupling current is in the same direction as the voltage, and the power decoupling circuit absorbs energy;

Mode 4 (ie, the fourth working mode): when U _inv <0, the decoupling current and voltage are in opposite directions, and the power decoupling circuit releases energy.

FIG. 4 is a schematic diagram of the working mode sequence of the coupling circuit in one grid cycle. As shown in Figure 4, Mode 1 and Mode 2 work in the positive half cycle of the grid voltage, and Mode 3 and Mode 4 work in the negative half cycle. A cycle can be divided into 6 parts, which are Mode 1 → Mode 2 → Mode 1 → Mode 3 → Mode 4 → Mode 3. The absorption and release of the input power by the power decoupling circuit are respectively absorption → release → absorption → absorption → release → absorb.

FIG. 5 is a schematic diagram of four operating modes of the power decoupling circuit. As shown in Figure 5, the power decoupling circuit realizes the power decoupling function through the inductor and the capacitor. The inductor connects the voltage and current of the micro-inverter and the power decoupling circuit, and the capacitor absorbs and releases the energy. The polarities of the two ends of the decoupling capacitor are fixed. If the power decoupling circuit absorbs energy, the voltage and current are in the same direction, and the direction of the capacitor is the same as the current direction; if the power decoupling circuit releases energy, the voltage and current are reversed, and the direction of the capacitor is also the same as the direction of the current. on the contrary. The positive direction of voltage is assumed to be up and down and negative, and the positive direction of current is from left to right.

When U _inv >0, the power decoupling circuit absorbs energy, the capacitor voltage increases, and the direction of the voltage and current is judged. The power decoupling circuit can be equivalent to a Boost circuit as shown in Figure 5(A); when U _inv >0, the power decoupling The coupling circuit releases energy, the capacitor voltage decreases, and the direction of the voltage and current is judged. The power decoupling circuit can be equivalent to a Buck circuit as shown in Figure 5(B); when U _inv < 0, the power decoupling circuit absorbs energy and the capacitor voltage increases, To judge the direction of voltage and current, the power decoupling circuit can be equivalent to a Boost circuit as shown in Figure 5(C); when U _inv < 0, the power decoupling circuit releases energy, the capacitor voltage decreases, and to judge the direction of voltage and current, the power decoupling circuit can The equivalent Buck circuit is shown in Figure 5(D).

Based on the six-switch power decoupling circuit provided by the present invention, the present invention also provides a control method for the six-switch power decoupling circuit, the control method comprising:

obtaining the output voltage of the AC output side of the micro-inverter and the decoupling current of the six-switch power decoupling circuit;

Judging whether the output voltage of the AC output side of the micro-inverter is greater than 0, and obtaining a first judgment result;

If the first determination result is that the output voltage at the AC output side of the micro-inverter is greater than 0, determine whether the decoupling current is in the same direction as the output voltage, and obtain a second determination result;

If the second judgment result is that the decoupling current is in the same direction as the output voltage, controlling the six-switch power decoupling circuit to operate in the first operating mode to absorb energy;

If the second judgment result is that the decoupling current and the output voltage are in opposite directions, controlling the six-switch power decoupling circuit to work in the second working mode to release energy;

If the first judgment result is that the output voltage at the AC output side of the micro-inverter is less than 0, judge whether the decoupling current is in the same direction as the output voltage, and obtain a third judgment result;

If the third judgment result is that the decoupling current and the output voltage are in the same direction, controlling the six-switch power decoupling circuit to operate in a third operating mode to absorb energy;

If the third determination result is that the decoupling current and the output voltage are in opposite directions, the six-switch power decoupling circuit is controlled to work in a fourth working mode to release energy.

The first working mode (Mode I) to the fourth working mode (Mode IV) are shown in Figures 6 to 9, respectively, and Figure (a) in Figures 6 to 9 is the main control switch on-off control and current Schematic diagram of the circulation path, and Figure (b) is a schematic diagram of an equivalent circuit. The output of the micro-inverter is taken as the equivalent voltage source, which is represented by U _inv , U _inv+ is the positive electrode of the equivalent voltage source, U _inv- is the negative electrode of the equivalent voltage source, and P _pv is the DC input of the micro-inverter side power, P _ac is the output power of the AC side of the micro-inverter, C _d1+ represents the positive electrode of the coupling capacitor C _d1 , and C _d1- represents the negative electrode of the coupling capacitor C _d1 .

Specifically, FIG. 6 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention operating in the first working mode. As shown in FIG. 6 , in the first working mode, U _inv > 0, and P _pv > P _ac , S ₂ , S ₄ , S ₅ and S ₆ are disconnected, S ₃ is always on, and S ₁ is the master The switch is controlled by the PEM signal. At this time, the decoupling capacitor C _d1 absorbs energy and the voltage rises. When S ₁ is turned on, the flow path of id is U _inv+ →S ₁ → _{D 2} →L _d →U _inv- , and when S ₁ is turned off, the flow path of _id is U _inv+ →S ₃ →D ₄ →C _d1 → L _d →U _inv- .

FIG. 7 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention operating in a second working mode. As shown in Figure 7, in this working mode, U _inv > 0, and P _pv < P _ac , S ₁ , S ₃ , S ₅ and S ₆ are disconnected, S ₂ is normally on, and S ₄ is used as the master switch by PEM signal control. At this time, the decoupling capacitor C _d1 releases energy and the voltage drops. When S ₄ is turned on, the id flow path is C _d1+ →S ₄ →D ₃ →U _inv →L _d →C _d1- , and when S ₄ is turned off, the _{id flow path is U inv- →} L _d → _{S 2} →D ₁ →U _inv+ . Wherein C _d1+ represents the positive electrode of the coupling capacitor C _d1 , and C _d1- represents the negative electrode of the coupling capacitor C _d1 .

FIG. 8 is a schematic diagram of the six-switch power decoupling circuit operating in a third working mode. As shown in Figure 8, the circuit is a buck-boost circuit and works as Boost. In this working mode, U _inv < 0, and P _pv > P _ac , S ₁ , S ₃ , S ₄ and S ₅ are disconnected, S ₆ is always on, and S ₂ is controlled by the PEM signal as the master switch. At this time, the decoupling capacitor C _d2 absorbs energy and the voltage rises. When S2 is turned on, the _id flow path is U _inv+ →L _d →S ₂ → _{D 1} →U _inv- , and when S2 is _{turned off, the id flow path is C d2- → S 6} →D ₅ →U _inv →L _d →C _d2+ . Wherein C _d2+ represents the positive electrode of the coupling capacitor C _d2 , and C _d2- represents the negative electrode of the coupling capacitor C _d2 .

FIG. 9 is a schematic diagram of the six-switch power decoupling circuit provided by the present invention operating in a fourth working mode. As shown in Figure 9, the circuit is a buck-boost circuit and works as a Buck. In this working mode, U _inv < 0, and P _pv < P _ac , S ₂ , S ₃ , S ₄ and S ₆ are disconnected, S ₁ is normally on, and S ₅ is controlled by the PEM signal as the master switch. At this time, the decoupling capacitor C _d2 releases energy and the voltage rises. When S5 is turned on, the _id flow path is C _d2+ →L _d →U _inv →S ₅ →D ₆ →C _d2- , and when S5 is turned off, the _{id flow path is U inv- →} S _{1 → D 2} →L _d →U _inv+ .

In each working mode, only one switch is in the On/Off (on/off) state, which is the master switch, and its drive signal is generated by the PEM, and the rest of the switch states are fixed. The main control switches S ₁ , S ₂ , S ₄ , S ₅ and S ₆ are controlled by R ₁ , R ₂ and PEM, and their logical relationship is shown in formula (1):

In the formula, R ₁ represents the grid voltage symbol, R ₁ =0 in the positive half cycle, and R ₁ =1 in the negative half cycle, which can be represented by R ₁ =sgn(-u _o ); R ₂ represents the decoupling power symbol of the micro-inverter. When the coupling power is positive, R ₂ =1, and when the decoupling power is negative, R ₂ =0, which can be represented by R ₂ =sgn[-P _pv cos(2ωt)], where sgn is the sign function and ω is the angular frequency.

Figure 10 shows the control circuit established to control six switches in the embodiment of the present invention, wherein the MATLAB simulation diagram of the PEM signal generation circuit is shown in Figure 11, and the MATLAB simulation diagram of the power decoupling circuit composed of six switches is shown in Figure 11. Figure 12. The driving signal shown in FIG. 13 is the driving signal of the six-switch power decoupling circuit used in the embodiment of the present invention. The experiment is carried out on the basis of simulation. The main circuit of the experiment is a two-stage micro-inverter, and the power supply is a 1500W regulated DC power supply. The voltage-stabilizing large electrolytic capacitor of the front-stage Boost circuit in the two-stage micro-inverter replaces the 10μF film capacitor. The experimental waveform can be obtained when the decoupling capacitor is not connected, as shown in Figure 14. The input voltage of the Boost in this experiment is 30V , when the decoupling circuit is not connected, it can be seen that there is a secondary ripple with obvious jitter at both ends of the output measurement film capacitor of the Boost circuit, and the amplitude of the secondary ripple is about 20V. You can see that the waveform is distorted significantly. After connecting the decoupling circuit, the experimental effect that can be achieved is shown in Figure 15. It can be seen that there is a secondary ripple with obvious jitter at both ends of the output measurement film capacitor of the Boost circuit, and the amplitude of the secondary ripple is about 15V. , the waveform can be seen to be significantly improved on the output side of the H-bridge. The decoupling circuit obviously plays a role in reducing the capacitance value of the Boost side capacitor.

The invention discloses a novel electrolytic capacitor-free micro-inverter technology, which is innovatively embodied in the topology structure of the power coupling circuit. The inverter part adopts the traditional voltage source topology, and the power coupling circuit is connected in parallel to the AC output end of the micro-inverter to replace the electrolytic capacitor to realize the power coupling function and improve the efficiency of the micro-inverter. Since the input power of the DC side is constant, and the AC output power is sinusoidal, the instantaneous values of the two are inconsistent, and the power coupling circuit plays the role of energy buffering. Therefore, the micro-inverter circuit of the present invention has the following advantages and innovations:

1. The AC output side of the micro-inverter is connected to the power decoupling circuit, which undertakes energy buffering, greatly reduces the coupling capacitance value, improves the performance and life of the micro-inverter, and realizes a micro-inverter without electrolytic capacitors. .

2. Carry out closed-loop control of the entire system, control the duty cycle of the switch tube of the front-stage Boost circuit by measuring the bus voltage U _dc and bus current I _dc , and control the power grid voltage U _ac and the output voltage of the AC side of the micro-inverter. The measurement moment of U _inv and decoupling capacitor voltage U _d controls the duty cycle of the four-switch H-bridge to control the grid voltage waveform and reduce the secondary disturbance power.

3. A six-switch power decoupling circuit is connected in parallel on the AC output side of the micro-inverter, which is equivalent to an active power filter to balance the pulsating energy, thereby suppressing the secondary disturbance power in the micro-inverter, and greatly reducing the high voltage on the AC side. the coupling capacitor value.

4. Using the pulse modulation technology PEM, in the DCM mode, the six-switch power coupling circuit is controlled, the structure is simple, and the control is convenient.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other.

The principles and implementations of the present invention are described herein using specific examples, and the descriptions of the above embodiments are only used to help understand the core idea of the present invention; There will be changes in the specific implementation manner and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. A six-switch power decoupling circuit, comprising: first switch tube S₁A second switch tube S₂A third switch tube S₃And a fourth switching tube S₄The fifth switch tube S₅The sixth switching tube S₆A first diode D₁A second diode D₂A third diode D₃A fourth diode D₄A fifth diode D₅A sixth diode D₆A first capacitor C_d1A second capacitor C_d2And an inductance L_d；

The first switch tube S₁Collector electrode of (1), the third switching tube S₃Collector and the fifth switching tube S₅The collectors of the micro-inverters are connected with one end of the AC output side of the micro-inverter;

the first switch tube S₁And the second switch tube S₂The emitter of (3) is connected; the first switch tube S₁And the first diode D₁Reverse parallel connection; the second switch tube S₂And a second diode D₂Reverse parallel connection;

the third switch tube S₃And the fourth switching tube S₄The emitter of (3) is connected; the fourth switch tube S₄Collector electrode of and the first capacitor C_d1Is connected with one end of the connecting rod; the third switch tube S₃And the third diode D₃Reverse parallel connection; the fourth switch tube S₄And the fourth diode D₄Reverse parallel connection;

the fifth switch tube S₅The emitter of the six-switch tube is connected with the emitter of the six-switch tube; the collector of the six switching tubes is connected with the second capacitor C_d2One end of (a); the fifth switch tube S₅And the fifth diode D₅Reverse parallel connection; the sixth switching tube S₆And the sixth diode D₆Reverse parallel connection;

the second switch tube S₂Collector electrode of, the first capacitor C_d1And the other end of the second capacitor C_d2And the other end of the inductor L is connected with the inductor L_dIs connected with one end of the connecting rod; the inductance L_dThe other end of the second inverter is connected with the other end of the micro-inverter on the alternating current output side.

2. The six-switch power decoupling circuit of claim 1 wherein the antiparallel connection is such that the emitter of the switch is connected to the anode of the diode and the collector of the switch is connected to the cathode of the diode.

3. The six-switch power decoupling circuit of claim 1, wherein the inductance L_dThe other end of the micro-inverter is connected with the common ground end of the micro-inverter alternating current output side and the power grid voltage.

4. The six-switch power decoupling circuit of claim 1, wherein the first capacitance C is_d1And a second capacitor C_d2Are all decoupling capacitors.

5. A control method of a six-switch power decoupling circuit is characterized in that the six-switch power decoupling circuit comprises the following steps: first switch tube S₁A second switch tube S₂A third switch tube S₃And a fourth switching tube S₄The fifth switch tube S₅The sixth switching tube S₆A first diode D₁A second diode D₂A third diode D₃A fourth diode D₄A fifth diode D₅A sixth diode D₆A first capacitor C_d1A second capacitor C_d2And an inductance L_d(ii) a The first switch tube S₁Collector electrode of (1), the third switching tube S₃Collector and the fifth switching tube S₅The collectors of the micro-inverters are connected with one end of the AC output side of the micro-inverter; the first switch tube S₁And the second switch tube S₂The emitter of (3) is connected; the first switch tube S₁And the first diode D₁Reverse parallel connection; the second switch tube S₂And a second diode D₂Reverse parallel connection; the third switch tube S₃And the fourth switching tube S₄The emitter of (3) is connected; the fourth switch tube S₄Collector electrode of and the first capacitor C_d1Is connected with one end of the connecting rod; the third switch tube S₃And the third diode D₃Reverse parallel connection; the fourth switch tube S₄And the fourth diode D₄Reverse parallel connection; the fifth switch tube S₅The emitter of the six-switch tube is connected with the emitter of the six-switch tube; the collector of the six switching tubes is connected with the second capacitor C_d2One end of (a); the fifth switch tube S₅And the fifth diode D₅Reverse parallel connection; the sixth switching tube S₆And the sixth diode D₆Reverse parallel connection; the second switch tube S₂Collector electrode of, the first capacitor C_d1And the other end of the second capacitor C_d2And the other end of the inductor L is connected with the inductor L_dIs connected with one end of the connecting rod; the inductance L_dIs connected with the other end of the micro-inverterThe other end of the AC output side of the device;

the control method comprises the following steps:

acquiring output voltage of the micro-inverter alternating current output side and decoupling current of the six-switch power decoupling circuit;

judging whether the output voltage of the alternating current output side of the micro inverter is greater than 0 or not, and obtaining a first judgment result;

if the first judgment result is that the output voltage at the alternating current output side of the micro inverter is greater than 0, judging whether the decoupling current is in the same direction as the output voltage, and obtaining a second judgment result;

if the second judgment result is that the decoupling current and the output voltage are in the same direction, controlling the six-switch power decoupling circuit to work in a first working mode to absorb energy;

if the second judgment result is that the decoupling current is opposite to the output voltage, controlling the six-switch power decoupling circuit to work in a second working mode to release energy;

if the first judgment result is that the output voltage at the alternating current output side of the micro inverter is less than 0, judging whether the decoupling current is in the same direction as the output voltage, and obtaining a third judgment result;

if the third judgment result is that the decoupling current and the output voltage are in the same direction, controlling the six-switch power decoupling circuit to work in a third working mode to absorb energy;

and if the third judgment result is that the decoupling current is opposite to the output voltage, controlling the six-switch power decoupling circuit to work in a fourth working mode to release energy.

6. The method for controlling the six-switch power decoupling circuit according to claim 5, wherein the controlling the six-switch power decoupling circuit to operate in the first operating mode to absorb energy specifically comprises:

controlling the second switch tube S₂The fourth switch tube S₄The fifth switch tube S₅And the sixth switching tube S₆Are all brokenOn, the third switch tube S₃Is conducted, the first switch tube S₁As a master switch, is controlled by a pulse energy modulation PEM signal; at this time, the first capacitor C_d1Energy is absorbed.

7. The method for controlling the six-switch power decoupling circuit according to claim 5, wherein the controlling the six-switch power decoupling circuit to operate in the second operating mode to absorb energy specifically comprises:

controlling the first switch tube S₁The third switch tube S₃The fifth switch tube S₅And the sixth switching tube S₆Are all off, the second switch tube S₂On, the fourth switching tube S₄As a master switch, controlled by PEM signals; at this time, the first capacitor C_d1Energy is released.

8. The method for controlling the six-switch power decoupling circuit according to claim 5, wherein the controlling the six-switch power decoupling circuit to operate in a third operating mode to absorb energy specifically comprises: the first switch tube S₁The third switch tube S₃The fourth switch tube S₄And the fifth switch tube S₅Are all disconnected, the sixth switching tube S₆On, the second switch tube S₂As a master switch, controlled by PEM signals; at this time, the second capacitor C_d2Energy is absorbed.

9. The method for controlling the six-switch power decoupling circuit according to claim 5, wherein the controlling the six-switch power decoupling circuit to operate in a fourth operating mode to absorb energy specifically comprises: the second switch tube S₂The third switch tube S₃The fourth switch tube S₄And the sixth switching tube S₆Are all disconnected, the first switch tube S₁Is conducted, the fifth switch tube S₅As a master switch, controlled by PEM signals; at this time, the second capacitor C_d2Release energyAmount of the compound (A).

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