CN105897024A - Single-phase Cuk integrated boost-buck inverter and control method and control system thereof - Google Patents

Abstract

The invention discloses a single-phase Cuk integrated boost-buck inverter and a control method and control system thereof. The single-phase Cuk integrated boost-buck inverter comprises a boost capacitor C1, a capacitor C2, switching tubes S1, S2, S3 and S4, an inductor L1, an inductor L2, a diode D1 and a diode D2, wherein a junction point a of the switching tubes S1 and S2 is connected with the positive electrode of the diode D1, a junction point b of the switching tubes S3 and S4 is connected with the positive electrode of the diode D2, the positive electrodes of the diode D1 and the diode D2 are jointly connected with one end of the boost capacitor C1, the other end of the boost capacitor C1 is connected with one end of the inductor L2, the other end of the inductor L2 is connected with one end of the capacitor C2, the switching tube S2 and the switching tube S4 separately, and the other end the inductor L2 is connected with the inductor L1, the switching tube S1 and the switching tube S3 separately. Through the common switching tubes, a Cuk converter and a traditional full-bridge inverter are integrated, a multi-control composite modulation strategy is adopted, meanwhile, the pumping DC bus voltage of the inverter and the sine output voltage are achieved, and the single-phase Cuk integrated boost-buck inverter has the advantages of simplicity in topology, high integration, high voltage grain, low cost and the like.

Description

Single-phase Cuk integrated buck-boost inverter, control method, and control system

technical field

The invention relates to an inverter and a control method thereof, in particular to a single-phase Cuk integrated buck-boost inverter, a control method, and a control system.

Background technique

The output voltage of new power sources such as photovoltaic cells and fuel cells will vary in a wide range, which requires that the supporting inverter must have the ability to step up and down, so that it can output stable AC power within the entire input voltage range. The above-mentioned problems can be easily solved by adopting a two-stage structure, that is, cascading a DC-DC step-up/down converter and a traditional PWM voltage-type inverter. However, this scheme has disadvantages such as complex structure and high cost. In contrast, a single-stage buck-boost inverter would be a more appropriate topology choice.

The study found that the current single-stage inverters with buck-boost capability mainly include: Z-source inverters, combined inverters (such as dual Buck-Boost inverters), and active buck-boost inverters. Unfortunately, Z-source or quasi-Z-source inverters have insufficient voltage gain, large start-up inrush current, large number of components, and complex structure. Due to the inconsistency of the actual components of the combined inverter, there is a large DC component in the output, and it is difficult to take into account the rapidity and stability of the system, which easily leads to the left-right asymmetry of the output waveform. The number of switching tubes in the active buck-boost inverter is large (8), and its gain is insufficient at the same time, and the control is more complicated.

Contents of the invention

Purpose of the invention: The purpose of the invention is to solve the deficiencies in the prior art, to provide a kind of integration of Cuk converter and traditional full-bridge inverter, and to adopt multi-control variable composite modulation strategy, and to realize inverter DC at the same time Pumping of the bus voltage and sinusoidalization of the output voltage, a single-phase Cuk integrated buck-boost inverter, a control method, and a control system with the advantages of simple topology, high integration, high voltage gain, and low cost.

Technical solution: A single-phase Cuk integrated buck-boost inverter according to the present invention, including boost capacitor C ₁ , capacitor C ₂ , switch tubes S ₁ -S ₄ , inductor L ₁ , inductor L ₂ , diodes D ₁ and diode D ₂ , the switch tubes S ₁ and S ₂ are connected in series to form a first bridge arm circuit, the switch tubes S ₃ and S ₄ are connected in series to form a second bridge arm circuit, and the first bridge arm circuit and the first bridge arm circuit are connected in series. _The two bridge arm circuits are connected in parallel to form a full bridge circuit _; the junction _a of the switching tubes S1 and S2 is connected to the anode of the diode D1, and the junction point b _of the switching tubes S3 and S4 is connected to the anode _of the diode _D2 anode, the _cathodes of the diode D1 and the diode D2 are commonly connected to _one end of the boost capacitor _C1 , the other end of the boost capacitor _C1 is connected to one end of the inductor _L2 , and the other end of the inductor _L2 One end of the capacitor C ₂ , the switch tube S ₂ , and the switch tube S ₄ are respectively connected, and the other end of the capacitor C ₂ is respectively connected with the inductor L ₁ , the switch tube S ₁ , and the switch tube S ₃ .

Further, the _cathodes of the diode D1 and the diode D2 are commonly connected to the anode of the boost capacitor _C1 , and the cathode of the boost capacitor _C1 is connected to _one end of the inductor _L2 .

Further, _an input power supply is provided between the positive pole of the boost capacitor _C1 and the inductor L1.

Further, a filter circuit is also connected between the junction a and the junction b.

Further, the filter circuit adopts an LC filter circuit or an LCL filter circuit, and the filter circuit is also connected with a load.

Further, each of the switch tubes S ₁ -S ₄ includes body diodes D _s1 -D _s4 .

The present invention also discloses a control method of the above-mentioned single-phase Cuk integrated buck-boost inverter: the inverter adopts a compound modulation strategy of multiple control quantities, that is, the modulation circuit contains multiple control quantities: S _a , S _b and S _c ; among them, S _a is used to control the sine degree of the output voltage, S _b is the positive and negative polarity judgment signal of the AC voltage, and S _c is used to control the DC bus voltage to meet the voltage conditions required by the inverter, S _a The absolute value output by the output voltage loop regulator and the carrier signal are generated after being handed over by the modulation circuit, while _Sc is generated by the output of the bus voltage loop regulator and the carrier signal after being handed over by the modulation circuit. These two carrier signals are exactly the same and can be It is an asymmetrical triangle wave, a front edge sawtooth wave or a rear edge sawtooth wave. Based on the above three related control signals, the drive signals S ₁ -S ₄ ultimately required by the inverter can be obtained by further logic operations.

Further, the working process of the inverter in each switching period of the positive half-wave of the sine modulation wave includes the following three modes:

(1) Mode 1, t ₀ -t ₁ : Before time t ₀ , S ₂ and S ₄ are turned on, and L ₁ and L ₂ are linearly discharged due to the reverse voltage (U _C2 -U _in ) and U _C1 respectively ; At time t ₀ , S ₂ is turned off, S ₁ is turned on, and at time t ₁ , mode 1 ends; in this mode, for the boost part of Cuk, diode D ₁ is turned on, and the power supply voltage is fully applied to the input inductor On L ₁ , the inductor current i _L1 (t) increases linearly, and at the same time, due to the discharge of capacitor C ₂ , the current i _L2 of the output inductor L ₂ also increases linearly;

(2) Mode 2, t ₁ -t ₂ : at time t ₁ , S ₄ is turned off, S ₃ is turned on, and at time t ₂ , mode 2 ends; for the Cuk booster part, D ₁ and D ₂ are turned on , L ₁ , L ₂ still bear the forward voltage U _in and (U _C2 -U _C1 ), the current i _L1 (t), i _L2 (t) continue to rise linearly;

(3) Mode 3, t ₂ -t ₃ : At time t ₂ , S ₁ is turned off, S ₂ is turned on, and at time t ₃ , mode 3 ends, and the next switching cycle starts, repeating the above process; The voltage part, D ₁ and D ₂ are turned on, the current i _L1 (t), i _L2 (t) continues to flow through D _s2 and D _s4 , and the energy stored in the inductor L ₁ is transferred to the capacitor C _2. At this time, L ₁ , L ₂ withstand reverse voltage (U _C2 -U _in ) and U _C1 , i _L1 (t), i _L2 (t) decrease linearly.

Further, the voltage transmission ratio of the inverter In the formula, M _spwm is the modulation ratio, and D _boost is the duty cycle of Cuk.

The present invention further discloses a single-phase Cuk integrated buck-boost inverter control system, which includes the above-mentioned single-phase Cuk integrated buck-boost inverter.

Beneficial effects: the present invention integrates the Cuk converter and the traditional full-bridge inverter by sharing the power switch tube, and adopts a compound modulation strategy of multiple control quantities to simultaneously realize the pumping of the DC bus voltage of the inverter and the sinusoidal output voltage It has the advantages of simple topology, high integration, high voltage gain, and low cost.

Description of drawings

Fig. 1 is a schematic diagram of the main circuit topology of the inverter of the present invention;

Fig. 2 is the schematic diagram of hybrid SPWM modulation logic circuit of the present invention;

Fig. 3 is the main waveform diagram of the control mode of the present invention;

Fig. 4 is the equivalent schematic diagram of mode 1 in the control method of the present invention;

Fig. 5 is the equivalent schematic diagram of mode 2 in the control method of the present invention;

Fig. 6 is the equivalent schematic diagram of mode 3 in the control method of the present invention;

Fig. 7 is a structural block diagram of the control system of the present invention;

Figure 8 is a schematic diagram of the DC bus voltage u _dc waveform when the input voltage is 170V in the simulation verification;

Figure 9 is a schematic diagram of the input and output voltage u _in and u _o waveforms when the input voltage is 170V in the simulation verification;

Figure 10 is a schematic diagram of the DC bus voltage u _dc waveform when the input voltage is 105V in the simulation verification;

Figure 11 is a schematic diagram of the input and output voltage u _in and u _o waveforms when the input voltage is 105V in the simulation verification.

detailed description

The working principle of the present invention is described in further detail below in conjunction with specific embodiment and accompanying drawing:,

Fig. 1 has provided the circuit structure of the single-phase Cuk integrated buck-boost inverter proposed by the present invention, which evolved from the Cuk converter, by multiplexing the body diode (D) of the lower switching tube of the full-bridge inverter _S2 , D _S4 ) and upper switching tubes (S ₁ , S ₃ ), realize the integration of Cuk converter and full-bridge inverter, and realize the functions originally realized by two-stage power conversion by one-stage power conversion.

Specifically, the inverter includes boost capacitor C ₁ , capacitor C ₂ , switch tubes S ₁ -S ₄ , inductor L ₁ , inductor L ₂ , diode D ₁ and diode D ₂ , and the switch tubes S ₁ and S ₂ are connected in series to form a first bridge arm circuit, the switch tubes _S3 and _S4 are connected in series to form a second bridge arm circuit, and the first bridge arm circuit and the second bridge arm circuit are connected in parallel to form a full bridge circuit; the switch tube S ₁ and _S2 junction _a is connected to the anode of diode D1, the junction b _of the switching tubes S3 and _S4 is connected to the anode of diode D2, and the _{cathodes of} diode D1 and diode _D2 are commonly connected There is one end of the boost capacitor _C1 , the other end of the boost capacitor _C1 is connected to one end of the inductor _L2 , and the other end of the inductor L2 is respectively connected to one end of the capacitor _C2 , the switch _{tube S2} , the switch Tube S ₄ , the other end of the capacitor C ₂ is respectively connected with inductor L ₁ , switch tube S ₁ , and switch tube S ₃ .

It can be seen that compared with the traditional full-bridge inverter, it only adds two anti-reverse diodes (D ₁ , D ₂ ), a boost capacitor (C ₁ ) and two inductors (L ₁ , L ₂ ). And only by using hybrid SPWM modulation, the DC voltage pumping and inverter functions can be realized at the same time. Therefore, the inverter has the advantages of high efficiency, high integration, convenient control, simple structure, and low cost.

The Cuk integrated buck-boost inverter proposed by the present invention adopts a compound modulation strategy of multiple control quantities. Different from the traditional unipolar modulation (including unipolar frequency doubling modulation) and bipolar modulation, the multi-control compound modulation circuit contains multiple control variables: S _a , S _b and S _c ; among them, S _a It is used to control the sine degree of the output voltage, S _b is the positive and negative polarity judgment signal of the AC voltage, and S _c is used to control the DC bus voltage to meet the voltage conditions required by the inverter. S _a is generated by the absolute value output by the output voltage loop regulator and the carrier signal after the modulation circuit is handed over, and S _c is generated by the output of the bus voltage loop regulator and the carrier signal after the modulation circuit is handed over, and the two carrier signals are exactly the same , which can be an asymmetrical triangle wave, a leading-edge sawtooth wave, or a trailing-edge sawtooth wave. Based on the above three related control signals, the drive signals S ₁ -S ₄ ultimately required by the inverter can be obtained by further logic operations.

The switching sequence of the inverter in a switching cycle is shown in Table 1. In the table, "1" indicates that the switch tube is in the on state during the switching cycle, and "0" indicates that the switch tube is in the off state. Combined with the switching sequence, the working principle and characteristics of the inverter can be analyzed.

Table 1 Switching tube conduction state

For the inverter, the working process in the positive and negative half waves of the sine modulation wave is similar, here we take a switching cycle in the positive half wave as an example for analysis.

In order to simplify the analysis, it is first assumed that the inverter has reached a steady state and meets the following conditions: ①All power transistors, inductors, and capacitors are ideal components; ②The output filter inductor L _o is large enough, and its current is basically constant, so it can be equivalent to a constant current source I _o ; ③capacitors C ₁ and C ₂ are large enough, and their terminal voltages U _C1 and U _C2 are approximately constant, so they can be equivalent to a constant voltage source; ④The potential of n ₀ point is zero. Correspondingly, in each switching cycle of the positive half cycle, the work of the inverter can be divided into three modes, the main waveforms of which are shown in Figure 3, and the equivalent circuit corresponding to each working mode is also shown in Figure 4- 6.

Considering that the control signals S _c and S _a of the inverter determine the DC bus voltage gain and the inverter modulation ratio of the inverter respectively, the working principle of the inverter can be analyzed based on the superposition principle, that is, the work of the inverter can be decomposed into Cuk The two processes of step-up and full-bridge inverter are analyzed separately and then superimposed. Based on this idea, the equivalent circuit of mode 1 shown in Figure 4 can be split into two parts accordingly, as shown in Figure 4(b) and 4(c).

Therefore, the current of the switch tubes S ₁ -S ₄ in Figure 4(a) can be regarded as the sum of the corresponding current components in Figure 4(b) and Figure 4(c), that is:

i _Sk (t)=i _Sk1 (t)+i _Sk2 (t)k=1,2,3,4 (1)

In the formula, i _Sk1 (t) and i _Sk2 (t) are the Cuk step-up component and the full-bridge inverter component of each switch tube, respectively.

Similarly, the same processing can be done for modes 2 and 3.

(1) Mode 1: [t ₀ -t ₁ ] (the equivalent circuit is shown in Fig. 4(a)).

Before time t ₀ , S ₂ and S ₄ are turned on, and L ₁ and L ₂ are linearly discharged due to bearing the reverse voltage (U _C2 -U _in ) and U _C1 respectively. At t ₀ , S ₂ is turned off, S ₁ is turned on, and at t ₁ , mode 1 ends.

In this mode, for the Cuk step-up part, the diode D ₁ is turned on, the power supply voltage is fully applied to the input inductor L ₁ , and the inductor current i _L1 (t) increases linearly. At the same time, due to the discharge of the capacitor _C2 , the current i _L2 of the output inductor _L2 also increases linearly. (The equivalent circuit is shown in Figure 4(b))

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

i _D1 (t) = i _S11 (t) (4)

For the full bridge inverter part, the output current I _o flows through the switch tubes S ₁ and S ₄ . (The equivalent circuit is shown in Figure 4(c))

i _S4 (t) = i _S12 (t) = I _o (5)

Then there are:

i _S2 (t) = i _S3 (t) = i _D2 (t) = 0 (6)

(2) Mode 2: [t ₁ -t ₂ ] (the equivalent circuit is shown in Fig. 5(a)).

_At time _t1 , S4 is turned off, S3 is turned on, and at time _t2 , mode ₂ ends.

For the Cuk step-up part, D ₁ and D ₂ are turned on, L ₁ and L ₂ still bear the forward voltage U _in and (U _C2 -U _C1 ), and the current i _L1 (t), i _L2 (t) continues to rise linearly . (The equivalent circuit is shown in Figure 5(b))

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

i _D1 (t) = i _S11 (t) (9)

i _D2 (t) = i _S31 (t) (10)

For the full _- bridge inverter part, the output current I _o continues to flow through the body diodes _of the switch tubes S1 and S3. (The equivalent circuit is shown in Figure 5(c))

i _S12 (t) = i _S32 (t) = I _o (11)

Then there are:

i _S2 (t) = i _S4 (t) = 0 (12)

(3) Mode 3: [t ₂ -t ₃ ] (the equivalent circuit is shown in Fig. 6(a)).

At _t2 , S1 is turned off, S2 is turned _on , and at _t3 , mode ₃ ends. The next switching cycle begins and the above process is repeated.

In the boosting part of Cuk, D ₁ and D ₂ are turned on, current i _L1 (t), i _L2 (t) freewheel through D _s2 , D _s4 , and the energy stored in inductor L ₁ is transferred to capacitor C ₂ . At this time, L ₁ and L ₂ bear the reverse voltage (U _C2 -U _in ) and U _C1 , i _L1 (t), i _L2 (t) decrease linearly. (The equivalent circuit is shown in Figure 6(b))

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

i _D1 (t) = i _S21 (t) (15)

i _D2 (t) = i _S41 (t) (16)

For the full bridge inverter part, the output current I _o continues to flow through the body diodes of the switch tubes _S4 and S2 _. (The equivalent circuit is shown in Figure 6(c))

i _S22 (t) = i _S42 (t) = I _o (17)

Then there are:

i _S1 (t) = i _S3 (t) = 0 (18)

It can be seen from Figure 3 that the switching period of the inverter is T _s (that is, the time period t ₀ -t ₃ ), combined with Figure 4(b)-6(b), it can be seen that the time period for the Cuk part to charge the boost inductor is (t ₀ -t ₂ ), the discharge time period is (t ₂ -t ₃ ). Here, the duty cycle D _boost during the charging time of the boost inductor is defined as:

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 19</span>}<span\; class="notranslate">\; )</span>$

According to the transmission ratio relationship between the output voltage of the Cuk circuit and the input voltage, the terminal voltage U _C1 of the capacitor _C1 can be obtained as:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; )</span>$

Then the inverter DC bus voltage U _dc , namely U _C2 is:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

For the inverter part of the full bridge shown in Figure 4(c)-6(c), the output voltage U _o of the inverter bridge and the DC bus voltage U _dc satisfy the equation:

U _o ＝ M _spwm U _dc (22)

In the formula, M _spwm is the modulation ratio of the inverter bridge, and M _spwm <D _boost is satisfied.

The voltage transfer ratio of the inverter can be obtained as:

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; three</span>}<span\; class="notranslate">\; )</span>$

It can be seen from formula (23) that the voltage transmission ratio G of the inverter is related to the modulation ratio M _spwm and the duty ratio D _boost of Cuk, G increases with the increase of M _spwm and D _boost , but at the same time Limited by the constraint M _spwm < D _boost . Among them, 1/(1-D _boost ) is the boost gain of the boost part of Cuk. When M _spwm is greater than (1-D _boost ), G>1, that is, the inverter has the boost function; otherwise, the inverter device has the ability to step down.

Fig. 7 is a system closed-loop control block diagram of a single-phase Cuk integrated buck-boost inverter. In the figure, the DC bus voltage loop and the output voltage loop of the inverter can use linear regulators such as PI and PID, and the two are independently controlled. The modulation signal output by the regulator 1 and the absolute value modulation signals u _r1 and u _r2 output by the regulator 2 respectively pass through the signal modulation circuit and the carrier signal to generate control signals S _c and S _a . Wherein, the carrier signals of the two modulating circuits are exactly the same, which may be an asymmetrical triangular wave, a front edge sawtooth wave or a rear edge sawtooth wave. Finally, S _a , S _c and the AC voltage positive and negative polarity determination signal S _b are sent to the logic operation circuit shown in Figure 2 to obtain the drive signals S ₁ -S ₄ of the four switching tubes of the inverter.

In order to verify the feasibility of the Cuk integrated buck-boost inverter proposed by the present invention and the correctness of its theoretical analysis, a 500W/20kHz prototype was built for simulation verification, and its design indicators are as follows:

DC input voltage U _in ＝105V-170V, DC bus voltage U _dc ＝330V, output voltage U _o ＝110V/50Hz, filter inductance L ₁ ＝5mH, L ₂ ＝1mH, boost capacitor C ₁ ＝2000μF, bus capacitor C ₂ = 2000μF, S ₁ ~ S ₂ adopt IPW60R0410C6, D ₁ and D ₂ adopt IDW30G65C5.

Fig. 8, Fig. 9 and Fig. 10, Fig. 11 show the simulation waveforms of the inverter's DC bus voltage u _dc , output voltage u _o , and input voltage u _in when U _in =170V and 105V respectively. Among them, the benchmarks of the DC bus voltage loop and the AC output voltage loop are 3.3V and 1.56V respectively, and the sampling coefficients are both 0.01.

It can be seen that the inverter adopts the hybrid SPWM modulation method, when the input voltage is 170V, the average value of u _dc is 330.11V, and the amplitude of u _o is 156.11V, which shows that the system has well realized the step-down and Inversion function; when the input voltage is 105V, the average value of u _dc is 330.18V, and the amplitude of u _o is 156.05V, which shows that the system has realized the boost and inversion functions well. These simulation results are consistent with The theoretical analysis is in good agreement.

The invention integrates the Cuk converter and the traditional full-bridge inverter together by sharing the power switch tube, adopts a compound modulation strategy of multiple control quantities, and simultaneously realizes the pumping of the DC bus voltage of the inverter and the sinusoidalization of the output voltage, and has a topology Simple, high integration, high voltage gain, low cost and other advantages.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, can use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes. Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solution of the present invention.

Claims (10)

1. A single-phase Cuk integrated buck-boost inverter, characterized in that it includes boost capacitor C ₁ , capacitor C ₂ , switch tubes S ₁ -S ₄ , inductor L ₁ , inductor L ₂ , and diode D ₁ and diode D2, the switching tubes S1 and S2 are connected in series to form the _first bridge arm circuit, the switching tubes _S3 and _S4 are connected in series to form the _second bridge arm circuit, the first bridge arm circuit and the _second bridge arm circuit _The arm circuits are connected in parallel to form a full bridge circuit _; the junction _a of the switch tubes S1 and S2 is connected to the anode of the diode D1, and the junction point b _of the switch tubes S3 and S4 is connected to the anode _of the diode _D2 , _The cathodes of the diode D1 and the diode D2 are commonly connected to _one end of the boost capacitor _C1 , the other end of the boost capacitor _C1 is connected to one end of the inductor _L2 , and the other ends of the inductor _L2 are respectively connected to There are one end of the capacitor C ₂ , the switch tube S ₂ , and the switch tube S ₄ , and the other end of the capacitor C ₂ is respectively connected to the inductor L ₁ , the switch tube S ₁ , and the switch tube S ₃ . 2. A kind of single-phase Cuk integrated buck-boost inverter according to claim 1, characterized in that: the cathodes of the diode D ₁ and the diode D ₂ are commonly connected to the positive pole of the boost capacitor C ₁ , boosting _The negative pole of the piezoelectric capacitor _C1 is connected to one end of the inductor L2. 3. A single-phase Cuk integrated buck-boost inverter according to claim ₁ or 2, characterized in that: an input power supply is provided between the positive pole of the boost capacitor _C1 and the inductor L1. 4 . The single-phase Cuk integrated buck-boost inverter according to claim 1 , wherein a filter circuit is connected between the junction a and b. 4 . 5 . The single-phase Cuk integrated buck-boost inverter according to claim 4 , wherein the filter circuit is an LC filter circuit or an LCL filter circuit, and the filter circuit is also connected to a load. 6 . The single-phase Cuk integrated buck-boost inverter according to claim 1 , wherein the switching tubes S ₁ -S ₄ respectively include body diodes D _s1 -D _s4 . 7. The control method of a single-phase Cuk integrated buck-boost inverter according to any one of claims 1-6, characterized in that: the inverter adopts a multi-control variable composite modulation strategy, that is, the modulation circuit Contains multiple control quantities: S _a , S _b and S _c ; among them, S _a is used to control the sine degree of the output voltage, S _b is the positive and negative polarity judgment signal of the AC voltage, and S _c is used to control the DC bus voltage , to meet the voltage conditions required by the inverter, S _a is generated by the absolute value output by the output voltage loop regulator and the carrier signal through the modulation circuit, and S _c is generated by the output of the bus voltage loop regulator and the carrier signal through the modulation circuit After generation, the two carrier signals are exactly the same, which can be asymmetrical triangular wave, front edge sawtooth wave or rear edge sawtooth wave. Based on the above three related control signals, the final driving signal of the inverter can be obtained by further logical operation. S ₁ -S ₄ . 8. The control method of a kind of single-phase Cuk integrated buck-boost inverter according to claim 7, characterized in that: the work of the inverter in each switching cycle of the positive half wave of the sinusoidal modulation wave The process includes the following three modes: (1) Mode 1, t ₀ -t ₁ : Before time t ₀ , S ₂ and S ₄ are turned on, and L ₁ and L ₂ are linearly discharged due to the reverse voltage (U _C2 -U _in ) and U _C1 respectively ; At time t ₀ , S ₂ is turned off, S ₁ is turned on, and at time t ₁ , mode 1 ends; in this mode, for the boost part of Cuk, diode D ₁ is turned on, and the power supply voltage is fully applied to the input inductor On L ₁ , the inductor current i _L1 (t) increases linearly, and at the same time, due to the discharge of capacitor C ₂ , the current i _L2 of the output inductor L ₂ also increases linearly; (2) Mode 2, t ₁ -t ₂ : at time t ₁ , S ₄ is turned off, S ₃ is turned on, and at time t ₂ , mode 2 ends; for the Cuk booster part, D ₁ and D ₂ are turned on , L ₁ , L ₂ still bear the forward voltage U _in and (U _C2 -U _C1 ), the current i _L1 (t), i _L2 (t) continue to rise linearly; (3) Mode 3, t ₂ -t ₃ : At time t ₂ , S ₁ is turned off, S ₂ is turned on, and at time t ₃ , mode 3 ends, and the next switching cycle starts, repeating the above process; The voltage part, D ₁ and D ₂ are turned on, the current i _L1 (t), i _L2 (t) continues to flow through D _s2 and D _s4 , and the energy stored in the inductor L ₁ is transferred to the capacitor C _2. At this time, L ₁ , L ₂ withstand reverse voltage (U _C2 -U _in ) and U _C1 , i _L1 (t), i _L2 (t) decrease linearly. 9. The control method of a single-phase Cuk integrated buck-boost inverter according to claim 8, characterized in that: the voltage transfer ratio of the inverter is In the formula, M _spwm is the modulation ratio of the inverter, and D _boost is the duty cycle of the Cuk step-up part. 10. A single-phase Cuk integrated buck-boost inverter control system, characterized in that it comprises the single-phase Cuk integrated buck-boost inverter according to any one of claims 1-6.