CN106787692A - A kind of quasi- Z source converters of type switching capacity altogether - Google Patents

Abstract

The present invention provides a kind of quasi- Z source converters of type switching capacity altogether, mainly include input dc power potential source, by the first inductance, the first electric capacity, first diode, the quasi- Z source networks that second inductance and the second electric capacity are constituted, by the 3rd electric capacity, the 3rd diode, the switched capacitor network that 4th electric capacity and the 4th diode are constituted, switching tube, the second diode, the 5th electric capacity and load resistance.Whole circuit structure is simple, a switching tube is only used, source current is continuous, input and output common ground, combine the characteristic of the single-stage buck characteristic and switching capacity of quasi- Z source impedance networks charging discharged in series parallel, output voltage gain higher is made it have, and circuit opens the dash current of moment in the absence of inrush current and switching tube.

Description

A Common Ground Switched Capacitor Quasi-Z Source Converter

technical field

The invention relates to the technical field of power electronic converters, in particular to a common-ground switched capacitor quasi-Z source converter.

Background technique

In recent years, due to the massive development, utilization and consumption of traditional fossil energy, in order to achieve sustainable development, countries around the world are vigorously developing new renewable energy, such as solar energy, wind energy, and fuel cells. Among them, solar photovoltaic power generation has become one of the most widely implemented ways of using solar energy to generate electricity. However, due to the low output voltage level of the photovoltaic array battery, it cannot meet the requirements of some existing electrical equipment and grid connection. Therefore, the output voltage of the photovoltaic array battery must be boosted by a high-gain DC/DC converter before it can be used. The most commonly used traditional Boost converter, because when the output voltage gain is required to be very high, the duty cycle of the switching tube will be close to 1, which will cause excessive switching loss and reduce the overall efficiency of the system. However, the Z-source DC-DC converter proposed in recent years, although the Z-source impedance network is used to realize the boost, its voltage gain still has a lot of room for improvement. advanced questions.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a common-ground type switched capacitor quasi-Z source converter, and the specific technical scheme is as follows.

A common ground type switched capacitor quasi-Z source converter, which includes an input DC voltage source, a quasi-Z source impedance network composed of a first inductance, a first capacitor, a first diode, a second inductance, and a second capacitor, A switched capacitor network consisting of a third capacitor, a third diode, a fourth capacitor, a fourth diode, a switch tube, a second diode, a fifth capacitor and a load resistor.

The specific connection mode of the circuit of the present invention is as follows: one end of the input DC voltage source is connected to one end of the first inductance; the other end of the first inductance is respectively connected to the negative pole of the first capacitor and the anode of the first diode; The cathode of the first diode is respectively connected to the anode of the second capacitor and one end of the second inductance; the other end of the second inductance is respectively connected to the anode of the first capacitor, the drain of the switch tube, and the second diode The anode of the tube is connected to the negative pole of the third capacitor; the cathode of the second diode is respectively connected to the anode of the third diode, the negative pole of the fourth capacitor and the positive pole of the fifth capacitor; the third diode The cathode of the third capacitor and the anode of the fourth diode are respectively connected; the cathode of the fourth diode is respectively connected with the positive electrode of the fourth capacitor and one end of the load resistor; the other end of the load resistor is respectively It is connected with the negative pole of the fifth capacitor, the source pole of the switch tube, the negative pole of the second capacitor and the negative pole of the input DC voltage source.

The voltage gain G of the converter at steady state output is:

Among them, V _o represents the output voltage on the load side of the converter, V _i is the input DC voltage source, and D is the duty cycle.

Compared with the prior art, the present invention has the following advantages: no additional power switch tube is needed, the structure is simple, and the control is convenient; and compared with the traditional switched capacitor Boost converter (its output voltage gain is G=2/(1-D )) and Z-source boost converter (its corresponding output voltage gain is G=1/(1-2D)), in the case of the same input voltage and duty cycle, it has a higher output voltage gain of G =2/(1-2D). Moreover, the power supply current is continuous, the input and output share a common ground, the switching stress is relatively low, and there is no circuit start-up inrush current, etc. Therefore, the circuit of the present invention has a very wide application prospect.

Description of drawings

Fig. 1 is a circuit diagram of a common-ground switched capacitor quasi-Z source converter in an embodiment.

Fig. 2a is an equivalent circuit diagram of the circuit shown in Fig. 1 in working mode 1 (the switch tube is turned on).

Fig. 2b is an equivalent circuit diagram of the circuit shown in Fig. 1 in working mode 2 (the switch tube is turned off).

Fig. 3a is a comparative graph of the output voltage gain of the converter described in the example of the present invention, a switched capacitor Boost converter and a traditional quasi-Z source converter.

Fig. 3b is a simulation result diagram of circuit-related variables in the example of the present invention given as an example of V _i =15V and duty cycle D=0.3.

detailed description

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. It should be noted that, if there are any processes or parameters that are not specifically described in detail below, those skilled in the art can understand or implement them with reference to the prior art.

The basic topology and main components of this example are shown in Figure 1. For the convenience of verification, the devices in the circuit structure are regarded as ideal devices unless otherwise specified. A common-ground switched capacitor quasi-Z source converter, which includes an input DC voltage source V _i , composed of a first inductor L ₁ , a first capacitor C ₁ , a first diode D ₁ , a second inductor L ₂ , and a first The quasi-Z source impedance network composed of two capacitors C ₂ , the switched capacitor network composed of the third capacitor C ₃ , the third diode D ₃ , the fourth capacitor C ₄ , and the fourth diode D ₄ , the switch tube S, the second diode D ₂ , the fifth capacitor C ₅ and the load resistor _RL ;

In this example, it is set that the driving signal of the switching tube S is V _GS , the current of the first inductor L ₁ is i _L1 , the current of the second inductor L ₂ is i _L2 , the voltage of the first capacitor C ₁ is V _C1 , and the voltage of the second capacitor C ₂ the voltage is V _C2 , the voltage of the third capacitor C ₃ is V _C3 , the voltage of the fourth capacitor C ₄ is V _C4 , and the voltage of the fifth capacitor C ₅ is V _C5 . The direct duty cycle when the switch tube is turned on is set as D, and the switching period is set as T _s .

As shown in Figure 2a and Figure 2b, the solid line in the figure indicates the part where current flows in the converter, and the dotted line indicates the part where no current flows in the converter. The two working modes at different stages in the cycle (0,T _s ) are described as follows:

Working mode 1 (0<t<DT _s ): As shown in Figure 2a, the switch tube S is turned on, and the first diode D ₁ , the second diode D ₂ and the fourth diode D ₄ are reverse-blocked , the third diode _D3 is forward conducting. At this time, the input DC voltage source V _i and the first capacitor _C1 charge the _first inductor L1 together through the switch tube S, the _second capacitor C2 charges the _second inductor L2 through the switch tube S, and the fifth capacitor _C5 The _third capacitor C3 is charged through the third diode _D3 and the switch tube S, and at the same time, the fifth capacitor _C5 and the fourth capacitor _C4 are connected in series to supply power to the load resistor _RL .

In this working mode, the relevant electrical parameter relational formula is:

V _{L1_on} =V _i +V _C1 (1)

V _{L2_on} = V _C2 , V _C5 = V _C3 (2)

V _o =V _C4 +V _C5 (3)

Wherein, V _L1-on and V _L2-on represent the voltages at both ends of the first inductor L ₁ and the second inductor L ₂ during the conduction period of the switch tube S respectively, and V _o represents the output voltage at the load side of the converter.

Working mode 2 (DT _s <t<T _s ): As shown in Figure 2b, the switch tube S is turned off, then the first diode D ₁ , the second diode D ₂ and the fourth diode D ₄ is turned on, and the third diode _D3 is turned off. At this time, the input DC voltage source V _i and the first inductor L ₁ charge the second capacitor C ₂ through the first diode D ₁ , and the second inductor L ₂ charges the first capacitor C ₁ through the first diode D ₁ For charging, the input DC voltage source V _i is connected in series with the first inductor L ₁ and the second inductor L ₂ to charge the fifth capacitor C ₅ , and the third capacitor C ₃ charges the fourth capacitor C ₄ . At the same time, the input DC voltage source V _i is connected in series with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ to supply power to the load resistor _RL . In this working mode, the relevant electrical parameter relational formula is:

V _L1-off ＝V _i -V _C2 (4)

V _L2-off = -V _C1 (5)

V _C5 ＝V _i -V _L1-off -V _L2-off (6)

V _C3 = V _C4 (7)

V _o =V _C3 -V _L1-off -V _L2-off +V _i (8)

Wherein, V _L1-off and V _L2-off represent the voltages at both ends of the first inductor L ₁ and the second inductor L ₂ respectively when the switch tube S is turned off.

According to the above analysis, the principle of volt-second balance is applied to the first inductance L ₁ and the second inductance L ₂ respectively, that is, the average value of the inductance voltage in one switching cycle is zero, and the simultaneous formulas (1), (2), (4 ), (5) are available

D(V _i +V _C1 )+(1-D)(V _i -V _C2 )＝0 (9)

DV _C2 +(1-D)(-V _C1 )＝0 (10)

Then the simultaneous formulas (6), (7), (8), (9) and (10) can obtain the expressions of capacitor voltage and output voltage in steady state respectively as follows:

Then the voltage gain G when the quasi-Z source converter of a common ground type switched capacitance quasi-Z source converter of the present invention outputs is:

As shown in Figure 3a, the output voltage gain curve of this example circuit is compared with the voltage gain curves of the switched capacitor Boost converter and the traditional quasi-Z source converter. It can be seen from the figure that when the duty ratio D of the circuit of the present invention does not exceed 0.5, the output voltage gain G can reach a large value, which is obviously higher than the voltage gain of the other two converters, and the duty ratio D of the circuit of the present invention is will not exceed 0.5.

As shown in Fig. 3b, taking V _i =15V and duty cycle D=0.3 as an example, the simulation results of relevant variables in the circuit of the present invention are given. When D=0.3, the corresponding output voltage gain is G=5, capacitor voltage V _C1 =11.25V, V _C2 =26.25V, V _C3 =V _C4 =V _C5 =37.5V, output voltage V _o =75V. In addition, Fig. 3b also shows the waveform of the inductor current (i _L1 , i _L2 ) and the waveform of the driving signal V _GS of the switching tube S.

To sum up, the common-ground switched capacitor quasi-Z source converter proposed by the present invention does not require an additional power switch tube, has a simple structure and is easy to control. Compared with the switched capacitor Boost converter and the traditional quasi-Z source converter, under the same input voltage and duty cycle, it has a higher output voltage gain, and the power supply current is continuous, and the input and output share a common ground , there is no start-up inrush current at the moment of circuit start-up, so the circuit of the present invention has a very wide application prospect.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (6)

1. A common-ground switched capacitor quasi-Z source converter, characterized in that it includes an input DC voltage source ( V _i ), composed of a first inductor ( L ₁ ), a first capacitor ( C ₁ ), a first diode ( D ₁ ), the second inductance ( L ₂ ), and the second capacitor ( C ₂ ) form a quasi-Z source impedance network, composed of the third capacitor ( C ₃ ), the third diode ( D ₃ ), the fourth capacitor (C ₄ ), the fourth diode (D ₄ ) constitutes the switched capacitor network, the switch tube ( S ), the second diode ( D ₂ ), the fifth capacitor ( C ₅ ) and the load resistor ( _RL ) ; One end of the input DC voltage source ( V _i ) is connected to one end of the first inductor (L ₁ ); the other end of the first inductor (L ₁ ) is respectively connected to the negative pole of the first capacitor (C ₁ ) and the second The anode of a diode (D ₁ ) is connected; the cathode of the first diode (D ₁ ) is respectively connected to the anode of the second capacitor (C ₂ ) and one end of the second inductor (L ₂ ); the The other end of the second inductor (L ₂ ) is respectively connected to the anode of the first capacitor (C ₁ ), the drain of the switch tube (S), the anode of the second diode (D ₂ ) and the third capacitor (C ₃ ) The cathode of the second diode (D ₂ ) is connected to the anode of the third diode (D ₃ ), the cathode of the fourth capacitor (C ₄ ) and the anode of the fifth capacitor (C ₅ ) respectively. connection; the cathode of the third diode (D ₃ ) is respectively connected to the anode of the third capacitor (C ₃ ) and the anode of the fourth diode (D ₄ ); the fourth diode (D ₄ ) of the cathode are respectively connected to the positive pole of the fourth capacitor (C ₄ ) and one end of the load resistor ( _{RL )} ; the other end of the load resistor ( RL ) is respectively connected to the negative pole of the fifth capacitor (C ₅ ) The source of (S), the negative of the second capacitor (C ₂ ) and the negative of the input DC voltage source (V _i ) are connected. 2. A common ground type switched capacitor quasi-Z source converter according to claim 1, characterized in that when the switch tube is turned on, the first diode, the second diode and the fourth diode are reversely blocked , the third diode is forward conducting. 3. At this time, the input DC voltage source and the first capacitor charge the first inductor together through the switch tube, the second capacitor charges the second inductor through the switch tube, and the fifth capacitor charges the third inductor through the third diode and switch tube. The capacitor is charged, and the fifth capacitor and the fourth capacitor are connected in series to supply power to the load resistance; when the switch tube is turned off, the first diode, the second diode and the fourth diode are turned on, and the third diode off. 4. At this time, the input DC voltage source and the first inductor charge the second capacitor through the first diode, and the second inductor charges the first capacitor through the first diode. The input DC voltage source and the first inductor, the second The two inductors are connected in series to charge the fifth capacitor, and the third capacitor charges the fourth capacitor. 5. At the same time, the input DC voltage source is connected in series with the first inductor, the second inductor and the third capacitor to supply power to the load resistor. 6. A kind of common ground type switched capacitor quasi-Z source converter according to claim 1, it is characterized in that the voltage gain G when this converter steady-state output is: , D is the duty cycle.