TWI740562B - Bidirectional voltage converter - Google Patents

Abstract

A bidirectional voltage converter, including first and second capacitors, first and second intermediate capacitors, first and second inductors, first to fifth switches, suitable for high voltage conversion ratio, high efficiency and high power new bidirectional The converter meets the practical requirements of the bidirectional converter connecting the energy storage battery and the high-voltage DC row in the renewable energy power system. The bidirectional converter has a high voltage conversion ratio to achieve the purpose of high step-up/high step-down, but the converter does not have to operate at the extreme maximum/minimum conduction ratio. The power switch has low voltage stress, and a low rated withstand voltage with a small on-resistance can be used to reduce the conduction loss of the power switch and improve the efficiency.

Description

Bidirectional voltage converter

The present invention relates to a voltage converter, in particular to a bidirectional voltage converter for connecting a renewable energy power system and a battery energy storage system.

As shown in Figure 1, a conventional step-up/step-down bidirectional DC-DC Converter (bidirectional DC-DC Converter). By power switch control, when the power flow flows from low voltage to high voltage, it is called boost mode operation. The voltage gain is V _H /V _L =1/(1-D), and the parameter D is the conduction of the switch. Ratio (duty ratio). When power flow flows from high voltage to low voltage, it is called step-down mode operation, and the voltage gain is V _L /V _H =D. The voltage stress of the two power switches is V _H.

Therefore, it has the following shortcomings. For the boost mode, the switching operation can obtain high voltage gain at a very high conduction ratio, but in practice it is affected by parasitic elements. The voltage gain of a boost converter operating at a very large conduction ratio is There are limitations and poor conversion efficiency. For the step-down mode, the converter needs to step down high, and the main switch must be operated at a very small conduction ratio. Not only is it easy to cause the converter to malfunction due to noise interference, but also when there are input voltage fluctuations and load fluctuations, very small conduction The ratio is difficult to be adjusted and controlled, and the output cannot be regulated. In the power switch voltage stress and efficiency considerations: As the efficiency requirements of the converter are becoming more and more stringent, the power loss caused by the power electronic switch must be carefully considered. The voltage stress of the power switch of a typical boost converter is a high-voltage output voltage. Due to the high withstand voltage MOSFET, generally has the characteristic of high on-resistance R _DS(ON) , resulting in higher conduction loss.

Therefore, an object of the present invention is to provide a bidirectional voltage converter that can overcome the disadvantages of the prior art.

Therefore, the voltage converter is suitable for receiving one of a first input voltage provided from a first voltage source and a second input voltage provided from a second voltage source, and includes a first port, A second port, a first capacitor, a first inductor, a first switch, a second switch, a second inductor, a third switch, a fourth switch, a first intermediate capacitor, a second intermediate A capacitor, a fifth switch, and a second capacitor.

The first capacitor has a first end electrically connected to the first port and a second end connected to the ground. The first inductor has a first end electrically connected to the first end of the first capacitor, and a second end. The first switch has a first terminal electrically connected to the second terminal of the first inductor and a grounded second terminal, and is controlled to switch between conduction and non-conduction. The second switch has a The first end of the first end of the first capacitor is electrically connected to a second end, and is controlled to switch between conduction and non-conduction. The second inductor has a first end electrically connected to the second end of the second switch, and a second end connected to the ground. The third switch has a first terminal electrically connected to the first terminal of the first capacitor, and a second terminal, and is controlled to switch between conduction and non-conduction. The fourth switch has a first terminal electrically connected to the second terminal of the first capacitor, and a second terminal, and is controlled to switch between conduction and non-conduction. The first intermediate capacitor is electrically connected between the second terminal of the first inductor and the second terminal of the third switch. The second intermediate capacitor is electrically connected between the first terminal of the second inductor and the second terminal of the fourth switch. The fifth switch has a first end electrically connected to the second end of the second switch, and a second end electrically connected to the second port, and is controlled to switch between conduction and non-conduction. The second capacitor has a first end that is electrically connected to the second end of the second port, and a second end that is grounded.

Wherein, when operating in a boost mode, the first port receives the first input voltage and the second port generates a voltage greater than the first input voltage and proportional to the cross voltage of the first intermediate capacitor and the second intermediate The second output voltage that is the sum of the voltage across the capacitor. Wherein, when operating in a step-down mode, the second port receives the second input voltage and the first port generates a first output voltage smaller than the second input voltage.

The effect of the present invention is that it has a high voltage conversion ratio, and does not need to operate at a maximum/minimum extreme conduction ratio to achieve the purpose of high boost/high voltage drop.

1: the first port

2: second port

3: control unit

C _L : first capacitor

C _H : second capacitor

L ₁ : first inductance

L ₂ : second inductance

C ₁ : The first intermediate capacitor

C ₂ : second intermediate capacitor

S ₁ : The first switch

S ₂ : The second switch

S ₃ : third switch

S ₄ : Fourth switch

S ₅ : Fifth switch

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: FIG. 1 is a circuit diagram of a conventional boost converter; FIG. 2 is a circuit diagram of a bidirectional voltage converter of the present invention A circuit diagram of the embodiment; FIG. 3 is an operation timing diagram of the boost mode of this embodiment; FIG. 4 is an operation timing diagram of the buck mode of this embodiment; FIG. 5 is the boost mode operation of the embodiment in the first Fig. 6 is a circuit diagram of the step-up mode operation in the second stage of the embodiment; Fig. 7 is a circuit diagram of the step-down mode operation of the embodiment in the first stage; and Fig. 8 is the embodiment A circuit diagram of the step-down mode of operation in the second stage.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same numbers.

Referring to FIG. 2, for an embodiment of the bidirectional voltage converter with step-up/step-down function of the present invention, for different power flows, it is suitable for receiving a first voltage source provided by a first voltage source. One of the input voltage and a second input voltage provided by a second voltage source, and includes a first port 1, a second port 2, a first capacitor C _L , a first inductor L ₁ , A first switch S ₁ , a second switch S ₂ , a second inductor L ₂ , a third switch S ₃ , a fourth switch S ₄ , a first intermediate capacitor C ₁ , and a second intermediate capacitor C ₂ , A fifth switch S ₅ , a second capacitor C _H , and a control unit 3.

The first capacitor _CL is a low-voltage capacitor and has a first terminal electrically connected to the first port 1 and a second terminal connected to the ground.

The first inductor L ₁ having a first electrical terminal, and a second end connected to the first terminal of the first capacitor C _L.

Having a first switch S ₁ is electrically connected to the first end of the second end of the first inductor L ₁ and a second ground terminal, and controlled to switch between conducting and non-conducting. The first switch S ₁ is an N-type power semiconductor transistor, and a first terminal of the first switch S ₁ is the drain, the second terminal of the first switch S ₁ is the source.

Having a second switch S ₂ is electrically connected to a first terminal of the first capacitor C _1, a first end and a second end, and controlled to switch between conducting and non-conducting. The second switch S ₂ is an N-type power semiconductor transistor, and a first terminal of the first switch S ₁ is the drain, the second terminal of the first switch S1 is a source.

The second inductor L ₂ has a first terminal electrically connected to the second _{terminal of the second switch S 2} and a second terminal grounded.

The third switch S ₃ is electrically connected with a first terminal of the first capacitor C ₁ of a first end and a second end, and controlled to switch between conducting and non-conducting, the third switch S ₃ is a N type power semiconductor transistor, and a first terminal of the first switch S ₁ is the drain, the second terminal of the first switch S ₁ is the source.

Having a fourth switch S ₄ is electrically connected to a first terminal of the first capacitor C _1, a second end, and a second end, and controlled to switch between conducting and non-conducting, the fourth switch S ₄ is an N-type the power semiconductor transistor, and a first terminal of the first switch S ₁ is the drain, the second terminal of the first switch S ₁ is the source.

The first intermediate capacitor C _{1 is} electrically connected between the _{second end of the first inductor L 1 and} the second end of the third switch S ₃ . The second intermediate capacitor C _{2 is} electrically connected between the _{first end of the second inductor L 2 and} the second end of the fourth switch S ₄ .

_{S. 5} having a fifth switch electrically connected to a first terminal of the second switch S _2, a second end, and is electrically connected to the second port of the second terminal 2, and controlled to switch between conducting and non-conducting, the fifth switch S _{N-type. 5} is a power semiconductor transistor, and a first terminal of the first switch S ₁ is the drain, the second terminal of the first switch S ₁ is the source.

The second capacitor C _H is a high voltage capacitor having a first port electrically connected to the second end of the second end 2, a second terminal and a ground.

Wherein, when operating in a boost mode, the power flow flows from low voltage to high voltage, the first port 1 receives the first input voltage and the second port 2 generates a voltage greater than the first input voltage and The second output voltage is proportional to the sum of the cross voltage of the first intermediate capacitor C _{1 and} the cross voltage of the second intermediate capacitor C _2.

Wherein, when operating in a step-down mode, the power flow changes from high voltage to low voltage, the second port 2 receives the second input voltage, and the first port 1 generates a first output voltage that is less than the second input voltage .

The control unit 3 switches the first switch to generate a first pulse signals S ₁ and a switch to switch the second signal S ₂ of the second pulse, a third switching the third switch S ₃ of the pulse wave signal, the fourth switch with a fourth switching pulse signal _{S. 4,} and a fifth switch switches the fifth pulse signal S _5. The first pulse wave signal, the second pulse wave signal, the third pulse wave signal, and the fourth pulse wave signal have the same cycle time and are synchronized in phase. The phase of the fifth pulse wave signal is complementary to the phase of the first pulse wave signal

Referring to Figures 3 and 4, which are respectively the operation timing diagrams of the boost mode and the buck mode of this embodiment, the parameters v _gs1 , v _gs2 , v _gs3 , v _gs4 , and v _gs5 respectively represent the control of the first to fifth The voltage of the pulse signal whether the switches S ₁ ~ S _{5 are turned on, the parameters v ds1} , v _ds2 , v _ds3 , v _ds4 , and v _ds5 respectively represent the voltage across the two terminals of the first to fifth switches S ₁ to S ₅ , the parameter v _L1, v _L2 respectively represent the first and second inductors L _1, L ₂ of the voltage across the two ends, the parameter i _L1, i _L2 the first and second current inductor L _1, L ₂ represent, parameters i _C1, i _C2 respectively represent the first intermediate capacitor C _1, a second intermediate capacitor C _2, T _S parameter is the cycle time of the first pulse signal.

The following are circuit diagrams of the embodiment operating in the boost mode, in which all capacitance values are large enough so that the capacitor voltage in one switching period can be regarded as a constant. .The inductor current is operated in continuous conduction mode (CCM). The inductance value L ₁ =L ₂ =L. D is the duty ratio. The conductive elements are represented by solid lines, and the non-conductive elements are represented by dashed lines. The following describes each stage separately.

<Boost Mode>

The first stage (time: t0~t1): Referring to FIG. 3 and FIG. 5, the first switch S ₁ to the fourth switch S _{4 are} turned on, and the fifth switch S _{5 is} not turned on.

The first inductor L ₁ and the second inductor L _{2 are} electrically connected to the first voltage source to receive the low voltage V _L , V _L1 =V _L2 =V _{L The} inductor current rises linearly, and the inductor acts as an energy storage function

The voltages of the first intermediate capacitor C ₁ and the second intermediate capacitor C _{2 are V C1} =V _L and V _C2 =V _L.

The second stage (time: t1~t2): referring to FIG. 3 and FIG. 6, the first switch S1 to the fourth switch S4 are turned non-conductive, and the fifth switch S5 is turned on.

A first voltage source powered by a low-pressure side of the first inductor L ₁ and the second inductor L ₂ and the first intermediate capacitor C and a second capacitor C _{H 1} transmits a second intermediate capacitor C ₂ to the high pressure side through. The voltage across the second capacitor C _{H is V H} , and the voltage across the first inductor L ₁ and the second inductor L _{2 is V L1} =V _L2 =1/2×(V _L +V _C1 +V _C2 -V _H ) .

The first and second inductor currents decrease linearly, and the inductor discharges energy.

Analysis of voltage gain in boost mode operation: When in steady state, the first inductance L ₁ and the second inductance L ₂ satisfy the volt-second balance theorem, so D×V _L +(1-D)×1/2×(V _L +V _C1 +V _C2 -V _H )=0

Because V _C1 =V _C2 =V _L , substituting into the above formula, we can get V _H /V _L =(3-D)/(1-D)

Comparing the above formula with the boost formula of the conventional bidirectional converter, it can be seen that this embodiment has a higher voltage conversion ratio when operating in the boost mode.

<Buck Mode>

The first stage (time: t0 ~ t1): refer to FIG. 4 and FIG. 7, the first switch S ₁ is to turn to the fourth switch S ₄ is not turned on, and the fifth switch S ₅ is turned on.

The first capacitor C _L , the first inductor L ₁ , the second inductor L ₂ , the first intermediate capacitor C ₁ , the second intermediate capacitor C ₂ and the second capacitor C _H form a loop, so V _L1 =V _L2 =1/ 2×(V _H -V _L -V _C1 -V _C2 )

The inductor currents of the first inductor L ₁ and the second inductor L ₂ rise linearly, and the slope is (V _H -V _L -V _C1 -V _C2 )/2L

The second stage (time: t1 ~ t2): Refer to FIG. 3 and FIG. 8, a first switch S ₁ is to turn to the fourth switch S ₄ is turned on, and the fifth switch S5 is not turned on.

The voltages of the first intermediate capacitor C ₁ and the second intermediate capacitor C _{2 are V C1} =V _L and V _C2 =V _L.

The voltages of the first inductor L ₁ and the second inductor L _{2 are V L1} =-V _C1 and V _L2 =-V _{C2, respectively} .

The currents of the first inductor L ₁ and the second inductor L ₂ decrease linearly, and the slopes thereof are -V _L /L ₁ and -V _C2 /L _{2, respectively} .

For voltage gain analysis of step-down mode operation, in order to simplify the analysis, the following conditions are assumed. The inductance value L1=L2=L. The power switch is ideal, and the turn-on voltage drop is equal to zero. The capacitance is large enough, and its voltage can be regarded as a constant. Fifth switch S ₅ is turned time D × T, the fifth switch S ₅ is non-conducting period (1-D) × T.

In the steady state, the first inductance L ₁ and the second inductance L ₂ satisfy the volt-second balance theorem, _{and the average voltage of the first inductance L 1} and the second inductance L ₂ is equal to 0, which can be deduced

D×1/2(V _H -V _L -V _C1 -V _C2 )+(1-D)×(-V _L )=0

Because V _C1 =V _C2 =V _L , substituting into the above formula, we can get V _L /V _H =D/(2+D)

Comparing the above formula with the step-down formula of the conventional bidirectional converter, it can be seen that this embodiment has a better voltage conversion ratio when operating in the step-down mode.

The voltage stress of the first switch S ₁ and the second switch S _{2 is (V H} -V _L )/2, and the voltage stress of the _{third switch S 3} and the fourth switch S _{4 is (V H} +V _L )/2, The voltage stress of the fifth switch S _{5 is V H} -V _L.

The voltage stress of each switch is less than the voltage V _{H on the} high-voltage side. Generally speaking, the on-resistance of a high-voltage MOSFET is larger, which will cause an increase in the conduction loss. In terms of the voltage stress of the switch, this embodiment is better than the conventional bidirectional converter, and the power switch can be selected by using a MOSFET with a smaller on-resistance to reduce the conduction loss.

The above embodiment has the following advantages:

1. The bidirectional converter has a high voltage conversion ratio to achieve the purpose of high step-up/high step-down, but the converter does not need to operate at the extreme maximum/minimum conduction ratio.

2. Since the first to fifth switches S ₁ to S ₅ have low voltage stress, a low-rated withstand voltage MOSFET with a smaller on-resistance can be used to reduce the conduction loss of the power switch and improve the efficiency. Therefore, it can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to Within the scope covered by the patent of the present invention.

1: the first port

2: second port

3: control unit

C _L : first capacitor

C _H : second capacitor

L ₁ : first inductance

L ₂ : second inductance

C ₁ : The first intermediate capacitor

C ₂ : second intermediate capacitor

S ₁ : The first switch

S ₂ : The second switch

S ₃ : third switch

S ₄ : Fourth switch

S ₅ : Fifth switch

Claims (10)

A bidirectional voltage converter is suitable for receiving one of a first input voltage provided from a first voltage source and a second input voltage provided from a second voltage source, and includes: a first port A second port; a first capacitor having a first end electrically connected to the first port and a second end connected to the ground; a first inductor having a first end electrically connected to the first end of the first capacitor One end and a second end; a first switch having a first end electrically connected to the second end of the first inductor and a second end connected to the ground, and controlled to switch between conduction and non-conduction; Two switches, having a first end electrically connected to the first end of the first capacitor, and a second end, and controlled to switch between conduction and non-conduction; a second inductor having an electrical connection to the second switch A first end of the second end of the second end, and a second end that is grounded; a third switch having a first end electrically connected to the first end of the first capacitor, and a second end, and is controlled to be switched on Between conduction and non-conduction; a fourth switch, having a first end electrically connected to the second end of the first capacitor, and a second end, and controlled to switch between conduction and non-conduction; a first intermediate capacitor, electrical Is connected between the second terminal of the first inductor and the second terminal of the third switch; a second intermediate capacitor is electrically connected between the first terminal of the second inductor and the Between the second end of the fourth switch; a fifth switch having a first end electrically connected to the second end of the second switch, and a second end electrically connected to the second port, and controlled to switch between on and Non-conductive; a second capacitor having a first end electrically connected to the second end of the second port and a second end connected to the ground; wherein, when operating in a boost mode, the first port receives the The first input voltage and the second port generate a second output voltage greater than the first input voltage and proportional to the sum of the cross voltage of the first intermediate capacitor and the cross voltage of the second intermediate capacitor; wherein, when operating In a buck mode, the second port receives the second input voltage and the first port generates a first output voltage less than the second input voltage. The bidirectional voltage converter according to claim 1, further comprising a control unit that generates a first pulse signal for switching the first switch, a second pulse signal for switching the second switch, A third pulse signal for switching the third switch, and a fourth pulse signal for switching the fourth switch. The bidirectional voltage converter according to claim 2, wherein the first pulse signal, the second pulse signal, the third pulse signal, and the fourth pulse signal have the same cycle time and are synchronized. The bidirectional voltage converter according to claim 2, wherein the control unit further generates a fifth pulse signal for switching the fifth switch. The bidirectional voltage converter according to claim 4, wherein the fifth pulse signal The phase of the signal is complementary to the phase of the first pulse wave signal. The bidirectional voltage converter according to claim 1, wherein the first switch is an N-type power semiconductor transistor, the first terminal of the first switch is a drain, and the second terminal of the first switch is a source pole. The bidirectional voltage converter according to claim 1, wherein the second switch is an N-type power semiconductor transistor, the first terminal of the first switch is a drain, and the second terminal of the first switch is a source pole. The bidirectional voltage converter according to claim 1, wherein the third switch is an N-type power semiconductor transistor, the first terminal of the first switch is a drain, and the second terminal of the first switch is a source pole. The bidirectional voltage converter according to claim 1, wherein the fourth switch is an N-type power semiconductor transistor, the first terminal of the first switch is a drain, and the second terminal of the first switch is a source pole. The bidirectional voltage converter according to claim 1, wherein the fifth switch is an N-type power semiconductor transistor, the first terminal of the first switch is a drain, and the second terminal of the first switch is a source pole.

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