CN110061625A - Four Port Translation devices and its control method with double-polarity control - Google Patents

Abstract

The invention discloses a four-port converter with bipolar output. The input port includes a DC power source V _in1 and a DC power source V _in2 with charging and discharging functions, and the output port includes a load R ₁ and a load R ₂ . By controlling the switch tube, the converter can be operated in a dual-input dual-output mode or a single-input and three-output mode. In dual-input dual-output mode, V _in1 and V _in2 provide energy for both load R ₁ and load R ₂ ; in single-input and three-output mode, V _in1 provides energy for load R ₁ and load R ₂ , and V _in2 absorbs excess energy . The beneficial effects of the invention are: simple structure, low cost, high power density and high system efficiency. It can output symmetrical and common ground bipolar voltage, and can also connect loads of three voltage levels, with a wide range of applications and high reliability. The voltage relationship between the input and output ports of the converter is flexible and can be boosted or stepped down.

Description

Four-port converter with bipolar output and control method thereof

technical field

The invention relates to the technical field of power electronics, in particular to a four-port converter with bipolar output and a control method thereof.

Background technique

In recent years, with the intensification of environmental pollution and energy crisis, the use of solar energy, hydrogen energy, wind energy and other new energy sources to generate electricity has become a research hotspot. The new energy power generation system is divided into grid-connected operation and independent operation according to whether it is connected to the power grid or not. The independent operation of the new energy power generation system is widely used in remote mountainous areas, islands, industrial parks, etc. because of its simple structure and high power supply quality. In addition to the power supply in areas without power grids, independent new energy power generation systems are also widely used in the power supply of new energy vehicles and independent LED lighting systems. However, since the output characteristics of new energy power generation systems are often closely related to environmental factors, the output characteristics of new energy power generation systems under different environmental conditions are random and fluctuating. Therefore, energy storage must be equipped in independently operating new energy power generation systems. The unit is used to store and adjust electrical energy to meet the requirements of the electrical load on the continuity and stability of the power supply.

The traditional new energy power generation system uses multiple independent converters for power conversion, the system structure is complex, the efficiency is low, the cost is high, and centralized control cannot be realized. However, the existing multi-port converters usually include only one load terminal and can only provide a DC bus of one voltage level, which cannot meet the requirements of multiple loads of different voltage levels being connected to the system at the same time. . Therefore, some scholars have proposed new energy power generation systems with bipolar output, which can output symmetrical positive and negative voltages at the same time. Compared with the unipolar new energy power generation system, the bipolar new energy power generation system has the following advantages: 1) when one of the outputs fails to work normally, the other output can still work normally, and the system reliability is higher; 2) the flow through The current of the ground wire is very small, and when the two loads are the same, the current flowing through the ground wire is 0; 3) When the load power is equal, the power transmitted on a single bus in the bipolar new energy power generation system is unipolar. 4) It can provide output of three voltage levels, and the application range is wider. The traditional implementation of bipolar voltage output is to use an isolated forward converter or a flyback converter to wind the transformer with multiple output windings by sharing a transformer core to achieve bipolar output. The disadvantage is that the transformer design is complex, the system is bulky, and the efficiency is low. Therefore, it is necessary to propose a bipolar new energy power generation system based on a non-isolated multi-port converter to overcome the problems of large volume, high cost and low efficiency in the prior art.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention proposes a four-port converter with bipolar output. The converter can output symmetrical and common ground bipolar voltages at the same time, and with one converter, two power sources and multiple loads can be connected to the system at the same time. energy management.

The technical scheme that realizes the object of the present invention is as follows:

A four-port converter with bipolar output includes a DC power source V _in1 and a DC power source V _in2 with charging and discharging functions; the positive pole of V _in1 is connected to the input end of the inductor L ₁ , and the output end of L ₁ is connected to _The drain of the switch S1 and the positive pole of the intermediate storage capacitor _Cx , the negative pole of _Cx is connected to the input terminal of the inductor L2 and the anode of the diode _D2 , and the cathode of _D2 is connected to the input terminal _of the load R1 _; V The negative pole of _in1 , the source of S ₁ , the output terminal of L ₂ and the output terminal of R ₁ are all connected to the reference ground; it also includes an input filter capacitor C _in1 connected in parallel to both ends of V _in1 and an output filter capacitor connected in parallel to both ends of R _{1 C1} ; The anode of V _in2 is connected to the cathode of the diode _D3 , the anode of _D3 is connected to the source _of the switch tube S3, the drain _of S3 is connected to the anode of the intermediate storage capacitor _Cy , and the cathode of _Cy is connected To the anode of diode D ₄ and the input terminal of inductor L ₃ , the output terminal of inductor L ₃ is connected to the input terminal of load R ₂ ; the cathode of V _in2 , the cathode of D ₄ and the output terminal of R ₂ are all connected to the reference ground; It also includes an input filter capacitor C _in2 connected in parallel to both ends of V _in2 and an output filter capacitor C _{2 connected in parallel to both ends of R 2 ;} also includes a diode D ₁ and a switch tube S ₂ , the anode of D ₁ is connected to the input end of L ₁ , D _The cathode of ₁ is connected to the source of S2, and the drain of S2 is connected to the cathode _{of D3 ;} the drain of S1 is also connected to the drain _of S3.

Further, a load R ₃ is also included, and two ends of R ₃ are respectively connected to the input terminals of R ₁ and R ₂ .

The control method of the above four-port converter is to always turn off the switch S ₃ to make the converter operate in the dual-input and dual-output mode; or, always turn off the switch S ₂ to make the converter operate in the single-input three-output mode.

Compared with the prior art, the beneficial effects of the present invention are:

1. Simple structure, low cost, high power density and high system efficiency.

2. It can output symmetrical and common ground bipolar voltage, and can also connect loads of three voltage levels, with a wide range of applications and high reliability.

3. The voltage relationship between the input and output ports of the converter is flexible, which can be boosted or stepped down.

Description of drawings

FIG. 1 is a schematic diagram of a four-port converter with bipolar output according to the present invention.

FIG. 2 is an equivalent circuit diagram of a dual-input dual-output mode.

Figure 3 (a), Figure 3 (b) are the two main working waveforms under the dual-input dual-output mode.

Figure 4 is an equivalent circuit diagram of the single-input three-output mode.

Figure 5 is the main working waveform under the single-input three-output mode.

FIG. 6 is a schematic diagram of a control method of a four-port converter with bipolar output.

Figure 7(a) and Figure 7(b) are the two steady-state waveforms in the dual-input dual-output mode, respectively.

Figure 8 is the steady-state waveform in the single-input three-output mode.

Figure 9 is the transient response waveform of load transition in dual-input dual-output mode.

Figure 10 is the transient response waveform of load transition in single-input three-output mode.

Figure 11 is a simulation waveform of switching between dual-input dual-output mode and single-input three-output mode.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

A four-port converter with bipolar output, the converter can be connected to a first power source V _in1 , a second power source V _in2 and a load at the same time, and can output a symmetrical and common ground bipolar voltage, the circuit Fewer components, high power density, and wide application range.

FIG. 1 shows a schematic circuit diagram of a four-port converter with bipolar output, including a first power source V _in1 , a second power source V _in2 , a positive output port V _o1 , and a negative output port V _o2 , the first input filter capacitor C _in1 , the second input filter capacitor C _in2 , the first intermediate energy storage capacitor C _x , the second intermediate energy storage capacitor C _y , the first output filter capacitor C ₁ , the second output filter capacitor C ₂ , the first inductor L ₁ , the second inductor L ₂ , the third inductor L ₃ , the first switch S ₁ , the second switch S ₂ , the third switch S ₃ , the first diode D ₁ , the second Diode D ₂ , third diode D ₃ , fourth diode D ₄ , first load R ₁ , second load R ₂ . In addition, the third load R ₃ can also be increased according to actual needs.

The first power source V _in1 uses a photovoltaic unit as an input, the second power source V _in2 uses an energy storage unit as an input, and the first load R ₁ , the second load R ₂ and the third load R ₃ all use pure resistance.

The anode of the first power source V _in1 is connected to one end of the first inductor L ₁ and the cathode of the first diode D ₁ , the cathode is connected to the reference ground, and the other end of the first inductor L ₁ is connected to the first switch tube S ₁ . The drain is connected to the positive pole of the first intermediate energy storage capacitor _Cx , the source of the _first switch tube S1 is connected to the reference ground, and the negative pole of the first intermediate energy storage capacitor _Cx is connected to one end of the _second inductor L2 and the second _The anode of the diode D2 is connected, the other end of the _second inductor L2 is connected to the reference ground, and the cathode of the _second diode D2 is used as the anode of the positive output port V _{o1 of} the converter, and is connected with the load R1. Positive connection.

The cathode of the second power source V _in2 is connected to the reference ground, the anode is connected to the drain of the _second switch S2 and the cathode of the third diode _D3 , and the source of the _second switch S2 is connected to the first diode _The anode of the tube D1 is connected, the anode of the third diode _D3 is connected to the source of the _third switch tube S3, the drain of the _third switch tube S3 is connected to the drain of the _first switch tube S1 and the second The positive pole of the intermediate energy storage capacitor C _y is connected, the negative pole of the second intermediate energy storage capacitor C _y is connected to the anode of the fourth diode D ₄ and one end of the third inductor L ₃ respectively, and the cathode of the fourth diode D ₄ Connected to the reference ground, the other end of the third inductor L ₃ serves as the positive pole of the positive output port V _o2 of the converter, and is connected to the positive pole of the load R ₂ .

If a third load R ₃ is set in the system, the two ends of the load R ₃ are respectively connected to the positive poles of the load R ₁ and the load R ₂ .

The first input filter capacitor C _in1 and the second input filter capacitor C _in2 are respectively connected in parallel to both ends of the photovoltaic input port and the input port of the energy storage unit; the first output filter capacitor C ₁ and the second output filter capacitor C ₂ are connected in parallel to Both ends of the positive output port and the negative output port.

In the system, the first power source V _in1 may be various power sources capable of providing DC output, and the second power source V _in2 may be various energy storage devices with charging and discharging functions.

In specific applications, in order to achieve strict symmetrical bipolar output, it is necessary to ensure that the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ all work in the inductor current continuous conduction mode (CCM). Therefore, L ₁ , L ₂ , and L ₃ should all take larger inductance values.

In order to achieve strict symmetrical bipolar output, it is also necessary to ensure that the voltages of the first intermediate energy storage capacitor C _x and the second intermediate energy storage capacitor C _y are basically constant. Therefore, both C _x and C _y should take larger capacitance values. .

In the dual-input dual-output mode, the _third switch S3 is always turned off, and the first power source V _in1 and the second power source V _in2 provide energy for the load unit at the same time. In one switching cycle, the system includes four switching states, They are: State 1 (S ₁ and S ₂ are both on); State 2 (S ₁ on, S ₂ off); State 3 (S ₁ off, S ₂ on); State 4 (S ₁ and S ₂ are both turned off), if the on-duty ratio d ₁ of S ₁ is greater than the on-duty ratio d ₂ of S ₂ , then state 1, state 2, and state 4 appear in turn in one switching cycle. If S ₁ The on-duty ratio d ₁ of S ₂ is smaller than the on-duty ratio d ₂ of S 2 , then state 1, state 3, and state 4 appear in turn in one switching cycle.

In the single-input three-output mode, the _second switch S2 is always turned off, only the first power source V _in1 provides energy for the load, and the second power source V _in2 absorbs excess energy. In one switching cycle, the system includes three The switch states are: state 1 (S ₁ is turned on, S ₃ is turned off); state 2 (S ₁ is turned off, S ₃ is turned on); state 3 (S ₁ and S ₃ are both turned off).

Figure 2 shows the equivalent circuit of a four-port converter with bipolar output in dual-input dual-output mode. In the dual-input dual-output mode, the photovoltaic unit V _in1 and the energy storage unit V _in2 provide energy for the load at the same time, and the switch tube _S3 is constantly turned off.

Figure 3 shows the main working waveforms of the four-port converter with bipolar output in the dual-input dual-output mode, where d1 is the _{on -} duty ratio _of the switch S1, and _d2 is the switch S2 On-duty ratio, i _L is the current flowing through the inductor L ₁ , v _L is the voltage across the inductor L ₁ , V _cx is the voltage across the first intermediate energy storage capacitor C _x , and V _cy is the first intermediate energy storage Voltage across capacitor _Cy . In the dual-input dual-output mode, the converter may appear in two working states, namely d ₁ >d ₂ and d ₁ <d ₂ , as shown in Figure 3(a) and Figure 3(b).

In the dual-input dual-output mode, according to the volt-second balance relationship of the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ , whether d ₁ >d ₂ or d ₁ <d ₂ , the positive polarity output can be obtained. The terminal voltage V _o1 and the negative output terminal voltage V _o2 are:

It can be seen from the above formula that in the dual-input dual-output mode, the positive output voltage V _o1 and the negative output voltage V _o2 have the same amplitude and opposite voltage polarity, and when the switch S1 is turned _on When the duty cycle d ₁ varies between 0 and 1, the positive terminal voltage V _o1 can vary from 0 to positive no-cluster, and the negative terminal voltage V _o2 can vary from 0 to negative no-cluster. Therefore, the converter of the present invention can realize both step-up and step-down in the dual-input dual-output mode.

Figure 4 shows the equivalent circuit of a four-port converter with bipolar output in single-input three-output mode. In the single-input three-output mode, only the photovoltaic unit provides energy for the load, the energy storage unit absorbs the excess energy generated by the photovoltaic unit, and the switch tube _S2 is constantly turned off.

Figure 5 shows the main working waveforms of the four-port converter with bipolar output in the single-input _three -output mode, wherein d1 is the on _- duty ratio _of the switch S1, and _d3 is the switch S3 On-duty ratio, i _L is the current flowing through the inductor L ₁ , v _L is the voltage across the inductor L ₁ , V _cx is the voltage across the first intermediate energy storage capacitor C _x , and V _cy is the first intermediate energy storage Voltage across capacitor _Cy .

In the single-input three-output mode, according to the volt-second balance relationship between the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ , the voltages at the positive output terminal and the negative output terminal can be obtained as:

It can be seen from the above formula that in the single-input _three -output mode, the voltages at the positive output terminal and the negative output terminal have the same amplitude and opposite voltage polarities, and when the switch S1 and the switch S3 are turned _on When the duty cycle sum d ₁ +d ₃ changes between 0 and 1, the positive terminal voltage V _o1 can vary between 0 and the positive terminal voltage, and the negative terminal voltage V _o2 can be between 0 and negative. change between large. Therefore, the converter of the present invention can realize both step-up and step-down in the single-input three-output mode.

Figure 6 shows a control circuit for a four-port converter with bipolar outputs. The control circuit includes a first power source controller, a second power source controller, an output voltage controller, a mode selection circuit and a pulse modulation circuit. In this example, the first power source controller implements maximum power point tracking (MPPT) control, and performs MPPT operation by sampling the voltage V _in1 and current I _in1 of the input terminal of the photovoltaic unit to obtain the control signal v _e1 , thereby The maximum power output of photovoltaic is realized; the second power source controller controls the voltage and current of the energy storage unit, and compares with the preset threshold by sampling the voltage V _in2 and the charging and discharging current I _in2 at both ends of the energy storage unit, thereby Make the energy storage unit realize overcharge protection and overdischarge protection; the output voltage controller samples two output voltages V _o1 and V _o2 , then calculates V _ox =0.5*V _o1 -0.5*V _o2 , and compares V _ox with the reference The voltage V _{o_ref} is compared to control the output voltage to be constant; the mode selection circuit determines the operating mode of the system according to the size of the output v _oe of the output voltage controller. If v _oe <0, the system operates in dual output mode _. >0, the system operates in dual-input mode; the pulse modulation circuit compares the output of the mode selection circuit with the sawtooth wave to generate a pulse signal to control the on and off of the switches S ₁ , S ₂ and S ₃ . It should be noted that the above-mentioned control circuit is not the only control circuit of the present invention.

Use PSIM simulation software to simulate and analyze the system in time domain. The simulation parameters of the system are set as: C _in1 =C _in2 =C ₁ =C ₂ 470μF, C _x =C _y =1000μF, L ₁ =L ₂ =L ₃ =330μH , the positive output port voltage V _o1 =24V, the negative output port voltage V _o2 =-24V, the energy storage unit voltage V _in2 =30V, the switching frequency is f _s =100kHz, the system simulation results are shown in Figure 7 to Figure 11 .

Figure 7 is the steady-state waveforms of the switch drive signal, the current i _L of the inductor L ₁ and the voltage v _L across the inductor in the dual-input dual-output mode of the four-port converter with bipolar output, in which Figure 7(a) is the steady-state waveform of d ₁ >d ₂ , and Fig. 7(b) is the steady-state waveform of d ₁ <d _2. It can be seen from the figure that the simulation results are consistent with the theoretical analysis.

Figure 8 shows the steady-state waveforms of the switch drive signal, the current i _L of the inductor L ₁ and the voltage v _L across the inductor under the single-input three-output mode of the four-port converter with bipolar output, as can be seen from the figure , the simulation results are consistent with the theoretical analysis.

Figure 9 is the transient response waveform of the four-port converter with bipolar output under the dual-input dual-output mode of load jumping. At this time, the maximum output power of the photovoltaic is 75W. The power consumption is 100W, the power provided by the energy storage unit is 25W, the load power increases from 100W to 150W in 0.1s, the power provided by the energy storage unit suddenly changes to 75W, and the load power decreases from 150W to 100W in 0.15s, The operation of the system is consistent with the initial state. As can be seen from the figure, when the load changes, both the positive output voltage and the negative output voltage remain constant.

Figure 10 is the transient response waveform of the four-port converter with bipolar output under the single-input three-output mode of the load jump. At this time, the maximum output power of the photovoltaic is 125W. At the initial moment, the photovoltaic module outputs at the maximum power and the load The power consumption is 100W, the power absorbed by the energy storage unit is 25W, the load power is reduced from 100W to 50W at 0.1s, the power absorbed by the energy storage unit suddenly changes to 75W, and the load power is increased from 50W to 100W at 0.15s, the system The operation is the same as the initial state. As can be seen from the figure, when the load changes, both the positive output voltage and the negative output voltage remain constant.

Figure 11 is the simulation waveform of the four-port converter with bipolar output switching between the single-input three-output mode and the dual-input dual-output mode. At the initial moment, the photovoltaic output is at the maximum power of 125W, the load power consumption is 100W, and the storage power is 100W. The power absorbed by the energy unit is 25W. The system works in the single-input and three-output mode. The maximum output power of the photovoltaic changes from 125W to 50W in 0.1s. The output power of the photovoltaic is greater than the power required by the load. In order to ensure the normal operation of the system, the system runs When the mode is switched to dual-input and dual-output mode, the power provided by the energy storage unit is 50W. In 0.15s, the maximum output power of the photovoltaic suddenly changes from 50W to 125W, and the system operation is consistent with the initial state.

According to the above theoretical analysis and simulation, it can be seen that the four-port converter with bipolar output proposed by the present invention has the advantages of simple structure, low cost, high power density and high system efficiency, and can output symmetrical and common ground. The bipolar voltage can be connected to loads of at least three voltage levels, with a wide range of applications, high reliability, and few switching devices, enabling centralized control, making the design of the control circuit simpler, and the input and output ports of the converter. The voltage relationship between the two is flexible, and it can be boosted or stepped down. Therefore, the converter proposed by the present invention has obvious advantages compared with the prior art.

Claims (3)

1. a four-port converter with bipolar output, characterized in that it comprises a DC power source V _in1 and a DC power source V _in2 with charging and discharging functions; The positive pole of V _in1 is connected to the input terminal of the inductor L ₁ , the output terminal of L ₁ is connected to the drain terminal of the switch S ₁ and the positive pole of the intermediate storage capacitor C _x , and the negative pole of C _x is connected to the input terminal of the inductor L ₂ and _The anode of diode D2, the cathode of D2 is connected to the input of load R1 _; the cathode of V _in1 , the source _{of S1} , the output _{of L2} and the output of R1 are all connected to the reference ground; also includes parallel connection to the input filter capacitor C _in1 at both ends of V _in1 and the output filter capacitor C _{1 connected in parallel to both ends of R 1 ;} The anode of V _in2 is connected to the cathode of the diode _D3 , the anode of _D3 is connected to the source _of the switch S3, the drain _of S3 is connected to the anode of the intermediate storage capacitor _Cy , and the cathode of _Cy is connected to the diode D The anode of ₄ and the input terminal of inductor L ₃ , the output terminal of inductor L ₃ is connected to the input terminal of load R ₂ ; the negative terminal of V _in2 , the cathode terminal of D ₄ and the output terminal of R ₂ are all connected to the reference ground; also includes parallel connection to the input filter capacitor C _in2 at both ends of V _in2 and the output filter capacitor C _{2 connected in parallel to both ends of R 2 ;} It also includes _a diode D1 and _a switch tube _S2 , the anode of D1 is connected to the input terminal _of L1, the cathode _of D1 is connected to the source of _S2 , and the drain of S2 is connected to the cathode of _{D3 ; The} drain of S1 is also connected to the drain _of S3. 2 . The four-port converter according to claim 1 , further comprising a load R ₃ , and two ends of R ₃ are respectively connected to the input terminals of R ₁ and R ₂ . 3 . 3. The control method of a four-port converter according to claim 1 or 2, wherein the switch tube S ₃ is always turned off, so that the converter operates in a dual-input and dual-output mode; or, the switch tube S is always turned off ₂ , make the converter operate in single-input three-output mode.