CN104038049B - Non-isolated three-port series-parallel integrated converter - Google Patents

Abstract

The invention discloses a non-isolated three-port series-parallel integrated converter topology, belonging to the technical field of power electronic conversion_in1And V_in2Voltage stabilizing capacitor C₁And C₂A first switch unit, a second switch unit, a third switch unit, a fourth switch unit, and an output diode D_OAn inductor L, an output capacitor C and a load R; an energy storage capacitor is connected in parallel at each input side, and a fourth switching unit is introduced to connect the two input sources. When the photovoltaic operation is stopped, the capacitor at the photovoltaic side is discontinuously charged through the introduced switching tube, so that the input voltage at the side is kept stable, and the stability of the load voltage is further ensured; when the photovoltaic energy is sufficient, the direct energy transfer of the photovoltaic port and the storage battery port is realized, and the utilization rate of new energy is improved. The invention has the advantages of small volume, low cost, high integration level, realization of power conversion among ports, flexible compensation, high system stability and reliability and the like.

Description

Non-isolated three-port series-parallel integrated converter

technical field

The invention relates to the technical field of power electronic conversion, in particular to a three-port series-parallel integrated converter.

Background technique

With the increasing demand for electricity, the large-scale exploitation and utilization of fossil energy has made the world's energy situation increasingly tense. At the same time, the large amount of waste gas produced by the combustion of fossil fuels has caused serious environmental pollution. Since new energy is clean, pollution-free and rich in resources, using new energy to generate electricity is an important way to solve the contradiction between energy development and environmental protection. At present, wind power generation, photovoltaic power generation, fuel cell power generation, geothermal power generation and tidal power generation are widely used in the form of new energy power generation. A variety of complementary new energy sources are usually combined and equipped with energy storage devices to form a new energy joint power supply system.

In the traditional new energy joint power supply system, each energy form usually requires a DC/DC converter to convert various energy sources into DC output, and connect them in parallel to the common DC bus to supply DC loads, but its structure is relatively complicated. higher cost. In addition, from the perspective of control, each converter must ensure coordination with other ports while being independently controlled. Therefore, a communication network between each port must be established during actual operation, which will increase the complexity of the system.

In order to achieve centralized control and management, new energy power supply systems based on multi-input converters have received more and more attention and applications. Multi-input converters can be divided into two types: isolated and non-isolated topologically. Isolated multi-input converters mostly use high-frequency isolation transformers to realize the electrical isolation of multiple input sources and loads, and realize the matching of different voltage levels of input sources by adjusting the number of turns of the transformer windings. However, in applications that do not require electrical isolation, the non-isolated multi-input converter can omit the transformer, which not only helps to reduce the system size and improve system efficiency, but also reduces the electromagnetic interference caused by the use of magnetic components. However, the current research on non-isolated multi-input converters is limited to the fact that energy can be transferred between input sources and loads, and energy cannot be directly transferred between input sources. In addition, once a certain input source stops working, it will either increase the load of other input sources, or make the voltage and current on the load unable to meet the safe operation requirements, causing the system to stop, and even damage the equipment in severe cases. Therefore, the stability and flexibility of this type of topology are not strong, the utilization rate of new energy is not very high, and the application range is relatively limited. Therefore, it is necessary to seek a method that can directly transfer energy between input sources and has flexible compensation and fault tolerance. The non-isolated topology of the solution is significant.

Contents of the invention

The purpose of the present invention is to provide a non-isolated three-port series-parallel integrated converter capable of directly transferring energy between input sources and having flexible compensation and fault tolerance schemes.

In order to achieve the above purpose, the following technical solution is adopted: the integrated converter of the present invention includes a first input DC voltage source V _in1 , a second input DC voltage source V _in2 , a first input voltage stabilizing capacitor C ₁ , a second input voltage stabilizing capacitor C ₂ , a first switch unit, a second switch unit, a third switch unit, a fourth switch unit, an output diode D _O , an inductor L, an output capacitor C and a load R;

The first switch unit includes a diode D ₁ and a first main switch S ₁ ; the first input DC voltage source V _in1 is connected in parallel with a capacitor C ₁ , the anode of the capacitor C ₁ is connected to the cathode of the diode D ₁ , and the anode of the diode D ₁ is connected to The collector of the _first main switch S1, and the emitter of the _first main switch S1 are connected to the negative pole of the capacitor _C1 ;

The second switch unit includes a diode D ₂ and a second main switch S ₂ ; the second input DC voltage source V _in2 is connected in parallel with a capacitor C ₂ , and the anode of the capacitor C ₂ is connected to the collector of the second main switch S ₂ , The cathode of the capacitor _C2 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the emitter of the _second main switch _{S2; the} emitter of the _second main switch S2 is connected to the collector of the _first main switch S1 ;

The third switch unit includes a diode _D3 and a _third main switch S3; the emitter of the _third main switch S3 is connected to the anode of the diode _D3 , and the cathode of the diode _D3 is connected to the second main switch in the second switch unit _The collector of S2 is connected; the collector of the _third main switch S3 is respectively connected to one end of the inductor L and the anode of the output diode D _O , and the other end of the inductor L is respectively connected to the anode of the first input DC voltage source V _in1 and the diode D ₁ ; the cathode of the output diode D _O is respectively connected to the positive pole of the output capacitor C and one end of the load R, and the other end of the output capacitor C and the load R are respectively connected to the negative pole of the _second input DC voltage source V _in2 and the anode of the diode D2 , the cathode of capacitor C2 _;

The _fourth switch unit includes a _fourth main switch S4 and a diode D4 _; the emitter of the _fourth main switch S4 is connected to the anode of the diode D4, and the collector of the _fourth main switch S4 is connected to the first input DC voltage source The cathode of V _in1 ; the cathode of diode D ₄ is connected to the cathode of the second input DC voltage source V _in2 .

Compared with prior art, the present invention has following advantage:

1. There is only one magnetic inductance element in the topology, which effectively reduces the system volume and cost, and has a high degree of integration. It can realize single-stage power conversion between ports, and has high system efficiency;

2. It has the working state of series and parallel connection of input sources, adapts to the characteristics of random and intermittent power generation of renewable energy, and has flexible compensation function;

3. The direct energy transfer between the photovoltaic port and the battery port is suitable for occasions where the battery voltage is lower than the load voltage, which can effectively reduce the number of batteries connected in series, avoid the risk of system collapse due to damage to a single battery, and effectively improve system reliability;

4. It can be used in the new energy joint power supply system, which reduces the impact of the unstable power supply of new energy on the load, and also improves the utilization rate of the system for new energy, which meets the requirements of environmental protection and energy saving.

Description of drawings

Fig. 1 is the electrical schematic diagram of the present invention;

Fig. 2 is the working mode diagram of the present invention under the dual-input mode;

Fig. 3 is the working wave diagram of the present invention under the dual-input mode;

Fig. 4 is the working mode diagram of the present invention under the dual output mode;

Fig. 5 is the working wave diagram of the present invention under the dual output mode;

Fig. 6 is a working process diagram of the present invention in charging mode;

Fig. 7 is a working waveform diagram of the present invention in charging mode;

Fig. 8 is a schematic diagram of energy management in the present invention.

detailed description

The present invention will be further described below in combination with the accompanying drawings and specific embodiments.

As shown in the electrical schematic diagram of the present invention shown in Fig. 1 , the integrated converter of the present invention includes a first input DC voltage source V _in1 , a second input DC voltage source V _in2 , a first input voltage stabilizing capacitor C ₁ , a second Two input voltage stabilizing capacitors C ₂ , a first switch unit, a second switch unit, a third switch unit, a fourth switch unit, an output diode D _O , an inductor L, an output capacitor C and a load R;

The first switch unit includes a diode D ₁ and a first main switch S ₁ ; the first input DC voltage source V _in1 is connected in parallel with a capacitor C ₁ , the anode of the capacitor C ₁ is connected to the cathode of the diode D ₁ , and the anode of the diode D ₁ is connected to The collector of the _first main switch S1, and the emitter of the _first main switch S1 are connected to the negative pole of the capacitor _C1 ;

The second switch unit includes a diode D ₂ and a second main switch S ₂ ; the second input DC voltage source V _in2 is connected in parallel with a capacitor C ₂ , and the anode of the capacitor C ₂ is connected to the collector of the second main switch S ₂ , The cathode of the capacitor _C2 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the emitter of the _second main switch _{S2; the} emitter of the _second main switch S2 is connected to the collector of the _first main switch S1 ;

The third switch unit includes a diode _D3 and a _third main switch S3; the emitter of the _third main switch S3 is connected to the anode of the diode _D3 , and the cathode of the diode _D3 is connected to the second main switch in the second switch unit _The collector of S2 is connected; the collector of the _third main switch S3 is respectively connected to one end of the inductor L and the anode of the output diode D _O , and the other end of the inductor L is respectively connected to the anode of the first input DC voltage source V _in1 and the diode D ₁ ; the cathode of the output diode D _O is respectively connected to the positive pole of the output capacitor C and one end of the load R, and the other end of the output capacitor C and the load R are respectively connected to the negative pole of the _second input DC voltage source V _in2 and the anode of the diode D2 , the cathode of capacitor C2 _;

The _fourth switch unit includes a _fourth main switch S4 and a diode D4 _; the emitter of the _fourth main switch S4 is connected to the anode of the diode D4, and the collector of the _fourth main switch S4 is connected to the first input DC voltage source The cathode of V _in1 ; the cathode of diode D ₄ is connected to the cathode of the second input DC voltage source V _in2 .

In the converter, the first input DC voltage source V _in1 is connected to renewable energy sources such as photovoltaic cells and wind power generation units, and the second input DC voltage source V _in2 is connected to energy storage devices such as batteries and supercapacitors, and V _in2 < V _O < V _in1 . Assume that the input power of the renewable energy is P _in1 , and the load power is P _o . Assuming that when P _in1 <P _o , the photovoltaic cell and the storage battery supply power to the load together, the converter is equivalent to a dual-input converter (DIC). In this mode, the _third main switch S3 and the _fourth main switch S4 are always off, and according to the switching states of the _first main switch S1 and the _second S2, the converter has four switching modes in total.

Each modal equivalent circuit is shown in Fig. 2.

As shown in Fig. 2a, in mode I, the first main switch S ₁ and the second main switch S ₂ are turned on, at this time, the photovoltaic power supply and the storage battery are connected in series, and the inductor current i _L increases linearly.

As shown in Figure 2b, in mode II, the first main switch S ₁ is turned on, the second main switch S ₂ is turned off, and the inductor current i _L increases linearly under the action of photovoltaics.

As shown in Figure 2c, in mode III, the second main switch S ₂ is turned on, the first main switch S ₁ is turned off, and the inductor current i _L decreases linearly under the action of the battery.

As shown in FIG. 2d , in mode IV, both the first main switch S ₁ and the second main switch S ₂ are turned off, and the inductor current i _L decreases linearly.

As shown in FIG. 3 , the duty ratios of the first main switch S ₁ and the second main switch S ₂ in the dual-input mode are d ₁ and d ₂ respectively. When d ₁ >d ₂ , the converter experiences modes 1, 2, and 4 sequentially within one switching cycle; when d ₁ <d ₂ , the converter experiences modes 1, 3, and 4 sequentially within one switching cycle. In this mode, the photovoltaic output power is controlled by adjusting the duty cycle d1 _of the _first main switch S1, and the discharge power of the battery is controlled by adjusting the duty cycle _d2 of the _second main switch S2 to maintain the load voltage stability.

When P _in1 >P _o , the PV powers the load and charges the battery at the same time, and the converter is equivalent to a dual output converter (DOC). In this mode, the _second main switch S2 and the _fourth main switch S4 are always off. According to the switching states of the _first main switch S1 and the third main switch S3, the converter has _three switching modes, each The modal equivalent circuit is shown in Figure 4.

As shown in Fig. 4a, in mode I, the first main switch S ₁ and the third main switch S ₃ are turned on, the photovoltaic is charging the battery, and the inductor current i _L increases linearly.

As shown in Figure 4b, in mode II, the first main switch S ₁ is turned on, the third main switch S ₃ is turned off, the photovoltaic supplies power to the load, and the inductor current i _L increases linearly.

As shown in FIG. 4c, in mode III, both the first main switch S ₁ and the third main switch S ₃ are turned off, and the inductor current i _L decreases linearly.

As shown in FIG. 5 , the duty ratios of the first main switch S ₁ and the third main switch S ₃ in the dual output mode are d ₁ and d ₃ respectively. In this mode, the photovoltaic output power is controlled by adjusting the duty cycle d1 _of the _first main switch S1, and the charging power of the battery is controlled by adjusting the duty cycle _d3 of the _third main switch S3 to maintain the load voltage stability.

When the photovoltaic cannot output energy due to environmental factors or its own failure, that is, when P _in1 = 0, the battery and capacitor C ₁ form a series-parallel connection to supply power to the load, which is a unique charging mode of the converter. In this mode, the _third main switch S3 is always off, and the _second main switch S2 is always on. According to the switching states of the first main switch S ₁ and the fourth main switch S ₄ , the converter has two switching modes, and the equivalent circuit of each mode is shown in Fig. 6 .

As shown in Figure 6a, in mode I, the fourth main switch S ₄ is turned on, and the first main switch S ₁ is turned off. While the battery supplies power to the load, it supplies power to the capacitor through the loop formed by S ₂ →D ₁ →D ₄ →S ₄ C ₁ is charged, and the inductor current i _L decreases linearly under the action of the battery.

As shown in Fig. 6b, in mode II, the _first main switch S1 is turned on, the _fourth main switch S4 is turned off, the battery and the capacitor _C1 are connected in series to supply power to the load, and the inductor current i _L increases linearly.

As shown in FIG. 7 , the duty ratio of the first main switch S ₁ in the charging mode is d ₁ . In this mode, the load voltage is kept stable by adjusting the duty ratio d ₁ of the first main switch S ₁ .

As shown in Figure 8, according to the energy management schematic diagram of the present invention, in the non-isolated three-port series-parallel integrated converter, the master-slave control mode is adopted to realize the input power distribution of the two input sources:

(1) When the energy provided by photovoltaics is not enough to meet the needs of the load, ensure that photovoltaics emit as much energy as possible, and the remaining energy is supplemented by batteries. At this time, the output ports Ao, Bo, and Co of the multiplex switches MUX1 and MUX2 are respectively connected to AX, BX, and CX. The current regulator is used to control the duty ratio d ₁ of S ₁ to further control the photovoltaic output power, and the voltage regulator is used to control the duty ratio d ₂ of S ₂ to stabilize the output voltage.

(2) When the energy provided by photovoltaics is greater than the needs of the load, the photovoltaics will supply power to the load alone, and the remaining energy will be transferred to the battery. At this time, the output ports Ao, Bo, and Co of the multiplex switches MUX1 and MUX2 are respectively connected to AY, BY, and CY. The current regulator is used to control the duty ratio d ₁ of S ₁ to further control the photovoltaic output power, and the voltage regulator is used to control the duty ratio d ₃ of S ₃ to stabilize the output voltage.

(3) When the photovoltaic cannot output energy due to environmental factors or its own failure, the load power is completely provided by the battery, and the capacitor and the power supply cooperate to supply power to the load. At this time, the output ports Ao, Bo, and Co of the multiplex switches MUX1 and MUX2 are respectively connected to AZ, BZ, and CZ. In this mode, the current regulator stops working, and only the voltage regulator forms a single closed-loop system. At this time, control S2 to be normally _on , adjust the duty ratio _of S1 to ensure the stability of the output voltage, and the driving signal of _S4 is generated by the logic circuit.

Claims (1)

1. A non-isolated three-port series-parallel integrated converter, characterized in that: the integrated converter includes a first input DC voltage source V _in1 , a second input DC voltage source V _in2 , a first input stabilized voltage Capacitor C ₁ , second input voltage stabilizing capacitor C ₂ , first switch unit, second switch unit, third switch unit, fourth switch unit, output diode D _O , inductor L, output capacitor C and load R; The first switch unit includes a diode D ₁ and a first main switch S ₁ ; the first input DC voltage source V _in1 is connected in parallel with a capacitor C ₁ , the anode of the capacitor C ₁ is connected to the cathode of the diode D ₁ , and the anode of the diode D ₁ is connected to The collector of the _first main switch S1, and the emitter of the _first main switch S1 are connected to the negative pole of the capacitor _C1 ; The second switch unit includes a diode D ₂ and a second main switch S ₂ ; the second input DC voltage source V _in2 is connected in parallel with a capacitor C ₂ , and the anode of the capacitor C ₂ is connected to the collector of the second main switch S ₂ , The cathode of the capacitor _C2 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the emitter of the _second main switch _{S2; the} emitter of the _second main switch S2 is connected to the collector of the _first main switch S1 ; The third switch unit includes a diode _D3 and a _third main switch S3; the emitter of the _third main switch S3 is connected to the anode of the diode _D3 , and the cathode of the diode _D3 is connected to the second main switch in the second switch unit _The collector of S2 is connected; the collector of the _third main switch S3 is respectively connected to one end of the inductor L and the anode of the output diode D _O , and the other end of the inductor L is respectively connected to the anode of the first input DC voltage source V _in1 and the diode D ₁ ; the cathode of the output diode D _O is respectively connected to the positive pole of the output capacitor C and one end of the load R, and the negative pole of the output capacitor C and the other end of the load R are respectively connected to the negative pole of the second input DC voltage source V _in2 and the diode D ₂ The anode of the capacitor C ₂ and the negative pole; The _fourth switch unit includes a _fourth main switch S4 and a diode D4 _; the emitter of the _fourth main switch S4 is connected to the anode of the diode D4, and the collector of the _fourth main switch S4 is connected to the first input DC voltage source The cathode of V _in1 ; the cathode of diode D ₄ is connected to the cathode of the second input DC voltage source V _in2 .