TWI413336B - Device of bi-directional inverter and direct current power system thereof - Google Patents

Abstract

A device of bi-directional inverter adapts to convert electric power between a direct current micro-grid, a battery, and a local distribution network. The device of bi-directional inverter includes a bi-directional charger/discharger, a bi-directional inverter, and a switch circuit. The bi-directional charger/discharger is used to charge or discharge the battery. The switch circuit is used to couple the bi-directional inverter to the local distribution network or the battery. When the bi-directional inverter is coupled to the local distribution network, the bi-directional inverter operates in a local distribution network coupled mode or a rectification and power factor correction mode. When the bi-directional inverter is decoupled with the local distribution network, the bi-directional inverter is coupled to the battery for charging or discharging the battery. Accordingly, the device of bi-directional inverter could decrease the production cost of the direction current power system.

Description

Bidirectional converter device and its DC power supply system

The present invention relates to an inverter, and more particularly to a bidirectional commutation device for an inverter and a DC power supply system therefor.

Since the twentieth century, the energy crisis has become increasingly serious. In order to reduce human dependence on natural energy such as oil, media and natural gas, countries around the world are pushing hard to promote the development of green energy devices. Green energy must be inexhaustible, inexhaustible and will not cause environmental pollution. The current development of green energy devices mainly uses natural resources such as solar energy, wind power, hydropower and geothermal energy as sources of power generation.

In general, the green energy device is a DC power plant. The green energy device must first pass through a DC/DC converter to boost the output voltage of the green energy device, and then convert it into an AC power supply through an AC/DC converter. Electric grid. If the green energy device is directly connected in parallel to the mains, and then the power is supplied to the general electrical products, the output of the green energy device must be converted into an AC power source, and then converted through a full-bridge rectifier component and a Power Factor Corrector (PFC). DC power supply to electrical products. However, each conversion will reduce efficiency. Therefore, if the energy generated by the green energy device can be directly supplied to the load, unnecessary power conversion can be avoided. Therefore, if a DC power supply system can be used and the power output from the green energy device is directly supplied to the DC electric appliance, the energy use efficiency can be improved.

Please refer to FIG. 1. FIG. 1 is a block diagram of a conventional DC power supply system. The conventional DC power supply system 1 includes a green energy power generation system 10, an energy storage device 11, a DC load 12, and a bidirectional inverter 13. The green energy power generation system 10 may include a green energy device such as a solar photovoltaic panel 104, a wind turbine 105, a fuel cell 106, and electrical energy processors 101-103, and a corresponding energy processor. The energy storage device 11 includes a battery 112 and a bidirectional charge and discharge device 111. The DC load 12 may include a lighting system 121, an inverter air conditioning system 122, a charging station 123, a DC electrical test platform 124, and the like.

The green energy power generation system 10, the energy storage device 11, the DC load 12 and the bidirectional converter 13 are electrically connected to the DC microgrid, respectively. The bidirectional converter 13 is more electrically connected to the AC grid. The green energy power generation system 10 is used to provide DC power to the DC load 12. The energy storage device 11 is used to store excess power generated by the green energy power generation system 10, and the energy storage device 11 can also provide DC load 12 power when the green energy power generation system 10 generates insufficient power. The bidirectional converter 13 converts power between the AC grid and the DC grid.

As shown in FIG. 1, the bidirectional converter 12 plays a very important role in the conventional DC power supply system 1, and the bidirectional converter 13 converts the power output from the green energy power generation system 10 into an AC power source to feed the mains. On the other hand, when the output of the green energy power generation system 10 is insufficient to provide the DC load 12, the bidirectional converter 13 converts the power of the AC grid into DC power and feeds it into the DC microgrid, which may be referred to as grid-connected DC power supply. DC Uninterruptible Power System.

However, when the bidirectional converter 13 is disconnected from the AC grid (mains), or in the area where there is no mains grid, the battery 112 is used to maintain the system uninterrupted. Therefore, it is possible to add a larger power DC/DC charge and discharge device for storing the excess energy output from the green energy power generation system 10 to the battery 112 and converting the energy of the battery 112 into the DC load 12 for use. In terms of practicality and scalability, DC power supply systems may have to design different power architectures for different situations, which may cause inconvenience in the promotion of DC power supply systems.

Embodiments of the present invention provide a bidirectional commutation device suitable for converting power between a DC microgrid, a battery, and a utility. The bidirectional commutation device comprises a bidirectional charge and discharge device, a bidirectional converter and a switching circuit. The bidirectional charge and discharge device is used to charge and discharge the battery. The switching circuit causes the bidirectional converter to be connected to the battery in parallel or electrically. When the bidirectional converter is connected in parallel with the mains, the bidirectional converter operates in the mains parallel mode or the rectification and power factor correction mode. When the bidirectional converter is connected to the city, the bidirectional converter is electrically connected to the battery to enable the bidirectional converter to charge and discharge the battery.

Embodiments of the present invention provide a DC power supply system including a DC load, a regenerative energy device, a DC converter, and a bidirectional commutation device. The DC converter supplies the power of the regenerative energy device to the DC load. The bidirectional commutation device comprises a bidirectional charge and discharge device, a bidirectional converter and a switching circuit. The bidirectional charge and discharge device is used to charge and discharge the battery. The switching circuit causes the bidirectional converter to be connected to the battery in parallel or electrically. When the bidirectional converter is connected in parallel with the mains, the bidirectional converter operates in the mains parallel mode or the rectification and power factor correction mode. When the bidirectional converter is connected to the city, the bidirectional converter is electrically connected to the battery to enable the bidirectional converter to charge and discharge the battery.

In summary, the bidirectional commutation device and the DC power supply system provided by the embodiments of the present invention can have the function of a DC/AC bidirectional converter when connected to the mains grid, and include the mains parallel and rectification and power factor correction modes. . When the bidirectional converter device and its DC power supply system are disconnected from the mains grid, the inverter of the bidirectional converter device is connected to the battery as a DC/DC charger and discharger. This architecture saves the high-power DC/DC charge and discharge devices in the system, thereby reducing the production cost of the DC power supply system.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

[Embodiment of DC Power Supply System]

Please refer to FIG. 2. FIG. 2 is a block diagram of a DC power supply system according to an embodiment of the present invention. The DC power supply system 2 includes a regenerative energy device 20, a DC converter 21, a bidirectional commutation device 22, a DC load 23, and a DC microgrid 24. The bidirectional commutation device 22 includes a bidirectional charge and discharge device 221, a battery 222, a bidirectional inverter 223, and a switching circuit 224. The renewable energy device 20 can be, for example, a device that uses natural resources such as solar energy, wind power, water power, and geothermal energy as a source of power generation.

The regenerative energy device 20 is electrically connected to the DC converter 21. The DC converter 21, the bidirectional commutation device 22 and the DC load 23 are electrically connected to the DC microgrid 24, respectively. One end of the bidirectional charge and discharge device 221 is electrically connected to the DC microgrid 24, and the other end of the bidirectional charge and discharge device 221 is electrically connected to the battery 222. One end of the bidirectional converter 223 is electrically connected to the DC microgrid 24. The other end of the bidirectional converter 223 is selectively electrically connected to the battery 222 or the mains Vac via the switch circuit 224.

The regenerative energy device 20 and the DC converter 21 constitute a DC power source. The DC converter 21 can track the maximum power point of the regenerative energy device 20 and feed the output of the regenerative energy device 20 to the DC microgrid 24 to provide a DC load. The bidirectional charge and discharge device 221 can be a low power bidirectional converter for charging and discharging the battery 222. Low-rated power bidirectional converter can micro-charge or micro-discharge battery 222 To extend the life of the battery 222. When the voltage of the battery 222 is low, excess energy in the DC microgrid 24 can be microcharged to the battery 222 through the bidirectional charge and discharge device 221. Conversely, battery 222 can also micro-discharge excess energy to DC microgrid 24.

The bidirectional converter 223 is electrically connected to the mains Vac or the battery 222 through the switch circuit 224. When the bidirectional converter 223 is connected in parallel with the mains Vac, the bidirectional inverter 223 can operate in a mains parallel mode or a rectification and power factor correction mode. When the bidirectional converter 223 operates in the mains parallel mode, the bidirectional converter 223 can supply the power of the DC power source constituted by the regenerative energy device 20 and the DC converter 21 to the mains Vac. When the bidirectional converter 223 operates in the rectification and power factor correction mode, the bidirectional inverter 223 supplies the power of the mains Vac to the DC load 23. When the bidirectional converter 223 is disconnected from the mains Vac, the bidirectional converter 223 is electrically connected to the battery 222 to cause the bidirectional converter 223 to charge and discharge the battery 222.

In other words, when electrically connected to the mains Vac, the bidirectional inverter 223 is used to convert power between the DC microgrid 24 and the mains Vac. When the bidirectional converter 223 is electrically connected to the battery 222, the bidirectional inverter 223 can charge and discharge the battery 222. When the DC microgrid 24 has excess energy, the bidirectional inverter 223 can charge the battery 222, thereby storing excess energy to the battery 222. When the energy provided by the regenerative energy device 20 is insufficient for the DC load 23 to be used, the bidirectional inverter 223 can discharge the battery 222 to provide power to the DC load 23.

Please refer to FIG. 2 and FIG. 3 simultaneously. FIG. 3 is a circuit diagram of a bidirectional commutation device and a DC power supply system thereof according to an embodiment of the present invention. When the DC power supply system 2 is connected in parallel with the mains power grid, the bidirectional converter 223 of FIG. 2 includes the functions of mains parallel and rectification and power factor correction. In this embodiment, a single-phase inverter is taken as an example, as shown in FIG. In addition to the components described in FIG. 2, the bidirectional converter 223 further includes switches S _AH , S _AL , S _BH , S _BL , rectifying elements D _AH , D _AL , D _BH , D _BL and an inductor L1. The bidirectional charge and discharge device 221 further includes a transformer T1, switches S1 and S2, and rectifying elements D1 and D2. The rectifying elements are exemplified by a rectifying diode.

The switches S _AH , S _AL , S _BH , S _BL , and the rectifying elements D _AH , D _AL , D _BH , and D _BL constitute a full bridge rectifier. Switch S _AH, S _AL rectifying element D _AH, D _AL constituting a first leg (leg), and the switch S _AH and the rectifying element D _AH becomes parallel arm (arm), and the rectifying switching element S _AL becomes lower parallel arm D _AL (arm). One end of the inductor L1 is electrically connected between the upper arm and the lower arm of the first leg, and the other end of the inductor L1 is electrically connected to the mains Vac. The switches S _BH and S _BL and the rectifying elements D _BH and D _BL constitute a second leg, and the switch S _BH and the rectifying element D _BH are connected in parallel to form an upper arm, and the switch S _BL and the rectifying element D _BL are connected in parallel to form a lower arm.

The switch S1 and the rectifying element D1 are electrically connected to the positive end of the battery 222. The positive end of the left side winding of the transformer T1 is electrically connected to the positive terminal of the battery 222 through the parallel switch S1 and the rectifying element D1. The negative terminal of the left winding of the transformer T1 is electrically connected to the negative terminal of the battery 222. The switch S2 and the rectifying element D2 are connected in parallel between the positive terminal of the right side winding of the transformer T1 and the negative terminal of the direct current microgrid 24. The negative terminal of the right side winding of the transformer T1 is electrically connected to the positive pole of the DC microgrid 24.

Switch circuit 224 is electrically coupled to bidirectional converter 223 to battery 222 via node A' and node B'. Alternatively, the switch circuit 224 is electrically connected to the bidirectional converter 223 to the mains Vac via the node A and the node B.

Please refer to FIG. 4A to FIG. 4D . FIG. 4A to FIG. 4D are schematic diagrams showing the operation of the bidirectional commutation device in the mains parallel mode according to an embodiment of the present invention. The bidirectional commutation device 22 can control the switch of the bidirectional commutation device 22 itself by a microcontroller (not shown) to operate the bidirectional commutation device 22 in the mains parallel mode, the rectification and power factor correction mode, or charge the battery 222. Discharge. In FIGS. 4A and 4B, the AC power supply of the commercial battery Vac is in the positive half cycle. In the positive half cycle, the switch S _{BL is} maintained in an ON state, and the switching of the switch S _{AH is performed} to achieve the excitation and demagnetization operations. First, in FIG. 4A, the switch S _{AH is} turned "ON", causing the DC voltage Vdc to excite the inductor L1 and feed the current to the mains Vac. Next, the switch S _AH is turned off (OFF), and the inductor L1 is demagnetized by the rectifying element D _AL while the energy is also fed to the mains Vac, as shown in FIG. 4B. When in the negative half cycle, the switching of the bidirectional commutation device 22 is switched as shown in Figures 4C and 4D. The switch S _BH is always maintained in an ON state. First, the switch S _{AL is} turned ON to excite the inductor L1 as shown in FIG. 4C. Then, the switch S _AL turned off (OFF), so that the demagnetization inductor L1, shown in Figure 4D. In short, in the second half of the cycle, the switch S _{AL is} passed through to switch the energy in the DC microgrid 24 into the mains Vac.

Referring to FIG. 5A to FIG. 5D , FIG. 5A to FIG. 5D are schematic diagrams showing the operation of the bidirectional commutation device in the power factor correction mode according to an embodiment of the present invention. When the bidirectional converter 223 operates in the rectification and power factor correction mode, the positive and negative half cycles of the AC power supply of the commercial battery are switched by the switches S _AL and S _AH , respectively, and the excitation and demagnetization are performed through the rectifying elements to make the mains The power of Vac is fed into the DC microgrid 24. During the positive half cycle, switch _{SAL is} turned "ON" to energize inductor L1 as shown in Figure 5A. Then, the switch _SAL is turned off (OFF) to demagnetize the inductor L1 by the rectifying element D _AH as shown in FIG. 5B. During the negative half cycle, switch S _{AH is} turned "ON" to energize inductor L1 as shown in Figure 5C. Then, the switch S _AH is turned off (OFF) to demagnetize the inductor L1 by the rectifying element D _BH as shown in FIG. 5D.

Please refer to FIG. 6A to FIG. 6B . FIG. 6A to FIG. 6B are schematic diagrams showing the charging and discharging of the battery by the bidirectional converter according to the embodiment of the present invention. If the DC power supply system 2 is disconnected from the mains Vac or in the no mains grid area, the bidirectional converter 223 will act as a high power DC/DC charge and discharge device. When the regenerative energy device 20 does not generate electricity or the supplied power is insufficient to supply the DC load 23, the bidirectional converter 223 can operate in the discharge mode, and the circuit of the bidirectional converter 223 can be equivalent to a boost converter. . 6A, the switch S _AL used for switching, and stimulated through degauss rectifying element D _AH and D _BL, the energy from the battery 222 provided to the DC microgrid 24. However, when the bidirectional converter 223 operates in the charging mode, the bidirectional converter 223 can be equivalent to a buck converter, the switch S _AH is responsible for switching and the switch S _BL is forced to remain ON (ON). A path of the demagnetization is provided as shown in FIG. 6B.

[Another embodiment of a DC power supply system]

Please refer to FIG. 7. FIG. 7 is a circuit diagram of a bidirectional commutation device and a DC power supply system according to another embodiment of the present invention. The DC power supply system 7 includes a regenerative energy device 20, a DC converter 21, a bidirectional commutation device 72, a DC load 23, and a DC microgrid 24. The bidirectional commutation device 72 includes a bidirectional charge and discharge device 221, a battery 222, a bidirectional inverter 723, and a switch circuit 724. The bidirectional converter 723 further includes switches S _AH , S _AL , S _BH , S _BL , S _CH , S _CL , rectifying elements D _AH , D _AL , D _BH , D _BL10 , D _CH , D _CL and inductors L2 ～ L4 . The bidirectional charge and discharge device 221 further includes a transformer T1, switches S1 and S2, and rectifying elements D1 and D2.

The DC power supply system 7 is substantially the same as the DC power supply system 2 of FIG. 3, except that the above-described bidirectional converter 223 is a single-phase inverter, and the bidirectional converter 723 is a three-phase inverter. When the bidirectional converter 723 operates in the mains parallel mode and the rectification and power factor correction mode, the contacts R, S, and T of the bidirectional inverter 723 are connected to the contacts A, B, and C of the mains Vac via the switch circuit 724, respectively. . When the bidirectional inverter 723 charges and discharges the battery 222, the contacts A' and B' of the battery 222 can be connected to any two of the contacts R, S, and T of the bidirectional inverter 723 via the switch circuit 724.

The principle of operation of each phase (including phases R, S, T) of the bidirectional converter 723 is the same as that of the bidirectional converter 223. In other words, when each phase of the bidirectional converter 723 (including the phases R, S, T) operates in the mains parallel mode, the operation of the bidirectional inverter 723 can refer to the switching sequence of FIGS. 4A through 4D. When each phase of the bidirectional inverter 723 (including the phases R, S, T) is operated in the rectification and power factor correction mode, the operation of the bidirectional converter 723 can refer to the switching sequence of FIGS. 5A to 5D. The operation of charging and discharging the battery 222 by the bidirectional inverter 723 can be referred to the switching sequence of the switches of FIGS. 6A to 6B.

[Possible efficacy of the embodiment]

According to the embodiment of the invention, the above-mentioned bidirectional converter device and its DC power supply system can be applied to a grid-connected or independent type green energy DC power supply system. The output of the regenerative energy device is passed through a DC converter to transfer power to the DC microgrid to supply a DC load. A bidirectional charge and discharge device with low power rating can charge and discharge the battery to extend battery life. This two-way charge and discharge device saves a lot of volume and cost compared to conventional high-power DC/DC chargers and dischargers. On the other hand, when the regenerative energy device generates electricity to supply a DC load, excess power can be fed into the commercial power through the bidirectional converter. When the regenerative energy device generates insufficient power to supply the DC load, the bidirectional converter can rectify the power of the mains into the DC microgrid by the rectification and power factor correction mode. In addition, when the bidirectional converter device and its DC power supply system are connected to the city or in the area without the mains grid, the bidirectional converter is connected to the battery to charge and discharge the battery, and can regulate the DC microgrid. Therefore, the bidirectional converter device and the DC power supply system thereof provided by the invention can not only reduce the cost of the conventional design, but also improve the practicability of the DC power supply system.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

1. . . Traditional DC power supply system

10. . . Green energy power generation system

11. . . Energy storage equipment

12, 23. . . DC load

13, 223, 723. . . Bidirectional converter

104. . . Solar photovoltaic panel

105. . . Wind Turbines

106. . . The fuel cell

101～103. . . Energy processor

112, 222. . . Battery

111, 221. . . Bidirectional charge and discharge device

121. . . Lighting system

122. . . Inverter air conditioning system

123. . . charging station

124. . . DC electrical test platform

2, 7. . . DC power supply system

20. . . Renewable energy device

twenty one. . . DC converter

22, 72. . . Two-way commutation device

twenty four. . . DC microgrid

224, 724. . . Switch circuit

S1, S2, S _AH , S _AL , S _BH , S _BL , S _CH , S _CL . . . switch

D1, D2, D _AH , D _AL , D _BH , D _BL , D _CH , D _CL . . . Rectifying component

T1. . . transformer

L1～L4. . . inductance

V _ac . . . Mains

Figure 1 is a block diagram of a conventional DC power supply system.

2 is a block diagram of a DC power supply system according to an embodiment of the present invention.

3 is a circuit diagram of a bidirectional commutation device and a DC power supply system thereof according to an embodiment of the present invention.

4A to 4D are schematic diagrams showing the operation of the bidirectional commutation device in the mains parallel mode according to an embodiment of the present invention.

5A to 5D are schematic diagrams showing the operation of the bidirectional commutation device in the rectification and power factor correction mode according to an embodiment of the present invention.

6A to 6B are schematic diagrams showing the charging and discharging of a battery by a bidirectional converter according to an embodiment of the present invention.

FIG. 7 is a circuit diagram of a bidirectional commutation device and a DC power supply system thereof according to another embodiment of the present invention.

2. . . DC power supply system

20. . . Renewable energy device

twenty one. . . DC converter

twenty two. . . Two-way commutation device

twenty three. . . DC load

twenty four. . . DC microgrid

221. . . Bidirectional charge and discharge device

222. . . Battery

223. . . Bidirectional converter

224. . . Switch circuit

V _ac . . . AC power

Claims (10)

A bidirectional commutation device is adapted to convert power between a DC microgrid, a battery and a mains, the bidirectional converter comprising: a bidirectional charge and discharge device for charging and discharging the battery; a switching circuit; a bidirectional converter electrically connected between the switching circuit and the DC microgrid; wherein the switching circuit electrically or electrically connects the bidirectional converter to the battery in parallel, when the bidirectional converter is connected in parallel with the mains, The bidirectional converter is operated in a mains parallel mode or a rectification and power factor correction mode. When the bidirectional converter is electrically connected to the city, the bidirectional converter is electrically connected to the battery to make the bidirectional commutation The battery is charged and discharged. The bidirectional converter device of claim 1, wherein the bidirectional converter is a full bridge rectifier having a plurality of switches and a plurality of rectifying elements. . The bidirectional converter device of claim 1, wherein the bidirectional converter supplies the DC power of the DC microgrid to the mains when the bidirectional converter is operated in the mains parallel mode, the bidirectional commutation When the rectifier operates in the rectification and power factor correction mode, the bidirectional converter supplies power of the mains to the DC microgrid. The bidirectional converter device of claim 2, further comprising: a microcontroller for controlling the switches of the bidirectional converter. The bidirectional converter device of claim 1, wherein the bidirectional charge and discharge device comprises: a transformer having a first side winding and a second side winding, wherein the negative side of the first side winding is electrically Connecting the negative pole of the battery, the negative end of the second side winding is electrically connected to the anode of the DC microgrid; a first switch; a second switch; a first rectifying element; and a second rectifying element; a switch and the first rectifying element are connected between the positive end of the first side winding and the positive terminal of the battery, and the second switch and the second rectifying element are connected to the positive end of the second side winding and the Between the negative poles of the DC microgrid. The bidirectional converter device of claim 1, wherein the bidirectional converter is a single-phase inverter or a three-phase inverter. A DC power supply system for providing power required for a DC load, the DC power supply system comprising: a regenerative energy device; a DC converter that supplies power of the regenerative energy device to the DC load; and a bidirectional commutation The device comprises: a bidirectional charge and discharge device for charging and discharging a battery; a switch circuit; a bidirectional converter electrically connected between the switch circuit and the DC microgrid, the bidirectional converter having a full bridge rectifier having a plurality of switches and a plurality of rectifying elements; and wherein the switching circuit causes the bidirectional converter to be electrically or electrically connected to the battery in parallel, and when the bidirectional converter is connected in parallel with the mains, the bidirectional converter Operating in a mains parallel mode or a rectification and power factor correction mode, when the bidirectional converter is electrically connected to the city, the bidirectional inverter is electrically connected to the battery, so that the bidirectional converter charges the battery Discharge. The DC power supply system of claim 7, wherein the bidirectional converter supplies power from the regenerative energy device of the DC converter to the mains when the bidirectional converter is operated in the mains parallel mode. The bidirectional inverter operates in the rectification and power factor correction mode, and the bidirectional inverter supplies power of the mains to the DC load. The DC power supply system of claim 7, further comprising: a microcontroller for controlling the switches of the bidirectional converter. The DC power supply system of claim 7, wherein the bidirectional converter is a single-phase inverter or a three-phase inverter.