TWI601353B - Distributed module type grid connection conversion device and its control method - Google Patents

Description

Decentralized modular grid-connected conversion device and control method thereof

The invention relates to a conversion device of a fuel cell; in particular to a decentralized modular grid-connecting device and a control method thereof.

As global climate change has alerted people, various green energy technologies have developed rapidly, and power generation technologies such as solar energy, wind energy and hydrogen energy have made significant breakthroughs. In particular, fuel cells, fuel cells can directly convert chemical energy into electrical energy continuously, with low pollution, low noise, no charging, high efficiency, long life, wide application range and decentralized power supply, etc. The space program can also be applied to people's livelihood power generation, transportation vehicles, military, portable power supplies, and electronic products.

The conventional fuel cell power generation system is a multi-stage serial power conversion architecture, usually equipped with a back-up battery, and the system includes a boost converter and a DC/AC converter, wherein the boost converter is used. The low voltage input is converted to a DC high voltage level, and the DC/AC converter at the back end is used to convert DC high voltage to AC power for use by a household load.

However, controllers that use multi-stage power conversion must be independently designed to control the DC link voltage and AC output separately, which has the disadvantages of complexity, high cost, and reduced system reliability. On the other hand, the process of energy transmission passes through Multiple high-frequency power conversion, conversion efficiency is poor; coupled with the conventional fuel cell converter products for high-voltage start-up specifications, not suitable for all types of low-pressure output fuel cells. Therefore, in order to improve the energy efficiency and reduce the pollution caused by the energy production process, how to improve the conversion efficiency of the fuel cell power generation system is indeed a problem that must be faced in the current development of green energy.

In view of the above, the object of the present invention is to provide a distributed modular grid-connected conversion device, which has the characteristics of high-efficiency power conversion, large modularization, flexible expansion and application, and is applicable to various standard low-voltage output fuel cells.

In order to achieve the above objective, the present invention provides a decentralized modular grid-connecting device for electrically connecting to a power grid for providing AC power to the power grid. The distributed modular grid-connecting device includes a battery module. a power conversion module is electrically connected to the battery module and the power grid, and the power conversion module includes at least two converters, and the converters are connected in parallel. The power conversion module is configured to receive the DC power output by the battery module and convert it into an AC power output, and the output AC power is supplied to the power grid; a power management module, the battery module, and the The power conversion module is electrically connected, and the power management module performs power regulation on each of the converters according to the load power consumption of the power grid to output AC power corresponding to the load power consumption.

The invention further provides a control method for a distributed modular grid-connected device, which comprises the following steps: A, detecting the load power consumption of the power grid; B, according to the load power consumption detected in step A, One of the following steps: B1, when the load power consumption of the power grid is greater than a first threshold, the power management module sends a start signal to at least two of the converters to enable at least two of the converters to operate; When the power consumption of the power grid is less than a second threshold, the power management module sends a shutdown signal to at least one of the converters to stop at least one of the converters from operating.

The effect of the invention is that the decentralized modular grid-connecting device can directly transfer the power of the battery module to the municipal grid to save the battery component, and the decentralized grid-connected converter adopts a flyback converter. It can meet the requirements of the wide input voltage range of the fuel cell, making it suitable for all kinds of standard low-voltage output fuel cells. The decentralized modular grid-connecting device uses the controller area network bus bar, which can greatly reduce the modules. The amount of wires used during the connection is also relatively reduced on many lines, effectively improving the reliability of the distributed modular grid-connecting device; and the parallel structural design makes the expansion and application more flexible, convenient to green The scale of energy generation is adjusted, and when a single converter fails, the fault converter can be trouble-shooted and repaired without stopping the whole system.

In order to explain the present invention more clearly, a preferred embodiment will be described in detail with reference to the drawings. Referring to FIG. 1 , a decentralized modular grid-connected device 100 for electrically connecting to a grid 10 and providing AC power to the grid 10 is shown in FIG. 1 . More specifically, the power grid 10 is used to provide power transmission lines, which may be different types of power grids, such as a home type micro grid, a community type power grid, and a city type power grid. In this embodiment, The grid 10 is based on the municipal power (urban power grid), but it is not limited to other practical implementations.

The decentralized modular grid-connecting device 100 includes a battery module 20, a power conversion module 30, and a power management module 40.

The battery module 20 is configured to output DC power. In the present embodiment, a DC battery fuel cell system is selected as the battery module 20, and its starting voltage is 15V. In addition, due to the electrical characteristics of the fuel cell itself, the current is large when the output is low voltage, and the voltage varies with the output current, that is, when the current supplied by the battery module 20 to the load is larger, the battery module 20 The voltage will be lower.

As shown in FIG. 2 and FIG. 3 , the power conversion module 30 is electrically connected to the battery module 20 and the power grid 10 for receiving DC power output by the battery module 20 and converting it into an AC power output. It is supplied to the grid 10. In this embodiment, the power conversion module 30 includes a plurality of converters 32, a plurality of rectifier circuits 34, and a plurality of filter circuits 36. The filter circuits 36 are disposed in front of the power grid 10. In this embodiment, The filter circuits 36 employ LC filter circuits. Each of the converters 32 is electrically connected to the corresponding rectifier circuit 34. Each of the rectifier circuits 34 is electrically connected to the corresponding filter circuit 36, and the converters 32 are connected in parallel. Each of the converters 32 is designed as a single-stage flyback converter, and each of the converters 32 is a multi-directional shunt design, and the rectifying circuits 34 are low-frequency full-bridge shaping switches; The current collector 32 has a primary side 322 (ie, the DC side defined by the present invention) and a secondary side 324 (the AC side defined by the present invention) coupled to the battery module 20, The secondary side 324 is coupled to the rectifier circuit 34. The purpose of the power conversion module 30 is that the fuel cell selected by the battery module 20 generates energy through a chemical reaction, and the transient response is long. If the power supply load instantaneously draws a large current, the battery module The group 20 will have a sudden drop in the output voltage, which may cause a decrease in the conduction loss of the circuit and a decrease in the conversion efficiency, thereby causing a decrease in the overall power generation performance of the battery module 20, and accordingly, through the respective current changes. The circuit of the device 32 is designed for multi-directional shunting, and the current of the battery module 20 is averaged through each of the converters 32, so that the circuit conduction loss is reduced, and the high-frequency current chopping is suppressed, thereby effectively reducing the high-frequency loss of the circuit, and The power control response of the battery module 20 is also improved.

It is worth mentioning that in the embodiment, the converter 32 adopts a single-stage flyback converter and simultaneously introduces a quasi-resonant switching technology, which can realize the effect of the analog DC link operation principle, so as to achieve high efficiency power. The voltage gain of the conversion and flyback converter circuit is adjustable for buck-boost, making it suitable for all types of standard low-voltage output (15V~80V) fuel cells. In addition, the circuit structure of the quasi-resonant switching technology includes at least one main switching element (not shown), at least one main switching parasitic capacitance (not shown), and a leakage inductance (not shown), the main switching element, the main switching element The primary switch parasitic capacitance and the leakage inductance are located on the primary side 322. By quasi-resonant switching technology and utilizing the leakage inductance to resonate with the parasitic capacitance of the main switch, the stress of the main switching element of the primary side 322 can be reduced, the main switching element can achieve zero voltage flexible switching, and the main switching element can be greatly reduced. The reverse recovery current loss of the secondary side 324 enables each of the converters 32 of the power conversion module 30 to achieve high conversion efficiency.

In addition, each of the rectifying circuits 34 adopts a design of a low-frequency full-bridge shaping switch to form a half-sine wave current into a sine wave current, and each of the filtering circuits 36 connected to the front of the power grid 10 can filter high-frequency impurities. The signal is used to make the waveform output to the grid 10 smoother, and the effect of reducing distortion and harmonics can be achieved. When the current transformer 32 is synchronized with the mains voltage frequency, the mains voltage and the output current of each of the converters 32 can be obtained through feedback of the AC voltage/current, and the power management module 40 is provided to determine whether the energy is suitable for energy. Feed into the mains operation. In addition, in the embodiment, the power conversion module 30 further includes two film capacitors 38, and each of the film capacitors 38 is coupled between the converter 32 and a rectifier circuit 34, respectively. The half-sine wave voltage outputted from each of the converters 32 is filtered and output to each of the rectifier circuits 34. In this way, the circuit of the power conversion module 30 operates on the film capacitor 38 of the secondary side 324 to form a half sine wave waveform voltage by using an analog DC link operation principle, so that no additional high voltage electrolytic capacitor is needed. This feature gives the converters 32 the advantage of a long life.

Referring to FIG. 4 , the power management module 40 is electrically connected to the battery module 20 and the power conversion module 30. In this embodiment, the power management module 40 includes a controller 42 and a display 44. An input device 46 and an auxiliary power source 48. The input device 46 is configured to allow the user to input information about various states of the power management module 40, and display information about various states of the power management module 40 through the display 44. The auxiliary power source 48 is configured to provide the power. The controller 42 is configured to detect the load power consumption of the power grid 10, and output a control signal to each of the converters 32 according to the load power consumption. Preferably, in an embodiment, the power management module 40 can transmit a corresponding control signal to each of the converters 32 through a controller area network bus (CAN-BUS), for example, the power supply. The management module 40 can individually adjust the power of each of the converters 32 through the variable frequency pulse width modulation control signal to output AC power corresponding to the load power consumption.

The controller 42 continuously monitors the converters 32 and performs fault detection on the converters 32. In addition, the controller 42 can communicate with a home energy management system 50 (HEMS). The home energy management system 50 is configured to issue an immediate dispatch command and notify the controller 42 via the display 44 of the user's system status or via communication to achieve immediate processing and improved system reliability.

For example, when the supply wattage of each converter 32 can reach 300 watts, when the load power consumption of the power grid 10 is greater than a first threshold (1000 watts set in this embodiment), it needs to be activated. The power converter module 40 sends a start signal to each of the corresponding converters 32 to enable four of the converters 32 to operate to supply the converters 32. Sufficient power is used for the load of the grid 10; in addition, when the load power consumption of the grid 10 is less than a second threshold (500 watts set in this embodiment), only a part of the converter needs to be activated. At this time, the power management module 40 sends a shutdown signal to each of the corresponding converters 32, so that part of the converter 32 stops operating, and only two of them remain in operation. Sufficient power is provided for use by the grid 10.

In this way, by controlling the amount of power consumption of the load to control the activation of the corresponding number of the converters 32, the energy saving effect can be further achieved.

In addition, in this embodiment, each of the converters 32 and the power management module 40 performs bidirectional information through a controller area network bus 60 (CAN-BUS) (eg, fuel cell voltage/current, power grid). The voltage/current, etc. transmission, the advantage of using the controller area network bus 60 is to greatly reduce the amount of wire used, and also reduce the contact on the line, thereby reducing wiring costs and increasing Line stability. In addition, when any of the converters 32 is damaged, the home energy management system 50 can be returned to the power management module 40 through the controller area network bus 60 for maintenance. Then, the power conversion module 30 can be further controlled to close the abnormal converter 32 to perform the load-down operation mode. This innovative method improves the problem that the conventional converter system must be shut down, and effectively reduces the power generation of the client. loss. In addition, the controller area network bus 60 has more stable, effective communication distance, fault tolerance and anti-interference ability, and can improve the versatility of the distributed modular grid-connecting device 100.

As shown in FIG. 5, after the decentralized modular grid-connected device 100 is activated, the power management module 40, which is the operation hub, will be activated and detected whether there is a connection between the home energy management system 50 and the home energy management system 50. In the case of the time, if it is, it indicates that the system is faulty or abnormal. At this time, the power management module 40 controls the converters to stop supplying power; if not, the power management module 40 and the home energy management system 50 Normal operation; the receiver can collect all the information of the converter 32 through the CAN-BUS (for example, information on the fault of the converter, actual power generation, command and feedback), so as to learn about each converter. Information such as the current working status; and then, the load power consumption and the energy conversion command returned by the home energy management system 20 are updated, so that the power management module 40 can change the power according to the load power consumption and the energy conversion command. The streamer issues a control signal, wherein, preferably, a self-checking program can be executed to mark the converter that can be put into the grid and generate electricity before issuing a control signal to each of the converters. Number and / or ID mark converter not work.

Referring to FIG. 6, an embodiment of the self-checking program first sets a variable N, initializes the variable N to 0, and clears all the tags (or status tags) on the converter. Then, enter a check loop, and check whether the Nth machine of the converter has an abnormality in the order of incrementing N by each time. If the Nth machine of the converter is in a normal available state, the flag is marked. The converter No. N is a converter that can be put into grid-connected power generation until all the converters have been tested, that is, until the variable N has increased to be greater than the maximum number of converters, to end the self-test program of. Through the self-checking program, it can be checked whether the state of each of the converters (for example, the first to Nth converters) is normal.

Then, as shown in FIG. 5, after the self-checking procedure is executed, the subsequent steps are performed according to whether the energy conversion command is executed, and if not, all the converters are controlled to stop supplying power; if yes, the load power is further determined. Whether the quantity is greater than the total power converter of the marked (referred to as the working mark), if it is, then control all marked converters to be fully loaded with electricity; if not, according to the amount of power used by the load By assigning an appropriate number of converters to the grid and generating electricity, it is possible to control the activation of the corresponding number of converters according to the amount of power used by the load, thereby achieving the effect of saving energy.

It is worth mentioning that, based on the above architecture, the MK64FN1M0VLL12 digital signal processor (DSP) can be used as the controller 42 of the power management module 40, and the output current of the fuel cell can be adjusted through the CAN-BUS. The current waveform of side 322 follows a rectified sine wave current command, and then a half bridge sinusoidal low frequency switching is performed using a full bridge switching circuit, and the current of the secondary side 324 is further injected into the grid 10 via the LC filter circuit in positive and negative half cycles. In addition, in the converter to control the firmware implementation, the TMS320F28335 (with A/D converter, counter, PWM output and other functional modules) can be used together with the peripheral sensing circuit design for firmware calculation, thereby reducing the hard The complexity of the body circuit. In addition, the power management module 40 and the communication interface 49 developed in this embodiment may adopt an RS-232/RS-485 communication standard to implement the relationship between the home energy management system 50 and the power management module 40. Remote communication, and the above design can achieve the effect of regulating fuel cell output power and grid-connected current. It should be noted that the power source of the power management module 40 is provided by the auxiliary power source 48 (AC/DC) to provide three sets of isolated five volts. The power management module 40 can also pass through the input unit 46 (this embodiment) The KEYPAD is used to input information about the state of the system and display information of the system status on the display 44 (in this embodiment, LCD) or back to the home energy management system 50. In addition, in an embodiment, the communication interface 49 may also adopt CAN-BUS or other communication standards, and is not limited to the above description.

In summary, the decentralized modular grid-connected device 100 of the present invention can directly transfer the power of the battery module 20 to the city grid to save the battery component, and the decentralized modular grid-connecting device 100 With the flyback converter, the voltage gain of the circuit of the flyback converter is the buck-boost characteristic, which can be applied to various standard low-voltage output fuel cells, so it has market versatility; The grid-connected switching device 100 adopts the controller area network bus bar 60, which can greatly reduce the amount of wires used when connecting the converters 32, and relatively reduce the contacts on many lines, thereby effectively improving the dispersion. The reliability of the modular grid-connected conversion device 100; and the structural design of the converters 32 in parallel makes the expansion and application more flexible, facilitates the adjustment of the scale of the green energy power generation, and when a single converter 32 fails, The faulty converter 32 can be trouble-shooted and repaired, and the whole system is not required to be stopped, thereby effectively reducing the power generation loss of the client. In this way, the invention improves the problem of poor conversion efficiency when the application of green energy is applied, and successfully improves the conversion efficiency of green energy, thereby increasing people's willingness to use green energy.

The above is only a preferred embodiment of the present invention, and equivalent changes to the scope of the present invention and the scope of the patent application are intended to be included in the scope of the present invention.

[this invention]

100‧‧‧Distributed modular grid-connected converter

10‧‧‧ Grid

20‧‧‧Battery module

30‧‧‧Power Conversion Module

32‧‧‧Converter

322‧‧‧primary side

324‧‧‧second side

34‧‧‧Rectifier circuit

36‧‧‧Filter circuit

38‧‧‧ Film Capacitance

40‧‧‧Power Management Module

42‧‧‧ Controller

44‧‧‧ display

46‧‧‧ Inputs

48‧‧‧Auxiliary power supply

49‧‧‧Communication interface

50‧‧‧Home Energy Management System

60‧‧‧Controller area network bus

1 is a schematic diagram of a circuit architecture of a distributed modular grid-connected conversion device according to a preferred embodiment of the present invention. 2 is a circuit diagram of a single converter of the distributed modular grid-connected converter of the above preferred embodiment. 3 is a circuit operation waveform diagram of a single converter of the distributed modular grid-connected device of the above preferred embodiment. 4 is a schematic diagram showing the circuit structure of a power management module of the distributed modular grid-connected device of the above preferred embodiment. FIG. 5 is a flow chart of the decentralized modular grid-connecting device of the above preferred embodiment. Fig. 6 is a flow chart showing the self-checking procedure of the distributed modular grid-connecting device of the above preferred embodiment.

100‧‧‧Distributed modular grid-connected converter

10‧‧‧ Grid

20‧‧‧Battery module

30‧‧‧Power Conversion Module

32‧‧‧Converter

40‧‧‧Power Management Module

50‧‧‧Home Energy Management System

60‧‧‧Controller area network bus

Claims (10)

A decentralized modular grid-connecting device for electrically connecting to a grid for providing AC power to the grid, the decentralized grid-connected converter includes: a battery module for outputting DC power a power conversion module electrically connected to the battery module and the power grid, the power conversion module includes at least two converters, the converters are connected in parallel, and the power conversion module is configured to receive The DC power outputted by the battery module is converted into an AC power output, and the output AC power is supplied to the power grid; a power management module is electrically connected to the battery module and the power conversion module The power management module performs power regulation on each of the converters according to the load power consumption of the power grid to output AC power corresponding to the load power consumption; wherein the power consumption of the power grid is greater than one At the first threshold, the power management module sends a start signal to at least two of the converters to enable at least two of the converters to operate; when the load power of the grid is less than a second threshold, Electricity At least a management module issues a shut-down signal of the converter, so that at least a stop operation of the converter; wherein the second threshold value is less than the first threshold value. The decentralized modular grid-connecting device of claim 1, wherein each of the converters and the power management module transmits bidirectional information through a controller area network bus (CAN-BUS). The decentralized modular grid-connecting device of claim 1, wherein each of the converters is a flyback converter. The decentralized modular grid-connected conversion device of claim 1, wherein the power management module separately outputs an inverter-type pulse width modulation control signal to each of the converters to individually control each of the converters. The device performs power regulation. The decentralized modular grid-connecting device of claim 1, wherein the power conversion module further comprises at least two rectifier circuits; each of the converters has a DC side and an AC side, and each of the converters The DC side is coupled to the battery module, and the AC side is coupled to the rectifier circuit; each of the rectifier circuits is configured to convert a half-sine wave voltage outputted by the converter into a sine wave voltage and output the voltage to the power grid. The decentralized modular grid-connected device of claim 5, wherein the power conversion module further comprises at least two filter circuits, each of the filter circuits being coupled between the rectifier circuit and the power grid for The high frequency harmonic component of the sine wave voltage is filtered to output the alternating current power to the power grid. The decentralized modular grid-connected device of claim 5 or 6, wherein the power conversion module further comprises at least two film capacitors, each of the film capacitors being coupled to the converter and the rectifier circuit The half-sine wave voltage outputted by the converter is filtered and output to the rectifier circuit. A control method for a distributed modular grid-connected device as claimed in claim 1, comprising the steps of: A, detecting a load power consumption of the power grid; B, and detecting the load according to step A The power consumption is performed as one of the following steps: B1, when the load power of the power grid is greater than a first threshold, the power management module sends a start signal to at least two of the converters to enable at least two of the current changes. When the load of the power grid is less than a second threshold, the power management module sends a shutdown signal to at least one of the converters to stop at least one of the converters from being operated. The control method of the distributed modular grid-connected device of claim 8, wherein the second threshold is less than the second threshold. The control method of the distributed modular grid-connected device according to claim 8, wherein before step B, a self-checking program is executed to mark the converter that can be put into grid-connected power generation.