CN110581569B - Auxiliary power supply circuit - Google Patents
Auxiliary power supply circuit Download PDFInfo
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- CN110581569B CN110581569B CN201910857317.XA CN201910857317A CN110581569B CN 110581569 B CN110581569 B CN 110581569B CN 201910857317 A CN201910857317 A CN 201910857317A CN 110581569 B CN110581569 B CN 110581569B
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Abstract
The application provides an auxiliary power supply circuit, which is applied to a grid-connected power generation system, wherein the grid-connected power generation system comprises at least two power generation subsystems, a grid-connected inverter and auxiliary power supplies, wherein the auxiliary power supplies correspond to the grid-connected inverter and each power generation subsystem one by one and provide working power for the grid-connected inverter and the power generation subsystems; the output end of each power generation subsystem is connected with a system direct current bus through an anti-reverse diode; the input end of each auxiliary power supply is connected with a system direct current bus, and the auxiliary power supply and the direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system. The invention changes the traditional mode of respectively obtaining the auxiliary power supply from the output end of each power generation subsystem or directly obtaining the auxiliary power supply of the grid-connected inverter from the power grid, adopts the mode of uniformly taking power from the direct current bus by the auxiliary power supply, ensures that each power generation subsystem and the grid-connected inverter are in a working or standby state to the greatest extent, and improves the response speed and the power supply reliability of the system.
Description
Technical Field
The invention relates to the technical field of distributed power generation, in particular to an auxiliary power supply circuit.
Background
The distributed power generation is power generation equipment directly arranged on a power distribution network or distributed near a load, is economic, efficient and reliable, and is beneficial to promoting the sustainable development of energy, improving the environment and improving the competitiveness of green energy.
The existing distributed power generation grid-connected system is provided with a switching power supply for auxiliary power supply and is used for providing working voltage of circuits such as a single chip microcomputer control circuit, a switching tube driving circuit and the like. Because the distributed power generation grid-connected system is provided with a plurality of power generation subsystems which are distributed, and each power generation subsystem corresponds to one control circuit, the common power taking mode of the auxiliary switching power supply in the prior art is to obtain direct current from the rectification output end of each power generation subsystem, and for the grid-connected power generation system, the grid-connected inverter can also obtain the direct current after rectification from a power grid.
However, the auxiliary power supply method has the following disadvantages:
1. when the electric energy provided by a certain power generation subsystem is insufficient to supply power for the auxiliary power supply, the power generation subsystem is in a shutdown state; in addition, when the grid fails, the grid-connected inverter will be in a shutdown state, which results in a decrease in the reliability of the power supply of the entire distributed power generation grid-connected system.
2. The system recovery work is slow and the response sensitivity is reduced due to the fact that each power generation subsystem and the grid-connected inverter cannot be guaranteed to be in a working or standby state to the greatest extent.
Disclosure of Invention
In view of the above-mentioned deficiencies of the switching power supply circuit design of the distributed power generation grid-connected system in the prior art, the present invention aims to provide an auxiliary power supply circuit, which changes the traditional way of respectively obtaining auxiliary power from the output ends of each power generation subsystem or directly obtaining auxiliary power of a grid-connected inverter from a power grid, and adopts a way of uniformly obtaining power from a dc bus by the auxiliary power, so as to ensure that each power generation subsystem and the grid-connected inverter are in a working or standby state to the maximum extent, and improve the response speed and the power supply reliability of the system.
In order to achieve the purpose, the invention adopts the following scheme:
an auxiliary power supply circuit is applied to a grid-connected power generation system, wherein the grid-connected power generation system comprises at least two power generation subsystems, a grid-connected inverter and auxiliary power supplies which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystems; the output end of each power generation subsystem is connected with a system direct current bus through an anti-reverse diode, the input end of each auxiliary power supply is connected with the system direct current bus, and the auxiliary power supply and the direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system.
In an embodiment of the present invention, the power generation subsystem includes a power generation device and a current transformation module, an output end of the power generation device is connected to an input end of the current transformation module, and the current transformation module is configured to transform electric energy output by the power generation device into direct current.
In an embodiment of the present invention, the power generator is an ac power generator or a dc power generator.
In an embodiment of the present invention, the power generation device is an ac power generation device, the current conversion module includes a first rectification unit, a first unloading unit, a first voltage conversion unit and a first filter capacitor, an ac input end of the first rectification unit is connected to an output end of the power generation device, a dc output end of the first rectification unit is connected to an input end of the first unloading unit, an output end of the first unloading unit is connected to an input end of the first voltage conversion unit, and an output end of the first voltage conversion unit is connected to the first filter capacitor.
In an embodiment of the present invention, the first rectifying unit is a three-phase uncontrolled rectifier bridge circuit; the first voltage conversion unit is a Boost booster circuit or a phase-shifted full-bridge isolation booster circuit.
In an embodiment of the present invention, the power generation device is an ac power generation device, the current transformation module includes a second rectification unit, a second unloading unit and a second filter capacitor, an ac input end of the second rectification unit is connected to an output end of the power generation device, a dc output end of the second rectification unit is connected to an input end of the second unloading unit, and an output end of the second unloading unit is connected to the second filter capacitor, where the second rectification unit is a three-phase half-controlled rectifier bridge circuit.
In an embodiment of the present invention, the power generation device is a dc power generation device, the current conversion module includes a second voltage conversion unit, a third unloading unit and a third filter capacitor, an input end of the third unloading unit is connected to an output end of the power generation device, an output end of the third unloading unit is connected to an input end of the second voltage conversion unit, and an output end of the second voltage conversion unit is connected to the third filter capacitor.
In an embodiment of the present invention, the auxiliary power supply circuit further includes a third rectification module, an ac input end of the third rectification module is connected to a power grid, a dc output end of the third rectification module is connected to the system dc bus, and the third rectification module is configured to convert ac output by the power grid into dc and input the dc to the system dc bus.
In an embodiment of the present invention, an anti-reverse diode is disposed between the system dc bus and the grid-connected inverter; and the direct current input end of the grid-connected inverter is connected with a fourth filter capacitor.
In an embodiment of the present invention, the power generating device is a wind power generator or a photovoltaic power generating module.
The application also discloses an auxiliary power supply method which is applied to a grid-connected power generation system, wherein the grid-connected power generation system comprises at least two power generation subsystems, a grid-connected inverter and auxiliary power supplies which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystems; the power supply method comprises the following steps: the electric energy output by each power generation subsystem is input into the system direct current bus through an anti-reverse diode, and the auxiliary power supply obtains the electric energy from the system direct current bus and supplies the electric energy to the grid-connected power generation system for working.
In an embodiment of the present invention, the electric energy of the system dc bus is provided by each of the power generation subsystems or the power grid.
In an embodiment of the present invention, a method for providing electric energy of the system dc bus by a power grid includes: when the voltage of the system direct current bus is detected to be smaller than the preset power grid supply voltage value, the electric energy of the power grid is input into the system direct current bus after being rectified, and the voltage of the system direct current bus is controlled to be smaller than the preset grid-connected voltage stabilizing value.
In an embodiment of the present invention, a method for providing electric energy of the system dc bus by each power generation subsystem includes: when the voltage of the system direct current bus is detected to be larger than or equal to a preset power grid supply voltage value, each power generation subsystem supplies power to the system direct current bus, and when the voltage of the system direct current bus reaches a preset grid-connection starting voltage value, grid-connection operation of a grid-connected inverter is controlled, meanwhile, the voltage of the system direct current bus is controlled to be stabilized at a preset grid-connection voltage stabilizing value, and when grid-connection power is smaller than a preset grid-connection power value, voltage stabilizing control on the system direct current bus is stopped, and grid connection is stopped.
In an embodiment of the present invention, when it is detected that the voltage of the dc bus of the system reaches a preset unloading voltage value, the power generation subsystem is controlled to unload.
As described above, the auxiliary power supply circuit of the invention is applied to a grid-connected power generation system, and the grid-connected power generation system includes at least two power generation subsystems, a grid-connected inverter, and auxiliary power supplies which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystem; the output end of each power generation subsystem is connected with a system direct-current bus through an anti-reverse diode respectively, and the anti-reverse diode is used for preventing the electric energy of the system direct-current bus from flowing backwards; the input end of each auxiliary power supply is connected with a system direct current bus, and the auxiliary power supply and the system direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system. The auxiliary power supply directly gets power from the system direct current bus and then converts the power into working power of circuits such as a matching system single chip microcomputer control circuit, a switching tube driving circuit and the like, wherein the electric energy of the system direct current bus comes from direct current output and summarized by each power generation subsystem or direct current output by a power grid after rectification conversion.
Compared with the prior art that a switching power supply acquires direct current from the output end of each power generation device or a grid-connected power generation system acquires direct current after rectification from a power grid, the scheme of the invention can improve the power supply reliability of a distributed power generation grid-connected system, and when the electric energy output by a certain power generation subsystem is insufficient to supply power to an auxiliary power supply of the power generation subsystem, the auxiliary power supply of the power generation subsystem can take power from a direct current bus so as to maintain the system in a standby state; under the condition of power grid failure, the auxiliary power supply of the grid-connected inverter can also take power from the direct current bus to provide a switching power supply of the grid-connected inverter, so that the power supply mode of the auxiliary power supply can ensure that each power generation subsystem and the grid-connected inverter are in a working standby state to the greatest extent, and the robustness of the system is improved; the system can quickly recover in a standby state, and the response sensitivity is high; the system has strong structural adaptability, and is convenient for forming a wind power and photovoltaic single or mixed power generation system; the system adopts a modular structure, is convenient to produce and maintain, and is easy to change the grid-connected scale of the system.
Drawings
Fig. 1 is a block diagram of a power supply circuit of an auxiliary power supply in a grid-connected power generation system according to an embodiment of the present disclosure.
Fig. 2 is a schematic structural diagram of an auxiliary power supply circuit in a grid-connected power generation system according to an embodiment of the present application.
Fig. 3 is a flowchart of a method for supplying power to an auxiliary power source in a grid-connected power generation system according to an embodiment of the present application.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in the actual implementation, the type, quantity and proportion of the components in the actual implementation can be changed freely, and the layout of the components can be more complicated.
As shown in fig. 1, an embodiment of the present application provides a distributed power generation grid-connected system, where the distributed power generation grid-connected system includes at least two power generation subsystems, a grid-connected inverter, and auxiliary power supplies, which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystem; the output end of each power generation subsystem is connected with a system direct current bus through an anti-reverse diode, the input end of each auxiliary power supply is connected with the system direct current bus, and the auxiliary power supply and the direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system. The auxiliary power supply is used for converting the electric energy of the system direct current bus into electric energy matched with the electric energy driven by each current conversion module or a power switch tube in the grid-connected inverter and the electric energy of the work of the single chip microcomputer, and also provides a working power supply of the system.
In the embodiment of the application, the power generation subsystem comprises a power generation device and a current conversion module, the power generation device can be a direct current power generation device or an alternating current power generation device, an output end of the power generation device is connected with an input end of the current conversion module, and the current conversion module is used for converting electric energy output by the power generation device into direct current.
Referring to fig. 2, when the power generation device is an ac power generation device, the current conversion module includes a first rectifying unit, a first unloading unit, a first voltage conversion unit, and a first filter capacitor C1, an ac input end of the first rectifying unit is connected to an output end of the power generation device, a dc output end of the first rectifying unit is connected to an input end of the first unloading unit, an output end of the first unloading unit is connected to an input end of the first voltage conversion unit, an output end of the first voltage conversion unit is connected to a first filter capacitor C1, an output positive end of the first filter capacitor C1 is connected to a positive electrode of a first anti-reflection diode VD1, a negative electrode of the first anti-reflection diode VD1 is connected to a positive electrode cable of a system dc bus, and a negative electrode of the first filter capacitor C1 is connected to a negative electrode cable of the system dc bus. The first rectifying unit is used for converting alternating current generated by the power generation device into direct current, and the first voltage conversion unit is used for performing voltage-boosting and voltage-reducing conversion on the direct current output by the first rectifying unit so as to output direct current matched with the working voltage range of a direct current bus of the system.
As an example, the first rectifying unit may be a three-phase uncontrolled rectifier bridge circuit, and the first voltage converting unit may be a Boost voltage boosting circuit or a phase-shifted full-bridge isolated voltage boosting circuit. The Boost circuit controls the inductor to store and release energy through the on and off of the switching tube, so that the output voltage is higher than the input voltage.
As an example, when the power generation device is an ac power generation device, the current conversion module may have the following structure: the power generation device comprises a second rectifying unit, a second unloading unit and a second filter capacitor C2, wherein the alternating current input end of the second rectifying unit is connected with the output end of the power generation device, the direct current output end of the second rectifying unit is connected with the input end of the second unloading unit, the output end of the second unloading unit is connected with a second filter capacitor C2, the positive electrode output end of the second filter capacitor C2 is connected with the positive electrode of a second anti-reverse diode VD2, the negative electrode of the second anti-reverse diode VD2 is connected with the positive electrode cable of a system direct current bus, and the output negative electrode end of the second filter capacitor C2 is connected with the negative electrode cable of the system direct current bus, wherein the second rectifying unit is a three-phase half-control rectifying bridge circuit. It should be noted here that the three-phase half-controlled rectifier bridge circuit can simultaneously implement the rectification and boosting functions.
The three-phase half-controlled rectifier bridge circuit comprises three bridge arms connected in parallel, each bridge arm comprises a diode and a power switch tube connected in series, the upper positions and the lower positions of the diodes and the power switch tubes can be interchanged, the upper bridge arms are diodes, and the lower bridge arms are power switch tubes in the example shown in fig. 2; each phase power supply of three-phase power output by the power generation device is respectively connected to the joints of the diodes in the three bridge arms and the power switch tube, the diodes and the anti-parallel diodes in the power switch tube are combined to realize a rectification function, and a boosting function can be realized by controlling the power switch tube to be switched on and off. Therefore, the three-phase half-control rectifier bridge circuit can realize both a rectification function and a boosting function, and a voltage conversion unit is omitted, so that the circuit structure is simplified.
Rectification and boosting control principle: when three power switching devices in the three-phase half-controlled rectifier bridge circuit are turned off, the three-phase half-controlled rectifier bridge circuit is equivalent to an uncontrolled rectifier circuit and has a rectification function; when the three power switch devices are switched on and off alternately, the boosting process is completed by utilizing the alternating current electric energy stored by the winding inductance of the generator and superposing the alternating current induced electromotive force of the generator.
The power generation device in this application may also be a dc power generation device, at this time, the current conversion module includes a second voltage conversion unit, a third unloading unit and a third filter capacitor C3, an input end of the third unloading unit is connected to an output end of the power generation device, an output end of the third unloading unit is connected to an input end of the second voltage conversion unit, an output end of the second voltage conversion unit is connected to a third filter capacitor C3, an anode output end of the third filter capacitor C3 is connected to an anode of a third protection inverse diode VD3, a cathode of the third protection inverse diode VD3 is connected to an anode cable of a system dc bus, and an output cathode end of the third filter capacitor C3 is connected to a cathode cable of the system dc bus. The second voltage conversion unit is used for performing buck-boost conversion on the direct current generated by the direct current generator so as to output the direct current matched with the working voltage range of the direct current bus of the system. When the power generation device is a direct current power generation device, the circuit topology of the power generation subsystem is omitted, and direct current voltage generated by the power generation device is directly converted and then input into a direct current bus.
In this embodiment, the auxiliary power supply circuit further includes a third rectification module, an ac input end of the third rectification module is connected to a power grid, a dc output end of the third rectification module is connected to a system dc bus, and the third rectification module is configured to convert ac output by the power grid into dc and input the dc to the system dc bus. Thus, the electric energy of the system direct current bus is derived from two paths: a power generation subsystem and a power grid. When the electric energy output by the power generation subsystem is not enough to provide an auxiliary power supply, the electric energy can be supplied by a power grid, the electric energy is input into a system direct-current bus after being rectified by the third rectifying module, and the auxiliary power supply gets electricity from the system direct-current bus to serve as system working electricity. In order to prevent the current input into the system direct current bus after rectification from being overlarge, a fuse wire is arranged at the direct current output end of the third rectification unit.
Referring to fig. 2, as an example, the grid-connected inverter includes a three-phase inverter bridge circuit and a filter circuit (not shown), the three-phase inverter bridge circuit may be composed of 6 power switching devices, and the power switching devices are controlled to be turned on and off by SVPWM signals, so that direct current output by a direct current bus is converted into alternating current and input to a power grid (grid connection). It should be noted that only one grid-connected inverter is provided in the embodiment of the present application, and in other embodiments, a plurality of grid-connected inverters may correspond to a plurality of power generation subsystems, and at this time, coordination control between the grid-connected inverters is required to ensure effective utilization of electric energy.
In the embodiment of the application, the grid-connected inverter is connected with a system direct-current bus through a fourth anti-reverse diode VD4, and the direct-current input end of the grid-connected inverter is connected with a fourth filter capacitor C4. The voltage across the fourth filter capacitor C4 is set to Ubus，UbusThe direct-current voltage is used for reflecting the direct-current voltage input into the grid-connected inverter. After neglecting VD4 pressure dropIn the case of (1), UbusCan be regarded as the voltage of the direct current bus.
In this application, the effect of first anti-reflection diode VD1, second anti-reflection diode VD2 and third anti-reflection diode VD3 is: when one of the power generation subsystems is unloaded, the other power generation subsystems are prevented from being also affected to be unloaded. The anti-reverse diode VD4 is used for preventing the current of the power grid from flowing back into the direct current bus of the system.
It should be noted that, under the normal grid-connected condition, the working voltage of the system dc bus is a preset fixed value, and the preset fixed value simultaneously satisfies the requirement of the dc input voltage of the grid-connected inverter. In the invention, the voltage of the direct current bus of the system is always kept at the preset value, which is beneficial to reducing the bus loss.
In the embodiment of the application, each power generation subsystem is provided with an unloading unit, and the unloading unit is used for converting electric energy into heat energy to be consumed when the electric energy output by the power generation device is surplus. By way of example, the unloading circuit comprises a filter capacitor, an unloading resistor and a power switch tube, wherein the unloading resistor is connected with the power switch tube in series and then connected with the filter capacitor in parallel. The control component (such as a singlechip) controls the on and off of the power switch tube, the unloading resistor is not connected when the power switch tube is switched off, and the unloading resistor is connected when the power switch tube is switched on, so that redundant electric energy output by the wind driven generator can be unloaded. For example, the control unit may obtain an output voltage of the power generation device, and when the output voltage of the power generation device is higher than a preset unloading voltage, the control unit may adjust a time for which the unloading resistor is connected by adjusting a duty ratio of the power switching tube by using a PWM (Pulse Width Modulation) control strategy to unload the power generation device. When the duty ratio of the power switch tube is 100%, the power generation device is completely unloaded, and damage caused by overhigh output voltage of the power generation device is avoided. The duty ratio can be changed within the range of 0-100%, so that the adjustment precision of the unloading circuit is high.
The grid-connected power generation system comprises various topological structures, for example, a power generation device can be an alternating current power generation system consisting of a plurality of permanent magnet synchronous wind power generators, a current transformation module is also a wind power generator controller, and the controller type comprises one or any combination of the uncontrolled rectifying circuit + Boost voltage booster circuit, the rectifying and boosting integrated circuit or the uncontrolled rectifying circuit + phase-shifted full-bridge isolation voltage booster circuit. The grid-connected inverter can be one or more, and can be a unidirectional inverter or a bidirectional inverter.
The power generation device in the application can also be a direct current power generation system formed by a plurality of photovoltaic power generation components, or an alternating current and direct current hybrid power generation system formed by a wind driven generator and the photovoltaic power generation components. The various topologies are readily understood and established based on the foregoing description, and need not be described in detail herein.
The application also discloses an auxiliary power supply method, which is applied to a grid-connected power generation system, wherein the grid-connected power generation system comprises at least two power generation subsystems, a grid-connected inverter and auxiliary power supplies which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystems. The power supply method comprises the following steps: electric energy output by each power generation subsystem is input into a system direct current bus through an anti-reverse diode, and the auxiliary power supply obtains the electric energy from the system direct current bus and supplies the electric energy to the grid-connected power generation system for working.
In the embodiment of the application, when the voltage of the system direct current bus is detected to be smaller than the preset power supply voltage value of the power grid, the electric energy of the system direct current bus is provided by the power grid; and when the voltage of the system direct current bus is detected to be larger than or equal to the preset power grid supply voltage value, the electric energy of the system direct current bus is provided by each power generation subsystem. The method for providing the electric energy of the system direct current bus by the power grid comprises the following steps: the electric energy of the power grid is input into a system direct current bus after being rectified, and at the moment, the voltage of the system direct current bus should be controlled to be smaller than a preset grid-connected voltage stabilizing value, so that the energy of the power grid is prevented from being input into the power grid after passing through a grid-connected inverter, and energy circulation waste is caused.
The method for providing the electric energy of the system direct current bus by each power generation subsystem comprises the following steps: and when the voltage of the system direct-current bus reaches a preset grid-connected starting voltage value, controlling the grid-connected inverter to operate in a grid-connected mode, and controlling the voltage of the system direct-current bus to be stabilized at the preset grid-connected voltage stabilizing value all the time by the grid-connected inverter under the action of the voltage outer ring. The control process is divided into the following two cases:
1. when the grid-connected power reaches the output maximum power value of the grid-connected inverter, the stability of the system direct-current bus voltage cannot be controlled, the system direct-current bus voltage is increased, and when the direct-current bus voltage is increased to a preset unloading voltage value, the power generation subsystem starts unloading; and if the voltage of the direct current bus of the system continues to rise and reaches the preset complete unloading voltage value, the grid-connected inverter stops inverting work, so that the system is protected.
2. And when the grid-connected power is smaller than the preset grid-connected power value and lasts for the preset time, stopping voltage stabilization control on the system direct-current bus voltage and stopping grid connection.
Referring to fig. 3, this embodiment provides a specific method for supplying power to an auxiliary power source in a grid-connected power generation system according to the present application.
The method comprises the following steps:
s1, judging whether the output voltage of any power generation subsystem is larger than a preset power grid supply voltage value, if so, entering S2; if not, go to S3;
s2, the power generation subsystem provides electric energy for the system direct current bus and enters S6;
s3, supplying power supply voltage of the system direct-current bus by a power grid, and entering S4;
s4, the power grid provides system direct-current bus voltage, the voltage of the system direct-current bus is controlled to be smaller than a preset grid-connected voltage stabilizing value, and the operation enters S5;
s5, the grid-connected power generation system is in a power supply standby state of a power grid;
s6, judging whether the voltage of the direct-current bus of the system is larger than a preset grid-connected starting voltage value or not, and if so, entering S8; if not, go to S7;
s7, the grid-connected power generation system is in a power supply standby state of the power generation subsystem;
s8, starting grid-connected operation of the grid-connected power generation system, and entering S9;
s9, controlling the voltage of the direct-current bus of the system to be at a preset grid-connected voltage stabilizing value, and entering S10;
s10, judging whether grid-connected power is smaller than a preset value and keeping preset time, if so, entering S11; if not, returning to S9;
s11, the inverter stops controlling the voltage stabilization of the direct current bus and enters S12;
and S12, stopping grid connection.
It should be noted that, in the embodiments of the present application, some preferred parameter setting values are given, but the present application is not limited thereto, and other parameter values may also be set as needed.
In summary, the auxiliary power supply circuit provided by the invention is applied to a grid-connected power generation system, and the grid-connected power generation system comprises at least two power generation subsystems, a grid-connected inverter and auxiliary power supplies which are in one-to-one correspondence with the grid-connected inverter and each power generation subsystem and provide working power for the grid-connected inverter and the power generation subsystems; the output end of each power generation subsystem is connected with a system direct current bus through an anti-reverse diode, the input end of each auxiliary power supply is connected with the system direct current bus, and the auxiliary power supply and the system direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system. The auxiliary power supply directly gets electricity from the system direct current bus and then converts the electricity into working electricity matched with a system single chip microcomputer control circuit, a switching tube driving circuit and the like, wherein the electric energy of the system direct current bus is from direct current output and summarized by each power generation subsystem or direct current output by a power grid after rectification conversion.
Compared with the prior art that a switching power supply acquires direct current from the output end of each power generation device or a grid-connected power generation system acquires direct current after rectification from a power grid, the scheme of the invention can improve the power supply reliability of a distributed power generation grid-connected system, and when the electric energy output by a certain power generation subsystem is insufficient to supply power to an auxiliary power supply of the power generation subsystem, the auxiliary power supply of the power generation subsystem can take power from a direct current bus so as to maintain the system in a standby state; under the condition of power grid failure, the auxiliary power supply of the grid-connected inverter can also take power from the direct current bus to provide a switching power supply of the grid-connected inverter, so that the power supply mode of the auxiliary power supply can ensure that each power generation subsystem and the grid-connected inverter are in a working standby state to the greatest extent, and the robustness of the system is improved; the system can quickly recover in a standby state, and the response sensitivity is high; the system has strong structural adaptability, and is convenient for forming a wind power and photovoltaic single or mixed power generation system; the system adopts a modular structure, is convenient to produce and maintain, and is easy to change the grid-connected scale of the system.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (7)
1. The utility model provides an auxiliary power supply circuit which characterized in that, is applied to the grid-connected power generation system, the grid-connected power generation system includes:
at least two power generation subsystems;
a grid-connected inverter; and
the auxiliary power supplies correspond to the grid-connected inverter and each power generation subsystem one by one and provide working power for the grid-connected inverter and the power generation subsystems; the alternating current input end of the third rectifying module is connected with a power grid, the direct current output end of the third rectifying module is connected with a system direct current bus, and the third rectifying module is used for converting alternating current output by the power grid into direct current to be input into the system direct current bus;
the output end of each power generation subsystem is connected with a system direct current bus through an anti-reverse diode, the input end of each auxiliary power supply is connected with the system direct current bus, and the auxiliary power supply and the direct current bus form an auxiliary power supply circuit for supplying power to the grid-connected power generation system;
the power generation subsystem comprises a power generation device and a current transformation module, wherein the output end of the power generation device is connected with the input end of the current transformation module, and the current transformation module is used for transforming the electric energy output by the power generation device into direct current; the power generation device is an alternating current power generation device or a direct current power generation device;
the electric energy output by each power generation subsystem is input into a system direct current bus through an anti-reverse diode respectively, and the auxiliary power supply obtains the electric energy from the system direct current bus and supplies the electric energy to the grid-connected power generation system for working;
the electric energy of the system direct current bus is provided by each power generation subsystem or a power grid; the method for providing the electric energy of the system direct current bus by the power grid comprises the following steps: when the voltage of the system direct current bus is detected to be smaller than a preset power grid supply voltage value, the electric energy of the power grid is input into the system direct current bus after being rectified, and the voltage of the system direct current bus is controlled to be smaller than a preset grid-connected voltage stabilizing value;
the method for providing the electric energy of the system direct current bus by each power generation subsystem comprises the following steps: when the voltage of the system direct current bus is detected to be larger than or equal to the preset power grid supply voltage value, each power generation subsystem supplies power to the system direct current bus; when the voltage of the system direct-current bus reaches a preset grid-connected starting voltage value, controlling a grid-connected inverter to operate in a grid-connected mode, and simultaneously controlling the voltage of the system direct-current bus to be stabilized at a preset grid-connected voltage stabilization value; when the grid-connected power is smaller than the preset grid-connected power value, stopping voltage stabilization control on the system direct-current bus voltage and stopping grid connection; when the grid-connected inverter operates in a grid-connected mode, when the fact that the voltage of the direct-current bus of the system reaches a preset unloading voltage value is detected, the power generation subsystem is controlled to unload.
2. The auxiliary power supply circuit according to claim 1, wherein the power generation device is an ac power generation device, the current conversion module includes a first rectification unit, a first unloading unit, a first voltage conversion unit and a first filter capacitor, an ac input terminal of the first rectification unit is connected to an output terminal of the power generation device, a dc output terminal of the first rectification unit is connected to an input terminal of the first unloading unit, an output terminal of the first unloading unit is connected to an input terminal of the first voltage conversion unit, and an output terminal of the first voltage conversion unit is connected to the first filter capacitor.
3. The auxiliary power supply circuit according to claim 2, wherein said first rectifying unit is a three-phase uncontrolled rectifier bridge circuit; the first voltage conversion unit is a Boost booster circuit or a phase-shifted full-bridge isolation booster circuit.
4. The auxiliary power supply circuit according to claim 1, wherein the power generation device is an ac power generation device, the current transformation module includes a second rectification unit, a second unloading unit, and a second filter capacitor, an ac input end of the second rectification unit is connected to an output end of the power generation device, a dc output end of the second rectification unit is connected to an input end of the second unloading unit, and an output end of the second unloading unit is connected to the second filter capacitor, and the second rectification unit is a three-phase half-controlled rectifier bridge circuit.
5. The auxiliary power supply circuit according to claim 1, wherein the power generation device is a dc power generation device, the current conversion module includes a second voltage conversion unit, a third unloading unit and a third filter capacitor, an input terminal of the third unloading unit is connected to an output terminal of the power generation device, an output terminal of the third unloading unit is connected to an input terminal of the second voltage conversion unit, and an output terminal of the second voltage conversion unit is connected to the third filter capacitor.
6. The auxiliary power supply circuit according to claim 1, wherein an anti-reverse diode is provided between the system dc bus and the grid-connected inverter; and the direct current input end of the grid-connected inverter is connected with a fourth filter capacitor.
7. The auxiliary power supply circuit according to claim 1, wherein the power generation device is a wind power generator or a photovoltaic power generation assembly.
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