CN112701719A - Grid-connected soft start method, device, equipment and storage medium - Google Patents
Grid-connected soft start method, device, equipment and storage medium Download PDFInfo
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Abstract
A grid-connected soft start method, a grid-connected soft start device, grid-connected soft start equipment and a computer readable storage medium are provided, wherein the grid-connected soft start method is applied to a grid-connected circuit, the grid-connected circuit comprises a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit which are sequentially connected, and the grid-connected soft start method comprises the following steps: obtaining phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter; independently controlling phase current input to each phase of the three-phase LCL filter respectively so as to pre-charge a filter capacitor of the three-phase LCL filter; when the voltage of a filter capacitor of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid, the three-phase contactor is closed, and the problems that grid connection impact current is too large and the like caused by grid connection and closing under the condition of three-phase unbalanced power grid are solved.
Description
Technical Field
The invention belongs to the technical field of four-quadrant frequency converters, and particularly relates to a grid-connected soft start method, a grid-connected soft start device, grid-connected soft start equipment and a computer readable storage medium.
Background
The four-quadrant frequency converter is widely applied to the fields of steel, petrifaction, spinning, electric power and the like at present, an industrial power grid in the fields adopts a three-phase three-wire system, and a large number of nonlinear, impulsive and unbalanced power electronic loads of different types exist at the same time, so that the conditions of voltage fluctuation, flicker, three-phase imbalance and the like of the three-phase power grid exist for a long time; the rectification grid-connected unit of the four-quadrant frequency converter needs to consider the application of a severe industrial power grid, and optimization measures are introduced in a targeted manner.
However, the existing grid-connected circuit has the problem of overlarge impact current in the grid-connected process of a three-phase unbalanced power grid.
Disclosure of Invention
In view of this, embodiments of the present invention provide a grid-connected soft start method, a grid-connected soft start apparatus, a grid-connected soft start device, and a computer-readable storage medium, which can solve the problems that the existing grid-connected soft start technology cannot satisfy grid-connected closing conditions and grid-connected inrush current are large under the condition of a three-phase unbalanced grid.
The first aspect of the embodiment of the invention provides a grid-connected soft start method, which is applied to a grid-connected circuit, wherein the grid-connected circuit comprises a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit which are sequentially connected, the three-phase contactor is connected with a three-phase power grid, the three-phase rectification circuit is connected with an inverter circuit to be incorporated into a power grid load, and the method comprises the following steps:
obtaining phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter;
independently controlling phase current input to each phase of the three-phase LCL filter respectively so as to pre-charge a filter capacitor of the three-phase LCL filter;
and when the voltage of the filter capacitor of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid, closing the three-phase contactor.
Optionally, the obtaining phase voltages of the phases of the three-phase power grid includes:
acquiring line voltage of the three-phase power grid;
and converting the line voltage of the three-phase power grid according to a preset formula to obtain the phase voltage of each phase of the three-phase power grid.
Optionally, the separately and independently controlling the phase current input to each phase of the three-phase LCL filter includes:
respectively adopting a voltage-current double closed loop to control the phase current of each phase output by the three-phase rectifying circuit;
and performing pulse width modulation on the output current of each voltage-current double closed loop, and inputting the modulated current to the three-phase LCL filter.
Optionally, the voltage-current double closed loop comprises a voltage outer loop and a current inner loop,
the method for controlling the phase current of each phase output by the three-phase rectification circuit by adopting the voltage and current double closed loops respectively comprises the following steps:
taking the three-phase power grid phase voltage as the voltage outer loop reference value, and taking the filter capacitor voltage of the three-phase LCL filter as the voltage outer loop feedback value;
taking the current output by the voltage outer ring as the reference value of the current inner ring, and taking the phase current output by the three-phase rectification circuit as the feedback value of the current inner ring;
and taking the output current of the current inner loop as the output current of the voltage-current double closed loop.
Optionally, after obtaining the phase voltage of each phase of the three-phase power grid and the filter capacitor voltage of each phase of the three-phase LCL filter, the method further includes:
and judging whether the three-phase contactor is adhered or not according to the filter capacitor voltage of each phase of the three-phase LCL filter.
Optionally, the grid-connected circuit further includes a bus capacitor, a buffer circuit, and a buffer relay connected to the buffer circuit, the bus capacitor is connected in parallel between the inverter circuit and the three-phase rectification circuit, and the inverter circuit to be incorporated into the grid load is connected to the three-phase grid via the buffer circuit and the buffer relay;
before the three-phase contactor is closed, the method further comprises the following steps:
closing the buffer relay to charge the bus capacitor;
and when the bus capacitor finishes charging, the buffer relay is disconnected.
Optionally, after the three-phase contactor is closed, the method further includes:
and obtaining a feedback signal after the three-phase contactor is closed, and adjusting the phase current input to each phase of the three-phase LCL filter according to the feedback signal.
In a second aspect, the present invention provides a grid-connected soft start device, which is applied to a grid-connected circuit, wherein the grid-connected circuit includes a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit connected in sequence, the three-phase contactor is connected to a three-phase power grid, the three-phase rectification circuit is connected to an inverter circuit to be incorporated into a power grid load,
the grid-connected soft start device comprises:
the sampling unit is used for acquiring phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter;
a phase current control unit which independently controls phase current input to each phase of the three-phase LCL filter to pre-charge a filter capacitor of the three-phase LCL filter;
and the contactor control unit is used for closing the three-phase contactor when the voltage of the filter capacitor of each phase of the three-phase LCL filter is respectively equal to the phase voltage of the corresponding three-phase power grid.
A third aspect of the embodiments of the present invention provides a grid-connected soft start device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor, when executing the computer program, implements the method according to any one of the above.
A fourth aspect of the embodiments of the present invention provides a computer-readable storage medium, which stores a computer program, wherein the computer program, when executed by a processor, implements the method according to any one of the above. .
In the embodiment of the invention, the grid-connected soft start method is applied to a grid-connected circuit, the grid-connected circuit comprises a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit which are sequentially connected, and the grid-connected soft start method comprises the following steps: obtaining phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter; independently controlling phase current input to each phase of the three-phase LCL filter respectively so as to pre-charge a filter capacitor of the three-phase LCL filter; when the voltage of a filter capacitor of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid, the three-phase contactor is closed, and the problems that grid connection impact current is too large and the like caused by grid connection and closing under the condition of three-phase unbalanced power grid are solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a circuit structure diagram of a grid-connected circuit according to an embodiment of the present disclosure;
fig. 2 is a schematic flow chart of a grid-connected soft start method according to an embodiment of the present application;
fig. 3 is a schematic flowchart of step S10 in the grid-connected soft start method provided in the embodiment of the present application;
FIG. 4 is a schematic diagram illustrating a control of a four-quadrant inverter precharge loop according to an embodiment of the present disclosure;
fig. 5 is a circuit structure diagram of a grid-connected circuit provided in an embodiment of the present application;
fig. 6 is a circuit structure diagram of a rectifier bridge according to an embodiment of the present disclosure;
fig. 7 is a structural block diagram of a grid-connected soft start device according to an embodiment of the present application;
fig. 8 is a block diagram of a structure of a grid-connected soft start device according to an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Fig. 1 is a schematic circuit structure diagram of a grid-connected circuit provided in an embodiment of the present application, and referring to fig. 1, in this embodiment, the grid-connected circuit includes a three-phase contactor 10, a three-phase LCL filter 20, and a three-phase rectification circuit 30, which are connected in sequence, where the three-phase contactor 10 is connected to a three-phase power grid 00, and the three-phase rectification circuit 20 is connected to an inverter circuit 40 to be incorporated into a power grid load.
The grid-connected soft start method provided by the embodiment of the application is applied to a grid-connected circuit, and specifically, as shown in fig. 2, the grid-connected soft start method in the embodiment includes steps S10 to S30.
In step S10, phase voltages of the phases of the three-phase power grid and filter capacitor voltages of each phase of the three-phase LCL filter are obtained.
In this embodiment, three input ends of the three-phase contactor 10 are respectively connected to three phase lines of the three-phase power grid 00 in a one-to-one correspondence manner, three output ends of the three-phase contactor 10 are respectively connected to three input ends of the three-phase LCL filter 20 in a one-to-one correspondence manner, three output ends of the three-phase LCL filter 20 are connected to the inverter circuit 40, and the inverter circuit 40 is connected to the grid-connected load 50.
In a specific application embodiment, for example, when a four-quadrant inverter rectification grid-connection unit needs to consider a severe industrial power grid application, by collecting line voltages at three input ends of a three-phase contactor, the line voltages may be line voltages of an unbalanced or balanced power grid, phase voltages of each phase of the three-phase power grid are calculated based on the line voltages, and when a filter capacitor voltage of each phase in the three-phase LCL filter 20 is equal to a corresponding phase voltage of the three-phase power grid, the three-phase contactor is closed.
In step S20, the phase currents input to each phase of the three-phase LCL filter are independently controlled to precharge the filter capacitors of the three-phase LCL filter.
In the present embodiment, the phase current of each phase in the three-phase LCL filter is independently controlled, so that the precharging process of the three-way filter capacitor in the three-phase LCL filter 20 is separately adjusted.
In step S30, when the filter capacitor voltage of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase grid, the three-phase contactor is closed.
In this embodiment, when the filter capacitor voltage of each phase in the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid 00, the three-phase contactor 10 is closed, and the three-phase rectification circuit 30 is controlled to access the three-phase power grid 00.
In one embodiment, referring to fig. 3, in step S10, obtaining phase voltages of each phase of the three-phase grid includes steps S11 and S12.
In step S11, a line voltage of the three-phase grid is acquired.
In step S12, the line voltage of the three-phase power grid is converted according to a preset formula, so as to obtain the phase voltage of each phase of the three-phase power grid.
In this embodiment, the line voltage between three phase lines in the three-phase power grid 00 is obtained by sampling the line voltage in the three-phase power grid 00, and the line voltage of each phase line in the three-phase power grid is converted according to a preset formula to obtain the phase voltage of each phase in the three-phase power grid 00.
In one embodiment, the predetermined formula is:
wherein, UANPhase voltage of A-phase line, UBNPhase voltage of B-phase line, UCNPhase voltage of C-phase line, UABLine voltage between A phase and B phase, UCALine voltage between C phase and A phase, UBCThe line voltage between the B phase and the C phase.
In this embodiment, UANPhase voltage of A phase, UBNPhase voltage of B phase, UCNPhase voltage of C phase, i.e. UAN、UBN、UCNThe three-phase power grid is a loop control reference value which is obtained by calculating line voltages of an A phase, a B phase and a C phase, and phase voltages of all phases in the three-phase power grid are used for independently controlling a filter capacitor in an LCL filter circuit to carry out pre-chargingFor example, in one application, the DSP control unit operates the line voltage on the grid side to obtain a soft start voltage reference value on the inverter side, where the soft start voltage reference value is the voltage of each phase in the three-phase grid, and when the filter capacitor voltage in the LCL filter is precharged to be equal to the corresponding phase voltage of the three-phase grid, the DSP control unit controls the three-phase contactor to be closed, so as to connect the inverter side circuit to the three-phase grid.
In specific application, due to poor adaptability of a three-phase unbalanced power grid, for example, a LCL filter circuit is required to be pre-charged before a grid-connected unit is connected to the grid, when capacitor voltage and grid voltage realize accurate same frequency and same amplitude, the grid-connected unit controls a relay to be switched on, and a photovoltaic inverter is generally directly connected to a residential power grid or is connected to a power transmission grid through a transformer and works under the condition of the three-phase balanced power grid; the photovoltaic grid-connected inverter adopts a vector control technology, active current and reactive current are controlled under a DQ coordinate system, three-phase balanced voltage is output, grid-connected switching-on conditions under the condition of three-phase unbalanced power grid cannot be met, and large grid-connected impact current is easily caused. In the embodiment, the phase current is calculated in the ABC coordinate system to replace the calculation mode in the DQ coordinate system in the prior art, so that the adaptability of the grid-connected unit soft start technology to a three-phase unbalanced power grid can be effectively enhanced, and meanwhile, the reliability of a relay/contactor and the like is improved by effectively inhibiting grid-connected impact current, so that the grid-connected unit soft start technology can have a good practical effect in different power grids.
In one embodiment, in step S20, independently controlling the phase current input to each phase of the three-phase LCL filter includes: and respectively adopting voltage and current double closed loops to control the phase current of each phase output by the three-phase rectification circuit, carrying out pulse width modulation on the output current of each voltage and current double closed loop, and inputting the modulated current to the three-phase LCL filter.
In this embodiment, three independent voltage-current double closed loops are respectively adopted to control the phase current of each phase output by the three-phase rectification circuit 30, so as to pre-charge each filter capacitor in the three-phase LCL filter 20, specifically, the pulse width modulation signal is used to perform pulse width modulation on the output current of each voltage-current double closed loop, and the modulated current is input to the three-phase LCL filter 20, so as to independently control the charging process of each filter capacitor in the three-phase LCL filter 20.
In one embodiment, fig. 4 is a schematic control diagram of a four-quadrant frequency converter precharge loop provided in an embodiment of the present application, and referring to fig. 4, a voltage-current double closed loop in the embodiment includes a voltage outer loop and a current inner loop.
In this embodiment, the controlling the phase current of each phase output by the three-phase rectification circuit by using a voltage-current double closed loop respectively includes:
taking the three-phase power grid phase voltage as the voltage outer loop reference value, and taking the filter capacitor voltage of the three-phase LCL filter as the voltage outer loop feedback value;
taking the current output by the voltage outer ring as the reference value of the current inner ring, and taking the phase current output by the three-phase rectification circuit as the feedback value of the current inner ring;
and taking the output current of the current inner loop as the output current of the voltage-current double closed loop.
In this embodiment, phase voltages of each phase of a three-phase power grid are used as voltage outer loop reference values, filter capacitor voltages of three filter capacitors in a three-phase LCL filter are used as voltage outer loop feedback values, output currents of the voltage outer loop are used as current inner loop reference values, phase currents output by a three-phase rectification circuit are used as current inner loop feedback values, and output currents of a current inner loop are used as output currents of a voltage-current double closed loop.
In this embodiment, before a three-phase contactor in a four-quadrant frequency converter rectification grid-connected unit is not attracted, the three-phase contactor is in an off-grid inversion working state, inversion output voltage is independently controlled by three-phase output voltage, three independent voltage and current closed-loop control is used, voltage outer loop reference is virtual three-phase grid phase voltage, voltage outer loop feedback is filter capacitor voltage, voltage outer loop output is used as control reference of a current inner loop, and the current inner loop PI loop output controls wave generation of an inverter bridge through SPWM modulation.
Referring to FIG. 4, UCANA-phase filter capacitor voltage, UC, sampled for DSP control unitBNB-phase filter capacitor voltage, UC, sampled for DSP control unitCNThe UAgridRef is phase voltage U of an A phaseANUBgridRef is phase voltage U of phase BBNUCgridRef is phase voltage U of phase CCNThe voltage outer ring refers to the virtual three-phase power grid phase voltage, and the voltage outer ring feeds back the filter capacitor voltage.
Specifically, the A-phase filter capacitor voltage UCANThe phase voltage UAgridRef serving as a reference is processed by a PI (PI regulator) and then output by a voltage outer ring, the voltage outer ring is output as a control reference of a current inner ring, and a DSP control unit acquires phase current I of an A phase in a three-phase LCL filter 20ANPhase current I of the A phaseANThe control reference as the current inner loop feedback value and the current inner loop is PI-processed and SPWM-modulated, and then a corresponding SPWM-modulated signal (i.e., DutyA in fig. 4) is output to adjust the phase current of the a phase in the three-phase LCL filter 20.
B-phase filter capacitor voltage UCBNThe phase voltage UBgridRef serving as a reference is processed by a PI (PI regulator) and then output by a voltage outer ring, the voltage outer ring is output as a control reference of a current inner ring, and a DSP control unit acquires phase current I of a phase B in a three-phase LCL filter 20BNPhase current I of the B phaseBNThe control reference as the current inner loop feedback value and the current inner loop is PI-processed and SPWM-modulated, and then a corresponding SPWM-modulated signal (i.e., DutyB in fig. 4) is output to adjust the phase current of the B phase in the three-phase LCL filter 20.
C-phase filter capacitor voltage UCCNThe phase voltage UCgridRef serving as a reference is processed by a PI (PI regulator) and then output by a voltage outer ring, the voltage outer ring is output as a control reference of a current inner ring, and the DSP control unit collects phase current I of a C phase in a three-phase LCL filter 20BNPhase current I of the C phaseCNAfter PI processing and SPWM modulation are carried out as the control reference of the current inner loop feedback value and the current inner loop, a corresponding SPWM modulation signal (namely DutyC in figure 4) is output to filter the three-phase LCLThe phase current of the C phase in the machine 20 is adjusted.
In one embodiment, after obtaining the phase voltages of the phases of the three-phase power grid and the filter capacitor voltages of each phase of the three-phase LCL filter, the method further includes: and judging whether the three-phase contactor is adhered or not according to the filter capacitor voltage of each phase of the three-phase LCL filter.
Fig. 5 is a schematic structural diagram of a grid-connected circuit according to AN embodiment of the present application, and referring to fig. 5, voltage sampling points of filter capacitors in phases of the three-phase LCL filter 20 are AN, BN and CN, where AN, BN and CN are all present in the three-phase LCL filter 20, the main contactor KML (i.e. the three-phase contactor 10) is between the three-phase grid and the three-phase LCL filter 20, is used for connecting the three-phase power grid 00 and the three-phase LCL filter 20, if the main contactor KML is not adhered, the three-phase alternating current of the three-phase power grid 00 can not be input into the three-phase LCL filter 20, the three-phase LCL filter 20 is not powered, the voltages of the sampling points AN, BN and CN are the same, the main control circuit 60 detects that the voltages of the sampling points AN, BN and CN are the same, the main contactor KML can be judged not to be adhered, and if the main control circuit 60 detects that the voltages of the AN, the BN and the CN are different, the main contactor KML can be judged to be adhered.
In specific application, the existing grid-connected soft start control adopts a vector control technology to convert an ABC coordinate system three-phase sampling current into a DQ coordinate system, so that active current and reactive current are controlled in a decoupling mode, but only whole current is limited, when single-phase or multi-phase abnormity occurs, for example, when a relay is adhered to a single path, current limiting processing cannot be performed on each phase of current, and larger grid-connected impact current is easily caused. In this embodiment, the DSP control unit samples the filter capacitor voltage of each phase of the three-phase LCL filter, and determines the adhesion condition of each phase circuit in the three-phase contactor, for example, the DSP control unit collects the capacitor voltage on the filter side in real time, and detects whether the contactor is adhered or not through the capacitor voltage.
Referring to fig. 5, the grid-connected circuit further includes a bus capacitor 12, a buffer circuit 11, and a buffer relay 13 connected to the buffer circuit 11, the bus capacitor 12 is connected in parallel between the inverter circuit 40 and the three-phase rectification circuit 30, and the inverter circuit 40 to be incorporated into the grid load is connected to the three-phase grid 00 via the buffer circuit 11 and the buffer relay 13.
In this embodiment, before closing the three-phase contactor, the method further includes: closing the buffer relay to charge the bus capacitor; and when the bus capacitor finishes charging, the buffer relay is disconnected.
In this embodiment, the three-phase power grid 00 outputs three-phase ac power and pre-charges the bus capacitor 12 through the buffer circuit 11 and the buffer relay 13, the three-phase rectifier circuit 30 controls the phase current of each phase according to the pulse width modulation signal output from the DSP unit, thereby independently controlling the pre-charge process of each filter capacitor in the three-phase LCL filter 20, and then carry on the current-limiting treatment to each phase current that the three-phase rectifier circuit 30 outputs, at this moment, the voltage reference of contravariant side promotes slowly, the loop operation controls the wave through outputting the correspondent pulse width modulation signal control three-phase LCL filter capacitor to charge the voltage and rise slowly in advance in DSP control unit, the voltage of the filter capacitor is the same with voltage reference value (namely the line voltage of the three-phase electric wire netting) that the voltage of the side of the net corresponds finally, buffer and finish, the zero crossing point actuation in the three-phase contactor 10, avoid connecting the electric wire netting the process and producing the greater impact current.
Further, by independently controlling each phase circuit in the three-phase rectification circuit 30, the three-phase rectification circuit can also be used for maintaining the bus voltage stable, providing energy for the inversion side, or feeding back energy from the load end to the four-quadrant operation of the power grid.
In one embodiment, after closing the three-phase contactor, the method further includes: and obtaining a feedback signal after the three-phase contactor is closed, and adjusting the phase current input to each phase of the three-phase LCL filter according to the feedback signal.
In this embodiment, the DSP control unit receives a feedback signal after the three-phase contactor 10 is pulled in, and adjusts the phase current input to each phase of the three-phase LCL filter by controlling the switching of the operation loop, so as to stabilize the bus voltage.
In this embodiment, the DSP control unit may adjust each phase of current output by the three-phase rectification circuit 30 through a pulse width modulation signal, to achieve accurate tracking of a balanced/unbalanced three-phase power grid, reduce a voltage difference between two sides of the grid-connected contactor, and reduce grid-connected current impact; the three independent current rings of inner loop restrict three-phase precharge current respectively, and when the contactor takes place unusually, independent current ring can the restriction current rush to promote the unit reliability of being incorporated into the power networks.
In one embodiment, as shown in fig. 5, the three-phase contactor 10 may be a main contactor KML.
In one embodiment, referring to fig. 5, the buffer circuit 11 includes: the rectifier circuit comprises a first buffer resistor R1, a second buffer resistor R2, a third buffer resistor R3 and a rectifier bridge UR; the buffer relay 13 includes: a first bumper relay KM1 and a second bumper relay KM 2.
IN this embodiment, the first input pin IN1 of the main contactor KML is connected to the first input pin IN1 of the rectifier bridge UR through a first buffer resistor R1, the second input pin IN2 of the main contactor KML is connected to the second input pin IN2 of the rectifier bridge UR through a second buffer resistor R2, the third input pin IN3 of the main contactor KML is connected to the third input pin IN3 of the rectifier bridge UR through a third buffer resistor R3, the first end of the first buffer relay KM1 is connected to the positive output pin + of the rectifier bridge UR, the second end of the first buffer relay KM1 is connected to the positive input terminal of the inverter circuit 40, the first end of the second buffer relay KM2 is connected to the negative output pin of the rectifier bridge UR, and the second end of the second buffer relay KM2 is connected to the negative input terminal of the inverter circuit 40.
IN this embodiment, the first input pin IN1 of the main contactor KML is connected to the first three-phase power input terminal R of the three-phase power grid 00, the second input pin IN2 of the main contactor KML is connected to the second three-phase power input terminal S of the three-phase power grid 00, the third input pin IN3 of the main contactor KML is connected to the third three-phase power input terminal T of the three-phase power grid 00, the first output pin OUT1 of the main contactor KML is connected to the first three-phase power input terminal of the three-phase LCL filter 20, the second output pin OUT1 of the main contactor KML is connected to the second three-phase power input terminal of the three-phase LCL filter 20, and the third output pin OUT1 of the main contactor KML is connected to the third three-phase power input terminal of the three-phase lc.
In the present embodiment, the snubber circuit 11 is composed of three snubber resistors (a first snubber resistor R1, a second snubber resistor R2, and a third snubber resistor R3) and a rectifier bridge UR.
The buffer relay 13 is composed of a first buffer relay KM1 and a second buffer relay KM2, and the buffer circuit 11 and the buffer relay 13 are used for pre-charging the bus capacitor 12 when the three-phase power grid 00 is electrified, so that grid-connected impact current is effectively reduced.
In one embodiment, the rectifier bridge UR may be a three-phase uncontrolled rectifier bridge.
In one embodiment, the three-phase ac power output from the three-phase power grid 00 enters the three-phase LCL filter 20 through the main contactor KML, the main contactor KML controls the connection state between the three-phase power grid 00 and the three-phase LCL filter 20, and the detection output pin COUT of the main contactor KML is connected to the detection terminal of the main contactor of the main control circuit 60.
In one embodiment, the three-phase alternating current provided by the three-phase power grid 00 is further output to a rectifier bridge UR, the rectifier bridge UR converts the three-phase alternating current provided by the three-phase power grid 00 into corresponding direct current, the direct current enters the inverter circuit 40 through a first buffer relay KM1 and a second buffer relay KM2 to provide a power supply for the inverter circuit 40, and the first buffer relay KM1 and the second buffer relay KM2 can control the connection state between the rectifier bridge UR and the inverter circuit 40.
In one embodiment, referring to fig. 5, a three-phase LCL filter 20 includes: a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a fifth inductor L5, a sixth inductor L6, a first capacitor C1, a second capacitor C2 and a third capacitor C3, wherein a first end of the first inductor L1 is a first three-phase power input end of the three-phase LCL filter 20, a second end of the first inductor L1 is connected with the first three-phase power input end of the inverter circuit 40 through the fourth inductor L4, a first end of the second inductor L2 is a second three-phase power input end of the three-phase LCL filter 20, a second end of the second inductor L2 is connected with the second three-phase power input end of the inverter circuit 40 through the fifth inductor L5, a first end of the third inductor L3 is a third three-phase power input end of the three-phase LCL filter 20, a second end of the third inductor L5 is connected with the third three-phase power input end of the inverter circuit 40, a first end of the first capacitor C1 is connected with the first three-phase filter capacitor of the first three-phase voltage of, a first end of the second capacitor C2 is connected to a voltage end of the second three-phase filter capacitor of the main control circuit 60, a first end of the third capacitor C3 is connected to a voltage end of the third three-phase filter capacitor of the main control circuit 60, a second end of the first capacitor C1 is connected to a common node AN between the first inductor L1 and the fourth inductor L4, a second end of the second capacitor C2 is connected to a common node BN between the second inductor L2 and the fifth inductor L5, and a second end of the third capacitor C3 is connected to a common node CN between the third inductor L3 and the sixth inductor L6.
In one embodiment, the three-phase LCL filter 20 performs filtering processing on three-phase ac power provided by the three-phase power grid 00, and the inductor has a large impedance to higher-frequency harmonics and the capacitor has a small impedance to higher-frequency harmonics, so that the three-phase LCL filter 20 formed by the inductor and the capacitor can effectively filter higher-frequency harmonics.
In one embodiment, referring to fig. 5, the three-phase rectification circuit 30 includes: a first switching tube QT1, a second switching tube QT2, a third switching tube QT3, a fourth switching tube QT4, a fifth switching tube QT5, and a sixth switching tube QT 6; the drain of the first switch tube QT1, the drain of the third switch tube QT3 and the drain of the fifth switch tube QT5 are connected to the positive input end of the inverter circuit 40 in common, the source of the second switch tube QT2, the source of the fourth switch tube QT4 and the source of the sixth switch tube QT6 are connected to the negative input end of the inverter circuit 40 in common, the source of the first switch tube QT1 and the drain of the second switch tube QT2 are connected to the first three-phase power input end of the three-phase rectifier circuit 30 in common, the source of the third switch tube QT3 and the drain of the fourth switch tube QT4 are connected to the second three-phase power input end of the three-phase rectifier circuit 30 in common, and the source of the fifth switch tube QT5 and the drain of the sixth switch tube QT6 are connected to the third three-phase power input end of the three-phase.
In one embodiment, referring to fig. 5, the inverter circuit 40 includes: a seventh switching tube QT7, an eighth switching tube QT8, a ninth switching tube QT9, a tenth switching tube QT10, an eleventh switching tube QT11 and a twelfth switching tube QT 12; the drain of the seventh switch tube QT7, the drain of the ninth switch tube QT9 and the drain of the tenth switch tube QT10 are connected in common to form the positive input terminal of the inverter circuit 40, the source of the eighth switch tube QT8, the source of the tenth switch tube QT10 and the source of the twelfth switch tube QT12 are connected in common to form the negative input terminal of the inverter circuit 40, the source of the seventh switch tube QT7 and the drain of the eighth switch tube QT8 are connected in common to form the first three-phase power output terminal of the inverter circuit 40, the source of the ninth switch tube QT9 and the drain of the tenth switch tube QT10 are connected in common to form the second three-phase power output terminal of the inverter circuit 40, and the source of the eleventh switch tube QT11 and the drain of the twelfth switch tube QT12 are connected in common to form the third three-phase power output terminal of the inverter circuit.
Referring to fig. 5, the grid-connected circuit in this embodiment further includes a main control circuit 60, and the main control circuit 60 may be configured to execute the grid-connected soft driving method according to any one of the embodiments. In this embodiment, the gate of the first switching tube QT1 is connected to the first control terminal T1 of the main control circuit 60, the gate of the second switching tube QT2 is connected to the second control terminal T2 of the main control circuit 60, the gate of the third switching tube QT3 is connected to the third control terminal T3 of the main control circuit 60, the gate of the fourth switching tube QT4 is connected to the fourth control terminal T4 of the main control circuit 60, the gate of the fifth switching tube QT5 is connected to the fifth control terminal T5 of the main control circuit 60, the gate of the sixth switching tube QT6 is connected to the sixth control terminal T6 of the main control circuit 60, the gate of the seventh switching tube QT7 is connected to the seventh control terminal T7 of the main control circuit 60, the gate of the eighth switching tube QT8 is connected to the eighth control terminal T8 of the main control circuit 60, the gate of the ninth switching tube QT6 is connected to the ninth control terminal T9 of the main control circuit 60, and the gate of the tenth switching tube QT10 is connected to the tenth control terminal T10, a gate of the eleventh switching tube QT11 is connected to the eleventh control terminal T11 of the main control circuit 60, and a gate of the twelfth switching tube QT12 is connected to the twelfth control terminal T12 of the main control circuit 60.
In one embodiment, the first three-phase power input terminal, the second three-phase power input terminal, and the third three-phase power output terminal of the inverter circuit 40 are configured to output the inverted three-phase ac power to the outside.
In one embodiment, the bus capacitor 12 includes a fourth capacitor C4 and a fifth capacitor C5; specifically, after the fourth capacitor C4 and the fifth capacitor C5 are connected in series, a first end of the fourth capacitor C4 is connected to the positive input end of the inverter circuit 40, and a second end of the fourth capacitor C5 is connected to the negative input end of the inverter circuit 40.
In one embodiment, the series circuit of the fourth capacitor C4 and the fifth capacitor C5 can implement the pre-charging function.
In one embodiment, the first switch tube QT1, the second switch tube QT2, the third switch tube QT3, the fourth switch tube QT4, the fifth switch tube QT5, the sixth switch tube QT6, the seventh switch tube QT7, the eighth switch tube QT8, the ninth switch tube QT9, the tenth switch tube QT10, the eleventh switch tube QT11, and the twelfth switch tube QT12 are all independently controlled by the main control circuit 60, and the control phases between the switch tubes are not affected by each other, so that the working state of each phase circuit can be independently changed, and the voltage of the three-phase alternating current circuit is balanced.
In one embodiment, the master control circuit 60 includes a DSP chip U1; a voltage signal input pin U _ IN of the DSP chip U1 is a voltage signal input end of the main control circuit 60, and the voltage signal input end of the main control circuit 60 is connected with the three-phase power grid 00; a current signal input pin I _ IN of the DSP chip U1 is a current signal input end of the main control circuit 60, the current signal input end of the main control circuit 60 is divided into a contact IA, a contact IB and a contact IC, the contact IA is connected with a first three-phase electric output end of the three-phase LCL filter 20, the contact IB is connected with a second three-phase electric output end of the three-phase LCL filter 20, and the contact IC is connected with a third three-phase electric output end of the three-phase LCL filter 20; a first phase voltage input pin AI of the DSP chip U1 is a first phase voltage input end of the main control circuit 60, the first phase voltage input end of the main control circuit 60 is connected to a node AN of the three-phase LCL filter 20, a second phase voltage input pin BI of the DSP chip U1 is a second phase voltage input end of the main control circuit 60, the second phase voltage input end of the main control circuit 60 is connected to a node BN of the three-phase LCL filter 20, a third phase voltage input pin CI of the DSP chip U1 is a third phase voltage input end of the main control circuit 60, the third phase voltage input end of the main control circuit 60 is connected to a node CN of the three-phase LCL filter 20, a detection end of a main contactor of the main control circuit 60 is connected to a detection output pin COUT of the main contactor KML, a first control pin T1 of the DSP chip U1 is a first control end of the main control circuit 60, the first control end of the main control circuit 60 is connected to a gate of the first switching tube, a second control pin T2 of the DSP chip U1 is a second control terminal of the main control circuit 60, a second control terminal of the main control circuit 60 is connected to a gate of the second switch tube QT2, a third control pin T3 of the DSP chip U1 is a third control terminal of the main control circuit 60, the third control terminal of the main control circuit 60 is connected to a gate of the third switch tube QT3, a fourth control pin T4 of the DSP chip U1 is a fourth control terminal of the main control circuit 60, a fourth control terminal of the main control circuit 60 is connected to a gate of the fourth switch tube QT4, a fifth control pin T5 of the DSP chip U1 is a fifth control terminal of the main control circuit 60, a fifth control terminal of the main control circuit 60 is connected to a gate of the fifth switch tube QT5, a sixth control pin T6 of the DSP chip U1 is a sixth control terminal of the main control circuit 60, a sixth control terminal of the main control circuit 60 is connected to a gate of the sixth switch tube QT6, and a seventh control pin T3985 of the main control circuit 60, the seventh control terminal of the main control circuit 60 is connected to the gate of the seventh switch QT7, the eighth control pin T8 of the DSP chip U1 is the eighth control terminal of the main control circuit 60, the eighth control terminal of the main control circuit 60 is connected to the gate of the eighth switch QT8, the ninth control pin T9 of the DSP chip U1 is the ninth control terminal of the main control circuit 60, the ninth control terminal of the main control circuit 60 is connected to the gate of the ninth switch QT9, the tenth control pin T10 of the DSP chip U1 is the tenth control terminal of the main control circuit 60, the tenth control terminal of the main control circuit 60 is connected to the gate of the tenth switch QT10, the eleventh control pin T11 of the DSP chip U1 is the eleventh control terminal of the main control circuit 60, the eleventh control terminal of the main control circuit 60 is connected to the gate of the eleventh switch QT11, the twelfth control pin T12 of the DSP chip U1 is the twelfth control terminal of the main control circuit 60, and the twelfth control terminal of the switch QT12 is connected to the twelfth control terminal of the switch QT 3535.
IN one embodiment, the voltage signal input pin U _ IN of the DSP chip U1 is used to collect three-phase line voltage sampling signals input from the three-phase power grid 00 access terminal, the current signal input pin I _ IN of the DSP chip U1 is used to collect three-phase current signals output by the three-phase LCL filter 20, and the first phase voltage input pin AI, the second phase voltage input pin BI, and the third phase voltage input pin CI of the DSP chip U1 are used to receive three-phase filter capacitor voltages output by the three-phase LCL filter 20, that is, voltage signals of the nodes AN, BN, and CN.
In one embodiment, the main control circuit 60 is configured to output a pulse width modulation signal to control the four-quadrant operation state of the rectifying circuit 30, so as to independently control the pre-charging process of each filter capacitor in the LCL filter circuit 20, thereby adjusting the magnitude of each phase current and avoiding the occurrence of a rush current during the grid connection process.
In one embodiment, after the DSP chip U1 receives a feedback signal picked up by the main contactor KML, the DSP chip U1 determines whether the current main contactor KML is in an attracted state or in a non-attracted state, and if the current main contactor KML is in the attracted state, the DSP chip U1 generates corresponding control signals to control the switching states of the first switching tube QT1, the second switching tube QT2, the third switching tube QT3, the fourth switching tube QT4, the fifth switching tube QT5, the sixth switching tube QT6, the seventh switching tube QT7, the eighth switching tube QT8, the ninth switching tube QT9, the tenth switching tube QT10, the eleventh switching tube QT11, and the twelfth switching tube QT12 according to the collected three-phase line voltage sampling signal input from the access end of the three-phase power grid 00, the three-phase current signal output by the three-phase LCL filter 20, and the three-phase filter capacitor voltage output by the three-phase LCL filter 20 by PI control, thereby controlling the inverter circuit 40 to output a stable three-phase alternating current.
Referring to fig. 6, an embodiment of the present application provides a rectifier bridge circuit, and in this embodiment, the rectifier bridge UR includes: a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6; cathodes of the first diode D1, the second diode D2 and the third diode D3 are commonly connected to an anode of the rectifier bridge UR, anodes of the fourth diode D4, the fifth diode D5 and the sixth diode D6 are commonly connected to a cathode of the rectifier bridge UR, an anode of the first diode D1 and a cathode of the fourth diode D4 are commonly connected to a first input pin IN1 of the rectifier bridge UR, an anode of the second diode D2 and a cathode of the fifth diode D5 are commonly connected to a second input pin IN2 of the rectifier bridge UR, and an anode of the third diode D3 and a cathode of the sixth diode D6 are commonly connected to a third input pin IN3 of the rectifier bridge UR.
IN one embodiment, if the first input pin IN1 of the rectifier bridge UR is connected with a positive voltage, the first diode D1 is turned on, the voltage at the first input pin IN1 of the rectifier bridge UR outputs a positive voltage through the first diode D1 to the positive pole of the rectifier bridge UR, if the first input pin IN1 of the rectifier bridge UR is connected with a negative voltage, the fourth diode D4 is turned on, the voltage at the first input pin IN1 of the rectifier bridge UR outputs a negative voltage through the fourth diode D4 to the negative pole of the rectifier bridge UR, if the second input pin IN2 of the rectifier bridge UR is connected with a positive voltage, the second diode D2 is turned on, the voltage at the second input pin IN2 of the rectifier bridge UR outputs a positive voltage through the second diode D2 to the positive pole of the rectifier bridge UR, if the second input pin IN2 of the rectifier bridge UR is connected with a negative voltage, the fourth diode D4 is turned on, the voltage at the second input pin IN2 of the rectifier bridge UR outputs a negative voltage through the negative pole of the rectifier bridge UR 4, if the third input pin IN3 of the rectifier bridge UR is connected to a positive voltage, the third diode D3 is turned on, the voltage at the third input pin IN3 of the rectifier bridge UR is connected to the positive electrode of the rectifier bridge UR through the third diode D3 to output a positive voltage, and if the third input pin IN3 of the rectifier bridge UR is connected to a negative voltage, the sixth diode D6 is turned on, and the voltage at the third input pin IN3 of the rectifier bridge UR is connected to the negative electrode of the rectifier bridge UR through the sixth diode D6 to output a negative voltage.
When the three-phase ac is connected to the rectifier bridge UR, the rectifier bridge UR can output the rectified dc.
Referring to fig. 7, fig. 7 is a block diagram of a grid-connected soft start device according to an embodiment of the present disclosure. In this embodiment, each unit included in the grid-connected soft start device is used to execute each step in the embodiments corresponding to fig. 2 to 3. Please refer to fig. 2 to 3 and fig. 2 to 3 for the corresponding embodiments. For convenience of explanation, only the portions related to the present embodiment are shown. Referring to fig. 7, grid-connected soft start device 80 includes: a sampling unit 81, a phase current control unit 82, and a contactor control unit 83. Wherein:
and the sampling unit 81 is configured to obtain a phase voltage of each phase of the three-phase power grid and a filter capacitor voltage of each phase of the three-phase LCL filter.
And a phase current control unit 82 for independently controlling phase currents input to each phase of the three-phase LCL filter, respectively, to precharge filter capacitors of the three-phase LCL filter.
And the contactor control unit 83 is configured to close the three-phase contactor when the filter capacitor voltage of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid.
In this embodiment, the sampling unit 81 collects line voltages of three input ends of a three-phase contactor, where the line voltages may be line voltages of an unbalanced or balanced power grid, phase voltages of each phase of the three-phase power grid are calculated based on the line voltages, the phase current control unit 82 respectively and independently controls phase currents input to each phase of the three-phase LCL filter to pre-charge filter capacitors of the three-phase LCL filter, and when the filter capacitor voltages of each phase of the three-phase LCL filter 20 are respectively equal to the phase voltages of the corresponding three-phase power grid, the contactor control unit 83 controls the three-phase contactor to be closed, so that grid connection impact is small.
In one embodiment, the sampling unit 81 collects a three-phase line voltage on a network side in real time, provides network phase information through a phase-locking technology, and collects a capacitor voltage on a filter side in real time to obtain a filter capacitor voltage of each phase in a three-phase LCL filter, and further, can detect whether a three-phase contactor is adhered or not through the filter capacitor voltage of each phase.
In a specific application embodiment, after the frequency converter receives the operation command, the grid-connected soft start device 80 operates the grid-side line voltage to obtain an inverter-side soft start voltage reference value (i.e., a phase voltage), the three-phase LCL filter on the inverter side pre-charges under the action of the buffer circuit, the inverter-side voltage reference is slowly increased at this time, the loop operation controls the wave generation to control the pre-charge voltage of each filter capacitor in the three-phase LCL filter to be slowly increased, the voltage of each filter capacitor is equal to the voltage reference value corresponding to the grid-side voltage of the three-phase grid, and at this time, the buffering is completed, the buffer relay is opened, and the three-phase contactor is controlled to be closed, so that grid-connected impact.
Fig. 8 is a block diagram of a grid-connected soft start device 90 according to an embodiment of the present application. As shown in fig. 8, the grid-connected soft start device 90 of this embodiment includes: a processor 91, a memory 92 and a computer program 93, e.g. a program for a grid-connected soft start method, stored in said memory 92 and executable on said processor 91. The processor 91 executes the computer program 93 to implement the steps of each of the embodiments of the grid-connected soft start method, such as S11 to S12 shown in fig. 2. Alternatively, when the processor 91 executes the computer program 93, the functions of the units in the embodiment corresponding to fig. 7, for example, the functions of the units 81 to 83 shown in fig. 7, are implemented, for which reference is specifically made to the relevant description in the embodiment corresponding to fig. 7, which is not repeated herein.
Illustratively, the computer program 93 may be divided into one or more units, which are stored in the memory 92 and executed by the processor 91 to accomplish the present application. The one or more units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution process of the computer program 93 in the grid-connected soft start device 90. For example, the computer program 93 may be divided into a determination unit, an execution unit and a reporting unit, and the specific functions of each unit are as described above.
The grid-connected soft start device 90 may include, but is not limited to, a processor 91 and a memory 92. Those skilled in the art will appreciate that fig. 8 is merely an example of the grid-connected soft start device 90, and does not constitute a limitation of the grid-connected soft start device 90, and may include more or less components than those shown, or combine some components, or different components, for example, the grid-connected soft start device 90 may further include an input-output device, a network access device, a bus, etc.
The Processor 91 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The storage 92 may be an internal storage unit of the grid-connected soft start device 90, such as a hard disk or a memory of the grid-connected soft start device 90. The memory 92 may also be an external storage device of the grid-connected soft start device 90, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), or the like, provided on the grid-connected soft start device 90. Further, the memory 92 may also include both an internal storage unit and an external storage device of the grid-connected soft start device 90. The memory 92 is used for storing the computer program and other programs and data required by the grid-connected soft start device 90. The memory 92 may also be used to temporarily store data that has been output or is to be output.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. A grid-connected soft start method is applied to a grid-connected circuit, the grid-connected circuit comprises a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit which are sequentially connected, wherein the three-phase contactor is connected with a three-phase power grid, the three-phase rectification circuit is connected with an inversion circuit to be incorporated into a power grid load,
the grid-connected soft start method comprises the following steps:
obtaining phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter;
independently controlling phase current input to each phase of the three-phase LCL filter respectively so as to pre-charge a filter capacitor of the three-phase LCL filter;
and when the voltage of the filter capacitor of each phase of the three-phase LCL filter is equal to the phase voltage of the corresponding three-phase power grid, closing the three-phase contactor.
2. The grid-connected soft start method according to claim 1, wherein the obtaining phase voltages of the phases of the three-phase power grid comprises:
acquiring line voltage of the three-phase power grid;
and converting the line voltage of the three-phase power grid according to a preset formula to obtain the phase voltage of each phase of the three-phase power grid.
3. The grid-connected soft start method according to claim 1, wherein the independently controlling the phase current input to each phase of the three-phase LCL filter comprises:
respectively adopting a voltage-current double closed loop to control the phase current of each phase output by the three-phase rectifying circuit;
and performing pulse width modulation on the output current of each voltage-current double closed loop, and inputting the modulated current to the three-phase LCL filter.
4. The grid-connected soft start method according to claim 3, wherein the voltage-current double closed loop comprises a voltage outer loop and a current inner loop;
the method for controlling the phase current of each phase output by the three-phase rectification circuit by adopting the voltage and current double closed loops respectively comprises the following steps:
taking the three-phase power grid phase voltage as the voltage outer loop reference value, and taking the filter capacitor voltage of the three-phase LCL filter as the voltage outer loop feedback value;
taking the current output by the voltage outer ring as the reference value of the current inner ring, and taking the phase current output by the three-phase rectification circuit as the feedback value of the current inner ring;
and taking the output current of the current inner loop as the output current of the voltage-current double closed loop.
5. The grid-connected soft start method according to claim 1, wherein after obtaining the phase voltages of the phases of the three-phase power grid and the filter capacitor voltages of each phase of the three-phase LCL filter, the method further comprises:
and judging whether the three-phase contactor is adhered or not according to the filter capacitor voltage of each phase of the three-phase LCL filter.
6. The grid-connected soft start method according to claim 1, wherein the grid-connected circuit further comprises a bus capacitor, a buffer circuit and a buffer relay connected with the buffer circuit, the bus capacitor is connected in parallel between the inverter circuit and the three-phase rectification circuit, and the inverter circuit to be incorporated into the grid load is connected with the three-phase grid via the buffer circuit and the buffer relay;
before the three-phase contactor is closed, the method further comprises the following steps:
closing the buffer relay to charge the bus capacitor;
and when the bus capacitor finishes charging, the buffer relay is disconnected.
7. The grid-connected soft start method according to claim 1, further comprising, after closing the three-phase contactor:
and obtaining a feedback signal after the three-phase contactor is closed, and adjusting the phase current input to each phase of the three-phase LCL filter according to the feedback signal.
8. A grid-connected soft start device is applied to a grid-connected circuit, the grid-connected circuit comprises a three-phase contactor, a three-phase LCL filter and a three-phase rectification circuit which are sequentially connected, wherein the three-phase contactor is connected with a three-phase power grid, the three-phase rectification circuit is connected with an inversion circuit to be incorporated into a power grid load,
the grid-connected soft start device comprises:
the sampling unit is used for acquiring phase voltages of all phases of the three-phase power grid and filter capacitor voltages of all phases of the three-phase LCL filter;
a phase current control unit which independently controls phase current input to each phase of the three-phase LCL filter to pre-charge a filter capacitor of the three-phase LCL filter;
and the contactor control unit is used for closing the three-phase contactor when the voltage of the filter capacitor of each phase of the three-phase LCL filter is respectively equal to the phase voltage of the corresponding three-phase power grid.
9. A grid-tied soft start device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method of any one of claims 1 to 7.
10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1 to 7.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102916437A (en) * | 2011-12-24 | 2013-02-06 | 许继集团有限公司 | Soft grid connection method of grid-connected converter |
| CN103259282A (en) * | 2013-04-08 | 2013-08-21 | 许继集团有限公司 | Soft cut-in method for non-isolated type photovoltaic grid-connected inverter and isolated type photovoltaic grid-connected inverter |
| CN103915852A (en) * | 2014-04-08 | 2014-07-09 | 中国计量学院 | Flexible switching system based on single-phase grid-connected inverter and switching method thereof |
| CN104300777A (en) * | 2014-11-07 | 2015-01-21 | 深圳市永联科技有限公司 | Inverter synchronous grid connection method |
| CN105896597A (en) * | 2016-04-02 | 2016-08-24 | 深圳朗拓新能源有限公司 | Current stationary coordinate controlled photovoltaic grid connected inversion control method |
| CN111245277A (en) * | 2020-03-30 | 2020-06-05 | 科华恒盛股份有限公司 | Grid-connected inverter starting method, photovoltaic power generation system and terminal equipment |
-
2020
- 2020-12-11 CN CN202011444226.2A patent/CN112701719A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102916437A (en) * | 2011-12-24 | 2013-02-06 | 许继集团有限公司 | Soft grid connection method of grid-connected converter |
| CN103259282A (en) * | 2013-04-08 | 2013-08-21 | 许继集团有限公司 | Soft cut-in method for non-isolated type photovoltaic grid-connected inverter and isolated type photovoltaic grid-connected inverter |
| CN103915852A (en) * | 2014-04-08 | 2014-07-09 | 中国计量学院 | Flexible switching system based on single-phase grid-connected inverter and switching method thereof |
| CN104300777A (en) * | 2014-11-07 | 2015-01-21 | 深圳市永联科技有限公司 | Inverter synchronous grid connection method |
| CN105896597A (en) * | 2016-04-02 | 2016-08-24 | 深圳朗拓新能源有限公司 | Current stationary coordinate controlled photovoltaic grid connected inversion control method |
| CN111245277A (en) * | 2020-03-30 | 2020-06-05 | 科华恒盛股份有限公司 | Grid-connected inverter starting method, photovoltaic power generation system and terminal equipment |
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