CN109768579B - Reliable smooth grid connection method for island energy storage power station - Google Patents
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Abstract
The invention discloses a reliable smooth grid-connection method of an island energy storage power station, wherein the island energy storage power station comprises a photovoltaic power generation device, a storage battery energy storage device and a high-power inverter; the photovoltaic power generation device is controlled by maximum power tracking, the high-power inverter is controlled by a control system through virtual synchronization, and the preset nominal power grid angular frequency omega is usednCorrecting; the phase angle of the output signal of the high-power inverter and the phase angle of the power grid are subjected to phase synchronization, so that the problem of impact on the power grid caused by the fact that the energy storage power station controlled by the virtual synchronizer is connected to the power grid is solved, grid connection impact can be effectively reduced, direct current side lifting in the moment of grid connection is avoided, and normal grid connection and safe and stable operation of the energy storage power station are guaranteed.
Description
Technical Field
The embodiment of the invention relates to the field of power electronics, in particular to a reliable smooth grid connection method for an island energy storage power station.
Background
China has numerous islands and rich resources such as petroleum, fishery, tourism, mineral products and the like which are stored around the islands, most of the islands are distributed in subtropical ocean monsoon climate areas, and renewable energy sources such as solar energy, wave energy, wind energy and the like can be utilized, so that the islands have very important economic and strategic significance. Due to the complementarity of solar energy and wind energy, the island power grid generally integrates wind power and solar power generation, and the intermittence and the fluctuation of single power generation are reduced; the storage battery energy storage system is usually used for maintaining energy balance and ensuring system stability.
At present, most distributed power supplies are connected into a power grid through a high-power inverter, and the high-power inverter is essentially different from a traditional synchronous generator. The high-power inverter has the characteristics of quick dynamic response, small overload capacity, low rotational inertia, low short-circuit capacity and the like, so that the high-power inverter has an influence on the static and dynamic stability of a power grid which is difficult to ignore. Therefore, the virtual synchronous generator technology is adopted, and the characteristics of a body model, active frequency modulation, reactive voltage regulation and the like of the synchronous generator are simulated, so that the inverter can be compared favorably with the traditional synchronous generator in terms of an operation mechanism and external characteristics. However, when the energy storage power station controlled by the virtual synchronous machine is connected to the grid, if proper grid connection preparation is not made, a large impact is brought to the grid, and improper control may cause the impact on the energy storage system caused by the voltage rise on the direct current side of the energy storage power station, so that a reliable smooth grid connection method needs to be researched.
Disclosure of Invention
The invention provides a reliable smooth grid-connection method for an island energy storage power station, which is used for ensuring normal grid-connection, reducing grid-connection impact, avoiding direct-current side lifting at the moment of grid-connection and ensuring normal grid-connection and safe and stable operation.
The embodiment of the invention provides a reliable smooth grid-connection method for an island energy storage power station, wherein the island energy storage power station comprises a photovoltaic power generation device, a storage battery energy storage device and a high-power inverter; the photovoltaic power generation device adopts maximum power tracking control, and the high-power inverter adopts a control system to perform virtual synchronous machine control;
the method comprises the following steps:
for a preset nominal grid angular frequency omeganCorrecting;
and carrying out phase synchronization on the phase angle of the output signal of the high-power inverter and the phase angle of the power grid.
Further, the method further comprises:
collecting output voltage signal v of the high-power invertera、vb、vcAnd output current signal ia、ib、ic；
Calculating the real-time peak value V of the output phase voltage of the high-power inverterp；
For the output voltage signal v of the high-power invertera、vb、vcAnd output current signal ia、ib、icCarrying out coordinate conversion and calculating to obtain instantaneous active power Pe and instantaneous reactive power Q of the high-power invertere；
Real-time peak value V of the output phase voltagepAnd said instantaneous reactive power QeInputting the output voltage amplitude information E to a reactive power controllermThe calculation formula is as follows:
the instantaneous active power PeInputting the active power controller to obtain output voltage phase angle information theta, wherein the calculation formula is as follows:
wherein, ω isrefAs reference frequency, ωnFor a predetermined nominal grid angular frequency, omegavTo output angular frequency, PsetIssuing active commands, Q, for the top layersetIssue none for the top layerWork instruction, DpAs active adjustment factor, DqTo a reactive regulation factor, VnThe effective value of the nominal power grid voltage is obtained, J is an active rotation inertia coefficient, and K is a reactive rotation inertia coefficient;
the pair of preset nominal grid angular frequencies omeganPerforming a correction comprising:
when P is presentsetAt 0, reference angular frequency ωrefFrom nominal grid angular frequency omeganAdding a preset angular frequency correction quantity delta omeganTo prevent the power grid from generating power backflow and cutting off due to frequency fluctuation;
when P is presentsetNot 0, namely when the island energy storage power station receives an active instruction and sends out active power, the reference angular frequency omegarefTaken as the nominal grid angular frequency omeganTo ensure accurate power tracking;
i.e. the reference angular frequency omegarefThe calculation formula of (2) is as follows:
wherein f ismaxTo allow maximum grid frequency, Δ ωnIs a preset angular frequency correction;
the phase synchronization of the phase angle of the output signal of the high-power inverter and the phase angle of the power grid includes:
collecting the phase angle information theta of the power gridgSubtracting the phase angle information theta of the output voltage to obtain a phase angle difference delta theta;
sending the phase angle difference delta theta into a proportion adjustment controller for proportion calculation to obtain an output angular frequency omegavError adjustment amount Δ ω ofv；
Adjusting the error by an amount Δ ωvWith said output angular frequency ωvAnd after addition, performing integral calculation to obtain updated output voltage phase angle information theta ', wherein a calculation formula of the updated output voltage phase angle information theta' is as follows:
according to the updated output voltage phase angle information theta' and output voltage amplitude information EmObtaining a three-phase modulation wave signal;
modulating the three-phase modulation wave signal by using a PWM (pulse-width modulation) modulator to obtain a driving signal, wherein the driving signal is used for controlling the on-off of each phase in the high-power inverter so as to incorporate the high-power inverter into a power grid;
the method further comprises the following steps:
after the high-power inverter is successfully integrated into a power grid, a phase pre-synchronization link is cancelled so as to enable the output angular frequency omega to be in a zero-phase modevError adjustment amount Δ ω ofvSetting the value to be 0 to ensure that the control system works correctly, wherein the calculation formula of the output voltage phase angle information theta is as follows:
further, the grid phase angle information thetagThe method for acquiring the power grid line voltage by adopting the zero-crossing detection comprises the following steps:
when the rising edge zero crossing point of the power grid line voltage is captured, a counter in a power grid phase angle calculation unit in the control system is accumulated according to control frequency, and the value of the counter is represented by n;
during the counter accumulation process, the phase angle theta including three phases of the power grid is determinedga、θgb、θgcThe grid phase angle information thetagPhase angle theta of three phases of said networkga、θgb、θgcThe calculation formula of (2) is as follows:
wherein f iscIs the control frequency; n is the ratio of the control frequency to the grid frequency, expressed as N ═ fc/(ω n2 pi); n is catching the power network cableThe rising edge of the voltage is set to zero 0.
The island energy storage power station comprises a photovoltaic power generation device, a storage battery energy storage device and a high-power inverter; the photovoltaic power generation device is controlled by maximum power tracking, the high-power inverter is controlled by a control system through virtual synchronization, and the preset nominal power grid angular frequency omega is usednCorrecting; the phase angle of the output signal of the high-power inverter is in phase synchronization with the phase angle of a power grid, the problem of impact on the power grid caused by the fact that an energy storage power station controlled by a virtual synchronizer is adopted in grid connection is solved, on the basis of control of the virtual synchronizer, a preset frequency correction quantity and phase synchronization based on zero crossing capture of the power grid are introduced, the high-power inverter can be compared favorably with a traditional synchronous generator in terms of an operation mechanism and external characteristics, and a generator tripping caused by overlarge impact on the power grid cannot be caused in grid connection, meanwhile, impact on an energy storage system caused by direct current side voltage lifting of the energy storage power station can be avoided, safe and reliable operation of the island energy storage power station is guaranteed, and the application.
Drawings
FIG. 1 is a flow chart of a reliable smooth grid connection method for an island energy storage power station according to an embodiment of the present invention;
FIG. 2 is a block diagram of an island energy storage plant in accordance with one embodiment of the present invention;
FIG. 3 is a control schematic diagram of a high power inverter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a zero-crossing detection and capture circuit in accordance with an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Referring to fig. 2-3, the island energy storage power plant includes a photovoltaic power generation apparatus 100, a storage battery energy storage apparatus 200, and a high-power inverter 300; the photovoltaic power generation device 100 adopts maximum power tracking control, and the island energy storage power station further comprises: and the control system 400 is adopted for the high-power inverter 300 to perform virtual synchronous machine control by adopting the control system 400.
Specifically, the photovoltaic power generation apparatus 100 in the present embodiment includes a photovoltaic array and a direct current-to-direct current (DC/DC) converter. The photovoltaic power generation apparatus 100 employs a mature control technology, i.e., Maximum Power Point Tracking (MPPT), commonly used in wind generators and photovoltaic solar systems, and adjusts a working point of a photovoltaic array by changing an equivalent load carried by the photovoltaic array so as to always work near the Maximum power point. The high power inverter 300 in the present embodiment generally refers to an inverter having a power of 50KW or more, and is generally a sine wave inverter. The high-power inverter 300 adopts a virtual synchronous machine control technology, and simulates the traditional synchronous generator from the operation mechanism and external characteristics by simulating the characteristics of a body model, active frequency modulation, reactive voltage regulation and the like of the synchronous generator. The control system 400 in this embodiment is used to control the on/off of the switching tubes in the high power inverter 300, so as to integrate or separate the high power inverter 300 into or from the power grid. Specifically, the control system 400 controls the virtual synchronous machine of the high-power inverter 300.
Further, while the control system 400 performs virtual synchronous control on the high-power inverter 300, the present embodiment solves the problem of impact on the power grid caused by the adoption of the virtual synchronous control when the energy storage power station is connected to the power grid by using the reliable smooth grid connection method of the island energy storage power station. Referring to fig. 1, the method specifically includes the following steps:
s101, aiming at preset nominal power grid angular frequency omeganAnd (6) correcting.
And S102, carrying out phase synchronization on the phase angle of the output signal of the high-power inverter 300 and the phase angle of a power grid.
In this embodiment, on the basis of the virtual synchronous machine control, the preset nominal grid angular frequency ω is adjustednThe phase angle of the output signal of the high-power inverter 300 is synchronized with the phase angle of the grid, so that the output signal is largeThe power inverter 300 can be compared with the traditional synchronous generator in terms of the operation mechanism and external characteristics, and can not cause the tripping due to overlarge impact on the power grid during grid connection, and meanwhile, the impact of the direct-current side voltage lifting of the energy storage power station on the energy storage system can be avoided, the safe and reliable operation of the island energy storage power station is ensured, and the application prospect is wide.
It should be noted that, in this embodiment, before implementing steps S101 and S102, the electrical parameters of the island energy storage power station may be acquired, where the electrical parameters at least include: output voltage amplitude information E of the high power inverter 300mOutput voltage phase angle information theta of high-power inverter 300 and power grid phase angle information thetag. In this embodiment, the output voltage amplitude information E of the high power inverter 300 will be usedmOutput voltage phase angle information theta of high-power inverter 300 and power grid phase angle information thetagAnd waiting the electrical parameters of the island energy storage power station to provide basic data for realizing the reliable smooth grid connection method of the island energy storage power station.
Referring to the control system 400 in fig. 3, the control system 400 is used to implement virtual synchronous machine control of the high power inverter 300. Further, the control system 400 may include: instantaneous power calculation unit 410, zero crossing detection unit 420, phase angle calculation unit 430, reactive power controller 440, active power controller 450, three-phase modulated wave calculation unit 460 and the like.
Further, in this embodiment, the amplitude information E of the output voltage of the high-power inverter 300 can be obtained through the cooperation of the instantaneous power calculation unit 410, the reactive power controller 440 and the active power controller 450mThe output voltage phase angle information θ of the high-power inverter 300 specifically includes the following steps:
1) collecting the output voltage signal v of the high-power inverter 300a、vb、vcAnd output current signal ia、ib、ic。
2) Calculating the real-time peak value V of the output phase voltage of the high-power inverter 300p。
3) For the output voltage signal v of the high power inverter 300a、vb、vcAnd output current signal ia、ib、icCoordinate conversion is carried out, and the instantaneous active power P of the high-power inverter 300 is obtained through calculationeAnd instantaneous reactive power Qe。
4) Real-time peak value V of the output phase voltagepAnd said instantaneous reactive power QeInputting the output voltage amplitude information E to the reactive power controller 440mThe calculation formula is as follows:
5) the instantaneous active power PeThe input to the active power controller 450 obtains the phase angle information θ of the output voltage, and the calculation formula is:
wherein, ω isrefAs reference frequency, ωnFor a predetermined nominal grid angular frequency, omegavTo output angular frequency, PsetIssuing active commands, Q, for the top layersetIssuing a reactive instruction for the top layer, DpAs active adjustment factor, DqTo a reactive regulation factor, VnThe effective value of the nominal power grid voltage is J, the active rotation inertia coefficient is J, and the reactive rotation inertia coefficient is K.
Still further, in this embodiment, the grid phase angle information θgThe acquisition can be carried out by adopting a mode of carrying out zero-crossing detection on the voltage of the power grid line. The line voltage is between two lines of the multiphase power supply system, and the line voltage is the voltage between three-phase outgoing lines of A, B, C by taking three phases as an example. Zero-crossing detection is used to detect the instant when the line voltage is converted from a negative voltage to a positive voltage. In an embodiment, the grid phase angle information θ may be obtained through the matching processing of the zero-crossing detection unit 420 and the phase angle calculation unit 430gThe method specifically comprises the following steps:
1) when a rising edge zero crossing of the grid line voltage is captured, a counter in the grid phase angle calculation unit 430 in the control system 400 is incremented by the control frequency and the value of the counter is denoted by n.
Further, fig. 4 is a schematic diagram of a zero-crossing detection and capture circuit according to an embodiment of the present invention, which can detect and capture a zero-crossing of a rising edge of a grid line voltage through the circuit provided in fig. 4.
2) During the counter accumulation process, the phase angle theta including three phases of the power grid is determinedga、θgb、θgcThe grid phase angle information thetagPhase angle theta of three phases of said networkga、θgb、θgcThe calculation formula of (2) is as follows:
The present embodiment will describe a specific implementation manner of step S101 and step S102 in detail. Specifically, the step S101 may be further detailed as the following steps:
1) when P is presentsetAt 0, reference angular frequency ωrefFrom nominal grid angular frequency omeganAdding a preset angular frequency correction quantity delta omeganSo as to prevent the power grid from being cut off due to the backflow of active power caused by frequency fluctuation.
2) When P is presentsetNot 0, namely when the island energy storage power station receives an active instruction and sends out active power, the reference angular frequency omegarefTaken as the nominal grid angular frequency omeganTo ensure accurate power tracking.
That is, the angular frequency ω is referred torefThe calculation formula of (2) is as follows:
wherein f ismaxTo allowMaximum grid frequency, Δ ωnIs a preset angular frequency correction.
Further, step S102 may be further refined into the following steps:
1) collecting the phase angle information theta of the power gridgAnd subtracting the phase angle information theta of the output voltage to obtain a phase angle difference delta theta.
2) Sending the phase angle difference delta theta into a proportion adjustment controller for proportion calculation to obtain an output angular frequency omegavError adjustment amount Δ ω ofv。
3) Adjusting the error by an amount Δ ωvWith said output angular frequency ωvAnd after addition, performing integral calculation to obtain updated output voltage phase angle information theta ', wherein a calculation formula of the updated output voltage phase angle information theta' is as follows:
4) According to the updated output voltage phase angle information theta' and output voltage amplitude information EmAnd obtaining a three-phase modulation wave signal.
5) And modulating the three-phase modulation wave signal by using a PWM (pulse width modulation) modulator to obtain a driving signal, wherein the driving signal is used for controlling the on-off of each phase in the high-power inverter 300 so as to integrate the high-power inverter 300 into a power grid.
On the basis of the above embodiment, referring to fig. 3, for the active controller 450, after the high-power inverter 300 is successfully incorporated into the power grid, the phase pre-synchronization link is cancelled (the originally tangential "pre-synchronization" switch in fig. 3 is switched to "grid-connected operation"), so as to switch the output angular frequency ω to the output angular frequency ωvError adjustment amount Δ ω ofvSet to 0 to ensure the control system 400 works correctly, and the calculation formula of the output voltage phase angle information θ is as follows:
it is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (2)
1. A reliable smooth grid-connection method of an island energy storage power station is characterized in that the island energy storage power station comprises a photovoltaic power generation device, a storage battery energy storage device and a high-power inverter; the photovoltaic power generation device adopts maximum power tracking control, and the high-power inverter adopts a control system to perform virtual synchronous machine control;
the method comprises the following steps:
for a preset nominal grid angular frequency omeganCorrecting;
carrying out phase synchronization on the phase angle of the output signal of the high-power inverter and the phase angle of a power grid;
the method further comprises the following steps:
collecting output voltage signal v of the high-power invertera、vb、vcAnd output current signal ia、ib、ic；
Calculating the real-time peak value V of the output phase voltage of the high-power inverterp；
For the output voltage signal v of the high-power invertera、vb、vcAnd output current signal ia、ib、icCarrying out coordinate conversion and calculating to obtain the instantaneous active power P of the high-power invertereAnd instantaneous reactive power Qe；
Real-time peak value V of the output phase voltagepAnd the instant messageTime reactive power QeInputting the output voltage amplitude information E to a reactive power controllermThe calculation formula is as follows:
the instantaneous active power PeInputting the active power controller to obtain output voltage phase angle information theta, wherein the calculation formula is as follows:
wherein, ω isrefAs reference frequency, ωnFor a predetermined nominal grid angular frequency, omegavTo output angular frequency, PsetIssuing active commands, Q, for the top layersetIssuing a reactive instruction for the top layer, DpAs active adjustment factor, DqTo a reactive regulation factor, VnThe effective value of the nominal power grid voltage is obtained, J is an active rotation inertia coefficient, and K is a reactive rotation inertia coefficient;
the pair of preset nominal grid angular frequencies omeganPerforming a correction comprising:
when P is presentsetAt 0, reference angular frequency ωrefFrom nominal grid angular frequency omeganAdding a preset angular frequency correction quantity delta omeganTo prevent the power grid from generating power backflow and cutting off due to frequency fluctuation;
when P is presentsetNot 0, namely when the island energy storage power station receives an active instruction and sends out active power, the reference angular frequency omegarefTaken as the nominal grid angular frequency omeganTo ensure accurate power tracking;
i.e. the reference angular frequency omegarefThe calculation formula of (2) is as follows:
wherein f ismaxTo allow maximum grid frequency, Δ ωnIs a preset angular frequency correction;
the phase synchronization of the phase angle of the output signal of the high-power inverter and the phase angle of the power grid includes:
collecting the phase angle information theta of the power gridgSubtracting the phase angle information theta of the output voltage to obtain a phase angle difference delta theta;
sending the phase angle difference delta theta into a proportion adjustment controller for proportion calculation to obtain an output angular frequency omegavError adjustment amount Δ ω ofv；
Adjusting the error by an amount Δ ωvWith said output angular frequency ωvAnd after addition, performing integral calculation to obtain updated output voltage phase angle information theta ', wherein a calculation formula of the updated output voltage phase angle information theta' is as follows:
according to the updated output voltage phase angle information theta' and output voltage amplitude information EmObtaining a three-phase modulation wave signal;
modulating the three-phase modulation wave signal by using a PWM (pulse-width modulation) modulator to obtain a driving signal, wherein the driving signal is used for controlling the on-off of each phase in the high-power inverter so as to incorporate the high-power inverter into a power grid;
the method further comprises the following steps:
after the high-power inverter is successfully integrated into a power grid, a phase pre-synchronization link is cancelled so as to enable the output angular frequency omega to be in a zero-phase modevError adjustment amount Δ ω ofvSetting the value to be 0 to ensure that the control system works correctly, wherein the calculation formula of the output voltage phase angle information theta is as follows:
2. the method of claim 1, wherein the grid phase angle information θgThe method for acquiring the power grid line voltage by adopting the zero-crossing detection comprises the following steps:
when the rising edge zero crossing point of the power grid line voltage is captured, a counter in a power grid phase angle calculation unit in the control system is accumulated according to control frequency, and the value of the counter is represented by n;
during the counter accumulation process, the phase angle theta including three phases of the power grid is determinedga、θgb、θgcThe grid phase angle information thetagPhase angle theta of three phases of said networkga、θgb、θgcThe calculation formula of (2) is as follows:
wherein f iscIs the control frequency; n is the ratio of the control frequency to the grid frequency, expressed as N ═ fc/(ωn2 pi); n is set to 0 when capturing the zero crossing point of the rising edge of the grid line voltage.
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| Virtual impedance-based virtual synchronous generator control for grid-connected inverter under the weak grid situations;Gaoxiang Li等;《IET Power Electronics》;20181101;第11卷(第13期);第1-8页 * |
| 序阻抗视角下虚拟同步发电机与传统并网逆变器的稳定性对比分析;伍文华等;《中国电机工程学报》;20190305;第39卷(第5期);第1411-1420、S16页 * |
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