CN113629765A - Multi-mode operation control system of optical storage virtual synchronous machine - Google Patents
Multi-mode operation control system of optical storage virtual synchronous machine Download PDFInfo
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- H—ELECTRICITY
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- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
- H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a multi-mode operation control system of a light storage virtual synchronous machine, which belongs to the technical field of new energy power generation and comprises a photovoltaic unit, an energy storage unit, a unidirectional DC/DC converter unit, a bidirectional DC/DC converter unit, a VSG voltage type grid-connected inverter unit, an LCL filter unit, an active-frequency control unit and a power grid unit; the output end of the photovoltaic unit is electrically connected with the unidirectional DC/DC converter unit, the output end of the unidirectional DC/DC converter unit is electrically connected with the VSG voltage type grid-connected inverter unit, the output end of the energy storage unit is electrically connected with the bidirectional DC/DC converter unit, and the VSG voltage type grid-connected inverter unit changes the operation mode under the control of PWM, so that the control of different operation modes of the light storage system is realized. The invention provides an all-weather and all-state solution for the VSG virtual synchronous machine, provides a novel solution for new energy grid connection, and is beneficial to the consumption of new energy.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a multi-mode operation control system of a light storage virtual synchronous machine.
Background
At present, new energy power generation enters a large-scale application stage, inertia is an important parameter of a power system and plays a vital role on frequency, inertia power cannot be provided by photovoltaic, so that the inertia of a photovoltaic high-proportion power grid is greatly weakened, and in order to solve the problem of insufficient inertia of the power system, a virtual synchronous motor is provided by students. The existing research is developed from the angles of the light storage VSG realization principle, the capacity configuration and the limit parameters, different operation modes of the light storage VSG are not considered, and the improvement of the energy storage service life is not considered.
Meanwhile, the photovoltaic unit and the energy storage unit which are relatively cheap are integrated by the light storage system, and the expensive cost for setting the energy storage unit is greatly reduced, so that the current method for providing inertia for the power grid by using the light storage system is an effective way for improving the energy storage economy.
In order to have different operation modes according to different energy storage configuration capacities and function locations, the optical storage VSG may have different operation modes, and therefore, it is necessary to develop a multi-mode operation control system for an optical storage virtual synchronous machine.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a multi-mode operation control system of an optical storage virtual synchronous machine, which can effectively realize the control of different operation modes of an optical storage system by means of different operation modes of an optical storage VSG and operation control strategies thereof.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a multi-mode operation control system of a light storage virtual synchronous machine comprises a photovoltaic unit, an energy storage unit, a unidirectional DC/DC converter unit, a bidirectional DC/DC converter unit, a VSG voltage type grid-connected inverter unit, an LCL filter unit, an active-frequency control unit and a power grid unit;
the output end of the photovoltaic unit is electrically connected with the unidirectional DC/DC converter unit, and the output end of the unidirectional DC/DC converter unit is electrically connected with the VSG voltage type grid-connected inverter unit; the output end of the VSG voltage type grid-connected inverter unit is electrically connected with the LCL filter unit, the output end of the LCL filter unit is electrically connected with the power grid unit, and the output end of the power grid unit is electrically connected with the ground;
the output end of the energy storage unit is electrically connected with the bidirectional DC/DC converter unit, and the output end and the input end of the bidirectional DC/DC converter unit are respectively and electrically connected with the output end and the input end of the VSG voltage type grid-connected inverter unit;
the input end of the VSG voltage type grid-connected inverter unit is also electrically connected with PWM, and the input end of the PWM is electrically connected with the active-frequency control unit; the output end of the LCL filter unit is also electrically connected with the input end of the active-frequency control unit;
the photovoltaic unit transmits electric energy to the VSG voltage type grid-connected inverter unit through the unidirectional DC/DC converter unit, and the VSG voltage type grid-connected inverter unit enters the power grid unit through the LCL filter unit; the VSG voltage type grid-connected inverter unit enables electric power to enter the energy storage unit through the bidirectional DC/DC converter unit; in order to control the constant voltage and the power balance of the bus, the energy storage unit transmits electric energy to the VSG voltage type grid-connected inverter unit through the bidirectional DC/DC converter unit and is connected with the power grid unit through the LCL filter unit;
and the VSG voltage type grid-connected inverter unit changes the working mode under the control of PWM, thereby realizing the control of different running modes of the system.
The technical scheme of the invention is further improved as follows: the VSG voltage grid-connected inverter in the VSG voltage grid-connected inverter unit has four working modes: a constant power VSG mode, a tracking photovoltaic VSG mode, a zero power VSG mode and a unidirectional VSG mode; the constant-power VSG mode and the tracking photovoltaic VSG mode are two basic operation modes of a VSG voltage type grid-connected inverter, and the zero-power VSG mode and the unidirectional VSG mode are two derivative operation modes of the VSG voltage type grid-connected inverter; two basic operation modes of the VSG voltage grid-connected inverter are determined based on the initial charge state of the energy storage unit, and two derivative operation modes of the VSG inverter are determined based on weather conditions and the power distribution and power upper limit conditions of the whole system.
The technical scheme of the invention is further improved as follows: the energy storage capacity is obtained by measuring the charge state of the energy storage unit, the current energy storage capacity is compared with the configured energy storage capacity, and if the current energy storage capacity is larger than the configured energy storage capacity, the VSG voltage type grid-connected inverter works in a constant power VSG mode; if the current energy storage capacity is smaller than the configured energy storage capacity, the VSG voltage type grid-connected inverter works in a photovoltaic tracking VSG mode; whether the given power of active power is 0 or not is obtained through observing weather data and the existence or nonexistence of illumination, and if the given power of active power is 0, the VSG voltage type grid-connected inverter works in a zero-power VSG inverter working mode; by measuring the power data of an energy storage unit, a photovoltaic unit, a VSG voltage grid-connected inverter unit, a load unit and a power grid unit in the whole microgrid, when the operating point of the VSG voltage grid-connected inverter reaches the upper power limit, the optical storage system can only respond to the frequency rise caused by negative disturbance of the power grid, virtual inertia for inhibiting the frequency rise is generated, the frequency reduction caused by positive disturbance of the power grid cannot be responded, and at the moment, the VSG voltage grid-connected inverter works in a one-way VSG mode.
The technical scheme of the invention is further improved as follows: the capacitance value of the energy storage unit is 220-150000 mu F, and the capacitor of the energy storage unit is a can-shaped spiral terminal capacitor; in order to ensure that the energy storage unit has enough electric energy burden, the energy storage configuration capacity in a constant power VSG mode is large enough to balance the photovoltaic output peak-valley change and can participate in the peak regulation of a power grid, and the VSG voltage type grid-connected inverter can output power according to the given power, is equivalent to a controllable power supply and can respond to the frequency change of the power grid; the configuration capacity of energy storage under the photovoltaic VSG tracking mode is small, the configuration capacity is mainly used for stabilizing the random fluctuation of photovoltaic output, and the output power of the grid-connected inverter under the steady-state operation is required to track the photovoltaic output value after the energy storage stabilization; meanwhile, the VSG voltage type grid-connected inverter can still provide inertia and damping for a power grid, but the system cannot provide primary frequency modulation capability due to small energy storage capacity; the zero-power VSG mode is an operation mode in which the reference power of the light storage system in the constant-power VSG mode is zero or the photovoltaic VSG mode is tracked to provide virtual inertia and damping in an operation state that the photovoltaic output is close to zero at night or in rainy days, the virtual inertia and the damping can be provided, and the VSG voltage type grid-connected inverter is required to have a bidirectional characteristic; when the operating point of the VSG voltage type grid-connected inverter or the energy storage converter reaches the upper power limit in the unidirectional VSG mode, the optical storage system can only respond to the frequency increase caused by the negative disturbance of the power grid, generates virtual inertia for inhibiting the frequency increase, and cannot respond to the frequency decrease caused by the positive disturbance of the power grid.
The technical scheme of the invention is further improved as follows: the energy storage unit adopts a typical PI control mode of a voltage outer ring current inner ring, the photovoltaic capacity in the photovoltaic unit is 250kW, the power of the energy storage unit is 250kW, the power of the VSG voltage type grid-connected inverter unit is 500kW, and the power grid capacity is twenty times of the photovoltaic unit capacity.
The technical scheme of the invention is further improved as follows: the photovoltaic unit is made of single crystal silicon.
The technical scheme of the invention is further improved as follows: the rated input voltage of the bidirectional DC/DC converter unit is 0-DC 300V, and the rated output voltage is 0-DC 600V.
The technical scheme of the invention is further improved as follows: the bidirectional DC/DC converter unit comprises a voltage sampling unit and a current sampling unit; one path of the voltage sampling unit is input voltage, the other path of the voltage sampling unit is output voltage, the accuracy is 5%, the response time is less than 40 microseconds, and the frequency is 200 Hz; one path of the current sampling unit is input current, the other path of the current sampling unit is output current, the accuracy is 5%, the response time is less than 1 mu s, and the frequency is 100 Hz.
The technical scheme of the invention is further improved as follows: the voltage sampling unit and the current sampling unit both adopt Hall current sensors.
Due to the adoption of the technical scheme, the invention has the technical progress that:
1. in order to enhance the inertia of a power grid and improve the frequency characteristic of the power grid, the four VSG operation modes and power are coordinated with each other, four working modes of a VSG grid-connected inverter are formed on the basis of the control of a traditional virtual synchronous machine, and the VSG grid-connected inverter can well respond to the frequency change of the power grid and output inertia power in a constant power mode; under the photovoltaic tracking mode, the power of the VSG grid-connected inverter can well track the change condition of the photovoltaic; the zero power mode provides a resolvable solution for bad weather conditions and the system working at night; the unidirectional VSG grid-connected inverter provides a solution at extreme power conditions.
2. The photovoltaic unit converts light energy into electric energy through single crystal silicon, the electric energy enters the unidirectional DC/DC converter unit through electric connection, then the unidirectional DC/DC converter unit enters the VSG voltage type grid-connected inverter unit through electric connection, then the VSG voltage type grid-connected inverter unit enters the power grid unit through the LCL filter unit, the VSG voltage type grid-connected inverter unit enables the electric power to enter the energy storage unit through the bidirectional DC/DC converter unit, and in order to control the bus voltage to be constant and the power balance, the energy storage unit transmits the electric energy to the VSG voltage type grid-connected inverter unit.
3. According to the invention, the output end and the input end of the bidirectional DC/DC converter unit are respectively and electrically connected with the output end and the input end of the VSG voltage type grid-connected inverter unit, the output end of the power grid unit is electrically connected with the ground, and the output end of the LCL filter unit is electrically connected with the input end of the active-frequency control unit, so that mutual power transmission between the energy storage unit and the VSG voltage type grid-connected inverter unit can be realized, and meanwhile, the damage of power leakage to the whole equipment is avoided.
4. The energy storage unit adopts a bidirectional DC/DC converter unit, can perform energy storage charging and discharging bidirectional power exchange and control constant bus voltage and power balance, the photovoltaic unit works in a maximum power tracking mode under the normal working condition, in order to realize mutual balance between the photovoltaic unit and the energy storage unit, the light energy generated by the photovoltaic unit is utilized to a greater extent, and meanwhile, the working stability between the energy storage assembly and each link is maintained.
5. The photovoltaic unit is made of single crystal silicon, the output end of the LCL filter unit is electrically connected with the power grid unit, the high efficiency of the photovoltaic unit in the stage of converting solar radiation into electric energy can be improved, the LCL filter unit has an independent working effect, and meanwhile, the electricity can be utilized and converted in a storage mode.
6. According to the invention, the photovoltaic unit with relatively low price and the energy storage unit are integrated, so that the expensive cost for arranging the energy storage unit is greatly reduced, and the purpose of providing inertia for a power grid by using an optical storage system to improve the economy of energy storage is realized.
7. The invention provides an all-weather and all-state solution for the VSG virtual synchronous machine, provides a novel solution for new energy grid connection, and is beneficial to the consumption of new energy.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a block diagram of VSG control logic in the present invention;
FIG. 3 is a graph of load, generator, VSG power in a constant power mode of the present invention;
FIG. 4 is a graph of load, generator, VSG power in the tracking photovoltaic mode of the present invention;
FIG. 5 is a load, generator, VSG power curve for the 0 power mode of the present invention;
FIG. 6 is a graph of the charging power of the energy storage battery in the present invention;
FIG. 7 is a graph of energy storage cell discharge power in accordance with the present invention;
the photovoltaic grid-connected inverter comprises a photovoltaic unit 1, a photovoltaic unit 2, an energy storage unit 3, a unidirectional DC/DC converter unit 4, a bidirectional DC/DC converter unit, a VSG voltage type grid-connected inverter unit 5, a LCL filter unit 6, an active-frequency control unit 7, an active-frequency control unit 8 and a power grid unit.
Detailed Description
The invention is described in further detail below with reference to the following figures and examples:
as shown in fig. 1, a multi-mode operation control system of a virtual synchronous machine for optical storage (hereinafter referred to as an optical storage system) includes a photovoltaic unit 1, an energy storage unit 2, a unidirectional DC/DC converter unit 3, a bidirectional DC/DC converter unit 4, a VSG voltage type grid-connected inverter unit 5, an LCL filter unit 6, an active-frequency control unit 7, and a power grid unit 8;
the output end of the photovoltaic unit 1 is electrically connected with the unidirectional DC/DC converter unit 3, the output end of the unidirectional DC/DC converter unit 3 is electrically connected with the VSG voltage type grid-connected inverter unit 5, the output end of the energy storage unit 2 is electrically connected with the bidirectional DC/DC converter unit 4, the input end of the VSG voltage type grid-connected inverter unit 5 is electrically connected with PWM, the input end of the PWM is electrically connected with the active-frequency control unit 7, the output end of the VSG voltage type grid-connected inverter unit 5 is electrically connected with the LCL filter unit 6, and the output end of the LCL filter unit 6 is electrically connected with the grid unit 8.
The VSG controller in fig. 1 refers to four operation modes of the VSG voltage source grid-connected inverter.
The PWM is an abbreviation of Pulse Width ModulaTIon, and changes the Pulse Width of the Pulse sequence according to a certain rule to adjust the output quantity and the waveform.
The output end and the input end of the bidirectional DC/DC converter unit 4 are respectively and electrically connected with the output end and the input end of the VSG voltage type grid-connected inverter unit 5, the output end of the power grid unit 8 is electrically connected with the ground, and the output end of the LCL filter unit 6 is electrically connected with the input end of the active power-frequency control unit 7, so that the mutual power transmission between the energy storage unit 2 and the VSG voltage type grid-connected inverter unit 5 is realized, and meanwhile, the damage of power leakage to the whole equipment is avoided.
As shown in fig. 1, specifically: s1-S6Form a three-phase inverter bridge and an inverter side inductor LsFilter capacitor C, and network side inductor LgForm LCL-type filters, RsEquivalent series resistance, i, representing filter and grid-connected inverterabcFor the measured value of the three-phase current signal at the grid-connected end, uabcFor measured values of three-phase voltage signals at the grid-connected end, three-phase voltage signals uabcAnd three-phase current signal iabcPassing through workThe power calculation unit obtains the active power P output by the VSGeReactive power Qe，PsetGiven value of active power, QsetGiven value of reactive power, active power PeReactive power QeGiven value of active power PsetGiven value of reactive power QsetThe four power signals are processed by VSG control algorithm to obtain three-phase modulation wave signal eamebmecmAfter passing through a PWM modulator, Q is obtained1-Q6And the drive signals of the six switching tubes control the on-off of the IGBT of the full-control device.
Wherein P isPVGenerating power for photovoltaic units, PinvOutput power command value, P, for VSG voltage type grid-connected inverter unitSCFor charging power command of the energy storage unit, LF is a low-pass filter for filtering fluctuation of photovoltaic power, PrefThe power reference value of the light storage system is determined by the power grid regulation and control center according to the economic dispatching principle. i.e. iabcFor the measured value of the three-phase current signal at the grid-connected end, uabcThe measured value is a three-phase voltage signal measured value of a grid-connected end. Real-time voltage u measurement of optical storage systemabcAnd current iabcValue, voltage signal uabcAnd a current signal iabcThe active power P output by the VSG is obtained through the power calculation uniteReactive power Qe，PsetGiven value of active power, QsetThe given value of reactive power.
As shown in fig. 2, the active loop of the VSG simulates the inertia and primary frequency modulation characteristics of the synchronous generator, and the expression of the inertia equation is:
in the formula, K is the droop coefficient of active power, omega is the angular frequency of VSG, omeganAt a nominal angular frequency, ωGThe angular frequency of the power grid side, J is the virtual moment of inertia, D is the virtual damping coefficient, and the inverter side inductance L1Simulating the synchronous reactance of a synchronous generator, ea，ebAnd ecSimulates synchronous power generationInternal potential of the machine, PPVFor photovoltaic power generation, PinvOutput power command value, P, for VSG voltage type grid-connected inverterSCIs a charging power command of the energy storage unit, LF is a low pass filter,
for filtering out fluctuations in photovoltaic power, PrefIs the power reference value of the light storage system and is determined by a power grid regulation and control center according to an economic dispatching principle, PsetGiven value of active power, PeActive power output for the VSG.
As shown in fig. 1, the energy storage unit 2 adopts a bidirectional DC/DC converter unit 4, which can perform energy storage charging, discharging bidirectional power exchange and control of bus voltage constancy and power balance, the photovoltaic unit 1 works in a maximum power tracking manner under normal operation conditions, in order to realize mutual balance between the photovoltaic unit 1 and the energy storage unit 2, so that the light energy generated by the photovoltaic unit 1 is utilized more, and meanwhile, the stability of work between the energy storage assembly and each link is maintained, the capacitance value of the energy storage unit 2 is 220-150000 muf, and the capacitor of the energy storage unit 2 is a can-shaped spiral terminal capacitor.
As shown in fig. 2, there are four modes of the VSG voltage grid-connected inverter unit 5, which are a constant-power VSG mode, a tracking photovoltaic VSG mode, a zero-power VSG mode, and a unidirectional VSG mode.
When the switch is at the position 1, the VSG voltage type grid-connected inverter operates according to a constant power VSG mode;
in order to ensure that the energy storage unit 2 has enough electric energy burden, the energy storage configuration capacity in the constant power VSG mode is very large; the output power instruction of the VSG voltage grid-connected inverter in the mode is Pinv＝Pref+K(ωnω) from the power reference value P of the optical storage systemrefAnd primary frequency modulation power K (omega)n- ω) of the power reference value PrefThe power grid regulation and control center determines according to an economic dispatching principle, a dispatcher remotely controls the switch selector, a switch action instruction is issued through a communication network, and a substation worker can manually complete the operation; output power P of energy storage unit 2SCCommanding photovoltaic output and inverter outputForming a difference; the VSG voltage grid-connected inverter can output power according to given power, is equivalent to a controllable power supply, and can respond to the change of the grid frequency.
As shown in fig. 2, when the switch is in position 2, the VSG voltage grid-connected inverter operates in a tracking photovoltaic VSG mode; if the configuration capacity of the stored energy is small, the stored energy is mainly used for stabilizing the random fluctuation of the photovoltaic output, and the output power of the VSG grid-connected inverter under the steady-state operation is required to track the photovoltaic output value after the energy storage stabilization; in the mode, the light storage system obtains a smooth power curve through a low-pass filter link, and the power is used as an output instruction of the grid-connected inverter; the photovoltaic power fluctuation component is used as the charging command power P of the energy storage unit 2SCThe photovoltaic is stabilized; the VSG voltage grid-connected inverter can still provide inertia and damping for a power grid, but the system cannot provide primary frequency modulation capability due to small energy storage capacity.
As shown in FIG. 2, when the switch is at position 1, the power reference value P of the optical storage system is zero when the power reference value given by the dispatching command is zero, or the weather condition is bad, or the power reference value P is at nightrefAnd the voltage source grid-connected inverter VSG is 0, and the voltage source grid-connected inverter VSG runs in a zero-power VSG mode.
When the switch is at the position 2, and when the operating point of the VSG voltage grid-connected inverter or the energy storage converter reaches the upper power limit, the optical storage system can only respond to the frequency increase caused by the negative disturbance of the power grid, so that the virtual inertia for inhibiting the frequency increase is generated, the frequency reduction caused by the positive disturbance of the power grid cannot be responded, and the VSG voltage grid-connected inverter operates according to a unidirectional VSG mode.
As shown in fig. 1, the energy storage unit 2 adopts a typical PI control mode of voltage outer loop current inner loop, the photovoltaic capacity in the photovoltaic unit 1 is 250kW, the power of the energy storage unit 2 is 250kW, the VSG voltage type grid-connected inverter unit 5 is 500kW, and the power grid capacity is twenty times of the capacity of the photovoltaic unit, in order to maintain the light storage DC bus voltage, the real-time balance of the energy storage, the photovoltaic and the inverter power can be indirectly realized through the bus voltage control, when the bus voltage is a parameter to realize the power balance, the bus voltage fluctuation is large, and simultaneously the safety of the load stage of the VSG voltage type grid-connected inverter unit 5 is ensured, the rated input voltage of the bidirectional DC/DC converter unit 4 is 0-DC 300V, the rated output voltage is 0-DC 600V, and the bidirectional DC/DC converter unit 4 includes a voltage sampling unit and a current sampling unit, and one path of the voltage sampling unit inputs voltage, another way output voltage, the accuracy is 5%, response time is less than 40 mus, the frequency is 200Hz, current sampling unit, input current all the way, another way output current, the accuracy is 5%, response time is less than 1 mus, the frequency is 100Hz, and voltage sampling unit and current sampling unit all adopt hall current sensor, the flexibility of system has been increased, the power supply wiring of being convenient for, the photovoltaic unit material is single crystalline silicon, LCL filter unit 6's output electricity is connected with the electric wire netting, in order to improve photovoltaic unit 1 and be converting the solar radiation into the high efficiency of electric energy stage, possess the effect of independent work simultaneously, realize the utilization conversion of electric power restorage simultaneously.
Examples
When the system is used, as shown in fig. 1 and fig. 2, the optical storage virtual synchronous machine multi-mode operation control system (hereinafter referred to as optical storage system) operates in a constant power mode, and the VSG inertia parameter J is 2.0 × 104kg.m2Reference value of power Pset150kW, 150kW and 350kW power are provided to the load respectively by the light storage system before disturbance and the electric wire netting, dynamic power is provided to the load by the light storage VSG and the electric wire netting together at the moment of disturbance, the sum of the two is 800kW, the light storage power is restored to the original value of 150kW after stabilization, the load increment is completely transferred to the electric wire netting for bearing, the VSG can respond to the frequency change of the electric wire netting and output inertia power, and the power curve is shown in figure 3.
When the inertia of the VSG is increased, the grid frequency reduction speed, the dynamic frequency deviation and the recovery speed under the same disturbance are all reduced. Under the above conditions, the light storage system operates in a tracking photovoltaic mode, the initial photovoltaic output power is 150kW, the photovoltaic power at the 20s moment is suddenly changed to 200kW, the photovoltaic power at the 40s moment is suddenly changed to 250kW, and the power curve is shown in fig. 4.
And then, the optical storage system is enabled to work in a tracking photovoltaic mode, the photovoltaic power is 0, the optical storage system is in a zero power mode, the energy storage power is 0 in a normal state because the VSG is in the zero power mode, but certain inertia power is released by energy storage at the moment of disturbance to participate in disturbance stabilization, and a power curve is shown in fig. 5.
When the energy storage charge capacity is lower than the lower limit or higher than the upper limit, the optical storage system operates according to a designated mode and generates VSG dynamic power, and additionally has energy storage charge-discharge power, the lower limit and the upper limit allowed value of the energy storage charge capacity in simulation are respectively set to be 20% and 80%, the actual energy storage charge capacity is respectively set to be 15% and 85%, when the energy storage charge state exceeds the limit, a control link can correctly control energy storage charge-discharge, and the optical storage VSG can still respond to load disturbance to adjust inertia power in the charge-discharge process, so that different operation modes and operation control strategies of the optical storage VSG are realized, and the control of different operation modes of the optical storage system can be effectively realized. The energy storage charging power is shown in fig. 6, the energy storage discharging power is shown in fig. 7, and the load sudden change occurs at the moment of 30 s.
In summary, on the basis of the control of the traditional virtual synchronous machine, four working modes of the VSG grid-connected inverter are formed, and in the constant power mode, the VSG grid-connected inverter can well respond to the frequency change of the power grid and output inertial power; under the photovoltaic tracking mode, the power of the VSG grid-connected inverter can well track the change condition of the photovoltaic; the zero power mode provides a resolvable solution for bad weather conditions and the system working at night; the unidirectional VSG grid-connected inverter provides a solution under the limit power state, provides a novel solution for new energy grid connection, and is beneficial to the consumption of new energy.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical scope of the present invention and the equivalent alternatives or modifications according to the technical solution and the inventive concept of the present invention within the technical scope of the present invention.
Claims (9)
1. A multi-mode operation control system of an optical storage virtual synchronous machine is characterized in that: the photovoltaic grid-connected inverter comprises a photovoltaic unit (1), an energy storage unit (2), a unidirectional DC/DC converter unit (3), a bidirectional DC/DC converter unit (4), a VSG voltage type grid-connected inverter unit (5), an LCL filter unit (6), an active-frequency control unit (7) and a power grid unit (8);
the output end of the photovoltaic unit (1) is electrically connected with the unidirectional DC/DC converter unit (3), the output end of the unidirectional DC/DC converter unit (3) is electrically connected with the VSG voltage type grid-connected inverter unit (5), the output end of the VSG voltage type grid-connected inverter unit (5) is electrically connected with the LCL filter unit (6), the output end of the LCL filter unit (6) is electrically connected with the power grid unit (8), and the output end of the power grid unit (8) is electrically connected with the ground;
the output end of the energy storage unit (2) is electrically connected with the bidirectional DC/DC converter unit (3), and the output end and the input end of the bidirectional DC/DC converter unit (4) are respectively and electrically connected with the output end and the input end of the VSG voltage type grid-connected inverter unit (5);
the input end of the VSG voltage type grid-connected inverter unit (5) is also electrically connected with PWM, and the input end of the PWM is electrically connected with an active-frequency control unit (7); the output end of the LCL filter unit (6) is also electrically connected with the input end of the active-frequency control unit (7);
the photovoltaic unit (1) transmits electric energy to the VSG voltage type grid-connected inverter unit (5) through the unidirectional DC/DC converter unit (3), and the VSG voltage type grid-connected inverter unit (5) enters the power grid unit (8) through the LCL filter unit (6); the VSG voltage type grid-connected inverter unit (5) enables electric power to enter the energy storage unit (2) through the bidirectional DC/DC converter unit (4); in order to control the constant bus voltage and the power balance, the energy storage unit (2) transmits electric energy to the VSG voltage type grid-connected inverter unit (5) through the bidirectional DC/DC converter unit (4) and is connected with the power grid unit (8) through the LCL filter unit (6);
and the VSG voltage type grid-connected inverter unit (5) changes the working mode under the PWM control, so that the control of different running modes of the system is realized.
2. The system according to claim 1, wherein the system comprises: the VSG voltage grid-connected inverter in the VSG voltage grid-connected inverter unit (5) has four working modes: a constant power VSG mode, a tracking photovoltaic VSG mode, a zero power VSG mode and a unidirectional VSG mode; the constant-power VSG mode and the tracking photovoltaic VSG mode are two basic operation modes of a VSG voltage type grid-connected inverter, and the zero-power VSG mode and the unidirectional VSG mode are two derivative operation modes of the VSG voltage type grid-connected inverter; two basic operation modes of the VSG voltage grid-connected inverter are determined based on the initial charge state of the energy storage unit (2), and two derivative operation modes of the VSG inverter are determined based on weather conditions and the power distribution and power upper limit conditions of the whole system.
3. The system according to claim 2, wherein the system comprises: the energy storage capacity is obtained by measuring the charge state of the energy storage unit (2), the current energy storage capacity is compared with the configured energy storage capacity, and if the current energy storage capacity is larger than the configured energy storage capacity, the VSG voltage type grid-connected inverter works in a constant power VSG mode; if the current energy storage capacity is smaller than the configured energy storage capacity, the VSG voltage type grid-connected inverter works in a photovoltaic tracking VSG mode; whether the given power of active power is 0 or not is obtained through observing weather data and the existence or nonexistence of illumination, and if the given power of active power is 0, the VSG voltage type grid-connected inverter works in a zero-power VSG inverter working mode; by measuring power data of an energy storage unit (2), a photovoltaic unit (1), a VSG voltage grid-connected inverter unit (5), a load unit and a power grid unit (8) in the whole microgrid, when the operating point of the VSG voltage grid-connected inverter reaches the upper power limit, the optical storage system can only respond to frequency rise caused by negative disturbance of the power grid, virtual inertia for inhibiting the frequency rise is generated, frequency reduction caused by positive disturbance of the power grid cannot be responded, and the VSG voltage grid-connected inverter works in a unidirectional VSG mode at the moment.
4. The system according to claim 3, wherein the system comprises: the capacitance value of the energy storage unit (2) is 220-150000 mu F, and the capacitor of the energy storage unit (2) is a can-shaped spiral terminal capacitor; in order to ensure that the energy storage unit (2) has enough electric energy burden, the energy storage configuration capacity in a constant power VSG mode is large enough to balance the photovoltaic output peak-valley change and can participate in the peak regulation of a power grid, and the VSG voltage type grid-connected inverter can output power according to the given power, is equivalent to a controllable power supply and can respond to the frequency change of the power grid; the configuration capacity of energy storage under the photovoltaic VSG tracking mode is small, the configuration capacity is mainly used for stabilizing the random fluctuation of photovoltaic output, and the output power of the grid-connected inverter under the steady-state operation is required to track the photovoltaic output value after the energy storage stabilization; meanwhile, the VSG voltage type grid-connected inverter can still provide inertia and damping for a power grid, but the system cannot provide primary frequency modulation capability due to small energy storage capacity; the zero-power VSG mode is an operation mode in which the reference power of the light storage system in the constant-power VSG mode is zero or the photovoltaic VSG mode is tracked to provide virtual inertia and damping in an operation state that the photovoltaic output is close to zero at night or in rainy days, the virtual inertia and the damping can be provided, and the VSG voltage type grid-connected inverter is required to have a bidirectional characteristic; when the operating point of the VSG voltage type grid-connected inverter or the energy storage converter reaches the upper power limit in the unidirectional VSG mode, the optical storage system can only respond to the frequency increase caused by the negative disturbance of the power grid, generates virtual inertia for inhibiting the frequency increase, and cannot respond to the frequency decrease caused by the positive disturbance of the power grid.
5. The system for controlling the multi-mode operation of the optical storage virtual synchronous machine according to any one of claims 1 to 4, wherein: the energy storage unit (2) adopts a typical PI control mode of a voltage outer ring current inner ring, the photovoltaic capacity in the photovoltaic unit (1) is 250kW, the power of the energy storage unit (2) is 250kW, the power of the VSG voltage type grid-connected inverter unit (5) is 500kW, and the power grid capacity (8) is twenty times of the capacity of the photovoltaic unit (1).
6. The system for controlling the multi-mode operation of the optical storage virtual synchronous machine according to any one of claims 1 to 4, wherein: the photovoltaic unit (1) is made of single crystal silicon.
7. The system for controlling the multi-mode operation of the optical storage virtual synchronous machine according to any one of claims 1 to 4, wherein: the rated input voltage of the bidirectional DC/DC converter unit (4) is 0-DC 300V, and the rated output voltage is 0-DC 600V.
8. The system according to claim 7, wherein the system comprises: the bidirectional DC/DC converter unit (4) comprises a voltage sampling unit and a current sampling unit; one path of the voltage sampling unit is input voltage, the other path of the voltage sampling unit is output voltage, the accuracy is 5%, the response time is less than 40 microseconds, and the frequency is 200 Hz; one path of the current sampling unit is input current, the other path of the current sampling unit is output current, the accuracy is 5%, the response time is less than 1 mu s, and the frequency is 100 Hz.
9. The system according to claim 8, wherein the system comprises: the voltage sampling unit and the current sampling unit both adopt Hall current sensors.
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