Compressed air energy storage wind power hybrid system and virtual synchronous control method thereof
Technical Field
The invention belongs to the field of wind power generation and energy storage, and particularly relates to a compressed air energy storage wind power hybrid system and a virtual synchronous control method thereof.
Background
At present, distributed wind power projects are developed in various regions in China according to local conditions. The distributed access wind power project is a wind power project which is located near a load center and aims at large-scale long-distance power transmission, and generated power is accessed to a local power grid nearby for consumption. The distributed access wind power project has the following characteristics:
(1) the existing transformer substation and the existing transmission line of the power grid are utilized, and no new transmission line and power transmission and transformation facilities are built;
(2) a step-down transformer connected to a local power system at 110 kV or below 66 kV;
(3) the installed capacity of the project unit is not more than the minimum load of the existing substation of the accessed power grid in principle, and multipoint access is encouraged;
(4) the total installed capacity of the project is lower than 5 ten thousand kilowatts.
With the connection of distributed wind power and small wind power in various regions to a power grid in large batch, the disadvantages that the peak load regulation and frequency modulation capabilities are weak, the inertia of the power grid matched with the capacity cannot be provided are gradually amplified, and even the stability of the regional power grid is affected.
Disclosure of Invention
The invention aims to provide a compressed air energy storage wind power hybrid system and a virtual synchronous control method thereof, and aims to solve the problems of poor distributed wind power, small wind power peak shaving and frequency modulation capability in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a compressed air energy storage wind power hybrid system comprises a wind power system and an air energy storage power generation system, wherein the wind power system and the air energy storage power generation system are converged on a direct current bus and are connected to a power grid through a bidirectional grid side converter and a step-up transformer in sequence; when the output power of the wind power system can not be absorbed by the power grid, the electric energy is stored in the air energy storage power generation system, and when the output power of the fan is lower, the electric energy is fed back to the power grid through the air energy storage power generation system.
Specifically, the air energy storage power generation system comprises an air compression system and an expansion power generation system, wherein the air compression system and the expansion power generation system are connected to a direct current bus through a bidirectional energy storage side converter.
Specifically, the air compression system comprises a compressor system and a compressed air energy storage device, wherein the compressor system is used for compressing air into the compressed air energy storage device by using electric energy which cannot be absorbed by a power grid.
Specifically, the expansion power generation system comprises an air expansion power generator, and the air expansion power generator is communicated with the compressed air energy storage device and is used for generating power by utilizing compressed air in the compressed air energy storage device.
Specifically, the wind power system comprises a wind turbine generator and a rectifier, and the wind turbine generator is connected to a direct current bus through the rectifier.
Specifically, the direct current bus is a 1200V direct current bus.
The invention provides another technical scheme that:
a virtual synchronous control method of a compressed air energy storage wind power hybrid system comprises the following steps:
setting the current frequency f of the power grid and the target nominal frequency f of the power grid as f0Generating a frequency deviation signal delta f by taking the difference;
the frequency deviation signal delta f is used as an input signal to a primary frequency modulation controller with a built-in droop curve to obtain an output power command signal Pref;
Will output the power command signal PrefInputting the signal into a virtual synchronous simulation module with a built-in inertia link to simulate the inertia response characteristic of a common synchronous generator to obtain an output power instruction signal P after the virtual synchronous simulation linkref2;
Will output the power command signal Pref2And inputting a control system power reference value input end of the hybrid system to complete the virtual synchronization control function of the converter.
Specifically, the power command signal P is outputref2The calculation method of (c) is as follows:
in the formula: t is P from the last momentref2The time elapsed since the instruction was issued; h is a first-order inertia link coefficient; k is a first order inertia ratio coefficient; j is a virtual rotational inertia value.
Specifically, the power output command signal PrefThe calculation method of (c) is as follows:
in the formula: pmaxThe maximum power output capacity of the hybrid system; pminIs the minimum power output capability of the hybrid system; f. ofmaxThe maximum operation power of the system; f is the current frequency of the power grid; f. of0Is the target nominal frequency.
Specifically, the control system of the hybrid system is a master controller of the wind power system and the compressed air energy storage power generation system, and is used for sending instructions to the wind power system controller and the compressed air energy storage power generation system controller respectively to realize the control of the whole power output.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the hybrid system provided by the embodiment of the invention, the small compressed air energy storage is matched with the wind generating set, so that the utilization efficiency of wind energy is effectively improved, when wind power is generated greatly, the compressed air energy storage stores redundant wind energy in a compressed air mode, and the wind power is released when the wind power output is insufficient, so that the output stability and the schedulability of distributed wind power generation are enhanced.
2. The virtual synchronous control method of the hybrid system provided by the embodiment of the invention is applied to the bidirectional network side converter of the wind power-compressed air energy storage hybrid system, can effectively control the bidirectional power output of the hybrid system, reduces the cost for the grid connection of the compression system and the expansion system, and improves the energy utilization efficiency.
3. The virtual synchronous reference power generation method and the virtual synchronous reference power generation logic effectively simulate the primary frequency modulation response characteristic of a synchronous machine with any rotational inertia within the range of energy storage response capacity, thereby improving the rotational inertia of the whole system in a power grid and providing inertial support for the operation of the power grid.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a structure diagram of a compressed air energy storage wind power hybrid system according to an embodiment of the present invention.
Fig. 2 is a diagram showing a virtual synchronization algorithm of the hybrid system according to the embodiment of the present invention.
FIG. 3 is a graph showing the primary frequency modulation curve of the hybrid system according to the embodiment of the present invention.
FIG. 4 is a schematic diagram of the overall controller control of the hybrid system in an embodiment of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The following detailed description is exemplary in nature and is intended to provide further details of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.
The embodiment of the invention provides a compressed air energy storage wind power hybrid system and a virtual synchronous control method thereof, which are used for matching wind power with energy storage and introducing a virtual synchronous inertia control method, so that peak clipping and valley filling can be effectively performed on wind power output. Meanwhile, the output of the large synchronous motor can be accurately simulated by adjusting the inertia parameters of the virtual system, so that the stability of the synchronous power grid is enhanced.
As shown in fig. 1, a compressed air energy storage wind power hybrid system includes a wind power system and an air energy storage power generation system, both the wind power system and the air energy storage power generation system converge on a 1200V DC bus, and are sequentially connected to a grid bus through a DC/AC bidirectional grid-side converter and a step-up transformer.
In this embodiment, the wind power system includes a wind turbine and a rectifier, and the wind turbine is connected to the dc bus through the rectifier. The air energy storage power generation system comprises an air compression system and an expansion power generation system, wherein the air compression system and the expansion power generation system are connected to a direct current bus through an AC/DC bidirectional energy storage side converter. The air compression system comprises a compressor system and a compressed air energy storage device, wherein the compressor system is used for compressing air into the compressed air energy storage device by utilizing electric energy which cannot be absorbed by a power grid. The expansion power generation system comprises an air expansion power generator which is communicated with the compressed air energy storage device and used for generating power by utilizing compressed air in the compressed air energy storage device.
When the output power of the wind power system is higher, the electric energy can be stored in the compressed air energy storage device through the compressor system, and when the output power of the wind power system is lower, the air expansion generator utilizes the compressed air in the compressed air energy storage device to generate electricity and feed back to the power grid, so that the purpose of stabilizing the wind power output fluctuation is achieved.
The virtual synchronous control method of the compressed air energy storage wind power hybrid system in the invention is described in detail below with reference to fig. 2 and 3, and comprises the following steps:
s1, setting the target nominal frequency f required to be achieved by grid connection of the alternating current power grid0The bidirectional network side converter collects the current frequency f of the grid-connected point power grid, and the current frequency f of the power grid and the target nominal frequency of the power grid are set as f0A frequency deviation signal Deltaf is generated by subtracting.
S2, using the frequency deviation signal delta f as input signal to the primary frequency modulation controller with built-in droop curve, obtaining the output power command signal P by the curve corresponding method of figure 3ref;
Power output command signal PrefThe calculation method of (c) is as follows:
in the formula: pmaxThe maximum power output capacity of the hybrid system; pminIs the minimum power output capability of the hybrid system; f. ofmaxThe maximum operation power of the system; f is the current frequency of the power grid; f. of0Is the target nominal frequency.
S3, outputting power command signal PrefInputting the signal into a virtual synchronous simulation module with a built-in inertia link to simulate the inertia response characteristic of a common synchronous generator to obtain an output power instruction signal P after the virtual synchronous simulation linkref2;
Output power command signal Pref2The calculation method of (c) is as follows:
in the formula: t is P from the last momentref2The time of the command sending start is second; h is a first-order inertia link coefficient; k is a first order inertia ratio coefficient; j is a virtual rotational inertia value with the unit of kg.m2。
S4, outputting power command signal Pref2And inputting a control system power reference value input end of the hybrid system to complete the virtual synchronization control function of the converter. As shown in fig. 4, in this embodiment, the control system of the hybrid system is a master controller of the wind power system and the compressed air energy storage power generation system, such as a bidirectional grid-side converter, and is used for sending instructions to the wind power system controller, such as a rectifier, and the compressed air energy storage power generation system controller, such as the bidirectional energy storage-side converter, respectively, so as to control the overall power output.
It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.