CN113972687B - Island micro-grid secondary control method based on switching topology - Google Patents
Island micro-grid secondary control method based on switching topology Download PDFInfo
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- CN113972687B CN113972687B CN202111203973.1A CN202111203973A CN113972687B CN 113972687 B CN113972687 B CN 113972687B CN 202111203973 A CN202111203973 A CN 202111203973A CN 113972687 B CN113972687 B CN 113972687B
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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Abstract
The invention discloses a secondary control method of an island micro-grid based on switching topology, which comprises the following steps of S1, taking a mobile emergency generator as a distributed generator for island micro-grid dispatching; s2, designing a fixed time distributed secondary control method to compensate frequency and voltage errors caused by primary control so as to accurately distribute active power; step S3, designing a distributed limited time controller to regulate the voltage and frequency of all distributed generators to a fixed reference level. According to the scheme, the frequency and the voltage of each distributed generator are guaranteed to be restored to the reference level within the limited time through switching the topological structure of the micro-grid, meanwhile, the accurate distribution of active power is realized within the specified limited time, and the robustness of the micro-grid to the sudden extreme conditions is further improved.
Description
Technical Field
The invention relates to the technical field of emergency control of power systems, in particular to a secondary control method of an island micro-grid based on switching topology.
Background
In recent years, natural disasters and the subsequent damaging events have caused a number of serious blackout incidents. For example, hurricane Sandy attacks the east coast of the united states and causes nearly 835 tens of thousands of users to lose power, this outage causing a significant economic loss and a significant threat to life health. This time of accident has led us to the importance of improving the elasticity of power systems, in particular of micro-grid based power distribution systems. The micro-grid may accommodate different types of distributed energy sources (DER), including Mobile Emergency Generators (MEG).
In order to achieve DER coordination, droop control is widely used in electrical systems to provide active damping thereof, while it can lead to frequency and voltage deviations. When any disturbance occurs in the microgrid, the instantaneous frequency varies depending on the disturbance location and the type DER. This difference may impair power sharing between DERs and deteriorate the input of secondary control, which relies on local measurements in a decentralized scheme. The secondary control is implemented using a master controller that gathers and processes information provided by a local controller. Such centralized schemes require powerful communication and computing capabilities, which may be affected by a single point of failure.
Thus, distributed secondary control is applied based on a continuous communication network connecting various distributed energy sources. DER (e.g., natural gas turbine, wind turbine generator, photovoltaic panel) installed in a microgrid is defined herein as a local DER. In addition, mobile Emergency Resources (MERs), typically on-board generators with battery storage, are believed to provide mobility, fast response, and critical flexibility in the formation and regulation of micro-grids. MERs can provide spatial flexibility to enhance the flexibility of the distribution system through the traffic network. By utilizing the redundancy of the mesh structure and the traffic network, the MER can effectively enhance the survivability and the elasticity of the power system. MER integration technology in island micro-networks presents the following challenges:
in view of frequent MER operations (i.e. connection/disconnection) in the micro-grid, the distributed secondary control should provide guaranteed convergence in a limited time, independent of the initial state. Considering the uncertainty of the load and the variability of the DER, the response of the existing scheme under the operation condition of the micro-grid with rapid change is slow, and the convergence speed of the distributed secondary control is generally improved by adopting a convergence control rule in a limited time, wherein the frequency following, the voltage recovery and the active power distribution are realized in the limited time. However, the upper limit of the finite convergence time depends on the initial state of the micro-grid before the control scheme is activated. Therefore, the finite time control scheme cannot ensure whether to converge, as a priori the initial operating state is generally not reachable. In particular, when serious disturbances cause status errors outside a given range, these schemes may be inefficient unless certain event triggering mechanisms are applied. Thus, the upper limit of convergence time should be independent of the initial system state to accommodate frequent MER operations.
Disclosure of Invention
The invention aims to provide an island micro-grid secondary control method based on switching topology, which ensures that the frequency and the voltage of each distributed generator are recovered to the reference level in the limited time through switching the topology structure of the micro-grid, and simultaneously realizes the accurate distribution of active power in the specified limited time, thereby further improving the robustness of the micro-grid to the sudden extreme condition.
In order to achieve the technical purpose, the technical scheme provided by the invention is an island micro-grid secondary control method based on switching topology, which comprises the following steps:
step S1, using a mobile emergency generator as a distributed generator for island micro-grid dispatching;
s2, designing a fixed time distributed secondary control method to compensate frequency and voltage errors caused by primary control so as to accurately distribute active power;
step S3, designing a distributed limited time controller to regulate the voltage and frequency of all distributed generators to a fixed reference level.
According to the scheme, the distributed secondary control problem is formulated by considering the switching topology, because the post-disaster communication topology may become unstable, based on the Lyapunov theory, a distributed control scheme is provided, the frequency of each Distributed Generator (DG) is restored to the reference level in the limited time, meanwhile, the accurate distribution of active power is realized in the specified limited time, the initial deviation generated by primary control is further ignored, the distributed limited time controller is designed to adjust the voltages of all DGs to the reference level, and the robustness of the micro-grid against the sudden extreme condition is further improved.
Preferably, the step S1 includes the steps of:
each island micro-grid area is provided with n distributed generators and a plurality of loads, each generator is provided with a distributed controller, and the n distributed generators are in communication connection with the plurality of loads through the distributed controllers; the topology of the load and distributed generators in the island microgrid is characterized by undirected graphs.
Preferably, step S2 includes the steps of:
s21, adjusting the frequency and the voltage sag amplitude to balance active and reactive demands in the micro-grid, wherein a control loop formula is as follows:
wherein omega i (t) is the angular frequency of DGi, DGi is the ith distributed generator,for primary control reference quantity, m, of DGi angular frequency i Is the falling coefficient of DGi; p (P) i (t) is the measured active power of DGi; />Voltage amplitude of DGi;a primary control reference value for the DGi voltage output; k (k) i Is the pressure drop coefficient of DGi; q (Q) i And (t) is the measured reactive power of DGi.
Preferably, the control strategy of the primary voltage is:
V qi (t)＝0
satisfy the following requirementsIs V di (t) and V qi Sum of squares of (t); the droop control loop formula is:
preferably, the active power allocation comprises the steps of:
at a fixed time T f The internal cancellation frequency and voltage bias is given by:
the accurate active power distribution is realized, and the formula is as follows:
by voltage secondary control of V di (t) can follow a fixed voltage reference value V ref 。
Preferably, the design of the distributed finite time controller includes ensuring frequency following with a frequency recovery method for a fixed time and voltage following with a voltage recovery method for a fixed time.
Preferably, the frequency adjustment input and the active power adjustment input in the frequency recovery method within a fixed time are as follows:
where a and b are positive odd integers such that a < b, α, β, and γ are given positive control gains, sig () is a sign function.
Preferably, the voltage quadratic control formula in the voltage recovery method in the fixed time is as follows:
where ε is a given positive scalar, let e V (t)＝[e V1 (t),e V2 (t),...,e Vn (t)] T ，e Vi (t)＝V di (t)-V ref ,The given quadratic lyapunov function is as follows:
further estimating an upper limit of the settling time; the formula is as follows:
the invention has the beneficial effects that: according to the island micro-grid secondary control method based on the switching topology, the switching topology is considered to formulate a distributed secondary control problem, because the post-disaster communication topology may become unstable, based on the Lyapunov theory, a distributed control scheme is provided, the frequency of each Distributed Generator (DG) is restored to the reference level in the limited time, meanwhile, the accurate distribution of active power is realized in the specified limited time, the initial deviation generated by primary control is further ignored, a distributed limited time controller is designed to regulate the voltage of all DGs to the reference level, and the robustness of the micro-grid in response to the sudden extreme condition is further improved.
Drawings
Fig. 1 is a flow chart of an island micro-grid secondary control method based on switching topology.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples, it being understood that the detailed description herein is merely a preferred embodiment of the present invention, which is intended to illustrate the present invention, and not to limit the scope of the invention, as all other embodiments obtained by those skilled in the art without making any inventive effort fall within the scope of the present invention.
Examples:
as shown in fig. 1, a technical solution is an island micro-grid secondary control method based on switching topology, which is characterized in that: the method comprises the following steps:
step S1, using a mobile emergency generator as a distributed generator for island micro-grid dispatching; each island micro-grid area is provided with n distributed generators and a plurality of loads, each generator is provided with a distributed controller, and the n distributed generators are in communication connection with the plurality of loads through the distributed controllers; the topology of the load and distributed generators in the island microgrid is characterized by undirected graphs.
And S2, designing a fixed time distributed secondary control method to compensate frequency and voltage errors caused by primary control so as to accurately distribute active power.
Step S2 includes the steps of:
s21, adjusting the frequency and the voltage sag amplitude to balance active and reactive demands in the micro-grid, wherein a control loop formula is as follows:
wherein omega i (t) is the angular frequency of DGi, DGi is the ith distributed generator,for primary control reference quantity, m, of DGi angular frequency i Is the falling coefficient of DGi; p (P) i (t) is the measured active power of DGi; v (V) mi (t) is the voltage magnitude of DGi;a primary control reference value for the DGi voltage output; k (k) i Is the pressure drop coefficient of DGi; q (Q) i And (t) is the measured reactive power of DGi.
The control strategy of the primary voltage is:
V qi (t)＝0
satisfy the following requirementsIs V di (t) and V qi Sum of squares of (t); the droop control loop formula is:
the active power allocation comprises the steps of:
at a fixed time T f The internal cancellation frequency and voltage bias is given by:
the accurate active power distribution is realized, and the formula is as follows:
by voltage secondary control of V di (t) can follow a fixed voltage reference value V ref 。
Step S3, designing a distributed limited time controller to regulate the voltage and frequency of all distributed generators to a fixed reference level.
The design of the distributed finite time controller comprises the steps of adopting a frequency recovery method in fixed time to ensure frequency following and adopting a voltage recovery method in fixed time to ensure voltage following.
The frequency adjustment input and the active power adjustment input in the frequency recovery method within a fixed time are as follows:
where a and b are positive odd integers such that a < b, α, β, and γ are given positive control gains, sig () is a sign function.
The voltage secondary control formula in the voltage recovery method in the fixed time is as follows:
where ε is a given positive scalar, let e V (t)＝[e V1 (t),e V2 (t),...,e Vn (t)] T ，e Vi (t)＝V di (t)-V ref ,The given quadratic lyapunov function is as follows:
further estimating an upper limit of the settling time; the formula is as follows:
in this embodiment, the problem of distributed secondary control is formulated by considering the switching topology, because the post-disaster communication topology may become unstable, based on lyapunov theory, a distributed control scheme is proposed, the frequency of each Distributed Generator (DG) is restored to the reference level in a limited time, meanwhile, the active power is accurately distributed in a specified limited time, the initial deviation generated by primary control is further ignored, and the distributed limited time controller is designed to adjust the voltages of all DG to the reference level, so as to further improve the robustness of the micro grid against the sudden extreme condition.
The above embodiments are preferred embodiments of the switching topology-based island micro-grid secondary control method of the present invention, and are not limited to the specific embodiments, but the scope of the present invention is not limited to the specific embodiments, and all equivalent changes of the shape and structure according to the present invention are within the scope of the present invention.
Claims (4)
1. A secondary control method of an island micro-grid based on switching topology is characterized by comprising the following steps: the method comprises the following steps:
step S1, using a mobile emergency generator as a distributed generator for island micro-grid dispatching;
s2, designing a fixed time distributed secondary control method to compensate frequency and voltage errors caused by primary control so as to accurately distribute active power;
step S3, designing a distributed limited time controller to adjust the voltage and frequency of all distributed generators to a fixed reference value level;
the step S2 comprises the following steps:
s21, adjusting the frequency and the voltage sag amplitude to balance active and reactive demands in the micro-grid, wherein a control loop formula is as follows:
wherein omega i (t) is the angular frequency of DGi, DGi is the ith distributed generator,for primary control reference quantity, m, of DGi angular frequency i Is the falling coefficient of DGi; p (P) i (t) is the measured active power of DGi; />Voltage amplitude of DGi; v (V) i * (t) is a primary control reference value for the DGi voltage output; k (k) i Is the pressure drop coefficient of DGi; q (Q) i (t) is the measured reactive power of DGi; the design of the distributed finite time controller comprises the steps of adopting a frequency recovery method in fixed time to ensure frequency following and adopting a voltage recovery method in fixed time to ensure voltage following;
the frequency adjustment input and the active power adjustment input in the frequency recovery method within a fixed time are as follows:
where a and b are positive odd integers such that a < b, α, β, and γ are given positive control gains, sig () is a sign function;
the voltage secondary control formula in the voltage recovery method in the fixed time is as follows:
where ε is a given positive scalar, let e V (t)＝[e V1 (t),e V2 (t),...,e Vn (t)] T ，The given quadratic lyapunov function is as follows:
and further an upper limit of the settling time is estimated.
2. The island micro-grid secondary control method based on switching topology according to claim 1, wherein the island micro-grid secondary control method based on switching topology is characterized in that:
step S1 comprises the steps of:
each island micro-grid area is provided with n distributed generators and a plurality of loads, each generator is provided with a distributed controller, and the n distributed generators are in communication connection with the plurality of loads through the distributed controllers; the topology of the load and distributed generators in the island microgrid is characterized by undirected graphs.
3. The island micro-grid secondary control method based on switching topology according to claim 1, wherein the island micro-grid secondary control method based on switching topology is characterized in that:
the control strategy of the primary voltage is:
V di (t)＝V i * (t)-k i Q i (t)
V qi (t)＝0
satisfy the following requirementsIs V di (t) and V qi Sum of squares of (t); the droop control loop formula is:
V di (t)＝V i * (t)-k i Q i (t)。
4. the island micro-grid secondary control method based on switching topology according to claim 1, wherein the island micro-grid secondary control method based on switching topology is characterized in that:
the active power allocation comprises the steps of:
at a fixed time T f The internal cancellation frequency and voltage bias is given by:
the accurate active power distribution is realized, and the formula is as follows:
by voltage secondary control of V di (t) can follow a fixed voltage reference value V ref 。
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| CN107465211A (en) * | 2017-09-06 | 2017-12-12 | 重庆大学 | The distributed set time control method for coordinating of isolated island micro-capacitance sensor |
| EP3591784A1 (en) * | 2018-07-06 | 2020-01-08 | ENSEA - Ecole Nationale Supérieure de l'Electronique et de ses Applications | Active electrical compensation device |
| CN110768289A (en) * | 2019-09-29 | 2020-02-07 | 哈尔滨工程大学 | Self-adaptive containment control method for voltage and frequency of island type microgrid |
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