CN117175704A - Distributed power tracking control method for aggregation energy storage cluster - Google Patents
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Abstract
The invention discloses a distributed power tracking control method for an aggregation energy storage cluster, and belongs to the field of electrical engineering. The method comprises the following steps: obtaining power error variables of an aggregator and each energy storage unit in the aggregate energy storage cluster based on a discrete average dynamic consistency algorithm; updating respective power state variables according to the power error variables of the aggregator and each energy storage unit; calculating an energy coefficient related to the remaining adjustment energy of each energy storage unit according to the charge state, the energy capacity and the actual output power of the energy storage unit; and comparing the product of the energy coefficient related to the residual energy adjustment of each energy storage unit, the cost coefficient related to the charge and discharge cost and the power state variable with the upper limit and the lower limit of the active power of the energy storage unit to determine the active reference power of the energy storage unit. Accurate total power tracking can be achieved without measuring the total power of the energy storage clusters, and a more efficient and low-cost power distribution scheme can be obtained.
Description
Technical Field
The invention belongs to the field of electrical engineering, and particularly relates to a distributed power tracking control method for an aggregation energy storage cluster.
Background
Renewable energy sources such as photovoltaic and wind energy are connected to provide clean and sustainable power supply for a power grid, however, the intermittence and randomness of the renewable energy sources provide challenges for power balance of a power system. In the case of continuously increasing permeability of renewable energy sources, power regulation is an indispensable capability of an electric power system to compensate for power fluctuations and to maintain reliable operation of the system. In a traditional power system, a synchronous generator is a main active power regulating device in the power system, and in a modern power system, an energy storage system has high response speed and is an effective power regulating support mode. For large energy storage systems with capacity up to several MWh, the market operation is generally directly affected by the energy storage power station, but for small-capacity distributed energy storage systems, the individual contribution is small, but a large number of small-scale distributed energy storage systems still have considerable scheduling capability for power adjustment of the power system. In order to achieve the aggregation of a large number of small-scale energy storage systems, an energy storage system aggregation system is introduced. By the energy storage cluster aggregator, the energy storage system follows the collective control objective, thereby representing an aggregated large-scale energy storage cluster to the upper layer.
Unlike large energy storage systems, where the internal connections are tight, distributed energy storage, which is geographically dispersed, of varying states and parameters, presents challenges to the control of the energy storage system. The centralized control structure is an effective method for the energy storage system aggregator to realize the control of the energy storage system. However, the central communication infrastructure employed limits the flexibility of implementation. In addition, this approach suffers from poor plug and play performance and inherent privacy exposure. In contrast, distributed control has received attention as an alternative to coordinated centralized control of energy storage systems. In distributed control, individuals need only communicate with neighbors to collectively achieve a particular global control objective. Distributed control thus has advantages in terms of achieving flexibility, plug-and-play performance, and privacy protection over centralized control. In terms of power distribution, the energy storage system aggregator controls the energy storage units to track the power references, employing distributed control of the leader-follower, with the energy storage system aggregator acting as the leader and the energy storage units acting as the follower. However, unlike the common leader-follower control approach, the goal of distributed power tracking control is to track external instructions by the sum of follower states rather than by the follower states themselves. In addition, in terms of power allocation of the energy storage units, the complementary characteristics, capacities and SoC states of the different energy storage systems are different, which results in different power allocation methods.
Disclosure of Invention
Aiming at the blank of the prior art, the invention provides a distributed power tracking control method aiming at an aggregation energy storage cluster, so that the aggregation energy storage cluster accurately tracks a given total power reference value, and a power distribution scheme for determining each energy storage unit by considering different types, soC levels and capacity differences is provided.
To achieve the above object, according to a first aspect of the present invention, there is provided a distributed power tracking control method for an aggregated energy storage cluster, including:
obtaining power error variables of an aggregator and each energy storage unit in the aggregate energy storage cluster based on a discrete average dynamic consistency algorithm;
updating respective power state variables according to the power error variables of the aggregator and each energy storage unit, wherein the power state variables are related to corresponding active reference power;
calculating an energy coefficient related to the remaining adjustment energy of each energy storage unit according to the charge state, the energy capacity and the actual output power of the energy storage unit;
and comparing the product of the energy coefficient related to the residual energy adjustment of each energy storage unit, the cost coefficient related to the charge and discharge cost and the power state variable with the upper limit and the lower limit of the active power of the energy storage unit to determine the active reference power of the energy storage unit.
Further, the power error variable θ of the aggregator and each energy storage unit i Expressed as:
where k is the number of iterations, P r,k (k) Is given a total power reference value, P e,i (k) Is the actual output power of the i-th energy storage unit, the subscript i=1, n e Numbering the energy storage units, n e For the total number of energy storage units, the subscript i=0 denotes the aggregator, z c,i (k) Is an intermediate variable;
wherein h is c For controlling the sampling interval of the mode g p As a first proportional parameter, N i A, numbering a collection of energy storage units ij A is the communication weight between the ith and jth energy storage units ij > 0 represents a communication link between two energy storage units, a ij And =0 indicates that there is no communication link between the two energy storage units.
Further, the power state variable x of the aggregator and each energy storage unit p,i Expressed as:
wherein g θ 、g x The second proportion parameter and the third proportion parameter are respectively.
Further, an energy coefficient k related to the remaining adjustment energy of the ith energy storage unit soc,i Expressed as:
wherein, soC i SoC for the state of charge of the i-th energy storage cell min,i 、SoC max,i Is SoC i Upper and lower limit of E e,i For the energy capacity of the ith energy storage cell, P e,i Is the actual output power of the ith energy storage cell.
Further, the active reference power P of the ith energy storage cell r,i Expressed as:
wherein k is p,i ＝k soc,i k cost,i ，k cost,i P is a cost coefficient related to the charge and discharge cost of the ith energy storage unit max,i 、P min,i The upper limit value and the lower limit value of the active power of the ith energy storage unit, x p,i Is the power state variable of the ith energy storage cell.
According to a second aspect of the present invention, there is provided a distributed power tracking control system for an aggregated energy storage cluster, comprising: a processor; a memory storing a computer executable program which, when executed by the processor, causes the processor to perform the distributed power tracking control method for an aggregated energy storage cluster as described in the first aspect.
According to a third aspect of the present invention, there is provided a computer readable storage medium having stored thereon a computer program, characterized in that the program, when executed by a processor, implements the distributed power tracking control method for an aggregated energy storage cluster as described in the first aspect.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
the invention provides a distributed power tracking control method aiming at an aggregation energy storage cluster, and the power error variables of an aggregator and each energy storage unit in the aggregation energy storage cluster are obtained based on a discrete average dynamic consistency algorithm, so that when the convergence requirement of the average dynamic consistency algorithm is met, the power error variables of the energy storage cluster aggregator and the energy storage unit are converged to a consistent value, and due to the property of a Laplace matrix, the steady state value of the power error variable is skillfully converged to the average value of the difference value between the actual total power value of the energy storage cluster and the given total power reference value, and the accurate total power tracking can be realized under the condition that the total power of the energy storage cluster is not measured. Meanwhile, the cost, capacity level and SoC state of the energy storage unit are considered, a reasonable active reference power distribution method of the energy storage unit is provided, and the method can be applied to a plurality of types of energy storage systems, so that a more effective and low-cost power distribution scheme is obtained.
Drawings
FIG. 1 is a flow chart of a distributed power tracking control method for an aggregated energy storage cluster provided by the invention;
FIG. 2 is a diagram of an IEEE Standard 33 node system for use with the simulation example provided by the present invention;
FIG. 3 is a block diagram of a distributed power tracking control method for an aggregate storage cluster according to the present invention;
FIG. 4 shows the total power response curve of the stored energy and the power curve and SOC curve of each energy storage unit in the embodiment of the invention;
FIG. 5 is a graph showing the estimated power tracking error values of each energy storage unit and the power state variables of each energy storage unit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
In the present invention, the terms "first," "second," and the like in the description and in the drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
Referring to fig. 1, the invention provides a distributed power tracking control method for an aggregation energy storage cluster, which comprises the following steps:
s1, obtaining power error variables of an aggregator and each energy storage unit in the aggregate energy storage cluster based on a discrete average dynamic consistency algorithm.
Power error variable θ for aggregator and each energy storage cell i Expressed as:
where k is the number of iterations, P r,k (k) Is given a total power reference value, P e,i (k) Is the actual output power of the i-th energy storage unit, the subscript i=1, n e Numbering the energy storage units, n e For the total number of energy storage units, the subscript i=0 denotes the aggregator, z c,i (k) Is an intermediate variable;
wherein h is c For controlling the sampling interval of the mode g p For the first proportional parameter (by adjusting the proportional parameter g p Thereby adjusting the sampling interval), N i A, numbering a collection of energy storage units ij A is the communication weight between the ith and jth energy storage units ij > 0 represents a communication link between two energy storage units, a ij And =0 indicates that there is no communication link between the two energy storage units.
By the above definition, when the convergence requirement of the average dynamic consistency algorithm is met, the power error variables of the energy storage cluster aggregator and the energy storage units are converged to a consistent value, and due to the property of the Laplace matrix, the power error variable theta i The steady state value of the energy storage cluster is skillfully converged to the average value of the difference value between the actual total power value of the energy storage cluster and the given total power reference value, so that accurate total power tracking can be realized under the condition that the total power of the energy storage cluster is not measured.
S2, updating respective power state variables according to the power error variables of the aggregator and each energy storage unit, wherein the power state variables are related to corresponding active reference power.
Power error variable θ according to S1 i The power state variables of the energy storage cluster aggregator and each energy storage unit are updated as follows:
wherein g θ 、g x Respectively a second proportion parameter and a third proportion parameter (likewise by adjusting proportion parameter g θ 、g x Thereby adjusting the sampling interval), x p,i Is the power state variable of the ith energy storage cell. By the mode, the initial distribution of the power instructions of the energy storage units can be realized, and the power error variable theta of the energy storage units is controlled i And realizing power tracking.
And S3, calculating an energy coefficient related to the residual regulation energy of each energy storage unit according to the charge state, the energy capacity and the actual output power of each energy storage unit.
Setting an energy coefficient k related to the remaining regulation energy of the energy storage units according to the charge state, the energy capacity and the actual output power of each energy storage unit soc,i Power allocation is performed. k (k) soc,i The coefficients are defined as follows:
wherein, soC i SoC for the state of charge of the i-th energy storage cell min,i 、SoC max,i Is SoC i Upper and lower limit of E e,i For the energy capacity of the ith energy storage cell, P e,i Is the actual output power of the ith energy storage cell. By definition of the coefficient, discharge in the energy storage unit, i.e. P e,i When the SoC value is more than or equal to 0, the energy storage unit with large capacity and high SoC value bears more output tasks, and ensures that the SoC value of the energy storage unit after discharging is not lower than the lowest SoC value limit;charging the energy storage unit, i.e. P e,i When the SoC value of the energy storage unit is less than the highest SoC value limit, the safety and the rationality of the charging and discharging process of the energy storage system are ensured.
S4, comparing the product of the energy coefficient related to the residual energy adjustment of each energy storage unit, the cost coefficient related to the charge and discharge cost and the power state variable with the upper limit and the lower limit of the active power of the energy storage unit to determine the active reference power of the energy storage unit.
The power state variable x obtained from S2 p,i The energy coefficient k obtained in S3 soc,i Taking the upper and lower limit values of the power of each energy storage unit, different types of cost and adjustment energy into consideration, obtaining corresponding power reference values according to the following modes:
wherein k is p,i ＝k soc,i k cost,i ，k cost,i P is a cost coefficient related to the charge and discharge cost of the ith energy storage unit max,i 、P min,i The upper limit value and the lower limit value of the active power of the ith energy storage unit, x p,i Is the power state variable of the ith energy storage cell. And ensuring that each energy storage unit in the energy storage cluster performs output distribution according to a certain proportion within a threshold range.
The control method of the present invention is verified in the IEEE standard 33 node system as shown in fig. 2, and the control method is shown in fig. 3. The bus system shown in fig. 2 includes 8 energy storage units, which are respectively installed on different buses, and the 8 energy storage units are divided into two types: type I energy storage units with long time scales of action and type II energy storage units with short time scales of action of energy storage. In this example, the type I and type II energy storage unit capacities were set at 100kW/100kWh and 100kW/2kWh. And authorizing the energy storage system aggregator to perform power tracking control on the energy storage units in the energy storage cluster. The communication link is used to support information interaction between the energy storage system aggregator and the energy storage unit. Each energy storage unit operates in a power control mode with a phase-locked loop, the sampling time interval is 10ms, and the system simulation parameters are shown in table 1.
Table 1 system simulation parameters
The control effect of the present invention was tested by randomly varying the total reference power reference value. In fig. 4 (a) is a system simulated power response, and from fig. 4 (a), it can be seen that the actual total power of the system can quickly track a given total power command. Furthermore, the single power trace in fig. 4 (b) indicates the power distribution between the single energy storage units in the energy storage cluster, and from fig. 4 (b), different types of energy storage units can be found, and the power distribution results are also different. The SoC traces of type I and type II are shown in fig. 4 (c) and (d), and the solid line and the dotted line are SoC variation processes of type I and type II energy storage units, respectively, and the total power distribution trend is different for different types of energy storage units. Due to the influence of the cost coefficient, the type II energy storage unit has quicker response power compared with the type I energy storage unit, so that the SoC of the corresponding type II energy storage unit changes more obviously. For the same type of energy storage unit, the power distribution ratio is different due to the fact that the real-time state and the preset energy capacity are different. Taking the energy storage unit 8 as an example, the SoC state value of the energy storage unit 8 is higher in the type I energy storage unit, so that compared with other type I energy storage units, the energy storage unit 8 has the greatest released power in the discharging process and the smallest power in the charging process. A similar distribution relationship is also embodied in the type II energy storage unit, as shown in (d) of fig. 4, the energy storage unit 6 and the energy storage unit 7 gradually decrease, so that SoC balance can be respectively realized according to different types of energy storage. During t=10s-16 s, the output power of some energy storage units reaches a critical value, but the power tracking and power distribution during this time are valid.
Fig. 5 shows a power error variable and a power state variable under the control method of the present invention, and (a) in fig. 5 reflects an average estimated value of a power tracking error, so that it can be found that the power error variable converges to zero in a steady state, thereby achieving the power tracking purpose. In fig. 5 (b), the change of the power state variable of each energy storage unit is reflected, and it can be found that the power state variable of each energy storage unit dynamically changes with the change of the total reference power and converges to be uniform. The convergence and equalization of the proposed distributed controller is thus verified.
Claims (7)
1. A distributed power tracking control method for an aggregate storage cluster, comprising:
obtaining power error variables of an aggregator and each energy storage unit in the aggregate energy storage cluster based on a discrete average dynamic consistency algorithm;
updating respective power state variables according to the power error variables of the aggregator and each energy storage unit, wherein the power state variables are related to corresponding active reference power;
calculating an energy coefficient related to the remaining adjustment energy of each energy storage unit according to the charge state, the energy capacity and the actual output power of the energy storage unit;
and comparing the product of the energy coefficient related to the residual energy adjustment of each energy storage unit, the cost coefficient related to the charge and discharge cost and the power state variable with the upper limit and the lower limit of the active power of the energy storage unit to determine the active reference power of the energy storage unit.
2. The distributed power tracking control method for an aggregated energy storage cluster according to claim 1, wherein the power error variable θ of the aggregator and each energy storage unit i Expressed as:
where k is the number of iterations, P r,k (k) Is given a total power reference value, P e,i (k) Is the actual output power of the i-th energy storage unit, the subscript i=1, n e Numbering the energy storage units, n e For the total number of energy storage units,subscript i=0 denotes an aggregator, z c,i (k) Is an intermediate variable;
wherein h is c For controlling the sampling interval of the mode g p As a first proportional parameter, N i A, numbering a collection of energy storage units ij A is the communication weight between the ith and jth energy storage units ij > 0 represents a communication link between two energy storage units, a ij And =0 indicates that there is no communication link between the two energy storage units.
3. A distributed power tracking control method for an aggregated energy storage cluster according to claim 2, characterized by an aggregated and per energy storage unit power state variable x p,i Expressed as:
wherein g θ 、g x The second proportion parameter and the third proportion parameter are respectively.
4. The distributed power tracking control method for an aggregated energy storage cluster according to claim 1, characterized by an energy coefficient k related to the i-th energy storage unit remaining adjustment energy soc,i Expressed as:
wherein, soC i SoC for the state of charge of the i-th energy storage cell min,i 、SoC max,i Is SoC i Upper and lower limit of E e,i For the energy capacity of the ith energy storage cell, P e,i For the actual output power of the ith energy storage cell。
5. The method of distributed power tracking control for an aggregated energy storage cluster as defined in claim 4, wherein the active reference power P of the ith energy storage unit r,i Expressed as:
wherein k is p,i ＝k soc,i k cost,i ，k cost,i P is a cost coefficient related to the charge and discharge cost of the ith energy storage unit max,i 、P min,i The upper limit value and the lower limit value of the active power of the ith energy storage unit, x p,i Is the power state variable of the ith energy storage cell.
6. A distributed power tracking control system for an aggregate storage cluster, comprising:
a processor;
a memory storing a computer executable program that when executed by the processor causes the processor to perform the distributed power tracking control method for an aggregated energy storage cluster of any of claims 1-5.
7. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements a distributed power tracking control method for an aggregated energy storage cluster according to any of claims 1-5.
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