Low voltage area energy storage coordination control method and system applied to power outage events

Abstract

The present invention provides a method and system for coordinated control of low-voltage energy storage in power outage events, the method comprising: mathematically modeling the power transmission characteristics of the low-voltage area to form the voltage and frequency coupling problem under the environment of the dominant characteristics of the distribution line resistance; establishing a voltage and frequency autonomous stability control method suitable for the network characteristics of the low-voltage area; proposing a balance adjustment coefficient to construct a virtual balanced active power; constructing a consistency average estimator based on a consistency algorithm to estimate the state of charge and the average value of the virtual balanced active power; constructing a virtual balanced active power secondary control loop to adjust the output active power of the distributed energy storage unit, and realize the rapid balance of the state of charge of each distributed energy storage unit and the equal distribution of active power. The distributed energy storage units of the present invention dynamically adjust their respective active power outputs through coordination and cooperation, realize dynamic SoC balance under the premise of inconsistent initial SoC, and finally ensure the load equalization effect.

Description

Technical Field

[0001] The present invention relates to the technical field of emergency power supply and energy management of low-voltage areas in distribution networks, and in particular to a method and system for coordinated control of energy storage in low-voltage areas applied in power outage events. Background Art

[0002] Line failures, tripping caused by internal user failures, and tripping caused by transformer overloads have led to frequent power outages in low-voltage distribution areas, which has seriously affected the reliability of power supply. Distributed energy storage units have considerable energy storage capacity, and as manufacturing costs are further controlled, they are increasingly appearing in the public eye. The capacity of distributed energy storage units generally ranges from tens of kWh to hundreds of kWh. The deployment of several distributed energy storage units in the low-voltage distribution area of ​​the distribution network can provide emergency power supply in a timely manner in the event of a sudden power outage in the distribution area, ensuring the safety of electricity use for users, especially important users. In the event of a power outage in a low-voltage distribution area, the distribution area is in an isolated grid operation state, and its energy supply can be supplied by the energy storage unit for a short time, thereby smoothly transitioning to normal power supply recovery. However, how to achieve coordinated control of multiple distributed energy storage units and achieve balanced control of the state of charge still requires an effective solution. Summary of the invention

[0003] In view of this, in order to solve the above-mentioned problems in the prior art, the present invention proposes a low-voltage substation energy storage coordination control method and system for use in power outage events, so as to achieve rapid balancing of the charge state of each distributed energy storage unit and equal distribution of active power.

[0004] The present invention solves the above problems by the following technical means:

[0005] On the one hand, the present invention provides a low voltage area energy storage coordinated control method applied to a power outage event, comprising the following steps:

[0006] Step S1, based on the port voltage phasor and the line impedance, a transmission power mathematical expression is established to obtain the power coupling characteristics of the low-voltage area;

[0007] Step S2: establishing a mathematical expression for improving the droop control rate of the distributed energy storage unit based on the power coupling characteristics of the low-voltage area;

[0008] Step S3: Based on the state of charge of the distributed energy storage unit and the global state of charge average value, a balancing adjustment coefficient is proposed to establish a virtual balanced active power;

[0009] Step S4: construct a consistency average estimator using a consistency algorithm to estimate the average values ​​of the virtual balanced active power and the state of charge;

[0010] Step S5: Establish a virtual balanced active power secondary control loop, and output a voltage amplitude compensation amount of the modified droop control loop.

[0011] As a supplement to the above technical solution, the mathematical expression of the transmission power in step S1 is as follows:

[0012]

[0013]

[0014] In the above formula, E s 、E c are the output voltage amplitude of the energy storage unit and the voltage amplitude of the grid connection point, θ s With θ c is the output voltage phase of the energy storage unit and the grid connection point voltage phase, Z line is the line impedance, P and Q are the active power and reactive power transmitted by the line respectively, Re and Im represent the real part and the imaginary part respectively.

[0015] As a supplement to the above technical solution, the mathematical expression of the improved droop control rate of the distributed energy storage unit in step S2 is as follows:

[0016] V refi =V nom -k pi (P bi -P 0 )

[0017] f refi =f nom -k qi (Q bi -Q 0 )

[0018] In the above formula, V refi , k pi , P bi 、f refi , k qi , Q bi are the reference voltage amplitude, active droop coefficient, output active power, reference frequency, reactive droop coefficient, and output reactive power of the i-th distributed energy storage unit, V nom , P 0 、f nom , Q 0 They are rated voltage amplitude, rated active power, rated frequency and rated reactive power.

[0019] As a supplement to the above technical solution, the balance adjustment coefficient in step S3 is expressed as follows:

[0020]

[0021] In the above formula, SoC i is the state of charge of the i-th distributed energy storage unit, is the average value of the state of charge of all distributed energy storage units, k min With k max is the lower limit and upper limit of the balance adjustment coefficient, e is a natural number, α i is the equilibrium adjustment coefficient.

[0022] As a supplement to the above technical solution, the calculation method of the virtual balanced active power in step S3 is as follows:

[0023] P eqi =a i P bi

[0024] In the above formula, P eqi is the virtual balanced active power of the i-th energy storage unit, P bi is the actual output active power of the i-th energy storage unit.

[0025] As a supplement to the above technical solution, the process of constructing a consistency average estimator based on the consistency algorithm in step S4 is as follows:

[0026]

[0027] In the above formula, is the average estimated value of the consistency of a state quantity of the i-th distributed energy storage unit, is the consistent average estimated value of a state quantity of the jth distributed energy storage unit, X i is the actual value of the state quantity, N i Represents the set of energy storage units adjacent to the i-th distributed energy storage unit.

[0028] As a supplement to the above technical solution, when the state quantity X i SoC i With P eqi When , the consistency estimators of state of charge and virtual balanced active power are constructed respectively.

[0029] As a supplement to the above technical solution, the average estimated value of the consistency of the state of charge is calculated according to the following formula:

[0030]

[0031] In the above formula, is the consistent average estimated value of the state of charge of the i-th distributed energy storage unit, is the consistent average estimated value of the state of charge of the jth distributed energy storage unit, SoC iis the actual value of the state of charge of the i-th distributed energy storage unit, β SoC Control gain for consistency;

[0032] The average estimated value of virtual balanced active power is obtained according to the following formula:

[0033]

[0034] In the above formula, is the consistent average estimate of the virtual balanced active power, is the consistent average estimated value of the virtual balanced active power of the jth distributed energy storage unit, P eqi is the virtual balanced active power of the i-th distributed energy storage unit, β P Control gain for consistency.

[0035] As a supplement to the above technical solution, the virtual balanced active power secondary control loop in step S5 includes: subtracting the virtual balanced active power from the virtual balanced active power consistency average estimated value, outputting a voltage balanced compensation amount through a PI controller, and finally acting on the input of the droop control loop.

[0036] On the other hand, the present invention provides a low voltage area energy storage coordination control system applied to a power outage event, comprising:

[0037] The transmission power mathematical model building module is used to establish the transmission power mathematical expression based on the port voltage phasor and line impedance, and obtain the power coupling characteristics of the low-voltage substation area;

[0038] Improved droop control rate establishment module, used to establish a mathematical expression for the improved droop control rate of the distributed energy storage unit based on the power coupling characteristics of the low-voltage station area;

[0039] A virtual balanced active power establishment module is used to propose a balanced adjustment coefficient and establish a virtual balanced active power based on the state of charge of the distributed energy storage unit and the average value of the global state of charge;

[0040] A consistency average estimator building module, used to build a consistency average estimator using a consistency algorithm to estimate the average value of virtual balanced active power and state of charge;

[0041] The voltage amplitude compensation output module is used to establish a virtual balanced active power secondary control loop and output the voltage amplitude compensation of the corrected droop control loop.

[0042] Compared with the prior art, the beneficial effects of the present invention include at least:

[0043] The present invention mathematically models the power transmission characteristics of low-voltage substations, forming the voltage and frequency coupling problem under the environment of distribution line resistance-dominated characteristics; establishes a voltage and frequency autonomous stability control method suitable for low-voltage substation network characteristics; proposes a balanced adjustment coefficient to construct a virtual balanced active power; constructs a consistent average estimator based on a consistency algorithm to estimate the state of charge and the average value of the virtual balanced active power; constructs a virtual balanced active power secondary control loop to adjust the output active power of the distributed energy storage unit, and realizes rapid balance of the state of charge of each distributed energy storage unit and equal distribution of active power. The distributed energy storage units of the present invention dynamically adjust their respective active power outputs through coordination and cooperation, realize dynamic SoC balance under the premise of inconsistent initial SoC, and finally ensure the load equalization effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A flowchart of a low voltage area energy storage coordination control method applied to a power outage event according to an embodiment of the present invention;

[0046] Figure 2 A control strategy diagram of a low voltage area energy storage coordinated control method applied to a power outage event according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the low-voltage area structure of the distribution network;

[0048] Figure 4 The SoC response of the low voltage area energy storage coordinated control method applied to a power outage event provided by an embodiment of the present invention;

[0049] Figure 5 The output active power response of the low voltage area energy storage coordinated control method applied to a power outage event provided by an embodiment of the present invention;

[0050] Figure 6 This is a structural diagram of a low-voltage area energy storage coordination control system applied to a power outage event according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] Specifically, the embodiment of the present invention discloses a low voltage area energy storage coordinated control method applied to a power outage event, such as Figure 1 As shown, the method comprises the following steps:

[0054] Step S1, based on the port voltage phasor and the line impedance, a transmission power mathematical expression is established to obtain the power coupling characteristics of the low-voltage area;

[0055] The mathematical expression of the transmission power is:

[0056]

[0057]

[0058] In the above formula, E s 、E c are the output voltage amplitude of the energy storage unit and the voltage amplitude of the grid connection point, θ s With θ c is the output voltage phase of the energy storage unit and the grid connection point voltage phase, Z line is the line impedance, P and Q are the active power and reactive power transmitted by the line respectively, Re and Im represent the real part and the imaginary part respectively.

[0059] Step S2, based on the low voltage area power coupling characteristics in S1, establish a mathematical expression for improving the droop control rate of the distributed energy storage unit;

[0060] By analyzing the power transmission mathematical model in step S1 and the coupling relationship between electrical signals, the following control ratio is constructed:

[0061] V refi =V nom -k pi (P bi -P 0 )

[0062] f refi =f nom -k qi (Q bi -Q 0 )

[0063] In the above formula, V refi , k pi , P bi 、f refi , k qi , Q bi are the reference voltage amplitude, active droop coefficient, output active power, reference frequency, reactive droop coefficient, and output reactive power of the i-th distributed energy storage unit, V nom , P 0 、f nom , Q 0 They are rated voltage amplitude, rated active power, rated frequency and rated reactive power.

[0064] Step S3: Based on the state of charge of the distributed energy storage unit and the global state of charge average value, a balancing adjustment coefficient is proposed to establish a virtual balanced active power;

[0065] The balancing adjustment coefficient is calculated based on the average value of the local state of charge and the global state of charge. The calculation process is as follows:

[0066]

[0067] In the above formula, SoC i is the state of charge of the i-th distributed energy storage unit, is the average value of the state of charge of all distributed energy storage units, k min With k max is the lower limit and upper limit of the balance adjustment coefficient, e is a natural number, α i is the equilibrium adjustment coefficient.

[0068] According to the balance adjustment coefficient, the virtual balanced active power can be further constructed. The calculation method is as follows:

[0069] P eqi =a i P bi

[0070] In the above formula, P eqi is the virtual balanced active power of the i-th energy storage unit, P bi is the actual output active power of the i-th energy storage unit.

[0071] Step S4: construct a consistency average estimator using a consistency algorithm to estimate the average values ​​of the virtual balanced active power and the state of charge;

[0072] The process of constructing a consistency average estimator based on the consistency algorithm is as follows:

[0073]

[0074] In the above formula, is the average estimated value of the consistency of a state quantity of the i-th distributed energy storage unit, is the consistent average estimated value of a state quantity of the jth distributed energy storage unit, X i is the actual value of the state quantity, N i Represents the set of energy storage units adjacent to the i-th distributed energy storage unit.

[0075] When the state quantity X i SoC i With P eqi When , the consistency estimators of state of charge and virtual balanced active power are constructed respectively.

[0076] The consistent average estimate of the state of charge is obtained according to the following formula:

[0077]

[0078] In the above formula, is the consistent average estimated value of the state of charge of the i-th distributed energy storage unit, is the consistent average estimated value of the state of charge of the jth distributed energy storage unit, SoC i is the actual value of the state of charge of the i-th distributed energy storage unit, β SoC Control gain for consistency.

[0079] The average estimated value of virtual balanced active power is obtained according to the following formula:

[0080]

[0081] In the above formula, is the consistent average estimate of the virtual balanced active power, is the consistent average estimated value of the virtual balanced active power of the jth distributed energy storage unit, P eqi is the virtual balanced active power of the i-th distributed energy storage unit, β P Control gain for consistency.

[0082] Step S5: Establish a virtual balanced active power secondary control loop, and output a voltage amplitude compensation amount of the modified droop control loop.

[0083] The virtual balanced active power average value estimated by the i-th distributed energy storage unit is subtracted from the virtual balanced active power, and the voltage amplitude compensation is obtained after passing through the PI controller, as shown in Figure 2 As shown, the compensation amount is related to the correction of the droop control loop input V ni The accumulated value is used as the new droop control loop input reference.

[0084] Figure 3A schematic diagram of a low-voltage area structure for a specific application of a low-voltage area energy storage coordination control method for a power outage event provided by the present invention. The area includes 4 energy storage units, and each energy storage unit supplies power to a local load.

[0085] Figure 4 The SoC response waveforms of each distributed energy storage unit after the low-voltage area energy storage coordination control method provided by the present invention is implemented when the area is in off-grid operation condition and applied to a power outage event. Figure 5 After implementing the low-voltage area energy storage coordination control method provided by the present invention for power outage events, each distributed energy storage unit outputs an active power response waveform. Combining the two figures, it can be seen that the distributed energy storage units dynamically adjust their active power outputs through coordination and cooperation, realize dynamic SoC balance under the premise of inconsistent initial SoC, and finally ensure the load balancing effect.

[0086] Example 2

[0087] like Figure 6 As shown, the present invention provides a low-voltage area energy storage coordination control system applied to power outage events, including a transmission power mathematical model establishment module, an improved droop control rate establishment module, a virtual balanced active power establishment module, a consistency average estimator construction module and a voltage amplitude compensation output module;

[0088] The transmission power mathematical model establishment module is used to establish a transmission power mathematical expression based on the port voltage phasor and the line impedance, and obtain the power coupling characteristics of the low-voltage station area;

[0089] The improved droop control rate establishment module is used to establish a mathematical expression for the improved droop control rate of the distributed energy storage unit based on the power coupling characteristics of the low-voltage station area;

[0090] The virtual balanced active power establishment module is used to propose a balanced adjustment coefficient based on the state of charge of the distributed energy storage unit and the global state of charge average value, and establish a virtual balanced active power;

[0091] The consistency average estimator construction module is used to construct a consistency average estimator using a consistency algorithm to estimate the average value of the virtual balanced active power and the state of charge;

[0092] The voltage amplitude compensation output module is used to establish a virtual balanced active power secondary control loop and output a voltage amplitude compensation amount for a corrected droop control loop.

[0093] The other features of this embodiment are the same as those of Embodiment 1, and therefore will not be described in detail here.

[0094] The various embodiments of the present invention can be combined arbitrarily to achieve different technical effects.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low voltage area energy storage coordination control method applied to a power outage event, characterized in that: The following steps are involved: Step S1, based on the port voltage phasor and the line impedance, a transmission power mathematical expression is established to obtain the power coupling characteristics of the low-voltage area; Step S2: establishing a mathematical expression for improving the droop control rate of the distributed energy storage unit based on the power coupling characteristics of the low-voltage area; Step S3: Based on the state of charge of the distributed energy storage unit and the global state of charge average value, a balancing adjustment coefficient is proposed to establish a virtual balanced active power; The balance adjustment coefficient in step S3 is expressed as follows: In the above formula, SoC i is the state of charge of the i-th distributed energy storage unit, is the average value of the state of charge of all distributed energy storage units, k min With k max is the lower limit and upper limit of the balance adjustment coefficient, e is a natural number, α i is the equilibrium adjustment coefficient; The calculation method of the virtual balanced active power in step S3 is as follows: P eqi =a i P bi In the above formula, P eqi is the virtual balanced active power of the i-th energy storage unit, P bi is the actual output active power of the i-th energy storage unit; Step S4: construct a consistency average estimator using a consistency algorithm to estimate the average values ​​of the virtual balanced active power and the state of charge; The consistent average estimate of the state of charge is obtained according to the following formula: In the above formula, is the consistent average estimated value of the state of charge of the i-th distributed energy storage unit, is the consistent average estimated value of the state of charge of the jth distributed energy storage unit, SoC i is the actual value of the state of charge of the i-th distributed energy storage unit, β SoC Control gain for consistency; The average estimated value of virtual balanced active power is obtained according to the following formula: In the above formula, is the consistent average estimate of the virtual balanced active power, is the consistent average estimated value of the virtual balanced active power of the jth distributed energy storage unit, P eqi is the virtual balanced active power of the i-th distributed energy storage unit, β P Control gain for consistency; Step S5: Establish a virtual balanced active power secondary control loop, and output a voltage amplitude compensation amount of the modified droop control loop.

2. The low voltage area energy storage coordination control method applied to power outage events according to claim 1 is characterized in that: The transmission power mathematical expression in step S1 is as follows: In the above formula, E s 、E c are the output voltage amplitude of the energy storage unit and the voltage amplitude of the grid connection point, θ s With θ c is the output voltage phase of the energy storage unit and the grid connection point voltage phase, Z line is the line impedance, P and Q are the active power and reactive power transmitted by the line respectively, Re and Im represent the real part and the imaginary part respectively.

3. The low voltage area energy storage coordination control method applied to power outage events according to claim 1 is characterized in that: The mathematical expression of the improved droop control rate of the distributed energy storage unit in step S2 is as follows: IN refi =V nom -to pi (P bi -P0) F refi =f nom -to qi (Q bi -Q0) In the above formula, V refi , k pi , P bi 、f refi , k qi , Q bi are the reference voltage amplitude, active droop coefficient, output active power, reference frequency, reactive droop coefficient, and output reactive power of the i-th distributed energy storage unit, V nom ,P0,f nom , Q0 are the rated voltage amplitude, rated active power, rated frequency and rated reactive power respectively.

4. The low voltage area energy storage coordination control method applied to power outage events according to claim 1 is characterized in that: The process of constructing a consistency average estimator using the consistency algorithm in step S4 is as follows: In the above formula, is the average estimated value of the consistency of a state quantity of the i-th distributed energy storage unit, is the consistent average estimated value of a state quantity of the jth distributed energy storage unit, X i is the actual value of the state quantity, N i Represents the set of energy storage units adjacent to the i-th distributed energy storage unit.

5. The low voltage area energy storage coordination control method applied to power outage events according to claim 4 is characterized in that: When the state quantity X i SoC i With P eqi When , the consistency estimators of state of charge and virtual balanced active power are constructed respectively.

6. The low voltage area energy storage coordination control method applied to power outage events according to claim 1 is characterized in that: The virtual balanced active power secondary control loop in step S5 includes: subtracting the virtual balanced active power from the virtual balanced active power consistency average estimated value, outputting a voltage balanced compensation amount through a PI controller, and finally acting on the input of the droop control loop.

7. A low-voltage area energy storage coordination control system applied to a power outage event, used to execute the low-voltage area energy storage coordination control method applied to a power outage event according to any one of claims 1-6, characterized in that: include: The transmission power mathematical model building module is used to establish the transmission power mathematical expression based on the port voltage phasor and line impedance, and obtain the power coupling characteristics of the low-voltage substation area; Improved droop control rate establishment module, used to establish a mathematical expression for the improved droop control rate of the distributed energy storage unit based on the power coupling characteristics of the low-voltage station area; A virtual balanced active power establishment module is used to propose a balanced adjustment coefficient and establish a virtual balanced active power based on the state of charge of the distributed energy storage unit and the global state of charge average value; A consistency average estimator building module, used to build a consistency average estimator using a consistency algorithm to estimate the average value of virtual balanced active power and state of charge; The voltage amplitude compensation output module is used to establish a virtual balanced active power secondary control loop and output the voltage amplitude compensation of the corrected droop control loop.

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