Electric energy quality regulation resource reactive power regulation capability assessment method considering multiple uncertainties

Abstract

The invention provides an electric energy quality regulation resource reactive power regulation capability assessment method considering multiple uncertainties. According to the method, under the condition that equipment such as a reactor and a capacitor are connected in series or in parallel into a power grid, the influence of uncertain factors of adjustment resources is fully considered, and under the influence of multiple uncertain factors, a calculation method of a reachable set is introduced, so that the comprehensive reactive power adjustment capability of the equipment is evaluated. According to the method, the reactive power capability of the equipment under multiple uncertain disturbances can be evaluated.

Description

Technical Field

[0001] The invention belongs to the field of power evaluation, and in particular relates to a method for evaluating reactive power regulation capability of power quality regulation resources taking multiple uncertainties into consideration. Background Art

[0002] As the penetration rate of distributed power sources dominated by renewable energy in the power grid continues to increase, DC loads represented by electric vehicles and computing centers continue to increase. The uncertainty of load changes and broadband impedance changes lead to strong uncertainty in the reactive power of the system, which in turn leads to frequent power quality problems in the system. It is necessary to manage various types of power quality regulation resources such as source-grid-load-storage. Among them, for power quality problems such as harmonics and voltage, it is necessary to manage the regulation resources that can perform reactive regulation, such as capacitors, reactors and their different series and parallel combinations. At the same time, considering that there are certain uncertainty errors in the measured values ​​of capacitance and inductance, in addition, after such resources with reactive regulation capabilities are connected to the power grid, the voltage at the grid connection point of the power system equipment will also change with the reactive input of the equipment, which also has uncertainty. Under such multiple uncertainties, the reactive regulation capability of the power quality regulation resource is difficult to accurately evaluate using conventional deterministic methods. Therefore, the reactive regulation capability results obtained based on the traditional regulation resource capability evaluation method have low credibility, and cannot provide a reliable and quantifiable reactive regulation capability range for power quality management, thereby affecting the power quality management effect. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for evaluating the reactive regulation capability of power quality regulation resources taking into account multiple uncertainties. When equipment such as reactors and capacitors are connected to the power grid in series or in parallel, the influence of uncertainty factors of the regulation resources is fully considered. Under the influence of multiple uncertainty factors, a reachable set calculation method is introduced to realize the evaluation of the comprehensive reactive regulation capability of the equipment.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties comprises the following steps:

[0006] Step 1. Calculate the inductor and capacitor reactive power;

[0007] Step 2. Identify the equipment topology and calculate the total reactive power based on the inductive and capacitive reactive power in step 1 to provide a benchmark for reactive power capability assessment;

[0008] Step 3. Consider multiple disturbances and evaluate the reactive power capability.

[0009] Furthermore, the step 1 comprises:

[0010] (1) Calculate the inductor reactive power :

[0011] (1)

[0012] in, is the current angular frequency value, is the grid frequency; is the specific value of the connected inductor; is the current flowing through the inductor; is the grid voltage at the point where the inductor is connected; is an imaginary unit;

[0013] (2) Calculation of capacitor reactive power :

[0014] (2)

[0015] in, is the current angular frequency value, is the grid frequency; is the specific value of the connected capacitor; is the current flowing through the capacitor; is the grid voltage at the point where the inductor is connected.

[0016] Furthermore, the step 2 comprises:

[0017] Depending on the topology of the equipment, the reactive power calculation formula of the equipment is different in the series and parallel structures of inductance and capacitance;

[0018] (1) Capacitor and inductor connected in series:

[0019] When the inductor is connected in series with the capacitor, the overall impedance Z of the device is as follows:

[0020] (3)

[0021] Where R is the device resistance;

[0022] Ignoring the device resistance R, the calculation formula for the device impedance Z is as follows:

[0023] (4)

[0024] Based on the equipment impedance R and the relationship between reactive power and equipment impedance, the calculation formula for the reactive power Q of the equipment in series connection is as follows:

[0025] (5)

[0026] (2) Capacitor and inductor in parallel:

[0027] When the inductor and capacitor are connected in parallel, ignoring the device resistance, the overall impedance Z is as follows:

[0028] (6)

[0029] Based on the equipment impedance and the relationship between reactive power and impedance, the calculation formula for reactive power Q in parallel is as follows:

[0030] (7).

[0031] Furthermore, the step 3 comprises:

[0032] In the above-mentioned calculation formula for reactive power of equipment under different topologies, There is uncertainty in three variables, represented by a normal distribution:

[0033] (8)

[0034] in, ,Right now The value of satisfies the normal distribution, and its location parameter is , the scale parameter is , which can satisfy the voltage distribution between 0.95-1.05pu (pu is the per-unit value) under the 95% confidence interval; is a probability distribution function with location parameter , the scale parameter is The normal distribution of represents a normal distribution, is the voltage rating;

[0035] Inductance and capacitance are also expressed in the form of normal distribution as follows:

[0036] (9)

[0037] (10)

[0038] in, , ,Right now and The values ​​satisfy the normal distribution, the position parameters are the same as the rated values ​​of the inductor and capacitor, and the scale parameters are selected according to the requirements.

[0039] Furthermore, a set description method is introduced to define the uncertainty inputs of voltage, inductance and capacitance, and reachability analysis is further introduced, including:

[0040] 1) Based on the reachable set of the system at the current moment, calculate the reachable set formed by the corresponding solutions of formula (5) and formula (7) at the next moment;

[0041] 2) Perform convex hull calculation on the reachable set at the first moment and the reachable set at the last moment to obtain the overall reachable set running trajectory;

[0042] 3) Through a finite number of Taylor series expansions and using matrices to perform equivalent transformations on the remainders in the series, special solutions for different return trips are further added to modify the reachable set.

[0043] Furthermore, according to the basic principle of reachability analysis, The feasible domain of three variables:

[0044] (11)

[0045] (12)

[0046] (13)

[0047] Where: are the reachable sets of voltage, inductance and capacitance respectively; are the reachable set center points of voltage, inductance and capacitance respectively; are the reachable set generators of voltage, inductance and capacitance respectively;

[0048] The reachable set calculation formula of reactive power obtained by the collective calculation method of reachable sets is as follows:

[0049] (1) Capacitor and inductor connected in series:

[0050] (14)

[0051] (2) Capacitor and inductor in parallel:

[0052] (15)

[0053] in, is the reachable set of reactive power; is the reachable set of voltage; is the reachable set of the inductor; is the reachable set of capacitors.

[0054] Beneficial effects:

[0055] The present invention takes into account the input parameters , is the voltage, is the inductor, The uncertainty factor of the capacitor is used to obtain the feasible domain of reactive power capacity that satisfies the confidence interval within the 95% confidence interval. The reachability analysis method is introduced to consider the multiple uncertain disturbances of inductance and capacitance equipment. The feasible range of reactive power of the equipment can be obtained through only one calculation, realizing the reactive power capacity evaluation of the equipment under multiple uncertain disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The present invention is a flow chart of a method for evaluating reactive power regulation capability of power quality regulation resources taking into account multiple uncertainties. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] like Figure 1 As shown, a method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties of the present invention comprises the following steps:

[0059] Step 1. Calculate the inductor and capacitor reactive power for use in calculating the overall reactive power in step 2, including:

[0060] (1) Calculate the inductor reactive power :

[0061] (1)

[0062] in, is the current angular frequency value, is the grid frequency; is the specific value of the connected inductor; is the current flowing through the inductor; is the grid voltage at the inductor, Is an imaginary unit.

[0063] (2) Calculation of capacitor reactive power :

[0064] (2)

[0065] in, is the current angular frequency value, is the grid frequency; is the specific value of the connected capacitor; is the current flowing through the capacitor; is the grid voltage at the point where the inductor is connected.

[0066] Step 2. Identify the equipment topology and calculate reactive power for introducing multiple disturbances in step 3, including:

[0067] Depending on the topology of the equipment, the reactive power calculation formula of the equipment is different in the series and parallel structures of inductance and capacitance.

[0068] (1) Capacitor and inductor connected in series:

[0069] When the inductor is connected in series with the capacitor, the overall impedance Z of the device is as follows:

[0070] (3)

[0071] Where R is the device resistance.

[0072] Ignoring the device resistance R, the device impedance Z can be calculated as follows:

[0073] (4)

[0074] Based on the equipment impedance R and the relationship between reactive power and equipment impedance, the calculation formula for the reactive power Q of the equipment in series connection can be obtained as follows:

[0075] (5)

[0076] (2) Capacitor and inductor in parallel:

[0077] When the inductor and capacitor are connected in parallel, ignoring the device resistance, the overall impedance Z is as follows:

[0078] (6)

[0079] Based on the equipment impedance and the relationship between reactive power and impedance, the calculation formula for reactive power Q in parallel can be obtained as follows:

[0080] (7)

[0081] Step 3. Consider multiple disturbances and evaluate reactive power capability, including:

[0082] In the above-mentioned calculation formula for reactive power of equipment under different topologies, There is uncertainty in the three variables, which can be represented by a normal distribution.

[0083] (8)

[0084] Where: ,Right now The value of satisfies the normal distribution, and its location parameter is , the scale parameter is , which can satisfy the voltage distribution between 0.95-1.05pu (pu is the per-unit value) under the 95% confidence interval; is a probability distribution function with location parameter , the scale parameter is The normal distribution of represents a normal distribution, is the voltage rating.

[0085] Inductance and capacitance are also expressed in the form of normal distribution as follows:

[0086] (9)

[0087] (10)

[0088] Where: , ,Right now and The values ​​satisfy the normal distribution, the position parameters are the same as the rated values ​​of the inductor and capacitor, and the scale parameters are selected according to the requirements.

[0089] The present invention introduces a set description method to define the uncertain inputs of voltage, inductance and capacitance, and further introduces reachability analysis. Reachability analysis is a formal analysis method based on a state space model. Reachability analysis can calculate the set of all trajectories starting from the initial state set at one time, which can include all possible areas where the system trajectory may pass. Compared with the simulation method, reachability analysis has the advantages of fewer calculations, less calculation time, and is suitable for multiple disturbance calculations.

[0090] The basic process of reachability analysis is as follows:

[0091] 1) Based on the reachable set of the system at the current moment, calculate the reachable set formed by the corresponding solutions of formula (5) and formula (7) at the next moment.

[0092] 2) Perform convex hull operation on the reachable set at the first moment and the reachable set at the last moment to obtain the overall reachable set running trajectory.

[0093] 3) Through a finite number of Taylor series expansions and using matrices to perform equivalent transformations on the remainders in the series, special solutions for different return trips are further added to modify the reachable set.

[0094] According to the basic principle of reachability analysis, we can get The feasible domain of three variables:

[0095] (11)

[0096] (12)

[0097] (13)

[0098] Where: are the reachable sets of voltage, inductance and capacitance respectively; are the reachable set center points of voltage, inductance and capacitance respectively; are the reachable generators for voltage, inductance, and capacitance, respectively.

[0099] The reachable set calculation formula of reactive power can be obtained by the collective calculation method of reachable sets as follows:

[0100] (1) Capacitor and inductor connected in series:

[0101] (14)

[0102] (2) Capacitor and inductor in parallel:

[0103] (15).

[0104] in, is the reachable set of reactive power; is the reachable set of voltage; is the reachable set of the inductor; is the reachable set of capacitors.

Claims

1. A method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties, characterized in that: The steps include: Step 1. Calculate the inductor and capacitor reactive power; Step 2. Identify the equipment topology and calculate the total reactive power based on the inductive and capacitive reactive power in step 1 to provide a benchmark for reactive power capability assessment; Step 3. Consider multiple disturbances and evaluate the reactive power capability.

2. According to the method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties according to claim 1, it is characterized in that: The step 1 comprises: (1) Calculation of inductor reactive power : （1） in, is the current angular frequency value, is the grid frequency; is the specific value of the connected inductor; is the current flowing through the inductor; is the grid voltage at the point where the inductor is connected; is an imaginary unit; (2) Calculation of capacitor reactive power : （2） in, is the current angular frequency value, is the grid frequency; is the specific value of the connected capacitor; is the current flowing through the capacitor; is the grid voltage at the point where the inductor is connected.

3. According to the method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties according to claim 1, it is characterized in that: The step 2 comprises: Depending on the topology of the equipment, the reactive power calculation formula of the equipment is different in the series and parallel structures of inductance and capacitance; (1) Capacitor and inductor connected in series: When the inductor is connected in series with the capacitor, the overall impedance Z of the device is as follows: （3） Where R is the device resistance; Ignoring the device resistance R, the calculation formula for the device impedance Z is as follows: （4） Based on the equipment impedance R and the relationship between reactive power and equipment impedance, the calculation formula for the reactive power Q of the equipment in series connection is as follows: （5） (2) Capacitor and inductor in parallel: When the inductor and capacitor are connected in parallel, ignoring the device resistance, the overall impedance Z is as follows: （6） Based on the equipment impedance and the relationship between reactive power and impedance, the calculation formula for reactive power Q in parallel is as follows: （7）。 4. The method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties according to claim 2, characterized in that: The step 3 comprises: In the above-mentioned calculation formula for reactive power of equipment under different topologies, There is uncertainty in three variables, represented by a normal distribution: （8） in, ,Right now The value of satisfies the normal distribution, and its location parameter is , the scale parameter is , which can satisfy the voltage distribution between 0.95-1.05pu (pu is the per-unit value) under the 95% confidence interval; is a probability distribution function with location parameter , the scale parameter is The normal distribution of represents a normal distribution, is the voltage rating; Inductance and capacitance are also expressed in the form of normal distribution as follows: （9） （10） in, , ,Right now and The values ​​satisfy the normal distribution, the position parameters are the same as the rated values ​​of the inductor and capacitor, and the scale parameters are selected according to the requirements.

5. The method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties according to claim 4, characterized in that: A set description method is introduced to define the uncertainty inputs of voltage, inductance and capacitance, and reachability analysis is further introduced, including: 1) Based on the reachable set of the system at the current moment, calculate the reachable set formed by the corresponding solutions of formula (5) and formula (7) at the next moment; 2) Perform convex hull calculation on the reachable set at the first moment and the reachable set at the last moment to obtain the overall reachable set running trajectory; 3) Through a finite number of Taylor series expansions and using matrices to perform equivalent transformations on the remainders in the series, special solutions for different return trips are further added to modify the reachable set.

6. A method for evaluating reactive power regulation capability of power quality regulation resources considering multiple uncertainties according to claim 5, characterized in that: According to the basic principle of reachability analysis, The feasible domain of three variables: （11） （12） （13） Where: are the reachable sets of voltage, inductance and capacitance respectively; are the reachable set center points of voltage, inductance and capacitance respectively; are the reachable set generators of voltage, inductance and capacitance respectively; The reachable set calculation formula of reactive power obtained by the collective calculation method of reachable sets is as follows: (1) Capacitor and inductor connected in series: （14） (2) Capacitor and inductor in parallel: （15） in, is the reachable set of reactive power; is the reachable set of voltage; is the reachable set of the inductor; is the reachable set of capacitors.

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