A low-voltage distribution network power flow calculation and reactive power optimization method containing photovoltaic inverter negative sequence control

Abstract

A low-voltage distribution network power flow calculation and reactive power optimization method containing photovoltaic inverter negative sequence control, comprising the following steps: (1) establishing a distributed photovoltaic inverter mathematical model; (2) establishing an inverter negative sequence control method based on the distributed photovoltaic inverter mathematical model; (3) establishing a low-voltage three-phase four-wire power flow calculation model; (4) based on the low-voltage three-phase four-wire power flow calculation model, using the improved Newton method, and using the distributed photovoltaic inverter mathematical model and the inverter negative sequence control method, carrying out three-phase power flow calculation of low-voltage power grid containing distributed photovoltaic; (5) after completing the three-phase power flow calculation of the low-voltage power grid containing distributed photovoltaic, determining the reactive power optimization objective function and the constraint condition, and calculating the reactive power voltage optimization of the low-voltage power grid containing distributed photovoltaic by using the Lagrange multiplier method. Make full use of the regulation ability of new energy, effectively improve the voltage level of low-voltage distribution network, and reduce the network line loss.

Description

Technical Field

[0001] This invention relates to reactive power optimization and control in low-voltage distribution networks, and more specifically to power flow calculation and reactive power optimization in low-voltage distribution networks with negative sequence control of photovoltaic inverters. Background Technology

[0002] The rapid development of new energy sources in low-voltage distribution networks has brought clean energy directly to users, but it has also brought many new challenges to these networks. While new energy sources directly connect to the low-voltage distribution network to provide power to nearby loads, their volatility, intermittency, and uncertainty make voltage regulation difficult. Voltage rises significantly when new energy sources are generating electricity, and drops dramatically when they are not, resulting in large voltage fluctuations, difficulty in voltage regulation, and frequent voltage exceedances. Existing inverters all use symmetrical control methods when connected to the low-voltage distribution network, limiting their three-phase flexible regulation capabilities. Symmetrical control cannot improve three-phase imbalance and voltage quality, further restricting the inverter's ability to regulate three-phase power flow. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art. This invention considers a three-phase power flow calculation method for low-voltage distribution networks with negative-sequence control inverter power supply. In response to the problem that existing low-voltage distribution networks do not consider negative-sequence inverter power supply, this invention proposes a power flow calculation and reactive power optimization method for low-voltage distribution networks with negative-sequence control of photovoltaic inverters. This fully utilizes the regulation capabilities of new energy sources, effectively improves the voltage level of low-voltage distribution networks, and reduces network line losses.

[0004] A method for power flow calculation and reactive power optimization in low-voltage distribution networks with negative sequence control of photovoltaic inverters includes the following steps:

[0005] (1) Establish a mathematical model for distributed photovoltaic inverters;

[0006] (2) Establish a negative sequence control method for inverters based on the mathematical model of distributed photovoltaic inverters;

[0007] (3) Establish a low-voltage three-phase four-wire power flow calculation model;

[0008] (4) Based on the low-voltage three-phase four-wire power flow calculation model, the improved Newton method is used, along with the mathematical model of the distributed photovoltaic inverter and the inverter negative sequence control method, to carry out the three-phase power flow calculation of the low-voltage power grid containing distributed photovoltaics.

[0009] (5) After completing the three-phase power flow calculation of the low-voltage power grid with distributed photovoltaics, determine the reactive power optimization objective function and constraints, and use the Lagrange multiplier method to calculate the reactive power voltage optimization of the low-voltage power grid with distributed photovoltaics.

[0010] Establishing a mathematical model for distributed photovoltaic inverters, specifically including:

[0011] Distributed photovoltaic (PV) systems use inverters to transmit the electricity generated by the photovoltaic panels via alternating current (AC). The mathematical model for distributed PV is as follows:

[0012] (1);

[0013] in:

[0014] —Three-phase voltage output of distributed photovoltaic inverter;

[0015] —Distributed photovoltaic inverters are connected to the system's three-phase voltage;

[0016] —Three-phase current from the output of the distributed photovoltaic inverter to the system access point;

[0017] —Resistance and reactance from the output of the distributed photovoltaic inverter to the system access point.

[0018] Based on the mathematical model of a distributed photovoltaic inverter, a negative-sequence control method for the inverter is established, specifically including:

[0019] Positive and negative sequence component decomposition of the three-phase voltage and current output of the distributed photovoltaic inverter:

[0020] (2);

[0021] in:

[0022] — Peak positive sequence voltage and peak negative sequence voltage;

[0023] — Angular frequency of the AC system;

[0024] —Initial angle of positive sequence voltage and initial angle of negative sequence voltage;

[0025] (3);

[0026] in:

[0027] — Peak value of positive sequence current and peak value of negative sequence current;

[0028] ω — Angular frequency of the AC system;

[0029] —Initial angle of positive sequence current and initial angle of negative sequence current;

[0030] The positive and negative sequence components of the three-phase voltage and current output of the distributed photovoltaic inverter are transformed into the αβ coordinate system using the Clarke transform:

[0031] (4);

[0032] (5);

[0033] in:

[0034] —Components of voltage in the αβ coordinate system

[0035] — Positive and negative sequence components along the voltage α-axis

[0036] — Positive and negative sequence components of voltage along the β-axis

[0037] (6);

[0038] (7);

[0039] in:

[0040] —Components of the current in the αβ coordinate system

[0041] — Positive and negative sequence components of the current along the α-axis

[0042] — Positive and negative sequence components of the current along the β-axis

[0043] The formulas for calculating the active power and reactive power output of a distributed photovoltaic inverter are as follows:

[0044] (8);

[0045] —Active and reactive power output of distributed photovoltaic systems

[0046] When the grid voltage is unbalanced, the positive and negative sequence components of voltage and current in the αβ coordinate system are calculated using formulas (2)-(8), and then the output of the photovoltaic inverter is adjusted according to the negative sequence control theory.

[0047] Establish a calculation model for a low-voltage three-phase four-wire power flow system, specifically including:

[0048] The constant power and current balance equations for three-phase and single-phase loads in a low-voltage power grid are as follows:

[0049] (9);

[0050] This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j; This represents the d-phase current in the load model. Represents the neutral point current in the load model. This represents the d-phase load capacity in the load model. This represents the d-phase voltage in the load model. This represents the neutral point voltage in the load model;

[0051] The branch impedance matrix and its relationship with the branch admittance matrix in a typical low-voltage three-phase four-wire network are as follows:

[0052] (10);

[0053] in: It is the impedance between node i and node j in the x and y phases. It is the admittance of the x-phase and y-phase between node i and node j.

[0054] After completing the three-phase power flow calculation for a low-voltage power grid with distributed photovoltaic (PV) systems, the reactive power optimization objective function and constraints are determined. The Lagrange multiplier method is then used to calculate the reactive power and voltage optimization of the low-voltage power grid with distributed PV systems, specifically including:

[0055] The objective function for active power loss is as follows:

[0056] (11);

[0057] It studies the total active power loss of the network. It studies the total active power of network generators. It studies the total active power of network load;

[0058] The objective function for three-phase voltage imbalance is as follows:

[0059] (12);

[0060] It refers to the three-phase voltage imbalance. , , It refers to the ABC three-phase voltages at the node;

[0061] Therefore, the comprehensive objective function is obtained:

[0062] (13);

[0063] f(x) is a comprehensive objective function that includes active power loss and three-phase voltage imbalance. and These are the weight coefficients of the two sub-objective functions;

[0064] Constraints include equality constraints and inequality constraints;

[0065] The equality constraint is a current constraint, as detailed below:

[0066] (14);

[0067] This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j;

[0068] The inequality constraints are voltage and power constraints, where the voltage constraint is:

[0069] (15);

[0070] It is the voltage of each phase at node i. and These are the maximum and minimum values ​​of the phase voltage at node i;

[0071] Power constraints are for both active and reactive power of the generator:

[0072] (16);

[0073] It studies the total active power of all generators in the power grid. It is the maximum value of the sum of the active power of all generators in the power grid. It studies the total reactive power of all generators in the power grid. It is the maximum value of the total reactive power of all generators in the power grid. It is the minimum value of the total reactive power of all generators in the power grid.

[0074] After determining the reactive power optimization objective function and constraints, the Lagrange multiplier method is used to calculate the reactive power and voltage optimization of a low-voltage power grid containing distributed photovoltaic power:

[0075] (17);

[0076] in The objective function for reactive power optimization is... For reactive power optimization equality constraints, For reactive power optimization inequality constraints, The minimum value corresponding to the inequality constraint, The maximum value of the corresponding inequality constraint.

[0077] This invention fully utilizes the regulation capabilities of new energy sources and adopts negative sequence control theory to change the three-phase output of new energy sources in low-voltage distribution networks. It addresses the issues of unbalanced three-phase loads and single-phase load power supply in low-voltage distribution networks, which cause unbalanced three-phase power flow, voltage exceeding limits in some phases, and high line losses. This method can effectively reduce the three-phase imbalance level of low-voltage distribution networks, greatly alleviate the problem of voltage exceeding limits in low-voltage distribution networks caused by three-phase asymmetry, and reduce neutral point current, thereby reducing distribution network line losses. Attached Figure Description

[0078] Figure 1 This is a typical structural diagram of a distributed photovoltaic system;

[0079] Figure 2 This is a typical structural diagram of a low-voltage three-phase four-wire system;

[0080] Figure 3 This is a schematic diagram of a low-voltage three-phase four-wire load.

[0081] Figure 4 A block diagram for power flow calculation of a low-voltage distribution network containing photovoltaic inverters;

[0082] Figure 5 This is a diagram of the actual transformer substation structure containing distributed photovoltaic power in the embodiment. Detailed Implementation

[0083] A method for power flow calculation and reactive power optimization in low-voltage distribution networks with negative sequence control of photovoltaic inverters includes the following steps:

[0084] Step 1: Establish a mathematical model for a distributed photovoltaic (PV) inverter. Currently, distributed PV systems use inverters to transmit the electricity generated by the PV panels via alternating current (AC). Figure 1 A typical structure diagram of a distributed photovoltaic system is shown below, along with the mathematical model of a distributed photovoltaic system.

[0085] (1);

[0086] in:

[0087] —Three-phase voltage output of distributed photovoltaic inverter;

[0088] —Distributed photovoltaic inverters are connected to the system's three-phase voltage;

[0089] —Three-phase current from the output of the distributed photovoltaic inverter to the system access point;

[0090] —Resistance and reactance from the output of the distributed photovoltaic inverter to the system access point;

[0091] Step 2: Based on the mathematical model of the distributed photovoltaic inverter, establish the negative sequence control method for the inverter.

[0092] The positive and negative sequence components of the three-phase voltage and current output of a distributed photovoltaic inverter are decomposed as follows:

[0093] (2);

[0094] in:

[0095] — Peak positive sequence voltage and peak negative sequence voltage;

[0096] ω — Angular frequency of the AC system;

[0097] —Initial angle of positive sequence voltage and initial angle of negative sequence voltage;

[0098] (3);

[0099] in:

[0100] — Peak value of positive sequence current and peak value of negative sequence current;

[0101] ω — Angular frequency of the AC system;

[0102] —Initial angle of positive sequence current and initial angle of negative sequence current;

[0103] The positive and negative order components are transformed into the αβ coordinate system using the Clarke transform:

[0104] (4);

[0105] (5);

[0106] in:

[0107] —The components of voltage in the αβ coordinate system;

[0108] — Positive and negative sequence components along the voltage α-axis;

[0109] — Positive and negative sequence components of voltage along the β-axis;

[0110] (6);

[0111] (7);

[0112] in:

[0113] —The components of the current in the αβ coordinate system;

[0114] — Positive and negative sequence components of the current along the α-axis;

[0115] — Positive and negative sequence components of the current along the β-axis;

[0116] The calculated active and reactive power outputs of the distributed photovoltaic inverter are as follows:

[0117] (8);

[0118] —The active and reactive power output of distributed photovoltaic systems;

[0119] When the grid voltage is unbalanced, the positive and negative sequence components of voltage and current in the αβ coordinate system are calculated using formulas (2)-(8), and then the output of the photovoltaic inverter is adjusted according to the negative sequence control theory.

[0120] Step 3: Establish a power flow calculation model for a low-voltage three-phase four-wire system, and determine the load model and current balance equations. A typical structure diagram of a low-voltage three-phase four-wire system is shown below. Figure 2 Low-voltage three-phase four-wire load diagram as follows: Figure 3 ;

[0121] for Figure 3 The constant power model and current balance formula for medium and low voltage three-phase four-wire loads, and three-phase and single-phase loads in low voltage power grids are as follows:

[0122] (9);

[0123] This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j.

[0124] This represents the current in phase d (where d represents a, b, and c) of the load model. Represents the neutral point current in the load model. In the load model, phase d (where d represents the load capacity of phases a, b, and c) represents the load capacity of phase d. In the load model, phase d (where d represents phases a, b, and c) represents the voltage. This represents the neutral point voltage in the load model.

[0125] The branch impedance matrix and its relationship with the branch admittance matrix in a typical low-voltage three-phase four-wire network are as follows:

[0126] (10);

[0127] in: It is the impedance of the x-phase and y-phase between node i and node j. It is the admittance of the x-phase and y-phase between node i and node j.

[0128] Step 4: Based on the low-voltage three-phase four-wire power flow calculation model, the improved Newton method and the negative sequence control method of the distributed photovoltaic inverter in step (2) are used to carry out the three-phase power flow calculation of the low-voltage power grid containing distributed photovoltaic.

[0129] There are many good power flow calculation methods for low-voltage power grids, including forward and backward substitution methods, improved fast decoupled power flow, and advanced Newton's method. This invention proposes an advanced Newton's method for photovoltaic power plants. The power flow calculation block diagram for low-voltage distribution networks including photovoltaic inverters is shown below. Figure 4 As shown.

[0130] Step 5: After completing the three-phase power flow calculation of the low-voltage power grid with distributed photovoltaics, determine the reactive power optimization objective function and constraints, and use the Lagrange multiplier method to calculate the reactive power and voltage optimization of the low-voltage power grid with distributed photovoltaics.

[0131] The following presents an objective function and constraints, including equality and inequality constraints. The objective function consists of active power loss and three-phase voltage imbalance coefficient.

[0132] The objective function for active power loss is as follows:

[0133] (11);

[0134] (x) represents the total active power loss of the network. It studies the total active power of network generators. It studies the total active power of network load.

[0135] The objective function for three-phase voltage imbalance is as follows:

[0136] (12);

[0137] (x) represents the three-phase voltage imbalance. , , It refers to the three-phase voltages (A, B, and C) at the node.

[0138] Therefore, the comprehensive objective function is obtained:

[0139] (13);

[0140] f(x) is a comprehensive objective function that includes active power loss and three-phase voltage imbalance. and These are the weight coefficients of the two sub-objective functions.

[0141] The equality constraint is a current power constraint, as detailed below:

[0142] (14);

[0143] This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j.

[0144] Inequality constraints include voltage and power constraints. The voltage constraint is as follows:

[0145] (15);

[0146] It is the voltage of each phase at node i. and These are the maximum and minimum values ​​of the phase voltage at node i.

[0147] Power constraints include generator active power and reactive power constraints:

[0148] (16);

[0149] It studies the total active power of all generators in the power grid. It is the maximum value of the sum of the active power of all generators in the power grid. It studies the total reactive power of all generators in the power grid. It is the maximum value of the total reactive power of all generators in the power grid. It is the minimum value of the total reactive power of all generators in the power grid.

[0150] Once the reactive power optimization objective function and constraints are determined, the Lagrange multiplier method can be used to calculate the reactive power and voltage optimization of a low-voltage power grid containing distributed photovoltaic power.

[0151] (17)

[0152] in The objective function for reactive power optimization is... For reactive power optimization equality constraints, The inequality constraint is used for reactive power optimization.

[0153] Equality constraints ; For inequality constraints, , or ,when for hour, for , for ;when for hour, =0, for ;when for hour, for , for .

[0154] Example

[0155] The power flow calculation and reactive power optimization effect of low-voltage distribution network with negative sequence control of photovoltaic inverters were verified using a low-voltage grid with distributed photovoltaics.

[0156] Steps 1 and 2 are used to construct a mathematical model and control method for a distributed photovoltaic inverter. Steps 3 and 4 are used to calculate the three-phase power flow of a low-voltage power grid containing distributed photovoltaics. Finally, step 5 is used to obtain the reactive power and voltage optimization results of the low-voltage power grid containing distributed photovoltaics.

[0157] The specific example is as follows: the distribution area has 34 nodes and 79 users. Node 1 is the low-voltage distribution transformer for the area. The distance between nodes 5 and 6 is 40 meters, and the distance between nodes 6 and 7 is 80 meters. The distance between the remaining nodes is 20 meters. Two households in the distribution area have distributed photovoltaic (PV) systems. The actual structure diagram of the distribution area with distributed PV is shown below. Figure 5As shown in the figure. For this example, the voltage and power flow data of a typical transformer area at two time points were calculated using steps 1 to 4, as shown in Table 1.

[0158] Table 1. Power flow calculation results for typical transformer substations

[0159]

[0160] The calculation results show that the voltage compliance rate during the midday period is only 2.73%, with the acceptable voltage range between 198 V and 235.4 V. The highest voltage in the study area reached 249.8 V, exceeding the standard by 6.11 percentage points. The higher photovoltaic output is the main reason for the higher voltage in the study area during midday. The optimized reactive power voltage calculation results for the transformer area obtained using step 5 are as follows.

[0161] Table 2 Results of Power Flow Reactive Voltage Optimization Calculation for Typical Distribution Areas

[0162]

[0163] As can be seen from the table, through optimized calculations, the midday voltage qualification rate in the study area increased significantly from 2.73% to 86.36%. The photovoltaic systems of Nie Fengmei's and Liu Hongjiang's homes, which previously emitted reactive power, now absorb reactive power, which plays a positive role in improving the voltage qualification rate in the study area. The three-phase imbalance in the study area also decreased from 1.784% before optimization to 1.779% after optimization.

[0164] Detailed Description of Embodiments: To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the present invention described herein can be combined with each other as long as they do not conflict with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for power flow calculation and reactive power optimization in low-voltage distribution networks including negative sequence control of photovoltaic inverters, characterized in that: Includes the following steps: (1) Establish a mathematical model for distributed photovoltaic inverters; (2) Establish a negative sequence control method for inverters based on the mathematical model of distributed photovoltaic inverters; (3) Establish a low-voltage three-phase four-wire power flow calculation model; (4) Based on the low-voltage three-phase four-wire power flow calculation model, the improved Newton method is used, along with the mathematical model of the distributed photovoltaic inverter and the inverter negative sequence control method, to carry out the three-phase power flow calculation of the low-voltage power grid containing distributed photovoltaics. (5) After completing the three-phase power flow calculation of the low-voltage power grid with distributed photovoltaics, determine the reactive power optimization objective function and constraints, and use the Lagrange multiplier method to calculate the reactive power voltage optimization of the low-voltage power grid with distributed photovoltaics.

2. The method for low-voltage distribution network power flow calculation and reactive power optimization with negative sequence control of photovoltaic inverters according to claim 1, characterized in that: Establishing a mathematical model for distributed photovoltaic inverters, specifically including: Distributed photovoltaic (PV) systems use inverters to transmit the electricity generated by the photovoltaic panels via alternating current (AC). The mathematical model for distributed PV is as follows: （1）； in: —Three-phase voltage output of distributed photovoltaic inverter; —Distributed photovoltaic inverters are connected to the system's three-phase voltage; —Three-phase current from the output of the distributed photovoltaic inverter to the system access point; —Resistance and reactance from the output of the distributed photovoltaic inverter to the system access point.

3. The method for power flow calculation and reactive power optimization of low-voltage distribution networks with negative sequence control of photovoltaic inverters according to claim 1, characterized in that: Based on the mathematical model of a distributed photovoltaic inverter, a negative-sequence control method for the inverter is established, specifically including: Positive and negative sequence component decomposition of the three-phase voltage and current output of the distributed photovoltaic inverter: （2）； in: — Peak positive sequence voltage and peak negative sequence voltage; — Angular frequency of the AC system; —Initial angle of positive sequence voltage and initial angle of negative sequence voltage; （3）； in: — Peak value of positive sequence current and peak value of negative sequence current; ω — Angular frequency of the AC system; —Initial angle of positive sequence current and initial angle of negative sequence current; The positive and negative sequence components of the three-phase voltage and current output of the distributed photovoltaic inverter are transformed into the αβ coordinate system using the Clarke transform: （4）； ( 5 )； in: —Components of voltage in the αβ coordinate system — Positive and negative sequence components along the voltage α-axis — Positive and negative sequence components of voltage along the β-axis ( 6 )； ( 7 )； in: —Components of the current in the αβ coordinate system — Positive and negative sequence components of the current along the α-axis — Positive and negative sequence components of the current along the β-axis The formulas for calculating the active power and reactive power output of a distributed photovoltaic inverter are as follows: ( 8)； —Active and reactive power output of distributed photovoltaic systems When the grid voltage is unbalanced, the positive and negative sequence components of voltage and current in the αβ coordinate system are calculated using formulas (2)-(8), and then the output of the photovoltaic inverter is adjusted according to the negative sequence control theory.

4. The method for power flow calculation and reactive power optimization of low-voltage distribution networks with negative sequence control of photovoltaic inverters according to claim 1, characterized in that: Establish a calculation model for a low-voltage three-phase four-wire power flow system, specifically including: The constant power and current balance equations for three-phase and single-phase loads in a low-voltage power grid are as follows: ( 9 )； This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j; This represents the d-phase current in the load model. Represents the neutral point current in the load model. This represents the d-phase load capacity in the load model. This represents the d-phase voltage in the load model. This represents the neutral point voltage in the load model; The branch impedance matrix and its relationship with the branch admittance matrix in a typical low-voltage three-phase four-wire network are as follows: (10 )； in: It is the impedance between node i and node j in the x and y phases. It is the admittance of the x-phase and y-phase between node i and node j.

5. The method for power flow calculation and reactive power optimization of low-voltage distribution networks with negative sequence control of photovoltaic inverters according to claim 1, characterized in that: After completing the three-phase power flow calculation for a low-voltage power grid with distributed photovoltaic (PV) systems, the reactive power optimization objective function and constraints are determined. The Lagrange multiplier method is then used to calculate the reactive power and voltage optimization of the low-voltage power grid with distributed PV systems, specifically including: The objective function for active power loss is as follows: ( 11 )； It studies the total active power loss of the network. It studies the total active power of network generators. It studies the total active power of network load; The objective function for three-phase voltage imbalance is as follows: ( 12)； It refers to the three-phase voltage imbalance. , , It refers to the ABC three-phase voltages at the node; Therefore, the comprehensive objective function is obtained: ( 13 )； f(x) is a comprehensive objective function that includes active power loss and three-phase voltage imbalance. and These are the weight coefficients of the two sub-objective functions; Constraints include equality constraints and inequality constraints; The equality constraint is a current constraint, as detailed below: (14 )； This represents the generator current connected to node i. This represents the load current connected to node i. This represents the admittance between node i and node j. This represents the voltage at node j; The inequality constraints are voltage and power constraints, where the voltage constraint is: ( 15 )； It is the voltage of each phase at node i. and These are the maximum and minimum values ​​of the phase voltage at node i; Power constraints are for both active and reactive power of the generator: ( 16 )； It studies the total active power of all generators in the power grid. It is the maximum value of the sum of the active power of all generators in the power grid. It studies the total reactive power of all generators in the power grid. It is the maximum value of the total reactive power of all generators in the power grid. It is the minimum value of the total reactive power of all generators in the power grid. After determining the reactive power optimization objective function and constraints, the Lagrange multiplier method is used to calculate the reactive power and voltage optimization of a low-voltage power grid containing distributed photovoltaic power: ( 17 )； in The objective function for reactive power optimization is... For reactive power optimization equality constraints, For reactive power optimization inequality constraints, The minimum value corresponding to the inequality constraint, The maximum value of the corresponding inequality constraint.

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