CN113094898B - Power distribution network reliability analysis method based on time domain simulation under regional autonomy - Google Patents

Abstract

The invention discloses a distribution network reliability analysis method based on time domain simulation under regional autonomy. The steps include: establishing a mathematical model of typical distributed power sources of photovoltaic arrays, wind power generators, energy storage systems and micro gas turbines; The mathematical model of the distributed power supply is used to build the simulation model of each distributed power supply; each simulation model is simulated and analyzed separately to obtain the output characteristic curves of various distributed power supplies; based on the distributed power simulation model, the input load, line impedance, etc. parameters, build a simulation model of the distribution network connected to the main network, and make the distribution network work in the grid-connected mode; set the breaking time of the circuit breaker on the line connected to the main network to simulate the regional autonomous operation mode of the distribution network; The reliability of the distribution network is judged by the output power and voltage of each power supply, motor speed, frequency and other indicators. It can intuitively, quickly and effectively analyze the reliability of the distribution network running in the regional autonomous mode for a short time after being disconnected from the main network.

Description

A reliability analysis method of distribution network based on time domain simulation under regional autonomy

technical field

The invention belongs to the technical field of distribution network reliability analysis, in particular to a distribution network reliability analysis method based on time domain simulation under regional autonomy.

Background technique

Judging from the reasons for the occurrence of major power outages in various countries in recent years, in addition to controllable factors such as power grid planning and operation, dispatcher operations, etc., there are also uncontrollable factors such as equipment failures and natural disasters. The mode of passive defense to improve the reliability of distribution network is obviously not enough. For this reason, the concept of regional autonomy is introduced into the planning and operation of the distribution network. When encountering a sudden failure of the main network, the distribution network will actively disconnect from the main network and operate in the regional autonomy mode. Therefore, it is very important to analyze the reliability of the distribution network in this short-term process.

In the past, the reliability analysis of distribution network mainly used eigenvalue analysis method, Lyapunov method and nonlinear theoretical analysis method. However, the distribution network model constructed by the above method has high complexity, poor applicability, slow solution speed, and unintuitive analysis results, which is not conducive to analyzing the reliability of distribution network in a short time.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a distribution network reliability analysis method based on time domain simulation under regional autonomy, which can intuitively, quickly and effectively analyze the operation of the distribution network after being disconnected from the main network Short-term reliability in regional autonomous mode.

The object of the present invention can be realized through the following technical solutions:

A distribution network reliability analysis method based on time domain simulation under regional autonomy, comprising the following steps:

S1. Establish a mathematical model of typical distributed power sources of photovoltaic arrays, wind turbines, energy storage systems and micro gas turbines;

S2. Build a simulation model of each distributed power source based on the mathematical model of the typical distributed power source;

S3. Perform simulation analysis on each simulation model to obtain output characteristic curves of various distributed power sources;

S4. Based on the distributed power supply simulation model, input parameters such as load and line impedance, build a distribution network simulation model connected to the main network, and make the distribution network work in the grid-connected mode;

S5. Set the breaking time of the circuit breaker on the line connected to the main network to simulate the regional autonomous operation mode of the distribution network;

S6, judge the reliability of the distribution network through the output power and voltage of each power supply, motor speed, frequency and other indicators.

Further, the S1 specifically includes the following steps:

S1.1, establish a mathematical model of photovoltaic array;

P=U _oc I _L (3)

S1.2, establish the mathematical model of wind turbine;

S1.3. Establish a mathematical model of the energy storage system;

Establish a mathematical model of the energy storage system consisting of batteries, inverters and droop control systems, etc.

S1.4, establish the mathematical model of the micro gas turbine.

Further, in formulas (1), (2) and (3), _IL is the output current of the battery pack, I _ph is the short-circuit current when the light intensity is a fixed value, _{ID is the diode saturation current, and I sc is} the standard test The short-circuit current under the condition, N _p is the number of components in parallel, N _s is the number of components in series, U _oc is the terminal voltage of the battery components, R _s is the constant value resistance, the charge constant q = 1.6 × 10 ^{- 19} C, A is the diode polarity factor, Boltzmann constant K=1.38×10 ^-23 J/K, T is the ambient absolute temperature, K _t is the temperature coefficient, and G is the light intensity.

Further, formula (4) is the mathematical model of the wind turbine, p _f is the mechanical power captured by the wind turbine; R is the blade radius of the wind turbine; ρ is the density in the air, in (kg/m ³ ); V is the wind force The size of the speed, the unit is (m/s); C _p is the wind energy utilization coefficient, indicating the conversion efficiency of the wind turbine, which is a function of the blade pitch angle β and the tip speed ratio λ; C _i is various types of fans usage factor.

Further, formula (5) is the stator voltage equation of the synchronous generator, ud is the _d -axis component of the stator voltage, u _q is the q-axis component of the stator voltage, id is the _d -axis component of the stator current, and i _q is the stator The q-axis component of the current, L _d is the equivalent d-axis inductance of the synchronous generator, L _q is the equivalent q-axis inductance of the synchronous generator, R is the stator resistance, and formula (6) is the flux linkage equation of the synchronous generator, Formula (7) is the torque equation of the synchronous generator.

Further, formula (8) is the mathematical model of the battery, V _b is the outlet voltage, SOC is the state of charge, R _b is the internal resistance of the battery, V _o is the open circuit voltage of the battery, i _b is the charging current of the battery, and K is the polarization voltage. , Q is the battery capacity, A and B are the characteristic constants of the battery.

其中V_m是调制信号波的幅值，V_b是载波信号的幅值；ω_m是调制波的频率。Formula (9) is the three-phase fundamental wave component of the inverter output voltage, V _dc is the inverter DC side voltage; m is the modulation ratio.

Wherein V _m is the amplitude of the modulating signal wave, V _b is the amplitude of the carrier signal; ω _m is the frequency of the modulating wave.

Formulas (10) and (11) are the mathematical models of the inverter in the synchronous rotating coordinate system, L ₁ is the filter inductance, C ₁ is the filter capacitor; i _1k is the inverter output current, and i _2k is the filter capacitor C ₁ , i _3k is the current after the filter; u _1k is the output voltage of the inverter, and u _2k is the output voltage after the filter.

The formula (12) is the calculation formula of the output power of the inverter in the synchronous rotating coordinate system.

Formula (13) is the control principle of the droop control system, f is the actual frequency of the inverter, V is the actual output voltage of the inverter, _fn is the rated frequency of the microgrid, _Vn is the rated voltage of the microgrid, and P is the The actual value of the active power of the inverter, Q is the actual value of the reactive power of the inverter, P _n is the rated reference value of the active power, Q _n is the rated reference value of the active power, a is the inverter frequency droop coefficient, b is the inverter frequency voltage droop coefficient.

Further, the distributed power simulation model established in S2 specifically includes the following content:

(1) Photovoltaic array simulation model - The photovoltaic array simulation model consists of photovoltaic panels, a control system using the maximum power tracking control method and an inverter;

(2) Simulation model of wind turbine—the simulation model of wind turbine includes wind turbine, synchronous generator, AC-DC-AC converter and governor;

(3) Simulation model of energy storage system, including battery, droop control system power control loop and voltage and current control loop;

(4) Simulation model of micro gas turbine.

Beneficial effects of the present invention:

1. The reliability analysis method of distribution network based on time domain simulation under regional autonomy proposed by the present invention establishes simulation models of photovoltaic arrays, wind turbines, energy storage systems and micro gas turbines on the basis of the distributed power mathematical model, According to the power characteristics of each distributed power source, the output of various distributed power sources is simulated and analyzed, which establishes the foundation for the model construction and reliability analysis of the distribution network;

2. The reliability analysis method of the distribution network based on time domain simulation under regional autonomy proposed by the present invention adopts the time domain simulation analysis method to analyze the reliability of the distribution network. According to its topological structure, the whole system model is formed with corresponding modules, and then by simulating the change over time after the distribution network is separated from the main network, it reflects the change over time of the output power and voltage of each power supply, the frequency of the whole network, etc., so as to be Reliability analysis provides criteria.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. In other words, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the overall flow schematic diagram of the embodiment of the present invention;

FIG. 2 is a simulation model diagram of a photovoltaic array according to an embodiment of the present invention;

3 is a simulation model diagram of a wind turbine according to an embodiment of the present invention;

4 is a simulation model diagram of an energy storage system according to an embodiment of the present invention;

5 is a simulation model diagram of a power control loop of a droop control system of an energy storage system according to an embodiment of the present invention;

6 is a simulation model diagram of a voltage and current control loop of a droop control system of an energy storage system according to an embodiment of the present invention;

7 is a simulation model diagram of a micro gas turbine according to an embodiment of the present invention;

FIG. 8 is a diagram of a simulation model of a distribution network according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 1, a distribution network reliability analysis method based on time domain simulation under regional autonomy includes the following steps:

S1. Establish a mathematical model of typical distributed power sources of photovoltaic arrays, wind turbines, energy storage systems and micro gas turbines;

S1.1. Establish a mathematical model of photovoltaic array

P=U _oc I _L (3)

In the above formulas (1), (2), (3), _IL is the output current of the battery pack, I _ph is the short-circuit current when the light intensity is a fixed value, _{ID is the diode saturation current, and I sc is} the standard test condition. The short-circuit current of , N _p is the number of components in parallel, N _s is the number of components in series, U _oc is the terminal voltage of the battery components, R _s is the constant value resistance, the charge constant q = 1.6 × 10 ^-19 C, A is Diode polarity factor, Boltzmann constant K=1.38×10 ^-23 J/K, T is the absolute temperature of the environment, K _t is the temperature coefficient, and G is the light intensity.

S1.2. Establish mathematical model of wind turbine

The above formula (4) is the mathematical model of the wind turbine, p _f is the mechanical power captured by the wind turbine; R is the blade radius of the wind turbine; ρ is the density in the air in (kg/m ³ ); V is the wind speed. Size, unit is (m/s); C _p is the wind energy utilization coefficient, indicating the conversion efficiency of the wind turbine, which is a function of the blade pitch angle β and the tip speed ratio λ; C _i is the use of various types of fans coefficient.

The above formula (5) is the stator voltage equation of the synchronous generator, ud is the _d -axis component of the stator voltage, u _q is the q-axis component of the stator voltage, id is the _d -axis component of the stator current, and i _q is the stator current. q-axis component, L _d is the equivalent d-axis inductance of the synchronous generator, L _q is the equivalent q-axis inductance of the synchronous generator, and R is the stator resistance.

The above formula (6) is the flux linkage equation of the synchronous generator.

The above formula (7) is the torque equation of the synchronous generator.

S1.3. Establish a mathematical model of the energy storage system

Establish a mathematical model of the energy storage system consisting of batteries, inverters and droop control systems, etc.

The above formula (8) is the mathematical model of the battery, V _b is the outlet voltage, SOC is the state of charge, R _b is the internal resistance of the battery, V _o is the open circuit voltage of the battery, i _b is the charging current of the battery, K is the polarization voltage, Q is the battery capacity, A and B are the characteristic constants of the battery.

其中V_m是调制信号波的幅值，V_b是载波信号的幅值；ω_m是调制波的频率。The above formula (9) is the three-phase fundamental wave component of the inverter output voltage, V _dc is the DC side voltage of the inverter; m is the modulation ratio,

Wherein V _m is the amplitude of the modulating signal wave, V _b is the amplitude of the carrier signal; ω _m is the frequency of the modulating wave.

The above formulas (10) and (11) are the mathematical models of the inverter in the synchronous rotating coordinate system, L ₁ is the filter inductance, C ₁ is the filter capacitor; i _1k (subscript k represents the d-axis, q-axis) is the inverse The inverter output current, i _2k is the current of the filter capacitor C ₁ , i _3k is the current after the filter; u _1k (subscript k represents the d axis, q axis) is the inverter output voltage, u _2k is the filtered current output voltage after the device.

The above formula (12) is a formula for calculating the output power of the inverter in the synchronous rotating coordinate system, so as to realize the control and adjustment of the output power of the inverter.

The above formula (13) is the control principle of the droop control system, f is the actual frequency of the inverter, V is the actual output voltage of the inverter, _fn is the rated frequency of the microgrid, _Vn is the rated voltage of the microgrid, P is the actual value of the active power of the inverter, Q is the actual value of the reactive power of the inverter, P _n is the rated reference value of the active power, Q _n is the rated reference value of the active power, and a is the inverter frequency droop coefficient , b is the inverter frequency voltage droop coefficient.

S1.4, establish the mathematical model of the micro gas turbine

The synchronous generator is used as the micro gas turbine, so formulas (5) (6) (7) are also the mathematical model of the micro gas turbine.

S2. Build a simulation model of each distributed power source based on the mathematical model of the typical distributed power source;

The established distributed power simulation model includes the following contents:

(1) The photovoltaic array simulation model, as shown in Figure 2, the photovoltaic array simulation model consists of photovoltaic panels, a control system using the maximum power tracking control method and an inverter;

(2) Wind turbine simulation model, as shown in Figure 3, the wind turbine simulation model includes a wind turbine, a synchronous generator, an AC-DC-AC converter and a governor;

(3) Simulation model of energy storage system, including battery, droop control system power control loop and voltage and current control loop, as shown in Figure 4, Figure 5 and Figure 6 respectively;

(4) Simulation model of micro gas turbine, as shown in Figure 7.

S3. Perform simulation analysis on each simulation model to obtain output characteristic curves of various distributed power sources;

S4. Based on the distributed power supply simulation model, input parameters such as load and line impedance, build a distribution network simulation model connected to the main network, and make the distribution network work in the grid-connected mode;

As shown in Figure 8, a simulation model of the distribution network including photovoltaic arrays, wind turbines, energy storage systems and micro-turbines is established.

S5. Set the breaking time of the circuit breaker on the line connected to the main network to simulate the regional autonomous operation mode of the distribution network;

S6, judge the reliability of the distribution network through the output power and voltage of each power supply, motor speed, frequency and other indicators.

In the description of this specification, description with reference to the terms "one embodiment," "example," "specific example," etc. means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one aspect of the present invention. in one embodiment or example. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention.

Claims (2)

1. a distribution network reliability analysis method based on time domain simulation under regional autonomy, is characterized in that, comprises the steps: S1. Establish a mathematical model of typical distributed power sources of photovoltaic arrays, wind turbines, energy storage systems and micro gas turbines; S2. Build a simulation model of each distributed power source based on the mathematical model of the typical distributed power source; S3. Perform simulation analysis on each simulation model to obtain output characteristic curves of various distributed power sources; S4. Based on the distributed power supply simulation model, input load and line impedance parameters, build a distribution network simulation model connected to the main network, and make the distribution network work in the grid-connected mode; S5. Set the breaking time of the circuit breaker on the line connected to the main network to simulate the regional autonomous operation mode of the distribution network; S6. Determine the reliability of the distribution network through the output power and voltage of each power supply, motor speed, and frequency indicators; The S1 specifically includes the following steps: S1.1, establish a mathematical model of photovoltaic array;

P=U _oc I _L (3) S1.2, establish the mathematical model of wind turbine;

T _e =n _p [(L _d -L _q )i _d i _q +ψ _f i _q ] (7) S1.3. Establish a mathematical model of the energy storage system; Establish a mathematical model of the energy storage system consisting of battery, inverter and droop control system,

S1.4, establish the mathematical model of the micro gas turbine; In formulas (1), (2), (3), _IL is the output current of the battery pack, I _ph is the short-circuit current when the light intensity is a fixed value, _{ID is the diode saturation current, and I sc is} the standard test condition Short-circuit current, N _p is the number of components in parallel, N _s is the number of components in series, U _oc is the terminal voltage of the battery components, R _s is the constant value resistance, the charge constant q = 1.6×10 ^-19 C, and A is the diode Polarity factor, Boltzmann constant K=1.38×10 ^-23 J/K, T is the absolute temperature of the environment, K _t is the temperature coefficient, G is the light intensity; Formula (4) is the mathematical model of the wind turbine, p _f is the mechanical power captured by the wind turbine; R is the blade radius of the wind turbine; ρ is the density in the air, the unit is kg/m ³ ; V is the wind speed, the unit is m/s; C _p is the wind energy utilization coefficient, which represents the conversion efficiency of the wind turbine and is a function of the blade pitch angle β and the tip speed ratio λ; C _i is the utilization coefficient of various types of fans; Formula (5) is the stator voltage equation of the synchronous generator, ud is the _d -axis component of the stator voltage, u _q is the q-axis component of the stator voltage, id is the _d -axis component of the stator current, and i _q is the q-axis component of the stator current shaft component, L _d is the equivalent d-axis inductance of the synchronous generator, L _q is the equivalent q-axis inductance of the synchronous generator, R is the stator resistance, formula (6) is the flux linkage equation of the synchronous generator, formula (7) ) is the torque equation of the synchronous generator; Formula (8) is the mathematical model of the battery, V _b is the outlet voltage, SOC is the state of charge, R _b is the internal resistance of the battery, V _o is the open circuit voltage of the battery, i _b is the charging current of the battery, K is the polarization voltage, and Q is the Battery capacity, A and B are both characteristic constants of the battery; Formula (9) is the three-phase fundamental wave component of the inverter output voltage, V _dc is the DC side voltage of the inverter; m is the modulation ratio,

where V _m is the amplitude of the modulating signal wave, V _b is the amplitude of the carrier signal; ω _m is the frequency of the modulating wave; Formulas (10) and (11) are the mathematical models of the inverter in the synchronous rotating coordinate system, L ₁ is the filter inductance, C ₁ is the filter capacitor; i _1k is the inverter output current, and i _2k is the filter capacitor C ₁ , i _3k is the current after the filter; u _1k is the inverter output voltage, u _2k is the output voltage after the filter; Formula (12) is the calculation formula of the output power of the inverter in the synchronous rotating coordinate system; Formula (13) is the control principle of the droop control system, f is the actual frequency of the inverter, V is the actual output voltage of the inverter, _fn is the rated frequency of the microgrid, _Vn is the rated voltage of the microgrid, and P is the The actual value of the active power of the inverter, Q is the actual value of the reactive power of the inverter, P _n is the rated reference value of the active power, Q _n is the rated reference value of the active power, a is the inverter frequency droop coefficient, b is the inverter frequency voltage droop coefficient. 2. the distribution network reliability analysis method based on time domain simulation under a kind of regional autonomy according to claim 1, is characterized in that, the distributed power supply simulation model established in described S2, specifically comprises the following content: (1) Photovoltaic array simulation model - The photovoltaic array simulation model consists of photovoltaic panels, a control system using the maximum power tracking control method and an inverter; (2) Simulation model of wind turbine—the simulation model of wind turbine includes wind turbine, synchronous generator, AC-DC-AC converter and governor; (3) Simulation model of energy storage system, including battery, droop control system power control loop and voltage and current control loop; (4), the micro gas turbine simulation model.

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