Novel power system broadband resonance potential energy theory method

Abstract

The application discloses a novel power system broadband resonance potential energy theory method, which is based on the voltage of each node and the branch current of an electric network measured, defines the reactive resonance potential energy W Q of the electric network according to the energy driving nature of the power system broadband resonance, and performs separate analysis on the resonance component in the signal according to the superposition equivalent principle of the circuit. Q The network branches are classified and the reference direction is defined, the general formula of the reactive resonance potential energy W Q of each type of branch is derived, and finally, it is judged whether W Q is inductive or capacitive, thereby providing a new thought and reference for the identification, quantitative analysis and oscillation tracing of the novel power system broadband resonance.

Description

Technical Field

[0001] This invention belongs to the field of broadband oscillation technology of power systems, and relates to a novel theoretical method for broadband resonant potential energy of power systems. Background Technology

[0002] Broadband oscillation analysis of novel power systems is fundamental for broadband oscillation mechanism analysis, oscillation identification, source tracing, and oscillation path exploration. The same applies to broadband resonance analysis. Traditional methods for broadband resonance analysis of novel power systems, such as numerical analysis, eigenvalue analysis, and impedance analysis, all rely heavily on the accuracy of system parameter identification and modeling, and are prone to the curse of dimensionality. These methods cannot perform broadband resonance analysis when system parameters are unknown, and have limitations for analyzing large systems. Furthermore, these methods cannot effectively reflect the dynamic characteristics of strongly nonlinear power system oscillations. Different analytical methods may lead to different conclusions regarding broadband resonance, resulting in an unclear mechanism for the participation of power electronic devices in broadband resonance. Summary of the Invention

[0003] The purpose of this invention is to provide a novel theoretical method for broadband resonant potential energy in power systems, which solves the problems of limitations in the analysis of large systems and the inability to effectively reflect the dynamic characteristics of oscillations in strongly nonlinear power systems in existing technologies.

[0004] The technical solution adopted in this invention is a novel broadband resonant potential energy theory method for power systems, which is implemented according to the following steps: Step 1, broadband resonance component analysis; Step 2: Derive the general formula for reactive resonant potential energy of various branches; Step 3: Determine whether the reactive resonant potential energy is inductive or capacitive.

[0005] The invention is further characterized by: Step 1 specifically involves: analyzing the broadband resonant components in the sampled voltage and current signals separately based on the superposition equivalence principle of the circuit. Step 1 specifically involves: When a network exhibits single-mode broadband resonance, the network is equivalent to a power frequency AC voltage source U. S With high-frequency AC excitation voltage source U h The resonant circuit formed by their combined effects is simply equivalent to a second-order LC resonant circuit; based on the direction of the voltage and current relationship in each branch, the port voltage u and current i of the equivalent voltage source are:

[0006] (1); In the formula, w s For the power frequency angular frequency, wh U is a high-frequency angular frequency; s U represents the effective value of the power frequency voltage at the equivalent power supply port. h Represents the effective value of the high-frequency voltage superimposed on the equivalent power supply ports; I s I represents the effective value of the branch fundamental frequency current. h Represents the effective value of the high-frequency current superimposed on the branch; φ su φ is the initial phase angle of the power frequency voltage. si φ is the initial phase angle of the power frequency current. hu φ is the initial phase angle of the high-frequency voltage. hi This is the initial phase angle of the high-frequency current; Step 2 specifically involves defining the reactive resonant potential energy W based on the energy-driven nature of broadband resonance in power systems. Q Furthermore, the network branches are classified and reference directions are defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula; Step 2 specifically involves defining three types of branches based on the interaction characteristics of the reactive energy of each branch, defining reference directions, and deriving the reactive resonant potential energy W of each type of branch. Q The general formula: Based on its voltage and current characteristics and the interaction characteristics of reactive quantities between branches, the branch definitions and reference directions in the system are specified as follows: A branch containing a power source and directly grounded is defined as a power source branch to ground; a branch containing a load at the end of a distribution network and directly grounded is defined as a load branch to ground; a branch connecting a node in the power network and not directly grounded is defined as a node branch; the voltage and current of a power source branch to ground use a non-associated reference direction; and the load branch to ground and the node branch use an associated reference direction. In the ground load branch model, the inductor L j / Capacitor C j Resistance R j composition; Define the resonant potential energy W of the earth branch. Qj : (2); In the formula, Q j For high-frequency reactive power of the ground branch, W s T is the angular frequency corresponding to f=50Hz. s This is the period corresponding to the power frequency f=50Hz, that is: (3); In the formula, u j For the load node voltage, i jn To calculate the current of the branch to ground load, and u j and i jnThe node voltages and branch currents corresponding to the high-frequency resonances are all analyzed independently. If we extend the concept of ground load branches to the general form of multiple ground load branches connected in parallel, the general expression for multiple ground load branches connected in parallel is derived as follows: (4); The power supply branch to ground is supplied by voltage source U. s Inductor L i Resistance R i Composition, that is, the ground power supply branch includes an excitation source and the reference direction is a non-associated reference direction, thus deriving the general expression for the parallel form of multiple ground power supply branches: (5); In the formula, u i and i in The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The node branch has a current i flowing through it. ij The voltage drop is u ij The voltage at which the branch current flows into the node is u. i The voltage at the node from which the branch current flows out is u. j ; The voltage u flowing into the node from the branch current i With branch current i ij The calculated reactive resonant potential energy is defined as: the resonant potential energy W flowing into branch ij. Qijin The formula is: (6); In the formula, u i and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage drop from the two ends of the branch u ij With branch current i ij The calculated reactive resonant potential energy is defined as: W, the resonant potential energy stored in branch ij. Qij The formula is: (7); In the formula, u ij and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage u of the node through which the branch current flows. j With branch current i ij The calculated reactive resonant potential energy is defined as: the reactive resonant potential energy W flowing out of branch ij. Qijout The calculation formula is as follows: (8); In the formula, u j and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. In step 2, all the reactive resonant potential energies W are calculated. Q In the calculation process, u and i correspond to the voltage and current of the high-frequency resonant components, but the period and frequency involved in the calculation process are the period and frequency corresponding to the power frequency. The obtained reactive resonant potential energy is a multiple of the electric field or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency. This multiple relationship is related to the multiple of the high-frequency resonant frequency to the power frequency. That is, the obtained reactive energy corresponds to the reactive energy interacting in the network, and it is amplified to the time scale of ms as virtual broadband resonant potential energy. If the period and frequency involved in the calculation are the period and frequency corresponding to the high-frequency resonant component, the resulting reactive resonant potential energy is the electric or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency. It is the real broadband resonant potential energy, and the period and frequency corresponding to the power frequency are used for calculation. If it is to more realistically reflect the driving essence of the network energy, the frequency of the corresponding high-frequency resonant component is used for calculation. Step 3 specifically involves: based on the extracted node voltage u and branch current i corresponding to the high-frequency resonant components, and after determining the lead and lag relationship, the following definitions are given: If the voltage leads the current, the branch exhibits inductive behavior, and the circuit is equivalent to a resistor R connected in series with an equivalent inductor. That is, the energy nature of the branch participating in the network energy interaction is magnetic field energy. If the current leads the voltage, the branch exhibits capacitive behavior, and the energy nature of the branch participating in the network energy interaction is electric field energy.

[0007] The beneficial effects of this invention are: The novel broadband resonant potential energy theory method for power systems of this invention first analyzes the high-frequency resonant signals in the sampled voltage u and current i independently based on the superposition equivalence principle of resonant circuits, avoiding the influence of power frequency signals on the resonant analysis. Then, starting from the energy-driven nature of broadband resonance in power systems, based on the node voltage u and branch current i corresponding to the high-frequency resonant components, three types of branches are defined according to the interaction characteristics of reactive power in each branch, a reference direction is defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula is used to calculate the reactive resonant potential energy W. Q The method of broadband resonant potential energy theory of the present invention can analyze broadband resonance from the perspective of non-functional quantities by measuring voltage and current in the case of unknown system parameters, and provides new ideas and references for broadband oscillation mechanism analysis, oscillation identification, source tracing and oscillation path exploration. Attached Figure Description

[0008] Figure 1This is a schematic diagram of the superposition equivalent principle of resonant circuits in the novel broadband resonant potential energy theory method for power systems of the present invention; Figure 2 This is a schematic diagram of system branch classification in the novel broadband resonant potential energy theory method for power systems of the present invention; Figure 3 This is a schematic diagram of multiple ground load branches connected in parallel in the novel broadband resonant potential energy theory method for power systems of the present invention; Figure 4 This is a schematic diagram of multiple ground power supply branches connected in parallel in the novel broadband resonant potential energy theory method for power systems of the present invention; Figure 5 This is a schematic diagram of the node branch in the novel broadband resonant potential energy theory method for power systems of the present invention. Detailed Implementation

[0009] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. This invention provides a novel theoretical method for broadband resonant potential energy in power systems, which is implemented according to the following steps: Example 1 Step 1, broadband resonance component analysis; Step 2: Derive the general formula for reactive resonant potential energy of various branches; Step 3: Determine whether the reactive resonant potential energy is inductive or capacitive; In this embodiment, step 1 is performed as follows: like Figure 1 As shown, the specific process of step 1 is as follows: based on the superposition equivalence principle of the circuit, the broadband resonant component in the sampled voltage and current signal is analyzed separately; When power electronic equipment resonates with the power network over a wideband frequency, the equipment can be equivalent to a power frequency AC voltage source U. S Superimposed high-frequency AC excitation voltage source U h Through the filter inductor L f When combined with the local circuit of the electrical network, it forms a resonant circuit, which can be simply equivalent to a second-order LC resonant circuit.

[0010] When a network exhibits single-mode broadband resonance, the network can be equivalently represented as a power frequency AC voltage source U. S With high-frequency AC excitation voltage source U h The resonant circuit formed by their combined action can be simply equivalent to a second-order LC resonant circuit.

[0011] Based on the direction of voltage and current correlation in each branch, the port voltage u and current i of the equivalent voltage source are:

[0012] (1) In the formula, ws For the power frequency angular frequency, w h U is a high-frequency angular frequency; s U represents the effective value of the power frequency voltage at the equivalent power supply port. h Represents the effective value of the high-frequency voltage superimposed on the equivalent power supply ports; I s I represents the effective value of the branch fundamental frequency current. h Represents the effective value of the high-frequency current superimposed on the branch; φ su φ is the initial phase angle of the power frequency voltage. si φ is the initial phase angle of the power frequency current. hu φ is the initial phase angle of the high-frequency voltage. hi This is the initial phase angle of the high-frequency current; That is, the network in single-mode broadband resonance can be regarded as being jointly acted by the power frequency voltage source and the high frequency resonance source. According to the principle of circuit superposition equivalence, the broadband resonance component is analyzed separately.

[0013] Example 2 Step 1, broadband resonance component analysis; Step 2: Derive the general formula for reactive resonant potential energy of various branches; Step 3: Determine whether the reactive resonant potential energy is inductive or capacitive; In this embodiment, step 2 is performed as follows: Step 2 is as follows: Based on the interaction characteristics of the reactive energy of each branch, three types of branches are defined, reference directions are defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula; The specific process is as follows: Each branch in the system, such as Figure 2 As shown, based on its voltage and current characteristics and the interaction characteristics of reactive quantities between branches, the branch definitions in the system are as follows: A branch that includes a power source and is directly grounded is defined as a power source branch to ground (where the power source refers to the power source in the system when the network is in a stable operating state). A branch containing loads at the end of a distribution network that is directly grounded is defined as a load branch to ground (similar to a power source, the load here also refers to the load in the system when the network is in a stable operating state). A branch that connects a node in an electrical network but is not directly grounded is defined as a node branch; The reference directions for the three types of branches are defined as follows: Figure 3 , Figure 4 and Figure 5 As shown: The voltage and current of the power supply branch to ground adopt a non-associated reference direction; Associative reference direction is used for ground load branches; Node branches use associated reference directions; In the ground load branch model, the inductor L i / Capacitor C i Resistance R i composition; Define the resonant potential energy W of the earth branch. Qi First, calculate T. s Energy W consumed by the resistor within a time period i for: (2-1); In the formula, u j For the load node voltage, i j To calculate the current of the corresponding load branch, and u j and i j The node voltages and branch currents corresponding to the high-frequency resonances are all analyzed independently, T s Given the period corresponding to a power frequency of 50Hz; calculate the power consumption of the resistive element. The active power Pj is: (2-2); Calculate apparent power: (2-3); That is, the product of the effective values ​​of the voltage and current of the load branch to ground; The effective value of the voltage of the load branch to ground is calculated as follows: (2-4); The effective value of the current in the branch circuit to ground load is calculated as follows: (2-5); Calculate the high-frequency reactive power Q of the ground branch. j : (2-6); Calculate the resonant potential energy W of the load branch to ground. Qj : (2); Among them, Q j For high-frequency reactive power of the ground branch, W s The angular frequency corresponding to f=50Hz is, i.e. (3); In the formula, u j For the load node voltage, i jn To calculate the current of the branch to ground load, and u j and i jn The node voltages and branch currents corresponding to the high-frequency resonances are all analyzed independently. If we extend the concept of ground load branches to the general form of multiple ground load branches connected in parallel, the general expression for the parallel form of multiple ground load branches can be derived as follows: (4); The difference between the power supply branch to ground and the load branch to ground is that there is a voltage source U. s Inductor L i Resistance R i The composition is that the ground power supply branch includes an excitation source and the reference direction is a non-associated reference direction. Thus, the general expression for the parallel connection of multiple ground power supply branches is derived as follows: (5); In the formula, u i and i in The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. For a node branch, the current flowing through the node branch is i. ij The voltage drop is u ij The voltage at which the branch current flows into the node is u. i The voltage at the node from which the branch current flows out is u. j ; The voltage u flowing into the node from the branch current i With branch current i ij The calculated reactive resonant potential energy is defined as: the resonant potential energy W flowing into branch ij. Qijin The formula is: (6); In the formula, u i and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage drop from the two ends of the branch u ij With branch current i ij The calculated reactive resonant potential energy is defined as: W, the resonant potential energy stored in branch ij. Qij The formula is: (7); In the formula, u ij and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage u of the node through which the branch current flows. j With branch current i ij The calculated reactive resonant potential energy is defined as: the reactive resonant potential energy W flowing out of branch ij. Qijout The calculation formula is as follows.

[0014] (8); In the formula, u j and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. In step 2 of this embodiment, all the reactive resonant potential energies W are calculated. Q In the calculation process, u and i correspond to the voltage and current of the high-frequency resonant components, but the period and frequency involved in the calculation process are the period and frequency corresponding to the power frequency. The obtained reactive resonant potential energy is a multiple of the electric field or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency. This multiple relationship is related to the multiple of the high-frequency resonant frequency to the power frequency. That is, the obtained quantity corresponds to the functional quantity interacting in the network by a multiple, and it is amplified to the time scale of ms as the virtual broadband resonant potential energy.

[0015] In step 2 of this embodiment, if the period and frequency used in the calculation process are those corresponding to the high-frequency resonant components, the resulting reactive resonant potential energy is the electric or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency, which is the true broadband resonant potential energy. For ease of data processing, the period and frequency corresponding to the power frequency are used for calculation. However, to more accurately reflect the driving nature of network energy, the frequency of the corresponding high-frequency resonant component can also be used for calculation.

[0016] Example 3 Step 1, broadband resonance component analysis; Step 2: Derive the general formula for reactive resonant potential energy of various branches; Step 3: Determine whether the reactive resonant potential energy is inductive or capacitive; In this embodiment, step 3 is performed as follows: The specific process is as follows: Determine the reactive resonant potential energy W. Q For sensibility or tolerance; Based on the extracted node voltage u and branch current i corresponding to the high-frequency resonant components, and after determining the lead and lag relationship, the following definitions are given: If the voltage leads the current, the branch is inductive, and the circuit is equivalent to a resistor R connected in series with an equivalent inductor. That is, the energy nature of the branch participating in the network energy interaction is magnetic field energy. If the current leads the voltage, the branch exhibits capacitive behavior, and the circuit is equivalent to a resistor R connected in series with an equivalent capacitor. That is, the energy nature of the branch participating in the network energy interaction is electric field energy. The novel broadband resonant potential energy theory method for power systems of this invention first analyzes the high-frequency resonant signals in the sampled voltage u and current i independently based on the superposition equivalence principle of resonant circuits, avoiding the influence of power frequency signals on the resonant analysis. Then, starting from the energy-driven nature of broadband resonance in power systems, based on the node voltage u and branch current i corresponding to the high-frequency resonant components, three types of branches are defined according to the interaction characteristics of reactive power in each branch, a reference direction is defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula is used to calculate the reactive resonant potential energy W. Q The method of broadband resonant potential energy theory of the present invention can analyze broadband resonance from the perspective of non-functional quantities by measuring voltage and current in the case of unknown system parameters, and provides new ideas and references for broadband oscillation mechanism analysis, oscillation identification, source tracing and oscillation path exploration.

Claims

1. A novel theoretical method for broadband resonant potential energy in power systems, characterized in that, The specific steps are as follows: Step 1, broadband resonance component analysis; Step 2: Derive the general formula for reactive resonant potential energy of various branches; Step 3: Determine whether the reactive resonant potential energy is inductive or capacitive; Step 2 specifically involves defining the reactive resonant potential energy W based on the energy-driven nature of broadband resonance in power systems. Q Furthermore, the network branches are classified and reference directions are defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula; The specific process of step 2 is as follows: Based on the interaction characteristics of the reactive energy of each branch, three types of branches are defined, a reference direction is defined, and the reactive resonant potential energy W of each type of branch is derived. Q The general formula: Based on its voltage and current characteristics and the interaction characteristics of reactive quantities between branches, the branch definitions and reference directions in the system are specified as follows: A branch containing a power source and directly grounded is defined as a power source branch to ground; a branch containing a load at the end of a distribution network and directly grounded is defined as a load branch to ground; a branch connecting a node in the power network and not directly grounded is defined as a node branch; the voltage and current of a power source branch to ground use a non-associated reference direction; and the load branch to ground and the node branch use an associated reference direction. In the ground load branch model, the inductor L j / Capacitor C j Resistance R j composition; Define the resonant potential energy W of the earth branch. Qj : （1）； In the formula, Q j For high-frequency reactive power of the ground branch, W s T is the angular frequency corresponding to f=50Hz. s This is the period corresponding to the power frequency f=50Hz, that is: （2）； In the formula, u j For the load node voltage, i jn To calculate the current of the branch to ground load, and u j and i jn The node voltages and branch currents corresponding to the high-frequency resonances are all analyzed independently. If we extend the concept of ground load branches to the general form of multiple ground load branches connected in parallel, the general expression for multiple ground load branches connected in parallel is derived as follows: （3）； The power supply branch to ground is supplied by voltage source U. s Inductor L i Resistance R i Composition, that is, the ground power supply branch includes an excitation source and the reference direction is a non-associated reference direction, thus deriving the general expression for the parallel form of multiple ground power supply branches: （4）； In the formula, u i and i in The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The node branch has a current i flowing through it. ij The voltage drop is u ij The voltage at which the branch current flows into the node is u. i The voltage at the node from which the branch current flows out is u. j ; The voltage u flowing into the node from the branch current i With branch current i ij The calculated reactive resonant potential energy is defined as: the resonant potential energy W flowing into branch ij. Qijin The formula is: （5） In the formula, u i and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage drop from the two ends of the branch u ij With branch current i ij The calculated reactive resonant potential energy is defined as: W, the resonant potential energy stored in branch ij. Qij The formula is: （6） In the formula, u ij and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently. The voltage u of the node from which the branch current flows. j With branch current i ij The calculated reactive resonant potential energy is defined as: the reactive resonant potential energy W flowing out of branch ij. Qijout The calculation formula is as follows: （7） In the formula, u j and i ij The voltage drop and branch current corresponding to the high-frequency resonant components are all analyzed independently.

2. The novel broadband resonant potential energy theory method for power systems according to claim 1, characterized in that, Step 1 specifically involves: analyzing the broadband resonant components in the sampled voltage and current signals separately based on the superposition equivalence principle of the circuit.

3. The novel broadband resonant potential energy theory method for power systems according to claim 2, characterized in that, Step 1 specifically involves: When a network exhibits single-mode broadband resonance, the network is equivalent to a power frequency AC voltage source U. S With high-frequency AC excitation voltage source U h The resonant circuit formed by their combined effects is simply equivalent to a second-order LC resonant circuit; based on the direction of the voltage and current relationship in each branch, the port voltage u and current i of the equivalent voltage source are: （8） In the formula, w s For the power frequency angular frequency, w h U is a high-frequency angular frequency; s U represents the effective value of the power frequency voltage at the equivalent power supply port. h Represents the effective value of the high-frequency voltage superimposed on the equivalent power supply ports; I s I represents the effective value of the branch fundamental frequency current. h Represents the effective value of the high-frequency current superimposed on the branch; φ su φ is the initial phase angle of the power frequency voltage. si φ is the initial phase angle of the power frequency current. hu φ is the initial phase angle of the high-frequency voltage. hi This is the initial phase angle of the high-frequency current.

4. The novel broadband resonant potential energy theory method for power systems according to claim 1, characterized in that, All the reactive resonant potential energies W calculated in step 2 Q In the calculation process, u and i correspond to the voltage and current of the high-frequency resonant components, but the period and frequency involved in the calculation process are the period and frequency corresponding to the power frequency. The obtained reactive resonant potential energy is a multiple of the electric field or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency. This multiple relationship is related to the multiple of the high-frequency resonant frequency to the power frequency. That is, the obtained reactive energy corresponds to the reactive energy interacting in the network, and it is amplified to the time scale of ms as virtual broadband resonant potential energy. If the period and frequency used in the calculation are those corresponding to the high-frequency resonant components, the resulting reactive resonant potential energy is the electric or magnetic field energy under the action of the high-frequency resonant source at the corresponding frequency. This is the true broadband resonant potential energy, calculated using the period and frequency corresponding to the power frequency. If it is to more realistically reflect the driving nature of network energy, the frequency of the corresponding high-frequency resonant components is used for calculation.

5. The novel broadband resonant potential energy theory method for power systems according to claim 1, characterized in that, Step 3 specifically involves: based on the extracted node voltage u and branch current i corresponding to the high-frequency resonant components, and after determining the lead and lag relationship, the following definitions are given: If the voltage leads the current, the branch exhibits inductive behavior, and the circuit is equivalent to a resistor R connected in series with an equivalent inductor. That is, the energy nature of the branch participating in the network energy interaction is magnetic field energy. If the current leads the voltage, the branch exhibits capacitive behavior, and the energy nature of the branch participating in the network energy interaction is electric field energy.

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