Power system stabilizing system and power system stabilizing method

Abstract

The present application provides a power system stabilization system and a power system stabilization method, which can fundamentally cope with the problem of insufficient voltage maintenance capability and frequency maintenance capability and its variation. In the power system stabilization system, a power station having a synchronous machine subjected to excitation control is connected to a power system, the synchronous machine is controlled by an excitation control device, and the power system stabilization system has a compensation circuit that corrects a control constant of the excitation control device of the synchronous machine based on a power system stability maintenance index that is an index reflecting the amount of renewable energy in the power system.

Description

Technical Field

[0001] This invention relates to power system stabilization systems and methods, and particularly to power system stabilization systems and methods suitable for achieving power system stability in situations where renewable energy sources lack power system stabilization functions (voltage regulation and frequency regulation functions) and increase in power system stability. Background Technology

[0002] Regarding power systems, stable operation is achieved by rapidly controlling voltage and frequency to predetermined values ​​in response to fluctuations in electricity supply and demand. Voltage regulation is primarily maintained through excitation control of generators in power plants and phase-regulating equipment in substations. Furthermore, the power system frequency is maintained by controlling the supply and demand relationship between the mechanical input and power output of generators in power plants.

[0003] Regarding this point, the mainstream power plants currently consist of thermal power plants, nuclear power plants, and hydropower plants (hereinafter referred to as existing power plants) that possess system stabilization functions (voltage regulation and frequency regulation). However, in recent years, the proportion of renewable energy sources that lack these functions has increased. As a result, from the perspective of the power system as a whole, there is a tendency for insufficient voltage and frequency regulation capabilities.

[0004] Therefore, the application of power systems that take into account renewable energy sources such as solar power generation and wind power generation has been proposed. For example, in Patent Document 1, the purpose is to provide a power system voltage and reactive power monitoring and control device that can maintain the balance of voltage and reactive power of the power system even when the output of renewable energy changes over time due to weather, or when the power supply structure or system structure is changed, and can improve economic efficiency. The following is a power system voltage and reactive power monitoring and control device that provides transmission data to a separate device that can adjust the voltage and reactive power of the power system. The power system voltage and reactive power monitoring and control device uses one or more indicators representing the stability of the power system to determine one or more target value constraints, obtains information about the target value based on the target value constraints, and provides transmission data containing the information about the target value to a separate device, which then adjusts the voltage and reactive power of the set part.

[0005] Furthermore, Patent Document 2 aims to provide a reactive power control system that, when using AQR control (Automatic Reactive Power Regulator) to control reactive power, prevents it from becoming leading reactive power and enables the reactive power control PF (power factor) to be 1.0. The aforementioned AQR control is achieved through the switching on / off control of leading capacitors. Prior art document 2 proposes a reactive power control system that is interconnected with a commercial power supply and includes distributed power supplies. It controls the reactive power at the receiving point from the commercial power supply using AQR control with leading capacitors. This system includes: a detection unit that detects the reactive power at the receiving point before AQR control, i.e., the first reactive power; AQR, which determines whether AQR control is needed based on the value of the first reactive power and performs AQR control; and AVR, which performs AVR control before AQR control in AQR to correct the value of the first reactive power to a value that can be offset in AQR control.

[0006] It is believed that the trend of increasing renewable energy will further expand in the future, and some predict that renewable energy will account for 50% by 2050.

[0007] Furthermore, this proportion doesn't simply increase; it fluctuates significantly. For example, during the day when solar power is generated, the proportion of renewable energy sources, including wind power, increases, while at night when solar power is not generated, the proportion of renewable energy sources, primarily wind power, decreases. Moreover, this ratio variation not only occurs within a single day but also varies by month, season, or region.

[0008] It is anticipated that such structural changes to the power system will pose some obstacles to voltage and frequency maintenance. For example, disconnecting some existing power plants from the power system will cause a voltage drop that is difficult to restore. This is because the overall voltage maintenance capability of the power system is reduced. Furthermore, as a countermeasure, measures to enhance voltage and frequency maintenance capabilities (by increasing the generating capacity of existing power plants and the capacity of phase-regulating equipment) are envisioned, but even configuring equipment according to the most severe fluctuations throughout the day is not the most cost-effective approach.

[0009] In contrast, Patent Document 1 monitors the entire power system to control individual problem areas in a specific region, but it does not fundamentally solve the problem of insufficient voltage maintenance capability and its fluctuations in the entire power system. Furthermore, the method of using phase-switching equipment in Patent Document 2 is also ineffective in addressing the problem of insufficient voltage maintenance capability and its fluctuations, and this approach requires equipment capacity designed for the most severe conditions, inevitably leading to higher costs.

[0010] Patent Document 1: Japanese Patent Application Publication No. 2016-208654

[0011] Patent Document 2: Japanese Patent Application Publication No. 2008-182789 Summary of the Invention

[0012] Based on the above, this invention provides a power system stabilization system and a power system stabilization method that can fundamentally address the problems of insufficient voltage maintenance capability and frequency maintenance capability and their fluctuations.

[0013] Based on the above, in this invention, in a power system stabilization system, a power plant equipped with a synchronous machine that is excitation controlled is connected to the power system, and the synchronous machine is controlled by an excitation control device. The power system stabilization system is equipped with a compensation circuit that corrects the control constant of the excitation control device of the synchronous machine based on a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0014] Furthermore, in this invention, in the power system stabilization system, a power station equipped with a synchronous machine driven by a prime mover is connected to the power system, and the prime mover is controlled by a prime mover control device. The power system stabilization system is equipped with a compensation circuit that corrects the control constant of the prime mover control device based on a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0015] Furthermore, in this invention, in the power system stabilization system, a power station equipped with a reactive power compensation device is connected to the power system, and the reactive power compensation device is controlled by a reactive power control device. The reactive power compensation device is configured to include a capacitor and a power semiconductor. The power system stabilization system includes a compensation circuit, which corrects the control constant of the reactive power control device based on a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0016] Furthermore, in the present invention, in the power system stabilization method, a power plant equipped with an excitation-controlled synchronous machine is connected to the power system, and the synchronous machine is controlled by an excitation control device. The control constant of the excitation control device of the synchronous machine is corrected according to the power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0017] Furthermore, in the present invention, in the power system stabilization method, a power plant equipped with a synchronous machine driven by a prime mover is connected to the power system, and the prime mover is controlled by a prime mover control device. The control constant of the prime mover control device is corrected according to the power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0018] Furthermore, in this invention, in the power system stabilization method, a power plant equipped with a reactive power compensation device is connected to the power system, and the reactive power compensation device is controlled by a reactive power control device. The reactive power compensation device is configured to include a capacitor and a power semiconductor. The control constant of the reactive power control device is corrected according to the power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system.

[0019] It can provide a power system stabilization system and a power system stabilization method that can fundamentally address the problems of insufficient voltage and frequency maintenance capabilities and their fluctuations in power systems. Attached Figure Description

[0020] Figure 1 Examples of the structure of general power systems and control devices.

[0021] Figure 2 This represents the equivalent circuit of generator G when it is an open-circuit terminal.

[0022] Figure 3 This represents the relationship between the excitation current If, the electromotive force E, and the synchronous reactance Xs.

[0023] Figure 4 This represents the equivalent circuit from the generator to the load that serves as the consumption point.

[0024] Figure 5 This represents the response characteristics of the armature coil's time constant τ, electromotive force E, and terminal voltage Vg.

[0025] Figure 6 Examples of various control devices within the excitation control device 5 that help maintain the voltage of the power system are summarized.

[0026] Figure 7 This illustrates a structural example of the excitation control device for the generator according to Embodiment 1 of the present invention.

[0027] Figure 8a The relationship between the generator and the power system is represented as a single-machine-to-infinite-system model.

[0028] Figure 8b This indicates the relationship between the voltage of the transmission line bus, the voltage at the generator terminals, and the reactive power of the generator when the system voltage decreases, when the system voltage is controlled by the power transmission voltage control excitation device PSVR and the automatic voltage regulator AVR.

[0029] Figure 9 This illustrates the structure of a typical power transmission voltage controlled excitation device (PSVR).

[0030] Figure 10 This section illustrates a specific structural example of an automatic reactive power regulation (AQR) device.

[0031] Figure 11 This shows a specific structural example of an automatic power factor adjustment (APFR) device.

[0032] Figure 12 This section shows a specific structural example of the system stabilization device (PSS).

[0033] Figure 13 This refers to the arithmetic module in the load frequency control (LFC).

[0034] Figure 14 This shows a typical structural example of the power plant control device 4 in a thermal power plant.

[0035] Figure 15 This shows a structural example of an automatic equipment control device (APC).

[0036] Figure 16 This section illustrates the structure of a Static Var Compensator (SVC). Detailed Implementation

[0037] The embodiments of the present invention will be described below.

[0038] To address the aforementioned issues, the present invention proposes the following solution: a power system stability maintenance index (VRI) is defined as an index reflecting the amount of renewable energy in a power system, and control is implemented based on this index to improve power system stability.

[0039] Specifically, based on the Power System Stability Maintenance Index (VRI), the excitation control device of the generator participates in ensuring voltage regulation, or based on the VRI, it participates in the supply and demand regulation functions of the generator's mechanical input and power output to ensure frequency regulation. Furthermore, based on the VRI, it participates in the phase regulation function in the substation to ensure voltage regulation.

[0040] In describing embodiments of the present invention below, the relationship between generator excitation control and power stability will be specifically explained in particular, regarding the prerequisite prior knowledge. Generally, to adjust the voltage of a power system, there are methods for controlling the phase-shifting equipment of a substation and methods for controlling the generators of a power station; however, the latter will be primarily described here.

[0041] first, Figure 1 This illustrates a typical power system and control device structure. Figure 1In this system, multiple power plants are connected to the power system 1. These power plants are renewable energy sources such as wind power plants 2A and solar power plants 2B that do not have system stabilization functions (voltage regulation and frequency regulation functions). In addition, there are existing power plants 2C (2C1, 2C2...2Cn) such as thermal power, hydropower, and nuclear power that have system stabilization functions (voltage regulation and frequency regulation functions).

[0042] In order to generate electricity corresponding to the load 10 of the entire power system, the central power supply command station 3, which controls the entire power system, has, for example, a central control function 50, to issue commands to the existing power plant 2C. This central control function 50 includes a regulator 56, which uses a subtractor 21 to calculate the difference between the detected system frequency f and the constant frequency f0, generating output command values ​​D (D1, D2…Dn). This function of the central control function 50 is called Load Frequency Control (LFC).

[0043] In addition, the central power supply command station 3 is equipped with a power system stability maintenance index calculation unit 30 for calculating the power system stability maintenance index (VRI). The power system stability maintenance index calculation unit 30 will be described in detail later.

[0044] In the existing power plant 2C, the power plant control device 4 controls the steam input from the boiler B to the mechanically connected turbine T and generator G via the steam regulating valve CV. Furthermore, the control is performed using the output command value D as the target value and the speed obtained by the speed detector 51 and the generator output calculated by the power detector 52 as feedback values. The power detector 52 calculates the generator output based on the terminal voltage Vg of the generator G obtained by the voltage converter PT1 and the terminal current Ig of the generator G obtained by the converter CT1. The power output of the generator G is supplied to the power system 1 via the transformer Tr and transmission lines 11, 12…1n. While the boiler and steam turbine are described as the controlled objects of the power plant control device 4, the controlled objects can also include waste heat recovery boilers that utilize waste heat from gas turbines to generate steam and waste heat recovery equipment for steam turbines. The main control functions of the power plant control device 4 are the Automatic Plant Control (APC) and the Electro-Hydraulic Control System (EHC).

[0045] In addition, the excitation control device 5 in the existing power plant 2C uses the secondary winding of the synchronous generator G as the excitation coil 6, uses the thyristor 8 to convert the AC power supply 7 to DC, and uses the automatic voltage regulator (AVR) which is the main control function of the excitation control device 5 to control the DC excitation current If supplied to the excitation coil 6, thereby adjusting the generator terminal voltage Vg to the set voltage Vg0.

[0046] The excitation control device 5 uses an automatic voltage regulator (AVR) as its main control function, forming a series control device that essentially corrects the target value of the AVR according to instructions from the upper-level control system. The upper-level control system, in... Figure 1 In the example, it refers to control devices such as the power system voltage regulator (PSVR), power system stabilizer (PSS), automatic reactive power regulator (AQR), and automatic power factor regulator (APFR). These instructions essentially correct the target value of the automatic voltage regulator (AVR) as a lower-level control system.

[0047] Correction methods include: directly moving the voltage target setter 90R of the automatic voltage regulator (AVR) to correct the target value, and performing addition and subtraction calculations on the voltage deviation. Figure 1 The diagram shows the method of adding and subtracting voltage deviations in adder 24, but this can also be achieved by changing the target value. In the automatic voltage regulator (AVR), the terminal voltage Vg of the generator G, which is a synchronous machine, is detected by voltage converter PT1. The difference between the voltage Vg and the set voltage Vg0 set by voltage target setter 90R is calculated by subtractor 21. The thyristor 8 is adjusted by regulator (AVR calculation unit) 22 with proportional-integral function, thereby adjusting the excitation current If supplied to the excitation coil 6. Other control systems will be described in detail later with reference to the accompanying drawings. As signal inputs to other control systems, the terminal voltage Vg of generator G from voltage converter PT1, the bus voltage Vh from voltage converter PT2, and the terminal current Ig of generator G from converter CT2 are provided.

[0048] Figure 2This represents the equivalent circuit of generator G when it is an open-circuit terminal. Therefore, generator G can be represented by a series circuit of the internal induced voltage E (sometimes called electromotive force), synchronous reactance Xs = jωLs, and resistance R. The externally measurable values ​​are generator current Ig and generator terminal voltage Vg. Thus, the internal induced voltage E is calculated as an estimated value obtained from synchronous reactance Xs = jωLs, resistance R, generator current Ig, and generator terminal voltage Vg. Furthermore, ω = 2πf, where f is the frequency.

[0049] Figure 3 The relationship between the excitation current If on the horizontal axis, the electromotive force E on the vertical axis, and the synchronous reactance Xs is shown. In summary, relative to the increase of the excitation current If, the electromotive force E exhibits saturation characteristics, and the synchronous reactance Xs shows a decreasing tendency.

[0050] Figure 4 This represents the equivalent circuit from the generator to the load, which serves as the consumption point. The inductance within the generator is L1, and the resistance is R1. The inductance on the load side is L2, and the resistance is R2. According to... Figure 4 The equivalent circuit, as shown in equation (1), allows us to determine the time constant τ[sec] representing the following speed of the system voltage V relative to the electromotive force E of the generator.

[0051] τ[sec]=(L1+L2)÷(R1+R2)‥‥‥(1)

[0052] Figure 5 The response characteristics of the electromotive force (EMF) E and the terminal voltage Vg are shown for both large and small armature coil time constants τ. Here, as shown in the upper left, the instantaneous and effective values ​​are displayed when the maximum value of the EMF E increases from 100% to 150% at time 0.1 seconds; this condition is the same for the case with a large time constant τ (as shown in the upper right). To distinguish between instantaneous and effective values, the effective value is represented by a thick line, and the instantaneous value by a thin line. For this change, when the time constant τ is small, as shown in the lower left, the system voltage V responds quickly to the generator's EMF E (reaching its final value immediately). On the other hand, when the time constant is large, as shown in the lower right, the response is slow, and it is difficult to reach the final value. That is, the response speed of the system voltage V to the generator's EMF E is not constant and varies depending on the excitation current If.

[0053] Here, the control gain (Ka, etc.) for the voltage sustaining function is a fixed value. In the design of practical control devices, these proportional gains are determined by assuming representative control states (the time constant of the circuit).

[0054] Based on the above, as the proportion of renewable energy increases in the future, in order to maintain the voltage of the power system, the excitation current, synchronous reactance, and response time constant of the generator will change significantly. This is very different from the premise in the control design and may not be able to be properly controlled.

[0055] Based on the above viewpoints, in the voltage control of the present invention, the control constant of the excitation control device participating in maintaining the voltage is changed according to the power system stability maintenance index VRI. Here, the control constant refers to the proportional gain Ka in proportional control, and the integral gain Ki and integral time constant Ti in integral control. In the following description of embodiments, examples of changing the proportional gain Ka will be mainly described. Examples of changing the integral time constant Ti (integral gain Ki = 1 / integral time constant Ti) will be discussed later. Figure 13 Example 9 will be described later.

[0056] Return to Figure 1 The excitation control device 5 is an assembly of multiple control devices, with the automatic voltage regulator (AVR) as the main control device. Figure 1 The example shown is an excitation control device 5 comprising a transmission voltage control excitation device (PSVR), a power system stabilization device (PSS), an automatic reactive power regulator (AQR), and an automatic power factor regulation device (APFR). The inputs and processing of each control device are described in detail, but their outputs are configured to ultimately control the generator's excitation current via the automatic voltage regulator (AVR).

[0057] Figure 6 Examples of various control devices within the excitation control unit 5 that help maintain the voltage of the power system are summarized here. The excitation control unit is organized from the perspectives of control quantities, operating quantities, and control objectives. According to the diagram, these control quantities vary depending on their control objectives; in contrast, operating quantities directly control the generator excitation current or indirectly control the generator excitation current via the automatic voltage regulator (AVR).

[0058] The present invention will be described in sequence below. First, in Embodiment 1 and Embodiment 2, the power system stability maintenance index VRI is clearly explained as an index reflecting the amount of renewable energy in the power system. In particular, an example of an automatic voltage regulator (AVR) participating in the excitation control device 5 to improve the voltage stability of the power system is described.

[0059] In Example 3, the case of using a distributed system structure to calculate the power system stability maintenance index (VRI) is explained.

[0060] Examples 4 to 8 illustrate how the power system stability maintenance index VRI is incorporated into the excitation control device 5, other than the automatic voltage regulator (AVR).

[0061] Examples 9 to 11 illustrate how the power system stability maintenance index (VRI) participates in the supply and demand adjustment of the mechanical input and power output of the generator to ensure the frequency adjustment function.

[0062] In Example 12, an application example to other devices is further described.

[0063] The power system stabilization system of this invention includes a main unit and a control unit. In the case of a power plant, the main unit consists of a generator and prime movers such as turbines and boilers that provide mechanical input to the generator. The control unit, when improving the frequency stability of the power system, is the prime mover control device; when improving voltage stability, it is the excitation control device. Furthermore, in the case of phase regulation, the main unit refers to the main body of the synchronous condenser (rotating capacitor), STATCOM (Self-Excited Static Var Compensator), and SVC connected to the power system, while the control unit refers to the control device used to control voltage and reactive power. In the power system stabilization system of this invention, the main unit and the control unit are interconnected and can adjust the stability of frequency and voltage.

[0064] Similarly, the power system stabilization method of the present invention includes a main unit and a control unit. The main unit refers to a generator and a prime mover such as a turbine or boiler that provides mechanical input to the generator. The control unit achieves stabilization by means of a control method for a prime mover control device when improving the frequency stability of the power system, or by means of a control method for an excitation control device when improving voltage stability. Furthermore, in the case of phase modulation functionality, the main unit refers to the main body of a synchronous condenser (rotating capacitor), STATCOM, or SVC connected to the power system, and the control unit achieves stabilization by means of a control method used in a control device for controlling voltage and reactive power. In the power system stabilization method of the present invention, the main unit and the control method are interconnected, enabling the adjustment of frequency and voltage stability.

[0065] [Example 1]

[0066] In Embodiment 1 of the present invention, the power system stability maintenance index (VRI), which reflects the amount of renewable energy in the power system, is an index that changes the control gain of the regulator of the excitation control device based on the renewable energy composition ratio M. Therefore, the definition and calculation method of the renewable energy composition ratio M will be explained first below.

[0067] exist Figure 1The renewable energy composition ratio M is calculated in the power system stability maintenance index calculation unit 30 installed within the central power supply command station 3 and other central devices. The reason for installing this unit is that it gathers and inputs most of the information about the power system 1, which is the object of monitoring. [The remaining text appears to be incomplete and requires further context.] Figure 1 The renewable energy composition ratio M, calculated in the power system stability maintenance index calculation unit 30, is provided to a predetermined specific power plant (in Figure 1 In the example, the excitation control device 5 is the generator G within 2C1).

[0068] The renewable energy composition ratio M is defined by equation (2).

[0069] Renewable energy composition ratio M (Power System Stability Maintenance Index VRI) = Renewable energy generation / (Renewable energy generation + Existing power plant generation) (2)

[0070] Here, the renewable energy generation and existing power plant generation, which serve as the basis for calculating the renewable energy composition ratio M, are calculated in the following manner: In the power system stability maintenance index calculation unit 30, the generation of each power generation device is summed up and the ratio is calculated from the generation of the central power supply command station 3 and other central devices, which are input via communication. Most existing power plants and large-capacity renewable energy devices have communication equipment with the central devices, so calculations and distribution of calculation results can be performed based on the above-mentioned data collection.

[0071] However, most small-scale renewable energy installations, such as solar power systems in individual households, do not have this communication equipment, so this should be taken into account in the calculation of the more stringent renewable energy composition ratio M. As a countermeasure, the power generation of solar power systems connected to transmission and distribution lines and generating electricity is estimated on a per-substation basis.

[0072] In this estimation, for example, active power P and reactive power Q are measured at each substation. Based on the relationship between the no-load characteristics of the transmission and distribution lines displayed on the PQ plane (represented by active power P and reactive power Q) and the load points located on that plane via active power P and reactive power Q, the detected active power is corrected to estimate the solar power generation. Furthermore, the estimated load on the transmission and distribution lines (equivalent to the power generation of existing power plants) can be calculated based on the detected active power and the estimated solar power generation. Equation (2) can be executed using these cumulative results from all substations.

[0073] By sequentially executing equation (2) at a frequency corresponding to, for example, the control cycle of the computer device, the processing result is continuously reflected in the time sequence to the excitation control device 5 of the generator G in each existing power station, thereby functioning in the direction of convergence of power system changes in the short term.

[0074] The renewable energy composition ratio M obtained by equation (2) is provided to the excitation control device 5 of the generator in a predetermined specific power plant. The excitation control device 5 is configured to include multiple excitation control devices. In embodiment 1, it is an example of an automatic voltage regulator (AVR) participating as a specific adjustment object within the excitation control device 5.

[0075] Figure 7 This is a structural example of the excitation control device for the generator according to Embodiment 1 of the present invention. Figure 7 The automatic voltage regulator (AVR) detects the terminal voltage Vg of the generator G, which is a synchronous machine, through the voltage converter PT1. It calculates the difference between this voltage and the set voltage Vg0 set by the voltage target setter 90R using the subtractor 21. This difference is then adjusted by the thyristor 8 via the proportional-integral (AVR) calculation unit 22, thereby adjusting the excitation current If supplied to the excitation coil 6. The AVR calculation unit 22 may include a lead-delay compensation circuit within the AVR control device.

[0076] An automatic voltage regulator (AVR) is installed within the excitation control device 5 of the synchronous machine G, serving the following purposes: maintaining a constant voltage in the synchronous machine G during stable operation; improving dynamic stability by maintaining voltage and adjusting reactive power during load changes; and suppressing voltage rise during load disconnection by rapidly restoring voltage after sudden voltage changes, thereby improving transient stability. To achieve these objectives, the AVR needs to reduce the overall voltage variability (control deviation), possess sufficient instantaneous responsiveness, and be sufficiently stable as a control system (with stable gain and phase margins).

[0077] In this invention, the control constants (control gain Ka, integral time constant Ti) of the regulator 22 with proportional-integral function within the automatic voltage regulator (AVR) are varied according to the renewable energy composition ratio M (power system stability maintenance index VRI). In this example, the control gain Ka is changed. The compensation circuit 20 for changing the gain is configured as, for example, a function generator with the renewable energy composition ratio M as input, to change the proportional gain Ka of the regulator 22. The function at this time is Equation (3).

[0078] Ka[A / V]=f(M)‥‥‥(3)

[0079] Furthermore, the function is characterized by a decrease in the proportional gain Ka of regulator 22 as the renewable energy composition ratio M increases. This function's characteristics are determined in advance through simulation or experimentation. Furthermore, the function can be determined through learning control. In learning control, the control device or control system itself stores the relationship between the control scheme and the execution results of that scheme, and improves the control scheme based on this relationship. This is used when the characteristics of the controlled object and the surrounding environmental conditions cannot be fully grasped, and when it is impossible to pre-design an appropriate control scheme. With a learning function, it possesses the ability not only to immediately adapt to past or similar situations, but also to gradually adapt to new, unexperienced situations. The function thus determined is generally a piecewise linear function.

[0080] Equation (3) explains the change of the proportional gain Ka of the regulator 22 with proportional-integral function within the automatic voltage regulator (AVR), but it can also change the integral time constant Ti of the regulator 22 with proportional-integral function. However, generally speaking, since the proportional gain Ka and the integral time constant Ti are different functions, different compensation circuits 20 are provided for the proportional gain Ka and the integral time constant Ti respectively. In addition, the compensation circuit 20 can compensate for either the proportional gain Ka or the integral time constant Ti, or it can compensate for both. In the case of compensating for both, two sets of compensation circuits are prepared.

[0081] Furthermore, in this invention, the term used to summarize the proportional gain Ka and integral time constant Ti is defined as the control constant in the regulator 22. This is also to consider the case where the control constant is also used to control the regulators in the various control devices described later. When there are multiple control constants that are subject to compensation, a compensation circuit 20 can be prepared for each of the multiple control constants. Additionally, changing the integral time constant Ti means changing the integral time constant.

[0082] The generator in this invention more generally refers to a synchronous motor, and this concept also includes synchronous condensers. A synchronous condenser connects a synchronous motor to the power system under no-load conditions. When the synchronous condenser is operated with overexcitation, it functions as a capacitor drawing leading current from the line; when the synchronous condenser is operated with underexcitation, it functions as a reactor drawing lagging current from the line. The synchronous condenser is used in such a way that when the power system is overloaded, the load power factor of the line decreases in the retardation direction; therefore, by overexciting the synchronous condenser, the load power factor is improved, thereby improving the voltage drop of the line. Conversely, when the power system is lightly loaded and the charging current of the line is large, the load power factor of the line decreases in the leading direction; therefore, by underexciting the synchronous condenser, the load power factor is improved, thereby suppressing voltage rise in the line. The synchronous condenser is equipped with an automatic voltage regulator (AVR) for constant voltage control, thus allowing direct application of the same compensation control as described in Embodiment 1 of this invention.

[0083] According to Embodiment 1 of the present invention, even when the proportion of renewable energy in the system increases, the voltage of the power system fluctuates significantly, the excitation current of the generator changes, and the control characteristics of the generator-automatic voltage regulator (AVR) system change, the gain Ka of the automatic voltage regulator (AVR) automatically changes to the optimal value, thus enabling stable and rapid control of the power system voltage back to its original value. That is, robustness is improved.

[0084] [Example 2]

[0085] In Example 1, the control gain Ka of the excitation control device regulator is varied according to the renewable energy composition ratio M, which serves as the power system stability maintenance index VRI. In contrast, in Example 2, the control gain Ka of the excitation control device regulator is varied according to the voltage fluctuation level N, which serves as the power system stability maintenance index VRI.

[0086] In this case, Figure 1 The power system stability maintenance index calculation unit 30 installed in the central power supply command station 3 and other central devices calculates the voltage fluctuation level N as follows and provides it to the excitation control device 5 of the generator in each existing power station.

[0087] The voltage variation N is calculated through the following series of processes. First, the standard deviation σ is calculated using equation (4). Here, STD is the formula for calculating the standard deviation. Thus, if there is no voltage variation, then σ = 0; if the variation is large, then σ also increases (only positive values).

[0088] Standard deviation σ[V] = STD[Power system voltage(t) - Power system voltage reference value] (4)

[0089] Next, the proportional integral of the standard deviation of equation (4) is calculated using equation (5), and this result is used as the power system stability maintenance index VRI, represented by the voltage variation degree N. Thus, control calculations are performed with σs-σ becoming zero. Ka is the proportional gain, Ti is the integral time, and t is time.

[0090] Voltage fluctuation degree N (Power system stability maintenance index VRI) = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt (5)

[0091] In the excitation control device 5 of the generator in each power station, the control gain is changed according to the magnitude of the voltage fluctuation N, similar to the renewable energy composition ratio M.

[0092] In Example 2, the voltage refers to the voltage at one or more predetermined locations within the power system. Voltage fluctuations at these locations are continuously monitored, and the degree of voltage fluctuation N is determined using a time series. Furthermore, the predetermined locations may not be specific geographical locations, but rather infinitely large locations, or virtual points on the power system, such as those determined by the centroid of the impedance.

[0093] According to Embodiment 2 of the present invention, when the proportion of renewable energy in the system increases and the overall voltage maintenance capability decreases, the control gain of the voltage maintenance function becomes the optimal control gain corresponding to the state of the power system. Therefore, even when certain disturbances are applied to the power system, the voltage of the power system can be stably and quickly controlled back to its original value. That is, robustness can be improved.

[0094] Equation (4) calculates the voltage variation N (power system stability maintenance index VRI) based on the standard deviation of the voltage deviation, but Equation (4) can also calculate the frequency variation N′ based on the frequency deviation using the same consideration method. If they are expressed in general terms, they can be called the stability variation.

[0095] The Power System Stability Maintenance Index (VRI), which incorporates the concepts of the renewable energy composition ratio (M) and the degree of stability variation (voltage variation N, frequency variation N′) mentioned above, can be considered an indicator reflecting the stability maintenance capability of a power system that reflects the amount of renewable energy. If the proportion of renewable energy in the power system increases, it becomes more prone to voltage fluctuations and its responsiveness decreases.

[0096] [Example 3]

[0097] In Examples 1 and 2, a conventional centralized communication control system architecture is used as a premise. This centralized architecture gathers and inputs most of the information of the power system 1, which is the object of monitoring, in a central device such as the central power supply command station 3. In contrast, most recent communication control systems adopt a distributed system architecture in response to changes in the communication environment such as the Internet and cloud computing, as well as the improvement of computer computing power.

[0098] In Example 3, as a distributed system architecture, the generator-side computer retrieves the necessary information from various locations in the cloud, calculates the power system stability maintenance index (VRI), and controls its own excitation control function. In this case, the "various locations in the cloud" mainly refer to other power plants and substations within the power system. Each power plant maintains the power system information it measures in its own database and shares its information with other power plants upon request. This invention can be implemented even if the communication and computer systems are either centralized or distributed.

[0099] [Example 4]

[0100] In the following Examples 4 to 7, the following situation is explained: As the power system stability maintenance index VRI, the control gain of the regulator of each control device in the excitation control device 5 is changed according to either the renewable energy composition ratio M of Example 1 or the stability variation degree (voltage variation degree N, frequency variation degree N′) of Example 2.

[0101] Under this premise, the power transmission voltage control excitation device PSVR is specifically adjusted in Example 4. Figure 1 Within the excitation control device 5, a structural example is shown where the output of the transmission voltage control excitation device PSVR is input in the form of adding the voltage deviation of the automatic voltage regulator AVR.

[0102] Here, the so-called transmission voltage controlled excitation device PSVR is based on the setting... Figure 1 The voltage converter PT2 on the secondary side of transformer Tr calculates the deviation between the transmission line output bus voltage Vh and its reference voltage Vh0 to control the generator excitation current If, thus maintaining the transmission line output bus voltage Vh at the reference value Vh0. The transmission line output bus voltage represents the voltage at the interconnection point of the power system. In short, the automatic voltage regulator (AVR) controls the generator terminal voltage Vg to be constant, while the transmission voltage controlled excitation device (PSVR) controls the bus voltage Vh to be constant.

[0103] use Figure 8a and Figure 8b The principle of the power transmission voltage controlled excitation device (PSVR) is explained. Figure 8aThe relationship between the generator and the power system is represented as a single-machine-to-infinite-system model. Furthermore, Figure 8b This diagram illustrates the relationship between the transmission line bus voltage (upper section of the diagram), generator terminal voltage (middle section of the diagram), and generator reactive power (lower section of the diagram) when the system voltage decreases, under the control of the transmission voltage control excitation device PSVR (shown by the solid line) and the automatic voltage regulator AVR (shown by the dashed line).

[0104] Therefore, within the normal operating range of the system voltage, the two controls operate in roughly the same state. When the system voltage drops, the transmission voltage is kept constant by the transmission voltage control excitation device PSVR. Thus, the reactive power is increased by reducing the reactance of the step-up transformer to automatically increase the generator voltage.

[0105] In contrast, in the control of an automatic voltage regulator (AVR), the generator terminal voltage Vg is kept constant, thus generating less reactive power, and the transmission voltage decreases proportionally to the voltage drop. Consequently, the purpose of the transmission voltage control excitation device (PSVR) is to generate more reactive power in the ramp portion to increase the transmission voltage and maintain it constant, thereby mitigating the system voltage drop and improving the overall voltage stability of the system.

[0106] Figure 9 This illustrates a typical power transmission voltage control excitation device (PSVR) structure. In this circuit structure example, the PSVR comprises, for instance, the following components: a voltage detection reference voltage setting unit 31, which performs reactive current correction on the difference between the detected bus voltage Vh and the set voltage Vh0 set by the voltage target setting unit 90H in the subtractor 21; a reactive power distribution unit 32, which multiplies the calculated voltage difference by a gain KH to specifically compensate for the voltage drop in the step-up transformer Tr section; a lead-delay phase compensation circuit unit 33; and an output limiter 34, which limits the difference between the output of the phase compensation circuit unit 33 obtained by the subtractor 21 and the generator terminal voltage Vg. The output of the PSVR is added to the generator terminal voltage deviation signal in the adder 24 within the automatic voltage regulator (AVR), adjusted in the regulator 22 within the AVR, and then used to control the excitation current via the thyristor 8.

[0107] According to this circuit structure, the output of the transmission voltage control excitation device PSVR reaches the excitation control via the regulator 22 within the automatic voltage regulator AVR. In this invention, the control gain of the excitation control device is varied according to the magnitude of the power system stability maintenance index VRI. To achieve this variation, it is only necessary to... Figure 7The compensation circuit 20 is used to change the control gain Ka of any one of the excitation control devices in a series of excitation control devices that reach the excitation control via the regulator 22 in the automatic voltage regulator (AVR) from the transmission voltage controlled excitation device PSVR. That is, it is only necessary to change the control gain Ka of the regulator in the open-loop transfer function associated with the transmission voltage controlled excitation system. Figure 9 In this process, the control gain Ka of regulator 22 within the automatic voltage regulator (AVR) was changed.

[0108] Specifically, one of the parts within the control device that can change the control gain is... Figure 7 Similarly, by changing the gain of regulator 22 within the automatic voltage regulator (AVR), the control gain KH within the transmission voltage control excitation device (PSVR) can be adjusted using other methods. This invention can be any of the following, referring to other control devices.

[0109] However, when changing the gain of the regulator 22 within the automatic voltage regulator (AVR) and when changing the control gain of the regulator within a separate control unit, the characteristics that the compensation circuit 20 should possess are different, so an appropriate function should be set accordingly. Furthermore, when keeping the control gain of the separate control unit unchanged, if the gain of the regulator 22 within the AVR is changed universally regardless of the control situation, the control gain may not be optimized depending on the control unit; therefore, it is considered necessary to allow for a degree of averaging.

[0110] The reason for using a transmission voltage control exciter (PSVR) to control the voltage of the power system is as follows. First, the bus voltage Vh is detected and input into the PSVR. The processing result is reflected in the voltage deviation of the automatic voltage regulator (AVR). The AVR determines the electromagnetic current, changes the generator terminal voltage, and reflects it in the power system voltage Vh via the transformer transmission line.

[0111] Figure 9 The control device can be termed a cascaded control based on a power transmission voltage control exciter (PSVR) and an automatic voltage regulator (AVR). In this case, either the method of determining the set voltage of the AVR based on the output of the PSVR, or the method of adding the output of the PSVR to the voltage deviation of the AVR, can be used. In either case, the result is an adjustment to the voltage deviation of the AVR. This is also true in the processing of other control systems that are essentially cascaded.

[0112] In this control system, when the power system voltage decreases, the transmission voltage control excitation device (PSVR) functions by increasing the set voltage of the automatic voltage regulator (AVR), thereby increasing the excitation current. Figure 3 As shown, the synchronous inductance increases accordingly, and simultaneously, the generator's response characteristics change from an optimal state to a suboptimal state due to variations in the excitation current. To address this, in this invention, the control gain is varied according to the magnitude of the power system stability maintenance index (VRI), resulting in improved responsiveness.

[0113] In composition Figure 9 In such a cascaded control device, the compensation circuit 20 can be applied to any one or more of the upstream and downstream control devices, with a compensation circuit provided for each application location. Furthermore, the compensation circuit can be applied to either or both of the proportional gain and integral time constant; when applied to both, it includes a proportional gain compensation circuit and an integral time constant compensation circuit. This can be described as the following cascaded control device.

[0114] [Example 5]

[0115] In Example 5, the Automatic Reactive Power Regulator (AQR) is the specific object of adjustment. The AQR automatically controls the excitation current, making the generator's reactive power output a reference value given by the active power output as a function of the reactive power output. This method is sometimes used in thermal power plants or pumped-slip hydroelectric power plants located close to the demand side and with a large reactive power adjustment effect, aiming to reduce transmission losses and optimize reactive power flow.

[0116] It shows in Figure 1 The excitation control device 5 includes an automatic reactive power adjustment (AQR) device. Furthermore, Figure 10 This illustrates a specific structural example of an automatic reactive power regulator (AQR). Based on... Figure 10 The reactive power is calculated in the reactive power detection unit 13 based on the generator terminal voltage Vg and the load current Ig. The difference ΔQ between the reactive power and the set reactive power given by the reactive power setting unit 14 is obtained by the subtractor 21. This difference is integrated, for example, in the integrator circuit 16 to obtain the set voltage. This set voltage is reflected in the set voltage of the automatic voltage regulator AVR.

[0117] Regarding the variable adjustment of the proportional gain Ka in Example 5, it can be changed according to the magnitude of the power system stability maintenance index VRI, just as in the above examples.

[0118] exist Figure 10The automatic reactive power regulator (AQR) includes a compensation circuit 20 that provides an appropriate control gain based on the power system stability index (VRI) as input, thereby changing the control gain within the excitation control device. When the power system stability index (VRI) is high, the compensation circuit 20 reduces the control gain of the regulator in the excitation control device. In this case, determining the appropriate location within the excitation control device where the control gain can be varied is a matter that can be appropriately considered. Figure 10 In this case, the control gain Ka of the regulator 22 within the automatic voltage regulator AVR is set to be variable.

[0119] [Example 6]

[0120] In Example 6, the Automatic Power Factor Adjustment (APFR) device is specifically included as the adjustment target. The APFR is a device that automatically adjusts the excitation current to keep the generator power factor constant. When reactive power is generated in a small-capacity generator to maintain a constant generator voltage, the generator sometimes experiences overcurrent; therefore, the APFR is typically installed.

[0121] It shows in Figure 1 The excitation control device 5 includes an automatic power factor adjustment (APFR) device. Furthermore, Figure 11 A specific structural example of the Automatic Power Factor Adjustment (APFR) device is shown. According to... Figure 11 The Automatic Power Factor Adjustment (APFR) device has the following control structure: the active power of the generator G is detected by the active power detector 42; the power factor PF is calculated by the power factor calculator 43; the difference between the target power factor and the measured power factor is processed by the calculator 44; and the processing result is reflected in the voltage deviation of the Automatic Voltage Regulator (AVR). When reflecting this in the voltage deviation, there are methods for changing the set voltage of the voltage target setter 90R and methods for adding the deviation voltage; either method can be used in this invention. This is also true in other control devices.

[0122] Figure 11 The automatic power factor correction device (APFR) includes a compensation circuit 20 that takes the power system stability maintenance index (VRI) as input to provide an appropriate control gain, thereby variably adjusting the control gain within the excitation control device. When the power system stability maintenance index (VRI) is high, the compensation circuit 20 reduces the control gain of the regulator in the excitation control device. Figure 11 In this embodiment, the control gain Ka of the regulator 22 within the automatic voltage regulator (AVR) is set to be variable. In the case of embodiment 6, it is appropriate to determine where within the excitation control device the control gain of the regulator can be made variable.

[0123] [Example 7]

[0124] In Example 7, the System Stabilization Device (PSS) is specifically involved in the adjustment. The PSS responds promptly to voltage fluctuations at the generator terminals during an accident, rapidly increasing the excitation current. This increases the induced voltage within the generator, enhancing synchronization and improving stability. Consequently, dynamic stability during operation with a leading power factor, where stability is particularly problematic, can be significantly improved. However, while a high-speed, high-gain Automatic Voltage Regulator (AVR) increases synchronization, it also weakens braking force. Depending on the system structure or operating state, secondary oscillations caused by the AVR may occur. As a countermeasure, the generator's speed and output changes are detected, and a stabilization signal is input to the AVR to increase braking force.

[0125] It shows in Figure 1 The excitation control device 5 includes a system stabilization unit (PSS). Furthermore, Figure 12 This illustrates a specific structural example of the system stabilization device (PSS). Based on... Figure 12 Based on the system frequency f detected by the frequency detector 111 and the active power P detected by the power calculator 112, the system stabilization signal is calculated in the arithmetic unit (power variation calculation unit) 113, and the system stabilization signal is used to correct the voltage deviation of the automatic voltage regulator AVR.

[0126] In this system, the initial objective of the present invention can be achieved by setting up the same compensation circuit 20 as in Embodiment 1. Figure 12 In this process, the control gain Ka of the regulator (AVR calculation unit) 22 within the automatic voltage regulator (AVR) is set to be variable.

[0127] [Example 8]

[0128] In Example 8, it is proposed to change the control gain of the regulator described in Examples 1 to 7 according to the operating state of the generator system.

[0129] Here, operating state refers to the difference between startup, normal output operation, and shutdown, etc. For example, even if the excitation current is the same in these operating states, the control gain must be set to a suitable value. This is the case where the proportional gain Ka of the regulator 22 shown in equation (3) is different in each operating state.

[0130] According to Embodiment 6, it is possible to operate based on a control gain that has been appropriately adjusted according to the operating state.

[0131] The above examples 1 to 8 illustrate how the excitation control device involved in the generator changes the excitation based on the power system stability maintenance index (VRI). Furthermore, the power system stability maintenance index (VRI) can be generated at either the central power supply command station or at a separate power station. It can also be applied to any control system within the generator's excitation control device.

[0132] In summary, these methods can be described as "a power system stabilization system in which a power plant equipped with an excitation-controlled synchronous machine is connected to the power system, the synchronous machine is controlled by an excitation control device, and the power system stabilization system has a compensation circuit that corrects the control gain of the excitation control device of the synchronous machine according to a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system."

[0133] [Example 9]

[0134] Examples 9 to 11 illustrate how the power system stability maintenance index (VRI) participates in the supply and demand adjustment function of the generator's mechanical input and power output to ensure frequency adjustment function.

[0135] If other actions are taken, it involves participating in the control of the prime mover side that provides mechanical input to the generator, and changing the mechanical input according to the power system stability maintenance index (VRI). When changing the mechanical input, adjustments are made to the output command value D given by the central power supply command station and through the control device on the power plant side. Example 9 describes the case where the output command value D given by the central power supply command station is adjusted, while Examples 10 and 11 describe the case where adjustments are made through the control device on the power plant side.

[0136] First, Example 9 involves participating in the power system stability maintenance index (VRI). Figure 1 An example of the central control function 50 within the central power supply command station 3. In the central control function 50, load frequency control (LFC) is performed.

[0137] The structure of the central control function 50 is, for example, like Figure 13 The function is as follows: the subtractor 21 calculates the deviation (frequency deviation Δf) between the system frequency f detected by the frequency detector 61 and the reference frequency f0; the proportional and integral quantities are calculated in the proportional calculation unit 53 and the integral calculation unit 54 in the regulator 56, respectively; and the proportional-integral signal obtained by adding by the adder 24 is used as the output command value D (D1, D2...Dn) and assigned to the conventional power plant 2C.

[0138] Regarding the operation of regulator 56, when the proportional gain is set to Ka and the integral time constant is set to Ti, it can be represented by equation (6).

[0139] The output of regulator 56 = Ka × Δf + (1 / Ti)∫Δfdt (6)

[0140] In this case, for the output command value D1 for a specific power plant (2C1 in this case), the compensation circuit 20 performs a correction of the control gain of the regulator corresponding to the power system stability maintenance index VRI, and reflects this correction to the proportional calculation unit 53 and the integral calculation unit 54 of the regulator 56. Specifically, the compensation circuit 20 includes a proportional gain Ka compensation circuit 20P and an integral time constant Ti compensation circuit 20I, which reflect their respective compensations Ka and Ti to the proportional calculation unit 53 and the integral calculation unit 54.

[0141] The specific power plant 2C1 that received the corrected output command value D1 controls the mechanical input of the prime mover in the power plant control device 4. As a result, unlike other power plants that received the uncorrected output command value D, it executes mechanical input control that reflects the amount of renewable energy, thereby improving the frequency response control of the power system.

[0142] [Example 10]

[0143] In Example 10, participation is based on the Power System Stability Maintenance Index (VRI). Figure 1 The corresponding example is the automatic plant control (APC) device in the power plant control device 4 within a specific power plant 2C1.

[0144] Figure 14 This diagram illustrates a typical structural example of the power plant control unit 4 in a thermal power plant. In this diagram, the structure, consisting of the boiler B (the main unit), turbine T, and generator G, except that steam generated in the boiler B is supplied to the turbine T via the steam regulating valve CV, is... Figure 1 Same, with explanation omitted.

[0145] The main control functions in the power plant control device 4 are the Automatic Equipment Control (APC) and the Turbine Control (EHC). The APC receives the output command value D from the central power supply command station 3 and provides the boiler control command BID for the boiler control device 69 for boiler B and the load command Pd for the turbine control device EHC. First, referring to Example 10... Figure 15 The automatic equipment control device (APC) will be described below, and then referred to as Example 11. Figure 14 The turbine control unit EHC will be explained.

[0146] Figure 15 Example of the structure of the automatic equipment control device (APC): Regarding the boiler control command (BID) side, the deviation between the main steam pressure Pm supplied to the turbine and its set pressure Pm0, i.e., the main steam pressure deviation ΔPm, is calculated by subtractor 21. Proportional-integral operation is performed in regulator 75, and the output command value D from the central power supply command station 3 is added to the output of regulator 75 in adder 24, resulting in the boiler control command (BID) for boiler B from boiler control device 69. This boiler control command (BID) is a command that corrects the output command value D using the main steam pressure deviation ΔP.

[0147] In addition, Figure 15 In the Automatic Control Processor (APC), regarding the load command Pd for the turbine control unit EHC, the subtractor 21 calculates the deviation (load deviation) between the output command value D and the generator output P calculated by the power detector 52. This deviation is then transformed into a load change rate between the high load change rate limit value and the low load change rate limit value in the high load change rate limit circuit 72 and the low load change rate limit circuit 73, thus serving as the appropriate load change rate. In the regulator 74, the load deviation is proportionally integrated to set the load command Pd for the turbine control unit EHC.

[0148] Based on the above example of the structure of the automatic equipment control device (APC), regulators 74 and 75 can be used as the correction components for the control constant corresponding to the power system stability maintenance index (VRI). That is, a compensation circuit 20A for regulator 74 and a compensation circuit 20B for regulator 75 are provided. In each compensation circuit 20A and 20B, a total of four sets of compensation circuits are provided, considering that the proportional gain and integral time constant of regulators 74 and 75 are changed individually.

[0149] In the illustrated example, the compensation circuit 20A targeting regulator 74 consists of a proportional gain Ka compensation circuit 20AP and an integral time constant Ti compensation circuit 20AI. The compensation circuit 20B targeting regulator 75 consists of a proportional gain Ka compensation circuit 20BP and an integral time constant compensation circuit 20BI. A larger power system stability maintenance index VRI results in a smaller control gain Ka, but a larger VRI also results in a larger integral time constant Ti.

[0150] In particular, regulator 74 is a crucial part of the regulator related to the load command Pd, and therefore is preferably described as follows. In load control, the load command Pd is obtained by performing proportional-integral calculations in regulator 74 as shown in equation (7) based on the output command value D specified from the central power supply command station 3 and the generator output P detected by the generator. Here, Ka is the proportional gain, GI is the integral gain, Ti is the integral time, t is time, and other control constants are constant.

[0151] Pd[%]=Ka×(D-P)+(1 / Ti)×∫(Ps-P)dt (7)

[0152] Regarding the boiler control command (BID) side, in the boiler control device 69 that receives the command, the fuel, air, and water supplied to the boiler are controlled respectively through the fuel control system, air control system, and water supply control system according to the boiler control command (BID). Therefore, the correction part for the control gain corresponding to the power system stability maintenance index (VRI) can replace the upstream APC internal compensation and be set as the compensation for the downstream fuel control system, air control system, and water supply control system.

[0153] More specifically, although not illustrated, it comprises a main control unit, a fuel control unit, an air control unit, and a water supply control unit. The main control unit operates the target values ​​for fuel, air, and water supply based on the deviation between the boiler control command BID obtained from the output command value D provided to the power plant 2C1 and the generator output. The aforementioned fuel control unit, air control unit, and water supply control unit operate the fuel control signal, air control signal, and water supply control signal based on the deviation between these target values ​​and the corresponding feedback values. These control units all possess regulators that perform proportional-integral control on the deviation inputs (generator output deviation, fuel quantity deviation, water quantity deviation, and air quantity deviation). Therefore, by correcting this control gain according to the power system stability maintenance index VRI, the effect of improving power system stability can also be achieved.

[0154] However, improving the stability of the power system via the boiler control device takes a long time. Therefore, in order to achieve the improvement effect in a shorter time, the response on the EHC side of the turbine control device described in Example 11 is effective. The response of the above formula (7) is the response on the EHC side of the turbine control device.

[0155] [Example 11]

[0156] In Example 11, participation is based on the Power System Stability Maintenance Index (VRI). Figure 1 The corresponding example is the turbine control device EHC in the power plant control device 4 within a specific power plant 2C1.

[0157] The structure of the turbine control unit EHC, for example Figure 14 As shown. The turbine control unit EHC adjusts the turbine load and the turbine speed ω. Regarding the former, the load command Pd of the above equation (7) is provided to the steam regulating valve CV via the adder 24 and the servo mechanism 62 to adjust the opening of the steam regulating valve, thereby adjusting the turbine load.

[0158] In contrast, the rotational speed ω of turbine T is detected by speed detector 51, and the difference between it and the reference speed ωs is calculated by subtractor 21. This difference is multiplied by a certain ratio in regulator 66, added to the load command Pd in ​​adder 24, and then provided to steam regulating valve CV via servo mechanism 62 to adjust the opening of the steam regulating valve, thereby adjusting the rotational speed ω. Therefore, the output of adder 24 is sometimes referred to as the speed / load signal.

[0159] Thus, the control of the turbine and generator is calculated according to the turbine / generator speed ω and its predetermined reference speed ωs, load command Pd, as in equation (8). Based on the calculation result, the opening degree (Acv) of the steam regulating valve CV used to adjust the amount of steam flowing into the turbine is operated. In addition, C is a constant in equation (8).

[0160] Acv[%]=(ωs-ω) / C+Pd (8)

[0161] In Example 11, the correction part of the control gain corresponding to the power system stability maintenance index VRI is the regulator 66. The constant C (=1 / set rate) in the regulator 66 is corrected by the control gain corresponding to the power system stability maintenance index VRI.

[0162] In the case of hydroelectric power plants and nuclear power plants, it also has the same prime mover input control system and speed control system, which can correct the control gain when executing proportional-integral control for each deviation input according to the power system stability maintenance index VRI.

[0163] The above embodiments 9 to 11 describe the control of the prime mover side, which participates in providing mechanical input to the generator, and how the mechanical input is changed according to the power system stability maintenance index (VRI). Furthermore, regarding the change of mechanical input, in embodiment 9, the output command value D provided by the central power supply command station is adjusted; and in embodiments 10 and 11, the automatic equipment control device (APC) and the turbine control device (EHC) are made to function as control devices on the power plant side. These methods directly or indirectly correct the control gain of the prime mover's control device. Here, the central control function within the central power supply command station 3 can also be broadly defined as the prime mover's control device.

[0164] In summary, these methods constitute "a power system stabilization system in which a power station equipped with a synchronous machine driven by a prime mover and controlled by excitation is connected to the power system, the prime mover is controlled by a prime mover control device, and the power system stabilization system has a compensation circuit that corrects the control gain of the prime mover control device according to a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system."

[0165] [Example 12]

[0166] In Example 12, examples of application to other devices are also described.

[0167] First, regarding the excitation control device 5 in Examples 1 to 7, this excitation control device can be applied to any synchronous machine, which includes a synchronous condenser (rotating capacitor). A synchronous condenser is a synchronous motor operating without load and is one type of phase-shifting device. The control of the synchronous condenser is achieved by an automatic voltage regulator (AVR) for excitation control, in conjunction with... Figure 7 The structures are roughly the same. And... Figure 7 The structural difference is that the synchronous condenser is a synchronous motor, and therefore is not driven by a turbine.

[0168] Applying this invention to synchronous condensers offers the following advantages. First, by adjusting the excitation current, reactive power can be continuously adjusted over a wide range from its supply to its absorption. Furthermore, since its own voltage is established based on the internal induced voltage, a constant reactive power supply can be maintained even when the system voltage decreases.

[0169] In summary, the means of Embodiment 12 regarding synchronous condensers is "a power system stabilization system, wherein an excitation-controlled synchronous motor is connected to the power system, the synchronous motor is controlled by an excitation control device, the power system stabilization system includes a compensation circuit that corrects the control gain of the excitation control device of the synchronous motor according to a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system."

[0170] Furthermore, the application of this invention can also be applied to phase-regulating devices such as STATCOM and SVC. SVC (Static Var Compensator) is a type of static phase-regulating device, generally composed of a step-down transformer, a series reactor, a phase-leading capacitor, and a high-voltage, high-capacity thyristor device. By utilizing high-speed control of power semiconductors, it can continuously change reactive power under load conditions, providing fast-response reactive power compensation. It includes a regulator for reactive power control, thus this part can be used as a correction component for the control gain corresponding to the power system stability index (VRI).

[0171] STATCOM is a type of static phase-changing device, typically consisting of a step-down transformer, an inverter using IGBTs, and an energy storage unit. Through high-speed control of the inverter, it can continuously adjust reactive power under load conditions, providing fast-response reactive power compensation. The inverter includes a regulator for reactive power control, which can therefore be used as a correction component for the control gain corresponding to the Power System Stability Index (VRI).

[0172] Figure 16 This figure illustrates an application example of the present invention based on SVC. In this figure, the static var compensator 100 is connected to the transmission line 1 via a circuit breaker 102. The static var compensator 100 consists of a transformer Tr connected to the primary side and the transmission line side, a reactor L connected to the bus 101 on the secondary side of the transformer, a capacitor C, and a series or parallel circuit of thyristors 8.

[0173] The SVC control device 110 takes voltage and current input from the voltage converter PT10 (which measures the voltage of the transmission line 1) and the converter CT10 (which measures the current flowing through the static var compensator 100), and controls the voltage of the transmission line 1 through the static var compensator 100.

[0174] The SVC control device 110 includes a voltage sensor 80, a voltage reference circuit 103, a current sensor 87, a multiplier 86, a subtractor 21, a reactive power control unit 83, and a gate pulse output unit 84. When the subtractor 21 detects that the system voltage output by the voltage sensor 80 is lower than the set voltage given by the voltage reference circuit 103, the SVC control device 110 controls the static var compensator 100 via the reactive power control unit 83 to provide leading reactive power. Conversely, when the system voltage rises, the static var compensator 100 is controlled to provide lagging reactive power.

[0175] The SVC control device 110 defines the following slope characteristic: the voltage signal changes at a predetermined ratio relative to the change in reactive power generated by the static var compensator 100. Therefore, the multiplier 86 achieves this function by multiplying the current signal output from the current sensor 87 by a predetermined gain. Figure 16 In this embodiment, the gain is set to a variable gain from the compensation circuit 20. The subtractor 21 outputs the difference obtained by subtracting the product between the current value output by the multiplier 86 and the gain from the compensation circuit 20 from the variable voltage output as the variable voltage generation unit 41.

[0176] The SVC control device 110 calculates and outputs the reactive power output value of the static var compensator 100 to make the output of the subtractor 21 zero. The reactive power control unit 83 controls the bus voltage by calculating the reactive power output value. Then, the gate pulse output unit 84 generates a gate pulse signal and outputs it to the thyristor 8 of the static var compensator 100, causing the calculated reactive power value to be generated. The static var compensator 100 generates reactive power according to the gate pulse signal.

[0177] When applying the present invention to the static var compensator 100, it is only necessary to change the control gain of the SVC control device 110 via the compensation circuit 20 according to the power system stability maintenance index VRI.

[0178] The application of this invention to STATCOM can also be implemented with essentially the same idea. Detailed explanations of the usage illustrations are omitted. It generally consists of a step-down transformer, an inverter using IGBTs (power semiconductors), and an energy storage device. It includes a STATCOM connected to the transmission line and a STATCOM control device, which controls the IGBTs. The STATCOM control device includes a control unit for reactive power control, and the control gain within this unit is adjusted based on a power system stability maintenance index, which reflects the amount of renewable energy in the power system.

[0179] In summary, the means of Embodiment 12 regarding SVC and STATCOM is "a power system stabilization system in which a substation equipped with a reactive power compensation device 100 (SVC or STATCOM) is connected to the power system, and the reactive power compensation device 100 is controlled by a reactive power control device 110 (SVC control device or STATCOM control device), wherein the reactive power compensation device 100 is configured to include a capacitor (capacitor, storage device or battery) and a power semiconductor (thyristor or IGBT), and the power system stabilization system includes a compensation circuit 20, which corrects the control gain of the reactive power control device 110 according to a power system stability maintenance index, which is an index reflecting the amount of renewable energy in the power system."

[0180] Explanation of reference numerals in the attached figures

[0181] 1: Power System

[0182] 2A: Wind power station

[0183] 2B: Solar power station

[0184] 2C1~2Cn: Existing power plants

[0185] 3: Central Power Supply Command Station

[0186] 4: Power plant control device

[0187] 5: Excitation control device

[0188] 6: Excitation coil

[0189] 7: AC power supply

[0190] 8: Thyristor

[0191] 10: Load of the entire power system

[0192] 11, 12, ... 1n: power transmission lines

[0193] 14: Reactive power setting unit

[0194] 20: Compensation Circuit

[0195] 20AP, 20BP: Compensation circuit for proportional gain Ka

[0196] 20AI, 20BI: Compensation circuit for integration time constant Ti

[0197] 21: Subtractor

[0198] 22: Regulator (AVR Computing Unit)

[0199] 24: Adder

[0200] 30: Power System Stability Maintenance Index Calculation Department

[0201] 31: Voltage detection reference voltage setting unit

[0202] 32: Reactive power distribution unit

[0203] 33: Phase Compensation Circuit Section

[0204] 34: Output limiter

[0205] 42: Active power detector

[0206] 43: Power Factor Calculator

[0207] 44: Arithmetic Unit

[0208] 50: Central control function

[0209] 51: Speed ​​Detector

[0210] 52: Power Detector

[0211] 53: Proportional Calculation Section

[0212] 54: Integral Operations Department

[0213] 56: Regulator

[0214] 61, 111: Frequency detectors

[0215] 62: Servo mechanism

[0216] 66: Regulator

[0217] 69: Boiler control device

[0218] 72: High load change rate limiting circuit

[0219] 73: Low load change rate limiting circuit

[0220] 74, 75: Regulator

[0221] 80: Voltage sensor

[0222] 83: Reactive Power Control Department

[0223] 84: Gate pulse output section

[0224] 86: Multiplier

[0225] 87: Current sensor

[0226] 90R, 90H: Voltage target setting device

[0227] 100: Static Var Compensator

[0228] 101: Busbar on the secondary side of the transformer

[0229] 102: Circuit breaker

[0230] 103: Voltage Reference Circuit

[0231] 110: SVC control device

[0232] 112: Power Calculator

[0233] 113: Arithmetic Unit

[0234] AVR: Automatic Voltage Regulator

[0235] AQR: Automatic Reactive Power Adjustment Device

[0236] APFR: Automatic Power Factor Adjuster

[0237] B: Boiler

[0238] C: Capacitor

[0239] CT1, CT2, CT10: Converters

[0240] CV: Steam regulating valve

[0241] D1, D2, ..., Dn: Output instruction values

[0242] f: System frequency

[0243] f0: constant frequency

[0244] τ: Time constant

[0245] G: Generator

[0246] If: DC excitation current

[0247] Ig: Generator terminal current

[0248] L: Reactor

[0249] Pm: Main steam pressure

[0250] Pm0: Set pressure

[0251] ΔPm: Main steam pressure deviation

[0252] PSVR: Power Transmission Voltage Controlled Excitation Device

[0253] PSS: Power System Stabilization Device

[0254] PT1, PT2, PT10: Voltage converters

[0255] Q: Reactive power

[0256] T: Turbo

[0257] Tr: Transformer

[0258] Vg: Generator terminal voltage

[0259] Vg0: Set voltage

[0260] Vh: Bus voltage

[0261] Vh0: Reference voltage

[0262] ω: Turbine speed

[0263] ωs: Reference turbine speed.

Claims

1. A power system stabilization system, wherein a power station equipped with a synchronous machine for excitation control is connected to a power system, and the synchronous machine is controlled by an excitation control device. Its features are, The power system stabilization system includes a compensation circuit that corrects the control constant of the synchronous machine's excitation control device based on a power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio that represents the proportion of renewable energy generation in the power system, or a proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, representing the degree of voltage variation.

2. The power system stabilization system according to claim 1, characterized in that, The synchronizing machine is a synchronous motor.

3. The power system stabilization system according to claim 1 or 2, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

4. The power system stabilization system according to claim 1 or 2, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

5. The power system stabilization system according to claim 1 or 2, characterized in that, The power station is connected to a central device via communication and receives the power system stability maintenance index calculated by the central device to change the control constant.

6. The power system stabilization system according to claim 1 or 2, characterized in that, The power plant calculates the power system stability maintenance index based on information obtained via communication and changes the control constant accordingly.

7. The power system stabilization system according to claim 1 or 2, characterized in that, The excitation control device of the synchronous machine includes an automatic voltage regulator (AVR) and a compensation circuit. The AVR operates the current flowing through the excitation coil of the synchronous machine according to the terminal voltage deviation of the synchronous machine, and the compensation circuit changes the control constant of the AVR according to the power system stability maintenance index.

8. The power system stabilization system according to claim 1, characterized in that, The excitation control device of the synchronous machine includes a transmission voltage control excitation device (PSVR) and a compensation circuit. The PSVR adjusts the terminal voltage deviation of the automatic voltage regulator (AVR) based on the interconnection point voltage deviation of the synchronous machine. The AVR operates the current flowing through the excitation coil of the synchronous machine based on the terminal voltage deviation of the synchronous machine. The compensation circuit changes the control constant of the excitation control device from the PSVR to the AVR based on the power system stability maintenance index.

9. The power system stabilization system according to claim 1, characterized in that, The excitation control device of the synchronous machine includes an automatic reactive power regulator (AQR) and a compensation circuit. The AQR adjusts the terminal voltage deviation of the automatic voltage regulator (AVR) based on the reactive power deviation of the synchronous machine. The AVR operates the current flowing through the excitation coil of the synchronous machine based on the terminal voltage deviation. The compensation circuit changes the control constant of the excitation control device from the AQR to the AVR based on the power system stability maintenance index.

10. The power system stabilization system according to claim 1, characterized in that, The excitation control device of the synchronous machine includes an automatic power factor adjustment device (APFR) and a compensation circuit. The APFR adjusts the terminal voltage deviation of an automatic voltage regulator (AVR) to keep the power factor of the synchronous machine constant. The AVR operates the current flowing through the excitation coil of the synchronous machine according to the terminal voltage deviation. The compensation circuit changes the control constant of the excitation control device from the APFR to the AVR according to the power system stability maintenance index.

11. The power system stabilization system according to claim 1, characterized in that, The excitation control device of the synchronous machine includes a system stabilization device (PSS) and a compensation circuit. The PSS adjusts the terminal voltage deviation of the automatic voltage regulator (AVR) based on a power stabilization signal derived from the power of the synchronous machine and the system frequency. The AVR operates the current flowing through the excitation coil of the synchronous machine based on the terminal voltage deviation. The compensation circuit changes the control constant of the excitation control device from the PSS to the AVR based on the power system stability maintenance index.

12. The power system stabilization system according to claim 1 or 2, characterized in that, The compensation circuit reduces the control gain in the control constant when the power system stability maintenance exponent is large.

13. The power system stabilization system according to claim 1 or 2, characterized in that, The control constant is the control gain, integral gain, or integral time constant.

14. A power system stabilization system, comprising a power station connected to a power system and equipped with a synchronous machine driven by a prime mover, wherein the prime mover is controlled by a prime mover control device. Its features are, The power system stabilization system includes a compensation circuit that corrects the control constant of the prime mover control device based on a power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio representing the proportion of renewable energy generation in the power system, or a voltage variation degree representing the proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, or a frequency variation degree representing the proportional integral of the standard deviation of the power system frequency relative to the power system frequency reference value.

15. The power system stabilization system according to claim 14, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

16. The power system stabilization system according to claim 14, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

17. The power system stabilization system according to claim 14, characterized in that, The degree of frequency variation is defined by the following formula: Frequency variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system frequency relative to the power system frequency reference value.

18. The power system stabilization system according to claim 14, characterized in that, The power station is connected to a central device via communication and receives the power system stability maintenance index calculated by the central device to change the control constant.

19. The power system stabilization system according to claim 14, characterized in that, The power plant calculates the power system stability maintenance index based on information obtained via communication and changes the control constant accordingly.

20. The power system stabilization system according to claim 14, characterized in that, The compensation circuit reduces the control gain in the control constant when the power system stability maintenance exponent is large.

21. The power system stabilization system according to claim 14, characterized in that, The prime mover control device obtains the signal obtained by proportional integration of the frequency deviation of the power system in the regulator as the output command value, and corrects the control constant in the regulator according to the power system stability maintenance index.

22. The power system stabilization system according to claim 14, characterized in that, The prime mover control device includes a regulator that operates the prime mover input, and the control constant in the regulator is corrected according to the power system stability maintenance index.

23. The power system stabilization system according to claim 22, characterized in that, The regulator that operates the prime mover input operates by performing a proportional-integral calculation on the difference between the output command value provided to the power plant and the load of the synchronous machine.

24. The power system stabilization system according to claim 22, characterized in that, The regulator that operates the prime mover input is operated by performing a proportional calculation on the difference between the prime mover's rotational speed and its reference rotational speed.

25. The power system stabilization system according to claim 14, characterized in that, The control constant is the control gain, integral gain, or integral time constant.

26. A power system stabilization system, wherein a power station equipped with a reactive power compensation device is connected to a power system, and the reactive power compensation device is controlled by a reactive power control device, wherein the reactive power compensation device is configured to include a capacitor and a power semiconductor. Its features are, The power system stabilization system includes a compensation circuit that corrects the control constant of the reactive power control device based on a power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio that represents the proportion of renewable energy generation in the power system, or a proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, representing the degree of voltage variation.

27. The power system stabilization system according to claim 26, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

28. The power system stabilization system according to claim 26, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

29. The power system stabilization system according to claim 26, characterized in that, The power station is connected to a central device via communication and receives the power system stability maintenance index calculated by the central device to change the control constant.

30. The power system stabilization system according to claim 26, characterized in that, The power plant calculates the power system stability maintenance index based on information obtained via communication and changes the control constant accordingly.

31. The power system stabilization system according to claim 26, characterized in that, The compensation circuit reduces the control gain in the control constant when the power system stability maintenance exponent is large.

32. The power system stabilization system according to claim 26, characterized in that, The control constant is the control gain, integral gain, or integral time constant.

33. A power system stabilization method, wherein a power station equipped with an excitation-controlled synchronous machine is connected to a power system, and the synchronous machine is controlled by an excitation control device. Its features are, The control constant of the excitation control device of the synchronous machine is corrected based on the power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio that represents the proportion of renewable energy generation in the power system, or a proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, representing the degree of voltage variation.

34. The power system stabilization method according to claim 33, characterized in that, The synchronizing machine is a synchronous motor.

35. The power system stabilization method according to claim 33 or 34, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

36. The power system stabilization method according to claim 33 or 34, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

37. The power system stabilization method according to claim 33 or 34, characterized in that, When the power system stability maintenance exponent is large, the control gain in the control constant is reduced.

38. A power system stabilization method, comprising a power station connected to a power system and equipped with a synchronous machine driven by a prime mover, wherein the prime mover is controlled by a prime mover control device. Its features are, The control constant of the prime mover control device is corrected based on the power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio representing the proportion of renewable energy generation in the power system, or a voltage variation degree representing the proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, or a frequency variation degree representing the proportional integral of the standard deviation of the power system frequency relative to the power system frequency reference value.

39. The power system stabilization method according to claim 38, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

40. The power system stabilization method according to claim 38, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

41. The power system stabilization method according to claim 38, characterized in that, The degree of frequency variation is defined by the following formula: Frequency variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system frequency relative to the power system frequency reference value.

42. The power system stabilization method according to claim 38, characterized in that, When the power system stability maintenance exponent is large, the control gain in the control constant is reduced.

43. A power system stabilization method, wherein a power station equipped with a reactive power compensation device is connected to a power system, and the reactive power compensation device is controlled by a reactive power control device, wherein the reactive power compensation device is configured to include a capacitor and a power semiconductor. Its features are, The control constant of the reactive power control device is corrected based on the power system stability maintenance index, which reflects the amount of renewable energy generated in the power system. The power system stability maintenance index is a renewable energy composition ratio that represents the proportion of renewable energy generation in the power system, or a proportional integral of the standard deviation of the power system voltage relative to the power system voltage reference value, representing the degree of voltage variation.

44. The power system stabilization method according to claim 43, characterized in that, The renewable energy composition ratio is defined by the following formula: Renewable energy composition ratio = Renewable energy power generation / (Renewable energy power generation + Power generation from existing power plants).

45. The power system stabilization method according to claim 43, characterized in that, The degree of voltage variation is defined by the following formula: Voltage variation degree = Ka × (σs - σ) + (1 / Ti) × ∫(σs - σ)dt Where Ka is the proportional gain, Ti is the integral time, t is time, and σ is the standard deviation of the power system voltage relative to the power system voltage reference value.

46. ​​The power system stabilization method according to claim 43, characterized in that, When the power system stability maintenance exponent is large, the control gain in the control constant is reduced.

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