A method and simulation system for primary frequency modulation cooperative control based on hydroelectric generating units

Abstract

A method and simulation system for primary frequency modulation cooperative control of a hydroelectric generating set, belonging to the technical field of hydroelectric generating set power generation control. The method constructs a refined dynamic simulation model of the hydroelectric generating set governor, follow-up system, water diversion system, water turbine and generator, and integrates a storage system model. On this basis, a comprehensive droop control strategy is proposed, including a virtual inertia control link that dynamically adjusts the storage charge and discharge power according to the frequency change rate to enhance the system inertia response, and an adaptive droop control link that adjusts the droop coefficient in real time according to the state of charge (SOC) of the storage, and distinguishes between the charging / discharging process to balance the frequency modulation performance and the storage life. A hardware-in-the-loop simulation system is built through a DSP, and verification shows that, compared with traditional primary frequency modulation, the method effectively suppresses the power reverse regulation caused by water hammer effect, significantly shortens the frequency recovery time, and improves the system frequency stability and regulation accuracy.

Description

Technical Field

[0001] This invention belongs to the field of hydropower generation control, and specifically relates to a primary frequency regulation coordinated control method and simulation system based on hydropower units. Background Technology

[0002] With the large-scale development and construction of new energy sources such as wind power and photovoltaics, and the continuous increase in the scale and load of the power grid, how to balance the randomness and volatility of wind and solar power output and ensure the safe and stable operation of the power system has gradually become a research hotspot in the industry. Primary frequency regulation is one of the important means to maintain the stability of the power grid frequency. When the deviation between the power grid frequency and the set value exceeds the dead zone, each generator unit can quickly adjust its active power through the speed governor to reduce the system frequency change, which has the advantages of fast response speed and high degree of automation.

[0003] Currently, hydropower units are one of the main frequency-regulating power sources in my country, characterized by strong regulation capabilities, fast ramp-up speeds, and clean and environmentally friendly operation. However, the following problems exist in the actual hydropower frequency regulation process: 1. The climbing speed of hydropower units is constrained, and the adjustment process requires a certain amount of time; 2. Hydropower units are non-minimum phase systems with hydroelectric coupling. Their unique water hammer effect will increase the risk of system frequency exceeding limits, which may cause ultra-low frequency oscillations in the hydropower system and thus reduce the stability of the power system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a primary frequency regulation coordinated control method and simulation system based on hydropower units. This method effectively suppresses the power back-regulation caused by water hammer effect, significantly shortens the frequency recovery time, and improves the frequency stability and regulation accuracy of the system.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A primary frequency regulation coordinated control method based on hydropower units includes the following steps: S1. Construct a dynamic simulation model of the hydropower unit speed governor to characterize the system frequency regulation characteristics; S2. Construct a dynamic simulation model of the hydropower unit's servo system to simulate the control signal execution process; S3. Construct a dynamic simulation model of the water intake system of the hydropower unit to characterize the hydraulic inertial response characteristics; S4. Construct a dynamic simulation model of the turbine of the hydropower unit to characterize the mechanical-hydraulic conversion relationship; S5. Construct a dynamic simulation model of the hydropower generator to characterize its electrical response characteristics; S6. Construct a power conversion and state of charge calculation model for the energy storage system to achieve dynamic power management; S7. A virtual inertial control loop is proposed to enhance the sensitivity of the energy storage system to changes in system frequency; when the system frequency changes significantly, the energy storage charging and discharging power is increased; when the system frequency changes slightly, the energy storage charging and discharging power is decreased. S8. An adaptive droop control loop is proposed, which adaptively adjusts the droop coefficient according to the energy storage state of charge, with different adjustment relationships during the discharge and charging processes.

[0006] Preferably, in step S1, the dynamic simulation model of the hydropower unit governor includes the permanent slip coefficient, proportional gain, integral gain, differential gain, and Laplace transforms of the measured frequency and the given frequency; the expression of the dynamic simulation model of the hydropower unit governor is: ; in Y gov (s), f *(s) and f (s) represent the output signals of the speed controller. Y gov Given frequency f *and measurement frequency f Laplace transform, s For the Laplace operator, b p This is the permanent slip coefficient; k p , k i , k d These are proportional gain, integral gain, and derivative gain, respectively. f Represents the measurement frequency. f * represents a given frequency; Y gov This is the output signal of the speed controller.

[0007] Preferably, in step S2, the dynamic simulation model of the hydropower unit servo system includes the integrated amplifier gain coefficient, the electro-hydraulic converter gain coefficient, the auxiliary relay response time constant, the main relay response time constant, and the internal feedback gain coefficient. The expression of the dynamic simulation model of the hydropower unit servo system is as follows: ; in K 1 represents the overall amplifier gain coefficient. K 2 represents the gain coefficient of the electro-hydraulic converter. T 1 represents the reaction time constant of the auxiliary relay. T 2 is the main relay reaction time constant. K 3 represents the internal feedback gain coefficient. Y This is the output of the servo system.

[0008] Preferably, in step S3, the dynamic simulation model of the hydropower unit's water intake system includes the water flow inertia time constant and water hammer phase construction, and the expression of the dynamic simulation model of the hydropower unit's water intake system is:

[0009] in, T w Let be the inertial time constant of the water flow. T r This represents the mutual generation and growth of water.

[0010] Preferably, in step S4, the input signal of the dynamic simulation model of the hydropower turbine is the guide vane opening, and the output signals are unit flow rate and unit torque. The expression of the dynamic simulation model of the hydropower turbine is: ; Among them, the turbine torque m t and traffic q t As the dependent variable, water head h Unit speed n Guide vane opening Y As an independent variable.

[0011] Preferably, in step S5, the dynamic simulation model of the hydropower generator includes parameters such as d-axis and q-axis voltages, synchronous reactance, and transient reactance, and the expression of the dynamic simulation model of the hydropower generator is: ; In the formula, u d and u q For d-axis and q-axis voltages, X q For q-axis synchronous reactance, For d-axis transient reactance, The transient potential along the q-axis. r s This is the stator resistance. Let d be the open-circuit transient time constant. p This represents the number of pole pairs of the motor. The magnetizing electromotive force. X d This is the d-axis synchronous reactance. and Let dq be the d-axis transient potential. and Let dq be the secondary transient reactance. Let be the q-axis open-circuit transient time constant. Let d be the open-circuit subtransient time constant. X a This is the stator synchronous reactance.

[0012] Preferably, in step S6, the power conversion model of the energy storage system adopts a first-order inertial element, and the input of the state of charge calculation model of the energy storage system includes the power output, rated capacity, and initial capacity of the energy storage system, and the output is the state of charge of the energy storage system. The power conversion model of the energy storage system is divided into two parts: a power conversion model and a state of charge calculation model.

[0013] Preferably, in step S7, the virtual inertial control element of the integrated droop control strategy enhances the sensitivity of the energy storage system to changes in system frequency.

[0014] Preferably, in step S7, the virtual inertial control loop enhances the energy storage system's sensitivity to system frequency changes. The specific method is as follows: The introduction of virtual inertial control is primarily to enhance the sensitivity of the energy storage system to system frequency changes. When the system frequency changes significantly, the charging and discharging power of the energy storage is increased to quickly suppress the frequency change; when the system frequency change is small, the charging and discharging power of the energy storage is reduced to shorten the system frequency recovery time. Its expression is as follows:

[0015] in, I b This is the virtual inertia coefficient.

[0016] Preferably, in step S8, the adaptive droop control loop adaptively adjusts the droop coefficient according to the energy storage state of charge, wherein the adjustment relationship is different for the discharge process and the charging process; The adaptive droop control element will adjust the droop coefficient according to the changes in the SOC of the energy storage system. K b Adjustments are made to the relationships; the calculation formula is as follows: Discharge process: ; Charging process: ; in, K b,max This represents the maximum droop coefficient. S oc,min , S oc,max as well as S oc,ref This represents the minimum, maximum, and expected state of charge of the energy storage.

[0017] The overall expression for the comprehensive droop control strategy is as follows: .

[0018] A primary frequency regulation coordinated control system based on a hydropower unit, employing the aforementioned primary frequency regulation coordinated control method for hydropower units, includes: The hydropower unit simulation device is used to simulate the dynamic models of the hydropower unit governor, servo system, water intake system, turbine and generator constructed in steps S1 to S5. The energy storage system simulation device is used to run the energy storage system power conversion model and state of charge calculation model constructed in step S6, and to execute the virtual inertial control and adaptive droop control links described in steps S7 and S8. A communication interface module is configured between the hydropower unit simulation device and the energy storage system simulation device, and is used to transmit system frequency signals and energy storage system power signals in real time through analog quantity interaction. The host computer is connected to the hydropower unit simulation device and the energy storage system simulation device via TCP / IP protocol, and is used to issue simulation condition commands and receive operating status data.

[0019] The present invention can achieve the following beneficial effects: (1) Establish a refined model of hydropower unit and energy storage system, propose a comprehensive improved droop control strategy to improve system response capability, and take into account the state of charge management of energy storage system; (2) Establishing a hydropower-storage combined primary frequency regulation system can effectively verify the proposed method.

[0020] (3) Compared with the conventional primary frequency regulation method of hydropower units, the present invention adopts a primary frequency regulation method that combines hydropower and energy storage, and introduces a comprehensive droop control strategy, which can effectively adapt to changes in the operating state of the system, and at the same time realize the management of the energy storage charge state. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a simulation model diagram of the hydroelectric generator speed governor of the present invention; Figure 2 This is a simulation model diagram of the hydroelectric generator follow-up system of the present invention; Figure 3 This is a model diagram of the hydroelectric turbine of the present invention; Figure 4 This is a diagram of the energy storage state of charge calculation model of the present invention; Figure 5 The sag coefficient of this invention K b Change diagram; Figure 6This is a simulation system architecture diagram for the present invention; Figure 7 This is a comparison chart of the frequency response results of the system of the present invention; Figure 8 This is a comparison chart of the power response results of the system of the present invention. Detailed Implementation

[0022] Preferred solutions include Figures 1 to 8 As shown, a primary frequency regulation coordinated control method and simulation system based on hydropower units are presented. The implementation plan is mainly divided into two parts: model building and comprehensive droop control strategy design and simulation system verification.

[0023] 1. Model building and comprehensive droop control strategy This invention provides a primary frequency regulation control method and simulation system for combined hydropower and energy storage. First, a refined model of the hydropower unit and the energy storage system is built. The specific steps are as follows: S1. Establish a simulation model of the hydropower unit speed governor.

[0024] Model structure as follows Figure 1 As shown, b p This is the permanent slip coefficient; k p , k i , k d These are proportional gain, integral gain, and derivative gain, respectively. f Represents the measurement frequency. f * represents a given frequency; Y gov This is the output signal of the speed controller. The overall transfer function is shown in the following equation:

[0025] in Y gov (s), f *(s) and f (s) represent the output signals of the speed controller. Y gov Given frequency f *and measurement frequency f Laplace transform, s For the Laplace operator.

[0026] S2. Establish a simulation model of the hydropower unit's follow-up system.

[0027] Model structure as follows Figure 2 As shown, where K 1 represents the overall amplifier gain coefficient. K2 represents the gain coefficient of the electro-hydraulic converter. T 1 represents the reaction time constant of the auxiliary relay. T 2 is the main relay reaction time constant. K 3 represents the internal feedback gain coefficient. Y This is the output of the servo system.

[0028] Its complete transfer function is as follows:

[0029] S3. Establish a simulation model of the water intake system for the hydropower unit.

[0030] In this invention, the water diversion system adopts an approximate elastic water hammer model, and its transfer function is as follows:

[0031] in, T w Let be the inertial time constant of the water flow. T r This represents the mutual generation and growth of water.

[0032] S4. Establish a simulation model of the hydroelectric turbine of the hydroelectric unit.

[0033] With the torque of the water turbine m t and traffic q t As the dependent variable, water head h Unit speed n Guide vane opening y The characteristics of a water turbine, as the independent variable, can be expressed by the following equation:

[0034] Due to the complex internal flow of a water turbine, there is no explicit analytical method for the above equations. Therefore, this paper adopts an interpolation method to establish, as shown in the figure below. Figure 3 The nonlinear model is shown. The input signals of the model are guide vane opening and unit rotational speed, and the output signals are unit flow rate and unit torque.

[0035] S5. Establish the generator model of the hydroelectric power unit. The generator model is a detailed 7th-order model:

[0036] In the formula, u d and u q For d-axis and q-axis voltages, X q For q-axis synchronous reactance, For d-axis transient reactance, The transient potential along the q-axis.r s This is the stator resistance. Let d be the open-circuit transient time constant. p This represents the number of pole pairs of the motor. The magnetizing electromotive force. X d This is the d-axis synchronous reactance. and Let dq be the d-axis transient potential. and Let dq be the secondary transient reactance. Let be the q-axis open-circuit transient time constant. Let d be the open-circuit subtransient time constant. X a This is the stator synchronous reactance.

[0037] S6. Establish a simulation model for the energy storage system.

[0038] To facilitate the study of the amplitude-frequency characteristics of the energy storage frequency regulation process, this invention divides the energy storage simulation model into two parts: a power conversion model and a state of charge calculation model, as follows: a: Power conversion model This invention describes the external characteristics of the energy storage system participating in the power grid using a first-order inertial element, as shown in the following equation:

[0039] In the formula, T b This is the time constant of the energy storage power conversion device.

[0040] b: Charge state calculation model The energy storage system state-of-charge calculation model established in this paper is as follows: Figure 4 As shown. Among them. P b For the power output of the energy storage system, S n For the rated capacity of the energy storage system, SOC The state of charge of the energy storage system. SOC ov This represents the initial energy storage capacity.

[0041] To achieve coordinated frequency regulation control of hydropower and energy storage systems, this invention proposes a comprehensive droop control strategy. This strategy introduces virtual inertial control to adapt to system changes, and adaptively adjusts the droop coefficient based on the energy storage SOC, thereby enabling rapid system frequency regulation and energy storage SOC management. A detailed description follows: S7, Virtual Relationship Control Link The introduction of virtual inertial control is primarily to enhance the sensitivity of the energy storage system to system frequency changes. When the system frequency changes significantly, the power of energy storage charging and discharging is increased to quickly suppress the frequency change. When the system frequency change is small, the power of energy storage charging and discharging is reduced to shorten the system frequency recovery time. Its expression is as follows:

[0042] in, I b This is the virtual inertia coefficient.

[0043] S8, Adaptive droop control loop The adaptive droop control element will adjust the droop coefficient according to the changes in the SOC of the energy storage system. K b Adjustments are made, such as adjusting relationships. Figure 5 As shown.

[0044] The detailed calculation formula is as follows: Discharge process:

[0045] Charging process:

[0046] in, K b,max This represents the maximum droop coefficient. S oc,min , S oc,max as well as S oc,ref This represents the minimum, maximum, and expected state of charge of the energy storage.

[0047] The overall expression for the comprehensive droop control strategy is shown below:

[0048] 2. Simulation system verification Using a DSP as the core, simulation devices for hydropower units and energy storage systems were designed separately, with load reduction as the verification condition. The detailed steps are as follows: S1. Establish a joint simulation system for hydropower and energy storage. The system architecture is as follows: Figure 6 As shown, using DSP as the hardware foundation, simulation devices for hydropower units and energy storage systems are designed according to mathematical models. The two simulation devices transmit system frequency and energy storage system power through analog quantity interaction. The host computer and each simulation device interact with each other through TCP / IP to exchange operating status and control commands. S2. Simulation Operating Condition Verification. The simulation operating conditions are controlled by the host computer to simulate the load status of the power grid at a specific time. By disconnecting or connecting two simulation devices, the effects of frequency regulation without energy storage and frequency regulation combined with water storage can be observed to verify the method proposed in this paper.

[0049] Figure 7 and Figure 8 These are simulation comparisons of grid load reduction. The host computer issues a command at 30 seconds, and the system load suddenly drops from 0.45 to 0.4 within 30 seconds. Figure 7 For comparison of system frequency response results, Figure 8 A comparison of the system power response results is presented. Table 1 shows a comparison of the back-regulation power and settling time between the two control methods: Table 1 Comparison of back-regulation power and settling time between the two control methods

[0050] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A primary frequency regulation coordinated control method based on a hydropower unit, characterized in that, Includes the following steps: S1. Construct a dynamic simulation model of the hydropower unit speed governor to characterize the system frequency regulation characteristics; S2. Construct a dynamic simulation model of the hydropower unit's servo system to simulate the control signal execution process; S3. Construct a dynamic simulation model of the water intake system of the hydropower unit to characterize the hydraulic inertial response characteristics; S4. Construct a dynamic simulation model of the turbine of the hydropower unit to characterize the mechanical-hydraulic conversion relationship; S5. Construct a dynamic simulation model of the hydropower generator to characterize its electrical response characteristics; S6. Construct a power conversion and state of charge calculation model for the energy storage system to achieve dynamic power management; S7. A virtual inertial control loop is proposed to enhance the sensitivity of the energy storage system to changes in system frequency; when the system frequency changes significantly, the energy storage charging and discharging power is increased; when the system frequency changes slightly, the energy storage charging and discharging power is decreased. S8. An adaptive droop control loop is proposed, which adaptively adjusts the droop coefficient according to the energy storage state of charge, with different adjustment relationships during the discharge and charging processes.

2. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S1, the dynamic simulation model of the hydropower unit governor includes the permanent slip coefficient, proportional gain, integral gain, differential gain, and the Laplace transform of the measured frequency and the given frequency; the expression of the dynamic simulation model of the hydropower unit governor is: ； in Y gov (s), f *(s) and f (s) represent the output signals of the speed controller. Y gov Given frequency f *and measurement frequency f Laplace transform, s For the Laplace operator, b p This is the permanent slip coefficient; k p , k i , k d These are proportional gain, integral gain, and derivative gain, respectively. f Represents the measurement frequency. f * represents a given frequency; Y gov This is the output signal of the speed controller.

3. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S2, the dynamic simulation model of the hydropower unit servo system includes the integrated amplifier gain coefficient, the electro-hydraulic converter gain coefficient, the auxiliary relay response time constant, the main relay response time constant, and the internal feedback gain coefficient. The expression of the dynamic simulation model of the hydropower unit servo system is as follows: ； in K 1 represents the overall amplifier gain coefficient. K 2 represents the gain coefficient of the electro-hydraulic converter. T 1 represents the reaction time constant of the auxiliary relay. T 2 is the main relay reaction time constant. K 3 represents the internal feedback gain coefficient. Y This is the output of the servo system.

4. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S3, the dynamic simulation model of the hydropower unit's water intake system includes the water flow inertia time constant and the water hammer phase length. The expression for the dynamic simulation model of the hydropower unit's water intake system is: in, T w Let be the inertial time constant of the water flow. T r This represents the mutual generation and growth of water.

5. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S4, the input signal of the dynamic simulation model of the hydropower turbine is the guide vane opening, and the output signals are unit flow rate and unit torque. The expression of the dynamic simulation model of the hydropower turbine is: ； Among them, the turbine torque m t and traffic q t As the dependent variable, water head h Unit speed n Guide vane opening Y As an independent variable.

6. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S5, the dynamic simulation model of the hydropower generator includes parameters such as d-axis and q-axis voltages, synchronous reactance, and transient reactance. The expression of the dynamic simulation model of the hydropower generator is: ； In the formula, u d and u q For d-axis and q-axis voltages, X q For q-axis synchronous reactance, For d-axis transient reactance, The transient potential along the q-axis. r s Stator resistance; Let d be the open-circuit transient time constant. p This represents the number of pole pairs of the motor. The magnetizing electromotive force. X d For d-axis synchronous reactance; and Let dq be the d-axis transient potential. and The dq axis is the transient reactance; Let be the q-axis open-circuit transient time constant. Let d be the open-circuit subtransient time constant. X a This is the stator synchronous reactance.

7. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S6, the energy storage system power conversion model adopts a first-order inertial element. The input of the energy storage system state of charge calculation model includes the energy storage system power output, rated capacity, and initial capacity. The output is the energy storage system state of charge. The energy storage system power conversion model is divided into two parts: a power conversion model and a state of charge calculation model.

8. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S7, the virtual inertial control element of the integrated droop control strategy enhances the energy storage system's sensitivity to system frequency changes.

9. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S7, the virtual inertial control loop enhances the energy storage system's sensitivity to system frequency changes. The specific method is as follows: The introduction of virtual inertial control is primarily used to enhance the sensitivity of the energy storage system to changes in system frequency. When the system frequency changes significantly, the power of energy storage charging and discharging is increased to quickly suppress the frequency change; when the system frequency changes slightly, the power of energy storage charging and discharging is reduced to shorten the system frequency recovery time. Its expression is as follows: in, I b This is the virtual inertia coefficient.

10. The primary frequency regulation coordinated control method based on hydropower units according to claim 1, characterized in that, In step S8, the adaptive droop control loop adaptively adjusts the droop coefficient according to the energy storage state of charge, wherein the adjustment relationship is different for the discharge process and the charging process. The adaptive droop control element will adjust the droop coefficient according to the changes in the SOC of the energy storage system. K b Adjustments are made to the relationships; the calculation formula is as follows: Discharge process: ； Charging process: ； in, K b,max This represents the maximum droop coefficient. S oc,min , S oc,max as well as S oc,ref This represents the minimum, maximum, and expected values ​​of the energy storage state of charge. The overall expression for the comprehensive droop control strategy is as follows: 。 11. A primary frequency regulation coordinated control system based on a hydropower unit, characterized in that, The system employs the primary frequency regulation coordinated control method based on hydropower units according to any one of claims 1-10, and includes: The hydropower unit simulation device is used to simulate the dynamic models of the hydropower unit governor, servo system, water intake system, turbine and generator constructed in steps S1 to S5. The energy storage system simulation device is used to run the energy storage system power conversion model and state of charge calculation model constructed in step S6, and to execute the virtual inertial control and adaptive droop control links described in steps S7 and S8. A communication interface module is configured between the hydropower unit simulation device and the energy storage system simulation device, and is used to transmit system frequency signals and energy storage system power signals in real time through analog quantity interaction. The host computer is connected to the hydropower unit simulation device and the energy storage system simulation device via TCP / IP protocol, and is used to issue simulation condition commands and receive operating status data.

Images