Modeling and working condition conversion simulation method for doubly-fed variable-speed pumped storage unit under water pumping working condition

Abstract

The invention relates to a modeling and working condition conversion simulation method for a double-fed variable-speed pumped storage unit under a water pumping working condition, and belongs to the technical field of pumped storage simulation. The method comprises the following steps: constructing a doubly-fed variable-speed pumped storage unit simulation model under a water pumping working condition, wherein the doubly-fed variable-speed pumped storage unit simulation model comprises a water delivery system sub-model, a reversible pump turbine sub-model, a guide vane servo execution mechanism sub-model, a doubly-fed asynchronous motor sub-model, a back-to-back converter sub-model and a rotating speed and guide vane opening optimizer sub-model; on the basis of the simulation model, all stages of water pumping working condition starting, load increasing and decreasing, steady-state operation and shutdown of the water pumping working condition of the doubly-fed variable-speed pumped storage unit are simulated, and when the active power dispatching value changes, the response conditions of the actual value of the motor rotating speed, the actual value of the guide vane opening, the actual value of the active power and the actual value of the reactive power are recorded. According to the method, the conversion process of the water pumping working condition is realized through accurate modeling and simulation of each part of the doubly-fed variable-speed pumping and storage unit under the water pumping working condition, and a basis is provided for studying that the pumping and storage unit maintains efficient operation.

Description

Technical Field

[0001] The invention belongs to the technical field of pumped storage simulation, and in particular relates to a method for modeling and operating condition conversion simulation of a double-fed variable-speed pumped storage unit under pumping operating conditions. Background Art

[0002] As the penetration rate of new energy in the power system continues to increase, the flexibility of the power grid, its support for frequency and the absorption of new energy are facing severe challenges due to the general randomness, volatility and indirectness of the output of new energy such as wind power and photovoltaics, and the continuous widening of the peak-to-valley difference in the power grid's load. The power system's demand for flexible power supply adjustment is further increased.

[0003] As the most flexible power source with large-scale development capability and lower operation and maintenance cost, pumped storage units have multiple functions such as peak load regulation, frequency regulation, and system standby, and play an active role in improving the flexibility of the power grid and the level of new energy consumption. Among them, the double-fed variable-speed pumped storage unit has the advantages of wide power regulation range, fast start-stop speed, and high operation efficiency, which can better support the power grid. Most of the existing technologies for the simulation of double-fed asynchronous motors have simplified the hydraulic-mechanical side, and cannot accurately simulate the operating condition conversion of the double-fed variable-speed pumped storage unit, and there will be large deviations when simulating the operating condition changes. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a modeling and operating condition conversion simulation method for a double-fed variable-speed pumped-storage unit under pumping conditions, accurately model the double-fed variable-speed pumped-storage unit, simulate the conversion process of each operating stage of the pumping condition, and provide a basis for studying the maintenance of efficient operation of the pumped-storage unit.

[0005] The present invention provides a method for modeling and operating condition conversion simulation of a double-fed variable-speed pumped storage unit under pumping conditions, which specifically includes the following steps:

[0006] Construct a simulation model of a double-fed variable-speed pumped storage unit under pumping conditions, including a water delivery system sub-model, a reversible pump-turbine sub-model, a guide vane servo actuator sub-model, a double-fed asynchronous motor sub-model, a back-to-back converter sub-model, and a speed and guide vane opening optimizer sub-model;

[0007] Based on the simulation model, the pumping start-up, load increase and decrease, steady-state operation and shutdown stages of the pumping condition of the double-fed variable-speed pumped storage unit are simulated, and the responses of the actual values ​​of the motor speed, the guide vane opening and the active power are recorded when the active power dispatch value changes.

[0008] Furthermore, the simulation of the pumping operation start-up, load increase and decrease, steady-state operation and shutdown stages of the pumping operation of the double-fed variable-speed pumped storage unit based on the simulation model includes:

[0009] In the start-up phase of pumping operation: based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the off-grid start-up mode is adopted, the stator winding is short-circuited, and a three-phase symmetrical current is applied to the rotor-side converter, and the doubly-fed asynchronous motor starts to rotate; when the motor speed reaches near the rated speed, the excitation control is disconnected; the voltage regulation control is applied to the rotor-side converter to adjust the stator-side voltage, and when the stator-side voltage reaches the grid-connected condition, the stator-side switch is closed to complete the grid-connected operation;

[0010] In the load increase and decrease stage and steady-state operation stage of pumping conditions: simulate the active power reference value by adjusting the external input of the simulation model; determine the optimal speed and optimal guide vane opening based on the speed and guide vane opening optimizer sub-model and the active power reference value; obtain the actual motor speed value and guide vane opening value based on the water delivery system sub-model, reversible pump turbine sub-model, and guide vane servo actuator sub-model; adjust the active power actual value to track the active power reference value based on the doubly fed asynchronous motor sub-model and back-to-back converter sub-model;

[0011] During the transition from the pumping condition to the shutdown condition: based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the excitation current of the rotor-side converter is reduced to reduce the load, so that the stator current gradually decreases. When the current approaches zero, the grid-connected circuit breaker is disconnected and the unit is disconnected from the grid; the stator winding is short-circuited, and the excitation voltage is applied to the rotor-side converter. The unit generates a braking torque, which gradually reduces the rotor speed to near zero; the control of the rotor-side converter and the stator winding short-circuit circuit breaker are disconnected, so that the unit gradually reduces the speed to zero under the action of its own damping.

[0012] Furthermore, during the steady-state operation stage of the pumping condition of the doubly-fed variable-speed pumped-storage unit, the active power dispatch value is increased or decreased in a step-by-step manner.

[0013] Furthermore, the doubly-fed asynchronous motor sub-model includes a mathematical model of the doubly-fed asynchronous motor, an active power P s , stator reactive power Q s and electromagnetic torque T e The calculation formula and motor motion equation;

[0014] Among them, the mathematical model of the doubly fed asynchronous motor is expressed as:

[0015]

[0016] Among them, u sq 、u sd 、i sq 、i sd are the q-axis and d-axis components of the stator voltage and the q-axis and d-axis components of the stator current respectively; u rq 、urd 、i rq 、i rd are the q-axis and d-axis components of the rotor voltage and the q-axis and d-axis components of the rotor current respectively; R s , R r are stator and rotor resistance respectively; ω s ,ω r are the system synchronous speed and rotor speed respectively; p is the differential operator; ψ sq , sd , rq , rd are the q-axis and d-axis components of the stator flux and the q-axis and d-axis components of the rotor flux respectively; L s , L r are the stator and rotor equivalent self-inductance respectively; L m is the stator-rotor equivalent mutual inductance;

[0017] Active power P s , stator reactive power Q s , electromagnetic torque T e The calculation formula and the motor motion equation are expressed as:

[0018]

[0019] Among them, n p is the number of pole pairs of the doubly-fed asynchronous motor; T L is the load torque; D is the damping coefficient; J is the moment of inertia of the unit.

[0020] Furthermore, the back-to-back converter sub-model includes: the grid-side and rotor-side converters respectively adopt grid voltage and stator voltage oriented control strategies; the grid-side converter control system consists of two parts: a DC voltage outer loop and a current inner loop; the rotor-side converter control system consists of two parts: a speed outer loop and a current inner loop.

[0021] Furthermore, the speed and guide vane opening optimizer sub-model includes:

[0022] Determine the optimal speed ω of the unit based on the initial head and active power dispatch value opt and the optimal guide vane opening G opt , expressed as:

[0023]

[0024] Among them, H0 is the initial head, P ref is the active power dispatch value.

[0025] Furthermore, the water delivery system sub-model includes a head loss model and an elastic water hammer model, wherein:

[0026] The head loss model is expressed as:

[0027]

[0028] Among them, H loss is the head loss, f g 、f p 、f t are the friction coefficients of the guide vane, water pipe, and water tunnel, respectively, d is the dynamic flow, G is the guide vane opening, H d is the dynamic head, H s is the static head, G max is the maximum opening of the guide vane;

[0029] The elastic water hammer model is expressed as:

[0030]

[0031] Among them, Q c is the dynamic flow rate at the connection between the water pipeline and the water tunnel, Q d is the dynamic flow of the pump turbine, T et and Z ht are the elastic time constant and hydraulic impedance of the water tunnel, T ep and Z hp are the elastic time constant and hydraulic impedance of the water pipeline, respectively, and s represents the Laplace operator;

[0032] Among them, the elastic time constant of the water tunnel is T et , elastic time constant T of water pipeline ep The calculation formula of the hyperbolic tangent value of each elastic time constant is:

[0033]

[0034] Among them, when the numerator of formula (1) is the length of the water tunnel, the calculation results of formula (1) and formula (2) are the elastic time constant of the water tunnel and the hyperbolic tangent value of the elastic time constant of the water tunnel respectively; when the numerator of formula (1) is the length of the water pipeline, the calculation results of formula (1) and formula (2) are the elastic time constant of the water pipeline and the hyperbolic tangent value of the elastic time constant of the water pipeline respectively.

[0035] Furthermore, the water pump and water wheel mechanism sub-model is expressed as:

[0036]

[0037] Among them, T m is the mechanical torque of the pump turbine, P m is the mechanical power output of the pump turbine; ω r H is the speed of the pump turbine, i.e. the rotor speed;d is the dynamic head; Q d is the dynamic flow of the pump turbine; η is the efficiency.

[0038] Furthermore, the pump-turbine operating characteristics are fitted based on the factory data of the pump-turbine, including the dynamic head H d And efficiency η, expressed as:

[0039]

[0040] Among them, a i 、b i 、c i are the fitting coefficients of the polynomial, i∈[0,3].

[0041] Furthermore, the guide vane servo mechanism sub-model includes a main pressure regulating valve, a main servomotor, a guide vane opening regulator, and a guide vane opening control.

[0042] The present invention can achieve at least one of the following beneficial effects:

[0043] By considering dividing the doubly-fed variable-speed pumped storage unit into a hydraulic-mechanical part and an electrical-control part, and accurately modeling and simulating each part separately, the conversion process of each operating stage from the start-up stage of the pumping condition, the load increase and decrease stage, the steady-state operation stage, and the transition from the pumping condition to the shutdown condition stage is realized, providing accurate simulation results and reference basis for studying the safe and stable operation of the pumped storage unit.

[0044] By constructing a water delivery system sub-model, a reversible pump-turbine sub-model, a guide vane servo actuator sub-model, a doubly-fed asynchronous motor sub-model, a back-to-back converter sub-model, and a speed and guide vane opening optimizer sub-model, during the simulation process, highly decoupled control of active and reactive control can be achieved under various operating conditions, and the tracking changes of the actual guide vane opening value to the optimal guide vane opening, the actual speed value to the optimal speed, and the actual active power value to the active power reference value can be accurately simulated, so that the unit operating efficiency can always be maintained at a high level.

[0045] Other features and advantages of the present invention will be described in the following description, and some advantages may become apparent from the description, or may be understood by practicing the present invention. The purpose and other advantages of the present invention may be realized and obtained through the contents particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0047] Figure 1 is a flow chart of the method of the present invention;

[0048] Figure 2 It is a simulation circuit diagram of the water delivery system sub-model of the present invention;

[0049] Figure 3 It is a simulation circuit diagram of the reversible water pump turbine sub-model of the present invention;

[0050] Figure 4 A circuit diagram of a sub-model of a guide vane servo actuator of the present invention;

[0051] Figure 5 , Figure 6 They are respectively a grid-side converter simulation circuit diagram and a rotor-side converter circuit diagram of the present invention;

[0052] Figure 7 This is a diagram of the change in active power of the unit when the load changes during the steady-state stage of the pumping condition of the present invention;

[0053] Figure 8 It is a diagram showing the reactive power variation of the unit when the load changes during the steady-state stage of the pumping condition of the present invention;

[0054] Fig. 9 This is a diagram showing the change in guide vane opening when the load changes during the steady-state stage of the pumping condition of the present invention;

[0055] Fig.10 This is a diagram showing the speed change of the unit when the load changes during the steady-state stage of the pumping condition of the present invention. DETAILED DESCRIPTION

[0056] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0057] A specific embodiment of the present invention discloses a method for modeling and operating condition conversion simulation of a double-fed variable-speed pumped storage unit in a pumping operating condition, which specifically includes step S01 and step S02.

[0058] Step S01, constructing a simulation model of a double-fed variable-speed pumped storage unit under pumping conditions, including a water delivery system sub-model, a reversible pump-turbine sub-model, a guide vane servo actuator sub-model, a double-fed asynchronous motor sub-model, a back-to-back converter sub-model, and a speed and guide vane opening optimizer sub-model;

[0059] Among them, the water delivery system sub-model, reversible pump turbine sub-model, and guide vane servo actuator sub-model are the modeling of the hydraulic-mechanical part of the pumped storage unit, and the doubly-fed asynchronous motor sub-model, back-to-back converter sub-model, and speed and guide vane opening optimizer sub-model are the modeling of the electrical-control part of the pumped storage unit;

[0060] The stator of the doubly-fed asynchronous motor is connected to the infinite system, and the rotor is connected to the power grid via the rotor-side converter and the grid-side converter.

[0061] Specifically, the water delivery system submodel (such as Figure 2 The simulation circuit diagram of the water delivery system submodel of the present invention includes a head loss model and an elastic water hammer model, wherein:

[0062] The head loss model is expressed as:

[0063]

[0064] Among them, H loss is the head loss, f g 、f p 、f t are the friction coefficients of the guide vane, water pipe, and water tunnel, respectively, d is the dynamic flow, G is the guide vane opening, H d is the dynamic head, H s is the static head, G max is the maximum opening of the guide vane.

[0065] The elastic water hammer model is expressed as:

[0066]

[0067] Among them, Q c is the dynamic flow rate at the connection between the water pipeline and the water tunnel, Q d is the dynamic flow of the pump turbine, T et and Z ht are the elastic time constant and hydraulic impedance of the water tunnel, T ep and Z hp are the elastic time constant and hydraulic impedance of the water pipeline respectively, and s represents the Laplace operator.

[0068] Among them, the elastic time constant of the water tunnel is T et , elastic time constant T of water pipeline ep The calculation formula of the hyperbolic tangent value of each elastic time constant is:

[0069]

[0070] Among them, when the numerator of formula (1) is the length of the water tunnel, the calculation results of formula (1) and formula (2) are the elastic time constant of the water tunnel and the hyperbolic tangent value of the elastic time constant of the water tunnel respectively; when the numerator of formula (1) is the length of the water pipeline, the calculation results of formula (1) and formula (2) are the elastic time constant of the water pipeline and the hyperbolic tangent value of the elastic time constant of the water pipeline respectively.

[0071] Similarly, the calculation formulas for the hyperbolic sine value and the hyperbolic sine value of each elastic time constant are:

[0072]

[0073] Specifically, when constructing the reversible pump-turbine sub-model, the pump-turbine operating characteristics are first fitted based on the factory data of the pump-turbine, including the dynamic head H d And efficiency η, expressed as:

[0074]

[0075] Among them, a i , b i 、c i are the fitting coefficients of the polynomial, i∈[0,3].

[0076] Further, the reversible pump turbine sub-model (such as Figure 3 The simulation circuit diagram of the reversible pump-turbine sub-model is shown as:

[0077]

[0078] Among them, T m is the mechanical torque of the pump turbine, P m is the mechanical power output of the pump turbine; ω r H is the speed of the pump turbine, i.e. the rotor speed; d is the dynamic head; Q d is the dynamic flow of the pump turbine; η is the efficiency. From the formula of the reversible pump turbine sub-model, it can be seen that the input of the reversible pump turbine sub-model is the motor speed, and the output is the mechanical torque of the pump turbine.

[0079] Specifically, the guide vane servo actuator sub-model includes a main pressure regulating valve, a main servomotor, a guide vane opening regulator, and a guide vane opening controller, wherein the guide vane opening controller is used to implement the guide vane opening change rate limit and the guide vane opening limit. The function of the guide vane servo actuator sub-model is to convert electrical signals into mechanical signals, thereby adjusting the guide vane opening.

[0080] like Figure 4 : is the circuit diagram of the guide vane servo actuator sub-model of the present invention. opt is the optimal guide vane opening; K g 、T g is the correlation coefficient of the guide vane opening regulator (the position shown in the figure corresponds to the guide vane opening regulator); K p 、T p Correlation coefficient of the main pressure distribution valve (the position shown in the figure corresponds to the main pressure distribution valve); V max 、Vmin is the maximum and minimum value of the guide vane opening change rate (the position shown in the figure corresponds to the guide vane opening control); G max , G min are the maximum and minimum limits of the guide vane opening (the position shown in the figure corresponds to the guide vane opening control); The position corresponds to the main relay.

[0081] Specifically, the doubly-fed asynchronous motor sub-model in step S01 includes a mathematical model of the doubly-fed asynchronous motor, an active power P s , stator reactive power Q s and electromagnetic torque T e The calculation formula and motor motion equation.

[0082] Furthermore, factors such as spatial harmonics, magnetic circuit saturation, and core loss are ignored, the rotor winding is converted to the stator side, and the motor convention is adopted to construct the mathematical model of the doubly fed asynchronous motor in a two-phase synchronously rotating dq coordinate system.

[0083] Among them, the mathematical model of the doubly fed asynchronous motor is expressed as:

[0084]

[0085] Among them, u sq 、u sd 、i sq 、i sd are the q-axis and d-axis components of the stator voltage and the q-axis and d-axis components of the stator current respectively; u rq 、u rd 、i rq 、i rd are the q-axis and d-axis components of the rotor voltage and the q-axis and d-axis components of the rotor current respectively; R s , R r are stator and rotor resistance respectively; ω s ,ω r are the system synchronous speed and rotor speed respectively; p is the differential operator; ψ sq , sd , rq , rd are the q-axis and d-axis components of the stator flux and the q-axis and d-axis components of the rotor flux respectively; L s , L r are the stator and rotor equivalent self-inductance respectively; L m is the stator-rotor equivalent mutual inductance;

[0086] Active power P s , stator reactive power Q s , electromagnetic torque T e The calculation formula and the motor motion equation are expressed as:

[0087]

[0088] Among them, n p is the number of pole pairs of the doubly-fed asynchronous motor; T L is the load torque; D is the damping coefficient; J is the moment of inertia of the unit.

[0089] Specifically, the back-to-back converter sub-model described in step S01 includes: the grid-side and rotor-side converters respectively adopt grid voltage and stator voltage oriented control strategies; the grid-side converter control system consists of two parts: a DC voltage outer loop and a current inner loop; the rotor-side converter control system consists of two parts: a speed outer loop and a current inner loop.

[0090] Figure 5 , Figure 6 The grid-side converter simulation circuit diagram and the rotor-side converter circuit diagram are shown respectively.

[0091] In the figure, is the reference value of DC voltage; U dc is the DC side voltage of the grid-side converter; PI is the PI regulator; is the reference value of active and reactive current of the grid-side converter; i gd 、i gq is the dq-axis component of the AC side current of the grid-side converter; ω s ,ω r are the rotation angular velocity of the stator magnetic field and the rotor speed of the doubly-fed asynchronous motor respectively; L g is the inductance of the grid-side converter; is the reference value of the dq-axis component of the AC side voltage of the grid-side converter; u gd 、u gq is the dq axis component of the grid-side converter grid-connected point voltage; U g is the magnitude of the grid voltage vector; is the reference value of the q-axis component of the rotor current; is the reference value of the d-axis component of the rotor current; i rq 、i rd is the dq axis component of the rotor current; is the reference value of the dq-axis component of the rotor voltage; is the magnetic leakage coefficient; Q set is the reactive power reference value absorbed by the double-fed asynchronous motor; Q G It is the actual value of reactive power absorbed by the doubly-fed asynchronous motor.

[0092] The following instructions Figure 5 and Figure 6 Principle:

[0093] against Figure 5, the mathematical model of the grid-side converter in the two-phase synchronous rotating dq coordinate system can be expressed as:

[0094]

[0095] Among them, R g is the AC side resistance of the grid-side converter.

[0096] Since the grid-side converter is directly connected to the AC grid, the voltage is basically stable near the rated value, so the stator voltage oriented control strategy is adopted:

[0097]

[0098] Combining equations (3) and (4), we get

[0099]

[0100] The grid-side inverter usually adopts a dual closed-loop control method of DC voltage outer loop and current inner loop. In order to achieve fast and error-free tracking, both the inner and outer loops are designed as PI control. The control equations of the inner and outer current loops are:

[0101]

[0102] Among them, K p1 K is the proportional gain of the PI regulator; I1 is the integral adjustment gain of the PI regulator;

[0103] Then the DC voltage outer loop control equation is:

[0104]

[0105] According to the DC voltage outer loop control equation, Figure 5 Control diagram of the grid-side converter.

[0106] against Figure 6 :

[0107] Considering that the variable speed pumped storage unit has a high requirement for speed control under pumping conditions, a speed control outer loop is used in the rotor side converter to replace the power control outer loop widely used in the existing control strategy to achieve direct control of the speed, and the speed control loop generates a reference value of the q-axis component of the rotor current;

[0108] When the rotor-side converter adopts stator voltage oriented control,

[0109]

[0110] At this time, the reactive power on the stator side can be expressed as It can be seen that the reactive power of the doubly-fed asynchronous motor is related to the rotor d-axis current component, so the current obtained by the reactive power deviation is used as the reference value of the rotor d-axis current. s is the magnitude of the stator voltage vector;

[0111] According to the mathematical model of the doubly-fed asynchronous motor in the two-phase synchronous rotating dq coordinate system,

[0112]

[0113] It can be seen that under stator voltage oriented control, the dq-axis components of the rotor current can be expressed as:

[0114]

[0115] The rotor current dynamic term in the equation is controlled by a PI regulator, and the rotor voltage control equation is as follows:

[0116]

[0117] Among them, K irP K is the proportional gain of the rotor current inner loop PI regulator; irI is the integral regulation gain of the rotor current inner loop PI regulator;

[0118] Based on this, it can be constructed Figure 6 Control diagram of the rotor-side converter.

[0119] Specifically, the speed and guide vane opening optimizer sub-model in step S01 includes:

[0120] Determine the optimal speed ω of the unit based on the initial head and active power dispatch value opt and the optimal guide vane opening G opt , expressed as:

[0121]

[0122] Among them, H0 is the initial head, P ref is the active power dispatch value.

[0123] Step S02, based on the simulation model, simulate the pumping start-up, load increase and decrease, steady-state operation and shutdown stages of the pumping condition of the double-fed variable-speed pumped storage unit, and record the response of the actual value of the motor speed, the actual value of the guide vane opening and the actual value of the active power when the active power scheduling value changes.

[0124] Specifically, during the start-up phase of the pumping operation:

[0125] Based on the doubly-fed asynchronous machine sub-model and the back-to-back converter sub-model, the off-grid starting method is adopted, the stator winding is short-circuited and a three-phase symmetrical current is applied to the rotor-side converter. At this time, the mechanical torque T m =0, electromagnetic torque T e If it is not 0, the double-fed asynchronous motor starts to rotate;

[0126] When the motor speed reaches near the rated speed, the excitation control is disconnected;

[0127] The voltage regulation control is applied to the rotor-side converter to adjust the stator-side voltage. When the stator-side voltage reaches the grid-connected condition (the frequency, voltage amplitude, and voltage phase sequence of the motor are the same as the grid voltage), the stator-side switch is closed to complete the grid-connected operation.

[0128] Specifically, during the load increase and decrease phase of pumping conditions:

[0129] The active power reference value, i.e., the active power dispatch value, is simulated by adjusting the external input of the simulation model. It should be noted that, in the load increase and decrease stage, a speed priority control strategy is adopted, and the speed is controlled by the rotor-side converter, which has a faster response speed. Therefore, when the load changes, the speed will fluctuate, and the greater the change and the faster the change rate, the more drastic the speed fluctuation. Therefore, according to the load increase and decrease requirements, the active power reference value is increased or decreased in a step-by-step manner to avoid excessive short-term fluctuations in the speed.

[0130] Furthermore, the optimal speed and guide vane opening are determined based on the speed and guide vane opening optimizer sub-model and the active power reference value; since there is a deviation between the current speed and the optimal speed, a speed deviation signal is generated; this deviation signal can change the q-axis component of the rotor current through the rotor-side converter. When the q-axis component of the rotor current changes, the electromagnetic power of the motor will also change, so that the electromagnetic power of the motor gradually tracks the active power reference value; at the same time, due to the imbalance between the electromagnetic torque and the mechanical torque of the pump-turbine, the speed of the unit will change accordingly. The change in speed causes the flow rate and dynamic head to change accordingly, resulting in a change in the output mechanical power. Based on the water delivery system sub-model, the reversible pump-turbine sub-model, and the guide vane servo actuator sub-model, the actual value of the motor speed and the actual value of the guide vane opening are obtained through simulation; based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the actual value of the active power is adjusted to track the active power reference value; when the dynamic process ends and the electromagnetic power is balanced with the mechanical power, the stable speed is the optimal speed corresponding to the current active power reference value;

[0131] Furthermore, in the steady-state operation stage of pumping conditions:

[0132] The simulation process is the same as the process of increasing and decreasing load in the pumping condition. The active power reference value is simulated by adjusting the external input of the simulation model; the optimal speed and the optimal guide vane opening are determined based on the speed and guide vane opening optimizer sub-model and the active power reference value; the actual motor speed value and the actual guide vane opening value are obtained by simulation based on the water delivery system sub-model, the reversible pump-turbine sub-model, and the guide vane servo actuator sub-model; the actual active power value is adjusted based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model to track the active power reference value; in the steady-state operation stage of the pumping condition, based on the demand of the power grid, the active power reference value is also increased or decreased in a step-by-step manner to observe the response of the motor speed, guide vane opening and the actual active power value when the active power reference value changes;

[0133] During the transition from the pumping condition to the shutdown condition: based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the excitation current of the rotor-side converter is reduced to reduce the load, so that the stator current gradually decreases. When the current approaches zero, the grid-connected circuit breaker is disconnected and the unit is disconnected from the grid; the stator winding is short-circuited, and the excitation voltage is applied to the rotor-side converter. The unit generates a braking torque, which gradually reduces the rotor speed to near zero; the control of the rotor-side converter and the stator winding short-circuit circuit breaker are disconnected, so that the unit gradually reduces the speed to zero under the action of its own damping.

[0134] like Figure 7 This is a diagram of the change in active power of the unit when the load changes in the steady-state stage of the pumping condition during the simulation process. From the diagram, we can see that the initial active power absorbed by the unit is 0.8pu. The unit has a small fluctuation condition at the 25th second, and the active power command of the unit is reduced to 0.65pu. When the active reference value decreases in a step, under the control of the guide vane opening, the actual value of the active power absorbed by the unit will decrease to the given value.

[0135] Figure 8 This is a diagram showing the change in reactive power of the unit when the load changes during the steady-state stage of the pumping condition during the simulation. As can be seen from the diagram, when the reactive power reference value changes, the reactive power absorbed by the unit responds quickly and reaches the given value quickly. Moreover, when the reactive power changes, the active power does not change; Figure 7 It can be seen that when the active power changes, the reactive power does not change. This shows that there is no inherent correlation between active and reactive power control, and active and reactive power decoupling control is achieved.

[0136] Fig. 9 This is a diagram showing the change in the guide vane opening of the unit when the load changes during the steady-state stage of the pumping condition during the simulation. As can be seen from the diagram, during the active reference value change stage, under the control of the guide vane opening optimizer, the guide vane opening reference value will change accordingly. Through the control of the guide vane servo actuator, the guide vane opening of the unit can accurately track the reference value.

[0137] Fig.10This is a diagram showing the speed change of the unit when the load changes during the steady-state stage of the pumping condition during the simulation. It can be seen that under the control of the speed optimizer, when the active power reference value changes, the speed reference value will also change accordingly. Under the control of the rotor-side converter, the unit speed can quickly and accurately track the reference value.

[0138] The embodiment discloses a method for modeling and operating condition conversion simulation of a double-fed variable-speed pumped storage unit under pumping conditions. By considering dividing the double-fed variable-speed pumped storage unit into a hydraulic-mechanical part and an electrical-control part, and accurately modeling and simulating each part, the conversion process of each operating stage from the start-up stage of the pumping condition, the load increase and decrease stage, the steady-state operation stage, and the transition from the pumping condition to the shutdown condition stage is realized, providing accurate simulation results and reference basis for studying the safe and stable operation of the pumped storage unit. By constructing a water delivery system sub-model, a reversible pump-turbine sub-model, a guide vane servo actuator sub-model, a double-fed asynchronous motor sub-model, a back-to-back converter sub-model, and a speed and guide vane opening optimizer sub-model, in the simulation process, highly decoupled control of active and reactive control can be achieved under various working conditions, and the tracking changes of the actual guide vane opening value to the optimal guide vane opening, the actual speed value to the optimal speed, and the actual active power value to the active power reference value can be accurately simulated, so that the unit operation efficiency can always be maintained at a high level.

[0139] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for modeling and operating mode conversion simulation of a double-fed variable-speed pumped storage unit under pumping conditions, characterized in that: include: Construct a simulation model of a double-fed variable-speed pumped storage unit under pumping conditions, including a water delivery system sub-model, a reversible pump-turbine sub-model, a guide vane servo actuator sub-model, a double-fed asynchronous motor sub-model, a back-to-back converter sub-model, and a speed and guide vane opening optimizer sub-model; Based on the simulation model, the pumping start-up, load increase and decrease, steady-state operation and shutdown stages of the pumping condition of the double-fed variable-speed pumped storage unit are simulated, and the responses of the actual values ​​of the motor speed, the guide vane opening, the active power and the reactive power are recorded when the active power dispatch value changes.

2. The method for modeling and operating condition conversion of a pumped storage unit according to claim 1, characterized in that: The simulation of the pumping operation start-up, load increase and decrease, steady-state operation and shutdown stages of the pumping operation of the double-fed variable-speed pumped storage unit based on the simulation model includes: In the start-up phase of pumping operation: based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the off-grid start-up mode is adopted, the stator winding is short-circuited, and a three-phase symmetrical current is applied to the rotor-side converter, and the doubly-fed asynchronous motor starts to rotate; when the motor speed reaches near the rated speed, the excitation control is disconnected; the voltage regulation control is applied to the rotor-side converter to adjust the stator-side voltage, and when the stator-side voltage reaches the grid-connected condition, the stator-side switch is closed to complete the grid-connected operation; In the load increase and decrease stage and steady-state operation stage of pumping conditions: simulate the active power reference value by adjusting the external input of the simulation model; determine the optimal speed and optimal guide vane opening based on the speed and guide vane opening optimizer sub-model and the active power reference value; obtain the actual motor speed value and guide vane opening value based on the water delivery system sub-model, reversible pump turbine sub-model, and guide vane servo actuator sub-model; adjust the active power actual value to track the active power reference value based on the doubly fed asynchronous motor sub-model and back-to-back converter sub-model; During the transition from the pumping condition to the shutdown condition: based on the doubly-fed asynchronous motor sub-model and the back-to-back converter sub-model, the excitation current of the rotor-side converter is reduced to reduce the load, so that the stator current gradually decreases. When the current approaches zero, the grid-connected circuit breaker is disconnected and the unit is disconnected from the grid; the stator winding is short-circuited, and the excitation voltage is applied to the rotor-side converter. The unit generates a braking torque, which gradually reduces the rotor speed to near zero; the control of the rotor-side converter and the stator winding short-circuit circuit breaker are disconnected, so that the unit gradually reduces the speed to zero under the action of its own damping.

3. The method for modeling and operating condition conversion of a pumped storage unit according to claim 2 is characterized in that: During the steady-state operation stage of the doubly-fed variable-speed pumped-storage unit's pumping condition, the active power dispatch value is increased or decreased in a step-by-step manner.

4. The method for modeling and operating condition conversion of a pumped storage unit according to claim 3 is characterized in that: The double-fed asynchronous motor sub-model includes a mathematical model of the double-fed asynchronous motor, an active power P s , stator reactive power Q s and electromagnetic torque T e The calculation formula and motor motion equation; Among them, the mathematical model of the doubly fed asynchronous motor is expressed as: Among them, u sq 、u sd 、i sq 、i sd are the q-axis and d-axis components of the stator voltage and the q-axis and d-axis components of the stator current respectively; u rq 、u rd 、i rq 、i rd are the q-axis and d-axis components of the rotor voltage and the q-axis and d-axis components of the rotor current respectively; R s , R r are stator and rotor resistance respectively; ω s ,ω r are the system synchronous speed and rotor speed respectively; p is the differential operator; ψ sq , sd , rq , rd are the q-axis and d-axis components of the stator flux and the q-axis and d-axis components of the rotor flux respectively; L s , L r are the stator and rotor equivalent self-inductance respectively; L m is the stator-rotor equivalent mutual inductance; Active power P s , stator reactive power Q s , electromagnetic torque T e The calculation formula and the motor motion equation are expressed as: Among them, n p is the number of pole pairs of the doubly-fed asynchronous motor; T L is the load torque; D is the damping coefficient; J is the moment of inertia of the unit.

5. The method for modeling and operating condition conversion of a pumped storage unit according to claim 4 is characterized in that: The back-to-back converter sub-model includes: the grid-side and rotor-side converters adopt grid voltage and stator voltage oriented control strategies respectively; the grid-side converter control system consists of a DC voltage outer loop and a current inner loop; the rotor-side converter control system consists of a speed outer loop and a current inner loop.

6. The method for modeling and operating condition conversion simulation of a pumped storage unit according to claim 5, characterized in that: The speed and guide vane opening optimizer sub-model includes: Determine the optimal speed ω of the unit based on the initial head and active power dispatch value opt and the optimal guide vane opening G opt , expressed as: Among them, H0 is the initial head, P ref is the active power dispatch value.

7. The method for modeling and operating condition conversion of a pumped storage unit according to claim 6 is characterized in that: The water delivery system submodel includes a head loss model and an elastic water hammer model, wherein: The head loss model is expressed as: Among them, H loss is the head loss, f g 、f p 、f t are the friction coefficients of the guide vane, water pipe, and water tunnel, respectively, d is the dynamic flow, G is the guide vane opening, H d is the dynamic head, H s is the static head, G max is the maximum opening of the guide vane; The elastic water hammer model is expressed as: Among them, Q c is the dynamic flow rate at the connection between the water pipeline and the water tunnel, Q d is the dynamic flow of the pump turbine, T et and Z ht are the elastic time constant and hydraulic impedance of the water tunnel, T ep and Z hp are the elastic time constant and hydraulic impedance of the water pipeline, respectively, and s represents the Laplace operator; Among them, the elastic time constant of the water tunnel is T et , elastic time constant T of water pipeline ep The calculation formula of the hyperbolic tangent value of each elastic time constant is: Among them, when the numerator of formula (1) is the length of the water tunnel, the calculation results of formula (1) and formula (2) are the elastic time constant of the water tunnel and the hyperbolic tangent value of the elastic time constant of the water tunnel respectively; when the numerator of formula (1) is the length of the water pipeline, the calculation results of formula (1) and formula (2) are the elastic time constant of the water pipeline and the hyperbolic tangent value of the elastic time constant of the water pipeline respectively.

8. The method for modeling and operating condition conversion simulation of a pumped storage unit according to claim 7, characterized in that: The pump-wheel mechanism submodel is expressed as: Among them, T m is the mechanical torque of the pump turbine, P m is the mechanical power output of the pump turbine; ω r H is the speed of the pump turbine, i.e. the rotor speed; d is the dynamic head; Q d is the dynamic flow of the pump turbine; η is the efficiency.

9. The method for modeling and operating condition conversion of a pumped storage unit according to claim 8, characterized in that: Based on the factory data of the pump-turbine, the pump-turbine operating characteristics are fitted, including the dynamic head H d And efficiency η, expressed as: Among them, a i , b i 、c i are the fitting coefficients of the polynomial, i∈[0,3].

10. The method for modeling and operating condition conversion of a pumped storage unit according to claim 9, characterized in that: The guide vane servo mechanism sub-model includes a main pressure regulating valve, a main servomotor, a guide vane opening regulator, and a guide vane opening control.

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