A split module simulation method of a direct-drive variable-speed pumped storage unit

Abstract

This invention discloses a modular simulation method for a direct-drive variable-speed pumped-storage unit, belonging to the field of hydropower storage technology. A piecewise linearized control block diagram for the direct-drive pumped-storage unit is established. The pump-turbine in the pumped-storage unit operates under two modes: power generation and motoring. Since the simulation analysis methods for power generation and motoring are largely similar, only the power generation mode is used as an example to establish the control block diagram. The value ranges of the PI regulation parameters for the power closed-loop and power multi-state modules are solved. After obtaining the value ranges, the Bode plot analysis method is used to design the power closed-loop regulation parameters. Simulation analysis under the power generation mode is performed based on the designed parameters to verify the effectiveness of the piecewise linear simulation method. The simulation method of this invention combines the simplicity of traditional fixed-parameter PID regulation with the adaptability of novel PID regulation to multiple operating modes in the new energy power grid, effectively suppressing fluctuations in the new energy power grid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydroelectric energy storage, and particularly relates to a split module simulation method of a direct-drive variable-speed pumped storage unit. BACKGROUND

[0002] With the rapid development of new energy generation such as wind power and photovoltaic, the pumped storage system with the ability of peak load shifting and maintaining system power balance has begun to be studied by more and more scholars. Due to the fluctuation characteristics of the new energy power grid, in the pumped storage system, the direct-drive variable-speed pumped storage unit can quickly adjust the active and reactive power by adjusting the speed, effectively suppressing the fluctuation of the new energy power grid and improving the stability of the power system.

[0003] Many scholars have studied the simulation control method of the variable-speed pumped storage unit. In the prior art document [1] Zuo Y, Chang L, Ding T, et al. Study on Adaptive Nonlinear Control of Reversible Unit [C]. 27th Chinese Control and Decision Conference, Qingdao: IEEE, 2015: 1747-1752, a series of nonlinear descriptions of the pump-turbine are first established, then a linearized nonlinear model of all unknown parameters is built, and finally the adaptive law of the model is studied. Through simulation, it is proved that the control strategy can stabilize the unit under multiple different working conditions; in the prior art document [2] Hu Jianjun, Chang Li, Ding Tan, et al. Robust Control Strategy Research of Reversible Unit [J]. Water Energy Science, 2016, 34(11): 142-147, a sliding mode robust control method with strong adaptability and convenient application is proposed on the premise that the speed regulation parameters of the unit are uncertain; in the prior art document [3] Huang Wentao, Chang Li, Ding Tan, et al. Research on Accurate Linearization Control of Reversible Unit Based on Nonlinear Model [J]. Large Motor Technology, 2015(02): 34-41, the calculus geometry theory is also applied to the typical working condition conversion process of the pumped storage unit, and the purpose is to study the accurate linearization control strategy. This research result makes the performance of the reversible unit excellent, especially the dynamic performance.

[0004] However, the above technologies have some problems. Although the new PID simulation control method combining various advanced algorithms can have certain working condition adaptive ability, the complexity of its operation principle and mechanism makes it difficult for actual operators to debug and master when it is applied to actual units in the future. SUMMARY

[0005] The application aims to provide a segmented module simulation method for a direct-drive variable-speed pumped storage unit, characterized in that it comprises the following steps:

[0006] First, a segmented linearization control block diagram of the direct-drive pumped storage unit is established; the pump-turbine in the pumped storage unit has two operating conditions of power generation and motoring; since the simulation analysis methods for the power generation condition and the motoring condition are similar, only the power generation condition is taken as an example to establish the control block diagram;

[0007] Second, the control block diagram is decomposed, and the power closed loop is analyzed to obtain a decomposed control structure diagram;

[0008] Third, the parameter space graphic method is used to solve the value range of the PI regulation parameters of the power multi-state module, after the value range is obtained, the transfer function bode diagram analysis method is used to design the power closed loop regulation parameters;

[0009] Fourth, the control block diagram is decomposed, and the speed closed loop is analyzed to obtain a decomposed control structure diagram;

[0010] Fifth, the parameter space graphic method is used to solve the value range of the PI regulation parameters of the speed multi-state module, after the value range is obtained, the zero-pole diagram analysis method is used to design the speed closed loop regulation parameters;

[0011] Sixth, the designed parameters are used for simulation analysis under the power generation condition to verify the effectiveness of the segmented linear simulation method of the direct-drive variable-speed pumped storage unit.

[0012] In the second step, the control block diagram is decomposed, and the power closed loop is analyzed, and the parameter space graphic method is used to solve the value range of the regulation parameters in the power closed loop multi-state module, and the specific principle of the method is as follows:

[0013] If the power closed loop polynomial of the system to be solved is:

[0014] Δ(s)=sD(s)+N(s)(k i +k p s)e -Ls (1)

[0015] Wherein, D(s) is the denominator of the open-loop transfer function of the system, N(s) is the numerator of the open-loop transfer function of the system, e -Ls is the time delay factor, if there is no time delay factor here, L=0; k i and k p are the parameters to be solved; let s=jω in the above formula (1), and obtain:

[0016] Δ(jω)=jωD(jω)+N(jω)(k i +jk p ω) (2)

[0017] in,

[0018] N(jω)=N r (ω)+jN i (ω) (3)

[0019] D(jω)=D r (ω)+jD i (ω) (4)

[0020] By decomposing Δ(jω) into real and imaginary parts using equations (3) and (4) above, we have:

[0021] Δ r (ω)=-ωD i (ω)+k i N r (ω)-k p ωN i (ω) (5)

[0022] Δ i (ω)=ωD r (ω)+k i N r (ω)+k p ωN r (ω) (6).

[0023] The fourth step involves analyzing the speed closed-loop. In the speed control section, the current guide vane opening information of the pump turbine is transmitted to different PI controllers through state selection. The parameters of each PI controller are also different, corresponding to the optimal parameters under different guide vane openings. That is, no matter how the pump turbine module changes, the speed closed-loop PI controller can maintain a good regulation effect.

[0024] The beneficial effect of this invention is that simulation results demonstrate that the simulation method proposed in this invention has both the simplicity of traditional fixed-parameter PID control and the adaptability of new energy power grids to multiple operating conditions of the new PID control, thus achieving effective suppression of fluctuations in the new energy power grid. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a direct-drive variable-speed pumped storage unit.

[0026] Figure 2 This is a schematic diagram of the modular control of a direct-drive variable-speed pumped storage unit under power generation conditions; where a is a functional diagram and b is a specific control block diagram.

[0027] Figure 3 Power closed loop structure diagram for direct drive variable speed pumped storage unit in power generation condition;

[0028] Figure 4 PI stable domain of power closed loop for direct drive variable speed pumped storage unit in power generation condition;

[0029] Figure 5 Speed closed loop structure diagram for direct drive variable speed pumped storage unit in power generation condition;

[0030] Figure 6 PI stable domain of speed closed loop for direct drive variable speed pumped storage unit in different guide vane opening;

[0031] Figure 7 Set composite power fluctuation signal diagram;

[0032] Figure 8 No switching power output diagram of multi-state module II inside of direct drive variable speed pumped storage unit;

[0033] Figure 9 No switching speed fluctuation diagram of multi-state module II inside of direct drive variable speed pumped storage unit. DETAILED DESCRIPTION

[0034] The application provides a simulation method of a direct drive variable speed pumped storage unit, comprising the following steps:

[0035] Firstly, a segmented linearization control block diagram of the direct drive pumped storage unit is established; the water pump turbine in the pumped storage unit has two operation conditions of power generation and motoring; since the simulation analysis methods of the power generation condition and the motoring condition are similar, only the control block diagram of the power generation condition is established;

[0036] Secondly, the control block diagram is decomposed, and the power closed loop is analyzed to obtain a decomposed control structure diagram;

[0037] Thirdly, the parameter space graphic method is used to solve the value range of the PI regulation parameters of the power multi-state module; after the value range is obtained, the transfer function bode diagram analysis method is used to design the power closed loop regulation parameters;

[0038] Fourthly, the control block diagram is decomposed, and the speed closed loop is analyzed to obtain a decomposed control structure diagram;

[0039] Fifthly, the parameter space graphic method is used to solve the value range of the PI regulation parameters of the speed multi-state module; after the value range is obtained, the zero pole diagram analysis method is used to design the speed closed loop regulation parameters;

[0040] The sixth step is to carry out simulation analysis under the power generation condition according to the designed parameters, and verify the effectiveness of the segmented linear simulation method of the direct-drive variable-speed pumped storage unit. The method proposed in the application will be further described below with reference to the drawings.

[0041] Figure 1 As shown in the direct-drive variable-speed pumped storage unit structure schematic diagram. In Figure 1 , the pump-turbine and the direct-drive electric machine form the main body of the pumped storage unit; the MSC and the GSC are the machine-side converter and the grid-side converter, respectively, the power winding of the synchronous electric machine is connected with the machine-side converter, the grid-side converter is connected with the power grid, and the machine-side converter is connected with the grid-side converter through the DC link. The synchronous electric machine and the machine-side converter control system realize the control of the unit speed, the pump-turbine control system realizes the control of the unit output active and reactive power, and the grid-side converter realizes the control of the DC bus voltage and the unit power factor grid connection.

[0042] Figure 2 As shown in the direct-drive variable-speed pumped storage unit power generation condition sub-module schematic diagram, wherein, a functional schematic diagram, b specific control block diagram; in Figure 2 , in the power control part, the new energy power grid power shortage signal instruction is decomposed into power signals of different frequencies through Fourier decomposition, and is adjusted through sub-module control. The sub-module control is controlled by different power modules, and the PI regulator parameters of each module are different, corresponding to different frequency input signals, and the difference in parameters makes them have good output effect on power signals of different frequencies. Looking at the speed control part, the current guide vane opening information of the pump-turbine is transmitted to different PI regulators through state selection, and the parameters of each PI regulator are also different, corresponding to the optimal parameters under different guide vane openings. That is, no matter how the pump-turbine module changes, the speed closed-loop PI regulator can maintain good regulation effect.

[0043] Figure 3 As shown in the power closed-loop structure diagram of the direct-drive variable-speed pumped storage unit under the power generation condition. Wherein, P ref is the active power reference value; P s is the active power output by the unit; FDM is the Fourier decomposition module; i qref is the reference value of the q-axis current; i q is the actual value of the q-axis current; K PWM is the proportional coefficient of the PWM link, K PWM is related to the PWM link itself, T s is its time constant; V qs is the voltage amplitude of the motor stator side. First, the parameter space diagram method is used to obtain the value range of the regulation parameters in the power closed-loop multi-state module I, and the specific principle of this method is as follows:

[0044] If the sought system power closed-loop quasi-characteristic polynomial is:

[0045] Δ(s) = sD(s) + N(s)(k i +k p s)e -Ls (1)

[0046] where D(s) is the denominator of the system open-loop transfer function, N(s) is the numerator of the system open-loop transfer function, e -Ls is the time delay factor (there is no time delay factor here, and L can be taken as 0), k i and k p are the sought parameters.

[0047] Let s = jω in the above formula, and the following is obtained:

[0048] Δ(jω) = jωD(jω) + N(jω)(k i +jk p ω) (2)

[0049] where,

[0050] N(jω) = N r (ω) + jN i (ω) (3)

[0051] D(jω) = D r (ω) + jD i (ω) (4)

[0052] Δ(jω) is decomposed into real and imaginary parts through the above two formulas, and the following is obtained:

[0053] Δ r (ω) = -ωD i (ω) + k i N r (ω) - k p ωN i (ω) (5)

[0054] Δ i (ω) = ωD r (ω) + k i N r (ω) + k p ωN r (ω) (6)

[0055] It can be seen from formula (5) and formula (6) that the sizes of Δ r (ω) and Δ i (ω) are related to k p , k iand ω three parameters closely related to the value, can be written as:

[0056] Δ r = Δ r (k p , k i , ω) (7)

[0057] Δ i = Δ i (k p , k i , ω) (8)

[0058] Based on the above formula, using the parameter space diagram method, the specific method of studying the stability of closed-loop quasi-characteristic polynomial on the parameter plane (k p , k i ) is as follows:

[0059] Let the parameters (k p 0 , k i 0 , ω) make the closed-loop system have a root on the imaginary axis, that is:

[0060]

[0061]

[0062] Then by the implicit function theorem, because the Jacobi matrix at this time is:

[0063]

[0064] Since J is a nonsingular matrix, then from formula (9), (10) we can solve the locally unique continuous curve [k p (0), k i (0)] (ignore the superscript 0):

[0065]

[0066]

[0067] When ω = 0, corresponding to the starting point of the reference curve:

[0068]

[0069] The transfer function of the power closed loop of the double-fed unit is changed to the corresponding form as follows:

[0070]

[0071] At this time, the critical stability parameter curve for ω>0 can be plotted on the parameter plane (k p , k i ) by the first two equations in equation (15), and the third equation in equation (15) determines the starting point for ω=0. According to the determinant of the Jacobi matrix being less than zero, it can be determined that the right side of the parameter curve is the stability domain to be solved.

[0072] In Figure 3 , the power open-loop transfer function of the direct-drive variable-speed pumped storage system can be obtained as:

[0073]

[0074] wherein,

[0075]

[0076] The power open-loop transfer function of the full-power variable-speed pumped storage unit is:

[0077]

[0078]

[0079] The calculation result is:

[0080]

[0081] The critical stability curve equation of the power closed loop in the full-power power generation working condition is as follows:

[0082]

[0083] At this time, the critical stability parameter curve for ω>0 can be plotted on the parameter plane (k p , k i ) by equation (21), and the starting point of the curve is determined by equation (22):

[0084] [k p (0), k i (0)] = (-0.00107, 0) (22)

[0085] And according to the determinant of the Jacobi matrix being less than zero at this time, it can be determined that the right side of the parameter curve in Figure 4 is the stability domain to be solved.

[0086] Then the power closed loop adjustment parameter design is carried out. The control of the pumped storage unit in the application is oriented to the new energy power grid. According to the relevant literature, the main output fluctuation frequency intervals of wind power and photovoltaic have no overlapping area, so it is necessary to analyze and control the two frequency interval segments respectively. By observing the frequency spectrum, 0.01, 0.5 and 1 Hz are selected as the characteristic frequency values. Next, the corresponding appropriate PI parameters are designed for the input frequencies f i = 0.01 Hz, 0.5 Hz and 1 Hz respectively:

[0087] The method adopted is to analyze the bode diagram of the whole power closed loop by taking different PI parameters, and summarize the design rules of the PI parameters. According to the relevant simulation, by observing the power closed loop bode cluster when k p and k i parameters are different, the sensitivity of the bode cluster to k p and k i is comprehensively considered, and the reference for setting the parameters of the double-fed machine is considered. Finally, in the principle of making the output characteristics of the power closed loop as excellent as possible for different frequency input signals, the PI module parameters in the multi-state module of the closed loop are selected as shown in the following table 1.

[0088] Table 1 Parameter values of the power closed loop multi-state module

[0089]

[0090] Figure 4 The PI stability domain of the power closed loop of the direct-driven variable-speed pumped storage unit under the power generation condition is shown. The right side of the parameter curve is the stability domain to be solved.

[0091] Figure 5 The speed closed loop structure diagram of the direct-driven variable-speed pumped storage unit under the power generation condition is shown. w ref is the speed reference value; w r is the unit speed; SSM is the state selection module; P base is the power reference value; T w is the water flow inertia coefficient of the pump-turbine; T e is the electromagnetic torque; T m is the mechanical torque; y is the guide vane opening of the pump-turbine; and J is the rotational inertia of the double-fed machine. Similarly, the speed closed loop of the direct-driven variable-speed pumped storage unit also needs to add a multi-state module to have good output characteristics under different guide vane openings. At this time, the open loop transfer function of the speed closed loop is:

[0092]

[0093] Let it also be defined according to the parameter space graph method:

[0094]

[0095] Let s = jω in the above two equations, then we get:

[0096]

[0097] Further, we obtain equations A(ω) and B(ω) as follows:

[0098]

[0099] The critical stability curve equation for the closed-loop rotational speed is then obtained as follows:

[0100]

[0101] In the above formula, N(ω) is as follows:

[0102] |N(ω)| 2 =9.828225×10 16 ×f 2 (y)×ω 2 +3.93129×10 17 (28)

[0103] Using equations (27) and (28), the stability region of the PI parameter of the direct-drive variable-speed pumped storage unit under different guide vane openings is plotted as follows: Figure 6 As shown.

[0104] Then, the design of the speed closed-loop control parameters is carried out. Since the speed closed-loop output requirement focuses on whether the speed operates within the allowable range and does not need to consider the frequency of speed command changes, selecting parameters by analyzing the Bode plot of the speed closed-loop is not intuitive. This invention chooses to analyze the zero-pole plot of the speed closed-loop transfer function to determine the PI value for different guide vane openings. Here, we consider summarizing the pattern by analyzing the change graph of the speed closed-loop zeros and poles with the PI parameter under a representative guide vane opening, and then using this pattern to select the optimal parameters for each guide vane opening. Then... Figure 6 As can be seen, when the guide vane opening y = 0.05, its parameter stability region is the largest and includes the parameter stability regions under other guide vane openings, so it is chosen as the representative. Simulations were conducted to observe different k... i Parameters and k p The zero-pole diagram of the closed loop at the rotational speed was used to obtain the PI parameters under different guide vane openings, as shown in Table 2.

[0105] Table 2 Parameter values ​​for the speed closed-loop multi-state module

[0106]

[0107] Figure 7The figure shows the set composite power fluctuation signal. Fluctuation signal P flu The duration is still 10s, consisting of 0.01Hz signal with amplitude 35MW, 0.5Hz signal with amplitude 5MW and 1Hz signal with amplitude 1MW.

[0108] Figure 8 The figure shows the internal no-switching power output figure of the multi-state module II of the direct-drive variable-speed pumped storage unit. In the figure, a full-power variable pumped storage unit operating in a steady state outputting 85% rated power is given a fluctuation signal P Figure 8 as shown in the figure. Figure 7 The figure shows the fluctuation signal P flu When it receives the input signal at 400s, the output power of the pumped storage unit can effectively suppress the power fluctuation of the new energy power grid.

[0109] Figure 9 The figure shows the internal no-switching speed fluctuation figure of the multi-state module II of the direct-drive variable-speed pumped storage unit. In the figure, a full-power variable pumped storage unit operating in a steady state outputting 85% rated power is given a fluctuation signal P Figure 9 as shown in the figure. Figure 7 The figure shows the fluctuation signal P flu When it receives the input signal at 400s, the speed then starts to approach the command value under the action of the speed closed loop, and the unit is stabilized at 20 revolutions / minute after about 30 seconds, which can effectively suppress the power fluctuation of the new energy power grid.

Claims

1. A method for simulating sub-modules of a direct drive variable speed pumped storage unit, the method comprising: receiving a plurality of inputs; determining a plurality of outputs based on the plurality of inputs; and outputting the plurality of outputs. Comprise the following steps: First, first establish direct drive pumped storage unit piecewise linearization control block diagram; Pump turbine in pumped storage unit exists two kinds of operation conditions of power generation and motor: Because the simulation analysis method of power generation condition and motor condition is similar, therefore only take power generation condition as an example to establish control block diagram; Second, the control block diagram is decomposed and the power closed loop is analyzed, and the decomposed control structure diagram is obtained; The second step, the control block diagram is decomposed, and the power closed loop is analyzed, the value range of the adjusting parameter in the power closed loop multi-state module is solved by parameter space graphic method, and the specific principle of the method is as follows: If the power closed loop polynomial of the system to be solved is: Δ(s) = sD(s) + N(s)(k i +k p s)e -Ls (1) Where D(s) is the denominator of the open-loop transfer function of the system, N(s) is the numerator of the open-loop transfer function of the system, e -Ls is the time delay factor, if there is no time delay factor here, L=0 can be taken; k i and k p is the parameter to be solved; let s=jω in the above formula (1), and get: Δ(jω) = jωD(jω) + N(jω) (k i + jk p ω) (2) Wherein, N(jω) = N r (ω) + jN i (ω) (3) D(jco) = D r (ω) + jD i (ω) (4) By the above formula (3), formula (4) is decomposed into real part and imaginary part, and formula (5) is obtained: Δ r (ω) = -ωD i (ω) + k i N r (ω) - k p ωN i (ω) (5) Δ i (ω) = ωD r (ω) + k i N r (ω) + k p ωN r (ω) (6) Third, the value range of the PI adjusting parameter of the power multi-state module is solved by parameter space graphic method, after the value range is obtained, the power closed loop adjusting parameter is designed by using transfer function bode diagram analysis method; Fourth, the control block diagram is decomposed and the speed closed loop is analyzed, and the decomposed control structure diagram is obtained; Fifth, the value range of the PI adjusting parameter of the speed multi-state module is solved by parameter space graphic method, after the value range is obtained, the speed closed loop adjusting parameter is designed by using zero pole diagram analysis method; Sixth, according to the designed parameters, the simulation analysis under power generation condition is carried out, and the effectiveness of the piecewise linear simulation method of direct drive variable speed pumped storage unit is verified.

2. The method of claim 1, wherein the method is a sub-module simulation method of a direct drive variable speed pumped storage unit. The fourth step is to analyze the speed closed loop, and in the speed control part, the guide vane opening information of the pump turbine is transmitted to different PI regulators through state selection, and the parameters of each PI regulator are also different, which correspond to the optimal parameters under different guide vane openings respectively;That is, no matter how the pump turbine module changes, the speed closed loop PI regulator can maintain good adjusting effect.

Images