A grid-connected simulation model of an electrochemical energy storage power station and a construction method thereof

Abstract

The present invention discloses a grid-connected simulation model of an electrochemical energy storage power station and a construction method thereof, which relates to the technical field of power systems. It comprises: a primary system and a control system; the input end of the primary system is connected to the output end of the control system through a real-complex interface, and the output end of the primary system is connected to the input end of the control system through a complex-real interface. The output signal of the electrochemical energy storage power station is processed by a multi-scale voltage source converter and an LC filter in sequence, and the processed signal is input into the control system through a complex-real interface for signal demodulation to obtain an analytical modulation signal, and the analytical modulation signal is fed back to the primary system as a feedback input of the multi-scale voltage source converter to complete the grid-connected simulation of the electrochemical energy storage power station. The present invention can adapt to the complex and changeable environment of transient processes and improve the simulation efficiency and accuracy of the grid-connected simulation model.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a grid-connected simulation model of an electrochemical energy storage power station and a construction method thereof. Background Art

[0002] Electrochemical energy storage power stations play an important role in energy storage and regulation. By conducting research on the grid-connected simulation model of electrochemical energy storage power stations, the performance of electrochemical energy storage power stations can be evaluated, their planning and control strategies can be optimized, and their impact on power balance, voltage stability, frequency response, etc. of the power system can also be evaluated. In the research on the grid-connected model, accurate and efficient transient simulation is an important supporting technology required for the operation and control of large AC / DC interconnected power grids.

[0003] At present, in order to simulate the electromagnetic transients that may occur in the system, the electromagnetic transient simulation program EMTP based on the DOMMEL algorithm is usually used for simulation to process the transient signals in the system to track the natural waveforms of voltage and current. The main process is: according to the actual power system topology, equipment parameters, line parameters and other information, use simulation software to build a power system model. After setting the model parameters, simulation calculations are performed to simulate the impact of various fault types and parameter changes in the power system on the system. The simulation results are analyzed in depth to understand the operating status of the system and the performance of each device during the electromagnetic transient process.

[0004] The defects of the above-mentioned prior art are: with the continuous increase in the proportion of power electronic switching devices, the transient processes of different frequencies in the grid-connected system of the entire electrochemical energy storage power station are complex and changeable, resulting in limitations in the process of establishing a grid-connected simulation model using the existing electromagnetic transient simulation method, and the simulation efficiency and accuracy of the grid-connected simulation model are very low. Summary of the invention

[0005] Based on this, it is necessary to provide a grid-connected simulation model of an electrochemical energy storage power station and a construction method thereof in response to the above technical problems.

[0006] The embodiment of the present invention provides a grid-connected simulation model of an electrochemical energy storage power station, comprising: a primary system and a control system; the input end of the primary system is connected to the output end of the control system via a real-complex interface, and the output end of the primary system is connected to the input end of the control system via a complex-real interface;

[0007] The primary system comprises: an electrochemical energy storage power station, a multi-scale voltage source converter and an LC filter;

[0008] The output end of the electrochemical energy storage power station is connected to the DC input end of the multi-scale voltage source converter, the output end of the multi-scale voltage source converter is connected to the input end of the LC filter and the first input end of the complex-real interface, the ground voltage output end of the LC filter is connected to the second input end of the complex-real interface, and the current output end of the LC filter is connected to the third input end of the complex-real interface;

[0009] The output end of the complex-real interface is connected to the input end of the control system, and the output end of the control system is connected to the input end of the real-complex interface;

[0010] The output end of the real-complex interface is connected to the modulation signal input end of the multi-scale voltage source converter;

[0011] Among them, the output signal of the electrochemical energy storage power station is processed by the multi-scale voltage source converter and the LC filter in sequence, and the processed signal is input into the control system for signal demodulation to obtain an analytical modulation signal, and the analytical modulation signal is fed back to the primary system as a feedback input of the multi-scale voltage source converter to complete the grid-connected simulation of the electrochemical energy storage power station.

[0012] In addition, the electrochemical energy storage power station includes: a controlled voltage source, an internal resistor R and a power supply v batt The positive electrode of the controlled voltage source is connected to one end of the internal resistance R, and the negative electrode of the controlled voltage source is connected to the power supply v batt The negative pole of the power supply v batt The positive electrode is connected to the other end of the internal resistor R.

[0013] In addition, the multi-scale voltage source converter is specifically used for:

[0014] The signal will be parsed m abc (t) is used as the input of the multi-scale voltage source converter, which consists of an average value model and a switch function model. When the switch is connected to A, the modulated signal m A,abc (t) is set to be the same as the control signal m abc (t) equal;

[0015] m A,abc (t)= m abc (t)

[0016] The control signal obtained m A,abc (t) is used to calculate the AC terminal voltage of the multi-scale voltage source converter u out,abc(t);

[0017] u out,abc (t) = 0.5v dc m A,abc (t)

[0018] Among them, v dc is the DC link voltage, which is equal to the DC voltage output by the electrochemical energy storage power station model:

[0019] v dc =v batt

[0020] In the operation mode, an averaged multi-scale voltage source converter model is selected to track the envelope waveforms of the AC voltage and current;

[0021] When the switch is connected to SW, the modulated signal m abc (t) is taken as the real part and then sent to the pulse width modulation (PWM) generator model. The output of the PWM generator model is the switching pulse q sw,abc ;

[0022] The switching pulse q sw,abc Process and calculate the control signal m sw,abc , m sw,abc The calculation is expressed as:

[0023] m sw,abc (t) = 2q sw,abc -1

[0024] The real control signal m is obtained sw,abc (t) Reconstruct the complex analytical signal to obtain the complex control signal m sw,abc (t), used to calculate the AC terminal voltage of the multi-scale voltage source converter u out,abc (t):

[0025] u out,abc (t) = 0.5v dc m sw,abc (t)

[0026] According to the AC terminal voltage u out,abc (t) Multi-scale voltage source converter model for selecting switching function.

[0027] In addition, the primary system further includes a PCC node and a power grid, the output end of the LC filter is connected to one end of the PCC node, and the other end of the PCC node is connected to the power grid.

[0028] In addition, the control system includes: a measurement processing module, a dq0 conversion module, a power calculation module, a power controller, a current controller and a dq0 inverse conversion module;

[0029] The input end of the dq0 conversion module is connected to the output end of the complex-real interface, and the output end of the dq0 conversion module is respectively connected to the input end of the power calculation module and the input end of the current controller;

[0030] The output end of the power calculation module is connected to the first input end of the power controller, the output end of the power controller is connected to the input end of the current controller, the output end of the current controller is connected to the input end of the dq0 inverse transformation module, and the output end of the dq0 inverse transformation module is connected to the input end of the real-complex interface;

[0031] The second input terminal of the power controller is connected to the power calculation module.

[0032] In addition, the output of the power controller is the reference current value of the converter and What you get and It is the input of the current inner loop controller;

[0033] The output of the current controller is expressed as a voltage signal in the dq0 coordinate system. Indicates that the signal is divided by 0.5 times the output DC voltage of the energy storage battery to obtain the modulation voltage signal m dq0 (t); then use the dq0 inverse transform to convert the signal m dq0 (t) is transformed into a real signal m in the three-phase coordinate system abc (t), and finally the three-phase modulation signal of the multi-scale voltage source converter is obtained through the real-complex interface m abc (t).

[0034] In addition, the complex-real interface is specifically used for:

[0035] Energy storage measured signal u abc (t), i abc (t) and i g,abc (t) is the analytical signal;

[0036] Current analysis signal of the output of multi-scale voltage source converteri abc Make a prediction and get the prediction signal i pre,abc for:

[0037] i pre,abc (k)=(1+ξ)e jωτ(k) i abc (k-1)-ξe jω[τ(k)+τ(k-1)] i abc (k-2)

[0038] Among them, ω is the angular frequency set during prediction, τ is the time step, k represents the kth discrete simulation point; ξ represents the ratio of the current time step to the previous time step;

[0039] The prediction signal i pre,abc , i g,abc (t) and u abc (t) The three signals, ignoring their real parts, are converted into real output signals.

[0040] In addition, the real-complex interface is specifically used for:

[0041] Using the obtained voltage control signal m dq0 (t) Construct the analytical modulation voltage signal in the dq0 coordinate system m dq0 (t):

[0042] m dq0 (t) = (I + jT) m dq0 (t)

[0043] Analytical modulation voltage signal in dq0 coordinate system m dq0 The real part Re[ m dq0 (t)] and the imaginary part Im[ m dq0 (t)] is:

[0044] Im[ m dq0 (t)] = TRe[ m dq0 (t)]

[0045] Applying the inverse dq0 transform on both sides yields:

[0046] Im[ m abc(t)]=QRe[ m abc (t)]

[0047] Construct the analytical modulation signal m in the abc three-phase coordinate system abc (t):

[0048] m abc (t) = (I + jQ) m abc (t)

[0049] Among them, m abc (t) is the real modulated signal in the three-phase coordinate system, I is the unit matrix,

[0050] In addition, a method for constructing a grid-connected simulation model of an electrochemical energy storage power station includes:

[0051] The three-phase electrical instantaneous real number signal output by the electrochemical energy storage power station is obtained, and the three-phase electrical instantaneous real number signal is subjected to Hilbert transformation to obtain the complex analytical signal corresponding to the three-phase electrical instantaneous real number signal; the frequency of the complex analytical signal is subjected to frequency shift operation to obtain a complex envelope, and then the complex envelope is processed by a trapezoidal integration method to obtain a multi-scale voltage source converter;

[0052] A complex analytical signal is introduced into the multi-scale voltage source converter to obtain a multi-scale voltage source converter based on the complex analytical signal; and according to the connection relationship of the topological diagram, the electrochemical energy storage power station is connected with the multi-scale voltage source converter based on the complex analytical signal and the LC filter model to obtain a primary system;

[0053] The signal prediction method is introduced to establish a complex-real interface; based on the transformation relationship between the dq0 coordinate system and the abc three-phase coordinate system and the relationship between the real part and the imaginary part of the signal, a real-complex interface is established;

[0054] The complex analytical signal is converted into a three-phase real signal through the complex-real interface, and then a power and current double closed-loop control system is established by decoupling through dq0 transformation;

[0055] The output signal of the primary system is input into the control system through the complex-real interface for signal demodulation to obtain an analytical modulation signal; the analytical modulation signal is fed back to the primary system through the real-complex interface to represent the feedback input of the multi-scale voltage source converter to realize the grid-connected simulation of the electrochemical energy storage power station and obtain a grid-connected simulation model of the electrochemical energy storage power station.

[0056] Compared with the prior art, the grid-connected simulation model of the electrochemical energy storage power station and the construction method thereof provided by the embodiment of the present invention have the following beneficial effects:

[0057] With the continuous increase in the proportion of power electronic switching devices, the transient processes of different frequencies in the grid-connected system of the entire electrochemical energy storage power station are complex and changeable, resulting in the existing electromagnetic transient simulation method having great limitations in the process of establishing a grid-connected simulation model. The present invention processes the output signal of the electrochemical energy storage power station through a multi-scale voltage source converter and an LC filter in sequence, so that the output signal of the electrochemical energy storage power station remains stable when electromagnetic transients occur; the processed signal is input into the control system through the complex-real interface for signal demodulation, so that the analytical modulation signal adapts to the complex and changeable environment of the transient process, and improves the simulation efficiency and accuracy of the grid-connected simulation model. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A model diagram of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0059] Figure 2 An energy storage battery equivalent circuit diagram of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0060] Figure 3 A frequency shift operation diagram of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0061] Figure 4 A diagram of a multi-scale voltage source converter of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0062] Figure 5 A controller model diagram of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0063] Figure 6 A simulation result diagram comparing the proposed prediction method and two other prediction methods for a grid-connected simulation model of an electrochemical energy storage power station provided in an embodiment;

[0064] Figure 7 A simulation result diagram of the a-phase AC current at the grid-connected point of an EMTP model of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0065] Figure 8 A simulation result diagram of phase a AC current at a grid-connected point of a multi-scale model of a grid-connected simulation model of an electrochemical energy storage power station provided in one embodiment;

[0066] Fig. 9 A diagram showing simulation results of the output active power of a grid-connected simulation model of an electrochemical energy storage power station provided in an embodiment. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0068] In one embodiment, a grid-connected simulation model of an electrochemical energy storage power station is provided. The model consists of two parts: a primary system and a control system. Its specific structure is as follows: Figure 1 shown.

[0069] The primary system includes an electrochemical energy storage power station, a multi-scale voltage source converter, an LC filter, a PCC node and a power grid.

[0070] The output end of the electrochemical energy storage power station is connected to the DC input end of the multi-scale voltage source converter, the output end of the multi-scale voltage source converter is connected to the input end of the LC filter and the first input end of the complex-real interface, the ground voltage output end of the LC filter is connected to the second input end of the complex-real interface, and the current output end of the LC filter is connected to the third input end of the complex-real interface.

[0071] The output end of the complex-real interface is connected to the input end of the control system, the output end of the control system is connected to the input end of the real-complex interface, and the output end of the real-complex interface is connected to the modulation signal input end of the multi-scale voltage source converter.

[0072] The electrochemical energy storage power station includes: a controlled voltage source, an internal resistance R, a power supply v batt The positive electrode of the controlled voltage source is connected to one end of the internal resistor R, and the negative electrode of the controlled voltage source is connected to the power supply v batt The negative pole of the power supply v batt The positive electrode is connected to the other end of the internal resistor R. The output end of the electrochemical energy storage power station is connected to the DC input end of the multi-scale voltage source converter, the output end of the multi-scale voltage source converter is respectively connected to the input end of the LC filter and the first input end of the complex-real interface, the current output end of the LC filter is connected to the third input end of the complex-real interface, and the second input end of the complex-real interface is connected to the ground voltage output end of the LC filter. The output end of the LC filter is connected to one end of the PCC node, and the other end of the PCC node is connected to the power grid.

[0073] The control system consists of a measurement and processing module, a dq0 conversion module, a power calculation module, a power controller, a current controller and a dq0 inverse conversion module. The input end of the dq0 conversion module is connected to the output end of the complex-real interface, and the output end of the dq0 conversion module is respectively connected to the input end of the power calculation module and the input end of the current controller. The output end of the power calculation module is connected to the first input end of the power controller, the output end of the power controller is connected to the input end of the current controller, the output end of the current controller is connected to the input end of the dq0 inverse conversion module, the output end of the dq0 inverse conversion module is connected to the input end of the real-complex interface, and the second input end of the power controller is connected to the power calculation module. Its function is to control the current power in the network. The three-phase AC voltage and current signals of the primary system are calculated by constructing analytical signals according to the Hilbert transform, and the control system uses real signals in the dq coordinate system. For this reason, an interface between the primary system and the control system is designed.

[0074] The output signal of the electrochemical energy storage power station is processed in turn by the multi-scale voltage source converter and the LC filter, and the processed signal is input into the control system for signal demodulation to obtain an analytical modulation signal, which is fed back to the primary system as a feedback input of the multi-scale voltage source converter to complete the grid-connected simulation of the electrochemical energy storage power station.

[0075] In this model, the DC voltage v dc The equivalent output voltage of the external circuit of the electrochemical energy storage power station is used as the DC voltage input of the multi-scale voltage source converter. The multi-scale voltage source converter is connected to the PCC through an LC filter. The LC filter includes an inductor with an inductance value of L and a capacitor with a capacitance value of C. The implementation of the LC filter is to reduce the undesirable harmonics in the output voltage. The external input voltage complex signal i abc (t) i g,abc (t) and u abc (t) is the input of the complex-real interface, which converts the complex signal i abc (t) i g,abc (t) and u abc (t) is converted into a real signal u abc (t),i abc (t) and i g,abc (t). Then, the obtained real signal is used as the input of the control system, and the output of the control system is the modulation signal m abc (t). The real-complex interface will abc (t) is converted into an analytical modulation signal mabc (t), analyzing the modulated signal m abc (t) is the input signal of the multi-scale voltage source converter.

[0076] The construction of a multi-scale model for the grid-connected electrochemical energy storage power station based on frequency shift theory will be introduced in detail below.

[0077] 1. Electrochemical energy storage power station unit model

[0078] As an energy storage battery, electrochemical cells are an important part of energy storage power stations. Their models can generally be divided into three types: experimental model, electrochemical model and equivalent circuit model. The present invention adopts a universal equivalent circuit model, which consists of a controlled voltage source and a constant internal resistance in series, such as Figure 2 shown.

[0079] The model has the following assumptions:

[0080] 1) The internal resistance of the battery remains constant during the charging and discharging process;

[0081] 2) The model parameters of the battery are obtained through the discharge characteristic curve and are fully applicable to the charging characteristics;

[0082] 3) The battery capacity remains unchanged;

[0083] 4) Temperature has no effect on the battery model;

[0084] 5) The self-discharge and memory characteristics of the battery are not considered.

[0085] The expression of the controlled source E is:

[0086]

[0087] Where: E is the no-load voltage of the energy storage battery; E0 is the constant voltage of the battery; K is the polarization overvoltage; Q full is the capacity of the battery; i is the operating current of the battery; A is the amplitude of the exponential region of the discharge characteristic curve; B is the reciprocal value of the time constant in the exponential region.

[0088] The parameter calculation formula is:

[0089]

[0090] The internal resistance R of the energy storage battery can be approximately estimated by the discharge efficiency:

[0091]

[0092] Usually I nom It is known that the efficiency η is generally around 0.995, from which the internal resistance R can be estimated.

[0093] The terminal voltage of the energy storage battery can be expressed as:

[0094] V batt =E-Ri(4)

[0095] Therefore, we can get Figure 1 The DC voltage v shown in the system dc as follows:

[0096] v dc =v batt (5)

[0097] In addition, the state of charge SOC of the energy storage battery can be expressed as:

[0098]

[0099] Where N s and N p are the number of energy storage batteries in series and in parallel respectively.

[0100] 2. Frequency shift theory

[0101] In the electromagnetic transient simulation of power systems, electrical signals (such as voltage and current) are represented by real signals. Due to the existence of the system carrier frequency, the spectrum of the actual signal s(t) is usually concentrated around the base frequency of 50Hz or 60Hz. By adding an orthogonal component as the imaginary part to the real signal through Hilbert transform, the analytical signal is obtained as follows:

[0102] s (t)=s(t)+jH[[s(t)] (7)

[0103] Where s(t) is the original real signal; H is the Hilbert transform; the underline represents that the signal is an analytical signal. The Fourier spectrum of the original real signal in the system is a double-sided spectrum, such as Figure 3 Shown on the left.

[0104] The effect of constructing an analytical signal is as follows Figure 3 As shown in the figure, the spectrum of the original real signal s(t) contains both positive and negative frequency components, while the constructed analytical signal s (t) contains only positive frequency components. Therefore, the analytical signal can be frequency-shifted as follows:

[0105]

[0106] From equation (8), we can see that when the moving frequency is set to the base frequency f c When , the spectrum of the analytical signal is shifted to the left through the frequency shift matrix, such as Figure 3 As shown on the right, the highest frequency of the frequency-shifted signal is lower than the highest frequency of the original signal.

[0107] The frequency shift operation in equation (8) does not change the analytical signal s (t), according to the Nyquist sampling theorem, the theoretical maximum simulation step size is τ Ny =1 / (2(f c +Δf)), in order to accurately describe the transient process, it should satisfy (f c +Δf)τ<<1. After the frequency shift operation of formula (8), the sampling step size should satisfy the condition from (f c +Δf)τ<<1 is transformed into (f c +Δf-f c )τ<<1=Δfτ<<1. Therefore, a larger simulation step size can be used for the signal after frequency shift.

[0108] According to the frequency shift theory and the frequency adaptive transient simulation modeling method (FAST), the frequency adaptive adjoint model of basic components such as inductors and capacitors can be established using the traditional trapezoidal integration method.

[0109] For an inductor with a related reference direction for voltage and current, when a complex analytical signal is used, its differential equation is Its adjoint model becomes: i L (k)= G L v L (k)+ η L (k)

[0110] in,

[0111] For a capacitor with voltage and current in a related reference direction, when a complex analytical signal is used, its differential equation is Its adjoint model becomes: i C (k)= G C v C (k)+ η C (k)

[0112] in,

[0113] In the above formula, τ is the integration step size, ω is sis the moving angular frequency, k is the integration time point of the discrete integral, and the other quantities are the basic current, voltage, and inductance and capacitance values. According to the above-mentioned adjoint model of capacitance and inductance and the corresponding series-parallel relationship, a multi-scale model of the LC filter in the primary system of the grid-connected simulation model of the electrochemical energy storage power station can be established.

[0114] In these models, all AC quantities are represented by analytical signals and a variable parameter called the moving angular frequency is introduced. When the moving angular frequency is set to 100π (rad / s) or 120π (rad / s), i.e., the AC carrier frequency is 50 Hz or 60 Hz, the carrier is removed and electromechanical transients can be effectively simulated with large step size simulations. On the other hand, when the moving angular frequency is set to 0 (rad / s), the AC carrier is visible and can be simulated with small step size to track the natural waveform, such as the traditional EMTP type model.

[0115] 3. Multi-scale model of voltage source converter

[0116] In the grid-connected model of electrochemical energy storage power station, voltage source converter is an important interface to connect AC and DC power grids, and a multi-scale model of grid-connected converter must be established. This section focuses on the multi-scale voltage source converter of the grid-connected system based on the relevant principles of frequency shift theory. The structure of the multi-scale voltage source converter is shown in Figure 4 shown.

[0117] The signal will be parsed m abc (t) is used as the input of the multi-scale voltage source converter. The multi-scale voltage source converter consists of an average value multi-scale voltage source converter model and a switch function multi-scale voltage source converter model. When the switch is connected to A, the averaged multi-scale voltage source converter model is selected to track the envelope waveform. m A,abc (t) is set to be the same as the control signal m abc (t) are equal, as shown in (9).

[0118] m A,abc (t) ＝ m abc (t) (9)

[0119] The control signal obtained m A,abc (t) is used to calculate the AC terminal voltage of the multi-scale voltage source converter u out,abc (t), as shown in (10).

[0120] u out,abc (t) = 0.5v dc m A,abc (t) (10)

[0121] where v dc is the DC link voltage, which is equal to the output voltage v of the energy storage battery model batt .

[0122] v dc =v batt (11)

[0123] According to equations (10) and (11), the average value multi-scale voltage source converter model is selected in this operation mode.

[0124] The average value model does not involve switching action. When the switching transients are not of interest, multiscale simulation can process phasor signals, effectively tracking the envelope waveforms of the AC voltage and current.

[0125] When the switch is connected to SW, the modulated signal m abc (t) is taken as the real part and then passed to the pulse width modulation (PWM) generator model. The output of the PWM generator model is the switching pulse q sw,abc Then, the switching pulse q sw,abc Process and calculate the control signal m sw,abc . m sw,abc The calculation can be expressed as:

[0126] m sw,abc (t) = 2q sw,abc -1 (12)

[0127] The real control signal m obtained in (12) sw,abc (t) Reconstruct the complex analytical signal to obtain the complex control signal m sw,abc (t) is used to calculate the AC terminal voltage of the multi-scale voltage source converter. u out,abc (t), as shown in (13).

[0128] u out,abc (t) = 0.5v dc m sw,abc (t) (13)

[0129] In this operation mode, the switching function model of the multi-scale voltage source converter is selected, which is suitable for accurately simulating high-frequency switching transients.

[0130] When using the average value model, a large time step can be adapted to track the envelope waveform. This mode of operation allows for efficient simulation of slow transients in the entire grid-connected system. When using the switch function model, a small time step can be used to track the natural waveform. This mode of operation is suitable for accurate simulation of fast transients in the entire grid-connected system.

[0131] 4. Control system design

[0132] Using the complex-real interface, the measured analytical signal u abc (t), i abc (t) and i g,abc (t) is converted into a real signal u abc (t),i abc (t) and i g,abc (t). These real-number signals are the inputs of the grid-connected system. The control system is a power-current dual closed-loop control based on dq-axis decoupling. It can exchange active and reactive power with the grid side simultaneously and independently. Among them, the power controller is composed of a traditional PI controller, and its output is the reference current value of the converter and What you get and is the input of the current inner loop controller, such as Figure 5 The output of the current controller is expressed as a voltage signal in the dq0 coordinate system. Indicates that the signal is divided by 0.5 times the output DC voltage of the energy storage battery, that is, 0.5v batt , and finally the modulated voltage signal m can be obtained dq0 (t). Then use the dq0 inverse transform to convert the signal m dq0 (t) is transformed into a real signal m in the three-phase coordinate system abc (t), and finally the three-phase modulation signal of the multi-scale voltage source converter is obtained through the real-complex interface m abc (t).

[0133] 5. Interface design

[0134] In multi-scale simulation, in order to connect real signals and analytical signals, it is necessary to design complex-real interfaces and real-complex interfaces. The design of interfaces is introduced below. Specifically, the complex-real interface is designed to convert complex analytical signals into real signals, and the real-complex interface is designed to convert real signals into complex analytical signals.

[0135] 5.1 Complex Analytic Signal to Real Signal Interface (Complex-Real Interface)

[0136] Energy storage measured signalu abc (t), i abc (t) and i g,abc (t) is the analytical signal. These analytical signals need to be converted into real signals before they can be used as inputs to the control system. The design of the complex-real interface is introduced below.

[0137] In order to offset the simulation error caused by a time step delay, a prediction is required to compensate the input signal. Therefore, the current analytical signal of the output of the multi-scale voltage source converter is i abc A new prediction processing method is used to predict the signal i pre,abc for:

[0138] i pre,abc (k)=(1+ξ)e jωτ(k) i abc (k-1)-ξe jω[τ(k)+τ(k-1)] i abc (k-2) (14)

[0139] Where ω is the angular frequency set during prediction. When ω is set to 0, it is suitable for high-frequency electromagnetic transient processes simulated under a small simulation step size. When ω is set to the angular frequency corresponding to the fundamental frequency (such as 50 Hz or 60 Hz), the phase factor e is introduced. jωτ(k) Compensation is performed, which is applicable to low-frequency electromechanical transient processes simulated under large simulation steps; τ is the time step, k represents the kth discrete simulation point. ξ represents the ratio of the current time step to the previous time step.

[0140] The prediction signal i pre,abc , i g,abc (t) and u abc (t) The three signals, ignoring their real parts, are converted into real output signals.

[0141] 5.2 Real-to-complex analytic signal interface (real-complex interface)

[0142] Next, a real-complex interface is constructed to connect the real signal and the input analytical signal of the multiscale voltage source converter.

[0143] Using the obtained voltage control signal m o,dq0 (t), the analytical modulation voltage signal can be constructed m o,dq0(t), as shown in (15).

[0144] m dq0 (t) = (I + jT) m dq0 (t) (15)

[0145] in, I is the identity matrix.

[0146] Analyzing the modulated voltage signal m o,dq0 The real part Re[ m dq0 (t)] and the imaginary part Im[ m dq0 (t)] can be described as

[0147] Im[ m dq0 (t)] = TRe[ m dq0 (t)] (16)

[0148] Applying dq0 transformation on both sides of equation (16) yields

[0149] Im[ m abc (t)]=QRe[ m abc (t)] (17)

[0150] in,

[0151] Analyzing Modulated Signals m o,abc (t) can be constructed by formula (18).

[0152] m abc (t) = (I + jQ) m abc (t) (18)

[0153] 6. Example verification

[0154] 6.1 Example verification of the proposed prediction method

[0155] In order to verify the accuracy of the proposed prediction method, a prediction example test was carried out on a given current signal, and two methods, the traditional linear extrapolation prediction method and the complex signal prediction method, were established for comparative analysis with the proposed prediction method.

[0156] The calculation example is designed as follows: the actual current signal is set to i ref(t) = sin(2π0.1t)·sin(2π50t), and the simulation step τ is set to 2ms.

[0157] like Figure 6 As shown, Figure 6 The simulation results of the proposed prediction method and the other two prediction methods are shown in Figure 2. Figure 6 The black solid line in is the reference curve. Figure 6 The blue circled solid line in the figure is the prediction curve of the linear extrapolation method. Figure 6 The green solid line with square marks in the figure is the prediction curve of the complex signal prediction method. Figure 6 The red solid line with a star in the figure is the prediction curve of the proposed prediction method.

[0158] From the simulation results, it can be seen that compared with the other two prediction methods, the prediction results of the proposed prediction method are less different from the results of the actual reference curve, and the prediction accuracy is higher. The example verifies that the proposed prediction method still has high accuracy under large simulation steps and can meet the needs of multi-scale grid-connected simulation.

[0159] 6.2 Example verification of the proposed multi-scale grid-connected simulation model

[0160] In order to verify the accuracy and efficiency of the proposed model, a PQ command step test and a three-phase grounding fault test were carried out on a storage grid-connected system, and an EMTP model for energy storage power station grid-connected simulation was built for comparative analysis with the proposed multi-scale grid-connected simulation model.

[0161] The calculation example is designed as follows: at 0.2 seconds, the active power and reactive power command steps are performed, and the active power command changes from -0.01MW to 0.06MW; the reactive power command changes from 0.02MVar to -0.01MVar. Among them, the negative command indicates that the energy storage power station absorbs power from the grid side, and vice versa, it means that the energy storage power station sends power to the grid side. At 0.5 seconds, a three-phase grounding fault test was performed, and the grounding resistance was 0.1Ω. The total simulation time is set to 0.7 seconds.

[0162] Among them, the relevant parameters of the energy storage power station are: the energy storage battery capacity is 9600Ah; the terminal voltage is 864.3V; the nominal voltage is 800V; the nominal discharge current is 4173.9A; the internal resistance of the battery is 0.000833Ω. The grid-side filter inductance value is 5mH; the filter capacitor value is 73.1μF. The system three-phase power line voltage effective value is 381V.

[0163] Among them, the simulation step size of the EMTP model is set to 50μs; the moving frequency, simulation time step size and settings of the multi-scale voltage source converter model in the multi-scale model are shown in Table 1.

[0164] Table 1 Frequency shift parameters, simulation step size and settings of multi-scale voltage source converter model in multi-scale simulation example test

[0165]

[0166] The simulation results are as follows Figure 7 , 8 , as shown in Figure 9. Figure 7 The simulation result of the a-phase AC current at the grid connection point of the EMTP model is shown in Figure 2. Figure 8 The simulation results of the a-phase AC current at the grid connection point of the proposed multi-scale grid-connected simulation model are shown in Figure 2. Fig. 9 This is the simulation result of the output active power. Fig. 9 The solid line in is the curve of the EMTP model output active power. Fig. 9 The dotted line in is the output active power curve of the proposed multi-scale grid-connected simulation model.

[0167] It can be seen from the simulation results that there is no significant difference between the results of the proposed multi-scale grid-connected simulation model of the energy storage power station and the EMTP simulation model. However, the proposed multi-scale model can be simulated by flexibly setting the simulation step size and moving frequency: when simulating high-frequency transient processes that may occur in the system, a small simulation time step can be set to track the natural waveform; when simulating low-frequency transient processes that may occur in the system, a large simulation time step can be set to track the envelope waveform. Due to the use of a larger simulation step size, the calculation time is greatly saved. The example verifies the accuracy and efficiency of the proposed model.

[0168] In one embodiment, a method for constructing a grid-connected simulation model of an electrochemical energy storage power station is provided, the method comprising:

[0169] The three-phase electrical instantaneous real number signal output by the electrochemical energy storage power station is obtained, and the three-phase electrical instantaneous real number signal is subjected to Hilbert transformation to obtain the complex analytical signal corresponding to the three-phase electrical instantaneous real number signal; the frequency of the complex analytical signal is subjected to frequency shift operation to obtain a complex envelope, and then the complex envelope is processed by a trapezoidal integration method to obtain a multi-scale voltage source converter;

[0170] A complex analytical signal is introduced into the multi-scale voltage source converter to obtain a multi-scale voltage source converter based on the complex analytical signal; and according to the connection relationship of the topological diagram, the electrochemical energy storage power station is connected with the multi-scale voltage source converter based on the complex analytical signal and the LC filter model to obtain a primary system;

[0171] The signal prediction method is introduced to establish a complex-real interface; based on the transformation relationship between the dq0 coordinate system and the abc three-phase coordinate system and the relationship between the real part and the imaginary part of the signal, a real-complex interface is established;

[0172] The complex analytical signal is converted into a three-phase real signal through the complex-real interface, and then a power and current double closed-loop control system is established by decoupling through dq0 transformation;

[0173] The output signal of the primary system is input into the control system through the complex-real interface for signal demodulation to obtain an analytical modulation signal; the analytical modulation signal is fed back to the primary system through the real-complex interface to represent the feedback input of the multi-scale voltage source converter to realize the grid-connected simulation of the electrochemical energy storage power station and obtain a grid-connected simulation model of the electrochemical energy storage power station.

[0174] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A grid-connected simulation model for an electrochemical energy storage power station, characterized in that: include: A primary system and a control system; the input end of the primary system is connected to the output end of the control system via a real-complex interface, and the output end of the primary system is connected to the input end of the control system via a complex-real interface; The primary system comprises: an electrochemical energy storage power station, a multi-scale voltage source converter and an LC filter; The output end of the electrochemical energy storage power station is connected to the DC input end of the multi-scale voltage source converter, the output end of the multi-scale voltage source converter is connected to the input end of the LC filter and the first input end of the complex-real interface, the ground voltage output end of the LC filter is connected to the second input end of the complex-real interface, and the current output end of the LC filter is connected to the third input end of the complex-real interface; The multi-scale voltage source converter is specifically used for: The signal will be parsed m abc (t) is used as the input of the multi-scale voltage source converter, which consists of an average value model and a switch function model. When the switch is connected to A, the modulated signal m A,abc (t) is set to be the same as the control signal m abc (t) equal; m A,abc (t)= m abc (t) The control signal obtained m A,abc (t) is used to calculate the AC terminal voltage of the multi-scale voltage source converter u out,abc (t); u out,abc (t)=0.5v dc m A,abc (t) Among them, v dc is the DC link voltage, which is equal to the DC voltage output by the electrochemical energy storage power station model: v dc =v batt In the operation mode, an averaged multi-scale voltage source converter model is selected to track the envelope waveforms of the AC voltage and current; When the switch is connected to SW, the modulated signal m abc (t) is taken as the real part and then sent to the pulse width modulation (PWM) generator model. The output of the PWM generator model is the switching pulse q sw,abc ; The switching pulse q sw,abc Process and calculate the control signal m sw,abc , m sw,abc The calculation is expressed as: m sw,abc (t)=2q sw,abc -1 The obtained real control signal m sw,abc (t) Reconstruct the complex analytical signal to obtain the complex control signal m sw,abc (t), used to calculate the AC terminal voltage of the multi-scale voltage source converter u out,abc (t): u out,abc (t)=0.5v dc m sw,abc (t) According to the AC terminal voltage u out,abc (t) Multi-scale voltage source converter model for selecting switching function; The output end of the complex-real interface is connected to the input end of the control system, and the output end of the control system is connected to the input end of the real-complex interface; The output end of the real-complex interface is connected to the modulation signal input end of the multi-scale voltage source converter; The real-complex interface is specifically used for: Using the obtained voltage control signal m dq0 (t) Construct the analytical modulation voltage signal in the dq0 coordinate system m dq0 (t): m dq0 (t)=(I+jT)m dq0 (t) Analytical modulation voltage signal in dq0 coordinate system m dq0 The real part of (t) Re[ m dq0 (t)] and the imaginary part Im[ m dq0 (t)] is: Im[ m dq0 (t)]=TRe[ m dq0 (t)] Applying the inverse dq0 transform on both sides yields: Im[ m abc (t)]=QRe[ m abc (t)] Constructing the analytical modulation signal in the abc three-phase coordinate system m abc (t): m abc (t)=(I+jQ)m abc (t) Among them, m abc (t) is the real modulated signal in the three-phase coordinate system, I is the unit matrix, Among them, the output signal of the electrochemical energy storage power station is processed by the multi-scale voltage source converter and the LC filter in sequence, and the processed signal is input into the control system for signal demodulation to obtain an analytical modulation signal, and the analytical modulation signal is fed back to the primary system as a feedback input of the multi-scale voltage source converter to complete the grid-connected simulation of the electrochemical energy storage power station.

2. A grid-connected simulation model for an electrochemical energy storage power station as claimed in claim 1, characterized in that: The electrochemical energy storage power station comprises: a controlled voltage source, an internal resistor R and a power source v batt The positive electrode of the controlled voltage source is connected to one end of the internal resistance R, and the negative electrode of the controlled voltage source is connected to the power supply v batt The negative pole of the power supply v batt The positive electrode is connected to the other end of the internal resistor R.

3. A grid-connected simulation model for an electrochemical energy storage power station as claimed in claim 1, characterized in that: The primary system further includes a PCC node and a power grid, the output end of the LC filter is connected to one end of the PCC node, and the other end of the PCC node is connected to the power grid.

4. A grid-connected simulation model for an electrochemical energy storage power station as claimed in claim 1, characterized in that: The control system includes: a measurement processing module, a dq0 conversion module, a power calculation module, a power controller, a current controller and a dq0 inverse conversion module; The input end of the dq0 conversion module is connected to the output end of the complex-real interface, and the output end of the dq0 conversion module is respectively connected to the input end of the power calculation module and the input end of the current controller; The output end of the power calculation module is connected to the first input end of the power controller, the output end of the power controller is connected to the input end of the current controller, the output end of the current controller is connected to the input end of the dq0 inverse transformation module, and the output end of the dq0 inverse transformation module is connected to the input end of the real-complex interface; The second input terminal of the power controller is connected to the power calculation module.

5. A grid-connected simulation model for an electrochemical energy storage power station as claimed in claim 4, characterized in that: The output of the power controller is the reference current value of the converter and What you get and It is the input of the current inner loop controller; The output of the current controller is expressed as a voltage signal in the dq0 coordinate system. Indicates that the signal is divided by 0.5 times the output DC voltage of the energy storage battery to obtain the modulation voltage signal m dq0 (t); then use the dq0 inverse transform to convert the signal m dq0 (t) is transformed into a real signal m in the three-phase coordinate system abc (t), and finally the three-phase modulation signal of the multi-scale voltage source converter is obtained through the real-complex interface m abc (t).

6. A grid-connected simulation model for an electrochemical energy storage power station as claimed in claim 1, characterized in that: The complex-real interface is specifically used for: Energy storage measured signal u abc (t), i abc (t) and i g,abc (t) is the analytical signal; Current analysis signal of the output of multi-scale voltage source converter i abc Make a prediction and get the prediction signal i pre,abc for: i pre,abc (k)=(1+ξ)e jωτ(k) i abc (k-1)-ξe jω[τ(k)+τ(k-1)] i abc (k-2) Among them, ω is the angular frequency set during prediction, τ is the time step, k represents the kth discrete simulation point; ξ represents the ratio of the current time step to the previous time step; The prediction signal i pre,abc , i g,abc (t) and u abc (t) The three signals, ignoring their real parts, are converted into real output signals.

7. A method for constructing a grid-connected simulation model of an electrochemical energy storage power station according to any one of claims 1 to 6, characterized in that: The following steps are involved: The three-phase electrical instantaneous real number signal output by the electrochemical energy storage power station is obtained, and the three-phase electrical instantaneous real number signal is subjected to Hilbert transformation to obtain the complex analytical signal corresponding to the three-phase electrical instantaneous real number signal; the frequency of the complex analytical signal is subjected to frequency shift operation to obtain a complex envelope, and then the complex envelope is processed by a trapezoidal integration method to obtain a multi-scale voltage source converter; A complex analytical signal is introduced into the multi-scale voltage source converter to obtain a multi-scale voltage source converter based on the complex analytical signal; and according to the connection relationship of the topological diagram, the electrochemical energy storage power station is connected with the multi-scale voltage source converter based on the complex analytical signal and the LC filter model to obtain a primary system; The signal prediction method is introduced to establish a complex-real interface; based on the transformation relationship between the dq0 coordinate system and the abc three-phase coordinate system and the relationship between the real part and the imaginary part of the signal, a real-complex interface is established; The complex analytical signal is converted into a three-phase real signal through the complex-real interface, and then a power and current double closed-loop control system is established by decoupling through dq0 transformation; The output signal of the primary system is input into the control system through the complex-real interface for signal demodulation to obtain an analytical modulation signal; the analytical modulation signal is fed back to the primary system through the real-complex interface to represent the feedback input of the multi-scale voltage source converter to realize the grid-connected simulation of the electrochemical energy storage power station and obtain a grid-connected simulation model of the electrochemical energy storage power station.

Images