SE voltage sag control method and system based on flexible reuse of energy storage system

Abstract

The present invention relates to the field of energy storage technology and voltage sag control technology, and discloses a SE voltage sag control method and system based on flexible reuse of energy storage systems. Supercapacitors are used to achieve rapid control of voltage sags in the early stage, and energy storage system energy is used to achieve continuous control of voltage sags in the later stage; a detection method based on TKEO and KC to improve VMD is proposed to achieve real-time and accurate detection of voltage sags on the grid side and the load side; optimal energy compensation is achieved through flexible switching in the input and output stages to avoid SE tripping due to phase jumps caused by optimal energy compensation; power frequency division control is performed on the DC / DC side according to the difference in response characteristics between supercapacitors and energy storage systems; on the DC / AC side, a composite control system including a voltage feedforward loop, a voltage feedback outer loop and a current feedback inner loop is proposed to improve the control system's rapid response capability and anti-disturbance stability capability, and a PIQR controller is used to eliminate the secondary effects of harmonics on SE.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage technology and voltage sag control technology, and specifically to a method and system for SE (Sensitive equipment SE) voltage sag control based on flexible reuse of energy storage systems. Background Art

[0002] As an important carrier for the scale and clustering of modern manufacturing, industrial parks provide support for the development of high-tech industries. With the development and application of energy storage technology, the business model of installing energy storage systems in industrial parks for peak-valley arbitrage has been widely promoted. A large number of sensitive equipment containing power electronic devices are configured in modern industrial parks. In order to avoid the problem of sensitive equipment tripping and causing industrial process failure, extremely high requirements are placed on the power quality of industrial parks. When the energy storage system is discharged, the industrial park is in an isolated operation and is completely powered by the energy storage system. At this time, since the industrial park is disconnected from the power grid, there is usually no voltage sag problem. When the energy storage system is charging or on standby, the industrial park is completely powered by the power grid. Due to short-circuit faults, the industrial park has a serious risk of voltage sag, which poses a major potential hazard to sensitive equipment. In addition, the harmonic problem associated with voltage sag will also have secondary effects on sensitive equipment in the industrial park. According to statistics, the energy storage system is idle for about 12 hours a day. In order to further ensure the power supply of industrial parks, it is of great value and significance to realize the flexible reuse of energy storage systems to control voltage sags.

[0003] Insufficient topology: The energy storage system uses an island operation mode to supply power to the industrial park for peak-valley arbitrage. However, the peak-valley arbitrage topology cannot control voltage sags, and the energy storage system is in standby mode for a long time, resulting in idle resources and waste. Energy storage systems are usually made of lithium batteries. Due to the long response time of lithium batteries, voltage sags cannot be controlled even if they are connected in series with sensitive equipment. If the industrial park adds voltage sag control devices, it will bring high investment costs to sensitive users.

[0004] Deficiencies in the detection algorithm: Calculate the voltage root mean square value of two adjacent windows, and take the absolute value of the difference as the effective value difference index to determine the start and end time. However, due to the transition phase in the window calculation, the instantaneous amplitude and phase information are lost, resulting in errors in the voltage sag detection results. The method of constructing a hybrid morphological filter by combining dq transformation and morphological filtering to detect voltage sag characteristics is easily affected by the harmonics and noise of the distribution network and may cause false detection. The two-dimensional complex matrix after the digital prolate spherical window correction S transformation is used to detect voltage sags, but the detection efficiency is reduced due to the cumbersome correction process.

[0005] Insufficient compensation strategies: In the traditional same-phase voltage sag compensation strategy or complete voltage sag compensation strategy, the output of large active power leads to excessive energy consumption, and large-capacity supercapacitors are required. In the minimum energy compensation strategy, the phase of the compensation voltage is adjusted to make it as perpendicular to the load current as possible to reduce the active output. However, the phase jump of the load voltage caused by the minimum energy compensation will cause sensitive equipment to trip.

[0006] Insufficient control systems: On the DC / DC side, the response speeds of lithium batteries and supercapacitors are significantly different, making it difficult to coordinate their output power. On the DC / AC side, the traditional voltage feedback loop has insufficient rapid response capabilities and poor anti-interference stability, and cannot achieve rapid and effective control when voltage sags occur. In addition, voltage sags are usually accompanied by harmonic problems, which have secondary effects on sensitive equipment, and harmonic control needs to be taken into account. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a SE voltage sag control method and system based on flexible reuse of energy storage systems. Compared with the energy storage systems used for peak-valley arbitrage in traditional industrial parks, flexible reuse is achieved, which can prevent sensitive equipment from tripping and causing major industrial losses, and provide important support for high-quality power supply in industrial parks. The technical solution is as follows:

[0008] The SE voltage sag control method based on flexible reuse of energy storage system includes the following steps:

[0009] Step 1: construct a topological structure for a hybrid energy storage system to manage voltage sags, wherein the hybrid energy storage system includes a lithium battery energy storage system and a supercapacitor, wherein the supercapacitor is used to manage the early stage of voltage sags, and the lithium battery energy storage system is used to achieve continuous management of the later stage of voltage sags;

[0010] Step 2: Realize real-time and accurate detection of grid-side and load-side voltage sags through the detection method based on the improved variational mode decomposition of the Teager-Kaiser energy operator and the kurtosis coefficient;

[0011] Step 3: Adopt a flexible optimal energy compensation strategy to achieve optimal energy compensation through flexible switching between the input and output stages to avoid sensitive equipment from tripping due to phase jumps caused by optimal energy compensation;

[0012] Step 4: On the DC / DC side, based on the differences in the response characteristics of the supercapacitor and lithium battery energy storage systems, the output is coordinated through power frequency division control;

[0013] On the DC / AC side, composite control is performed through a voltage feedforward loop, a voltage feedback outer loop, and a current feedback inner loop, and a proportional-integral quasi-resonant controller is used to eliminate the secondary effects of harmonics on sensitive equipment.

[0014] The SE voltage sag management system based on flexible reuse of energy storage systems includes:

[0015] Topology of hybrid energy storage system for voltage sag control: including hybrid energy storage system composed of lithium battery energy storage system and super capacitor, which can achieve early control of voltage sag through super capacitor and continuous control of voltage sag through lithium battery energy storage system;

[0016] Detection unit: Through the detection method of improved variational mode decomposition based on Teager-Kaiser energy operator and kurtosis coefficient, the real-time and accurate detection of voltage sag on the grid side and load side is realized;

[0017] Compensation unit: adopts flexible optimal energy compensation strategy, and realizes optimal energy compensation through flexible switching in the input and output stages, so as to avoid the sensitive equipment from tripping due to phase jump caused by optimal energy compensation;

[0018] Control system: On the DC / DC side, the output is coordinated through power frequency division control according to the difference in response characteristics between the supercapacitor and lithium battery energy storage systems;

[0019] On the DC / AC side, composite control is performed through a voltage feedforward loop, a voltage feedback outer loop, and a current feedback inner loop, and a proportional-integral quasi-resonant controller is used to eliminate the secondary effects of harmonics on sensitive equipment.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. In terms of topological structure, the present invention proposes a hybrid energy storage system composed of a lithium battery energy storage system and a supercapacitor, which uses the extremely fast response speed of the supercapacitor to achieve rapid control in the early stage of voltage sag, and uses the huge energy reserve of the energy storage system to achieve continuous control in the later stage of voltage sag;

[0022] 2. In terms of detection algorithm, the present invention proposes a detection method based on Teager-Kaiser energy operator and improved variational mode decomposition of kurtosis coefficient, which realizes real-time and accurate detection of voltage sag on the grid side and load side;

[0023] 3. In terms of compensation strategy, the present invention proposes a flexible optimal energy compensation strategy, which realizes optimal energy compensation through flexible switching between the input and output stages, thus avoiding the tripping of sensitive equipment due to phase jumps caused by optimal energy compensation;

[0024] 4. In terms of the control system, the present invention proposes a power frequency division control system that coordinates the output conditions on the DC / DC side based on the differences in the response characteristics of the supercapacitor and the energy storage system; on the DC / AC side, a composite control system including a voltage feedforward loop, a voltage feedback outer loop and a current feedback inner loop is proposed to improve the control system's rapid response capability and anti-disturbance stability capability, and a proportional integral quasi-resonance (PIQR) controller is used to eliminate the secondary effects of harmonics on sensitive equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Topological diagram for controlling voltage sag in a hybrid energy storage system (HESS).

[0026] Figure 2 (a) is a peak-valley arbitrage charging mode diagram.

[0027] Figure 2(b) is a peak-to-valley arbitrage discharge mode diagram.

[0028] Figure 2 (c) is the modal diagram of the early stage of voltage sag, when the supercapacitor and lithium battery are powered at the same time.

[0029] Figure 2 (d) is the modal diagram at the later stage of voltage sag, when only lithium battery is used for power supply.

[0030] Figure 3 This is the PQ control strategy diagram for grid-connected operation.

[0031] Figure 4 VF control strategy diagram for island operation.

[0032] Figure 5 (a) is a vector diagram of the optimal energy compensation strategy when a shallow voltage sag occurs.

[0033] Figure 5(b) is a vector diagram of the optimal energy compensation strategy when a deep voltage sag occurs.

[0034] Figure 6 (a) shows the flexible compensation strategy in the commissioning phase - the amplitude diagram of the compensation voltage.

[0035] Fig. 6(b) shows the phase diagram of the compensation voltage of the flexible compensation strategy in the commissioning stage.

[0036] Figure 7 (a) shows the flexible compensation strategy in the cut-out phase - the amplitude diagram of the compensation voltage.

[0037] Fig. 7(b) shows the phase diagram of the compensation voltage in the flexible compensation strategy during the cut-out phase.

[0038] Figure 8 This is the power frequency division control system diagram.

[0039] Fig. 9 This is a composite control system diagram.

[0040] Fig.10 Bode diagram of the PIMQR controller. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] The present invention is based on the method for managing voltage sag of sensitive equipment with flexible reuse of energy storage system in industrial park, and realizes the management of voltage sag of sensitive equipment with flexible reuse of energy storage system in industrial park. The present invention comprises the following steps:

[0043] Step S1: In terms of topology, a hybrid energy storage system composed of a lithium battery energy storage system and a supercapacitor is proposed. The extremely fast response speed of the supercapacitor is used to achieve rapid control in the early stage of voltage sag, and the huge energy reserve of the energy storage system is used to achieve continuous control in the later stage of voltage sag.

[0044] Figure 1 This is the topological structure diagram of the hybrid energy storage system for voltage sag management. The front end is connected in parallel with the grid for peak-valley arbitrage, and the back end is connected in series with sensitive equipment for voltage sag management. The hybrid energy storage system consists of supercapacitors represented by purple lines and lithium battery energy storage systems for peak-valley arbitrage represented by blue lines, which are connected to the same DC bus through a DC / DC boost circuit.

[0045] As shown in Figures 2(a) to 2(d), the topological structure of the present invention includes four operating modes, among which the two peak-valley arbitrage charging modes are Figures 2(a) and 2(b), and the two voltage sag pre-stage modes are Figures 2(c) and 2(d).

[0046] 1. Mode 1 is the peak-valley arbitrage charging mode: during the low electricity price period, the thyristor is turned on and the switch Closed, the load is in grid-connected operation, the grid voltage For load Power supply, using constant power control (PQ control) to charge lithium batteries and supercapacitors from the power grid, such as Figure 3 When charging is completed, the PQ control stops outputting pulse signals to the inverter, and the hybrid energy storage system HESS is in standby state with full charge.

[0047] Voltage sampling collects the instantaneous value of the grid-side voltage , the voltage phase is obtained through the phase-locked loop , through the abc / dq conversion transformation, the instantaneous value of the grid-side voltage in the dq coordinate system is obtained Similarly, the current sampling collects the instantaneous value of the inductor current , after abc / dq conversion, the instantaneous value of the inductor current in the dq coordinate system is obtained , the active power reference value and reactive power reference The actual value of active power P and the actual value of reactive power Q The error value is compared and the value is obtained after the PI controller is operated. The reference value of the current inner loop; the reference value of the current inner loop The instantaneous value of the inductor current The error value is compared and the output value after the PI controller operation is added and subtracted from the feedforward and decoupling terms to obtain the output voltage value. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then the SVPWM (Space vector pulse width modulation) modulation wave is generated, and then 12-channel PWM (pulse width modulation) wave drive signals are generated to achieve grid-connected constant power control.

[0048] The output value of the error value after the PI controller operation is added or subtracted from the feedforward and the decoupling term. Specifically, the d-axis component of the PI controller output value is subtracted from the feedforward and added to the decoupling term, and the q-component is added to the feedforward and also added to the decoupling term.

[0049] 2. Mode 2 is the peak-valley arbitrage discharge mode: during the high electricity price period, the thyristor is turned off and the switch Disconnect, the load is in an island operation state, constant voltage and frequency control (VF control) is adopted, and the lithium battery is used as the load Power supply, such as Figure 4 As shown. When the discharge is completed, the thyristor is turned on and the load resumes the grid-connected operation state, that is, the load is powered by the grid. Since it is a period of high electricity prices, the hybrid energy storage system HESS is in a standby state with surplus power, waiting for the arrival of a period of low electricity prices to start charging.

[0050] The control target of the voltage outer loop is the load side voltage. The instantaneous value of the three-phase voltage in the abc coordinate system is obtained by voltage sampling. , and then the instantaneous value of the three-phase voltage in the dq coordinate system is obtained through abc / dq conversion , the voltage reference value And the instantaneous value of voltage The error value is compared and the current value output after the PI controller is calculated. As the reference value of the current inner loop. The instantaneous value of the three-phase inductor current in the abc coordinate system is obtained by current sampling. , and then the instantaneous value of the current in the dq coordinate system is obtained through abc / dq conversion , the current reference value The instantaneous value of current The error value obtained by the PI controller is added and subtracted from the voltage feedforward and the load term to obtain the output voltage value. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then the SVPWM modulation wave is generated to generate 12 PWM wave drive signals.

[0051] 3. Mode 3 is the early stage of voltage sag control: when voltage sag occurs, the grid voltage and the hybrid energy storage system jointly supply power to the load. Closed, the supercapacitor and lithium battery supply power at the same time. The supercapacitor has an extremely fast response speed and outputs a huge amount of power in a very short time, which can achieve rapid control of voltage sag. As the power of the lithium battery increases, the power of the supercapacitor decreases.

[0052] 4. Mode 4 is the mode in the later stage of voltage sag control. As the output power of the lithium battery increases, when the compensation power required by the load is reached, the output power of the supercapacitor is 0, and the switch Disconnect, the load is powered by the grid and lithium batteries at the same time. Lithium batteries have huge energy reserves and can achieve continuous control of voltage sags.

[0053] The traditional topology is configured with supercapacitors, namely dynamic voltage restorers (DVRs), which are used to manage the entire process of voltage sags, and the configuration management time is usually in the order of seconds. Since the investment cost of supercapacitors is high, reducing the configuration capacity of supercapacitors can reduce investment costs. Therefore, according to the response time of lithium batteries, the improved topology configuration supercapacitors are only used to manage the early stage of voltage sags, and the configuration management time is shortened to milliseconds.

[0054] Step S2: In terms of detection method, a detection method based on improving VMD (Variational mode decomposition, VMD) based on TKEO (Teager-Kaiser energy operatorTeager-Kaiser energy operator, TKEO) and KC (Kurtosis coefficient, KC) is proposed to achieve real-time and accurate detection of voltage sag on the grid side and load side.

[0055] The step S2 comprises the following sub-steps:

[0056] Step S21: TKEO converts the instantaneous voltage value into an envelope to enhance the voltage sag characteristic. The expression is:

[0057] ;

[0058] In the formula, For TKEO, is the instantaneous value of voltage, is the voltage peak value, is the angular frequency, The initial phase.

[0059] Step S22: Establish a variational constraint model, the expression is:

[0060] ;

[0061] In the formula, For the The decomposed IMF components are is the decomposition mode number, It is the voltage sag signal. is the impulse function, For the The center frequency of the IMF components, is the gradient operation, is a constraint condition.

[0062] Step S23: By introducing the augmented Lagrangian function as shown below L , the constrained variational problem is transformed into an unconstrained variational problem, and the expression is:

[0063] ;

[0064] In the formula, is the penalty factor, is the Lagrangian operator, is the inner product operation.

[0065] Step S24: Update iterative solution using the multiplication operator alternating direction method IMF (Intrinsic Mode Function, IMF) and residual components with fixed bandwidth and center frequency. Based on Fourier isometric transform, , and Update the formula and iteration termination condition, the expression is:

[0066] ;

[0067] ;

[0068] ;

[0069] ;

[0070] In the formula, and They are and The Fourier transform of is the noise tolerance, is the convergence accuracy; and Respectively The number of samples decomposed intrinsic mode function components and the center frequencies of the intrinsic mode function components; , and They are the original signal after Fourier transform, the The decomposed intrinsic mode function components and the Lagrangian operator after Fourier transformation; The center frequency is No. The Lagrangian operator after Fourier transformation of the number of samples; The center frequency is No. The number of samples Fourier transform of the decomposed intrinsic mode function components; For the The number of samples Fourier transform of the decomposed eigenmode function components.

[0071] Step S25: Calculate the kurtosis coefficient of each IMF and residual component , The larger the value, the more transient characteristics the signal contains. The largest component is taken as the optimal component, and the expression is:

[0072] ;

[0073] In the formula, is the kurtosis coefficient, To detect the signal, is the expected value, is the mean, is the standard deviation.

[0074] Step S26: Determine the mutation sampling point in the optimal component based on the calculation of the change rate, and the expression is:

[0075] ;

[0076] In the formula, is the rate of change, is the sampling point, is the value of the optimal component, is the time interval between sampling points.

[0077] Calculate different starting thresholds based on 500 sets of measured voltage sag data and termination threshold The standard deviation between the detection result and the actual result is calculated, and the threshold corresponding to the minimum standard deviation is determined as the optimal detection threshold. When , it indicates that voltage sag occurs; when , indicating that the voltage sag is over.

[0078] Step S27: Taking phase a voltage as an example, record the time when the sag occurs according to the detection results and the end time of the temporary landing The instantaneous value of voltage and , instantaneous voltage change , the expression is:

[0079] ;

[0080] In the formula, for Voltage reference value at the moment.

[0081] Step S28: Since most of the existing equipment currently does not have a phase monitoring function, the instantaneous value of the three-phase voltage after the sag occurs is reconstructed into a space vector.

[0082] because The phase voltage vector is in the same direction as the three-phase voltage space vector. and for The angle between the phase voltage vector and the positive direction of the real axis. Therefore, The starting and ending phases of the phase voltage sag are ,in, and Respectively expressed as:

[0083] ;

[0084] In the formula, is the imaginary part, is the real part; and The time when the temporary drop occurs and the end time of the temporary landing The instantaneous value of voltage and The space vector of and for and Three-phase voltage space vector at time; and for and The angle with the positive direction of the real axis.

[0085] Step S29: Similarly, we can obtain Harmony Phase voltage sag characteristics.

[0086] Step S3: In terms of compensation strategy, a flexible optimal energy compensation strategy is proposed to achieve optimal energy compensation through flexible switching between the dynamic input and output stages, thereby avoiding the tripping of sensitive equipment due to phase jumps caused by optimal energy compensation.

[0087] Taking phase a as an example, the basic principle of the optimal energy compensation strategy is shown in Figure 5 (a) to Figure 5 (b). is the grid current without voltage sag, is the grid voltage without voltage sag, is the voltage of the sensitive equipment (Sensitiveequipment SE) before the voltage sag, is the grid voltage during voltage sag, is the SE voltage during voltage sag, The compensation voltage provided to HESS, is the SE current before the voltage sag, is the SE current during voltage sag, is the power factor angle, is the phase jump when the voltage drops temporarily, The compensation voltage phase provided for HESS, for and The phase of for and phase. is the voltage of the supercapacitor, is the voltage of the lithium battery.

[0088] The specific steps are as follows:

[0089] Step S31: When a voltage sag occurs, the active power output by the HESS The expression is:

[0090] ;

[0091] In the formula, is the voltage of sensitive equipment during voltage sag, is the grid voltage during voltage sag, It is the current of sensitive equipment during voltage sag; is the power factor angle, The grid voltage during voltage sag and sensitive equipment current phase.

[0092] As shown in Figure 5(a), when a shallow voltage sag occurs, that is, :The phase is adjusted by the compensation voltage provided by the hybrid energy storage system , so that the compensation voltage provided by the hybrid energy storage system Current of sensitive equipment during voltage sag Mutually perpendicular, that is, active power At this time, the hybrid energy storage system only provides reactive power to achieve voltage sag control, and the compensation voltage The expression is:

[0093] ;

[0094] In the formula, is the voltage of sensitive equipment before the temporary drop; phase The compensation voltage phase provided by the hybrid energy storage system, θ is the phase jump during temporary sag.

[0095] As shown in Figure 5(b), when a deep voltage sag occurs, that is, :The compensation voltage provided by HESS is used to adjust δ, so that and The phases are the same. At this time, the grid bears more active power, and the active power provided by HESS is the smallest. The expression is:

[0096] ;

[0097] The optimal energy compensation strategy uses zero active power compensation during shallow voltage sag and optimal active power compensation during deep voltage sag, which can effectively reduce the energy consumption of HESS. However, when the voltage sag is controlled according to the optimal energy compensation strategy, a large phase jump will occur, causing SE to trip. Therefore, a flexible compensation strategy for the input and output stages is proposed to avoid large phase jumps.

[0098] Step S32: During the commissioning phase, the HESS provides a compensation voltage by flexibly switching the voltage phase to avoid causing a large phase jump.

[0099] As shown in Figure 6(a) and Figure 6(b), Provides the phase of the compensation voltage for HESS during the input phase, and are the initial phase and the final phase respectively, and They are the initial time and the end time of the investment phase, It is the transition stage of investment.

[0100] According to the vector relationship, the amplitude expression of the compensation voltage provided by HESS during the input stage during shallow and deep voltage sags is:

[0101] ;

[0102] According to the vector relationship, the initial phases of the compensation voltage provided by the HESS during the input phase during shallow and deep voltage sags are expressed as follows:

[0103] ;

[0104] ;

[0105] According to the vector relationship, when the voltage is shallow or deep, the termination phase of the compensation voltage provided by the HESS during the input phase is as shown in the compensation voltage phase of the above formula, that is, = α .

[0106] SE phase jump occurs during voltage sag control If no tripping occurs at this time, it means that the phase jump that SE can tolerate becomes During the startup phase, the initial phase of the compensation voltage provided by the HESS is , the load voltage maintains the phase state before the voltage sag After the transition phase of investment Flexible switching to the termination phase of the compensation voltage provided by the HESS , the load voltage reaches the phase state of the optimal energy compensation strategy .

[0107] According to the phase change in the input stage, the voltage phase flexible switching expression is:

[0108] ;

[0109] The transition phase of investment The expression is:

[0110] ;

[0111] In the formula, Phase jump before and after HESS treatment, shallow voltage drop , deep voltage sag .according to The number of steps is rounded up, and the transition phase of the input is calculated based on the switching step length of 2ms. Based on the flexible switching of the voltage phase during the input phase, the SE tripping caused by a large phase jump is avoided.

[0112] Step S33: In the cut-out stage, the HESS provides a compensation voltage by flexibly switching the voltage phase to avoid causing a large phase jump.

[0113] As shown in Figure 7 (a) to Figure 7 (b), Provides compensation voltage phase for HESS during the cut-out phase, , and are the initial phase, the middle phase and the final phase respectively. , and They are the initial time, intermediate time and terminal time of the cut-out phase, It is the transition stage of cutting out.

[0114] According to the vector relationship, the amplitude expression of the compensation voltage provided by HESS in the cut-out stage is:

[0115] ;

[0116] According to the vector relationship, the initial, intermediate and final phase expressions of the compensation voltage provided by the HESS during the cut-out phase are:

[0117] ;

[0118] In the cut-out phase, the starting phase of the compensation voltage provided by the HESS Equal to the end phase of the input phase . SE has a phase jump when the voltage sag is restored If no tripping occurs at this time, it means that the phase jump that SE can tolerate becomes Therefore, the starting phase of the compensation voltage provided by the HESS is Instantly switch to , maintain the load voltage at the phase state when the voltage sags At this time, SE has another phase jump Still no jump stop occurs. Then, after the transition phase of cutting out Flexible switching to the termination phase of the compensation voltage provided by the HESS , the load voltage returns to the normal grid voltage .

[0119] According to the phase change in the cut-out stage, the voltage phase flexible switching expression is:

[0120] ;

[0121] In the formula, Provides the phase of the compensation voltage for the hybrid energy storage system during the cut-out phase. and are the middle time and the end time of the cut-out phase respectively;

[0122] Cut-out transition stage The expression is:

[0123] ;

[0124] In the formula, The phase jump of voltage sag recovery is The number of steps is rounded up, and the cut-out transition phase is calculated based on the switching step length of 2ms. Based on the flexible switching of the voltage phase during the cut-out phase, the SE tripping caused by a large phase jump is avoided.

[0125] Harmony The flexible optimal energy compensation strategy of the phase is the same.

[0126] Step S4: In terms of the control system, on the DC / DC side, based on the differences in the response characteristics of the supercapacitor and lithium battery energy storage systems, a power frequency division control system that coordinates the output conditions is proposed.

[0127] On the DC / AC side, a composite control system including a voltage feedforward loop, a voltage feedback outer loop and a current feedback inner loop is proposed to improve the control system's rapid response capability and anti-disturbance stability capability, and a proportional integral quasi-resonant (PIQR) controller is used to eliminate the secondary effects of harmonics on sensitive equipment.

[0128] In the flexible optimal energy compensation strategy, HESS for shallow voltage sag only needs to provide active power in the cut-in and cut-out stages, while HESS for deep voltage sag needs to provide active power throughout the entire process. Under voltage sag, SE's demand for active power can be divided into low-frequency components and high-frequency components. At the moment of voltage sag, due to the rapid change of voltage, SE's demand for active power is a high-frequency component. According to the characteristics of supercapacitors with extremely fast response speed, the active power is quickly responded to and output to control the voltage sag of SE. In the process of evolving from the moment of occurrence to transient stability, the high-frequency component of SE's demand for active power gradually decreases, while the low-frequency component gradually increases. The active power output of supercapacitors gradually decreases, and the active power output of lithium batteries gradually increases, jointly controlling the voltage sag of SE. In the transient stability of voltage sag, since the active power required by SE is constant, SE's demand for active power is a low-frequency component. According to the characteristics of lithium batteries with extremely large energy reserves, continuous discharge outputs active power to control the voltage sag of SE.

[0129] Step S41: Power frequency division control:

[0130] Power frequency division control system Figure 8 As shown, the DC / DC converters in the lithium battery and the supercapacitor are controlled, as shown in the orange dotted box and the green dotted box respectively.

[0131] Active power provided by HESS in flexible optimal energy compensation strategy The sum of the three phases is the active power demand value . Through a low pass filter , is the time constant, is the Lagrangian operator. According to the low-frequency component and high-frequency component, the active power demand value of the hybrid energy storage system Allocate active power reference values ​​for lithium batteries and supercapacitors, i.e., active power demand value for lithium batteries and the active power demand of the supercapacitor ,like Figure 8 The red dashed box shows the power feedback outer loop. Figure 8 As shown in the blue dotted box. In lithium batteries, according to the active power demand value of lithium batteries and lithium battery active power measurement The difference between the current reference value and the .

[0132] Since lithium batteries respond slowly, supercapacitors need to output additional active power that lithium batteries cannot respond to in time, thereby avoiding the loss of SE active power, such as Figure 8 As shown by the red arrow. In the supercapacitor, the active power requirement of the supercapacitor and the active power measurement of the supercapacitor The difference needs to add the active power requirement of the lithium battery and lithium battery active power measurement The difference between the current reference value and the The current feedback inner loop is based on the current reference value of the lithium battery. and lithium battery current measurement value The difference and the current reference value of the supercapacitor and supercapacitor current measurement The difference between the duty cycle of the lithium battery and the supercapacitor is calculated respectively, such as Figure 8 As shown in the purple dotted box, the pulse signal is generated by PWM; D Indicates the pulse signal.

[0133] Step S42: Compensation voltage reference value provided by HESS according to the flexible optimal energy compensation strategy Construct a composite control system including a voltage feedforward loop, a voltage feedback outer loop and a current feedback inner loop to control the DC / AC converter, such as Fig. 9 As shown, For the Transfer function of quasi-resonant control of subharmonics.

[0134] The voltage feed-forward loop is based on the compensation voltage reference value of the hybrid energy storage system. Compensation voltage with HESS The difference between the HESS feedforward voltage reference value is calculated The voltage feedforward loop can quickly output the compensation voltage and improve the timeliness of the control system. Calculate SE current reference value The current feedback inner loop is based on With SE current The difference between the HESS feedback voltage reference value is calculated .according to and Calculating voltage reference The voltage feedback outer loop and current feedback inner loop can eliminate the problem of compensation voltage overshoot and enhance the anti-interference ability of the control system.

[0135] Step S43: Add a quasi-resonance controller to the PI controller of voltage feedback and current feedback to achieve zero-error tracking of the AC signal and eliminate harmonics of specific frequencies. The quasi-resonance (QR) controller has the characteristics of a wide bandwidth and can avoid the control error caused by the grid frequency deviation from worsening the power quality problem in the industrial park. Its transfer function expression is:

[0136] ;

[0137] In the formula, for The gain of the sub-resonant controller, is the fundamental frequency, is the resonant frequency bandwidth, is the Lagrangian operator.

[0138] In industrial parks, odd-order harmonics have the most serious impact on SE. Therefore, the transfer function expression of the proportional integral multiple quasi resonators (PIMQR) controller used to control odd-order harmonics is:

[0139] .

[0140] The Bode diagram of the PIMQR controller designed to control the 3rd harmonic (150Hz), 5th harmonic (250Hz), 7th harmonic (350Hz), 9th harmonic (450Hz), 11th harmonic (550Hz), 13th harmonic (650Hz) and 15th harmonic (750Hz) of SE is shown in the figure. Fig.10 shown.

[0141] The PIMQR controller has the characteristics of high gain at specific frequencies, and the specific frequencies do not interfere with each other, and non-specific frequencies do not produce resonance, so it can control harmonics at specific frequencies.

Claims

1. A SE voltage sag control method based on flexible reuse of energy storage system, characterized in that: The following steps are involved: Step 1: construct a topological structure for a hybrid energy storage system to manage voltage sags, wherein the hybrid energy storage system includes a lithium battery energy storage system and a supercapacitor, wherein the supercapacitor is used to manage the early stage of voltage sags, and the lithium battery energy storage system is used to achieve continuous management of the later stage of voltage sags; Step 2: Realize real-time and accurate detection of grid-side and load-side voltage sags through the detection method based on the improved variational mode decomposition of the Teager-Kaiser energy operator and the kurtosis coefficient; Step 3: Adopt a flexible optimal energy compensation strategy to achieve optimal energy compensation through flexible switching between the input and output stages to avoid sensitive equipment from tripping due to phase jumps caused by optimal energy compensation; Step 4: On the DC / DC side, based on the differences in the response characteristics of the supercapacitor and lithium battery energy storage systems, the output is coordinated through power frequency division control; On the DC / AC side, composite control is performed through a voltage feedforward loop, a voltage feedback outer loop, and a current feedback inner loop, and a proportional-integral quasi-resonant controller is used to eliminate the secondary effects of harmonics on sensitive equipment.

2. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 1 is characterized in that: The step 1 specifically includes: Constructing a topological structure of a hybrid energy storage system for managing voltage sag: The hybrid energy storage system includes supercapacitors and lithium batteries; supercapacitors and switches After being connected in series, they are connected in parallel with lithium batteries; the hybrid energy storage system is connected in parallel with the grid for peak-valley arbitrage, and is connected to the grid through DC / AC converters, LC filters, and thyristors in turn; the hybrid energy storage system is connected in series with sensitive equipment for voltage sag control, and is connected to the load through DC bus, DC / AC inverter, LC filter, and transformer coupling in turn. ; The topology described contains four operating modes: Mode 1 is the peak-valley arbitrage charging mode; during the low electricity price period, the thyristor is turned on and the switch Closed, Load In the grid-connected operation state, the grid voltage For load Power supply; the grid-connected constant power control is used to charge the lithium battery and the supercapacitor from the grid; when charging is completed, the grid-connected constant power control stops outputting the pulse signal to the DC / AC inverter, and the hybrid energy storage system is in a standby state with full power; Mode 2 is the peak-valley arbitrage discharge mode; during the high electricity price period, the thyristor is turned off and the switch Disconnect, load In the island operation state, constant voltage and constant frequency control is adopted with lithium battery as load Power supply; when the discharge is completed, the thyristor is turned on and the load The grid-connected operation state is restored, that is, the power grid supplies power to the load; the hybrid energy storage system is in standby state with surplus power, waiting for the arrival of a low electricity price period to start charging; Mode 3 is the early stage of voltage sag control; when voltage sag occurs, the grid voltage and the hybrid energy storage system act as loads. Power supply; switch Closed, the supercapacitor and lithium battery supply power at the same time; the supercapacitor outputs power exceeding a specific value within the set time threshold to achieve voltage sag control; and the power of the supercapacitor decreases as the output power of the lithium battery increases; Mode 4 is the late stage of voltage sag control; as the output power of the lithium battery increases, when the load reaches When the required compensation power is 0, the output power of the supercapacitor is 0, and the switch Disconnect, load Powered by both the grid and lithium batteries.

3. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 2 is characterized in that: In the peak-valley arbitrage charging mode of mode 1, the grid-connected constant power control is specifically as follows: Voltage sampling collects the instantaneous value of the grid-side voltage , the voltage phase is obtained through the phase-locked loop , through the abc / dq conversion transformation, the instantaneous value of the grid-side voltage in the dq coordinate system is obtained ; Current sampling collects the instantaneous value of the three-phase inductor current , after abc / dq conversion, the instantaneous value of the inductor current in the dq coordinate system is obtained ; The inductor current reference value in the dq coordinate system obtained after the power outer loop is calculated by the PI controller and the instantaneous value of the inductor current in the dq coordinate system The error value obtained by comparison is added and subtracted from the output value of the PI controller after operation, the feedforward value and the decoupling term to obtain the output voltage value in the dq coordinate system. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then a space vector pulse width modulation wave is generated, and then 12 pulse width modulation wave drive signals are generated to realize grid-connected constant power control.

4. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 2 is characterized in that: In the peak-valley arbitrage discharge mode of mode 2, the constant voltage and constant frequency control is specifically: The control target of the voltage outer loop is the load side voltage. The instantaneous value of the three-phase voltage in the abc coordinate system is obtained by voltage sampling. , and then the instantaneous voltage value in the dq coordinate system is obtained through abc / dq conversion , the voltage reference value in the dq coordinate system And the instantaneous value of voltage in dq coordinate system The error value obtained by comparison is the inductor current reference value in the dq coordinate system output by the PI controller. As the reference value of the current inner loop; the instantaneous value of the three-phase inductor current in the abc coordinate system is obtained through current sampling , and then the instantaneous value of the current in the dq coordinate system is obtained through abc / dq conversion , the inductor current reference value in the dq coordinate system and the instantaneous value of current in the dq coordinate system The error value obtained by the PI controller is added and subtracted from the voltage feedforward and the load term to obtain the output voltage value. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then a space vector pulse width modulation wave is generated, and then 12 pulse width modulation wave drive signals are generated to achieve constant voltage and constant frequency control.

5. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 1 is characterized in that: The step 2 specifically includes: Step S21: The Teager-Kaiser energy operator converts the instantaneous voltage value into an envelope to enhance the voltage sag feature. The expression is: ； In the formula, is the Teager-Kaiser energy operator, is the instantaneous value of voltage, is the voltage peak value, is the frequency, is the initial phase, is the instantaneous value of voltage The square of the first derivative, is the instantaneous value of voltage Second order derivative; Step S22: Establish a variational constraint model, the expression is: ； In the formula, For the The decomposed intrinsic mode function components, is the time t decomposed intrinsic mode function components; is the decomposition mode number, It is the voltage sag signal. is the impulse function, For the The center frequency of the eigenmode function components, is the gradient operation, is a constraint condition; is an imaginary unit; is the phase angle that changes with time t; Step S23: By introducing the augmented Lagrangian function L , the constrained variational problem is transformed into an unconstrained variational problem, and the expression is: ； In the formula, is the penalty factor, is the Lagrangian operator, is the inner product operation; is the Lagrangian operator at time t; represents the 2-norm; is the gradient operation; Step S24: Update iterative solution using the multiplication operator alternating direction method The intrinsic mode functions and residual components with fixed bandwidth and center frequency are obtained based on Fourier isometric transform. , and The expressions of the update formula and iteration termination condition are: ； ； ； ； In the formula, and They are and The Fourier transform of is the noise tolerance, is the convergence accuracy; and Respectively The number of samples decomposed intrinsic mode function components and the center frequencies of the intrinsic mode function components; , and They are the original signal after Fourier transform, the The decomposed intrinsic mode function components and the Lagrangian operator after Fourier transformation; The center frequency is No. The Lagrangian operator after Fourier transformation of the number of samples; The center frequency is No. The number of samples Fourier transform of the decomposed intrinsic mode function components; d is the symbol for differentiation; For the The number of samples Fourier transform of the decomposed intrinsic mode function components; Step S25: Calculate the kurtosis coefficient of each eigenmode function and residual component ,choose The largest component is taken as the optimal component, and the expression is; ； In the formula, is the kurtosis coefficient, To detect the signal, is the expected value, is the mean, is the standard deviation; Step S26: Determine the mutation sampling point in the optimal component based on the calculation of the change rate, and the expression is: ； In the formula, is the rate of change, is the sampling point, is the value of the optimal component, is the time interval of sampling points; Calculate different starting thresholds based on the measured voltage sag data and termination threshold The standard deviation between the detection result and the actual result is determined, and the threshold corresponding to the minimum standard deviation is determined as the optimal detection threshold; When When , it indicates that the voltage sag is over; Step S27: For Phase voltage, record the time when the sag occurs according to the detection results and the end time of the temporary landing The instantaneous value of voltage and ; The instantaneous change of voltage for: ； In the formula, is the voltage reference value at time t; for Phase voltage The instantaneous value of voltage at the moment; Reconstruct the instantaneous value of the three-phase voltage after the sag into a space vector, and for and The three-phase voltage space vector at time, and for and The angle with the positive direction of the real axis; The starting and ending phases of the phase voltage sag are ;in, and Respectively expressed as: ； In the formula, is the imaginary part, is the real part; and The time when the temporary drop occurs and the end time of the temporary landing The instantaneous value of voltage and The space vector of Similarly, obtain Harmony Phase voltage sag characteristics.

6. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 5 is characterized in that: The step 3 specifically includes: for The flexible optimal energy compensation strategy is: Step S31: When a voltage sag occurs, the active power output by the hybrid energy storage system The expression is: ； In the formula, is the voltage of sensitive equipment during voltage sag, is the grid voltage during voltage sag, It is the current of sensitive equipment during voltage sag; is the power factor angle, The grid voltage during voltage sag and sensitive equipment current The phase of When a shallow voltage sag occurs, :The phase δ is adjusted by the compensation voltage provided by the hybrid energy storage system, so that the compensation voltage provided by the hybrid energy storage system Current of sensitive equipment during voltage sag Mutually perpendicular, that is, active power At this time, the hybrid energy storage system only provides reactive power to achieve voltage sag control, and the compensation voltage The expression is: ； In the formula, is the voltage of sensitive equipment before the temporary drop, phase , The compensation voltage phase provided for the hybrid energy storage system, It is the phase jump during the temporary sag; When a deep voltage sag occurs, :The phase is adjusted by the compensation voltage provided by the hybrid energy storage system , so that the compensation voltage Current of sensitive equipment during voltage sag The phase is the same; at this time, the compensation voltage It is expressed as: ； Step S32: During the commissioning phase, the hybrid energy storage system provides a compensation voltage by flexibly switching the voltage phase to avoid causing a large phase jump; According to the vector relationship, the amplitude of the compensation voltage provided by the hybrid energy storage system during the shallow voltage sag and deep voltage sag is The expression is: ； According to the vector relationship, the initial phase of the compensation voltage provided by the hybrid energy storage system during the shallow voltage sag and deep voltage sag is The expression is: ； ； According to the vector relationship, during shallow voltage sag and deep voltage sag, the termination phase of the compensation voltage provided by the hybrid energy storage system during the input stage The compensation voltage phase ,Right now: ; During the commissioning phase, sensitive equipment experiences phase jumps when voltage sags are controlled If no tripping occurs at this time, it means that the phase jump that the sensitive equipment can tolerate becomes ; The initial phase of the compensation voltage provided by the hybrid energy storage system The load voltage maintains the phase state before the voltage sag , after the transition phase of investment The termination phase of flexible switching to the compensation voltage provided by the hybrid energy storage system The phase state of the load voltage to achieve the optimal energy compensation strategy ; According to the phase change in the input stage, the voltage phase flexible switching expression is: ； In the formula, Provides the phase of the compensation voltage for the hybrid energy storage system during the input phase. and They are the initial time and the end time of the investment phase respectively; for the current moment; The transition phase of investment The expression is: ； In the formula, Phase jump before and after the hybrid energy storage system is controlled, and the shallow voltage drop occurs , deep voltage sag ;according to Round up the number of steps and switch the step length accordingly Calculate the transition phase of input; Step S33: In the cut-out stage, the hybrid energy storage system provides a compensation voltage by flexibly switching the voltage phase to avoid causing a large phase jump; According to the vector relationship, the amplitude of the compensation voltage provided by the hybrid energy storage system during the cut-out phase , the expression is: ； In the formula, The phase jump occurs when the voltage sag is restored for sensitive equipment; Provides the intermediate phase of the compensation voltage for the hybrid energy storage system during the cut-out phase. Providing compensation voltage phase for the hybrid energy storage system during the cut-out phase; According to the vector relationship, the initial phase of the compensation voltage provided by the hybrid energy storage system during the cut-out phase , Middle Phase and termination phase The expression is: ； In the cut-out phase, the initial phase of the compensation voltage provided by the hybrid energy storage system is Equal to the end phase of the input phase ; Sensitive equipment experiences phase jump when voltage sag recovers If no tripping occurs at this time, it means that the phase jump that the sensitive equipment can tolerate becomes ; The starting phase of the compensation voltage provided by the hybrid energy storage system Instantaneous switching to mid-phase , maintain the load voltage at the phase state when the voltage sags , the sensitive device has a phase jump again Still no jump stop occurs; after the transition phase of cutting out The termination phase of flexible switching to the compensation voltage provided by the hybrid energy storage system , the load voltage returns to the normal grid voltage ; According to the phase change in the cut-out stage, the voltage phase flexible switching expression is: ； In the formula, Provides the phase of the compensation voltage for the hybrid energy storage system during the cut-out phase. and are the middle time and the end time of the cut-out phase respectively; Cut-out transition stage The expression is: ； In the formula, The phase jump of voltage sag recovery is Round up the number of steps and switch the step length accordingly Calculate the transition phase of cut-out; Harmony Flexible optimal energy compensation strategy for phase The same.

7. The SE voltage sag control method based on flexible reuse of energy storage system according to claim 2 is characterized in that: The step 4 specifically includes: Step S41: performing power frequency division control on the DC / DC converters in the lithium battery and the supercapacitor, specifically: Under voltage sag, the active power demand of sensitive equipment is divided into low-frequency component and high-frequency component; The three-phase summation gives the active power demand value of the hybrid energy storage system , through a low-pass filter, according to the low-frequency component and high-frequency component The active power demand value of lithium batteries and supercapacitors is allocated, that is, and ; In lithium batteries, according to the active power demand value of lithium batteries and lithium battery active power measurement The difference between the calculation of lithium battery current reference value ; In supercapacitors, the active power requirement of supercapacitors is and the active power measurement of the supercapacitor The difference addition and The difference between the supercapacitor current reference value is calculated ; The current feedback inner loop is based on the lithium battery current reference value and lithium battery current measurement value The duty cycle of the lithium battery is calculated based on the difference between and supercapacitor current measurement The duty cycle of the supercapacitor is calculated by the difference between the values ​​of and , thereby generating a pulse signal by pulse width modulation; Step S42: Compensation voltage reference value provided by the hybrid energy storage system according to the flexible optimal energy compensation strategy Construct a composite control system including a voltage feedforward loop, a voltage feedback outer loop, and a current feedback inner loop to control the DC / AC converter; The voltage feed-forward loop is based on the compensation voltage reference Compensation voltage with hybrid energy storage system u HESS The difference between the feedforward voltage reference value of the hybrid energy storage system is calculated by ; The voltage feedback outer loop is based on the feedforward voltage reference value Calculate the current reference value of sensitive equipment ; The current feedback inner loop is based on and sensitive equipment current The difference between the two is used to calculate the feedback voltage reference value of the hybrid energy storage system , and according to the feedforward voltage reference and feedback voltage reference Calculate voltage reference values ​​for sensitive devices ; Step S43: A quasi-resonant controller is added to the PI controller of voltage feedback and current feedback to achieve zero-error tracking of the AC signal and eliminate harmonics of a specific frequency; the transfer function expression of the quasi-resonant controller is: ； In the formula, for The gain of the sub-resonant controller, is the fundamental frequency, is the resonant frequency bandwidth; is the Lagrangian operator; The transfer function expression of the proportional-integral multi-quasi-resonant controller used to control odd-order harmonics is: ； In the formula, is the proportionality coefficient, is the integration coefficient.

8. The SE voltage sag management system based on flexible reuse of energy storage system is characterized by: include: Topology of hybrid energy storage system for voltage sag control: including hybrid energy storage system composed of lithium battery energy storage system and super capacitor, which can achieve early control of voltage sag through super capacitor and continuous control of voltage sag through lithium battery energy storage system; Detection unit: Through the detection method based on the Teager-Kaiser energy operator and the improved variational mode decomposition of the kurtosis coefficient, the real-time and accurate detection of the voltage sag on the grid side and the load side is realized; Compensation unit: adopts flexible optimal energy compensation strategy, and realizes optimal energy compensation through flexible switching in the input and output stages, so as to avoid the sensitive equipment from tripping due to phase jump caused by optimal energy compensation; Control system: On the DC / DC side, the output is coordinated through power frequency division control according to the difference in response characteristics between the supercapacitor and lithium battery energy storage systems; On the DC / AC side, composite control is performed through a voltage feedforward loop, a voltage feedback outer loop, and a current feedback inner loop, and a proportional-integral quasi-resonant controller is used to eliminate the secondary effects of harmonics on sensitive equipment.

9. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 8 is characterized in that: The hybrid energy storage system includes a super capacitor and a lithium battery in the topological structure of the hybrid energy storage system for managing voltage sag; the super capacitor and the switch After being connected in series, they are connected in parallel with lithium batteries; the hybrid energy storage system is connected in parallel with the grid for peak-valley arbitrage, and is connected to the grid through DC / AC converters, LC filters and thyristors in turn; the hybrid energy storage system is connected in series with sensitive equipment for voltage sag control, and is connected to the load through DC bus, DC / AC inverter and LC filter, and transformer coupling in turn. ; The topology described contains four operating modes: Mode 1 is the peak-valley arbitrage charging mode; during the low electricity price period, the thyristor is turned on and the switch Closed, Load In the grid-connected operation state, the grid voltage For load powered by; The grid-connected constant power control is adopted, and the power grid supplies the lithium battery U LB and supercapacitors C sc Charging; when charging is completed, the grid-connected constant power control stops outputting pulse signals to the DC / AC inverter, and the hybrid energy storage system is in a fully charged standby state; Mode 2 is the peak-to-valley arbitrage discharge mode; During high electricity price periods, the thyristor is turned off and the switch Disconnect, load In the island operation state, constant voltage and constant frequency control is adopted by lithium battery U LB For load Power supply; when the discharge is completed, the thyristor is turned on and the load The grid-connected operation state is restored, that is, the power grid supplies power to the load; the hybrid energy storage system is in standby state with surplus power, waiting for the arrival of a low electricity price period to start charging; Mode 3 is the early stage of voltage sag control; when voltage sag occurs, the grid voltage and the hybrid energy storage system act as loads. Power supply; switch Closed, supercapacitor C sc and lithium batteries U LB Power supply at the same time; super capacitor C sc Output power exceeding a specific value within a set time threshold to achieve voltage sag control; and supercapacitor C sc The power of lithium battery U LB The output power is reduced as it increases; Mode 4 is the late stage of voltage sag control; with the lithium battery U LB The output power is increased when the load The required compensation power is when the supercapacitor C sc The output power is 0, the switch Disconnect, load Powered by the grid and lithium batteries U LB Power supply at the same time.

10. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 9 is characterized in that: In the peak-valley arbitrage charging mode of mode 1, the grid-connected constant power control is specifically as follows: Voltage sampling collects the instantaneous value of the grid-side voltage , the voltage phase is obtained through the phase-locked loop , through the abc / dq conversion transformation, the instantaneous value of the grid-side voltage in the dq coordinate system is obtained ; Current sampling collects the instantaneous value of the three-phase inductor current , after abc / dq conversion, the instantaneous value of the inductor current in the dq coordinate system is obtained ; The inductor current reference value in the dq coordinate system obtained after the power outer loop is calculated by the PI controller and the instantaneous value of the inductor current in the dq coordinate system The error value obtained by comparison is added and subtracted from the output value of the PI controller after operation, the feedforward value and the decoupling term to obtain the output voltage value in the dq coordinate system. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then a space vector pulse width modulation wave is generated, and then 12 pulse width modulation wave drive signals are generated to realize grid-connected constant power control.

11. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 9 is characterized in that: In the peak-valley arbitrage discharge mode of mode 2, the constant voltage and constant frequency control is specifically: The control target of the voltage outer loop is the load side voltage. The instantaneous value of the three-phase voltage in the abc coordinate system is obtained by voltage sampling. , and then the instantaneous voltage value in the dq coordinate system is obtained through abc / dq conversion , the voltage reference value in the dq coordinate system And the instantaneous value of voltage in dq coordinate system The error value obtained by comparison is the inductor current reference value in the dq coordinate system output by the PI controller. As the reference value of the current inner loop; the instantaneous value of the three-phase inductor current in the abc coordinate system is obtained through current sampling , and then the instantaneous value of the current in the dq coordinate system is obtained through abc / dq conversion , the inductor current reference value in the dq coordinate system and the instantaneous value of current in the dq coordinate system The error value obtained by the PI controller is added and subtracted from the voltage feedforward and the load term to obtain the output voltage value. , and then the voltage component in the αβ coordinate system is obtained through dq / αβ coordinate transformation, and then a space vector pulse width modulation wave is generated, and then 12 pulse width modulation wave drive signals are generated to achieve constant voltage and constant frequency control.

12. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 8, characterized in that: The detection unit realizes real-time and accurate detection of grid-side and load-side voltage sags specifically as follows: The Teager-Kaiser energy operator converts the instantaneous voltage value into an envelope, and the voltage sag feature enhancement expression is: ； In the formula, is the Teager-Kaiser energy operator, is the instantaneous value of voltage, is the voltage peak value, is the frequency, is the initial phase, is the instantaneous value of voltage The square of the first derivative, is the instantaneous value of voltage Second order derivative; The expression of the variational constraint model is established as: ； In the formula, For the The decomposed intrinsic mode function components, is the time t decomposed intrinsic mode function components; is the decomposition mode number, is the voltage sag signal, is the impulse function, For the The center frequency of the eigenmode function components, is the gradient operation, is a constraint condition; is an imaginary unit; is the phase angle that changes with time t; By introducing the augmented Lagrangian function L , the constrained variation problem is transformed into an unconstrained variation problem expression: ； In the formula, is the penalty factor, is the Lagrangian operator, is the inner product operation; is the Lagrangian operator at time t; represents the 2-norm; is the gradient operation; The multiplication operator alternating direction method is used to update the iterative solution K an intrinsic mode function and residual components with fixed bandwidth and center frequency; Based on Fourier isometric transform, , and The update formula and iteration termination condition expression are: ； ； ； ； In the formula, and They are and The Fourier transform of is the noise tolerance, is the convergence accuracy; and Respectively The number of samples decomposed intrinsic mode function components and the center frequencies of the intrinsic mode function components; , and They are the original signal after Fourier transform, the The decomposed intrinsic mode function components and the Lagrangian operator after Fourier transformation; The center frequency is No. The Lagrangian operator after Fourier transformation of the number of samples; The center frequency is No. The number of samples Fourier transform of the decomposed intrinsic mode function components; d is the symbol for differentiation; For the The number of samples Fourier transform of the decomposed intrinsic mode function components; Calculate the kurtosis coefficient of each eigenmode function and residual component ,choose The largest component is expressed as the optimal component: ； In the formula, is the kurtosis coefficient, To detect the signal, is the expected value, is the mean, is the standard deviation; The expression for determining the mutation sampling point in the optimal component based on the calculation of the change rate is: ； In the formula, is the rate of change, is the sampling point, is the value of the optimal component, is the time interval of sampling points; Calculate different starting thresholds based on the measured voltage sag data and termination threshold The standard deviation between the detection result and the actual result is determined, and the threshold corresponding to the minimum standard deviation is determined as the optimal detection threshold; When When , it indicates that the voltage sag is over; for Phase voltage, record the time when the sag occurs according to the detection results and the end time of the temporary landing The instantaneous value of voltage and ; The instantaneous change of voltage The expression is: ； In the formula, is the voltage reference value at time t; for Phase voltage The instantaneous value of voltage at the moment; Reconstruct the instantaneous value of the three-phase voltage after the sag into a space vector, and for and The three-phase voltage space vector at time, and for and The angle with the positive direction of the real axis; The starting and ending phases of the phase voltage sag are ;in, and Respectively expressed as: ； In the formula, is the imaginary part, is the real part; and The time when the temporary drop occurs and the end time of the temporary landing The instantaneous value of voltage and The space vector of Similarly, obtain Harmony Phase voltage sag characteristics.

13. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 12, characterized in that: The compensation unit realizes optimal energy compensation specifically including: For phase a, the flexible optimal energy compensation strategy is: When a voltage sag occurs, the active power output of the hybrid energy storage system It is expressed as: ； In the formula, is the voltage of sensitive equipment during voltage sag, is the grid voltage during voltage sag, It is the current of sensitive equipment during voltage sag; is the power factor angle, The grid voltage during voltage sag and sensitive equipment current The phase of When a shallow voltage sag occurs, :The phase is adjusted by the compensation voltage provided by the hybrid energy storage system , so that the compensation voltage provided by the hybrid energy storage system Current of sensitive equipment during voltage sag Mutually perpendicular, that is, active power At this time, the hybrid energy storage system only provides reactive power to achieve voltage sag control, and the compensation voltage It is expressed as: ； In the formula, is the voltage of the sensitive equipment before the temporary drop, phase , The compensation voltage phase provided for the hybrid energy storage system, It is the phase jump during the temporary sag; When a deep voltage sag occurs, :The phase is adjusted by the compensation voltage provided by the hybrid energy storage system , so that the compensation voltage Current of sensitive equipment during voltage sag The phases are the same; at this time, the compensation voltage The expression is: ； During the commissioning phase, the hybrid energy storage system provides compensation voltage by flexibly switching the voltage phase to avoid large phase jumps. According to the vector relationship, the amplitude of the compensation voltage provided by the hybrid energy storage system during the shallow voltage sag and deep voltage sag is The expression is: ； According to the vector relationship, the initial phase of the compensation voltage provided by the hybrid energy storage system during the shallow voltage sag and deep voltage sag is The expression is: ； ； According to the vector relationship, during shallow voltage sag and deep voltage sag, the termination phase of the compensation voltage provided by the hybrid energy storage system during the input stage The compensation voltage phase ,Right now: ; During the commissioning phase, sensitive equipment experiences phase jumps when voltage sags are controlled If no tripping occurs at this time, it means that the phase jump that the sensitive equipment can tolerate becomes ; The initial phase of the compensation voltage provided by the hybrid energy storage system The load voltage maintains the phase state before the voltage sag , after the transition phase of investment The termination phase of flexible switching to the compensation voltage provided by the hybrid energy storage system The phase state of the load voltage to achieve the optimal energy compensation strategy ; From the phase change in the input stage, the voltage phase flexibly switches to: ； In the formula, Provides the phase of the compensation voltage for the hybrid energy storage system during the input phase. and are the initial time and the end time of the investment phase respectively. for the current moment; The transition phase of investment The expression is: ； In the formula, Phase jump before and after the hybrid energy storage system is controlled, and the shallow voltage drop occurs , deep voltage sag ;according to Round up the number of steps and switch the step length accordingly Calculate the transition phase of input; In the cut-out phase, the hybrid energy storage system provides compensation voltage by flexibly switching the voltage phase to avoid large phase jumps; According to the vector relationship, the amplitude of the compensation voltage provided by the hybrid energy storage system during the cut-out phase The expression is: ； In the formula, The phase jump occurs when the voltage sag is restored for sensitive equipment; Provides the intermediate phase of the compensation voltage for the hybrid energy storage system during the cut-out phase. Providing compensation voltage phase for the hybrid energy storage system during the cut-out phase; According to the vector relationship, the initial phase of the compensation voltage provided by the hybrid energy storage system during the cut-out phase , Middle Phase and termination phase The expression is: ； In the cut-out phase, the initial phase of the compensation voltage provided by the hybrid energy storage system is Equal to the end phase of the input phase ; Sensitive equipment experiences phase jump when voltage sag recovers If no tripping occurs at this time, it means that the phase jump that the sensitive equipment can tolerate becomes ; The starting phase of the compensation voltage provided by the hybrid energy storage system Instantaneous switching to mid-phase , maintain the load voltage at the phase state when the voltage sags ; At this time, the sensitive device has a phase jump again Still no jump stop occurs; then, after the transition phase of cutting out The termination phase of flexible switching to the compensation voltage provided by the hybrid energy storage system , the load voltage returns to the normal grid voltage ; According to the phase change in the cut-out stage, the voltage phase flexible switching expression is: ； In the formula, Provides the phase of the compensation voltage for the hybrid energy storage system during the cut-out phase. and are the middle time and the end time of the cut-out phase respectively; Cut-out transition stage The expression is: ； In the formula, The phase jump of voltage sag recovery is Round up the number of steps and switch the step length accordingly Calculate the transition phase of cut-out; Harmony Flexible optimal energy compensation strategy for phase The same.

14. The SE voltage sag management system based on flexible reuse of energy storage system according to claim 9, characterized in that: The control system performs power frequency division control on the DC / DC converters in the lithium battery and supercapacitor, specifically: Under voltage sag, the active power demand of sensitive equipment is divided into low-frequency component and high-frequency component; The three-phase summation gives the active power demand value of the hybrid energy storage system , through a low-pass filter, according to the low-frequency component and high-frequency component The active power demand value of lithium batteries and supercapacitors is allocated, that is, and ; In lithium batteries, according to the active power demand value of lithium batteries and lithium battery active power measurement The difference between the calculation of lithium battery current reference value ; In supercapacitors, the active power requirement of supercapacitors is and the active power measurement of the supercapacitor The difference addition and The difference between the supercapacitor current reference value is calculated ; The current feedback inner loop is based on the lithium battery current reference value and lithium battery current measurement value The duty cycle of the lithium battery is calculated based on the difference between and supercapacitor current measurement The duty cycle of the supercapacitor is calculated by the difference between the values ​​of and , thereby generating a pulse signal by pulse width modulation; The control system is based on the compensation voltage reference value provided by the hybrid energy storage system according to the flexible optimal energy compensation strategy Construct a composite control system including a voltage feedforward loop, a voltage feedback outer loop and a current feedback inner loop to control the DC / AC converter; specifically: The voltage feed-forward loop is based on the compensation voltage reference Compensation voltage with hybrid energy storage system u HESS The difference between the feedforward voltage reference value of the hybrid energy storage system is calculated by ; The voltage feedback outer loop is based on the feedforward voltage reference value Calculate the current reference value of sensitive equipment ; The current feedback inner loop is based on and sensitive equipment current The difference between the two is used to calculate the feedback voltage reference value of the hybrid energy storage system , and according to the feedforward voltage reference and feedback voltage reference Calculate voltage reference values ​​for sensitive devices ; A quasi-resonant controller is added to the PI controller of voltage feedback and current feedback to achieve zero-error tracking of the AC signal and eliminate harmonics of specific frequencies. The transfer function expression of the quasi-resonant controller is: ； In the formula, for The gain of the sub-resonant controller, is the fundamental frequency, is the resonant frequency bandwidth; is the Lagrangian operator; The transfer function expression of the proportional-integral multi-quasi-resonant controller used to control odd-order harmonics is: ； In the formula, is the proportionality coefficient, is the integration coefficient.

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