Network construction type energy storage control method and system suitable for black start

Abstract

The invention discloses a network construction type energy storage control method and system suitable for black start, and the method comprises the steps: obtaining a three-phase current actual value of a converter side to judge whether an overcurrent fault occurs or not, and switching off a pulse modulation signal of a switching device in a converter when the overcurrent fault is judged to occur; when it is judged that the overcurrent fault does not occur, a three-phase voltage instruction value, output by the power control loop, of the converter is obtained; obtaining a three-phase current actual value of the converter side, enabling the three-phase current actual value to sequentially pass through the virtual resistor and the high-pass filter to obtain a three-phase voltage compensation value, and obtaining a three-phase capacitance current actual value, corresponding to the three-phase voltage compensation value, in the high-pass filter; the difference value between the three-phase voltage instruction value and the three-phase voltage compensation value is used as a compensated three-phase voltage instruction value; and determining a pulse modulation signal of a switching device in the converter according to a difference value between the actual value of the three-phase capacitance current passing through the damping coefficient and the compensated three-phase voltage instruction value. Wave sealing control is applied, fault current limiting is achieved, and the stability of a power grid is improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy technology, and in particular, relates to a grid-connected energy storage control method and system suitable for black start. Background Art

[0002] With the rapid development of new power systems, the proportion of new energy grids is increasing, and its volatility, uncertainty, and weak inertia support are becoming more and more obvious. Since the voltage frequency and amplitude of distributed energy are not completely consistent with the grid standards, they usually need the help of power electronic converters to successfully connect to the grid. In the case of low installed capacity of new energy, this control method has little impact on the stability of the system because traditional generators can provide the necessary stability support for the power system. However, as new energy continues to be connected to the grid and its proportion increases, traditional generators are no longer sufficient to ensure the stable operation of the power system. In addition, distributed power generation systems that use power electronic converters as interfaces lack the inertia and damping effects inherent in traditional motors, making the power system more susceptible to power fluctuations and system failures.

[0003] In the prior art, a three-loop network control strategy is proposed to address the above problems, that is, closed-loop control is performed for power, current, and voltage respectively, which can not only ensure the tracking accuracy of the network control strategy for electrical quantities such as voltage and current, but also effectively limit the voltage and current output by the energy storage unit to prevent the system from damaging the IGBT of the converter due to overcurrent. However, this control technology not only has problems such as complex parameter design and serious interaction between multiple control loops, but also affects the stability of the entire system. In addition, the most commonly used control strategy is PI control, which will have a steady-state error when tracking sinusoidal inputs. Although the three-phase alternating current is converted from a three-phase stationary coordinate system to a two-phase rotating coordinate system, the transformation further increases the complexity and control difficulty of the system, resulting in a further reduction in the transient stability of the system, making it impossible for the network control strategy to suppress disturbances in time, resulting in a reduction in the dynamic response performance of the system. The network control technology based on a single power loop not only enhances the robustness of the system, but also improves the dynamic support capability and transient stability of the system. However, this technical route does not have the current limiting capability. The maximum impact current under extreme conditions such as short circuit can reach more than 10 times the rated current of the system, which seriously limits the application prospects of this technical route. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a grid-type energy storage control method and system suitable for black start, which is based on a single-power ring grid-type control method and combines the application of IGBT switch "wave sealing" technology in a closed-loop control strategy to achieve single-ring grid-type control with adaptive current limiting capability. It has high flexibility and accuracy, and at the same time has a stable fault current limiting function. It can quickly adjust the working state of the energy storage inverter according to the actual situation of the power grid, help balance the supply and demand relationship of the power grid, and make the system present a stable impedance characteristic, thereby improving the stability and reliability of the power grid.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a grid-type energy storage control method suitable for black start, and the converter of the grid-type energy storage adopts a power control loop, including:

[0007] The actual value of the three-phase current on the converter side is obtained to determine whether an overcurrent fault occurs. When it is determined that an overcurrent fault occurs, the pulse modulation signal of the switch device in the converter is turned off; when it is determined that no overcurrent fault occurs, the three-phase voltage command value of the converter of the grid-type energy storage output by the power control loop is obtained;

[0008] The actual value of the three-phase current on the converter side of the grid-type energy storage is obtained, and the three-phase current actual value is sequentially passed through a virtual resistor and a high-pass filter to obtain a three-phase voltage compensation value. At the same time, the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value is obtained; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, the pulse modulation signal of the switching device in the converter is determined.

[0009] Preferably, when the actual value of the three-phase current on the converter side is greater than a set current threshold, it is determined that an overcurrent fault has occurred, wherein the set current threshold is not greater than 3 times the rated current of the inverter.

[0010] Preferably, the power control loop comprises: an active power control loop;

[0011] A fault phase difference feedback loop and an active power droop coefficient correction unit are established in the active power droop control loop, including: obtaining the grid-side frequency and the converter-side frequency output by the active power droop control loop, feeding back the deviation of the converter-side frequency relative to the grid-side frequency to the input end of the active power droop control loop after passing through the frequency adjustment coefficient, and at the same time using the converter-side frequency to correct the active power droop coefficient.

[0012] Preferably, the power control loop comprises: a reactive power control loop;

[0013] A fault voltage difference compensation unit is established in the reactive power droop control loop, including: feeding back the deviation of the actual voltage amplitude value relative to the voltage amplitude reference value to the reactive power droop control loop after passing through the reactive loop proportional coefficient, compensating the voltage amplitude after reactive droop adjustment, and taking the sum of the compensated voltage amplitude after passing through the reactive loop integral coefficient and the voltage amplitude reference value as the d-axis component of the voltage amplitude command value output by the reactive power droop control loop, and the q-axis component of the voltage amplitude command value output by the reactive power droop control loop is 0.

[0014] Preferably, the transfer function of the improved power control loop satisfies the following relationship:

[0015]

[0016] Where P ref is the active power reference value, P is the actual active power value, f dit is the frequency adjustment coefficient, f is the frequency on the converter side, and f g is the grid side frequency, T1 is the filter coefficient, D p is the active droop coefficient, J is the virtual moment of inertia, s is the operator, and θ is the phase of the internal potential of the VSG;

[0017] Q ref is the reactive power reference value, Q is the reactive power actual value, D q is the reactive power droop coefficient, U ref is the voltage amplitude reference value, U is the voltage amplitude actual value, k v is the reactive loop proportional coefficient, K i is the reactive loop integral coefficient, V md and V mq They are respectively the d-axis component and q-axis component of the voltage amplitude command value output by the reactive power droop control loop.

[0018] Preferably, the value range of each parameter in the transfer function of the improved power control loop includes:

[0019] T1∈(0.01, 0.1), J∈(1, 100), f dit ∈(20,100),D p ∈(10,50),D q ∈(0.1, 1), k v ∈(0.1, 10), K i =1.

[0020] Preferably, the phase of the internal potential of the improved power control loop output VSG, the d-axis component and the q-axis component of the voltage amplitude command value are synthesized through three-phase voltage to obtain a three-phase voltage command value.

[0021] Preferably, the actual value of the three-phase current on the converter side is abc Through the virtual resistor R v And high-pass filter HPF to obtain the three-phase voltage compensation value; the three-phase voltage command value u abc The difference between the three-phase voltage compensation value and the three-phase voltage command value u′ after compensation abc , satisfying the following relationship:

[0022] u′ abc =u abc -HPF(R v ·i abc )

[0023] Where HPF() represents the transfer function of the high-pass filter.

[0024] Preferably, the virtual resistance range is R v ∈(1,5), the cutoff frequency of the high-pass filter is greater than or equal to 100 Hz and less than or equal to 300 Hz.

[0025] Preferably, the actual value i of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value is cabc After the damping coefficient, the three-phase voltage command value u′ after compensation abc The difference u′ a ' bc , satisfying the following relationship:

[0026] u′ a ' bc =u′ abc -K p i cabc

[0027] In the formula, K p is the damping coefficient.

[0028] Preferably, K p ∈(0.2, 2).

[0029] The present invention also proposes a grid-connected energy storage control system suitable for black start, comprising:

[0030] The pulse control module is used to obtain the actual value of the three-phase current on the converter side to determine whether an overcurrent fault occurs. When it is determined that an overcurrent fault occurs, the pulse modulation signal of the switch device in the converter is turned off; when it is determined that no overcurrent fault occurs, the three-phase voltage command value of the converter with grid-type energy storage output by the power control loop is obtained to be input into the pulse modulation module;

[0031] The pulse modulation module is used to obtain the actual value of the three-phase current on the converter side of the grid-type energy storage. The actual value of the three-phase current passes through the virtual resistor and the high-pass filter in sequence to obtain the three-phase voltage compensation value, and at the same time obtains the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, the pulse modulation signal of the switching device in the converter is determined.

[0032] The beneficial effects of the present invention are that, compared with the prior art, at least the present invention proposes a control strategy for grid-connected energy storage suitable for black start. Since the present invention proposes to abandon the traditional current inner loop PI control and only retain the improved power control loop, the problems of strong coupling, high order, and complex design in the traditional three-loop control strategy are avoided; and without the current inner loop PI control, the IGBT is directly "wave-sealed" controlled, avoiding the variable tracking offset and coupling problems caused by the dq coordinate transformation in the traditional three-loop control strategy; since the above-mentioned various problems are avoided, it is more conducive to giving full play to the rapid response capability of the grid-connected energy storage under black start. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a block diagram of a single-loop control system of a grid-type energy storage converter of the present invention;

[0034] Figure 2 is a current waveform diagram under a three-phase zero-through fault after applying a grid-forming energy storage control method suitable for black start in an embodiment of the present invention;

[0035] Figure 3 is a voltage waveform diagram under a three-phase zero-through fault after a grid-forming energy storage control method suitable for black start is applied in an embodiment of the present invention;

[0036] Figure 4 is a current waveform diagram under a positive mutation of the grid phase angle of 60° after the grid-forming energy storage control method suitable for black start is applied in the embodiment of the present invention;

[0037] Figure 5 is a voltage waveform diagram under a positive mutation of the grid phase angle of 60° after the grid-forming energy storage control method suitable for black start is applied in the embodiment of the present invention;

[0038] Figure 6 The embodiment of the present invention is an active power waveform diagram under a positive sudden change of the grid phase angle by 60° after the grid-forming energy storage control method suitable for black start is applied in the embodiment of the present invention;

[0039] Figure 71 is a Bode diagram of amplitude-frequency and phase-frequency characteristics under three working conditions in the embodiment of the present invention.

[0040] Flowchart of a proposed grid-connected energy storage control method suitable for black start; DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0042] The converter of grid-type energy storage adopts a single-loop control system, such as Figure 1 shown.

[0043] The present invention proposes a grid-type energy storage control method suitable for black start, which realizes the rapid response control of the grid-type energy storage converter. The grid-type energy storage converter adopts a power control loop 10, which includes: an active power control loop and a reactive power control loop; Figure 2 As shown, the control method includes:

[0044] Step 1, obtain the actual value of the three-phase current on the converter side to determine whether an overcurrent fault occurs. When it is determined that an overcurrent fault occurs, turn off the pulse modulation signal of the switching device in the converter; when it is determined that no overcurrent fault occurs, enter step 2.

[0045] Specifically, the converter of the grid-type energy storage uses IGBT components. For IGBT current limiting, the present invention proposes to abandon the traditional current inner loop PI control and introduce a new IGBT "wave-sealing" control strategy, including:

[0046] The control system of the converter determines whether an overcurrent fault occurs by monitoring the actual value of the three-phase current on the converter side. When an overcurrent fault is determined to occur, the control system turns off the pulse modulation signal of the IGBT to shut down all the IGBTs, that is, "wave blocking". At this time, it is equivalent to opening the inverter branch, and the current drops rapidly, thereby limiting the inverter current. At the same time, the control system starts the fault recording function and performs systematic work such as fault recording. The IGBT "wave blocking" control strategy proposed in the present invention can timely perform current limiting protection on the circuit. Compared with traditional VSG control, it further optimizes the overall performance of the system while ensuring stable operation of the system.

[0047] In the embodiment, when the actual value of the three-phase current on the converter side is greater than a set current threshold, it is determined that an overcurrent fault occurs, wherein the set current threshold is not greater than 3 times the rated current of the inverter.

[0048] The IGBT "wave blocking" control strategy proposed in the present invention can only be implemented on the basis of a sufficiently high stability margin guarantee. The IGBT "wave blocking" control strategy can perform current limiting control very accurately. When applied in the power grid system, it can significantly improve the current limiting capability of grid-type energy storage. In addition, it can also effectively protect the IGBT switching device.

[0049] Step 2: When it is determined that no overcurrent fault occurs, the three-phase voltage command value of the grid-type energy storage converter output by the power control loop is obtained.

[0050] Specifically, a fault phase difference feedback loop and an active power droop coefficient correction unit are established in the active power droop control loop, and a fault voltage difference compensation unit is established in the reactive power droop control loop to obtain an improved power control loop; the improved power control loop outputs the phase of the internal potential of VSG, the d-axis component and the q-axis component of the voltage amplitude command value, and obtains the three-phase voltage command value through three-phase voltage synthesis.

[0051] In the embodiment, the conventional power control loop of the grid-type energy storage converter includes: a PQ droop control loop, wherein the transfer function of the reactive power droop control loop satisfies the following relationship:

[0052]

[0053] Where U cn is the rated value of the terminal voltage, U c is the actual value of the terminal voltage, D q is the reactive power droop coefficient, Q set is the reactive power command value, Q0 is the reactive power output by VSG, is the integrator gain, s is the operator, U is the actual voltage, U n is the no-load voltage;

[0054] The transfer function of the active power droop control loop satisfies the following relationship:

[0055]

[0056] In the formula, ω g is the rated angular velocity, ω is the actual angular velocity, D P is the active power droop coefficient, P set is the active power command value, P0 is the active power output by VSG, J is the virtual moment of inertia, and θ is the phase of the internal potential of VSG;

[0057] Combining equations (1) and (2), the PQ droop control loop is improved, including:

[0058] 1) Establishing a fault phase difference feedback loop and an active power droop coefficient correction unit in the active power droop control loop, including: obtaining the grid side frequency and the converter side frequency output by the active power droop control loop, feeding back the deviation of the converter side frequency relative to the grid side frequency to the input end of the active power droop control loop after passing through the frequency adjustment coefficient, and at the same time using the converter side frequency to correct the active power droop coefficient;

[0059] Specifically, Figure 1 As shown in the figure, in the active power droop control loop before improvement, the active power reference value and the filtered The active power difference between the processed active power actual values ​​is used as the input data of the active power droop control loop, and the active power droop coefficient is used directly; in the improved active power droop control loop, the active power difference and the feedback value of the fault phase difference feedback loop The sum is used as the input data of the active power droop control loop, and the active power droop coefficient is corrected by using the converter side frequency to obtain the corrected active power droop coefficient (f-1)D p .

[0060] The improved active power droop control loop outputs the phase of the internal potential of the VSG; the present invention proposes to establish a fault phase difference feedback loop in the active power droop control loop, which can reduce the phase difference of the internal potential of the VSG during the fault process, and improve the stability margin of the grid-type energy storage control from the phase perspective of the internal potential of the VSG, providing a basis for realizing the "wave-closing" current limiting control of the IGBT.

[0061] 2) Establishing a fault voltage difference compensation unit in the reactive power droop control loop, including: feeding back the deviation of the actual voltage amplitude value relative to the voltage amplitude reference value to the reactive power droop control loop after passing through the reactive loop proportional coefficient, compensating the voltage amplitude after reactive droop adjustment, and taking the sum of the compensated voltage amplitude after passing through the reactive loop integral coefficient and the voltage amplitude reference value as the d-axis component of the voltage amplitude command value output by the reactive power droop control loop, and the q-axis component of the voltage amplitude command value output by the reactive power droop control loop is 0;

[0062] The transfer function of the improved power control loop satisfies the following relationship:

[0063]

[0064] Where P ref is the active power reference value, P is the actual active power value, f dit is the frequency adjustment coefficient, f is the frequency on the converter side, and f g is the grid side frequency, T1 is the filter coefficient, D p is the active droop coefficient, J is the virtual moment of inertia, s is the operator, and θ is the phase of the internal potential of the VSG;

[0065] Q ref is the reactive power reference value, Q is the reactive power actual value, D q is the reactive power droop coefficient, U ref is the voltage amplitude reference value, U is the voltage amplitude actual value, k v is the reactive loop proportional coefficient, K i is the reactive loop integral coefficient, V md and V mq They are respectively the d-axis component and q-axis component of the voltage amplitude command value output by the reactive power droop control loop.

[0066] In the embodiment, T1∈(0.01, 0.1), J∈(1, 100), f dit ∈(20,100),D p ∈(10,50),D q ∈(0.1, 1), k v ∈(0.1, 10), K i = 1. The above parameters have high robustness and can be set to any value within the range of the above parameters to ensure system stability.

[0067] The improved reactive power droop control loop outputs the d-axis component and q-axis component of the voltage amplitude command value; the present invention proposes to establish a fault voltage difference compensation unit in the reactive power droop control loop, which can improve the reactive support capability during the fault process, improve the stability margin of the grid-type energy storage control from the perspective of reactive support performance, and provide a basis for realizing the IGBT "wave blocking" current limiting control.

[0068] The improved power control loop outputs the phase of the internal potential of VSG, the d-axis component and the q-axis component of the voltage amplitude command value, and synthesizes the three-phase voltage to obtain the three-phase voltage command value u abc .

[0069] Step 2, obtain the actual value of the three-phase current on the converter side of the grid-type energy storage, the actual value of the three-phase current passes through the virtual resistor and the high-pass filter in turn to obtain the three-phase voltage compensation value, and at the same time obtain the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, determine the pulse modulation signal m of the switching device in the converter abc .

[0070] Specifically, the actual value of the three-phase current on the converter side is abc Through the virtual resistor R v And high-pass filter HPF to obtain the three-phase voltage compensation value; the three-phase voltage command value u abcThe difference between the three-phase voltage compensation value and the three-phase voltage command value u′ after compensation abc , satisfying the following relationship:

[0071] u′ abc =u abc -HPF(R v ·i abc )

[0072] Where HPF() represents the transfer function of the high-pass filter.

[0073] In the embodiment, R v ∈(1,5), the cutoff frequency of the high-pass filter is greater than or equal to 100 Hz and less than or equal to 300 Hz.

[0074] Specifically, one end of the virtual resistor is input with the three-phase current on the converter side, the other end of the virtual resistor is connected with the input end of the high-pass filter, and the output end of the high-pass filter outputs the compensation value of the three-phase voltage.

[0075] When the grid voltage drops, the three-phase current i collected on the converter side abc After setting the virtual resistance R v , the three-phase voltage is compensated in the form of negative feedback, realizing the function of reducing the three-phase voltage amplitude when the three-phase current amplitude increases, thereby reducing the voltage difference between the converter side and the grid side, and ultimately achieving a reduction in the three-phase current.

[0076] When a three-phase short circuit fault occurs in the power grid, the three-phase current on the converter side increases significantly. Based on the traditional virtual impedance current limiting control, it may cause over-compensation of the three-phase voltage, thereby generating voltage oscillation. Therefore, the present invention sets a high-pass filter HPF in the virtual impedance current limiting controller. Under the action of the high-pass filter, the voltage threshold value is set to obtain a suitable three-phase voltage compensation value, thereby reducing the three-phase voltage while avoiding oscillation caused by over-compensation; and under the joint action of the virtual resistor and the high-pass filter, when the inverter has a low voltage ride-through, the impact of the impact current can be effectively suppressed. The present invention improves the stability margin of the grid-type energy storage control during the power grid short circuit fault process through the virtual resistor and the high-pass filter, and provides a basis for realizing the "wave-sealing" current limiting control of the IGBT.

[0077] Get the actual value i of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value cabc , the actual value of the three-phase capacitor current passes through the damping coefficient K p Finally, it is used as the negative feedback value of the compensated three-phase voltage command value to suppress the harmonics introduced by the high-pass filter to the compensated three-phase voltage command value, thereby ensuring the rapidity and accuracy of the grid-type energy storage control.

[0078] The actual value i of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value cabc After the damping coefficient, the three-phase voltage command value u′ after compensation abc The difference satisfies the following relationship:

[0079] u′ a ' bc =u′ abc -K p i cabc

[0080] In the formula, K p is the damping coefficient.

[0081] In the embodiment, K p ∈(0.2, 2).

[0082] Based on the existing power control loop, the present invention not only retains the advantages of power droop control performance, but also improves the stability margin of grid-type energy storage control from the perspective of the phase of the internal potential of the VSG and the perspective of reactive support performance by improving the power control loop, thereby providing a basis for realizing IGBT "wave-sealing" current limiting control; on the premise of improving the three-phase voltage command output by the power control loop to effectively support the stability margin during the fault process, the three-phase voltage command value under short-circuit fault is dynamically compensated by using virtual resistors and high-pass filters to further improve the stability margin under short-circuit fault, and at the same time, the harmonics of the three-phase voltage command value are dynamically compensated by using the capacitor current of the high-pass filter to obtain a more accurate pulse modulation signal.

[0083] In addition, the present invention dynamically compensates for the three-phase voltage command value under a short-circuit fault and dynamically compensates for the harmonics of the three-phase voltage command value to achieve active damping of the three-phase voltage command value. This innovative application of active damping and IGBT "wave-sealing" current limiting control, active damping provides a guarantee for the implementation of IGBT "wave-sealing" current limiting control. At the same time, the combination of active damping and IGBT "wave-sealing" current limiting control can not only make the grid-type energy storage control proposed in the present invention have good stability and fast response capabilities to meet the needs of black start, but also obtain sufficient current limiting capability to ensure the smooth progress of the black start.

[0084] Compared with the complex and less robust three-loop control strategy, the present invention only retains the power loop, which enhances the robustness of the system. The combination of virtual resistance and high-pass filter realizes current suppression when a short-circuit fault occurs in the circuit. The capacitor current feedback of the high-pass filter is used to suppress the harmonics introduced by the high-pass filter to the compensated three-phase voltage command value, and the resonance of the high-pass filter can be effectively suppressed. Compared with the traditional three-loop control strategy, on the basis of simplifying the complexity of the control strategy, the overcurrent protection of the system is further enhanced.

[0085] When an overcurrent fault occurs, the PWM control strategy is adjusted and the IGBT "wave blocking" strategy is adopted to achieve current limiting. Compared with the traditional three-loop control strategy, the present invention further provides current limiting protection for the system, while avoiding the risk of the converter being subjected to excessive voltage due to grid-side faults, thereby ensuring system stability. When an overcurrent fault occurs, the IGBT "wave blocking" strategy is enabled, so that by judging whether the instantaneous value of the fault current exceeds the high (low) threshold of the current hysteresis loop of the overcurrent fault, the PWM wave function is switched between deactivation and recovery, thereby achieving hard current limiting and protecting the switching device.

[0086] In order to ensure the accuracy and stability of the system, the capacitor current of the filter is introduced to suppress the harmonics of the filter, further optimizing the system performance.

[0087] The present invention also proposes a grid-connected energy storage control system suitable for black start, comprising:

[0088] The pulse control module is used to obtain the actual value of the three-phase current on the converter side to determine whether an overcurrent fault occurs. When it is determined that an overcurrent fault occurs, the pulse modulation signal of the switch device in the converter is turned off; when it is determined that no overcurrent fault occurs, the three-phase voltage command value of the converter with grid-type energy storage output by the power control loop is obtained to be input into the pulse modulation module;

[0089] The pulse modulation module is used to obtain the actual value of the three-phase current on the converter side of the grid-type energy storage. The actual value of the three-phase current passes through the virtual resistor and the high-pass filter in sequence to obtain the three-phase voltage compensation value, and at the same time obtains the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, the pulse modulation signal of the switching device in the converter is determined.

[0090] Under the grid-connected condition, the control method proposed in the present invention is applied, and the corresponding control results are as follows: Figures 2 to 6 As shown by Figures 2 to 3 It can be seen that when a three-phase zero-through fault occurs in the power system and the voltage at the converter AC port deviates from the normal operating range, the present invention can limit the fault current to about three times the rated current, which not only effectively suppresses system overcurrent but also has a good fault current support capability.

[0091] Depend on Figures 4 to 6It can be seen that when the phase angle suddenly changes by 60°, the present invention has good adaptive active support capability for frequency changes, and has a response support capability with close to zero delay for phase mutations. The "wave sealing" strategy can ensure that during the transient support process, the active current support is also limited to about three times the current. While ensuring the current limiting capability, it has a strong inertia support capability.

[0092] In MATLAB / Simulink simulation software, a three-phase grid-connected inverter model and control system are established, the parameters of each control link are designed, and the proposed grid-connected single-loop control strategy is verified through simulation to ensure the rapidity of system response while ensuring the stability and inertia of the system. The Bode diagram corresponding to the impedance characteristics of the design control system is shown in the figure below. Figure 7 shown.

[0093] The method is simple to implement and easy to operate. On the basis of the single-power ring-structured network control technology, the IGBT "wave-sealing" control technology based on the secondary protection principle is introduced. It can retain the advantages of the single-power ring-structured network control technology with fast response speed, strong robustness and good stability without affecting the steady-state operation effect of the system. At the same time, it can effectively solve the technical bottleneck that limits the application of the single-ring-structured network control technology, that is, the problem of fault current limiting. And it has good transient / steady-state support consistency during the fault support process, ensuring rapid response while improving the robustness of the system to meet the development needs of the power grid.

[0094] In the method proposed by the present invention, only the power loop is retained to enhance the robustness of the system; a combination of a virtual resistor and a high-pass filter is introduced to realize a current suppression strategy when a short-circuit fault occurs in the circuit; the resonance of the filter is suppressed by means of capacitor current feedback of the filter; when an overcurrent fault occurs, the PWM control strategy is adjusted and the IGBT "wave sealing" strategy is adopted to achieve current limiting; the voltage difference of the reactive loop is adaptively adjusted to adjust the proportional coefficient to realize fast and effective reactive power support of the power grid within a specified time.

[0095] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0096] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0097] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0098] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

[0100] References [1] Ma Zhijun, Liu Jinjun. Research on three-level converter control compatible with fault ride-through[J]. Power Electronics Technology, 2020, 54(11): 106-111.

Claims

1. A grid-type energy storage control method suitable for black start, the grid-type energy storage converter adopts a power control loop, characterized in that: include: The actual value of the three-phase current on the converter side is obtained to determine whether an overcurrent fault occurs. When it is determined that an overcurrent fault occurs, the pulse modulation signal of the switch device in the converter is turned off; When it is determined that no overcurrent fault has occurred, a three-phase voltage command value of a grid-type energy storage converter output by a power control loop is obtained; The actual value of the three-phase current on the converter side of the grid-type energy storage is obtained, and the three-phase current actual value is sequentially passed through a virtual resistor and a high-pass filter to obtain a three-phase voltage compensation value. At the same time, the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value is obtained; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, the pulse modulation signal of the switching device in the converter is determined.

2. The grid-connected energy storage control method suitable for black start according to claim 1, characterized in that: When the actual value of the three-phase current on the converter side is greater than the set current threshold, it is determined that an overcurrent fault has occurred, wherein the set current threshold is not greater than 3 times the rated current of the inverter.

3. The grid-connected energy storage control method suitable for black start according to claim 1, characterized in that: The power control loop includes: an active power control loop; A fault phase difference feedback loop and an active power droop coefficient correction unit are established in the active power droop control loop, including: obtaining the grid-side frequency and the converter-side frequency output by the active power droop control loop, feeding back the deviation of the converter-side frequency relative to the grid-side frequency to the input end of the active power droop control loop after passing through the frequency adjustment coefficient, and at the same time using the converter-side frequency to correct the active power droop coefficient.

4. The grid-connected energy storage control method suitable for black start according to claim 3, characterized in that: The power control loop includes: reactive power control loop; A fault voltage difference compensation unit is established in the reactive power droop control loop, including: feeding back the deviation of the actual voltage amplitude value relative to the voltage amplitude reference value to the reactive power droop control loop after passing through the reactive loop proportional coefficient, compensating the voltage amplitude after reactive droop adjustment, and taking the sum of the compensated voltage amplitude after passing through the reactive loop integral coefficient and the voltage amplitude reference value as the d-axis component of the voltage amplitude command value output by the reactive power droop control loop, and the q-axis component of the voltage amplitude command value output by the reactive power droop control loop is 0.

5. The grid-connected energy storage control method suitable for black start according to claim 4, characterized in that: The transfer function of the improved power control loop satisfies the following relationship: Where P ref is the active power reference value, P is the actual active power value, f dit is the frequency adjustment coefficient, f is the frequency on the converter side, and f g is the grid side frequency, T1 is the filter coefficient, D p is the active droop coefficient, J is the virtual moment of inertia, s is the operator, and θ is the phase of the internal potential of the VSG; Q ref is the reactive power reference value, Q is the reactive power actual value, D q is the reactive power droop coefficient, U ref is the voltage amplitude reference value, U is the voltage amplitude actual value, k v is the reactive loop proportional coefficient, K i is the reactive loop integral coefficient, V md and V mq They are respectively the d-axis component and q-axis component of the voltage amplitude command value output by the reactive power droop control loop.

6. The grid-connected energy storage control method suitable for black start according to claim 5, characterized in that: The value ranges of the parameters in the transfer function of the improved power control loop include: T1∈(0.01,0.1),J∈(1,100),f dit ∈(20,100),D p ∈(10,50),D q ∈(0.1,1),k v ∈(0.1,10),K i =1。 7. The grid-connected energy storage control method suitable for black start according to claim 5, characterized in that: The improved power control loop outputs the phase of the internal potential of the VSG, the d-axis component and the q-axis component of the voltage amplitude command value, and obtains the three-phase voltage command value through three-phase voltage synthesis.

8. The grid-connected energy storage control method suitable for black start according to claim 1, characterized in that: The actual value of the three-phase current on the converter side is i abc Through the virtual resistor R v And high-pass filter HPF to obtain the three-phase voltage compensation value; the three-phase voltage command value u abc The difference between the three-phase voltage compensation value and the three-phase voltage command value u′ after compensation abc , satisfying the following relationship: u′ abc =u abc -HPF(R v ·i abc ) Where HPF() represents the transfer function of the high-pass filter.

9. The grid-connected energy storage control method suitable for black start according to claim 8, characterized in that: The virtual resistance range is R v ∈(1,5), the cutoff frequency of the high-pass filter is greater than or equal to 100 Hz and less than or equal to 300 Hz.

10. The grid-connected energy storage control method suitable for black start according to claim 8, characterized in that: The actual value i of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value cabc After the damping coefficient, the three-phase voltage command value u′ after compensation abc The difference u″ abc , satisfying the following relationship: in" abc =u′ abc -K p and cabc In the formula, K p is the damping coefficient.

11. The grid-connected energy storage control method suitable for black start according to claim 10, characterized in that: K p ∈(0.2，2)。 12. A grid-type energy storage control system suitable for black start, characterized in that: include: A pulse control module is used to obtain the actual value of the three-phase current on the converter side to determine whether an overcurrent fault occurs. When an overcurrent fault is determined to occur, the pulse modulation signal of the switch device in the converter is turned off; When it is determined that no overcurrent fault occurs, the three-phase voltage command value of the grid-type energy storage converter output by the power control loop is obtained to be input into the pulse modulation module; The pulse modulation module is used to obtain the actual value of the three-phase current on the converter side of the grid-type energy storage. The actual value of the three-phase current passes through the virtual resistor and the high-pass filter in sequence to obtain the three-phase voltage compensation value, and at the same time obtains the actual value of the three-phase capacitor current in the high-pass filter corresponding to the three-phase voltage compensation value; the difference between the three-phase voltage command value and the three-phase voltage compensation value is used as the compensated three-phase voltage command value; according to the difference between the actual value of the three-phase capacitor current after the damping coefficient and the compensated three-phase voltage command value, the pulse modulation signal of the switching device in the converter is determined.

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