Unbalanced load control method, device and equipment based on parallel energy storage converter

Abstract

This disclosure presents an embodiment of an unbalanced load control method, apparatus, and device based on parallel energy storage converters. One specific implementation of the method includes: acquiring a converter electrical information set; for each parallel energy storage converter, performing the following generation steps: extracting the three-phase voltage and current information of the converter in sequence; performing voltage-frequency recovery control on the parallel energy storage converter to obtain a positive-sequence voltage component set; performing voltage and current inner and outer loop control on the positive-sequence voltage component set to obtain a converter arm voltage control information set; performing suppression control on the three-phase negative-sequence electrical information set and the three-phase zero-sequence electrical information set to obtain a converter compensation signal set; generating a converter switching control information set; and performing unbalanced load control processing on the parallel energy storage converters. This implementation can efficiently adjust the regulation capability and timeliness of the parallel energy storage converters under unbalanced load conditions, improving the safety of the energy storage converters.

Description

Technical Field

[0001] The embodiments disclosed herein relate to the field of computer technology, and more specifically to an unbalanced load control method, apparatus, and device based on a parallel energy storage converter. Background Technology

[0002] In microgrids, energy storage is used to mitigate fluctuations in renewable energy generation. An architecture employing multiple energy storage converters operating in parallel can increase system capacity and ensure operational reliability. Furthermore, modular parallel technology can adapt to different load conditions, facilitating system expansion, improving robustness, and reducing equipment maintenance costs. For unbalanced load control based on parallel energy storage converters, the common approach is to use a droop control algorithm to manage the unbalanced load in the parallel energy storage converter system.

[0003] However, in practice, it has been found that when using the above method to control unbalanced loads based on parallel energy storage converters, the following technical problems often arise: When the load is unbalanced, the output voltage of the energy storage converter will generate negative sequence and zero sequence components, resulting in three-phase voltage asymmetry, affecting power quality. In parallel operation, due to the difference in line impedance of each PCS module, droop control cannot achieve a reasonable distribution of active and reactive power (especially negative sequence and zero sequence power), leading to increased circulating current, equipment overload, or low utilization. When virtual impedance is introduced to improve power distribution, it will exacerbate the reduction of the PCC (point of common coupling) voltage and cause frequency differences between each converter module, affecting system stability, thereby reducing the safety of the parallel energy storage converter and resulting in low system stability.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background of the present disclosure concept, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The summary portion of this disclosure is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description portion. This summary portion is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0006] Some embodiments of this disclosure propose unbalanced load control methods, apparatuses, and devices based on parallel energy storage converters to solve one or more of the technical problems mentioned in the background section above.

[0007] In a first aspect, some embodiments of this disclosure provide an unbalanced load control method based on parallel energy storage converters, comprising: acquiring a converter electrical information set of a parallel energy storage converter system under islanded operation, wherein the converter electrical information includes at least one of the following: three-phase voltage information, three-phase current information, and capacity information of the converter; for each parallel energy storage converter included in the parallel energy storage converter system, performing the following generation steps: performing sequence extraction processing on the three-phase voltage information and the three-phase current information of the parallel energy storage converter to obtain a three-phase positive sequence electrical information set, a three-phase negative sequence electrical information set, and a three-phase zero sequence electrical information set; generating positive sequence virtual impedance voltage values, negative sequence virtual impedance voltage values, and zero sequence virtual impedance voltage values ​​based on the three-phase positive sequence electrical information set, the three-phase negative sequence electrical information set, and the three-phase zero sequence electrical information set; and performing voltage frequency recovery control on the parallel energy storage converter based on the three-phase positive sequence electrical information set to obtain a positive sequence voltage component set. Based on the aforementioned positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values, voltage and current inner and outer loop control is performed on the aforementioned positive-sequence voltage component set to obtain the converter arm voltage control information set; based on the aforementioned converter arm voltage control information set, suppression control processing is performed on the aforementioned three-phase negative-sequence electrical information set and the aforementioned three-phase zero-sequence electrical information set to obtain the converter compensation signal set; based on the aforementioned converter compensation signal set, a converter switching control information set is generated, and based on the aforementioned converter switching control information set, unbalanced load control processing is performed on the aforementioned parallel energy storage converter.

[0008] Secondly, some embodiments of this disclosure provide an unbalanced load control device based on parallel energy storage converters, comprising: an acquisition unit configured to acquire a set of converter electrical information of a parallel energy storage converter system under islanded operation, wherein the converter electrical information includes at least one of the following: three-phase voltage information, three-phase current information, and capacity information of the converter; and an execution unit configured to perform the following generation steps for each parallel energy storage converter included in the parallel energy storage converter system: performing sequence extraction processing on the three-phase voltage information and the three-phase current information of the converter of the parallel energy storage converter to obtain a three-phase positive sequence electrical information set, a three-phase negative sequence electrical information set, and a three-phase zero sequence electrical information set; and performing a sequence extraction processing on the three-phase positive sequence electrical information set, the three-phase negative sequence electrical information set, and the three-phase zero sequence electrical information set. The system generates positive-sequence, negative-sequence, and zero-sequence virtual impedance voltage values. Based on the three-phase positive-sequence electrical information set, voltage and frequency recovery control is performed on the parallel energy storage converter to obtain a positive-sequence voltage component set. Based on the positive-sequence, negative-sequence, and zero-sequence virtual impedance voltage values, voltage and current inner and outer loop control is performed on the positive-sequence voltage component set to obtain a converter arm voltage control information set. Based on the converter arm voltage control information set, suppression control processing is performed on the three-phase negative-sequence electrical information set and the three-phase zero-sequence electrical information set to obtain a converter compensation signal set. Based on the converter compensation signal set, a converter switching control information set is generated, and based on the converter switching control information set, unbalanced load control processing is performed on the parallel energy storage converter.

[0009] Thirdly, some embodiments of this disclosure provide an electronic device, including: one or more processors; and a storage device having one or more programs stored thereon, such that when the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any implementation of the first aspect.

[0010] Fourthly, some embodiments of this disclosure provide a computer-readable medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method as described in any implementation of the first aspect.

[0011] The above embodiments of this disclosure have the following beneficial effects: The unbalanced load control method based on parallel energy storage converters in some embodiments of this disclosure can efficiently adjust the regulation capability and timeliness of parallel energy storage converters under unbalanced load conditions, and improve the safety of energy storage converters. Specifically, the reasons for the reduced safety and lower system stability of parallel energy storage converters are as follows: When the load is unbalanced, the output voltage of the energy storage converter will generate negative sequence and zero sequence components, resulting in three-phase voltage asymmetry, affecting power quality. In parallel operation, due to the difference in line impedance of each PCS module, droop control cannot achieve reasonable distribution of active and reactive power (especially negative sequence and zero sequence power), resulting in increased circulating current, equipment overload or low utilization. When virtual impedance is introduced to improve power distribution, it will exacerbate the reduction of the PCC (point of common coupling) voltage and cause frequency differences between each converter module, affecting system stability, thereby reducing the safety and lowering the system stability of parallel energy storage converters. Based on this, some embodiments of the unbalanced load control method based on parallel energy storage converters disclosed herein can first obtain a set of converter electrical information of the parallel energy storage converter system under islanded operation conditions. This converter electrical information includes at least one of the following: three-phase voltage information, three-phase current information, and capacity information. This set of converter electrical information facilitates subsequent unbalanced load control processing. Then, for each parallel energy storage converter in the aforementioned parallel energy storage converter system, the following generation steps are performed: First, the three-phase voltage information and three-phase current information of the aforementioned parallel energy storage converter are processed by sequence extraction to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set. Here, sequence extraction facilitates the identification of factors causing unbalanced loads in the system, enabling subsequent precise control based on different sequences. The second step involves generating positive-sequence, negative-sequence, and zero-sequence virtual impedance voltage values ​​based on the aforementioned three-phase positive-sequence, negative-sequence, and zero-sequence electrical information sets. Here, virtual impedances are introduced for each sequence to compensate for differences in actual line impedance, ensuring consistent equivalent output impedance for each parallel energy storage converter. This improves power distribution (especially the equalization of negative-sequence and zero-sequence currents) and reduces the impact of circulating currents on the system. Each sequence impedance voltage value achieves zero steady-state error control, simplifying the voltage outer loop design. The generated voltage reference value is more stable and used for precise control of the output voltage amplitude and phase. The third step involves performing voltage-frequency recovery control on the parallel energy storage converters based on the aforementioned three-phase positive-sequence electrical information set, obtaining the positive-sequence voltage component set. This avoids negative-sequence power interference and achieves reasonable adjustment of active power-frequency and reactive power-voltage.The fourth step involves applying voltage and current inner and outer loop control to the positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​to obtain the converter arm voltage control information set. Here, the outer voltage loop in the dual-loop structure stabilizes the output voltage, while the inner current loop provides a fast dynamic response, ensuring system stability. The fifth step involves applying suppression control to the three-phase negative-sequence electrical information set and the three-phase zero-sequence electrical information set to obtain the converter compensation signal set. This effectively suppresses negative-sequence voltage, improves output voltage THD (Total Harmonic Distortion), and zero-axis control suppresses zero-sequence current. Neutral point potential control balances the DC-side capacitor voltage, preventing output voltage distortion caused by neutral point offset. The sixth step involves generating a converter switching control information set based on the converter compensation signal set, and then applying unbalanced load control to the parallel energy storage converter based on this information set. Here, for a three-phase four-wire topology, zero-sequence components are considered in the modulation to generate a suitable converter switching control information set, ensuring that the inverter outputs high-quality voltage under unbalanced loads. Therefore, this unbalanced load control method based on parallel energy storage converters can efficiently adjust the regulation capability and timeliness of parallel energy storage converters under unbalanced load conditions, improving the safety of the energy storage converters. Attached Figure Description

[0012] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements are not necessarily drawn to scale.

[0013] Figure 1 This is a flowchart of some embodiments of the unbalanced load control method based on parallel energy storage converter according to the present disclosure; Figure 2 This is a topology diagram of a parallel energy storage converter in some embodiments of the unbalanced load control method based on a parallel energy storage converter according to the present disclosure. Figure 3 This is a schematic diagram of the structure of some embodiments of the unbalanced load control device based on parallel energy storage converter according to the present disclosure; Figure 4 This is a schematic diagram of the structure of an electronic device suitable for implementing some embodiments of the present disclosure. Detailed Implementation

[0014] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0015] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0016] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0017] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0018] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0019] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] Figure 1 A flow chart 100 of some embodiments of an unbalanced load control method based on a parallel energy storage converter according to the present disclosure is shown. This unbalanced load control method based on a parallel energy storage converter includes the following steps: Step 101: Obtain the converter electrical information set of the parallel energy storage converter system under islanded operation conditions.

[0021] In some embodiments, the execution entity (e.g., electronic device) of the above-described unbalanced load control method based on parallel energy storage converters can acquire the converter electrical information set of the parallel energy storage converter system under islanded operation conditions via wired or wireless connection. The converter electrical information includes at least one of the following: converter three-phase voltage information, converter three-phase current information, and converter capacity information. The islanded operation condition can be a condition where the system continues to supply power independently after being disconnected from the grid. The parallel energy storage converter system can be a system in which at least two energy storage converters are connected in parallel within a distributed generation system. The converter electrical information can be voltage and current information related to the parallel energy storage converters. The energy storage converter can be an energy storage converter with a three-phase four-wire NPC (three-phase four-wire NPC type, neutral point clamping) inverter topology. Figure 2 The topology of the parallel energy storage converter is shown. Figure 2 middle The voltage across the DC side can be represented by O, which can be the negative terminal of the DC side. A, B, and C can be represented as the neutral points of the positive, negative, and zero-sequence bridge arms, respectively. N can be represented as the neutral line node, used to carry zero-sequence current. It can be a capacitor on the DC side. It can be a DC-side capacitor. This can be expressed as, This can be represented as the individual diodes in each of the three-phase bridge arms, with each phase bridge arm containing two diodes. This can be represented as the auxiliary / freewheeling diodes included in each of the three-phase bridge arms, with each phase bridge arm containing four diodes. This can be expressed as the internal resistance of a three-phase inductor. This can be represented as the three-phase inductance of an LC filter. This can be represented as the three-phase capacitor of an LC filter. This can be represented as the inductance on the neutral line. This can be expressed as three-phase inductor current. This can be represented as the current flowing through the neutral line. This can be represented as three-phase output current. The aforementioned converter electrical information may also include microgrid operating condition information. This microgrid operating condition information characterizes the state information of the microgrid under islanded operation conditions. This microgrid operating condition information may include: point of common coupling voltage information, load active power and load reactive power, microgrid DC bus equalizing capacitor voltage, and microgrid angular frequency. The aforementioned converter three-phase voltage information may be the output voltage set of the three phase lines of the parallel energy storage converter. The aforementioned converter three-phase current information may be the output current set of the three phase lines of the parallel energy storage converter and the neutral current information. The aforementioned converter capacity information may be the maximum apparent power that each parallel energy storage converter can continuously output under rated operating conditions.

[0022] Step 102: For each parallel energy storage converter included in the above-mentioned parallel energy storage converter system, perform the following generation steps: Step 1021: Sequence extraction processing is performed on the three-phase voltage information and three-phase current information of the parallel energy storage converter to obtain the three-phase positive sequence electrical information set, the three-phase negative sequence electrical information set, and the three-phase zero sequence electrical information set.

[0023] In some embodiments, the execution entity can perform sequence extraction processing on the three-phase voltage information and three-phase current information of the parallel energy storage converter to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set. The three-phase positive-sequence electrical information can be the positive voltage and current information of the three phase lines of the parallel energy storage converter in a two-phase stationary coordinate system (αβ0 coordinate system) under three-phase unbalanced conditions. The three-phase negative-sequence electrical information can be the negative voltage and current information of the three phase lines of the parallel energy storage converter in a two-phase stationary coordinate system. The three-phase zero-sequence electrical information can be the voltage and current information of the neutral current in the parallel energy storage converter in a two-phase stationary coordinate system.

[0024] In some optional implementations of certain embodiments, the above-mentioned sequential extraction processing of the three-phase voltage information and three-phase current information of the parallel energy storage converter to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set may include the following steps: The first step, based on the three-phase voltage information of the parallel energy storage converter mentioned above, is to perform the following determination steps: Sub-step 1 involves performing coordinate system transformation on the aforementioned three-phase voltage information of the converter to obtain the first transformed three-phase voltage, the second transformed three-phase voltage, and the three-phase zero-sequence voltage. The first transformed three-phase voltage can be the voltage located on the α-axis in a three-dimensional two-phase stationary coordinate system. The second transformed three-phase voltage can be the voltage located on the β-axis in a two-phase stationary coordinate system. The three-phase zero-sequence voltage can be the voltage located on the 0-axis in a three-dimensional two-phase stationary coordinate system. The coordinate system transformation can be performed using the Clarke transform algorithm to convert the converter three-phase voltage information located in the natural coordinate system (abc coordinate system) into the two-phase stationary coordinate system. The three-phase zero-sequence voltage can be the sum of the output voltages of the three phase lines and their ratio to 3, which are included in the converter's three-phase voltage information.

[0025] Sub-step 2 involves filtering and offsetting the three-phase voltages of the first and second converted converters, respectively, to obtain a first in-phase voltage component, a first quadrature voltage component, a second in-phase voltage component, and a second quadrature voltage component. The first in-phase voltage component can be a voltage component of the most basic sinusoidal component that is completely synchronized with the waveform, frequency, and phase of the three-phase voltage of the first converted converter. The first quadrature voltage component can be a voltage component with the same waveform and frequency as the three-phase voltage of the first converted converter, but with a phase 90 degrees later than the first in-phase voltage component. The second in-phase voltage component can be a voltage component of the most basic sinusoidal component that is completely synchronized with the waveform, frequency, and phase of the three-phase voltage of the second converted converter. The second quadrature voltage component can be a voltage component with the same waveform and frequency as the three-phase voltage of the first converted converter, but with a phase 90 degrees later than the second in-phase voltage component. The filtering and offsetting process can be performed using a SOGI (Second-Order Generalized Integrator). The closed-loop transfer function of the above SOGI can be: .

[0026] in, This indicates that it has the same characteristics as a bandpass filter. This indicates that it has the same characteristics as a low-pass filter. This represents the proportionality coefficient of the system. This represents the angular frequency of the signal. express.

[0027] Sub-step 3: Based on the aforementioned first in-phase voltage component, first quadrature voltage component, second in-phase voltage component, and second quadrature voltage component, generate a first static positive-sequence voltage, a second static positive-sequence voltage, a first static negative-sequence voltage, and a second static negative-sequence voltage. The first static positive-sequence voltage can be a positive-sequence voltage located on the α-axis. The second static positive-sequence voltage can be a positive-sequence voltage located on the β-axis. The first static negative-sequence voltage can be a negative-sequence voltage located on the α-axis. The second static negative-sequence voltage can be a negative-sequence voltage located on the β-axis.

[0028] As an example, the aforementioned executing entity may first determine the sum of the first in-phase voltage component and the first quadrature voltage component, and its ratio to 2, as the first stationary positive-sequence voltage. Next, it may determine the sum of the second in-phase voltage component and the second quadrature voltage component, and its ratio to 2, as the second stationary positive-sequence voltage. Then, it may determine the difference between the first in-phase voltage component and the first quadrature voltage component, and its ratio to 2, as the first stationary negative-sequence voltage. Finally, it may determine the difference between the second in-phase voltage component and the second quadrature voltage component, and its ratio to 2, as the second stationary negative-sequence voltage.

[0029] The second step involves generating a first static positive-sequence current, a second static positive-sequence current, a first static negative-sequence current, a second static negative-sequence current, and a three-phase zero-sequence current based on the aforementioned three-phase current information from the converter. The first static positive-sequence current can be a positive-sequence current located on the α-axis. The second static positive-sequence current can be a positive-sequence current located on the β-axis. The first static negative-sequence current can be a negative-sequence current located on the α-axis. The second static negative-sequence current can be a negative-sequence current located on the β-axis. The three-phase zero-sequence current can be the sum of the output currents of the three phases of the parallel energy storage converter included in the three-phase current information, and the ratio of this sum to 3. The specific implementation of this step can be referenced from the implementation of the first step and will not be repeated here.

[0030] The third step is to determine the first static positive sequence voltage, the second static positive sequence voltage, the first static positive sequence current, and the second static positive sequence current as the three-phase positive sequence electrical information set; to determine the first static negative sequence voltage, the second static negative sequence voltage, the first static negative sequence current, and the second static negative sequence current as the three-phase negative sequence electrical information set; and to determine the three-phase zero sequence voltage and the three-phase zero sequence current as the three-phase zero sequence electrical information set.

[0031] Step 1022: Generate positive sequence virtual impedance voltage value, negative sequence virtual impedance voltage value and zero sequence virtual impedance voltage value based on the three-phase positive sequence electrical information set, the three-phase negative sequence electrical information set and the three-phase zero sequence electrical information set.

[0032] In some embodiments, the execution entity can generate positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the three-phase positive-sequence electrical information set, the three-phase negative-sequence electrical information set, and the three-phase zero-sequence electrical information set. Specifically, the positive-sequence virtual impedance voltage value can be the voltage value of a virtual impedance that is virtually introduced into the inverter's control loop to change the positive direction of the equivalent output power of the parallel energy storage converter. The negative-sequence virtual impedance voltage value can be the voltage value of a virtual impedance that is virtually introduced into the inverter's control loop to change the negative direction of the equivalent output power of the parallel energy storage converter. The zero-sequence virtual impedance voltage value can be the voltage value of a virtual impedance that is virtually introduced into the inverter's control loop to change the voltage value of the virtual impedance on the neutral line of the equivalent output power of the parallel energy storage converter.

[0033] In some optional implementations of certain embodiments, generating positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the three-phase positive-sequence electrical information set, the three-phase negative-sequence electrical information set, and the three-phase zero-sequence electrical information set may include the following steps: The first step is to determine the line resistance impedance difference between the parallel energy storage converters and the common coupling point in the parallel energy storage converter system. The common coupling point can be the power supply access point between the parallel energy storage converter system and the power grid. The line resistance impedance difference can be the difference between the maximum and minimum line impedance values ​​from each parallel energy storage converter to the common coupling point, obtained from centralized collection of converter electrical information.

[0034] The second step is to determine the virtual inductance and virtual impedance values ​​based on the aforementioned line resistance impedance difference. The virtual inductance value can be the inductance value of a purely inductive impedance. The virtual impedance value can be an introduced purely inductive impedance value. As an example, the executing entity can first, due to the actual requirements of the parallel energy storage converter system, need the virtual inductance value to be much larger than the line resistance impedance difference, which can be 5-10 times larger. Therefore, the virtual inductance value can be obtained by dividing the line resistance impedance difference by a multiple and then dividing by the system angular frequency of the parallel energy storage converter system. The aforementioned system angular frequency can be 2π. 50 rad / s. The virtual impedance value can be obtained because the actual requirements of the parallel energy storage converter system require that the product of the virtual inductance value and the system angular frequency be 10-20 times the virtual impedance value. Therefore, the virtual impedance value can be obtained by dividing the product of the virtual inductance value and the system angular frequency by the corresponding multiple.

[0035] The third step is to determine the difference between the product of the virtual impedance value and the first static positive sequence current included in the three-phase positive sequence electrical information set, and the product of the virtual inductance value, the system angular frequency and the second static positive sequence current included in the three-phase positive sequence electrical information set, as the first positive sequence virtual impedance voltage drop.

[0036] The fourth step is to determine the sum of the product of the virtual impedance value and the second static positive sequence current, and the product of the virtual inductance value, the system angular frequency, and the first static positive sequence current, as the second positive sequence virtual impedance voltage drop.

[0037] The fifth step is to determine the product of the virtual impedance value and the first static negative sequence current included in the three-phase positive sequence electrical information set, the opposite of the virtual inductance value, the system angular frequency and the second static negative sequence current included in the three-phase negative sequence electrical information set, and use the difference as the first negative sequence virtual impedance voltage drop.

[0038] The sixth step is to determine the sum of the product of the virtual impedance value and the second static negative sequence current, the opposite of the virtual inductance value, and the product of the system angular frequency and the first static negative sequence current, as the second negative sequence virtual impedance voltage drop.

[0039] Step 7: Determine the product of the virtual impedance value and the three-phase zero-sequence current included in the three-phase zero-sequence electrical information, as the zero-sequence virtual impedance voltage drop.

[0040] Step 8: Perform coordinate system transformation on the first positive-sequence virtual impedance voltage drop, the second positive-sequence virtual impedance voltage drop, the first negative-sequence virtual impedance voltage drop, the second negative-sequence virtual impedance voltage drop, and the zero-sequence virtual impedance voltage drop to obtain the first transformed positive-sequence voltage drop, the second transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, the second transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop, which are used as the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value. The coordinate system transformation can be performed using the Park transformation algorithm, converting the two-phase stationary coordinate system into a synchronously rotating coordinate system (dq0 coordinate system).

[0041] Step 1023: Based on the three-phase positive sequence electrical information set, perform voltage and frequency recovery control on the parallel energy storage converter to obtain the positive sequence voltage component set.

[0042] In some embodiments, the aforementioned execution entity can perform voltage-frequency recovery control on the aforementioned parallel energy storage converter based on the aforementioned three-phase positive sequence electrical information set to obtain a positive sequence voltage component set. The positive sequence voltage component in the aforementioned positive sequence voltage component set can be the adjustment voltage value of the positive sequence voltage that needs to be adjusted to ensure that the output power of each parallel energy storage converter in the parallel energy storage converter system is the same.

[0043] In some optional implementations of certain embodiments, the above-mentioned voltage frequency recovery control of the parallel energy storage converter based on the above-mentioned three-phase positive sequence electrical information set to obtain the positive sequence voltage component set may include the following steps: The first step is to perform a coordinate system transformation on the aforementioned three-phase positive sequence electrical information set to obtain a transformed three-phase positive sequence electrical information set. The transformed three-phase positive sequence electrical information in this set can be the positive sequence voltage and current values ​​located in a synchronous rotating coordinate system. This coordinate system transformation can be performed using the Park transform algorithm.

[0044] The second step involves determining the positive-sequence instantaneous active power and reactive power of the parallel energy storage converter based on the converted three-phase positive-sequence electrical information set. The positive-sequence instantaneous active power can be the positive-sequence active power generated by the parallel energy storage converter within an instant. Similarly, the positive-sequence instantaneous reactive power can be the positive-sequence reactive power generated by the parallel energy storage converter within an instant. For example, the executing entity can first determine the positive-sequence instantaneous active power as the sum of the product of the first axial voltage and the first axial current, the product of the second axial voltage and the second axial current, and three-half of the product of the converted three-phase positive-sequence electrical information set. The first axial voltage can be the voltage on the d-axis, which is aligned with the main magnetic field direction of the motor rotor poles in a synchronous rotating coordinate system. The first axial current can be the current on the d-axis in a synchronous rotating coordinate system. The second axial voltage can be the voltage on the q-axis, which is 90 electrical degrees ahead of the d-axis in a synchronous rotating coordinate system. The aforementioned second axial current can be the current located on the q-axis in a synchronous rotating coordinate system. Then, the product of the second axial voltage and the first axial current, the difference between the product of the first axial voltage and the second axial current, and the product of two-thirds are determined as the positive-sequence instantaneous reactive power.

[0045] The third step involves filtering the aforementioned positive-sequence instantaneous active power and reactive power to obtain filtered positive-sequence instantaneous active power and reactive power, respectively. This filtering can be performed using a first-order low-pass filter. Furthermore, this filtering process can remove high-frequency noise generated by switching frequency noise and transient disturbances from the DC components of the positive-sequence instantaneous active and reactive power.

[0046] The fourth step is to determine the droop adjustment coefficient set for the parallel energy storage converter. These droop adjustment coefficients characterize the frequency and voltage adjustment range of the parallel energy storage converter when the power changes; that is, when the output power changes from 0 to the rated value, the frequency and voltage deviations should be within the allowable range. In practice, the implementing entity can first obtain the no-load voltage angular frequency and no-load output voltage amplitude of the parallel energy storage converter when it is unloaded (i.e., the output power is 0), as well as the rated active power and rated reactive power of the parallel energy storage converter for long-term stable operation, and obtain the frequency deviation range, voltage deviation range, maximum active power, and maximum reactive power of the parallel energy storage converter system. The frequency deviation can be the deviation range of the number of periodic repetitions of the AC current in the parallel energy storage converter system, with a value range of [59.5, 50.5]. The aforementioned voltage deviation range can be the deviation range between the parallel energy storage converter system and the system mains voltage (e.g., 311 volts), with a value range of [0.95, 1.05] of the mains voltage. Next, the minimum value of the frequency deviation range and the product of 2π are determined as the target frequency. Then, the minimum value of the voltage deviation range and the product of the system mains voltage are determined as the target system voltage. Next, the ratio of the difference between the no-load voltage angular frequency and the target angular frequency to the difference between the maximum active power and the rated active power is determined as the frequency droop coefficient. Then, the ratio of the difference between the no-load output voltage amplitude and the target system voltage to the difference between the maximum reactive power and the rated reactive power is determined as the voltage droop coefficient. The frequency droop coefficient and the voltage droop coefficient are then used to determine the droop adjustment coefficient set.

[0047] The fifth step involves generating converter voltage amplitude regulation information and system angular frequency regulation information based on the filtered positive-sequence instantaneous active power, the filtered positive-sequence instantaneous reactive power, and the droop adjustment coefficient set. The converter voltage amplitude information can be a value used to suppress voltage fluctuations in multiple parallel energy storage converters under unbalanced load conditions. The system angular frequency regulation information can be a value used to suppress frequency fluctuations in multiple parallel energy storage converters under unbalanced load conditions. For example, the executing entity can first determine the product of the difference between the filtered positive-sequence instantaneous active power and the rated active power, and the frequency droop coefficients included in the droop adjustment coefficient set, as the angular frequency regulation value. Secondly, it can determine the difference between the no-load voltage angular frequency and the angular frequency regulation value, as the system angular frequency regulation information. Then, it can determine the product of the difference between the filtered positive-sequence instantaneous reactive power and the rated reactive power, and the voltage droop coefficients included in the droop adjustment coefficient set, as the voltage regulation value. Finally, the difference between the no-load output voltage amplitude and the voltage regulation value is determined as the converter voltage amplitude regulation information.

[0048] Step 6: Based on the converter voltage amplitude adjustment information and the system angular frequency adjustment information, generate a positive sequence voltage component set. The positive sequence voltage components in this set can be balanced, forward-rotating components of the voltage values ​​included in the three-phase positive sequence electrical information.

[0049] As an example, the aforementioned execution entity can first integrate the system angular frequency adjustment information to obtain the frequency phase angle. Secondly, it determines the product of the converter voltage amplitude adjustment information and the cosine function value of the frequency phase angle as the first phase positive sequence voltage. Thirdly, it determines the product of the converter voltage amplitude adjustment information and the cosine function value of the difference between the converter voltage amplitude adjustment information and the frequency phase angle and 2 / 3π as the second phase positive sequence voltage. Subsequently, it determines the product of the converter voltage amplitude adjustment information and the cosine function value of the sum of the converter voltage amplitude adjustment information and the frequency phase angle and 2 / 3π as the third phase positive sequence voltage. Then, it performs coordinate system transformation on the first, second, and third phase positive sequence voltages to obtain the positive sequence voltage component set.

[0050] Step 1024: Based on the positive-sequence virtual impedance voltage value, negative-sequence virtual impedance voltage value, and zero-sequence virtual impedance voltage value, perform voltage and current inner and outer loop control on the positive-sequence voltage component set to obtain the converter bridge arm voltage control information set.

[0051] In some embodiments, the execution entity can perform voltage and current inner and outer loop control on the positive-sequence voltage component set based on the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value to obtain a converter arm voltage control information set. The converter arm voltage control information in the converter arm voltage control information set can be information used to control the output voltage of the arms of the parallel energy storage converter.

[0052] In some optional implementations of certain embodiments, the above-mentioned voltage and current inner and outer loop control of the positive-sequence voltage component set based on the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value to obtain the converter bridge arm voltage control information set may include the following steps: The first step is to determine the difference between the first positive-sequence voltage component and the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop, which are included in the aforementioned positive-sequence voltage component set, as the first voltage outer loop reference value. Here, the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop are data from the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value, respectively. The aforementioned first voltage outer loop reference value can be a reference value located on the d-axis in a synchronous rotating coordinate system, used to maintain voltage stability in the parallel energy storage converter system.

[0053] The second step involves determining the difference between the second positive-sequence voltage component and the second transformed positive-sequence voltage drop and the second transformed negative-sequence voltage drop, which are included in the aforementioned positive-sequence voltage component set, as the second voltage outer loop reference value. Here, the aforementioned second transformed positive-sequence voltage drop and second transformed negative-sequence voltage drop are data from the positive-sequence virtual impedance voltage value and the aforementioned negative-sequence virtual impedance voltage value. The aforementioned second voltage outer loop reference value can be a reference value located on the q-axis in a synchronous rotating coordinate system, used to maintain voltage stability in the parallel energy storage converter system.

[0054] The third step involves determining the differences between the aforementioned first voltage outer loop reference value, the aforementioned second voltage outer loop reference value, and the converted three-phase positive sequence electrical information set corresponding to the aforementioned three-phase positive sequence electrical information set, as the system voltage error value set. The system voltage error value in the aforementioned system voltage error value set can be the difference between the actual output voltage of the energy storage converter and the voltage outer loop reference value, located on the d-axis or q-axis; that is, the voltage value that the parallel energy storage converter system needs to adjust. In practice, the aforementioned executing entity can first determine the difference between the first voltage outer loop reference value and the first converted three-phase positive sequence voltage included in the converted three-phase positive sequence electrical information set, as the first system voltage error value. Then, it can determine the difference between the second voltage outer loop reference value and the second converted three-phase positive sequence voltage included in the converted three-phase positive sequence electrical information set, as the second system voltage error value. Finally, the first system voltage error value and the second system voltage error value are determined as the system voltage error value set.

[0055] The fourth step involves applying external voltage control to the aforementioned system voltage error value set to obtain the current inner loop reference value set. The current inner loop reference values ​​in this set can be the values ​​of the current that the parallel energy storage converter system needs to adjust in a synchronous rotating coordinate system. In practice, the aforementioned actuator can use a PI controller to apply external voltage control to the aforementioned system voltage error value set to obtain the current inner loop reference value set.

[0056] The fifth step involves performing feedforward decoupling on the aforementioned current inner loop reference value set to obtain a decoupled current inner loop reference value set. In practice, the execution entity can first determine the difference between each current inner loop reference value in the aforementioned current inner loop reference value set and the corresponding converted three-phase positive sequence current in the aforementioned converted three-phase positive sequence electrical information set, thus obtaining a first positive sequence current error value and a second positive sequence current error value. Next, the first and second positive sequence current error values ​​are input into the PI controller to obtain a first error voltage component and a second error voltage component. Then, the first and second error voltage components are input into the feedforward decoupling function to obtain the decoupled current inner loop reference value set. The aforementioned feedforward decoupling function can be: .

[0057] in, This represents the inner loop reference value of the current inner loop on the d-axis after decoupling. This represents the inner loop reference value of the current inner loop on the q-axis after decoupling. This represents the proportional gain of the PI controller. This represents the error value of the first positive sequence current. This represents the integral coefficient of the PI controller. This represents the error value of the second positive sequence current. This represents the angular frequency of the synchronously rotating coordinate system. This represents the filter inductance of the LC filter in a parallel energy storage converter. This represents the reference value of the inner current loop on the q-axis. This represents the reference value of the inner current loop on the d-axis. This represents the component of the positive sequence voltage at point PCC along the d-axis in the dq0 coordinate system. This represents the component of the positive sequence voltage at point PCC along the d-axis in the dq0 coordinate system.

[0058] The sixth step is to perform an inverse coordinate system transformation on the aforementioned decoupled inner current reference value set to obtain the converter bridge arm voltage control information set. This inverse coordinate system transformation can be a transformation from a synchronous rotating coordinate system to a two-phase stationary coordinate system.

[0059] Step 1025: Based on the converter bridge arm voltage control information set, suppress control processing is performed on the three-phase negative sequence electrical information set and the three-phase zero sequence electrical information set to obtain the converter compensation signal set.

[0060] In some embodiments, the aforementioned execution entity can perform suppression control processing on the aforementioned three-phase negative-sequence electrical information set and the aforementioned three-phase zero-sequence electrical information set based on the aforementioned converter arm voltage control information set, to obtain a converter compensation signal set. The aforementioned converter compensation signal set can be the amount of negative-sequence compensation voltage and zero-sequence compensation voltage that needs to be injected into the transformer of the parallel energy storage converter to suppress the negative-sequence voltage in the parallel energy storage converter and the zero-sequence voltage on the bus.

[0061] In some optional implementations of certain embodiments, the above-mentioned suppression control processing of the three-phase negative sequence electrical information set and the three-phase zero sequence electrical information set based on the converter arm voltage control information set to obtain the converter compensation signal set may include the following steps: The first step involves performing negative sequence component suppression processing on the parallel energy storage converter based on the current inner loop reference value set corresponding to the converter arm voltage control information set and the three-phase negative sequence electrical information set, thereby obtaining the converter negative sequence compensation voltage value set. The converter negative sequence compensation voltage values ​​in this set can be used to suppress the negative sequence voltage generated by the energy storage converter under unbalanced load control conditions.

[0062] As an example, the aforementioned execution entity can first perform coordinate system transformation on the three-phase negative-sequence current set included in the aforementioned three-phase negative-sequence electrical information set to obtain a negative-sequence rotating current set in a synchronous rotating coordinate system. Secondly, it determines the negative-sequence current difference between each current inner loop reference value in the aforementioned current inner loop reference value set and the corresponding negative-sequence rotating current in the negative-sequence rotating current set, obtaining a negative-sequence current difference set. Then, it inputs the aforementioned negative-sequence current difference set into the negative-sequence quasi-resonant control function to perform negative-sequence component suppression processing on the aforementioned parallel energy storage converter, obtaining a converter negative-sequence compensation voltage value set. The aforementioned negative-sequence quasi-resonant control function can be: .

[0063] in, This represents the transfer function of the negative-sequence quasi-resonant controller. Represents the resonant gain, used at the resonant frequency. It provides high gain and enables zero steady-state error tracking. This indicates the cutoff frequency, which controls the width (bandwidth) of the resonant peak. This represents the resonant frequency, with a value of 2π. 100 rad / s. This indicates that the Laplace operator is obtained by performing a Laplace transform on the time-domain differential equation of the parallel energy storage converter system.

[0064] The second step is to determine the difference between the zero-sequence voltage included in the aforementioned three-phase zero-sequence electrical information set and the preset zero-sequence reference voltage, thus obtaining the zero-sequence voltage difference. The preset zero-sequence reference voltage can be the three-phase zero-sequence voltage converted from an unbalanced load condition to a balanced load condition. The preset zero-sequence reference voltage can be 0.

[0065] The third step involves performing discretized dual-path control on the parallel energy storage converter based on the aforementioned zero-sequence voltage difference to obtain the zero-sequence voltage compensation amount. This zero-sequence voltage compensation amount can be a voltage value used to suppress the zero-sequence voltage.

[0066] As an example, the aforementioned execution entity can first use the bilinear transform algorithm to discretize the resonant transfer function in the zero-sequence dual-path control function, obtaining the discretized zero-sequence resonant control function. The aforementioned zero-sequence dual-path control function can be: .

[0067] in, This represents a zero-sequence dual-path control function. This represents the proportional gain, a proportional control function used to improve the system's response speed. This represents the transfer function of the resonant component.

[0068] The discretized zero-sequence resonance control function described above can be: .

[0069] in, This represents the discretized zero-sequence resonance control function. This represents the formula for the bilinear transformation. This represents the transformation of a continuous s-domain model into a discrete z-domain model.

[0070] Next, the proportional control function in the discretized zero-sequence resonant control function and zero-sequence dual-path control function is differentially processed to obtain the resonant differential control function and the proportional-differential control function. The resonant differential control function can be: .

[0071] in, This represents a dual-path differential control function. Indicates the sampling period. This represents the discrete-time index, indicating the k-th sampling time. This represents the zero-sequence voltage difference.

[0072] .

[0073] in, This represents the proportional differential control function.

[0074] Finally, the zero-sequence voltage difference is input to the resonant differential control function and the proportional differential control function to obtain the resonant voltage compensation amount and the proportional voltage compensation amount. The sum of the resonant voltage compensation amount and the proportional voltage compensation amount is determined as the zero-sequence voltage compensation amount.

[0075] The fourth step is to determine the DC bus voltage difference between the upper and lower capacitors on the DC side, which is included in the above-mentioned converter electrical information set.

[0076] Fifth, based on the aforementioned DC bus voltage difference, voltage control processing is performed on the parallel energy storage converter to obtain the DC bus midpoint voltage compensation value. This DC bus midpoint voltage compensation value can be a voltage amount used to suppress midpoint offset of the parallel energy storage converter. As an example, the execution unit can utilize a PI controller to perform voltage control processing on the parallel energy storage converter based on the aforementioned DC bus voltage difference to obtain the DC bus midpoint voltage compensation value.

[0077] The sixth step is to determine the sum of the zero-sequence voltage compensation value and the DC bus midpoint voltage compensation value, which is taken as the zero-sequence component voltage compensation value.

[0078] The seventh step is to determine the above zero-sequence component voltage compensation value and the above converter negative-sequence compensation voltage value set as the converter compensation signal set.

[0079] In addressing the aforementioned technical problems in the process of adopting technical solutions, and considering the application scenario—a microgrid operating in an isolated state in a remote area—the following technical issues often arise: In islanded operation, the microgrid needs to maintain voltage stability independently, significantly reducing its tolerance to load imbalance. Furthermore, load imbalance introduces zero-sequence and negative-sequence currents that impact the DC side, leading to weak microgrid stability, low power quality, voltage fluctuations, and high loss rates in the energy storage converter. Based on the characteristics of this application scenario—three-phase four-wire NPC, zero-sequence voltage and current, negative-sequence voltage and current, and islanded operation—we have decided to adopt the following solution: In some optional implementations of certain embodiments, the above-mentioned suppression control processing of the three-phase negative sequence electrical information set and the three-phase zero sequence electrical information set based on the converter arm voltage control information set to obtain the converter compensation signal set may include the following steps: The first step involves inputting the aforementioned converter arm voltage control information set and converter electrical information set into the sequence electrical sensing and prediction model to obtain the negative-sequence prediction information set and the zero-sequence prediction information set. The negative-sequence prediction information set can be grid parameter sensing information and negative-sequence current and voltage information related to the negative-sequence component. This negative-sequence prediction information set may include: negative-sequence grid impedance information and negative-sequence current prediction information, i.e., the negative-sequence current amplitude for the next control cycle. The negative-sequence grid impedance information can be the state observation value of the grid-side transmission circuit for the true physical impedance of the negative-sequence component, and may include negative-sequence impedance identification value and negative-sequence inductance identification value. Similarly, the zero-sequence prediction information set can be grid parameter sensing information and zero-sequence current and voltage information related to the zero-sequence component. This zero-sequence prediction information set may include: zero-sequence grid impedance information and zero-sequence current prediction information, i.e., the zero-sequence current amplitude for the next control cycle. The zero-sequence grid impedance information can be the state observation value of the grid-side transmission circuit for the true physical impedance of the zero-sequence component, and may include zero-sequence impedance identification value and zero-sequence inductance identification value. The aforementioned positive and zero-sequence grid impedance information can be represented as: the sum of the products of the negative-sequence impedance identification value, the negative-sequence inductance identification value, the imaginary unit, and the microgrid angular frequency; and the sum of the products of the zero-sequence impedance identification value, the zero-sequence inductance identification value, the imaginary unit, and the microgrid angular frequency. The aforementioned sequential electrical sensing prediction model can be a deep neural network model that performs time-series prediction after fusing the input converter arm voltage control information set and the aforementioned converter electrical information set. For example, the aforementioned sequential electrical sensing prediction model can be a model composed of a long short-term memory neural network model, a global average pooling layer, a fully connected layer including a ReLU activation function, and a fully connected layer connected in series. The aforementioned sequential electrical sensing prediction model can also be a model trained and optimized using a meta-learning framework.

[0080] In practice, the aforementioned implementing entity can first standardize the aforementioned converter arm voltage control information set, the microgrid operating condition information corresponding to the aforementioned converter electrical information set, and the three-phase positive-sequence electrical information set, three-phase negative-sequence electrical information set, three-phase zero-sequence electrical information set, sequence droop data, inner and outer loop control data, and virtual impedance-related data corresponding to the converter arm voltage control information set, and then fuse the data to obtain fused input data. The aforementioned negative-sequence droop data may include: positive and negative sequence active power droop coefficients, positive and negative sequence reactive power droop coefficients, voltage positive and negative sequence reference values, and frequency reference values ​​involved in obtaining the positive-sequence voltage component set. The aforementioned inner and outer loop control data may include: voltage outer loop PI parameters, current inner loop PI parameters, resonant frequency, and gain of the quasi-resonant controller involved in obtaining the converter arm voltage control information set. The virtual impedance-related data may be positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values. Then, the fused input data is sequentially input into the sequenced electrical sensing prediction model to obtain the negative-order prediction information set and the zero-order prediction information set.

[0081] The second step is to construct a multi-objective optimization function for zero-sequence and negative-sequence suppression. This multi-objective optimization function can be an adaptive function used to effectively suppress negative-sequence and zero-sequence current and voltage in the microgrid. It can include a multi-objective function set and a constraint function set. The multi-objective function set can include: a function to minimize the negative-sequence current amplitude, a function to minimize the zero-sequence current amplitude, a positive-sequence power equalization function (to ensure that the positive-sequence active and reactive power of the parallel energy storage converter are distributed according to the capacity ratio), a droop coefficient smoothing function, a virtual impedance smoothing function (to avoid microgrid oscillations caused by sudden changes in droop coefficient and virtual impedance), and a voltage deviation function. The constraint function set can include: a constraint function for the range of positive-sequence active droop coefficient values, a constraint function for the range of negative-sequence droop coefficient values, a constraint function for the upper limit of the zero-sequence compensation coefficient, and a constraint function for virtual impedance values. The multi-objective optimization function for zero-sequence and negative-sequence suppression can be expressed as: .

[0082] in, This represents a zero-order negative-order suppression multi-objective optimization function. This indicates information about negative sequence current prediction. This indicates zero-sequence current prediction information. This indicates a parallel-connected parallel energy storage converter. The predicted value of positive sequence active power. This indicates another parallel-connected parallel energy storage converter. The predicted value of positive sequence active power. Indicates the control cycle. This represents the increment of the positive-sequence active power droop coefficient. This represents the increment of the negative order droop coefficient. This represents the negative-sequence virtual impedance increment. This represents the zero-sequence virtual impedance increment. This indicates the voltage amplitude at point PCC in the next cycle. This represents the rated peak value of the positive sequence voltage, with a value of 311. This represents the weight coefficients of each multi-objective function. This represents the function that minimizes the magnitude of the negative sequence current. This represents the function that minimizes the zero-sequence current magnitude. This represents the positive-sequence power distribution function. This represents the droop coefficient smoothing function. This represents the virtual impedance smoothing function. This represents the voltage deviation function.

[0083] The third step involves performing initial suppression processing on the aforementioned negative-sequence electrical information set and zero-sequence electrical information set based on the aforementioned zero-sequence compensation adjustment information set and zero-sequence compensation adjustment information set. Specifically, the negative-sequence droop adjustment information in the aforementioned negative-sequence droop adjustment information set can be the optimized positive-sequence droop coefficient output after the initial suppression processing. The aforementioned zero-sequence compensation adjustment information set can be the negative-sequence droop coefficient and zero-sequence compensation coefficient output after the initial suppression processing. The aforementioned virtual impedance correction information set can be the zero-sequence virtual impedance correction value obtained by matching 40% of the grid impedance and the negative-sequence virtual impedance correction value obtained by matching 30% of the grid impedance. As an example, the aforementioned execution entity can use the constructed prediction model and multi-objective optimization function, employing the MPC (Model Predictive Control) framework, and solve the finite-time optimization problem using a quadratic programming algorithm within each control cycle to obtain the negative-sequence droop adjustment information set, zero-sequence compensation adjustment information set, and virtual impedance correction information set.

[0084] The fourth step involves performing gain-adaptive impedance optimization on the aforementioned negative-sequence electrical information set and zero-sequence electrical information set based on the virtual impedance correction value set, the aforementioned negative-sequence prediction information set, and the aforementioned zero-sequence prediction information set, to obtain negative-sequence virtual impedance adjustment information and zero-sequence virtual impedance adjustment information. The negative-sequence virtual impedance adjustment information can be the sum of the negative-sequence virtual impedance correction values ​​in the virtual impedance correction value set and the negative-sequence grid impedance information in the negative-sequence prediction information set. Similarly, the zero-sequence virtual impedance adjustment information can be the sum of the zero-sequence virtual impedance correction values ​​in the virtual impedance correction value set and the zero-sequence grid impedance information in the zero-sequence prediction information set. As an example, the execution entity can use a virtual impedance adaptive correction algorithm and a PI controller to perform gain-adaptive impedance optimization on the aforementioned negative-sequence electrical information set and the aforementioned zero-sequence electrical information set based on the aforementioned virtual impedance correction value set, the aforementioned negative-sequence prediction information set, and the aforementioned zero-sequence prediction information set, to obtain negative-sequence virtual impedance adjustment information and zero-sequence virtual impedance adjustment information.

[0085] Fifth, based on the aforementioned negative-sequence droop adjustment information set, perform sequence-based droop optimization adjustment processing on the aforementioned three-phase negative-sequence electrical information set and the aforementioned three-phase zero-sequence electrical information set to obtain the negative-sequence voltage adjustment values ​​and the zero-sequence voltage adjustment values. The aforementioned negative-sequence voltage adjustment values ​​and zero-sequence voltage adjustment values ​​can be obtained by replacing the original parameters in the sequence-based droop algorithm with the negative-sequence droop adjustment information set to obtain the adjusted value set.

[0086] Step 6: Based on the aforementioned zero-sequence compensation adjustment information set, negative-sequence virtual impedance adjustment information, and zero-sequence virtual impedance adjustment information, perform inner and outer loop optimization adjustment processing on the aforementioned converter arm voltage control information set to obtain inner and outer loop voltage adjustment information sets. The inner and outer loop voltage adjustment information in the aforementioned inner and outer loop voltage adjustment information sets can be information sets obtained after optimizing and adjusting the converter arm voltage control information set. As an example, the execution entity can be a dual closed-loop control algorithm that inputs the aforementioned zero-sequence compensation adjustment information set, the aforementioned negative-sequence virtual impedance adjustment information set, and the aforementioned zero-sequence virtual impedance adjustment information set to the voltage outer loop and the current inner loop to obtain inner and outer loop current and voltage adjustment information sets.

[0087] Step 7: The aforementioned inner and outer loop voltage adjustment information sets, the aforementioned negative-sequence voltage adjustment values, and the zero-sequence voltage adjustment values ​​are superimposed and compensated to obtain a converter compensation signal set. Based on this converter compensation signal set, unbalanced load control processing is performed on the aforementioned parallel energy storage converter. In practice, the executing entity can first perform phase calibration on the inner and outer loop voltage adjustment information sets, the aforementioned negative-sequence voltage adjustment values, and the zero-sequence voltage adjustment values ​​to obtain calibrated negative-sequence voltage adjustment values, calibrated zero-sequence voltage adjustment values, and calibrated inner and outer loop voltage adjustment information sets. Finally, the calibrated voltage adjustment values ​​and the calibrated inner and outer loop voltage adjustment information sets are weighted and summed to obtain negative-sequence compensation voltage information, and the calibrated zero-sequence voltage adjustment values ​​and the calibrated inner and outer loop voltage adjustment information sets are weighted and summed to obtain zero-sequence compensation voltage information, which serves as the converter compensation signal set. The aforementioned unbalanced load control processing can be implemented as in step 1026.

[0088] The above-described technical solution and its related content, as an inventive point of this disclosure, solve the technical problem of "low accuracy in suppressing zero-sequence current voltage and negative-sequence current voltage, weak microgrid stability, low power quality, voltage fluctuations, and high loss rate of energy storage converters." The factors leading to low accuracy in suppressing zero-sequence current voltage and negative-sequence current voltage, weak microgrid stability, low power quality, voltage fluctuations, and high loss rate of energy storage converters are often as follows: In islanded operation, the microgrid needs to maintain voltage stability independently, significantly reducing its tolerance to load imbalance. Furthermore, zero-sequence current voltage and negative-sequence current voltage impact the DC side, resulting in low accuracy in suppressing these voltages, weak microgrid stability, low power quality, voltage fluctuations, and high loss rate of energy storage converters. Solving these factors can improve the accuracy of zero-sequence current voltage and negative-sequence current voltage suppression, enhance microgrid stability and power quality, effectively avoid voltage fluctuations, and reduce the loss rate of energy storage converters. To achieve this effect, this disclosure firstly uses a sequence electrical sensing prediction model for prediction and microgrid condition sensing. Microgrid sensing provides a static operating condition basis for subsequent accurate adaptation to the current microgrid impedance characteristics, effectively avoiding the problem of increased circulating current caused by fixed parameters. The predicted values ​​are used for subsequent feedforward compensation terms embedded in the inner and outer loops, which can offset the fluctuations of negative-sequence and zero-sequence components in advance, improving the dynamic suppression accuracy. Secondly, a multi-objective optimization function for zero-sequence and negative-sequence suppression is generated, incorporating the positive-sequence power distribution function, droop coefficient smoothing function, virtual impedance smoothing function, and voltage deviation function into the imbalance suppression optimization objective. The priority optimization function of different objectives is coordinated by weight coefficients, taking into account multiple aspects of information, which can improve the comprehensiveness of the optimization objective to further improve the effectiveness of suppression. The constraint function can avoid overcurrent and voltage distortion in parallel energy storage converters caused by parameter out-of-bounds. Next, the multi-objective optimization function for zero-sequence and negative-sequence suppression is subjected to initial suppression processing based on the prediction model solution, which can improve the accuracy of the initial suppression processing and effectively reduce the system oscillation amplitude. Subsequently, gain-adaptive impedance optimization enables dynamic matching and improves suppression robustness. Sequence droop optimization, through sequence decoupling, generates precise voltage adjustment values. Inner and outer loop optimization, through closed-loop calibration, improves control accuracy. Then, superposition compensation precisely synthesizes compensation signals, preventing mutual cancellation and ensuring no attenuation of the suppression effect. Finally, based on the aforementioned converter compensation signal set, unbalanced load control is applied to the parallel energy storage converter, improving the suppression accuracy of negative-sequence and zero-sequence components, microgrid stability, and power quality, effectively preventing voltage fluctuations and reducing the loss rate of the energy storage converter.

[0089] Step 1026: Generate a converter switching control information set based on the converter compensation signal set, and perform unbalanced load control processing on the parallel energy storage converter based on the converter switching control information set.

[0090] In some embodiments, the execution entity may generate a converter switching control information set based on the converter compensation signal set, and perform unbalanced load control processing on the parallel energy storage converter based on the converter switching control information set.

[0091] In addressing the aforementioned technical problems in the process of adopting technical solutions, the application scenario—a microgrid operating in an islanded state—often presents the following technical issues: Under unbalanced load conditions, a three-phase four-wire topology parallel energy storage converter in islanded operation exhibits a zero-sequence component that cannot be compensated for through modulation. Two-dimensional space vector pulse width modulation (SVM) cannot provide a modulation path for this zero-sequence component, causing zero-sequence current to flow into the filter capacitor, leading to three-phase voltage imbalance. This results in voltage distortion and increased circulating current in the energy storage converter, increasing the failure rate and stability of the parallel energy storage converter, increasing its switching losses, and ultimately reducing the stability and efficiency of the microgrid. Based on the characteristics of this application scenario—unbalanced three-phase load, independently operating grid, zero-sequence component, and three-phase four-wire NPC—we have decided to adopt the following solution: In some optional implementations of certain embodiments, the process of generating a converter switching control information set based on the converter compensation signal set, and performing unbalanced load control processing on the parallel energy storage converter based on the converter switching control information set, may include the following steps: The first step is to perform an inverse coordinate transformation on the above converter compensation signal set to obtain the inverse-transformed converter compensation signal set. The transformed converter compensation signal in the inverse-transformed converter compensation signal set can be the compensation signal obtained by transforming the dq0 coordinate system to the αβ0 coordinate system using the inverse Park transform algorithm.

[0092] The second step is to determine the set of switching state information for the aforementioned parallel energy storage converter. This switching state information can be used to characterize the on / off combinations of the power switches in each phase arm of the parallel energy storage converter, thereby controlling the output voltage level of each phase arm (P state for positive output, O state for zero output (connected to the neutral point via clamping diodes), and N state for negative output). This switching state information can include 27 on / off states of the switches, represented by N, P, and O in the αβ0 coordinate system. For example, (P, O, N) can represent positive output in phase A (switches S1 and S2 on and S3 and S4 off), zero-direction output in phase B (switches S2 and S3 on and S1 and S4 off), and negative output in phase C (switches S3 and S4 on and S1 and S2 off).

[0093] The third step is to determine the converter switch space vector set based on the aforementioned switch state information set. The converter switch space vectors in this set represent the switch state information in the αβ0 three-dimensional space in the form of hexagonal prisms. As an example, the executing entity can first determine the zero-sequence component of each switch state information in the aforementioned switch state information set, obtaining a set of switch zero-sequence components. Then, the switch zero-sequence component set and the α-axis and β-axis component sets of the aforementioned switch state information set are projected onto the αβ0 three-dimensional space respectively to obtain the converter switch space vector set.

[0094] The fourth step is to perform hierarchical space partitioning on the aforementioned converter switch space vector set to obtain a three-dimensional hierarchical space set of switch vectors. Specifically, the three-dimensional hierarchical space of the switch vectors in the aforementioned three-dimensional hierarchical space set can be a hierarchical space obtained by partitioning the hexagonal prism corresponding to the converter switch space vector set according to the zero-sequence component. This hierarchical space partitioning can be performed according to the zero-sequence component (for example, the zero-sequence component is 0).

[0095] The fifth step involves dividing each of the three-dimensional hierarchical spaces of the aforementioned switch vectors into three-dimensional sectors to generate a set of three-dimensional sector regions for the switch vectors. The three-dimensional sector regions within these regions can be sectors containing the switch state information, determined by dividing the space according to the phase angle in the αβ two-dimensional plane. This three-dimensional sector division can be achieved by dividing the αβ0 three-dimensional space into six large sectors of 60 degrees each to determine the sector information where the aforementioned switch state information is located within the divided three-dimensional sectors.

[0096] Step 6: Divide the aforementioned three-dimensional sector region set of switch vectors into tetrahedral regions to obtain a three-dimensional tetrahedral region set of switch vectors. The three-dimensional tetrahedral regions of the switch vectors in this set can be composed of the four nearest-neighbor converter switch space vectors, and these space vectors are linearly independent. In practice, the execution entity can first divide each 60-degree large sector according to the three medians projected onto the αβ plane to obtain a triangular region set. Next, stretch the triangular region set along the zero axis to obtain a set of switch triangular prisms. Then, divide the switch triangular prism set according to the plane connecting the converter switch space vectors to obtain the three-dimensional tetrahedral region set of switch vectors.

[0097] Step 7: Determine the compensation tetrahedral region group of each inverse-transformed converter compensation signal in the above-mentioned three-dimensional tetrahedral region group of the switch vector in the above-mentioned inverse-transformed converter compensation signal set, and obtain the compensation tetrahedral region set.

[0098] Step 8: Based on the aforementioned set of compensated tetrahedral regions, generate a set of switching action time information. This set of switching action time information can include the on / off duration of each of the 12 switching transistors in the parallel energy storage converter.

[0099] As an example, the aforementioned execution entity can input the space vectors of the four converter switches corresponding to each of the four compensated tetrahedral regions in the aforementioned compensated tetrahedral region set into the volt-second balance equation to obtain the set of switch action time information.

[0100] The ninth step involves generating pulse width modulation (PWM) signal information for the three-phase arms of the parallel energy storage converter based on the aforementioned switch action time information set. This PWM signal serves as the converter switch control information set. Unbalanced load control is then performed on the parallel energy storage converter based on this information set. The PWM signal information in the converter switch control information set can be the width (duty cycle) of the pulse signal used to control the switching of the parallel energy storage converter. In practice, the executing entity can first divide the switch action time information set using a seven-segment principle to obtain a divided set. Secondly, a zero vector is inserted into the start, middle, and end positions of each divided switch action time information in the divided set to obtain an inserted set. Then, the inserted set is encoded to obtain a pulse width transition value set. Finally, a switch state lookup table is used to map the pulse width transition value set to the inserted set to obtain the converter switch control information set.

[0101] The described technical solution and related content, as an inventive point of this disclosure, solve the technical problem of "increased voltage distortion and current circulation of energy storage converters, increased damage rate and reduced stability of parallel energy storage converters, increased switching losses of energy storage converters, and reduced stability and efficiency of microgrids." The factors that cause increased voltage distortion and current circulation of energy storage converters, increased damage rate and reduced stability of parallel energy storage converters, increased switching losses of energy storage converters, and reduced stability and efficiency of microgrids are often as follows: Under islanded operation, parallel energy storage converters in a three-phase four-wire topology, under unbalanced load conditions, possess zero-sequence components that cannot be compensated for by modulation. Two-dimensional space vector pulse width modulation cannot provide a modulation path for the zero-sequence components, causing zero-sequence current to flow into the filter capacitor, triggering three-phase voltage imbalance, leading to increased voltage distortion and current circulation of energy storage converters, increased damage rate and reduced stability of parallel energy storage converters, increased switching losses of energy storage converters, and reduced stability and efficiency of microgrids. Solving the above factors can reduce the damage rate and improve the stability of parallel energy storage converters, reduce switching losses of energy storage converters, and improve the stability and efficiency of microgrids. To achieve this effect, this disclosure first performs an inverse coordinate transformation on the converter compensation signal set, converting it from a global synchronous rotating coordinate system to a local stationary coordinate system, providing basic data for the subsequent generation of switching action time information. Second, it determines the converter switching space vector set of the switching state information set, transforming discrete switching state information into vector points in continuous space, providing a data basis for subsequent region partitioning. Next, it performs hierarchical space partitioning, three-dimensional sector partitioning, and tetrahedral partitioning on the converter switching space vector set, considering the influence of zero-sequence components. The complex hexagonal prism structure is divided into layers according to zero-sequence components, which simplifies the search space. Three-dimensional sector partitioning uses angles for coarse positioning, which improves computational efficiency. Tetrahedral partitioning enables precise positioning. By discretizing the continuous three-dimensional space, a set of efficient rules for quickly finding reference suitable sitting regions is established, which can greatly reduce the amount of computation and quickly and accurately locate vector positioning. Then, by determining the compensation tetrahedral region group of the converter compensation signal in the three-dimensional tetrahedral region group of the switching vector, it can be ensured that the error between the synthesized voltage vector and the reference vector is minimized, thereby achieving the lowest output current harmonics and voltage distortion.Subsequently, a set of switching action time information and a set of converter switching control information are generated. Unbalanced load control is then performed on the parallel energy storage converter. The generated switching action time information transforms the space vector modulation concept into a pulse width modulation waveform to calculate how long each switch needs to be on within a switching cycle, ensuring that the average output voltage equals the desired reference voltage. This improves the accuracy of control and the precision of the switching action time information. Furthermore, the converter switching control information considers the execution sequence of the switches, reducing the number of switching operations and smoothing the switching action, thereby reducing switching losses and improving the efficiency of the parallel energy storage converter. This further enhances the stability of the parallel energy storage converter, reduces equipment losses, and improves the stability and efficiency of the microgrid.

[0102] Further reference Figure 3 As an implementation of the methods shown in the above figures, this disclosure provides some embodiments of an unbalanced load control device based on a parallel energy storage converter. These device embodiments are similar to... Figure 1 Corresponding to the method embodiments shown, this unbalanced load control device based on parallel energy storage converter can be specifically applied to various electronic devices.

[0103] like Figure 3As shown, an unbalanced load control device 300 based on a parallel energy storage converter includes an acquisition unit 301 and an execution unit 302. The acquisition unit 301 is configured to acquire a set of converter electrical information of the parallel energy storage converter system under islanded operation conditions, wherein the converter electrical information includes at least one of the following: converter three-phase voltage information, converter three-phase current information, and converter capacity information. Execution unit 302 is configured to perform the following generation steps for each parallel energy storage converter included in the above-mentioned parallel energy storage converter system: performing sequence extraction processing on the three-phase voltage information and three-phase current information of the converter of the above-mentioned parallel energy storage converter to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set; generating positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the above-mentioned three-phase positive-sequence electrical information set, the above-mentioned three-phase negative-sequence electrical information set, and the above-mentioned three-phase zero-sequence electrical information set; and performing electrical... Voltage frequency recovery control is used to obtain the positive sequence voltage component set. Based on the positive sequence virtual impedance voltage value, the negative sequence virtual impedance voltage value, and the zero sequence virtual impedance voltage value, voltage and current inner and outer loop control is performed on the positive sequence voltage component set to obtain the converter arm voltage control information set. Based on the converter arm voltage control information set, suppression control processing is performed on the three-phase negative sequence electrical information set and the three-phase zero sequence electrical information set to obtain the converter compensation signal set. Based on the converter compensation signal set, the converter switching control information set is generated, and based on the converter switching control information set, unbalanced load control processing is performed on the parallel energy storage converter.

[0104] It is understandable that the units described in the unbalanced load control device 300 based on the parallel energy storage converter are related to the reference. Figure 1 The steps in the described method correspond accordingly. Therefore, the operations, features, and beneficial effects described above for the method also apply to the unbalanced load control device 300 based on the parallel energy storage converter and the units contained therein, and will not be repeated here.

[0105] The following is for reference. Figure 4 It shows a schematic diagram of the structure of an electronic device (e.g., an electronic device) 400 suitable for implementing some embodiments of the present disclosure. Figure 4 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of the embodiments of this disclosure.

[0106] like Figure 4As shown, electronic device 400 may include a processing device (e.g., a central processing unit, a graphics processor, etc.) 401, which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 402 or a program loaded from storage device 408 into random access memory (RAM) 403. RAM 403 also stores various programs and data required for the operation of electronic device 400. Processing device 401, ROM 402, and RAM 403 are interconnected via bus 404. Input / output (I / O) interface 405 is also connected to bus 404.

[0107] Typically, the following devices can be connected to I / O interface 405: input devices 406 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 407 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 408 including, for example, magnetic tapes, hard disks, etc.; and communication devices 409. Communication device 409 allows electronic device 400 to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 4 An electronic device 400 with various devices is shown; however, it should be understood that it is not required to implement or possess all of the devices shown. More or fewer devices may be implemented or possessed alternatively. Figure 4 Each box shown can represent a device or multiple devices as needed.

[0108] In particular, according to some embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, some embodiments of this disclosure include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication device 409, or installed from storage device 408, or installed from ROM 402. When the computer program is executed by processing device 401, it performs the functions defined above in the methods of some embodiments of this disclosure.

[0109] It should be noted that, in some embodiments of this disclosure, the computer-readable medium described above may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium may be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In some embodiments of this disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In some embodiments of this disclosure, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0110] In some implementations, clients and servers can communicate using any currently known or future-developed network protocol such as HTTP (Hypertext Transfer Protocol) and can interconnect with digital data communication (e.g., communication networks) of any form or medium. Examples of communication networks include local area networks (“LANs”), wide area networks (“WANs”), the Internet (e.g., the Internet of Things), and peer-to-peer networks (e.g., ad hoc peer-to-peer networks), as well as any currently known or future-developed networks.

[0111] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device. The aforementioned computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to: acquire a set of converter electrical information for a parallel energy storage converter system under islanded operation conditions, wherein the converter electrical information includes at least one of the following: converter three-phase voltage information, converter three-phase current information, and converter capacity information; and for each parallel energy storage converter included in the aforementioned parallel energy storage converter system, perform the following generation steps: for the converter of the aforementioned parallel energy storage converter... The three-phase voltage information and the three-phase current information of the converter are extracted and processed separately to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set. Based on the three-phase positive-sequence electrical information set, the three-phase negative-sequence electrical information set, and the three-phase zero-sequence electrical information set, positive-sequence virtual impedance voltage value, negative-sequence virtual impedance voltage value, and zero-sequence virtual impedance voltage value are generated. Based on the three-phase positive-sequence electrical information set, voltage-frequency recovery control is performed on the parallel energy storage converter to obtain a positive-sequence voltage component set. Based on the aforementioned positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values, voltage and current inner and outer loop control is performed on the aforementioned positive-sequence voltage component set to obtain the converter arm voltage control information set; based on the aforementioned converter arm voltage control information set, suppression control processing is performed on the aforementioned three-phase negative-sequence electrical information set and the aforementioned three-phase zero-sequence electrical information set to obtain the converter compensation signal set; based on the aforementioned converter compensation signal set, a converter switching control information set is generated, and based on the aforementioned converter switching control information set, unbalanced load control processing is performed on the aforementioned parallel energy storage converter.

[0112] Computer program code for performing operations of some embodiments of this disclosure can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can 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 can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0113] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0114] The units described in some embodiments of this disclosure can be implemented in software or hardware. The described units can also be housed in a processor; for example, a processor may be described as including an acquisition unit and an execution unit. The names of these units do not necessarily limit the unit itself; for example, an acquisition unit may also be described as "a unit that acquires a set of converter electrical information for a parallel energy storage converter system under islanded operation conditions."

[0115] The functions described above in this document can be performed at least in part by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip (SoCs), complex programmable logic devices (CPLDs), and so on.

[0116] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. An unbalanced load control method based on a parallel energy storage converter, comprising: Acquire the converter electrical information set of the parallel energy storage converter system under islanded operation conditions, wherein the converter electrical information includes at least one of the following: converter three-phase voltage information, converter three-phase current information and converter capacity information; For each parallel energy storage converter included in the parallel energy storage converter system, the following generation steps are performed: The three-phase voltage information and three-phase current information of the parallel energy storage converter are processed by sequence extraction to obtain a three-phase positive sequence electrical information set, a three-phase negative sequence electrical information set and a three-phase zero sequence electrical information set; Based on the three-phase positive sequence electrical information set, the three-phase negative sequence electrical information set, and the three-phase zero sequence electrical information set, generate positive sequence virtual impedance voltage value, negative sequence virtual impedance voltage value, and zero sequence virtual impedance voltage value; Based on the three-phase positive sequence electrical information set, voltage frequency recovery control is performed on the parallel energy storage converter to obtain the positive sequence voltage component set; Based on the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value, voltage and current inner and outer loop control is performed on the positive-sequence voltage component set to obtain the converter bridge arm voltage control information set, including: determining the difference between the first positive-sequence voltage component and the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence voltage drop included in the positive-sequence voltage component set, as the first voltage outer loop reference value, wherein the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence voltage drop are data from the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value; determining the second positive-sequence voltage component and the second transformed positive-sequence voltage drop included in the positive-sequence voltage component set. The difference between the voltage drop and the second transformed negative-sequence voltage drop is used as the second voltage outer loop reference value, wherein the second transformed positive-sequence voltage drop and the second transformed negative-sequence voltage drop are data from the positive-sequence virtual impedance voltage value and the negative-sequence virtual impedance voltage value; the difference between the first voltage outer loop reference value, the second voltage outer loop reference value, and the transformed three-phase positive-sequence electrical information set corresponding to the three-phase positive-sequence electrical information set is determined as the system voltage error value set; voltage external control is performed on the system voltage error value set to obtain the current inner loop reference value set; feedforward decoupling processing is performed on the current inner loop reference value set to obtain the decoupled current inner loop reference value set; inverse coordinate system transformation is performed on the decoupled current inner loop reference value set to obtain the converter bridge arm voltage control information set; Based on the converter arm voltage control information set, suppression control processing is performed on the three-phase negative-sequence electrical information set and the three-phase zero-sequence electrical information set to obtain a converter compensation signal set. This includes: performing negative-sequence component suppression processing on the parallel energy storage converter based on the current inner loop reference value set corresponding to the converter arm voltage control information set and the three-phase negative-sequence electrical information set to obtain a converter negative-sequence compensation voltage value set; determining the difference between the zero-sequence voltage included in the three-phase zero-sequence electrical information set and the preset zero-sequence reference voltage to obtain the zero-sequence voltage difference; and based on the zero-sequence voltage difference... The zero-sequence voltage compensation value is obtained by performing discretized dual-path control on the parallel energy storage converter; the DC bus voltage difference between the upper and lower capacitors on the DC side, which is included in the converter electrical information set, is determined; the voltage control processing of the parallel energy storage converter is performed according to the DC bus voltage difference to obtain the DC bus midpoint voltage compensation value; the sum of the zero-sequence voltage compensation value and the DC bus midpoint voltage compensation value is determined as the zero-sequence component voltage compensation value; the zero-sequence component voltage compensation value and the converter negative-sequence compensation voltage value set are determined as the converter compensation signal set. Based on the converter compensation signal set, a converter switching control information set is generated, and based on the converter switching control information set, unbalanced load control processing is performed on the parallel energy storage converter.

2. The method according to claim 1, wherein, The three-phase voltage information and three-phase current information of the parallel energy storage converter are extracted in sequence to obtain a three-phase positive sequence electrical information set, a three-phase negative sequence electrical information set, and a three-phase zero sequence electrical information set, including: Based on the three-phase voltage information of the parallel energy storage converter, the following determination steps are performed: The three-phase voltage information of the converter is transformed into a coordinate system to obtain the three-phase voltage of the converter after the first transformation, the three-phase voltage of the converter after the second transformation, and the three-phase zero-sequence voltage. The three-phase voltages of the first and second converted converters are filtered and offset respectively to obtain the first in-phase voltage component, the first quadrature voltage component, the second in-phase voltage component, and the second quadrature voltage component. Based on the first in-phase voltage component, the first quadrature voltage component, the second in-phase voltage component, and the second quadrature voltage component, a first static positive sequence voltage, a second static positive sequence voltage, a first static negative sequence voltage, and a second static negative sequence voltage are generated. Based on the three-phase current information of the converter, a first static positive sequence current, a second static positive sequence current, a first static negative sequence current, a second static negative sequence current, and a three-phase zero sequence current are generated; The first static positive sequence voltage, the second static positive sequence voltage, the first static positive sequence current, and the second static positive sequence current are determined as the three-phase positive sequence electrical information set; the first static negative sequence voltage, the second static negative sequence voltage, the first static negative sequence current, and the second static negative sequence current are determined as the three-phase negative sequence electrical information set; and the three-phase zero sequence voltage and the three-phase zero sequence current are determined as the three-phase zero sequence electrical information set.

3. The method according to claim 1, wherein, The step of generating positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the three-phase positive-sequence electrical information set, the three-phase negative-sequence electrical information set, and the three-phase zero-sequence electrical information set includes: Determine the line resistance impedance difference between the parallel energy storage converters and the common coupling point in the parallel energy storage converter system. Based on the difference in line resistance, determine the virtual inductance value and the virtual impedance value; The difference between the product of the virtual impedance value and the first static positive sequence current included in the three-phase positive sequence electrical information set, and the product of the virtual inductance value, the system angular frequency, and the second static positive sequence current included in the three-phase positive sequence electrical information set, is determined as the first positive sequence virtual impedance voltage drop. The product of the virtual impedance value and the second static positive sequence current, and the sum of the product of the virtual inductance value, the system angular frequency, and the first static positive sequence current, are determined as the second positive sequence virtual impedance voltage drop. The product of the virtual impedance value and the first static negative sequence current included in the three-phase positive sequence electrical information set, the inverse of the virtual inductance value, and the product of the system angular frequency and the second static negative sequence current included in the three-phase negative sequence electrical information set are determined as the first negative sequence virtual impedance voltage drop. The product of the virtual impedance value and the second static negative sequence current, the negative of the virtual inductance value, and the sum of the product of the system angular frequency and the first static negative sequence current are determined as the second negative sequence virtual impedance voltage drop. The product of the virtual impedance value and the three-phase zero-sequence current included in the three-phase zero-sequence electrical information is determined as the zero-sequence virtual impedance voltage drop. The first positive-sequence virtual impedance voltage drop, the second positive-sequence virtual impedance voltage drop, the first negative-sequence virtual impedance voltage drop, the second negative-sequence virtual impedance voltage drop, and the zero-sequence virtual impedance voltage drop are transformed in a coordinate system to obtain the first transformed positive-sequence voltage drop, the second transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, the second transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop, which are used as the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value.

4. The method according to claim 1, wherein, The step of performing voltage and frequency recovery control on the parallel energy storage converter based on the three-phase positive sequence electrical information set to obtain a positive sequence voltage component set includes: The coordinate system is transformed into the three-phase positive sequence electrical information set to obtain the transformed three-phase positive sequence electrical information set. Based on the converted three-phase positive sequence electrical information set, determine the positive sequence instantaneous active power and positive sequence instantaneous reactive power of the parallel energy storage converter; The positive-sequence instantaneous active power and the positive-sequence instantaneous reactive power are respectively filtered to obtain filtered positive-sequence instantaneous active power and filtered positive-sequence instantaneous reactive power. Determine the set of droop adjustment coefficients for the parallel energy storage converter; Based on the filtered positive-sequence instantaneous active power, the filtered positive-sequence instantaneous reactive power, and the droop adjustment coefficient set, converter voltage amplitude regulation information and system angular frequency regulation information are generated. Based on the converter voltage amplitude adjustment information and the system angular frequency adjustment information, a positive sequence voltage component set is generated.

5. An unbalanced load control device based on a parallel energy storage converter, comprising: The acquisition unit is configured to acquire a set of converter electrical information of the parallel energy storage converter system under islanded operation conditions, wherein the converter electrical information includes at least one of the following: converter three-phase voltage information, converter three-phase current information and converter capacity information; The execution unit is configured to perform the following generation steps for each parallel energy storage converter included in the parallel energy storage converter system: performing sequence extraction processing on the three-phase voltage information and three-phase current information of the parallel energy storage converter to obtain a three-phase positive-sequence electrical information set, a three-phase negative-sequence electrical information set, and a three-phase zero-sequence electrical information set; generating positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the three-phase positive-sequence electrical information set, the three-phase negative-sequence electrical information set, and the three-phase zero-sequence electrical information set; performing voltage-frequency recovery control on the parallel energy storage converter based on the three-phase positive-sequence electrical information set to obtain a positive-sequence voltage component set; and generating positive-sequence virtual impedance voltage values, negative-sequence virtual impedance voltage values, and zero-sequence virtual impedance voltage values ​​based on the positive-sequence virtual impedance voltage values, The negative-sequence virtual impedance voltage value and the zero-sequence virtual impedance voltage value are used to perform voltage and current inner and outer loop control on the positive-sequence voltage component set to obtain the converter bridge arm voltage control information set, including: determining the difference between the first positive-sequence voltage component and the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop included in the positive-sequence voltage component set, as the first voltage outer loop reference value, wherein the first transformed positive-sequence voltage drop, the first transformed negative-sequence voltage drop, and the zero-sequence transformed voltage drop are data from the positive-sequence virtual impedance voltage value, the negative-sequence virtual impedance voltage value, and the zero-sequence virtual impedance voltage value; determining the second positive-sequence voltage component and the second transformed positive-sequence voltage drop, the second transformed negative-sequence voltage drop, and the second transformed negative-sequence voltage drop included in the positive-sequence voltage component set. The voltage difference is used as the second voltage outer loop reference value, wherein the second transformed positive-sequence voltage drop and the second transformed negative-sequence voltage drop are data from the positive-sequence virtual impedance voltage value and the negative-sequence virtual impedance voltage value; the difference between the first voltage outer loop reference value, the second voltage outer loop reference value, and the transformed three-phase positive-sequence electrical information set corresponding to the three-phase positive-sequence electrical information set is determined as the system voltage error value set; voltage external control is performed on the system voltage error value set to obtain the current inner loop reference value set; feedforward decoupling processing is performed on the current inner loop reference value set to obtain the decoupled current inner loop reference value set; inverse coordinate system transformation is performed on the decoupled current inner loop reference value set to obtain the converter bridge arm voltage control information set; according to the converter The bridge arm voltage control information set is used to suppress and control the three-phase negative-sequence electrical information set and the three-phase zero-sequence electrical information set to obtain a converter compensation signal set. This includes: performing negative-sequence component suppression processing on the parallel energy storage converter based on the current inner loop reference value set corresponding to the converter bridge arm voltage control information set and the three-phase negative-sequence electrical information set to obtain a converter negative-sequence compensation voltage value set; determining the difference between the zero-sequence voltage included in the three-phase zero-sequence electrical information set and the preset zero-sequence reference voltage to obtain a zero-sequence voltage difference; performing discretized dual-path control on the parallel energy storage converter based on the zero-sequence voltage difference to obtain a zero-sequence voltage compensation amount; and determining the DC bus voltage difference between the upper and lower DC capacitors included in the converter electrical information set.Based on the DC bus voltage difference, voltage control processing is performed on the parallel energy storage converter to obtain the DC bus midpoint voltage compensation value; the sum of the zero-sequence voltage compensation amount and the DC bus midpoint voltage compensation value is determined as the zero-sequence component voltage compensation value; the zero-sequence component voltage compensation value and the converter negative-sequence compensation voltage value set are determined as the converter compensation signal set; based on the converter compensation signal set, a converter switching control information set is generated, and based on the converter switching control information set, unbalanced load control processing is performed on the parallel energy storage converter.

6. An electronic device, comprising: One or more processors; Storage device, on which one or more programs are stored, When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-4.

7. A computer-readable medium having a computer program stored thereon, wherein, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-4.

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