Three-port energy storage composite chain STATCOM topology structure, system and control method

Abstract

The present invention belongs to the technical field of power electronic converters, and discloses a three-port energy storage composite cascaded STATCOM topology and a control method. The topology includes three connecting reactors L, a cascaded STATCOM, an autotransformer, a three-phase inverter circuit, and two energy storage devices DC1 and DC2; the cascaded STATCOM includes three cascaded H-bridge circuits; the three-phase inverter circuit includes three arms each containing two IGBTs, a low-voltage DC port, and a high-voltage DC port; one end of the cascaded STATCOM is connected to the 10 kV AC feeder of the power grid through the connecting reactor L, and the other end is connected to the primary side of the autotransformer; the secondary side of the autotransformer is connected to the AC side of the three-phase inverter circuit, and the neutral point of the secondary side is connected to the low-voltage energy storage device DC1; the DC ports of the three-phase inverter circuit are respectively connected to the low-voltage energy storage device DC1 and the high-voltage energy storage device DC2.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic converters, and in particular relates to a three-port energy storage composite chain STATCOM topology structure and a control method. Background Art

[0002] Static Synchronous Compensator (STATCOM) is a bidirectional reactive power compensation device that uses high-frequency fully controlled switching devices such as IGBT and MOSFET. Compared with reactive power compensation devices such as shunt capacitors and synchronous condensers, STATCOM has the advantages of fast dynamic response, low harmonic content, wide adjustment range, and low operating cost. With the development of power electronics technology, STATCOM has been more widely used in improving system damping, suppressing system resonance, and stabilizing grid operation.

[0003] In order to obtain better control performance, such as compensating for circuit resistive voltage drop, damping oscillation, improving transient stability, and extending the support time in the event of an accident, STATCOM is often required to deliver active power to the power system for a period of time. However, STATCOM itself does not have the ability to control the active power flow. However, if STATCOM and energy storage devices can be integrated together, active power flow and reactive power flow can be controlled at the same time, thereby providing more flexible and diverse power regulation functions.

[0004] Through the above analysis, the problems and defects of the existing technology are: STATCOM itself has no ability to control the active power flow and cannot deliver active power to the power system within a period of time.

[0005] The existing technology similar to the proposed three-port energy storage composite chain STATCOM topology is the traditional static synchronous compensator (STATCOM). STATCOM is usually used in power systems to provide reactive power support, improve voltage stability and power quality. It is mainly based on voltage source inverter (VSI) technology and realizes its function through a transformer connected to the grid.

[0006] Technical problems existing in the existing technology:

[0007] 1) Limited functional scope: Traditional STATCOM is mainly used for reactive power control, and its functions are relatively limited in active power management and energy storage. This limits its utility in more complex grid applications, especially in scenarios that require comprehensive energy management and regulation.

[0008] 2) Low energy storage capacity: Traditional STATCOMs usually do not have integrated energy storage devices and therefore cannot effectively store or release energy to cope with fluctuations in grid demand. This means they cannot act as a buffer between power supply and demand.

[0009] 3) System complexity and cost: When energy storage function needs to be added, traditional STATCOM requires additional system integration, such as an external battery storage system, which increases system complexity and cost.

[0010] 4) Insufficient adaptability and flexibility: The design of traditional STATCOM is usually not flexible enough to adapt to changing grid conditions and demands, especially in the evolving renewable energy integration and smart grid environment.

[0011] 5) Efficiency and performance limitations: Conventional STATCOM cannot provide optimal performance under high dynamic range of load or grid conditions, especially under rapidly changing voltage and load conditions.

[0012] In contrast, the proposed three-port energy storage composite chain STATCOM topology structure provides an effective solution to the limitations of the above existing technologies by integrating energy storage devices and providing enhanced power conversion and control functions. This not only improves the flexibility and adaptability of the system, but also enhances the overall performance and stability of the power grid. Summary of the invention

[0013] In view of the problems existing in the prior art, the present invention provides a three-port energy storage composite chain STATCOM topology structure and a control method.

[0014] The present invention is implemented in this way: reactive power compensation is achieved through a chain STATCOM connected to a 10kV AC port of a power grid, a three-phase inverter circuit controls active power, a DC side of the three-phase inverter circuit is connected to a high-voltage DC port, a zigzag transformer connects the chain STATCOM and the AC port of the three-phase inverter circuit, a neutral point of the zigzag transformer is connected to a low-voltage DC port, and a 10kV AC port forms a three-port structure with high and low voltage DC ports, and the high and low voltage DC ports can provide active support for the chain STATCOM and deliver active power to the power system. The present invention has both the function of reactive power compensation of the chain STATCOM and can control the active power flow, deliver active power to the power system, and has flexible and diverse electric energy regulation functions.

[0015] The present invention proposes a three-port energy storage composite chain STATCOM topology structure, including three connected reactors L, a chain STATCOM, a zigzag transformer, a three-phase inverter circuit and two energy storage devices DC 1 、DC 2 ;

[0016] The chain STATCOM consists of three cascaded H-bridge circuits, namely H A , H B , H C ;

[0017] The cascade H-bridge circuit includes several H-bridge circuits, which are represented by numbers 1, 2, ..., n, respectively. Several of them can be selected according to specific application scenarios, cost and space constraints;

[0018] The H-bridge circuit consists of two bridge arms with two IGBTs and a DC side capacitor C Hd composition;

[0019] Zigzag transformer primary L T1 The same-name terminal is connected to the chain STATCOM, and the three L T2 The same-name terminal is connected as the neutral point and connected to the filter inductor L on the low-voltage DC side. dc Connected, L dc The other end is connected to the low voltage DC side capacitor C d1 The other end of the secondary side is connected to the AC side of the three-phase inverter circuit;

[0020] The three-phase inverter circuit includes three bridge arms containing two IGBTs, a low-voltage DC port and a high-voltage DC port;

[0021] The AC port of the three-phase inverter circuit is connected to the secondary side of the zigzag transformer, and the DC port includes a low-voltage DC port and a high-voltage DC port; the low-voltage DC port includes a low-voltage DC capacitor C d1 , and low voltage energy storage device DC 1 connected; the high voltage DC port includes a high voltage DC capacitor C d2 , and high voltage energy storage device DC 2 connected;

[0022] The power conversion from the low voltage DC port to the high voltage DC port can be realized by a three-phase inverter circuit in the form of three-way Boost, and the Boost inductor is L T2 ;

[0023] Two energy storage devices DC 1 、DC 2 For photovoltaic power generation systems and battery energy storage equipment;

[0024] The three-port structure includes a grid 10kV AC port, a low-voltage DC port, and a high-voltage DC port.

[0025] Furthermore, the chain STATCOM is used to realize reactive power compensation of the grid-connected port. In the three-port energy storage composite chain STATCOM topology structure, the chain STATCOM grid-connected three-phase voltage is: u sa、u sb 、u sc ; The three-phase current of the chain STATCOM grid-connected is: i sa 、i sb 、i sc ; The DC side voltage of each H-bridge circuit in each phase of the chain STATCOM is: U Hdx-A , U Hdx-B , U Hdx-C ,x=1,2,…,n;The sum of the DC side voltages of all H-bridge circuits of each phase of the chain STATCOM is: U HdΣ-A , U HdΣ-B , U HdΣ-C。

[0026] Furthermore, the three-phase inverter circuit is used to control the active power P. In the three-port energy storage composite chain STATCOM topology structure, the three-phase voltage on the AC side of the three-phase inverter circuit is: u ia 、u ib 、u ic ; The three-phase current on the AC side of the three-phase inverter circuit is: i ia 、i ib 、i ic .

[0027] Furthermore, the power conversion from the low voltage DC port to the high voltage DC port can be realized by a three-way Boost structure, which includes three Boost inductors L T2 , the three-phase inverter circuit has three IGBT switch tubes in the lower bridge arms and three diodes in the upper bridge arms.

[0028] Another object of the present invention is to provide a method for realizing the three-port energy storage composite chain STATCOM topology control structure, wherein the chain STATCOM reactive power control is realized by DC voltage outer loop and current inner loop control, comprising the following steps:

[0029] (1) Perform PARK transformation on the output voltage and current of the 10 kV AC feeder of the power grid to obtain the voltage u in the two-phase synchronous rotating coordinate system sd 、u sq and current i sd 、i sq ;

[0030] (2) The sum of the DC side voltages of all H-bridge circuits in each phase of the chained STATCOM is U HdΣ-A , U HdΣ-A , U HdΣ-A Add them together and multiply by 1 / 3 to get the total DC voltage average value U HdΣ ;

[0031] (3) Set the DC voltage reference value U HdΣ*, with the total DC voltage average value U HdΣ Subtract, the difference is input into the voltage loop proportional integral controller, and the output d-axis current reference value i sd *;

[0032] (4) Set the reactive power reference value Q*, subtract it from the actual reactive power Q of the grid-connected port, and input the difference into the reactive power proportional integral controller to output the q-axis current reference value i sq *;

[0033] (5) Set the d-axis current reference value i sd * and d-axis current i sd Subtract the difference, and input the current loop proportional integral controller to convert the angular velocity ω, the reactor L and the q-axis current i sq The product of the d-axis voltage u sd Add and subtract the output value of the current loop proportional integral controller to obtain the d-axis voltage reference value; the q-axis current reference value i sq * and q-axis current i sq Subtract the difference, and input the current loop proportional integral controller to convert the q-axis voltage u sq Subtract the angular velocity ω, the reactor L, and the d-axis current i sd The product of , minus the output value of the current loop proportional integral controller, is used to obtain the q-axis voltage reference value;

[0034] (6) Inverse PARK transformation of the d-axis voltage reference value and the q-axis voltage reference value to generate the modulation voltage u sma 、u smb 、u smc And input PWM generator to form PWM signal g sax , g sbx , g scx , to control each H-bridge module of the chain STATCOM.

[0035] Furthermore, the active power control of the three-phase inverter circuit is realized by power outer loop and voltage inner loop control, including the following steps:

[0036] (1) Perform PARK transformation on the voltage and current on the AC side of the three-phase inverter circuit to obtain the voltage u in the two-phase synchronous rotating coordinate system id 、u iq and current i id 、i iq ;

[0037] (2) Set the active power reference value P*, subtract it from the actual active power P at the port, and input the difference into the active power proportional integral controller to output the d-axis voltage reference value u id *, q-axis voltage reference value u iq * Set to 0;

[0038] (3) The d-axis voltage reference value u id * and d-axis voltage u id Subtract the difference, and input the voltage loop proportional integral controller; the q-axis voltage reference value u iq * and q-axis voltage u iq Subtract them, and the difference is input into the voltage loop proportional integral controller;

[0039] (4) Perform an inverse PARK transformation on the output value of the voltage loop proportional integral controller to generate a three-phase voltage reference value u ima 、u imb 、u imc , and input the PWM generator.

[0040] Furthermore, in the three-way Boost structure, the DC power is output by controlling the on-duty ratio N of the three lower bridge arm IGBT switch tubes, including the following steps:

[0041] (1) Set the specified value of the low voltage DC port output current to i dc1 *, the specified value of the output current i dc1 *The actual output current value of the low voltage DC port i dc1 Subtract, the difference is input into the DC current loop proportional integral controller, the proportional integral controller outputs the per unit value of the DC bias voltage U abc , so that the duty cycle N can be controlled abc +1) / 2.

[0042] The three-phase voltage reference value u ima 、u imb 、u imc Respectively with U abc Add together to generate the modulation voltage u a 、u b 、u c And input PWM generator to generate PWM signal g i1～6 , to control six IGBTs.

[0043] Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the three-port energy storage composite chain STATCOM topology structure control method.

[0044] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to execute the steps of the three-port energy storage composite chain STATCOM topology structure control method.

[0045] Another object of the present invention is to provide a three-port energy storage composite chain STATCOM system, characterized in that the system comprises:

[0046] Chain STATCOM: It consists of three cascaded H-bridge circuits, marked as H A , H B , H C Each cascaded H-bridge circuit includes a number of H-bridge circuits numbered 1, 2, ..., n, and the number of these H-bridge circuits is selected according to specific application scenarios, cost, and space constraints.

[0047] H-bridge circuit composition: Each H-bridge circuit consists of two bridge arms containing two IGBTs and a DC side capacitor C Hd composition.

[0048] Zigzag transformer and three-phase inverter circuit: The primary side L of the zigzag transformer T1 Connected to the chain STATCOM, the three L T2 The same-name ends form a neutral point and are connected to the filter inductor Ldc on the low-voltage DC side. The other end of Ldc is connected to the low-voltage DC side capacitor C d1 The other end of the secondary side is connected to the AC side of a three-phase inverter circuit, which includes three bridge arms including two IGBTs, a low-voltage DC port and a high-voltage DC port.

[0049] The DC port is connected to the energy storage device: the low-voltage DC port includes a low-voltage DC capacitor C d1 , and low voltage energy storage device DC 1 connected; the high voltage DC port includes a high voltage DC capacitor C d2 , and high voltage energy storage device DC 2 connected.

[0050] Power conversion mechanism: The power conversion from the low-voltage DC port to the high-voltage DC port is realized through a three-phase inverter circuit in the form of three-way Boost, where the Boost inductor is L T2 .

[0051] Energy storage device type: Two energy storage devices DC 1 、DC 2 It can be a photovoltaic power generation system, battery energy storage equipment, etc.

[0052] Three-port structure: including grid 10kV AC port, low-voltage DC port and high-voltage DC port.

[0053] Another object of the present invention is to provide a three-port energy storage composite chain STATCOM system for efficient conversion and control of electric energy, characterized in that the system combines advanced power electronics technology and energy storage technology, specifically including:

[0054] Chain STATCOM configuration: contains three cascaded H-bridge circuits, each of which is composed of several small H-bridge circuits numbered 1, 2, ..., n to adapt to different grid loads and conversion requirements.

[0055] Circuit and transformer design: Each H-bridge circuit consists of two bridge arms containing IGBTs and a DC side capacitor; the primary side of the zigzag transformer is connected to the chain-type STATCOM, and the secondary side is connected to the three-phase inverter circuit to achieve efficient power conversion.

[0056] Three-phase inverter circuit and energy storage connection: The three-phase inverter circuit has low-voltage and high-voltage DC ports, which are connected to low-voltage energy storage devices DC 1 and high voltage energy storage devices DC 2 , to achieve energy storage and release at different voltage levels.

[0057] Flexible application of energy storage equipment: DC 1 and DC 2 Different types of energy storage devices can be selected, such as photovoltaic power generation systems or battery energy storage devices, to adapt to different energy needs and operating conditions.

[0058] Three-port system integration: The system integrates the grid's 10kV AC port, low-voltage DC port and high-voltage DC port to achieve efficient interconnection between the grid and various energy storage methods.

[0059] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0060] First, in view of the fact that the current STATCOM itself has no ability to control the active power flow and cannot deliver active power to the power system within a period of time, the design idea of ​​the present invention is: by performing energy storage compounding, active power support is provided for the chain STATCOM, and active power is delivered to the power system; in order to control the active power, a three-phase inverter circuit is introduced, and its DC side is used as a high-voltage DC port; further, a zigzag transformer is introduced, and its neutral point can be led out as a low-voltage DC port for connection. The present invention forms a flexible interconnection between the two energy storage devices and the 10kV AC feeder of the power grid. The introduction of the three-phase inverter circuit can control the active power flow, and the introduction of the energy storage device can provide certain active support for the chain STATCOM and deliver active power to the power system.

[0061] Second, the present invention realizes reactive power compensation through a chain STATCOM connected to the 10kV AC port of the power grid. The three-phase inverter circuit controls active power. The DC side of the three-phase inverter circuit is connected to the high-voltage DC port. The zigzag transformer connects the chain STATCOM and the AC port of the three-phase inverter circuit. The neutral point of the zigzag transformer is connected to the low-voltage DC port. The 10kV AC port and the high and low voltage DC ports form a three-port structure. The high and low voltage DC ports can provide active support for the chain STATCOM and deliver active power to the power system. The present invention not only has the reactive power compensation function of the chain STATCOM, but also can control the active power flow and deliver active power to the power system. It has flexible and diverse power regulation functions.

[0062] Third, the expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: based on the 10kV medium-voltage chain STATCOM, the present invention can simultaneously control the active power flow and the reactive power flow, thereby having a more flexible and diverse power regulation function, and for the subsequent further power quality management such as compensating for circuit resistive voltage drop, damping oscillation, improving transient stability, and extending the support time in the event of an accident, etc., it provides a novel solution.

[0063] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad: the present invention realizes reactive power compensation through a chain STATCOM connected to the 10kV AC port of the power grid, and the three-phase inverter circuit controls the active power. The DC side of the three-phase inverter circuit is connected to the high-voltage DC port. The zigzag transformer connects the chain STATCOM and the AC port of the three-phase inverter circuit. The neutral point of the zigzag transformer is connected to the low-voltage DC port. It not only has the function of reactive power compensation of the chain STATCOM, but also can control the active power flow and transmit active power to the power system. It has flexible and diverse power regulation functions and provides a new type of energy storage STATCOM solution.

[0064] The technical solution of the present invention solves a technical problem that people have been eager to solve but have never been successful: most of the current energy storage STATCOMs add energy storage devices to the DC side of each H-bridge circuit of the cascaded H-bridge circuit, and need to add corresponding DC-DC converters. Due to the large number of H-bridge circuits required, this solution is complex to control, has a large number of components, and is costly. How to reduce costs and simplify control are technical difficulties that energy storage STATCOMs need to solve. The present invention connects the chain STATCOM to the AC side of the three-phase inverter circuit through a zigzag transformer. The DC side of the three-phase inverter circuit is a high-voltage DC port, and the midpoint of the zigzag transformer is led out as a low-voltage DC port. The two DC ports provide active support for the chain STATCOM and transmit active power to the power system. In comparison, the present invention has simpler control, fewer components, and lower costs, providing a new idea for energy storage STATCOM.

[0065] Fourth, the three-port energy storage composite chain STATCOM topology structure of the present invention brings the following significant technical advances:

[0066] 1. Enhanced grid stability and flexibility: By combining the chain STATCOM and the three-phase inverter circuit, the present invention provides a more flexible and efficient grid reactive and active power control. This control not only improves the stability of the grid, but also enhances the ability to cope with grid fluctuations and load changes.

[0067] 2. Efficient energy management: two energy storage devices DC 1 and DC 2 The introduction of makes energy management more efficient, allowing energy to be released during peak demand and stored during low demand. This helps balance the load on the grid and improve overall energy efficiency.

[0068] 3. Improvement of power quality: Through precise control of reactive power of the power grid and effective management of active power, the present invention can improve the quality of the power grid, such as reducing voltage fluctuations and harmonic content, and improving the quality and reliability of power.

[0069] 4. Flexible energy storage options: The present invention allows the use of multiple types of energy storage devices, such as batteries, photovoltaics, etc., providing more flexibility and options for different grid applications and conditions.

[0070] 5. Adaptability to different grid conditions: The design of the three-port structure enables the system to adapt to different grid conditions, including different voltage levels and load types, which increases its adaptability and application scope in diversified power systems.

[0071] 6. Promote the integration of renewable energy: This invention is crucial for the integration of large-scale renewable energy such as wind power, solar power, etc. It can provide the necessary grid support to ensure the stable and efficient access of renewable energy to the grid.

[0072] The three-port energy storage composite chain STATCOM topology structure of the present invention shows significant technical progress in improving grid stability and efficiency, promoting renewable energy integration, and providing flexible energy management solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0074] Figure 1 It is a topological structure diagram of a three-port energy storage composite chain STATCOM provided in an embodiment of the present invention;

[0075] Figure 2 is a control block diagram of a chained STATCOM provided by an embodiment of the present invention;

[0076] Figure 3 is a control block diagram of a three-phase inverter circuit provided by an embodiment of the present invention;

[0077] Figure 4 is a three-way Boost structure diagram provided by an embodiment of the present invention;

[0078] Figure 5 It is a reactive power waveform diagram of the grid-connected port of the chained STATCOM provided by an embodiment of the present invention;

[0079] Figure 6 is a waveform diagram of active power at an AC port of a three-phase inverter circuit provided by an embodiment of the present invention;

[0080] Figure 7 is a low-voltage DC port current waveform diagram under overall operation provided by an embodiment of the present invention;

[0081] Figure 8 It is a voltage waveform diagram of a high-voltage DC port during overall operation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0082] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0083] The present invention realizes reactive power compensation through a chain STATCOM connected to a 10kV AC port of a power grid, a three-phase inverter circuit controls active power, a DC side of the three-phase inverter circuit is connected to a high-voltage DC port, a zigzag transformer connects the chain STATCOM and the AC port of the three-phase inverter circuit, a neutral point of the zigzag transformer is connected to a low-voltage DC port, and a 10kV AC port and high- and low-voltage DC ports form a three-port structure, and the high- and low-voltage DC ports can provide active support for the chain STATCOM and transmit active power to the power system.

[0084] The three-port energy storage composite chain STATCOM topology structure of the present invention provides an efficient and flexible power conversion and control method, which is suitable for modern power systems. The following are two specific embodiments and their implementation schemes:

[0085] Example 1

[0086] 1) System construction:

[0087] Construct a circuit consisting of three cascaded H-bridges (H A , H B , H C ) chain STATCOM.

[0088] Each H-bridge circuit is composed of a number of small H-bridge circuits numbered 1, 2, ..., n, and the specific number is determined according to application requirements and cost considerations.

[0089] The H-bridge circuit includes two bridge arms and a DC side capacitor C Hd .

[0090] 2) Transformer and inverter circuit:

[0091] The primary side of the zigzag transformer L T1 Connected to the chain STATCOM, the secondary side forms a neutral point and is connected to the low-voltage DC side filter inductor L dc connect.

[0092] The three-phase inverter circuit is connected to the secondary side of the zigzag transformer and includes three bridge arms containing IGBTs and low / high voltage DC ports.

[0093] 3) DC port and energy storage equipment:

[0094] The low voltage DC port is connected to the low voltage DC capacitor C d1 and low voltage energy storage devices DC 1 .

[0095] The high voltage DC port is connected to the high voltage DC capacitor C d2 and high voltage energy storage devices DC 2 (Such as photovoltaic systems, battery energy storage equipment, etc.).

[0096] 4) Operation control:

[0097] The chain STATCOM controls the reactive power of the grid-connected port, and the three-phase inverter controls the active power of the port.

[0098] Realize flexible interconnection between the two energy storage devices and the grid’s 10kV AC feeder.

[0099] Example 2

[0100] 1) System optimization:

[0101] Based on Example 1, the number and configuration of H-bridge circuits are optimized to adapt to higher power requirements or different operating conditions.

[0102] 2) Control strategy:

[0103] Develop advanced control strategies to ensure stable system operation under various load and grid conditions.

[0104] Optimize power conversion efficiency and reduce energy loss.

[0105] 3) Intelligent management:

[0106] Integrated intelligent management system for real-time monitoring and adjustment of system performance.

[0107] The system can automatically adjust the flow and conversion rate of electrical energy according to grid demand and the status of energy storage equipment.

[0108] 4) Application extension:

[0109] Apply this system to a wider range of fields, such as large-scale renewable energy access, grid quality improvement, etc.

[0110] By coordinating with other power grid equipment (such as FACTS equipment), the overall performance and stability of the power grid can be further improved.

[0111] The two embodiments provided by the present invention demonstrate the flexibility and scalability of the present invention under different application scenarios and requirements, highlighting its practical value and potential in modern power systems.

[0112] In view of the problems existing in the prior art, the present invention provides a three-port energy storage composite chain STATCOM topology structure and a control method. The present invention is described in detail below with reference to the accompanying drawings.

[0113] Figure 1 The three-port energy storage composite chain STATCOM topology structure provided by the embodiment of the present invention includes three connected reactors L, a chain STATCOM, a zigzag transformer, a three-phase inverter circuit and two energy storage devices DC1 、DC 2 ;

[0114] The chain STATCOM consists of three cascaded H-bridge circuits, namely H A , H B , H C ;

[0115] The cascade H-bridge circuit includes several H-bridge circuits, which are represented by numbers 1, 2, ..., n, respectively. Several of them can be selected according to specific application scenarios, cost and space constraints.

[0116] The H-bridge circuit consists of two bridge arms with two IGBTs and a DC side capacitor C Hd composition;

[0117] Zigzag transformer primary L T1 The same-name terminal is connected to the chain STATCOM, and the three L T2 The same-name terminal is connected as the neutral point and connected to the filter inductor L on the low-voltage DC side. dc Connected, L dc The other end is connected to the low voltage DC side capacitor C d1 The other end of the secondary side is connected to the AC side of the three-phase inverter circuit;

[0118] The three-phase inverter circuit includes three bridge arms containing two IGBTs, a low-voltage DC port and a high-voltage DC port;

[0119] The AC port of the three-phase inverter circuit is connected to the secondary side of the zigzag transformer, and the DC port includes a low-voltage DC port and a high-voltage DC port; the low-voltage DC port includes a low-voltage DC capacitor C d1 , and low voltage energy storage device DC 1 connected; the high voltage DC port includes a high voltage DC capacitor C d2 , and high voltage energy storage device DC 2 connected;

[0120] The power conversion from the low voltage DC port to the high voltage DC port can be realized by a three-phase inverter circuit in the form of three-way Boost, and the Boost inductor is L T2 ;

[0121] Two energy storage devices DC 1 、DC 2 It can be photovoltaic power generation system, battery energy storage equipment, etc.

[0122] The three-port structure includes a grid 10kV AC port, a low-voltage DC port, and a high-voltage DC port.

[0123] The three-port energy storage composite chain STATCOM topology structure provided by the embodiment of the present invention controls the reactive power of the grid-connected port through the chain STATCOM, and the three-phase inverter controls the active power of the port during steady-state operation, thereby realizing flexible interconnection between the two energy storage devices and the 10kV AC feeder of the power grid. Figures 1 to 8 The specific implementation modes of the present invention are introduced.

[0124] Figure 1 A three-port energy storage composite chain STATCOM topology structure in steady-state operation:

[0125] In the three-port energy storage composite chain STATCOM topology structure, the three-phase voltage of the chain STATCOM grid-connected is: sa 、u sb 、u sc ;

[0126] In the three-port energy storage composite chain STATCOM topology structure, the chain STATCOM grid-connected three-phase current is: i sa 、i sb 、i sc ;

[0127] In the three-port energy storage composite chain STATCOM topology structure, the DC side voltage of each H-bridge circuit in each phase of the chain STATCOM is: U Hdx-A , U Hdx-B , U Hdx-C , x=1,2,…,n;

[0128] In the three-port energy storage composite chain STATCOM topology structure, the sum of the DC side voltages of all H-bridge circuits of each phase of the chain STATCOM is: U HdΣ-A , U HdΣ-B , U HdΣ-C ;

[0129] In the three-port energy storage composite chain STATCOM topology structure, the three-phase voltage on the AC side of the three-phase inverter circuit is: ia 、u ib 、u ic ;

[0130] In the three-port energy storage composite chain STATCOM topology structure, the three-phase current on the AC side of the three-phase inverter circuit is: i ia 、i ib 、i ic ;

[0131] Figure 2A control block diagram of a chain STATCOM in a three-port energy storage composite chain STATCOM topology structure and a control method thereof includes the following steps:

[0132] (1) Perform PARK transformation on the output voltage and current of the 10 kV AC feeder of the power grid to obtain the voltage u in the two-phase synchronous rotating coordinate system sd 、u sq and current i sd 、i sq ;

[0133] (2) The sum of the DC side voltages of all H-bridge circuits in each phase of the chained STATCOM is U HdΣ-A , U HdΣ-A , U HdΣ-A Add them together and multiply by 1 / 3 to get the total DC voltage average value U HdΣ ;

[0134] (3) Set the DC voltage reference value U HdΣ *, with the total DC voltage average value U HdΣ Subtract, the difference is input into the voltage loop proportional integral controller, and the output d-axis current reference value i sd *;

[0135] (4) Set the reactive power reference value Q*, subtract it from the actual reactive power Q of the grid-connected port, and input the difference into the reactive power proportional integral controller to output the q-axis current reference value i sq *;

[0136] (5) Set the d-axis current reference value i sd * and d-axis current i sd Subtract the difference, and input the current loop proportional integral controller to convert the angular velocity ω, the reactor L and the q-axis current i sq The product of the d-axis voltage u sd Add and subtract the output value of the current loop proportional integral controller to obtain the d-axis voltage reference value; the q-axis current reference value i sq * and q-axis current i sq Subtract the difference, and input the current loop proportional integral controller to convert the q-axis voltage u sq Subtract the angular velocity ω, the reactor L, and the d-axis current i sd The product of , minus the output value of the current loop proportional integral controller, is used to obtain the q-axis voltage reference value;

[0137] (6) Inverse PARK transformation of the d-axis voltage reference value and the q-axis voltage reference value to generate the modulation voltage u sma 、u smb 、u smc And input PWM generator to form PWM signal g sax , g sbx, g scx , to control each H-bridge module of the chain STATCOM.

[0138] Figure 3 The present invention is a control block diagram of a three-phase inverter circuit in a three-port energy storage composite chain STATCOM topology structure and a control method thereof, wherein the control of active power P includes the following steps:

[0139] (1) Perform PARK transformation on the voltage and current on the AC side of the three-phase inverter circuit to obtain the voltage u in the two-phase synchronous rotating coordinate system id 、u iq and current i id 、i iq ;

[0140] (2) Set the active power reference value P*, subtract it from the actual active power P at the port, and input the difference into the active power proportional integral controller to output the d-axis voltage reference value u id *, q-axis voltage reference value u iq * Set to 0;

[0141] (3) The d-axis voltage reference value u id * and d-axis voltage u id Subtract the difference, and input the voltage loop proportional integral controller; the q-axis voltage reference value u iq * and q-axis voltage u iq Subtract them, and the difference is input into the voltage loop proportional integral controller;

[0142] (4) Perform an inverse PARK transformation on the output value of the voltage loop proportional integral controller to generate a three-phase voltage reference value u ima 、u imb 、u imc , and input the PWM generator.

[0143] The three-way Boost circuit outputs DC power by controlling the on-duty ratio N of the three lower bridge arm IGBT switch tubes, including the following steps:

[0144] (1) Set the specified value of the low voltage DC port output current to i dc1 *, the specified value of the output current i dc1 *The actual output current value of the low voltage DC port i dc1 Subtract, the difference is input into the DC current loop proportional integral controller, the proportional integral controller outputs the per unit value of the DC bias voltage U abc , so that the duty cycle N can be controlled abc +1) / 2.

[0145] The three-phase voltage reference value u ima 、u imb 、uimc Respectively with U abc Add together to generate the modulation voltage u a 、u b 、u c And input PWM generator to generate PWM signal g i1～6 , to control six IGBTs.

[0146] An application embodiment of the present invention provides a computer device, which includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor executes the steps of a three-port energy storage composite chain STATCOM topology structure control method.

[0147] The application embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of a three-port energy storage composite chain STATCOM topology structure control method.

[0148] The present invention uses the MATLAB / Simulink simulation experiment platform to build a three-port energy storage composite chain STATCOM simulation model. The initial phase of the 10kV AC grid is 0 and the frequency is 50Hz; the connected reactor L=1mH; the chain STATCOM uses 12 H-bridge submodules per phase, the DC voltage setting value of each H-bridge module is 800V, and the DC side capacitance is 5mF; the turns ratio of the primary winding to the secondary winding of the zigzag transformer is 1:2, and the nominal power is 10 6 VA, the nominal frequency is 50Hz, the nominal voltages of the primary and secondary windings are 380Vrms and 220Vrms respectively, and the nominal excitation inductance is 50pu; the low-voltage DC side of the three-phase inverter circuit is connected via C d1 =5mF connected to 500V battery, high voltage DC side through C d2 =10mF connected to 1000V battery, L dc =3mH; the initial reference values ​​of the port output reactive power and active power are 4kvar and 50kW respectively.

[0149] The scheme proposed by the present invention is verified by using the MATLAB / Simulink simulation experiment platform. The reactive power waveform is as follows: Figure 5 As shown, the active power waveform is as follows Figure 6 As shown, the low voltage DC port current waveform is as follows Figure 7 As shown, the voltage waveform of the high-voltage DC port is as follows Figure 8 shown.

[0150] Figure 5In the initial stage, the reactive power is maintained constant at 4kvar. At 0.2s, the command value increases from 4kvar to 5kvar. The reactive power responds quickly to the change in the command value, and the output reactive power increases to 5kvar. Figure 6 In the initial stage, the active power is kept constant at 50kW. At 0.1s, the command value increases from 50kW to 80kW. The active power responds quickly to the command value change, and the output active power increases to 80kW. It can be seen that the topology has high dynamic response and flexible adjustment of reactive power and active power. Figure 7 Medium and low voltage DC port current i DC1 After 0.1s, it stabilizes at the set value of 130A. Figure 8 The voltage of the medium and high voltage DC ports stabilizes at 1000V after 0.1s.

[0151] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0152] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0153] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A three-port energy storage composite chain STATCOM system, comprising a three-phase grid feeder, a reactor L, a three-phase chain STATCOM, a zigzag transformer, a three-phase inverter circuit, a high-voltage energy storage device, and a low-voltage energy storage device, characterized in that: The three-phase grid feeder is connected to one end of the three-phase chain STATCOM through three reactors L, and the other end of the three-phase chain STATCOM is connected to the primary side of the zigzag transformer; the primary side of the zigzag transformer includes three inductors L T1 , three L T1 The same-name end of the three-phase chain STATCOM is connected to the other end. T1 The secondary side includes six inductors L T2 , among which three L T2 The same-name terminal is connected as the neutral point and connected to the low-voltage DC filter inductor L dc One end is connected to L dc The other end is connected to the low voltage DC capacitor and one end of the low voltage energy storage device. T2 The other end passes through three other L T2 The midpoints of the three bridge arms of the three-phase inverter circuit are connected, each bridge arm contains two IGBTs, the upper ends of the three bridge arms are connected to the high-voltage energy storage device and one end of the high-voltage DC capacitor, and the lower ends of the three bridge arms are connected to the high-voltage energy storage device, the high-voltage DC capacitor, the low-voltage DC capacitor and the other end of the low-voltage energy storage device; the three-phase chain STATCOM is a three-phase cascade H-bridge circuit, each phase cascade H-bridge circuit includes n H-bridge circuits, and each H-bridge circuit consists of two bridge arms containing two IGBTs and a DC side capacitor; the low-voltage energy storage device is a photovoltaic power generation system, and the high-voltage energy storage device is a battery energy storage device.

2. A control method for a three-port energy storage composite chain STATCOM, characterized in that: The control method is applied to the three-port energy storage composite chain STATCOM system according to claim 1, The control method of the three-phase chain STATCOM includes the following steps: (1) Perform PARK transformation on the output voltage and current of the three-phase grid feeder to obtain the voltage u in the two-phase synchronous rotating coordinate system sd 、u sq and current i sd 、i sq ; (2) The sum of the DC side voltages of all H-bridge circuits in each phase is the total DC side voltage of that phase. The sum of the DC side voltages of the three phases is added together and multiplied by 1 / 3 to obtain the total DC voltage average value U HdΣ ; (3) Set the DC voltage reference value U HdΣ *, with the total DC voltage average value U HdΣ The difference is input into the first voltage loop proportional integral controller, and the output d-axis current reference value i sd *; (4) Set the reactive power reference value Q*, subtract it from the actual reactive power Q of the grid-connected port, and input the difference into the first reactive power proportional integral controller to output the q-axis current reference value i sq *; (5) Set the d-axis current reference value i sd * and d-axis current i sd Subtract the difference, and input the first current loop proportional integral controller to convert the angular velocity ω, the reactor L and the q-axis current i sq The product of the d-axis voltage u sd Add and subtract the output value of the first current loop proportional integral controller to obtain the d-axis voltage reference value; the q-axis current reference value i sq * and q-axis current i sq Subtract the difference, and input the second current loop proportional integral controller to convert the q-axis voltage u sq Subtract the angular velocity ω, the reactor L, and the d-axis current i sd The product of , minus the output value of the second current loop proportional integral controller, to obtain the q-axis voltage reference value; (6) performing an inverse PARK transformation on the d-axis voltage reference value and the q-axis voltage reference value to generate a modulation voltage and input the modulation voltage into a first PWM generator to form a first PWM signal to control each H-bridge circuit of the three-phase chain-type STATCOM; The control method of the three-phase inverter circuit comprises the following steps: (1) Perform PARK transformation on the voltage and current on the AC side of the three-phase inverter circuit to obtain the voltage u in the two-phase synchronous rotating coordinate system id 、u iq and current i id 、i iq ; (2) Set the active power reference value P* transmitted by the three-phase inverter circuit, subtract it from the actual active power P transmitted by the three-phase inverter circuit, and input the difference into the first active power proportional integral controller to output the d-axis voltage reference value u id *, q-axis voltage reference value u iq * Set to 0; (3) The d-axis voltage reference value u id * and d-axis voltage u id Subtract the difference, and input the second voltage loop proportional integral controller; the q-axis voltage reference value u iq * and q-axis voltage u iq Subtracting, the difference is input into the third voltage loop proportional integral controller; (4) The output values ​​of the second and third voltage loop proportional integral controllers are subjected to inverse PARK transformation to generate a three-phase voltage reference value u ima 、u imb 、u imc ; (5) Set the specified value of the low voltage DC port output current to i dc1 *, the specified value of the output current i dc1 *The actual output current value of the low voltage DC port i dc1 The difference is input into the first DC current loop proportional integral controller, and the first DC current loop proportional integral controller outputs the per unit value U of the DC bias voltage abc ; The three-phase voltage reference value u ima 、u imb 、u imc Respectively with U abc Add together to generate the modulation voltage u a 、u b 、u c The second PWM generator is input to generate a second PWM signal to control the six IGBTs of the three-phase inverter circuit.

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