RTDS simulation method and device for new energy grid-connected dc booster

Abstract

The application relates to an RTDS simulation method and device for a direct-current booster for new energy grid connection. The method is used for reducing the demand of the direct-current booster on simulation resources by using a DC / AC equivalent module to simulate a power module, and a corresponding module controller construction method and an unlocking and locking process processing sequence are proposed for the simulated direct-current booster. The power module is simplified, the demand of the direct-current booster model on simulation hardware is greatly reduced, the number of the simulated direct-current boosters is expanded to 6 times of the original number under the same hardware condition, and the flexibility of the control system is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of new energy grid connection control technology, and in particular to an RTDS simulation method and device for DC boost converters used for new energy grid connection. Background Technology

[0002] With increasing user demands for power quality, the need for distributed renewable energy and energy storage systems to be integrated into distribution networks is growing stronger, and the widespread application of power electronic equipment means that traditional AC distribution networks are increasingly unable to meet the electricity demands of modern society. DC distribution networks, with their unique advantages such as high reliability, good economic efficiency, favorable access to distributed energy resources, and high power quality, have gradually attracted more and more attention and research in recent years.

[0003] In the development of DC power distribution, DC boost converters, as core equipment connecting medium and low voltage buses, are a key node for power transmission. With the increase in distribution network capacity and the rise in the number of distributed renewable energy sources, the demand for DC boost converters, as intermediaries for renewable energy grid connection, is also gradually increasing.

[0004] In system design and debugging, simulating a large number of energy terminals and their grid-connected equipment to more realistically construct system simulation models is of great significance for the development of key equipment such as DC distribution network control and protection.

[0005] Currently, there are various types of DC boost converters. Traditional BUCK and BOOST circuits cannot achieve high-ratio voltage conversion. DC boost converters for medium-voltage ±10kV distribution levels generally use a series-parallel connection of power modules, with the low-voltage side connected in parallel and the high-voltage side connected in series to improve the system's transmission capacity. Depending on the power module, they can be further divided into phase-shifted dual active bridge converters and series resonant dual active bridge converters. The power module integrates power electronic switches and high-frequency transformers, enabling power control, electrical isolation, and voltage conversion. During simulation, each component can be implemented in detail according to the converter's topology, and then a system controller can be constructed to achieve accurate simulation of the DC boost converter.

[0006] However, in existing technologies, regardless of the type of DC-DC boost converter, a large number of power electronic components are required. This results in an excessive number of electrical nodes during model building, leading to excessive computational load and resource consumption during simulation on the RTDS platform, making it unsuitable for modeling complex-stage DC-DC boost converters in DC distribution networks. Furthermore, these DC-DC boost converters generally employ high-frequency PWM modulation. The performance of power electronic components in RTDS is significantly affected by frequency; high-frequency switching results in excessive switching losses, leading to substantial discrepancies between simulation results and actual characteristics. Summary of the Invention

[0007] Based on the above-mentioned situation of the prior art, the purpose of this invention is to propose an RTDS simulation method and device for DC boost converters used in grid connection of new energy sources, so as to solve the problem that the prior art cannot realize system-level online simulation of multiple photovoltaic, energy storage and other energy sources and their grid-connected DC boost converters.

[0008] To achieve the above objectives, according to one aspect of the present invention, an RTDS simulation method for DC boost converters used in grid-connected new energy sources is provided, comprising the following steps:

[0009] A DC / AC equivalent module is used to equivalently simulate all the power devices on the low-voltage side of the DC boost converter.

[0010] The high-frequency transformer in the DC boost converter is replaced with a power frequency transformer.

[0011] A DC / AC equivalent module is used to equivalently simulate all the power devices on the high-voltage side of the DC boost converter.

[0012] A control system based on a dual-loop control method is constructed using equivalent DC / AC modules on both sides.

[0013] Furthermore, the control system for constructing the DC / AC equivalent modules on both sides includes constructing an outer loop controller and an inner loop controller on the high-voltage side;

[0014] The high-voltage side outer loop controller adopts islanded control to control the amplitude and phase of the AC voltage, while the inner loop controller controls the AC current to follow the outer loop output.

[0015] Furthermore, the control system for constructing the DC / AC equivalent modules on both sides includes constructing an outer loop controller and an inner loop controller on the low-voltage side.

[0016] The low-voltage side outer loop controller uses power control or DC voltage control, while the inner loop controller controls the AC current to follow the outer loop output.

[0017] Furthermore, the control system for constructing the DC / AC equivalent modules on both sides also includes system unlocking and locking control.

[0018] Furthermore, the unlocking and locking control includes:

[0019] Connect the DC boost converter to both DC buses. When an unlock signal is received, first unlock the DC / AC equivalent module on the high-voltage side, and after a preset delay, unlock the DC / AC equivalent module on the low-voltage side.

[0020] Furthermore, the unlocking and locking control includes:

[0021] When a blocking signal is received, the low-voltage side DC / AC equivalent module is blocked first, and after a preset delay, the high-voltage side DC / AC equivalent module is blocked.

[0022] Furthermore, in the locked state, the reference voltage output of the DC / AC equivalent module on the high-voltage side is 0, and upon unlocking, the reference voltage of the equivalent module is switched to the output of the high-voltage side controller.

[0023] Furthermore, in the locked state, the reference voltage of the DC / AC equivalent module on the low-voltage side is taken as the output of the low-voltage side voltage of the transformer, and at the moment of unlocking, the reference voltage of the equivalent module is switched to the output of the low-voltage side controller.

[0024] Furthermore, if photovoltaic power generation equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC voltage control; if energy storage equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC power control.

[0025] According to another aspect of the present invention, an RTDS simulation device for DC boost converters used in grid-connected new energy sources is provided, comprising an equivalent simulation module and a control system construction module; wherein,

[0026] The equivalent simulation module uses a DC / AC equivalent module to equivalently simulate all power devices on the low-voltage side of the DC-DC boost converter; it replaces the high-frequency transformer in the DC-DC boost converter with a power frequency transformer; and it uses a DC / AC equivalent module to equivalently simulate all power devices on the high-voltage side of the DC-DC boost converter.

[0027] The control system construction module is a control system for constructing equivalent DC / AC modules on both sides based on the dual-loop control method.

[0028] In summary, this invention provides an RTDS simulation method and apparatus for DC-DC boost converters used in grid-connected new energy sources. By utilizing DC / AC equivalent modules to simulate power modules, the simulation resource requirements of DC-DC boost converters are reduced. Furthermore, for the simulated DC-DC boost converter, a corresponding module controller construction method and unlocking and locking process sequence are proposed. By simplifying the power modules, the simulation hardware requirements of the DC-DC boost converter model are greatly reduced. Under the same hardware conditions, the number of DC-DC boost converters that can be simulated is increased to 6 times the original number, and the flexibility of the control system is also greatly improved. Attached Figure Description

[0029] Figure 1 This is a DC-DC boost converter topology diagram;

[0030] Figure 2 This is a flowchart of the RTDS simulation method for DC boost converters used in grid-connected new energy sources, as described in this invention.

[0031] Figure 3 It is a schematic diagram of the equivalent simulation of the DC boost converter topology and its control system;

[0032] Figure 4 This is a block diagram of the RTDS simulation device for DC boost converters used in grid-connected new energy sources, as per the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. According to one embodiment of the present invention, an RTDS simulation method for DC-DC boost converters used in grid-connected new energy sources is provided. A common DC-DC boost converter topology circuit diagram is shown below. Figure 1 As shown, the system includes a low-voltage side power converter and a high-voltage side power converter, as well as a transformer connecting the low-voltage side power converter and the high-voltage side power converter. The simulation method provided in this embodiment reduces the simulation resource requirements of the DC-DC boost converter by using a DC / AC equivalent module to simulate the power module. The flowchart of this method is shown below. Figure 2 As shown, the steps include:

[0035] A DC / AC equivalent module is used to simulate all the power devices on the low-voltage side of the DC boost converter: a DC / AC equivalent module is used to simulate all the power modules on the low-voltage side, the DC side is connected to the output bus of the photovoltaic or energy storage device, and the AC side is connected to the low-voltage winding of the AC transformer.

[0036] The high-frequency transformer in the DC boost converter is replaced with a power frequency transformer, and the turns ratio is taken as the step-up ratio of the DC voltages on both sides.

[0037] A DC / AC equivalent module is used to simulate all the power devices on the high-voltage side of the DC boost converter: a DC / AC equivalent module is used to simulate all the power modules on the high-voltage side, the DC side is connected to the medium-voltage DC bus, and the AC side is connected to the high-voltage winding of the AC transformer.

[0038] Both the low-voltage and high-voltage side DC / AC equivalent modules are bidirectional converter modules.

[0039] Based on control requirements, the AC and DC bus voltages and currents on each side are sampled. A control system for the equivalent DC / AC modules on both sides is constructed based on a dual-loop control method.

[0040] The dual-loop control theory of traditional flexible DC transmission can be used to construct a DC / AC control system on both sides. The equivalent simulation results of the DC boost converter topology and its control system are shown in the figure below. Figure 3 As shown, the DC-DC boost converter includes a low-voltage side DC / AC equivalent module, a high-voltage side DC / AC equivalent module, and a power frequency transformer connecting the low-voltage side DC / AC equivalent module and the high-voltage side DC / AC equivalent module. Figure 3 The document also illustrates the control system of the constructed dual-side DC / AC equivalent modules, including a low-voltage side controller and a high-voltage side controller. Both the low-voltage side controller and the high-voltage side controller employ power + current dual-loop control and include stages such as DC quantity acquisition, AC quantity acquisition, phase-locked loop and current conversion, and control variable processing. The control system for constructing the dual-side DC / AC equivalent modules includes the following aspects:

[0041] Constructing a high-voltage side outer loop controller and an inner loop controller: The high-voltage side outer loop controller adopts islanded control to control the amplitude and phase of the AC voltage, while the inner loop controller controls the AC current to follow the outer loop output. In the control system design of the DC-DC boost converter, the high-voltage side outer loop controller can adopt an islanded controller to control the amplitude and phase of the AC voltage, providing a stable and reliable DC voltage for the low-voltage side DC / AC, while the inner loop controller controls the AC current to follow the outer loop output.

[0042] Construct a low-voltage side outer loop controller and an inner loop controller: The low-voltage side outer loop controller uses power control or DC voltage control, while the inner loop controller controls the AC current to follow the outer loop output. The low-voltage side DC / AC controller outer loop can use a power controller or a DC voltage controller, while the inner loop controller controls the AC current to follow the outer loop output.

[0043] System unlocking and locking control: The DC-DC boost converter is connected to both DC buses. When an unlocking signal is received (which can be sent from the backend), the high-voltage side DC / AC equivalent module is unlocked first, followed by a preset delay (e.g., 10ms), and then the low-voltage side DC / AC equivalent module is unlocked. When a locking signal is received (which can also be sent from the backend), the low-voltage side DC / AC equivalent module is locked first, followed by a preset delay (e.g., 10ms), and then the high-voltage side DC / AC equivalent module is locked. In the locked state, the converter reference voltage should be processed accordingly. In the locked state, the high-voltage side DC / AC equivalent module reference voltage output is 0. Upon unlocking, the equivalent module reference voltage is switched to the output of the high-voltage side dual-loop controller. In the locked state, the low-voltage side DC / AC equivalent module reference voltage is taken as the transformer low-voltage side voltage as the output. Upon unlocking, the equivalent module reference voltage is switched to the output of the low-voltage side dual-loop controller. If photovoltaic power generation equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC voltage control; if energy storage equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC power control.

[0044] In addition, for energy storage devices, the function of controlling the high-voltage side DC voltage can also be added. In this control mode, the outer loop controller of the low-voltage side converter is switched to the high-voltage side DC voltage control.

[0045] According to another aspect of the present invention, an RTDS simulation device for DC boost converters used in grid-connected new energy sources is provided, comprising an equivalent simulation module and a control system construction module, the block diagram of which is shown below. Figure 4 As shown.

[0046] The equivalent simulation module uses a DC / AC equivalent module to equivalently simulate all power devices on the low-voltage side of the DC-DC boost converter; it replaces the high-frequency transformer in the DC-DC boost converter with a power frequency transformer; and it uses a DC / AC equivalent module to equivalently simulate all power devices on the high-voltage side of the DC-DC boost converter.

[0047] The control system construction module is based on a dual-loop control method to construct the control system of the DC / AC equivalent modules on both sides. The control system of the DC / AC equivalent module includes a low-voltage side controller and a high-voltage side controller. The low-voltage side controller includes an outer loop controller and an inner loop controller: the outer loop controller uses power control or DC voltage control, and the inner loop controller controls the AC current to follow the outer loop output. The outer loop of the low-voltage side DC / AC controller can use a power controller or a DC voltage controller, and the inner loop controller controls the AC current to follow the outer loop output. The high-voltage side controller includes an outer loop controller and an inner loop controller: the outer loop controller uses islanded control to control the amplitude and phase of the AC voltage, and the inner loop controller controls the AC current to follow the outer loop output. In the design of the DC boost converter control system, the outer loop controller of the high-voltage side controller can use an islanded controller to control the amplitude and phase of the AC voltage, providing a stable and reliable DC voltage for the low-voltage side DC / AC, and the inner loop controller controls the AC current to follow the outer loop output.

[0048] In summary, this invention relates to an RTDS simulation method and apparatus for DC-DC boost converters used in grid-connected new energy sources. By utilizing DC / AC equivalent modules to simulate power modules, it reduces the simulation resource requirements of the DC-DC boost converter. Furthermore, for the simulated DC-DC boost converter, it proposes a corresponding module controller construction method, the unlocking and locking process sequence, and a conversion processing method for generating the converter controller reference voltage. The technical solution of this invention, by simplifying the power modules, significantly reduces the simulation hardware requirements of the DC-DC boost converter model. Under the same hardware conditions, the number of DC-DC boost converters that can be simulated is increased to six times the original number, and the flexibility of the control system is also greatly improved.

[0049] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An RTDS simulation method for DC boost converters used in grid-connected new energy sources, characterized in that, Including the following steps: A DC / AC equivalent module is used to equivalently simulate all the power devices on the low-voltage side of the DC boost converter. The high-frequency transformer in the DC boost converter is replaced with a power frequency transformer. An AC / DC equivalent module is used to equivalently simulate all the power devices on the high-voltage side of the DC boost converter. The DC / AC equivalent module, the power frequency transformer, and the AC / DC equivalent module are connected in sequence. A control system is constructed based on a dual-loop control method for a low-voltage side DC / AC equivalent module and a high-voltage side AC / DC equivalent module, and the control system is connected to the DC / AC equivalent module and the AC / DC equivalent module respectively.

2. The method according to claim 1, characterized in that, The control system that constructs a low-voltage side DC / AC equivalent module and a high-voltage side AC / DC equivalent module includes constructing a high-voltage side outer loop controller and an inner loop controller. The high-voltage side outer loop controller adopts islanded control to control the amplitude and phase of the AC voltage, while the inner loop controller controls the AC current to follow the outer loop output.

3. The method according to claim 1, characterized in that, The control system for the low-voltage side DC / AC equivalent module and the high-voltage side AC / DC equivalent module includes constructing a low-voltage side outer loop controller and an inner loop controller. The low-voltage side outer loop controller uses power control or DC voltage control, while the inner loop controller controls the AC current to follow the outer loop output.

4. The method according to claim 1, characterized in that, The control system for constructing the low-voltage side DC / AC equivalent module and the high-voltage side AC / DC equivalent module also includes system unlocking and locking control.

5. The method according to claim 4, characterized in that, The unlocking and locking control includes: Connect the DC boost converter to both DC buses. When an unlock signal is received, first unlock the AC / DC equivalent module on the high-voltage side, and after a preset delay, unlock the DC / AC equivalent module on the low-voltage side.

6. The method according to claim 5, characterized in that, The unlocking and locking control includes: When a blocking signal is received, the low-voltage side DC / AC equivalent module is blocked first, and after a preset delay, the high-voltage side AC / DC equivalent module is blocked.

7. The method according to claim 5, characterized in that, In the locked state, the reference voltage output of the AC / DC equivalent module on the high-voltage side is 0. Upon unlocking, the reference voltage of the equivalent module is switched to the output of the high-voltage side controller.

8. The method according to claim 5, characterized in that, In the locked state, the reference voltage of the DC / AC equivalent module on the low-voltage side is taken as the output voltage of the transformer on the low-voltage side. At the moment of unlocking, the reference voltage of the equivalent module is switched to the output of the low-voltage side controller.

9. The method according to any one of claims 6-8, characterized in that, If photovoltaic power generation equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC voltage control; if energy storage equipment is connected to the low-voltage side, the outer loop control of the DC / AC equivalent module on the low-voltage side adopts DC power control.

10. An RTDS simulation device for DC boost converters used in grid-connected new energy sources, characterized in that, It includes an equivalent simulation module and a control system construction module; among which, The equivalent simulation module uses a DC / AC equivalent module to equivalently simulate all power devices on the low-voltage side of the DC-DC boost converter; a power frequency transformer replaces the high-frequency transformer in the DC-DC boost converter; and an AC / DC equivalent module is used to equivalently simulate all power devices on the high-voltage side of the DC-DC boost converter; the DC / AC equivalent module, the power frequency transformer, and the AC / DC equivalent module are connected in sequence. The control system construction module is based on a dual-loop control method to construct a control system for a low-voltage side DC / AC equivalent module and a high-voltage side AC / DC equivalent module. The control system is connected to the DC / AC equivalent module and the AC / DC equivalent module respectively.

Images