Parallel isolated pair test platform and method for stringed pcs

Abstract

The application relates to a parallel isolated parallel test platform and method of a group string type PCS, and the innovation lies in that: the energy test loop is formed by two group string type PCSs, a transformer unit and a parallel test unit, the DC sides of the sub-modules of the two group string type PCSs are connected in a one-to-one corresponding and electrically isolated manner through the parallel test unit to form multiple independent parallel test channels, and the AC sides are respectively connected in parallel to the power grid; during the test, different working modes are set and the energy mutual feedback in the channels is controlled to realize the synchronous parallel test of all the sub-modules. The application adopts the topology of parallel connection on the AC side and channel isolation on the DC side, discards the complex and expensive multi-winding transformer and a large number of switching devices, significantly improves the test efficiency and system economy on the premise of ensuring that the faults of the channels are strictly isolated, and solves the industry problem that high efficiency, safety and low cost are difficult to coordinate.

Description

Technical Field

[0001] This invention relates to a test platform and method for energy storage converters (PCS), specifically to a parallel isolation test platform and method for string PCS, belonging to the field of electrical performance technology. Background Technology

[0002] Currently, in the research and development and production of energy storage systems, the energy storage converter (PCS) is the core energy conversion unit, and its performance testing is crucial. To improve testing efficiency, existing technologies have mainly developed two approaches, but both have significant limitations: 1. Parallel testing schemes and their efficiency and safety bottlenecks This scheme connects multiple PCS units in parallel on their DC sides and interfaces them with an external high-power DC source to form a test loop. While this method aims to increase the scale of testing, it is essentially a non-closed-loop test of "one source to multiple units," resulting in low overall energy efficiency. More importantly, the parallel DC-side architecture makes it easy for any module fault to propagate through the common bus, resulting in inherent safety isolation deficiencies. Furthermore, the test mode relies on an external power supply, lacking flexibility.

[0003] 2. Point-to-point towing solutions and their complexity and cost bottlenecks To achieve efficient closed-loop testing, the industry has proposed a direct pairing solution between PCS units. For example, in a publicly disclosed solution (such as patent document CN120669041B), an architecture of "full isolation on the AC side and point-to-point interconnection on the DC side" is adopted: each PCS is equipped with an independent transformer winding, and pairing is achieved through DC circuit breakers. Although this solution achieves internal energy circulation and efficient pairing, the system complexity and cost are extremely high: its core relies on customized multi-winding transformers, resulting in expensive equipment, difficult manufacturing, and extremely poor scalability; at the same time, the introduction of a large number of circuit breakers and a central coordinating controller makes system control complex and poses challenges to reliability.

[0004] 3. Summary of Existing Technological Bottlenecks In summary, existing technologies struggle to balance high efficiency, high security, low cost, and structural simplicity: parallel solutions suffer from insufficient efficiency and security; while point-to-point / drag-and-drop solutions, while improving efficiency, introduce unacceptable system complexity and cost due to their pursuit of extreme isolation. Therefore, the current lack of a truly efficient, secure, and flexibly scalable PCS testing solution that achieves a simple architecture and controllable cost has become a key bottleneck restricting large-scale and cost-effective testing. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing PCS testing solutions cannot simultaneously achieve testing efficiency, intrinsic safety, system cost, and architectural simplicity. It provides a parallel isolation test platform and method for string PCS based on a dedicated testing system. Employing a topology of "AC-side parallel connection and DC-side channel isolation," it eliminates the need for complex and expensive multi-winding transformers and numerous switching devices. While ensuring strict isolation of faults in each channel, it significantly improves testing efficiency and system economy, solving the industry challenge of achieving a balance between high efficiency, safety, and low cost.

[0006] To achieve the above objectives, the first technical solution of the present invention is: a parallel isolated drag test platform with serial PCS, the innovation of which is: it includes a closed-loop energy test circuit constructed from a first set of serial PCS, a second set of serial PCS, a transformer unit, and a drag test unit. The AC sides of each submodule of the first set of serial PCS are connected in parallel and then connected to the corresponding connection terminals of the transformer unit. The AC sides of each submodule of the second set of serial PCS are connected in parallel and then connected to the corresponding connection terminals of the transformer unit. The drag test unit is used to connect the DC sides of the sub-modules of the first set of serial PCS and the second set of serial PCS in a one-to-one correspondence and electrically isolated manner, so that the first set of serial PCS and the second set of serial PCS form multiple independent drag test channels and constitute a DC side test circuit.

[0007] In the first technical solution described above, the transformer unit includes a first grid-connected transformer and a second grid-connected transformer. The AC sides of each sub-module A1, A2...An of the first series PCS are connected in parallel and connected to the first grid-connected transformer. The AC sides of each sub-module B1, B2...Bn of the second series PCS are connected in parallel and connected to the second grid-connected transformer.

[0008] In the first technical solution described above, the transformer unit consists of two double-winding transformers, each including a high-voltage side winding and a low-voltage side winding. The AC sides of each sub-module A1, A2...An of the first series PCS are connected in parallel to the low-voltage winding of one of the double-winding transformers. The AC sides of each sub-module B1, B2...Bn of the second series PCS are connected in parallel to the low-voltage winding of the other double-winding transformer. The high-voltage sides of both double-winding transformers are connected to the power grid.

[0009] In the first technical solution described above, the transformer unit is an integrated three-winding transformer. The three-winding transformer includes a high-voltage side common winding and two low-voltage side independent windings. The sub-modules A1, A2...An of the first string PCS are connected in parallel on the AC side and then connected to the first low-voltage winding of the three-winding transformer. The sub-modules B1, B2...Bn of the second string PCS are connected in parallel on the AC side and then connected to the second low-voltage winding of the three-winding transformer. The high-voltage side common winding of the three-winding transformer is connected to the power grid. The first string PCS and the second string PCS maintain electrical isolation on the AC side and share the high-voltage side common winding of the three-winding transformer.

[0010] In the first technical solution described above, the drag test unit includes a pre-charge circuit, which is used to provide an initial DC voltage for the first set of string PCS or the second set of string PCS. One pre-charge circuit is shared by multiple sub-modules of the first set of string PCS or the second set of string PCS, or a separate pre-charge circuit is set for each sub-module of the first set of string PCS or the second set of string PCS. The pre-charge circuit includes a pre-charge circuit and a pre-charge branch switch corresponding to each drag test channel. The pre-charge branch switch is connected to the connection terminal corresponding to the pre-charge circuit.

[0011] In the first technical solution described above, the pre-charging circuit includes a rectifier bridge, a current-limiting resistor, a pre-charging transformer, and a pre-charging circuit AC side switch. One end of the rectifier bridge is connected to one end of the current-limiting resistor, and the other end of the rectifier bridge is connected to one end of the pre-charging circuit AC side switch through the pre-charging transformer. The other end of the current-limiting resistor is simultaneously connected to one end of multiple pre-charging branch switches, and the other end of each pre-charging branch switch is simultaneously connected to the DC side of the sub-module of the first set of serial PCS and the second set of serial PCS.

[0012] In the first technical solution mentioned above, the drag test unit includes multiple fuses FU1, FU2, ... FUn, and the multiple fuses FU1, FU2, ... FUn are connected in series in the DC side connection path of each sub-module of the first set of serial PCS and the second set of serial PCS, respectively, to realize overcurrent protection.

[0013] In the first technical solution described above, an AC side switch control unit is also included. The AC side switch control unit includes a main AC side switch, a first AC side switch, and a second AC side switch. The first AC side switch is connected in series in the AC side connection paths of each sub-module A1, A2...An of the first grid-connected transformer and the first string PCS. The second AC side switch is connected in series in the AC side connection paths of each sub-module B1, B2...Bn of the second grid-connected transformer and the second string PCS. The first grid-connected transformer and the second grid-connected transformer are connected in parallel and then connected to the main AC side switch.

[0014] The first technical solution mentioned above also includes a control system composed of a host computer. The control system is communicatively connected to the first set of serial PCS and the second set of serial PCS to form a test platform control loop.

[0015] The first technical solution described above also includes at least one extended topology, which includes a pair of serial PCS units and an extended pair of drag test units connected to the pair of serial PCS units. The extended pair of serial PCS units includes a third pair of serial PCS units and a fourth pair of serial PCS units. The AC side of each submodule of the third set of serial PCS is connected in parallel with the AC side of each submodule of the first set of serial PCS to the transformer unit. The AC side of each submodule of the fourth set of serial PCS is connected in parallel with the AC side of each submodule of the second set of serial PCS to the transformer unit. The extended drag test unit is also used to connect the DC sides of multiple sub-modules of the third set of serial PCS and the fourth set of serial PCS in a one-to-one correspondence and electrically isolated manner to form at least another set of extended and mutually independent drag test channels.

[0016] To achieve the above objectives, the second technical solution of the present invention is: a parallel isolation drag-and-drop test method for a serial PCS, including the above-mentioned parallel isolation drag-and-drop test platform for a serial PCS, the innovation of which lies in the following specific test steps: S1. Establish a test channel The DC side of each submodule of the first and second set of serial PCS is connected to form multiple electrically isolated test channels. S2. Set working mode The first group of serial PCS and the second group of serial PCS are configured to operate in different working modes. S3. Start and establish power flow Start the two serial PCS in sequence to put the system into a test state. S4. Perform parallel drag testing The two string PCSs are controlled to simultaneously charge and discharge each other in the multiple independent channels, so that electrical energy circulates in each closed loop, thereby completing the complete performance evaluation of all sub-modules in the two string PCSs in a single test process.

[0017] In the second technical solution described above, in step S2, the first set of serial PCS is set to operate in DC voltage mode, and the second set of serial PCS is set to operate in AC power mode. The first set of string PCS operating in DC voltage mode is pre-charged to establish an initial voltage. Once this PCS starts up, its output voltage provides the startup conditions for the second set of string PCS operating in AC power mode. The second set of string PCS in AC power mode operates in rectification mode to simulate charging, while the first set of string PCS in DC voltage mode operates in inverter mode to simulate discharging; by switching the operating modes of the two, electrical energy is circulated in the closed loop.

[0018] In the second technical solution described above, the closed AC side switch control unit supplies AC power to the sub-modules A1, A2...An and B1, B2...Bn in the first and second series PCS via a transformer unit. Close the precharge branch switch of the precharge circuit in the test unit to connect the DC side of the sub-module of the first set of serial PCS with the precharge circuit of the precharge circuit, and establish the initial DC voltage for the corresponding sub-module. The system controls each submodule A1, A2...An in the first set of serial PCS to start up in DC voltage mode. The pre-charge circuit is deactivated, which includes disconnecting the AC side switch and the pre-charge branch switch in the pre-charge circuit, thereby isolating the DC side of each sub-module in the first set of serial PCS from the pre-charge circuit. The control system controls the output DC voltage of each submodule A1, A2...An in the first set of serial PCS, and provides DC voltage to each submodule A1, A2...An, B1, B2...Bn in the second set of serial PCS. Control each submodule B1, B2...Bn in the second set of serial PCS to start up in AC power mode. By controlling the charging or discharging of each submodule B1, B2...Bn in the second set of serial PCS by the control system, the charging or discharging of each submodule A1, A2...An in the first set of serial PCS will also occur. Once charging and discharging are complete, the control system stops each sub-module B1, B2...Bn in the second set of serial PCS. The control system controls the shutdown of each sub-module A1, A2...An in the first set of serial PCS. Disconnect the AC side switch control unit and complete the power test of all sub-modules in the first and second series PCS. If each sub-module operates stably at its rated power, the test is qualified.

[0019] The positive effects of this invention are as follows: After adopting the parallel isolation test platform and method of the string PCS of this invention, since the test platform of this invention includes two string PCS, a transformer unit and a test unit, the second string PCS and the transformer unit form a closed-loop energy test circuit. The DC side of the sub-modules of the two string PCS are connected in a one-to-one correspondence and electrically isolated manner through the test unit to form multiple independent test channels, while their AC side is connected in parallel to the power grid. During the test, by setting different working modes and controlling the energy mutual feedback in the channel, synchronous parallel testing of all sub-modules can be achieved.

[0020] Compared with the prior art, the present invention has the following significant advantages: 1. Achieved a unified architecture that combines high efficiency, high security, and low cost. This invention fundamentally solves the core contradiction that existing technologies struggle to address simultaneously. By employing a topology design of "AC-side parallel integration and DC-side channel isolation," it achieves efficient parallel parallel testing of multiple submodules within a string PCS without relying on complex multi-winding transformers and numerous switching components. It successfully separates the efficient "point-to-point" testing mode from complex and expensive systems (such as those relying on multi-winding transformers) and integrates it into a simpler architecture. Its effects are reflected in: Efficiency leap: Using strings as the test unit, a single process can synchronously complete the parallel evaluation of all sub-modules of at least two strings through multiple independent channels, achieving a step increase in test throughput compared to inefficient parallel solutions.

[0021] Simplified architecture and reduced costs: By eliminating customized multi-winding transformers and a large number of control and coordination switching devices (such as DC circuit breakers), and adopting standard transformers and test fixtures, the system cost, manufacturing difficulty and maintenance complexity are greatly reduced.

[0022] Flexible and efficient scalability: The scalability of this invention is rooted in its basic architecture. Based on the existing structure, simply adding additional string PCS (e.g., the third and fourth strings) and connecting them to the corresponding transformer units allows for the addition of independent parallel test loops (such as CD-to-PCS) without altering the core topology. This enables simultaneous, independent, and parallel testing of multiple pairs of PCS. This scalability fully utilizes existing equipment, offers low expansion costs and flexible deployment, linearly increases overall test throughput, and perfectly adapts to dynamically growing production testing needs.

[0023] 2. Provides an intrinsically safe solution for internal testing of serialized PCS. This invention provides a dedicated security testing architecture tailored to the internal structural characteristics of serial PCS: Absolute fault isolation: Each test channel achieves natural electrical isolation on the DC side through physical topology, eliminating any path for fault current to spread between channels from the source, strictly confining any submodule fault to its independent circuit, completely solving the inherent safety defect of easy fault propagation in the existing parallel architecture, and realizing the inherent safety of the testing process.

[0024] Enhanced active protection: The channel-level protection device fuse, combined with the inherent isolation topology, forms a dual barrier of "physical isolation + electrical protection", which completely ends the chain risk of "all are damaged if one is damaged" in the traditional parallel architecture and achieves inherent safety in the testing process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the first serial PCS parallel isolation drag test platform of the present invention; Figure 2 This is a schematic diagram of the structure of the second type of serial PCS parallel isolation drag test platform of the present invention; Figure 3 This is a flowchart of a serial PCS parallel isolation drag test method according to the present invention; Figure 4 This is a schematic diagram illustrating the specific process of the drag testing method of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] In this embodiment, the two serial PCS are the first serial PCS and the second serial PCS as defined in the claims. Example 1

[0030] like Figure 1 As shown, a parallel isolation test platform for parallel-to-drag test systems using serial PCS includes a closed-loop energy test circuit constructed from a first set of serial PCS10, a second set of serial PCS20, a transformer unit, and a test unit 30. The AC sides of each submodule of the first group of serial PCS10 are connected in parallel and then connected to the corresponding connection terminals of the transformer unit to obtain electrical energy. The AC sides of each submodule of the second group of serial PCS20 are connected in parallel and then connected to the corresponding connection terminals of the transformer unit to obtain electrical energy. The drag test unit 30 is used to connect the DC sides of the sub-modules of the first set of serial PCS10 and the second set of serial PCS20 in a one-to-one correspondence and electrically isolated manner, so that the first set of serial PCS10 and the second set of serial PCS20 form multiple independent drag test channels and constitute a DC side test circuit.

[0031] Specifically, the number of sub-modules in the first set of serial PCS10 is the same as the number of sub-modules in the second set of serial PCS20. The DC side of sub-modules A1, A2...An in the first set of serial PCS is connected to the DC side of sub-modules B1, B2...Bn in the second set of serial PCS via independent electrical paths of the drag test unit 30, thereby forming n physically parallel and electrically isolated drag test channels: "A1↔B1", "A2↔B2", ... "An↔Bn". This topology of "AC-side parallel integration and DC-side channel isolation" is the physical basis of this invention.

[0032] Furthermore, such as Figure 1As shown, in order to facilitate the acquisition of power by the string PCS, the transformer unit includes a first grid-connected transformer 40 and a second grid-connected transformer 50 as AC grid-connected equipment. The AC sides of each sub-module A1, A2...An of the first string PCS10 are connected in parallel and connected to the first grid-connected transformer 40. The AC sides of each sub-module B1, B2...Bn of the second string PCS20 are connected in parallel and connected to the second grid-connected transformer 50.

[0033] Of course, the transformer unit is not limited to this. Alternatively, the transformer unit can be two dual-winding transformers, each of which includes a high-voltage side winding and a low-voltage side winding. The AC sides of each sub-module A1, A2...An of the first set of series PCS10 are connected in parallel to the low-voltage winding of one of the dual-winding transformers. The AC sides of each sub-module B1, B2...Bn of the second set of series PCS20 are connected in parallel to the low-voltage winding of the other dual-winding transformer. The high-voltage sides of both dual-winding transformers are connected to the power grid.

[0034] Furthermore, the transformer unit can also be an integrated three-winding transformer, which includes a high-voltage common winding and two low-voltage independent windings. The sub-modules A1, A2...An of the first string PCS10 are connected in parallel on the AC side to the first low-voltage winding of the three-winding transformer. The sub-modules B1, B2...Bn of the second string PCS20 are connected in parallel on the AC side to the second low-voltage winding of the three-winding transformer. The high-voltage common winding of the three-winding transformer is connected to the power grid. The first string PCS10 and the second string PCS20 maintain electrical isolation on the AC side and share the high-voltage common winding of the three-winding transformer. Thus, the two string PCSs maintain electrical isolation on the AC side, and the total number of transformers is reduced by sharing the high-voltage winding. This further reduces system cost and floor space while meeting safety isolation requirements.

[0035] Furthermore, such as Figure 1 As shown, to facilitate the provision of initial DC voltage, the test unit 30 includes a pre-charge circuit. This pre-charge circuit provides an initial DC voltage to either the first set of serial PCS10 or the second set of serial PCS20. It can be flexibly configured according to test requirements; that is, one pre-charge circuit can be shared by multiple sub-modules of each of the first set of serial PCS10 or the second set of serial PCS20. Pre-charging is provided to the PCS in the DC voltage mode that needs to be started, through switching or allocation methods. Alternatively, separate pre-charge circuits can be set up for each submodule of the first set of serial PCS10 or the second set of serial PCS20. In other words, the pre-charge circuits can also be configured independently for each pair of test channels, with each channel having an independent pre-charge circuit to provide start-up pre-charge for its corresponding DC voltage mode PCS.

[0036] The following detailed description uses the shared pre-charge circuit method as an example. However, those skilled in the art will understand that the circuit structure and control logic of the independent configuration method can also be simply derived and implemented with reference to the teachings of this embodiment.

[0037] In a detailed embodiment employing a shared pre-charge circuit, the pre-charge circuit is shared by multiple towing test channels. The pre-charge circuit includes a pre-charge circuit and pre-charge branch switches 311, 312, ... 31n corresponding to each towing test channel, with the pre-charge branch switches connected to the corresponding connection terminals of the pre-charge circuit.

[0038] like Figure 1 The first side of each of the precharge branch switches 311, 312, ... 31n is connected to the DC output terminal of the precharge circuit, and the second side is connected to the DC side of each sub-module A1, A2, ... An in the string PCS10.

[0039] Furthermore, such as Figure 1 The pre-charging circuit includes a rectifier bridge 301, a current-limiting resistor 302, a pre-charging transformer 303, and a pre-charging circuit AC side switch 304. These components are interconnected to form a pre-charging circuit that draws power from the grid to provide the initial DC voltage required for the startup of the string PCS10. Specifically, one end of the rectifier bridge 301 is connected to one end of the current-limiting resistor 302, and the other end of the rectifier bridge 301 is connected to one end of the pre-charging circuit AC side switch 304 through the pre-charging transformer 303. The other end of the current-limiting resistor 302 is also connected to one end of multiple pre-charging branch switches, and the other end of each pre-charging branch switch is simultaneously connected to the DC side of the sub-modules of the first string PCS10 and the second string PCS20.

[0040] During the pre-charging phase, the corresponding pre-charging branch switches 311, 312, ... 31n and the AC side switch 304 of the pre-charging circuit are closed to establish the initial voltage for the corresponding sub-module through the branch. After the sub-module starts up, the corresponding pre-charging branch switches are opened to isolate them from the pre-charging circuit and prevent the DC side of each sub-module from forming a parallel path through the pre-charging circuit.

[0041] It is understood that the above-mentioned pre-charging function can also be implemented by other circuit forms, such as using the AC pre-charging unit built into the string PCS. Any device that can provide the function of pre-charging for PCS startup should be included in the scope of the pre-charging circuit described in this invention.

[0042] Furthermore, such as Figure 1 As shown, to achieve overcurrent protection, the test unit 30 includes multiple fuses FU1, FU2, ... FUn, which are connected in series in the DC-side connection paths of each submodule of the first string PCS10 and the second string PCS20 to achieve overcurrent protection. The number of fuses is consistent with the number of submodules in the first string PCS10 and the second string PCS20.

[0043] Furthermore, such as Figure 1 As shown, to facilitate the control of the AC side switching of the string PCS, the present invention also includes an AC side switch control unit. The AC side switch control unit includes a main AC side switch 70, a first AC side switch 80, and a second AC side switch 90. The first AC side switch 80 is connected in series in the AC side connection path of each sub-module A1, A2...An of the first grid-connected transformer 40 and the first string PCS 10. The second AC side switch 90 is connected in series in the AC side connection path of each sub-module B1, B2...Bn of the second grid-connected transformer 50 and the second string PCS 20. The first grid-connected transformer 40 and the second grid-connected transformer 50 are connected in parallel and then connected to the main AC side switch 70.

[0044] Furthermore, such as Figure 1 As shown, in order to facilitate the control of the status of different string PCS, a control system 60 composed of a host computer is also included. The control system 60 is communicatively connected to the first string PCS 10 and the second string PCS 20 to form a test platform control loop.

[0045] When the multiple sub-modules A1, A2...An of the first set of string PCS10 are configured to operate in DC voltage mode; and the multiple sub-modules B1, B2...Bn of the second set of string PCS20 are configured to operate in AC power mode; when all sub-modules of the second set of string PCS20 operate in rectification mode to simulate charging, then all sub-modules of the first set of string PCS10 operate in inverter mode to simulate discharging; when all sub-modules of the second set of string PCS20 operate in inverter mode to simulate discharging, then all sub-modules of the first set of string PCS10 operate in rectification mode to simulate charging. Example 2

[0046] like Figure 2As shown, the difference between Embodiment 2 and Embodiment 1 is that Embodiment 2 further includes at least one extended topology, which includes a string PCS pair and an extended pair test unit 300 connected to the string PCS pair. The extended string PCS pair includes a third string PCS 100 and a fourth string PCS 200. The AC side of each submodule of the third set of serial PCS100 is connected in parallel with the AC side of each submodule of the first set of serial PCS10 to the transformer unit. The AC side of each sub-module of the fourth group of serial PCS200 is connected in parallel with the AC side of each sub-module of the second group of serial PCS20 to the transformer unit. The extended drag test unit 300 is also used to connect the DC sides of multiple sub-modules of the third set of serial PCS100 and the fourth set of serial PCS200 in a one-to-one correspondence and electrically isolated manner to form at least another set of extended and mutually independent drag test channels.

[0047] Thus, based on the existing first and second grid-connected transformers, this invention only requires adding additional string-type PCS (e.g., third and fourth strings) and connecting them to the corresponding transformers (two independent transformers can be integrated into a three-winding transformer, further reducing system costs). This allows for the addition of independent parallel test circuits (such as CD parallel circuits) without altering the core topology, enabling simultaneous and independent testing of multiple pairs of PCS. This expansion method fully utilizes existing equipment, offers low expansion costs and flexible deployment, linearly increases overall test throughput, and perfectly adapts to dynamically growing production testing needs.

[0048] When testing Example 2, the drag test method is performed simultaneously on multiple pairs of serial PCS. Example 3

[0049] like Figure 3 As shown, a parallel isolation drag-and-drop test method for a string-type PCS includes the aforementioned parallel isolation drag-and-drop test platform for the string-type PCS. The specific test steps are as follows: S1. Establish a test channel The DC side of each submodule of the first and second set of serial PCS is connected to form multiple electrically isolated test channels. S2. Set working mode The first group of serial PCS and the second group of serial PCS are configured to operate in different working modes. S3. Starting and Establishing Power Flow Start the two serial PCS in sequence to put the system into a test state. S4. Perform parallel drag testing The two string PCSs are controlled to simultaneously charge and discharge each other in the multiple independent channels, so that electrical energy circulates in each closed loop, thereby completing the complete performance evaluation of all sub-modules in the two string PCSs in a single test process.

[0050] In step S2, the first set of serial PCS is set to operate in DC voltage mode, and the second set of serial PCS is set to operate in AC power mode. The first set of string PCS operating in DC voltage mode is pre-charged to establish an initial voltage. Once this PCS starts up, its output voltage provides the startup conditions for the second set of string PCS operating in AC power mode. The second set of string PCS in AC power mode operates in rectification mode to simulate charging, while the first set of string PCS in DC voltage mode operates in inverter mode to simulate discharging; by switching the operating modes of the two, electrical energy is circulated in the closed loop. Example 4

[0051] like Figure 4 As shown, a parallel isolation test method for a serial PCS in Example 3 is further described in detail, specifically as follows: Step S10: Close the main AC side switch 70, the first AC side switch 80, and the second AC side switch 90 of the AC side switch control unit. This draws power from the grid, and through the first grid-connected transformer 40 and the second grid-connected transformer 50 of the transformer unit, supplies AC power to each sub-module A1, A2...An, B1, B2...Bn in the first series PCS10 and the second series PCS20. Step S20: Perform a pre-charge operation to provide initial DC voltage to each sub-module A1, A2...An in the first group of serial PCS10. Close the precharge branch switches 311, 312, ... 31n of the precharge circuit in the test unit 30 to connect the DC side of the submodule of the first set of serial PCS to the precharge circuit of the precharge circuit. Close the AC side switch 304 of the precharge circuit to start the precharge circuit from the grid. The precharge circuit establishes an initial DC voltage for the corresponding submodule through the connected precharge branch. Step S30: Control each submodule A1, A2...An in the first group of serial PCS10 to start up in DC voltage mode. Step S40, pre-charge circuit exits. The precharge circuit exit includes disconnecting the precharge circuit AC side switch 304 in the precharge circuit to stop the precharge circuit from working, and disconnecting the closed precharge branch switches 311, 312, ... 31n to isolate the DC side of each submodule in the first set of serial PCS10 from the precharge circuit, thus preventing the DC side of each submodule from forming a parallel path through the precharge circuit. In step S50, the control system controls the output of DC voltage from each submodule A1, A2...An in the first set of serial PCS10, and provides DC voltage to each submodule A1, A2...An, B1, B2...Bn in the second set of serial PCS20. Step S60: Control each submodule B1, B2...Bn in the serial PCS to start up in AC power mode. In step S70, the control system 60 controls the charging or discharging of each submodule B1, B2...Bn in the second set of serial PCS, while the submodules A1, A2...An in the first set of serial PCS are discharging or charging. Step S80: Charging and discharging are complete. The control system 60 then controls each sub-module B1, B2...Bn in the second set of serial PCS to stop. In step S90, the control system 60 controls each sub-module A1, A2...An in the first group of serial PCS to stop. Step S100: Disconnect the main AC side switch 70, the first AC side switch 80, and the second AC side switch 90 of the AC side switch control unit to complete the power test of all sub-modules in the first and second series PCS. If each sub-module operates stably at its rated power, the test is qualified.

[0052] That is, if each submodule of the PCS operates at its rated power for 1 hour without any abnormal alarms and the module temperature rise does not exceed 35K, then the test is qualified.

[0053] The core objective of this invention is to achieve efficient parallel testing of multiple sub-modules within a string PCS by using a topology design of "AC-side parallel integration and DC-side channel isolation," without relying on complex multi-winding transformers and a large number of switching components. This fundamentally overcomes the bottlenecks of existing efficient solutions (such as point-to-point parallel testing) that are complex, costly, and have poor scalability.

[0054] Furthermore, through the channelized design with DC-side electrical isolation, any submodule fault is strictly confined to its independent circuit from a physical topology perspective, completely solving the inherent safety defects of easy fault propagation in the existing parallel architecture and achieving inherent safety in the testing process.

[0055] In summary, compared with the prior art, the present invention has the following significant advantages: 1. Achieved a unified architecture that combines high efficiency, high security, and low cost. This invention fundamentally solves the core contradiction that existing technologies struggle to address simultaneously. Through a unique "AC-side parallel integration, DC-side channel isolation" topology, it successfully separates the efficient "point-to-point drive" mode from complex and expensive systems (such as those relying on multi-winding transformers) and embeds it into a structurally simple architecture. Its effects are reflected in: Efficiency leap: Using strings as the test unit, a single process can synchronously complete the parallel evaluation of all sub-modules of at least two strings through multiple independent channels, achieving a step increase in test throughput compared to inefficient parallel solutions.

[0056] Simplified architecture and reduced costs: By eliminating customized multi-winding transformers and a large number of control and coordination switching devices (such as DC circuit breakers), and adopting standard transformers and test fixtures, the system cost, manufacturing difficulty and maintenance complexity are greatly reduced.

[0057] Flexible and efficient scalability: The scalability of this invention is rooted in its basic architecture. With the existing first and second grid-connected transformers, only additional string-type PCS (e.g., third and fourth strings) need to be added and connected to the corresponding transformers (two independent transformers can be integrated into a three-winding transformer, further reducing system costs). This allows for the addition of independent parallel test circuits (such as CD parallel circuits) without changing the core topology, enabling simultaneous and independent testing of multiple pairs of PCS. This scalability fully utilizes existing equipment, offers low scalability and flexible deployment, linearly increases overall test throughput, and perfectly adapts to dynamically growing production testing needs.

[0058] 2. Provides an intrinsically safe solution for internal testing of serialized PCS. This invention provides a dedicated security testing architecture tailored to the internal structural characteristics of serial PCS: Absolute fault isolation: Each test channel achieves natural electrical isolation on the DC side through physical topology, eliminating any path for fault current to spread between channels from the source, and strictly confining any submodule fault to its independent circuit.

[0059] Enhanced active protection: The channel-level protection device fuse, combined with the inherent isolation topology, forms a dual barrier of "physical isolation + electrical protection", which completely ends the chain risk of "all are damaged if one is damaged" in the traditional parallel architecture and achieves inherent safety in the testing process.

[0060] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A parallel isolation test platform for serial PCS, characterized in that: The energy testing circuit consists of a first set of series PCS (10), a second set of series PCS (20), a transformer unit, and a drag test unit (30), forming a closed loop. The AC sides of each submodule of the first set of serial PCS (10) are connected in parallel and then connected to the corresponding connection terminals of the transformer unit. The AC sides of each submodule of the second set of serial PCS (20) are connected in parallel and then connected to the corresponding connection terminals of the transformer unit. The drag test unit (30) is used to connect the DC side of each sub-module of the first set of serial PCS (10) and the second set of serial PCS (20) in a one-to-one correspondence and electrically isolated manner, so that the first set of serial PCS (10) and the second set of serial PCS (20) form multiple independent drag test channels and constitute a DC side test circuit.

2. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: The transformer unit includes a first grid-connected transformer (40) and a second grid-connected transformer (50). The AC sides of each sub-module A1, A2...An of the first set of serial PCS (10) are connected in parallel and connected to the first grid-connected transformer (40). The AC sides of each sub-module B1, B2...Bn of the second set of serial PCS (20) are connected in parallel and connected to the second grid-connected transformer (50).

3. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: The transformer unit consists of two double-winding transformers, each of which includes a high-voltage side winding and a low-voltage side winding. The AC sides of each sub-module A1, A2...An of the first set of series PCS (10) are connected in parallel to the low-voltage winding of one of the double-winding transformers. The AC sides of each sub-module B1, B2...Bn of the second set of series PCS (20) are connected in parallel to the low-voltage winding of the other double-winding transformer. The high-voltage sides of both double-winding transformers are connected to the power grid.

4. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: The transformer unit is an integrated three-winding transformer. The three-winding transformer includes a high-voltage side common winding and two low-voltage side independent windings. The sub-modules A1, A2...An of the first set of string PCS (10) are connected in parallel on the AC side to the first low-voltage winding of the three-winding transformer. The sub-modules B1, B2...Bn of the second set of string PCS (20) are connected in parallel on the AC side to the second low-voltage winding of the three-winding transformer. The high-voltage side common winding of the three-winding transformer is connected to the power grid. The first set of string PCS (10) and the second set of string PCS (20) are still electrically isolated on the AC side and share the high-voltage side common winding of the three-winding transformer.

5. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: The drag test unit (30) includes a pre-charge circuit, which is used to provide an initial DC voltage for the first set of serial PCS (10) or the second set of serial PCS (20). One pre-charge circuit is shared by multiple sub-modules of the first set of serial PCS (10) or the second set of serial PCS (20), or a separate pre-charge circuit is set for each sub-module of the first set of serial PCS (10) or the second set of serial PCS (20). The pre-charge circuit includes a pre-charge circuit and a pre-charge branch switch corresponding to each drag test channel. The pre-charge branch switch is connected to the connection terminal corresponding to the pre-charge circuit.

6. The parallel isolation drag test platform for serial PCS according to claim 5, characterized in that: The pre-charge circuit includes a rectifier bridge (301), a current-limiting resistor (302), a pre-charge transformer (303), and a pre-charge circuit AC side switch (304). One end of the rectifier bridge (301) is connected to one end of the current-limiting resistor (302), and the other end of the rectifier bridge (301) is connected to one end of the pre-charge circuit AC side switch (304) through the pre-charge transformer (303). The other end of the current-limiting resistor (302) is simultaneously connected to one end of multiple pre-charge branch switches, and the other end of each pre-charge branch switch is simultaneously connected to the DC side of the sub-module of the first set of serial PCS (10) and the second set of serial PCS (20).

7. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: The drag test unit (30) includes multiple fuses FU1, FU2, ... FUn, and the multiple fuses FU1, FU2, ... FUn are connected in series in the DC side connection path of each sub-module of the first set of serial PCS (10) and the second set of serial PCS (20) to realize overcurrent protection.

8. The parallel isolation drag test platform for serial PCS according to claim 2, characterized in that: It also includes an AC side switch control unit, which includes a main AC side switch (70), a first AC side switch (80) and a second AC side switch (90). The first AC side switch (80) is connected in series in the AC side connection paths of each sub-module A1, A2...An of the first grid-connected transformer (40) and the first set of serial PCS (10). The second AC side switch (90) is connected in series in the AC side connection paths of each sub-module B1, B2...Bn of the second set of serial PCS (20). The first grid-connected transformer (40) and the second grid-connected transformer (50) are connected in parallel and then connected to the main AC side switch (70).

9. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: It also includes a control system (60) composed of a host computer, which is communicatively connected to the first set of serial PCS (10) and the second set of serial PCS (20) to form a test platform control loop.

10. The parallel isolation drag test platform for serial PCS according to claim 1, characterized in that: It also includes at least one set of extended topologies, the topologies including a pair of serial PCS and an extended pair of drag test units (300) connected to the pair of serial PCS, the extended pair of serial PCS including a third pair of serial PCS (100) and a fourth pair of serial PCS (200). The AC side of each sub-module of the third set of serial PCS (100) is connected in parallel with the AC side of each sub-module of the first set of serial PCS (10) to the transformer unit. The AC side of each submodule of the fourth set of serial PCS (200) is connected in parallel with the AC side of each submodule of the second set of serial PCS (20) to the transformer unit. The extended drag test unit (300) is also used to connect the DC sides of multiple sub-modules of the third set of serial PCS (100) and the fourth set of serial PCS (200) in a one-to-one correspondence and electrically isolated manner to form at least another set of extended mutually independent drag test channels.

11. A parallel isolation drag-and-drop test method for a string PCS, comprising the parallel isolation drag-and-drop test platform for a string PCS as described in any one of claims 1-10, characterized in that: The specific testing steps are as follows: S1. Establish a test channel The DC side of each submodule of the first and second set of serial PCS is connected to form multiple electrically isolated test channels. S2. Set working mode The first group of serial PCS and the second group of serial PCS are configured to operate in different working modes. S3. Start and establish power flow Start the two serial PCS in sequence to put the system into a test state. S4. Perform parallel drag testing The two string PCSs are controlled to simultaneously charge and discharge each other in the multiple independent channels, so that electrical energy circulates in each closed loop, thereby completing the complete performance evaluation of all sub-modules in the two string PCSs in a single test process.

12. The parallel isolation drag test method for a serial PCS according to claim 11, characterized in that: In step S2, the first set of serial PCS is set to operate in DC voltage mode, and the second set of serial PCS is set to operate in AC power mode. The first set of string PCS operating in DC voltage mode is pre-charged to establish an initial voltage. Once this PCS starts up, its output voltage provides the startup conditions for the second set of string PCS operating in AC power mode. The second set of string PCS in AC power mode operates in rectification mode to simulate charging, while the first set of string PCS in DC voltage mode operates in inverter mode to simulate discharging; by switching the operating modes of the two, electrical energy is circulated in the closed loop.

13. The parallel isolation drag test method for a serial PCS according to claim 12, characterized in that: The closed AC side switch control unit supplies AC power to the sub-modules A1, A2...An and B1, B2...Bn in the first and second series PCS via the transformer unit. Close the precharge branch switch of the precharge circuit in the test unit to connect the DC side of the sub-module of the first set of serial PCS with the precharge circuit of the precharge circuit, and establish the initial DC voltage for the corresponding sub-module. The system controls each submodule A1, A2...An in the first set of serial PCS to start up in DC voltage mode. The pre-charge circuit is deactivated, which includes disconnecting the AC side switch and the pre-charge branch switch in the pre-charge circuit, thereby isolating the DC side of each sub-module in the first set of serial PCS from the pre-charge circuit. The control system controls the output DC voltage of each submodule A1, A2...An in the first set of serial PCS, and provides DC voltage to each submodule A1, A2...An, B1, B2...Bn in the second set of serial PCS. Control each submodule B1, B2...Bn in the second set of serial PCS to start up in AC power mode. By controlling the charging or discharging of each submodule B1, B2...Bn in the second set of serial PCS by the control system, the charging or discharging of each submodule A1, A2...An in the first set of serial PCS will also occur. Once charging and discharging are complete, the control system stops each sub-module B1, B2...Bn in the second set of serial PCS. The control system controls the shutdown of each sub-module A1, A2...An in the first set of serial PCS. Disconnect the AC side switch control unit and complete the power test of all sub-modules in the first and second series PCS. If each sub-module operates stably at its rated power, the test is qualified.

Images