A method and system for coordinated control of distributed compensators

Abstract

The application provides a kind of coordination control method and system of distributed compensator.The method comprises: assembling distributed compensator;Detecting the operating state of each phase converter each stage module;Calculate the number of modules that distributed compensator can effectively output voltage;Lock bypass when module fails;Convert the module that needs to be converted to hot standby state.According to the coordination control method and system of distributed compensator provided by the application, the coordination control of distributed compensator can be realized, the module fault of distributed compensator can be quickly and smoothly handled, and balanced control can be ensured after the module fault of a certain phase occurs in each phase of each loop line, to avoid unbalanced disturbance to the AC power grid.

Description

Technical Field

[0001] This application relates to the field of flexible AC transmission in power systems, and more specifically, to a coordinated control method and system for distributed compensators. Background Technology

[0002] With the interconnection of large-scale power systems and the use of various new equipment, while making power generation and transmission more economical and efficient, the scale and complexity of power systems have also increased. Furthermore, the integration of numerous distributed generation systems into the grid has reversed the traditional fixed power flow from the transmission network to the distribution network. The continuous growth of user load necessitates power flow control measures to improve existing power transmission capacity, and the complex power exchange between the rapidly developing smart grid and the electricity market also requires frequent power flow optimization control.

[0003] Distributed compensators (DCCs) can directly suspend each small-capacity compensator on power lines, achieving power flow control functions and effects similar to static synchronous series compensators (SSCs). This provides smart grids with more flexible and advanced control methods, effectively improving the power supply capacity and safety stability of the power system. DCCs are characterized by their small size and light weight. A large number of distributed sub-units ensure equipment redundancy, thereby improving the reliability of the device. Furthermore, DCC devices can be deployed dispersedly on transmission lines or substations, occupying a small area.

[0004] Currently, there are two demonstration projects of distributed compensators (distributed static synchronous series compensators) abroad. The control and protection systems of both projects are relatively simple, employing a modular local control mode, resulting in inflexible control methods and poor power flow regulation performance. Domestically, some universities and research institutes have conducted research on various distributed compensators (distributed series reactors, distributed static synchronous series compensators, distributed power flow controllers, etc.), mainly focusing on topology, simulation modeling, and system control strategies. There is currently no literature or patents regarding coordinated control between phases and circuits when a module of a distributed compensator experiences a module failure.

[0005] A common distributed compensator structure includes three-phase voltage source converters connected in series to a three-phase AC line respectively, each phase converter is composed of a plurality of modules connected in series, and the three phases are balanced. The distributed compensator has a single-loop operation mode and a multi-loop operation mode. In the single-loop operation mode, if a module fault occurs in one phase, the number of available modules in the phase is reduced. Without inter-phase coordinated control, the non-fault phase still operates in the original state, and the voltage output of the three-phase voltage source converter will be asymmetric, causing the equivalent impedance of the three-phase AC line to be asymmetric, thereby generating zero sequence and negative sequence currents in the AC line, affecting the normal operation of the AC line; in the multi-loop operation mode, each loop operates in parallel, and when a module fault occurs in one loop, without coordinated control between loops, the non-fault loop still operates in the original state, and the voltage output of the distributed compensator in each loop will be unbalanced, causing the equivalent impedance of each loop to be unbalanced, and asymmetric circulating current will be generated between loops, affecting the normal operation of the AC system.

[0006] Currently, for the case of a module fault in a certain phase, the processing method used in the power flow controller or flexible DC transmission project using modular multilevel converters is mostly without inter-phase coordinated control, but instead, redundant modules are put into the fault phase to replace the bypassed faulty module. When the number of faulty modules exceeds the set number of redundant modules, the converter will be triggered to be blocked. The distributed compensator has no specific redundancy design, each series module can operate independently, and the converter has the ability to operate with a single module. Therefore, only when all series modules in a certain phase fail, the converter needs to be triggered to be blocked.

[0007] Therefore, when a module fault occurs in a certain phase of the distributed compensator, in order to fully utilize the redundancy and flexibility of the distributed compensator and avoid the problems of three-phase asymmetry and loop imbalance caused by module faults, a coordinated control method is needed to quickly and smoothly handle module faults in each phase of the distributed compensator, ensuring that each loop and each phase can still be balanced after a module fault occurs.

[0008] In the background section, the disclosed above information is only used to strengthen the understanding of the background of the present application, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0009] The present application aims to provide a coordinated control method and system for a distributed compensator, which can quickly and smoothly handle module faults in each phase of the distributed compensator, ensure that each loop and each phase can still be balanced after a module fault occurs in a certain phase of a certain loop, and avoid causing unbalanced disturbance to the AC power grid.

[0010] According to an aspect of the present application, a coordinated control method for a distributed compensator is provided, comprising:

[0011] The distributed compensator is composed of three-phase converters connected in series to a three-phase alternating current line, each of the converters is composed of a plurality of modules connected in series.

[0012] During normal operation of the distributed compensator, the operating state of each module of each of the converters is detected in real time to obtain the number of available modules of each of the converters, wherein the number of available modules of each of the converters is the number of modules in each of the converters that have normal operating conditions and are not faulty.

[0013] The number of modules of the distributed compensator that can effectively output voltage is calculated in real time, wherein the number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each of the converters.

[0014] When any module of any of the converters fails, the failed module is blocked and bypassed, and the number of available modules of the converter of the faulty phase is reduced by one, while the number of available modules of the converter of the non-faulty phase remains unchanged.

[0015] The number of available modules of each of the converters is compared with the number of modules of the distributed compensator that can effectively output voltage calculated in real time, and if the number of available modules of any of the converters is greater than the number of modules of the distributed compensator that can effectively output voltage, the module of the converter of that phase that needs to be converted to a hot standby state is converted to a hot standby state.

[0016] The number of modules of each of the converters that need to be converted to a hot standby state is equal to the number of available modules of each of the converters minus the number of modules of the distributed compensator that can effectively output voltage.

[0017] According to some embodiments, the three-phase converter is a voltage source converter.

[0018] According to some embodiments, the distributed compensator is a single-loop operation mode, and only a single-loop alternating current line is connected in series to the distributed compensator.

[0019] According to some embodiments, the specific calculation method of the number of modules of the distributed compensator that can effectively output voltage is as follows:

[0020] The number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each of the converters in the single-loop alternating current line.

[0021] According to some embodiments, the distributed compensator is a multi-loop operation mode, and a plurality of parallel multi-loop alternating current lines are connected in series to the distributed compensator.

[0022] According to some embodiments, the specific calculation method of the number of modules that the distributed compensator can effectively output voltage is as follows:

[0023] The number of modules that the distributed compensator can effectively output voltage is equal to the minimum value obtained by comparing the minimum values of the available module numbers of each phase of the converter in each of the parallel multi-circuit AC lines.

[0024] According to some embodiments, the hot standby state is,

[0025] The module that needs to be converted to the hot standby state is unlocked and has voltage output capability, but the port output voltage is maintained at 0.

[0026] According to another aspect of the present application, a coordinated control system of a distributed compensator is provided, the distributed compensator comprising three-phase converters connected in series to a three-phase AC line respectively, each phase of the converter being composed of a plurality of modules connected in series, wherein the coordinated control system comprises:

[0027] A module state monitoring module that detects the operating state of each module in each phase of the converter in the distributed compensator in real time, the operating state including module unlocking, module locking and module failure;

[0028] An effective module number calculation module that calculates the available module number of each phase of the converter in real time according to the operating state of each module, and calculates the number of modules that the distributed compensator can effectively output voltage in real time;

[0029] A module hot standby state control module that calculates the number of modules in each phase of the converter that need to be converted to the hot standby state in real time, and converts the modules in each phase of the converter that need to be converted to the hot standby state to the hot standby state.

[0030] According to some embodiments, the coordinated control system further comprises:

[0031] A multi-circuit intercommunication module that is effective only when the distributed compensator is in multi-circuit operation mode, and sums up the minimum values of the available module numbers of each phase of the converter in each of the parallel multi-circuit AC lines.

[0032] According to some embodiments, the module hot standby state control module calculates the number of modules in each phase of the converter that need to be converted to the hot standby state in real time, and when the number of modules in that phase that need to be converted to the hot standby state is zero, no module in that phase is converted to the hot standby state.

[0033] According to the coordination control method and system of the distributed compensator provided in the application, the coordination control of the distributed compensator can be realized: when a fault module of a phase of a certain return line distributed compensator occurs, the fault module of the fault phase is bypassed quickly, the available module numbers of each phase of each return line are updated, the effective input module numbers of each return line are calculated in real time, and a corresponding number of modules are switched to a hot standby state according to the available module numbers of each phase and the effective input module numbers of each return line, so that the number of modules that can effectively output voltage of each phase of each return line is kept consistent, and then the output of each phase is kept consistent, and the coordination and balanced control of each phase of each return line is realized. By using the above coordination control scheme, the module fault of the distributed compensator can be quickly and smoothly handled, the balanced control of each phase of each return line after the module fault of a certain phase occurs can be ensured, and unbalanced disturbance to the alternating current power grid is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0034] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description of example embodiments thereof by referring to the accompanying drawings.

[0035] Figure 1 is a schematic diagram of the processing mode after a certain phase of a conventional power flow controller and flexible direct current transmission project has a module fault.

[0036] Figure 2 A flow chart of a coordination control method of a distributed compensator according to an example embodiment of the application is shown.

[0037] Figure 3 A structure schematic diagram of a coordination control system of a distributed compensator according to an example embodiment of the application is shown.

[0038] Figure 4 A structure schematic diagram of a coordination control system of a distributed compensator according to some embodiments of the application is shown.

[0039] Figure 5 A flow chart of a control method of a module hot standby state control module according to some embodiments of the application is shown.

[0040] Figure 6 A structure schematic diagram of a module hot standby state control module embodiment 1 provided in the application is shown.

[0041] Figure 7 A structure schematic diagram of a module hot standby state control module embodiment 2 provided in the application is shown. DETAILED DESCRIPTION

[0042] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the several views and, thus, description of the same will be simplified and eliminated.

[0043] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the

[0044] The flow charts shown in the drawings are merely exemplary and not necessarily all inclusive of all content and operations / steps, nor are they necessarily performed in the order described. For example, some operations / steps can be broken down further, while some operations / steps can be combined or partially combined, so the actual order of performance can vary depending on the actual situation.

[0045] Figure 1 is the principle diagram of the processing method after a certain phase of the existing current controller and flexible DC power transmission project appears module fault.

[0046] As shown in Figure 1 , if this method is used, a certain number of N_RE_N redundant modules are set in each phase converter of the distributed compensator in the N series modules of the distributed compensator, and the number of operating modules is set as N_OP_N. Among them, during the normal operation of the converter, the redundant modules do not output effective voltage. When a certain operating module of a certain phase appears a fault, the fault module is bypassed, and a redundant module is put into operation, the number of remaining redundant modules N_RE is reduced by 1, so as to keep the number of operating modules of the phase unchanged as N_OP_N, so as to maintain the original operating state of the converter. When the number of remaining redundant modules N_RE is 0, the redundant modules of the phase converter are exhausted, and the converter is locked.

[0047] Since each series module of the distributed compensator can be operated independently, the converter has the ability to operate with a single module, so when the above method is used, the redundancy and flexibility of the distributed compensator cannot be fully utilized. The present application provides a coordinated control method and system of a distributed compensator, which ensures that each phase of each return line can still be balanced controlled after a certain module fault occurs in a certain phase of a certain return line, and ensures that the distributed compensator can still operate normally, while avoiding unbalanced disturbance to the AC power grid.

[0048] The application aims to provide a coordinated control method and system of a distributed compensator, which can quickly and smoothly handle the fault of each phase module of the distributed compensator, ensure that each phase of each loop line can still be balanced controlled after a certain phase module of a certain loop line fails, and avoid causing unbalanced disturbance to the AC power grid.

[0049] The coordinated control method and system of the distributed compensator according to the embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0050] Figure 2 A flow chart of the coordinated control method of the distributed compensator according to the example embodiments of the application is shown.

[0051] Referring to Figure 2 In S210, the distributed compensator is assembled.

[0052] The distributed compensator is composed of three-phase converters connected in series to a three-phase AC line, and each phase of the converter is composed of multiple modules connected in series.

[0053] In S220, the operating state of each module of each phase converter is detected.

[0054] During the normal operation of the distributed compensator, the operating state of each module of each phase converter is detected in real time to obtain the number of available modules of each phase converter, wherein the number of available modules of each phase converter is the number of modules in each phase converter that have normal operating conditions and are not faulty.

[0055] In S230, the number of modules of the distributed compensator that can effectively output voltage is calculated.

[0056] The number of modules of the distributed compensator that can effectively output voltage is calculated in real time, wherein the number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each phase converter.

[0057] In S240, the bypass is blocked when a module fails.

[0058] When any phase of the converter fails, the failed module is blocked and bypassed, and the number of available modules of the faulty phase converter is reduced by one, while the number of available modules of the non-faulty phase converter remains unchanged.

[0059] In S250, the module to be converted is converted to a hot standby state.

[0060] comparing the available module number of the converter in each phase with the effective output voltage module number of the distributed compensator calculated in real time, if the available module number of the converter in any phase is greater than the effective output voltage module number of the distributed compensator, the module in the converter in the phase which needs to be converted to the hot standby state is converted to the hot standby state,

[0061] wherein the module number in each phase of the converter which needs to be converted to the hot standby state is equal to the available module number of the converter in each phase minus the effective output voltage module number of the distributed compensator.

[0062] According to some embodiments, the three-phase converter is a three-phase voltage source converter.

[0063] According to some embodiments, the distributed compensator is a single-circuit operation mode, and only a single-circuit AC line is connected in series to the distributed compensator. The specific calculation method of the effective output voltage module number of the distributed compensator is that the effective output voltage module number of the distributed compensator is equal to the minimum value of the available module number of the converter in each phase in the single-circuit AC line.

[0064] According to some embodiments, the distributed compensator is a multi-circuit operation mode, and the multi-circuit AC lines in parallel are connected in series to the distributed compensator. The specific calculation method of the effective output voltage module number of the distributed compensator is that the effective output voltage module number of the distributed compensator is equal to the minimum value obtained after comparison and collection of the minimum value of the available module number of the converter in each phase in each of the multi-circuit AC lines in parallel.

[0065] Figure 3 A structure schematic diagram of a coordination control system of a distributed compensator according to some embodiments of the present application is shown.

[0066] Referring to Figure 3 In each circuit, the distributed compensator includes a three-phase converter connected in series to a three-phase AC line, and each phase of the converter is composed of a plurality of modules connected in series.

[0067] Figure 4 A structure schematic diagram of a coordination control system of a distributed compensator according to some embodiments of the present application is shown.

[0068] Referring to Figure 4 The coordination control system of the distributed compensator of some embodiments includes a module state monitoring module 10, an effective module number calculation module 20, a module hot standby state control module 30, and a multi-circuit intercommunication module 40.

[0069] As Figure 4As shown, the module state monitoring module 10 detects the running state of each module in each phase converter in the distributed compensator in real time, and transmits the running state of each module to the effective module number calculation module 20. The multi-loop intercommunication module 40 is only effective when the distributed compensator is in multi-loop operation mode, and collects the minimum value of the available module number of each phase converter in each parallel multi-loop AC line, and transmits the minimum value of the available module number to the effective module number calculation module 20.

[0070] As shown, the effective module number calculation module 20 calculates the available module number of each phase converter in real time according to the running state of each module, and calculates the module number that can effectively output voltage of the distributed compensator in real time, and transmits the module number that can effectively output voltage to the module hot standby state control module 30. Figure 4 As shown, the module hot standby state control module 30 calculates the module number that needs to be converted to the hot standby state in each phase converter in real time, and converts the module that needs to be converted to the hot standby state in each phase converter to the hot standby state, wherein the module number that needs to be converted to the hot standby state in each phase converter is equal to the available module number of each phase converter minus the module number that can effectively output voltage of the distributed compensator.

[0071] Figure 4 According to some embodiments, the running state of each module includes module unlocking, module locking and module failure.

[0072] According to some embodiments, the running state of each module includes module unlocking, module locking and module failure.

[0073] Figure 5 A control method flow chart of the module hot standby state control module according to some embodiments of the present application is shown.

[0074] Referring to Figure 5 At S510, module state data is received.

[0075] The module hot standby state control module receives the available module number signal of each phase converter and the module number signal that can effectively output voltage of the distributed compensator.

[0076] At S520, the module number that needs to be converted to the hot standby state is calculated.

[0077] The module hot standby state control module calculates the module number that needs to be converted to the hot standby state in each phase converter in real time, wherein the module number that needs to be converted to the hot standby state in each phase converter is equal to the available module number of each phase converter minus the module number that can effectively output voltage of the distributed compensator.

[0078] At S530, it is detected whether a module needs to be converted to the hot standby state. ​

[0079] If there is a module that needs to be converted to the hot standby state, the module hot standby state control module first determines whether the current module is faulty, and if not, it is converted to the hot standby state.

[0080] At S540, the modules are detected in turn until there is no module that needs to be converted to the hot standby state.

[0081] If the detected module is faulty, the next module is determined, and the state of each module is determined in turn until the number of modules that need to be converted to the hot standby state is zero.

[0082] Embodiment 1

[0083] Figure 6 The structure diagram of the module hot standby state control module provided by the present application is shown in Embodiment 1.

[0084] If the number of available modules of the line commutated converter is greater than the number of effective input modules of the distributed compensator, it is first determined whether the first-level module is faulty, and if not, it is converted to the hot standby state, and if it is faulty, the second-level module is determined, and the state of each module is determined in turn until the number of hot standby modules is equal to the number of available modules of the line commutated converter minus the number of effective input modules of the distributed compensator.

[0085] Embodiment 2

[0086] Figure 7 The structure diagram of the module hot standby state control module provided by the present application is shown in Embodiment 2.

[0087] If the number of available modules of the line commutated converter is greater than the number of effective input modules of the distributed compensator, it is first determined whether the Nth-level module is faulty, and if not, it is converted to the hot standby state, and if it is faulty, the (N-1)th-level module is determined, and the state of each module is determined in turn until the number of hot standby modules is equal to the number of available modules of the line commutated converter minus the number of effective input modules of the distributed compensator.

[0088] The embodiments of the present application are described and explained in detail above. It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. Instead, based on the teachings of the disclosure, these principles can be applied to many other embodiments.

[0089] Through the description of the example embodiments, those skilled in the art can easily understand that the technical solutions according to the embodiments of the present application have at least one or more of the following advantages.

[0090] According to some embodiments of the present application, the present application can realize coordinated control of the distributed compensator: when a certain phase of a certain back line distributed compensator has a module fault, the fault module of the fault phase is bypassed quickly, the number of available modules of each phase of each back line is updated, the number of effective input modules of each back line is calculated in real time, and according to the number of available modules of each phase and the number of effective input modules of each back line, a corresponding number of modules are converted to hot standby state, so as to ensure that the number of modules that can effectively output voltage of each phase of each back line remains consistent, thereby ensuring that each phase outputs consistently, realizing coordinated and balanced control of each phase of each back line.

[0091] According to some embodiments of the present application, the coordinated control method of the distributed compensator of the present application can quickly and smoothly handle the module fault of the distributed compensator, ensure that each phase of each back line can be balanced after a certain phase has a module fault, and avoid causing unbalanced disturbance to the alternating current power grid.

[0092] The exemplary embodiments of the present application are specifically shown and described above. It should be understood that the present application is not limited to the detailed structure, arrangement or implementation method described herein; on the contrary, the present application is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims.

Claims

1. A method for coordinated control of distributed compensators, characterized in that, Comprise: The distributed compensator comprises three-phase converters connected in series to three-phase alternating current lines respectively, each phase of the converter is composed of a plurality of modules connected in series respectively, each module in the plurality of modules comprises a switch, a full-bridge sub-module, a capacitor and a resistor, the DC end of the full-bridge sub-module is connected in parallel with the capacitor and the resistor respectively, the AC end of the full-bridge sub-module is connected in parallel with the switch, and the plurality of modules are connected in series through the AC end of the full-bridge sub-module of each module; In the process of normal operation of the distributed compensator, the operating state of each module of each phase of the converter is detected in real time to obtain the number of available modules of each phase of the converter, wherein the number of available modules of each phase of the converter is the number of modules in each phase of the converter that have normal operating conditions and are free of faults; The number of modules of the distributed compensator that can effectively output voltage is calculated in real time, wherein the number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each phase of the converter; When any phase of the converter fails at any level, the failed module is blocked and bypassed, and the number of available modules of the faulty phase of the converter is reduced by one, while the number of available modules of the non-faulty phase of the converter remains unchanged; The number of available modules of each phase of the converter is compared with the number of modules of the distributed compensator that can effectively output voltage calculated in real time, and if the number of available modules of any phase of the converter is greater than the number of modules of the distributed compensator that can effectively output voltage, the modules in that phase of the converter that need to be converted to a hot standby state are converted to a hot standby state, Wherein, the number of modules in each phase of the converter that need to be converted to a hot standby state is equal to the number of available modules of each phase of the converter minus the number of modules of the distributed compensator that can effectively output voltage.

2. The method of claim 1, wherein, The three-phase converter is a voltage source converter.

3. The method of claim 1, wherein, The distributed compensator is a single-loop operation mode, and only a single-loop alternating current line is connected in series to the distributed compensator, and each loop of the alternating current line comprises three-phase alternating current lines.

4. The method of claim 3, wherein, The specific calculation method of the number of modules of the distributed compensator that can effectively output voltage is: The number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each phase of the converter in the single-loop alternating current line.

5. The method of claim 1, wherein, The distributed compensator is a multi-loop operation mode, and the parallel multi-loop alternating current lines are all connected in series to the distributed compensator, and each loop of the alternating current line comprises three-phase alternating current lines.

6. The method of claim 5, wherein, The specific calculation method of the number of modules of the distributed compensator that can effectively output voltage is: The number of modules of the distributed compensator that can effectively output voltage is equal to the minimum value of the number of available modules of each phase of the converter in each parallel multi-loop alternating current line after comparison and extraction.

7. The method of claim 1, wherein, The hot standby state is, The modules that need to be converted to a hot standby state are unlocked and operated and have voltage output capability, but the port output voltage is kept at 0.

8. A coordinated control system of distributed compensators, characterized in that, The coordination control system is used to execute the method of any one of claims 1-7, wherein the coordination control system comprises: A module state monitoring module is configured to detect, in real time, an operating state of each module in each converter in each phase of the distributed compensator, and the operating state includes module unlocking, module locking, and module failure; An effective module number calculation module is configured to calculate, in real time, a number of available modules of each converter in each phase according to the operating state of each module, and calculate, in real time, a number of modules that can effectively output voltage of the distributed compensator; A module hot standby state control module is configured to calculate, in real time, a number of modules in each converter in each phase that need to be converted into a hot standby state, and convert the modules in each converter in each phase that need to be converted into the hot standby state into the hot standby state.

9. The coordinated control system of claim 8, wherein, The coordinated control system further includes: A multi-loop line communication module is configured to take effect only when the distributed compensator is in a multi-loop line operation mode, and to collect a minimum value of the number of available modules of each converter in each phase in each parallel multi-loop AC line, wherein each AC line includes a three-phase AC line.

10. The coordinated control system of claim 8, wherein, The module hot standby state control module is configured to calculate, in real time, the number of modules in each converter in each phase that need to be converted into the hot standby state, and when the number of modules in the phase that need to be converted into the hot standby state is zero, no module in the phase is converted into the hot standby state.

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