Inverter, power station, control method and related device

Abstract

The invention discloses an inverter, a power station, a control method and a related device. The inverter comprises a power conversion circuit and a processor. The first end of the power conversion circuit is connected with a DC source, and the second end of the power conversion circuit is connected with an AC bus; the processor is used for generating a driving signal of the power conversion circuit according to the instruction current and the output current of the power conversion circuit, and starting the inverter; after the inverters are started, the phases of the inverters are controlled according to the number n of the started inverters in the power station and given load current, so that the n inverters are synchronized; the started inverters in the power station are connected with the alternating current bus; n is an integer greater than or equal to 1. According to the technical scheme of the invention, no quick communication device needs to be arranged between the inverters, the cost is saved, the circulating current between the black-start inverters can be reduced through synchronous control, black-start is carried out according to instruction current control, the output current of the inverters can be accurately controlled, and overcurrent of the output current of the inverters is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to an inverter, a power station, a control method and related devices. BACKGROUND

[0002] The power station of the current micro-grid system includes new energy and multiple inverters. The micro-grid system can effectively support the power grid, such as power fluctuation suppression, peak clipping and valley filling, power grid strength improvement, frequency or voltage fluctuation suppression, etc. Multiple inverters are connected to the AC bus through an isolation transformer, and the AC bus is connected to the power grid through a main transformer.

[0003] When a major accident occurs in the power grid, the power station is disconnected from the power grid, and the inverter of the power station needs to be restarted to establish an AC bus voltage for power supply to the load. This process is called black start.

[0004] After the power station enters the off-grid mode, how the inverter performs black start in the case of disconnection between the power station and the power grid is a key problem to be solved. SUMMARY

[0005] Therefore, the present application provides an inverter, a power station, a control method and related devices, which can control the inverter to perform black start and reduce the risk of overcurrent at a low cost.

[0006] The present application provides an inverter, comprising: a power conversion circuit and a processor;

[0007] A first end of the power conversion circuit is used to connect a DC source, and a second end of the power conversion circuit is used to connect an AC bus;

[0008] The processor is configured to generate a driving signal of the power conversion circuit according to an instruction current and an output current of the power conversion circuit to start the inverter; after the inverter is started, the processor is configured to control a phase of the inverter according to a number n of inverters that have been started in the power station and a given load current to synchronize the n inverters; the inverters that have been started in the power station are all connected to the AC bus; and n is an integer greater than or equal to 1.

[0009] In a possible implementation, the processor is configured to generate the driving signal of the power conversion circuit according to the instruction current and the output current of the power conversion circuit, specifically:

[0010] The voltage modulation signal is obtained according to the instruction current and the output current of the power conversion circuit, and the driving signal of the power conversion circuit is generated according to a given angle and the voltage modulation signal.

[0011] In a possible implementation, the processor is configured to, after the inverter is started, control the phase of the inverter according to the number n of inverter started in the power station and the given load current, so as to synchronize the n inverters, specifically:

[0012] After the inverter is started, the correction phase is obtained according to the instruction current, the number n of inverter started in the power station and the given load current, and the phase of the inverter is controlled according to the correction phase and the given angle, so as to synchronize the n inverters.

[0013] In a possible implementation, the processor is configured to, after the inverter is started, obtain a correction phase according to the instruction current, the number n of inverter started in the power station and the given load current, and control the phase of the inverter according to the correction phase and the given angle, so as to synchronize the n inverters, specifically:

[0014] After the inverter is started, the current average value is obtained according to the number n of inverter started in the power station and the given load current, the correction phase is obtained by proportional integral adjustment on the instruction current and the current average value, and the phase of the inverter is controlled according to the correction phase and the given angle, so as to synchronize the n inverters.

[0015] In a possible implementation, the processor is further configured to, when the output voltage of the inverter is greater than a voltage threshold, stop controlling the inverter according to the instruction current, and control the output voltage and the phase of the inverter by using a droop control mode.

[0016] In a possible implementation, before the processor controls the output voltage and the phase of the inverter by using the droop control mode, the processor further includes:

[0017] The output voltage of the inverter is assigned as a voltage reference value of a voltage loop of the inverter, the instruction current is assigned as an output of the voltage loop of the inverter, as a current reference value of a current loop of the inverter, and a reference angle obtained according to the correction phase and the given angle is assigned as an output phase of an active-power-frequency droop control loop in the droop control mode.

[0018] In a possible implementation, before the processor controls the output voltage and the phase of the inverter by using the droop control mode, the processor further includes:

[0019] A voltage amplitude output by a reactive-power-voltage droop control loop is assigned as a rated voltage, the reactive power of the inverter is assigned as a given reactive power of the reactive-power-voltage droop control loop in the droop control mode, and the active power of the inverter is assigned as a given active power of the active-power-frequency droop control loop.

[0020] The application also provides a power station, comprising: m inverters; an AC side of the m inverters being used for connecting an AC bus; a DC side of the m inverters being used for connecting corresponding DC sources;

[0021] For the i-th inverter of the black start, a driving signal of the i-th inverter is generated according to an instruction current and an output current of the i-th inverter, and the i-th inverter is started; after the i-th inverter is started, a phase of the i-th inverter is controlled according to a number n of inverters that have been started in the power station and a given load current, so that the n inverters are synchronized; the n is an integer greater than or equal to 1, and the m is an integer greater than or equal to n; the i-th inverter is any inverter of the black start.

[0022] In a possible implementation, the i-th inverter is configured to generate the driving signal of the i-th inverter according to the instruction current and the output current of the i-th inverter, and specifically:

[0023] A voltage modulation signal is obtained according to the instruction current and the output current of the i-th inverter, and the driving signal of the i-th inverter is generated according to a given angle and the voltage modulation signal.

[0024] In a possible implementation, the i-th inverter is configured to, after the i-th inverter is started, control the phase of the i-th inverter according to the number n of inverters that have been started in the power station and the given load current, so that the n inverters are synchronized, and specifically:

[0025] After the i-th inverter is started, a correction phase is obtained according to the instruction current, the number n of inverters that have been started in the power station and the given load current, and the phase of the i-th inverter is controlled according to the correction phase and the given angle, so that the n inverters are synchronized.

[0026] In a possible implementation, the i-th inverter is configured to obtain a correction phase according to the instruction current, the number n of inverters that have been started in the power station and the given load current, and control the phase of the inverter according to the correction phase and the given angle, so that the n inverters are synchronized, and specifically:

[0027] A current average value is obtained according to the number n of inverters that have been started in the power station and the given load current, a proportional-integral adjustment is performed on the instruction current and the current average value to obtain the correction phase, and the phase of the inverter is controlled according to the correction phase and the given angle, so that the n inverters are synchronized.

[0028] In a possible implementation, the i-th inverter is further configured to stop controlling the i-th inverter according to the instruction current and control the output voltage and phase of the i-th inverter by using a droop control mode when the output voltage of the i-th inverter is greater than a voltage threshold

[0029] In a possible implementation, before the i-th inverter controls the output voltage and phase of the i-th inverter by using the droop control mode, the i-th inverter further includes:

[0030] The output voltage of the i-th inverter is assigned to a voltage reference value of a voltage loop of the i-th inverter; the instruction current is assigned to an output of the voltage loop of the i-th inverter as a current reference value of a current loop of the i-th inverter; and a reference angle obtained according to the corrected phase and the given angle is assigned to an output phase of the droop control.

[0031] In a possible implementation, the power station further includes a host computer.

[0032] The host computer sends a black start instruction to the remaining m-n inverters, and the remaining m-n inverters perform synchronous starting by detecting the voltage of the AC bus.

[0033] In a possible implementation, the host computer is further configured to gradually increase a voltage control instruction and send the voltage control instruction to the m inverters, and the m inverters operate according to the voltage control instruction.

[0034] In a possible implementation, before the i-th inverter controls the output voltage and phase of the i-th inverter by using the droop control mode, the i-th inverter further includes:

[0035] A voltage amplitude output by a reactive power-voltage droop control loop is assigned to a rated voltage, a reactive power of the i-th inverter is assigned to a given reactive power of the reactive power-voltage droop control loop in the droop control mode, and an active power of the i-th inverter is assigned to a given active power of the active power-frequency droop control loop.

[0036] The application further provides a control method of an inverter, including:

[0037] The driving signal of the power conversion circuit is generated according to the instruction current and the output current of the power conversion circuit, and the inverter is started;

[0038] After the inverter is started, the phase of the inverter is controlled according to the number n of started inverters in the power station and a given load current, so that the n inverters are synchronized; the started inverters in the power station are all connected to an AC bus; and n is an integer greater than or equal to 1.

[0039] In a possible implementation, the driving signal of the power conversion circuit is generated according to the instruction current and an output current of the power conversion circuit, specifically as follows:

[0040] The voltage modulation signal is obtained according to the instruction current and the output current of the power conversion circuit, and the driving signal of the power conversion circuit is generated according to the given angle and the voltage modulation signal.

[0041] In a possible implementation, the phases of the inverters are controlled according to the number n of the inverters that have been started in the power station and the given load current, so that the n inverters are synchronized, specifically as follows:

[0042] The correction phase is obtained according to the instruction current, the number n of the inverters that have been started in the power station and the given load current, and the phases of the inverters are controlled according to the correction phase and the given angle, so that the n inverters are synchronized.

[0043] In a possible implementation, the correction phase is obtained according to the instruction current, the number n of the inverters that have been started in the power station and the given load current, and the phases of the inverters are controlled according to the correction phase and the given angle, so that the n inverters are synchronized, specifically as follows:

[0044] The current average value is obtained according to the number n of the inverters that have been started in the power station and the given load current, and the correction phase is obtained by proportional-integral adjustment on the instruction current and the current average value, and the phases of the inverters are controlled according to the correction phase and the given angle, so that the n inverters are synchronized.

[0045] In a possible implementation, the method further includes: when the output voltage of the inverter is greater than a voltage threshold, stopping the control of the inverter according to the instruction current, and controlling the output voltage and the phase of the inverter by using a droop control mode.

[0046] In a possible implementation, before the output voltage and the phase of the inverter are controlled by using the droop control mode, the method further includes:

[0047] The output voltage of the inverter is assigned to a voltage reference value of a voltage loop of the inverter, the instruction current is assigned to an output of the voltage loop of the inverter as a current reference value of a current loop of the inverter, and a reference angle obtained according to the correction phase and the given angle is assigned to an output phase of an active-frequency droop control loop in the droop control mode.

[0048] The application also provides a control device, including a processor and a memory, the memory is used for storing programs, instructions or codes, and the processor is used for executing the programs, instructions or codes in the memory to complete the control method as described above.

[0049] The application also provides a computer readable storage medium, characterized by storing a computer program, which is loaded by a processor to execute the control method as described above.

[0050] The inverter provided by the embodiments of the application can be black started according to the instruction current, when multiple inverters of a power station are started, the multiple inverters can perform phase synchronization control according to the number of started inverters and the given load current, so as to realize phase synchronization of the multiple inverters. The fast communication device does not need to be set between the inverters, cost is saved, and the synchronous control can reduce the circulating current between the black started inverters, and the black starting according to the instruction current control can accurately control the output current of the inverter, so that overcurrent of the output current of the inverter is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 A schematic diagram of a power station provided by the embodiments of the application

[0052] Figure 2 A schematic diagram of an inverter provided by the embodiments of the application

[0053] Figure 3 A control principle diagram of black starting of an inverter instruction current provided by the embodiments of the application

[0054] Figure 4 A control principle diagram of synchronization of an inverter provided by the embodiments of the application

[0055] Figure 5 A P-ω droop control block diagram of active frequency provided by the embodiments of the application

[0056] Figure 6 A Q-U droop control block diagram of reactive voltage provided by the embodiments of the application

[0057] Figure 7 A principle diagram of voltage-current double closed loop control provided by the embodiments of the application

[0058] Figure 8 A complete control principle diagram of an inverter provided by the embodiments of the application

[0059] Figure 9 A flowchart of a control method of an inverter provided by the embodiments of the application

[0060] Figure 10 A schematic diagram of a control device provided by the embodiments of the application DETAILED DESCRIPTION

[0061] In order for those skilled in the art to better understand and implement the technical solutions provided by the embodiments of the present application, the application scenarios of black start are first introduced in combination with a hardware architecture diagram.

[0062] Referring to Figure 1 , the figure is a schematic diagram of a power station provided by the embodiments of the present application.

[0063] The power station provided by the embodiments of the present application includes multiple energy storage systems, such as Figure 1 As shown in the figure, the energy storage systems include multiple, respectively, the first energy storage system BESS1, the second energy storage system BESS2, and the Nth energy storage system BESSN. One of the energy storage systems can include multiple inverters. The inverters in each energy storage system can be connected to a corresponding DC source, for example, the DC source can be at least one of a photovoltaic panel or an energy storage battery.

[0064] Each energy storage system is connected to an AC bus MVBUS through a corresponding isolation transformer, such as Figure 1 As shown in the figure, the first energy storage system BESS1 is connected to the AC bus MVBUS through the first isolation transformer T1, the second energy storage system BESS2 is connected to the AC bus MVBUS through the second isolation transformer T2, and the Nth energy storage system BESSN is connected to the AC bus MVBUS through the Nth isolation transformer TN.

[0065] The AC bus MVBUS is connected to the power grid through a series circuit of a circuit breaker MCB and a main transformer MT. The AC bus MVBUS is connected to a load.

[0066] The power station further includes a local controller, which can control the inverters in the energy storage systems to perform black start. In addition, the power station can further include an upper computer, which can send instructions to the local controller.

[0067] Black start refers to the disconnection of the AC bus MVBUS from the power grid, that is, the AC side of each inverter has no power support from the power grid, and each inverter needs to be started and supply power to the load.

[0068] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application will be further described in detail in combination with the drawings and specific embodiments.

[0069] Referring to Figure 2 , the figure is a schematic diagram of an inverter provided by the embodiments of the present application.

[0070] The inverter provided by the embodiments of the present application includes a power conversion circuit 10 and a processor 20. The inverter provided by the embodiments of the present application is only taken as an example of any inverter in the power station shown in the figure. Figure 1

[0071] ​The first end of the power conversion circuit 10 is used for connecting a DC source, and the second end of the power conversion circuit 10 is used for connecting an AC bus. As shown in Figure 1 the second end of the power conversion circuit 10 can be connected to the AC bus through a corresponding isolation transformer.

[0072] The embodiment of the present application does not specifically limit the type of the DC source, which can be at least one of photovoltaic or energy storage battery.

[0073] The processor 20 is used for generating a driving signal of the power conversion circuit 10 according to an instruction current and an output current of the power conversion circuit 10, and starting the inverter; after the inverter is started, the phase of the inverter is controlled according to the number n of the inverters that have been started in the power station and the given load current, so that the n inverters are synchronized; and the inverters that have been started in the power station are all connected to the AC bus.

[0074] The inverter provided by the embodiment of the present application is not controlled according to the voltage loop and the current loop to start the inverter during the black start, but is controlled according to the current loop to start the inverter, that is, the processor controls the output current of the inverter according to the instruction current. The processor obtains the actual output current of the power conversion circuit, compares the output current with the instruction current, and generates the driving signal of the power conversion circuit according to the comparison result, that is, sends a wave to the power conversion circuit, controls the action of the switch tube in the power conversion circuit, and makes the output current of the inverter consistent with the instruction current. The fast communication device does not need to be set between the inverters, the cost is saved, and the output current of the inverter can be accurately controlled during the black start according to the instruction current, so that the overcurrent of the inverter is avoided.

[0075] It should be understood that, in the conventional technology, the inverter is controlled according to the output voltage to start the inverter, when the number of the inverters in the power station is large, for example, hundreds of inverters, a single inverter is started according to a very small output voltage, but because the number of the inverters is large, the output current has reached the full current, at this time, the inverter is boosted to the rated voltage of the load, which will cause the overcurrent of the inverter and result in the failure of the black start. Moreover, the inverters that are started subsequently in the power station need to track the output voltage of the inverters that have been started to be synchronized, because the number of the inverters in the power station is large, if the overcurrent of the inverter is avoided, the output voltage of the inverter that is started first needs to be very small, which is not conducive to the voltage tracking of the inverters that are started subsequently to complete the synchronization. The present application does not use the voltage control to start the inverter, but uses the constant current closed loop to start the inverter, so that the overcurrent problem is avoided.

[0076] Since the power station includes multiple inverters, it's possible to control all inverters to start according to the commanded current, and the commanded currents corresponding to the black start of multiple inverters are equal. However, because there is no communication between the multiple inverters, they may start randomly. Therefore, the phases of the multiple inverters that start may differ. Taking starting two inverters first as an example, for instance, with a commanded current of I... npk Control two inverters to start with command current; the output current of both inverters after startup is I. npk If the output currents of the two inverters are in phase, i.e., the phase difference is 0, then the current superimposed on the load is 2*I. npk If the output currents of the two inverters are out of phase, i.e., the phase difference is 180 degrees, the current superimposed on the load will exactly cancel each other out, meaning the load current will be 0. For other phase differences between the two inverters, the load current will be between 0 and 2*I. npk between.

[0077] At this point, it is necessary to synchronize multiple inverters. Synchronization means that the phases of the inverters must be consistent.

[0078] Since multiple inverters are connected to loads, the processor can control the phase of the inverters using a given load current. For example, the given load current is expressed as I... load_pk The number of inverters already running in the power station is denoted by n, where n is an integer greater than or equal to 1. To ensure that the running inverters provide energy to the load evenly, the given load current can be evenly distributed; that is, the phase of each inverter can be determined according to I. load_pk / n adjustment.

[0079] The following is a detailed explanation with reference to the control principle diagram.

[0080] See Figure 3 The figure is a control principle diagram of black start of inverter command current provided in an embodiment of this application.

[0081] The inverter performs a black start using commanded current. It should be understood that after the black start is complete, the inverter typically employs dual-loop control during normal operation, consisting of a voltage loop and a current loop. However, this application uses a single-loop current control for black start. Inverter control generally uses parameters in the d,q coordinate system, including the direct-axis current I. dref and quadrature axis current I qref In this embodiment, command current control is used. The quadrature-axis current can be set as the command current, and the direct-axis current can be set to 0; conversely, the direct-axis current can also be set as the command current, and the quadrature-axis current can be set to 0. This embodiment is not specifically limited; the following description only uses setting the direct-axis current as the command current and the quadrature-axis current to 0 as an example.

[0082] In this embodiment of the application, (I) is setdref ,I qref ) = (I npk ,0) is the current loop control command, where I npk This can be the rated peak current of the inverter, and the inverter control angle is a given angle θ. ref_-St The control block diagram is as follows Figure 3 As shown, the inverter's output current is I at this time. npk This is independent of the load. Specifically, the given frequency of the inverter is ω. o Given frequency ω o Generally, it is the rated frequency. The given frequency ω o The given angle θ of the inverter is generated by integration. ref_St .

[0083] The processor is used to generate a drive signal for the power conversion circuit based on the instruction current and the output current of the power conversion circuit. Specifically, it obtains a voltage modulation signal based on the instruction current and the output current of the power conversion circuit, and generates a drive signal for the power conversion circuit based on a given angle and the voltage modulation signal.

[0084] like Figure 3 As shown, the actual output current i of the inverter a,b,c The direct-axis current component I in the d,q coordinate system is obtained through the Park transformation. d and cross-axis current component I q Where, the park transformation angle is a given angle θ ref_St Current loop control command (I) dref ,I qref ) = (I npk ,0) and the actual output current of the inverter in the d,q coordinate system I d ,I q They enter the current loop together, and the current loop generates a voltage modulation signal U in the d, q coordinate system. md U mq Voltage modulation signal U md U mq The voltage modulation signal U in the abc coordinate system is generated by inverse Park transform. my (y = a, b, c). The processor generates drive signals based on the voltage modulation signal to control the operation of the switching transistors in the power conversion circuit.

[0085] Figure 3 The diagram shows the command current start-up control for a single inverter. When the inverter output current reaches the command current, the start-up is successful. However, when starting multiple inverters in a power plant, it is also necessary to control the synchronization between them; otherwise, the required current and voltage may not be provided to the load. The following section will combine... Figure 4This section describes the synchronization between multiple inverters. The processor controls the phase of the inverters based on the number n inverters already running in the power station and the given load current, thus synchronizing the n inverters. All inverters already running in the power station are connected to the AC bus.

[0086] See Figure 4 The figure is a control principle diagram of inverter synchronization provided in an embodiment of this application.

[0087] The processor is used to control the phase of the inverters after the inverters are started, based on the number n of inverters already started in the power station and the given load current, so as to synchronize the n inverters. Specifically, after the inverters are started, the processor obtains the corrected phase based on the command current, the number n of inverters already started in the power station and the given load current, and controls the phase of the inverters based on the corrected phase and the given angle, so as to synchronize the n inverters.

[0088] Figure 4 This illustrates the principle of synchronous control of each inverter. For example, the power station may include a local controller, which can also interact with a host computer. The local controller can communicate with the processors of each inverter. For instance, the host computer knows the given load current I. load_pk And the number of inverters already started, n. The host computer will provide the load current I. load_pk The number of inverters already started, n, is sent from the local controller to each started inverter. Each inverter's processor obtains the average current I based on the number of started inverters, n, and the given load current. load_pk / n, the processors of each inverter will I load_pk / n and I npk The difference is compared and then adjusted using a proportional-integral (PI) converter to obtain the correction phase Δθ. The correction phase Δθ is used to correct a given angle θ. ref_St The corrected angle θ is obtained. ref θ ref As the instruction phase, the processor uses the voltage modulation signal U in the d,q coordinate system. md U mq and θ ref Together, input the inverse Park transform. When I load_pk / n and I npk When they are equal, all the inverters that have been started will be synchronized.

[0089] The inverter provided by the embodiment of the present application can be black started according to the instruction current, when multiple inverter of the power station are started, the multiple inverters can be controlled in phase synchronization according to the number of started inverters and the given load current, to realize the synchronous starting of the multiple black started inverters. The fast communication device does not need to be set between the inverters, the cost is saved, and the synchronous control can reduce the circulating current between the inverters. The black starting according to the instruction current control can accurately control the output current of the inverter, to avoid the overcurrent of the output current of the inverter.

[0090] It should be understood that the control of each inverter in the power station is ultimately through voltage control, therefore, the above-mentioned instruction current starting purpose is to make a part of the inverters first black start to provide the required current for the load, when the current demand of the load is met, the instruction current control can be stopped, and the droop control can be started. For example, the power station includes 100 inverters, 20 inverters are started by the instruction current, when the 20 inverters are started synchronously, the remaining 80 inverters can be started through automatic following.

[0091] The inverter provided by the embodiment of the present application, the condition for the processor to end the instruction current control is that when the output voltage of the inverter is greater than the voltage threshold, the inverter is controlled according to the instruction current is stopped, and the output voltage and phase of the inverter are controlled by the droop control mode. The embodiment of the present application does not specifically limit the value of the voltage threshold, for example, it can be set to 20% of the rated voltage of the load. It should be understood that it can also be set to other proportions of the rated voltage of the load.

[0092] The host computer can obtain the voltage of the load, because the output ends of the started inverters are connected in parallel to connect the load together, therefore, the voltage of the load can be equivalent to the output voltage of the inverter, when the output voltage of the inverter is greater than the voltage threshold, it indicates that the voltage of the load is also greater than the voltage threshold, at this time, the instruction current control can be ended, and the droop control is converted.

[0093] The droop control includes active frequency P-ω droop control and reactive voltage Q-U droop control.

[0094] Referring to Figure 5 , the figure is the active frequency P-ω droop control block diagram provided by the embodiment of the present application.

[0095] Referring to Figure 6 , the figure is the reactive voltage Q-U droop control block diagram provided by the embodiment of the present application.

[0096] P set ,Q set are the given active power and the given reactive power respectively; P e ,Q erespectively, are the actual measured active power and reactive power; k p , q respectively, are the active-frequency droop coefficient and reactive-voltage droop coefficient; ω i , n respectively, are the rated frequency and rated voltage; the active-frequency P-ω droop control generates an angle θ ref , the reactive-voltage Q-U droop control generates a voltage amplitude E m , ω is the actual output frequency of the inverter. The voltage amplitude E m and the angle θ ref can be directly modulated to generate the output voltage of the inverter, or can be generated through voltage closed-loop control of the inverter, or through voltage and current double closed-loop control of the inverter.

[0097] In the embodiments of the present application, the voltage and current double closed-loop control of the inverter is taken as an example for introduction.

[0098] Referring to Figure 7 , the figure is a schematic diagram of the voltage and current double closed-loop control provided by the embodiments of the present application.

[0099] The active power and the frequency have an inverse correlation, for example, when the active power consumption in the power system increases, the frequency of the power system will decrease, and the active-frequency droop control is to simulate the above process. From Figure 5 , it can be seen that when P e increases, k p (P set -P e ) decreases, and the frequency ω will decrease. At this time, if P set can be appropriately increased, the frequency ω can be improved.

[0100] Similarly, the reactive power and the voltage have an inverse correlation, for example, when the demand for reactive power in the power system increases, the voltage will decrease, and the reactive-voltage droop control is to simulate the above process. From Figure 6 , it can be seen that when Q e increases, k q (Q set -Q e ) decreases, and the voltage amplitude E m will decrease. At this time, if Q set can be appropriately increased, the voltage amplitude E m can be improved.

[0101] The voltage amplitude E m and the angle θ ref need to be generated by the inverter, and are realized through real-time voltage and current double closed-loop control of the inverter.

[0102] Figure 7 In the formula, U dref , Uqref These are the voltage loop commands in the inverter's d and q coordinate systems, respectively. The voltage amplitude Em,0 in the d and q coordinate systems is subtracted from the virtual impedance voltage drop (derived from the current feedback component I in the d and q coordinate systems). d ,I q The voltage loop control command U is obtained by multiplying by the virtual impedance. dref U qref U dref U qref The output voltage d, q-axis component U of the inverter d U q The voltage control loop is input together, and the voltage control loop generates the current loop control command I in the d,q coordinate system. dref ,I qref Current loop control command I dref ,I qref The inverter output current d, q-axis component I d ,I q The input current loop generates a voltage modulation signal U in the d, q coordinate system. md U mq The voltage modulation signal U in the abc coordinate system is generated by inverse Park transform. my (y = a, b, c).

[0103] It should be understood that, as described in the above embodiments, droop control is performed after the inverter command current is completed, which allows for the implementation of droop control according to... Figure 5-7 Perform as shown. Figure 5 and Figure 6 Output E m and θ ref Need to be entered Figure 7 The voltage and current dual closed-loop control is shown. The output signal of the voltage control loop serves as the reference signal for the current loop. Since voltage and current dual closed-loop control is a relatively mature technology, it will not be elaborated further here.

[0104] To achieve a smooth transition from command current control to droop control, the inverter provided in this application embodiment is further configured to assign the result of command current control to the parameters of droop control before performing droop control. This will be further elaborated below. Figure 5 and Figure 6 Let me introduce it.

[0105] The inverter provided in this application embodiment includes, prior to the controller using droop control mode to control the inverter's output voltage and phase, the following:

[0106] Assign the inverter's output voltage to the voltage reference value of the inverter's voltage loop; that is, the measured (U) d U q Assign a value to the voltage loop instruction (U) drefU qref ); will command current (I) npk The 0) value is assigned to the output of the inverter's voltage loop as the current reference value for the inverter's current loop; the reference angle obtained based on the corrected phase and the given angle is assigned to the output phase of the active-frequency droop control loop in the droop control mode. That is... Figure 4 The obtained θ ref Assign to Figure 5 θ ref .

[0107] In addition, the controller, before using droop control mode to control the inverter's output voltage and phase, also includes:

[0108] The voltage amplitude E output by the reactive power-voltage droop control loop m Assign a value to the rated voltage U n The reactive power Q of the inverter e (The actual reactive power output can be measured) is assigned to the given reactive power Q of the reactive-voltage droop control loop in the droop control mode. set The active power P of the inverter e The given active power P is assigned to the active-frequency droop control loop. set .

[0109] In addition, for smoother control, the processor can also... Assigned to virtual resistor r v , where x v For the given virtual reactance.

[0110] In addition, for smoother control, it can also be... Assign the value to Em.

[0111] For easier understanding, the inverter's smooth transition process and complete control principle can be found in [link to documentation]. Figure 8 Soon Figure 5 , Figure 6 and Figure 7 The integrated diagram is shown below. For details on the working principle, please refer to the diagrams below. Figure 5 , Figure 6 and Figure 7 The description will not be repeated here.

[0112] Once the above parameters are assigned values, the processor can stop the instruction current mode and start droop control. Because the parameters do not change abruptly, the instruction current control can smoothly switch to droop control, with little or no impact on the load or other already started inverters.

[0113] It should be understood that for each inverter which has been started and synchronized according to the instruction current, the transition to droop control can be completed according to the above assignment.

[0114] The remaining inverters of the power station can be started according to a conventional black start mode, for example, automatically detecting the voltage of the medium voltage bus, i.e., the load voltage, controlling the output voltage of the inverter according to the load voltage to complete black start in terms of amplitude and phase synchronization, and the remaining inverters do not have to be started according to the instruction current, so that the black start process of the entire power station can be accelerated.

[0115] It should be understood that after all the inverters are started, the host computer is further used to gradually increase the voltage control instruction, and the voltage control instruction is sent to the m inverters, and the m inverters operate according to the voltage control instruction.

[0116] It should be understood that after all the inverters of the power station are finally started, the output voltages of all the inverters can be output according to the required voltage of the load.

[0117] Based on the inverter provided in the above embodiment, the embodiment of the present application further provides a power station, which will be specifically introduced below.

[0118] It can be continued to refer to Figure 1 The power station provided in the embodiment of the present application comprises m inverters, the AC side of the m inverters is used to connect an AC bus, the DC side of the m inverters is used to connect a corresponding DC source, n is an integer greater than or equal to 1, and m is an integer greater than or equal to n.

[0119] For the i-th inverter of the black start, the i-th inverter is any inverter of the black start, a driving signal of the i-th inverter is generated according to the instruction current and the output current, and the i-th inverter is started; after the i-th inverter is started, the number n of the inverters which have been started in the power station and the given load current are used to control the phase of the i-th inverter, so that the n inverters are synchronized.

[0120] The i-th inverter of the embodiment of the present application can be the first inverter of the black start, or can be an inverter of subsequent black start, which is not limited in the embodiment of the present application.

[0121] For the i-th inverter instruction current black start and synchronization with other inverters which have been started, the specific introduction can be referred to the above embodiment of the inverter, which will not be described here.

[0122] The power station provided by the embodiment of the present application is not controlled by the voltage loop and the current loop to start the inverter during the black start, but is controlled by the current loop to start the inverter according to the specified current. The i-th inverter obtains the actual output current of the power conversion circuit, compares the output current with the instruction current, generates the driving signal of the power conversion circuit according to the comparison result, that is, sends the wave to the power conversion circuit, controls the switch tube in the power conversion circuit to act, and the output current of the i-th inverter is consistent with the instruction current. The fast communication device does not need to be set between the inverters, the cost is saved, and the output current of the inverter is controlled according to the instruction current to start the black start, so that the output current of the inverter can be accurately controlled and the overcurrent of the inverter can be avoided.

[0123] It should be understood that in the conventional technology, the power station controls each inverter to start the black start according to the output voltage of the inverter, when the number of inverters of the power station is large, for example, hundreds of inverters, a single inverter starts according to a very small output voltage, but because the number of inverters is large, the output current has reached the full current, at this time, if the inverter increases the voltage to reach the rated voltage of the load, the overcurrent of the inverter will occur, which causes the failure of the black start. Moreover, the inverters started subsequently need to track the output voltage of the inverter already started to synchronize, because the number of inverters of the power station is large, if the overcurrent of the inverter is to be avoided, the output voltage of the inverter started first needs to be very small, which is not conducive to the voltage tracking of the inverter started subsequently to complete the synchronization. The present application does not use the voltage control to start the black start of the inverter, but uses the constant current closed-loop control to start the black start of the inverter, so that the overcurrent problem does not occur.

[0124] In a possible implementation, the i-th inverter is configured to generate a driving signal of the i-th inverter according to an instruction current and an output current of the i-th inverter, specifically, to obtain a voltage modulation signal according to the instruction current and the output current of the i-th inverter, and to generate the driving signal of the i-th inverter according to a given angle and the voltage modulation signal.

[0125] In a possible implementation, the i-th inverter is configured to control a phase of the i-th inverter according to a number n of inverters already started in the power station and a given load current after the i-th inverter is started, so that the n inverters are synchronized, specifically, to obtain a correction phase according to the instruction current, the number n of inverters already started in the power station and the given load current after the i-th inverter is started, and to control the phase of the i-th inverter according to the correction phase and the given angle, so that the n inverters are synchronized.

[0126] In a possible implementation, the i-th inverter is configured to obtain a correction phase according to an instruction current, a number n of inverters already started in the power station and a given load current, and to control a phase of the i-th inverter according to the correction phase and a given angle, so that the n inverters are synchronized, specifically, to obtain the correction phase according to the instruction current, the number n of inverters already started in the power station and the given load current, and to control the phase of the i-th inverter according to the correction phase and the given angle, so that the n inverters are synchronized.

[0127] According to the number n of the started inverters in the power station and the given load current, the current average value is obtained, the proportional integral adjustment of the instruction current and the current average value is performed to obtain the correction phase, and the phase of the inverter is controlled according to the correction phase and the given angle, so that the n inverters are synchronized.

[0128] In a possible implementation, the i-th inverter is further configured to, when the output voltage of the i-th inverter is greater than the voltage threshold, stop controlling the i-th inverter according to the instruction current, and control the output voltage and the phase of the i-th inverter by using the droop control mode.

[0129] In a possible implementation, before the i-th inverter controls the output voltage and the phase of the i-th inverter by using the droop control mode, the i-th inverter further includes:

[0130] The output voltage of the i-th inverter is assigned to the voltage reference value of the voltage loop of the i-th inverter; the instruction current is assigned to the output of the voltage loop of the i-th inverter as the current reference value of the current loop of the i-th inverter; and the reference angle obtained according to the correction phase and the given angle is assigned to the output phase of the droop control.

[0131] The specific control of the power station can be referred to the specific introduction of the inverter embodiment.

[0132] The power station provided in the embodiment of the present application further includes a host computer; the host computer sends a black start instruction to the remaining m-n inverters, and the remaining m-n inverters detect the voltage of the AC bus to start synchronously.

[0133] In a possible implementation, the host computer is further configured to gradually increase the voltage control instruction, and send the voltage control instruction to the m inverters, so that the m inverters operate according to the voltage control instruction.

[0134] In a possible implementation, before the i-th inverter controls the output voltage and the phase of the i-th inverter by using the droop control mode, the i-th inverter further includes: assigning the voltage amplitude output by the reactive power-voltage droop control loop to the rated voltage, and assigning the reactive power of the i-th inverter to the given reactive power of the reactive power-voltage droop control loop in the droop control mode; and assigning the active power of the i-th inverter to the given active power of the active power-frequency droop control loop.

[0135] Based on the inverter and the power station provided in the above embodiment, the embodiment of the present application further provides a control method of the inverter, which will be specifically introduced below in combination with the drawings.

[0136] Referring to Figure 9 FIG. 1 is a flowchart of a control method of an inverter provided in the embodiment of the present application.

[0137] The control method of the inverter provided by the embodiment of the application comprises the following steps:

[0138] S801: generating a driving signal of a power conversion circuit according to an instruction current and an output current of the power conversion circuit, and starting the inverter;

[0139] S802: after the inverter is started, controlling the phase of the inverter according to the number n of the inverter that has been started in a power station and a given load current, so that n inverter units are synchronized; the inverter that has been started in the power station is connected to an AC bus; n is an integer greater than or equal to 1.

[0140] In a possible implementation, the driving signal of the power conversion circuit is generated according to the instruction current and the output current of the power conversion circuit, specifically: a voltage modulation signal is obtained according to the instruction current and the output current of the power conversion circuit, and the driving signal of the power conversion circuit is generated according to a given angle and the voltage modulation signal.

[0141] In a possible implementation, the phase of the inverter is controlled according to the number n of the inverter that has been started in the power station and the given load current, so that n inverter units are synchronized, specifically: a corrected phase is obtained according to the instruction current, the number n of the inverter that has been started in the power station and the given load current, and the phase of the inverter is controlled according to the corrected phase and the given angle, so that n inverter units are synchronized.

[0142] In a possible implementation, the corrected phase is obtained according to the instruction current, the number n of the inverter that has been started in the power station and the given load current, and the phase of the inverter is controlled according to the corrected phase and the given angle, so that n inverter units are synchronized, specifically: a current average value is obtained according to the number n of the inverter that has been started in the power station and the given load current, proportional-integral adjustment is performed on the instruction current and the current average value to obtain the corrected phase, and the phase of the inverter is controlled according to the corrected phase and the given angle, so that n inverter units are synchronized.

[0143] In a possible implementation, the method further comprises: when the output voltage of the inverter is greater than a voltage threshold, stopping the control of the inverter according to the instruction current, and controlling the output voltage and the phase of the inverter by using a droop control mode.

[0144] In a possible implementation, before the output voltage and phase of the inverter are controlled by using the droop control mode, the method further includes: assigning the output voltage of the inverter to a voltage reference value of a voltage loop of the inverter; assigning the instruction current to an output of the voltage loop of the inverter as a current reference value of a current loop of the inverter; and assigning a reference angle obtained according to the correction phase and the given angle to an output phase of an active-frequency droop control loop in the droop control mode.

[0145] In a possible implementation, refer to Figure 10 FIG. 1 is a schematic diagram of a control device provided by an embodiment of the present application.

[0146] The control device can include a memory 1011 and a processor 1012. The processor 1012 can be connected with the power converter and can drive the switches in each power conversion circuit in the power converter. As shown in the figure, Figure 10 The memory can be a random access memory (RAM), a flash memory, a read only memory (ROM), an EPROM memory, an Electronic Programmable ROM (EPROM), a register, a hard disk, a removable disk, or the like.

[0147] The memory 1011 can store computer instructions, and when the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be configured to perform the control method of the inverter. The memory 1011 can also store data, for example, the instruction current, the given load current, and the like information involved in the above embodiments.

[0148] In the embodiments described above, all or some of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or some of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded into and executed by a computer, all or some of the processes or functions according to the embodiments of the present application are generated. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatuses. The computer instructions can be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transmitted from one website site, computer, server or data center to another website site, computer, server or data center through a wired (for example, coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (for example, infrared, wireless, microwave, etc.) manner. The computer readable storage medium can be any available medium accessible by a computer or a data storage device such as a server, data center, etc. including one or more available media sets. The available media can be a magnetic medium (for example, floppy disk, hard disk, magnetic tape), or a semiconductor medium (for example, solid state disk (SSD)), etc.

[0149] The embodiments of the present application also provide a readable storage medium for storing the method provided by the above-mentioned embodiments. For example, random access memory (RAM), flash memory, read only memory (ROM), EPROM memory, non-volatile read only memory (Electronic Programmable ROM, EPROM), register, hard disk, removable disk or any other form of storage medium in the art.

[0150] It should be noted that the embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the method disclosed by the embodiments, since it corresponds to the product embodiments disclosed by the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the product embodiments.

[0151] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inverter, characterized in that, include: Power conversion circuits and processors; The first terminal of the power conversion circuit is used to connect to a DC source, and the second terminal of the power conversion circuit is used to connect to an AC bus. The processor is configured to generate a drive signal for the power conversion circuit based on the instruction current and the output current of the power conversion circuit, thereby starting the inverter. After the inverter is started, the phase of the inverter is controlled according to the number n of inverters already started in the power station and the given load current, so that the n inverters are synchronized; all the inverters already started in the power station are connected to the AC bus; n is an integer greater than or equal to 1.

2. The inverter according to claim 1, characterized in that, The processor is configured to generate a drive signal for the power conversion circuit based on the instruction current and the output current of the power conversion circuit, specifically: A voltage modulation signal is obtained based on the command current and the output current of the power conversion circuit, and a drive signal for the power conversion circuit is generated based on a given angle and the voltage modulation signal.

3. The inverter according to claim 2, characterized in that, The processor is configured to, after the inverter starts up, control the phase of the inverter based on the number n of inverters already started in the power station and a given load current, so as to synchronize the n inverters, specifically: After the inverter is started, a correction phase is obtained based on the command current, the number n of inverters already started in the power station, and the given load current. The phase of the inverter is controlled based on the correction phase and the given angle to synchronize the n inverters.

4. The inverter according to claim 3, characterized in that, The processor is configured to, after the inverter starts, obtain a corrected phase based on the command current, the number n of inverters already started in the power station, and a given load current; and control the phase of the inverter based on the corrected phase and a given angle to synchronize the n inverters, specifically: After the inverter is started, the average current is obtained based on the number n of inverters already started in the power station and the given load current. The corrected phase is obtained by proportional-integral adjustment of the command current and the average current. The phase of the inverter is controlled according to the corrected phase and the given angle to synchronize the n inverters.

5. The inverter according to claim 3, characterized in that, The processor is further configured to stop controlling the inverter according to the command current when the output voltage of the inverter is greater than the voltage threshold, and to control the output voltage and phase of the inverter using a droop control mode.

6. The inverter according to claim 5, characterized in that, The processor, prior to controlling the output voltage and phase of the inverter using a droop control mode, further includes: The output voltage of the inverter is assigned to the voltage reference value of the inverter's voltage loop; the command current is assigned to the output of the inverter's voltage loop as the current reference value of the inverter's current loop; and the reference angle obtained according to the corrected phase and the given angle is assigned to the output phase of the active-frequency droop control loop in the droop control mode.

7. The inverter according to claim 6, characterized in that, The processor, prior to controlling the output voltage and phase of the inverter using a droop control mode, further includes: The voltage amplitude output by the reactive power-voltage droop control loop is assigned to the rated voltage, and the reactive power of the inverter is assigned to the given reactive power of the reactive power-voltage droop control loop in the droop control mode; the active power of the inverter is assigned to the given active power of the active power-frequency droop control loop.

8. A power station, characterized in that, include: m inverters; The AC side of each of the m inverters is used to connect to the AC bus. The DC side of each of the m inverters is used to connect to the corresponding DC source. For the i-th inverter that starts from black, a drive signal for the i-th inverter is generated based on the command current and the output current to start the i-th inverter; After the i-th inverter is started, the phase of the i-th inverter is controlled according to the number n of inverters already started in the power station and the given load current, so that the n inverters are synchronized; where n is an integer greater than or equal to 1 and m is an integer greater than or equal to n; the i-th inverter is any inverter that has been black-started.

9. The power plant according to claim 8, characterized in that, The i-th inverter is used to generate a drive signal for the i-th inverter based on the command current and the output current of the i-th inverter, specifically as follows: A voltage modulation signal is obtained based on the command current and the output current of the i-th inverter, and a drive signal for the i-th inverter is generated based on a given angle and the voltage modulation signal.

10. The power plant according to claim 9, characterized in that, The i-th inverter, after its startup, is used to control its phase according to the number n of inverters already started in the power station and a given load current, so as to synchronize the n inverters. Specifically: After the i-th inverter is started, a correction phase is obtained based on the command current, the number n of inverters already started in the power station, and the given load current. The phase of the i-th inverter is controlled based on the correction phase and the given angle to synchronize the n inverters.

11. The power plant according to claim 10, characterized in that, The i-th inverter is configured to obtain a corrected phase based on the command current, the number n of inverters already started in the power station, and the given load current, and control the phase of the inverter based on the corrected phase and the given angle to synchronize the n inverters, specifically: The average current is obtained based on the number n of inverters already started in the power station and the given load current. The corrected phase is obtained by proportional-integral adjustment of the command current and the average current. The phase of the inverter is controlled according to the corrected phase and the given angle to synchronize the n inverters.

12. The power plant according to claim 8, characterized in that, The i-th inverter is further configured to stop controlling the i-th inverter according to the command current when the output voltage of the i-th inverter is greater than the voltage threshold, and to control the output voltage and phase of the i-th inverter using a droop control mode.

13. The power plant according to claim 10, characterized in that, The i-th inverter, before controlling its output voltage and phase using a droop control mode, further includes: The output voltage of the i-th inverter is assigned to the voltage reference value of the voltage loop of the i-th inverter; the command current is assigned to the output of the voltage loop of the i-th inverter as the current reference value of the current loop of the i-th inverter; and the reference angle obtained according to the correction phase and the given angle is assigned to the output phase of the droop control.

14. The power plant according to claim 12 or 13, characterized in that, The power station also includes: a host computer; The host computer sends a black start command to the remaining mn inverters, and the remaining mn inverters detect the voltage of the AC bus to start synchronously.

15. The power plant according to claim 14, characterized in that, The host computer is also used to gradually increase the voltage control command and send the voltage control command to the m inverters, and the m inverters operate according to the voltage control command.

16. The power plant according to claim 13, characterized in that, The i-th inverter, before controlling its output voltage and phase using a droop control mode, further includes: The voltage amplitude output by the reactive power-voltage droop control loop is assigned to the rated voltage, and the reactive power of the i-th inverter is assigned to the given reactive power of the reactive power-voltage droop control loop in the droop control mode; the active power of the i-th inverter is assigned to the given active power of the active power-frequency droop control loop.

17. A control method for an inverter, characterized in that, include: The inverter is started by generating a drive signal for the power conversion circuit based on the command current and the output current of the power conversion circuit. After the inverter is started, the phase of the inverter is controlled according to the number n of inverters already started in the power station and the given load current, so that the n inverters are synchronized; all the inverters already started in the power station are connected to the AC bus. n is an integer greater than or equal to 1.

18. The method according to claim 17, characterized in that, The drive signal for the power conversion circuit is generated based on the command current and the output current of the power conversion circuit, specifically as follows: A voltage modulation signal is obtained based on the command current and the output current of the power conversion circuit, and a drive signal for the power conversion circuit is generated based on a given angle and the voltage modulation signal.

19. The method according to claim 18, characterized in that, Based on the number n inverters already running in the power station and the given load current, the phase of the inverters is controlled to synchronize the n inverters, specifically as follows: The correction phase is obtained based on the command current, the number n of inverters already started in the power station, and the given load current. The phase of the inverter is controlled based on the correction phase and the given angle to synchronize the n inverters.

20. The method according to claim 19, characterized in that, The process involves obtaining a corrected phase based on the command current, the number n of inverters already activated in the power station, and the given load current; then controlling the phase of the inverters based on the corrected phase and the given angle to synchronize the n inverters. Specifically: The average current is obtained based on the number n of inverters already started in the power station and the given load current. The corrected phase is obtained by proportional-integral adjustment of the command current and the average current. The phase of the inverter is controlled according to the corrected phase and the given angle to synchronize the n inverters.

21. The method according to claim 19, characterized in that, Also includes: When the output voltage of the inverter is greater than the voltage threshold, the control of the inverter according to the command current is stopped, and the output voltage and phase of the inverter are controlled by droop control mode.

22. The method according to claim 21, characterized in that, Before using droop control mode to control the output voltage and phase of the inverter, the following steps are also included: The output voltage of the inverter is assigned to the voltage reference value of the inverter's voltage loop; the command current is assigned to the output of the inverter's voltage loop as the current reference value of the inverter's current loop; and the reference angle obtained according to the corrected phase and the given angle is assigned to the output phase of the active-frequency droop control loop in the droop control mode.

23. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method as described in any one of claims 17-22.

24. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to execute the control method as described in any one of claims 17-22.

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