Power system, control method therefor, power converter, bypass switch and control method therefor

Abstract

A power system, a control method therefor, a power converter, a bypass switch and a control method therefor. The power system comprises a bypass switch and a plurality of power converters; each power converter comprises an alternating current-direct current conversion circuit, a transfer switch, a first port and a second port, a first end of the transfer switch being connected to both an output end of the alternating current-direct current conversion circuit and the second port, and a second end of the transfer switch being connected to the first port; each first port is configured to connect to a first end of the bypass switch and an external power grid; each second port is configured to connect to a second end of the bypass switch and a load. When a grid-connected operating condition is met, the power system is configured to first control the bypass switch to be turned on and then control each transfer switch to be turned on.

Description

Power system and control method thereof, power converter, bypass switch and control method thereof

[0001] The present disclosure claims priority to the domestic application with the application number 202410993149.8, the invention name of "Power system and control method thereof, inverter, bypass switch and control method thereof", which was filed with the China Patent Office on July 23, 2024, and the entire content thereof is incorporated herein by reference.

[0002] The present disclosure claims priority to the domestic application with the application number 202510576159.6, the invention name of "Power system and control method thereof, power converter, bypass switch and control method thereof", which was filed with the China Patent Office on April 30, 2025, and the entire content thereof is incorporated herein by reference. TECHNICAL FIELD

[0003] Embodiments of the present disclosure relate to a power system and control method thereof, a power converter, a bypass switch and a control method thereof. BACKGROUND

[0004] The power converter multi-machine parallel centralized load system refers to a system in which multiple power converters are connected in parallel and can collectively provide power for a centralized load; wherein the grid-connected ports of the multiple power converters are connected to the external power network, and the off-grid ports of the multiple power converters are connected to the load.

[0005] When the grid-connected relay of a certain power converter in the power converter multi-machine parallel centralized load system is attracted first when the external grid is bypassed with a load, all the load current flows through the grid-connected relay, which may cause the grid-connected relay to be overloaded and stuck. SUMMARY

[0006] The following is a summary of the detailed description of the present disclosure. This summary is not intended to limit the scope of the claims. The present disclosure provides a power system and control method thereof, a power converter, a bypass switch and a control method thereof, and the present disclosure adopts the following technical solutions:

[0007] In a first aspect, the present disclosure provides a power system, the power system comprising a bypass switch and a plurality of power converters; the power converter comprising an AC / DC conversion circuit, a switching switch, a first port and a second port; wherein the first end of the switching switch is connected to the output end of the AC / DC conversion circuit and the second port, and the second end of the switching switch is connected to the first port; each first port is configured to connect the first end of the bypass switch and an external power network, and each second port is configured to connect the second end of the bypass switch and a load;

[0008] The power system is configured to:

[0009] When the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on.

[0010] In one of the embodiments, the power converters include a first power converter;

[0011] The first power converter performs the step of controlling the bypass switch to be turned on first and then the switching switches to be turned on when the grid-connected operation condition is met.

[0012] In one of the embodiments, the power converters include a second power converter; the second power converter is a power converter other than the first power converter among the power converters;

[0013] The first power converter is specifically configured to:

[0014] When it is detected that the grid-connected operation condition is met, a first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction;

[0015] After the bypass switch is turned on, the switching switches in the first power converter are controlled to be turned on, and a second control instruction for the switching switches is sent to a second power converter among the power converters to make the second power converter control the corresponding switching switches to be turned on after receiving the second control instruction.

[0016] In one of the embodiments, after the bypass switch and the switching switches are turned on, the first power converter is further configured to:

[0017] In response to the bypass switch and the switching switches being turned on, when the on duration of the bypass switch is greater than or equal to a preset duration, a third control instruction is sent to the bypass switch to make the bypass switch turned off.

[0018] In one of the embodiments, the first power converter is specifically configured to:

[0019] When it is detected that the grid-connected operation condition is met and the current operation state is a non-off-grid operation state, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on.

[0020] In one of the embodiments, the power system is further configured to:

[0021] When it is detected that the grid-connected operation condition is met and the current operation state is an off-grid operation state, the switching switches are controlled to be turned on.

[0022] In one of the embodiments, the power system is further configured to:

[0023] The operation power of the load is acquired;

[0024] In a case where it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters is greater than or equal to the operation power, the control unit controls the switching switches to be turned on.

[0025] In one of the embodiments, the power system is further configured to:

[0026] obtain the operation power of the load;

[0027] In a case where it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters is less than the operation power, the control unit controls the bypass switches to be turned on first and then controls the switching switches to be turned on.

[0028] In one of the embodiments, the power system is further configured to:

[0029] In a case where the external power network is abnormal and the current operation state of the power system is the grid-connected operation state, the control unit controls the switching switches to be turned off.

[0030] In one of the embodiments, the power converter is configured to:

[0031] In a case where the grid-connected operation condition is met, the control unit controls the corresponding bypass switches to be turned on first and then controls the corresponding switching switches to be turned on.

[0032] In a second aspect, the disclosure also provides a control method of a power system, the power system comprising bypass switches and a plurality of power converters; the power converter comprising an AC / DC conversion circuit, a switching switch, a first port and a second port, the first end of the switching switch being connected with the output end of the AC / DC conversion circuit and the second port; wherein the second end of the switching switch is connected with the first port; each first port is configured to be connected with the first end of the bypass switch and an external power network, and each second port is configured to be connected with the first end of the bypass switch and a load; the method comprising:

[0033] In a case where the grid-connected operation condition is met, the control unit controls the bypass switches to be turned on first and then controls the switching switches to be turned on.

[0034] In one of the embodiments, the plurality of power converters comprises a first power converter and at least one second power converter;

[0035] In a case where the grid-connected operation condition is met, the control unit controls the bypass switches to be turned on first and then controls the switching switches to be turned on, comprising:

[0036] When it is detected that the grid-connected operation condition is met, the control unit sends a first control instruction to the bypass switch, so that the bypass switch is turned on after receiving the first control instruction;

[0037] After the bypass switch is turned on, the switching switch in the first power converter is controlled to be turned on, and a second control instruction for the switching switch is sent to the second power converter, so that the second power converter controls the corresponding switching switch to be turned on after receiving the second control instruction.

[0038] In one of the embodiments, when the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on, including:

[0039] When it is detected that the grid-connected operation condition is met and the current operation state is the off-grid operation state, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on.

[0040] In one of the embodiments, when the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on, further including:

[0041] When it is detected that the grid-connected operation condition is met and the current operation state is the off-grid operation state, the switching switches are controlled to be turned on.

[0042] In one of the embodiments, when the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on, including:

[0043] The operation power of the load is obtained;

[0044] When the grid-connected operation condition is met and the total output power of the plurality of power converters is greater than or equal to the operation power, the switching switches are controlled to be turned on;

[0045] When it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters is less than the operation power, the bypass switch is controlled to be turned on first, and then the switching switches are controlled to be turned on.

[0046] In a third aspect, the disclosure also provides a power converter, including an AC / DC conversion circuit, a switching switch, a first port and a second port; wherein the first end of the switching switch is connected with the output end of the AC / DC conversion circuit and the second port, and the second end of the switching switch is connected with the first port; the first port is configured to connect the first end of the bypass switch and the external power network, and the second port is configured to connect the second end of the bypass switch and the load.

[0047] The power converter is configured to:

[0048] When the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switch is controlled to be turned on; or,

[0049] The switching switch is controlled to be turned on based on the received second control instruction; wherein the second control instruction is generated when the bypass switch is turned on.

[0050] In a fourth aspect, the disclosure also provides a control method of a bypass switch, a first end of the bypass switch is configured to be connected with a first port of a power converter and an external power network, and a second end of the bypass switch is configured to be connected with a load and a second port of the power converter respectively; wherein the power converter further comprises an AC / DC conversion circuit and a switching switch, a first end of the switching switch is connected with an output end of the AC / DC conversion circuit and the second port, and a second end of the switching switch is connected with the first port.

[0051] The method comprises:

[0052] Based on the received first control instruction, the bypass switch is controlled to be turned on; the first control instruction is generated before the switching switch is turned on under the condition that the power converter meets the grid-connected operation condition.

[0053] In a fifth aspect, the disclosure also provides a bypass switch, which should be configured in the control method of the bypass switch provided in any of the above-mentioned embodiments.

[0054] Other aspects can become apparent after reading and understanding the accompanying drawings and detailed description.

[0055] BRIEF DESCRIPTION OF DRAWINGS

[0056] FIG. 1A is a schematic diagram of the structure of a power system in an embodiment;

[0057] FIG. 1B is a schematic diagram of the topology of the power system in FIG. 1A when a photovoltaic array is connected thereto;

[0058] FIG. 1C is a schematic diagram of the topology of the power system in FIG. 1A when an energy storage device is connected thereto;

[0059] FIG. 1D is a schematic diagram of the topology of the power system in FIG. 1A when a photovoltaic array and an energy storage device are connected thereto;

[0060] FIG. 2 is a schematic diagram of the structure of another power system in an embodiment;

[0061] FIG. 3 is an interaction diagram of an internal controller of a power system and various inverters in an embodiment;

[0062] FIG. 4 is an interaction diagram between various inverters in a power system in an embodiment;

[0063] FIG. 5 is a flowchart of a step of controlling the bypass switch to be turned on first and then controlling the switching switches to be turned on under the condition that the power converter meets the grid-connected operation condition in an embodiment;

[0064] FIG. 6 is a flowchart of a step of controlling the bypass switch to be turned on first and then controlling the switching switches to be turned on under the condition that the power converter meets the grid-connected operation condition in another embodiment;

[0065] Fig. 7 is a schematic diagram of a structure of a power converter in an embodiment;

[0066] Fig. 8 is a schematic diagram of a structure of a power converter in another embodiment.

[0067] Reference signs: 100-power converter, 101-first power converter, 102-second power converter, 110-AC / DC conversion circuit, 120-switching switch, 130-first port, 140-second port, 200-bypass switch, 300-external power network, 400-load, 500-controller. DETAILED DESCRIPTION

[0068] In order to make the purposes, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and not to limit the present disclosure.

[0069] In a power system in which multiple power converters are connected in parallel, it is impossible to achieve complete synchronization when the grid-connected switches inside the multiple power converters are closed, and a large impact current is generated when the switching switches inside the power converters. When the impact current flows through the grid-connected switches inside the power converters, it can cause the grid-connected switches to be overloaded and stick, fail to be normally opened, and even exceed the short-time withstand current of the grid-connected switches inside the power converters, damaging the power converters.

[0070] Based on this, the present disclosure proposes a power system including a bypass switch and multiple power converters. Each power converter includes an AC / DC conversion circuit, a switching switch, a first port and a second port; wherein the first end of the switching switch is connected to the output end of the AC / DC conversion circuit and the second port, and the second end of the switching switch is connected to the first port. Each first port can be configured to connect the first end of the bypass switch and an external power network, and each second port can be configured to connect the second end of the bypass switch and a load. When the power system is connected to the grid, the bypass switch can be controlled to be turned on first, at which time the voltages across each switching switch are almost the same, and then each switching switch is controlled to be turned on. In this way, the impact current generated when each switching switch is turned on is almost zero, significantly reducing the impact current when each switching switch is switched on and closed, avoiding the situation that the switching switch is overloaded and stuck due to too large current flowing through the switching switch, and also avoiding the AC / DC conversion circuit being damaged due to too large current impact, improving the stability and safety of the power system.

[0071] The power system of the present disclosure will be described below with reference to the drawings.

[0072] In one embodiment, as shown in FIG. 1A and FIG. 2, the power system comprises a bypass switch 200 and a plurality of power converters 100. Each power converter 100 comprises an AC / DC conversion circuit 110, a switching switch 120, a first port 130 and a second port 140. The first end b1 of the switching switch 120 is connected to the output end a of the AC / DC conversion circuit 110 and the second port 140, and the second end b2 of the switching switch 120 is connected to the first port 130. Each first port 130 can be configured to connect the first end c1 of the bypass switch 200 and an external power network 300, and each second port 140 can be configured to connect the second end c2 of the bypass switch 200 and a load 400.

[0073] For example, referring to FIG. 1B, in the case that the input end of the power converter 100 is connected to only a photovoltaic array, the AC / DC conversion circuit 110 can be an inverter circuit capable of converting DC power into AC power. Referring to FIG. 1C, in the case that the input end of the power converter 100 is connected to only an energy storage device, the AC / DC conversion circuit 110 can be a converter circuit capable of converting DC power into AC power and converting AC power into DC power; alternatively, the AC / DC conversion circuit 110 can be an inverter circuit capable of converting DC power into AC power. Referring to FIG. 1D, in the case that the input end of the power converter 100 is connected to both an energy storage device and a photovoltaic array, the AC / DC conversion circuit 110 can be a converter circuit capable of converting DC power into AC power and converting AC power into DC power; alternatively, the AC / DC conversion circuit 110 can be an inverter circuit capable of converting DC power into AC power. The photovoltaic array comprises a plurality of solar panels, and the energy storage device comprises at least one energy storage cell.

[0074] For example, referring to FIG. 1B-1D, the power converter 100 can further comprise a DC / DC conversion circuit, each photovoltaic array is connected to the input end of the corresponding AC / DC conversion circuit 110 through a DC / DC conversion circuit, and each energy storage device is connected to the input end of the corresponding AC / DC conversion circuit 110 through a DC / DC conversion circuit.

[0075] For example, referring to FIG. 1B-1D, the power converter 100 can further comprise a control unit capable of controlling power electronic devices such as the power converter 100 and the bypass switch 200, and specifically capable of controlling power electronic devices such as the AC / DC conversion circuit 110, the switching switch 120 and the DC / DC conversion circuit in the power converter 100. The control unit can further generate and output control instructions, such as first control instructions, second control instructions and third control instructions.

[0076] It can be understood that the first port 130 of the plurality of power converters 100 is connected to the first end c1 of the bypass switch 200 and the external power network 300, and the second port 140 of the plurality of power converters 100 is connected to the second end c2 of the bypass switch 200 and the load 400, and the plurality of power converters are in parallel connection. The bypass switch 200 can be a contactor, a relay or the like, and the power level of the bypass switch 200 can be greater than or equal to the power level of the power system. Generally, the power level of the bypass switch 200 can be greater than or equal to the product of the rated load capacity of a single power converter 100 and the number of parallel power converters 100; if the load power is less than the product of the rated load capacity of a single power converter 100 and the number of parallel power converters 100, the power level of the bypass switch 200 can be greater than the load power. The bypass switch 200 can be arranged independently of the power converter 100, as shown in FIG. 1A, or can be integrated inside the power converter 100, as shown in FIG. 2.

[0077] The power system is configured to first control the bypass switch 200 to be turned on, and then control each switching switch 120 to be turned on, under the condition that the grid-connected operation condition is met.

[0078] The grid-connected operation condition of the power system means that the external power network 300 of the power system is normal, and each power converter 100 is voltage-synchronized with the external power network 300. In the power system, a voltage detection circuit is integrated in the first port 130, and the voltage of the external power network 300 can be detected through the first port 130 of the power converter 100. For example, the voltage of the external power network 300 can be detected through the first port 130 of any power converter 100, or the voltage of the external power network 300 can be detected through the first port 130 of the plurality of power converters 100 and then averaged to determine whether the external power network 300 is normal. For example, if the voltage information of the external power network 300 is between 190V and 240V, the external power network 300 can be considered normal. After detecting that the external power network 300 is normal, the power system controls the output voltage of the power converter 100 to be synchronized with the voltage of the external power network 300 through a phase-locked loop control or the like.

[0079] In the power system as shown in FIG. 1A, the power system can first control the bypass switch 200 to be turned on, and then control each switching switch 120 to be turned on, under the condition that the grid-connected operation condition is met.

[0080] In the power system as shown in FIG. 2, the power system, under the condition of meeting the grid-connected operation, can first control the bypass switch 200 integrated in any power converter 100 to be conductive, and then control each switching switch 120 to be conductive, to complete the grid connection. Alternatively, the power system can also control all the bypass switches 200 integrated in the power converters 100 to be conductive, and then control each switching switch 120 to be conductive, to complete the grid connection.

[0081] In addition, for the power system as shown in FIG. 1A or FIG. 2, under the condition of meeting the grid-connected operation, the power system can first control the bypass switch 200 to be conductive according to the control instruction sent by the external device, and then control each switching switch 120 to be conductive. Alternatively, the power system can also first control the bypass switch 200 to be conductive by the internal controller 500, and then control each switching switch 120 to be conductive. Exemplarily, as shown in FIG. 3, under the condition of meeting the grid-connected operation of the power system, the controller 500 first sends a first control instruction to the bypass switch 200, so that the bypass switch 200 is conductive, and then sends a second control instruction to each power converter 100, so that each power converter 100 controls the corresponding switching switch 120 to be conductive according to the second control instruction.

[0082] In the embodiment, the power system includes a bypass switch 200 and a plurality of power converters 100. Each power converter 100 includes an AC / DC conversion circuit 110, a switching switch 120, a first port 130 and a second port 140. The first end b1 of the switching switch 120 is connected with the output end a of the AC / DC conversion circuit 110 and the second port 140, and the second end b2 of the switching switch 120 is connected with the first port 130. Each first port 130 can be configured to connect the first end c1 of the bypass switch 200 and the external power network 300, and each second port 140 can be configured to connect the second end c2 of the bypass switch 200 and the load 400. Under the condition of meeting the grid-connected operation of the power system, the bypass switch 200 can be first controlled to be conductive, at this time the voltages across each switching switch 120 are almost the same, and then each switching switch 120 is controlled to be conductive. In this way, the impact current generated when each switching switch 120 is conductive is almost zero, which significantly reduces the impact current when each switching switch is closed, avoids the power converter 100 from being damaged due to the excessive current impact when the switching switch is closed, and improves the stability and safety of the power system.

[0083] In one embodiment, the plurality of power converters 100 includes a first power converter 101. The first power converter 101 is any one of the plurality of power converters 100. In the case that the initially selected first power converter fails, any one of the other normally operating power converters 100 in the power system can be selected as a new first power converter 101.

[0084] The first power converter 101 performs the step of controlling the bypass switch 200 to be turned on first and then controlling the switching switches 120 to be turned on when the grid-connected operation condition is met.

[0085] It can be understood that in the power system as shown in FIG. 1A, when the power system meets the grid-connected operation condition, the first power converter 101 can control the bypass switch 200 to be turned on first, at this time, the voltages across the switching switches 120 inside each power converter 100 are almost the same, and then the first power converter 101 can control the switching switches 120 to be turned on, to complete grid connection. The inrush current generated when the switching switches 120 are closed is very small.

[0086] In the power system as shown in FIG. 2, when the power system meets the grid-connected operation condition, the first power converter 101 can control the bypass switch 200 integrated inside the first power converter 101 to be turned on, and then control the switching switches 120 inside each power converter 100 to be turned on, to complete grid connection. Alternatively, the first power converter 101 can also send an instruction indicating to control the bypass switch 200 to be turned on to other power converters 100, so that the bypass switches 200 inside the other power converters 100 are turned on, and then the switching switches 120 inside each power converter 100 are controlled to be turned on, to complete grid connection.

[0087] In one embodiment, each power converter 100 includes a second power converter 102. The second power converter 102 is a power converter 100 other than the first power converter 101. The first power converter 101 and the second power converter 102 are in communication connection.

[0088] The first power converter 101 is specifically configured to, when detecting that the grid-connected operation condition is met, send a first control instruction to the bypass switch 200, so that the bypass switch 200 is turned on after receiving the first control instruction; after the bypass switch 200 is turned on, the switching switches 120 in the first power converter 101 are controlled to be turned on, and a second control instruction for the switching switches 120 is sent to the second power converter 102 of the plurality of power converters 100, so that the second power converter 102 controls the corresponding switching switches 120 to be turned on after receiving the second control instruction.

[0089] As shown in FIG. 4, the first power converter 101 controls the bypass switch 200 to be turned on by sending a first control instruction to the bypass switch 200. After the bypass switch 200 is turned on, the first power converter 101 controls the switching switch 120 inside the first power converter 101 to be turned on, and sends a second control instruction to the plurality of second power converters 102, so that the second power converters 102 control the corresponding switching switches 120 to be turned on after receiving the second control instruction, thereby realizing the grid-connected operation of the power system.

[0090] In an embodiment, after the bypass switch 200 and the switching switches 120 are turned on, the first power converter 101 is further configured to: in response to the bypass switch 200 and the switching switches 120 being turned on, send a third control instruction to the bypass switch 200 to turn off the bypass switch 200, if the on duration of the bypass switch 200 is greater than or equal to a preset duration. For example, the preset duration can be 20 ms. It can be understood that, if the on duration of the bypass switch 200 is greater than or equal to the preset duration, the first power converter 101 can send the third control instruction to the bypass switch 200, so that the bypass switch 200 is turned off after receiving the third control instruction, thereby avoiding affecting the seamless switching between grid-connected operation and off-grid operation of the power system.

[0091] If the on duration of the bypass switch 200 is less than the preset duration, the bypass switch 200 and the switching switches 120 can be kept in the current on state after being turned on. In this case, the on duration of the bypass switch 200 has little effect on the seamless switching between grid-connected operation and off-grid operation, which can be ignored. Alternatively, if the on duration of the bypass switch 200 is less than the preset duration, the first power converter 101 can also send the third control instruction to the bypass switch 200 to turn off the bypass switch 200.

[0092] In an embodiment, the first power converter 101 is specifically configured to: in the case that the grid-connected operation condition is detected to be met and the current operation state is the non-off-grid operation state, first control the bypass switch 200 to be turned on, and then control the switching switches 120 to be turned on.

[0093] The power system meets the grid-connected operation state and the current operation state is the non-off-grid operation state, i.e., the power system is in a non-grid-connected non-off-grid operation state, such as an initial start state, a standby state, etc.

[0094] Exemplarily, as shown in FIG. 4, in a case where the power system meets the grid-connected operation condition and the current operation state of each power converter is the non-off-grid operation state, the first power converter 101 can send a first control instruction to the bypass switch 200, so that the bypass switch 200 is turned on. After the bypass switch 200 is turned on, the voltages across each switching switch 120 are almost the same. The first power converter 101 can control the switching switch 120 in the first power converter 101 to be turned on, and send a second control instruction for the switching switch 120 to the second power converter 102 in the plurality of power converters 100, so that the second power converter 102 controls the corresponding switching switch 120 to be turned on after receiving the second control instruction. At this time, the current shock when each switching switch 120 is turned on is very small, and the safe grid connection of the power system is realized.

[0095] Alternatively, as shown in FIG. 5, in a case where the power system meets the grid-connected operation condition and the current operation state of each power converter 100 is the non-off-grid operation state, a controller 500 independent of each power converter 100 in the power system can first send a first control instruction to the bypass switch 200, so that the bypass switch 200 is turned on, and then send a second control instruction to each power converter 100, so that each power converter 100 controls the corresponding switching switch 120 to be turned on.

[0096] In one embodiment, the power system is further configured to, in a case where it is detected that the grid-connected operation condition is met and the current operation state is the off-grid operation state, control each switching switch to be turned on.

[0097] It can be understood that, in a case where the power system detects that the grid-connected operation condition is met and the current operation state of each power converter 100 is the off-grid operation state, each switching switch 120 can be controlled to be turned on by a controller 500 independent of each power converter 100 arranged inside the power system, or can be controlled to be turned on by an external device. In addition, each switching switch 120 can also be controlled to be turned on by the first power converter 101, that is, in a case where the power system is in the off-grid operation state, the first power converter 101 can directly control the switching switch 120 inside the first power converter 101 to be turned on, and send a second control instruction to each second power converter 102, so that the second power converter 102 controls the corresponding switching switch 120 to be turned on.

[0098] Although an impulse current is generated when each switching switch 120 in the power converter 100 is closed when the power system switches from the off-grid operation state to the grid-connected operation state, the impulse current is generally smaller than the short-time withstand current of each switching switch 120. Therefore, the first power converter 101 can not control the bypass switch 200 to be turned on, thereby reducing the actions that the power system can perform when grid-connected, and speeding up the switching from the off-grid operation state to the grid-connected operation state.

[0099] Further, when the grid-connected operation condition is met and the current operation state is the off-grid operation state, the power system can control the bypass switch 200 to be always in the off state, or can first control the bypass switch 200 to be in the on state before the switching switch 120 is turned on.

[0100] In one embodiment, the power system is further configured to acquire the operation power of the load 400, and when it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters 100 is greater than or equal to the operation power, control the switching switches 120 to be turned on.

[0101] Exemplarily, the power system can acquire the operation power of the load 400 through the direct current black start. That is, the power system can first operate with the voltage self-supporting and the load 400, and determine whether the total output power of the power system can support the normal operation of the load 400.

[0102] When the total output power of the power system is greater than or equal to the operation power of the load 400, the inrush current generated when the switching switch 120 in each power converter is turned on is generally less than the short-time withstand current of the switching switch 120, and therefore, the power system can directly control the switching switches 120 to be turned on. When the switching switches 120 are controlled to be turned on, the power system can control the switching switches 120 to be turned on through the controller 500 independent of each power converter 100, or can determine the first power converter 101 and control the switching switches 120 to be turned on by the first power converter 101.

[0103] When the total output power of the power system is greater than or equal to the operation power of the load 400, the power system can control the bypass switch 200 to be always in the off state, or can first control the bypass switch 200 to be in the on state before the switching switch 120 is turned on.

[0104] Further, the power system is further configured to, when it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters 100 is less than the operation power, first control the bypass switch 200 to be in the on state, and then control the switching switches 120 to be turned on.

[0105] When the total output power of the plurality of power converters 100, that is, the output power of the power system, is less than the operation power of the load 400, the inrush current generated when the switching switch 120 in the power converter 100 is turned on is large, and can even exceed the short-time withstand current of the switching switch 120, and therefore, the power system can first control the bypass switch 200 to be in the on state, so that the voltages across the switching switches 120 are almost the same and the voltage difference is almost zero, and then control the switching switches 120 to be turned on, so as to reduce the inrush current generated when the switching switches 120 are turned on and realize the safe grid connection of the power system.

[0106] Specifically, the power system can adopt the mode shown in FIG. 3, that is, the bypass switch 200 is first controlled to be turned on by the controller 500 independent of the controllers 500 of the power converters 100, and then the switching switches 120 are controlled to be turned on. Alternatively, the power system can also adopt the mode shown in FIG. 4, that is, the first power converter 101 first sends a first control instruction to the bypass switch 200 to make the bypass switch 200 turned on, and then the switching switch 120 in the first power converter 101 is controlled to be turned on, and a second control instruction is sent to each second power converter 102 to make the second power converter 102 control the corresponding switching switch 120 to be turned on.

[0107] In one embodiment, the power system is further configured to control the switching switches 120 to be turned off in the case that the external power network 300 is abnormal and the current operating state of the power system is the grid-connected operating state.

[0108] The abnormality of the external power network 300 includes power grid outage, power grid undervoltage, etc. It can be understood that the power system detects the voltage of the external power network 300 through the first port 130 of the power converter 100, and considers that the external power network 300 is abnormal in the case that the voltage of the external power network 300 is out of the normal range. Exemplarily, the voltage normal range can be 190V-240V. If the external power network 300 is abnormal and the power system is in the grid-connected operating state, the power system can control the switching switches 120 to be turned off to enter the off-grid operating state or the non-off-grid operating state, so as to avoid the influence of the abnormality of the external power network 300 on the normal operation of the load 400.

[0109] In one embodiment, the bypass switch 200 includes a relay, and the turn-off duration of the relay is less than or equal to 20ms. A relay with a relatively small turn-off duration can be used as the bypass switch 200 to reduce the influence of the turn-off duration of the bypass switch 200 on the seamless switching between the grid-connected operating state and the off-grid operating state of the power system. Exemplarily, the turn-off duration of the bypass switch 200 can be 10ms.

[0110] In one embodiment, each power converter 100 is configured to first control the corresponding bypass switch 200 to be turned on and then control the corresponding switching switch 120 to be turned on in the case that the grid-connected operating condition is met.

[0111] Referring to FIG. 2, a bypass switch 200 is arranged in each power converter 100, and each power converter 100 can control the corresponding bypass switch 200 to be closed and then control the corresponding switching switch 120 to be closed in the case that the power system meets the grid-connected operating condition.

[0112] In one embodiment, the disclosure also provides a control method of a power system, which can be configured in the power system as shown in FIG. 1A or FIG. 2. The control method of the power system comprises the steps of controlling the bypass switch to be turned on first, and then controlling the switching switch to be turned on, under the condition that the grid-connected operation condition is met.

[0113] The power system can first detect the voltage of the external power network 300 through the first port 130 of the power converter 100, and control the power converter 100 to be synchronized with the voltage of the external power network 300 under the condition that the voltage of the external power network 300 is within the normal range (for example, 190V-240V), so as to meet the grid-connected operation condition. Then, the power system can first control the bypass switch 200 to be turned on, so that the voltages across the switching switches 120 are almost the same, and then control the switching switches 120 of the power converter 100 to be turned on, so that the inrush current generated when the switching switches 120 are turned on is almost zero.

[0114] In this embodiment, by controlling the bypass switch 200 to be turned on first and then controlling the switching switches 120 to be turned on under the condition that the grid-connected operation condition is met, the inrush current generated when the switching switches 120 are turned on can be significantly reduced, the safe grid connection of the power system is realized, and the safety and stability of the power system are improved.

[0115] In one embodiment, as shown in FIG. 5, under the condition that the grid-connected operation condition is met, the bypass switch is controlled to be turned on first, and then the switching switch is controlled to be turned on, which comprises steps S110-S120.

[0116] S110, when it is detected that the grid-connected operation condition is met, a first control instruction is sent to the bypass switch, so that the bypass switch is turned on after receiving the first control instruction.

[0117] It can be understood that when it is detected that the power system meets the grid-connected operation condition, the first power converter 101 can first send a first control instruction to the bypass switch 200 to make the bypass switch 200 turned on. Alternatively, the first power converter 101 can send the first control instruction to the bypass switch 200 directly connected to the first power converter 101, or send an instruction indicating that the bypass switch 200 is turned on to the second power converter 102, so that the second power converter 102 controls the bypass switch 200 directly connected to the second power converter 102 to be turned on.

[0118] S120, after the bypass switch is turned on, the switching switch in the first power converter is controlled to be turned on, and a second control instruction for the switching switch is sent to the second power converter, so that the second power converter controls the corresponding switching switch to be turned on after receiving the second control instruction.

[0119] After the bypass switch 200 is turned on, the first power converter 101 can control the switching switch 120 in the first power converter 101 to be turned on, and send a second control instruction to the second power converter 102, so that the second power converter 102 controls the corresponding switching switch 120 to be turned on according to the second control instruction.

[0120] In the embodiment, when it is detected that the power system meets the grid-connected operation condition, the bypass switch 200 is first controlled to be closed by the first power converter 101, and then each switching switch 120 is controlled to be closed, so that the inrush current when each switching switch 120 is closed can be obviously reduced, and the safe grid-connected operation of the power system can be realized.

[0121] In one embodiment, when the grid-connected operation condition is met, the bypass switch is first controlled to be turned on, and then each switching switch is controlled to be turned on, including the step of controlling the bypass switch to be turned on, and then controlling each switching switch to be turned on when it is detected that the grid-connected operation condition is met and the current operation state is a non-off-grid operation state.

[0122] It can be understood that when it is detected that the power system meets the grid-connected operation condition and the current operation state is a non-off-grid operation state such as an initial start state, a standby state, etc., the power system can first control the bypass switch 200 to be turned on, so that the voltages across the switching switches 120 in the plurality of power converters 100 are almost the same, and the voltage difference is almost zero, and then each switching switch 120 can be controlled to be turned on. The power system can control the bypass switch 200 and the switching switch 120 to be turned on according to a control instruction of an external device, or can control the bypass switch 200 and each switching switch 120 to be turned on in the manner shown in FIG. 3 or FIG. 4.

[0123] In one embodiment, when the grid-connected operation condition is met, the bypass switch is first controlled to be turned on, and then each switching switch is controlled to be turned on, and the step of controlling each switching switch to be turned on when it is detected that the grid-connected operation condition is met and the current operation state is an off-grid operation state.

[0124] It can be understood that when it is detected that the grid-connected operation condition is met and the current operation state of the power system is an off-grid operation state, the power system controls each switching switch 120 to be turned on through a controller 500 which is independently set inside each power converter 100, or the first power converter 101 can be set to control each switching switch 120 to be turned on.

[0125] When the power system switches from off-grid operation to grid-connected operation, although the switching on of each switching switch 120 in the power converter 100 will also generate an impulse current, the impulse current is generally less than the short-time withstand current of each switching switch 120, and thus the first power converter 101 can not control the bypass switch 200 to be turned on, reducing the actions that the power system can perform when connected to the grid, and speeding up the switching from off-grid to grid-connected.

[0126] In one embodiment, as shown in FIG. 6, when the grid-connected operation condition is met, the bypass switch is first controlled to be turned on, and then each switching switch is controlled to be turned on, including steps S210-S230.

[0127] S210, obtaining the operating power of the load.

[0128] The power system can first run with voltage self-supporting and load through the DC black start mode, thereby obtaining the operating power of the load 400.

[0129] S220, when the grid-connected operation condition is met and the total output power of the plurality of power converters is greater than or equal to the operating power, controlling each switching switch to be turned on.

[0130] When the total output power of the power system is greater than or equal to the operating power of the load 400, the impulse current generated when the switching switch 120 in each power converter 100 is turned on is generally less than the short-time withstand current of the switching switch 120, and thus the power system can directly control each switching switch 120 to be turned on.

[0131] S230, when it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters is less than the operating power, first controlling the bypass switch to be turned on, and then controlling each switching switch to be turned on.

[0132] When the total output power of the plurality of power converters 100, that is, the output power of the power system, is less than the operating power of the load 400, the impulse current generated when the switching switch 120 in the power converter 100 is turned on can exceed the short-time withstand current of the switching switch 120, and thus the power system can first control the bypass switch 200 to be turned on, so that the voltage across each switching switch 120 is almost the same and the voltage difference is almost zero, and then control each switching switch 120 to be turned on, thereby reducing the impulse current generated when each switching switch 120 is turned on, and achieving safe grid connection of the power system.

[0133] In this embodiment, the power system determines whether to control the bypass switch 200 to be turned on according to the comparison result of the operating power of the load 400 and the total output power of the power system, which can reduce the usage frequency of the bypass switch 200, reduce the consumption of the bypass switch 200, and improve the service life of the bypass switch 200.

[0134] To better understand, two more specific examples are provided to illustrate the power system control method of this disclosure.

[0135] Example 1: The power system monitors the voltage of the external power network 300 in real time. If the external power network 300 is confirmed to be normal, the system controls the output voltage of each power converter 100 to be synchronized with the voltage phase of the external power network 300. If the power system is in standby or initial startup state, the first power converter 101 sends a first control command to the bypass switch 200 to turn it on. At this time, the voltage difference across each switching switch 120 is almost zero. After the bypass switch 200 turns on, the first power converter 101 controls its own switching switch 120 to turn on and sends a second control command to each second power converter 102 to turn it on. The first power converter 102 controls the corresponding switching switch 120 to conduct. When each switching switch 120 is closed, the inrush current is zero. Then, the first power converter 101 disconnects the bypass switch 200, achieving safe grid-connected operation of the power system. If the power system is in off-grid operation at this time, the first power converter 101 controls its own switching switch 120 to conduct and sends a second control command to each of the second power converters 102, causing the second power converters 102 to control their corresponding switching switches 120 to conduct. In this case, the inrush current generated by the switching switch 120 can be less than the short-time withstand current of the switching switch 120, and the bypass switch 200 remains open. Furthermore, the power system determines whether to close the bypass switch 200 when it is about to connect to the grid based on its own operating status, thereby reducing the frequency of operation of the bypass switch 200 and improving its service life.

[0136] Example 2: The power system monitors the voltage of the external power network 300 in real time. If the external power network 300 is confirmed to be normal, the system controls the output voltage of each power converter 100 to synchronize with the voltage of the external power network 300 to meet the grid connection operation conditions. Once the grid connection operation conditions are met, the power system can first establish its voltage through a DC black start to supply power to the load 400 and monitor the operating power of the load 400.

[0137] When the operating power of load 400 is less than the total output power of multiple power converters 100 in the power system, and the operating power of load 400 is greater than the output power of a single power converter 100, the first power converter 101 controls its own switching switch 120 to turn on and sends a second control command to each of the second power converters 102, so that the second power converter 102 controls the corresponding switching switch 120 to turn on, and the bypass switch 200 is always in the open state. In this way, unnecessary switching actions of the bypass switch 200 can be reduced and the service life of the bypass switch 200 can be improved.

[0138] In the case that the operating power of the load 400 is less than the total output power of the plurality of power converters 100 in the power system, and the operating power of the load 400 is less than the output power of a single power converter 100, the first power converter 101 controls the switching switch 120 of itself to be turned on, and sends a second control instruction to each second power converter 102, so that the second power converter 102 controls the corresponding switching switch 120 to be turned on, and the bypass switch 200 is always in an off state. In addition, in this case, the external power network 300 is normal, that is, it can be considered that the grid-connected condition is met, and since the power of the load 400 is small, seamless switching from off-grid to grid-connected can be realized even if the voltage synchronization of the power converter 100 and the external power network 300 is not performed.

[0139] In the case that the operating power of the load 400 is greater than or equal to the total output power of the plurality of power converters 100 in the power system, the first power converter 101 sends a first control instruction to the bypass switch 200 to control the bypass switch 200 to be turned on. After the bypass switch 200 is turned on, the first power converter 101 controls the switching switch 120 of itself to be turned on, and sends a second control instruction to each second power converter 102, so that the second power converter 102 controls the corresponding switching switch 120 to be turned on, and then the first power converter 102 turns off the bypass switch 200.

[0140] In one embodiment, as shown in FIG. 7, the present disclosure also provides a power converter. The power converter comprises an AC / DC conversion circuit 110, a switching switch 120, a first port 130 and a second port 140; wherein the first end b1 of the switching switch 120 is connected with the output end a of the AC / DC conversion circuit 110 and the second port 140, and the second end b2 of the switching switch 120 is connected with the first port 130. The first port 130 is configured to be connected with the first end c1 of the bypass switch and the external power network, and the second port 140 is configured to be connected with the second end c2 of the bypass switch and the load.

[0141] Optionally, as shown in FIG. 8, the power converter comprises an AC / DC conversion circuit 110, a switching switch 120, a first port 130, a second port 140 and a bypass switch 200; wherein the first end b1 of the switching switch 120 is connected with the output end a of the AC / DC conversion circuit 110, the second port 140 and the second end c2 of the bypass switch respectively, and the second end b2 of the switching switch 120 is connected with the first port 130 and the first end c1 of the bypass switch 200 respectively. The first port 130 is configured to be connected with the first end c1 of the bypass switch and the external power network, and the second port 140 is configured to be connected with the second end c2 of the bypass switch and the load.

[0142] The power converter is configured to control the bypass switch to be turned on first and then control the switching switch to be turned on under the condition that the grid-connected operation condition is met.

[0143] It can be understood that, under the condition that the power converter meets the grid-connected operation condition, the power converter can first control the bypass switch 200 to be turned on, so that the voltage difference across the switching switch 120 inside the power converter is zero, and then the power converter controls the switching switch 120 to be turned on. The current surge generated when the switching switch 120 is turned on is very small.

[0144] Optionally, the power converter can be configured to control the switching switch to be turned on based on the received second control instruction, wherein the second control instruction is generated under the condition that the bypass switch is turned on.

[0145] It can be understood that the power converter can receive the second control instruction sent by other devices (such as a controller or other power converters) after the bypass switch 200 is turned on, and control the switching switch 120 to be turned on according to the second control instruction.

[0146] In one embodiment, the disclosure also provides a control method of a bypass switch. The bypass switch 200 can be configured in a structure as shown in FIG. 1A or FIG. 2, the first end c1 of the bypass switch 200 is connected with the first port 130 of the power converter 100 and the external power network 300, respectively, and the second end c2 of the bypass switch 200 is connected with the second port 140 of the power converter 100 and the load 400, respectively. The power converter 100 includes an AC-DC conversion circuit 110 and a switching switch 120, the first end b1 of the switching switch 120 is connected with the output end a of the AC-DC conversion circuit 110 and the second port 140, and the second end b1 of the switching switch 120 is connected with the first port 130.

[0147] The control method of the bypass switch includes the step of controlling the bypass switch to be turned on based on the received first control instruction.

[0148] The first control instruction is generated by the power converter under the condition that the grid-connected operation condition is met and before the switching switch is turned on. For example, the first control instruction can also be generated before the control instruction configured to control the switching switch to be turned on is generated.

[0149] It can be understood that, under the condition that the power converter 100 meets the grid-connected operation condition, the bypass switch 200 can be controlled to be turned on according to the first control instruction sent by the power converter 100 or the first control instruction sent by the controller 500 independent of the power converter 100 in the power system before the switching switch 120 is turned on, so that the voltage difference across the switching switch 120 inside the power converter 100 is zero, and the current surge when the switching switch 120 is turned on is reduced.

[0150] In one embodiment, the disclosure also provides a bypass switch, which can be applied in the control method of the bypass switch provided by any of the above embodiments. The bypass switch can be a relay, and the off duration of the bypass switch can be less than or equal to 20 ms.

[0151] The technical features of the above embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the disclosure.

[0152] The above embodiments only express several implementation manners of the disclosure, and the description is specific and detailed, but it should not be understood as a limitation on the patent scope of the disclosure. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the disclosure, a number of modifications and improvements can be made, which are within the protection scope of the disclosure. Therefore, the protection scope of the disclosure should be subject to the appended claims.

Claims

1. A power system comprising a bypass switch and a plurality of power converters; the power converter comprising an AC-DC conversion circuit, a switching switch, a first port and a second port; wherein, The first end of the switch is connected with the output end of the AC-DC conversion circuit and the second port, and the second end of the switch is connected with the first port; each first port is configured to connect the first end of the bypass switch and an external power network, and each second port is configured to connect the second end of the bypass switch and a load; The power system is configured to: In the case of meeting the grid-connected operation condition, the bypass switch is controlled to be turned on first, and then the switches are controlled to be turned on.

2. The power system of claim 1, wherein, Each of the power converters includes a first power converter; The first power converter performs the step of, in the case of meeting the grid-connected operation condition, controlling the bypass switch to be turned on first, and then controlling the switches to be turned on.

3. The power system of claim 2, wherein, Each of the power converters includes a second power converter; the second power converter is a power converter other than the first power converter among the power converters; The first power converter is specifically configured to: When it is detected that the grid-connected operation condition is met, a first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction; After the bypass switch is turned on, the switch in the first power converter is controlled to be turned on, and a second control instruction for the switch is sent to the second power converter to make the second power converter control the corresponding switch to be turned on after receiving the second control instruction.

4. The power system of claim 2 or 3, wherein, The first power converter is further configured to: In response to the bypass switch and the switches being turned on, in the case of the turning-on duration of the bypass switch being greater than or equal to a preset duration, a third control instruction is sent to the bypass switch to make the bypass switch turned off.

5. The power system of claim 2, wherein, The first power converter is specifically configured to: In the case of detecting that the grid-connected operation condition is met and the current operation state is a non-off-grid operation state, the bypass switch is controlled to be turned on first, and then the switches are controlled to be turned on.

6. The power system of any one of claims 1-5, wherein, The power system is further configured to: In the case of detecting that the grid-connected operation condition is met and the current operation state is an off-grid operation state, the switches are controlled to be turned on.

7. The power system of any one of claims 1-6, wherein, The power system is further configured to: Obtain the running power of the load; In the case of detecting that the grid-connected operation condition is met and the total output power of the plurality of power converters is greater than or equal to the running power, the switches are controlled to be turned on.

8. The power system of any one of claims 1-7, wherein, The power system is further configured to: Obtain the running power of the load; In the case of detecting that the grid-connected operation condition is met and the total output power of the plurality of power converters is less than the running power, the bypass switch is controlled to be turned on first, and then the switches are controlled to be turned on.

9. The power system of any of claims 1-8, wherein, The power system is further configured to: In the case of the external power network being abnormal and the current operation state of the power system being a grid-connected operation state, the switches are controlled to be turned off.

10. The power system of any of claims 1-9, wherein, Each of the power converters is configured to: In the case of meeting the grid-connected operation condition, the corresponding bypass switch is controlled to be turned on first, and then the corresponding switch is controlled to be turned on.

11. A control method of a power system, the power system comprising a bypass switch and a plurality of power converters; the power converter comprising an AC / DC conversion circuit, a switching switch, a first port and a second port; wherein, The first end of the switch is connected with the output end of the AC-DC conversion circuit and the second port, and the second end of the switch is connected with the first port; each first port is configured to connect the first end of the bypass switch and an external power network, and each second port is configured to connect the second end of the bypass switch and a load; the method comprises: When the grid-connected operation condition is met, the bypass switch is first controlled to be turned on, and then the switch is controlled to be turned on.

12. The control method of a power system according to claim 11, wherein, Each power converter comprises a first power converter and at least one second power converter; The first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction when it is detected that the grid-connected operation condition is met; After the bypass switch is turned on, the switch in the first power converter is controlled to be turned on, and a second control instruction for the switch is sent to the second power converter, so that the second power converter controls the corresponding switch to be turned on after receiving the second control instruction. The first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction when it is detected that the grid-connected operation condition is met; 13. The control method of a power system according to claim 11 or 12, wherein, The bypass switch is first controlled to be turned on, and then the switch is controlled to be turned on when it is detected that the grid-connected operation condition is met and the current operation state is the non-off-grid operation state. The first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction when it is detected that the grid-connected operation condition is met; 14. The control method of a power system according to any one of claims 11-13, wherein, The bypass switch is first controlled to be turned on, and then the switch is controlled to be turned on when it is detected that the grid-connected operation condition is met and the current operation state is the off-grid operation state. The first control instruction is sent to the bypass switch to make the bypass switch turned on after receiving the first control instruction when it is detected that the grid-connected operation condition is met; 15. The control method of a power system according to any one of claims 11-14, wherein, The operation power of the load is acquired; The switch is controlled to be turned on when the grid-connected operation condition is met and the total output power of the plurality of power converters is greater than or equal to the operation power; The bypass switch is first controlled to be turned on, and then the switch is controlled to be turned on when it is detected that the grid-connected operation condition is met and the total output power of the plurality of power converters is less than the operation power. The first end of the switch is connected with the output end of the AC-DC conversion circuit and the second port, and the second end of the switch is connected with the first port; the first port is configured to connect the first end of the bypass switch and an external power network, and the second port is configured to connect the second end of the bypass switch and a load; 16. A power converter comprising an AC-DC conversion circuit, a switching switch, a first port and a second port; wherein, The power converter is configured to: The bypass switch is first controlled to be turned on, and then the switch is controlled to be turned on when the grid-connected operation condition is met; or The switch is controlled to be turned on based on the received second control instruction; wherein the second control instruction is generated when the bypass switch is turned on. ​ 17. A control method of a bypass switch, a first terminal of the bypass switch being configured to be connected with a first port of a power converter and an external power network, a second terminal of the bypass switch being configured to be connected with a load and a second port of the power converter; wherein, The power converter further comprises an AC / DC conversion circuit and a switching switch, a first end of the switching switch is connected with an output end of the AC / DC conversion circuit and the second port, and a second end of the switching switch is connected with the first port; The method comprises: Based on the received first control instruction, the bypass switch is controlled to be turned on; the first control instruction is generated before the switching switch is turned on under the condition that the grid-connected operation condition is met.

18. A bypass switch should be configured as in the control method of the bypass switch of claim 17.

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