A method for inhibiting port voltage rise when an isolated three-port converter power supply is disconnected

Abstract

This invention discloses a method for suppressing the rise of port voltage when the power supply of an isolated three-port converter is disconnected. The power supply port (1) supplies power to the energy storage port (2) or the load port (3). The feedback current signal Ix is subtracted from the compensation current signal Ixr and the energy storage system current setpoint signal Ixref. After PI control, the phase shift angle φ of the power supply port, the energy storage port (2), and the load port (3) can be obtained. 1x Where x represents the energy storage port (2) or the load port (3). This is achieved through a phase shift angle φ. 1x The control limits the bus voltage to a safe range, thereby suppressing the rise of DC bus voltage at the unclamped port.

Description

Technical Field

[0001] This invention relates to the control of power conversion devices, and more specifically to a method for suppressing the rise of port voltage when the port power supply of an isolated three-port converter is disconnected. Background Technology

[0002] With the increasing demand for new energy sources, the application scope of DC-DC converters is also expanding. Multi-port converters have been widely used in fuel cell-supercapacitor power generation systems, hybrid energy storage systems, and hybrid power systems. They enable the merging of circuit topologies and functions, reduce system costs, and achieve rational allocation of energy sources. Multi-port DC-DC converters can connect multiple DC sources, effectively solving the problems of complex structure, low power density, and difficult control in multi-DC-DC converter systems. However, to achieve zero-power input / output at the ports, whether using methods such as blocking the drive pulses of the idle port's switching transistors or using traditional methods like adding mechanical switches or relays to the full-bridge unit connected to the idle port, power can still flow to the idle end through the freewheeling diode, causing the capacitor voltage at the idle port to rise. Unavoidably, there will be situations where the power supply or energy storage battery is suddenly cut off. Therefore, it is necessary to develop a control strategy to limit the bus voltage of the idle port within a safe voltage range to address the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide a control method for suppressing the rise of DC bus voltage at the power-off clamping port when a three-port power supply or energy storage battery is disconnected.

[0004] A method for suppressing the rise of port voltage when the power supply of an isolated three-port converter is disconnected is proposed. The three ports are a power supply port (1), an energy storage port (2), and a load port (3). The power supply port (1) supplies power to the load and the energy storage battery at the same time. The feedback current signal Ix is subtracted from the compensation current signal Ixr and the energy storage system current setpoint signal Ixref. After PI control, the phase shift angle φ of the power supply port, the energy storage port (2), and the load port (3) can be obtained. 1x ; by phase shift angle φ 1x The control limits the bus voltage to a safe voltage range; where x represents the energy storage port (2) or the load port (3).

[0005] Furthermore, the compensation current signal I xr The magnitude is determined by judging the actual DC bus voltage V. x With respect to the maximum allowable voltage V xmax Determined, V xmax The actual DC bus voltage V cannot exceed the maximum allowable output voltage. x Greater than its maximum allowable voltage V xmax The actual DC bus voltage Vx Subtract its maximum allowable voltage V xmax Then multiply by the current sag coefficient K to obtain the current compensation signal I. xr Conversely, the current compensation signal I xr It is 0.

[0006] Beneficial effects:

[0007] This invention limits the bus voltage to a safe range by controlling the phase shift angle. When the power port is charging the energy storage battery, if the bus voltage rises and exceeds the maximum limit voltage, the compensation current signal will increase, the output phase shift angle will decrease, and the output current on the energy storage side will increase until the energy storage side bus voltage falls below the maximum limit voltage. This method applies not only to limiting the ESS port voltage V2 of the energy storage system but also to limiting the power port voltage V1. The same applies when the power port supplies power to the load. Attached Figure Description

[0008] Figure 1 Diagram of the topology of an isolated three-port converter.

[0009] Figure 2 Block diagram of the improved port current control strategy for an isolated three-port converter with voltage limiting function.

[0010] Figure 3 This is the bus voltage waveform of an energy storage system under a traditional control strategy.

[0011] Figure 4 The bus voltage waveform is obtained by employing the improved control strategy described in the patent.

[0012] Figure 1 middle:

[0013] V1, V2, and V3 represent the power supply voltage, energy storage system voltage, and load voltage, respectively; i1, i2, and i3 represent the power supply current, energy storage system current, and load current, respectively; L s1 L s2 L s3 These are the leakage inductances of the power supply transformer, the energy storage transformer, and the load transformer, respectively. Port 1 is the power supply port, port 2 is the energy storage port, and port 3 is the load port. Taking port 1 as a reference, φ... 12 φ is the phase shift angle between port 2 and port 1. 13 This is the phase shift angle between port 3 and port 1. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings.

[0015] Figure 1The isolated three-port converter shown has the characteristic of energy flow between any two ports. When the power supply to one port is cut off, the voltage of the unclamped port may rise. Taking an operating mode where the power port supplies power to the load and charges the energy storage battery as an example, when the energy storage port disconnects the battery, the voltage on the energy storage side bus will rise. Using conventional control methods, the voltage on the energy storage side bus will rise to a large value, which may seriously damage the power switching transistors and capacitors due to overvoltage.

[0016] This invention employs necessary control measures to limit the bus voltage within a safe voltage range. When the bus voltage rises and exceeds the maximum limit voltage, the compensation current signal increases, the output phase shift angle decreases, and the output current on the energy storage side increases until the energy storage side bus voltage falls below the maximum limit voltage. This method is applicable not only to limiting the ESS port voltage V2 of the energy storage system but also to limiting the power supply port voltage V1.

[0017] Taking the example of power supply port supplying power to load and charging energy storage battery, and disconnecting energy storage battery during control process (at this time) Figure 2 (x=2), such as Figure 2 The control method involves subtracting the compensation current signal I from the feedback current signal I2. 2r and the current command signal I of the energy storage system 2ref After PI control, the phase shift angle φ between the power supply port and the energy storage port can be obtained. 12 .

[0018] Among them, the compensation current signal I 2r The magnitude is determined by comparing the actual DC bus voltage V2 with its maximum allowable voltage V. 2max (V 2max The voltage is determined by the maximum allowable output voltage (V2 cannot exceed the maximum allowable output voltage). When the actual DC bus voltage V2 exceeds its maximum allowable voltage V... 2max Then the actual DC bus voltage V2 minus its maximum allowable voltage V 2max Then multiply by the current sag coefficient K to obtain the compensation current signal I. 2r Conversely, the compensation current signal I 2r It is 0.

[0019] If the bus voltage V2 is greater than its maximum allowable voltage V at this time 2max Then there is a compensation current signal I 2r The phase shift angle φ between the power supply port and the energy storage port exists. 12 The current will decrease, the energy storage system will output current I2, and the bus voltage V2 will drop rapidly until the bus voltage V2 is no greater than its maximum allowable voltage V. 2max And keep it within the allowable voltage range at all times.

[0020] Similarly, when the energy storage system ESS outputs power and disconnects the idle main power supply PS, the voltage V1 on the main power supply PS side will also rise due to the loss of voltage clamping. The above method is also applicable to limiting the rise of the voltage V1 at port 1 (at this time, Figure 2 (x = 1).

[0021] Figure 3 The bus voltage waveform is for a traditional control strategy. Figure 4 The bus voltage waveform is obtained using the improved control strategy.

[0022] The above-described specific embodiments are limited to explaining and illustrating the technical solutions of the present invention, but do not constitute a limitation on the scope of protection of the claims. Those skilled in the art should understand that any new technical solutions obtained by making simple modifications or substitutions based on the technical solutions of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for inhibiting the rise of port voltage when the isolated three-port converter power supply is disconnected, the three ports being a power supply port (1), an energy storage port (2) and a load port (3), characterized in that, The power port (1) supplies power to the load and the energy storage battery simultaneously, and sends a feedback current signal. Ix Subtract compensation current signal Ix and the current command signal of the energy storage system Ixref After PI control, the phase shift angles of the power supply port, energy storage port (2), and load port (3) can be obtained. φ 1x ; By phase shift angle φ 1x The control limits the bus voltage to a safe range; among which x Represents the energy storage port (2) or load port (3), compensation current signal Ix The magnitude is determined by judging the actual DC bus voltage. V x Compared with the maximum allowable voltage V xmax It is determined. V xmax The output voltage must not exceed the maximum allowable output voltage; when the actual DC bus voltage... V x Greater than its maximum allowable voltage V xmax The actual DC bus voltage V x Subtract its maximum allowable voltage V xmax Multiply by the current upswing factor K Obtain the compensation current signal Ix Conversely, compensation current signal Ix It is 0.

Images