A bidirectional controllable direct current source and a control method thereof

Abstract

The application relates to a bidirectional controllable direct current source and a control method thereof, which comprises a main power circuit, a first control board, a second control board, a third control board, a communication board and an auxiliary power supply; the main power circuit is used for converting marine three-phase 380V alternating current power supply into controllable direct current with controllable size and direction through an EMI filter, a soft start circuit, an LCL filter circuit, an APFC circuit, an LLC circuit and a high-frequency H-bridge commutation circuit, and providing the direct current to a load winding. When the output current of the bidirectional controllable direct current source is commutated, a reverse voltage is applied to the load winding, the load inductance current is rapidly reduced, the zero-crossing point out-of-control problem under a large inductance load is solved, and the current output requirement of the bidirectional controllable direct current source in a wide load range is met.

Description

Technical Field

[0001] The present invention relates to a ship electrical technology, in particular to a bidirectional controllable DC source adaptable to various resistive and inductive load windings and a control method thereof. Background Art

[0002] Marine bidirectional controllable DC sources can receive commands from control equipment and provide a controllable output current to the load windings. Currently, marine bidirectional controllable DC sources generally employ a static multipole topology, where the commutation circuit only changes polarity. In a static commutation structure, the commutation switch remains stationary when the output current direction remains unchanged. However, when the positive and negative polarity switches, i.e., when the load current command crosses zero, the voltage regulation can only reach zero, preventing the load from receiving a negative voltage. This results in a delay in shutting off the zero-crossing circuit. This static commutation structure can meet accuracy requirements for purely resistive or low-inductive loads, or when commands change slowly. However, when the load inductance increases to a certain value, the output current will not track the zero-crossing point. Forced zero-crossing switching can also cause voltage spikes across the load windings. Summary of the Invention

[0003] Aiming at the problem that the current bidirectional controllable DC source cannot adapt to the excessively large inductance of the load winding, a bidirectional controllable DC source and its control method are proposed. When the output current of the bidirectional controllable DC source is commutated, a reverse voltage is applied to the load winding to achieve a rapid reduction of the load inductance current, thereby solving the zero-crossing loss of control problem under large inductance loads and meeting the current output requirements of the bidirectional controllable DC source within a wide load range.

[0004] The technical solution of the present invention is: a bidirectional controllable DC source, including a main power circuit, a first control board, a second control board, a third control board, a communication board, and an auxiliary power supply; the main power circuit converts a marine three-phase 380V AC power supply into a DC current with controllable magnitude and direction through an EMI filter, a soft start circuit, an LCL filter circuit, an APFC circuit, an LLC circuit, and a high-frequency H-bridge commutation circuit, and supplies the DC current to a load winding;

[0005] The first control board collects the output voltage and input inductor current of the APFC circuit and the temperature on the APFC switch tube heat sink, outputs a soft start relay signal to the soft start circuit, and outputs a drive signal and a protection signal to the switch tube of the APFC circuit;

[0006] The second control board collects the output voltage value of the LLC circuit, the resonant inductor current value and the temperature on the LLC switch tube heat sink, and outputs a driving signal and a protection signal to the switch tube of the LLC circuit;

[0007] The third control board collects the output voltage value, output filter inductor current value, output current value and the temperature on the heat sink of the switch tube of the high-frequency H-bridge commutation circuit, and outputs a driving signal and a protection signal to the switch tube of the high-frequency H-bridge commutation circuit;

[0008] The first control board, the second control board, and the third control board communicate with each other via CAN. The communication board is connected to the host computer via Ethernet or CAN network, receives control instructions and uploads status information of the bidirectional controllable DC source; and is connected to the first control board, the second control board, and the third control board via CAN network, distributes current control instructions and receives status information.

[0009] The auxiliary power supply takes power from the DC bus, converts +680V DC power into weak current +24V and +5V, and supplies power to the fan, the first control board, the second control board, the third control board, and the communication board.

[0010] Preferably, the soft start circuit is used to avoid power-on shock, and the circuit includes a soft start resistor R1, a relay S1, a soft start resistor R2, and a relay S2. The soft start resistor R1 and the relay S1 are connected in parallel to the first phase output of the EMI filter output, and the soft start resistor R2 and the relay S2 are connected in parallel to the third phase output of the EMI filter output.

[0011] Preferably, the LCL filter circuit includes a filter inductor L 1～6 and filter capacitor C 1～3 , 6 filter inductors are connected in series in pairs to form 3 groups of filter inductors, which are respectively connected to the three-phase circuit output of the soft start circuit. One end of the filter capacitor C1, filter capacitor C2, and filter capacitor C3 are connected together, and the other ends are respectively connected to the series connection points of the 3 groups of filter inductors.

[0012] Preferably, the APFC circuit realizes rectification, including a diode D 1～6 , switch tube Q 1～6 And two output capacitors C4 and C5 in series; the anodes of diodes D1, D2 and D3 are connected to the three phases of the LCL filter circuit output respectively, and their cathodes are connected to the end of the output capacitor C4 far away from the output capacitor C5; the cathodes of diodes D4, D5 and D6 are connected to the three phases of the LCL filter circuit output respectively, and their anodes are connected to the end of the output capacitor C5 far away from the output capacitor C4. The switch tube Q 1～6 Two switches are connected in series to form a three-phase switch, and each phase switch is connected in series between one phase output of the LCL filter circuit and the series connection point of the output capacitor C4 and the output capacitor C5.

[0013] Preferably, the LLC circuit realizes voltage level conversion and electrical isolation, including a switch tube Q 7～10, resonant inductor L7, resonant capacitor C6, excitation inductor L8, transformer T1, rectifier diode D 7～10 and output capacitor C7, switch tube Q7 and switch tube Q9 are connected in series, switch tube Q8 and switch tube Q 10 are connected in series, and the two groups of switch tubes are connected in parallel across the APFC circuit output DC bus, resonant inductor L7 and resonant capacitor C6 are connected in series and connected to the primary side of transformer T1, excitation inductor L8 is connected in parallel to the primary side of transformer T1, and the secondary side of the transformer is connected to the midpoint of diode D7 and diode D9 in series and the midpoint of diode D8 and diode D 10 in series, and the two groups of diodes in series are connected in parallel across output capacitor C7.

[0014] Preferably, the high-frequency H-bridge commutation circuit comprises switch tube Q 11～14 , filter inductor L9, resonant capacitor C8, filter inductor L 10 and damping resistor R3, switch tube Q 11 and switch tube Q 13 are connected in series, switch tube Q 12 and switch tube Q 14 are connected in series, and the two series-connected switch tubes are connected in parallel at the output end of the LLC circuit, filter inductor L9, resonant capacitor C8 and damping resistor R3 are connected in series between the two series connection points, one end of filter inductor L 10 is connected to the filter inductor L 10 , and the other end of the filter inductor L 11 is connected to the load winding, and the damping resistor R3 is connected to the load winding at the other end away from the resonant capacitor C8.

[0015] A control method of a bidirectional controllable DC source, wherein the APFC circuit in the bidirectional controllable DC source adopts voltage and current double-loop control, the outer loop is output voltage closed loop, and the inner loop is inductance current closed loop, three-phase 380V alternating current is rectified to 680V direct current;

[0016] The LLC circuit in the bidirectional controllable DC source adopts open-loop control, the switching frequency is slightly lower than the resonant frequency, is used for realizing electrical isolation and voltage matching, and the duty ratio is fixed, 680V direct current is converted into 500V direct current;

[0017] The high-frequency H-bridge commutation circuit in the bidirectional controllable DC source adopts three-loop PI control from inside to outside, that is, inductance current inner loop, output voltage loop and output current outer loop, the open-loop transfer function of each loop is compensated by a PI regulator, and the closed-loop transfer function of each loop after compensation is taken as the compensation object of the next loop.

[0018] Further, when switch tube Q 11 and switch tube Q 14 are turned on at the same time, the circuit works in the forward power supply state; when switch tube Q12 and switch tube Q 13 When both are turned on, the circuit works in the reverse power supply state; when the switch tube Q 11 and switch tube Q 12 At the same time, the switch tube Q 13 and switch tube Q 14 When both are turned on at the same time, the circuit operates in the load freewheeling state.

[0019] The beneficial effects of the present invention are as follows: the bidirectional controllable DC source and the control method thereof can adapt to various resistive and inductive load windings, solve the zero-crossing loss of control problem under large inductive loads, and enhance the operating stability of the bidirectional controllable DC source on the basis of improving the dynamic response capability and speed of the output. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a principle block diagram of the bidirectional controllable DC source of the present invention;

[0021] Figure 2 This is a block diagram of a control method for a high-frequency H-bridge commutation circuit in a bidirectionally controllable DC source according to the present invention;

[0022] Figure 3 It is a common one-dimensional SVPWM pulse modulation mode of a single-stage inverter in the bidirectional controllable DC source of the present invention;

[0023] Figure 4 This is a switching state transition diagram of the high-frequency H-bridge commutation circuit in the bidirectional controllable DC source of the present invention;

[0024] Figure 5 This is the test waveform of the output current and output voltage switching when the inductive load in the bidirectional controllable DC source of the present invention reaches 1H. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] like Figure 1 As shown, the bidirectional controllable DC power supply includes a main power circuit, control boards 1, 2, and 3, a communication board, and an auxiliary power supply. The main power circuit converts the marine three-phase 380V AC power supply through an EMI filter, a soft-start circuit, an LCL filter circuit, an APFC circuit, an LLC circuit, and a high-frequency H-bridge commutation circuit, converting it into a controllable output current that is supplied to the load winding.

[0027] The soft-start circuit is used to avoid power-on shock and includes a soft-start resistor R1, a relay S1, a soft-start resistor R2, and a relay S2. The soft-start resistor R1 and the relay S1 are connected in parallel to the first phase output of the EMI filter, and the soft-start resistor R2 and the relay S2 are connected in parallel to the third phase output of the EMI filter.

[0028] The LCL filter circuit includes a filter inductor L 1～6 and filter capacitor C 1～3 , 6 filter inductors are connected in series in pairs to form 3 groups of filter inductors, which are respectively connected to the output three-phase circuit of the soft start circuit. One end of the filter capacitor C1, filter capacitor C2, and filter capacitor C3 are connected together, and the other ends are connected to the series connection points of the 3 groups of filter inductors;

[0029] The APFC (active power factor correction) circuit realizes the rectification function, including the diode D 1～6 , switch tube Q 1～6 And two output capacitors C4 and C5 in series; the anodes of diodes D1, D2 and D3 are connected to the three phases of the LCL filter circuit output respectively, and their cathodes are connected to the end of the output capacitor C4 far away from the output capacitor C5; the cathodes of diodes D4, D5 and D6 are connected to the three phases of the LCL filter circuit output respectively, and their anodes are connected to the end of the output capacitor C5 far away from the output capacitor C4. The switch tube Q 1～6 Two switches are connected in series to form a three-phase switch, and each phase switch is connected in series between one phase output of the LCL filter circuit and the series connection point of the output capacitor C4 and the output capacitor C5;

[0030] LLC circuit realizes voltage level conversion and electrical isolation, including switch tube Q 7～10 , resonant inductor L7, resonant capacitor C6, excitation inductor L8, transformer T1, rectifier diode D 7～10 And the output capacitor C7, the switch tube Q7 and the switch tube Q9 are connected in series, the switch tube Q8 and the switch tube Q 10 The two sets of switch tubes are connected in parallel at both ends of the APFC circuit output DC bus. The resonant inductor L7 and the resonant capacitor C6 are connected in series and connected to the primary side of the transformer T1. The excitation inductor L8 is connected in parallel to the primary side of the transformer T1. The secondary side of the transformer is connected to the midpoint of the series connection of diodes D7 and D9 and diodes D8 and D 10 The midpoint of the series connection is connected, and the two sets of series diodes are connected in parallel to both ends of the output capacitor C7;

[0031] The high-frequency H-bridge commutation circuit realizes the DC current output with controllable size and direction, including the switch tube Q 11～14 , filter inductor L9, resonant capacitor C8, filter inductor L 10 And the damping resistor R3, the switch tube Q 11 With the switch tube Q 13Series, switch tube Q 12 With the switch tube Q 14 Series connection, then parallel connection at the LLC circuit output end, the filter inductor L9, resonant capacitor C8 and damping resistor R3 are connected in series between the two series connection points, the filter inductor L9 and resonant capacitor C8 are connected in series with the filter inductor L 10 One end, filter inductor L 10 The other end of the resistor R3 is connected to the load winding, and one end of the damping resistor R3 away from the resonant capacitor C8 is connected to the other end of the load winding.

[0032] The bidirectional controllable DC source further includes control boards 1, 2, and 3. Control board 1 collects voltage, current, and temperature values ​​from the soft start circuit, LCL filter circuit, and APFC circuit. Based on the control algorithm of control board 1, it outputs a soft start relay signal to the soft start circuit and a drive signal and a protection signal to the APFC circuit. Control board 2 collects voltage, current, and temperature values ​​from the LLC circuit and, based on the control algorithm of control board 2, outputs a drive signal and a protection signal to the LLC circuit. Control board 3 collects voltage, current, and temperature values ​​from the high-frequency H-bridge commutation circuit and, based on the control algorithm of control board 3, outputs a drive signal and a protection signal to the high-frequency H-bridge commutation circuit. Communication between control boards 1, 2, and 3 is performed via CAN.

[0033] The bidirectional controllable DC source further includes a communication board, which is connected to a host computer via Ethernet or a CAN network, receives control instructions and uploads status information of the bidirectional controllable DC source; and is connected to control boards 1, 2, and 3 via a CAN network, distributes current control instructions and receives status information.

[0034] The bidirectional controllable DC source also includes an auxiliary power supply, which takes power from the DC bus at the output end of the APFC circuit and converts it into weak power to power the fan, control board 1, control board 2, control board 3, and communication board.

[0035] The APFC utilizes dual closed-loop control for voltage and current. The outer loop is the output voltage closed-loop, and the inner loop is the inductor current closed-loop. The circuit rectifies three-phase 380V AC power to 680V DC. Control board 1 collects the APFC circuit's output voltage, input inductor current, and the temperature of the APFC switch's heatsink. After applying its control algorithm, control board 1 outputs a soft-start relay signal to the soft-start circuit and a drive signal and protection signal to the APFC switch. The APFC employs a space vector modulation strategy. First, phase-locked loop (PLL) is used to determine the phase angles of the three-phase input voltages, thereby achieving PARK conversion of the three-phase input currents. The inner loop is the input current loop after PARK conversion, and the outer loop is the output voltage loop. Because the inner loop current feedback after PARK conversion is a DC quantity, the output of the outer voltage loop serves as the input current reference for the inner loop. The current loop utilizes PI control to eliminate steady-state errors in current tracking.

[0036] The LLC circuit uses open-loop control, with a switching frequency slightly below the resonant frequency to achieve electrical isolation and voltage matching. The duty cycle is fixed, converting 680V DC power to 500V DC. Control Board 2 collects the LLC circuit's output voltage, resonant inductor current, and the temperature of the LLC switch's heat sink. Through its control algorithm, Control Board 2 outputs drive and protection signals to the LLC circuit's switches.

[0037] High frequency H-bridge commutation uses the inner loop of the inductor current from inside to outside ( Figure 1 Current on the filter inductor L9), output voltage loop, output current outer loop ( Figure 1 Medium filter inductor L 10 The three-loop PI control of the upper current is as follows: Figure 2 As shown, the open-loop transfer function of each loop is compensated by a PI regulator, and the closed-loop transfer function of each loop after compensation serves as the compensation object of the next loop. Figure 2 In, H L 、H v 、H i They are the inductor current sampling coefficient, output voltage sampling coefficient, and output current sampling coefficient, respectively. m_L (s), C m_v (s), C m_i (s) are the differential sampling hysteresis links of the inductor current loop, output voltage loop, and output current loop, respectively. G dL (s) is the transfer function of the inductor current, G L (s), G v (s), G i (s) are the PI links of the inductor current loop, output voltage loop, and output current loop, respectively. m is the duty cycle modulation ratio, Z f (s), Z o(s) is the corresponding load impedance, and the output current is controllable in magnitude and direction from -20A to +20A. The output voltage varies accordingly from -400V to +400V. This control method not only improves the dynamic response capability and speed of the power supply output, but also enhances its operational stability.

[0038] Combined with the commutation function, the H-bridge should work in the inverter state, and the one-dimensional SVPWM pulse modulation method commonly used in single-stage inverter design should be selected, such as Figure 3 As shown. When the switch tube Q 11 and switch tube Q 12 At the same time, the switch tube Q 13 and switch tube Q 14 When the circuit is turned on at the same time, it works in the load freewheeling state, which is equivalent to introducing two zero vectors, and we can get Figure 4 The switching state transition diagram is shown. 11 and switch tube Q 14 When both are turned on, the circuit works in the forward power supply state; the switch tube Q 12 and switch tube Q 13 When both are turned on, the circuit works in the reverse power supply state; when the switch tube Q 11 and switch tube Q 12 At the same time, the switch tube Q 13 and switch tube Q 14 When both are on, the circuit operates in a load freewheeling state. Because the high-frequency H-bridge circuit can rapidly reduce the load inductor current by applying a reverse voltage, the output current zero-crossing point no longer presents a risk of runaway. Control board 3 collects the output voltage, output filter inductor current, and output current of the high-frequency H-bridge commutation circuit, as well as the temperature of the switching tube heat sink of the high-frequency H-bridge commutation circuit. Based on the control algorithm of control board 3, it outputs drive and protection signals to the high-frequency H-bridge commutation circuit.

[0039] Control boards 1, 2, and 3 communicate via CAN. The communication board connects to the host computer via Ethernet or CAN, receives control commands, and uploads status information about the bidirectional controllable DC source. It also connects to control boards 1, 2, and 3 via CAN, distributes current control commands, and receives status information.

[0040] The auxiliary power supply draws power from the DC bus, converting +680V DC power into weak currents +24V and +5V to power the fan, control board 1, control board 2, control board 3, and communication board.

[0041] Figure 5 This is the test waveform of the output current and output voltage switching when the inductive load reaches 1H. It can be seen that during the switching process, the zero-crossing output voltage and output current have a good transition. The test results verify the feasibility of the invention.

[0042] The above embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A control method for a bidirectional controllable DC source, characterized in that: The bidirectional controllable DC source includes a main power circuit, a first control board, a second control board, a third control board, a communication board, and an auxiliary power supply. The main power circuit converts the marine three-phase 380V AC power supply into a DC current with controllable magnitude and direction through an EMI filter, a soft start circuit, an LCL filter circuit, an APFC circuit, an LLC circuit, and a high-frequency H-bridge commutation circuit, and supplies the DC current to the load winding. The first control board collects the output voltage and input inductor current of the APFC circuit and the temperature on the APFC switch tube heat sink, outputs a soft start relay signal to the soft start circuit, and outputs a drive signal and a protection signal to the switch tube of the APFC circuit; The second control board collects the output voltage value of the LLC circuit, the resonant inductor current value and the temperature on the LLC switch tube heat sink, and outputs a driving signal and a protection signal to the switch tube of the LLC circuit; The third control board collects the output voltage value, output filter inductor current value, output current value and the temperature on the heat sink of the switch tube of the high-frequency H-bridge commutation circuit, and outputs a driving signal and a protection signal to the switch tube of the high-frequency H-bridge commutation circuit; The first control board, the second control board, and the third control board communicate with each other via CAN. The communication board is connected to the host computer via Ethernet or CAN network, receives control instructions and uploads status information of the bidirectional controllable DC source; and is connected to the first control board, the second control board, and the third control board via CAN network, distributes current control instructions and receives status information. The auxiliary power supply takes power from the DC bus and converts the +680V DC power into weak current +24V and +5V to power the fan, the first control board, the second control board, the third control board, and the communication board; The LLC circuit realizes voltage level conversion and electrical isolation, including the switch tube Q 7~10 , resonant inductor L7, resonant capacitor C6, excitation inductor L8, transformer T1, rectifier diode D 7~10 And the output capacitor C7, the switch tube Q7 and the switch tube Q9 are connected in series, the switch tube Q8 and the switch tube Q 10 The two sets of switch tubes are connected in parallel at both ends of the APFC circuit output DC bus. The resonant inductor L7 and the resonant capacitor C6 are connected in series and connected to the primary side of the transformer T1. The excitation inductor L8 is connected in parallel to the primary side of the transformer T1. The secondary side of the transformer is connected to the midpoint of the series connection of diodes D7 and D9 and diodes D8 and D 10 The midpoint of the series connection is connected, and the two sets of series diodes are connected in parallel to both ends of the output capacitor C7; The high frequency H-bridge commutation circuit includes a switch tube Q 11~14 , filter inductor L9, resonant capacitor C8, filter inductor L 10 And the damping resistor R3, the switch tube Q 11 With the switch tube Q 13 Series, switch tube Q 12 With the switch tube Q 14 Series connection, then parallel connection at the LLC circuit output end, the filter inductor L9, resonant capacitor C8 and damping resistor R3 are connected in series between the two series connection points, the filter inductor L9 and resonant capacitor C8 are connected in series with the filter inductor L 10 One end, filter inductor L 10 The other end of the resistor R3 is connected to the load winding, and the end of the damping resistor R3 away from the resonant capacitor C8 is connected to the other end of the load winding; The APFC circuit adopts voltage and current dual closed-loop control, with the outer loop being the output voltage closed-loop and the inner loop being the inductor current closed-loop, to rectify the three-phase 380V AC power into 680V DC power. The LLC circuit in the bidirectional controllable DC source adopts open-loop control with a switching frequency slightly lower than the resonant frequency to achieve electrical isolation and voltage matching. The duty cycle is fixed and the 680V DC power is converted into 500V DC power. The high-frequency H-bridge commutation circuit in the bidirectional controllable DC source adopts three-loop PI control from the inside to the outside, namely the inner loop of inductor current, the output voltage loop, and the outer loop of output current. The open-loop transfer function of each loop is compensated by the PI regulator, and the closed-loop transfer function of each loop after compensation serves as the compensation object of the next loop.

2. The control method of the bidirectional controllable DC source according to claim 1, characterized in that: The high-frequency H-bridge commutation circuit in the bidirectional controllable DC source is 11 and switch tube Q 14 When both are turned on, the circuit works in the forward power supply state; the switch tube Q 12 and switch tube Q 13 When conducting at the same time, the circuit works in the reverse power supply state; When the switch tube Q 11 and switch tube Q 12 At the same time, the switch tube Q 13 and switch tube Q 14 When both are turned on at the same time, the circuit operates in the load freewheeling state.

3. The control method of the bidirectional controllable DC source according to claim 1, characterized in that: The soft start circuit is used to avoid power-on shock. The circuit includes a soft start resistor R1, a relay S1, a soft start resistor R2, and a relay S2. The soft start resistor R1 and the relay S1 are connected in parallel to the first phase output of the EMI filter output, and the soft start resistor R2 and the relay S2 are connected in parallel to the third phase output of the EMI filter output.

4. The control method of the bidirectional controllable DC source according to claim 1, characterized in that: The LCL filter circuit includes a filter inductor L 1~6 and filter capacitor C 1~3 , 6 filter inductors are connected in series in pairs to form 3 groups of filter inductors, which are respectively connected to the three-phase circuit output of the soft start circuit. One end of the filter capacitor C1, filter capacitor C2, and filter capacitor C3 are connected together, and the other ends are respectively connected to the series connection points of the 3 groups of filter inductors.

5. The control method of the bidirectional controllable DC source according to claim 1, characterized in that: The APFC circuit realizes rectification, including diode D 1~6 , switch tube Q 1~6 And two output capacitors C4 and C5 in series; the anodes of diodes D1, D2 and D3 are connected to the three phases of the LCL filter circuit output respectively, and their cathodes are connected to the end of the output capacitor C4 far away from the output capacitor C5; the cathodes of diodes D4, D5 and D6 are connected to the three phases of the LCL filter circuit output respectively, and their anodes are connected to the end of the output capacitor C5 far away from the output capacitor C4. The switch tube Q 1~6 Two switches are connected in series to form a three-phase switch, and each phase switch is connected in series between one phase output of the LCL filter circuit and the series connection point of the output capacitor C4 and the output capacitor C5.

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