JP5189521B2 - Vehicle power system - Google Patents

Description

  The present invention relates to a power supply system for a vehicle, and more particularly to ripple current suppression control in a power supply system including a converter for controlling power supply to a main load including a vehicle drive motor.

  A power supply system that boosts a DC voltage from a power storage device such as a battery and uses it to drive a load has been proposed. For example, Japanese Patent Laying-Open No. 2006-101636 (Patent Document 1) describes a power supply device provided with a bidirectional DC / DC converter (boost converter) that boosts a DC voltage supplied from a battery. In particular, in the power supply device described in Patent Document 1, a minimum output is ensured within the capacity range of the power source by preventing the output from being interrupted by the protection function of the boost converter during a temporary overload. Such converter control is described.

  Japanese Patent Laying-Open No. 2007-318970 (Patent Document 2) describes the configuration of a power supply system including a boost converter in FIG. And when charging a battery with an external power supply, by adding a current control system for controlling the battery current to the target current to the converter control unit, by suppressing current pulsation (ripple current), the power storage device It is described that it can also contribute to the suppression of deterioration of the resin.

  Japanese Patent Laid-Open No. 2006-94588 (Patent Document 3) discloses a pulse width of an inverter that can suppress deterioration in running stability and sudden change in battery power consumption even when a running load suddenly changes in a vehicle using an electric torque. Modulation (PWM) control is described.

JP 2006-101636 A JP 2007-318970 A JP 2006-94588 A

  As described in Patent Document 2, when the power supplied from the power storage device (battery) to the load is controlled by the converter (boost converter), if the ripple current included in the output current from the battery increases, the battery There is a risk of deterioration of characteristics.

  Further, a booster chopper type converter generally uses a reactor as an energy storage element, but if a ripple current of a direct current flowing through the reactor is large, noise may be generated due to vibration.

  Therefore, in a power supply system including a converter that performs DC power conversion, reduction of ripple current in converter control becomes an issue. However, while the magnitude of the ripple current is mainly determined by the inductance of the reactor and the switching frequency of the converter, securing the inductance is accompanied by an increase in the size of the reactor, and when the switching frequency is increased, efficiency reduction due to switching loss increases. Therefore, there is a limit to the suppression of ripple current from the design aspect.

  The present invention has been made to solve such problems, and the object of the present invention is to reduce the ripple component of the input / output current of the power storage device without increasing the loss in the converter and increasing the circuit size. It is to suppress.

  A power supply system for a vehicle according to the present invention is a power supply system for a vehicle that controls power supply to a load including an electric motor for driving a vehicle, and is a rechargeable DC power supply, a current detector, a first converter, 2 converters, ripple detecting means, and adjusting means. The current detector is configured to detect an input / output current of the DC power supply. The first converter is configured to convert DC power from a DC power source and supply it to the main load by periodic on / off control of the power semiconductor switch. The second converter is configured to convert DC power from a DC power source and supply it to the auxiliary machine by periodic on / off control of the power semiconductor switching element under a switching frequency higher than that of the first converter. To do. The ripple detection means detects a ripple current included in the input / output current based on the output of the current detector. When the detected ripple current is greater than a predetermined level, the adjusting means uses a fluctuation component such that the output power of the second converter changes in the same period and opposite phase as the ripple current as the operation command value of the second converter. Superimpose.

  According to the present invention, the ripple component of the input / output current of the power storage device can be suppressed without increasing the loss in the converter and increasing the circuit size.

It is a block diagram explaining the structure of the power supply system of the vehicle by this Embodiment. FIG. 6 is an operation waveform diagram illustrating operations of a boost converter and a DC / DC converter in the vehicle power supply system according to the present embodiment. It is a flowchart explaining the ripple current suppression control in the power supply system of the vehicle by this Embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

FIG. 1 is a block diagram illustrating the configuration of a vehicle power supply system according to the present embodiment.
Referring to FIG. 1, a power supply system 100 according to an embodiment of the present invention includes a DC power supply 10, system relays SR <b> 1 and SR <b> 2, smoothing capacitors C <b> 1 and C <b> 2, a boost converter 20, and a control device 30.

  The DC power source 10 is a rechargeable power source. That is, as the DC power source 10, a secondary battery that generates electricity by chemical change or the like, or a power storage device such as a capacitor that stores electricity when supplied from the outside can be applied. As is well known, in an electric vehicle such as a hybrid vehicle or an electric vehicle, a secondary battery is typically applied as the DC power source 10, and hence the DC power source 10 is also referred to as a battery 10 below.

  The battery 10 includes a voltage sensor 11 for detecting the output voltage Vb (battery voltage), a temperature sensor 12 for detecting the battery temperature Tb, and a current sensor for detecting the output current Ib from the battery 10. 13 are arranged.

  System relay SR 1 is connected between the positive terminal of battery 10 and power line 6, and system relay SR 2 is connected between the negative terminal of battery 10 and ground line 5. System relays SR1 and SR2 are turned on / off by a relay control signal SE from control device 30. Smoothing capacitor C <b> 1 is connected between power line 6 and ground line 5.

  Boost converter 20 includes a reactor L, power semiconductor switching elements Q1, Q2, and diodes D1, D2.

  Power semiconductor switching elements Q 1 and Q 2 are connected in series between power line 7 and ground line 5. In the embodiment of the present invention, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). Etc. can be used. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2.

  On / off (switching operation) of power semiconductor switching elements Q 1 and Q 2 is controlled by switching control signals S 1 and S 2 from control device 30. Reactor L is connected between a connection node of switching elements Q 1 and Q 2 and power line 6. Further, the smoothing capacitor C <b> 2 is connected between the power line 7 and the ground line 5.

  Load 40 is connected to power line 7 and ground line 5 and receives a DC voltage supplied from boost converter 20. The load 40 includes, for example, a vehicle drive motor (not shown) mounted on an electric vehicle, a hybrid vehicle, and the like, and an inverter (not shown) that controls the motor (including a motor generator, the same applies hereinafter). A plurality of electric motors and inverters may be provided in parallel.

  In addition, when the load 40 generates power, the DC voltage from the load 40 may be converted into a voltage by the boost converter 20 and used for charging the DC power supply (battery) 10. Further, the DC power source (battery) 10 can be charged by a power generation / feeding mechanism (not shown) other than the load 40. For example, the regenerative power generated by the electric motor (motor generator) can be converted into a direct current and supplied from the load 40 to the boost converter 20.

  The control device 30 includes a CPU (Central Processing Unit) (not shown) and an electronic control unit having a built-in memory, and performs arithmetic processing using detection values from each sensor based on a map and a program stored in the memory. Configured as follows. Alternatively, at least a part of the ECU may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  Control device 30 generates relay control signal SE for controlling on / off of system relays SR1 and SR2 in accordance with a start / stop command for power supply system 100. Relay control signal SE is generated such that system relays SR1 and SR2 are turned on in accordance with activation of power supply system 100, and controlled so that system relays SR1 and SR2 are turned off when power supply system 100 is stopped.

  The control device 30 includes a battery voltage Vb from the voltage sensor 11, a battery temperature Tb from the temperature sensor 12, a battery current Ib from the current sensor 13, an input voltage VL from the voltage sensor 14, and an output voltage VH from the voltage sensor 15. The detected value is input. Control device 30 controls switching operation (on / off operation) of switching elements Q1 and Q2 so that boost converter 20 performs desired voltage conversion based on these detected values when power supply system 100 operates. Control signals S1 and S2 are generated.

  Power supply system 100 further includes a DC / DC converter 50 as an auxiliary converter, an auxiliary battery 41, and an auxiliary machine 45.

  The DC / DC converter 50 is connected between the power line 6 and the ground line 5, and steps down the DC voltage VL on the power line 6 to a predetermined DC voltage Vo and supplies it to the auxiliary battery 41 and the auxiliary machine 45. As the DC / DC converter 50, any type of DC / DC converter that performs DC voltage conversion can be applied, and the circuit configuration is not particularly limited. However, as will be apparent from the following description, the DC / DC converter 50 is a one-way voltage converter that converts the DC voltage VL to DC Vo by switching control (duty control) of the power semiconductor switching element, and The switching frequency of the power semiconductor switching element is required to be relatively higher than that of the boost converter 20.

  The auxiliary machine 45 is a generic name for devices that operate at a lower voltage than the output voltage of the battery 10. As an example, an ECU, a lighting device, an ignition device, and an electric pump that control the traveling of the vehicle such as the control device 30. Etc.

  The auxiliary battery 41 is made of a lead storage battery, for example, and is connected to the output side of the DC / DC converter 50. The auxiliary battery 41 is charged with the output voltage Vo of the DC / DC converter 50 and supplies the operating power supply voltage of the auxiliary machine 45. That is, the auxiliary battery 41 also functions as a power buffer for compensating for an imbalance between the output power of the DC / DC converter 50 and the demand power of the auxiliary machine 45.

Next, the operation of the power supply system 100 will be described.
The battery voltage Vb, which is the output voltage from the battery 10, is applied between the ground line 5 and the power line 6 while the system relays SR <b> 1 and SR <b> 2 are on. Voltage converter VL of smoothing capacitor C <b> 1 connected to ground line 5 and power line 6 is input to boost converter 20.

  Boost converter 20 boosts DC voltage VL input from battery 10 by the switching operation of switching elements Q1 and Q2 in accordance with switching control signals S1 and S2 from control device 30, so that ground line 5 and power line 7 A DC voltage VH can be generated between them. The DC voltage VH is smoothed by the smoothing capacitor C2 and supplied to the load 40. Boost converter 20 steps down DC voltage VH supplied from load 40 via smoothing capacitor C2 by the switching operation of switching elements Q1, Q2 in accordance with switching control signals S1, S2, and ground line 5 and A DC voltage VL can be generated between the power lines 6. The DC voltage VL is smoothed by the smoothing capacitor C <b> 1 and used for charging the battery 10.

  As described above, the boost converter 20 is configured to be capable of bi-directional power conversion, so that the power output (discharge) from the battery 10 and the power input (charge) to the battery 10 are controlled while controlling the voltage conversion ratio VH / VL. ).

  Basically, the switching elements Q1 and Q2 are controlled to be turned on and off in a complementary manner in each switching period. The voltage conversion ratio (VH / VL) between the DC voltages VH and VL is controlled by controlling the on-period ratio (duty) with respect to the switching period of the switching elements Q1 and Q2 by the switching control signals S1 and S2. . Specifically, the duty of boost converter 20 is feedforward and / or feedback controlled so that DC voltage VH is controlled to the voltage command value. Note that VH = VL can be obtained by fixing the switching element Q1 to ON (switching element Q2 is fixed to OFF).

  Next, operations of the boost converter and the DC / DC converter in the vehicle power supply system according to the present embodiment will be described with reference to FIG.

  Referring to FIG. 2, the DC voltage VH rises during the ON period of switching element Q1 in accordance with the ON / OFF operation of switching elements Q1 and Q2 in each switching period T of boost converter 20 as described above, while switching The DC voltage VH decreases during the ON period of the element Q2. In the ON period of the switching element Q2, the battery current Ib increases to accumulate electromagnetic energy in the reactor L, while the battery current Ib relatively decreases in the ON period of the switching element Q1.

  For this reason, a ripple which is an AC fluctuation component is generated in the battery voltage Vb and the battery current Ib in conjunction with the on / off of the switching elements Q1, Q2. In particular, if the ripple component in the battery current Ib (hereinafter, also simply referred to as “ripple current”) becomes excessive, there is a risk that the characteristics of the battery 10 will deteriorate. In addition, since the ripple current also passes through the coil of the reactor L, if the ripple current increases, vibration in the reactor L is generated, which may lead to generation of noise.

  For this reason, it is necessary to suppress the ripple current from exceeding a predetermined level. However, since the amplitude of the ripple current is basically determined by the switching period T of the boost converter 20 and the inductance of the reactor L, the inductance increases with the power switching frequency (1 / T) and the increase in the size of the element when the circuit design is used. Will be necessary. In particular, the boost converter 20 that controls the power supply to the load 40 including the vehicle drive motor flows a relatively large current. Therefore, when the switching frequency is increased, there is a problem of deterioration in fuel consumption due to an increase in power loss (switching loss). Concerned.

  Therefore, in power supply system 100 according to the present embodiment, control is performed to suppress ripple current using DC / DC converter 50, which is another consumer of battery current Ib.

  Specifically, for the command value (Vo command value) of the output voltage Vo of the DC / DC converter 50, an AC component that cancels the ripple current is superimposed on the original DC voltage command Vor. Specifically, with respect to the original voltage command value Vor (direct current), the ripple current and the ripple current are set so as to cancel out the voltage fluctuation of the battery voltage Vb so that the power consumption is performed in the same cycle and opposite phase as the ripple current. An AC component ΔVor having the same cycle and the same phase (the phase opposite to the battery voltage fluctuation) is superimposed. The converter duty in the DC / DC converter 50 is controlled according to the Vo command value.

  As described above, any type of DC / DC converter can be applied as the DC / DC converter 50. However, the DC / DC converter 50 is configured to perform direct-current voltage conversion by on / off control of the switching element. The switching frequency needs to be higher than the switching frequency (1 / T) of boost converter 20. If possible, it is preferable that the switching frequency be such that the Vo command value of the DC / DC converter 50 can be set independently at least during the ON period of the switching elements Q1 and Q2. That is, the boost converter 20 corresponds to a “first converter”, and the DC / DC converter 50 corresponds to a “second converter”.

  FIG. 3 shows a flowchart for explaining ripple current suppression control in the vehicle power supply system according to the present embodiment. Each step of the flowchart shown in FIG. 3 is realized by software or hardware processing by the control device 30.

  Referring to FIG. 3, control device 30 detects a battery current fluctuation, that is, a ripple current in step S100. Specifically, the amplitude of the ripple current is detected based on the battery current Ib detected by the current sensor 13. For example, the amplitude of the ripple current can be detected by extracting a frequency component corresponding to the switching frequency of the boost converter 20. That is, the current sensor 13 corresponds to a “current detector”, and the process in step S100 corresponds to a “ripple detection unit”.

  In step S110, control device 30 determines whether or not the current fluctuation (ripple current amplitude) detected in step S100 is greater than a predetermined determination value.

  When the ripple current is equal to or smaller than the determination value (NO determination in step S110), the control device 30 maintains the original voltage command value Vor (direct current) in step S140 and Vo of the DC / DC converter 50. Set the command value.

  On the other hand, when the ripple current is larger than the determination value (when YES is determined in step S110), control device 30 is superimposed on the Vo command value of DC / DC converter 50 for reducing the ripple current in step S120. AC component ΔVor is calculated. As described above, the AC component ΔVor is set in a phase opposite to the battery voltage fluctuation.

  The amplitude of the AC component ΔVor may be determined based on the ripple current amplitude or battery voltage fluctuation (ripple voltage) detected in step S100, and the frequency (period) and phase thereof are the on / off control signals of the switching elements Q1 and Q2. What is necessary is just to synchronize with the switching control signals S1 and S2.

  In step S130, the control device 30 adds the AC component ΔVor obtained in step S120 to the original voltage command value Vor (direct current) of the DC / DC converter 50, so that the Vo of the DC / DC converter 50 is increased. Set the command value. That is, the processing in step S120 corresponds to “adjustment means”.

  By superimposing the AC component ΔVor on the Vo command value of the DC / DC converter 50, the output power of the DC / DC converter 50 is increased when the ripple current increases (the AC component is positive), while the ripple current At the time of reduction (period in which the AC component is negative), the output power of the DC / DC converter 50 can be reduced. As a result, the ripple current in battery current Ib generated by the switching operation of boost converter 20 can be reduced.

  As described above, in the vehicle power supply system according to the present embodiment, control of the boost converter is complicated without increasing the switching frequency of the boost converter 20, without increasing the size of the circuit element (reactor). The battery current fluctuation (ripple current) generated by the boost converter 20 can be reduced without causing the voltage to rise. As a result, it is possible to appropriately protect the battery 10.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  5 Ground wire, 6, 7 Power line, 10 DC power supply (battery), 11, 14, 15 Voltage sensor, 12 Temperature sensor, 13 Current sensor, 20 Boost converter, 30 Control unit (ECU), 40 Load, 41 Auxiliary battery , 45 Auxiliary machine, 50 DC / DC converter, 100 power supply system, C1, C2 smoothing capacitor, D1, D2 antiparallel diode, Ib battery current, L reactor, Q1, Q2 power semiconductor switching element, S1, S2 switching control signal , SE relay control signal, SR1, SR2 system relay, T switching cycle (boost converter), Tb battery temperature, Vb battery voltage, VH DC voltage (boost converter), VL DC voltage, Vo DC output voltage (DC / DC converter) , Vor DC voltage command , ΔVor AC component.

Claims (1)

A power supply system for a vehicle that controls power supply to a load including a vehicle driving motor,
Rechargeable DC power supply,
A current detector for detecting an input / output current of the DC power supply;
A first converter that converts DC power from the DC power source and supplies it to the main load by periodic on / off control of a power semiconductor switch;
A second converter that converts DC power from the DC power source and supplies it to the auxiliary machine by periodic on / off control of the power semiconductor switching element under a switching frequency higher than that of the first converter;
Ripple detection means for detecting a ripple current included in the input / output current based on the output of the current detector;
When the detected ripple current is larger than a predetermined level, a fluctuation component that causes the output power of the second converter to change in the same period and opposite phase is used as the operation command value of the second converter. A power supply system for a vehicle comprising adjustment means for superimposing.

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