1 Introduction
2 FC-PCC MMC topology
3 FC-PCC MMC model
3.1 FC-PCC MMC mathematical model
3.2 FC-PCC MMC current dynamics
4 Compensation of the low-frequency energy fluctuations
5 Distributed digital control strategy
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faster processing and minimum data exchange between computational units (i.e., minimum latency), as compared to either fully centralized, characterized by a considerable operation queue and a lot of communication overhead, or a fully decentralized approach, limited by low computing performance derived from cost constraints;
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full scalability, allowing to build an MMC with an arbitrary number of SMs in the phase-leg (theoretically possible, provided that the required throughput of the communication bus is actually achievable).
5.1 Optimized communication architecture
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the need for a control unit in each submodule increases both the cost and the design complexity of the SM with respect to a fully centralized approach;
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the computational units require a reliable and fast communication channel for exchanging all the necessary information.
6 Pre-charge/Start-up strategy with L-C oscillations damping
7 Coupled sub-arm inductor design
8 Simulation results
Rated dc–bus voltage | \(U_{\mathrm{DC}}\) | 800 V |
Number of SM per arm | \(N\) | 8 |
SM capacitor rated voltage | \(U_{\mathrm{C}}\) | 100 V |
Rated peak phase voltage | \(\hat{U}_{x}\) | 400 V |
Rated peak phase current | \(\hat{I}_{x}\) | 75 A |
Total arm inductance | \(L_{\mathrm{arm}}\) | 1 mH |
Total arm resistance | \(R_{\mathrm{arm}}\) | 10 m\(\Upomega\) |
Rated SM capacitance | \(C_{\mathrm{SM}}\) | 3900 \(\upmu\)F |
Rated flying-capacitance | \(C_{f}\) | 50 \(\upmu\)F |
PWM carrier frequency | \(f_{t}\) | 10 kHz |
HF injection frequency | \(f_{h}\) | 1 kHz |
Rated torque | \(T_{n}\) | \(62.7\,\text{N}\text{m}\) |
Rated speed | \(n_{n}\) | \(4000\,\text{rpm}\) |
Pole pairs | \(p_{p}\) | \(3\) |
Rated current | \(I_{n}\) | \(52\,\text{A}\) |
Phase resistance | \(R_{s}\) | \(54\,\text{m}\Upomega\) |
Phase inductance | \(L_{d}=L_{q}\) | \(470\,\upmu\text{H}\) |
PM flux linkage | \(\Lambda_{mg}\) | \(0.187\,\text{Wb}\) |